Purpose: Enhancer of zeste homolog 2 (EZH2) activity is dysregulated in many cancers.Patients and Methods: This phase I study determined the safety, maximum-tolerated dose (MTD), pharmacokinetics, and pharmacodynamics of the intravenously administered, highly selective EZH2 inhibitor, GSK2816126, (NCT02082977). Doses of GSK2816126 ranged from 50 to 3,000 mg twice weekly, and GSK2816126 was given 3-weekson/1-week-off in 28-day cycles. Eligible patients had solid tumors or B-cell lymphomas with no available standard treatment regimen.Results: Forty-one patients (21 solid tumors, 20 lymphoma) received treatment. All patients experienced !1 adverse event (AE). Fatigue [22 of 41 (53.7%)] and nausea [20 of 41 (48.8%)] were the most common toxicity. Twelve (32%) patients experienced a serious AE. Dose-limiting elevated liver transaminases occurred in 2 of 7 patients receiving 3,000 mg of GSK2816126; 2,400 mg was therefore established as the MTD. Following intravenous administration of 50 to 3,000 mg twice weekly, plasma GSK2816126 levels decreased biexponentially, with a mean terminal elimination half-life of approximately 27 hours. GSK2816126 exposure (maximum observed plasma concentration and area under the plasmatime curve) increased in a dose-proportional manner. No change from baseline in H3K27me3 was seen in peripheral blood mononuclear cells. Fourteen of 41 (34%) patients had radiological best response of stable disease, 1 patient with lymphoma achieved a partial response, 21 of 41 (51%) patients had progressive disease, and 5 patients were unevaluable for antitumor response.Conclusions: The MTD of GSK2816126 was established at 2,400 mg, but the dosing method and relatively short half-life limited effective exposure, and modest anticancer activity was observed at tolerable doses.

resistant prostate cancer; CTCAE v4.0, Common Terminology Criteria for Adverse Events version 4.0; ECG, electrocardiogram; ECOG, Eastern Cooperative Oncology Group; ER + BC, estrogen receptorpositive breast cancer; FPKM, fragments per kilobase per million reads; FTIH, first time in human; GIST, gastrointestinal stromal tumor; GSEA, gene set enrichment analysis; HIV, human immunodeficiency virus; MSigDB, molecular signatures database; NC, nuclear protein in testis carcinoma; NUT, nuclear protein in testis; ORR, overall response rate; PD, progressive disease; PK, pharmacokinetic; PR, partial response; PSA, prostate-specific antigen; QTcF, QT interval assessment corrected for heart rate by Fridericia's formula; RECIST v1.1, Response Evaluation Criteria In Solid Tumors version 1.1 criteria; RP2D, recommended Phase 2 dose; SAE, serious adverse event; SCLC, small cell lung cancer; SD, stable disease; TNBC, triple-negative breast cancer; ULN, upper limit of normal.Antara Datta was working at GSK at the time of study design and initiation.

TPS391 Background: Metastatic castrate-resistant prostate cancer (mCRPC) remains an incurable illness as resistance develops after androgen deprivation therapy (ADT) and/or androgen receptor (AR) axis targeted therapies. The bromodomain (BRD) and extraterminal (BET) proteins are critical for transcription. Preclinically, one of these proteins, BRD4, acts in complex with AR to mediate androgen signaling that leads to prostate cell growth and proliferation. GSK525762 is an oral pan-BET inhibitor that suppresses BET dependent activated AR-driven transcription. Combined with androgen production or receptor targeted agents like abiraterone or enzalutamide, GSK525762 may enhance efficacy of or overcome resistance to either agent. Methods: This is a Phase Ib open-label, dose-escalation study to evaluate the safety and efficacy of oral administration of GSK525762 in combination with either abiraterone plus prednisone (Arm A) or enzalutamide (Arm B) in mCRPC patients whose disease has progressed on prior abiraterone or enzalutamide. Patients must have documented prostate cancer progression as assessed by rising PSA or radiographic progression of soft tissue by PCWG3-modified RECIST 1.1 criteria or bone metastasis. Dose escalation is designed to identify safe doses to move into dose expansion. Dose expansion will explore safety and efficacy in patients who failed in first line (L2 population) or after multiple lines of prior therapy (LX population). Primary objectives include defining the safety, tolerability and clinical activity of GSK525762 when combined with products in Arm A or Arm B. Primary clinical activity endpoint is defined as the response rate of subjects achieving a 50% or more reduction from baseline of PSA at 12 weeks or thereafter. Dose escalation will employ a modified Toxicity Probability Interval (mTPI) design. Dose expansion will use a Bayesian adaptive design, which will calculate posterior probability that utility of the dose is clinically significant at interim futility analysis for each dose level. Funding: GSK Clinical trial information: NCT03150056.

