The U.S. Food and Drug Administration granted Breakthrough Therapy designation to Merck's (NYSE: MRK) investigational drug calderasib in combination with Keytruda for treating certain patients with newly diagnosed metastatic non-small cell lung cancer.

The designation applies to patients with KRAS G12C-mutated tumors expressing PD-L1 with a tumor proportion score of at least 1%. This marks the first Breakthrough Therapy designation for calderasib, also known as MK-1084.

The FDA designation was supported by data from the Phase 1 KANDLELIT-001 trial. Calderasib is described as a next-generation KRAS G12C covalent inhibitor designed to target specific cancer-driving mutations.

The KRAS G12C mutation occurs in approximately 14% of patients with non-small cell lung cancer adenocarcinoma, according to the company's statement. This mutation represents the most frequently observed KRAS mutation in cancer patients.

Breakthrough Therapy designation expedites development and review of medicines for serious conditions that may demonstrate substantial improvement over available therapies. The designation provides benefits including intensive FDA guidance, rolling review, and potential Priority Review eligibility.

Merck is conducting five Phase 3 trials under the KANDLELIT clinical development program, testing calderasib across various tumor types and treatment stages. The studies evaluate combinations with Keytruda and other therapies for lung cancer and colorectal cancer patients.

Calderasib is being developed through a collaboration with Taiho Pharmaceutical and Astex Pharmaceuticals, established in January 2020.