HIV researchers have spent years looking into the protein shell—or capsid—that protects the virus’ genetic material. Now, Gilead Sciences is posting the first clinical evidence that a drug targeting this shell can tamp down viral load and become part of the arsenal to treat people with HIV.
The treatment, GS-6207, is an antiretroviral drug injected just below the skin. It works differently than other antiretrovirals by blocking the activity of the capsid. Gilead reckons this approach could disrupt multiple stages of the life cycle of HIV and potentially stop the virus from becoming infectious and invading healthy cells.
Gilead presented data from the first 24 patients in its phase 1b study Monday at the International AIDS Society Conference on HIV Science in Mexico City. The patients were divided into four groups of six: One group received placebo while the other three received a single dose of GS-6207 ranging from 50 mg to 450 mg, according to a statement.
Ten days after injection, the researchers saw levels of HIV-1 RNA drop to levels that were “significantly lower compared to placebo.” There were no serious side effects, though 15 of the 24 patients had reactions where they were injected, which can include redness, bruising, swelling and bleeding.
“This study provides the first clinical evidence that HIV capsid inhibition can lead to a significant decline in viral load and supports further evaluation of GS-6207 as a component of an effective antiretroviral regimen. In addition, a long-acting regimen can help some people living with HIV by reducing the burden of daily pill taking,” said lead author Eric Daar, M.D., chief of the Division of HIV Medicine at Harbor-UCLA Medical Center, in the statement. “These early trial results support advancing GS-6207 into the next phase of clinical development to understand its role as part of long-acting HIV therapy.”
“GS-6207's multi-stage mechanism of action profile is distinguishable from currently approved classes of antiretroviral agents and may provide a new avenue for the development of long-acting treatment regimens for people living with HIV." said Diana Brainard, M.D., senior vice president of HIV and emerging viruses at Gilead
One of the reasons HIV infection is hard to treat is that it is a moving target—the virus mutates to evade broadly neutralizing antibodies. And it keeps mutating over time, which means it can develop resistance to the drugs used to treat HIV. The capsid is an attractive target because the RNA that encodes it is fairly stable, so disrupting the shell could attack HIV without running the risk that it will mutate and quickly become resistant to the treatment.
That said, Gilead also reported preclinical data showing HIV-infected cells that became resistant to GS-6207 did not become resistant to other types of drugs used to treat HIV. The in vitro study looked at four HIV capsid mutations, finding that cells containing one or more of these mutations showed susceptibility to GS-6207 but did not become less vulnerable to other classes of antiretroviral drugs.