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Early insights into viability of Ebola monoclonal antibodies for the 2026 Bundibugyo virus disease outbreak

Genomic and structural analyses of the 2026 Bundibugyo virus outbreak suggest that while the mAb114 therapy may be compromised by specific mutations, the MBP134 cocktail remains a promising broadly protective option and the Inmazeb trimeric cocktail retains efficacy through synergistic binding, highlighting the critical need for urgent experimental validation.

Original authors: Daudi Jjingo, Kevin Cissy Nabukeera, Gradi Luakanda-Ndelemo, Syrus Semawule, Pascal Adroba Tandele, Andrew Walakira, Adrienne Amuri, Daan Jansen, Ronald Galiwango, Alisen Ayitewala, Eddy Kinganda-Lusa

Published 2026-07-15

📖 4 min read☕ Coffee break read

CC BY 4.0

Original authors: Daudi Jjingo, Kevin Cissy Nabukeera, Gradi Luakanda-Ndelemo, Syrus Semawule, Pascal Adroba Tandele, Andrew Walakira, Adrienne Amuri, Daan Jansen, Ronald Galiwango, Alisen Ayitewala, Eddy Kinganda-Lusamaki, Andrew Nsawotebba, Christian Ngandu, Aloysious Ssemaganda, Olivier Tshiani-Mbaya, Stephen Kanyerezi, Judith Kyokushaba, Prince Akil-Bandali, Caroline Makoha, Hellen Rosette, Servet Kimbonza, Stephen Balinandi, Daniel Mukadi-Bamuleka, Valeria Nakintu, Justus Nsio, Ibrahimm Mugerwa, Daniel Kadobera, Daniel Euriene, Sabue Mulangu, Ahidjo Ayouba, Eilu Micheal, Sam Gidudu, Henry Kyobe Bosa, Misaki Wayengera, Anne Rimoin, Bernard Lubwama, Atek Kagirita, Steve Ahuka-Mundeke, Dieudonné Mwamba, Andrew Kambugu, Pontiano Kaleebu, Christian Happi, Miles Carroll, Piet Maes, Jean Nachega, Martine Peeters, Pierre Akilimali, Ronnie Bahatungire, Allan Niyonzima, Jason Kindrachuk, Andrew Rambaut, Daniel Kyabayinze, Charles Olaro, Laurens Liesenborghs, Koen Vercauteren, Jean-Jacques Muyembe-Tamfum, Susan Nabadda, Diana Atwine, Tony Wawina-Bokalanga, Placide Mbala, Isaac Ssewanyana

Original paper licensed under CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). ⚕️ This is an AI-generated explanation of a preprint that has not been peer-reviewed. It is not medical advice. Do not make health decisions based on this content. Read full disclaimer

Imagine the Ebola virus as a master thief wearing a specific, high-tech disguise called a "glycoprotein" coat. This coat has special "locks" on it. To stop the thief, doctors use "keys" called monoclonal antibodies. For years, we've had a few trusted keys (like mAb114 and the Inmazeb trio) that work perfectly on the most common thief, the Zaire Ebola virus. But now, a different thief has shown up: the Bundibugyo virus (BDBV), which caused an outbreak in 2026 in the Democratic Republic of the Congo and Uganda.

The big question was: Do our old keys still fit the new thief's locks?

The "Lock-Picking" Test

Scientists took 44 samples of this new Bundibugyo thief (including 12 fresh ones from the 2026 outbreak) and ran a super-fast, computer-based simulation to see how the keys fit. Think of this as a virtual reality video game where they built 3D models of the virus and the antibodies to see if they could click together.

Here is what the simulation revealed:

1. The "Ebanga" Key (mAb114): The Wrong Door
The mAb114 key (also known as Ebanga) is a superstar for the Zaire virus. But for the Bundibugyo thief, the lock has changed. Two tiny spots on the lock, labeled E112 and P116, have swapped their shapes (mutated to D and A).

The Result: In the computer simulation, the mAb114 key didn't just fail to open the lock; it got confused and tried to jam itself into a completely different, random spot on the thief's coat.
The Math: The scientists calculated that these shape changes made the key 54% less sticky at the E112 spot and 34% less sticky at the P116 spot.
The Verdict: The paper suggests that mAb114 might not work well against this specific virus because it can't find the right door anymore.

