New research involving infant macaques has produced findings that may support further investigation of CytoDyn’s CCR5-targeting antibody leronlimab in HIV. The findings, published in Nature Microbiology, came from a study involving 55 infant macaques that received different combinations of broadly neutralizing antibodies (bNAbs), antiretroviral therapy, and leronlimab.
Among eight macaques that received all three treatments, researchers reported that the virus failed to gain a foothold. Those animals remained HIV-free for up to one year after treatment was stopped.
“The macaque immune system is very similar to the human immune system,” said Jonah Sacha, Ph.D., professor of pathobiology and immunology at Oregon Health & Science University’s Oregon National Primate Research Center and lead author of the study.
Treatment Was Initiated Three Days After Infection
For the study, researchers orally infected infant macaques with HIV and began treatment 72 hours later. The eight animals that remained HIV-free after one year received a single dose of two broadly neutralizing antibodies. They also received daily subcutaneous antiretroviral therapy for 27 weeks.
Leronlimab was administered weekly. Animals received either 10 mg/kg for three weeks or 50 mg/kg for six weeks.
Sacha explained that the broadly neutralizing antibodies were designed to target the HIV envelope and physically prevent the virus from attaching to target cells. The therapy remains experimental, has not been approved, and is being tested separately in clinical trials.
Researchers observed different outcomes when the therapies were used alone. Antiretroviral therapy by itself did not stop the viral reservoir from developing, and infection returned after treatment ended. Similar findings were observed when macaques received only bNAbs or only leronlimab.
Viral Reservoir Continues to Complicate HIV Treatment
Nearly 41 million people around the world are living with HIV. One reason the disease remains difficult to treat is the formation of a viral reservoir.
Sacha described the reservoir as the defining feature of infection because the virus integrates into host cells. He explained that antiretroviral therapy causes the virus to become inactive, but the virus remains inside cells. When treatment is discontinued, viral replication can resume.
According to Sacha, this is why people receiving approved antiretroviral therapies remain on treatment for life.
Researchers Seek Answers Before Human Studies
Sacha and his colleagues are working to understand the biological mechanism behind the animals that responded to the triple-drug regimen and hope to move the research into human trials.
However, he said several questions remain unanswered, including whether the approach would work in adults, whether it is specific to infants, and how long after infection treatment can be administered and remain effective.
Leronlimab is designed to block the CCR5 receptor, which serves as an essential co-receptor for T-cell tropic viruses such as HIV. The importance of CCR5 was discovered after a mutation in its gene was found to protect individuals from becoming infected.
ViiV Healthcare markets the CCR5 inhibitor Selzentry, which was originally launched by Pfizer. Leronlimab has faced challenges in development. In 2022, CytoDyn withdrew an approval application for a specific HIV indication because of issues involving data from the contract research organization that had overseen a successful phase 2b/3 trial.
CytoDyn has continued to study leronlimab in other diseases. This year, the company reported phase 2 data suggesting the therapy could improve outcomes in patients with metastatic colorectal cancer and also began a phase 2a study evaluating the treatment in Alzheimer’s disease.
Macaques Show Promising HIV Treatment Results
A new Oregon Health & Science University study has reported encouraging results in infant Macaques exposed to simian-human immunodeficiency virus. Researchers found that a combination of three therapies administered shortly after infection prevented detectable viral rebound for one year after treatment was stopped.
The study involved infant rhesus Macaques and examined whether early combination treatment could limit the establishment of persistent viral reservoirs. The research was published in Nature Microbiology.
Macaques Receive a Three-Part Treatment
The treatment tested in the Macaques combined antiretroviral therapy, broadly neutralizing antibodies, and the experimental CCR5-blocking antibody leronlimab. Researchers treated the infant Macaques approximately 72 hours after infection, when viral replication was already detectable.
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