U.S. — Leading patient advocacy groups issued a joint statement on August 11, 2026, urging clinicians to exercise caution when prescribing Vykat XR due to emerging safety risks. The Foundation for Prader-Willi Research, International Prader-Willi Syndrome Organization, and Prader-Willi Syndrome USA called for increased awareness following reports of deaths and serious adverse events submitted to federal regulators.

The Food and Drug Administration approved Vykat XR in March 2025 for treating hyperphagia in patients with Prader-Willi syndrome aged 4 years and older. The medication contains extended-release diazoxide choline and was developed by Soleno Therapeutics before Neurocrine Biosciences acquired the company for $2.9 billion in a deal completed in May 2026.

As of July 31, 2026, seven deaths have been reported to the FDA’s Adverse Event Monitoring System among patients prescribed the drug. More than 100 reports of serious adverse events associated with Vykat XR have been submitted to the system during the same period. The majority of these serious adverse event reports involved edema, respiratory problems, and cardiac complications.

More than 800 people have received prescriptions for Vykat XR since its launch. No deaths were reported in the clinical trials for the medication. Edema occurred in at least 10% of participants in those trials, a rate that was at least 2% higher than in the placebo group.

In August 2025, short-seller Scorpion Capital published a report alleging serious risks of fluid buildup, pulmonary edema, and heart failure with Vykat XR use. The report also raised concerns about clinical-trial data. The expert statement released this month noted that neither the deaths nor the severe side effects have been definitively linked to Vykat XR.

Severe or fatal cases of adverse events typically involved complex health conditions, multiple prescriptions, and pre-existing obesity. Prader-Willi syndrome has an annual mortality rate of 1% to 3% across all age groups.

Why It Matters

Vykat XR represents a significant development in the management of Prader-Willi syndrome, a rare genetic disorder characterized by constant hunger and obesity. The approval of the first FDA-sanctioned treatment for hyperphagia in this population marked a milestone, with research on the therapy published in 2026 in Annals of Medicine & Surgery and Genetics in Medicine Open. The acquisition of the developer by Neurocrine Biosciences for $2.9 billion reflected the commercial interest in addressing this unmet medical need.

The emergence of post-marketing safety signals, including deaths and serious cardiac and respiratory events, introduces uncertainty into the clinical application of the drug. While the causal link remains unproven, the volume of reports relative to the estimated prescription base has prompted leading advocacy organizations to issue specific monitoring guidelines. This development shows the challenges of evaluating safety in small patient populations with complex baseline health profiles.

Timeline

The Foundation for Prader-Willi Research, International Prader-Willi Syndrome Organization, and Prader-Willi Syndrome USA released a statement on Tuesday regarding safety risks associated with Vykat XR. The statement said the intention was to increase awareness of the risks for people with PWS when starting Vykat XR. The expert groups advised clinicians to conduct individualized baseline assessments, monitor patients closely, and consider slowing the dose titration process for Vykat XR. The expert groups recommended additional safety evaluations, such as echocardiograms or fluid retention assessments, before and during treatment with Vykat XR. Prescribers were urged to watch for warning signs including worsening edema, orthopnea, dyspnea, and unexpected weight gain in patients taking Vykat XR.

What's New

Research titled Vykat XR (diazoxide choline-extended release): a new FDA-approved treatment for hyperphagia in Prader–Willi syndrome was published in 2026 in Annals of Medicine & Surgery. Research titled Diazoxide choline (Vykat XR) for treatment of hyperphagia and obesity in Prader-Willi syndrome: A therapeutics bulletin of the American College of Medical Genetics and Genomics (AC was published in 2026 in Genetics in Medicine Open. The Foundation for Prader-Willi Research, International Prader-Willi Syndrome Organization, and Prader-Willi Syndrome USA released a statement on Tuesday regarding safety risks associated with Vykat XR.

The statement said the intention was to increase awareness of the risks for people with PWS when starting Vykat XR. Seven deaths have been reported to the FDA’s Adverse Event Monitoring System among patients prescribed Vykat XR as of July 31, 2026. The expert groups advised clinicians to conduct individualized baseline assessments, monitor patients closely, and consider slowing the dose titration process for Vykat XR. The expert groups recommended additional safety evaluations, such as echocardiograms or fluid retention assessments, before and during treatment with Vykat XR. Vykat XR is indicated for treating hyperphagia in patients with Prader-Willi syndrome aged 4 years and older.