BioXcel Therapeutics, Inc. announced promising top-line data from its Phase 2 trial of BXCL701, the Company's investigational, oral innate immune activator, in combination with KEYTRUDA(R) (pembrolizumab) in small cell neuroendocrine metastatic castration-resistant prostate cancer patients. Full data have been submitted to the 2023 American Society of Clinical Oncology Genitourinary Cancers Symposium. SCNC represents a rare, underserved, growing patient population, with SCNC cases increasing due to earlier and more widespread use of androgen receptor inhibitors.

In 2022, there were an estimated 268,500(1) new prostate cancer patients, with approximately 10,740 patients progressing to SCNC. The Phase 2a trial is an open-label, multicenter study to evaluate the safety and efficacy of BXCL701 in combination with pembrolizumab in men with SCNC. Eligibility criteria include histologically confirmed de novo or treatment-emergent SCNC, progression as defined by PCWG3 criteria, and at least 1 prior line of chemotherapy for locally advanced or metastatic prostate cancer.

28 evaluable SCNC patients received 0.3 mg of BXCL701 twice daily (BID) on days 1 through 14 of a 21-day cycle (0.2 mg BID the first week of Cycle 1) plus 200 mg of pembrolizumab administered intravenously on day 1 and every subsequent 21 days. The primary endpoint of the trial is a composite response rate defined as RECIST 1.1 and/or PSA(50) and/or CTC count conversion. Secondary endpoints include duration of response, progression-free survival, overall survival, and biomarker evaluation as measured by changes in circulating cytokines and correlation of outcome with baseline tumor characteristics.