Drug giants Pfizer and Merck & Co have presented positive late-stage data for their respective experimental HIV treatments at the 14th annual Conference on Retroviruses and Opportunistic Infections in Los Angeles.

Firstly, Pfizer said that maraviroc, the first CCR5 inhibitor, significantly outperformed placebo in patients who were failing anti-retroviral therapy, after unveiling 24-week results of two Phase III trials of maraviroc involving patients with CCR5-tropic HIV who had stopped responding to other treatments.

The first trial of 601 patients showed 60.4% of those who took maraviroc twice a day along with a background regimen of current HIV drugs achieved a level of less than 400 HIV copies per millilitre of blood, compared to 54.7% on a once-daily dose and 31.4% on just background therapy. The second study, involving 475 patients, found that 61.3% of twice-daily maraviroc patients achieved target HIV levels, compared with 55.5% on once-daily therapy and 23.1% treated only with other drugs.

Pfizer recently said that its marketing authorisations for maraviroc are receiving an accelerated review from regulators both in the USA and Europe and the company hopes to hear from the US Food and Drug Administration on or before April 24.

Also at the conference, Merck presented results from two late-stage trials of its integrase inhibitor Isentress (raltegravir), which showed that 61%-62% of patients with drug-resistant HIV who received two daily doses of the compound, in combination with other drugs, saw viral loads drop to undetectable levels, compared to between 33%-36% of patients who only received standard therapy. The company anticipates filing its HIV drug with US regulators by the end of the second quarter of 2007, for patients who are resistant to older HIV treatments.

If the drugs get approved, Deutsche Bank's Barbara Ryan estimates that maraviroc may see sales of $145 million in 2008, and Isentress should have revenues of $50 million.

- Meantime, Pfizer has announced plans to reduce staff by up to 20% over the next three years at its pharmaceuticals division in Japan, as part of its strategy of cutting some 10,000 jobs worldwide.

The president of Pfizer's Japan unit, Hiromitsu Iwasaki, said that as many as 800 jobs could go, including sales positions. "We have no other options to meet the global cost-cut target," he added.