A man with HIV is now virus-free after receiving a stem cell transplant, making him one of only a handful of people to be considered cured after the treatment. The HIV patient in Düsseldorf, Germany also had cancer and received a bone marrow transplant which replaced his cells with a donor’s HIV-resistant stem cells, according to a newly published study.

After being diagnosed with leukemia, the 53-year-old man, known as the “Düsseldorf Patient,” received a stem cell transplant in 2013. His stem cell donor had a mutation, which prevents the protein used by HIV to enter cells.

He had been receiving antiretroviral therapy, or ART, which is commonly given to HIV patients to make the virus nearly undetectable. It can also prevent the patient from transmitting the virus to others.

While HIV stays in the body during ART, the stem cell transplant can “substantially reduce the viral reservoir,” where the virus persists, according to the study published this week in Nature Medicine.

During his ART treatment, the doctors continued to assess the Düsseldorf patient’s reservoir. His HIV was considered undetectable, but he still had HIV reservoirs and tested for traces of virus DNA and RNA. However, additional tests showed the virus did not replicate.

The medical team decided to test what would happen if he stopped the therapy. In 2018, after 69 months, he stopped ART – and he has remained HIV-free since then.

“It shows it’s not impossible — it’s just very difficult — to remove HIV from the body,” said virologist Björn-Erik Jensen, who led the medical team during this patient’s treatment.

The first patient considered cured of HIV, Timothy Ray Brown, was known as the “Berlin Patient” because he had been living in the German city with both HIV and leukemia when he received the treatment.

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Brown underwent blood stem cell transplants from a donor who was immune to HIV when he became gravely ill while battling cancer. Doctors declared Brown “cured” in 2008, not long after his transplant.

Brown said in 2011 he had stopped taking his HIV medication the day he received the transplant and had not taken any since. He died in 2020 after his cancer returned, the AP reported. Brown appeared to have remained HIV-free until his death.

Another patient, 40-year-old Adam Castillejo, who was dubbed the “London Patient,” had a bone marrow transplant to treat Hodgkin’s lymphoma, which is untreatable. His donation also came from someone who had the mutation, and his HIV was cured in 2019.

Recent studies have shown promising results for two other patients. A patient at City of Hope Medical Center in Duarte, California, has been in remission for HIV since 2019 after receiving a stem cell transplant to treat acute myelogenous leukemia, according to an announcement published in the American Journal of Managed Care in 2022. Weill Cornell Medicine in New York announced last year an HIV patient appeared free of the virus after a cell transplant to treat the same type of cancer.

According to Nature Medicine, this treatment will likely not be used in HIV patients who don’t also have leukemia. Scientists are testing what would happen if a patient’s own stem cells were modified to have the mutation needed to block HIV, which would mean they would not need a donor.