BTAI: BXCL701 Shows Positive Overall Survival Results in Phase 2 Trial…
NASDAQ:BTAI
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Positive Overall Survival Results Seen in Phase 2 Trial of BXCL701
On October 10, 2023, BioXcel Therapeutics, Inc. (NASDAQ:BTAI) announced positive overall survival (OS) results from the single-arm, open-label Phase 2 clinical trial of BXCL701 in combination with Keytruda® in patients with small cell neuroendocrine prostate cancer (SCNC). A copy of the slides with the results can be found here. BXCL701 (talabostat) is an oral small molecule immunomodulator designed to activate the innate immune system through inhibition of dipeptidyl peptidase (DPP) 8/9 and fibroblast activation protein (FAP). Its purpose is to initiate inflammation in the tumor microenvironment, thus potentially turning “cold” tumors “hot” and making them more amenable to immunotherapy treatment.
The following slide gives an overview of the Phase 2 trial. An interim analysis was conducted for the first 15 patients with an additional 13 patients for a total of 28 patients. It was conducted at 13 centers across the U.S. and U.K. The primary objective was the composite response rate with additional endpoints examining the duration of response, OS, progression-free survival (PFS), and biomarker data.
The following slide shows the swimmer’s plot with a data cutoff of September 6, 2023. The median follow-up was 24 months. It should be noted that 6 patients continued to receive treatment after minor progression. Those patients were allowed to continue treatment if they were doing well in the opinion of the investigator.
The following slide shows the Kaplan-Meier curve, with the grey representing the 95% confidence interval. The median overall survival for this cohort was 13.6 months and the 12-month survival rate was 56.5%, which is higher than would normally be expected for a cohort of patients with SCNC.
As a means to put the data into perspective, the company made a comparison to the Phase 2 trial of avelumab in patients with aggressive-variant or neuroendocrine prostate cancer (Brown et al., 2022). On the conference call to discuss the data, management indicated that trial was chosen as it is the only published data involving a checkpoint inhibitor and patients with SCNC. The following table gives a comparability of patient populations between the two trials.
The following table shows that the Phase 2 trial with BXCL701 had an overall response rate of 20% while there was only one responder in the avelumab trial, a patient who is MSI-high. While there are a number of caveats to doing cross-trial comparisons, we feel that the data for BXCL701 compares favorably to the avelumab data, particularly given the fact that only 1/3rd of the patients in the avelumab trial had histology confirmed SCNC, meaning that patient cohort might be expected to have performed better than a cohort of 100% histology confirmed SCNC patients.
BioXcel now plans to discuss the trial data with the FDA, at which time the company is hoping to get feedback on a pivotal study design. The company plans on discussing with the agency that a surrogate endpoint study is the most feasible, as a properly powered survival study would take many years to complete. However, we are unsure of whether the FDA will agree to a surrogate endpoint for a pivotal trial and will await confirmation from the company following the meeting.
Meetings with FDA Regarding BXCL501
In regards to BXCL501, BioXcel recently conducted a Type B meeting with the FDA to discuss the data package for an sNDA for the approval of BXCL501 for the acute treatment of agitation in mild to moderate dementia patients with probable Alzheimer’s in assisted living facilities and the at-home setting. In addition, the company has a meeting with the FDA scheduled for November 8, 2023 to discuss the data package required for filing an sNDA seeking approval for the acute treatment of agitation associated with bipolar disorders I and II and schizophrenia in the at-home setting. We anticipate an update from the company regarding each of those meetings following receipt of the meeting minutes, which should occur approximately 30 days following the meeting.
IGALMI™ IP Strengthened
On October 4, 2023, BioXcel announced it recently received two Notices of Allowance (NOAs) from the U.S. Patent and Trademark Office for patent applications related to the method of use of sublingual dexmedetomidine for the treatment of agitation associated with bipolar disorders and schizophrenia. These patents will be listed in the FDA’s ‘Orange Book’ after they are granted. There are now four U.S. patents claiming formulations of dexmedetomidine with exclusivity until 2039 and the two new patents will expire no earlier than Dec. 29, 2037 (subject to patent term extension, adjustment, and terminal disclaimers).
Conclusion
The data presented for BXCL701 is very encouraging and we look forward to updates from the company as it charts the path forward for that program. With very few treatment options available to patients with SCNC we are hopeful the FDA will work with the company to determine a feasible outcome for a registration trial that can be accomplished in a reasonable amount of time. We are also looking forward to updates from the company regarding the potential sNDAs for the TRANQUILITY and SERENITY III programs. With no changes to our model, our valuation remains at $12 per share.
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