Abstract P2-23-12: The Mutational Landscape of 1172 Patients with Hormone Receptor-Positive, HER2-negative Metastatic Breast Cancer Treated with CDK4/6 Inhibitors

Background: Recent studies suggest differences in outcomes among patients (pts) with metastatic breast cancer (MBC) treated with abemaciclib, ribociclib, or palbociclib, but whether these differences have a genomic basis is unknown. Here, we utilize a large real-world dataset to compare the mutational landscapes of HR+/HER2- MBC samples in which CDK4/6 inhibitor (CDK4/6i) treatment was initiated ≥6 months prior to biopsy to describe variations in tumor biology associated with exposure to each CDK4/6i. We also compare mutations detected by solid tumor sequencing and liquid biopsy to better understand each assay’s ability to identify relevant alterations in this population.

Methods: De-identified data from a cohort of pts with HR+/HER2- MBC (n=1172) sequenced with the Tempus xT (DNA-seq of 595-648 genes, whole exome-capture RNA-seq) solid tumor and xF (105-gene panel focused on detecting oncogenic and resistance mutations from cell-free DNA) liquid biopsy assays were retrospectively analyzed. For pts with multiple samples sequenced, the most recent sample was analyzed. Pts were selected based on receipt of CDK4/6i between metastatic diagnosis date and biopsy collection and excluded if < 6 months elapsed between CDK4/6i initiation and biopsy collection. Demographics, clinical characteristics, and NGS findings were compared between groups by Chi-squared/Fisher’s Exact tests or Kruskal-Wallis tests, as applicable. The prevalence of individual gene alterations (consisting of pathogenic/likely pathogenic SNVs/indels and copy number alterations) were compared similarly with adjustment for false-discovery.

Results: We compared the immune biomarker and DNA mutational landscapes of 1172 samples collected after a period of treatment with abemaciclib, ribociclib, or palbociclib. Across all pts, the most commonly altered genes were TP53, PIK3CA, ESR1, CDH1, and GATA3. Abemaciclib-treated pts had the highest median TMB and MSI-high frequency (Table). Palbociclib-treated pts were less likely to have a high TMB (≥10 mutations/megabase) or RB1 mutations, a known biomarker of resistance to CDK4/6i (Table). We note that the total N for pts positive for TMB high or MSI-high was very low across all groups. We also compared DNA mutational landscapes between pts tested with solid tumor sequencing and liquid biopsy; the lower prevalence of RB1 mutations in palbociclib-treated pts trended towards significance in both groups (Table).

Conclusions: Results from our real-world dataset suggest that treatment with the different CDK4/6i drugs results in unique immune biomarkers and DNA mutational profiles. Detection of relevant alterations such as RB1 by both tissue testing and liquid biopsy supports a role for either assay in identifying mutations associated with CDK4/6i. Our findings raise the possibility that unique targeted treatment strategies and combination therapies may be warranted after progression on the different CDK4/6i drugs. Additional investigation into the differences in genomic alterations and outcomes among CDK4/6i drugs is necessary to further explore the hypotheses generated by this real-world study.

Prevalence of immune biomarkers and DNA mutations in pts treated with each CDK4/6i drug 1Pearson’s Chi-squared test; Fisher’s exact test; Kruskal-Wallis rank sum test 2False discovery rate correction for multiple testing 3,4N=464; 708 pts with missing data 5N=1163; 9 pts with missing data

Citation Format: Ami N. Shah, Bora Lim, Monica M. Mita, Elizabeth Mauer, Kayla V. Layng, Calvin Chao, Adam M. Brufsky. The Mutational Landscape of 1172 Patients with Hormone Receptor-Positive, HER2-negative Metastatic Breast Cancer Treated with CDK4/6 Inhibitors [abstract]. In: Proceedings of the 2022 San Antonio Breast Cancer Symposium; 2022 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2023;83(5 Suppl):Abstract nr P2-23-12.

Abstract OT2-11-01: A phase 1 study of the novel immunotoxin MT-5111 in patients with HER2+ tumors: interim results

MT-5111 is a 55kD engineered toxin body targeting HER2 in solid tumors that binds to an epitope distinct from trastuzumab and pertuzumab, offering potential combination strategies with other HER2-targeting agents. MT-5111 works by internalizing, self-routing through intracellular compartments to the cytosol, and inducing potent cell-kill via the enzymatic and permanent inactivation of ribosomes. This is a phase 1 study in adults with advanced HER2+ solid tumors. MT-5111 is dosed weekly IV over 30 min in every 21-day cycle until disease progression, unacceptable toxicity, death, or withdrawn consent. The study has dose escalation (Part A) cohorts enrolling patients (pts) with any HER2+ cancer (CA) and expansion (Part B) cohorts for HER2+ breast cancer (BC), Gastric or Gastroesophageal junction adenocarcinoma (GEA), or other HER2+ solid CA. As of 30 June 2022, 42 total pts had enrolled (36 in Part A on 0.5-23 µg/kg/dose, 6 pts with BC in Part B1 on 10 µg/kg/dose). Median age 65 years, 28 (66.78%) pts were female, median of 4 prior systemic and 2 prior HER2-targeting treatment (tx). 17 pts with BC, 6 with biliary CA, 9 with GEA, and 10 with other solid CA have enrolled. Of the 17 BC pts, 15 received ≥ 10 µg/kg/dose. Tx emergent adverse events (TEAEs) have been reported in 40 (95%) pts, and tx-related AEs (TRAE) occurred in 23 (55%) pts. No pt experienced G4-G5 TRAE. G1 troponin elevations were noted in 5 pts without clinical signs of cardiotoxicity (1 pt 6.75 µg/kg, 2 pts 10 µg/kg, 1 pt 17 µg/kg, 1 pt 23 µg/kg). Reversible G1/G2 infusion-related reactions were reported in 2 pts. Tx-related G1-G3 rash was observed in 5 pts (4 pts ≥ 10 µg/kg/dose); maculopapular in 2 pts, acneiform in 1 pt and associated with pruritus in 3 pts. The G3 rash developed one wk after first dose of 23 µg/kg, was declared a DLT, improved with systemic steroid therapy and the pt continued tx at the same dose without recurrence. Best overall response per RECIST thus far is stable disease (SD) in 17 pts, non-CR/non-PD in 1 pt, and progressive disease (PD) in 14 pts. 1 pt had non-CR/non-PD for 30 wks (1 μg/kg, BC); 1 pt had SD for 24wks (10 μg/kg, pancreatic); 1 pt is on tx with SD through 8 cycles (10 μg/kg, BC). Of the 10 BC pts who received ≥ 10 μg/kg/dose, the best response was 5 SD. The mean serum concentration of MT-5111 has increased in a dose-proportional manner starting at 6.75µg/kg/dose (Table 1). The soluble HER2 (sHER2) levels at end of tx were higher compared to baseline in cohorts that received ≤ 4.5µg/kg/dose, but similar or lower in cohorts that received ≥ 6.75µg/kg/dose. Higher MT-5111 doses have been well tolerated and may saturate circulating sHER2, leading to more predictable serum concentrations and tumor penetration. The Cmax in humans at doses ≥6.75 µg/kg/dose is above the in vitro IC50 for high HER2+ cell lines (0.029nM) and at 17 µg/kg/dose, above the IC50 for moderate HER2+ cells (1.6nM). In conclusion, the dose proportionate increase in serum concentration with levels above the in vitro IC50 and the leveling off/reduction of sHER2 indicate exposure to MT-5111 is at clinically therapeutic levels. Skin toxicity at higher doses may indicate on-target effect as observed in other EGFR-targeted therapies where it is associated with clinical response and a better prognosis. sHER2 biomarker data is expected for all cohorts with PK correlation and 23µg/kg safety and efficacy data.

PK profile of MT-5111, C1D1 values

Citation Format: Meena Okera, Brian A. Van Tine, Joleen M. Hubbard, Minal Barve, Erika Hamilton, Monica M. Mita, Frances Valdes-Albini, Daniel Ahn, Admasu Mamuye, Joshua Pelham, Amy Yuet, Diana Yurewicz, Yanning Liu, Andres Machado Sandri, William J. Edenfield, Aki Morikawa, William Gradishar, Rajiv Kumar, Zev A. Wainberg. A phase 1 study of the novel immunotoxin MT-5111 in patients with HER2+ tumors: interim results [abstract]. In: Proceedings of the 2022 San Antonio Breast Cancer Symposium; 2022 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2023;83(5 Suppl):Abstract nr OT2-11-01.

AKT/mTOR signaling modulates resistance to endocrine therapy and CDK4/6 inhibition in metastatic breast cancers

Endocrine therapy (ET) in combination with CDK4/6 inhibition is routinely used as first-line treatment for HR+/HER2- metastatic breast cancer (MBC) patients. However, 30-40% of patients quickly develop disease progression. In this open-label multicenter clinical trial, we utilized a hypothesis-driven protein/phosphoprotein-based approach to identify predictive markers of response to ET plus CDK4/6 inhibition in pre-treatment tissue biopsies. Pathway-centered signaling profiles were generated from microdissected tumor epithelia and surrounding stroma/immune cells using the reverse phase protein microarray. Phosphorylation levels of the CDK4/6 downstream substrates Rb (S780) and FoxM1 (T600) were higher in patients with progressive disease (PD) compared to responders (p = 0.02). Systemic PI3K/AKT/mTOR activation in tumor epithelia and stroma/immune cells was detected in patients with PD. This activation was not explained by underpinning genomic alterations alone. As the number of FDA-approved targeted compounds increases, functional protein-based signaling analyses may become a critical component of response prediction and treatment selection for MBC patients.

A phase 1 study of the novel immunotoxin MT-5111 in patients with HER2+ tumors: Interim results

2583

Background: MT-5111 is a 55kD engineered toxin body (ETB) targeting HER2 in solid tumors that binds to an epitope distinct from trastuzumab and pertuzumab, offering potential combination strategies with other HER2-targeting agents. MT-5111 may demonstrate efficacy in patients (pts) resistant to other HER2-targeting agents, as its mechanism of action induces direct cell kill via enzymatic and permanent ribosome destruction. Methods: This is a phase 1 study in adults with advanced HER2+ solid tumors. The dose-escalation portion (Part A) enrolls pts into sequential dose cohorts, followed by Part B expansion cohorts for HER2+ breast cancer (BC), gastroesophageal adenocarcinoma (GEA), and any other HER2+ cancer (CA). MT-5111 is dosed weekly IV over 30 min in each 21-day treatment (tx) cycle until disease progression, unacceptable toxicity, death or withdrawn consent. Results: As of Jan 2022, 27 pts had enrolled in Part A cohorts (0.5 to 10 µg/kg/dose) with completed DLT assessments: 9 (33%) pts were male and 18 (67%) female, median age 67 and a median of 4 prior systemic and 2 prior HER2-targeting tx. Common tissue types were BC (9/30%), biliary CA (6/22%), GEA (4/15%). The following safety data reflect 33 treated pts to date including ongoing 13 µg/kg/dose Part A and 10 µg/kg/dose BC expansion cohorts. No Grade (G) 4/5 tx-emergent adverse events (AEs) or DLTs occurred. Tx-related AEs occurred in 17 (52%) pts, most commonly G1/2 fatigue (8/24%). 3 pts had G1 troponin elevations without clinical signs or symptoms of cardiac distress: 1 at 6.75 µg/kg/dose, 2 at 10 µg/kg/dose. 2 pts (3 and 4.5 µg/kg/dose) had reversible G2 and G1, respectively, infusion-related reactions (IRR)s. A comparison of cytokines from baseline to on-treatment timepoints reveals no evidence of significant changes, even in pts with IRR. Best response per RECIST thus far was stable disease (SD) in 7 pts or non-CR/non-PD in 2 pts: 1 pt had SD for 12 weeks (wks) (4.5 μg/kg, pancreatic CA); 1 pt (1 μg/kg/dose, BC) had non-CR/non-PD for 30 wks; 1 pt (10 μg/kg/dose, GEA) has ongoing SD for 18 wks. AUClast data match PK simulations in non-human primate studies. Cmax at 10 µg/kg/dose is ≥5 times the IC50 values of high HER2 expressing gastric CA and BC cell lines while approaching the IC50 of a moderately HER2 expressing liver CA cell line. Conclusions: MT-5111 is well tolerated to-date with no clinically significant immuno/cardiotoxicity. Dose escalation is ongoing at a dose of 13µg/kg, expected to be required for efficacious exposure. Clinical trial information: NCT04029922.

