Dec 16 (Reuters) - Merck ( MRK ) said on Monday it has

discontinued the development of two experimental cancer drugs

after their failure in several trials.

The pharmaceutical giant's decision comes after several

setbacks for the drugs, vibostolimab and favezelimab, which were

being tested separately in combination with its top-selling drug

Keytruda for various forms of cancer.

On Monday, the company said it was stopping two trials of

vibostolimab with Keytruda to treat non-small cell lung cancer

after an analysis showed it was unlikely to succeed, while it

also decided to cease development of favezelimab after reviewing

its data.

"Following a careful analysis of the data, the decision has

been made to discontinue development of these candidates to

prioritize other ongoing programs," said Marjorie Green, head of

oncology, global clinical development at Merck's ( MRK ) research unit.

Shares of Merck ( MRK ) were up nearly 1% in extended trading.

Vibostolimab belonged to a promising new class of

immunotherapies called anti-TIGIT. This type of drug works by

selectively binding itself to TIGIT, a receptor on immune cells,

to activate the immune system against cancer cells and prevent a

misguided immune attack against healthy cells.

Favezelimab was designed to prevent a protein called LAG-3

from binding to certain molecules on tumor cells. This activates

the body's immune response and can reduce tumor growth.

Merck ( MRK ) said it is informing study investigators for these

trials and advised patients to contact their study team and

physicians regarding the next steps and treatment options.