A "London Patient" became the second person to be cured from HIV after receiving a stem-cell transplant that replaced their white blood cells with HIV-resistant versions. But researchers warn that it is too early to say that they have been cured.

The patient , whose identity hasn’t been disclosed, was able to stop taking antiretroviral drugs, with no sign of the virus returning 18 months later. The stem-cell technique was first used a decade ago for Timothy Ray Brown, known as the ‘Berlin patient’, who is still free of the virus.

Like Brown, the latest patient also had a form of blood cancer that wasn’t responding to chemotherapy. They required a bone-marrow transplant, in which their blood cells would be destroyed and replenished with stem cells transplanted from a healthy donor.

Such a transplant is not a realistic mass technique yet because it is very risky, has serious complications, and is difficult to replicate. Currently, doctors prescribe anti-HIV drugs, such as non-nucleoside reverse transcriptase inhibitors or entry inhibitors, that not only prevent HIV cells from duplication but also prevent them from entering white blood cells.

According to the doctors,  the latest patient received a less aggressive treatment than Brown to prepare for the transplant. The new patient was given a regimen consisting of chemotherapy alongside a drug that targets cancerous cells, while Brown received radiotherapy across his entire body in addition to a chemotherapy drug.

He adds, This suggests that, to be successful, stem-cell transplants in HIV patients would not necessarily need to be accompanied by aggressive treatments that might have particularly severe side effects.

Graham Cooke, a clinical researcher, points out that this kind of treatment wouldn’t be suitable for most people with HIV — who don’t have cancer and so don’t need a bone-marrow transplant, which is a serious procedure that can sometimes have fatal complications. “If you’re well, the risk of having a bone-marrow transplant is far greater than the risk of staying on tablets every day,” he says.