Phase 1b study of the novel first-in-class G protein-coupled estrogen receptor (GPER) agonist, LNS8801, in combination with pembrolizumab in patients with immune checkpoint inhibitor (ICI)-relapsed and refractory solid malignancies and dose escalation update

2574

Background: LNS8801 is an oral, highly selective, small molecule agonist of the G protein-coupled estrogen receptor (GPER). LNS8801 normalizes c-Myc levels in cancer cells, inhibits proliferation, suppresses invasion, and enhances immune recognition. In preclinical models, LNS8801 has demonstrated increased activity with ICIs. In the first-in-human dose escalation study, LNS8801 was safe and tolerable alone and in combination with pembrolizumab in patients with metastatic solid tumors (NCT04130516). Methods: Patients who are relapsed and refractory (r/r) to PD-1/L1 ICIs and have measurable disease are enrolling in a Phase 1b cohort and receive LNS8801 (125 mg, QD, PO) and pembrolizumab (200 mg, Q3W, IV) (NCT04130516). The primary objective is safety and tolerability assessed according to NCI CTCAE v5.0. Secondary endpoints include pharmacokinetic, pharmacodynamics (eg., increase in serum prolactin over the initial 10 hours of dosing to assess GPER engagement), objective response rate and clinical benefit rate per RECIST v1.1. Results: Updates from the dose escalation portion of the study include long term benefit in a monotherapy patient with cutaneous melanoma on treatment for 2 years with RECIST stable, metabolically inactive disease by PET; a metastatic uveal melanoma patient on therapy for a year, and growing confidence in LNS8801’s favorable safety profile and predictive systemic biomarkers. As of 2/1/22, 13 ICI r/r patients were treated with LNS8801 and pembrolizumab, including those who entered the study directly after confirmed progression on ICIs. Cancer types include lung (3), colorectal, vaginal, nasopharyngeal, neuroendocrine, uterine, and pancreatic cancer, mesothelioma (2), and cutaneous and uveal melanoma. 46% of patients had AEs possibly related to study drugs (31% grades 1-2 and 31% grade 3), with colitis (15%) and fatigue (23%) appearing in more than 10% of patients. Of the 10 evaluable patients, 7 had stable disease (SD), with 4 patients demonstrating tumor regression. At the data cut-off, duration of treatment ranged from 0.7–7.5 months with 4 patients treated between 4.8 and 7.5 months and 4 patients continuing on treatment. All evaluated patients with SD had a prolactin response indicative of systemic target engagement. Conclusions: The combination of LNS8801 and pembrolizumab is tolerable without unanticipated toxicities and demonstrates encouraging anti-tumor activity in patients that are r/r to ICIs, including patients who enrolled immediately after confirmed progression on pembrolizumab alone. These data, as well as continued follow-up on patients with long-term benefit from dose escalation, support further development of LNS8801 as a cancer therapeutic. Clinical trial information: NCT04130516.

Trial in progress: Phase I study of SY-5609, a potent, selective CDK7 inhibitor, with initial expansion in adults with metastatic pancreatic cancer

TPS4180

Background: SY-5609 is an oral, selective, potent CDK7 inhibitor that targets two fundamental processes in cancer: transcription and cell cycle control. Early results from the Phase 1 dose escalation portion in patients (pts) with advanced solid tumors reported improved tolerability of the intermittent 7 days on followed by 7 days off (7/7) schedule with ongoing dose escalation beyond the continuous daily dosing maximum tolerated dose. Single-agent clinical activity was demonstrated with durable stable disease, target lesion regressions, and reduction in tumor markers observed in multiple tumor types, notably in pancreatic cancer with a disease control rate (DCR) of 38.5% (Sharma 2021). Pancreatic ductal adenocarcinoma (PDAC) has a 5-year survival rate of 11% (ACS Cancer Facts and figures, 2022) with limited treatment options and therefore, is a disease in need of novel effective therapies. Oncogenic KRAS mutations are prevalent in PDAC. Mutant KRAS is a potent stimulator of mitogenic MAPK signaling and downstream transcriptional programs for cell proliferation. Preclinical studies have shown that CDK7 inhibition via SY-5609 inhibits tumor growth in KRAS mutant PDAC xenograft models, in many cases leading to regressions. SY-5609 also potentiates gemcitabine (gem) activity in PDAC cells in vitro and in xenografts in vivo (Henry 2021). Therefore, combining SY-5609 with gem +/- nab-paclitaxel (nab-pac) offers a potential new treatment strategy for metastatic PDAC (mPDAC). The expansion portion of this Phase 1 study will evaluate SY-5609 in combination with gem +/- nab-pac in mPDAC pts. Gem +/- nab-pac will be administered on a biweekly schedule as it has shown better tolerability and similar clinical activity compared to the standard of care (SOC) administration schedule (Rehman 2020). Methods: This is an ongoing Phase 1, multi-center study in select solid tumors, amended to open expansion cohorts for mPDAC and expected to enroll approximately 80 mPDAC pts who have progressed on SOC treatments. Objectives of the expansion cohorts include evaluation of safety and efficacy of SY-5609 in combination with gem +/- nab-pac. Key objectives of the two parallel safety lead-in cohorts 1) SY-5609 + gem and 2) SY-5609 + gem + nab-pac are safety and determination of the recommended combination dose of the doublet and triplet for subsequent cohort expansions using a 3+3 escalation design. Key objectives of expansion cohorts are to describe efficacy, defined by progression-free survival, overall response rate, and DCR. Additional objectives include evaluation of pharmacokinetics and pharmacodynamics of SY-5609 in combination with gem +/- nab-pac. SY-5609 will be administered orally once daily on a 7/7 regimen and gem +/- nab-pac will be administered intravenously, in a 4-week cycle. The expansion portion is now open to enrollment. Clinical trial information: NCT04247126.

Phase 1 study of OBT076, a first-in-class anti-DEC205 ADC, in patients with advanced/metastatic solid tumors: Safety, efficacy, and PK/PD results

3028

Background: OBT076, an Antibody Drug Conjugate (ADC) consisting of a fully human IgG1 antibody conjugated via a cleavable linker to the derivative microtubule inhibitor DM4. It has specificity for the CD205/Ly75 target antigen which is an endocytic receptor overexpressed on the cell surface and immunosuppressive dendritic cells. This phase 1 study evaluates safety, tolerability, PK/PD and preliminary efficacy of OBT076 in solid tumor patients with high expression of target protein CD205 (CAP-CLIA validated centralized IHC test). Methods: Open label, two parts trial in patients with metastatic CD205+ve solid tumors who progressed on standard therapy. Part 1 of the study consisted in dose escalation from 1.6 mg/kg to 3.5 mg/kg. An mTPI design is used to guide to determine the maximum tolerated dose (MTD) Treatment was given on day 1 every 3 weeks followed by GCSF on day 8. Blood samples and flow cytometry were used to assess PK/PD. Tumor response was assessed every three cycles. Part 2 of trial is an expansion basket trial enriched in indications where preliminary efficacy has been shown. Results: The study completed Part 1 dose escalation. Part 2 expansion phase is ongoing. Between Dec 2019 and January 2022, 20 patients were enrolled (18 patients in the dose escalation and 2 in the ongoing expansion). The median age 61, 9 patients were males and 9 had ECOG PS 0. All patients had at least one metastatic site and 90% received at least 2 lines of chemotherapy in the metastatic setting. Recommended dose for the expansion phase is 3.0 mg/kg. No other significant side effects have been observed. PK data showed that Cmax of 40.000-90.000 ng/ml was achieved between 2.5 and 3.5mg/kg dose and is comparable to the therapeutic dose in mouse models. In part 1 of the study, 7 patients derived clinical benefit despite being in disease progression at trial entry. One patient with gastric cancer with linitis plastica experienced major improvement with complete disappearance of ascites and metastatic adenopathy after cycle 3. The six other patients had lasting stable disease and received between 5-14+ cycles with median of 5 cycles. Two patients with low PD-L-1 expression received checkpoint inhibitor treatment with pembrolizumab after 2 and 5 cycles of OBT076, both patients experienced near complete response after only one to two cycles. Conclusions: OBT076 at 3.0mg/kg has shown favorable safety profile with manageable neutropenia. The preliminary efficacy has shown preliminary antitumoral single agent activity in gastric, ovarian and lung cancer. The two patients who received a sequential administration of pembrolizumab after OBT076 showed major tumor activity. Sequential administration of OBT076 followed by a PD-1 inhibitor was also supported by PD markers and warrants further evaluation. Clinical trial information: NCT04064359. [Table: see text]

Abstract OT2-15-01: Updated analysis of MCLA-128 (zenocutuzumab), trastuzumab, and vinorelbine in patients (pts) with HER2 positive/amplified (HER2+) metastatic breast cancer (MBC) who progressed on previous anti-HER2 ADCs

Background Zenocutuzumab is a humanized bispecific full-length IgG1 antibody targeting both HER2 and HER3 with enhanced ADCC activity. The unique Dock & Block mechanism inhibits HER3 from interacting with its ligands by targeting HER2 at a different epitope than trastuzumab, that optimally positions it to block HER2/HER3 dimerization and downstream PI3K/AKT/mTOR signaling. In MBC, HER3 overexpression and/or HER3 ligand upregulation are important drivers of carcinogenesis leading to trastuzumab resistance, indicating a potential role for zenocutuzumab. Preclinical activity was seen in HER2+ breast cancer models when zenocutuzumab was combined with trastuzumab. Single-agent zenocutuzumab showed consistent antitumor activity in heavily pretreated HER2+ MBC pts. This phase 2, open-label study explored zenocutuzumab/trastuzumab/vinorelbine in MBC. Methods This open-label study planned to enroll up to 40 evaluable pts with HER2+ MBC progressing after up to 5 anti-HER2 lines of therapy including trastuzumab, pertuzumab, and an anti-HER2 ADC. This sample size with a clinical benefit rate (CBR) of 45% would provide adequate precision to exclude 30% (lower limit of 90% CI > 30%). The threshold for the CBR rate at 24 w was based on the assumption that progression-free survival (PFS) follows an exponential distribution with a median of 5 months (clinically relevant) and 3.5 months (not clinically relevant).Pts received zenocutuzumab (750 mg, 2h IV), trastuzumab (8 mg/kg loading, then 6 mg/kg), and vinorelbine (25 mg/m², D1 and 8), q3w. A safety run-in of zenocutuzumab + trastuzumab ± vinorelbine was performed. The primary endpoint of the study was CBR at 24 w (tumor assessment [TA] by RECIST 1.1, per investigator), secondary endpoints include CBR at 24 w (TA by RECIST 1.1, per central review), overall response rate (ORR), safety, biomarkers, and pharmacokinetics. Cutoff date for the efficacy endpoints was 31Mar2021. This is an updated analysis of the 2020 ASCO abstract after all patients had completed at least 6 months of treatment or discontinued. Result total of 39 pts with a median of 3 lines (range 2-5) of prior anti-HER2 therapy including TDM1 received a median of 6 (range 1-23) cycles of zenocutuzumab. In the 37 pts evaluable for efficacy and with locally confirmed HER2 overexpression (3+ IHC or 2+ IHC confirmed by FISH), CBR at 24 w per investigator was 49% (90% CI: 34-63%); ORR was 27% (95% CI: 15-42%). The CBR at 24 w was consistent across different methods of HER2 overexpression/amplification detection (local vs central laboratory) and response assessment (investigator and central independent radiological review; see table below). As of a 12Jan2021 safety data update, the most common related AEs (all grades; G3-4) were neutropenia/neutrophil count decrease (61%; 46%), diarrhea (61%; 4%), asthenia/fatigue (46%; 0), and nausea (29%; 0). The PK half-life was 117h. The correlation of HER2-HER3 pathway activation at baseline with best ORR, duration of response, PFS, and overall survival was analyzed and will be presented in the poster. Conclusion Updated analyses confirm that the efficacy of zenocutuzumab combinations with trastuzumab/vinorelbine in heavily pretreated, HER2+ MBC, with progression after TDM-1, met prespecified protocol criteria for success. The regimen is safe and well tolerated with AEs mostly related to chemotherapy.

