Ductal, intraductal, and cribriform carcinoma of the prostate: Molecular characteristics and clinical management

Prostatic acinar adenocarcinoma accounts for approximately 95% of prostate cancer (CaP) cases. The remaining 5% of histologic subtypes of CaP are known to be more aggressive and have recently garnered substantial attention. These histologic subtypes - namely, prostatic ductal adenocarcinoma (PDA), intraductal carcinoma of the prostate (IDC-P), and cribriform carcinoma of the prostate (CC-P) - typically exhibit distinct growth characteristics, genomic features, and unique oncologic outcomes. For example, PTEN mutations, which cause uncontrolled cell growth, are frequently present in IDC-P and CC-P. Germline mutations in homologous DNA recombination repair (HRR) genes (e.g., BRCA1, BRCA2, ATM, PALB2, and CHEK2) are discovered in 40% of patients with IDC-P, while only 9% of patients without ductal involvement had a germline mutation. CC-P is associated with deletions in common tumor suppressor genes, including PTEN, TP53, NKX3-1, MAP3K7, RB1, and CHD1. Evidence suggests abiraterone may be superior to docetaxel as a first-line treatment for patients with IDC-P. To address these and other critical pathological attributes, this review examines the molecular pathology, genetics, treatments, and oncologic outcomes associated with CC-P, PDA, and IDC-P with the objective of creating a comprehensive resource with a centralized repository of information on PDA, IDC-P, and CC-P.

Harnessing artificial intelligence for prostate cancer management

Prostate cancer (PCa) is a common malignancy in males. The pathology review of PCa is crucial for clinical decision-making, but traditional pathology review is labor intensive and subjective to some extent. Digital pathology and whole-slide imaging enable the application of artificial intelligence (AI) in pathology. This review highlights the success of AI in detecting and grading PCa, predicting patient outcomes, and identifying molecular subtypes. We propose that AI-based methods could collaborate with pathologists to reduce workload and assist clinicians in formulating treatment recommendations. We also introduce the general process and challenges in developing AI pathology models for PCa. Importantly, we summarize publicly available datasets and open-source codes to facilitate the utilization of existing data and the comparison of the performance of different models to improve future studies.

Overcoming resistance to programmed cell death protein 1 (PD-1) blockade with allogeneic invariant natural killer T-cells (iNKT)

Gastric cancer is the 5th most common malignancy worldwide with only 36% of patients with metastatic disease surviving beyond 5 years. Despite therapeutic improvements with the advent of immune checkpoint inhibitors, most patients with gastric cancer develop disease progression related to tumor resistance. Novel immunotherapeutic approaches, including invariant natural killer (iNKT) cells, are in clinical development and represent potential therapeutic options to overcome resistance. AgenT-797 is an allogeneic human unmodified iNKT derived from healthy donors. Activation of iNKT cells by tumor lipid antigens can trigger direct cytotoxicity and promote indirect anti-tumor immune responses such as recruitment and activation of T cells, NK cells, and dendritic cells through secretion of cytokines and IFNγ. We describe immune modulation leading to durable tumor response in a patient with microsatellite instability-high (MSI-H) advanced gastric adenocarcinoma treated with agent-797 after progression on standard chemotherapy and anti-PD-1 therapy.

Predictive and prognostic biomarkers in urological tumours

Advancements in cutting-edge molecular profiling techniques, such as next-generation sequencing and bioinformatic analytic tools, have allowed researchers to examine tumour biology in detail and stratify patients based on factors linked with clinical outcome and response to therapy. This manuscript highlights the most relevant prognostic and predictive biomarkers in kidney, bladder, prostate and testicular cancers with recognised impact in clinical practice. In bladder and prostate cancer, new genetic acquisitions concerning the biology of tumours have modified the therapeutic scenario and led to the approval of target directed therapies, increasing the quality of patient care. Thus, it has become of paramount importance to choose adequate molecular tests, i.e., FGFR screening for urothelial cancer and BRCA1-2 alterations for prostate cancer, to guide the treatment plan for patients. While no tissue or blood-based biomarkers are currently used in routine clinical practice for renal cell carcinoma and testicular cancers, the field is quickly expanding. In kidney tumours, gene expression signatures might be the key to identify patients who will respond better to immunotherapy or anti-angiogenic drugs. In testicular germ cell tumours, the use of microRNA has outperformed conventional serum biomarkers in the diagnosis of primary tumours, prediction of chemoresistance, follow-up monitoring, and relapse prediction.

Development of a Practical Nomogram for Personalized Anemia Management in Patients Treated with Ataxia Telangiectasia and Rad3-related Inhibitor Camonsertib

PURPOSE

Camonsertib is a highly selective and potent inhibitor of ataxia telangiectasia and Rad3-related (ATR) kinase. Dose-dependent anemia is a class-related on-target adverse event often requiring dose modifications. Individual patient risk factors for the development of significant anemia complicate the selection of a "one-size-fits-all" ATR inhibitor (ATRi) dose and schedule, possibly leading to suboptimal therapeutic doses in patients at low risk of anemia. We evaluated whether early predictors of anemia could be identified to ultimately inform a personalized dose-modification approach.

PATIENTS AND METHODS

On the basis of preclinical observations and a mechanistic understanding of ATRi-related anemia, we identified several potential factors to explore in a multivariable linear regression modeling tool for predicting hemoglobin level ahead of day 22 (cycle 2) of treatment.

RESULTS

In patients treated with camonsertib monotherapy (NCT04497116), we observed that hemoglobin decline is consistently preceded by reticulocytopenia, and dose- and exposure-dependent decreases in monocytes. We developed a nomogram incorporating baseline and day 8 hemoglobin and reticulocyte values that predicted the day 22 hemoglobin values of patients with clinically valuable concordance (within 7.5% of observations) 80% of the time in a cross-validation performance test of data from 60 patients.

CONCLUSIONS

The prediction of future hemoglobin decrease, after a week of treatment, may enable a personalized, early dose modification to prevent development of clinically significant anemia and resulting unscheduled dose holds or transfusions.

Phase 1/2 study of monalizumab plus durvalumab in patients with advanced solid tumors

BACKGROUND

The combination of monalizumab (anti-NKG2A/CD94) and durvalumab (anti-programmed death ligand-1) may promote antitumor immunity by targeting innate and adaptive immunity. This phase 1/2 study of monalizumab and durvalumab evaluated safety, antitumor activity, and pharmacodynamics in patients with advanced solid tumors.

MAIN BODY

Immunotherapy-naïve patients aged ≥18 years with advanced disease, Eastern Cooperative Oncology Group performance status of 0-1, and 1-3 prior lines of systemic therapy in the recurrent/metastatic setting were enrolled. In part 1 (dose escalation), patients received durvalumab 1500 mg every 4 weeks (Q4W) with increasing doses of monalizumab Q2W/Q4W (n=15). Dose expansion in part 1 included patients with cervical cancer (n=15; durvalumab 1500 mg Q4W and monalizumab 750 mg Q2W) or metastatic microsatellite stable (MSS)-colorectal cancer (CRC) (n=15; durvalumab 1500 mg Q4W and monalizumab 750 mg Q4W). In part 2 (dose expansion), patients with MSS-CRC (n=40), non-small cell lung cancer (NSCLC; n=20), MSS-endometrial cancer (n=40), or ovarian cancer (n=40) received durvalumab 1500 mg Q4W and monalizumab 750 mg Q2W. The primary endpoint was safety. Secondary endpoints included antitumor activity per Response Evaluation Criteria In Solid Tumors version 1.1 (RECIST v1.1). Exploratory analyses included assessment of T-cell and natural killer (NK) cell activation and proliferation in peripheral blood and the tumor microenvironment (TME). The study enrolled 185 patients (part 1, 45; part 2, 140). No dose-limiting toxicities were observed and the maximum tolerated dose was not reached. In part 2, the most common treatment-related adverse events were fatigue (12.1%), asthenia (9.3%), diarrhea (9.3%), pruritus (7.9%), and pyrexia (7.1%). In the expansion cohorts, response rates were 0% (cervical), 7.7% (MSS-CRC), 10% (NSCLC), 5.4% (ovarian), and 0% (MSS-endometrial). Sustained NK cell activation, CD8+ T-cell proliferation, increased serum levels of CXCL10 (C-X-C motif chemokine ligand 10) and CXCL11, and increased tumor infiltration of CD8+ and granzyme B+ cells were observed.

CONCLUSIONS

Although efficacy was modest, monalizumab plus durvalumab was well tolerated and encouraging immune activation was observed in the peripheral blood and TME.

TRIAL REGISTRATION NUMBER

NCT02671435.

Phase I Study of Elraglusib (9-ING-41), a Glycogen Synthase Kinase-3β Inhibitor, as Monotherapy or Combined with Chemotherapy in Patients with Advanced Malignancies

PURPOSE

The safety, pharmacokinetics, and efficacy of elraglusib, a glycogen synthase kinase-3β (GSK-3β) small-molecule inhibitor, as monotherapy or combined with chemotherapy, in patients with relapsed or refractory solid tumors or hematologic malignancies was studied.

PATIENTS AND METHODS

Elraglusib (intravenously twice weekly in 3-week cycles) monotherapy dose escalation was followed by dose escalation with eight chemotherapy regimens (gemcitabine, doxorubicin, lomustine, carboplatin, irinotecan, gemcitabine/nab-paclitaxel, paclitaxel/carboplatin, and pemetrexed/carboplatin) in patients previously exposed to the same chemotherapy.

RESULTS

Patients received monotherapy (n = 67) or combination therapy (n = 171) elraglusib doses 1 to 15 mg/kg twice weekly. The initial recommended phase II dose (RP2D) of elraglusib was 15 mg/kg twice weekly and was defined, without dose-limiting toxicity observation, due to fluid volumes necessary for drug administration. The RP2D was subsequently reduced to 9.3 mg/kg once weekly to reduce elraglusib-associated central/peripheral vascular access catheter blockages. Other common elraglusib-related adverse events (AE) included transient visual changes and fatigue. Grade ≥3 treatment-emergent AEs occurred in 55.2% and 71.3% of patients on monotherapy and combination therapy, respectively. Part 1 monotherapy (n = 62) and part 2 combination (n = 138) patients were evaluable for response. In part 1, a patient with melanoma had a complete response, and a patient with acute T-cell leukemia/lymphoma had a partial response (PR). In part 2, seven PRs were observed, and the median progression-free survival and overall survival were 2.1 [95% confidence interval (CI), 2-2.6] and 6.9 (95% CI, 5.7-8.4) months, respectively.

CONCLUSIONS

Elraglusib had a favorable toxicity profile as monotherapy and combined with chemotherapy and was associated with clinical benefit supporting further clinical evaluation in combination with chemotherapy.

Opposing Roles of SPOP Mutations in Human Prostate and Endometrial Cancers

PURPOSE

Recurrent gene mutations in speckle-type POZ protein (SPOP), the substrate-binding component of E3 ubiquitin ligase, are associated with tumor progression in prostate and endometrial cancers. Here, we characterized SPOP mutations in these cancers and explored their association with molecular and immune signatures and patient outcomes.

METHODS

There were 7,398 prostate cancer and 19,188 endometrial cancer samples analyzed for clinical and molecular profiles at Caris Life Sciences. Overall survival (OS) was analyzed using Kaplan-Meier survival curves. Statistical significance was determined using chi-square and Mann-Whitney U tests, with P values adjusted for multiple comparisons.

RESULTS

SPOP mutations were identified in 9.2% of prostate and 4.3% of endometrial cancers. Mutations clustered in the SPOP meprin and TRAF-C homology domain, with no significant overlap between cancer types. SPOP mutation was associated with differential comutation profiles and opposing tumor immune microenvironment signatures for each cancer, with greater immune infiltration in SPOP-mutated endometrial cancer. SPOP-mutated prostate and endometrial cancers displayed altered epigenetic gene expression, including opposite regulation of BRD2 transcripts. In SPOP-mutant prostate cancer, higher expression of androgen receptor-regulated transcripts and improved OS after treatment with hormonal agents were observed. In endometrial cancer, hormone receptor expression was significantly lower in SPOP-mutated tumors and differences in OS were highly dependent on the particular hotspot mutation and histologic subtype.

CONCLUSION

These data indicate that SPOP mutations drive opposing molecular and immune landscapes in prostate and endometrial cancers-suggesting a loss-of-function mechanism in prostate cancer and gain-of-function mechanism in endometrial cancer-and provide a rationale for tailored therapeutic approaches.

Metastatic Prostate Cancers with BRCA2 versus ATM Mutations Exhibit Divergent Molecular Features and Clinical Outcomes

PURPOSE

In patients with metastatic prostate cancer (mPC), ATM and BRCA2 mutations dictate differences in PARPi inhibitor response and other therapies. We interrogated the molecular features of ATM- and BRCA2-mutated mPC to explain the divergent clinical outcomes and inform future treatment decisions.

EXPERIMENTAL DESIGN

We examined a novel set of 1,187 mPCs after excluding microsatellite-instable (MSI) tumors. We stratified these based on ATM (n = 88) or BRCA2 (n = 98) mutations. As control groups, mPCs with mutations in 12 other homologous recombination repair (HRR) genes were considered non-BRCA2/ATM HRR-deficient (HRDother, n = 193), whereas lack of any HRR mutations were considered HRR-proficient (HRP; n = 808). Gene expression analyses were performed using Limma. Real-world overall survival was determined from insurance claims data.

RESULTS

In noncastrate mPCs, only BRCA2-mutated mPCs exhibited worse clinical outcomes to AR-targeted therapies. In castrate mPCs, both ATM and BRCA2 mutations exhibited worse clinical outcomes to AR-targeted therapies. ATM-mutated mPCs had reduced TP53 mutations and harbored coamplification of 11q13 genes, including CCND1 and genes in the FGF family. BRCA2-mutated tumors showed elevated genomic loss-of-heterozygosity scores and were often tumor mutational burden high. BRCA2-mutated mPCs had upregulation of cell-cycle genes and were enriched in cell-cycle signaling programs. This was distinct from ATM-mutated tumors.

CONCLUSIONS

Tumoral ATM and BRCA2 mutations are associated with differential clinical outcomes when patients are stratified by treatments, including hormonal or taxane therapies. ATM- and BRCA2-mutated tumors exhibited differences in co-occurring molecular features. These unique molecular features may inform therapeutic decisions and development of novel therapies.

GSK-3 Inhibitor Elraglusib Enhances Tumor-Infiltrating Immune Cell Activation in Tumor Biopsies and Synergizes with Anti-PD-L1 in a Murine Model of Colorectal Cancer

Glycogen synthase kinase-3 (GSK-3) is a serine/threonine kinase that has been implicated in numerous oncogenic processes. GSK-3 inhibitor elraglusib (9-ING-41) has shown promising preclinical and clinical antitumor activity across multiple tumor types. Despite promising early-phase clinical trial results, there have been limited efforts to characterize the potential immunomodulatory properties of elraglusib. We report that elraglusib promotes immune cell-mediated tumor cell killing of microsatellite stable colorectal cancer (CRC) cells. Mechanistically, elraglusib sensitized CRC cells to immune-mediated cytotoxicity and enhanced immune cell effector function. Using western blots, we found that elraglusib decreased CRC cell expression of NF-κB p65 and several survival proteins. Using microarrays, we discovered that elraglusib upregulated the expression of proapoptotic and antiproliferative genes and downregulated the expression of cell proliferation, cell cycle progression, metastasis, TGFβ signaling, and anti-apoptotic genes in CRC cells. Elraglusib reduced CRC cell production of immunosuppressive molecules such as VEGF, GDF-15, and sPD-L1. Elraglusib increased immune cell IFN-γ secretion, which upregulated CRC cell gasdermin B expression to potentially enhance pyroptosis. Elraglusib enhanced immune effector function resulting in augmented granzyme B, IFN-γ, TNF-α, and TRAIL production. Using a syngeneic, immunocompetent murine model of microsatellite stable CRC, we evaluated elraglusib as a single agent or combined with immune checkpoint blockade (anti-PD-1/L1) and observed improved survival in the elraglusib and anti-PD-L1 group. Murine responders had increased tumor-infiltrating T cells, augmented granzyme B expression, and fewer regulatory T cells. Murine responders had reduced immunosuppressive (VEGF, VEGFR2) and elevated immunostimulatory (GM-CSF, IL-12p70) cytokine plasma concentrations. To determine the clinical significance, we then utilized elraglusib-treated patient plasma samples and found that reduced VEGF and BAFF and elevated IL-1 beta, CCL22, and CCL4 concentrations correlated with improved survival. Using paired tumor biopsies, we found that tumor-infiltrating immune cells had a reduced expression of inhibitory immune checkpoints (VISTA, PD-1, PD-L2) and an elevated expression of T-cell activation markers (CTLA-4, OX40L) after elraglusib treatment. These results address a significant gap in knowledge concerning the immunomodulatory mechanisms of GSK-3 inhibitor elraglusib, provide a rationale for the clinical evaluation of elraglusib in combination with immune checkpoint blockade, and are expected to have an impact on additional tumor types, besides CRC.

