Imagine you’re 27 years old and you start feeling ill. Ill enough that you go to the hospital, and after much poking and prodding and waiting for lab results you learn you’re HIV positive. Two weeks later you find out that’s not even the worst of it. You’ve got leukemia too.

Under any circumstances it would be a lot to take in. Especially in China, where HIV/AIDS is highly stigmatized. But for one young man living there, who this happened to in the late spring of 2016, there was one small but significant silver lining to this double whammy of a diagnosis. He would be eligible to participate in the first-ever clinical trial to assess the safety of trying to cure both the cancer and the infection in a single procedure using the gene-editing tool called Crispr.

In July of 2017, doctors in Beijing blasted the patient with chemicals and radiation to wipe out his bone marrow, making space for millions of stem cells they then pumped into his body through an IV. These new stem cells, donated by a healthy fellow countryman, would replace the patient’s unhealthy ones, hopefully resolving his cancer. But unlike any other routine bone marrow transplant, this time researchers edited those stem cells with Crispr to cripple a gene called CCR5, without which HIV can’t infiltrate immune cells.

Now, more than two years later, the patient is in good health, his cancer in full remission, as researchers report today in the New England Journal of Medicine. The edited stem cells survived and are still keeping his body supplied with all the necessary blood and immune cells, and a small percentage of them continue to carry the protective CCR5 mutation. Not enough to have cured him of HIV, though—he remains infected and on antiretroviral drugs to keep the virus in check. Still, experts say the new case study shows this use of Crispr appears to be safe in humans and moves the field one step closer toward creating drug-free HIV treatments.

“The safety profile appears to be acceptable,” pioneering cancer researcher Carl June wrote in an accompanying editorial, noting that the editing appeared to be precise, and that the engineered stem cells didn’t provoke an immune response in the patient. June did offer a caveat that the study’s single patient offered only limited data to draw on.

LEARN MORE The WIRED Guide to Crispr

What he found more striking was how quickly the science has moved from the first reports of using Crispr to treat HIV infection in mice to trying it in humans: only two years. At the University of Pennsylvania, June has led work in a groundbreaking cancer treatment called CAR-T, which involves genetically reprogramming immune cells into a clone army of tumor-targeting assassins. But it took him five years to go from studies in animals to trials involving humans. In this case, China’s more permissive biomedical research regulations might have expedited the work, or it could be that genetic engineering is lending new momentum to the race for an HIV/AIDS cure, he wrote. “In any case, the genie is out of the bottle with genome editing.”

This is the first time an HIV-positive patient has been treated with Crispr-edited cells. But scientists have been trying to find ways to genetically disable CCR5 for more than a decade now. It all started in 2007, when a German doctor took a 41-year-old man with HIV/AIDS and leukemia off of his antiretroviral drugs and hooked a thin tube up to a vein in his chest. Through it, the so-called Berlin Patient received blood cells from a bone marrow donor who had a naturally occurring mutation called CCR5 Δ32. He was missing a chunk of DNA that ultimately allows an HIV virus to enter immune cells. The patient survived his cancer and became the first (though no longer the only) person considered to be fully cured of HIV/AIDS.