The Foundation for Prader-Willi Research has recommended that doctors treating people with Prader-Willi syndrome (PWS) should closely track patients on VYKAT XR for fluid retention and related heart or breathing problems.

  • Neurocrine Biosciences gained VYKAT XR through its $2.9-billion acquisition of Soleno Therapeutics, completed in May.
  • FPWR noted seven reported deaths and more than 100 reports of serious adverse events involving heart or breathing issues in patients taking the drug.
  • In August 2025, short-seller Scorpion Capital published a lengthy report alleging serious risks of fluid buildup, pulmonary edema, and heart failure with Vykat XR use, along with concerns about clinical-trial data.

Shares of Neurocrine Biosciences closed 3% lower on Wednesday and further slipped 1% after-hours after the Foundation for Prader-Willi Research (FPWR) recommended that doctors treating people with Prader-Willi syndrome (PWS) should closely track patients on its drug VYKAT XR for fluid retention and related heart or breathing problems.

FPWR blog from Monday outlines practical steps for real-world use of the drug, the first FDA-approved treatment for extreme hunger (hyperphagia) in PWS patients aged four and older. FPWR further advises families to review the full prescribing information and consult PWS specialists so the potential benefits of reduced hyperphagia can be weighed carefully against the risks.

Since Vykat XR’s March 2025 launch, more than 800 people have received prescriptions. The medicine can help control appetite but may cause edema that, in some cases, has been linked to serious complications, according to experts.

Heightened Focus On Safety Signals

FPWR noted seven reported deaths and more than 100 reports of serious adverse events involving heart or breathing issues in patients taking the drug. Many of those individuals already had obesity, multiple medications, or untreated sleep apnea. The foundation stresses that PWS itself carries elevated baseline risks, so a direct link is not always clear. Still, it recommends safety tests before starting treatment, ongoing checks for swelling or breathing changes, and care from physicians experienced with the syndrome.

Neurocrine Adds Vykat XR

Neurocrine Biosciences gained VYKAT XR through its $2.9 billion acquisition of Soleno Therapeutics, completed in May. Soleno developed and launched the once-daily pill.

While still under Soleno, the drug faced scrutiny. In August 2025, short-seller Scorpion Capital published a lengthy report alleging serious risks of fluid buildup, pulmonary edema, and heart failure, along with concerns about clinical-trial data. The following month, Soleno disclosed the death of a 17-year-old patient who had been taking the medicine, though the company and treating physician assessed the death as unrelated to the drug. Investor lawsuits later claimed Soleno had downplayed fluid-retention signals.

Broader Impact On PWS Pipeline

Safety worries have slowed other PWS programs. Aardvark Therapeutics paused its late-stage trial of ARD-101 last year after cardiac observations in healthy volunteers, and the FDA later placed a clinical hold. Years earlier, Zafgen ended development of beloranib after patient deaths linked to blood clots. Acadia Pharmaceuticals also discontinued its candidate after a failed efficacy study.

How Did NBIX Retail Traders React?

On Stocktwits, retail sentiment around NBIX stayed within ‘bearish’ territory while message volume stayed at ‘normal’ levels.

A Stocktwits user highlighted that no clear link has been established between the drug’s use and the negative side effects.

“I always thought vykat/soleno was a bad drug and investment,” another user wrote.

NBIX stock has gained 10% year-to-date. 

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