Promontory Therapeutics has announced the completion of subject enrolment for its Phase II clinical trial of PT-112, a lead therapeutic candidate for metastatic castration-resistant prostate cancer (mCRPC).

The trial met the target enrolment of 109 participants, who were treated priorly with a minimum of three life-prolonging treatments and showed radiographic disease progression.

Subjects having bone-only metastatic disease are also part of the trial. These patients should have received standard of care of androgen receptor signalling inhibitors, taxane chemotherapies and any other FDA approved drug based on overall survival.

A small-molecule conjugate of pyrophosphate, PT-112 is being evaluated for its safety and efficacy in people with late-stage mCRPC.

The clinical trial is being conducted across 32 study centres in the US and France.

It will also assess immune activation triggered by PT-112 monotherapy and its effects on circulating tumour cells and circulating tumour deoxyribonucleic acid (ctDNA).

Promontory is preparing for a Type C meeting with the US regulator in the second half of this year, which will be followed by an End-of-Phase II meeting.

The company also plans to hold talks with European regulatory authorities.

On a first in-human trial, PT-112 showed to have a robust safety profile and demonstrated to provide durable responses in heavily pre-treated subjects.

Promontory Therapeutics chief medical officer Johan Baeck said: “ This clinical trial is the largest study to date of PT-112 and will establish the optimal dose in line with the FDA's Project Optimus, as well as proof of concept in our late-line mCRPC patient population.

“Data from our earlier Phase I/II studies have shown that PT-112 is clinically safe and active, and promotes immunogenic cancer cell death induced by the inhibition of ribosomal biogenesis, which is a promising mechanism of action for late-stage patients with prostate cancer — an  'immune-cold' disease with no broadly approved and effective immunotherapy.”

In October 2022, the company received a patent from United States Patent  and Trademark Office for PT-112 as an immuno-modulatory  agent, both as a monotherapy and in combination with other immunotherapy approaches.