First-in-Human Study with Preclinical Data of BCL-2/BCL-xL Inhibitor Pelcitoclax in Locally Advanced or Metastatic Solid Tumors

PURPOSE

B-cell lymphoma-extra-large (BCL-xL) regulates apoptosis and is an attractive anticancer therapeutic target. However, BCL-xL inhibition also kills mature platelets, hampering clinical development. Using an innovative prodrug strategy, we have developed pelcitoclax (APG-1252), a potent, dual BCL-2 and BCL-xL inhibitor. Aims of this study were to characterize the antitumor activity and safety of pelcitoclax and explore its underlying mechanisms of action (MOA).

PATIENTS AND METHODS

Cell line-derived xenograft and patient-derived xenograft (PDX) models were tested to evaluate antitumor activity and elucidate MOA. Subjects (N = 50) with metastatic small-cell lung cancer and other solid tumors received intravenous pelcitoclax once or twice weekly. Primary outcome measures were safety and tolerability; preliminary efficacy (responses every 2 cycles per RECIST version 1.1) represented a secondary endpoint.

RESULTS

Pelcitoclax exhibited strong BAX/BAK‒dependent and caspase-mediated antiproliferative and apoptogenic activity in various cancer cell lines. Consistent with cell-based apoptogenic activity, pelcitoclax disrupted BCL-xL:BIM and BCL-xL:PUMA complexes in lung and gastric cancer PDX models. Levels of BCL-xL complexes correlated with tumor growth inhibition by pelcitoclax. Combined with taxanes, pelcitoclax enhanced antitumor activity by downregulating antiapoptotic protein myeloid cell leukemia-1 (MCL-1). Importantly, pelcitoclax was well tolerated and demonstrated preliminary therapeutic efficacy, with overall response and disease control rates of 6.5% and 30.4%, respectively. Most common treatment-related adverse events included transaminase elevations and reduced platelets that were less frequent with a once-weekly schedule.

CONCLUSIONS

Our data demonstrate that pelcitoclax has antitumor activity and is well tolerated, supporting its further clinical development for human solid tumors, particularly combined with agents that downregulate MCL-1.

Preclinical Characterization and Phase I Trial Results of INBRX-109, A Third-Generation, Recombinant, Humanized, Death Receptor 5 Agonist Antibody, in Chondrosarcoma

PURPOSE

Patients with unresectable/metastatic chondrosarcoma have poor prognoses; conventional chondrosarcoma is associated with a median progression-free survival (PFS) of <4 months after first-line chemotherapy. No standard targeted therapies are available. We present the preclinical characterization of INBRX-109, a third-generation death receptor 5 (DR5) agonist, and clinical findings from a phase I trial of INBRX-109 in unresectable/metastatic chondrosarcoma (NCT03715933).

PATIENTS AND METHODS

INBRX-109 was first characterized preclinically as a DR5 agonist, with binding specificity and hepatotoxicity evaluated in vitro and antitumor activity evaluated both in vitro and in vivo. INBRX-109 (3 mg/kg every 3 weeks) was then evaluated in a phase I study of solid tumors, which included a cohort with any subtype of chondrosarcoma and a cohort with IDH1/IDH2-mutant conventional chondrosarcoma. The primary endpoint was safety. Efficacy was an exploratory endpoint, with measures including objective response, disease control rate, and PFS.

RESULTS

In preclinical studies, INBRX-109 led to antitumor activity in vitro and in patient-derived xenograft models, with minimal hepatotoxicity. In the phase I study, INBRX-109 was well tolerated and demonstrated antitumor activity in unresectable/metastatic chondrosarcoma. INBRX-109 led to a disease control rate of 87.1% [27/31; durable clinical benefit, 40.7% (11/27)], including two partial responses, and median PFS of 7.6 months. Most treatment-related adverse events, including liver-related events, were low grade (grade ≥3 events in chondrosarcoma cohorts, 5.7%).

CONCLUSIONS

INBRX-109 demonstrated encouraging antitumor activity with a favorable safety profile in patients with unresectable/metastatic chondrosarcoma. A randomized, placebo-controlled, phase II trial (ChonDRAgon, NCT04950075) will further evaluate INBRX-109 in conventional chondrosarcoma.

A phase 1/2 study of REGN7075 (EGFRxCD28 costimulatory bispecific antibody) in combination with cemiplimab (anti–PD-1) in patients with advanced solid tumors: Trial-in-progress update

TPS277

Background: There is a need to develop novel immunotherapeutic approaches to enhance responses to immune checkpoint blockade. REGN7075 is a human costimulatory bispecific antibody designed to bridge epidermal growth factor receptor (EGFR)-expressing tumor cells with CD28-positive T cells to support further T-cell activation by endogenous tumor antigens. Methods: This is an open-label, Phase 1/2, first-in-human study evaluating the safety, tolerability, pharmacokinetics, and preliminary anti-tumor activity of REGN7075 (EGFRxCD28) alone and in combination with cemiplimab (anti-programmed cell death [PD]-1) in patients with advanced solid tumors (NCT04626635). This study includes a dose-escalation (Bayesian optimal interval design; Part 1) and a dose-expansion phase (Part 2). Patients must have a protocol-defined advanced solid tumor, have an Eastern Cooperative Oncology Group performance status of 0 or 1, and be naive to anti–PD-1/anti–PD-ligand(L)1 therapy in the dose-expansion phase. In Part 1, heavily pre-treated patients with advanced solid tumors receive a lead-in of REGN7075 monotherapy every week for 3 weeks followed by combination therapy with cemiplimab 350 mg every 3 weeks. Planned dose levels (DLs) of REGN7075 are 0.03, 0.1, 0.3, 1, 3, 10, 30, 100, 300, and 900mg. Once the recommended Phase 2 dose is determined in Part 1, five tumor-specific expansion cohorts will be opened in Part 2: colorectal cancer (microsatellite stable [MSS-CRC]), non-small cell lung cancer (NSCLC, PD-L1 ≥50%), triple-negative breast cancer, cutaneous squamous cell carcinoma, and head and neck squamous cell carcinoma (PD-L1 combined positive score ≥1). Patients with MSS-CRC with RAS or BRAF wild type mutations must have received anti-EGFR therapy or anti-vascular endothelial growth factor (VEGF therapy). Primary endpoints are safety and tolerability of REGN7075 alone or in combination with cemiplimab for Part 1, and objective response rate per Response Evaluation Criteria in Solid Tumors version 1.1 for Part 2. For Part 2, a secondary objective is to assess the effect of REGN7075 on patient-reported outcomes as measured by several validated instruments including the European Organisation for Research and Treatment of Cancer Quality of Life Questionnaire (EORTC QLQ-C30), and EORTC QLQ-CR29 (CRC patients only). Approximately 400 patients will be enrolled in this phase 1/2 study, including ~80 patients in Part 1 and ~320 patients in Part 2 (including ~70 in the CRC cohort). As of September 13, 2022, 30 patients were treated in the dose-escalation phase, up to the 300 mg DL for REGN7075 in combination with cemiplimab. This study is ongoing and currently open to enrollment. Clinical trial information: NCT04626635 .

Abstract CT041: Monotherapy dose escalation of davoceticept (ALPN-202), a conditional CD28 costimulator and dual checkpoint inhibitor, in advanced malignancies (NEON-1)

Background: Strong preclinical rationale has emerged for combining checkpoint inhibition (CPI) with T cell costimulatory agonists, particularly CD28, a critical T cell costimulatory molecule recognized as a key target of checkpoint inhibition. Davoceticept (ALPN-202) is a variant CD80 vIgD-Fc fusion that mediates PD-L1-dependent CD28 costimulation and inhibits the PD-L1 and CTLA-4 checkpoints. It has demonstrated superiority to CPI-only therapies in vitro and in in vivo tumor models, while demonstrating favorable preclinical safety.

Methods: This is a first-in-human, cohort-based, open-label dose escalation and expansion study of davoceticept in adults with advanced solid tumors or lymphoma (NCT04186637). Patients with cancers refractory to standard therapies (including approved CPIs), or cancers without available standard or curative therapy are eligible. After two single-subject cohorts, a standard 3+3 dose escalation has been implemented with two dose schedules in parallel, Q1W and Q3W. Objectives include evaluation of safety and tolerability, PK, PD and preliminary anticancer activity. Disease assessments are evaluated by RECIST v1.1 for solid tumors. A prior presentation discussed the initial first 5 cohorts of the Q1W schedule; this presentation includes the remainder of dose escalation, including the Q3W schedule.

Results: As of December 2021, 57 adults with various advanced solid tumors, most commonly colorectal and pancreatic, received davoceticept monotherapy, which was well tolerated through 10 mg/kg Q3W. Davoceticept demonstrated dose-dependent PK and target saturation. Immune-related adverse events (irAEs), occurred in 20/54 (35%), mostly involving the skin, endocrine and gastrointestinal systems. All but 2 of the irAE were grade 1-2. One DLT, chronic active gastritis grade 3, was observed at 3 mg/kg Q3W. Among 47 evaluable, unconfirmed partial responses were observed in 2 (colorectal carcinoma and renal cell carcinoma). Stable disease, defined as first scan at 6 weeks, was observed in 22; 9 (41%) demonstrated tumor volume reduction, 2 (9%) demonstrated SD for &gt; 6 months, and 1 has an ongoing SD at 8 months. At doses above 0.1 mg/kg, pharmacodynamic ex vivo analyses demonstrated agonistic engagement of CD28 on T cells, and flow cytometry demonstrated increased circulating activated (ICOS+) and proliferating (Ki-67+) T cells, increased central memory T cells, and reduced regulatory T cells, consistent with active CD28 engagement.

Conclusion: First-in-human dose escalation with davoceticept was well tolerated at doses capable of engaging CD28 costimulation in vivo, with early signs of activity in a largely treatment-refractory, non-immunogenic tumor population. These findings suggest a potential additive benefit of combining CD28 agonism with checkpoint inhibition and identify biologically active dose regimens of davoceticept for subsequent single agent development, and demonstrate further rationale for combination development. Expansion cohorts, including cutaneous melanoma and PD-L1-positive cancers, are planned.

Citation Format: Michael Millward, Justin C. Moser, Diwakar Davar, Mark Voskoboynik, Nehal J. Lakhani, Rachel E. Sanborn, Jaspreet Grewal, Ajita Narayan, Mario Sznol, Keren Schieber, Hany Zayed, Christine Dela Cruz, Graciela Perez, Stanford L. Peng. Monotherapy dose escalation of davoceticept (ALPN-202), a conditional CD28 costimulator and dual checkpoint inhibitor, in advanced malignancies (NEON-1) [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr CT041.

Phase 1 study of SGN-ALPV, a novel, investigational vedotin antibody–drug conjugate directed to ALPP/ALPPL2 in advanced solid tumors (SGNALPV-001, trial in progress)

TPS3159

Background: Alkaline phosphatase placental (ALPP) and ALPP-like 2 (ALPPL2) are proteins with 98% sequence similarity that are highly expressed in ovarian, endometrial, gastric, and testicular cancers. Restricted normal tissue expression and efficient lysosomal trafficking of ALPP and ALPPL2 highlight their potential as anticancer targets. SGN-ALPV is a novel investigational vedotin antibody–drug conjugate composed of a humanized anti-ALPP/ALPPL2 monoclonal antibody, a protease-cleavable linker, and the microtubule disrupting agent monomethyl auristatin E (MMAE). The proposed mechanism of action of SGN-ALPV is binding to ALPP/ALPPL2 on the cell surface, where it is internalized and trafficked to the lysosome. Lysosomal proteases cleave the linker to release MMAE into the cytoplasm, where it binds and disrupts the microtubule network, causing cell cycle arrest and apoptosis. Additional mechanisms of action of SGN-ALPV include immunogenic cell death and apoptosis of neighboring cells via the bystander effect. Promising preclinical data support the evaluation of SGN-ALPV in a clinical trial. Methods: SGNALPV-001 (NCT05229900) is a phase 1, open-label, multicenter study designed to evaluate the safety, tolerability, pharmacokinetics (PK), and antitumor activity of SGN-ALPV in patients (pts) with select advanced solid tumors. This study consists of 3 parts: dose escalation (Part A), dose and schedule optimization (Part B), and dose-expansion in disease-specific cohorts and a biology cohort (Part C). Adult pts (≥18 years) with confirmed ovarian, endometrial, non-small cell lung, gastric, cervical cancer, or testicular germ-cell tumors, relapsed or refractory to approved therapies, with measurable disease per RECIST v1.1 and an ECOG PS 0–1 are eligible. Primary endpoints include incidence of adverse events, laboratory abnormalities, dose-limiting toxicities, and cumulative safety. Secondary endpoints include estimates of antidrug antibodies, PK parameters, objective response rate, duration of response, progression-free survival, and overall survival. Exploratory endpoints are pharmacodynamic and biomarker measurements. Safety and antitumor activity endpoints will be summarized using descriptive statistics. Enrollment for Part A is ongoing in sites in North America and Europe. Enrollment for Parts B and C will be opened upon completion of Part A. Clinical trial information: NCT05229900.