Metastatic renal cell carcinoma to the pancreas and other sites-a multicenter retrospective study

Background

Metastatic renal cell carcinoma (mRCC) is a heterogenous disease with poor 5-year overall survival (OS) at 14%. Patients with mRCC to endocrine organs historically have prolonged OS. Pancreatic metastases are uncommon overall, with mRCC being the most common etiology of pancreatic metastases. In this study, we report the long-term outcomes of patients with mRCC to the pancreas in two separate cohorts.

Methods

We performed a multicenter, international retrospective cohort study of patients with mRCC to the pancreas at 15 academic centers. Cohort 1 included 91 patients with oligometastatic disease to the pancreas. Cohort 2 included 229 patients with multiples organ sites of metastases including the pancreas. The primary endpoint for Cohorts 1 and 2 was median OS from time of metastatic disease in the pancreas until death or last follow up.

Findings

In Cohort 1, the median OS (mOS) was 121 months with a median follow up time of 42 months. Patients who underwent surgical resection of oligometastatic disease had mOS of 100 months with a median follow-up time of 52.5 months. The mOS for patients treated with systemic therapy was not reached. In Cohort 2, the mOS was 90.77 months. Patients treated with first-line (1L) VEGFR therapy had mOS of 90.77 months; patients treated with IL immunotherapy (IO) had mOS of 92 months; patients on 1L combination VEGFR/IO had mOS of 74.9 months.

Interpretations

This is the largest retrospective cohort of mRCC involving the pancreas. We confirmed the previously reported long-term outcomes in patients with oligometastatic pancreas disease and demonstrated prolonged survival in patients with multiple RCC metastases that included the pancreas. In this retrospective study with heterogeneous population treated over 2 decades, mOS was similar when stratified by first-line therapy. Future research will be needed to determine whether mRCC patients with pancreatic metastases require a different initial treatment strategy.

Funding

Statistical analyses for this study were supported in part by the University of Colorado Cancer Center Support Grant from the NIH/NCI, P30CA046934-30.

Camonsertib in DNA damage response-deficient advanced solid tumors: phase 1 trial results

Predictive biomarkers of response are essential to effectively guide targeted cancer treatment. Ataxia telangiectasia and Rad3-related kinase inhibitors (ATRi) have been shown to be synthetic lethal with loss of function (LOF) of ataxia telangiectasia-mutated (ATM) kinase, and preclinical studies have identified ATRi-sensitizing alterations in other DNA damage response (DDR) genes. Here we report the results from module 1 of an ongoing phase 1 trial of the ATRi camonsertib (RP-3500) in 120 patients with advanced solid tumors harboring LOF alterations in DDR genes, predicted by chemogenomic CRISPR screens to sensitize tumors to ATRi. Primary objectives were to determine safety and propose a recommended phase 2 dose (RP2D). Secondary objectives were to assess preliminary anti-tumor activity, to characterize camonsertib pharmacokinetics and relationship with pharmacodynamic biomarkers and to evaluate methods for detecting ATRi-sensitizing biomarkers. Camonsertib was well tolerated; anemia was the most common drug-related toxicity (32% grade 3). Preliminary RP2D was 160 mg weekly on days 1-3. Overall clinical response, clinical benefit and molecular response rates across tumor and molecular subtypes in patients who received biologically effective doses of camonsertib (>100 mg d-1) were 13% (13/99), 43% (43/99) and 43% (27/63), respectively. Clinical benefit was highest in ovarian cancer, in tumors with biallelic LOF alterations and in patients with molecular responses. ClinicalTrials.gov registration: NCT04497116 .

Activity of eftozanermin alfa plus venetoclax in preclinical models and patients with acute myeloid leukemia

Activation of apoptosis in malignant cells is an established strategy for controlling cancer and is potentially curative. To assess the impact of concurrently inducing the extrinsic and intrinsic apoptosis-signaling pathways in acute myeloid leukemia (AML), we evaluated activity of the TRAIL receptor agonistic fusion protein eftozanermin alfa (eftoza; ABBV-621) in combination with the B-cell lymphoma protein-2 selective inhibitor venetoclax in preclinical models and human patients. Simultaneously stimulating intrinsic and extrinsic apoptosis-signaling pathways with venetoclax and eftoza, respectively, enhanced their activities in AML cell lines and patient-derived ex vivo/in vivo models. Eftoza activity alone or plus venetoclax required death receptor 4/5 (DR4/DR5) expression on the plasma membrane but was independent of TP53 or FLT3-ITD status. The safety/tolerability of eftoza as monotherapy and in combination with venetoclax was demonstrated in patients with relapsed/refractory AML in a phase 1 clinical trial. Treatment-related adverse events were reported in 2 of 4 (50%) patients treated with eftoza monotherapy and 18 of 23 (78%) treated with eftoza plus venetoclax. An overall response rate of 30% (7/23; 4 complete responses [CRs], 2 CRs with incomplete hematologic recovery, and 1 morphologic leukemia-free state) was reported in patients who received treatment with eftoza plus venetoclax and 67% (4/6) in patients with myoblasts positive for DR4/DR5 expression; no tumor responses were observed with eftoza monotherapy. These data indicate that combination therapy with eftoza plus venetoclax to simultaneously activate the extrinsic and intrinsic apoptosis-signaling pathways may improve clinical benefit compared with venetoclax monotherapy in relapsed/refractory AML with an acceptable toxicity profile. This trial was registered at www.clinicaltrials.gov as #NCT03082209.

Abstract 937: Opposing roles of SPOP mutations in human prostate and endometrial cancers

Recurrent mutations in the gene encoding the Speckle Type POZ Protein, SPOP, the substrate-binding components of E3-ubiquitin ligase, have been identified as common alterations in prostate cancer (PCa) and endometrial cancer (EC). SPOP mutations are associated with PCa and EC growth and progression. Here, we characterized SPOP mutations in PCa and EC, and their association with molecular and immune signatures. 7,398 PCa and 19,188 EC samples were analyzed by next-generation sequencing (592, NextSeq; WES, NovaSeq), (WTS; NovaSeq) (Caris Life Sciences, Phoenix, AZ). Real world overall survival (rwOS) was extracted from insurance claims and depicted using Kaplan-Meier survival curves for molecularly defined cohorts from tissue collection to last contact. Statistical significance was determined using chi-square and Mann-Whitney U tests, with p-values adjusted for multiple comparisons (q<0.05). SPOP mutations were identified in 601 (8.1%) and 655 (3.4%) samples of PCa and EC, respectively. Mutations clustered in the SPOP MATH domain with hotspots at residues F133L (21.4%), F102C (11%), F133V (10.4%), F102V (7%) in PCa, and residues M117V (21.8%), R121Q (10.6 %), E47K (9%), E50K (8.5%) in EC. Importantly, no overlap of hotspot residues was noted in PCa and EC. SPOP-mutated PCa had higher frequency of APC (21.4% vs 5.8%) and BCOR (1.95% vs 0.2%) lesions, but SPOP-mutated EC had higher frequency of U2AF1 (4.28% vs 1.0%), POLE (5.24% vs 2.0%) and CASP8 (4.17% vs 1.79%) lesions (all q <0.05) compared to non-mutant SPOP. Analysis of epigenetic markers showed lower BRD2 (245.4 vs 312 TPM) transcripts in SPOP-mutated PCa, but higher BRD2 (227.0 vs 200.6) (all q <0.05) in SPOP-mutated EC, compared to non-mutant SPOP, the former diverging from earlier published data in PCa. Analysis of inferred immune cell infiltrates showed that in SPOP-mutated PCa, M1-MΦ (36.8% vs 48.1%), CD8 T cell (20.2% vs 30.4%) and DC (53.3% vs 79.4%) are decreased and M2-MΦ (100% vs 99.9%) are increased; while in SPOP-mutated EC, M1-MΦ (87.2% vs 83.3 %), CD8 T cells (56.8% vs 49.7%) and DC (94.9% vs 93.3%) are increased and M2-MΦ (98.8% vs 98.9%) are decreased (all q <0.05). In PCa, higher AR expression was found in SPOP-mutated vs non-mutated tumors (98.5% vs 97.3%, p=0.09), with improved OS outcomes after hormone targeting agents leuprolide (2125 vs 1803 days; HR: 0.71, 95% CI (0.51-0.99), p=0.04) and bicalutamide (2538 vs 1854 days; HR: 0.57, 95% CI (0.41-0.79), p<0.001). In EC, ER and PR expression was significantly lower in SPOP-mutated vs non-mutated tumors 50.8% vs 65.4% and 35.4 vs 49.5% (all q <0.05), respectively, although no difference in OS was noted in the overall EC population. These data indicate that SPOP-mutations drive different molecular and immune microenvironments in PCa and EC, with apparently opposing roles in these malignancies, and provide a rationale for tailored therapeutic approaches in SPOP-mutated PCa and EC.

Citation Format: Ludimila Cavalcante, Sachin K. Desmukh, Benedito A. Carneiro, Kartik Angara, Tyler E. Mattox, Sharon Wu, Joanne Xiu, Philip Walker, Matthew Oberley, Chadi Nabhan, Emmanuel S. Antonarakis. Opposing roles of SPOP mutations in human prostate and endometrial cancers [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 937.

Abstract 6706: Co-culture of circulating tumor cells (CTCs)-derived 3D organoids and autologous cytotoxic CD8+ T cells: A new functional precision oncology platform

Greater than 10 million patients succumb to cancer each year. Cancer metastasis is responsible for more than 90% of all cancer-associated deaths due to treatment resistance and increased tumor burden. As a seed for metastases, circulating tumor cells (CTCs) present a new dimension and horizon for clinical doctors in diagnosis, prognosis prediction, treatment monitoring, disease mechanism, and drug development. CTCs could gradually replace tissue biopsies which are painful and may be difficult to obtain depending on tumor location. CTC isolation is feasible after minimally invasive liquid biopsy and provides the basis for a multitude of ex vivo and in vivo studies including establishment of CTCs-derived 2D and 3D cultures. Organoids are miniscule models of tissues that grow in a 3D semisolid extracellular matrix medium with specific growth factors supplied. CTCs-derived 3D organoids play a vital role in precision oncology because they can preserve tumor heterogeneity, imitate the tumor microenvironment (TME), mimic cancer hypoxia in the TME, and maintain cancer and metastasis phenotypes. Cytotoxic CD8+ T cells are the most powerful effectors in the anticancer immune response. We hypothesized that co-culture of CTCs-derived 3D organoids and autologous cytotoxic CD8+ T cells could maximize patient-relevance of laboratory assessment of cancer-treatment immune-system interactions to facilitate precision oncology practice. TellBio’s novel TellDx CTC technology allows for isolation of viable and intact CTCs in liquid biopsies, regardless of cancer type. Unlabeled CTCs were cultured in growth factor reduced Matrigel with organoid culture WENRAS medium. Magnetic beads labeled white blood cells (WBCs) were cultured with T cell culture medium - WBCs and magnetic beads usually separate in three days - cytotoxic CD8+ T cells were isolated with the EasySep™ Human CD8+ T Cell Isolation Kit. CTCs-derived 3D organoids and autologous cytotoxic CD8+ T cells were co-cultured with or without different drug treatments - cytotoxicity was measured with CellTiterGlo® 3D Cell Viability Assay and imaging, and further mechanistic studies were feasible. Our co-culture platform enables us to utilize a patient's peripheral blood or pleural effusions to create a patient-specific, in vivo-like TME and immune microenvironment to model and assess ex vivo responses to investigational and FDA-cleared cancer therapies, and potentially provide oncologists with insights to improve clinical outcomes.

Citation Format: Lanlan Zhou, Leiqing Zhang, Lindsey Carlsen, Kelsey E. Huntington, Vida Tajiknia, Andrew George, Arielle De La Cruz, Arunasalam Navaraj, Praveen Srinivasan, Maximilian Schwermann, Benedito A. Carneiro, Wafik S. El-Deiry. Co-culture of circulating tumor cells (CTCs)-derived 3D organoids and autologous cytotoxic CD8+ T cells: A new functional precision oncology platform [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 6706.

Abstract 5636: Multiplex digital spatial profiling (DSP) of proteins in the tumor microenvironment in response to GSK-3 inhibition by 9-ING-41 (elraglusib) correlates with novel immunostimulatory effects observed in vivo

Glycogen synthase kinase 3 (GSK-3) is a serine/threonine kinase with key roles in myriad biological processes such as tumor progression, and inhibition of GSK-3 using the small molecule elraglusib has shown promising preclinical antitumor activity in multiple tumor types. Our preclinical experiments showed that elraglusib treatment increased tumor cell PD-L1 expression, downregulated angiogenic and immunosuppressive signaling pathways, and increased anti-tumor immune responses in vitro and in vivo. Subsequent studies showed that several circulating factors were predictive of response to PD-1/PD-L1 blockade and GSK-3 inhibition in a murine model of colorectal cancer. To determine the translational relevance of our prior results we evaluated tumor biopsies and plasma samples from patients with refractory solid tumors of multiple tissue origins enrolled in a Phase 1 clinical trial investigating elraglusib (NCT03678883). Plasma samples were collected from patients at baseline and 24 hours post-IV administration of elraglusib and were analyzed using Luminex technology. Paired FFPE tumor biopsies from patients with colorectal or pancreatic cancer before and after treatment were selected to analyze the tumor microenvironment using NanoString GeoMx DSP technology. The region of interest (ROI) selection strategy focused on mixed tumor and immune cell segments and ROIs were segmented using panCK+ and CD45+ morphology stains. Cytokine analysis revealed that elevated baseline plasma levels of IL-1 beta and reduced levels of VEGF correlated with improved progression-free survival (PFS) and overall survival (OS). PFS was also found to be positively correlated with elevated plasma levels of immunostimulatory analytes such as Granzyme B, IFN-gamma, and IL-2 at 24 hours post-treatment with elraglusib. CD45+ tumor-infiltrating immune cells had lower expression of VISTA, PD-1, and IDO-1 inhibitory checkpoint proteins and higher expression of OX40L and B7-H3 stimulatory checkpoint proteins in post-treatment biopsies as compared to pre-treatment biopsies. Moreover, time-on-study length negatively correlated with CD39 expression in PanCK+ segments and positively correlated with CD163 expression in CD45+ segments. This ongoing study, to our knowledge, represents the first digital spatial analysis of tumor biopsies from patients treated with elraglusib. These novel circulating biomarkers of response to GSK-3 inhibition could provide significant clinical utility and the spatial proteomics data may give us insights into the immunomodulatory mechanisms of GSK-3 inhibition.

