Merck immunotherapy fails to improve survival in head and neck cancer

July 24 (Reuters) - Merck & Co said on Monday that its Keytruda immunotherapy failed to extend survival in previously treated patients with advanced head and neck cancer more than the standard combination therapy in a late-stage trial.

The drug, which blocks a mechanism tumors use to hide from the immune system allowing it to recognize and attack the cancer, won accelerated U.S. approval last August for these patients based on its ability to shrink tumors.

As a condition of the accelerated approval, Merck was required to conduct a trial to demonstrate superiority over standard treatment and verify the clinical benefit of Keytruda in this patient population.

Despite the failure to improve survival, Merck said the current approval still stands. The U.S. drugmaker said it will continue a Phase III trial of Keytruda as an initial treatment for patients with advanced head and neck cancers.

It is a second rare setback for the medicine seen as the leading treatment among immunotherapies from the same class, known as PD-1 or PD-L1 inhibitors. Earlier this month, Keytruda trials in the blood cancer multiple myeloma were stopped due to more deaths among those who received Keytruda along with standard combination therapy than those on standard treatment alone.

Keytruda is also approved for advanced melanoma, non-small cell lung cancer, advanced bladder cancer and classical Hodgkin lymphoma. In May, Keytruda became the first drug to win U.S. approval based on a patient's specific genetic traits, regardless of where in the body the cancer originated, known as microsatellite instability-high cancer.

Merck shares fell about 1 percent to $61.99 in extended trading from a New York Stock Exchange close at $62.57.

(Reporting by Bill Berkrot; Editing by Lisa Shumaker)