The PALM trial (2018-19, DRC Kivu) showed that two monoclonal antibody therapies — Regeneron's REGN-EB3 (now Inmazeb) and NIAID/Ridgeback's mAb114 (now Ebanga) — reduced Zaire ebolavirus mortality significantly compared to ZMapp and remdesivir. Overall mortality was 33.5% for Inmazeb and 35.1% for Ebanga versus 49.7% for ZMapp. These results drove FDA approvals in 2020.Source: NEJM December 2019

Does the PALM trial data apply to the current Bundibugyo outbreak?

No. The PALM trial enrolled only patients infected with Zaire ebolavirus. The current Ituri outbreak is Bundibugyo ebolavirus. The glycoprotein-targeting mechanism of Inmazeb and Ebanga is species-specific; the PALM survival data does not translate across Ebola species.Source: NEJM 2019; FDA labels

Why is there no Ebola drug for Bundibugyo?

Bundibugyo has had only three documented outbreaks before 2026 — 2007 Uganda, 2012 DRC, and now Ituri — providing insufficient outbreak scale to run a randomised clinical trial. Drug development requires large enough patient cohorts for statistical power; without frequent outbreaks, the scientific and commercial imperative to develop species-specific products was too low. The WHO R&D Blueprint Filovirus roadmap named this gap in Q1 2026.Source: WHO R&D Blueprint; PALM trial history

Background

PALM (Pamoja Tulinde Maisha — Swahili for "Together Save Lives") was a randomised controlled trial of four candidate Ebola therapeutics conducted in the Democratic Republic of Congo during the 2018-19 Kivu outbreak, one of the largest Ebola outbreaks on record. The trial compared ZMapp (the previous standard), remdesivir, REGN-EB3 (Regeneron's triple monoclonal cocktail, now Inmazeb) and mAb114 (Ridgeback's single monoclonal, now Ebanga). Results published in the New England Journal of Medicine in December 2019 showed that REGN-EB3 and mAb114 were significantly more effective than ZMapp or remdesivir: overall mortality of 33.5% for REGN-EB3 and 35.1% for mAb114 versus 49.7% for ZMapp. Among patients with the lowest viral loads at admission, mortality fell to 11%.

The PALM trial represented a landmark in Ebola therapeutics development: it was the first adequately powered randomised trial for Ebola, conducted in the field during an active outbreak in a conflict zone, using an adaptive platform design. Its results directly led to the FDA approvals of Inmazeb in October 2020 and Ebanga in December 2020, making them the global standard of care for Zaire ebolavirus.

The critical limitation in the context of the 2026 Bundibugyo PHEIC is explicit in the trial design: PALM enrolled exclusively patients infected with Zaire ebolavirus. No Arm tested efficacy against Bundibugyo, Sudan or any other Ebola species. The glycoprotein-targeting design of both Inmazeb and Ebanga means the trial's mortality outcomes are species-specific. Nahid Bhadelia's 15 May 2026 panel identified PALM-trial ribavirin as the only candidate therapeutic with any cross-Ebola signal — ribavirin being the only comparator agent from the PALM era that had any non-Zaire exposure data, though under a very different mechanism and with significant hepatotoxicity monitoring requirements.

Source Material

A Randomized, Controlled Trial of Ebola Virus Disease Therapeutics

How the World Sees Them

Pharmaceutical companies

PALM data underpins both Inmazeb and Ebanga FDA approvals; no company has yet initiated a PALM-style trial for Bundibugyo, reflecting the small number of prior Bundibugyo outbreaks and limited commercial incentive.

Global health research community

PALM's adaptive platform design in a conflict-zone outbreak is the methodological precedent for any accelerated Bundibugyo trial; but organising a Bundibugyo arm requires a sponsor, a trial site with outbreak-scale cases, and ethics approval, none of which exist yet.

DRC communities and health authorities

PALM was conducted in Kivu using Congolese patients as trial participants; the resulting FDA-approved treatments are priced for US markets and remain largely inaccessible in DRC during the current outbreak.