Meeting with FDA paves way for phase 3 trial of PT-112 in mCRPC

Promontory Therapeutics Inc has reported a positive end of phase 2 (EOP2) meeting with the FDA, paving the way for the company to initiate a pivotal phase 3 trial of PT-112 monotherapy in patients with late-line metastatic castration-resistant prostate cancer (mCRPC).¹

Preliminary data from the phase 2 study of PT-112 will be presented at an upcoming medical meeting.

According to the company, PT-112 is a small molecule that “leads to immunogenic cancer cell death (ICD) and an anti-cancer immune response.” The bio-distribution of PT-112 also enables the therapy to be delivered to bone sites of disease.²

During the EOP2 meeting on PT-112, the FDA agreed on the proposed dosing regimen, study end points, comparator and statistical framework, and patient population within mCRPC, Promontory reported. The FDA also agreed on the proposal for an interim analysis, which would allow Promontory to potentially submit for regulatory approval of PT-112 before final completion of the trial.

The phase 3 study design will now be submitted for final review by the agency. Promontory also noted that they plan to conduct similar meetings with international regulatory agencies.

Phase 2 trial of PT-112

Preliminary data from the completed phase 2 study of PT-112 monotherapy in mCRPC are set to be presented at the upcoming American Society of Clinical Oncology (ASCO) meeting in Chicago, Illinois.

In total, the open-label phase 1/2 trial enrolled approximately 109 adult patients with mCRPC across clinical trial sites in the US and France.³ Patients included in the study were randomly assigned to 1 of 3 dosing arms: PT-112 dosed biweekly at 360 mg/m², PT-112 dosed biweekly at 250 mg/m², or PT-112 dosed at 360 mg/m² for 2 doses and 250 mg/m² for subsequent doses.

To be eligible for enrollment, patients needed to have received at least 3 prior lines of therapy and have an ECOG performance status of 0 or 1, progressive disease, and adequate organ function. Participants were excluded if they had received any cytotoxic chemotherapy within 21 days prior to study initiation, radiotherapy within 14 days prior to baseline, or major surgery within 28 days prior to study start.

The primary outcome measure for the study was to define the recommended dose level and dosing schedule for the pivotal trial of PT-112. Secondary outcome measures included disease control rate, objective response rate, median duration of response, and the percentage of patients who achieved at least a 50% decline in prostate-specific antigen levels.

Data presented at ASCO will span safety and efficacy data from all 3 dosing arms as well as biomarker responses and correlative research.⁴

PT-112 is also being investigated as a monotherapy in a phase 2 study in patients with thymic epithelial tumors. In 2018, the FDA awarded an orphan drug designation to PT-112 for this indication.⁵

REFERENCES

1. Promontory Therapeutics announces successful end of phase 2 meeting with US FDA on phase 3 registrational study design for PT-112 in patients with metastatic castration-resistant prostate cancer. News release. Promontory Therapeutics Inc. Published online and accessed May 20, 2025. https://promontorytx.com/news/promontory-therapeutics-announces-successful-end-of-phase-2-meeting-with-us-fda-on-phase-3-registrational-study-design-for-pt-112-in-patients-with-metastatic-castration-resistant-prostate-cancer

2. PT-112. Promontory Therapeutics. Accessed May 20, 2025. https://promontorytx.com/pt-112

3. A study evaluating the safety, pharmacokinetics, and clinical effects of intravenously administered PT-112 injection in subjects with advanced solid tumors and subsequent dose expansion cohorts. ClinicalTrials.gov. Last updated April 5, 2024. Accessed May 20, 2025. https://clinicaltrials.gov/study/NCT02266745

4. Promontory Therapeutics announces preliminary results from phase 2 study of PT-112 monotherapy in mCRPC to be presented at the ASCO 2025 Annual Meeting. News release. Promontory Therapeutics Inc. April 23, 2025. Accessed May 20, 2025. https://promontorytx.com/news/cd7eacod4ol9nrmti1uhxe5bfzylwc

5. Key milestones. Promontory Therapeutics Inc. Accessed May 20, 2025. https://promontorytx.com/key-milestones