Merck & Co. Inc.'s Keytruda reduced tumor size as a stand-alone treatment for patients with small-cell lung cancer in a midstage study.
Small-cell lung cancer accounts for about 10% to 15% of all lung cancers. The five-year survival rate for patients diagnosed in the U.S. with any stage of small-cell lung cancer is estimated to be 6%.
In the phase 2 trial named Keynote-158, 18.7% patients showed a reduction in tumor size, with 16% of the subjects showing a partial reduction in their disease and 3% of the patients having no detectable cancer — known as a complete response.
Keytruda as a monotherapy performed better in patients whose tumors expressed PD-L1, a protein on the surface of cancer cells that suppresses the immune system. Inhibiting or blocking this protein boosts the immune system's ability to fight cancer.
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The drug shrank tumors in 35.7% of patients whose cancer tested positive for PD-L1, with a complete response rate of 5% and a partial response rate of 31%.
Keytruda reduced tumors in 6% of patients whose tumors did not express PD-L1. The complete response rate was 2% and the partial response rate was 4% in this group.
The safety profile of the drug was consistent with the previous studies of Keytruda monotherapy in lung cancer.
The 2018 American Society of Clinical Oncology meeting is expected to bring together more than 32,000 professionals from all over the world, with more than 2,500 study abstracts to be presented on-site and an additional 3,350 abstracts to be published online.

