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Background: KEYNOTE-199 (NCT02787005) is a multicohort phase 2 study evaluating pembrolizumab in patients with metastatic castration-resistant prostate cancer (mCRPC). Results from cohorts 4 (C4) and 5 (C5) are presented., Methods: Eligible patients had not received chemotherapy for mCRPC and had responded to enzalutamide prior to developing resistance as defined by Prostate Cancer Clinical Trials Working Group 3 guidelines. Patients with RECIST-measurable disease were enrolled in C4, and patients with bone-only or bone-predominant disease were enrolled in C5. All patients received pembrolizumab 200 mg every 3 weeks for ≤35 cycles with ongoing enzalutamide until progression, unacceptable toxicity, or withdrawal. The primary end point was objective response rate (ORR) per RECIST v1.1 by blinded independent central review in C4. Secondary end points included disease control rate (DCR), overall survival, and safety in each cohort and both cohorts combined., Results: A total of 126 patients were treated (C4, n = 81; C5, n = 45). Median age was 72 years (range 43-92), and 87.3% had received ≥6 months of enzalutamide prior to study entry. Confirmed ORR was 12.3% (95% CI 6.1-21.5%) for C4. Median duration of response in C4 was 8.1 months (range, 2.5+ to 15.2), and 5 of these patients experienced an objective response lasting ≥6 months. DCR was 53.1% (95% CI 41.7-64.3%) in C4 and 51.1% (95% CI 35.8-66.3%) in C5. Median overall survival was 17.6 months (95% CI 14.0-22.6) in C4 and 20.8 months (95% CI 14.1-28.9) in C5. Grade ≥3 treatment-related adverse events occurred in 35 patients (27.8%); 2 patients in C4 died from immune-related adverse events (myasthenic syndrome and Guillain-Barré syndrome)., Conclusions: The addition of pembrolizumab to ongoing enzalutamide treatment in patients with mCRPC that progressed on enzalutamide after initial response demonstrated modest antitumor activity with a manageable safety profile., Clinical Trial Registry and Id: ClinicalTrials.gov, NCT02787005., (© 2024. This is a U.S. Government work and not under copyright protection in the US; foreign copyright protection may apply.)

With the increasing globalization of drug development and the publication of the International Council for Harmonisation (ICH) E17 guideline (ICH International Council for Harmonisation of Technical Requirements for Pharmaceuticals for Human Use 2017), multi-regional clinical trials (MRCTs) have become a preferred option to accelerate the availability of new medical products by design, execution and simultaneous submission under one protocol. MRCTs, with the participation of all major regions including countries from both developed and emerging markets, surely make new drug development more efficient. Even though the proposed estimand framework (ICH E9 (R1) (2019), came later in 2019 and was not mentioned in ICH E17, the application of the estimand framework has the potential to enhance the design, execution, and analysis in MRCTs. Defining an estimand within the regional context in MRCTs is an important issue that requires careful consideration. Given that consistency evaluation of treatment effects across regions is critical in MRCTs, the utilization of the estimand framework for regional consistency evaluation is also worth discussion. This paper aims to address these two questions. The five attributes of the estimand definition are discussed within a multi-regional context. It is imperative to thoroughly consider regional intrinsic/extrinsic factors when planning the estimand and estimation of MRCTs. A holistic approach is summarized to conduct consistency evaluation. When a regional inconsistency is observed, the possible reasons need to be further explored under five attributes of the estimand framework. Two real case studies are discussed to illustrate the application of the estimand framework in the consistency evaluation.

Current treatment for patients with metastatic hormone-sensitive prostate cancer (mHSPC) delays disease progression and improves survival, but resistance is inevitable. Additional therapies that prolong survival are needed. Androgen deprivation therapy (ADT) combined with next-generation hormonal agents, such as enzalutamide, is standard-of-care for men with mHSPC. Emerging evidence suggests potential synergism between enzalutamide and the PD-1 inhibitor pembrolizumab in prostate cancer. The phase III randomized, placebo-controlled, double-blind KEYNOTE-991 trial will investigate the efficacy and safety of pembrolizumab versus placebo in combination with enzalutamide when initiating ADT in participants with mHSPC naive to next-generation hormonal agents. Approximately 1232 patients will be randomly assigned 1:1 to receive pembrolizumab 200 mg every 3 weeks or placebo every 3 weeks, both with enzalutamide 160 mg once daily and ADT. Dual primary end points are overall survival and radiographic progression-free survival. Secondary end points include time to first subsequent therapy, time to symptomatic skeletal related event, objective response rate and safety and tolerability. Clinical Trial Registration: NCT04191096 (ClinicalTrials.gov).

