(Reuters) - Merck said on Thursday a combination treatment testing a new type of immunotherapy failed to significantly slow disease progression in lung cancer patients who did not respond to previous treatments, sending its shares down 1.5%.
The results mark another setback in an emerging class of immunotherapies called anti-TIGIT that have triggered research and deal activity.
Merck's experimental anti-TIGIT drug vibostolimab in combination with its approved therapy Keytruda also failed to improve overall survival in a study of patients with non-small-cell lung cancer that spreads to other organs of the body.
This is yet another failure for Merck's drug combination, after data released in March showed that it was less effective than a generic medicine called docetaxel in a non-blinded arm of the trial testing it in patients with the disease.
Gilead Sciences, Roche and GSK are among the half a dozen drugmakers looking to grab a share of the lucrative cancer market focused on the TIGIT receptor protein believed to help cancer cells thwart immune system detection.
Last year, data from Gilead and partner Arcus Biosciences' combo therapy, and Roche's lung cancer therapy fell short of expectations.
"While Merck has additional TIGIT trials ongoing, investors may be likely to remain sceptical of the TIGIT class," said Wells Fargo analyst Mohit Bansal.
Merck's vibostolimab works by selectively binding itself to TIGIT, a receptor on immune system cells that normally serves to prevent a misguided immune attack against healthy cells.
Separately, Merck also said it would discontinue a late-stage study testing its drugs Keytruda and Lynparza in patients with a type of lung cancer, after an independent data-monitoring committee deemed that the trial was unlikely to succeed.
(Reporting by Khushi Mandowara in Bengaluru; Editing by Devika Syamnath)
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