CBR with zenocutuzumab, trastuzumab, and vinorelbinePopulationNCBR at 24 wks, %. (90% CI)HER2+ by local test/TA by RECIST1.1 per investigator3749 (34-63)HER2+ by central test/TA by RECIST1.1 per investigator2955.1 (38-71)HER2+ by local test/TA by RECIST1.1 by central independent radiologist review3644 (30-59)HER2+ by central test/TA by RECIST1.1 by central independent radiologist review2850.0 (33-67)

Citation Format: Erika Hamilton, Thierry Petit, Barbara Pistilli, Anthony Goncalves, Ana Alexandra Ferreira, Florence Dalenc, Fatima Cardoso, Monica M Mita, Luis Manso, Syed M Karim, Francois-Clement Bidard, Philippe Aftimos, Santiago Escriváa-de-Romaníi, Noemia Afonso, Ernesto Wasserman, Kees Bol, Viktoriya Stalbovskaya, Anastasia Vliet, Anastasia Murat, Mohamed Bekradda, Thomas Bachelot. Updated analysis of MCLA-128 (zenocutuzumab), trastuzumab, and vinorelbine in patients (pts) with HER2 positive/amplified (HER2+) metastatic breast cancer (MBC) who progressed on previous anti-HER2 ADCs [abstract]. In: Proceedings of the 2021 San Antonio Breast Cancer Symposium; 2021 Dec 7-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2022;82(4 Suppl):Abstract nr OT2-15-01.

A phase 1 study of the novel immunotoxin MT-5111 in patients with HER2+tumors: Interim results

297

Background: MT-5111 is a 55 kD engineered toxin body (ETB) targeting HER2 in solid tumors that binds to an epitope distinct from trastuzumab and pertuzumab, offering potential combination strategies with other HER2-targeting agents. MT-5111 may demonstrate efficacy in patients (pts) resistant to other HER2-targeting agents, as its mechanism of action induces direct cell kill via enzymatic and permanent ribosome destruction and does not rely on inhibition of kinase signaling or cytoskeletal or DNA damage. Methods: This is a phase 1 study in adult pts with advanced HER2+ solid tumors. The dose-escalation portion (modified 3+3 design) enrolls pts into sequential cohorts followed by expansion cohorts for HER2+ breast cancer (BC), gastric or gastroesophageal junction adenocarcinoma (GEA), and other HER2+ tumors. MT-5111 is dosed weekly IV over 30 min in each 21-day treatment (tx) cycle until disease progression, unacceptable toxicity, death, or withdrawn consent. Results: As of Sep 2021 (contains preliminary data), 24 pts (mean age 64 yrs) were treated, 13 (54%) of whom had gastrointestinal (GI) tumors (6 biliary, 3 GEA, 2 pancreatic, 2 colo/rectal) (Table). Pts with GI tumors had a median of 3 prior systemic tx and 1 prior HER2-targeting tx. No Grade (G) 4/5 tx-emergent adverse events (AEs) occurred. Tx-related AEs occurred in 13 (54%) pts, most commonly fatigue (n=7, 29%). One pt with biliary cancer and concurrent lymphangitic carcinomatosis and H. influenzae infection (4.5 µg/kg) had a possibly related G3 serious AE (SAE) of dyspnea, which resolved 9 days later. Another related SAE occurred in a pt with GEA (6.75 µg/kg) who had a G1 transient troponin increase that resolved during hospitalization, with no clinical symptoms or ECG/ECHO changes; the pt withdrew from study before further dosing. All other related AEs were ≤G2. No other clinically significant changes in cardiac biomarkers (troponin, ECG, LVEF) or cases of capillary leak syndrome occurred. Two pts (3 and 4.5 µg/kg) had reversible G2 infusion-related reactions. Best response to date has been stable disease. AUClast data matched PK simulations based on non-human primate studies. Cmax data at 10 µg/kg indicate that current in-pt exposure was between IC50 values of high and medium HER2-expressing cell lines (approx 10-89 ng/mL). Thus, at least 10 µg/kg may be required to achieve effective exposure. No dose-limiting toxicities have been observed. The 10 µg/kg cohort is now accruing. Following this cohort, an expansion cohort for pts with BC will open. Conclusions: MT-5111 was well tolerated with no clinically significant immuno/cardiotoxicity. Dose escalation is ongoing and is nearing levels expected to be required for efficacious exposure. Clinical trial information: NCT04029922. [Table: see text]

Abstract CT130: Phase 1 study of the novel immunotoxin MT-5111 in patients with HER-2+tumors

Background: Engineered toxin bodies (ETBs), composed of an engineered Shiga-like Toxin A subunit genetically fused to an antibody-binding domain, can force receptor internalization, induce potent cell-kill via enzymatic and permanent inactivation of ribosomes, and may not be subject to resistance mechanisms of other targeted agents. MT-5111, a de-immunized 55 kD ETB targeting HER2 in solid tumors, also binds to an epitope distinct from trastuzumab and pertuzumab, which may permit combination strategies with other HER2 targeting agents. Methods: The primary objective is to determine maximum tolerated dose (MTD) of MT-5111 monotherapy in adult patients (pts) with advanced HER2+ solid tumors. Secondary objectives are PK, efficacy, and immunogenicity. Using a modified 3+3 design, the dose-escalation part of the study includes the following 7 cohorts: 0.5, 1, 2, 3, 4.5, 6.75, and 10 µg/kg. Three dose-expansion cohorts will follow for HER2+ breast cancer, gastro-esophageal cancer, and any other HER2+ tumors. All pts will receive MT-5111 weekly as a 30-min IV infusion in each 21-d treatment (tx) cycle (C) until disease progression (PD), unacceptable toxicity, death, or withdrawn consent (NCT04029922). Results: As of the data cut in December 2020, 16 pts were treated; cancer types included breast (n=6), gastric (n=1), colon (n=1), gallbladder (n=5), and other solid tumors (n=3). Mean age was 64 years (range, 34-78); 37.5% were male. Pts received a median of 4 prior lines of systemic therapies (range, 1-8). No G4 or G5 TEAEs occurred. Six pts had 11 G3 TEAEs; the most common were increased AST and dyspnea (both n=2). Three pts had tx-emergent serious adverse events (abdominal distension [n=1]; dyspnea [n=2]). Tx-related TEAEs occurred in 8 (50%) pts; the most common was fatigue (n=5, 31.3%) and all were ≤ grade 2 in nature, except for one grade 3 event of dyspnea. No cardiac TEAEs, clinically significant changes in cardiac biomarkers (troponin, electrocardiogram, left ventricular ejection fraction), or cases of capillary leak syndrome were observed. Fifteen pts discontinued with PD; 1 pt in cohort 5 (4.5 µg/kg) is on tx with stable disease. To date, no DLTs have been observed and the MTD has not been reached. One pt in cohort 2 (1 µg/kg) had resolution of all hepatic lesions (sub-centimeter lesions pre-tx) at the end of C8; however, the pt came off study due to clinical progression at the end of C10. PK data for the first 5 cohorts matched simulations based on non-human primate studies. Conclusions: MT-5111 was well tolerated with no clinically significant cardiotoxicity. Continued dose escalations are ongoing.

Citation Format: Zev A. Wainberg, Monica M. Mita, Minal A. Barve, Erika P. Hamilton, Andrew J. Brenner, Frances Valdes, Daniel Ahn, Joleen Hubbard, Jason Starr, Christine Burnett, Joshua Pelham, Eric T. Williams, Banmeet S. Anand, Thomas Strack, Andrés Machado Sandri, Brian A. Van Tine. Phase 1 study of the novel immunotoxin MT-5111 in patients with HER-2+tumors [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 CT130.

Phase 1 trial of a novel, first-in-class G protein-coupled estrogen receptor (GPER) agonist, LNS8801, in patients with advanced or recurrent treatment-refractory solid malignancies

3084

Background: The G protein-coupled estrogen receptor (GPER) is a broadly expressed G protein-coupled receptor that is tumor suppressive. LNS8801 is an oral, highly selective small molecule agonist of GPER. GPER activation results in c-Myc depletion, inhibition of tumor proliferation, and enhancement of tumor immune recognition. Preclinically, LNS8801 demonstrates potent single-agent and combinatorial anti-cancer activity and can overcome established resistance to standard-of-care anti-cancer therapies including immune checkpoint inhibitors. Methods: The primary objective of this phase 1/1B first-in-human, open-label, multicenter study (NCT04130516) was to determine the safety and tolerability and recommended phase 2 dose (RP2D) of LNS8801 in patients (pts) with locally advanced or metastatic solid tumor malignancies, both as monotherapy and in combination with the anti-PD-1 antibody, pembrolizumab. Dose levels were escalated in a 3+3 fashion and included 10, 40 and 125 mg dosed 3/7, 125 mg daily, and 125 and 250 mg twice daily. Dose limiting toxicity (DLT) was defined via NCI CTCAE v5.0 during the first 21 days of treatment. An increase in prolactin over the initial 12 hrs of dosing was measured to assess systemic GPER signaling. Tumor c-Myc expression was measured as a surrogate of treatment-related biologic response. Radiographic response (RECIST v1.1) was evaluated every 8 weeks until progression. Results: 33 pts (19 M/14 F) with median age 58.8 y and 4 (1-9) prior therapies enrolled. Median duration of treatment was 66 d (1–367+). With monotherapy (n = 28), no DLTs, treatment-related SAEs, or treatment-related study discontinuations were observed up through the maximum administered dose (250 mg bid). Possibly related AEs were grade 1 or 2 and did not correlate with dose level. Exposure was above that predicted for efficacy and t1/2 was ̃10 hr at all doses. Of 26 evaluable monotherapy pts, 8 (27%) experienced stable disease (SD) for up to a year. All SD pts had a prolactin response. Among tumors expressing GPER, c-Myc depletion was observed in 100% (5/5) of paired pre and on-treatment biopsies. In the combination cohort (n = 5), 2/2 evaluable pts demonstrated net tumor reductions on initial f/up scans, including one RECIST partial response. Based on PK/PD data, 125 mg daily has provisionally been identified as the monotherapy and combination RP2D. Conclusions: LNS8801 is well tolerated and demonstrates signals of anti-tumor activity when administered both as monotherapy and in combination with pembrolizumab. Confirmation of RP2Ds and updated efficacy data will be presented in June. A phase 2A expansion study to evaluate these RP2Ds in clinical settings of high unmet need is now in development. Clinical trial information: NCT04130516.

