By Bhanvi Satija and Sriparna Roy

(Reuters) -The U.S. Food and Drug Administration (FDA) on Wednesday approved French drugmaker Ipsen's drug for a rare bone disorder, making it the first treatment available to patients with the condition that causes abnormal bone growth.

The company said its drug, Sohonos, was approved in adults and pediatric patients with fibrodysplasia ossificans progressiva (FOP), a rare genetic connective tissue disorder that causes progressive loss of mobility and reduced life expectancy.

The regulator approved use of the drug in girls aged 8 years and above, and 10 years and above in boys.

Sohonos tablets will be sold at an estimated annual list price of $624,000 based for 5mg (dose) per day, the company told Reuters, adding that dose may vary based on an individual's weight and disease state.

The drug approval is based on data from a late-stage study, which showed a 54% reduction in the volume of new abnormal bone formation in patients compared to standard of care.

The approval puts Ipsen ahead of other drugmakers such as Regeneron Pharmaceuticals, which is also developing an experimental drug, garetosmab, for the disorder and expects to seek U.S. health regulator's approval in 2024.

Currently, FOP patients rely on high doses on steroids at the start of a 'flare-up', which entail unpredictable episodes of soft tissue swelling, pain, reduced movement and stiffness.

FOP occurs in about 1 in 1,600,000 newborns, according to U.S. government data, and about 800 people worldwide are known to have the disease.

Ipsen is also developing another FOP drug licensed from Blueprint Medicines Corp called BLU-782. It has been boosting its rare disease portfolio by helping develop a string of drugs licensed from other smaller developers.Sohonos will have a boxed warning for embryo-fetal toxicity and premature epiphyseal closure, which can lead to stunted growth and deformities in bone.

(Reporting by Bhanvi Satija, Sriparna Roy and Pratik Jain in Bengaluru; Editing by Shinjini Ganguli)