The Food and Drug Administration on Thursday accepted an application from Regeneron (REGN 0.06%) that could make Libtayo a new treatment option for a specific group of freshly diagnosed lung cancer patients in six months or less. Libtayo is one of several antibodies Sanofi (SNY -0.32%) markets in partnership with Regeneron. 

The agency has agreed to a priority review of Regeneron's application for the treatment of first-line non-small cell lung cancer (NSCLC) patients with tumor cells that express Libtayo's target, PD-L1, at least half of the time. The agency set an action date for Feb. 28, 2021, which is four months sooner than it would have been without priority status.

Two scientists working in a laboratory.

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During a clinical trial underpinning Regeneron's application, treatment with Libtayo as a monotherapy reduced the risk of death by 32% for patients with tumors that express high levels of PD-L1. That risk reduction increased to 43% compared with standard chemotherapy for patients with PD-L1 present on at least 50% of their tumor cells.

In 2018, Libtayo became the sixth drug of its class to earn at least one FDA approval, but this hasn't prevented it from generating impressive sales as the first and only treatment approved specifically for patients with advanced-stage cutaneous squamous cell carcinoma (CSCC). The FDA granted Libtayo its first approval in 2018, and it finished the first half of 2020 on pace to reach $320 million.

Far more patients have advanced-stage lung cancer than CSCC, but Libtayo will run into stiff competition for first-line NSCLC patients from Merck's (MRK 0.21%) mega-blockbuster PD-1 drug, Keytruda. Sales of Keytruda have soared to an annualized $14.8 billion during the third quarter since earning approval to treat first-line NSCLC patients in 2018.