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France’s Ipsen clears FDA hurdle for bone disorder drug Sohonos

HQ Team

August 17, 2023: Ipsen, a French drugmaker, has received FDA approval for its Sohonos capsules to treat a rare bone disorder in adults, and pediatric patients within the 8-10 years age group.

Sohonos, an Ipsen brand, is meant for treating fibrodysplasia ossificans progressiva, a rare condition of abnormal bone growth, known as heterotopic ossification. The disease in soft and connective tissues, causes debilitating mobility challenges and reduces life expectancy.

Ipsen’s oral drug is the first in the category to be approved in the US by the FDA, according to a company statement. The green light was given to Ipsen based on the pivotal efficacy and safety data from the final trial.

The experimental study with generic palovarotene showed a 54% reduction in the volume of new abnormal bone formation in patients compared to standard of care.

Reduced ossification

“The study results demonstrated palovarotene effectively reduced annualized heterotopic ossification volume compared with no treatment beyond standard of care— 54% reduction with weighted linear mixed effect model,” according to the company.

“FOP is life-altering to the individuals diagnosed and their families, Michelle Davis, Executive Director of International FOP Association said.

“There’s not a day that goes by where those impacted don’t worry about the debilitating physical pain of muscle that is replaced by bone, another joint locking, or the relentless emotional toll of losing the ability to do an activity they love or hold a loved one close.”

“The first treatment for FOP has been proven to reduce the volume of new abnormal bone growth, which may result in better health outcomes for people living with FOP.”

900 people globally

The disease impacts the lives of about 400 people in the US and 900 people globally.

As it continuously progresses with flare-up episodes causing rapid bone growth, heterotopic ossification severely restricts mobility and function.

Most people living with FOP inevitably lose the ability to eat and drink on their own, cannot provide self-care or use the restroom themselves, and are unable to maintain employment.

By the age of 30 years old, the majority of people with the disease require a wheelchair and full-time caregiver assistance.

The management of the disease has previously been limited to palliative care and ultimately, it shortens the median life expectancy to 56 years.

Breathing problems

Death is often caused by bone formation around the ribcage leading to breathing problems and cardiorespiratory failure or falls resulting in fractures or head injuries because joint ankylosis prevents bracing from a fall.

“As a clinician caring for patients with the disease, I personally see the daily challenges and stresses that our patients and their families must contend with,” said Dr Edward Hsiao, Professor of Medicine, Division of Endocrinology and Metabolism, University of California, San Francisco.

 “The published…study showed that Sohonos can decrease new heterotopic ossification, and that palovarotene can be tolerated by many patients. Sohonos is not for everyone. As with all medicines, there are risks in this case, especially for young children who may develop early growth plate closure.”

The most common treatment-emergent adverse reactions reported in the study were mucocutaneous events such as dry skin, lip dryness, alopecia, drug eruption, rash, pruritus, and musculoskeletal events such as arthralgia. 

Sohonos, under the generic name palovarotene, is also under review with a number of other regulatory authorities.

EU rejection 

In July 2023, the European Commission did not grant marketing authorization for palovarotene. Sohonos (palovarotene capsules) is currently authorized for use in eligible patients in the US, Canada, and with conditional approval in the United Arab Emirates.

Ipsen’s first analysis of trial data showed that palovarotene didn’t reduce bone formation, according to the International Fibrodysplasia Ossifications Progressive Association.

However, when Ipsen re-analyzed the data using other statistical approaches, the data showed palovarotene was effective in reducing bone formation.

There are other trials being conducted by companies such as Regeneron and Incyte for developing a drug for bone disorders.

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