Promontory Therapeutics Announces Interim Efficacy Requirement Reached on Phase 2 Study of PT-112 Monotherapy in Patients with Recurrent Thymoma

Three of the first 10 patients with thymoma evaluated by RECIST have partial responses.

Findings exceed protocol requirement of two responses among first 16 patients evaluated to proceed with stage 2 of efficacy assessment.

Recent immuno-profiling findings continue to be consistent with anti-cancer immune responses as presented by the National Cancer Institute (NCI), part of the National Institutes of Health at the AACR 2025 Annual Meeting

Promontory Therapeutics planning next stage of clinical development of PT-112 in thymoma, a disease with high unmet needs, with no currently label-approved drug by FDA, EMA or PMDA

NEW YORK, Dec. 22, 2025 /PRNewswire/ -- Promontory Therapeutics Inc., a clinical stage pharmaceutical company advancing small molecule oncology approaches with immunotherapeutic effects, today announced that the pre-specified efficacy requirement of its Phase 2 study of PT-112 for recurrent thymoma has been exceeded.

Patients with recurrent  thymoma have limited options for standard of care treatment, and there is no drug approved for this indication in the US, the European Union or Japan.

Of the first ten patients with thymoma assessed for tumor response in an ongoing phase 2 clinical trial at the NCI, three (30%) had experienced RECIST partial responses, an objective response rate that numerically exceeds that of the recent Phase 2 monotherapy data in the public domain with current off-label treatment options. PT-112 is well tolerated, and no new safety signals were observed. Patients treated with a dosing regimen based upon the PT-112 recommended Phase 3 dose (RP3D) achieved durable disease control without symptomatic toxicities, and no discontinuations due to adverse events (AEs). The PT-112 RP3D was agreed with the FDA at a recent end of Phase 2 (EOP2) Meeting on the separate PT-112 program in metastatic castration-resistant prostate cancer (mCRPC).

After reaching the interim efficacy requirement, enrollment of patients with recurrent thymoma continues at the National Cancer Institute (NCI), the single site leading the Phase 2 study of PT-112 under a formal Collaborative Research and Development Agreement (CRADA) with Promontory Therapeutics (NCT05104736).

At the American Association of Cancer Research (AACR) 2025 Annual Meeting, the investigators from the NCI presented data on anti-cancer immune responses among the first 15 thymic epithelial tumor (TET) patients treated with PT-112 monotherapy, with increases in both adaptive (CD8+ and CD4+) and innate (NK) cell types reaching statistical significance. This led to the investigators' conclusion that "PT-112 induces robust signals of immune activation… across the adaptive and innate immune systems… indicative that PT-112's immune effects play a significant role in its anti-cancer mechanism¹"

Consistent with the AACR data, recent on-treatment biopsies show increased CD8+ T cell infiltration in tumor tissue and absence of viable tumor in two participants with stable disease to date per RECIST.

Patients with thymoma are at risk for paraneoplastic autoimmune diseases, which in turn increases the risk of immune-related AEs (irAEs) that can occur with T cell-directed immunotherapy. irAEs with PT-112 are uncommon, and the risk is not higher than that observed with conventional systemic therapies. Early observations of an absence of increased incidence of new-onset irAEs in patients with thymoma receiving PT-112, coupled with evidence of clinical and immune activity, provides a unique opportunity to offer a novel immunomodulatory treatment that does not increase the risk of immune toxicity.  

Promontory Therapeutics is planning the next stage of development of PT-112 in recurrent thymoma, and the company leadership will be participating in industry partnering meetings during the JPMorgan Healthcare conference week (week of January 12^th) in San Francisco.

For more information about Promontory Therapeutics and PT-112 visit www.PromontoryTx.com.

¹Cancer Res (2025) 85 (8_Supplement_1): 5819. https://doi.org/10.1158/1538-7445.AM2025-5819

About Promontory Therapeutics

Promontory Therapeutics Inc. is a privately held, clinical stage drug development company based in New York, focused on small molecules with anti-cancer immune effects. Clinical data generated across six studies of lead molecule PT-112 have demonstrated single-agent and combination anti-cancer activity and an attractive tolerability profile. The Company's lead Phase 2 study in late-stage metastatic castration-resistant prostate cancer patients in the United States and France was the subject of an End of Phase 2 (EOP2) meeting with FDA, with pending regulatory meetings in other jurisdictions. The company has conducted research and development programs in the United States, Europe and Asia. As part of its recent clinical expansion into France, Promontory was selected as the first international company member of the Paris-Saclay Cancer Cluster, Europe's emerging biotech hub for oncology. The company also has an active Phase 2 trial underway at the National Cancer Institute under a Collaborative Research and Development Agreement, assessing PT-112 monotherapy in thymic epithelial tumors, a rare disease with no FDA approved drug, for which Promontory holds FDA Orphan Drug designation.

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Promontory Therapeutics
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Alexis Feinberg
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SOURCE Promontory Therapeutics Inc.