Many people in the PWS community have been following the development of new treatments for hyperphagia. Here is a summary of recent updates from Soleno Therapeutics and Aardvark Therapeutics, together with IPWSO’s comments.
Soleno Therapeutics and diazoxide choline prolonged release (Viokat – Europe; Vykat XR – USA)
The European Medicines Agency (EMA) announced on April 24th this year that Soleno Therapeutics Europe Limited has withdrawn its application for a marketing authorisation of Viokat (diazoxide choline) for the treatment of hyperphagia in people with Prader-Willi syndrome. (https://www.ema.europa.eu/en/news/meeting-highlights-committee-medicinal-products-human-use-chmp-20-23-april-2026). The application was withdrawn after the European Medicines Agency had evaluated the information from the company and prepared questions for the company. The company had responded to the last round of questions but withdrew the application before the Agency assessed the responses. EMA also stated that ‘Based on the review of the data, at the time of the withdrawal, the Agency had concerns and its provisional opinion was that Viokat could not have been authorised for the treatment of hyperphagia in people with Prader-Willi syndrome.’
EMA provides a question-and-answer document that provides a summary of the Committee for Medicinal Products for Human Use (who report and advise the EMA) at https://www.ema.europa.eu/en/medicines/human/EPAR/viokat
EMA states that ‘ In its letter notifying the Agency of the withdrawal of the application, the company stated that the decision to withdraw followed the preliminary assessment by the CHMP, which concluded that, the data provided were not sufficient to determine that the benefits of the medicine outweigh its risks’, and that ‘there are no consequences for patients in clinical trials or in compassionate use programmes using Viokat’. EMA goes on to say that ‘If you are in a clinical trial or compassionate use programme and need more information about your treatment, speak with your clinical trial doctor.’
Comment from IPWSO
It is clearly disappointing to the PWS community at large, but particularly those who have or continue to participate in clinical trials that the approval process that would make Viokat available in Europe has now halted. This news coincided with the news that Neurocrine Biosciences had agreed to acquire Soleno, the acquisition being completed on May 18th, 2026. IPWSO expresses its recognition of the EMA processes in approving marketing authorisations of Viokat that are designed to ensure efficacy and safety for people with PWS.
Note that the availability of Vykat in the USA is not affected. Soleno reported that the withdrawal was “based on business and strategic considerations.”
Aardvark Therapeutics and ARD 101
Aardvark voluntarily paused the phase 3 clinical trial of their lead compound ARD 101 (HERO trial and its open-label extension) in February 2026 after it found heart-related side effects in healthy volunteers given higher-than-planned doses of the drug, ARD-101. In the clinical trial of healthy volunteers with PWS, 2 of the 8 healthy volunteer participants experienced electrocardiogram (ECG) abnormalities (an increased QRS duration). Later, on May 14th 2026, Aardvark announced that the U.S. Food and Drug Administration (FDA) had placed a full clinical hold on its investigational new drug application for ARD-101 (https://ir.aardvarktherapeutics.com/news-releases/news-release-details/aardvark-therapeutics-plans-unblind-hero-and-ole-data-inform) related to the Company’s previous voluntary pause. In parallel with its ongoing engagement with the FDA, Aardvark plans to unblind data from the phase 3 trial and open-label extension in order to “assess the totality of available efficacy and safety data and to support an informed determination of next steps for the ARD-101 program”
Comment from IPWSO
Clinical trials are designed to assess the safety and efficacy of new medications, so the response to finding potential adverse effects is appropriate. IPWSO hopes that analysis of the unblinded data will allow a full evaluation of the reported adverse events and the resumption of Aardvark Therapeutics clinical trial programme.