A phase 1, first-in-human study of IK-930, an oral TEAD inhibitor targeting the Hippo pathway in subjects with advanced solid tumors

TPS3168

Background: The transcriptional enhanced associate domain (TEAD) family of proteins are key transcription factors in the Hippo signaling pathway and play a critical role in cell proliferation, migration, angiogenesis, and apoptosis. Published literature demonstrates that approximately 10% of all solid tumors present with a dysregulated Hippo pathway and subsequent constitutive activation of TEAD, which drives gene expression involved in cell growth and pro-survival signaling. Deficiencies in neurofibromin 2 (NF2), a key regulator of the Hippo pathway, can be found in over 40% of cases of malignant pleural mesothelioma (MPM). NF2 deficiency also occurs at high incidence in meningiomas, cholangiocarcinomas, thymoma, and schwannoma. Gene fusions in in Yes1 associated transcriptional regulator (YAP1) or WW domain containing transcription regulator 1 (TAZ/WWTR1) are also indicative of high TEAD activation and can be seen in solid tumors including epithelioid hemangioendothelioma (EHE) where >90% of cases are associated with TAZ-CAMTA1 gene fusion and the other 10% of cases have YAP1/TFE3 gene fusion. IK-930 is a novel, selective, small molecule inhibitor of TEAD that prevents palmitate binding and thereby disrupts aberrant TEAD-dependent transcription. In preclinical models, IK-930 demonstrates antitumor activity in mouse xenograft models with Hippo pathway genetic alterations. IK-930 is under clinical investigation as an oral agent in patients with advanced solid tumors. Methods: This is a phase 1, first-in-human, open-label, multicenter dose escalation and dose expansion study to evaluate the safety and tolerability of IK-930 as monotherapy, and to determine the recommended phase 2 dose (RP2D) and/or maximum tolerated dose (MTD) using the Bayesian Optimal Interval Design (BOIN). Eligible participants in dose escalation include adult patients with advanced or metastatic solid tumors for whom there is no available therapy known to confer clinical benefit. Patients will receive escalating doses of IK-930 starting at 25mg daily. IK-930 will be administered initially in a 28-day cycle and will progress to a 21-day cycle when evaluated as safe and well-tolerated. A dose expansion phase will follow with four genetically defined cohorts of solid tumors, including: NF2-deficient MPM (Cohort 1), other NF2-deficient solid tumors agnostic to tumor type (Cohort 2), EHE with TAZ-CAMTA1 or YAP1-TFE3 gene fusions (Cohort3), and solid tumors with YAP1/TAZ gene fusions agnostic to tumor type (Cohort 4). Primary endpoints include evaluation of dose-limiting toxicities and treatment-emergent adverse events and determination of RP2D and/or MTD. Secondary objectives include evaluation of preliminary antitumor activity by RECIST 1.1 and pharmacokinetic (PK) parameters. The study began in January 2022 and is currently enrolling. Clinical trial information: NCT05228015.

Phase 1b study of GS-3583, a novel FLT3 agonist Fc fusion protein, in patients with advanced solid tumors

2566

Background: We have previously shown that systemic administration of GS-3583, a Fms-like tyrosine kinase 3 (FLT3) agonist Fc fusion protein leads to expansion of conventional dendritic cells (cDC), both subtype 1 (cDC1) and subtype 2 (cDC2), in the periphery of healthy volunteers (Rajakumaraswamy N, et al. J Clin Oncol. 2021;39[suppl_15]:2559.). This mechanism may increase cDC in the tumor microenvironment and promote T cell mediated antitumor activity in patients with solid tumors. Methods: This ongoing, Phase 1b, open label study is investigating the safety, tolerability, immunogenicity, pharmacokinetics, and pharmacodynamics of escalating multiple doses of GS-3583 monotherapy in adult patients with advanced solid tumors using a standard 3 + 3 design. GS-3583 was administered intravenously on Days 1 and 15 of Cycle 1 and on Day 1 of each subsequent 28-day cycle for up to 52 weeks or until progressive disease or unacceptable toxicity. Dose-limiting toxicity (DLT) was evaluated during the first 28 days of GS-3583 therapy at each dose level. Results: At the time of the Dec 3, 2021 data cut-off, 9 patients have enrolled in 3 dose escalation cohorts. Median (range) age was 71 (44-79); 4 (44%) patients were male. Tumor types were pancreatic (n=3), ovarian (n=4), and rectal (n=2). To date, no DLTs or discontinuation due to adverse events (AE) have been observed. Three patients had Grade ≥3 AEs which were also recorded as serious AEs, none of which were considered related to GS-3583. Dose dependent increase in GS-3583 exposure was observed in the evaluated dose range 2 to 12 mg with target-mediated drug disposition appearing to be saturated at doses above Dose Level 2. GS-3583 accumulation was observed at higher dose levels. GS-3583 treatment resulted in expansions of cDC1 and cDC2 at all 3 doses (Table); a dose-dependent trend in the magnitude and the durability of cDC expansion was observed. At the highest dose evaluated, GS-3583 produced ≥100-fold expansion of both cDC1 and cDC2 at multiple time points. Dose escalation on the study is still ongoing. Conclusions: GS-3583 was safe and well tolerated and induced dose-dependent expansion of cDCs in the periphery in patients with advanced solid tumors up to doses of 12 mg. These findings support further dose escalation and clinical development of GS-3583 in combination with agents that would stimulate the expanded cDCs to produce anti-tumor responses. Clinical trial information: NCT04747470. [Table: see text]

Efficacy proof-of-concept from a phase 1 study of a novel therapeutic peptide, ST101, targeting the oncogenic transcription factor C/EBPβ in patients with refractory solid tumors

3014

Background: The oncogenic transcription factor CCAAT/enhancer-binding protein β (C/EBPβ) promotes tumor survival and proliferation and inhibits differentiation. ST101 is a peptide antagonist of C/EBPβ, with anti-tumor activity in prostate cancer (PC), glioblastoma (GBM), breast cancer (BC), melanoma, and other pre-clinical models. Methods: This phase 1 study enrolled patients (pts) with refractory solid tumors with varying histologies. The primary objective was to evaluate safety/tolerability of ST101 and to determine the recommended phase 2 dose (RP2D). Secondary and exploratory objectives included pharmacokinetics (PK), preliminary efficacy (RECIST 1.1), and pharmacodynamic (PD) evaluation. The study used a 3+3 dose-escalation design, with once-weekly IV infusion dosing of ST101 at 0.5, 1, 2, 4, 6, 9 mg/kg or a flat dose of 500 mg. Results: Enrollment in phase 1 was completed in November 2021 with a total of 25 pts with multi-metastatic disease that were refractory to standard therapy. As of February 15, 2022, five pts remain on study with a median treatment duration of 27 weeks’ (16-77). There were no DLTs, dose modifications, or serious adverse events (SAEs) related to ST101. The only AEs of note were G1-2 histaminergic infusion-related reactions (IRRs), largely pruritis and urticaria, managed with antihistamines, montelukast, and interruption/slowing of infusion. IRRs affected 93% of pts on the first dose at ≥4mg/kg and led to prolongation of infusion time. Intensity and frequency of IRRs decrease with repeat dosing. No other AEs were consistently reported. There was no evidence of accumulation upon continued exposure of ST101 and no anti-drug antibodies. Tumor immunohistochemistry showed dose-proportionate staining for ST101 and decreased tumor proliferation in several pts represented by decreased Ki67 expression. Population PK analysis supported flat dosing in phase 2. Five pts continue on treatment with one confirmed partial response in a patient with cutaneous melanoma lasting >42 weeks and four pts with ongoing stable disease. Conclusions: ST101 demonstrated safety at all doses explored and evidence of efficacy across dose levels, particularly higher doses and in pts with melanoma. PK and PD support a dose relationship for efficacy and selection of 500 mg as the RP2D. Pts are now enrolling in phase 2 cohorts to assess response in cutaneous melanoma, GBM, castrate-resistant PC, and HR+ BC. Clinical trial information: NCT04478279. [Table: see text]

Phase 1a/b open-label study of IK-175, an oral AHR inhibitor, alone and in combination with nivolumab in patients with locally advanced or metastatic solid tumors and urothelial carcinoma

TPS3169

Background: Aryl Hydrocarbon Receptor (AHR) is a ligand-activated transcription factor that regulates the activity of multiple innate and adaptive immune cells. Kynurenine, generated from tryptophan by IDO1 and TDO2, is a ligand that binds AHR and leads to a net immunosuppressive tumor microenvironment, making AHR an attractive therapeutic target in multiple cancer types. IK-175 is a selective, small molecule inhibitor of AHR being developed as an oral agent. In preclinical mouse tumor models, IK-175 demonstrates antitumor activity as a single agent or in combination with checkpoint inhibitors. AHR immunohistochemistry (IHC) tumor microarray analysis across 15 different tumor types revealed that bladder cancer has the highest level of AHR protein expression and nuclear localization indicative of ligand-bound and active AHR signaling. Therefore, nuclear AHR in urothelial carcinoma tumors is being investigated for potential predictive clinical benefit with IK-175. Methods: This is a first-in-human, phase 1a/b, open-label, multicenter, dose-escalation and expansion study of IK-175 as a single agent and in combination with nivolumab. The primary objectives are to determine the maximum tolerated dose (MTD) and/or maximum administered dose (MAD), identify the recommended phase 2 dose (RP2D), and evaluate the safety and tolerability of IK-175 alone and in combination with nivolumab. Secondary objectives are to evaluate the pharmacokinetics (PK) of IK-175, evaluate pharmacodynamic (PD) immune effects, and assess preliminary antitumor activity. Key exploratory objectives are to evaluate the PD effects on peripheral immune cells and target gene expression, to assess candidate baseline biomarkers, and correlative analyses of tumor AHR nuclear localization with clinical response. The study is exploring tumor AHR nuclear localization by IHC as a predictive biomarker in patients with urothelial carcinoma. A minimum of 10 patients with a positive AHR nuclear localization test (cutoff for positive AHR is 65% tumor cells positive for 2+/3+ nuclear AHR by a validated IHC assay) will be enrolled in the combination arm. IK-175 is administered daily in 21 or 28 day-cycles as a single agent, and in combination with nivolumab (480 mg q4w on Day 1 of every cycle), in adult patients with advanced solid tumors (dose escalation) and urothelial carcinoma (dose expansion). Key eligibility criteria include patients with histologically confirmed solid tumors (including urothelial carcinoma) who have locally recurrent or metastatic disease that have progressed on or following all standard of care therapies deemed appropriate by the treating physician including prior checkpoint inhibitors. Estimated enrollment is 93 patients; the study began in January 2020 and is ongoing. Clinical trial information: NCT04200963.

Phase 1 study of SGN-B7H4V, a novel, investigational vedotin antibody–drug conjugate directed to B7-H4, in patients with advanced solid tumors (SGNB7H4V-001, trial in progress)

TPS3155

Background: B7-H4, a B7 immune checkpoint ligand, is expressed at low levels in normal tissue and negatively regulates T-cell function by inhibiting T-cell proliferation and cytokine production. B7-H4 expression is elevated in solid tumors, including breast, ovarian, and endometrial cancers. Targeting B7-H4–expressing tumor cells may relieve B7-H4–mediated T-cell inhibition. SGN-B7H4V is a novel, investigational vedotin antibody–drug conjugate directed to B7-H4 with proposed mechanisms of action including monomethyl auristatin E (MMAE)-directed cytotoxicity, bystander effect, antibody-dependent cellular cytotoxicity, and antibody-dependent cellular phagocytosis. SGN-B7H4V elicited antitumor activity in cell line-derived xenograft models of triple-negative breast cancer (TNBC) and patient-derived xenograft models of TNBC and ovarian cancer (Gray et al 2021), providing a rationale to evaluate SGN-B7H4V in patients (pts) with advanced solid tumors. Methods: SGNB7H4V-001 (NCT05194072) is a phase 1, first-in-human, multicenter, open-label trial evaluating the safety, tolerability, pharmacokinetics (PK), and antitumor activity of SGN-B7H4V in pts with advanced solid tumors. This study includes 3 parts: dose escalation (Part A), dose and schedule optimization (Part B), and dose expansion in disease-specific cohorts and a biology cohort (Part C). Adult pts (≥18 years) with histologically/cytologically confirmed locally advanced unresectable or metastatic solid tumors including high-grade serous epithelial ovarian cancer, primary peritoneal cancer, fallopian tube cancer, human epidermal growth factor receptor 2-negative and hormone receptor-positive breast cancer, TNBC, endometrial carcinoma, squamous non-small cell lung cancer, cholangiocarcinoma, or gallbladder carcinoma, are eligible. Pts must have ECOG PS 0–1 and relapsed/refractory disease or be intolerant to standard-of-care therapies. Prior treatment with an MMAE-containing agent or a B7-H4–targeted agent is not permitted. Primary endpoints include the rate of adverse events, laboratory abnormalities, dose-limiting toxicities, and cumulative dose-level safety. Secondary endpoints are objective response rate (ORR), complete response rate, duration of objective response (DOR), progression-free survival (PFS), overall survival (OS), PK, and incidence of antidrug antibodies. Exploratory endpoints include pharmacodynamic (PD) analyses, PD and PK exposure measurements, B7-H4 characterization on malignant cells, and biomarker analyses. Safety and antitumor activity endpoints will be assessed using descriptive statistics. ORR will be analyzed by tumor type and dose. DOR, PFS, and OS will be estimated using the Kaplan–Meier method. Enrollment for Part A is ongoing in North America and is planned in Europe. Clinical trial information: NCT05194072.

