FDA approves palovarotene for treatment of rare bone disorder

The US Food and Drug Administration has approved oral retinoid palovarotene (Sohonos) for treatment of abnormal bone growth associated with fibrodysplasia ossificans progressiva.

“The FDA approval of Sohonos is a breakthrough for the U.S. FOP community. For the first time doctors have an approved medicine available to them, shown to reduce the formation of new, abnormal bone growth, known as heterotopic ossification (HO), which causes debilitating mobility challenges and has a devastating impact on the lives of people with FOP,” said Howard Mayer, Head of Research and Development, Ipsen. “Development of medicines for rare diseases takes commitment and belief from everyone involved. We at Ipsen are sincerely grateful to the FOP community of patients and medical experts, as the first-ever treatment in the U.S. for managing FOP would not be possible without their participation in the clinical trials and ongoing support.”

FOP impacts the lives of an estimated 400 people in the U.S. and 900 people globally. As the disease continuously progresses with flare-up episodes causing rapid bone growth, HO severely restricts mobility and function.3,4 Most people living with FOP inevitably lose the ability to eat and drink on their own, cannot provide selfcare or use the restroom themselves, and are unable to maintain employment. By the age of 30 years old, the majority of people with FOP require a wheelchair and full-time caregiver assistance.

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

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

The FDA approval is based on the pivotal efficacy and safety data from the Phase III MOVE trial, the first and largest multicenter, open-label trial in adult and pediatric patients. The 18-month data published in the Journal of Bone and Mineral Research,8 included 107 patients (12 percent of the estimated number of individuals worldwide living with FOP) who received oral palovarotene compared with untreated individuals from Ipsen’s global FOP Natural History Study.

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).8 The study also demonstrated that palovarotene has a well-characterized safety profile, with adverse events consistent with the systemic retinoid class. The most common treatment emergent adverse reactions reported in the study were mucocutaneous events such as dry skin, lip dryness, alopecia, drug eruption, rash, and pruritus and musculoskeletal events such as arthralgia and premature growth plate closure in growing children. 

“As a clinician caring for patients with FOP, 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 Phase III MOVE study showed that Sohonos can decrease new heterotopic ossification, and that palovarotene can be tolerated by many patients with FOP. 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. In addition, Sohonos has the same side effects as other retinoids, including dryness of the skin and mucus membranes. However, since the accumulation of HO in FOP is progressive, irreversible, and life altering, this medication is an important treatment option for our FOP community.”

Sohonos, the first and only treatment for FOP

Sohonos is an oral medicine with particular selectivity for the gamma subtype of retinoic-acid receptors, which are an important regulator of skeletal development and ectopic bone in the retinoid signaling pathway. The medicine is designed to mediate the interactions between the receptors, growth factors and proteins within the retinoid signaling pathway to reduce new abnormal bone formation in FOP. The recommended dosing for Sohonos includes a chronic daily dosage of 5 mg (or weight-based equivalent for pediatric patients under 14 years of age), which can be modified/increased for flare-up symptoms. Sohonos may be prescribed immediately in the U.S. for eligible patients.

To ensure access to Sohonos for eligible individuals in the U.S., Ipsen Cares patient support program is available as a resource to people living with FOP and their caregivers to provide educational support and address coverage, access and reimbursement questions .

Sohonos received Orphan Drug and Breakthrough Therapy Designations from the U.S. Food and Drug Administration (FDA) for the treatment of FOP and was granted Priority Review of the New Drug Application (NDA). Sohonos, under the generic name palovarotene, is also under review with a number of other regulatory authorities. In July 2023, the European Commission did not grant marketing authorization for palovarotene. SohonosTM (palovarotene capsules) is currently authorized for use in eligible patients in U.S., Canada,10 and with a conditional approval in the United Arab Emirates.

With this approval the FDA also issued a Rare Pediatric Disease Priority Review Voucher (PRV). The voucher can be used for subsequent drug applications that would not qualify for a priority review.