Background: ABT-378/r is a novel HIV protease inhibitor (PI) with mean pre-dose concentrations that exceed its serum adjusted EC₅₀ for wild type HIV by more than 75-fold when dosed at 400/100 mg BID. This increased inhibitory quotient should provide a pharmacologic barrier to the emergence of viral resistance, which is critical given variable patient adherence patterns.

Methods: Two groups of antiretroviral naïve patients received d4T/3TC with a randomly assigned, blinded ABT-378/r dose: 200/100 mg or 400/100 mg BID, n=32(Group I); 400/100 mg or 400/200 mg BID, n=68(Group II). After 48 weeks, patients in both groups began open-label 400/100 mg BID dosing.

Results: Median baseline (BL) VL and CD4 count were 5.0 log₁₀ copies/mL and 421 cells/µL (Group I) and 4.9 log₁₀ copies/mL and 301 cells/µL (Group II). At wk 96, 27/29 patients (93%) on treatment in Group I and 47/49 patients (96%) on treatment who have reached wk.96 in Group II had VL <400 copies/mL. Analyses using an ultrasensitive viral load assay (< 50 copies/mL) are in progress. The most common adverse events were diarrhea, nausea, asthenia, and headache. All doses have been well tolerated to date with only two patients discontinuing for adverse events related to ABT-378/r through 96 weeks.

Conclusion: ABT-378/r exhibits durable antiviral activity through 96 weeks of treatment in treatment-naïve HIV-infected patients.

U. Colorado¹, Northwestern², Duke³, U. N.Carolina⁴, Pacific Oaks Res. ⁵, Cornell⁶, AIDS Res. Consortium of Atlanta⁷, Baylor⁸, Harvard⁹, Rush¹⁰, and Abbott¹¹.

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