Perspectives on under-representation of minority patients (pts) in clinical trials

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Background: About 40% of the US population are from minority groups. Minority pts are under-represented in oncology clinical trials, which limits the applicability of results to the general population and perpetuates poor relationships between healthcare systems and minority communities. This assessment investigated underlying causes of this lack of minority representation in clinical trials and proposes plans to promote diversity. Methods: To better understand the limited inclusion of under-represented pts in oncology clinical trials, 10 specialists in cancer care were selected to provide their perspectives. Specialists were chosen because of their experience enrolling minority pts in clinical trials and met virtually in Dec 2020 via Within3, a secure digital communication platform, to discuss obstacles faced in recruiting minority pts and potential strategies to address these concerns. Specificity and alignment in responses were achieved through software analytics and follow-up queries. Results: The 10 specialists identified as Asian (10%), Black (30%), White (50%), and Hispanic (10%), and began practicing medicine in the 1980s-2010s. All are involved in clinical research and treat a range of minority pts in both urban and suburban settings. Most specialists (8/10) reported treating > 20 minority pts with cancer annually. However, few specialists (2/10) reported that > 20% of their minority pts have enrolled in clinical trials. Specialists agreed that minority pts experience barriers to participation in clinical research, including lack of trust in the healthcare system, materials in their native languages, financial support, minority investigators involved in clinical trials, and accessible study sites. The specialists proposed strategies that could be implemented to increase minority enrollment. These included study sites where minority populations live and industry funded outreach and educational efforts in minority communities. If sites are more accessible, this can reduce time and financial pressures associated with study participation. The specialists recommended that studies be designed to be more supportive of minority populations, specifically regarding inclusion and exclusion criteria and reimbursement of costs. They also advised that increased diversity among clinical researchers and allied personnel may increase the ability of the clinical team to connect with pts and assist in building trust in their communities. Finally, they emphasized the importance of providing informed consent forms and study materials in pts’ native languages. Conclusions: While challenges exist to increasing diversity in oncology clinical studies, a broad consortium of clinical specialists agreed that they can be addressed by community outreach and education, making study sites more accessible, availability of study materials in pts’ native languages, and improving diversity of clinical teams.

Initial results of a first-in-human, dose escalation study of a cell-based vaccine in HLA A*02+ patients (pts) with recurrent, locally advanced or metastatic HPV16+ solid tumors: SQZ-PBMC-HPV-101

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Background: Ineffective MHC-I presentation of tumor antigens to CD8+ T cells limits T cell activation and the efficacy of cancer vaccines. The Cell Squeeze technology drives peripheral blood mononuclear cells (PBMCs) through a microfluidic chip leading to temporary cell membrane disruption and delivery of HPV16 E6 and E7 antigens cytosolically. These antigen presenting cells (APC) were matured with CpG7909 and were not genetically modified. Preclinically, this approach showed improvement in MHC-I presentation for human and murine cells. In murine tumor studies, m-SQZ-PBMC-HPV elicited robust CD8+ T cell responses and improved anti-tumor effects when compared to other vaccine modalities. Methods: SQZ-PBMC-HPV-101 included pts with incurable HPV16+ cancers progressing after unlimited prior therapy, ECOG 0-1, adequate organ function and a biopsiable lesion. After leukapheresis at the study site, manufacturing of the cryopreserved product took < 24 hours with a vein-to-vein time of approx. 1 week. Out-patient SQZ-PBMC-HPV was given IV q 3 weeks without a conditioning regimen. Double antigen priming (DP) was introduced with Cohort 3 and occurred on Cycle 1 Days 1 and 2. Maximum treatment duration for each patient was determined by the cell batch size. Response was assessed via RECIST 1.1 and iRECIST. Investigational biomarkers were measured pre- and post-treatment. Results: 12 pts [anal (7), head and neck (3), and cervical (2)] were dosed in 3 cohorts (3 pts in 0.5 x10e6/kg, 5 pts in 2.5 x10e6/kg, and 4 pts in 2.5x 10e6/kg [DP]). Median lines of prior Tx were 4 (range 1 - 7) and all but one pt were pretreated with checkpoint inhibitors (CPI); 10 pts had liver or lung metastases. All batches of SQZ-PBMC-HPV demonstrated CD8 activation in vitro after thawing, and batch size did not limit therapy duration at dose levels tested to date. Median number of doses were 3 (3 - 10), 3 (2 - 4), and 3 (3 – 4) in the 3 cohorts, respectively. One pt (10 doses) remained on study for 42 weeks. Tx was well-tolerated and there were no DLTs, Grade (G) >3 related SAEs or related G >3 AEs. One pt in cohort 1 experienced both a G2 infusion-related reaction and cytokine release syndrome. One pt in cohort 2 was not evaluable for DLT. Four out of 10 evaluable pts had stable disease per RECIST 1.1 as the best response. Preliminary tumor analyses pre- and post-therapy indicated increased immune activity in some patients after SQZ infusion. Conclusions: SQZ-PBMC-HPV-101 demonstrated clinical feasibility of the Cell Squeeze technology and favorable tolerability of engineered APCs. The study allows for the characterization of the immunogenicity of engineered APCs in humans. Preliminary results warrant the testing in combination with CPI. Efficacy, safety, and correlative biomarker data will be presented, from pre- and post-therapy biopsies and blood samples. Clinical trial information: NCT04084951.

A phase 1, multicenter, open-label, dose-escalation, safety, pharmacodynamic, pharmacokinetic study of Q702 with a cohort expansion at the RP2D in patients with advanced solid tumors

TPS2673

Background: Immune checkpoint inhibitors directly targeting T cell activation have been successfully used in the treatment of various malignancies, nevertheless, the durable ORRs are low for certain indications. The low ORRs have been attributed to the immune suppressive tumor microenvironment (TME), composed of innate immune suppressive components such as tumor associated macrophages (TAM) and myeloid-derived suppression cells (MDSC). The potential contributions of innate immune modulation to anti-tumor immunity, suggest the need for the novel strategies to elicit a more efficient/robust immune response against the targeted malignant cells. Axl, Mer and CSF1R receptor tyrosine kinases play vital roles in promoting an immune suppressive TME by affecting TAM and MDSC populations and by decreasing antigen presentation on tumor cells. Q702 is a novel Axl/Mer/CSF1R inhibitor, able to modulate the TAM and MDSC population leading to CD8+ T cell activation and to increase antigen presentation of the tumor cells in syngeneic animal models. Q702, as a monotherapy, shows significant tumor growth inhibition in multiple syngeneic tumor models, and demonstrates synergistic effects with anti-PD-1 treatment particularly in high myeloid containing tumor models. Interestingly, intermittent administration of Q702 monotherapy demonstrates a more favorable immune cell population changes, possibly through preventing immune exhaustion secondary to negative feedback with continuous activation. These results suggest that Q702 monotherapy or in combination with existing therapies have a good potential to become a novel treatment strategy for patients with advanced solid tumors. Methods: “A Phase 1, Multicenter, Open-label, Dose-Escalation, Safety, Pharmacodynamic, Pharmacokinetic Study of Q702 with a Cohort Expansion at the RP2D in Patients with Advanced Solid Tumors. (NCT04648254)” is open and recruiting patients at 4 US investigative sites. Patients with histologically or cytologically confirmed advanced or metastatic solid tumors, that have progressed following SOC or for which there is no SOC which confers clinical benefit are being enrolled in this study. The study follows a standard dose escalation. The study will enroll up to 78 patients. The primary endpoint is to establish safety, PK profile and define the recommended phase 2 dose. The secondary and exploratory endpoints include establishing pharmacokinetic/pharmacodynamic relationship, potential biomarkers and preliminary anti-tumor activity. Clinical trial information: NCT04648254.

A phase I open-label study to investigate safety and tolerability, efficacy, pharmacokinetics, pharmacodynamics, and immunogenicity of MT-5111 in patients with HER2-positive tumors

TPS258

Background: Engineered toxin bodies (ETBs) are comprised of a proprietarily engineered form of Shiga-like Toxin A subunit genetically fused to antibody-like binding domains. ETBs work through novel mechanisms of action & are capable of forcing internalization, self-routing through intracellular compartments to the cytosol & inducing potent cell-kill via the enzymatic & permanent inactivation of ribosomes. MT-5111 is a de-immunized ETB targeting HER2+ solid tumors. Its novel mechanism of action, via enzymatic ribosome inactivation, may not be subject to resistance mechanisms that exist for tyrosine kinase inhibitors, antibody-drug conjugates, or antibody modalities. MT-5111 binds an epitope on HER2, distinct from trastuzumab or pertuzumab, that may provide for combination potential with other HER2-targeting agents. MT-5111 is a 55 kilodalton protein & may have improved tumor penetration capability. The objective of this trial will be to determine the safety, tolerability, & maximum tolerated dose (MTD) of MT-5111 in patients (pts) with advanced HER2+ solid tumors. Methods: This Phase 1, first-in-human, open-label, dose escalation & expansion study will evaluate MT-5111 monotherapy in pts with HER2-positive solid tumors. The primary objective is to determine the MTD; secondary objectives include pharmacokinetics, tumor response & immunogenicity. Part 1 consists of MT-5111 dose escalation (0.5, 1.0, 2.0, 3.0, 4.5, 6.75, 10µg/kg/dose) based on a modified 3+3 design (n≤42 pts); Part 2 (dose expansion) will evaluate MT-5111 at the MTD in ≤98 pts. All pts will be administered MT-5111 over 30 min via IV infusion on Days 1, 8, & 15 of each 21-day cycle until disease progression, unacceptable toxicity, death, withdrawal of consent, or another reason for withdrawal. Part 1 will include pts with any HER2+ solid cancers. Part 2 will enroll 3 expansion cohorts: HER2+ breast (BC), HER2+ gastric or gastroesophageal junction adenocarcinomas (collectively referred as gastroesophageal adenocarcinomas [GEA]) & other HER2+ solid cancers. Immunohistochemistry (IHC) status must be 2+ or 3+, regardless of in situ hybridization (ISH) results; if no IHC is available for pts with BC or GEA, ISH criteria per the American Society of Clinical Oncology College of American Pathologists guidelines will be used. In metastatic cases, HER2 positivity must be demonstrated on metastatic lesions. Pts with HER2+ BC should have had ≥2 lines of HER2-directed therapy; pts with HER2+ GEA should have received or been intolerant to trastuzumab. Pts with evaluable disease may be included in Part 1; in Part 2, all pts must have ≥1 measurable lesion per Response Evaluation Criteria in Solid Tumors v1.1. Further details can be found on clinicaltrials.gov (NCT04029922). Enrollment, which began in September 2019, is ongoing. Clinical trial information: NCT04029922.

Bromodomain inhibitors a decade later: a promise unfulfilled?

Over the last decade, bromodomain inhibitors have emerged as a promising class of anticancer drugs. However, the clinical progress of these agents has faced significant obstacles, which precluded their regulatory approval. This editorial will review the challenges and opportunities associated with the development of bromodomain inhibitors.

Abstract CT153: SDX-7320 elicits improvements in tumor-related and metabolic biomarkers: Results of a phase 1 dose-escalation study in patients with advanced refractory or late-stage solid tumors

Background and Rationale: Metabo-oncology is the study of specific tumor types whose growth and/or metastasis is accelerated by metabolic dysfunction, often associated with hyper-adiposity. In this setting the metabolic hormones leptin, adiponectin and insulin are potential mediators. SDX-7320 is a novel methionine aminopeptidase type 2 inhibitor (MetAP2) being developed for use in combination with other anti-cancer agents to treat the metabo-oncology patient population.