Citation Format: Kelsey E. Huntington, Christoph Schorl, Shaolei Lu, Daniel Newhouse, Benedito A. Carneiro, Wafik S. El-Deiry. Multiplex digital spatial profiling (DSP) of proteins in the tumor microenvironment in response to GSK-3 inhibition by 9-ING-41 (elraglusib) correlates with novel immunostimulatory effects observed in vivo. [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 5636.

Abstract 3952: Preclinical anti-tumor effects of MDM4/MDMX inhibitor XI-006 in breast cancer and prostate cancer cell lines mediated through reduced tumor cell migration

MDM2 and MDM4/MDMX have emerged as potential mediators of tumor progression, organ-specific metastasis, and hyper-progression after immune checkpoint blockade therapy. While there are currently a number of MDM2 inhibitors in clinical trials, we found no pure MDM4/MDMX inhibitors under clinical investigation. Because hormone-resistant cancers pose a significant challenge for clinical intervention, the identification of translatable novel therapeutic targets remains an important goal. Analysis of triple-negative breast cancer (TNBC) and castration-resistant prostate cancer (CRPC) reveals overexpression of p53 negative regulator MDM4/MDMX as a frequent alteration in these cancers. There is an urgent need to study and target MDM4/MDMX in cancer therapy and this may ultimately include dual MDM2 and MDM4/MDMX inhibitors. However, it is clear that MDM4/MDMX is a primary oncogenic driver that requires specific therapeutic targeting. As metastasis is often observed clinically in patients diagnosed with breast and prostate cancer, we sought to expand our understanding of the metastasis reduction potential of a previously described preclinical MDM4/MDMX inhibitor, a 4-nitrobenzofuroxan derivative, XI-006 (NSC207895). In a scratch assay using breast and prostate cancer cell lines, increasing doses of XI-006 decreased tumor cell migration in a time and dose-dependent manner, demonstrating the benefit of MDMX inhibition in preventing the induction of tumor cell migration. The exact mechanism of this result remains unclear, and further investigation is needed to elucidate the impact of XI-006 on TNBC and CRPC cell proliferation and migration. Our future directions include identifying the synergistic potential of combining MDM4/MDMX inhibitor XI-006 with other cancer therapies, assessing the impact of XI-006 on immune responses in co-culture studies, and testing therapeutic efficacy in vivo.

Citation Format: Arielle De La Cruz, Andrew George, Payton De La Cruz, Maximilian P. Pinho-Schwermann, Kimberly S. Meza, Taylor Arnoff, Ilyas Sahin, Stephanie L. Graff, Benedito A. Carneiro, Wafik S. El-Deiry. Preclinical anti-tumor effects of MDM4/MDMX inhibitor XI-006 in breast cancer and prostate cancer cell lines mediated through reduced tumor cell migration. [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 3952.

Abstract 4185: Inclusive basic and advanced translational laboratory research competencies for research in cancer biology and therapeutics

Our Laboratory was established in 1994 at Univ. of Pennsylvania. Lab members demonstrated initial competencies by performing cell culture, western blots, immunofluorescence, and flow cytometry showing induction of p53/p21(WAF1) in cells treated with chemotherapy. Years later, our Laboratory of Translational Oncology & Experimental Cancer Therapeutics moved to Penn State Univ., Fox Chase Cancer Center/Temple Univ. and then Brown Univ. By 2020, with desire for inclusiveness (everyone succeeds), scientific rigor/reproducibility mandated by NIH, and as a training and mentoring activity (lab scientists/trainees/students mentoring others at High School level and beyond), we established a process for onboarding and training new cancer researchers. By Fall of 2022, there were 17 current Brown University undergraduate students (10 receiving research credit and 7 not receiving credit), HS students, 7 graduate students (PhD, masters, MD/PhD), and 6 medical students working with collaborating faculty at our laboratory at Brown’s Legorreta Cancer Center. After completion of biosafety training, and required trainings such as by IACUC, new lab members complete basic competencies in cell culture, cell viability, and western blot analysis that include technical, presentation quality output, and quantitative/statistical rigor to satisfy current standards for journal publication. For cell culture this includes pathogen free conditions, authentication, attention to details of routine procedures, documentation of morphology, freezing, thawing, passaging, seeding density, and managing cell populations to not run out of cells. Cell viability assessment includes attention to culture conditions, synergy analysis, data robustness, and presentation, and for western blots attention to quality of blots, protein quantification, loading, labeling, antibody specificity and sensitivity controls, presentation at 2022 standards, conventions for splicing, and issues with reproducibility including biological replicates, and generalizability. Additional and advanced competencies include RT-PCR, long-term colony assays, 3-D cultures (spheroids, organoids), transfection (overexpression, knockdown, CRISPR), co-culture and triculture with immune cells and fibroblasts, cytokine profiling, in vivo studies, in vivo imaging, immunohistochemistry, flow cytometric analysis, single cell techniques, viral infection, circulating tumor cell isolation, blood immune and cytokine analysis, and work with transgenic organoids and inducible cancer predisposing alleles. Modeling the tumor microenvironment, relevance to human cancer and translational directions are emphasized. Shared online lab resources, protocols, practices, videos, and manuscripts are available for lab members. The framework herein may be of interest to others involved in similar training programs.

Citation Format: Wafik S. El-Deiry, Andrew George, Francesca Di Cristofano, Praveen Srinivasan, Lindsey Carlsen, Kelsey E. Huntington, Arielle De La Cruz, Leiqing Zhang, Marina Hahn, Shuai Zhao, Attila Seyhan, Bradley D. DeNardo, Aaron W. Maxwell, Dae Hee Kim, Alex Raufi, Hina Khan, Stephanie L. Graff, Don S. Dizon, Christopher Azzoli, Abbas E. Abbas, Roxanne Wood, Rishi R. Lulla, Howard P. Safran, Benedito A. Carneiro, Arunasalam Navaraj, Xiaobing Tian, Shengliang Zhang, Lanlan Zhou. Inclusive basic and advanced translational laboratory research competencies for research in cancer biology and therapeutics. [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 4185.

Abstract 1070: The anti-tumor efficacy of combining oral ATR kinase inhibitor ceralasertib with TIC10/ONC201, an oral Akt/ERK inhibitor, TRAIL pathway and integrated stress response inducer, in prostate cancer treatment

Prostate cancer is the most common cancer and the second leading cause of cancer death among men in the United States. There are 268,490 estimated new cases and 34,500 estimated deaths in 2022 according to the NIH. Patients with metastatic castration resistant prostate cancer (mCRPC) have a poor prognosis and the current treatment options show limited efficacy. From the TRAP trial, 20% of mCRPC patients are reported to bear DNA repair defects. Ceralasertib, formerly known as AZD6738, is a potent and selective orally bioavailable inhibitor of the ataxia tenlangiectasia and Rad3-related (ATR) kinase, which is involved in DNA repair in response to DNA damage and replication stress. Ceralasertib’s antitumor activity as a monotherapy in treating prostate cancer is moderate. Thus, we investigated a combination therapy of ceralasertib with ONC201, a potent and cytotoxic orally bioavailable inhibitor of the serine/threonine protein kinase Akt and extracellular signal-regulated kinase (ERK). Upon administration, ONC201 can induce tumor cell apoptosis mediated by tumor necrosis factor (TNF)-related apoptosis-inducing ligand (TRAIL) and activate integrated stress response (IRS). Preliminary results demonstrate synergistic activity with the combination therapy in vitro using CellTiterGLO viability assay 72 hours in a 96 well plate post treatment. Ongoing studies using western blotting and cytokine profiling are intended to illustrate the mechanism behind the proven synergy. Our results aim to solve the overarching need in developing novel therapeutic strategies to overcome resistance in current prostate cancer treatments.

Citation Format: Yutong Xia, Maximilian P. Schwermann, Andrew George, Anna Ochsner, Benedito A. Carneiro, Wafik S. El-Deiry. The anti-tumor efficacy of combining oral ATR kinase inhibitor ceralasertib with TIC10/ONC201, an oral Akt/ERK inhibitor, TRAIL pathway and integrated stress response inducer, in prostate cancer treatment [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 1070.

Abstract 1066: PARP inhibitor rucaparib in combination with imipridones ONC201 or ONC212 demonstrates preclinical synergy against BRCA1/2-deficient breast, ovarian, and prostate cancer cells

BRCA1/2 genes encode proteins that mediate homologous recombination and repair (HRR). BRCA1/2 mutations increase risk of breast, ovarian, prostate and other cancers. BRCA1/2 mutated tumor cells are sensitive to PARP inhibitors (PARPi), that cause DNA replication fork to collapse. Approximately 40% of patients develop PARPi resistance through different mechanisms. One of the mechanisms of PARPi resistance is through P13k/Akt pathway activation. Imipridones are TRAIL-inducing compounds which are PERK-independent activators of the integrated stress response, and dual inhibitors of Akt/ERK. We hypothesized that combining imipridones with PARPi would overcome PARPi resistance due to Akt activation. PARPi also sensitize various solid tumors to recombinant TRAIL and DR5 agonist antibodies thereby further suggesting possible synergies between imipridones and PARPi. Our lab previously showed efficacy of imipridone ONC201 in BRCA-deficient cancer cells and potential synergy with olaparib (2017 AACR annual meeting abstract), without further investigating potential synergistic mechanisms. We explored combination drug synergy of rucaparib (PARP inhibitor) and imipridones (ONC212 and ONC201) in BRCA1/2-deficient breast, ovarian and prostate cancer cell lines. CellTiterGLO viability assays were performed after 72 hours to demonstrate synergistic effects of combination treatment. Western blots were performed to investigate the effect of combination treatment on the Akt pathway, as well as expression of cellular metabolic stress protein ATF4. Cytokine profiling using the Luminex 200 technology was used to study the effect of treatment on the tumor microenvironment. Combination treatment (rucaparib and ONC212, rucaparib and ONC201) in BRCA–deficient cell lines (HCC1937, PEO1, KURAMOCHI, 22RV1, LNCAP) showed synergistic reduction in cell viability. In the HCC 1937 cell line, combination studies of rucaparib-ONC212 and rucaparib-ONC201 showed a synergystic effect, as calculated by Compusyn software, combination indexes below one were observed at concentration of 0.29-37.5 of µM rucaparib with ONC201 at 1.25-5 µM and ONC212 6.25-50 nM with the best combination index of 0.7 for rucaparib-ONC201 combination and 0.31 for rucaparib-ONC212. We similarly observed synergy in other cell lines with combination treatment. Western blot analysis of rucaparib-ONC212 combination showed total Akt protein reduction and an increase in ATF4 consistent with the synergistic effects. Further studies are ongoing to characterize possible mechanisms and effects of PARP inhibitor-imipridone combination treatment on immune-mediated killing. Our findings identify novel PARP inhibitor-imipridone therapy combinations that can be further developed for treatment of BRCA1/2 deficient cancers.

Citation Format: Maryam Ghandali, Kelsey E. Huntington, praveen Srinivasan, Don S. Dizon, Stephanie L. Graff, Benedito A. Carneiro, Wafik S. El-Deiry. PARP inhibitor rucaparib in combination with imipridones ONC201 or ONC212 demonstrates preclinical synergy against BRCA1/2-deficient breast, ovarian, and prostate cancer cells [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 1066.

Comprehensive Genomic Profiling of NF2-Mutated Kidney Tumors Reveals Potential Targets for Therapy

Genomic alterations (GA) in NF2 tumor-suppressor gene have been associated with aggressive behavior in kidney tumors. We used comprehensive genomic profiling (CGP) to evaluate the frequencies of NF2 GA in histologic subtypes of kidney tumors and co-occurring GA in other genes and biomarkers. Advanced kidney tumors included 1875 clear cell (ccRCC), 405 papillary (pRCC), 108 chromophobe (chRCC), 171 sarcomatoid (sRCC), 61 collecting duct (cdRCC), 49 medullary (mRCC), 134 unclassified (uRCC), 906 urothelial carcinoma of renal pelvis (UC), and 147 Wilms tumors underwent hybrid-capture based CGP to evaluate all classes of GA. 192 (4.9%) of kidney tumors featured NF2 GA which were predominantly structural variant mutations (89%), followed by copy number alterations (9%). Gender and age were similar between NF2-mutant (NF2mut) and NF2-wild type (NF2wt) cohorts with male preponderance. NF2 GA frequency was highest in cdRCC (30%), sRCC (21%), uRCC (15%), and pRCC (12%) while lowest in ccRCC (3%), UC (3%) Wilms tumor (1%), and chRCC (0%). NF2 mutational status was associated with loss of Ch 22 (P < .001). NF2mut RCC harbored co-occurring GA including CDKN2A, CDKN2B, SETD2, and BAP1. VHL, PBRM1, PTEN, and FGFR3 GA were significantly more frequent in NF2wt than in NF2mut tumors. MTOR pathway GAs were uncommon in NF2mut tumors. No NF2 mutated RCC featured MSI-high or high TMB. sRCC was associated with high PD-L1 expression. PD-L1 SP142 tumoral (P = .04) and immune cells (P = .013) were more frequent in NF2mut as compared to NF2wt group. Among histologic subtypes of RCC, cdRCC, sRCC, pRCC, and uRCC are enriched in NF2 GA. Co-occurrent GA in CDKN2A/B, SETD2, and BAP1 may represent potential therapeutic targets. Higher level of PD-L1 expression in NF2mut cohort suggests that these tumors might be sensitive to immune checkpoint inhibitor therapies.

Clinical and molecular features of ATM and BRCA2 mutations in metastatic prostate cancer

245

Background: Homologous recombination repair (HRR) genes are mutated in about 20% of metastatic prostate cancer (mPC) patients. Of these, ATM and BRCA2 mutations exhibit stark differences in response to PARP inhibitors (PARPi). We aimed to investigate the underlying genomic and molecular features of ATM- and BRCA2-mutated mPC and if these contribute to divergent clinical outcomes or future treatment decisions. Methods: Building upon our prior study, we examined a novel subset of mPC 1066 mPCs after exclusion of microsatellite instable (MSI) tumors to prevent elevation of bystander non-driver BRCA2 mutation. NextGen sequencing of DNA (592-gene and/or whole exome) and RNA (whole transcriptome) from mPCs including bone, lymph nodes, and liver metastases, was performed at Caris Life Sciences (Phoenix, AZ). mPCs were stratified by ATM (n= 91) or BRCA2 (n=102) mutations, as well as HRR-deficiency (HRD) based on mutations in 23 other HRR genes (n = 237), and HRR-proficiency (HRP) based on lack of mutations in any HRR genes (n=636). High tumor mutational burden (TMB-high) was defined as ≥10 mutations/Mb. The differential expression analyses were conducted by Limma. Real-world overall survival (OS) was determined from insurance claims data and Kaplan-Meier estimates were calculated. Results: Mutations in ATM and BRCA2 were associated with worse OS compared to the HRP group (HR 0.4, 0.5; CI 0.305-0.81, 0.339-0.845; P < 0.001). ATM or BRCA2 mutations also predicted worse response to the AR-targeted abiraterone/enzalutamide therapies (HR 0.4, 0.3; CI 0.244-1.003, 0.172 – 0.6; P = 0.047, p < 0.001). ATM-mutated tumors exhibited significantly lower levels of TP53 mutations (11.1% vs 35.1% and 40.8% in BRCA2 and HRP, p < 0.01) and RB1 loss (2.1% vs 15.5% in BRCA2, p < 0.05), and harbored genomic amplification of genes in 11q13 (~10% vs ~1.5% in HRP, p < 0.001), which includes CCND1 and genes in the FGF family. BRCA2-mutated tumors were enriched for amplifications in PDCD1 (PD-1) (3.1% vs 0% in HRP, p < 0.005), and were more frequently TMB-High (7.1% vs 0.63% in HRP, p < 0.001). At the gene expression level, BRCA2-mutated mPC exhibited robust correlations with increased KCNJ3 and decreased ALDH1A3, while ATM mutated tumors exhibited decreased correlation with HES4. BRCA2-mutated mPCs were enriched in cell cycle signaling, a potential indicator of platinum sensitivity (Normalized Enrichment Score > 2, FDR < 0.001) but AMT mutated tumors were not enriched of these profiles . Conclusions: We found that somatic ATM and BRCA2 mutations associated with differential OS outcomes, which may help tailor treatment decisions. At the molecular level, ATM- and BRCA2-mutated tumors exhibited differences in the landscape of co-occurring genomic and transcriptional features. These features unique to ATM or BRCA2 mutations can inform rationale for divergent treatment strategies and should be investigated.

