FDA approves first treatment for Prader-Willi Syndrome

USA – The U.S. Food and Drug Administration (FDA) has approved Soleno Therapeutics’ Vykat XR, making it the first-ever treatment for Prader-Willi syndrome (PWS).

PWS is a rare genetic disorder that causes constant hunger and severe obesity, impacting around 50,000 people in the U.S. and up to 400,000 worldwide. Soleno estimates that about 10,000 patients in the U.S. are eligible for treatment.

Vykat XR (diazoxide choline) is designed to treat hyperphagia—an overwhelming urge to eat constantly, which is the main symptom of PWS and the leading cause of death for those with the condition.

This oral, once-daily drug is approved for patients aged four years and older. PWS can also cause other complications like learning difficulties, behavioral issues, restricted growth, and reduced life expectancy.

According to Soleno Therapeutics, based in Redwood City, California, the drug will be launched in April.

The cost of Vykat XR will depend on the patient’s weight, priced at US $5.92 per kilogram. Soleno estimates the average yearly cost of treatment to be around US $466,200 based on the average weight of subjects in their clinical trial.

The approval of Vykat XR follows a phase 3 clinical trial that assessed its effectiveness in reducing hyperphagia.

While the initial results did not show a statistically significant improvement at the primary endpoint, extended follow-up revealed meaningful progress.

Patients who continued taking Vykat XR experienced reduced hyperphagia, while those who switched to placebo during a 16-week withdrawal phase showed significant worsening of symptoms.

The average time patients were on the drug before the withdrawal phase was more than three years.

In addition to reducing hyperphagia, Vykat XR was found to improve other symptoms associated with PWS, including aggressive behavior, fat mass, and various metabolic parameters.

Common side effects observed during the trial included excessive hair growth, fluid retention, high blood sugar levels, and rash.

Stacy Ward, Chief Executive Officer of the PWS Association USA, described the approval as a “monumental step forward in addressing the longstanding unmet needs of individuals living with PWS and their families.”

Soleno Therapeutics is also pursuing approval for Vykat XR in Europe, with plans to file for regulatory clearance in the first half of this year.

The company estimates that there are approximately 9,500 diagnosed PWS patients in the UK and the four largest EU markets.

Soleno remains financially strong, having ended 2024 with more than US $318 million in cash reserves, which will support the drug’s rollout.

PWS is caused by genetic mutations affecting a group of genes on chromosome 15. The disorder’s most prominent symptom, hyperphagia, is persistent and can result in dangerous weight gain and other health issues if untreated.

Despite its rarity, the approval of Vykat XR represents a critical advancement in PWS management, offering a new level of care for those affected by the condition.