New Drug of Last Resort Tackles Resistant HIV

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HIV, the virus that causes AIDS, is typically a manageable infection, but medications that keep the virus at bay don’t work for everyone. Now, researchers have developed a new medication to help them.

The U.S. Food and Drug Administration approved the drug — ibalizumab (Trogarzo) — in March. Phase 3 trial results were published in the Aug. 16 issue of the New England Journal of Medicine.

“For those who have exhausted their current [drug] regimen, we now have another hope,” the study’s senior author, Dr. Stanley Lewis, said of the new drug. He’s chief medical officer for TaiMed Biologics, maker of the drug and sponsor of the trial.

“HIV is probably the most dynamic pathogen in medicine. It’s been a challenge to stay one step ahead of it,” Lewis said.

The new drug is called a monoclonal antibody. It works by binding to receptors on CD4 cells. (CD4 is a type of immune system cell also known as T cells.) This blocks the virus from entering CD4 cells.

In an editorial accompanying the study, the FDA’s Dr. Virginia Sheikh and colleagues wrote that “patients with multidrug-resistant HIV infection are at risk for illness and death because of their limited remaining treatment options.”

Because of these serious risks, the FDA allowed a streamlined clinical trial of ibalizumab.

The study included 40 adults with multidrug-resistant HIV-1 infection. More than half had been treated unsuccessfully with a median of 10 drugs.

The researchers observed for a week how well the study participants’ current treatment regimens were working. Then they added ibalizumab. Eighty-three percent saw a reduction in the amount of HIV in their body (called “viral load”), the findings showed.

After the first week of ibalizumab, participants were given the drug once every two weeks for 25 weeks. Their drug regimens also were optimized to ensure they were getting at least one drug that the virus was sensitive to, according to Lewis.

At week 25, the drug successfully reduced patients’ overall viral load. In fact, almost half had viral loads that were considered undetectable.

However, the drug did have side effects — some serious.

More than 5 percent of patients reported having diarrhea, dizziness, nausea and rash, Sheikh said.

One patient had “immune reconstitution inflammatory syndrome,” or IRIS, which Lewis described as an immune system overreaction. HIV hampers the body’s ability to respond to infections. With IRIS, that immune system response is out of balance and causes inflammation, he said. This side effect is temporary.

Four patients in the trial died; their deaths were believed to be related to the underlying HIV infection.

Sheikh said the FDA will continue to monitor side effects, and update safety information on drug labels as needed.

Both Lewis and Sheikh said it’s possible that HIV will eventually develop resistance to ibalizumab, too.

Lewis said he doesn’t know what the drug costs, but said it was expected to be in line with other monoclonal antibodies. He added that it would likely be cheaper than some other drugs in that class.

More information

Learn more about the drug resistance that develops with HIV from the U.S. Department of Health and Human Services.

Source: HealthDay

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