A randomized phase 2 trial of pembrolizumab versus pembrolizumab and acalabrutinib in patients with platinum-resistant metastatic urothelial cancer.

Inhibition of the programmed cell death protein 1 (PD-1) pathway has demonstrated clinical benefit in metastatic urothelial cancer (mUC); however, response rates of 15% to 26% highlight the need for more effective therapies.

Bruton tyrosine kinase (BTK) inhibition may suppress myeloid-derived suppressor cells (MDSCs) and improve T-cell activation.

The Randomized Phase 2 Trial of Acalabrutinib and Pembrolizumab Immunotherapy Dual Checkpoint Inhibition in Platinum-Resistant Metastatic Urothelial Carcinoma (RAPID CHECK; also known as ACE-ST-005) was a randomized phase 2 trial evaluating the PD-1 inhibitor pembrolizumab with or without the BTK inhibitor acalabrutinib for patients with platinum-refractory mUC. The primary objectives were safety and objective response rates (ORRs) according to the Response Evaluation Criteria in Solid Tumors, version 1.1. Secondary endpoints included progression-free survival (PFS) and overall survival (OS). Immune profiling was performed to analyze circulating monocytic MDSCs and T cells.

Seventy-five patients were treated with pembrolizumab (n = 35) or pembrolizumab plus acalabrutinib (n = 40). The ORR was 26% with pembrolizumab (9% with a complete response [CR]) and 20% with pembrolizumab plus acalabrutinib (10% with a CR). The grade 3/4 adverse events (AEs) that occurred in ≥15% of the patients were anemia (20%) with pembrolizumab and fatigue (23%), increased alanine aminotransferase (23%), urinary tract infections (18%), and anemia (18%) with pembrolizumab plus acalabrutinib. One patient treated with pembrolizumab plus acalabrutinib had high MDSCs at the baseline, which significantly decreased at week 7. Overall, MDSCs were not correlated with a clinical response, but some subsets of CD8+ T cells did increase during the combination treatment.

Both treatments were generally well tolerated, although serious AE rates were higher with the combination. Acalabrutinib plus pembrolizumab did not improve the ORR, PFS, or OS in comparison with pembrolizumab alone in mUC. Baseline and on-treatment peripheral monocytic MDSCs were not different in the treatment cohorts. Proliferating CD8+ T-cell subsets increased during treatment, particularly in the combination cohort. Ongoing studies are correlating these peripheral immunome findings with tissue-based immune cell infiltration.

Cancer. 2020 Aug 05 [Epub ahead of print]

Tian Zhang, Michael R Harrison, Peter H O'Donnell, Ajjai S Alva, Noah M Hahn, Leonard J Appleman, Jeremy Cetnar, John M Burke, Mark T Fleming, Matthew I Milowsky, Amir Mortazavi, Neal Shore, Guru P Sonpavde, Emmett V Schmidt, Bojena Bitman, Veerendra Munugalavadla, Raquel Izumi, Priti Patel, Janet Staats, Cliburn Chan, Kent J Weinhold, Daniel J George

Duke Cancer Institute, Division of Medical Oncology, Department of Medicine, Duke University Medical Center, Durham, North Carolina., University of Chicago, Chicago, Illinois., University of Michigan Medical Center, Ann Arbor, Michigan., Johns Hopkins University, Baltimore, Maryland., University of Pittsburgh, Pittsburgh, Pennsylvania., Oregon Health and Science University Center for Health, Portland, Oregon., Rocky Mountain Cancer Centers, Aurora, Colorado., Virginia Oncology Associates, Norfolk, Virginia., Lineberger Comprehensive Cancer Center, University of North Carolina-Chapel Hill, Chapel Hill, North Carolina., Ohio State University Comprehensive Cancer Center, Columbus, Ohio., Carolina Urologic Research Center, Myrtle Beach, South Carolina., Dana-Farber Cancer Institute, Boston, Massachusetts., Merck & Co, Inc, North Wales, Pennsylvania., Acerta Pharma (a member of the AstraZeneca group), South San Francisco, California., Division of Surgical Sciences, Department of Surgery, Duke University Medical Center, Durham, North Carolina., Department of Biostatistics and Bioinformatics, Duke University Medical Center, Durham, North Carolina.

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