By Nathan Gomes

(Reuters) -The U.S. Food and Drug Administration on Thursday approved BioMarin Pharmaceutical's gene therapy for hemophilia A, the company said, giving patients with the inherited bleeding disorder an option to reduce regular blood infusions.

BioMarin's gene therapy, which would be the first for hemophilia A, is a potentially one-time treatment that would enable patients to forego or reduce infusions of factor proteins into their bloodstream several times a week for life.

Shares of the California-based company closed 3.6% lower on Thursday.

The approval was pretty widely expected and now there's debate on how the uptake will pan out, said Joel Beatty, senior research analyst at Robert W Baird.

Roctavian, which is manufactured at the company's facility in Novato, California, works by delivering a functional copy of the missing gene that would help hemophilia A patients make a blood-clotting protein known as factor VIII.

"Roctavian's launch will probably be a little slow at first, because there are already some effective treatment options on the market. But longer-term, one-time dosing will likely end up being attractive to a lot of patients," Beatty added.

BioMarin's therapy was approved for the same condition in the European Union last year, and is sold under the same brand name.

In April, BioMarin cut its annual sales forecast range for Roctavian to $50 million to $100 million, from $100 milliion to $200 million.

The company said on Thursday it expects about 2,500 of around 6,500 adults living with severe hemophilia A in the United States to be eligible to receive Roctavian with this initial approval.

There are about 16,000 patients in the United States with hemophilia A in which they are missing the factor VIII clotting protein.

(Reporting by Khushi Mandowara, Bhanvi Satija, Nathan Gomes and Akash Sriram in Bengaluru; Editing by Krishna Chandra Eluri and Maju Samuel)