Dose escalation of davoceticept, a conditional CD28 costimulator and dual checkpoint inhibitor, in advanced malignancies (NEON-1)

2560

Background: Strong preclinical rationale supports combining checkpoint inhibition (CPI) with T cell costimulatory agonists, particularly of CD28, a critical T cell costimulatory molecule recognized as a key target of checkpoint inhibition. Davoceticept (ALPN-202) is a variant CD80 vIgD-Fc fusion that mediates PD-L1-dependent CD28 costimulation and inhibits the PD-L1 and CTLA-4 checkpoints. It has demonstrated superiority to CPI-only therapies in multiple tumor models in vitro and in vivo, while demonstrating favorable preclinical safety. Methods: This is an open-label dose escalation and expansion study of davoceticept in adults with advanced solid tumors or lymphoma (NCT04186637). Patients with cancers refractory to standard therapies including CPIs, or cancers without available standard or curative therapy are eligible. Dose escalation studied two dose schedules, Q1W and Q3W. Objectives include safety and tolerability, PK, PD and preliminary anticancer activity. Disease assessments are evaluated by RECIST v1.1 for solid tumors. A prior presentation discussed the first 5 cohorts of the Q1W schedule; this presentation updates progress in dose escalation, including the Q3W schedule. Results: As of January 2022, 57 adults with various advanced solid tumors, most commonly colorectal and pancreatic, received davoceticept monotherapy, which was well tolerated through 10 mg/kg Q3W. It demonstrated dose-dependent PK and target saturation. Immune-related AEs (irAEs), occurred in 20/57 (35%), mostly of the skin, endocrine and gastrointestinal systems. All but 4 of the irAE were grade 1-2. Only one DLT (chronic active gastritis grade 3) was observed at 3 mg/kg Q3W. Among 48 evaluable patients, unconfirmed partial responses were observed in 2 (colorectal and renal cell). Stable disease, at first scan at 6 weeks, was observed in 23 (48%); 11 (23%) demonstrated volume reduction (target lesion ΔSLD < 0%); 2 had SD for > 6 months, and 1 had an ongoing SD at 8 months. At doses above 0.1 mg/kg, ex vivo analyses showed agonism of T cell CD28, and flow cytometry demonstrated increased circulating activated (ICOS+), proliferating (Ki-67+) and central memory T cells, and reduced regulatory T cells, consistent with CD28 engagement. Conclusions: Davoceticept was well tolerated at doses capable of engaging CD28 costimulation in vivo, with early signs of activity and peripheral immune activation in a largely treatment-refractory, non-immunogenic tumor population. These findings support an additive benefit of combining CD28 agonism with checkpoint inhibition and identify biologically active dose regimens of davoceticept for subsequent single agent development, and provide further rationale for combination study. Expansion cohorts, including cutaneous melanoma and PD-L1-positive cancers, are planned, and a combination study with pembrolizumab has initiated (NCT04920383). Clinical trial information: NCT04186637.

Davoceticept (ALPN-202), a PD-L1-dependent CD28 costimulator and dual checkpoint inhibitor, in combination with pembrolizumab in patients with advanced malignancies (NEON-2)

TPS2683

Background: Despite successes with checkpoint inhibition (CPI) in a wide range of tumors, most demonstrate primary or acquired resistance, warranting better therapeutic strategies. PD-1 is now recognized to effect much of its benefit by disinhibiting CD28 signaling – a mechanism expected to require intra-tumoral engagement of CD28 by its ligands CD80/CD86. Davoceticept (ALPN-202), a variant CD80 vIgD-Fc fusion protein, was engineered to provide tumor localizing PD-L1-dependent CD28 agonism, while inhibiting PD-L1 and CTLA-4. Davoceticept has demonstrated superiority to CPI-only therapies in both in vitro and in vivo tumor models, while also demonstrating additional benefit in combination with targeted PD-1 axis blockade (Lewis et al. (2019) J Immunother Cancer 7(S1): P467). The benefit appeared at least additive in models of poorly immunogenic tumors, suggesting the possibility of meaningful clinical benefit where CPI therapeutic efficacy is limited, such as noninflamed tumors. Single agent safety and tolerability of davoceticept has been demonstrated along with pharmacodynamic evidence of CD28 engagement with immune checkpoint inhibition (Moser et al. (2021) J Clin Oncol 39(s15): 2547). Methods: NEON-2 is an open-label dose escalation and expansion study of davoceticept combined with pembrolizumab in adults with advanced solid tumors or lymphoma that was initiated in June 2021 (NCT04920383). Eligibility includes tumors where single agent PD-(L)1 antagonists are SOC, are refractory or resistant to standard therapies (including approved CPIs), or have no standard or curative therapy. The study employs a standard 3+3 dose escalation design with two schedules, Q1W and Q3W of davoceticept. Pembrolizumab is given per label at 400 mg IV Q6W. Objectives include evaluation of safety and tolerability, identification of the recommended phase 2 dose(s) (RP2D), PK, PD, exploratory predictive biomarker analysis (i.e., PD-L1, CD28, CD80 and CD86 expression, as well as immunophenotyping of immune cell populations on treatment) and preliminary anticancer activity of davoceticept in combination with pembrolizumab. Disease assessments are evaluated by RECIST v1.1 for solid tumors or by Lugano Classification for lymphoma. Efficacy endpoints include ORR, duration of response and disease control rate. Once the RP2D combination is identified, tumor-specific expansion cohorts of ̃ 30- 35 patients will be performed, including histologies that have not been demonstrated to be CPI responsive, as well as those where CPIs are approved SOC. The 0.1 mg/kg cohorts have been completed without DLT. Enrollment to the 0.3 mg/kg cohorts began in September 2021. Clinical trial information: NCT04920383.

ARTISTRY-3: Effect of nemvaleukin alfa with a less frequent IV dosing schedule as monotherapy and in combination with pembrolizumab and impact on the tumor microenvironment (TME) in patients (pts) with advanced solid tumors

TPS2684

Background: Nemvaleukin alfa (nemvaleukin, ALKS 4230) is a novel engineered cytokine that selectively binds the intermediate-affinity interleukin-2 (IL-2) receptor, preferentially activating and expanding antitumor CD8+ T cells and NK effector cells, with minimal effect on regulatory T cells. Nemvaleukin was designed to leverage antitumor effects of the IL-2 pathway while limiting typical IL-2‒associated toxicity. In ARTISTRY-1, the recommended phase 2 dose (RP2D) for nemvaleukin monotherapy of 6 µg/kg IV on days 1 to 5 of a 21-day cycle elicited durable and deep responses in pts with advanced melanoma and renal cell carcinoma (Boni et al. ASCO 2021:abstr 2513). Responses with nemvaleukin plus pembrolizumab were also observed in platinum-resistant ovarian, breast, cervical, gastrointestinal, and genitourinary cancers. ARTISTRY-3 will investigate the effects of nemvaleukin as monotherapy and in combination with pembrolizumab on the TME in pts with advanced solid tumors, and in an additional cohort (Cohort 2), to further assess a less frequent IV dosing schedule for nemvaleukin. Methods: The phase 1/2, open-label ARTISTRY-3 (NCT04592653) study will enroll adults (≥18 years) with select advanced solid tumors, ≥1 accessible lesion for biopsy, ≥1 target lesion (per RECIST v1.1), ECOG PS of 0 or 1, estimated life expectancy of ≥3 months, adequate hematologic reserve, and adequate hepatic and renal function. Primary objectives: to evaluate effects of nemvaleukin monotherapy on the TME (Cohort 1) and to determine RP2D for less frequent dosing schedule (Cohort 2). Additional objectives are to evaluate: efficacy, safety, immunogenicity, and pharmacokinetics of nemvaleukin monotherapy; effects of nemvaleukin plus pembrolizumab on the TME; and correlative biomarkers of nemvaleukin as monotherapy and combination. Following the protocol amendment, additional pts enrolled in Cohort 1 will receive lead-in monotherapy at a dose selected based on results from Cohort 2, and pre- and on-treatment biopsies will be collected for TME assessments. Subsequent cycles will be administered in combination with pembrolizumab, and a biopsy may be collected at cycle 4 or 5. Tumor types eligible for Cohort 2 are selected based on activity observed in the ARTISTRY-1 study. A quantitative system pharmacology model was applied to identify a less frequent schedule for nemvaleukin monotherapy and combination. Cohort 2 will initially assess safety and tolerability of nemvaleukin at 1 dose per 21-day cycle. Two doses per 21-day cycle may be implemented to achieve optimal PK/PD parameters. Bayesian optimal interval design methodology with open enrollment will be applied to facilitate dose escalation decisions. Clinical trial information: NCT04592653.

Dual checkpoint targeting of B7-H3 and PD-1 with enoblituzumab and pembrolizumab in advanced solid tumors: interim results from a multicenter phase I/II trial

BACKGROUND

Availability of checkpoint inhibitors has created a paradigm shift in the management of patients with solid tumors. Despite this, most patients do not respond to immunotherapy, and there is considerable interest in developing combination therapies to improve response rates and outcomes. B7-H3 (CD276) is a member of the B7 family of cell surface molecules and provides an alternative immune checkpoint molecule to therapeutically target alone or in combination with programmed cell death-1 (PD-1)-targeted therapies. Enoblituzumab, an investigational anti-B7-H3 humanized monoclonal antibody, incorporates an immunoglobulin G1 fragment crystallizable (Fc) domain that enhances Fcγ receptor-mediated antibody-dependent cellular cytotoxicity. Coordinated engagement of innate and adaptive immunity by targeting distinct members of the B7 family (B7-H3 and PD-1) is hypothesized to provide greater antitumor activity than either agent alone.

METHODS

In this phase I/II study, patients received intravenous enoblituzumab (3-15 mg/kg) weekly plus intravenous pembrolizumab (2 mg/kg) every 3 weeks during dose-escalation and cohort expansion. Expansion cohorts included non-small cell lung cancer (NSCLC; checkpoint inhibitor [CPI]-naïve and post-CPI, programmed death-ligand 1 [PD-L1] <1%), head and neck squamous cell carcinoma (HNSCC; CPI-naïve), urothelial cancer (post-CPI), and melanoma (post-CPI). Disease was assessed using Response Evaluation Criteria in Solid Tumors version 1.1 after 6 weeks and every 9 weeks thereafter. Safety and pharmacokinetic data were provided for all enrolled patients; efficacy data focused on HNSCC and NSCLC cohorts.

RESULTS

Overall, 133 patients were enrolled and received ≥1 dose of study treatment. The maximum tolerated dose of enoblituzumab with pembrolizumab at 2 mg/kg was not reached. Intravenous enoblituzumab (15 mg/kg) every 3 weeks plus pembrolizumab (2 mg/kg) every 3 weeks was recommended for phase II evaluation. Treatment-related adverse events occurred in 116 patients (87.2%) and were grade ≥3 in 28.6%. One treatment-related death occurred (pneumonitis). Objective responses occurred in 6 of 18 (33.3% [95% CI 13.3 to 59.0]) patients with CPI-naïve HNSCC and in 5 of 14 (35.7% [95% CI 12.8 to 64.9]) patients with CPI-naïve NSCLC.

CONCLUSIONS

Checkpoint targeting with enoblituzumab and pembrolizumab demonstrated acceptable safety and antitumor activity in patients with CPI-naïve HNSCC and NSCLC.

TRIAL REGISTRATION NUMBER

NCT02475213.

Abstract OT2-01-01: Phase 1 study of ST101, a first-in-class peptide antagonist of CCAAT/enhancer-binding protein β (C/EBPβ), in patients with advanced solid tumors, with a phase 2 expansion in patients with hormone receptor positive breast cancer (HR+ BC)

Background: CCAAT/Enhancer Binding Protein Beta (C/EBPβ) is a transcription factor that is active during embryofetal development but held in an inactive state in most mature cells. C/EBPβ is upregulated or overactivated in multiple cancers, where it inversely correlates with disease prognosis. In breast cancer, C/EBPβ drives the expression of factors that promote tumor survival, proliferation and inhibit differentiation. ST101 is a cell-penetrating all D amino acid peptide antagonist of C/EBPβ. ST101 exposure inhibits C/EBPβ target gene expression, leading to selective tumor cell death in multiple human cancer cell lines, including hormone receptor positive breast cancer (HR+ BC) and triple negative breast cancer (TNBC), without impacting normal cell viability. In vivo, ST101 displays rapid uptake into multiple organs, the ability to cross the blood-brain barrier, and a long plasma half-life due to its resistance to proteolytic degradation. Potent ST101 anti-tumor activity, demonstrated by dose-dependent inhibition of tumor growth in subcutaneous HR+ and orthotopic TNBC xenograft models in vivo, supported advancing ST101 into clinical development.Trial design: This phase 1-2 study uses a standard 3+3 design with dose doubling for the first 4 dose levels then 50% escalations thereafter. The recommended phase 2 dose will be used in 4 expansion cohorts in specific tumor types, including HR+ BC. Patients receive intravenous ST101 once weekly.Eligibility criteria: The dose-escalation phase is enrolling patients ≥18 years of age with advanced, unresectable metastatic solid tumors refractory to or intolerant of other therapeutic options. In expansion, patients with HR+ BC must have progressed after 1-3 prior hormone-based therapies. Previous treatment with CDK 4/6 inhibitor, mTOR inhibitor, or chemotherapy is allowed as monotherapy or in combination. Specific aims: The primary objective of phase 1 is to evaluate safety and tolerability of ST101. Secondary objectives include the recommendation of a dose and regimen of ST101 for further evaluation, analysis of pharmacokinetics, assessment of several pharmacodynamic measures, and to assess preliminary efficacy. Statistical design: The recommended phase 2 dose will be used in a 15-30 patient HR+ BC expansion cohort, with a Simon 2-stage design, which requires one response to expand the cohort to 30 patients. Up to 120 patients are planned in a total of four expansion cohorts, which should be enrolling by Q3 2021.Accrual: We began recruitment in August 2020. Enrollment is ongoing, and by July 2021, 18 patients were recruited in five dose-escalation cohorts up to 6 mg/kg; a 6th cohort (9 mg/kg) is ongoing. Dose escalation should be complete by Sept 2021, and the phase 2 portion in the HR+ BC cohort will be underway (n=15-30). Please contact rob.michel@bexonclinical.com if you have a specific interest in this trial.

