Seven deaths and more than 100 serious adverse events have now been logged in connection with Vykat XR, the first-ever drug approved to treat the dangerous, insatiable hunger that defines Prader-Willi syndrome. The reports, tallied through the FDA's post-marketing safety database as of July 31, have triggered fresh warnings from patient advocacy groups even as the drug's maker insists there is no proof the medication caused any of the deaths.
The U.S. Food and Drug Administration's Adverse Event Reporting System recorded the deaths and other serious incidents, with peripheral edema and drug ineffectiveness logged as the most frequent complaints, according to Investing.com. Vykat XR has also been linked in reported adverse events to edema, respiratory complications and cardiac complications, according to Reuters, which first tied the growing safety concerns to warnings from Prader-Willi experts. Neurocrine Biosciences did not immediately respond to a Reuters request for comment, and the FDA likewise did not immediately respond to the outlet's inquiry.
Neurocrine Biosciences Chief Executive Officer Kyle Gano said Wednesday that the company sees no causal link between Vykat XR and the reported fatalities, though he said potential updates to the drug's prescribing label or physician instructions remain under active consideration, per Investing.com's report. The company's shares fell 3.1% in premarket trading following the news, according to Reuters.
Federal Regulators Reviewing the Data
A U.S. Department of Health and Human Services spokesperson confirmed Wednesday that the FDA is actively evaluating post-marketing data for Vykat XR to determine whether formal regulatory action is necessary, as reported by BioSpace. That review comes as the Foundation for Prader-Willi Research and the International Prader-Willi Syndrome Organisation said the adverse event reports were concerning, while stressing that the reports do not establish a causal relationship between Vykat XR and the reported outcomes.
Those two groups, along with PWSA | USA, published joint clinical recommendations on Tuesday advising providers to conduct baseline blood tests, perform cardiac screenings such as echocardiograms, and implement slower dose titration for patients starting on the drug. The organizations said the statement is meant to encourage informed prescribing, careful patient selection and close monitoring rather than a retreat from the treatment. They also said patients and families deserved transparency regarding Vykat XR's safety profile, noting that serious adverse events had been reported through post-marketing surveillance.
A Rare Disease With No Other Options
Prader-Willi syndrome is a rare genetic disorder caused by deletions on chromosome 15, and hyperphagia — an unrelenting, dangerous hunger — is one of its hallmark symptoms. The condition affects an estimated 10,000 to 20,000 people in the United States, with severe hyperphagia driving high risks of severe obesity, diabetes, stomach rupture and accidental choking, according to background compiled by Global Genes.
When the FDA approved Vykat XR on March 26, 2025, for patients aged 4 and older, it marked the first approved therapy specifically targeting hyperphagia and the first new treatment for Prader-Willi syndrome since growth hormone in 2000. The drug, known generically as diazoxide choline extended-release, works by activating adenosine triphosphate-sensitive potassium channels in the hypothalamus, using a modified form of diazoxide — an active ingredient that has been approved for decades to treat hypertension and hyperinsulinism, per Drugs.com.
A Fast Launch, Now Facing Headwinds
The drug's rise was swift. Vykat XR generated $190 million in net revenue for Soleno Therapeutics in 2025 following its second-quarter commercial launch, including $92 million in the fourth quarter alone, according to SEC filings. That commercial promise drove San Diego-based Neurocrine Biosciences to acquire Redwood City's Soleno Therapeutics for $2.9 billion, or $53 per share in cash, in May.
Now analysts at BMO Capital Markets say increased physician caution and potential regulatory scrutiny could slow prescribing momentum and constrain Vykat XR's commercial expansion in the coming quarters, per BioSpace. It is a notable shift for a drug that, just months ago, was being hailed as a long-awaited breakthrough for a patient population that had gone a quarter-century without a new pharmaceutical option.
Because hyperphagia is a severe, life-threatening symptom with no other approved drug treatment, families and physicians embraced Vykat XR quickly after its launch — a dynamic that also means any safety signal draws intense scrutiny. Experts caution that voluntary databases like the FDA's adverse event reporting system do not prove a drug directly caused a reported death; they only flag patterns that regulators and companies are then obligated to investigate. For now, the patient groups and federal regulators appear aligned on a middle path: closer monitoring and possible label changes, rather than pulling the drug from the market.