Germline mutational profile in metastatic urothelial malignancy

550

Background: 24% of patients with high-risk urothelial carcinoma have pathogenic germline mutations (Nassar, Genetics in Medicine 2020). In that study, demographics, metachronous/synchronous tumors, and family history did not differ between germline and sporadic cases of bladder cancer. We report herein the prevalence of actionable mutations and de novo metastatic disease in patients with germline mutations who developed metastatic urothelial carcinoma. Methods: We retrospectively analyzed a database of 90 patients with metastatic urothelial carcinoma (urethral, bladder, and upper tract disease) at our institution who had genetic testing performed on tumor specimens. T-student test was performed to calculate statistical significance for the distribution of age, while Chi-square test evaluated the frequency distribution of gender, actionable mutations, and de novo metastatic disease. Patients’ tumors were sequenced by a 700 gene panel for both somatic and germline mutations. Comprehensive chart review was performed to extract clinical data. Results: Out of the 90 patients reviewed, 11 (11.1%) had germline mutations. Of these patients, 5 had upper tract urothelial carcinoma, 5 had bladder cancer, and 1 had urethral cancer. Nine patients had pathogenic germline mutations: MUTYH, BRCA2 (each representing 1.8% of patients); APC, BRCA1, CDKN2A, FH, MSH2 (each representing 0.9% of patients). Two patients had germline mutations of unknown significance ( APC, CHEK2). Age (T-value 1.62053, p=1.08453), gender (Chi-square 0.0024, p=0.961037) or de novo metastatic presentation (Chi-square 0.5, p=0.4795) were not statistically significant between patients with germline and sporadic mutations. Somatic actionable mutations included ATR, BRCA2, BRAF, CDK12, ERBB2, FBXW7, FGFR3, HRAS, MTAP, and PIK3CA. Microsatellite instability high (MSI-H) status was only present in the patient with germline MSH2 mutation. PD-L1 expression was high (CPS ≥10) in 4 patients with germline mutations. Tumor mutational burden ranged from 1.1 to 28.4 mutations per Megabase. Conclusions: Our findings further define the clinical and genomic characteristics of patients with metastatic urothelial carcinoma and germline mutations in a tertiary center. Further investigation is warranted to validate these findings in national sequencing databases.

Preliminary results from a phase 1/2 study of co-stimulatory bispecific PSMAxCD28 antibody REGN5678 in patients (pts) with metastatic castration-resistant prostate cancer (mCRPC)

154

Background: Pts with mCRPC have a poor prognosis with limited treatment options, including minimal response to immunotherapies. REGN5678 is a first-in-class, full-length anti-PSMAxCD28 bispecific costimulatory antibody designed to target prostate cancer cells and enhance T-cell activation. We report preliminary results from the dose escalation part of a first-in-human, open-label, Phase 1/2 study (NCT03972657) examining REGN5678 in combination with cemiplimab, a PD-1 blocking antibody. Methods: Pts with mCRPC had received ≥2 lines of systemic therapy in the metastatic and/or castration-resistant setting, including ≥1 second-generation anti-androgen. Pts received REGN5678 weekly at dose levels [DL] 0.1–300 mg, initially as monotherapy for 3 weeks, followed by combination with cemiplimab (350 mg Q3W) until progression or toxicity. Primary objectives are safety, tolerability, and pharmacokinetics. Preliminary efficacy measurements include decline in prostate-specific antigen (PSA) from the start of combination treatment and radiographic response from baseline. Results: At the data cutoff (DCO; July 27 2022), 35 pts had been treated. Treatment-emergent adverse events (TEAEs) ≥Grade (G)3 occurred in 54% (19/35) of pts. Cytokine release syndrome occurred in 6 pts (all G1) and there were 2 dose-limiting toxicities (both G3): pain (at 1 mg) and Guillain-Barré syndrome (at 300 mg). 4 pts (11%) experienced a ≥G3 immune-mediated adverse event (imAE; at DLs 30–300 mg). REGN5678 exposure was non-linear over the tested DLs (more than dose proportional). There were minimal signs of efficacy at lower DLs (REGN5678 0.1–10 mg), with only 1/16 pts showing a PSA decline (of 21%). More PSA declines occurred at higher DLs: 1/4 pts at 30 mg (a PSA decline of 100%), 3/8 at 100 mg (>99%, 44%, 22%), and 3/4 at 300 mg (>99%, 99%, 82%). Notably, all ≥G3 imAEs occurred in pts with PSA declines. Among pts with measurable disease and ≥1 on-treatment scan, radiographic response per RECIST 1.1 occurred in 1/3 pts at 30 mg (complete response), 1/4 at 100 mg (unconfirmed partial response [PR]), and 1/1 at 300 mg (PR confirmed after DCO). Conclusions: Preliminary data on REGN5678 plus cemiplimab in pts with mCRPC provide first evidence of clinical activity of a CD28 co-stimulatory bispecific antibody in solid tumors. Clinical activity was observed at DLs 30–300 mg. ≥G3 imAEs occurred in pts with PSA declines, suggesting a possible association. The study is ongoing to determine the maximum tolerated and recommended Phase 2 doses. Clinical trial information: NCT03972657 . [Table: see text]

GSK-3 inhibitor elraglusib enhances tumor-infiltrating immune cell activation in tumor biopsies and synergizes with anti-PD-L1 in a murine model of colorectal cancer

Inhibition of GSK-3 using small-molecule elraglusib has shown promising preclinical antitumor activity. Using in vitro systems, we found that elraglusib promotes immune cell-mediated tumor cell killing, enhances tumor cell pyroptosis, decreases tumor cell NF-κB-regulated survival protein expression, and increases immune cell effector molecule secretion. Using in vivo systems, we observed synergy between elraglusib and anti-PD-L1 in an immunocompetent murine model of colorectal cancer. Murine responders had more tumor-infiltrating T-cells, fewer tumor-infiltrating Tregs, lower tumorigenic circulating cytokine concentrations, and higher immunostimulatory circulating cytokine concentrations. To determine the clinical significance, we utilized human plasma samples from patients treated with elraglusib and correlated cytokine profiles with survival. Using paired tumor biopsies, we found that CD45+ tumor-infiltrating immune cells had lower expression of inhibitory immune checkpoints and higher expression of T-cell activation markers in post-elraglusib patient biopsies. These results introduce several immunomodulatory mechanisms of GSK-3 inhibition using elraglusib, providing a rationale for the clinical evaluation of elraglusib in combination with immunotherapy.

Statement of significance

Pharmacologic inhibition of GSK-3 using elraglusib sensitizes tumor cells, activates immune cells for increased anti-tumor immunity, and synergizes with anti-PD-L1 immune checkpoint blockade. These results introduce novel biomarkers for correlations with response to therapy which could provide significant clinical utility and suggest that elraglusib, and other GSK-3 inhibitors, should be evaluated in combination with immune checkpoint blockade.

Clinical features of patients with MTAP-deleted bladder cancer

Advanced urothelial carcinoma continues to have a dismal prognosis despite several new therapies in the last 5 years. FGFR2 and FGFR3 mutations and fusions, PD-L1 expression, tumor mutational burden, and microsatellite instability are established predictive biomarkers in advanced urothelial carcinoma. Novel biomarkers can optimize the sequencing of available treatments and improve outcomes. We describe herein the clinical and pathologic features of patients with an emerging subtype of bladder cancer characterized by deletion of the gene MTAP encoding the enzyme S-Methyl-5'-thioadenosine phosphatase, a potential biomarker of response to pemetrexed. We performed a retrospective analysis of 61 patients with advanced urothelial carcinoma for whom demographics, pathologic specimens, next generation sequencing, and clinical outcomes were available. We compared the frequency of histology variants, upper tract location, pathogenic gene variants, tumor response, progression free survival (PFS) and overall survival (OS) between patients with tumors harboring MTAP deletion (MTAP-del) and wild type tumors (MTAP-WT). A propensity score matching of 5 covariates (age, gender, presence of variant histology, prior surgery, and prior non-muscle invasive bladder cancer) was calculated to compensate for disparity when comparing survival in these subgroups. Non-supervised clustering analysis of differentially expressed genes between MTAP-del and MTAP-WT urothelial carcinomas was performed. MTAP-del occurred in 19 patients (31%). Tumors with MTAP-del were characterized by higher prevalence of squamous differentiation (47.4 vs 11.9%), bone metastases (52.6 vs 23.5%) and lower frequency of upper urinary tract location (5.2% vs 26.1%). Pathway gene set enrichment analysis showed that among the genes upregulated in the MTAP-del cohort, at least 5 were linked to keratinization (FOXN1, KRT33A/B, KRT84, RPTN) possibly contributing to the higher prevalence of squamous differentiation. Alterations in the PIK3 and MAPK pathways were more frequent when MTAP was deleted. There was a trend to inferior response to chemotherapy among MTAP-del tumors, but no difference in the response to immune checkpoint inhibitors or enfortumab. Median progression free survival after first line therapy (PFS1) was 5.5 months for patients with MTAP-WT and 4.5 months for patients with MTAP-del (HR = 1.30; 95% CI, 0.64-2.63; P = 0.471). There was no difference in the time from metastatic diagnosis to death (P = 0.6346). Median OS from diagnosis of localized or de novo metastatic disease was 16 months (range 1.5-60, IQR 8-26) for patients with MTAP-del and 24.5 months (range 3-156, IQR 16-48) for patients with MTAP-WT (P = 0.0218), suggesting that time to progression to metastatic disease is shorter in MTAP-del patients. Covariates did not impact significantly overall survival on propensity score matching. In conclusion, MTAP -del occurs in approximately 30% of patients with advanced urothelial carcinoma and defines a subgroup of patients with aggressive features, such as squamous differentiation, frequent bone metastases, poor response to chemotherapy, and shorter time to progression to metastatic disease.

Phase I study of anti-epidermal growth factor receptor antibody-drug conjugate serclutamab talirine: Safety, pharmacokinetics, and antitumor activity in advanced glioblastoma

Background

Serclutamab talirine (Ser-T, formerly ABBV-321) is an antibody-drug conjugate consisting of an antibody (AM-1-ABT-806) directed against activated epidermal growth factor receptor (EGFR) and a pyrrolobenzodiazepine dimer. We investigated Ser-T monotherapy in a phase I, first-in-human, dose-escalation, and dose-expansion study in patients with advanced solid tumors associated with EGFR overexpression.

Methods

Eligible patients (≥18 years) had advanced, histologically confirmed solid tumors associated with EGFR overexpression (centralized testing). Patients received Ser-T intravenously once every 4 weeks (Q4W; 5-50 μg/kg) in the dose-escalation phase. Herein, preliminary antitumor activity at the recommended phase II dose (RP2D) is reported only for patients with glioblastoma (n = 24); additional assessments included all treated patients.

Results

Sixty-two patients (median age: 58 years) were enrolled within the dose-escalation (n = 43) and dose-expansion (n = 19) phases. One dose-limiting toxicity, grade 3 aspartate aminotransferase and alanine aminotransferase elevation, occurred at 20 μg/kg during dose escalation. The Ser-T RP2D regimen of 50 μg/kg × 1 (loading dose) followed by 25 μg/kg Q4W (maintenance dose) was administered during dose expansion. Fatigue (37%) was the only treatment-emergent adverse event (AE) occurring in >25% of patients. Two patients (3%) reported mild treatment-related ocular AEs (eye pruritus). Responses in patients with glioblastoma included 1 partial response (~33 months), 6 stable disease, and 14 progressive disease (not evaluable: n = 3).

Conclusions

Ser-T monotherapy at doses up to 50 μg/kg initial dose, followed by 25 μg/kg Q4W demonstrated a tolerable safety profile with minimal antitumor activity observed in patients with glioblastoma. The glioblastoma dose-expansion cohort was closed due to a lack of efficacy (NCT03234712).

Eftozanermin alfa (ABBV-621) monotherapy in patients with previously treated solid tumors: findings of a phase 1, first-in-human study

Eftozanermin alfa (eftoza), a second-generation tumor necrosis factor-related apoptosis-inducing ligand receptor (TRAIL-R) agonist, induces apoptosis in tumor cells by activation of death receptors 4/5. This phase 1 dose-escalation/dose-optimization study evaluated the safety, pharmacokinetics, pharmacodynamics, and preliminary activity of eftoza in patients with advanced solid tumors. Patients received eftoza 2.5-15 mg/kg intravenously on day 1 or day 1/day 8 every 21 days in the dose-escalation phase, and 1.25-7.5 mg/kg once-weekly (QW) in the dose-optimization phase. Dose-limiting toxicities (DLTs) were evaluated during the first treatment cycle to determine the maximum tolerated dose (MTD) and recommended phase 2 dose (RP2D). Pharmacodynamic effects were evaluated in circulation and tumor tissue. A total of 105 patients were enrolled in the study (dose-escalation cohort, n = 57; dose-optimization cohort, n = 48 patients [n = 24, colorectal cancer (CRC); n = 24, pancreatic cancer (PaCA)]). In the dose-escalation cohort, seven patients experienced DLTs. MTD and RP2D were not determined. Most common treatment-related adverse events were increased alanine aminotransferase and aspartate aminotransferase levels, nausea, and fatigue. The one treatment-related death occurred due to respiratory failure. In the dose-optimization cohort, three patients (CRC, n = 2; PaCA, n = 1) had a partial response. Target engagement with regard to receptor saturation, and downstream apoptotic pathway activation in circulation and tumor were observed. Eftoza had acceptable safety, evidence of pharmacodynamic effects, and preliminary anticancer activity. The 7.5-mg/kg QW regimen was selected for future studies on the basis of safety findings, pharmacodynamic effects, and biomarker modulations. (Trial registration number: NCT03082209 (registered: March 17, 2017)).

Clinical activity of 9-ING-41, a small molecule selective glycogen synthase kinase-3 beta (GSK-3β) inhibitor, in refractory adult T-Cell leukemia/lymphoma

GSK-3β is a serine/threonine kinase implicated in tumorigenesis and chemotherapy resistance. GSK-3β blockade downregulates the NF-κB pathway, modulates immune cell PD-1 and tumor cell PD-L1 expression, and increases CD8 + T cell and NK cell function. We report a case of adult T-cell leukemia/lymphoma (ATLL) treated with 9-ING-41, a selective GSK-3β inhibitor in clinical development, who achieved a durable response. A 43-year-old male developed diffuse lymphadenopathy, and biopsy of axillary lymph node showed acute-type ATLL. Peripheral blood flow cytometry revealed a circulating clonal T cell population, and CSF was positive for ATLL involvement. After disease progression on the 3^rd line of treatment, he started treatment with 9-ING-41 monotherapy in a clinical trial (NCT03678883). CT imaging after seven months showed a partial response. Sustained reduction of peripheral blood ATLL cells lasted 15 months. Treatment of patient-derived CD8 + T cells with 9-ING-41 increased the secretion of IFN-γ, granzyme B, and tumor necrosis factor-related apoptosis-inducing ligand (TRAIL). In conclusion, treatment of a patient with refractory ATLL with the GSK-3β inhibitor 9-ING-41 resulted in a prolonged response. Ongoing experiments are investigating the hypothesis that 9-ING-41-induced T cell activation and immunomodulation contributes to its clinical activity. Further clinical investigation of 9-ING-41 for treatment of ATLL is warranted.

