BioXcel Therapeutics Reports Positive Overall Survival Results From Single-Arm, Open-Label Phase 2 Trial of BXCL701 in Patients With Small Cell Neuroendocrine Prostate Cancer

BioXcel Therapeutics, Inc. recently announced positive overall survival (OS) data from its Phase 2 trial of BXCL701, the company’s investigational oral innate immune activator, in combination with KEYTRUDA (pembrolizumab) in patients with small cell neuroendocrine prostate cancer (SCNC). As of a data cutoff of September 6, 2023, evaluable patients with SCNC (n=28) showed a median OS of 13.6 months (95% CI 10.9–NR), and a 12-month survival rate of 56.5%.

“OS is the most meaningful measure by which the effectiveness of an oncology treatment is evaluated. Though these results are based on a non-randomized cohort of patients, observing a median OS of this duration including patients with long-term survival at 12 months and beyond shows exceptional promise, bearing in mind historic data with checkpoint inhibitor monotherapy in this high-risk subset of prostate cancer,” said Rahul Aggarwal, MD, Principal Investigator, Associate Director for Clinical Sciences, Helen Diller Family Comprehensive Cancer Center, and Professor of Medicine at the University of California San Francisco (UCSF). “SCNC represents a major unmet medical need, with the majority of patients unfortunately succumbing to their disease in less than 1 year following chemotherapy. The results of this trial suggest that BXCL701 has the potential to extend the lives of patients, and I look forward to its continued clinical development.”

SCNC, classified as a “cold” tumor, represents an underserved, growing patient population, with cases increasing due to earlier and more widespread use of androgen receptor inhibitors. In 2023, there will be an estimated 288,300 new patients with prostate cancer in the US, with approximately 11,532 patients progressing to SCNC.

“We believe our trial results are highly encouraging for patients with this disease and have potential implications for our evaluation of BXCL701 for the treatment of other high-grade neuroendocrine tumors, such as small cell lung cancer, where effective therapies are lacking,” said Vincent J. O’Neill, MD, Chief R&D Officer, OnkosXcel Therapeutics, a wholly owned subsidiary of BioXcel Therapeutics. “We intend to discuss these data with the FDA to help determine our next steps with clinical development.”

The Phase 2 trial is an open-label, multicenter study to evaluate the safety and efficacy of BXCL701 in combination with pembrolizumab in men with SCNC. Twenty-eight (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 objective of the trial is a composite response rate defined as either objective response by RECIST 1.1 criteria and/or PSA₅₀ and/or CTC count conversion.

Secondary objectives 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.

The company is continuing to actively evaluate strategic options for OnkosXcel Therapeutics, including potential financing, strategic partnership, or M&A.

mCRPC is a form of advanced prostate cancer that is no longer responding to testosterone-lowering hormone treatments and has spread to other areas of the body such as the lymph nodes, bones, bladder, rectum, liver, or lungs. Treatment-emergent SCNC is a particularly difficult-to-treat histologic subtype of mCRPC that emerges in approximately 20% of mCRPC patients, though this number is increasing due to earlier and more widespread use of androgen blockers.

OnkosXcel Therapeutics, LLC is a wholly owned subsidiary of BioXcel Therapeutics, Inc., focused on developing transformative medicines in oncology utilizing artificial intelligence. The subsidiary was formed in 2022 to develop BXCL701.

BXCL701 is an investigational, oral innate immune activator designed to initiate inflammation in the tumor microenvironment. Approved and experimental immunotherapies often fail to address cancers that appear “cold.” Therefore, BXCL701 is being evaluated to determine if it can render “cold” tumors “hot,” making them more detectable by the adaptive immune system and thereby facilitating the development of a strong anti-cancer immune response. OnkosXcel Therapeutics’ preclinical data support BXCL701’s potential synergy with both current checkpoint inhibitors and emerging immunotherapies directed to activate T-cells. BXCL701 is currently being developed as a potential therapy for the treatment of aggressive forms of prostate cancer and advanced solid tumors that are refractory or treatment naïve to checkpoint inhibitors. BXCL701 has received Orphan Drug Designation from the US FDA in four indications: acute myelogenous leukemia, pancreatic cancer, stage IIb to IV melanoma, and soft tissue sarcoma. An approximately 800-subject clinical database, with data collected by the company and others, supports the ongoing development of BXCL701.

BioXcel Therapeutics, Inc. (Nasdaq: BTAI) is a biopharmaceutical company utilizing artificial intelligence to develop transformative medicines in neuroscience and immuno-oncology. The company’s drug re-innovation approach leverages existing approved drugs and/or clinically validated product candidates together with big data and proprietary machine learning algorithms to identify new therapeutic indications. For more information, visit bioxceltherapeutics.com.