By Mariam Sunny and Sruthi Narasimha Chari

March 21 (Reuters) - The U.S. FDA has approved privately

held Italfarmaco Group's drug to treat Duchenne muscular

dystrophy (DMD), an inherited muscle-wasting disorder, the

health regulator said on Thursday.

The oral drug, to be sold under the brand name Duvyzat, is

the first nonsteroidal drug approved to treat patients with all

genetic variants of DMD, according to the FDA.

Duvyzat has been approved for patients six years of age and

older.

DMD affects an estimated one-in-3,500 male births worldwide,

and most patients lack the protein dystrophin which keeps

muscles intact.

Duvyzat, chemically known as givinostat, helps regulate a

group of enzymes responsible for causing muscle damage and

deterioration in DMD patients.

Italfarmaco's application for the drug was based on data

from a late-stage study conducted on 120 patients on chronic

steroids, in which the drug helped slow disease progression in

ambulant boys with DMD aged 6 years and above after 18 months of

treatment.

The approval pits the drug against already approved DMD

treatments in the market, including Sarepta Therapeutics' ( SRPT )

bestselling medicine Exondys 51, as well as its other

therapies Vyondys and Amondys.

These belong to a class of "exon-skipping" therapies, which

work by skipping specific parts of genes, called exons, helping

the body make shorter forms of dystrophin.

Unlike other available treatments, Duvyzat tries to

"counterbalance" the effects caused by a lack of dystrophin,

Italfarmaco Chief Medical Officer Paolo Bettica said ahead of

the decision.

"When you give givinostat, you have less muscle damage, less

inflammation, less fibrosis and fat replacement, and an increase

in muscle regeneration," Bettica added.

The FDA, last year, approved Sarepta's first-of-its-kind

gene therapy for DMD patients aged between 4 and 5 years who can

walk, based on trial data that showed it was able to produce a

mini version of the dystrophin protein.

The therapy, Elevidys, is one of the world's most expensive

treatments with a wholesale cost of $3.2 million per patient.