Abstract CT030: Genomic and pathologic determinants of response to RP-3500, an ataxia telangiectasia and Rad3-related inhibitor (ATRi), in patients (pts) with DNA damage repair (DDR) loss-of-function (LOF) mutant tumors in the Phase 1/2 TRESR trial

Background: RP-3500 is a potent, oral ATRi developed to treat tumors with LOF gene alterations predicted to exhibit synthetic lethality with ATRi (STEP2 genes). Biomarker analyses from TRESR (NCT04497116) identified predictors of sensitivity to RP-3500.

Methods: Biomarker data were centrally assessed from: Tumor/normal sequencing including zygosity analysis (SNiPDx targeted NGS panel), ctDNA, and ATM IHC. Correlations with clinical outcomes: Overall Response (OR: RECIST 1.1 confirmed/unconfirmed CR/PR, PSA or CA125 response), PFS, and CBR (OR or therapy duration &gt;16 weeks [w]) were assessed.

Results: 120 pts (ovarian [n=22], prostate [n=22], breast [n=17], pancreatic [n=12], other [n=47]) with LOF alterations (ATM [n=44], BRCA1 [n=25], BRCA2 [n=15], CDK12 [n=9], RNASEH2 [n=5], PALB2 [n=5], SETD2 [n=5], other [n=12]) were enrolled based on local tumor NGS (n=71), germline testing (n=29), ctDNA (n=13), or IHC (n=7). Prior therapies included PARPi (39/120) and platinum (81/120). Locally and centrally assessed biomarker status were concordant for tumor NGS (45/46), germline (20/20) and ctDNA (7/8). Alterations were germline in 50/88 (57%) and somatic in 36/88 (41%) pts; clonal hematopoiesis was the source of ATM LOF in 2/88 (2%) pts. Gene zygosity was biallelic in 49/68 (72%) and monoallelic in 19/68 (28%) tumors. ATM protein loss was detected in 11/13 (85%) biallelic (discordance explained by missense mutations) and 5/8 (63%) monoallelic ATM LOF. Reversions were detected at baseline in 6 pt tumors (BRCA1 [n=3], BRCA2 [n=1], PALB2 [n=1], NBN [n=1]). In pts receiving RP-3500 &gt;100mg and ≥1 response evaluation, OR was 13% (13/98; responses in tumors with ATM, BRCA1, BRCA2, CDK12, RAD51C, SETD2 genotypes); CBR was 47% in 77 pts with follow-up &gt;16w , mPFS was 15w; 40/98 pts remain on RP-3500 (up to 50+w). CBR was &gt;60% and mPFS not reached on 17 pts with ovarian tumors. Compared with monoallelic loss, tumors with biallelic loss had significantly higher CBR (20/34 [59%] vs 1/10 [10%], p=0.01) and trend for longer mPFS (19w vs 6w, p=0.08). CBR was 64% (7/11) vs 0% (0/3) in biallelic vs monoallelic tumors with ATM LOF (p=0.19), and 64% (7/11) vs 0% (0/2) in tumors with BRCA1 LOF (p=0.19). Two pts with post-PARPi BRCA1 reversions had treatment durations of 17w and 29w.

Conclusions: RP-3500 has clinical activity across STEP2 genotypes including those pretreated with PARPi and with BRCA1 reversions. IHC is an imperfect surrogate for ATM zygosity. ATM alterations originating from clonal hematopoiesis of indeterminate potential (CHIP) can be misdiagnosed as tumor derived. High concordance of local and central testing supports the use of local NGS to identify LOF alterations. Improved CBR with RP-3500 therapy in tumors with biallelic LOF supports the use of gene zygosity as a predictor of benefit.

Citation Format: Timothy A. Yap, Ian M. Silverman, Elisa Fontana, Elizabeth Lee, David Spigel, Martin Højgaard, Stephanie Lheureux, Niharika Mettu, Benedito A. Carneiro, Louise Carter, Ruther Plummer, Joseph D. Schonhoft, Danielle Ulanet, Parham Nejad, Peter Manley, Jorge S. Reis-Filho, Yi Xu, Victoria Rimkunas, Maria Koehler, Ezra Rosen. Genomic and pathologic determinants of response to RP-3500, an ataxia telangiectasia and Rad3-related inhibitor (ATRi), in patients (pts) with DNA damage repair (DDR) loss-of-function (LOF) mutant tumors in the Phase 1/2 TRESR trial [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr CT030.

Abstract 4166: Small-molecule inhibition of glycogen synthase kinase-3 (GSK-3) increases the efficacy of anti-PD-L1 therapy in a murine model of microsatellite stable colorectal cancer (CRC); Therapeutic response correlates with T cell ratios and serum cytokine profiles in mice

Immune checkpoint blockade (ICB) with αPD-1/PD-L1 has impressive efficacy in microsatellite unstable (MSI+) CRC but no significant activity in the 85% of CRC cases that are microsatellite stable (MSS). Our group previously demonstrated that 9-ING-41, a small-molecule inhibitor of GSK-3 in clinical development, stimulates both NK and T cell activity. This project characterizes the effects of 9-ING-41 in combination with ICB in vivo. In a syngeneic murine colon carcinoma BALB/c model using MSS cell line CT-26, we compared isotype, 9-ING-41 (70 mg/kg 2x/wk), αPD-1 (10 mg/kg 2x/wk), αPD-L1 (10 mg/kg 2x/wk), 9-ING-41 + αPD-1, and 9-ING-41 + αPD-L1 treatment groups. The median overall survival was 19 days (d) with 9-ING-41 (hazard ratio for death (HR) 0.12; 95% confidence interval (CI), 0.03-0.54; p=0.008), 16 d for 9-ING-41 + isotype (HR 0.40; 95% CI, 0.08-1.9; p=0.14), 20.5 d for αPD-1 (HR 0.15; 95% CI, 0.03-0.67; p=0.0185), 18 d for αPD-L1 (HR 0.21; 95% CI, 0.05-0.89; p=0.0559), 17 d for 9-ING-41 + αPD-1 (HR 0.37; 95% CI, 0.09-0.1.5; p=0.29), and 45.5 d for 9-ING-41 + αPD-L1 (HR 0.08; 95% CI, 0.02-0.36; p=0.0019), compared to 16 d for the isotype control group. Tumor response rates observed were 33.3% in the 9-ING-41 + αPD-L1 group, 16.6% in the αPD-1 group, and a 0% for all other treatment groups. We hypothesize that the 9-ING-41-mediated upregulation of PD-L1 in CRC cells (HCT-116, HT-29) observed via both flow cytometry (FC) and western blot analysis may contribute to the increased efficacy of combination therapy with αPD-L1, as compared to αPD-1. Significant differences between responders and non-responders in intratumoral and splenic natural killer (NK) and T cell subsets 14-days post-treatment initiation were shown by multi-color FC. Compared to non-responders, regardless of treatment group, responders had lower percentages of splenic CD4+ (p=0.0145) and CD8+ T cells (p=0.0001), increased percentages of splenic CD69+ activated T cells (p=0.0070) and FOXP3+ regulatory T cells (p=0.001), and increased percentages of tumor-infiltrating CD3+ (p=0.0006) and CD4+ T cells (p&lt;0.0001). Responders had lower splenic CD8+/Treg (p=0.0007) and CD4+/Treg (p=0.001) ratios and higher intra-tumoral CD8+/Treg (p=0.0032) and CD4+/Treg (p=0.0001) ratios. Murine serum cytokine profiling showed that responders had lower concentrations of tumorigenic cytokines (BAFF, CCL7, CCL12, VEGF, VEGFR2, CCL21) and higher concentrations of immunomodulatory cytokines (CCL4, TWEAK, GM-CSF, CCL22, IL-12p70) compared to non-responders. These results demonstrate that small-molecule inhibition of GSK-3 with 9-ING-41 may increase the anti-tumor effects of ICB and improve response in patients with MSS CRC via modulation of anti-tumor immunity and cytokine signaling.

Citation Format: Kelsey E. Huntington, Anna Louie, Lanlan Zhou, Benedito A. Carneiro, Wafik El-Deiry. Small-molecule inhibition of glycogen synthase kinase-3 (GSK-3) increases the efficacy of anti-PD-L1 therapy in a murine model of microsatellite stable colorectal cancer (CRC); Therapeutic response correlates with T cell ratios and serum cytokine profiles in mice [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 4166.

Abstract 5699: Overexpression of KMT2A is associated with worse prognosis and specific immune signatures in patients with TP53-mutated hepatocellular carcinomas

Background: Aberrant expression of epigenetic regulators is often associated with pathogenesis. Histone H3K4 methyltransferase, known as KMT2A, has been implicated in regulation of chromosome segregation, mitosis and DNA replication in pediatric leukemia and myeloma. However, the role of KMT2A expression in solid tumors is under-investigated. Here we examine the implications of KMT2A overexpression in prognosis, gene pathway enrichment, aneuploidy and immune infiltration patterns using a large, real-world clinical HCC dataset.

Methods: A total of 403 HCC samples underwent comprehensive molecular profiling at Caris Life Sciences, including DNA-(592 Gene Panel, NextSeq, or whole exome sequencing, NovaSeq) and RNA- (NovaSeq, whole transcriptome sequencing, WTS) sequencing. Wilcoxon, Fisher’s exact test were used to determine statistical significance (p value without and q value with multi comparison correction). Aneuploidy scores were generated from CNVkit. Apoptotic index (AI), GSEA were assessed using mRNA levels (FDR&lt;0.25 as cutoff). Overall survival was calculated from date of tissue collection to date of last contact from insurance claims data and used for Kaplan-Meier method.

Results: Overexpression of KMT2A predicts poor survival in patients with HCC (HR 2.6, 95% CI [1.4 - 5.2], p&lt;.01). KMT2Ahigh HCC has higher TP53 (57.9% vs 28.8%, p&lt;.001) and lower CTNNB1 (14.1% vs 34.6%, p &lt;.01) mutation rates (mt). GSEA analysis showed that pathways such as mitotic spindle (NES = 2.1), DNA repair (NES = 2.0), E2F regulation (NES = 2.0) and MYC (NES = 1.9) are significantly enriched in KMT2Ahigh HCC. Interestingly, in KMT2Ahigh HCC, TP53 mutation status is a stratification factor for several HCC features: 1) TP53 mt HCC displayed significantly lower aneuploidy score (median 6 vs 13.5, p&lt;.01) and higher apoptotic index (median 1.1 vs 1.2, p&lt;.05); 2) inflammatory response pathways (NES = 2.1) and IL6 JAK STAT3 signaling (NES = 2.1) are specifically enriched in TP53 mt HCC and 3) TP53 mt HCC has more infiltration of B cells (5.3% vs 3.3%, q&lt;.05), Macrophage M1 (6.4% vs 2.9%, q&lt;.01), CD8 + T cells and myeloid dendritic cells (1.1% vs 1%, q&lt;.01) while TP53 wt is associated with more infiltration of Macrophage M2 (5.5% vs 3.3%, q&lt;.05) cells.

Conclusions: KMT2A could act as an independent prognostic marker in HCC. The negative correlation between KMT2A expression and aneuploidy scores in TP53 mt indicates potential roles of KMT2A in maintaining genome stability. Furthermore, our results suggest TP53 status is an important stratification factor for HCC with KMT2A overexpression. Our results warrant further investigation on the impact of KMT2A level on immune modulation and may define a subset of HCC that responds most effectively to immune checkpoint inhibition.

Citation Format: Liang Sha, Jun Yin, Sungming Kim, Woojin An, Jian Zhang, Alex Farrell, Joanne Xiu, David Spetzler, Shuanzeng Wei, Dave S. Hoon, Stephen V. Liu, Emil Lou, Misako Nagasaka, Wafik S. El-Deiry, Benedito A. Carneiro, Wolfgang Michael Korn, Heinz-Josef Lenz, Yali Dou. Overexpression of KMT2A is associated with worse prognosis and specific immune signatures in patients with TP53-mutated hepatocellular carcinomas [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 5699.

Abstract CT183: First-in-human study of MEDI1191 (mRNA encoding IL-12) plus durvalumab in patients (pts) with advanced solid tumors

Background: IL-12 is a key mediator of antitumor immune response. In preclinical models, IT IL-12 mRNA led to IFNγ release and CD8+ T cell-dependent tumor regression and potentiated PD-L1 blockade. MEDI1191, a lipid nanoparticle-formulated mRNA encoding IL-12 delivered by IT injection, drives IL-12 production and enhances antitumor immune response with improved tolerability. We hypothesized that combining MEDI1191 with PD-L1 blockade would augment antitumor immunity in vivo. Here we report updated results from the dose-escalation phase of the first-in-human study of IT MEDI1191 and IV durvalumab (D; anti-PD-L1) for advanced/metastatic solid tumors (NCT03946800).

Methods: In this multicenter, open-label study, MEDI1191 was dosed sequentially (seq, Part 1A) or concurrently (conc, Part 1B) with D. In Part 1A, MEDI1191 was given IT on Days 1 and 22 followed by D 1500 mg on day 43 and then Q4W IV. In Part 1B, MEDI1191 was given IT on Days 1, 29, 57 and then Q8W, along with D on Day 1 and then Q4W. Treatment continued until progression or unacceptable toxicity for up to 2 years. Eligible adult pts had any solid tumor with cutaneous or subcutaneous lesions suitable for IT injection and progression on standard therapy for recurrent/metastatic disease. Primary objectives were safety and tolerability and determination of maximum tolerated dose (MTD); secondary objectives included preliminary antitumor activity by RECIST v1.1.

Results: Starting in May 2019, 31 pts received seq MEDI1191 with D (Part 1A cohorts 0.1-12 μg; n=20) or conc MEDI1191 with D (Part 1B cohorts 1.0-3.0 μg; n=11); 23 pts had received prior anti-PD-1/PD-L1 therapy. Most common tumor types were melanoma, n=8; head and neck cancer, n=4; and breast cancer, n=4. At the data cutoff of Dec 7, 2021, there were no dose-limiting toxicities and no MTD was identified. One pt (3.2%) had a Gr ≥3 MEDI1191-related AE (Gr 3 pyrexia, resolved within 24 hr) and 1 (3.2%) had a MEDI1191-related serious AE (SAE; Gr 2 confusion). Two pts had Gr 3 D-related AEs (6.5%, pyrexia also related to MEDI1191 and pruritus; each n=1); none had a D-related SAE. There were no Gr 4 related AEs. 3 pts had partial responses (PR): 1 with head and neck cancer (unconfirmed, off study) and 2 with anti-PD-1 resistant melanoma (1 confirmed, &gt;12 months on treatment; 1 unconfirmed, off study); 10 pts had stable disease (including the 2 unconfirmed PRs). Among pts with available biomarker data (up to 3 μg in Part 1A and 1 μg in Part 1B), MEDI1191 increased serum IL-12 in 15/17 pts, increased CD8+ T cell tumor infiltration by &gt;2-fold in 8/14 pts and increased tumor PD-L1 expression in 6/14 pts.

Conclusions: IT MEDI1191 plus systemic anti-PD-L1 was safe and feasible. Preliminary antitumor efficacy and pharmacodynamics, including tumor CD8+ T cell recruitment, were consistent with expected mechanism of action. Pts with injectable deep visceral and superficial lesions are being recruited.

Citation Format: Benedito A. Carneiro, Dmitriy Zamarin, Thomas Marron, Inderjit Mehmi, Sandip P. Patel, Vivek Subbiah, Anthony El-Khoueiry, David Grand, Kirema Garcia-Reyes, Sanjay Goel, Phillip Martin, Jixin Wang, Yuling Wu, Steven Eck, Benjamin Ridgway, Nairouz Elgeioushi, Jim Eyles, Nicholas Durham, Analia Azaro, Omid Hamid. First-in-human study of MEDI1191 (mRNA encoding IL-12) plus durvalumab in patients (pts) with advanced solid tumors [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr CT183.