Study Design: This first-in-human study used a 3+3 design with dose expansion at the RP2D. Measurements included standard assessments of safety, tolerability, as well as inhibition of MetAP2 in whole blood, plasma levels of protein biomarkers and drug exposure. Tumor response was measured using RECIST v.1.1.

Results: 32 patients with an average of 5.3 prior treatment regimens were dosed. Sub-cutaneous dosing of SDX-7320 began at 1.7 mg/m2 once per week (Q7D, 28 days/cycle) and was escalated to 49 mg/m2. Repeated Q7D administration at 49 mg/m2 resulted in dose-limiting (G3-G4) thrombocytopenia. Expansion at 49 mg/m2 confirmed thrombocytopenia as the dose-limiting toxicity (DLT), reversible upon cessation of dosing. Dose-escalation was re-initiated at 36 mg/m2 every two weeks (Q14D). Repeated dosing at 65 mg/m2 (Q14D) resulted in G3 reversible thrombocytopenia. Expansion at 49 mg/m2 (Q14D) confirmed that this was the maximum tolerated dose (MTD) on a Q14D schedule. No deaths or Grade 5 TEAEs attributable to SDX-7320 were reported. Six patients had a combined total of 9 Grade 3/4 TEAEs considered by the Investigator to be at least possibly SDX-7320-related: thrombocytopenia (4 patients) and single cases of anemia, anorexia, fatigue, QTc prolonged, and vasculitis. Fourteen patients (44% had stable disease &gt2 cycles and three patients had stable disease for ≥6 cycles. Inhibition of MetAP2 in whole blood was 100% at all doses evaluated while the time to reach 100% inhibition was inversely related to dose. When stratified for elevated baseline levels, the following biomarkers declined after initiating SDX-7320 (average of each patient's maximum % change relative to baseline +/- SD): bFGF (-53 +/- 76%), VEGF-C (-35 +/- 39%), and insulin (-55 +/- 30%). Without stratification, leptin levels declined (-51 +/-29%) and levels of adiponectin increased after SDX-7320 (+74 +/- 63% relative to baseline).

Conclusions and Next Steps : SDX-7320 was well-tolerated with prolonged stable disease in an open-label, phase I first-in-human study. Improvements were observed in both tumor-related and metabolic biomarkers. Additional studies of SDX-7320 (in combination with other anti-cancer agents) in patients with solid tumors sensitive to metabolic hormones are scheduled. SDX-7320 is the first novel agent in clinical development to treat the metabo-oncology patient population.

Citation Format: Monica M. Mita, Johanna Bendell, Alain C. Mita, Michael Gordon, Jasgit Sachdev, Bradley J. Carver, James Shanahan, Benjamin Mayes, Kris Awerkamp, David Browning, Neal Salomon, Kimberly Sullivan, Alfred Anderson-Villaluz, Joe Johnson, John S. Petersen, David J. Turnquist, Peter Cornelius. SDX-7320 elicits improvements in tumor-related and metabolic biomarkers: Results of a phase 1 dose-escalation study in patients with advanced refractory or late-stage solid tumors [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr CT153.

Abstract CT146: RGX-104, a first-in-class immunotherapy targeting the liver-X receptor (LXR): Initial results from the phase 1b RGX-104 plus docetaxel combination dose escalation cohorts

Background: RGX-104 is a small-molecule LXR agonist that modulates innate immunity via transcriptional activation of the ApoE gene. Binding of ApoE to its receptor LRP8 robustly inhibits angiogenesis and depletes myeloid derived suppressor cells (MDSC), thereby activating cytotoxic T-lymphocytes. MDSCs are associated with resistance to both checkpoint inhibitors (CPI) and chemotherapy, providing a rationale for combination therapy with RGX-104. We previously reported results of the RGX-104 monotherapy dose escalation for which 26 patients with refractory solid tumors were treated in 5 dose cohorts. On-target AEs included hyperlipidemia and neutropenia. Flow-cytometry demonstrated MDSC depletion with associated T cell activation, which correlated with clinical benefit. A 40% disease control rate (DCR; SD+PR) was observed with a confirmed partial response (PR) by irRC (&gt;79% reduction in index lesions) in a patient with platinum-refractory small cell lung cancer (SCLC). Methods: Here, we present the safety, biomarker and efficacy results of the docetaxel combination arm of the RGX-104 trial. Cohort 1- RGX-104 80 mg BID, and docetaxel at 35 mg/m2 days 1, 8, and 15 of a 28-day cycle; Cohort 2- RGX-104 80 mg BID, 5 days-on/2 days-off (5/2), and docetaxel at 28 mg/m2 on above schedule. Cohort 3- RGX-104 100 mg BID (5/2), and docetaxel as per cohort 2. Results: As of February 7, 2020, 11 patients with refractory solid tumors have been treated in 3 dose escalation cohorts with RGX-104 plus docetaxel. AEs were consistent with the individual toxicity profiles of docetaxel and RGX-104, with neutropenia being the most common AE and dose-limiting in cohort 1. The 5/2 dosing regimen in cohorts 2 and 3 resulted in significantly fewer episodes of neutropenia and no DLTs, while maintaining pharmacodynamic effects including &gt;50% sustained MDSC depletion. A 66% DCR was observed in 9 evaluable patients including 2 patients in cohort 2 with PRs, a CPI-refractory SCCHN patient and a CPI-refractory melanoma patient, who remains on treatment at 36 weeks. A patient with melanoma in Cohort 3 had an initial assessment of SD and continues on study at 14 weeks. Clinical responses were associated with increases in T cell activation markers exceeding that generally observed with RGX-104 alone (up to a 5-fold increase in total CD8 T cells, a 7-fold increase in LAG-3+ CD8 T cells, and a 75-fold induction of serum IFNγ). Conclusion: The safety profile and marked pharmacodynamic and clinical activity of the RGX-104/docetaxel combination in CPI-refractory patients supports further development of this regimen. Consequently, the RGX-104/docetaxel regimen will be evaluated in a Phase 1b/2 expansion cohort in patients with relapsed/refractory ES-SCLC/high grade-neuroendocrine tumors.

Citation Format: Emerson Lim, Erika P. Hamilton, Rebecca Redman, Michael A. Postow, Russell J. Schilder, Monica M. Mita, Alain C. Mita, Bartosz Chmielowski, James Strauss, Angela Jain, Shubham Pant, Olivier Rixe, Tomislav Dragovich, R. Donald Harvey, Igor Puzanov, Kevin B. Kim, Eric K. Rowinsky, Michael Szarek, Foster Gonsalves, Isabel Kurth, Celia Andreu, Robert W. Busby, David Darst, Masoud Tavazoie, Syed Raza, Narayan Lebaka16, Robert Wasserman, Gerald Falchook. RGX-104, a first-in-class immunotherapy targeting the liver-X receptor (LXR): Initial results from the phase 1b RGX-104 plus docetaxel combination dose escalation cohorts [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr CT146.

SGNLVA-001: A phase I open-label dose escalation and expansion study of SGN-LIV1A administered weekly in breast cancer

TPS1104

Background: LIV-1 is a highly prevalent transmembrane protein in breast cancer cells. Ladiratuzumab vedotin (LV), SGN-LIV1A, is an investigational antibody-drug conjugate (ADC) that targets LIV-1 via a humanized IgG1 monoclonal antibody conjugated to monomethyl auristatin E (MMAE) by a protease-cleavable linker. LV is internalized when it binds LIV-1 on cell surfaces and MMAE is released, which binds tubulin and induces apoptosis. LV has been shown to be active and tolerable in metastatic breast cancer (mBC) at a recommended dose of 2.5 mg/kg every 21 days (Modi 2017). More frequent, fractionated dosing has improved the activity and/or safety of other ADCs. Thus, this study is actively accruing subjects with metastatic triple negative breast cancer (mTNBC; estrogen receptor (ER)/progesterone receptor (PR)/human epidermal growth factor receptor 2 (HER2) receptor-negative) and endocrine-resistant ER+ or PR+ (hormone receptor [HR+])/HER2-negative mBC to test weekly dosing of LV (Days 1, 8, and 15 of every 3-week cycle). Methods: This study is enrolling up to 82 subjects (42 HR+/HER2-negative and 40 mTNBC) into dose escalation and dose expansion cohorts (NCT01969643). Eligible subjects are females ≥18 years old with pathologically and radiologically confirmed metastatic HR+/HER2-negative or mTNBC with at least 1 measurable lesion per RECIST v1.1. Subjects with HR+/HER2-negative disease must have received no more than 1 prior line of cytotoxic chemotherapy in the locally advanced (LA)/mBC setting, either as single agent or combination therapy. Subjects with mTNBC must have received 1 prior line of cytotoxic chemotherapy in the LA/mBC setting. Progression within 6 months of completion of neoadjuvant or adjuvant therapy is considered an LA/mBC regimen. Subjects must have adequate organ function, ECOG status of ≤1, and no ≥ Grade 2 peripheral neuropathy. Subjects with brain lesions must have received definitive treatment of the lesions. Prior therapy with MMAE-containing agents is not allowed. Dose escalation follows the modified toxicity probability interval method (Ji 2010). Dose expansion cohorts will provide data about activity and tolerability. Tumor assessments will be conducted every 2 cycles per RECIST v1.1 and all subjects will be followed for safety. Pharmacokinetics and markers of pharmacodynamics will be assessed. Primary safety endpoint is the incidence of adverse events and dose-limiting toxicities. Key efficacy endpoints include confirmed overall response rate, duration of response, and progression-free survival. Clinical trial information: NCT01969643 .

A phase I study of the novel immunotoxin, MT-5111, in subjects (subj) with HER-2 positive tumors: Interim results

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Background: Engineered toxin bodies (ETBs), composed of a Shiga-like Toxin A subunit genetically fused to antibody-like binding domains, can force receptor internalization, self-route through intracellular compartments to the cytosol, and induce potent cell-kill via the enzymatic and permanent inactivation of ribosomes. MT-5111, a de-immunized 55 kD ETB targeting HER2 in solid tumors, binds to an epitope distinct from and non-competitive with trastuzumab and pertuzumab. Methods: The primary objective is to determine the maximum tolerated dose (MTD) of MT-5111 monotherapy in adults with advanced HER2+ solid tumors. Secondary objectives are pharmacokinetics, efficacy, and immunogenicity. Part 1 will identify the MTD via MT-5111 dose escalation (0.5, 1.0, 2.0, 3.0, 4.5, 6.75, 10 µg/kg/dose) according to a modified 3+3 design. Part 2 will further evaluate the safety of MT-5111 at the recommended phase 2 dose (RP2D) in 3 separate cohorts of subjs with a HER2 immunohistochemistry score ≥2 in a metastatic lesion of primary breast, gastroesophageal, or other cancers. All subjs receive MT-5111 as a 30-minute IV infusion on Days 1, 8, and 15 of each 21-day treatment (tx) cycle (C) until disease progression, unacceptable toxicity, death, or withdrawn consent. Details can be found on clinicaltrials.gov (NCT04029922). Results: The first cohort (0.5 µg/kg/dose) enrolled 4 subjs (metastatic breast cancer, n = 2; metastatic cholangiocarcinoma, n = 2). Three subjs were female and the mean age was 69 years (median 65, range 64-78). Subjs received a mean of 5 prior lines of therapy (median 4.5, range 3-8). Three subjs completed C1 of tx without dose-limiting toxicities; 1 subj was inevaluable. Two subjs had progressive disease in C2. A total of 23 AEs occurred in 4 subjs; all were grade (G) 1-2 except one G3 event of hypertension in a subj with a history of hypertension. There were 2 tx-related AEs (G1 chills; G2 aspartate aminotransferase increased in the setting of progressive liver metastases). There was 1 serious, non-tx-related AE (G2 dyspnea) that occurred in the inevaluable subj. No cardiac AEs were noted, nor clinically significant changes in cardiac biomarkers, an important safety parameter given non-human primate toxicity. Conclusions: MT-5111 appears to be well tolerated at the lowest dose with no apparent cardiotoxicity to date. Drug concentrations are expected to be below the level required for in vitro tumor cell killing. Safety and efficacy data from subsequent dose escalation cohorts are expected by May 2020. Clinical trial information: NCT04029922.

