Pfizer’s recently-approved HIV drug Celsentri/Selzentry (maraviroc) is to be tested as an oral treatment for rheumatoid arthritis, part of a new effort by the drugmaker to squeeze every last drop of revenue out of its current portfolio of products.

If successful the new use could triple peak sales of the drug, according to analysts reported by Bloomberg. After gaining approval for HIV in both the USA and Europe in the last couple of months, the US drugmaker is looking forward to revenues from maraviroc that could top $500 million at peak, according to Lehman Brothers.

But if Pfizer’s drug makes it through as an arthritis treatment this could lift by $1 billion or more, as maraviroc could provide a new oral treatment for a disease which, in its more severe incarnations, tends to be managed with injections or infusions of drugs such as Wyeth/Amgen’s Enbrel (etanercept) and Johnson & Johnson/Schering-Plough’s Remicade (infliximab).

One possibility is that maraviroc could be used to delay progression of treatment to these biologic drugs. While the latter work by blocking the pro-inflammatory cytokine tumor necrosis factor (TNF) maraviroc is thought to inhibit TNF production in the body.

New uses for existing products

Earlier this year, Pfizer set up a programme to find new uses for its existing products in a bid to boost their revenues as it copes with pressure on some of its biggest-selling drugs, notably cholesterol-lowerer Lipitor (atorvastatin). The launch of generic versions of Merck & Co’s rival product Zocor (simvastatin) which lost patent protection in the USA June last year has led to patients switching to the cheaper products. In the second quarter of 2007, sales of Lipitor fell by a quarter to $2.7 billion in the USA, where patent expiry for the drug is also looming on the horizon (in 2010).

Pfizer is recruiting for a Phase II trial of maraviroc in rheumatoid arthritis patients to see if adding the drug to standard treatment with methotrexate provides an additional clinical benefit, and whether there are any drug-drug interactions.

Maraviroc acts as a CCR5 receptor, which has been implicated in the abnormal inflammatory reactions seen in arthritis, and the 130-patient study will look at arthritis symptoms scores at 12 weeks.

Pfizer set up a dedicated unit to find expanded indications for its current products earlier this year, as part of a major reorganisation of its R&D that also saw it close three facilities and exit a number of therapeutic categories. The company is currently working on 14 potential new indications or enhancements for maraviroc, cancer drug Sutent (sunitinib), central nervous system drug Lyrica (pregabalin), antipsychotic Geodon (ziprasidone), and anti-infectives Eraxis (anidulafungin) and Vfend (voriconazole).