Pfizer and Monogram Biosciences have entered into a non-exclusive collaboration deal to make Monogram's HIV co-receptor tropism assay available around the world, which they say will physicians to determine the most appropriate therapeutic regimen for a patient.

The product is designed to predict the developmental pathway that an HIV infection in an individual is likely to take, in terms of the protein receptor type that the virus uses to enter the CD4 cells.

80%-85% of newly diagnosed HIV infections, which have yet to receive therapy, are ‘CCR5-tropic’, that is to say they access CD4 cells via interaction with the cell's CCR5 co-receptor. This figure drops to 50%-60% in patients who have received antiretroviral therapy.

Currently, Pfizer which is assessing its developmental CCR5 receptor antagonist maraviroc in Phase III trials, is using Monogram's assay to select patients suitable for enrollment in its clinical programme.

Meantime, Monogram said that Pfizer will invest $25 million in its business through a 3% senior secured convertible note, which is payable in 2010.

Alfred Merriweather, Monogram's chief financial officer, said that the investment would allow the firm to address business and financial opportunities, while providing a firm basis for its continued growth.