CDK 4/6 drug target activation mapping of HR+/HER2- metastatic breast cancer for treatment selection and response prediction

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Background: Despite the fact that a number of CDK 4/6 inhibitors have become FDA approved as the main frontline therapy for HR+/HER2- metastatic breast cancer (MBC), there are no validated predictive markers of response to this class of drugs. Additionally, approximately 30-40% of patients (pts) have little to no response to these agents, with disease progression occurring in weeks to a few months after therapy initiation. We have initiated a clinical trial (NCT03195192) to utilize cutting edge proteomic technologies to map the functional activation of the signaling architecture of tumors taken from HR+/HER2- MBC pts at diagnosis. We plan to correlate these functional phosphoprotein-based signaling patterns with PFS intervals to identify candidate markers associated with response to CDK 4/6 inhibitor therapy. Methods: Pre-treatment diagnostic FFPE biopsy material from 26 individuals enrolled on study were analyzed by an LCM- reverse phase protein array workflow. Quantitative measurements of a focused set of 8 qualifying (pre-hypothesized) protein/phosphoprotein CDK 4/6 kinase pathway biomarkers, total Rb, Rb (S780), total Cyclin D1, Cyclin D1 (S286), total pI6INK, total p27, p27 (T187), FoxM1 (T600) were measured. Results: Baseline tumor tissue was successfully analyzed for 26 pts, 17 (65%) White, 8 (31%) African American, and 1 (4%) Asian; average age 62 (range 36-79); 4 pts (15%) had prior endocrine therapy and 4 (15 %) had chemotherapy in the adjuvant setting. Seven pts remain on study treatment. Unsupervised analysis revealed substantial concordance between a number of the total-phosphoprotein paired biomarkers, with 8/26 (31%) patients having relatively low activation/expression pattern (within the bottom quartile of the data range of the 8 markers) and 6/26 (23%) having relatively high activation/expression pattern within the top quartile of the data range of the 8 markers). Conclusions: Functional CDK 4/6 drug target pathway mapping analysis is possible from the pre-treatment diagnostic FFPE material and revealed sub-populations of patients who had systematically low and high levels of CDK 4/6 kinase substrate proteins and phosphoproteins that indicate overall drug target activity. Correlations of those patterns with PFS outcome data is ongoing with final analysis planned for Summer 2020. Clinical trial information: NCT03195192 .

A phase I dose escalation study evaluating the safety and tolerability of a novel anti-HER2 antibody-drug conjugate (PF-06804103) in patients with HER2-positive solid tumors

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Background: PF-06804103 is an anti-HER2 immunoglobulin G1 antibody-drug conjugate (ADC), comprising an anti-HER2 monoclonal antibody conjugated with a cleavable linker to the cytotoxic agent Aur0101. PF-06804103 demonstrated strong activity in low to high HER2-expressing preclinical tumor models. In this study, the safety and tolerability of PF-06804103 was assessed in patients with advanced breast cancer (BC) or gastric cancer (GC). Methods: This multi-center, open-label, first-in-patient, phase I study (NCT03284723) has two parts: dose escalation (Part 1) and dose expansion (Part 2). In Part 1, groups of adult patients (pts) with HER2+ BC or HER2+ GC, who are resistant or intolerant to standard therapy or for which no standard therapy is available, received PF-06804103 intravenously once every 21 days (Q3W); dosage was escalated per cohort. Primary objectives were to evaluate the safety and tolerability of PF-06804103, characterize its dose-limiting toxicities (DLTs), and determine the recommended phase 2 dose. Response was assessed using RECIST v1.1. Objective response rate (ORR) was calculated for response-evaluable pts with target lesions at baseline and ≥1 post-baseline assessment (including unconfirmed responses). Results: A total of 35 pts (BC: n = 20; GC: n = 15) received PF-06804103 at escalating dose levels (0.15 mg/kg: n = 2; 0.5 mg/kg: n = 2; 1.2 mg/kg: n = 2; 2 mg/kg: n = 4; 3 mg/kg: n = 10; 4 mg/kg: n = 9; 5 mg/kg: n = 6). The median (range) number of prior therapies was 6 (3–18) and 3 (1–6) for BC and GC groups, respectively (all pts had prior HER2-targeted therapy). The 3 most common, drug-related adverse events (any grade) were alopecia (n = 17, 48.6%), fatigue (n = 15, 42.9%), and neuropathy (n = 9, 25.7%). DLTs (mostly grade 3) occurred in 3 pts and included arthralgia, neuropathy, myalgia, fatigue, and osteomuscular pain. Preliminary ORR in the patients treated with doses ≥3mg/kg was 52.4% (11/21). Conclusions: The PF-06804103 ADC demonstrated manageable toxicity and promising anti-tumor activity in this small, heavily pretreated study population. Clinical trial information: NCT03284723 .

Clinical activity of MCLA-128 (zenocutuzumab), trastuzumab, and vinorelbine in HER2 amplified metastatic breast cancer (MBC) patients (pts) who had progressed on anti-HER2 ADCs

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Background: MCLA-128 (zenocutuzumab ), a HER3 pathway inhibitor, is a humanized bispecific full-length IgG1 antibody targeting both HER2 and HER3 with enhanced ADCC activity. The unique Dock & Block mechanism inhibits HER3 from interacting with its ligands and targets HER2 at a different epitope than trastuzumab, blocking HER2/HER3 dimerization and downstream PI3K/AKT/mTOR signaling. In MBC, HER3 overexpression and/or HER3 ligand upregulation are important drivers leading to trastuzumab resistance, indicating a role for MCLA-128. Preclinical activity was seen in HER2+ breast models when MCLA-128 was combined with trastuzumab. Furthermore, single agent MCLA-128 showed consistent antitumor activity in heavily pretreated HER2+ MBC pts. A phase 2, open-label study explored the MCLA-128/trastuzumab plus vinorelbine triplet in an MBC population. Methods: This open-label trial planned for up to 40 evaluable women with HER2+/amplified MBC progressing on up to 5 anti-HER2 lines including trastuzumab, pertuzumab and an anti-HER2 ADC. Pts received MCLA-128 (750 mg, 2h IV), trastuzumab (8 mg/kg loading, then 6 mg/kg) and vinorelbine (25 mg/m², D1 and 8), q3w. A safety run-in of MCLA-128 + trastuzumab ± chemotherapy was performed. Disease control rate (DCR; RECIST 1.1, per investigator), best overall response (BOR), overall response rate (ORR), safety, and PK are evaluated. Data cutoff was 14Nov2019. Results: 28 pts with a median 3 lines (range 2-5) of anti-HER2 therapy (metastatic setting) and 3 (range 1-6) metastatic sites, received a median of 5 (range 1-17) MCLA-128 cycles. Among 26 pts evaluable for efficacy, 20 patients had CR/PR/SD as BOR; DCR was 77% (90%CI: 60-89) with 1 confirmed CR and 4 PRs (2 unconfirmed). Common related AEs (all grades; G3-4) were neutropenia/neutrophil count decrease (61%; 46%), diarrhea (61%; 4%), asthenia/fatigue (46%; 0), nausea (29%; 0). No clinically significant LVEF decline was seen. At the end of cycle 1, mean trough levels of MCLA-128 was 19.1 µg/mL, and mean terminal half-life was 112 h (n = 8-11). Data on the primary endpoint, clinical benefit rate at 24 weeks, and biomarkers will be provided. Conclusions: The triplet MCLA-128-based combination is active in heavily pretreated pts with HER2+/amplified MBC. The regimen is safe and well tolerated with a manageable AE profile mostly related to the chemotherapy component. Clinical trial information: NCT03321981 .

Determination of the recommended phase II dose of birinapant in combination with pembrolizumab: Results from the dose-escalation phase of BPT-201

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Background: Birinapant is a bivalent SMAC mimetic targeting cIAP1. Synergistic effects of combining birinapant with immune checkpoint inhibitors have been demonstrated in preclinical models. Based on these observations, a clinical trial with birinapant and pembrolizumab was initiated (NCT02587962). Methods: Patients ≥18 years with advanced solid tumors without further suitable standard therapeutic options were eligible for inclusion. Birinapant (5.6-22 mg/m2) was administered IV on day 1 and 8 in addition to pembrolizumab 200 mg on day 1 in a 21-day cycle until disease progression using standard 3+3 dose-escalation. The primary objective was to determine the safety and tolerability of the recommended phase 2 dose (RP2D) of birinapant in combination with pembrolizumab. Secondary and exploratory objectives included antitumor activity assessed by RECIST 1.1 and iRECIST, pharmacokinetics and assessment of biomarkers including serum cytokines, cIAP1, PD-L1 expression and tumor infiltrating lymphocytes. Results: Nineteen patients were enrolled at 4 dose levels of 5.6 (n = 3), 11 (n = 3), 17 (n = 6) and 22 (n = 7) mg/m2. Most common tumors were pancreatic (n = 5), colorectal (n = 4), ovarian (n = 3) and sarcoma (n = 3). Median prior therapies were 4 (0-12). The most common AE related to any of the study drugs was rash occurring in 3 patients. Ten patients had 17 SAE's of which only one (stomatitis) was judged related to birinapant. Increased ALT/AST (G3/G2) leading to missed day 8 dose constituted a DLT at 22 mg/m2. Grade 2 lipase increases were seen in 2 patients. No cases of Bell’s palsy were detected. ORR by RECIST 1.1 was 5.6% (n = 1) in 18 evaluable patients. The responding patient had microsatellite stable colorectal carcinoma (MSS-CRC)) and remains on therapy 13+ months after first dose. By iRECIST, ORR was 11.1%. CBR (PR+SD) by RECIST was 22.2%. The exposure to birinapant generally increased with dose. The RP2D was determined to be 22 mg/m2. Conclusions: Birinapant and pembrolizumab is a safe and tolerable combination that has shown encouraging signals of efficacy. A phase 2 study evaluating efficacy of this combination in MSS-CRC is ongoing. Clinical trial information: NCT02587962.

A phase Ib dose-escalation and expansion study of the oral MEK inhibitor pimasertib and PI3K/MTOR inhibitor voxtalisib in patients with advanced solid tumours

BACKGROUND

This phase Ib study evaluated the safety, maximum-tolerated dose (MTD), pharmacokinetics, pharmacodynamics, and preliminary efficacy of pimasertib (MSC1936369B), a MEK1/2 inhibitor, in combination with voxtalisib (SAR245409), a pan-PI3K and mTORC1/mTORC2 inhibitor, in patients with advanced solid tumours.

METHODS

This study included a dose escalation and expansion in patients with select tumour types and alterations in the MAPK or PI3K pathways. A 3 + 3 design was used to determine MTD. Patients were evaluated for adverse events and tumour response.

RESULTS

146 patients were treated, including 63 in dose escalation and 83 in expansion. The MTD was pimasertib 90 mg and voxtalisib 70 mg daily. Based on the safety profile, the recommended phase 2 dose (RP2D) was pimasertib 60 mg and voxtalisib 70 mg. The most frequent treatment-emergent adverse events (TEAEs) were diarrhoea (75%), fatigue (57%), and nausea (50%). Responses included a complete response in one patient (1%), partial response in five (5%), and stable disease in 51 (46%). At the RP2D, 74 patients required dose interruption (73%), 20 required dose reduction (20%), and 26 discontinued treatment due to TEAEs (26%).

