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ATLANTA -- The addition of PRO 140 SC, a subcutaneous injection of a monoclonal antibody, to an existing HIV drug treatment regimen was effective at reducing viral load in previously treated HIV patients, a late-breaking trial presented here found.

An ongoing phase IIb/III efficacy trial found that a significantly higher proportion of patients treated with PRO 140 had a 0.5 log₁₀ or greater reduction in viral load compared with patients treated with placebo (64% versus 23%, P=0.0032), reported Kush Dhody, MBBS, of Amarex Clinical Research in Washington, D.C., and colleagues at the .

PRO 140, which has FDA Fast Track status, is a humanized IgG4 monoclonal antibody that binds to the C-C motif chemokine receptor 5 gene (). "In patients infected exclusively with CCR5-topic HIV-1, the therapy showed antiviral activity of ≥1.65 log₁₀ mean viral load reduction as a weekly subcutaneous injection," the researchers reported.

Along with ibalizumab, PRO 140 is one of two monoclonal antibodies for treating HIV that have recently shown promise in previously treated HIV patients.

At a at the meeting, Dhody told 番茄社区app that this new option would be particularly useful for HIV patients with resistance to drugs, because such patients have "limited options to construct a new regimen."

Those enrolled in the study had to be previously treated adults (defined as having a documented resistance to at least one antiretroviral therapy (ART) within three drug classes or within two drug classes and have limited treatment options), with exclusive R5-tropic virus and a viral load of ≥400 copies/mL.

Overall, 52 subjects were randomized to receive either PRO 140 350 mg subcutaneously, along with their existing combination ART for 1 week. Patients were a median 53 years old, and almost three-quarters were men. About 52% were white and 46% were black, with a median 21-year duration of HIV infection. Patients were treated with a mean number of 11 ART drugs prior to enrollment in the study, with resistance to nine.

Because patients on the treatment had a significant reduction in HIV-1 copies/mL (P<0.001 in intent-to-treat population), the primary outcome was met. Overall, 32 patients completed the study, with 17 ongoing and three who discontinued the study early.

There were 32 patients who had at least one adverse event, but none discontinued treatment due to these adverse events. A separate safety study of PRO 140 is ongoing, which examines the treatment as a monotherapy, "where patients stop their current therapy and receive a once-a-week supplemental injection," Dhody said.

In addition, he said, the company has a meeting scheduled with the FDA later this month to discuss the product license application summation, where this research and the safety data will be presented. After that, Dhody said, the plan is to determine the submission strategy.

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