10 of 16 HIV Patients Still Undetectable After Weekly Injections of Antibody PRO 140

Self-injected monotherapy with a monoclonal antibody that binds to the CCR5 chemokine receptor on CD4 immune T-cells maintained viral suppression in 10 of 16 study participants for 41 to 123 weeks. Five participants experienced virologic failure, and one person dropped out because of relocation.

In study participants who achieved viral suppression with daily oral antiretroviral therapy switched to PRO 140 monotherapy, injected weekly at a subcutaneous dose of 350 mg.

PRO 140 is a humanised IgG4 monoclonal antibody that blocks HIV-1 from entering CD4 cells via the CCR5 coreceptor without upsetting the natural activity of CCR5. A single weekly injection of PRO 140 reduces HIV RNA by an average 45-fold. The monoclonal antibody inhibits replication of multidrug-resistant HIV-1, including virus resistant to maraviroc, a CCR5 antagonist.

Participants received PRO 140 monotherapy for up to 12 weeks, overlapping one week with oral therapy. In a phase 2b extension of the study, participants who maintained viral suppression through 12 weeks of PRO 140 monotherapy became eligible to continue weekly self-administered monotherapy.

No serious toxicity pattern or adverse events were judged related to PRO 140. The investigators are working to identify predictors of PRO 140 treatment success and currently recruiting phase 2b/3 trials.