Dive Brief:

• Compared to chemotherapy, first-line treatment with Merck & Co.'s Keytruda significantly improved overall survival (OS) in patients with locally advanced or metastatic non-small cell lung cancer (NSCLC) who tested positive for PD-L1 expression, according to interim clinical data.
• The big pharma didn't detail any figures related to the OS benefit, but said the clinical study in question, KEYNOTE-042, would continue based on the recommendation of an independent data monitoring committee. Investigators will be assessing whether Keytruda also improves progression-free survival.
• The trial enrolled more than 1,200 patients, given either 200 mg of Keytruda every three weeks or standard of care platinum-based chemotherapy. The interim analysis indicated Merck's drug was effective at lengthening OS in patients with PD-L1 expression greater than or equal to 1%.

Dive Insight:

Lung cancer has become a battleground area for the handful of drugmakers with marketed checkpoint inhibitors. So far, Merck has been winning the fight.

Keytruda (pembrolizumab) is the only checkpoint inhibitor approved in the first-line setting for metastatic NSCLC — both as a monotherapy and as a combination therapy with carboplatin and Eli Lilly & Co.'s Alimta (pemetrexed). The status has helped Merck close the revenue gap between Keytruda and Bristol-Myers Squibb's market leader Opdivo (nivolumab).

Merck isn't resting on its laurels, however. The company is investigating Keytruda in more than 700 clinical trials, including 15 registration-enabling studies for lung cancer that are collectively evaluating close to 9,000 patients, according to an April 9 statement.

PD-L1 expression, which has proven vital to Keytruda's success, is a particular focus.

As a combination therapy, Keytruda is OK'd for metastatic nonsquamous NSCLC patients regardless of their PD-L1 expression. But as a monotherapy, it's only cleared for metastatic NSCLC patients with PD-L1 expression at levels greater than or equal to 50%.

Therein lies the importance of KEYNOTE-042, which could aid Merck in getting Keytruda monotherapy approved as a first-line treatment across a broader range of patients. The drug's apparent effect on OS — largely considered the gold standard of clinical outcomes and a more difficult endpoint to hit — is also a positive for Merck.

"Improvement in overall survival is the ultimate objective in the treatment of advanced lung cancer," said Tony Mok, a professor in the department of clinical oncology at the Chinese University of Hong Kong, in an April 9 statement.

Investors seemed to take the news well. Merck shares opened at $55 apiece Monday morning, up 3% from Friday's close.

The company said it plans to present further data from KEYNOTE-042 at an upcoming medical conference.