A fixed-dose all-in-one pill combining Tibotec’s experimental non-nucleoside reverse transcriptase inhibitor (NNRTI) rilpivirine (TMC278) with Gilead’s Truvada (tenofovir plus emtricitabine) is expected to achieve “blockbuster sales” in the coming decade—earning up to $2 billion per year in the United States, Japan and five European countries—according to a news release by industry analyst Decision Resources.

Rilpivirine is in Phase III studies. It is currently added as a single agent to regimens containing other drugs, notably Truvada. Tibotec is hoping the Phase III studies prove the new drug is as effective as Sustiva (efavirenz)—but with fewer side effects—in first-time treatment takers.

The fixed-dose combination tablet containing rilpivirine and Truvada is in earlier stages of development.

Atripla, which combines Sustiva and Truvada in one pill, is one of the best-selling HIV drugs, with $1.5 billion in sales in 2008. Sustiva’s patent expires in 2012, at which time it will likely become available as a generic.

“Thought leaders we interviewed believe that if a coformulation of rilpivirine and Truvada shows efficacy that is at least equal to Atripla and maintains a cleaner side-effect profile, the drug will be poised to capture a significant share of early lines of therapy,” said Decision Resources director Danielle Drayton, PhD.

“Assuming that Tibotec and Gilead are successful in developing a fixed-dose coformulation of rilpivirine and Truvada with a more favorable side-effect profile than that of Atripla’s efavirenz component,” Drayton added, “we forecast the fixed-dose agent will become Atripla’s successor and will generate blockbuster sales in 2018.”