Genomic and immunologic profiles of concurrent RB1 and CDKN1A/p21(WAF1) truncating mutations (RW+) in bladder cancer

4571

Background: p53 target and cell cycle inhibitor CDKN1A/p21(WAF1) was initially not found to be mutated in cancer. TCGA analysis identified CDKN1A mutations are present but rare with frequencies of < 1%, but enrich in bladder cancer (̃8%). Truncating WAF1 mutations are associated with sensitivity to cisplatin and are associated with truncating Rb mutations in bladder cancer (RW+). We hypothesized RW+ bladder cancers may represent a unique subgroup with sensitivity to therapeutics. Methods: A total of 1104 urothelial tumors underwent molecular profiling at Caris Life Sciences (Phoenix, AZ) utilizing NGS of DNA (592 Gene Panel, NextSeq, or WES, NovaSeq) and RNA (NovaSeq, WTS). Wilcoxon, Fisher’s exact were used for statistical significance (p value without and q value with multi comparison correction). Immune cell fraction (QuanTIseq) and pathway analysis (ssGSEA) were assessed by mRNA analysis. Immune epitope prediction was performed using the NetMHCpan v4.0 method in the Immune Epitope Database. Results: Concurrent truncating mutation (frameshift, nonsense) for RB1 and WAF1 were detected in 47 tumors (RW+, 4.25%) and tumors with wild-type status for both RB1 and WAF1 genes were classified as RW- group (54.08%). Tumors harboring only one RB1 or WAF1 mutation were excluded for further analysis. When compared to RW- group, RW+ tumors showed lower mutation rate of TP53 (54.5% vs 80.9%, q < 0.05), ARID1A (23.5% vs 38.3%, p < 0.05), and PIK3CA (18.4% vs 31.9%, p < 0.05). Interestingly, RW+ was mutually exclusive with FGFR3 mutation (18.0% vs 0%, p < 0.05). We further evaluated RNA expression of DNA repair and checkpoint arrest pathways. Notably, E2F pathway (Normalized Enrichment Scores, NES: 0.89 vs 0.86, q < 0.01) and DNA G2M checkpoint (NES: 0.89 vs 0.86, q < 0.01) were found to be the most enriched in RW+ with respect to RW- group. In addition, mRNA levels of FANCC/A, CHEK1, WEE1, CDC25A/C, PALB2 and BRCA1/2 were found to be overexpressed in RW+ group (q < 0.05). RW+ tumors also displayed a distinct immunological profile: They were associated with higher PD-L1 status (63.8% vs 37.3%, q < 0.01), higher median TMB (11 mut/Mb vs 8 mut/Mb, q < 0.01) and with less frequent loss of heterozygosity for HLA-DPA1 (51.1% vs 66.7%, p < 0.05), with more high-binding-affinity neoantigen load (4.78 vs 3.89, p < 0.05) to MHC proteins, consistent with the significantly more myeloid dendritic cells in in RW+ group (0.3 vs 0.04, q < 0.001). Conclusions: Concurrent truncating mutation in RB1 and WAF1 (RW+) bladder carcinomas have fewer p53, ARID1A, and PIK3CA mutations but are enriched for E2F targets, G2/M checkpoint genes, FANCC/A, CHEK1, WEE1, CDC25A/C, PALB2 and BRCA1/2 and have a distinct immunological profile. The findings suggest therapeutic strategies for RW+ bladder cancers including Chk1/Wee1, PARP inhibitors, -/+ immunotherapy that may impact on clinical outcomes.

Circulating tumor DNA (ctDNA) determinants of improved outcomes in patients (pts) with advanced solid tumors receiving the ataxia telangiectasia and Rad3-related inhibitor (ATRi), RP-3500, in the phase 1/2a TRESR trial (NCT04497116)

3082

Background: RP-3500 is a selective and potent oral ATRi in development for advanced solid tumors harboring loss-of-function (LOF) alterations in genes associated with ATRi sensitivity. We determined whether ctDNA can facilitate enrollment/monitoring of pts treated with RP-3500. Methods: Serial plasma samples collected at baseline (BL, 99 pts) and early timepoints on therapy (89 pts, 3-9 weeks [wks]) were profiled for ctDNA (Tempus xF or Guardant360). Targeted next generation sequencing (NGS) (SNiPDx panel) was performed on matched peripheral blood mononuclear cells and tumor samples collected at BL. Molecular ctDNA response (MR) was defined as ≥50% reduction in mean variant allele frequency (VAF) from BL to any timepoint ≤9 wks on-therapy. Clonal hematopoiesis (CH) or germline alterations were excluded from the analysis. Efficacy was assessed in pts treated with > 100 mg RP-3500/day with ≥1 post-BL response assessment. Endpoints included progression-free survival (PFS) and clinical benefit rate (CBR; CR/PR by RECIST1.1 or PSA/CA-125, or > 16 wks on treatment). Results: BL ctDNA was detected in 82% (81/99) of pts. Eligibility alterations were evaluable by the ctDNA panel in 61% (60/99) of pts, excluding structural/copy number variants and genes/exons not on the panel. Percent agreement between BL ctDNA and local eligibility NGS test was 93% (56/60). CH variants were identified in 26 pts (1-14 per pt); median VAF was 0.4% (0.1-12.4%). Two pts with pathogenic ataxia-telangiectasia mutated ( ATM) alterations were determined to be from CH. MRs were observed in 44% (24/55) of pts with median time to MR of 3.3 wks and were across tumors harboring ATM (10/20), BRCA2 (7/10), BRCA1 (4/15), CDK12 (1/3), PALB2 (1/3) and RAD51C (1/1) pathogenic alterations. Four pts with BRCA1 mutant tumors had MRs, 2 of whom (breast cancer) had received prior PARPi and had confirmed BRCA1 reversion mutations and clinical benefit (CB). One pt with g ATM pancreatic cancer with CB had > 90% reduction in KRAS mutant VAF at 3 wks. MR was associated with longer mPFS (29 vs 12 wks, p = 0.0002) and significantly higher CBR (17/22 (77%) vs. 8/28 (29%); p = 0.001) than those without MR. Pts with MRs not achieving CB (N = 5) included 4 with RP-3500 dose interruptions/reductions and 1 who discontinued early (10 wks) due to clinical progression but with decreased target lesions and stable disease. Conclusions: ctDNA testing is a reliable method to detect DNA damage repair LOF alterations but is limited to alterations and genes/exons covered by the ctDNA test. CH alterations are frequent, especially for ATM, thus matched normal analysis is preferred. Changes in ctDNA as early as 3 wks were associated with improved outcomes and may be useful for evaluating drug activity in heterogenous tumors outside of traditional efficacy endpoints. Clinical trial information: NCT04497116.

innovaTV 207: New combination dosing cohorts in the open label phase 2 study of tisotumab vedotin in solid tumors

TPS6100

Background: Tisotumab vedotin (TV; TIVDAK) is a tissue factor (TF)-directed antibody-drug conjugate that has been granted accelerated approval in the US for treatment of adults with recurrent/metastatic (r/m) cervical cancer with disease progression on or after chemotherapy. TV remains investigational in other tumor types including squamous cell carcinoma of the head and neck (HNSCC) and squamous non-small cell lung cancer (sqNSCLC). This abstract presents the addition of Part D to innovaTV 207 (NCT03485209), a global, open label, multicenter phase 2 trial investigating the safety, tolerability, and activity of TV in solid tumors. Untreated patients (pts) with r/m HNSCC or sqNSCLC enrolled in Part D will receive either TV in combination with pembrolizumab (pembro) or TV + pembro and a platinum agent. Based on encouraging preliminary safety and efficacy results with 2.0 mg/kg TV once every 3 weeks (Q3W) in combination with pembro or carboplatin (carbo) in innovaTV 205 cervical cancer study cohorts, TV is being evaluated at 2.0 mg/kg Q3W in combination with pembro or pembro + carbo (or cisplatin). Methods: Up to 140 treatment-naive pts with r/m HNSCC or sqNSCLC will be enrolled in Part D of innovaTV 207. First, the All-Comers cohorts for HNSCC and sqNSCLC will each enroll up to 30 pts, regardless of PD-L1 expression, for Q3W dosing with 2.0 mg/kg TV in combination with 200 mg pembro and AUC 5 carbo. After enrollment in the HNSCC All-Comers Cohort is complete, up to 20 pts with HNSCC will be enrolled into a Cisplatin Safety Cohort for dosing with 2.0 mg/kg TV in combination with 200 mg pembro and 100 mg/m2 cisplatin. Completion of enrollment in the All-Comers Cohort for each tumor type will also be followed by enrollment of up to 30 pts with HNSCC (CPS ≥1) and 30 pts with sqNSCLC (TPS ≥1%) into PD-L1 Selected cohorts for dosing with TV in combination with 200 mg pembro. Response will be assessed every 6 weeks for the first 6 months, every 12 weeks for the next 6 months, and then every 6 months after that. Pts with HNSCC must have had no previous systemic therapy for metastatic disease (exception is systemic therapy given as part of multimodal treatment for locally advanced disease completed > 6 months prior). Pts with NSCLC must have histologically or cytologically documented squamous cell NSCLC and must not have had any previous systemic therapy for metastatic disease or radiation therapy to the lung that is > 30 Gy within 6 months of the first dose of study drug. The primary endpoint is investigator-determined confirmed ORR per RECIST v1.1. Secondary endpoints include confirmed and unconfirmed ORR per RECIST v1.1, disease control rate, duration of response, time to response, PFS, OS, safety and tolerability, pharmacokinetics, and immunogenicity. The trial opened in June 2018 and was amended to add Part D in November 2021. Part D enrollment will begin in early 2022; updates will be provided at the meeting. Clinical trial information: NCT03485209.

A pancancer analysis of impact of MDM2/MDM4 on immune checkpoint blockade (ICB)

2630

Background: MDM2/MDM4 are implicated in hyperprogression after immune checkpoint blockade (ICB). Our preclinical studies showed reduced T-cell killing of MDM2-amplified tumor cells that was overcome by an MDM2 antagonist or gene knockdown, and we observed additional tumor killing by T-cells with MDM2 inhibition plus anti-PD1. We hypothesized that MDM2/4 gene amplification/overexpression correlates with resistance to ICB and investigated the association of MDM2/4 alterations to overall survival (OS) following ICB across multiple solid tumors. Methods: Solid tumors tested at Caris Life Sciences (Phoenix, AZ) with NextGen Sequencing on DNA (NGS) were analyzed. MDM2/4 amplification (amp) was tested by NGS and determined as either amp4 (cutoff of >=4.0 copies) or amp6 (>=6.0) or amp8 (>=8.0). Real-world OS was obtained from insurance claims data and calculated from treatment start or tissue collection to last contact. Kaplan-Meier estimates were calculated for molecularly defined groups. X2/Fisher-Exact were used and significance determined as P-value adjusted for multiple comparisons (q<0.05). Results: In a large cohort of TP53-wild type solid tumors, 2785 had MDM2 amp4 (262 were ICB-treated), 2108 had MDM2 amp6 (ICB: 192), 1721 had MDM2 amp8 (ICB: 149); 1040 tumors had MDM4 amp4 (ICB: 59), 293 had MDM4 amp6 (ICB: 8) and 217 had amp8 (ICB: 4). NSCLC, GBM, breast, bladder cancer and liposarcoma had the highest MDM2 amp and breast cancer, GBM, uterine, NSCLC and ovarian cancers had the highest MDM4 amp. When all tumors were considered, MDM2 amp4, 6 and 8 significantly associated with shortened OS (amp4: HR 1.31; amp6: HR 1.31; amp8: 1.29, all p<0.0001); similar results were seen with MDM4 (amp4: HR 1.14, p=0.004; amp6: HR 1.51, p<0.00001 and amp8: HR 1.6, p<0.00001). Of note, MDM4 amp4 but not MDM2 amp4 was associated with significantly worse post-ICB survival (HR: 1.55, p=0.009).When comparing molecular differences between MDM2 amp4 and MDM4 amp4, significantly higher PDL1 expression was associated with MDM2 amp (Ab clone 28.8: 58% vs. 28%; clone 22c3: 48% vs.25%, q<0.05); while higher mutation rates of ARID1A, PIK3CA, PTEN, KRAS and CTNNB1 were associated with MDM4 amp (all q<0.05). When investigating NSCLC, MDM4 amp4 was associated with decreased post-ICB survival in NSCLC (HR: 2.59, p=0.001) but not MDM2; when comparing the molecular alterations, MDM2 amp was associated with significantly higher PDL1 (22c3) (54% vs. 27%), EGFR mutation (36% vs. 14%) but less prevalent KRAS (15% vs. 50%), STK11 (11% vs. 41%), KEAP1 (2.5% vs. 27%) and BRAF (2% vs. 16%) mutations. The association with poor prognosis of MDM2 amp4/6 (HR: 1.2 and 1.3, p<0.05) and MDM4 amp4/6 (HR: 1.3 and 1.6, p<0.05) was seen in breast cancer, but not in NSCLC, GBM, bladder or uterine cancers. Conclusions: MDM2 and MDM4 amplification are negative prognostic factors in TP53-WT breast cancer while MDM4 amp is associated with reduced survival in ICB-treated NSCLC.

Reversion mutations in BRCA1 or BRCA2 genes: Resistant mechanism(s) in patients treated with platinum-based agents or poly (ADP-ribose) polymerase(PARP) inhibitors

3132

Background: Reversion mutations (RM) in homologous recombination pathway genes including BRCA1/2 have been identified in patients with ovarian, breast, and prostate cancers whose tumors have become refractory to platinum chemotherapy or PARP inhibition. Utilizing a multi-institutional molecular database, we report the prevalence of BRCA1/2 RM in a large cohort across various tumor types. Methods: Primary and/or metastatic tumor samples underwent DNA (underwent NextSeq, 592 genes; NovaSeq, whole-exome) and RNA (NovaSeq, whole transcriptome) sequencing (Caris Life Sciences, Phoenix, AZ). RM were identified by a board-certified molecular geneticist and called only if the patient had been treated with a PARPi or a platinum agent. Baseline clinical and outcomes data were obtained through linked insurance claims data. Results: Among 118,000 solid tumors profiled, RM were observed in 54 tumors samples. RMs were seen most commonly in ovarian cancer (OC), 1.5% (23/1500) of tumors with BRCA1/2 pathogenic mutations (mut), followed by breast cancer (BC) (2.4%, 17/700), endometrial cancer (1.0%, 4/400), pancreatic cancer (1.0%, 2/210), cholangiocarcinoma (2.5%, 2/80), prostate cancer (1.3%, 3/230), cervical cancer (1.4%, 1/70), cancer of unknown primary (1.0%, 1/100), and a neuroendocrine tumor of prostate (1 RM of 9 BRCA mut). Among all RM, we detected 17 in BRCA1 and 6 in BRCA2 in OC. In BC, we identified 7 RM in BRCA1 and 10 in BRCA2. Frameshift mut that restored the reading frame in BRCA1/2 were the most common type of RM. Molecular profiles of 14 high-grade serous ovarian cancers (HGSOC) with RM were compared to 87 control HGSOC with pathogenic BRCA1/2 mut without RM. Tumors with RM had lower ER expression (25% vs. 64%, p = 0.024) and higher KDM6A mut rate (15% vs. 0, p = 0.016). Additionally, TP53 mut rates were similar in RM and control (100% vs. 95%), seen in HGSOC. In patients with RM, 7 of the 14 (50%) TP53 mut were gain-of-function (GOF) while only 19 of 84 (23%) TP53 mut in the control group were GOF (p = 0.048). More detailed clinical data were available for 29 patients with RM (17 BRCA1 & 12 BRCA2). Among these patients, 7 had received prior platinum-based chemotherapy (carboplatin or cisplatin), 7 patients were treated with PARP inhibitors (olaparib or rucaparib), or both (n = 7). Notably, 5 patients had been treated with carboplatin (n = 2, ovarian), olaparib (n = 1, breast), or both agents (n = 2, ovarian and prostate) after the detection of RM. Conclusions: This dataset is one of the largest reporting on the prevalence of BRCA1/2 RM across various tumor types. We demonstrate that the rate of RM was low among BRCA1/2 mutated tumors; this may be because some patients may not have repeat profiling post-treatment. Repeating tumor profiling at times of treatment resistance can help inform therapy selection in the refractory disease setting.