CONCLUSIONS

The combination of pimasertib and voxtalisib showed poor long-term tolerability and limited anti-tumour activity in patients with advanced solid tumours.

A Phase II Study of Pelareorep (REOLYSIN®) in Combination with Gemcitabine for Patients with Advanced Pancreatic Adenocarcinoma

Pancreatic ductal adenocarcinoma (PDAC) has a poor prognosis, with 1 and 5-year survival rates of ~18% and 7% respectively. FOLFIRINOX or gemcitabine in combination with nab-paclitaxel are standard treatment options for metastatic disease. However, both regimens are more toxic than gemcitabine alone. Pelareorep (REOLYSIN®), a proprietary isolate of reovirus Type 3 Dearing, has shown antitumor activity in clinical and preclinical models. In addition to direct cytotoxic effects, pelareorep can trigger antitumor immune responses. Due to the high frequency of RAS mutations in PDAC, we hypothesized that pelareorep would promote selective reovirus replication in pancreatic tumors and enhance the anticancer activity of gemcitabine. Chemotherapy-naïve patients with advanced PDAC were eligible for the study. The primary objective was Clinical Benefit Rate (complete response (CR) + partial response (PR) + stable disease (SD) ≥ 12 weeks) and secondary objectives include overall survival (OS), toxicity, and pharmacodynamics (PD) analysis. The study enrolled 34 patients; results included one partial response, 23 stable disease, and 5 progressive disease. The median OS was 10.2 months, with a 1- and 2-year survival rate of 45% and 24%, respectively. The treatment was well tolerated with manageable nonhematological toxicities. PD analysis revealed reovirus replication within pancreatic tumor and associated apoptosis. Upregulation of immune checkpoint marker PD-L1 suggests future consideration of combining oncolytic virus therapy with anti-PD-L1 inhibitors. We conclude that pelareorep complements single agent gemcitabine in PDAC.

Phase 1 Study of Monotherapy with KHK2866, an Anti-Heparin-Binding Epidermal Growth Factor-Like Growth Factor Monoclonal Antibody, in Patients with Advanced Cancer

BACKGROUND

KHK2866 is a recombinant, humanized, non-fucosylated, monoclonal antibody directed at heparin-binding epidermal growth factor-like growth factor (HB-EGF).

OBJECTIVE

To determine the safety, tolerability, maximum tolerated dose (MTD), pharmacokinetics, pharmacodynamics, potential immunogenicity, and preliminary clinical efficacy of KHK2866 monotherapy in patients with advanced and refractory cancer in a first-in-human, phase 1 study.

MATERIALS AND METHODS

Using a standard 3 + 3 dose-escalation design, 20 patients received KHK2866 (0.3, 1, and 3 mg/kg) intravenously once weekly. Two additional patients received 0.1 mg/kg in a cohort which was subsequently added following protocol amendment.

RESULTS

The first three patients enrolled experienced grade 2 hypersensitivity (acute infusion reactions) after the first dose of KHK2866. After prophylactic treatment with an H1-blocker and corticosteroids in subsequently recruited patients, two grade 2 hypersensitivity reactions were observed in the remaining 19 patients. Grade 2/3 neurotoxicity appeared to be dose-limiting at 3 mg/kg in the original dose-escalation cohorts (n = 2), at 1 mg/kg in the MTD dose expansion cohort (n = 1), and at 0.1 mg/kg (n = 1). Neurotoxicity was manifested as complex partial seizure activity, aphasia, and confusion after first-dose administration. Pharmacokinetic exposure to KHK2866 increased proportionally to dose. Mean elimination half-life was 71.9-118 h over the dose range from 0.3 to 3 mg/kg. All KHK2866 doses decreased serum free HB-EGF levels, generally below the lower limit of quantification.

CONCLUSIONS

The study was terminated because of neuropsychiatric toxicity. The only predictive factor for neuropsychiatric toxicity was administration of KHK2866. These effects were reversible, but were not predictable. Their etiology is not presently understood. [Study registered at ClinicalTrials.gov #NCT0179291].

Phase 1 safety, pharmacokinetic and pharmacodynamic study of the cyclin-dependent kinase inhibitor dinaciclib administered every three weeks in patients with advanced malignancies

Background:

Dinaciclib is a potent inhibitor of cell cycle and transcriptional cyclin-dependent kinases. This Phase 1 study evaluated the safety, tolerability and pharmacokinetics of various dosing schedules of dinaciclib in advanced solid tumour patients and assessed pharmacodynamic and preliminary anti-tumour activity.

Methods:

In part 1, patients were enrolled in escalating cohorts of 2-h infusions administered once every 3 weeks, utilising an accelerated titration design until a recommended phase 2 dose (RP2D) was defined. In part 2, 8- and 24-h infusions were evaluated. Pharmacokinetic parameters were determined for all schedules. Pharmacodynamic effects were assessed with an ex vivo stimulated lymphocyte proliferation assay performed in whole blood.

Effects of dinaciclib on retinoblastoma (Rb) phosphorylation and other CDK targets were evaluated in skin and tumour biopsies. In addition to tumour size, metabolic response was evaluated by 18F-fluorodeoxyglucose-positron emission tomography.

Results:

Sixty-one patients were enrolled to parts 1 and 2. The RP2Ds were 50, 7.4 and 10.4 mg m⁻² as 2- 8- and 24-hour infusions, respectively. Dose-limiting toxicities included pancytopenia, neutropenic fever, elevated transaminases, hyperuricemia and hypotension. Pharmacokinetics demonstrated rapid distribution and a short plasma half-life. Dinaciclib suppressed proliferation of stimulated lymphocytes. In skin and tumour biopsies, dinaciclib reduced Rb phosphorylation at CDK2 phospho-sites and modulated expression of cyclin D1 and p53, suggestive of CDK9 inhibition. Although there were no RECIST responses, eight patients had prolonged stable disease and received between 6 and 30 cycles. Early metabolic responses occurred.

Conclusions:

Dinaciclib is tolerable at doses demonstrating target engagement in surrogate and tumour tissue.

Abstract 137: FT-1518, a new generation selective and potent mTORC1 and mTORC2 inhibitor: an in vitro and in vivo profile

Mammalian target of rapamycin (mTOR) is a clinically validated target in the treatment of cancer. mTOR forms two distinct multiprotein complexes, mTORC1 and mTORC2 which regulate cell growth, metabolism, proliferation, and survival. Rapamycin analogues target only the mTORC1 complex but do not affect the mTORC2 complex, which is an important driver for cancer cell growth and survival. The new generation of “Selective” mTOR inhibitors, blocking both mTORC1 and mTORC2 signaling might increase the efficacy and safety while expanding the therapeutic potential of these anticancer agents. Herein we describe FT-1518, a low nanomolar potent, kinase and PI3K sub family selective mTOR inhibitor. FT-1518 not only exhibited high oral bioavailability in preclinical species but has demonstrated excellent microsomal stability with no inhibitory activity towards undesired CYPs. FT-1518 showed high sustained tumor exposure and target Inhibition in a single oral dose xenograft model. FT-1518 depicted very good growth inhibitory activity across a large panel of hematologic and solid tumor cell lines with most activities falling into low nanomolar range. mTOR kinase inhibition in cells, by FT-1518, resulted in more potent inhibition of the mTOR pathway biomarkers (mTORC 1 & 2 biomarkers [pAkt(S473) and pS6(S240/244) or p70 S6K), no inhibition of PI3K biomarker [pAkt(T308)], and improved anti-proliferative activity as compared with rapamycin. FT-1518 exhibited dose-dependent and higher tumor growth inhibition (TGI) in multiple solid tumor xenografts compared with rapalogs and is poised to enter the clinic with a favorable toxicology profile.

Citation Format: Alain C. Mita, Monica M. Mita, Anthony D. William, Khalid Pasha, Chandra Siddamadappa, Kevin Zikaras, Felix T. Garzon. FT-1518, a new generation selective and potent mTORC1 and mTORC2 inhibitor: an in vitro and in vivo profile [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 137. doi:10.1158/1538-7445.AM2017-137

A phase Ia study of CC-90003, a selective extracellular signal-regulated kinase (ERK) inhibitor, in patients with relapsed or refractory BRAF or RAS-mutant tumors

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Background: CC-90003 is an irreversible inhibitor of ERK 1/2 with potent anti-proliferative activity in KRAS and BRAF mutant tumor models. We conducted a first-in-human study of CC-90003 in patients with RAS or BRAF mutant tumors. Methods: Patients received escalating doses of oral CC-90003 on a 21/28 day cycle. Standard safety (adverse events, chemistry/hematology, physical findings, ECGs and cardiac ECHO/MUGA scans) and PK parameters were assessed. Response was assessed per RECIST 1.1. A proprietary ELISA-based assay measured ERK levels unbound to CC-90003 in peripheral blood mononuclear cells. Results: Nineteen patients (median age: 60 yrs) harboring KRAS (n = 15), NRAS (n = 1), or BRAF (n = 3) mutant tumors received CC-90003 doses from 20 to 160 mg /day. The MTD was 120 mg based on the occurrence of Grade 3 transaminase elevations (n = 2) and hypertension (n = 1) observed at 160 mg (the NTD). Patients completed a median of 2 cycles (range: 1 to 5). AEs (mostly Grade 1 or 2) reported in ≥ 3 patients included constitutional (asthenia, fatigue), gastrointestinal (anorexia, nausea/vomiting, diarrhea), hepatic (transaminase elevations) and neurologic (dizziness, gait disturbance, paresthesias) toxicities. Grade 1-3 neurotoxicity was observed primarily at doses from 80 to 160 mg/day and resolved with dose reduction/interruption. PK parameters were highly variable, with AUC and Cmax increasing overall, with increasing dose. CC-90003 accumulation was observed after multiple doses. There were no objective responses. Levels of free ERK were reduced by ≥80% compared to baseline by C1D8 at doses ≥ 80 mg/day. Conclusions: ERK inhibition may be an attractive target for the management of mutant RAS or BRAF-driven tumors, however proof-of-concept demonstration for CC-90003 was limited by a lack of objective responses, an unfavorable PK profile and unanticipated neurotoxicity. Clinical trial information: NCT02313012.

Statins and pancreatic cancer

Pancreatic cancer remains among the most lethal cancers, despite ongoing advances in treatment for all stages of the disease. Disease prevention represents another opportunity to improve patient outcome, with metabolic syndrome and its components, such as diabetes, obesity and dyslipidemia, having been recognized as modifiable risk factors for pancreatic cancer. In addition, statins have been shown to potentially reduce pancreatic cancer risk and to improve survival in patients with a combination of metabolic syndrome and pancreatic cancer. Furthermore, preclinical studies have demonstrated that statins exhibit antitumor effects in pancreatic cancer cell lines in vitro and animal models in vivo, in addition to delaying the progression of pancreatic intraepithelial neoplasia to pancreatic ductal adenocarcinoma (PDAC) and inhibiting PDAC formation in conditional K-Ras mutant mice. The mechanisms by which statins produce anticancer effects remain poorly understood, although appear to involve inhibition of the mevalonate/cholesterol synthesis pathway, thus blocking the synthesis of intermediates important for prenylation and activation of the Ras/mitogen-activated protein kinase 1 signaling pathway. Furthermore, statins have been identified to modulate the phosphoinositide 3-kinase/Akt serine/threonine kinase 1 and inflammation signaling pathways, and to alter the expression of genes involved in lipid metabolism, which are important for PDAC growth and proliferation. In addition, statins have been demonstrated to exhibit further antitumor mechanisms in a number of other cancer types, which are beyond the scope of the present review. In the present review, current evidence highlighting the potential of statins as chemopreventive agents in pancreatic cancer is presented, and the antitumor mechanisms of statins elucidated thus far in this disease are discussed.

