The U.S. Food and Drug Administration said on Friday that it has approved an injectable version of Bristol Myers Squibb's blockbuster cancer drug, Opdivo.

Opdivo is part of a class of drugs called PD-1 inhibitors, which enhance the immune system's ability to fight cancer by removing its natural brakes.

Like other PD-1 drugs such as Merck's Keytruda, it was previously available through infusions and patients received it via an intravenous drip in a health office.

The new injectable form is expected to be more convenient for patients and could help shield the company from erosion of sales when the patent for the intravenous version expires later this decade.