Citation Format: Alice S Bexon, Hendrik-Tobias Arkenau, Jeff Evans, Gerald S Falchook, Stefan N Symeonides, Meredith A McKean, Elisa Fontana, Manojkumar Bupath, Alistair McLaren, Sreenivasa Chandana, Tze-en Ding, Emerson A Lim, Jim Rotolo, Gina Capiaux, Rob Michel, Stephen Kaesshaefer, Nehal J Lakhani. Phase 1 study of ST101, a first-in-class peptide antagonist of CCAAT/enhancer-binding protein β (C/EBPβ), in patients with advanced solid tumors, with a phase 2 expansion in patients with hormone receptor positive breast cancer (HR+ BC) [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 OT2-01-01.

Abstract P06-03: ST101, a peptide targeting oncogenic transcription factor C/EBPβ: initial safety, efficacy, pharmacokinetic (PK) and pharmacodynamic (PD) data from an ongoing phase 1 dose escalation study in patients with advanced, metastatic solid tumors

Introduction: The oncogenic transcription factor CCAAT/enhancer-binding protein β (C/EBPβ) is normally active in embryofetal development, but inactive and suppressed in mature cells. Upregulation or activation of C/EBPβ in cancer promotes tumor survival and proliferation while inhibiting its differentiation. ST101 is a peptide antagonist of C/EBPβ, with anti-tumor activity in glioblastoma (GBM), breast cancer (BC), prostate cancer (PC), melanoma, and other models. ST101 penetrates the blood-brain barrier, as demonstrated in a mouse model and biodistribution studies. We have also demonstrated the tumor-specificity of ST101 in numerous in vitro cell lines. Methods: We conducted the phase 1 portion of a phase 1-2 study in patients with refractory solid tumors. The primary objective was to evaluate safety and tolerability of ST101. Secondary and exploratory objectives included PK, preliminary efficacy, and PD from serial biopsies. The study used a 3+3 design, dosing ST101 IV at 0.5, 1, 2, 4, 6, and 8 (now modified to 9) mg/kg weekly (QW). Phase 2 will include four cohorts of patients with specific cancers: HR+ breast cancer, cutaneous melanoma, GBM, and castrate-resistant PC at the recommended phase 2 dose (RP2D). Results: As of July 2021, 18 pts were enrolled, and the last cohort (9 mg/kg) is underway. Patients received a median of 6 weeks’ treatment (range 2 – 45). There were no dose-limiting toxicities, dose modifications, or SAEs related to ST101. The only adverse events (AEs) of note were G1-2 histaminergic infusion-related reactions (IRRs), largely pruritis and urticaria, managed with antihistamines, montelukast, and interruption/slowing of infusion. IRRs affected 100% pts on the 1st dose of ST101 at 4mg/kg. Montelukast was added to the antihistamine premedication regimen in the 6 mg/kg cohort, which attenuated IRRs. 66% of patients in the 6 mg/kg experienced an IRR on the first dose. The intensity and frequency of IRRs decreased with repeat dosing across all cohorts. No other AEs were consistently reported. PK was dose-proportionate, with continued exposure. There was no evidence of accumulation, and no anti-drug antibodies were detected. Tumor immunohistochemistry showed dose-proportionate staining for ST101 and a trend of decreased Ki67 staining (proliferation marker) after ST101 exposure. One confirmed partial response in a patient with metastatic cutaneous melanoma refractory to standard therapy is still on study, and 3 pts with varied histologies have had stable disease lasting 18-45 weeks (1 ongoing). Conclusions: ST101 demonstrated safety at all doses explored and evidence of efficacy across dose levels, particularly higher doses. PK and PD support a dose relationship for efficacy, and we will select a QW RP2D for the phase 2 expansion cohorts by September 2021.

Citation Format: Nehal J. Lakhani, Hendrik-Tobias Arkenau, Stefan N. Symeonides, Jeffry Evans, Meredith A. McKean, Elisa Fontana, Manojkumar Bupath, Alistair McLaren, Sreenivasa Chandana, Tze-en Ding, Emerson A. Lim, Jim Rotolo, Gina Capiaux, Rob Michel, Stephen Kaesshaefer, Alice S. Bexon, Gerald S. Falchook. ST101, a peptide targeting oncogenic transcription factor C/EBPβ: initial safety, efficacy, pharmacokinetic (PK) and pharmacodynamic (PD) data from an ongoing phase 1 dose escalation study in patients with advanced, metastatic solid tumors [abstract]. In: Proceedings of the AACR-NCI-EORTC Virtual International Conference on Molecular Targets and Cancer Therapeutics; 2021 Oct 7-10. Philadelphia (PA): AACR; Mol Cancer Ther 2021;20(12 Suppl):Abstract nr P06-03.

Evorpacept alone and in combination with pembrolizumab or trastuzumab in patients with advanced solid tumours (ASPEN-01): a first-in-human, open-label, multicentre, phase 1 dose-escalation and dose-expansion study

BACKGROUND

Both innate and adaptive immune responses are important components of anticancer immunity. The CD47-SIRPα interaction could represent an important pathway used by tumour cells to evade immune surveillance. We aimed to evaluate the safety, pharmacokinetics, pharmacodynamics, and anticancer activity of evorpacept (also known as ALX148), a high-affinity CD47-blocking protein with an inactive IgG Fc region in patients with solid tumours.

METHODS

We did a first-in-human, open-label, multicentre, phase 1 dose-escalation and dose-expansion study at nine hospitals and one clinic in the USA and Korea. Eligible patients for the dose-escalation and safety lead-in phases were aged 18 years or older with histological or cytological diagnosis of advanced or metastatic solid tumours with no available standard therapy, measurable or unmeasurable disease according to the Response Evaluation Criteria in Solid Tumors version 1.1, and an Eastern Cooperative Oncology Group performance status score of 0 or 1. In the dose-escalation phase, which used a 3 + 3 design, patients received intravenous evorpacept at either 0·3, 1, 3, or 10 mg/kg once per week in 21-day cycles, or 30 mg/kg once every other week in 28-day cycles. In the safety lead-in phase, patients were given the maximum tolerable dose of evorpacept from the dose-escalation phase plus either intravenous pembrolizumab (200 mg administered once every 3 weeks) or intravenous trastuzumab (8 mg/kg loading dose followed by 6 mg/kg once every 3 weeks). In the dose-expansion phase, additional patients aged 18 years or older with second-line or later-line advanced malignancies were enrolled into three parallel cohorts: those with head and neck squamous cell carcinoma (HNSCC) and those with non-small-cell lung cancer (NSCLC) were given the maximum tolerated dose of evorpacept plus intravenous pembrolizumab (200 mg administered once every 3 weeks), and patients with HER2-positive gastric or gastroesophageal junction cancer were given the maximum tolerated dose of evorpacept plus intravenous trastuzumab (8 mg/kg loading dose followed by 6 mg/kg once every 3 weeks) until disease progression, voluntary withdrawal from the study, or unacceptable toxicity. The primary endpoint was the maximum tolerated dose of evorpacept administered as a single agent and in combination with pembrolizumab or trastuzumab, measured by the occurrence of dose-limiting toxicities during the first cycle, and was assessed in all patients who had received at least one dose of evorpacept. Secondary outcomes included the safety, tolerability, and antitumour activity of evorpacept, alone or in combination with pembrolizumab or trastuzumab. The primary outcome, safety, and tolerability were assessed in all patients who had received at least one dose of evorpacept, and antitumour activity was assessed in those who recieved at least one dose of study treatment and underwent at least one post-baseline tumor assessment. This trial is registered with ClinicalTrials.gov, NCT03013218.

FINDINGS

Between March 6, 2017, and Feb 21, 2019, 110 patients received single-agent evorpacept (n=28), evorpacept plus pembrolizumab (n=52), or evorpacept plus trastuzumab (n=30), and were included in the safety analysis. Median follow-up was 29·1 months (95% CI not calculable [NC]-NC) in the single-agent cohort, 27·0 months (25·1-28·8) in the evorpacept plus pembrolizumab cohort, and 32·7 months (27·0-32·7) in the evorpacept plus trastuzumab cohort. Two (7%) dose-limiting toxicities in the first cycle were reported in patients who received single-agent evorpacept; neutropenia with an associated infection in one patient with gastroesophageal junction cancer who received 3 mg/kg once per week, and thrombocytopenia with associated bleeding in one patient with pancreatic cancer who received 30 mg/kg once every other week. No maximum tolerated dose was reached; the maximum administered doses were 10 mg/kg once per week or 30 mg/kg once every other week. The 10 mg/kg once per week dose was used in the expansion cohorts in combination with pembrolizumab or trastuzumab. The most common grade 3 or worse treatment-related adverse events were thrombocytopenia with single-agent evorpacept (two [7%] patients) and evorpacept plus pembrolizumab (two [4%]), and thrombocytopenia (two [7%]) and neutropenia (two [7%]) with evorpacept plus trastuzumab. In patients who received single-agent evorpacept, four treatment-related serious adverse events were reported. Five serious treatment-related adverse events related to evorpacept plus pembrolizumab were reported, and one serious adverse event related to evorpacept plus trastuzumab was reported. In response-evaluable patients in the dose-escalation phase (n=15) receiving single-agent evorpacept once per week, four (27%) had a best overall response of stable disease (two received 0·3 mg/kg, one received 3 mg/kg, and one received 10 mg/kg); in the 11 patients who received single-agent evorpacept at the highest dose of 30 mg/kg once every other week, two (18%) had stable disease. In the dose-expansion cohort, overall responses were recorded in four (20·0%; 95% CI 5·7-43·7) of 20 patients with HNSCC who received evorpacept plus pembrolizumab, in one (5·0%; 0·1-24·9) of 20 patients with NSCLC who received evorpacept plus pembrolizumab, and in four (21·1%; 6·1-45·6) of 19 patients with gastric or gastroesophageal junction cancer who received evorpacept plus trastuzumab.

INTERPRETATION

The safety findings support the use of evorpacept in combination with pembrolizumab or trastuzumab for patients with advanced solid tumours. Preliminary antitumour activity results support future investigation of evorpacept combined with pembrolizumab or trastuzumab in patients with HNSCC, gastric or gastroesophageal junction cancer, and NSCLC.

FUNDING

ALX Oncology.

A Phase 2 Study of PNT2258 for Treatment of Relapsed or Refractory B-Cell Malignancies

BACKGROUND

PNT2258 consists of a native, chemically unmodified, 24-base DNA oligonucleotide designed to target the regulatory region upstream of the BCL2 gene, delivered in a protective liposome. Derangement of BCL2-regulated control mechanisms is a defining characteristic of certain malignancies, and it was hypothesized that the oligonucleotide would promote anticancer activity via suppression of BCL2 transcription.

METHODS

PNT2258 was evaluated in this, multicenter, nonrandomized, open-label Phase 2 study in 13 participants with relapsed/refractory B-cell malignancies to investigate potential antitumor activity and safety. Participants with follicular lymphoma, diffuse large B-cell lymphoma, mantle cell lymphoma, or chronic lymphocytic leukemia received intravenous PNT2258 120 mg/m² on Days 1 to 5 of a 21-day cycle for up to 8 cycles, followed by 100 mg/m² on Days 1 to 2 of a 28-day cycle until study withdrawal.

RESULTS

All 13 participants were treated with PNT2258 monotherapy and evaluable for response and safety and tolerability. The overall response rate was 53.8% (7/13; 95% confidence interval [CI], 25.1%-80.8%). Median duration of response was 23.4 months (range, 3, 31.5). The disease control rate of participants with stable disease or better was 84.6% (95% CI, 54.6%-98.1%). The most frequently (≥50%) observed adverse events (AEs) were nausea, chills, diarrhea, fatigue, headache, vomiting, and back pain. Hypertension (30.8%) and diarrhea (23.1%) were the most frequent grade ≥3 AEs. No deaths were observed.

CONCLUSION

Clinically meaningful and durable activity with an acceptable safety profile was observed in participants with relapsed/refractory B-cell malignancies who received single-agent PNT2258.

TRIAL REGISTRATION

NCT01733238, first posted 26-Nov-2012. https://clinicaltrials.gov/ct2/show/NCT01733238.