Survival is generally poor for Chinese patients with advanced melanoma because of high rates of acral and mucosal melanoma and limited therapeutic options. The first analysis of the phase 1b KEYNOTE-151 study showed second-line pembrolizumab was well tolerated and had clinically meaningful antitumor activity in Chinese patients with advanced melanoma. Three-year follow-up is presented. Eligible patients were of Chinese descent and had unresectable stage III/IV melanoma that progressed after first-line therapy. Patients received pembrolizumab 2 mg/kg every 3 weeks for ≤35 cycles. Primary end points were safety and objective response rate (ORR). Secondary end points included duration of response (DOR), progression-free survival (PFS), and overall survival (OS). Response was assessed per RECIST v1.1 by blinded independent central review. Subgroup analyses were conducted by melanoma subtype and BRAF and PD-L1 status (acral melanoma only). 103 patients were enrolled; median follow-up duration (time from first dose to data cutoff [July 13, 2020]) was 44.6 months (IQR, 39.1-46.2). Any-grade treatment-related adverse events (TRAEs) occurred in 85.4% of patients, and grade 3/4 TRAEs in 12.6%. No grade 5 TRAEs occurred. Three patients discontinued pembrolizumab because of TRAEs (immune-mediated hepatitis, pneumonia, and arthritis). Immune-mediated AEs and infusion reactions occurred in 34.0% (grade 3/4, 2.9%). ORR was 17.6% (95% CI, 10.8-26.4; 1 complete response/17 partial responses), and median DOR was 13.8 months (range, 2.7-37.4+). Median PFS was 2.8 months (95% CI, 2.7-3.5) and 36-month PFS rate was 5.0%. Median OS was 13.2 months (95% CI, 10.4-16.5) and 36-month OS rate was 22.3%. Median OS for patients with known melanoma subtype was 14.8 months for acral, 13.5 months for nonacral cutaneous, and 7.4 months for mucosal melanoma. Among the acral subgroup, median OS was 22.8 months for PD-L1-positive disease, 8.4 months for PD-L1-negative disease, 18.5 months for BRAF wild-type disease, and 5.8 months for BRAF -mutant disease. Over 3 years' follow-up, second-line pembrolizumab continued to show manageable safety, clinically meaningful antitumor activity, and durable responses in Chinese patients with advanced melanoma. Subgroup analysis suggested particular benefit in PD-L1-positive and BRAF wild-type acral melanoma, although small subgroup sizes preclude definitive conclusions., Clinical Trial Registration: https://clinicaltrials.gov, identifier NCT02821000., Competing Interests: The study received funding from Merck Sharp and Dohme LLC, a subsidiary of Merck and Co., Inc., Rahway, NJ, USA. The funder had the following involvement with the study: the funder of the study collaborated with academic advisers in designing the study, gathering, analyzing, and interpreting the results, and payment of open access publication fees for the current manuscript. LS reports receiving honoraria from MSD, Roche, Juushi Bio, and Novartis. XW reports receiving grants to their institution from Oriengene. SD reports employment at Merck Sharp and Dohme LLC, a subsidiary of Merck and Co., Inc., Rahway, NJ, USA, and is a shareholder of Merck and Co., Inc., Rahway, NJ, USA. CN reports employment at MSD, China, and receiving honoraria from MSD, China. JFL reports employment at Merck Sharp and Dohme LLC, a subsidiary of Merck and Co., Inc., Rahway, NJ, USA. HD reports employment at MSD, China, and receiving honoraria from MSD, China. JG reports advisory/consultancy roles with MSD, Roche, Bayer, Novartis, Simcere Pharmaceutical Group, Shanghai Junshi Biosciences, and Oriengene. The remaining authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2022 Si, Zhang, Shu, Pan, Wu, Liu, Mao, Wang, Wen, Gu, Zhu, Lan, Cai, Diede, Dai, Niu, Li and Guo.)

Purpose: Standard-dose pembrolizumab plus alternative-dose ipilimumab (1 mg/kg Q3W for 4 doses) were tolerable and had robust antitumor activity in advanced melanoma in cohort B of the phase 1 KEYNOTE-029 study. Cohort C evaluated standard-dose pembrolizumab with two other alternative ipilimumab regimens., Patients and Methods: Patients with treatment-naive unresectable stage III/IV melanoma were randomly assigned 1:1 to pembrolizumab 200 mg Q3W for ≤24 months plus ipilimumab 50 mg Q6W for 4 doses (PEM200+IPI50), or the same pembrolizumab regimen plus ipilimumab 100 mg Q12W for 4 doses (PEM200+IPI100). Primary end points were incidence of grade 3-5 treatment-related adverse events (TRAE) and objective response rate (ORR) per RECIST v1.1 by independent central review. Per protocol-defined thresholds, grade 3-5 TRAE incidence ≤26% indicated meaningful toxicity reduction and ORR ≥48% indicated no decrease in efficacy versus data reported for other PD-1 inhibitor/ipilimumab combinations., Results: Median follow-up on February 18, 2019, was 16.3 months in PEM200+IPI50 (N = 51) and 16.4 months in PEM200+IPI100 (N = 51). Grade 3-5 TRAEs occurred in 12 (24%) patients in PEM200+IPI50 and 20 (39%) in PEM200+IPI100. One patient in PEM200+IPI50 died from treatment-related autoimmune myocarditis. Immune-mediated AEs or infusion reactions occurred in 21 (42%) patients in PEM200+IPI50 and 28 (55%) in PEM200+IPI100. ORR was 55% in PEM200+IPI50; 61% in PEM200+IPI100., Conclusions: Pembrolizumab 200 mg Q3W plus ipilimumab 50 mg Q6W or 100 mg Q12W demonstrated antitumor activity above the predefined threshold; pembrolizumab plus ipilimumab 50 mg Q6W had lower incidence of grade 3-5 TRAEs than the predefined threshold, suggesting a reduction in toxicity. See related commentary by Jameson-Lee and Luke, p. 5153., (©2021 The Authors; Published by the American Association for Cancer Research.)