There are currently 27 drugs in development to combat HIV, providing additional weapons in the fight against the disease. However, warns Datamonitor, the majority are in Phase II or earlier, thus it is unlikely “any major treatment advances will be made before 2009/10.”

The HIV market experienced relatively strong annual growth of almost 12% between 1999 and 2003, and the current HIV pipeline is predicted to generate an additional $4.6 billion in sales by 2015, says Datamonitor. However, this looks set to change as price constraints, the onset of patent expiries, generic competition and a reduced increase in patient numbers limit growth to 5.5% between 2004 and 2015. Despite this, says Datamonitor infectious diseases analyst Faisal Latif, by 2015 pipeline products will account for 38% of total antiretroviral sales.

The most advanced pipeline products are Boehringer Ingelheim’s tipranavir and Pfizer’s capravirine, which are due to be launched in 2005 and 2007 respectively. Although both drugs were initially viewed optimistically, more recent data have tempered enthusiasm, with adverse pharmacokinetic data, inconsistent activity and a lack of clarity as to their positioning in the market. Thus both tipranavir and capravirine are being viewed as ‘holding drugs,’ notes Latif, adding: “In essence; they satisfy an immediate unmet need, but will be superseded and replaced as new more efficacious products are subsequently launched. For example, it is widely believed that the launch of Tibotec’s PI TMC-114 will lead to switching away from tipranavir, positioning TMC-114 as the drug of choice for PI-experienced, resistant patients.”

The greatest optimism has been created for drugs in the entry inhibitor class, to which Roche’s Fuzeon (enfuvirtide) belongs, however their potential impact remains unclear. Datamonitor has suggested two scenarios: that the so-called CCR5 inhibitors will be used in first-line therapy, creating a treatment-paradigm shift; and secondly that EI drugs will be used in late-stage and salvage therapy, possibly in combination with Fuzeon, resulting in class sales of just under $1 billion by 2015, Latif says.“Pipeline EIs include Schering-Plough’s SCH-417690, Pfizer’s UK-427,857 and GlaxoSmithKline’s GW873140, which comprise the CCR5 inhibitor class, as well as Panacos’s PA-457 and Progenic’s PRO-140 and PRO-542.”