Novel Drug-Immunotherapy Combo Boosts Survival in Rare Prostate Cancer

The addition of the novel drug, BXCL701 to the immunotherapy agent, Keytruda (pembrolizumab) tended to improve survival over Keytruda alone in patients with small cell neuroendocrine prostate cancer (SCNC), according to findings from a phase 2 trial.

SCNC is a rare type of high-grade neuroendocrine carcinoma that tends to be aggressive and have a poor prognosis. According to the National Institutes of Health, the disease accounts for approximately 0.5% to 1% of all prostate cancer diagnoses.

According to findings from the phase 2 trial, which were announced by Bioxcel Therapeutics, the manufacturer of BXCL701, the average overall survival (OS; time from treatment until death of any cause) was 13.6 months in patients who received BXCL701 plus Keytruda, compared with 7.6 month for patients who received Keytruda alone. Additionally, at the 12-month mark, more than half (56.5%) of patients who received the novel drug were still alive.

“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,” Dr. Rahul Aggarwal, 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), said in the press release.

The trial included 28 patients with SCNC who were treated with intravenous Keytruda and oral BXCL701. The main goal of the study is to determine complete response rates (percentage of patients whose disease completely disappears after treatment). Researchers are also analyzing duration of response, progression-free survival (time until disease worsening or death), OS and biomarker evaluations, which will be measured by changes in cytokines (an inflammatory molecule) in the blood stream.

BXCL701 — which is also being investigated for other solid tumors that were not treated with or did not respond to immunotherapy — works by making “cold” tumors “hot,” meaning that the drug makes cancer cells more detectable by the immune system. The novel drug accomplishes this by sparking inflammation within the tumor microenvironment.

Keytruda also works by harnessing the power of the immune system. This drug, known as a checkpoint inhibitor, inhibits a protein that helps cancer cells hide from the immune system. In doing so, T cells can then find and attack the tumors.

The two-drug combination will continue to be studied for the treatment of patients with SCNC.

“SCNC represents a major unmet medical need, with the majority of patients unfortunately succumbing to their disease in less than one 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,” Aggarwal said.

Down the road, BXCL701 may also be studied for other types of cancers, according to the release.

“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,” Dr. Vincent J. O’Neill, Chief R&D Officer, OnkosXcel Therapeutics, a wholly owned subsidiary of BioXcel Therapeutics, said in the release.

For more news on cancer updates, research and education, don’t forget to subscribe to CURE®’s newsletters here.