Hoping to make its new long-acting injectable a standard treatment option for HIV, GSK’s ViiV Healthcare is touting an important win for the launch.
In a head-to-head study, GSK’s Cabenuva, dosed every two months, matched up against Gilead Sciences’ popular daily oral drug Biktarvy. Specifically, the GSK drug demonstrated antiviral efficacy that was similar to the Gilead drug after one year of treatment in patients who had been virally suppressed on the Gilead drug.
The phase 3b data, from the SOLAR study, add to the body of evidence supporting Cabenuva’s ability to help patients manage their HIV at longer treatment intervals. Results from two earlier phase 3 trials that demonstrated the long-acting, two-drug regimen works as well as several other popular therapies.
“We were so confident in Cabenuva. We’re certain that people, no matter what they were on, actually could derive a benefit from being on Cabenuva,” ViiV’s R&D head Kim Smith, M.D., said in an interview.
In the SOLAR trial, five of 447 patients (about 1%) who switched from Biktarvy to Cabenuva had detectable HIV at or above 50 viral copies per milliliter of blood at 12 months. Among 223 patients who stayed on their original Biktarvy regimen, one (less than 1%) had detectable HIV.
With an adjusted difference of 0.7%, the trial came within a 4% noninferiority threshold for Cabenuva. The data were presented at the 30th Conference on Retroviruses and Opportunistic Infections.
The analysis came after an adjustment in which ViiV removed all patients at one trial site because of major protocol deviations, Smith said. Even when those patients were included, Cabenuva was found to be non-inferior to Biktarvy.
Although the trial hit its goal, critics can point to the two participants (0.4%) who had confirmed virologic failures in the Cabenuva arm—versus none in the Biktarvy arm—as a weak point in Cabenuva’s profile.
Still, Smith argued that in HIV switching studies, the drug that patients switch to suffers from an inherent disadvantage. For the SOLAR study specifically, people in the Biktarvy arm were unlikely to fail because they were already stable on the Gilead drug, Smith noted.
To Smith, the three phase 3 Cabenuva trials “demonstrated unquestionably” the drug's non-inferior efficacy to rival drugs.
Beyond similar efficacy, Cabenuva’s less frequent dosing could be attractive for some patients. Heading into the SOLAR trial, 47% of patients reported challenges with their daily therapy, including being worried about missing a dose and dealing with the repeated reminder of their HIV status.
After the study, 90% of participants who switched to Cabenuva and completed a survey preferred the long-acting therapy versus daily oral pills.
Feedback from doctors and patients in the real world corroborates those findings, ViiV CEO Deborah Waterhouse said during the same interview. Many patients favor Cabenuva because they become less concerned about drug compliance, and they experience an overall improvement in quality of life, she said.
As it stands, around three-quarters of Cabenuva prescriptions are for patients who are coming from a GSK competitor, Waterhouse said. Around 60% are from Gilead, mostly Biktarvy, she said.
Nevertheless, GSK doesn’t expect Cabenuva—or long-acting injectables in general—will completely supplant oral drugs like Biktarvy. In fact, GSK projects 70% of the HIV market will never switch to long-acting therapies because many patients are totally satisfied with their current treatments, Waterhouse said.
More frequent doctors’ visits for the injections and a dislike of needles are two other reasons for people to stick with pills.
Even after Cabenuva’s FDA approval in early 2021, Biktarvy’s dominance hasn’t really been affected. In 2022, as the clear HIV market leader, Biktarvy saw its U.S. sales jump 20.7% to $8.51 billion, bringing its global total to $10.39 billion. By comparison, Cabenuva’s global sales reached $340 million last year.
In its current form, Cabenuva may garner 15% of market share, Waterhouse said. But to attract more uptake, ViiV is working on a self-injectable formulation and has partnered with Halozyme to develop potentially ultralong-acting versions with possible dosing of every six months.
Both of those offerings would be several years off, Smith said.