Preliminary testing of two long-acting injectable drugs indicates it might be possible to keep HIV at bay indefinitely with injections every month or two.
Johnson & Johnson and partner ViiV Healthcare, which specializes in HIV drugs, on Tuesday announced results from the first 32 weeks of the planned 96-week study, which combines one drug from each company.
Significant additional testing is needed, but the combination treatment would be a first if approved and could eventually be a huge advance over a disease once almost universally fatal.
The 309 patients tested first all had prior treatment with daily pills that reduced the HIV virus to undetectable levels in their blood. About 95 percent of those who then got the experimental injections had the bloodborne virus kept in check over the 32 weeks, versus 91 percent in a comparison group taking three pills each day. The two groups continue to receive medication and periodic testing of their blood.
Dr. Daniel Kuritzkes, an AIDS expert and professor of medicine at Harvard Medical School, said the companies' reported results "provide an extremely important proof of concept that this approach is feasible."
Kuritzkes, who serves as a consultant to ViiV but is not involved in this research, stressed that the injections must undergo additional testing, in many more patients and for much longer. He said other drug companies are working on similar approaches but none is as advanced in testing.
Only a small fraction of experimental drugs prove to be effective and safe enough to eventually win approval by government regulators.
However, Kuritzkes noted one of the drugs in the combination, rilpivirine, is on the market in pill form, approved for patients who haven't previously taken HIV drugs and who don't have a very high level of HIV in their blood. Johnson & Johnson's Janssen unit sells it as Edurant. The other component, ViiV Healthcare's experimental drug cabotegravir, is similar to an HIV drug already approved, dolutegravir, sold under the brand name Tivicay.
HIV patients typically take a combination of three medicines every day, often in combination pills. That can keep them relatively healthy for many years, and some HIV patients infected long ago are now senior citizens.
However, not adhering to that strict schedule can result in the HIV virus coming back and growing resistant to the treatment, as often happens with patients struggling with other problems in their lives, Kuritzkes said.
"Having longer-acting drugs ... goes a long way in relieving a burden on patients," he said, adding that's also important because those who keep HIV at bay aren't likely to infect sexual partners.
The new report is based on a mid-stage study, usually the next-to-last round before seeking approval.
The 309 study participants all received three pills until the HIV virus was undetectable in their blood: cabotegravir and two drugs from the widely used class called NRTIs, or nucleoside reverse transcriptase inhibitors. NRTIs prevent HIV's genetic material from being incorporated into the patient's cells and those cells then producing more virus.
The participants then were divided into three groups and received injections of rilpivirine and cabotegravir every four weeks or every eight weeks, or they continued taking the three pills.
Among those getting the "maintenance therapy" injections every eight weeks, the virus remained suppressed in 95 percent. That happened with 94 percent getting injections every four weeks and 91 percent staying on the pills. The treatment failed and HIV bounced back in one patient each in the pill and eight-week injection groups.
The main side effect, significant pain at the injection sites due to the large volume of fluid being injected, was reported by 93 percent getting the shots. Two patients dropped out of the study due to that pain.
Cabotegravir, or Tivicay, is an INSTI, or integrase strand transfer inhibitor. It blocks integrase, an enzyme the HIV virus needs to make copies of itself. Rilpivirine is an NNRTI, or non-nucleoside reverse transcriptase inhibitor. It blocks an HIV enzyme called reverse transcriptase, which prevents HIV from multiplying and can reduce the level of HIV in the body.
Since the AIDS epidemic began in the early 1980s, almost 75 million people around the world have been infected with the HIV virus, which causes the deadly immune disorder. An estimated 35 million are still living with HIV, and about 2.5 million more people are infected each year, according to the World Health Organization.
ViiV is a joint venture of GlaxoSmithKline PLC, Pfizer Inc. and Shionogi Ltd.
Follow Linda A. Johnson @LindaJ_onPharma