Molecular correlates of Delta-like-ligand 3 (DLL3) expression in neuroendocrine neoplasms (NENs)

4127

Background: NENs can occur in many locations but have limited precision therapy options. DLL3 is a cell surface protein that is emerging as a promising therapeutic target in NENs including neuroendocrine prostate cancer (NEPC) and small cell lung cancer (SCLC). Our recent study indicated that ̃77% of NEPCs expressed DLL3, with expression in circulating tumor cells being highly concordant with matched biopsies. While there are ongoing clinical trials of drugs targeting DLL3, the repertoire of clinical and genomic features shared across other DLL3-expressing NEN cancers is ill-defined. Methods: We analyzed WES and WTS data from NENs identified across 29 different sites of origin using the Caris Life Sciences platform, excluding SCLC and including neuroendocrine carcinomas and neuroendocrine tumors. We used values above or below median DLL3 expression of all NEN samples to define DDL3-High/Low (H/L). Significance of molecular alterations in DLL3-H vs L was determined using Fisher’s-Exact/Mann Whitney/X2 test with Benjamini-Hochberg correction. Results: DLL3 expression across all 2672 NEN samples was observed in 27 of 29 NENs after excluding SCLC. NENs of anus, prostate, lung, bladder, and bile duct exhibited the greatest median DLL3 expression, whereas adrenal gland, small bowel, and nervous system displayed the lowest. Certain tissues of origin displayed more robust DLL3 expression, with 71% (50/66) of NEPC, 75% (87/122) of lung, and 77.3% (51/66) of bladder being DLL3-H compared to 14.4% (13/90) of adrenal and 7.9% (12/151) of small bowel NENs. DLL3-H NENs were associated with TMB-high status ( > 10 muts/Mb; 12.1% vs 4.5%, OR 2.7, q < 0.001) and more genomic alterations in several driver genes, including tumor suppressors TP53 (51% vs 23%, OR 2.3, q < 0.001) and RB1 (42% vs 10%, OR 4.2, q < 0.001), and oncogenes KRAS (14% vs 5.4%, OR 2.5, q < 0.001), MYC (5.7% vs 0.9%, OR 6.3, q < 0.001) and CCNE1 (5.3% vs 1.3%, OR 4.0, q = 0.001). Conversely, DLL3-L NENs exhibited more alterations in CTNNB1 (2.2% vs 5.2%, OR 0.42, q = 0.04), MEN1 (3.3% vs 11%, OR 0.30, q < 0.001), and BCOR (1.3% vs 4.1%, OR 0.32, q = 0.02). DLL3-H NENs also had significantly more alterations in PIK3CA (6.4% vs 3.0%, OR 2.1, q = 0.04), chromatin remodeling genes KMT2D (6.7% vs 2.6% OR 2.6, q = 0.005) and CREBBP (3.2% vs 0.9%, OR 3.6, q = 0.03), and WNT signaling gene APC (9.7% vs 5.2%, OR 1.9, q = 0.02). Conclusions: We confirmed DLL3 expression in NENs across different tissues of origin, with highest expression in poorly differentiated NENs. DLL3-H expression was associated with genomic features considered “undruggable” based on current precision therapy approaches. Therefore, DLL3-targeted therapies may serve as a promising strategy for NEN patients with functional loss of tumor suppressors TP53 and RB1, as well as increased activity of KRAS, WNT and MYC signaling.

A Phase Ib/II Study of the CDK4/6 Inhibitor Ribociclib in Combination with Docetaxel plus Prednisone in Metastatic Castration-Resistant Prostate Cancer

PURPOSE

Ribociclib, a CDK4/6 inhibitor, demonstrates preclinical antitumor activity in combination with taxanes. We evaluated the safety and efficacy of ribociclib plus docetaxel in a phase Ib/II study in metastatic castration-resistant prostate cancer (mCRPC).

PATIENTS AND METHODS

Patients had chemotherapy-naïve mCRPC with progression on ≥ 1 androgen receptor signaling inhibitor (ARSI). The phase II primary endpoint was 6-month radiographic progression-free survival (rPFS) rate, with an alternative hypothesis of 55% versus 35% historical control. Circulating tumor cells (CTC) were collected at baseline and genomically profiled.

RESULT

Forty-three patients were enrolled (N = 30 in phase II). Two dose-limiting toxicities were observed (grade 4 neutropenia and febrile neutropenia). The recommended phase II dose (RP2D) and schedule was docetaxel 60 mg/m2 every 21 days plus ribociclib 400 mg/day on days 1-4 and 8-15 with filgrastim on days 5-7. At the RP2D, neutropenia was the most common grade ≥ 3 adverse event (37%); however, no cases of febrile neutropenia were observed. The primary endpoint was met; the 6-month rPFS rate was 65.8% [95% confidence interval (CI): 50.6%-85.5%; P = 0.005] and median rPFS was 8.1 months (95% CI, 6.0-10.0 months). Thirty-two percent of evaluable patients achieved a PSA50 response. Nonamplified MYC in baseline CTCs was associated with longer rPFS (P = 0.052).

CONCLUSIONS

The combination of intermittent ribociclib plus every-3-weeks docetaxel demonstrated acceptable toxicity and encouraging efficacy in ARSI-pretreated mCRPC. Genomic profiling of CTCs may enrich for those most likely to derive benefit. Further evaluation in a randomized clinical trial is warranted.

BrUOG360: A phase Ib/II study of copanlisib combined with rucaparib in patients (pts) with metastatic castration-resistant prostate cancer (mCRPC)

128

Background: mCRPC with alterations in genes associated with homologous recombination (HR) DNA repair (e.g., BRCA1/2) is sensitive to poly ADP-ribose polymerase inhibitors (PARPi). Preclinical studies showed that PI3K inhibitors (PI3Ki) impairs HR and sensitize cancer cells to PARPi even in the absence of HR gene mutations. These results support our hypothesis that dual PI3K and PARP inhibition may improve clinical outcomes in progressive mCRPC. We describe preliminary results of a phase Ib/II study investigating safety of the combination of copanlisib (pan-class I PI3Ki) and rucaparib (PARP-1, -2 and -3 inhibitor). Methods: Enrollment criteria included progressive mCRPC, prior androgen inhibitors (abiraterone, enzalutamide, and/or apalutamide); prior taxane chemotherapy was allowed. HR-deficiency was not required for the phase Ib. The phase I followed a standard 3+3 escalation design. Dose schema: rucaparib (continuous oral administration twice daily) 400mg (dose level [DL] -1, 1), 500mg (DL 2) or 600mg (DL 3,4) and intravenous copanlisib (45mg D1, D15 (DL -1, -2); 45mg, D1, D8, D15 (DL 1, 2, 3); 60mg, D1, D8, D15 (DL 4); 28-day cycle). Adverse events (AE) were graded by CTCAE v5.0. The primary aim of the phase I was to establish the MTD and the recommended phase II dose (RP2D) of copanlisib in combination with rucaparib. Results: Eleven pts were enrolled with a median age of 63 (55-78) and median PSA of 12 ng/mL (0.018–2,101). Seven pts (63%) received prior chemotherapy (docetaxel [7], cabazitaxel [3]). Pathogenic HR mutations included BRCA1 (1), BRCA2 (3), CDK12 (1), and FANCA (1). Treatment-related AE included grade 2 (G2) leukopenia (30%), G2 anemia (20%), G2 rash (20%). Two dose-limiting toxicities (DLTs) were observed in DL 1: G3 rash and G3 AST/ALT elevation attributed to both drugs. Six pts were treated at DL -1 without DLTs. The RP2D was rucaparib 400mg BID with copanlisib 45mg (D1, D15; 28-day cycle). There were 2 confirmed PSA50 responses among 7 evaluable pts (28%). One pt had BRCA2 loss and 1 had PALB2 VUS (ongoing PSA response for 14 mo). Three stable disease and 1 partial response were observed among 6 pts evaluable by RECIST 1.1. Conclusions: The combination of rucaparib and copanlisib is well tolerated. The RP2D was rucaparib 400mg BID with copanlisib 45mg (D1, D15; 28-day cycle) with signal of efficacy. Enrollment in a phase 2 expansion cohort in HR-mutated mCRPC is ongoing. Clinical trial information: NCT04253262.

Malignant glioma subset from actuate 1801: Phase I/II study of 9-ING-41, GSK-3β inhibitor, monotherapy or combined with chemotherapy for refractory malignancies

Background

GSK3β serine/threonine kinase regulates metabolism and glycogen biosynthesis. GSK3β overexpression promotes progression and resistance through NF-κB and p53 apoptotic pathways. GSK3β inhibits immunomodulation by downregulating PD-L1 and LAG-3 checkpoints and increasing NK and T-cell tumor killing. 9-ING-41, a small-molecule, selective GSK3β inhibitor, showed preclinical activity in chemo-resistant PDX glioblastoma models, including enhanced lomustine antitumor effect.

Methods

Refractory malignancies (n = 162) were treated with 9-ING-41 monotherapy (n = 65) or combined with 8 cytotoxic regimens after prior exposure (NCT03678883). Recurrent gliomas (n = 18) were treated with 9-ING-41 IV TIW q21day cycles at 3.3, 5, 9.3, 15 mg/kg, as monotherapy or combined with lomustine 30 mg/m² PO weekly q84day cycles. Primary objective was safety.

Results

RP2D of 15 mg/kg IV TIW was confirmed across all 9 regimens, no accentuated chemotherapy toxicity noted. Glioma subtypes included: 13 glioblastoma, 2 anaplastic astrocytomas, 1 anaplastic oligodendroglioma, 1 astrocytoma. Median age 52 (30-69) years; 6 female, 12 male; median ECOG 1 (0-2); median recurrences 3 (1-6). All received upfront radiation/temozolomide (18/18), plus salvage nitrosoureas (15/18), bevacizumab (8/18), TTFields (6/18), or immunotherapy (4/18). IDH/mutation(3/18); 1p19q/codeletion(1/18); MGMT/methylated(1/18). Four received 9-ING-41 monotherapy, 14 concurrent with lomustine. No severe toxicities were attributed to 9-ING-41, only mild vision changes (9/18, 50%), or infusion reactions (4/18, 22%). Lomustine-related toxicities: G3/4 thrombocytopenia (3/14, 21%), G1/2 fatigue (4/14, 28%). Median days on therapy was 55 (4-305); 1 partial response (>50%) was noted. Median OS was 5.5 (95% CI: 2.8-11.4) months and PFS-6 was 16.7%.

Conclusion

9-ING-41 plus/minus lomustine is safe and warrants further study in glioma patients.

Phase 2 study of 9-ING-41, a small molecule selective glycogen synthase kinase-3 beta (GSK-3β) inhibitor, with gemcitabine/nab-paclitaxel (GnP) in first-line advanced pancreatic ductal adenocarcinoma (PDAC)

578

Background: GSK-3β overexpression is associated with worse prognosis and chemotherapy resistance in PDAC. GSK-3β inhibition reverses chemotherapy-resistance by inhibiting chemotherapy-induced, ATR-mediated, DNA damage response. 9-ING-41 has significant anti-tumor activity through apoptosis induction, anti-fibrotic activity and NK/T-cell effector stimulation. We hypothesized that 9-ING-41 in combination with GnP chemotherapy would lead to anti-tumor activity, with improved tumor responses in patients with advanced PDAC in the first line setting. Methods: Primary endpoint is disease control rate (DCR). DCR = confirmed complete response (CR), partial response (PR), or stable disease (SD) ≥ 16 weeks (wks). Secondary endpoints are safety and ORR (overall response rates). Eligibility: Advanced PDAC, ECOG PS 0-2, no prior therapy in the metastatic setting and no systemic therapy in prior 6 months. Pts received 9-ING-41 15mg/kg IV twice-weekly with G 1,000 mg/m2 and nP 125 mg/m2 on days 1,8,15 of a 28-day cycle. Simon 2-Stage Design for DCR of 65% and null hypothesis of 50% (historical control), 80% power and 2 sided-significance level of.05. Up to 23 fully evaluable pts planned for stage 1 and if ≥ 12 evaluable patients achieve a DCR 37 additional pts will be enrolled on a second stage or a randomized study commenced. Results: As of Sept 27, 2021, 42 pts enrolled. Median age: 67. 24 females, 18 males. 38 pts with metastatic and 4 with locally advanced disease. Prior adjuvant therapy: 4 pts each FOLFIRINOX and gemcitabine-based. No 9-ING-41-attributable SAEs to date. 9-ING-41 attributed AEs: visual disturbance: 24 (75%) G1/2, 1 (3%) G3; infusion reactions 9 (28%) G1/2. Chemotherapy-related AEs: anemia 13 (40%) G1/2, 1 (3%) G3; neutropenia 2 (6%) G1/2, 13 (40%) G3/4; thrombocytopenia 9 (28%) G1/2, 2 (6%) G3/4; diarrhea 8 (25%) G1/2, 4 (13%) G3; fatigue 9 (28%) G1/2, 3 (9%) G3; nausea/vomiting 24 (75%) G1/2, 1 (3%) G3; constipation 9 (28%) G1/2; febrile neutropenia 5 (16%) G3/4. In 21 pts currently evaluable for response, DCR was 62% and ORR 43%. There were 2 confirmed CRs, 6 confirmed and 1 unconfirmed PRs, 4 SD and 8 disease progressions were observed. Amongst responder’s median duration of response has not yet been reached. Conclusions: 9-ING-41 plus GnP demonstrated encouraging clinical activity but chemotherapy-related AEs were significant. Based on efficacy data to date, including confirmed CRs, we have commenced a randomized phase 2 study, evaluating 9-ING-41 plus GnP vs Gn P alone. Enrollment to the randomized study is now open (NCT03678883). Clinical trial information: NCT03678883.

Combination of ONC201 and TLY012 induces selective, synergistic apoptosis in vitro and significantly delays PDAC xenograft growth in vivo

The five-year survival rate for pancreatic ductal adenocarcinoma (PDAC) has remained a dismal 9% for approximately 40 years with an urgent need for novel therapeutic interventions. ONC201 is the founding member of the imipridone class, comprised of orally bioavailable small molecules that have shown efficacy in multiple tumor types both in animal models and in Phase I/II clinical trials. ONC201 is a potent inducer of the tumor necrosis factor related apoptosis inducing ligand (TRAIL) pathway. TRAIL is an innate immune mechanism which induces programmed cell death of cancer cells. We observed that PDAC cells upregulated ATF4, CHOP, and DR5 after treatment with ONC201. This occurred in cell lines that are susceptible to ONC201-induced apoptosis and in ones that are not. In response to ONC201, PDAC cells downregulated anti-apoptotic proteins including c-FLIP, BclXL, XIAP, cIAP1, and survivin. We hypothesized that TRAIL receptor agonists might induce selective, synergistic apoptosis in pancreatic cancer cell lines treated with ONC201. We screened 7 pancreatic cancer cell lines and found synergy with ONC201 and rhTRAIL or the novel TRAIL receptor agonist TLY012 in 6 of the 7 cell lines tested. In vivo experiments using BxPC3 and HPAFII xenograft models showed that the combination of ONC201 plus TLY012 significantly delays tumor growth as compared to controls. Immunohistochemical analysis of the tumors after three doses of the combination showed significantly increased cleavage of caspase 3 in vivo as compared to controls. Taken together, the preclinical efficacy of ONC201 and TLY012 represents a novel therapeutic option for further testing in pancreatic cancer patients. This combination showed marked efficacy in tumor cells that are both sensitive and resistant to the pro-apoptotic effects of ONC201, providing rationale to further investigate the combination of ONC201 plus TLY012 in patients with pancreatic cancer.

