Aug 29 (Reuters) - Merck ( MRK ) has stopped two

separate late-stage studies of its immunotherapy Keytruda in

patients with skin and lung cancers, the company said on

Thursday, marking the latest set of trial failures for the

blockbuster drug.

The company has been seeking to test Keytruda in combination

with other treatments and expand its use in types of cancers not

yet treated by immunotherapies, as the drug faces loss of patent

protection at the end of the decade.

A trial of the drug in patients with an advanced type of

skin cancer called cutaneous squamous cell carcinoma was stopped

for "futility", meaning it was likely to fail, the company said.

The drug also did not help extend how long patients remain

free of complications when it was tested for stage 1 or 2 of

non-small cell lung cancer in combination with a type of

radiotherapy.

"Unmet needs remain across different types of cancer and

stages of disease," said Marjorie Green, head of oncology,

global clinical development at Merck Research Laboratories.

"That is why we continue our rigorous exploration of

innovative treatment approaches in cancers with high unmet

need."

This year, Merck's ( MRK ) combination immunotherapy of vibostolimab

and Keytruda faced two separate trial discontinuations when

evaluated as treatments for lung and skin cancer.

In recent months, the Keytruda-AstraZeneca Lynparza

combination and Keytruda with Eisai's ( ESALF ) Lenvima also

failed separate trials as cancer treatments.

Keytruda belongs to a class of medicines called PD-1

inhibitors that work by increasing the ability of the body's

immune system to help detect and fight tumor cells.