Promontory Therapeutics Completes Enrollment of Phase 2 Trial of PT-112 in Late-Line Patients with Metastatic Castration-Resistant Prostate Cancer

Ongoing clinical trial has reached target enrollment of 109 patients across clinical sites in the United States and France

Open-label dose optimization and proof of concept study of PT-112 monotherapy includes interim data results, with top-line read-out and conference presentations expected in late 2024

NEW YORK, March 8, 2024 /PRNewswire/ -- Promontory Therapeutics Inc., a clinical stage pharmaceutical company advancing immunogenic small molecule approaches in oncology, has completed enrollment of its Phase 2 clinical trial of lead therapeutic candidate, PT-112, reaching its target enrollment of 109 patients with late-line metastatic castration-resistant prostate cancer (mCRPC) (ClinicalTrials.gov Identifier: NCT02266745).

The study is evaluating PT-112 in patients who have been treated with at least three prior life-prolonging therapies for mCRPC, and who exhibited radiographic evidence of disease progression at study entry. Patients with bone-only metastatic disease are also included in the study. These requirements create a representative treatment population following standard of care of androgen receptor signaling inhibitors, taxane chemotherapies, and any other drug approved by FDA on the basis of overall survival. The clinical trial enrolled patients across leading sites in the United States (23) and France (9).

"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," said Promontory Therapeutics Chief Medical Officer Johan Baeck, MD. "Data from our earlier Phase 1/2 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."

Promontory Therapeutics plans for a Type C meeting with the FDA in the second half of 2024, followed by an End-of-Phase 2 meeting with FDA and further engagement with European regulatory authorities. In addition to safety and efficacy findings among late-stage metastatic patients, the study aims to generate meaningful supportive data via correlative research, including on immune activation by PT-112 monotherapy as evaluated by the propagation of new T cell populations, as well as reductions in circulating tumor cells and ctDNA.

"Promontory is grateful to our clinical partners across the U.S. and France, including Gustave Roussy Paris, for completing enrollment of this critical Phase 2 study. We are confident in PT-112's potential as an effective treatment for patients with mCRPC who have progressed on androgen receptor directed therapy, chemotherapy or radioligand therapy and who lack any effective immunotherapy," said Promontory Therapeutics Chief Executive Officer Robert Fallon. "We look forward to presenting topline safety, efficacy, and correlative data at relevant research and medical conferences later this year."  

About PT-112
PT-112 is the first small-molecule conjugate of pyrophosphate in clinical development in oncology. PT-112 has numerous advantages — including its tolerability and inhibition of ribosomal biogenesis which leads to immunogenic cell death, through the release of damage associated molecular patterns that bind to dendritic cells and lead to downstream immune effector cell recruitment in the tumor microenvironment. PT-112 represents a highly potent inducer of this immunological form of cancer cell death. Further, PT-112 harbors a property known as osteotropism, or the propensity of the drug to reach its highest concentrations in certain areas of the bone, making it a candidate for treatment of patients with cancers that originate in, or metastasize to, the bone. The first in-human study of PT-112 demonstrated an attractive safety profile and evidence of long-lasting responses among heavily pre-treated patients and data were published in eClinicalMedicine, part of The Lancet.  The combination Phase 1b dose escalation study of PT-112 with PD-L1 checkpoint inhibitor avelumab in solid tumors was reported in a mini-oral presentation at the ESMO 2020 Virtual Congress, and the Phase 2a dose confirmation cohort in non-small cell lung cancer patients was reported at ESMO I-O 2022. The Phase 1 study in patients with relapsed or refractory multiple myeloma presented at ASH 2020 is the third completed Phase 1 study of PT-112.  Monotherapy Phase 2 development is ongoing in mCRPC, and includes the Phase 2 proof of concept study in thymic epithelial tumors under the company's formal CRADA with the NCI. Interim data from the NCI study were published at ASCO 2023.

About Promontory Therapeutics
Promontory Therapeutics Inc. is a privately held, clinical stage pharmaceutical company focused on small molecule immunotherapy, based in New York City. Clinical data generated across three Phase 1 studies have demonstrated single-agent and combination anti-cancer activity and an attractive tolerability profile, and two Phase 2 studies of PT-112 are underway. The company's research and development work has been conducted in the United States, Europe and Asia. The company sponsored the completed clinical study of PT-112 in combination with the PD-L1 inhibitor avelumab, and has an active Phase 2 trial under formal CRADA collaboration with the National Cancer Institute (NCI), utilizing PT-112 in thymic epithelial tumors, rare cancers with no FDA approved drug, where PT-112 has received Orphan Drug designation. Promontory Therapeutics is also a company member of the Paris-Saclay Cancer Cluster, Europe's emerging bio-cluster for oncology, and was a 2023 Nominee for Best Startup by the Prix Galien USA.

To learn more about Promontory Therapeutics, visit the company's website here.

CONTACTS:

Promontory Therapeutics
Brooke Raphael, MS
VP, Strategy & Operations
Tel: +1 (646) 974-6453
Email: [email protected]

Investors: 
Stan Musial
Tel: +1 (646) 222-6932
Email: [email protected]

ICR Westwicke

Media: 
Alexis Feinberg
Tel: +1 (203) 939-2225
Email: [email protected]

SOURCE Promontory Therapeutics Inc.