GS 9137 is an integrase inhibitor under development by Gilead Sciences. Integrase inhibitors block the incorporation of HIV's genetic material into the host cell's DNA, a necessary step for the virus's life-cycle.

Promising results from a trial of GS 9137 were presented in early 2006. Thirty patients were randomly assigned to receive G3 9137 with food for ten days. Six patients each received doses of 200, 400 or 800mg gs 9137 twice daily, 800mg GS 9137 once daily or 50mg GS 9137 boosted with 100mg ritonavir (Norvir) once daily. Adding a low dose of ritonavir increases blood levels of GS 9137 by 20-fold, since it is metabolised through the CYP3A enzyme, which ritonavir inihibits.

The GS 9137 arms of the study showed significantly greater reductions in viral load than a compison group of patients taking placebo. The greatest reduction of 2.03 log₁₀ was seen in the ritonavir-boosted arm. The drug was well tolerated with no discontinuations or serious side-effects (de Jesus 2006).

GS 9137 is currently being tested at three once-daily doses of 20, 50 and 125mg, boosted by 100mg ritonavirin HIV-positive patients. Results are expected in late 2006.

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