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Parthenon Launches Phase I Trial of DDR1 Inhibitor in Solid Tumors

NEW YORK – Parthenon Therapeutics on Tuesday said it has started a Phase I trial of its DDR1-targeted monoclonal antibody PRTH-101 involving patients with heavily pretreated solid tumors, including those with high DDR1 expression and immune exclusion.

Discoidin domain receptor 1 (DDR1) is a collagen receptor with tyrosine kinase activity found on the surface of tumor cells. It aligns collagen fibers around the tumor, which obstructs infiltration of T cells, creating a condition known as immune exclusion. PRTH-101 is designed to disable DDR1, creating gaps in the tumor barrier to allow T cells to enter and attack cancer cells.

According to data the Boston-based company presented at the American Association for Cancer Research's annual meeting this month, more than 40 percent of triple-negative breast, non-small cell lung, pancreatic, and colorectal tumors are immune excluded. Ovarian cancer and certain sarcoma subtypes showed low levels of immune exclusion, as well.

In preclinical models, PRTH-101 demonstrated anti-tumor activity alone and in combination with a checkpoint inhibitor. In the Phase I trial, investigators will enroll up to 270 patients with advanced or metastatic solid tumors and evaluate safety and tolerability of the drug as well as its anti-tumor activity as a single agent and in combination with a PD-1 inhibitor in select indications. The trial will also establish a dosing regimen for a Phase II trial and evaluate expression of DDR1 and other proteins in the related pathway as predictive biomarkers for response.

"With no FDA-approved therapies that target DDR1-associated tumors, we believe that PRTH-101 could uniquely improve patient outcomes by breaking down the barrier that various types of tumors construct to protect them from immune attack," Parthenon Chief Medical Officer J. Paul Eder said in a statement.