2. The "Inmazeb" Trio: The Power of Teamwork
The Inmazeb treatment is a three-person team of keys: Atoltivimab, Odesivimab, and Maftivimab.

The Solo Struggle: When the scientists tested Maftivimab (one of the keys) by itself in the simulation, it also got confused. It couldn't find its target lock on the Bundibugyo thief and ended up binding to the wrong spot, losing its grip.
The Team Win: However, when the three keys worked together as a complete team (the trimeric cocktail), something magical happened in the simulation. They held on tight! Even though the lock had changed, the three keys supported each other, allowing the whole team to bind firmly to the virus.
The Verdict: The paper suggests that while Maftivimab alone might fail, the full Inmazeb team could still be effective, but only if all three are used together.

3. The "MBP134" Super-Key: The Universal Fit
Then there is MBP134, a special two-key combo designed to be a "pan-ebolavirus" weapon (meaning it's built to fight all types of Ebola thieves).

The Result: The simulation showed that the locks MBP134 targets haven't changed at all. The keys fit perfectly, just like they do for the Zaire virus.
The Verdict: This suggests MBP134 is a very promising "universal" tool that could work against both the old and new thieves.

The "What We Don't Know" Warning

It's important to remember that this whole story was told inside a computer. The scientists used powerful software (like AlphaFold 3 and Rosetta) to build these 3D models and calculate the energy of the bonds.

The Confidence Level: The paper explicitly states these are simulations and predictions. They are like a very detailed weather forecast, not a report of what actually happened in a storm.
The Missing Piece: The authors warn that computers can't perfectly mimic how a virus wiggles and moves in a real human body. They haven't yet tested these keys on real live viruses in a lab (neutralization assays) to prove the computer was right.
The Conclusion: The findings suggest that mAb114 might be less effective, that Inmazeb needs its full team to work, and that MBP134 looks great. But until real-world lab tests confirm these computer guesses, we can't say for sure that these treatments will definitely work or fail in a hospital.

In short: The computer says the old single key might be broken, the three-key team needs to stick together, and the new universal key looks perfect. But we still need to take these keys out of the video game and try them on the real virus to be certain.

Technical Summary: Early Insights into Viability of Ebola Monoclonal Antibodies for the 2026 Bundibugyo Virus Disease Outbreak

Problem Statement
The 2026 Bundibugyo virus disease (BVD) outbreak in the Democratic Republic of the Congo (DRC) and Uganda has raised critical questions regarding the efficacy of existing monoclonal antibody (mAb) therapeutics, which were primarily developed and approved for Ebola virus (EBOV; Orthoebolavirus zairense). While mAb114 (Ebanga™) and the REGN-EB3 cocktail (Inmazeb; comprising Atoltivimab, Odesivimab, and Maftivimab) are FDA-approved for EBOV, their effectiveness against Bundibugyo virus (BDBV; Orthoebolavirus bundibugyoense) remains uncertain. Conversely, the experimental pan-ebolavirus therapeutic MBP134 targets highly conserved epitopes but requires validation against circulating BDBV strains. The study addresses the urgent need to determine if epitope mutations in the 2026 BDBV outbreak compromise the binding affinity and neutralization potential of these established and experimental therapeutics.

Methodology
The authors employed a combined genomic and structural modeling approach to evaluate in silico the viability of EBOV-targeted mAbs against BDBV.

Genomic Analysis: The study analyzed 44 whole-genome BDBV sequences, including 12 from the 2026 outbreak (4 from Uganda, 8 from DRC) and historical sequences from 2007 and 2012. Sequences were retrieved from Pathoplexus and the Central Public Health Laboratories (Uganda), filtered for quality, and aligned against the 2007 BDBV reference (YP_003815435.1) and EBOV reference (NP_066246.1) using Nextclade, EMBOSS, and Geneious Prime.
Epitope Mapping: Functional epitopes for mAb114, Inmazeb (Atoltivimab, Odesivimab, Maftivimab), and MBP134 (ADI-15878, ADI-15946) were mapped onto the BDBV glycoprotein (GP) to identify conserved versus mutated residues.
Structural Modeling:
- AlphaFold 3 (AF3): Used to predict the 3D structures of BDBV GP complexes with mAb114, the full Inmazeb trimer, and individual Inmazeb components. These were compared against experimental structures (e.g., PDB: 5FHC for mAb114/EBOV).
- Rosetta In Silico Mutagenesis: The E112D and P116A mutations unique to the 2026 BDBV outbreak were introduced into the EBOV GP-mAb114 complex (PDB: 5FHC) and the EBOV GP-Inmazeb complex (PDB: 7TN9). Rosetta FastRelax and ddG protocols were used to calculate changes in binding free energy ( $\Delta\Delta G$ ) to quantify the thermodynamic impact of these mutations on antibody affinity and protein stability.

