A clinical trial testing a combination immunotherapy treatment for patients with a type of lung cancer has been discontinued. The trial, sponsored by Merck, was evaluating the combination of an experimental drug, vibostolimab, with Keytruda. An interim analysis showed that the drug was unlikely to succeed in meeting the study's endpoints.

Patients who received the combination of vibostolimab and Keytruda experienced a higher rate of immune-related side effects. As a result, the sponsor has advised that patients should stop ongoing treatment with this therapy.

The discontinuation of the trial marks another setback for vibostolimab and the class of immunotherapies called anti-TIGIT, to which it belongs. Several other pharmaceutical companies, including Gilead Sciences, Roche, and GSK, are also researching anti-TIGIT cancer drugs, but the field has experienced multiple challenges.

Vibostolimab works by selectively binding to TIGIT, a receptor on immune cells, to activate the immune system against cancer cells while preventing a misguided immune attack against healthy cells.

In the discontinued late-stage study, the combination therapy was being tested as a first-line treatment for patients with extensive-stage small cell lung cancer.

Last year, the combination therapy failed to significantly slow disease progression in lung cancer patients who did not respond to previous treatments. In May, another late-stage study testing the combination therapy in patients with a severe form of skin cancer was discontinued after side effects led to high discontinuation rates.