Regeneron's Ebola Therapy REGN-EB3 Shows Superior Efficacy in Preventing Deaths, Leading to Early Termination of Phase II PALM Trial

Compiled by: Fan Dongdong

On August 12 local time, Regeneron announced that the PALM randomized controlled trial, which evaluated four drugs for treating Ebola virus infection, would be terminated early because its REGN-EB3 therapy demonstrated superiority over ZMapp in preventing Ebola-related deaths.

The PALM trial is a randomized, multicenter, controlled study that was initially launched in 2018 with three treatment arms, in which patients received mAb114, remdesivir, or ZMapp, respectively. ZMapp is a cocktail of three monoclonal antibodies; however, it is effective only against the Zaire ebolavirus species and not against the other two Ebola virus species—Sudan and Bundibugyo. ZMapp served as the standard of care in the PREVAIL II clinical trial. After evaluating all preclinical and clinical data, the World Health Organization’s expert panel revised the protocol to add REGN-EB3 as a fourth treatment arm.

REGN-EB3 (also known as REGN3470-3471-3479) is an anti-Ebola therapy developed by Regeneron using its VelociSuite technology. This therapy combines three fully human monoclonal antibodies and has previously received orphan drug designation from the U.S. FDA and the European EMA. Dr. Neil Stahl, Executive Vice President of Research and Development at Regeneron, stated, “The Regeneron team developed REGN-EB3 in record time, and we look forward to a comprehensive review of the trial data and to working with governments and other collaborators to make REGN-EB3 available for controlling the current outbreak and for future clinical use.”

It was clearly stated before the trial began that early termination would only occur if highly statistically significant results were obtained. By August 2019, nearly 700 participants had been enrolled across four treatment centers in the Democratic Republic of the Congo. After reviewing interim mortality data from 499 patients, the Independent Data Safety Monitoring Board ultimately decided to halt the trial.

Reference Source: PALM Ebola Clinical Trial Stopped Early as Regeneron's REGN-EB3 Therapy Shows Superiority to ZMapp in Preventing Ebola Deaths