Vykat XR safely quiets the intense Prader-Willi hunger for years
Families saw lasting improvements in both uncontrollable appetite and behavior
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Long-term treatment with Vykat XR (diazoxide choline) safely provides lasting relief from the uncontrollable hunger and behavioral struggles associated with Prader-Willi syndrome (PWS), according to new clinical data. Recent trial results also show that patients who temporarily paused the treatment quickly regained its benefits after restarting.
These findings come from up to three years of pooled data across three clinical trials: the Phase 3 DESTINY PWS study (NCT03440814), its open-label extension called C602 (NCT03714373), and a long-term extension study called C614 (NCT05701774). Researchers presented the data in three posters at the recent Endocrine Society Annual Meeting 2026. Vykat XR is sold by Soleno Therapeutics, a subsidiary of Neurocrine Biosciences.
“These compelling data further reinforce our confidence in VYKAT XR as a safe and effective long-term treatment for hyperphagia [insatiable hunger] in individuals four years of age and older living with Prader-Willi syndrome,” Sanjay Keswani, MD, Neurocrine’s chief medical officer, said in a company press release. “This completes the presentation of data from our comprehensive Phase 3 development program and further confirms the long-term benefit of VYKAT XR for people living with PWS.”
PWS is a genetic disorder marked by abnormalities in development. People with PWS may experience a range of behavioral and mental health issues, and the condition is also usually marked by hyperphagia.
Last year, Vykat XR became the first medication approved in the U.S. for hyperphagia in people with PWS. Available as a once-daily extended-release tablet, the therapy is indicated for use in PWS patients 4 years and older.
Long-term reductions in hunger
The therapy’s approval was based on data from the three-month, placebo-controlled DESTINY PWS study, which involved 127 PWS patients 4 and older, and its C602 study, where all participants received Vykat XR for years (OLE portion) before a randomized withdrawal period. During this latter period, patients were randomly assigned to receive either the therapy or a placebo for four months.
One year of continuous Vykat XR treatment in DESTINY PWS and C602-OLE significantly reduced hyperphagia and behavioral symptoms. Conversely, the withdrawal period worsened hunger for patients who switched from Vykat XR to a placebo.
In two posters, researchers compared the three-year outcomes of patients taking Vykat XR in DESTINY PWS and C602-OLE against data from a natural history study, which tracks the normal course of the disease without treatment.
One poster focused on changes in hyperphagia as measured by the Hyperphagia Questionnaire for Clinical Trials (HQ-CT). This standardized assessment rates hyperphagia severity on a scale from zero to 36, with higher numbers reflecting more severe uncontrolled hunger.
In the natural history study, the average HQ-CT score dropped slightly from 18.2 points to 15 points after a year and stayed stable for up to three years. In contrast, patients on Vykat XR saw their scores drop significantly from 21.6 points down to 11.4 after one year, 9.7 after two years, and 9.4 after three years.
Consequently, the reduction in hunger was significantly greater with Vykat XR at every time point compared to the natural course of the disease.
The second poster reported changes in behavioral scores using the PWSP questionnaire, which measures six issues common in PWS, including anxiety, depression, aggression, irritability/rigidity, disordered thinking, and compulsivity.
While behavioral scores remained virtually unchanged over three years in the natural history study, patients on Vykat XR showed a marked reduction in behavioral symptoms within six months, and these improvements lasted for up to three years.
Vykat XR treatment “significantly improved PWS-related behaviors over 3 years as demonstrated by improved scores across all domains of the PWSP questionnaire as compared to natural history controls,” the researchers wrote.
After completing C602’s withdrawal period, participants could enter another extension study, C614, where all are being treated with Vykat XR for up to five years.
A third poster highlighted outcomes for 77 participants in the C614 extension study. Two years of Vykat XR treatment led to sustained reductions in hunger and behavioral scores for both the patients who were on continuous therapy and those who had temporarily switched to a placebo.
Notably, patients who restarted Vykat XR after taking the placebo reached similar low hunger scores as those who stayed on the therapy continuously. In fact, patients restarting the treatment generally experienced larger shifts in their scores during this extension period.
“These data show that participants who resumed VYKAT XR after randomized withdrawal experienced recovery of treatment benefit, while those who continued therapy maintained durable improvements in hyperphagia and other PWS-related behaviors,” the release stated.
Vykat XR’s long-term safety findings were consistent with its previously known profile.
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