CROI 2015: Cabotegravir and Rilpivirine Effective for HIV Maintenance Therapy at 96 Weeks

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A combination of 2 once-daily oral antiretrovirals -- the next-generation integrase inhibitor cabotegravir (GSK1265744) and the approved NNRTI rilpivirine -- was as effective as an efavirenz-based regimen when used as maintenance therapy to keep viral load suppressed, according to a poster presented at the recent 2015 Conference on Retroviruses and Opportunistic Infections (CROI) in Seattle.

David Margolis from GlaxoSmithKline and colleagues presented findings from the Phase 2b LATTE (Long-Acting Antiretroviral Treatment Enabling) trial, which was designed to select the best oral dose of cabotegravir and to evaluate cabotegravir plus rilpivirine (Edurant, also in Complera) as a simple 2-drug maintenance regimen for people who had already achieved undetectable HIV using a standard combination antiretroviral regimen. Showing that the 2 drugs are effective when taken as once-daily pills is intended to lay the groundwork for studies of long-acting injectable formulations of both drugs.

LATTE started with a 24-week induction phase comparing 3 oral doses of cabotegravir plus 2 nucleoside/nucleotide reverse transcriptase inhibitors (NRTIs). After 24 weeks, participants with stable viral suppression discontinued the NRTIs and substituted rilpivirine. The 3-drug lead-in for initial viral suppression was done because rilpivirine has been shown not to work as well for people with high baseline viral loads (>100,000 copes/mL) in some prior studies.

This multicenter trial included 243 participants starting their first antiretroviral regimen. Almost all were men, about 60% were white, and the median age was about 33 years. (The low number of women was in part due to a restriction on use of hormonal contraception, since interactions with cabotegravir were not yet known.) The median baseline CD4 T-cell count was about 410 cells/mm3 and 14% had an initial viral load >100,000 copies/mL. About 5% were coinfected with hepatitis C.

Participants in this partially-blinded trial were randomly assigned to start on one of 3 doses of cabotegravir (10, 30, or 60 mg) or 600 mg efavirenz (Sustiva), all once-daily, taken with 2 NRTIs selected by their provider; about 60% used tenofovir/emtricitabine (Truvada) while the rest used abacavir/lamivudine (Epzicom or Kivexa). Cabotegravir recipients with HIV RNA <50 copies/mL at 24 weeks stopped their NRTIs and substituted 25 mg rilpivirine, while those in the efavirenz group stayed on their same regimen. At 96 weeks cabotegravir recipients could continue on the same treatment in an open-label phase while efavirenz recipients finished the study.

The primary endpoint was viral suppression at 48 weeks, which Margolis reported at last year's CROI. At 24 weeks, 87% of participants in the cabotegravir arm (with little difference between doses) and 74% in the efavirenz arm had undetectable viral load. At that point, 160 people taking cabotegravir and 47 taking efavirenz switched to the maintenance phase.

At 48 weeks, 82% of all participants who started on cabotegravir and 71% of participants taking efavirenz (including those who discontinued at week 24) had continued viral suppression -- not a statistically significant difference. The higher rate of treatment failure with efavirenz was driven by more discontinuations due to adverse events, in particular neuropsychiatric side effects.

This year the researchers presented 96-week findings.

Results

These results confirm that cabotegravir plus rilpivirine is an effective maintenance regimen for people who have achieved undetectable viral load on a standard regimen, supporting evaluation of long-acting injectable formulations of these drugs. Other recent research has shown that long-acting injectable cabotegravir remains at therapeutic levels in the blood with either monthly or quarterly dosing.

The long-acting injectable formulations of cabotegravir and rilpivirine are also being studied for pre-exposure prophylaxis, or PrEP. In animal studies monthly cabotegravir injections protected macaque monkeys against infection with an HIV-like virus delivered via either rectal exposure or vaginal exposure. Other recent research has shown that injectable cabotegravir may reach adequate levels in rectal and vaginal tissue to work as PrEP. However, drug level studies suggest that injectable rilpivirine does not last as long and may be more effective at preventing rectal infection than vaginal infection.

3/17/15

Reference

DA Margolis, CC Brinson, GH Smith, et al. Cabotegravir and Rilpivirine as 2-Drug Oral Maintenance Therapy: LATTE W96 Results. 2015 Conference on Retroviruses and Opportunistic Infections. Seattle, February 23-24, 2015. Abstract 554LB.