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Repare Therapeutics Doses First Patient in Phase I Trial of PKMYT1 Inhibitor

NEW YORK – Repare Therapeutics said on Monday it had dosed the first patient in a Phase I study of its PKMYT1 inhibitor RP-6306 in advanced solid tumors.

The trial will enroll up to 70 participants with CCNE1-amplified, FBXW7-altered, and other undisclosed cancers that are sensitive to PKMYT1 inhibitors. Researchers will screen patients for the study using next-generation sequencing.

Patients will receive RP-6306 as a monotherapy in this dose escalation study to determine the recommended Phase II dose and to assess safety and tolerability. Repare plans to explore RP-6306 as a monotherapy and in combination with chemotherapy and other treatments in future studies.

"We are pleased to have initiated this trial six months ahead of what we projected at our IPO launch last June," Repare CEO Lloyd Segal said in a statement. "Patients with tumors carrying CCNE1, FBXW7, and certain other genetic alterations we have identified as sensitive to PKMYT1 inhibition have few treatment options available, and the incidence of these cancers is rising. This Phase I trial will assess the safety and tolerability of RP-6306, as well as dosing schedule, to inform Repare's planned Phase II program."

Montreal-based Repare discovered the PKMYT1 target in house with its SNIPRx CRISPR-enabled discovery platform. The firm then uses its STEP2 screen to identify other genomic alterations that have synthetic lethality with the mutation targeted by its drug candidate. For the PKMYT1 target, Repare has only disclosed its activity with CCNE1-amplified and FBXW7-altered tumors. Earlier this year, Repare partnered with Valence Discovery to develop precision oncology drugs using artificial intelligence and its SNIPRx platform.

Repare is also developing other synthetic lethality products including an ATR inhibitor that is being studied in combination with the PARP inhibitor talazoparib (Pfizer's Talzenna) and a Pol inhibitor program.