GSK's ViiV touts 2-month HIV data as sister injection Cabenuva awaits FDA redemption

GlaxoSmithKline GSK House in Brentford, UK
"This two-drug regimen may provide an opportunity for people living with HIV to break the cycle of taking a daily pill," Kimberly Smith, R&D chief of GSK's ViiV Healthcare, said of the cabotegravir-rilpivirine duo. (GlaxoSmithKline)

After the FDA rejected its once-monthly HIV injection Cabenuva in December, GlaxoSmithKline’s keeping the talk going about its long-acting options. Now, it has rolled out detailed data showing a bimonthly sister version works as well.

A combo injection of GSK subsidiary ViiV Healthcare’s cabotegravir and Johnson & Johnson’s rilpivirine—sold in pill form as Edurant—given every two months was “similarly effective” at suppressing existing HIV patients’ viral load as its once-monthly regimen Cabenuva in a phase 3 study, ViiV said Monday.

Nine of the 522 patients (1.7%) on the two-month arm and five of 523 (1.0%) who got the one-month injection had plasma HIV at or above 50 copies per milliliter at week 48, according to data revealed at the Conference on Retroviruses and Opportunistic Infections. With an adjusted difference of 0.8% between the two groups, the outcome is “well within the 4% noninferiority margin,” Kimberly Smith, ViiV’s head of R&D, explained to FiercePharma in an interview.

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An HIV level below 50 c/mL is generally considered the optimal outcome for an HIV treatment. Because patients were already virally suppressed before entering this Atlas-2M study, the primary outcome was set to measure the number of patients who had virologic nonresponse, Smith said.

Currently, mainstay HIV treatment consists of three-drug combos, but ViiV’s trying to cut the number to two. Previously, once-monthly Cabenuva showed it could work as well as daily three-drug regimens after 48 weeks. In the phase 3 Atlas study, 1.6% of Cabenuva patients had HIV copies at or above 50 c/mL, while 1% on existing oral antiretroviral therapy experienced that.

Reducing the number of drugs patients need to take could lessen side effects and drug-drug interactions, but the idea hasn’t exactly been embraced widely. Industry watchers have raised the possibility of increased drug resistance when fewer meds are used. For 2019, combined sales from GSK’s two-drug regimens, Juluca and Dovato, came in at £422 million ($552 million).

RELATED: No holiday gift for GSK: FDA sends long-acting HIV injectable back to work

In the Atlas-2M study, the confirmed virologic failure rate was higher in the two-month arm than in the one-month arm, or eight patients (1.5%) versus two (0.2%), respectively. Resistance-associated viral mutations were found in five of eight instances in the two-month arm.

But Smith noted that five of the eight individuals in that group had preexisting resistance when they entered the study, as archived HIV DNA tests showed, which means the problem isn’t a two-drug versus three-drug question.

Patients who experienced virologic failure with the cabotegravir-rilpivirine regimen and developed resistance can go back to taking pills with ingredients outside the non-nucleoside reverse transcriptase inhibitor class, to which rilpivirine belongs.

“I think the most important thing is that you have a 1% chance that you could end up back on orals, which is the situation you’re in now,” Smith said.

Being able to cut the frequency HIV patients take their meds is an even more important selling point for ViiV’s long-acting regimens. “This two-drug regimen may provide an opportunity for people living with HIV to break the cycle of taking a daily pill and reduce their total treatment dosing days from 365 to six,” Smith said in a statement.

RELATED: GSK's ViiV launches first campaign for new HIV med Dovato with real patient ambassadors

About 98% of trial participants preferred the bimonthly drug over daily oral therapy, according to ViiV. “People describe it as being liberating for them, that it’s life-changing,” Smith said. “When we come back to the risk of virologic failure versus the really transformative impact of not having a take a pill every day for the patients who want to do that, I think the value proposition [of long-acting regimen] is very clear.”

Despite ViiV’s excitement over the long-acting option, its effort to get Cabenuva on the market recently hit a snag. In December, the FDA slapped a complete response letter on the four-week therapy due to chemistry manufacturing and controls issues.

On GSK’s fourth-quarter earnings call in February, David Redfern, GSK’s chief strategy officer and chairman of ViiV, said the company planned to meet with the FDA by March to determine the way forward for Cabenuva. Smith declined to offer more detailed timeline during the interview.

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