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KSQ Therapeutics Begins Combination Dosing in Trial of USP1 Inhibitor for Advanced Solid Tumors

NEW YORK – KSQ Therapeutics on Thursday said that it dosed the first patient in the combination therapy portion of a Phase I trial of its small molecule cancer drug KSQ-4279 in patients with advanced solid tumors.

KSQ-4279 targets USP1, which regulates DNA damage response. In preclinical studies, it showed an enhanced response in cancers with BRCA1/2 mutations and homologous recombination defects. It demonstrated activity as a monotherapy in BRCA1-mutant ovarian PDX models, and a combination of KSQ-4279 and a PARP inhibitor led to durable tumor regression in patient-derived triple-negative breast cancer xenograft models resistant to PARP inhibitors alone.

Study KSQ-4279-1101 is designed to enroll 140 patients with advanced solid tumors to receive KSQ-4279 once daily as a monotherapy, and then begin combination dosing once the maximum tolerated dose is established. The trial will include cohorts receiving KSQ-4279 with a PARP inhibitor and with chemotherapy.

The company said that the drug has been well tolerated with no dose-limiting toxicities in the dose-escalation portion of the trial. The primary endpoints of the trial are safety and establishing a recommended Phase II dose. As a secondary endpoint, the trial will also explore potential predictive biomarkers and other genetic factors that may correlate with clinical outcomes.