An experimental monoclonal antibody designed to prevent COVID-19 has entered the final phase of human testing. The treatment, called VYD2311, delivers ready-made antibodies instead of training the immune system to produce its own.
Invivyd, the biotech firm behind the drug, confirmed that enrollment in its phase 3 LIBERTY trial is complete. The study compares the antibody’s safety and tolerability against an mRNA COVID vaccine rather than a placebo.
The LIBERTY trial is part of Invivyd’s REVOLUTION clinical program. A second study, DECLARATION, tests whether VYD2311 reduces symptomatic infections compared to a placebo.
“Vaccines don’t particularly stop people from getting sick,” said Marc Elia, Invivyd’s chairman. “They prevent deaths, but most other outcomes—like avoiding illness—are areas where we believe our approach works better.”
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Elia explained that vaccines depend on the body’s immune response, which can cause inflammation and side effects. Monoclonal antibodies like VYD2311 provide immediate protection without requiring the immune system to react. “We supply the antibody the body wishes it could make,” he said.
The company expects the treatment to appeal to those who avoid vaccines due to poor tolerability, a concern Elia described as a major barrier to vaccination.
VYD2311 was developed from pemivibart, an earlier antibody authorized for emergency use. Scientists modified a few sites in its binding region to increase potency and extend how long it remains active in the body.
“These changes create a stronger antibody,” Elia said. “It lasts longer and works more effectively.”
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The initial focus is on groups most at risk for severe COVID-19: the immunocompromised, older adults, and infants. Elia noted the treatment could eventually serve anyone who wants to avoid illness. “Over time, it should be an option for anyone who doesn’t want to get sick,” he said.
Success in the REVOLUTION program could change how COVID-19 is managed. While vaccines have cut deaths, the virus still causes widespread illness, long-term health problems, and daily disruptions. Elia suggested the antibody might help reduce the ongoing damage caused by the virus. “The last seven years have involved a certain amount of medical dismay and ongoing damage, whether it’s in the form of acute infections or, for example, cardiothoracic issues and follow-ons from COVID.”
Results from the trials won’t arrive for months. Even if successful, regulatory approval and large-scale production would take more time. The approach highlights how monoclonal antibodies might address gaps left by vaccines, especially for those who cannot or will not use them.
For now, the priority is demonstrating the treatment’s safety and effectiveness. If it succeeds, it could join a shrinking set of tools against a virus that has persisted longer than expected.