Abstract P239: Safety and efficacy of copanlisib in combination with nivolumab: A phase Ib study in patients with advanced solid tumors

Introduction: Copanlisib (C) is a pan-class I PI3K inhibitor, with predominant activity against the PI3K-α and -δ isoforms, approved for patients (pts) with relapsed follicular lymphoma. The PD-1 inhibitor nivolumab (N) is approved for several advanced or metastatic solid tumors. Following preclinical demonstration of the immunomodulatory activity of C (Glaeske et al. AACR 2018), we report Phase Ib results evaluating the safety and efficacy of C+N in pts with advanced solid tumors (NCT03735628). Methods: PD-1 inhibitor-naive adult pts with advanced solid tumors received C 45 mg or 60 mg i.v. (days 1, 8, and 15; 28-day cycle) and N 240 mg (day 15 of cycle 1 and days 1 and 15 of subsequent cycles). The primary objective was determination of the recommended Phase II dose (RP2D) of C in combination with N. Secondary endpoints were safety/tolerability, pharmacokinetics (PK), and efficacy. Exploratory real-time evaluation of 77 pharmacodynamic and predictive immune cell biomarkers by flow cytometry on whole blood was performed. Results: 16 pts were treated (C 45 mg + N 240 mg, n=5; C 60 mg + N 240 mg, n=11). Median age was 65 years (range 37–89), 12 pts (75%) were male, and 8 pts (50%) had stage IV disease at diagnosis; the most common tumor types were head and neck squamous cell carcinoma (HNSCC; 7 pts) and bladder cancer (BC; 4 pts). No dose-limiting toxicities were reported. The RP2D of C+N 240 mg was 60 mg. As of 13 May 2020, 4 pts remain on treatment. The most common treatment-emergent adverse events (TEAEs) of any grade were hypertension and diarrhea (7 pts [44%] each, ≤ grade [G] 3) and maculo-papular rash and fatigue (6 pts [38%] each, ≤G3). C-related TEAEs were reported in 88% of pts, all ≤G3. AEs leading to C dose interruption/reduction were reported in 31%/19% of pts; TEAEs led to C discontinuation in 1 pt (60 mg; hematuria). Serious AEs occurred in 5 pts (31%). One G5 TEAE occurred (45 mg; general physical health deterioration, unrelated to C or N). No PK interactions were observed between C and N. Two pts had a partial response: 1 in the C 45 mg group (HNSCC) and 1 in the 60 mg group (BC; benefit sustained after 19 cycles). Stable disease was seen in 10 pts and disease progression in 3 pts; disease control rate (DCR) was 75%. Maximum decrease in circulating monocytic myeloid-derived suppressor cells (M-MDSCs; p&lt;0.05) from baseline occurred on day 2 after C, returning to baseline on day 8. A significant increase in activated (HLA-DR+ and CD38+) natural killer and CD8+ T cells was seen 2 weeks post-treatment with C+N. Lower baseline levels of CD8+ Teffector memory (TEM) subset CD45RA-/CCR7- (CD3+/CD8+) seemed to associate with higher DCR. Conclusions: C+N showed acceptable safety and preliminary efficacy in pts with advanced solid tumors. The immunomodulatory effect of C on M-MDSCs was seen 2 days post-treatment, and lower TEM subset levels seemed to associate with better disease control. These results support further investigation of C+N in pts with advanced solid tumors. Funding: Bayer AG. Writing support: Complete HealthVizion.

Citation Format: Benedito A. Carneiro, Robert Jotte, Nashat Gabrail, Omid Hamid, Funan Huang, Shalini Chaturvedi, Matthias Herpers, Lidia Mongay Soler, Barrett H. Childs, Aaron Hansen. Safety and efficacy of copanlisib in combination with nivolumab: A phase Ib study in patients with advanced solid tumors [abstract]. In: Proceedings of the AACR-NCI-EORTC Virtual International Conference on Molecular Targets and Cancer Therapeutics; 2021 Oct 7-10. Philadelphia (PA): AACR; Mol Cancer Ther 2021;20(12 Suppl):Abstract nr P239.

Abstract P021: Genomic biomarkers for response to 9-ING-41, a small molecule selective glycogen synthase kinase-3 (GSK-3) inhibitor, in pancreas cancer: Preliminary results

Background: 9-ING-41, a small molecule specific GSK-3 inhibitor, demonstrated favorable efficacy and safety in a Phase I clinical trial evaluating 9-ING-41 monotherapy and 8 chemotherapy combinations in 236 patients (pts) that has since been expanded to a Phase II multicenter study (NCT03678883). Interim results documented encouraging clinical activity, especially in patients with advanced pancreatic ductal adenocarcinoma (PDAC) and durable responses in melanoma and ATLL. Potential genomic biomarkers for 9-ING-41 response have not yet been evaluated. Methods: Next-generation sequencing (NGS) of tumor samples was obtained, whenever possible, for those receiving 9-ING-41 alone or in combination with chemotherapy across all sites. Genomic sequencing reports were reviewed for somatic alterations deemed potentially actionable or biologically relevant. For those with PDAC, best response was determined using RECIST 1.1 for those who completed at least two cycles of treatment. Chi-square frequency statistics were used to show the observed versus expected rate of pathogenic variants between patients with disease control (complete response [CR], partial response [PR] or stable disease [SD]) and progressive disease (PD). Results: NGS results were available for 135 pts across 11 sites. Most common histologies were PDAC (n=32), colorectal (n=17), and melanoma (n=9). Among pts with PDAC, NGS results were available for 32 pts (23 tumor samples, 9 ctDNA). Four patients received 9-ING-41 monotherapy; 28 received 9-ING-41 combined with gemcitabine/nab-paclitaxel (n=18), gemcitabine (n=7), or irinotecan (n=3). The most frequently mutated genes among PDAC included KRAS (n=22 pts), TP53 (n=21), CDKN2A (n=12), SMAD4 (n=4), CDKN2B (n=4), MTAP (n=3), ATM (n=3), AKT2 (n=2), and ARID1A (n=2). Of these 32 pts, 25 pts were evaluable for response: 2 pts had CR, 2 PR, 9 SD, and 12 PD. Among the pts with CR, one had tumor without pathogenic variants, the other displayed TP53 and KRAS mutations. Pts with PR: one tumor had no pathogenic mutations, the other tumor harbored mutations in ARID1A, TP53, FGF14, and ROS1. Of the nine patients with SD, 8 had KRAS mutations, 5 had CDKN2A loss of function, and 4 inactivating mutations in SMAD4. Eight out of 12 pts with PD had KRAS mutations. There were no significant differences between pts who had disease control and those with PD in the frequency of KRAS (χ2= 0.0189, P=0.89), TP53 (χ 2= 0.0712, P=0.78), or SMAD4 (χ 2= 1.9631, P= 0.1611). Conclusions: 9-ING-41 has shown clinical benefit in patients with PDAC independent of tumor somatic mutational profile. Preliminary analysis does not reveal pathogenic mutations that are associated with clinical benefit. Additional biomarker studies are ongoing.

Citation Format: Brittany A. Borden, Andre De Souza, Devalingam Mahalingam, Steven Powell, Pamela N. Munster, Kelsey Huntington, Andrew Mazar, Ludmila Calvacante, Francis J. Giles, Wafik S. El-Deiry, Howard P. Safran, Benedito A. Carneiro. Genomic biomarkers for response to 9-ING-41, a small molecule selective glycogen synthase kinase-3 (GSK-3) inhibitor, in pancreas cancer: Preliminary results [abstract]. In: Proceedings of the AACR-NCI-EORTC Virtual International Conference on Molecular Targets and Cancer Therapeutics; 2021 Oct 7-10. Philadelphia (PA): AACR; Mol Cancer Ther 2021;20(12 Suppl):Abstract nr P021.

Abstract 2676: GSK3β inhibition by small molecule 9-ING-41 decreases VEGF and other cytokines, and boosts NK and T cell-mediated killing of colorectal tumor cells

The GSK3β/beta-catenin axis activates vascular endothelial growth factor (VEGF) signaling in endothelial cells to promote angiogenesis. VEGF has been noted as immunosuppressive, it dampens the immune cell response by promoting recruitment of tumor associated macrophages (TAMs), and has been proposed as a target to modulate antitumor immunity. A panel of human colorectal cell lines was chosen to provide a varied mutational background (TP53, KRAS, BRAF, TRK, APC, PIK3CA). Cells were treated with 9-ING-41, a selective and potent small molecule inhibitor of GSK3β, at doses up to 50 µM for 72 hours to determine IC10, IC30, IC50, and IC70. Cytokine, chemokine, and growth factor levels were analyzed in the tumor cell culture supernatants after treatment at IC10, IC30, IC50, and IC70 for 48 hours using a Luminex 200 multiplexing instrument. Co-culture experiments were conducted with GFP+ SW480 colorectal cancer cells and either NK-92 natural killer cells or TALL-104 T cells at various effector/target ratios in a 48-well plate, in the presence or absence of 9-ING-41. Overall cytokine levels showed a decreasing trend in response to increasing doses of 9-ING-41. Among the most prominently decreased growth factors in the profile was VEGF. In an immune cell-killing co-culture assay we observed a significant increase in natural killer (NK-92) cell and T cell (TALL-104) killing of the colorectal cancer cells in response to treatment with 9-ING-41 as compared to controls without drug treatment. Follow-up experiments compared the effect of pre-treating either the effector or the target cell population with 9-ING-41 before the co-culture experiment was started. Pre-treatment of the target tumor cells, but not the effector immune cells, bolstered cell-killing, implying that the drug is sensitizing the tumor cells to killing by the immune cells. Moreover, we saw an increase in the expression of chemokine CXCL14 (BRAK) in the tumor cell culture supernatant with increasing doses of 9-ING-41. BRAK is known to stimulate activated NK cell migration and could have a beneficial therapeutic effect by increasing NK cell migration into the tumor microenvironment. Furthermore, we saw a decrease in macrophage colony-stimulating factor (M-CSF) which, along with VEGF, has been associated with recruitment of TAMs. We hypothesize that a 9-ING-41-mediated decrease of VEGF in conjunction with a 9-ING-41-mediated increase of BRAK secreted by the tumor cells may increase the capacity of NK- and T cell-mediated killing of the tumor cells. Utilizing a compound such as 9-ING-41 could be a way to increase the host's anti-tumor immune response to decrease tumor burden in conjunction with other therapeutic agents.

Citation Format: Kelsey E. Huntington, Shengliang Zhang, Benedito A. Carneiro, Wafik S. El-Deiry. GSK3β inhibition by small molecule 9-ING-41 decreases VEGF and other cytokines, and boosts NK and T cell-mediated killing of colorectal tumor cells [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr 2676.

The Role of BCL-2 Proteins in the Development of Castration-resistant Prostate Cancer and Emerging Therapeutic Strategies

The development of androgen resistance in advanced prostate cancer remains a challenging clinical problem. Because androgen deprivation therapy constitutes the backbone of first-line treatments for metastatic prostate cancer, the phenotypic switch from an androgen-dependent to an androgen-independent growth state limits the treatment options for these patients. This critical change from an androgen-dependent to an androgen-independent growth state can be regulated by the B-cell lymphoma gene 2 (BCL-2) family of apoptotic proteins. While the roles of BCL-2 protein family members in the carcinogenesis of prostate cancer have been well-studied, emerging data also delineates their modulation of disease progression to castration-resistant prostate cancer (CRPC). Over the past 2 decades, investigators have sought to describe the mechanisms that underpin this development at the molecular level, yet no recent literature has consolidated these findings in a dedicated review. As new classes of BCL-2 family inhibitors are finding indications for other cancer types, it is time to evaluate how such agents might find stable footing for the treatment of CRPC. Several trials to date have investigated BCL-2 inhibitors as therapeutic agents for CRPC. These therapies include selective BCL-2 inhibitors, pan-BCL-2 inhibitors, and novel inhibitors of MCL-1 and BCL-XL. This review details the research regarding the role of BCL-2 family members in the pathogenesis of prostate cancer and contextualizes these findings within the contemporary landscape of prostate cancer treatment.

Abstract CT222: BrUOG360: A phase Ib/II study of copanlisib combined with rucaparib in patients with metastatic castration-resistant prostate cancer (mCRPC)

Background: Patients with metastatic prostate cancer invariably progress to a lethal state called metastatic castration-resistant prostate cancer (mCRPC). Approximately 23-28% of patients with mCRPC have molecular alterations in genes associated with homologous recombination (HR) DNA repair mechanisms (e.g., BRCA1/2). These alterations are associated with sensitivity to poly ADP-ribose polymerase inhibitors (PARPi). The responses to PARPi can be short-lived, and several mechanisms of resistance have been described. Preclinical studies demonstrated that PI3K suppression impairs HR and sensitizes cancer cells to PARPi even in the absence of mutations in DNA repair genes. The synergy between olaparib and PI3K inhibition led to marked tumor regression both in vitro and in vivo models of prostate cancer. These preclinical results, coupled with the importance of both the PI3K pathway and DNA damage repair mechanisms in mCRPC, support our hypothesis that dual inhibition of PI3K and PARP might improve clinical outcomes in mCRPC. We describe an ongoing phase Ib/II study aimed to evaluate the safety and determine the maximum tolerated dose (MTD) of the combination of copanlisib (pan-class I PI3K inhibitor) and rucaparib (a PARP-1, -2 and -3 inhibitor) followed by an expansion cohort exploring efficacy among patients with mCRPC. Methods: Phase I, dose-escalation part of the study, aims to establish the MTD and/or recommended phase II dose (RP2D) of copanlisib in combination with rucaparib. Dose escalation will follow a standard 3+3 escalation scheme. Evidence of HR-deficiency is not required to enroll in phase I, but is for phase II. All subjects will be treated with rucaparib (continuous oral administration twice daily) 400mg (dose level I), 500mg (II) or 600mg (III-IV) and intravenous copanlisib (D1, D8, D15; 28-day cycle; dose levels I-III: 45 mg; level IV: 60 mg). Once the RP2D of copanlisib and rucaparib in the phase I part of the study is determined, enrollment will commence into the phase II part of the trial. The primary objective of phase II is to estimate the preliminary efficacy of the combination of copanlisib and rucaparib among subjects with mCRPC carrying mutations in DNA repair genes, as measured by prostate-specific antigen (PSA) response. Up to 20 patients will enroll in the phase II using a Simon's two-stage design. In the first stage, 14 patients will be accrued. If there are 7 or fewer PSA responses in these 14 patients, the study will be stopped for futility. Otherwise, an additional 6 patients will be accrued. Patients with mCRPC need to have had disease progression during treatment with abiraterone, enzalutamide, and/or apalutamide. Prior therapy with taxanes is allowed. Translational objectives include the correlation of clinical outcomes with HR mutations and PI3K/mTOR pathway gene alterations in the tumor. Genomic analyses will also investigate biomarkers and mechanisms of action of the combination. The clinical trial is recruiting (NCT04253262).

Citation Format: Andre De Souza, Rahul Aggarwal, Howard Safran, Dragan Golijanin, Roxanne Wood, Adam Olszewski, Wafik S. El-Deiry, Anthony Mega, Benedito A. Carneiro. BrUOG360: A phase Ib/II study of copanlisib combined with rucaparib in patients with metastatic castration-resistant prostate cancer (mCRPC) [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr CT222.