A phase III study has shown that dolutegravir, an integrase inhibitor in development at ViiV Healthcare and Shionogi, was more effective than a widely-used triple-agent therapy in suppressing HIV infection.
The SINGLE study compared dolutegravir plus ViiV's Kivexa/Epzicom (abacavir/lamivudine) with Gilead Sciences/Bristol-Myers Squibb's big-selling Atripla (efavirenz/emtricitabine/tenofovir disoproxil fumarate), a fixed-dose triple therapy for HIV which achieved nearly $900m in sales in the first quarter of 2012.
ViiV, an HIV-focused joint venture set up by GlaxoSmithKline and Pfizer in 2009, said that 88 per cent of treatment-naïve patients treated with once-daily dolutegravir treatment saw their HIV levels suppressed to less than 50 copies per ml of blood plasma in the trial.
For comparison, 81 per cent of Atripla-treated patients achieved that objective, which was a statistically significant difference and a great achievement considering Atripla is the top-selling HIV medicine worldwide.
One of the main drivers for this difference in efficacy was that significantly fewer patients dropped out of therapy with the ViiV-Shionogi drug regimen, suggesting a more tolerable safety profile. All told, 10 per cent of patients on Atripla discontinued treatment with the drug, compared to two per cent of the dolutegravir group.
An earlier phase III study - called SPRING-2 - had shown that dolutegravir was at least as effective as rival HIV integrase inhibitor Merck & Co's Isentress (raltegravir), which has already achieved blockbuster status in the market with sales of $1.36bn last year.
Dolutegravir is given once-daily while Isentress requires twice-daily dosing, and this may confer a commercial advantage in the marketplace. Integrase inhibitors are a relatively new class of HIV drugs designed to block the virus's entry into cells.
ViiV and Shionogi said the dolutegravir programme is now on track to begin marketing applications by the end of the year. Dr Tsutae "Den" Nagata, Shionogi's chief medical officer, said the data suggest the drug will be "an important additional first-line option in the future".
Analysts have responded favourably to the data, with a number of sales estimates in the multibillion-dollar range. JPMorgan Chase & Co is now expecting dolutegravir will be a $5bn product at its peak.
Meanwhile, two additional phase III trials in later-stage HIV patients are also expected by the end of 2012.