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# Positive Efficacy Data on Zafgen Drug Placed on Hold
- URL: https://www.fdaweb.com/positive-efficacy-data-on-zafgen-drug-placed-on-hold/
- Published: 2016-01-21T12:00:00.000Z
- Updated: 2026-09-15T02:29:24.000Z
- Author: David McFarland
- Tags: Drugs, #legacy-id-D5134491

> Zafgen has announced positive efficacy results from the bestPWS ZAF-311 study, a pivotal, double-blind, placebo-controlled Phase 3 trial evaluating the safety and efficacy of beloranib, a MetAP2 inhibitor, in patients with Prader-Willi syndrome (PWS) during a six-month randomized treatment period. The trial was placed on clinical hold in December after two patients being treated died ([see earlier story](http://fdaweb.com/login.php?sa=v&aid=D5134099&searchWords=zafgen&cate=S&stid=%241%24ol..RK3.%24uClYMZ8%2FzUMU9%2FhzLGAL50&ref=fdaweb.com)).  
>  
> “The clinical trial achieved its co-primary efficacy endpoints, as beloranib demonstrated a statistically significant reduction in both body weight and hyperphagia-related behaviors, making it the first investigational drug to demonstrate a positive impact on these two hallmark challenges in PWS,” the company says. “Treatment with the 2.4 mg and the 1.8 mg doses of beloranib resulted in 9.45% (p<0.0001) and 8.20% (p<0.0001) reductions in body weight relative to placebo, respectively. Treatment with the 2.4 mg and the 1.8 mg doses of beloranib also resulted in reductions of hyperphagia-related behaviors of 7.0 units (p=0.0001) and 6.3 units (p=0.0003) relative to placebo, respectively, as measured by the Hyperphagia Questionnaire for Clinical Trials (HQ-CT).”  
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> The efficacy data are “a crucial first step” in moving discussions forward with FDA about beloranib’s continued development, Zafgen says. “While we take the previously reported adverse events very seriously, we now have the robust data to provide greater perspective on the benefit/risk relationship of beloranib in this high-risk patient population.”