BioXcel Therapeutics has reported positive top-line data from its Phase II trial of BXCL701 along with Keytruda (pembrolizumab) in patients with an aggressive form of rare prostate cancer.

The multicentre, open-label trial has been designed for assessing the efficacy and safety of the investigational, oral innate immune activator BXCL701, along with pembrolizumab, in men with small cell neuroendocrine metastatic castration-resistant prostate cancer (SCNC).

In the trial, 28 evaluable SCNC patients were given a 0.3mg dose of BXCL701 twice a day (BID) from day one to 14 of a 21-day cycle (0.2mg BID the first week of Cycle 1), along with pembrolizumab 200mg given intravenously on the first day and every subsequent 21 days.

Composite response rate, which is defined as RECIST 1.1 and/or PSA50 and/or CTC count conversion, is the trial’s primary endpoint.

Overall survival, progression-free survival, response duration, and biomarker evaluation that is measured by variations occurring in circulating cytokines, and the correlation of outcomes with baseline characteristics of tumours are some of the secondary endpoints of the study.

The company stated that the findings from the study showed encouraging response rates of BXCL701 along with pembrolizumab in SCNC patients.

BioXcel Therapeutics wholly owned subsidiary OnkosXcel Therapeutics chief research and development officer Vincent O’Neill said: “We are pleased that BXCL701, in combination with pembrolizumab, has demonstrated an encouraging response rate in this difficult-to-treat cancer with no currently approved FDA therapies.

“BXCL701’s promising profile as an oral innate immune activator with a large safety dataset and novel mechanism of action further supports OnkosXcel’s pipeline and use of BioXcel’s AI platform, and reinforces our confidence in BXCL701’s potential to enable checkpoint inhibitor therapy in traditionally cold cancers.”