Clinical activity of fianlimab (REGN3767), a human anti-LAG-3 monoclonal antibody, combined with cemiplimab (anti-PD-1) in patients (pts) with advanced melanoma

9515

Background: Fianlimab and cemiplimab are two high-affinity, fully human, hinge-stabilized IgG4 monoclonal antibodies. In a Phase 1 dose escalation study, fianlimab combined with cemiplimab showed an acceptable safety profile and some clinical activity in pts with advanced malignancies. Here, we present safety and clinical activity data from two expansion cohorts of pts with advanced melanoma (anti–programmed cell death/ligand-1 [anti–PD-(L)1] naïve or experienced) who were treated with fianlimab + cemiplimab and had an opportunity for first on-treatment tumor assessment (cut-off date: Jan 4, 2021). Methods: Pts with advanced melanoma who had no prior anti–PD-(L)1 treatment (naïve) or prior anti–PD-(L)1 treatment within 3 months of screening (experienced) received fianlimab 1600 mg + cemiplimab 350 mg by IV infusion every 3 weeks. Tumor measurements were performed every 6 weeks for the first 24 weeks and subsequently every 9 weeks per RECIST v1.1. Results: 48 pts with advanced melanoma were treated with the combination therapy: 33 were anti–PD-(L)1 naïve and 15 were anti–PD-(L)1 experienced (median age: 69 years vs 59 years; male: 66.7% vs 46.7%; Caucasian: 87.9% vs 60%). The safety profile (including immune-related adverse events [AEs]) of fianlimab + cemiplimab combination therapy was similar to that of anti–PD-1 monotherapy with one exception. The rate of adrenal insufficiency, 8.3% (4/48) of pts, is similar to the rate previously observed with anti–PD-1 + anti–cytotoxic T-lymphocyte-associated protein 4 (CTLA-4) combination therapy but higher than that observed with anti–PD-1 monotherapy. Grade ≥3 treatment-emergent AEs (TEAEs) occurred in 35.4% (17/48) of patients; Grade ≥3 serious TEAEs occurred in 22.9% (11/48) of patients; 8.3% (4/48) of patients discontinued treatment due to a TEAE. The most common TEAEs were fatigue (n = 15, 31.3%) and rash (n = 11, 22.9%). By investigator assessment, objective response rate (includes unconfirmed complete [CR] and partial responses [PR]) was 63.6% (3 CRs and 18 PRs) for anti–PD-(L)1 naïve pts and 13.3% (1 CR and 1 PR) for anti–PD-(L)1 experienced pts. Median progression-free survival and median duration of response for the anti–PD-(L)1 treatment naïve cohort have not been reached. Prognostic clinical markers and tumor biomarkers such as expression of LAG-3, PD-L1, and major histocompatibility complex II are being evaluated. Recruitment is ongoing. Conclusions: The safety profile of fianlimab + cemiplimab is similar to that observed with cemiplimab monotherapy and other anti–PD-1s, with the exception of higher rate of adrenal insufficiency. Fianlimab + cemiplimab combination has shown clinical activity for pts with advanced melanoma that is similar to anti–PD-1 + CTLA-4 combination therapy, but with lower demonstrated rates of TEAEs. Clinical trial information: NCT03005782.

First-in-human dose escalation of ALPN-202, a conditional CD28 costimulator and dual checkpoint inhibitor, in advanced malignancies

2547

Background: Strong preclinical rationale has emerged for combining checkpoint inhibition (CPI) with T cell costimulatory agonists, particularly CD28, a critical T cell costimulatory molecule recently recognized as a key target of checkpoint inhibition. ALPN-202 is a variant CD80 vIgD-Fc fusion that mediates PD-L1-dependent CD28 costimulation and inhibits the PD-L1 and CTLA-4 checkpoints. It has demonstrated superiority to CPI-only therapies in tumor models, while demonstrating favorable safety in preclinical toxicology studies. Methods: This is a cohort-based, open-label dose escalation and expansion study of ALPN-202 in adults with advanced solid tumors or lymphoma (NCT04186637). Subjects with cancers refractory to standard therapies (including approved CPIs), or cancers without available standard or curative therapy are eligible. After two planned single-subject cohorts, a standard 3+3 dose escalation has been implemented with two dose schedules in parallel, Q1W and Q3W. Objectives include evaluation of safety and tolerability, PK, PD and preliminary anticancer activity of ALPN-202. Disease assessments are evaluated by RECIST v1.1 for solid tumors or by Lugano Classification for lymphoma. Results: As of January 2021, 20 subjects with advanced malignancies have received ALPN-202. Dose-dependent PK and target saturation have been preliminarily observed. So far, ALPN-202 has been well tolerated at dose levels ranging from 0.001 to 1 mg/kg weekly, with no DLTs. Low-grade skin toxicities (grade 1-2 rash) have been observed in 4 subjects (20%). Among 11 evaluable subjects, an unconfirmed partial response has been observed in one subject with colorectal carcinoma, while stable disease has been observed in 5 subjects with colorectal carcinoma, mesothelioma (2), cholangiocarcinoma, and renal cell carcinoma -- for a preliminary clinical benefit (PR+SD) rate of 100% (4/4) at dose levels of 0.3 mg/kg and higher, or 54% (5/11) overall (table). The meeting presentation will update this data, which is expected to include the conclusion of Q1W dose escalation, as well as immune correlates. Conclusions: First-in-human dose escalation with ALPN-202 has been well tolerated at doses capable of engaging CD28 costimulation in vivo in association with dual PD-L1/CTLA-4 checkpoint inhibition, with early signs of anti-tumor activity. These findings suggest that CD28 agonism can be safely achieved in humans, and further suggest that dose expansion with ALPN-202 is warranted to assess the relevance of controlled CD28 costimulation as a novel approach to cancer immunotherapy. Clinical trial information: NCT04186637. [Table: see text]

A phase 1 first-in-human study of the anti-LAG-3 antibody MK4280 (favezelimab) plus pembrolizumab in previously treated, advanced microsatellite stable colorectal cancer

3584

Background: Patients (pts) with microsatellite stable (MSS) metastatic colorectal cancer (mCRC) that progressed on ≥2 prior therapies have limited treatment options, with median OS ranging from 6-9 months (mo). In the dose-escalation phase of this first-in-human multicohort study (NCT02720068), the anti-lymphocyte activation gene (LAG)-3 antibody favezelimab (fave) was well tolerated alone and with pembrolizumab (pembro) across all dose levels (Lakhani, SITC, 2018, abstract O26). Here, we evaluate the safety and efficacy of fave alone or in combination with pembro in pts with advanced MSS CRC from the dose confirmation phase. Methods: Eligible pts with MSS PD-1/PD-L1-treatment-naïve mCRC that progressed on prior standard-of-care (3L+) were enrolled (cohort A) to receive the RP2D of 800 mg fave alone (Arm 1), 800 mg fave + 200 mg pembro (Arm 2C), or 800 mg fave + 200 mg pembro (MK-4280A) co-formulation (Arm 5), all Q3W. Treatment continued for 35 cycles or until progression, unacceptable toxicity, or investigator/pt decision. Pts with confirmed progression per irRECIST v1.1 on fave alone could crossover to 800 mg fave + pembro. Safety was assessed in all treated pts; efficacy in the full analysis set (FAS) of all treated pts with baseline scan. Objectives included safety (primary), ORR (RECIST v1.1 by investigator [secondary]), and DOR, PFS, and OS (exploratory). Interim analysis data cut-off was: Oct. 23, 2020. Results: A total of 20 pts received fave (Arm 1); 89 pts (including 9 crossover) received fave + pembro (Arms 2C+5); 12 pts (Arm 1) and 36 pts (Arms 2C+5), had PD-L1 CPS ≥1 tumors. At data cut-off, median follow-up was 5.8 months (mo) in Arm 1 and 6.2 mo in Arms 2C+5. Treatment-related adverse events (TRAEs) were 65% with fave (Arm 1) and 65.2% with fave + pembro (Arms 2C+5). Grade ≥3 TRAEs were 15% (Arm 1), and 20% [Arms 2C+5]). No grade 5 TRAEs were reported. Common TRAEs (≥15%) included fatigue (20.0%), nausea (15%) with fave, and fatigue (16.9%) with fave + pembro. Confirmed ORR was 6.3% (4PR, 1CR) with fave + pembro (Arms 2C+5). No pt receiving fave alone responded. In Arms 2C+5, median DOR was 10.6 mo (range, 5.6-12.7). ORR, OS and PFS by PD-L1 status are reported in the Table. Conclusions: Favezelimab alone or in combination with pembrolizumab had a manageable safety profile, with no treatment-related deaths. Promising antitumor activity was observed with combination therapy, including with MK-4280A, compared with monotherapy most notably in pts with PD-L1 CPS ≥1 tumors. Clinical trial information: NCT02720068. [Table: see text]

Phase 1, first-in-human trial of JTX-8064, an anti-LILRB2/ILT4 monoclonal antibody, as monotherapy and in combination with anti-PD-1 in adult patients with advanced solid tumors (INNATE)

TPS2672

Background: Leukocyte Immunoglobulin-like receptor B2 [LILRB2; immunoglobulin-like transcript 4 (ILT4)] is an immunoinhibitory protein expressed on the surface of myeloid cells and is a therapeutic target of interest in immuno-oncology. Published data showed that antagonism of LILRB2 resulted in the repolarization of human macrophages from an M2 (suppressive) to M1 (pro-inflammatory) phenotype, and enhancement of anti-tumor immunity in a mouse model (Chen 2018). JTX-8064 is a novel humanized IgG4 monoclonal antagonist antibody that selectively binds LILRB2 and prevents it from binding its ligands, classical and non-classical MHC I molecules. By blocking the ability of LILRB2 to bind HLA-A/B and/or HLA-G, a marker of immunotolerance on cancer cells, JTX-8064 has been shown to enhance pro-inflammatory cytokine production in macrophages (Cohen 2019). Additionally, blocking HLA-A/B-LILRB2 binding with JTX-8064 may augment antigen presentation and has been shown to lead to enhanced T cell activation and IFNg production (McGrath 2021). Using an ex vivo tumor explant model, we observed an IFNg-associated pharmacodynamic response in tumor tissue treated with JTX-8064 and a PD-1 inhibitor (PD-1i) that was not observed with PD-1i alone. Biomarkers were identified that predicted this JTX-8064 driven response (Hashambhoy-Ramsay 2020). It is hypothesized that JTX-8064 is a novel macrophage immune checkpoint inhibitor that may overcome mechanisms of resistance to PD-1i in tumors not responsive to JTX-8064 or PD-1i alone. Methods: The primary objectives of this open-label, phase 1, first-in-human, multicenter trial are to determine the safety and tolerability, and the recommended phase 2 dose (RP2D) of JTX-8064 as a monotherapy and in combination with a PD-1i, JTX-4014 (a Jounce investigational agent) or pembrolizumab, in patients with advanced solid tumors (NCT04669899). The INNATE study will consist of 4 stages: 1) JTX-8064 monotherapy dose escalation, 2) JTX-8064 dose escalation in combination with a PD-1i, 3) JTX-8064 monotherapy in indication-specific expansion cohorts and 4) JTX-8064 in combination with a PD-1i in indication-specific expansion cohorts. Stages 1 and 2 will employ an innovative interval i3 + 3 design with Bayesian decision framework to guide dose escalation. Safety, pharmacokinetic and receptor occupancy data will be considered during dose escalation. INNATE will assess pharmacodynamic and potential predictive biomarkers of response, and the expansion cohorts will explore multiple patient populations, including PD-(L)1i sensitive and PD-(L)1i-resistant (primary or acquired) patients to address current unmet medical needs. Enrolment in INNATE began in January 2021. Clinical trial information: NCT04669899.

Phase 1/2 first-in-human (FIH) study of CPI-0209, a novel small molecule inhibitor of enhancer of zeste homolog 2 (EZH2) in patients with advanced tumors

3104

Background: Enhancer of Zeste homolog 2 (EZH2) is a histone methyltransferase and the catalytic subunit of Polycomb Repressive Complex 2 (PRC2). EZH2 is frequently overexpressed in cancers and correlates with poor prognosis. CPI-0209 is an oral, small molecule, second-generation, selective inhibitor of EZH2 designed to achieve comprehensive target coverage through extended on-target residence time. The compound demonstrates more potent anti-tumor activity in preclinical cancer models, compared to first-generation EZH2 inhibitors. CPI-0209 is currently being evaluated in a Phase 1/2, open-label, FIH study (NCT04104776). Methods: Patients (pts) with advanced tumors were enrolled in a 3+3 design. Primary objective is to determine maximum tolerated dose (MTD) and/or recommended phase 2 dose (RP2D) of CPI-0209. Secondary objectives are to evaluate the safety, PK, and PD in pts who received CPI-0209 QD in 28 days cycles (C). Results: As of December 16, 2020, 33 pts were treated: pancreatic cancer (n = 6), mesothelioma, breast, colorectal, and ovarian cancer (n = 5 each), leiomyosarcoma, melanoma, cholangiocarcinoma, prostate, bladder, endometrial clear cell and gastric cancer (n = 1 each). Pts received CPI-0209 at 50 mg (n = 4), 100 mg, 137.5 mg, and 187.5 mg (n = 6 each), 225 mg (n = 7), and 275 mg (n = 4) daily dose. Median treatment duration was 43 days (range 1-239); 4 pts are ongoing. Median age was 64 yrs (range 24-79); 15 (45%) pts were male. Patients were heavily pretreated, with 67% of pts had ≥ 3 prior lines of therapy. No dose limiting toxicities have been observed. The most frequent treatment-emergent adverse events (TEAEs) (≥10%) were fatigue (27%), diarrhea (24%), nausea (21%), abdominal pain, alopecia, anemia, thrombocytopenia, and dysgeusia (15% each), and vomiting, headache, decreased appetite, and alkaline phosphatase increased (12% each); usually grade 1 or 2 in severity. Thrombocytopenia was dose-dependent and not associated with bleeding or clinical sequalae. Three pts (9%) discontinued CPI-0209 due to TEAEs. Comprehensive target engagement (assessed by global reduction in H3K27me3 levels in monocytes) was observed within the first cycle at all dose levels. CPI-0209 also increased the expression of PRC2-controlled gene sets in blood in a dose-dependent manner. Updated safety, PK, PD, and preliminary efficacy results from Phase 1 will be presented. Conclusions: CPI-0209 achieved robust PD effects and a PK-PD relationship has been established. CPI-0209 monotherapy was generally well tolerated, and treatment related AEs were manageable and reversible. The MTD has not been reached. Clinical trial information: NCT04104776.

