UPDATE 1-FDA approves new dosing for Bristol-Myers Squibb's Opdivo

(Adds dosing details, background on PD-1 inhibitors)

March 6 (Reuters) - Bristol-Myers Squibb Co said on Tuesday the U.S. Food and Drug Administration had approved a four-week dosing schedule for its cancer drug, Opdivo.

Opdivo is approved to treat a number of cancers such as melanoma, and belongs to a fast-growing class of drugs called PD-L1 or PD-1 inhibitors that help the immune system attack cancer by blocking a mechanism tumors use to evade detection.

Opdivo was previously approved for a dosing schedule of every two weeks, along with a shorter, 30-minute infusion, the company said.

Other PD-1 inhibitors include drugs from rivals such as Merck & Co and Roche.

The FDA decision makes Opdivo the only PD-1 inhibitor to offer every four-week dosing, according to the company. (Reporting by Manas Mishra in Bengaluru; Editing by Maju Samuel)