Soleno secures FDA priority review for Prader-Willi treatment

The U.S. Food and Drug Administration (FDA) is on the brink of making a crucial decision regarding the approval of Soleno Therapeutics' lead therapy, diazoxide choline (DCCR), designed to treat hyperphagia associated with Prader-Willi syndrome, a rare genetic disorder that manifests as an excessive desire to eat.

The FDA has accepted the new drug application (NDA) for DCCR and granted it priority review status, which significantly shortens the review period to six months, compared to the usual ten months. A key date to mark is 27 December 2024, which the FDA has set as the Prescription Drug User Fee Act (PDUFA) target action date.

Moreover, the FDA has also decided to convene an advisory committee (AdComm) meeting to discuss the application for DCCR. These meetings are essential as they review and evaluate the safety and efficacy data of new therapies. Although the AdComm's recommendations play a significant role in the decision-making process, they are not binding, and the final decision rests with the FDA.

Following the announcement, Soleno's stock experienced a modest increase of 6.3% by the close of markets on 27 August. The current market capitalization of the company stands at $1.9 billion.

DCCR, the therapeutic agent in question, is an extended-release tablet that contains a crystalline salt formulation of diazoxide. This formulation acts as an activator of the adenosine triphosphate (ATP)-sensitive potassium (KATP) channels found in various cells such as pancreatic β cells and adipocytes. Proper regulation of these cells can help manage hyperphagia, a condition commonly observed in Prader-Willi syndrome.

The NDA for DCCR is supported by data amassed from five clinical studies, including a Phase I trial in healthy volunteers, three Phase II trials, and a pivotal Phase III trial. The Phase III DESTINY PWS study (NCT03440814) enrolled 125 participants with Prader-Willi syndrome aged four years or younger. Over the course of a year, the study successfully met its primary endpoint by showing significant improvements in the Hyperphagia Questionnaire for Clinical Trials (HQ-CT) score. Notably, patients with more severe baseline hyperphagia, with an HQ-CT score exceeding 22, experienced greater improvements. Additionally, patients treated with DCCR exhibited reductions in leptin, insulin, and insulin resistance, alongside an increase in adiponectin levels.

Beyond Prader-Willi syndrome, Soleno is also investigating the potential of DCCR to treat pediatric patients with various genetic obesity conditions, including SH2B1 deficiency obesity, obesity linked to PCSK1 mutation (rs6232 variant), and SIM1 deficiency obesity. The ongoing open-label Phase II trial (NCT05532020) aims to enroll around 30 patients aged five years or younger who are affected by one of these genetic obesity disorders. 

The developments surrounding DCCR represent a promising frontier in the treatment of hyperphagia associated with Prader-Willi syndrome and potentially other genetic obesity conditions. The priority review status and the upcoming AdComm meeting are critical milestones in the journey toward potential FDA approval, which could offer a significant therapeutic advancement for patients grappling with these challenging conditions.

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