Results of a completed phase I study of LAM-002 (apilimod dimesylate), a first-in-class phosphatidylinositol-3-phosphate 5 kinase (PIKfyve) inhibitor, administered as monotherapy or with rituximab or atezolizumab to patients with previously treated follicular lymphoma or other B-cell cancers

8017

Background: LAM-002 is a selective inhibitor of PIKfyve that disrupts lysosomal homeostasis, inducing cytotoxicity in B-cell lymphoma models as monotherapy or with anti-CD20 or anti-PDL1 antibodies (Gayle et al., Blood 2017;129(13):1768). Methods: In this study, patients received LAM-002 orally 2-3 times per day (BID or TID) in a 3+3 escalation. Additional patients received LAM-002 125 mg BID as monotherapy; with rituximab 375 mg/m2 intravenously (IV) and or subcutaneously weekly (Q1W) x 4 → Q8W x 4; or atezolizumab 1200 mg IV Q3W until disease progression or unacceptable toxicity. Pharmacokinetics (PK) were assessed for 8 hours postdose on Days 1 and 8. Efficacy was evaluated Q6-12W. Results: The study enrolled 62 patients (M:F n = 32/30); median [range] age = 69 [46-89] years; with diagnoses (n) of diffuse large B-cell lymphoma (25), follicular lymphoma (19), marginal zone lymphoma (8), mantle cell lymphoma (5), or chronic lymphocytic leukemia (5) to receive LAM-002 alone (n) at 50 mg BID (3), 100 mg BID (8), 150 mg BID (8), 75 mg TID (4), or 125 mg BID (20); LAM-002/rituximab (12); or LAM-002/atezolizumab (7). During LAM-002 dose-ranging (50 mg BID → 100 mg BID → 150 mg BID → 75 mg TID → 125 mg BID) transient, reversible nausea and/or diarrhea occurred at 150 mg BID and 75 mg TID, resulting in a LAM-002 recommended Phase 2 dosing regimen (RP2DR) of 125 mg BID. Among 39 patients receiving LAM-002, 125 mg BID, alone or in combination for up to 22 cycles (1.9 years), adverse events were typically low-grade. LAM-002 PK showed rapid absorption, dose proportionality, minimal accumulation, and no substantive changes with rituximab or atezolizumab coadministration. In patients with follicular lymphoma and median [range] prior therapies = 3 [1-9] treated with the RP2DR, objective response rates were 2/7 (29%; 1 complete response [CR], 1 partial response [PR]) with LAM-002, 5/8 (63%; 1 CR, 4 PRs) with LAM-002/rituximab, and 2/2 (100%; 2 PRs) with LAM-002/atezolizumab. Conclusions: LAM-002, the first clinical PIKfyve inhibitor, is safe alone or with full-dose anti-CD20 or anti-PD-L1 inhibition. LAM-002 does not cause the myelosuppressive or immune adverse events associated with lenalidomide or PI3K inhibitors. Promising efficacy supports registration-directed Phase 2/3 testing of LAM-002 monotherapy and combination therapy for patients with previously treated follicular lymphoma. Clinical trial information: NCT02594384 .

CX-2029, a PROBODY drug conjugate targeting CD71 (transferrin receptor): Results from a first-in-human study (PROCLAIM-CX-2029) in patients (Pts) with advanced cancer

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Background: CX-2029 is a PROBODY drug conjugate (PDC) of MMAE, a potent microtubule inhibitor, directed against CD71 (transferrin receptor 1). In addition to being an abundant tumor antigen, CD71 is highly expressed on normal cells, precluding targeting by a traditional antibody drug conjugate (ADC). PDCs are masked ADCs, unmasked predominantly by tumor-associated proteases, thereby restricting target engagement to tumors. Both a CD71 PDC and ADC displayed broad activity in multiple xenograft tumor models; in toxicology studies, the PDC was tolerable at doses consistent with efficacy in non-clinical tumor models while the ADC was not. Methods: In a phase 1/2 first-in-human study of PDC CX-2029 in advanced solid tumors (N CT03543813 ), pts with ECOG 0–1 and ≥1 prior systemic therapy were enrolled into escalating dose cohorts of the PDC CX-2029 given IV every 21 days. Endpoints included evaluation of MTD, safety, antitumor activity, and potential biomarkers; plasma and tissue samples were collected for PK/PD analyses. Preliminary results are reported. Results: As of 30 November 2019, 34 pts were enrolled (median age 59 y; 59% male; 71% ECOG 1; median [range] of 3 [1–16] prior therapies). Pts received a median of 3 (1–12) CX-2029 doses. Starting dose for escalation was 0.1 mg/kg. Following a single CX-2029 dose, median molar ratio of masked CX-2029 to total CX-2029 for AUCtau was 0.938 (0.864–0.942); the ratio of free MMAE to total CX-2029 was <0.03. Infusion-related reactions were the most common treatment-related AE (TRAE) of any grade (88%; primarily low grade and with first infusion), followed by anemia (56%), fatigue and nausea (24% each), neutropenia (21%), and leukopenia (12%). Grade 3+ TRAEs in ≥10% pts were anemia (35%) and neutropenia (18%). In 32 response-evaluable pts, 1 pt had a confirmed partial response (squamous NSCLC); 9 had stable disease including 1 pt with ocular melanoma treated for 36 weeks. Conclusions: The observed safety profile for CX-2029 effectively reduces on-target toxicity for this previously undruggable target, supporting the PROBODY platform. Evidence of anti-tumor activity was observed. Dose escalation continues. Clinical trial information: NCT03543813 .

First-in-human study of palcitoclax (APG-1252), a novel dual Bcl-2/Bcl-xL inhibitor, demonstrated advantages in platelet safety while maintaining anticancer effect in U.S. patients with metastatic solid tumors

3509

Background: Targeting Bcl-2/Bcl-xL proteins is considered as an important approach for anticancer drug development. Palcitoclax (APG-1252) was being developed to reduce on-target platelet toxicity without diminishing antitumor potency. Methods: The phase 1 study was to evaluate the safety/tolerability, pharmacokinetics (PK), and preliminary efficacy (assessed per RECIST 1.1) of palcitoclax in US patients with metastatic small-cell lung cancer (SCLC) or other solid tumors (NCT03080311). A standard “3+3” design was applied to the dose-escalation stage. Palcitoclax was administered IV infusion for 30 minutes, twice a week (BIW) or once a week (QW) for 3 weeks in a 28-day cycle. Once the maximum tolerated dose / recommended phase 2 dose (MTD/RP2D) was determined, additional patients were treated in a dose-expansion stage. Results: The dose-escalation phase has been completed with 42 patients (31 on BIW and 11 on QW) who received palcitoclax at 8 dose cohorts ranging 10 mg - 400 mg. Most adverse events (AEs) were grade 1 or 2 (G1 or G2), and 26.2% patients had ≥ G3 TRAEs. The most common TRAEs were platelet count decreased (14.3%), aspartate aminotransferase increased (9.5%), and alanine aminotransferase increased (7.1%). Rapid platelet drop was observed in patients treated at 320 mg and 400 mg, which was transient and resolved rapidly within 2-6 days. Palcitoclax at 240 mg once weekly was determined to be MTD/RP2D. Of 36 efficacy-evaluable patients, 3 patients with SCLC, neuroendocrine prostate cancer, and ovarian cancer respectively achieved partial response (PR) and 8 patients had stable disease (SD) as their best overall response. One patient with SCLC had a PR that lasted over 21 cycles. Preliminary PK analyses showed that Cmax and AUC were approximately dose proportional over the range of 10 mg to 320 mg following the IV infusion on Day 1, with a mean T1/2 of 3.0-13.0 hours. Conclusions: Palcitoclax is safe and well tolerated, with a favorable platelet toxicity profile. Its promising antitumor effect supports its further development in combination therapies for treatment of patients with SCLC and other solid tumors. Clinical trial information: NCT03080311 .

Phase Ib study of a novel bivalent IAP antagonist APG-1387 in combination of pembrolizumab for patients with advanced solid tumors

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Background: APG-1387 is an IAP (inhibitor of apoptosis proteins) antagonist that has strong antitumor activity in multiple xenograft cancer models and acts as a host immune modulator, supporting its exploration for use in combination with checkpoint inhibitors for cancer therapy. Methods: This “3+3” dose escalation and dose expansion study evaluated APG-1387 combined with pembrolizumab in patients with refractory or intolerant advanced solid tumors (NCT03386526). APG-1387 was administered IV once weekly with pembrolizumab 200 mg on day 1 of a 21-day cycle. Study aims were to assess safety/tolerability, recommended phase 2 dose (RP2D), pharmacokinetics (PK), pharmacodynamics (PD), and efficacy. Results: As of December 25, 2019, total 28 patients had been treated in 3 dose cohorts of APG-1387: 20 mg (n = 4), 30 mg (n = 3), and 45 mg (n = 21, 18 in dose expansion). The median line of prior systemic cancer therapies was 3.0 (1-12). No dose-limiting toxicity was observed. The most common treatment-related adverse events (TRAEs; ≥10%) were fatigue (28.6%), arthralgia (14.3%), headache (14.3%), and tumor pain (10.7%). One patient in the 45-mg cohort had grade 2 Bell’s Palsy. G3+ TRAEs were autoimmune colitis, hypoxia, increased lipase, mucosal inflammation, pneumonitis, and tumor pain in 1 patient each (3.6%). Treatment-related SAEs were 1 G3 autoimmune colitis, 1 G2 myocarditis, and 1 G3 pneumonitis. The maximum tolerated dose (MTD)/RP2D for APG-1387 was 45 mg. Among 25 efficacy-evaluable patients, 1 with ER+, HER2‒ breast cancer receiving APG-1387 30 mg after failing 5 lines of therapy (PD-1 treatment-naïve, microsatellite stable) achieved confirmed PR (-79.2%) for 6 cycles but discontinued due to pneumonitis; another patient with PD-L1‒ non‒small-cell lung cancer treated at 45 mg had confirmed PR (-65.0%) for 6 cycles (ongoing). Other 11 patients had SD for 2-11 cycles. The disease control rate was 52%. Preliminary PK data showed a dose-proportional increase in APG-1387 exposure from 20 mg to 45 mg. Preliminary PD data showed that APG-1387 induced rapid degradation of cellular IAP1 and X-linked IAP in peripheral blood mononuclear cell samples; Increased serum release of interleukins (IL-12, IL-10) and monocyte chemotactic protein 4 was dose and time dependent. Conclusions: APG-1387 combined with pembrolizumab is well tolerated. Encouraging antitumor effects were observed in patients with several tumor types. The ongoing study will further evaluate the efficacy of this combination. Clinical trial information: NCT03386526 .

AVID200, first-in-class TGF-beta 1 and 3 selective and potent inhibitor: Safety and biomarker results of a phase I monotherapy dose-escalation study in patients with advanced solid tumors

3587

Background: AVID200 is a rationally designed first-in-class, selective inhibitor of transforming growth factor-beta (TGF-beta) that neutralizes TGF-beta 1 & 3 with pM potency and 4,000 fold selectivity over TGF-beta 2. TGF-beta 1 & 3 signaling has been associated with immune checkpoint inhibitor resistance and immunosuppression in the tumor microenvironment while TGF-beta 2 is required for normal cardiac function and hematopoiesis. Methods: NCT03834662 (AVID200-03) is a multicenter Phase 1 study following a standard 3 + 3 dose escalation to evaluate safety and tolerability of AVID200 given IV every 3 weeks to patients (pts) with advanced solid tumors. Peripheral target engagement was assessed in blood by ELISA and a cell-based functional assay, and in skin biopsies by immunohistochemistry (IHC). Pharmacodynamic markers of TGF-beta signal modulation and immune activation were evaluated in serum using the InflammationMAP v 1.0 (Myriad RBM) and in paired tumor biopsies by IHC and Imaging Mass Cytometry. Results: Nineteen pts (ECOG 0-1, median age 63 [range 39-77], 52.6% male) received AVID200 at 3 planned dose levels of 180 (N = 7), 550 (N = 6), and 1100 mg/m2 (N = 6) (~5, 15, and 30 mg/kg). The maximum tolerated dose was not reached. Three Grade (G) 3 treatment-related adverse events (TRAEs) were reported in 2 pts (diarrhea and lipase elevation, anemia); no > G3 TRAEs were observed. Serum exposure was dose-proportional and AVID200 sequestered all active TGF-beta 1 & 3, but not beta 2, in blood across the entire dosing period at all dose levels, providing proof-of-mechanism of AVID200. SMAD2 phosphorylation in skin biopsies was detectably reduced on Day 4 at 15 and 30 mg/kg. Pro-inflammatory markers in serum were increased on Day 8 versus baseline in a dose-dependent manner. Tumor biopsies of pts treated at 15 mg/kg showed modulation of TGF-beta signaling and immune activation. A best response of RECIST stable disease > 12 weeks was observed in 2 pts: 1 with adenoid cystic carcinoma (5 mg/kg; 8.7 months); 1 with breast carcinoma (30 mg/kg; 3.1 months). Conclusions: AVID200 was safe and well tolerated at dose levels of 5-30 mg/kg, with peripheral target engagement across the entire dosing period. AVID200 led to TGF-beta target modulation and immune activation. These data provide proof-of-principle that AVID200-mediated selective and potent inhibition of TGF-beta 1 & 3 is feasible in the clinic. The AVID200 monotherapy data warrant exploration of rational combination with a PD-(L)1 inhibitor. Clinical trial information: NCT03834662 .

