BioXcel announces seven patients achieve composite response in BXCL701 trial

BioXcel Therapeutics announced full data from its Phase 2a trial of BXCL701, the company’s investigational, oral innate immune activator, in combination with Keytruda in small cell neuroendocrine, or SCNC, variant metastatic castration-resistant prostate cancer, or mCRPC, patients after at least one prior line of chemotherapy for locally advanced or metastatic prostate cancer. Results will be presented in a rapid abstract presentation and a poster presentation at the 2023 American Society of Clinical Oncology Genitourinary Cancers, or ASCO GU, Symposium on February 16. In the evaluable patient cohort, seven patients achieved a composite response, the primary endpoint of the trial. In patients with RECIST 1.1-defined measurable disease, partial response was observed in five patients. The disease control rate, defined as complete response + partial response + stable disease, was 48%. The median duration of response for both composite responses and RECIST 1.1-defined partial responses was 6+ months as of the data cutoff on December 19, 2022. Six out of 34 patients in the safety population experienced serious adverse events, or SAEs, possibly related or related to BXCL701 or pembrolizumab, and six patients discontinued any drug due to a treatment-related AE. No evidence found that BXCL701 potentiates immune-related AEs related to immune checkpoint inhibitors. DPP9 overexpression was identified as a potential predictive biomarker for BXCL701 response; biomarker evaluation is ongoing and additional findings will be presented at an upcoming medical meeting.