Phase I Study of PSMA-Targeted Docetaxel-Containing Nanoparticle BIND-014 in Patients with Advanced Solid Tumors

PURPOSE

First-in-human phase I trial to determine the safety, pharmacokinetics, and antitumor activity of BIND-014, a novel, tumor prostate-specific membrane antigen (PSMA)-targeted nanoparticle, containing docetaxel.

EXPERIMENTAL DESIGN

Patients with advanced solid tumors received BIND-014 every three weeks (n = 28) or weekly (n = 27), with dose levels ranging from 3.5 to 75 mg/m(2) and 15 to 45 mg/m(2), respectively.

RESULTS

BIND-014 was generally well tolerated, with no unexpected toxicities. The most common drug-related toxicities (>20% of patients) on either schedule included neutropenia, fatigue, anemia, alopecia, and diarrhea. BIND-014 demonstrated a dose-linear pharmacokinetic profile, distinct from docetaxel, with prolonged persistence of docetaxel-encapsulated circulating nanoparticles. Of the 52 patients evaluable for response, one had a complete response (cervical cancer on the every three week schedule) and five had partial responses (ampullary adenocarcinoma, non-small cell lung, and prostate cancers on the every-three-week schedule, and breast and gastroesophageal cancers on the weekly schedule). Responses were noted in both PSMA-detectable and -undetectable tumors.

CONCLUSIONS

BIND-014 was generally well tolerated, with predictable and manageable toxicity and a unique pharmacokinetic profile compared with conventional docetaxel. Clinical activity was noted in multiple tumor types. The recommended phase II dose of BIND-014 is 60 mg/m(2) every three weeks or 40 mg/m(2) weekly. Clin Cancer Res; 22(13); 3157-63. ©2016 AACR.

Clinical development of reovirus for cancer therapy: An oncolytic virus with immune-mediated antitumor activity

Reovirus is a double-stranded RNA virus with demonstrated oncolysis or preferential replication in cancer cells. The oncolytic properties of reovirus appear to be dependent, in part, on activated Ras signaling. In addition, Ras-transformation promotes reovirus oncolysis by affecting several steps of the viral life cycle. Reovirus-mediated immune responses can present barriers to tumor targeting, serve protective functions against reovirus systemic toxicity, and contribute to therapeutic efficacy through antitumor immune-mediated effects via innate and adaptive responses. Preclinical studies have demonstrated the broad anticancer activity of wild-type, unmodified type 3 Dearing strain reovirus (Reolysin^®) across a spectrum of malignancies. The development of reovirus as an anticancer agent and available clinical data reported from 22 clinical trials will be reviewed.

Abstract B144: Evaluation of total and encapsulated drug pharmacokinetics for BIND-014 (docetaxel nanoparticles for injectable suspension) in a phase 1 study

Background: BIND-014 is a novel, prostate-specific membrane antigen (PSMA) targeted AccurinTM (polymeric nanoparticle) containing docetaxel. PSMA is expressed on prostate cancer cells and on vasculature of many solid tumors. In a phase 1 study in patients with solid tumors BIND-014 was generally well-tolerated and displayed anti-tumor activity across a range of tumor types. Evaluation of total drug pharmacokinetics (PK) for BIND-014 in this study demonstrated differentiated plasma profiles compared to docetaxel, which is likely attributable to the vascular retention of the nanoparticle. Total docetaxel quantitation does not distinguish between docetaxel that remains encapsulated or that is released from the nanoparticle. Here we describe a method for separation of encapsulated docetaxel and characterization of the PK of total and encapsulated BIND-014 docetaxel in the phase 1 study.

Material and Methods: PK evaluation of BIND-014 was performed in 28 patients on Day 1 of a 21-day cycle (Q3W) over a dose range of 3.5 to 75 mg/m2. On Cycle 1, Day 1, blood was collected at pre-dose and at 30 minutes, 1, 2, 4, 6, 8, 24, 36, and 48 hours post-dose. A solid phase separation method in which released docetaxel binds to the matrix was developed for quantitation of encapsulated docetaxel. Encapsulated and total docetaxel were measured by LCMS. Peak concentration (Cmax), percent encapsulated, minimum concentration (Cmin), time to peak concentration (Tmax), area under the concentration-time curve (AUC), half-life (t1/2), clearance (CL) and volume of distribution (Vd) were determined for each patient using encapsulated and total plasma concentration data.

Results: Plasma concentrations of BIND-014 persisted for at least 48 hours at the higher dose levels. Clearance was independent of the administered dose, indicating a linear dose-concentration relationship following a single intravenous administration. Evaluation of encapsulated docetaxel plasma concentrations at all dose levels and all timepoints studied demonstrated mean values between 91% and 98% of total docetaxel, indicating that most circulating docetaxel was encapsulated in nanoparticles.

Conclusions: The total concentration of BIND-014 found in circulation compared to the concentration of encapsulated docetaxel was similar, indicating that the majority of docetaxel likely remains contained within the polymeric particle over the time course evaluated, and that the differentiated PK properties of BIND-014 compared to docetaxel, including greater Cmax and AUC and lower Vd and CL, are likely due largely to retention of encapsulated docetaxel within the vascular compartment. These results are consistent with the favorable tolerability profile of BIND-014 despite the markedly higher plasma concentrations for total BIND-014 compared to docetaxel at similar doses.

Citation Format: Jason M. Summa, Daniel D. Von Hoff, Jasgit C. Sachdev, Monica M. Mita, Patricia M. LoRusso, Peter D. Eisenberg, Howard A. Burris, Lowell L. Hart, Hagop Youssoufian, Donald M. Parsons, Susan C. Low. Evaluation of total and encapsulated drug pharmacokinetics for BIND-014 (docetaxel nanoparticles for injectable suspension) in a phase 1 study. [abstract]. In: Proceedings of the AACR-NCI-EORTC International Conference: Molecular Targets and Cancer Therapeutics; 2015 Nov 5-9; Boston, MA. Philadelphia (PA): AACR; Mol Cancer Ther 2015;14(12 Suppl 2):Abstract nr B144.

Activated ras signaling pathways and reovirus oncolysis: an update on the mechanism of preferential reovirus replication in cancer cells

The development of wild-type, unmodified Type 3 Dearing strain reovirus as an anticancer agent has currently expanded to 32 clinical trials (both completed and ongoing) involving reovirus in the treatment of cancer. It has been more than 30 years since the potential of reovirus as an anticancer agent was first identified in studies that demonstrated the preferential replication of reovirus in transformed cell lines but not in normal cells. Later investigations have revealed the involvement of activated Ras signaling pathways (both upstream and downstream) and key steps of the reovirus infectious cycle in promoting preferential replication in cancer cells with reovirus-induced cancer cell death occurring through necrotic, apoptotic, and autophagic pathways. There is increasing evidence that reovirus-induced antitumor immunity involving both innate and adaptive responses also contributes to therapeutic efficacy though this discussion is beyond the scope of this article. Here, we review our current understanding of the mechanism of oncolysis contributing to the broad anticancer activity of reovirus. Further understanding of reovirus oncolysis is critical in enhancing the clinical development and efficacy of reovirus.

Abstract A68: Activity of the TORC 1/2 kinase inhibitor, CC-223, in hormone receptor positive (HR+) breast cancer cell lines and patients (pts) with genetically characterized HR+ breast cancer in a Phase I clinical trial

Introduction: PIK3CA and PTEN are among the top five most frequently mutated genes in breast cancer. Activating mutation of PIK3CA or loss of function mutation in PTEN leads to constitutive activation of AKT and mTOR driving multiple downstream metabolic and proliferative pathways important to oncogenesis. There is also cross-talk between the PI3K/AKT/mTOR pathway and ER signaling and activation of the PI3K/AKT/mTOR pathway is associated with resistance to endocrine therapy. CC-223 is a potent and selective ATP-competitive mTOR kinase inhibitor, targeting both TORC1 and TORC2 complexes.

Results: Pre-clinically, CC-223 potently inhibits the growth of breast cancer cell lines with GI50 values below 1 uM in 38 of 43 lines. Luminal-derived cell lines are more sensitive to CC-223 than basal-derived lines. Within the luminal subset, ER+, HER2+, PIK3CA mutant, or wild-type TP53 cell lines are more sensitive to CC-223; PTEN loss is not associated with increased CC-223 sensitivity. During the dose escalation part of the phase I clinical trial, 3 pts with breast cancer were enrolled. One pt with HR+/Her2- breast cancer had a durable PR (31 weeks). An expansion cohort of HR+/Her2- breast cancer enrolled 17 pts at a CC-223 dose of 45 mg QD in 28-day cycles and 13 pts were evaluable for tumor response. Deep sequencing of tumors for multiple cancer-related genes was performed. The most common (&gt; 20%) related adverse events (all grades) reported in the breast cancer cohort were nausea, stomatitis, fatigue, anorexia, diarrhea, vomiting, hyperglycemia, rash, and thrombocytopenia. Exposure-dependent TORC1 (p4EBP1) and TORC2 (pAKT) inhibition was observed in blood cells; analysis of paired tumor biopsies is ongoing. Reduction in glucose uptake (&gt; 25% decrease in SUV) on PET imaging at day 15 was observed in 4 of 8 patients with PET imaging data currently available. Three pts demonstrated RECIST PR in target lesions (one categorized as PD due to a new bone lesion); PIK3CA mutations were present in all 3 subjects. Of the two additional pts with PIK3CA mutations, one had SD &gt; 6 months. The one PIK3CA mutated subject with PD at first restaging had a concurrent p53 mutation. Additional genetic abnormalities in mTOR and related pathways in subjects with target lesion PR involved PTEN, Rictor, and IGFR1 genes. Six subjects had SD after 2 cycles, with minor target lesion regression (0 to -30%) in 5 of 6, and with SD &gt; 24 weeks in 1 of 6.

Conclusion: The safety profile of CC-223 is typical for drugs targeting the mTOR pathway. Preclinical and clinical data support the activity of CC-223 in HR+ positive breast cancer, particularly in tumors with PIK3CA mutations.

Breast Cancer Accrual: Cedars-Sinai (Mita): 4; SCRIL (Arkenau): 4; IGR (Varga): 4; SCRI (Bendell): 3 (all Part A); Moffitt (Mahipal): 2; UCSF (Munster): 1; JSOM (Paz-Ares): 1; ICR (DeLord): 1.

Citation Information: Mol Cancer Ther 2013;12(11 Suppl):A68.

Citation Format: Monica M. Mita, Hendrik-Tobias Arkenau, Johanna C. Bendell, Pamela N. Munster, Amit Mahipal, Jean-Pierre Delord, Luis G. Paz-Ares, Jean-Charles Soria, Shuichan Xu, Tam Tran, Tao Shi, Xiaoling Wu, Rajesh Chopra, Kristen Hege, Andrea Varga. Activity of the TORC 1/2 kinase inhibitor, CC-223, in hormone receptor positive (HR+) breast cancer cell lines and patients (pts) with genetically characterized HR+ breast cancer in a Phase I clinical trial. [abstract]. In: Proceedings of the AACR-NCI-EORTC International Conference: Molecular Targets and Cancer Therapeutics; 2013 Oct 19-23; Boston, MA. Philadelphia (PA): AACR; Mol Cancer Ther 2013;12(11 Suppl):Abstract nr A68.