A phase I study of ALX148, a CD47 blocker, in combination with standard anticancer antibodies and chemotherapy regimens in patients with advanced malignancy

3056

Background: CD47 is a myeloid checkpoint upregulated by tumor cells to evade the host immune response. ALX148 (A) is a fusion protein comprised of a high affinity CD47 blocker linked to an inactive immunoglobulin Fc region. ALX148 enhances innate and adaptive immune responses against cancer and has previously been shown to be well tolerated in combination with the checkpoint inhibitor (CPI), pembrolizumab (P), and trastuzumab (T) in a range of solid tumors (ASCO 2019 #2514). ALX148 safety and activity in combination with T or P and standard chemotherapy regimens are reported in patients (pts) including head and neck squamous cell cancer (HNSCC) and HER2 positive gastric/gastroesophageal cancer (GC). Methods: Pts with advanced malignancy were administered AP or AT. Patients with ≥2L HNSCC progressed on platinum therapy received AP, while those with untreated advanced disease received AP+5FU (FU)+platinum. Pts with ≥2L GC progressed on T+FU+platinum received AT +/- ramucirumab (ram)+paclitaxel (pac). Safety, response, pharmacokinetic and pharmacodynamic (PD) markers were assessed. Data are reported as of 21, Jan. 2020. Results: Patients received AP (n=52); AP+FU+platinum (n=1); AT (n=30); or AT+ram+pac (n=3) as of data cutoff. Eighty-two pts experienced any adverse event (AE). Fifty-seven pts administered AP or AT regimens reported mostly low grade ALX148 treatment related (TR) AEs, the most common being fatigue (18%), AST increase (11%), platelets decreased (10%), ALT increase (8.5%), anemia (8.5%), and pruritus (8.5%). Pts receiving AP+FU+platinum or AT+ram+pac reported no TRAEs as of data cutoff. Anticancer activity was observed in response-evaluable pts. AP: HNSCC CPI-naïve (n=10) 40% ORR, mPFS 4.6 [95% CI:0.5;7.5], mOS not reached with 14.4m median follow-up; AP: HNSCC CPI-experienced (n=10) 0% ORR, mPFS 2.0 [95% CI:0.9;3.6], mOS 7.4 [95% CI:3.1;NC]; and AT: GC (n=20) 20% ORR, mPFS 2.2 [95% CI:1.9;5.4], mOS 8.1 [95% CI:3.4;12.8]. Full peripheral CD47 target occupancy and increased infiltrating immune cells in tumor biopsies were seen. Exploratory analysis of biomarkers associated with response is ongoing. Conclusions: Initial data suggests ALX148 demonstrates excellent tolerability in combination with anti cancer antibodies and standard chemotherapy. Clinical activity in pts with advanced CPI naïve HNSCC (including PD-L1 negative) and GC compares favorably with historic controls. Final data from AP and AT cohorts and initial data from chemotherapy combination cohorts will be presented. Clinical trial information: NCT03013218 .

A phase Ib study of the anti-CD47 antibody magrolimab with the PD-L1 inhibitor avelumab (A) in solid tumor (ST) and ovarian cancer (OC) patients

18

Background: Magrolimab (M, Hu5F9-G4) is an antibody targeting CD47, a “don’t eat me” signal for macrophages that enhances ovarian cancer cell phagocytosis in preclinical models in combination with the PD-L1 inhibitor avelumab. CD47 blockade can also enhance cross-priming of T cells. Methods: In Part 1 (P1) M+A doses were escalated in ST patients (pts) while Part 2 (P2) enrolled platinum-resistant or refractory OC pts. All received a 1 mg/kg Day 1 priming dose of M to mitigate on-target anemia due to macrophage-mediated extravascular hemolysis followed by 30 or 45 mg/kg maintenance doses in P1 or 45 mg/kg in P2, in combination with 800 mg of A Q2 wks. Results: In the 34 total pts (13 in P1 and 21 in P2), median age was 66 years (range 47-88), and median # of prior therapies was 5 (range 1-10). In P1, no dose limiting toxicities occurred. In P1+P2, no Grade (G) 4 or 5 treatment-related adverse events (TRAEs) occurred. TRAEs of any G in > 20% pts included headache 62%, fatigue 47%, infusion related reaction 44%, pyrexia 38%, chills 35%, nausea 35%, anemia 24%, and vomiting 21%. In P1, a patient (pt) with metastatic papillary adenocarcinoma of the finger on 45 mg/kg of M had a confirmed partial response (PR) lasting for 4 months before progressing. In P2, 1 pt had an unconfirmed PR but progressed per RECIST v1.1 on the next scan achieving a best response of stable disease (SD). In the 18 OC P1+P2 pts with at least one response evaluation, 56% had SD and 44% had progression. Analysis of tumor biopsies for immune cells infiltration and CD47, PD-L1, and other marker expression is ongoing. In the 13 OC tumors analyzed to date, only 2 were PD-L1 positive. One PD-L1+ tumor had PD-L1 expression only on infiltrating immune cells. The other PD-L1+ had tumor cell expression and was the only OC pt with tumor shrinkage. This supports the potential importance of PD-L1 expression for this combination. Pharmacokinetic profiles will be presented. Conclusions: M+A is a novel, well-tolerated combination treatment regimen with 1 observed PR in a ST pt and a 56% SD rate in OC pts. Tumor shrinkage was noted in the only OC pt with tumor cell expression of PD-L1 which warrants further evaluation in PD-L1+ OC pts. Clinical trial information: NCT03558139.

A phase Ib/II study of the anti-CD47 antibody magrolimab with cetuximab in solid tumor and colorectal cancer patients

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Background: Magrolimab (M, Hu5F9-G4) is an antibody targeting CD47, a macrophage “don’t eat me” signal that demonstrates preclinical synergy with cetuximab (C) in refractory KRAS wild type (KRASwt) and KRAS mutant (KRASm) colorectal (CRC) tumors. Methods: Phase (Ph) 1 doses of M+C were escalated in solid tumor patients (pts) and Ph 2 efficacy was explored in previously treated KRASwt and KRASm CRC patients. Day 1 priming with 1 mg/kg of M was used to mitigate on-target anemia followed by maintenance doses ranging from 10 to 45 mg/kg in combination with C. Ph 2 pts were treated with 30 or 45 mg/kg of M and 400/250 mg/m2 of C. Results: In 78 treated pts (32 Ph 1 and 46 Ph 2), the median age was 59 years (range 19-82), and median prior therapies was 5 (range 1-14). No maximum tolerated dose was reached. Treatment-related adverse events (TRAEs) of any Grade (G) included dermatitis acneiform 36%, dry skin 33%, fatigue 32%, infusion reactions 31%, headache 30%, diarrhea 23%, nausea 23%, chills 23%, and anemia 22%. There were no fatal TRAEs and 3/78 (4%) discontinued M treatment due to any adverse events. In the combined Ph 1+2 study, 2 of 30 evaluable KRASwt CRC pts had confirmed PRs for 7.0 and 12.5 months (mo), for a 6.7% objective response rate (ORR). Both had prior C treatment. The median progression-free survival (mPFS) and median overall survival (mOS) was 3.6 mo (95%CI 1.8-5.4) and 10.1 mo (95%CI: 6.9-14.4), respectively. In 40 evaluable KRASm pts, there were no responses but 45% had stable disease (SD) and the mPFS and mOS were 1.9 mo (95%CI: 1.8-3.5) and 10.4 mo (95%CI: 5.7-16.4), respectively. In 28 KRASm pts who were TAS102/regorafenib naïve, preliminary mOS was 12.4 mo (95%CI: 5.9-not reached) which is longer than that reported for historical controls. Tumor biopsies showed treatment-related increases in macrophage immune cell infiltrates in SD pts, and baseline T cell infiltration was associated with longer OS. Pharmacokinetic profiles will be presented. Conclusions: M+C is a novel, well-tolerated combination immunotherapeutic treatment regimen. Responses were observed in two previously treated CRC pts and survival is encouraging in KRASm pts. Funded by Forty Seven and California Institute for Regenerative Medicine. Clinical trial information: NCT02953782.

Abstract PR01: A phase I study targeting the APE1/Ref-1 DNA repair-redox signaling protein with the APX3330 inhibitor

APX3330 is an orally administered anti-cancer small molecule that targets the APE1/Ref-1 protein (apurinic endonuclease 1 / redox effector factor 1). APE1/Ref-1 is both a DNA repair and reduction-oxidation (redox) signaling protein that participates in the DNA base excision repair (BER) pathway. Additionally, APE1/Ref-1 regulates the redox status of a number of important transcription factors (TFs) in tumor cells. These include NFkB, STAT3, and HIF-1a. APE1/ref-1 converts these TFs from an off (oxidized) to an on (reduced) state allowing them to bind to the promoter sequence of genes regulating tumor growth, metastasis, metabolism and survival of tumor cells. APX3330 selectively binds to APE1/Ref-1, specifically inhibiting its redox signaling activity. APE1/Ref-1 also plays a key role in a variety of inflammatory disorders beyond cancers including diabetic macular edema, inflammatory bowel disorders and others. Data will be presented for study NCT03375086 evaluating APX3330 in patients with incurable malignancies. Eligibility required adequate organ function, PS 0-2 and tumors not amenable to curative therapy. Primary and secondary objectives included determining the recommended phase 2 dose (RP2D), the safety and PK/PD profiles of APX3330 and reporting any RECIST anti-tumor activity. Patients received APX3330 b.i.d., in 21-day cycles. APX3330 was well tolerated at dose levels from 240-600 mg/d. The most frequent treatment-related adverse events (all grades) included G1 nausea (16%) and fatigue (16%). Six subjects had disease stabilization for &gt; 4 cycles, and of these, four subjects with the following diagnosis, RECIST response and days on study included: colorectal cancer, PR (partial response), 357 days; endometrial, SD (stable disease), 421days; melanoma, SD, 337 days; prostate, SD, 252 days. All study objectives were completed and determined that APX3330 is safe for chronic dosing from 240 up to and including 600 mg/day. It provides clinical benefit to patients with a variety of tumor types (e.g., endometrial, colorectal, prostate and melanoma cancer). Pharmacodynamic (PD) studies from patient biopsy evaluation indicates APX3330-mediated effect upon cancer cells, including decrease in transcription factors activity for those regulated by the APE1/Ref-1 protein. Differentially expressed proteins (DEPs) were analyzed comparing pre-treatment and on-treatment tumor biopsies. Specifically studied were NFkB, HIFa and STAT3 genes downstream of these three TFs. Circulating tumor cell (CTC) analysis was performed on sixteen patients who had baseline and on-treatment samples that were evaluated longitudinally. Of these, 7/16 (44%) of patients showed a reduction in CTCs after initiation of treatment with APX3330. APE1/Ref-1 serum levels were determined to be elevated in aggressive tumors and were reduced following treatment with APX3330 in SD patients (past four treatment cycles). Pharmacokinetic (PK) data indicate confirmation of pre-clinical data. Conclusions: APX3330 is an orally administered inhibitor of APE1/Ref-1 specifically targeting the redox signaling function of this protein. This phase I study identified 600 mg PO daily as the RP2D for further development. RECIST evaluation identified signs of clinical activity in this un-selected population of patients with advanced cancer. PD analyses (proteomics, CTC, serum) indicate APX3330 mediated targeting of the APE1/Ref-1 protein.