BackgroundAutophagy is a catabolic process that is triggered in cells during periods of metabolic or hypoxic stress, which enables their survival during this challenge. Autophagy may also impart survival advantage to tumors cells undergoing attack from chemotherapy or radiation. Inhibition of early-stage autophagy can rescue cancer cells, while inhibition of late-stage autophagy enhances cell death due to accumulation of damaged organelles. The antiparasitic drugs chloroquine (CQ) and hydroxychloroquine (HCQ) inhibit late-phase autophagy. We assessed the safety, tolerability, and efficacy of combining CQ or HCQ with carboplatin and gemcitabine (CG) in patients with refractory advanced solid tumors.MethodsThis single institution phase 1 dose-escalation study was designed to evaluate the maximum tolerated dose (MTD) of CQ/HCQ, in combination with CG, in patients with advanced solid tumors. Secondary objectives were to determine overall response rate (ORR), progression-free survival (PFS), and overall survival (OS). A starting dose of CQ or HCQ 50 mg was used in conjunction with standard starting doses of CG and increased in increments of 50 mg in each patient dose cohort. Grade 3 or greater toxicity that is treatment related, and was not self-limited, or not controlled in <7 days was considered dose-limiting toxicity (DLT).ResultsTwenty-two patients were enrolled. All patients had at least one prior treatment, and 11 of them had 3 prior regimens. CQ/HCQ 100 mg daily was found to be the MTD in combination with CG with thrombocytopenia and/or neutropenia dose limiting. The median overall (OS) was 11 months, and the 1- and 3-year OS were 30% and 7%, respectively. Median progression-free survival was 5 months, and the 6-, 12-, and 18-month progression-free survivals were 48%, 21%, and 14%, respectively.ConclusionThe MTD identified for CQ/HCQ was lower than previously reported with concomitant use of chemotherapeutic regimes likely due to the myelosuppressive nature of CG in previously treated patients.

TPS501 Background: Urothelial cancer (UC) is the most common histological subtype of bladder cancer. For patients with metastatic UC, platinum-containing chemotherapy (CT) is the first-line standard of care. With 5 PD-(L)1 inhibitors approved for second-line treatment of platinum-refractory advanced UC, objective response rates (ORRs) in this setting (15% to 21%) and in first-line cisplatin-ineligible patients (23% to 31%) suggest that there remains a significant unmet need for improved outcomes. TGF-β signaling has been associated with resistance to PD-(L)1 inhibitors in patients with UC. Bintrafusp alfa (BA) is a first-in-class bifunctional fusion protein composed of the extracellular domain of the TGF-βRII receptor (a TGF-β “trap”) fused to a human IgG1 mAb blocking PD-L1. In murine models, BA resulted in improved antitumor activity vs TGF-β or PD-L1 monotherapies alone or in combination. In 2 phase I trials (NCT02517398 and NCT02699515), BA demonstrated a manageable safety profile and encouraging clinical efficacy in >670 patients with advanced solid tumors. Here we describe a phase Ib study (NCT04349280) that will assess the clinical activity and safety profile of BA in platinum-experienced patients with locally advanced/unresectable or metastatic UC. Colocalized, simultaneous inhibition of the TGF-β and PD-L1 pathways by BA is hypothesized to elicit greater antitumor activity than anti–PD-(L)1 therapies in patients with UC. Methods: This open-label, multicenter, single-arm trial is accruing patients with histologically confirmed locally advanced/unresectable or metastatic UC (ECOG PS ≤1) with disease progression or recurrence after platinum-based CT. Patients must not have received >2 lines of systemic therapy for metastatic disease or prior therapy targeting T-cell costimulation, or checkpoint or TGF-β pathways. Patients with pneumonitis or a history of noninfectious pneumonitis that required systemic immunosuppression are ineligible. Patients will receive BA 1200 mg every 2 weeks until progression, unacceptable toxicity, death, or study withdrawal, or for up to 2 years. The primary endpoint is investigator-assessed confirmed ORR per RECIST 1.1; key secondary endpoints include duration of response and progression-free survival per the investigator and IRC, overall survival, safety, immunogenicity, and pharmacokinetics. Exploratory biomarker analyses will be conducted using patient samples collected during screening and prior to administration of BA. The base ORR used for the null hypothesis is 21%, and the target ORR is 40%. Using a predictive probability design and an estimated enrollment of 40 patients, the type I error rate is 5.70% and the power is 85.39%. As of September 2020, 3 sites in 2 countries have been activated and no patients have been enrolled. Clinical trial information: NCT04349280.