Key Results

Genomic Divergence: BDBV shares approximately 63.9% genome-wide identity and 65% GP amino acid similarity with EBOV. The 2026 outbreak sequences exhibited a persistent evolutionary signature of ten amino acid substitutions shared with 2012 strains, plus two unique substitutions: Y387H and R506S.
mAb114 (Ebanga) Efficacy Compromised: The mAb114 epitope in BDBV contains E112D and P116A mutations. Structural modeling indicates these mutations alter the canonical binding interface, causing mAb114 to bind to an off-target site rather than the intended epitope. Rosetta analysis quantified a significant reduction in binding affinity: E112D resulted in a $\Delta\Delta G$ of +1.24 kcal mol⁻¹ (approx. 54% affinity reduction), and P116A resulted in a $\Delta\Delta G$ of +0.70 kcal mol⁻¹ (34% reduction).
Inmazeb (REGN-EB3) Combinatorial Binding:
- Individual Components: When modeled individually against BDBV GP, Odesivimab (REGN3471) maintained stable binding despite mutations ( $\Delta\Delta G$ = -50.8 kcal mol⁻¹). However, Atoltivimab (REGN3470) and Maftivimab (REGN3479) failed to bind their target epitopes, exhibiting high destabilizing energies ( $\Delta\Delta G$ > +146 kcal mol⁻¹) and off-target binding.
- Trimeric Cocktail: In contrast, the complete Inmazeb trimeric complex demonstrated firm, synergistic binding to BDBV GP with a total favorable binding energy ( $\Delta\Delta G$ = -397.4 kcal mol⁻¹). This suggests that the cocktail retains neutralizing potential through combinatorial effects, even though individual components like Maftivimab (often prioritized by WHO for BDBV evaluation) may fail as monotherapies.
MBP134 Conserved Efficacy: The epitopes targeted by MBP134 (ADI-15878 and ADI-15946) remained fully conserved across all 44 analyzed BDBV sequences. Structural docking confirmed that both antibodies bind to their designated sites on BDBV GP in a manner analogous to their interaction with EBOV GP, supporting its potential as a broad-spectrum therapeutic.

Significance and Claims
The paper provides early, in silico evidence that the efficacy of EBOV-directed mAbs against BDBV is highly dependent on epitope conservation. The authors claim that:

mAb114 is likely ineffective against the 2026 BDBV strains due to specific epitope mutations (E112D, P116A) that disrupt binding affinity and cause off-target interactions.
MBP134 holds significant promise as a broadly protective therapeutic for both EBOV and BDBV due to the high conservation of its target epitopes.
The Inmazeb cocktail relies on combinatorial synergy. While the WHO prioritizes Maftivimab as a monotherapy for BDBV, the study suggests that Maftivimab alone may fail to bind effectively; its efficacy may depend on the conformational stabilization provided by the full trimeric cocktail (Atoltivimab, Odesivimab, and Maftivimab).
Genomic surveillance is critical. The findings underscore that epitope conservation cannot be assumed across the Ebolavirus genus and highlight the necessity of integrating genomic surveillance with structural analysis to monitor therapeutic viability.

The authors explicitly state that these findings are hypothesis-generating based on predictive modeling. They emphasize that the static nature of in silico models cannot fully capture dynamic physiological flexing or allosteric shifts, and that definitive confirmation of efficacy requires experimental validation through neutralization assays and live-virus studies.

The "Lock-Picking" Test

The "What We Don't Know" Warning

Technical Summary: Early Insights into Viability of Ebola Monoclonal Antibodies for the 2026 Bundibugyo Virus Disease Outbreak

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