Weekly injections of a monoclonal antibody known as PRO 140 may work as a stand-alone treatment for individuals living with HIV, according to a study presented at ASM Microbe 2016, in Boston.
The phase-2b study followed 39 people who were living with CCR5-tropic HIV. CCR5 is a receptor on the CD4 cell that most strains of HIV use as a point of entry. PRO 140 is able to bind to CCR5, preventing HIV infection.
The study participants achieved undetectable viral loads (below 40 copies/mL) on standard once-daily antiretroviral therapy. They were then switched to weekly subcutaneous injections of PRO 140 monotherapy. After they maintained viral suppression for 13 weeks, 16 participants were trained to self-administer the weekly injections.
There were 15 participants included in the final results, with 86.7% male, 20% non-white, a median age of 55 years and median CD4 count of 586 cells/mm3. Out of those 15, 10 participants are still on PRO 140 monotherapy and have maintained viral suppression for almost 18 months, according to a study press release.
"The PRO 140 treatment was well tolerated by patients with no discontinuation or drug-related adverse effects," said lead author Paul J. Maddon, M.D., Ph.D., according to the study press release. "Importantly, PRO 140 monotherapy can allow patients to avoid the potential toxicity of [antiretroviral therapy] while preserving future drug options," Maddon added.
Three participants experienced virologic failure at a median time of 169 days. They were subsequently restarted on standard antiretroviral therapy and achieved an undetectable viral load after a median of 29 days. Additionally, one participant with an undetectable viral load discontinued the PRO 140 treatment at week 47 because of relocation.
"PRO 140 may offer a simple, long-acting, single-agent maintenance therapy after initial [antiretroviral therapy] in selected patients with HIV infection," Maddon concluded.
The researchers plan to move on to a larger phase-2b or phase-3 study.
PRO 140 is the experimental drug that the actor Charlie Sheen, who publicly disclosed his HIV status in November 2015, recently revealed he was receiving as part of a clinical trial.
Here's a video from the antibody developers showing how PRO 140 combats HIV: