Growth hormone trial aims to boost muscle in Prader-Willi patients

NCT ID NCT04697381

Completed Disease control Sponsor: Pfizer Source: ClinicalTrials.gov ↗

First seen Jun 27, 2026 · Last updated Jun 27, 2026

Summary

This completed Phase 3 study tested somatropin, a synthetic growth hormone, in 33 Japanese children and adults with Prader-Willi syndrome. The goal was to see if it safely improves body composition by increasing lean body mass and reducing fat. Participants were divided into three groups based on age and prior growth hormone use, and changes were measured over 12 months.

What this could mean

Our plain-language read of the trial. This is informational only — not medical advice or a prediction.

Active substance: somatropin (a synthetic growth hormone)
What this could lead to: If successful, this could confirm somatropin as a safe and effective way to improve body composition (more lean muscle, less fat) in people with Prader-Willi syndrome.
What could go wrong: This is a small, open-label study (no placebo group) in Japanese participants only, so results may not apply broadly. Growth hormone therapy has known side effects like joint pain and swelling.

This is an AI summary of the original study and may miss details. Read our disclaimer.

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Conditions

The condition(s) this trial relates to.

Prader-Willi syndrome

As listed by the trial registrant

The condition terms exactly as the trial's registrant entered them.

PRADER-WILLI SYNDROME

Contacts and locations

Locations

Dokkyo Medical University Saitama Medical Center

Koshigaya, Saitama, 343-8555, Japan
Hamamatsu University Hospital

Hamamatsu, Shizuoka, 431-3192, Japan
Kanagawa Children's Medical Center

Yokohama, Kanagawa, 232-8555, Japan
National Center for Child Health and Development

Setagaya-ku, Tokyo, 157-8535, Japan
Osaka Women's and Children's Hospital

Izumi, Osaka, 594-1101, Japan

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