Avexa halts HIV drug trials

Melbourne-based biotech Avexa has announced the closure of its lead HIV program for apricitabine after failing to attract a licensing partner for the Phase III drug.

“In the increasingly competitive HIV market, once-daily cross-class fixed-dose combinations (FDCs) will drive future growth, dwarfing the commercial opportunity for single nucleoside reverse transcriptase inhibitors like apricitabine” says Hedwig Kresse, lead healthcare analyst at Datamonitor.

“Atripla and other powerful once-daily cross-class FDCs in late-stage clinical development will drive future market growth, including Gilead's QuadPill (tenofovir/emtricitabine/efavirenz/GS-9350) and Gilead/Tibotec's combination of Truvada and rilpivirine. In the US alone, Datamonitor forecasts sales to peak at USD$2.4 billion for Atripla in 2011, and to grow to USD$1.4 billion and USD$2.2 billion for the QuadPill and for Truvada/rilpivirine, respectively, by 2019” comments Hedwig, based in London.

Avexa, under license from Shire Pharmaceuticals, was investigating apricitabine, a nucleoside reverse transcriptase inhibitor (NRTI), for use in treatment-experienced HIV patients. Despite promising Phase III safety and efficacy results, Avexa has failed to attract a major pharmaceutical licensing partner for apricitabine and has consequently decided to halt further development of the drug.

The shelving of apricitabine does not come as a surprise in the competitive HIV sector, in which market growth is increasingly being driven by fixed-dose combinations (FDCs) which offer improved patient convenience. Apricitabine's biggest competitor in the NRTI class would have been Gilead Sciences' FDC Truvada (tenofovir/emtricitabine). Truvada has demonstrated continued sales growth, reaching sales of $2.2 billion across the seven major markets in 2009, and is predicted to remain the most important backbone in anti-HIV therapy over the coming decade. This leaves little opportunity for single NRTIs such as apricitabine to penetrate the market.

Furthermore, apricitabine's twice-daily administration impedes its potential for combination with other antiretroviral drugs and limits its scope for use in FDCs. Datamonitor sees little commercial potential in novel NRTIs unless they offer significant improvements over the current nucleoside backbones. This is reflected in the fact that there are currently no other NRTIs in late-stage development for HIV.

“While Truvada would have been a significant competitor, cross-class FDCs posed an even greater challenge for apricitabine. The launch of the first once-daily cross-class FDC Atripla (tenofovir/emtricitabine/efavirenz) in 2006 was a major landmark, and has significantly raised the bar for HIV pipeline drugs with regards to efficacy and convenience. Additionally, major patent expiries in the next few years, together with rising pressure to reduce costs, will further increase competition in the already crowded HIV market. Consequently, it will become increasingly difficult for new drugs to offset time and capital invested in their development” concludes Hedwig.