Soleno Therapeutics has voluntarily withdrawn its marketing authorization application (MAA) to the European Medicines Agency (EMA) for Viokat (diazoxide choline) prolonged-release tablets, the company announced in an SEC filing. The application had sought approval for the treatment of hyperphagia in adults and children aged four years and older with Prader-Willi syndrome (PWS). The withdrawal removes what had been the only pending European regulatory pathway for a pharmacological therapy targeting hyperphagia in this rare genetic disorder.
The EMA had been reviewing the MAA with a decision anticipated in mid-2026, the company said. Soleno attributed the withdrawal to business and strategic considerations, and noted that the action preserves its ability to re-engage with European regulators should an appropriate pathway become available at a later date. No clinical or safety concerns were cited as factors in the decision. The same molecule is marketed in the United States as Vykat XR (diazoxide choline extended-release), which received US FDA approval in March 2025 as the first pharmacological treatment specifically indicated for hyperphagia in PWS.
The US approval was supported by the randomized-withdrawal study C602-RWP, a 16-week trial enrolling 77 participants. The primary endpoint was change in the Hyperphagia Questionnaire for Clinical Trials (HQ-CT) total score. Participants withdrawn to placebo showed statistically significant worsening of hyperphagia compared with those continuing diazoxide choline (P=0.0022), the company reported. Secondary endpoints including the Clinical Global Impression of Severity and Improvement scales favored the active arm but did not reach statistical significance. Exploratory anthropometric data showed a least-squares mean weight difference of −1.6 kg (95% CI −3.1, −0.1) favoring continued treatment. No serious adverse events were recorded in the active arm, and no discontinuations due to adverse events were reported. Results were subsequently published in the Journal of Clinical Endocrinology & Metabolism.