Citation Format: Mark R. Kelley, Safi Shahda, Nehal J. Lakhani, Bert O'Neil, Lincy Chu, Amanda K. Anderson, Jun Wan, Amber L. Mosley, Hao Liu, Richard A. Messmann. A phase I study targeting the APE1/Ref-1 DNA repair-redox signaling protein with the APX3330 inhibitor [abstract]. In: Proceedings of the AACR-NCI-EORTC International Conference on Molecular Targets and Cancer Therapeutics; 2019 Oct 26-30; Boston, MA. Philadelphia (PA): AACR; Mol Cancer Ther 2019;18(12 Suppl):Abstract nr PR01. doi:10.1158/1535-7163.TARG-19-PR01

A phase I study of ALX148, a CD47 blocker, in combination with established anticancer antibodies in patients with advanced malignancy

2514

Background: CD47 is a myeloid checkpoint upregulated by tumor cells to evade the host’s immune response. ALX148 (A) is a fusion protein comprised of a high affinity CD47 blocker linked to an inactive human immunoglobulin Fc region. ALX148 is well tolerated in combination with pembrolizumab (P) or trastuzumab (T) with no maximum tolerated dose (MTD) identified (ASCO 2018 #3068, SITC 2018 #P335). Safety and antitumor activity of ALX148 (10 mg/kg QW) in combination with T or P are reported in patients (pts) including those with anti-HER2 or checkpoint inhibitor (CPI) relapsed/refractory diseases. Methods: Patients with malignancy including non-small cell lung cancer (NSCLC: CPI resistant/refractory or PD-L1 tumor proportion score <50%) and head and neck squamous cell carcinoma (HNSCC: progressed on platinum therapy) received A+P. Patients with HER2 malignancy including gastric/gastroesophageal junction (GEJ) cancer (progressed on T + fluoropyrimidine-based therapy) received A+T. Safety, response, pharmacokinetic (PK), and pharmacodynamic (PD) markers were assessed. Preliminary data from fully enrolled cohorts are reported as of 20 Jan 2019 (safety)/28 Jan 2019 (efficacy). Results: Seventy-nine pts received A+P (All, n=50; NSCLC, n=23; HNSCC, n=20) or A+T (All, n=29; Gastric/GEJ, n=23) as of data cutoff. Forty-seven pts reported mostly low grade treatment related adverse events. The most common were fatigue (11%), AST increase (9%), ALT increase (8%), anemia (8%), and platelets decreased (6%). In select tumor histologies, anticancer activity was observed in initial response-evaluable pts [NSCLC (n=23) 1PR, 8SD; HNSCC (n=17) 3PR, 4SD; and Gastric/GEJ (n=21) 4PR, 6SD]. Preliminary results indicate favorable ALX148 PK and CD47 target occupancy profiles, and positive effects on tumor infiltrating immune cells. Results will be updated at presentation. Conclusions: ALX148 demonstrates excellent tolerability with favorable PK/PD characteristics to date. Objective responses were observed in patients with late line NSCLC, HNSCC, and Gastric/GEJ, including disease relapsed/refractory to prior CPI and HER2-targeted therapies. Clinical trial information: NCT03013218.

A phase I study of a novel MDM2 antagonist APG-115 in patients with advanced solid tumors

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Background: APG-115 is a potent and orally active small-molecule MDM2 protein inhibitor. Binding to MDM2 protein, APG-115 restores p53 tumor suppressive function via induction of apoptosis in tumor cells retaining wild-type p53. In addition, enhanced antitumor activity was demonstrated in the syngeneic tumor models after APG-115 combined with PD-1 blockade. Methods: This Phase I study (APG-115-US-001) was designed to enroll the patients with advanced solid tumors in US (NCT02935907). Study objectives included to assess safety, dose limited toxicity (DLT), pharmacokinetics (PK), pharmacodynamics (PD), and antitumor activity (assessed every 8 weeks per RECIST v1.1). The patients received APG-115 orally every other day (QOD) at the designated dose (ranging from 10 to 300 mg) for first 21 days of a 28-day cycle, until disease progression. Results: Up until Jan 4 2019, total 28 patients were treated with APG-115 at various doses (one patient at 10mg, 20mg and 50mg, respectively; 14 patients at 100mg, 6 patients at 200mg, and 5 patients at 300mg). The median number of prior systemic anticancer therapies was 4 (range 0-15). The DLTs were observed during cycle 1, including one grade 2 thrombocytopenia at 200mg, one grade 3 thrombocytopenia at 300mg, and one grade 3 fatigue at 100mg and 300mg respectively. The most common AEs (reported in ≥10% of pts) included: fatigue, nausea, vomiting, diarrhea, decreased appetite, dehydration, neutrophil count decreased, white blood cell count decreased, pain in extremity, thrombocytopenia. The most common Grade 3 or 4 treatment related AEs were fatigue (10.7%), and thrombocytopenia (10.7%). Six patients had stable disease (SD) after two cycle treatments, two of them are continuing in this study. PK analyses indicated that exposure (Cmax and AUC) generally increases with the increase of dose level from 20 mg to 300 mg. Conclusions: APG-115 was well tolerated and had manageable adverse events. The MTD/RP2D of APG-115 monotherapy with oral administration, QOD for 21 days of a 28-day cycle for treatment of patients with advanced solid tumors was determined as 100 mg. Further evaluation of APG-115 in combination with pembrolizumab in patients with advanced solid tumors is ongoing. Clinical trial information: NCT02935907.

First-in-human study of REGN3767 (R3767), a human LAG-3 monoclonal antibody (mAb), ± cemiplimab in patients (pts) with advanced malignancies

2508

Background: We present initial safety, pharmacokinetics (PK), and efficacy from the dose escalation study of R3767, alone (mono) or in combination with cemiplimab (REGN2810), a PD-1 mAb (combo), in pts with advanced malignancies (NCT03005782). Methods: Pts who had progressed on prior therapy(ies) and/or for whom no therapy with clinical benefit was available were enrolled; most pts had received no prior anti-PD-1/PD-L1. Pts received R3767 1, 3, 10, or 20 mg/kg every 3 weeks (Q3W) ± cemiplimab 3 mg/kg or 350 mg Q3W IV for ≤51 weeks. Crossover from mono to combo was allowed at progression. R3767 PK were evaluated. Tumor measurements were performed Q6W for the first 24 weeks and subsequently Q9W. Data cut-off date was Aug 25, 2018. Results: Mono: 27 pts (median age: 66 yr; ECOG PS: 0 [n=4], 1 [n=23]) were treated. There were no dose-limiting toxicities (DLTs). The most common treatment-emergent adverse event (TEAE) was nausea (22.2%). Grade ≥3 immune-related adverse events (irAEs) of increased alanine and aspartate aminotransferases (each 3.7%) were reported. By investigator-assessment (per RECIST 1.1; INV), best response was stable disease in 11 pts. Combo: 42 pts (median age: 60 yr; ECOG PS: 0 [n=15], 1 [n=27]) were treated. One pt treated with R3767 3 mg/kg Q3W + cemiplimab 3 mg/kg Q3W experienced DLT of grade 4 elevated blood creatine phosphokinase, associated with grade 3 myasthenia syndrome and grade 1 elevated troponin. The most common TEAEs were fatigue (33.3%) and nausea (21.4%). Grade 3 irAE of hypothyroidism (2.4%) was also reported. By INV, 2 (both small cell lung cancer) combo pts and 2 (endometrial cancer and cutaneous squamous cell carcinoma) of 12 additional pts who crossed over from mono to combo had partial responses. PK: R3767 concentrations in serum increased in a dose-dependent manner and were unaffected by combo. Conclusions: The safety profile of R3767 ± cemiplimab was generally tolerable; PK was linear. Early efficacy signals were detected despite the difficult-to-treat pt population. Biomarker studies are ongoing. R3767 20 mg/kg or 1600 mg fixed dose equivalent Q3W as mono and combo were selected for further evaluation. Clinical trial information: NCT03005782.

A phase I study of the APE1 protein inhibitor APX3330 in patients with advanced solid tumors

3097

Background: APX3330 is an orally administered anti-cancer, anti-CIPN agent targeting the APE1 protein. APE1 maintains NFkB, STAT3, AP-1 and HIF-1a in a reduced form, acting as a regulator of transcription factors. A dual function protein, APE1 also plays a role in protecting against oxidative DNA damage in neurons. APX3330 is a highly selective inhibitor of APE1 redox function in tumors that enhances the neuronal protection function of APE1. Methods: We report on study NCT03375086 evaluating APX3330 in patients with incurable malignancies. Eligibility required adequate organ function, PS 0-2 and tumors not amenable to curative therapy. 1° and 2° objectives included determining the recommended phase 2 dose (RP2D), the safety and PK/PD profiles of APX3330 and reporting any RECIST anti-tumor activity. Patients received APX3330 b.i.d, in 21-day cycles. AE evaluation included 1 pt/cohort until the occurrence of ≥ G2 toxicity at which time the study proceeded in a 3+3 design. Additional patient were also recruited in cohorts in order to attain PK/PD and biopsy samples. Results: Between 2/18 and 8/18, 19 subjects (13M, 6F) with median age of 69 y started therapy. Dose (mg/d) escalation and number of patients treated (n) per each cohort proceeded as follows: 240 mg (1), 360 (4), 480 (2), 600 (6) and 720 (6). APX3330 was well tolerated at dose levels from 240-600 mg/d. The most frequent treatment-related adverse event (all grades) was G1 fatigue. A G3 rash occurred in two subjects at the 720 mg level defining 600 mg/d as the RP2D for further development. Six subjects had disease stabilization for ≥ 4 cycles, and of these, four subjects with the following diagnosis, RECIST response and days on study included: (CRC, PR, 356), (Endometrial, SD, 316), (Melanoma, SD, 245), (Prostate, SD, 246). Final PK and PD data, including proteomic, transcriptome, APE1 serum levels and CTC analyses are pending and will be reported at the conference. Conclusions: APX3330 is an orally administered inhibitor of APE1. This phase I study identified 600 mg PO daily as the RP2D for further development. RECIST evaluation identified signs of clinical activity in this un-selected population of patients with advanced cancer. PD analyses indicate APX3330 mediated targeting of the APE1 protein. Clinical trial information: NCT03375086.

ASN003, a highly selective BRAF and PI3K inhibitor: Preclinical and phase 1 clinical data in patients with advanced solid tumors

e14102

Background: RAS-RAF-MEK and PI3K-AKT-mTOR are two major signaling pathways involved in tumorigenesis. Components of these two pathways are frequently mutated in a broad range of tumors. ASN003 is a novel and highly selective small-molecule inhibitor of the RAS-RAF-MEK and PI3K pathways. Methods: The activity of ASN003 was determined using PI3K and BRAF enzymes, and efficacy was studied in human tumor xenograft models in mice. ASN003 is currently being investigated in patients with solid tumors in a Phase 1 trial using an accelerated dose titration design. In Part A, safety and tolerability of ASN003 is being studied in patients with advanced solid tumors. In Part B, safety, tolerability and preliminary efficacy of ASN003 will be evaluated in melanoma, CRC and NSCLC patients with a BRAF, PIK3CA or PTEN mutation. Pharmacokinetic (PK) profile and the pharmacodynamic (PD) effects of ASN003 on biomarkers such as pERK and pS6 are investigated in both parts of the study. Results: ASN003 showed potent and highly selective inhibition of BRAF and PI3K-α and -δ, and low affinity for PI3K-ß. ASN003 showed strong antiproliferative activity in cell lines and caused significant tumor growth inhibition in xenograft models harboring BRAF and PIK3CA or PTEN mutations. ASN003 showed antiproliferative activity in B-RAF and MEK inhibitor resistant cell lines. ASN003 had a strong antitumor activity in a BRAFV600mutant melanoma PDX model resistant to BRAF inhibitors, vemurafenib and dabrafenib. In humans, to date, ASN003 was well tolerated at 10 and 20 mg QD. Adverse events were mild and peak plasma level of 120 nM at 10 mg QD was achieved with a half-life of > 12 h. Dose escalation is ongoing. Conclusions: ASN003 is a unique small molecule, with highly selective and potent inhibition of BRAF, PI3-α and -δ kinases. ASN003 has strong antitumor activity in various xenograft tumor models harboring both BRAF and PIK3CA/PTEN mutations, and in a BRAF inhibitor resistant melanoma PDX model. To date, ASN003 was well tolerated and achieved good systemic exposure. Updated and detailed clinical, PK and PD results will be presented. Clinical trial information: NCT02961283.

Phase I clinical trial of oral 2-methoxyestradiol, an antiangiogenic and apoptotic agent, in patients with solid tumors

PURPOSE

To determine the maximum-tolerated dose (MTD) and toxicity profile of the novel anticancer agent, 2-methoxyestradiol (2ME2) administered orally, in patients with solid tumors.

MATERIALS AND METHODS

Twenty patients with refractory solid tumors were enrolled. 2ME2 was given orally starting at 400 mg bid with dose escalation until 3000 mg bid. Tumor biopsies were taken before and after starting the drug to assess for microvessel density by CD 31 and cell proliferation by Ki67 immunohistochemistry. Serial plasma samples collected up to 50 hours after first single oral dose for characterization of pharmacokinetics, were analyzed using liquid chromatography tandem mass-spectrometry.

RESULTS

Eleven men and nine women received 2ME2 at dose levels of 400 mg bid (n = 3), 800 mg bid (n = 3), 1600 mg bid (n = 6), 2200 mg bid (n = 5) and 3000 mg bid (n = 3). There were no dose limiting toxicities, therefore the MTD was not defined. There was one episode of grade 4 angioedema in the 1600 mg bid dose level 38 days into 2ME2 treatment. Other toxicities were mild to moderate. A patient with clear cell carcinoma of the ovary had a partial response at 1600 mg bid dose level lasting over three years.

CONCLUSION

MTD for 2ME2 was not reached at dose of 3000 mg bid. The trial was closed due to extremely low plasma concentrations of 2ME2 relative to the doses administered. 2ME2 treatment had no effect on microvessel density (CD31 immunostaining) and cell proliferation (Ki-67 immunostaining). A new formulation of 2ME2 with improved bioavailability is currently being developed.