A large international study has shown that it is possible to prevent some HIV infections with infusions of a particularly potent protein known as a broadly neutralizing antibody, but it will likely take a combination of different and more potent proteins to block all strains of the shape-shifting virus.
Results of the Antibody Mediated Prevention, or AMP, trials released today are an “important proof of concept” that demonstrated the feasibility of blocking HIV with bimonthly infusions of such antibodies, according to trial leader Dr. Larry Corey, the acclaimed virologist and professor at Fred Hutchinson Cancer Research Center in Seattle.
The results come from a pair of AMP trials that since 2016 have enrolled 4,623 volunteers on four continents. The study was designed to evaluate whether a single broadly neutralizing antibody, known as VRC01, could be safely delivered by intravenous drip and to provide detailed information on how well it blocked infection by multiple strains of HIV.
For years, HIV vaccine researchers have been stymied by the ability of HIV to outmaneuver a range of antibodies that our immune system normally uses to control invading viruses. AMP was set up to test whether infusions of a broadly neutralizing antibody — one that HIV could not readily evade through mutation — could block new infections.
The VRC01 antibody was originally discovered in the blood of a patient living with HIV, and mass-produced in the laboratory as a so-called monoclonal antibody. It is the same process being used to treat COVID-19 patients with manufactured antibodies that target the spike protein of the coronavirus.
The trials found that this antibody completely blocked about 30% of HIV strains circulating in the communities where the infusions were tested, but it was not potent enough to block the other 70% of strains, and therefore by itself is not an effective candidate for HIV prevention.
Opens up the field for development
Consequently, Corey explained, this study showed that just as combinations of different antiretroviral drugs are needed to treat HIV, combinations of more potent antibodies — including some discovered since the AMP study launched — might be able to prevent it. Early trials testing such antibody cocktails in human volunteers are already underway.
“This trial was incredibly successful. It opens up the field for the development of cocktails of monoclonal antibodies,” Corey said today during a press conference in advance of the HIV Research for Prevention, an international conference on the science of HIV prevention that opens online Jan. 27.
In an interview, Corey said the study results gave him a sense of déjà vu, because decades ago he played a key role in the trials of AZT, the first antiviral found to inhibit HIV, the virus that causes AIDS. That drug, by itself, was shown to be effective at blocking HIV, but it could be overwhelmed within a few months by strains of the rapidly mutating virus that could sidestep it.
