A single infusion of genetically engineered immune cells suppressed HIV to undetectable levels in two people for nearly two years without their usual daily medications, according to early clinical data released Tuesday, raising cautious hope that the technology behind some cancer cures might also deliver a functional cure for the virus that causes AIDS.
The study, led by Dr. Steven Deeks of the University of California, San Francisco, tested a modified form of CAR-T cell therapy in nine people living with HIV. Participants stopped their antiretroviral drugs the day they received the infusion, and two of them saw the virus drop to undetectable levels — one for nearly a year and the other for nearly two years — with only occasional blips that researchers believe signal the engineered cells springing back into action.
Deeks called the duration of the responses “provocative.” “There is a real need for a one-and-done, safe and scalable cure,” he said, “and this is one of the strategies that we’re pursuing.”
The results were presented at a meeting of the American Society of Gene and Cell Therapy in Boston and have not yet been published in a peer-reviewed journal. The experiment was an early-stage safety trial designed to test different dosing strategies, not to prove efficacy, and Deeks cautioned that larger, longer studies are essential before any conclusions can be drawn.
Still, the findings represent the first evidence that CAR-T therapy, a treatment that has cured some blood cancers, might be re-engineered to tackle a chronic viral infection. Nearly 40 million people are living with HIV worldwide. Modern antiretroviral medicines can keep the virus at undetectable levels and prevent transmission, but they must be taken daily for life, and the virus quickly rebounds if treatment stops because it hides in latent reservoirs throughout the body.
Scientists have pursued a cure for decades, exploring rare gene mutations that confer natural resistance, as well as stem cell transplants that have left a handful of patients free of the virus — an approach too risky for widespread use.
CAR-T therapy works by extracting a patient’s T cells, genetically reprogramming them to recognize specific targets, and returning them as “living drugs.” For HIV, researchers at the nonprofit Caring Cross designed CAR-T cells with a dual function: they home in on and destroy HIV-infected cells, and they carry an engineered shield that protects them from being infected by the same virus they are supposed to fight.
“With that added armor, they should be able to reproduce enough to keep HIV in check,” said Caring Cross executive director Boro Dropulić.
The trial enrolled nine participants who had well-controlled HIV on medication. The first three received CAR-T cells alone and showed no response; they resumed their usual drug regimens. The next six received a small dose of chemotherapy beforehand to clear space in the immune system for the incoming cells. Among them, two people saw sustained suppression. A third had a temporary response and eventually restarted antiretroviral therapy. No serious side effects were reported.
Crucially, all three patients who showed any benefit had started their HIV treatment soon after infection, Deeks said. That pattern is logical, he explained, because people treated early tend to have smaller viral reservoirs and healthier immune systems — conditions that may make CAR-T therapy more likely to work.
Dr. Hans-Peter Kiem, a gene therapy expert at the Fred Hutchinson Cancer Center in Seattle who was not involved in the study, called the early responses “very fascinating” but stressed that much more research is needed to confirm that the approach truly works. He noted that the findings will need to be replicated in larger groups and followed over longer periods to assess durability and safety.
Andrea Gramatica, vice president for research at amfAR, The Foundation for AIDS Research, which is funding related work, said the strategy is exciting because it amplifies what the immune system already does. “It’s boosting what our body, our immune system, can already do,” she said.
If CAR-T therapy eventually proves effective against HIV, it would face the same access challenges that have limited its use in cancer: the treatment is complex, expensive, and requires specialized manufacturing for each patient. Caring Cross and other groups are already exploring ways to simplify and lower the cost of the process.
For now, the two patients who responded remain off their daily pills, their virus held at bay by cells engineered in a laboratory — a small but startling signal that a single intervention might one day replace a lifetime of medication.