3rd International Workshop on HIV Drug Resistance & Treatment Strategies 23-26 June 1999, San Diego, California, USA

ABT-378/RITONAVIR (ABT-378R) IN PROTEASE INHIBITOR-EXPERIENCED HIV-INFECTED PATIENTS: PRELIMINARY 24 WEEK RESULTS

Antiviral Therapy 1999;4 (Suppl 1):6 (abstract no. 7)

C Benson², S Brun¹, Y Xu¹, K Orth¹, S Deeks³, H Kessler⁴, R Murphy⁵, D Wheeler⁶, C Hicks⁷, J Eron⁸, J Feinberg⁹, R Gulick¹⁰, P Sax¹¹, R Stryker¹², S Riddler¹³, M Thompson¹⁴, M King¹, C Fields¹, A Potthoff¹, B Bernstein¹, A Hsu¹, R Bertz¹, A Molla¹, H Mo¹, D Kempf¹, E Sun¹ and A Japour^1
1Abbott Laboratories, Abbott Park, Illinois; ²University of Colorado, Denver, Colorado; ³UCSF, San Francisco, California; ⁴ Rush University, Chicago, Illinois; ⁵Northwestern University, Chicago, Illinois; ⁶Infectious Disease Physicians, Annandale, Virginia; 7 Duke University, Durham, North Carolina; ⁸University of North Carolina, Chapel Hill, North Carolina; ⁹University of Cincinnati, Cincinnati, Ohio; ¹⁰Cornell Medical College, New York, New York; ¹¹Harvard Medical School, Boston, Cambridge, Massachusetts; ¹²Pacific Oaks Research Beverley Hills, California; ¹³University of Pittsburgh, Pittsburgh, Pennsylvania; and ¹⁴AIDS Research Consortium Of Atlanta, Atlanta, Georgia, USA

BACKGROUND: ABT-378 is a novel HIV protease inhibitor (PI) with excellent in vitro activity. ABT378/r, stavudine and lamivudine suppressed HIV RNA to <400 copies/ml in 93-95% of antiretroviral (ARV)-naïve patients at 24 weeks with no discontinuations for adverse events (AEs) related to study drug.

OBJECTIVES: (i) To examine the antiviral activity of ABT-378/r in patients with viral load (VL) rebound after receiving a triple drug regimen including an initial single PI. (ii) To determine the safety/antiviral activity of a regimen containing ABT-378/r, nevirapine and two NRTIs.

METHODS: HIV-positive patients with VLs of 10³-10⁵ copies/ml while being treated with a PI and two NRTIs were included. Prior therapy with more than one PI or an NNRTI was not permitted. On day 1, patients were randomized to substitute blinded ABT378/r, 400 mg/100 mg twice daily or 400 mg/200 mg twice daily, for their original PI. On day 14, nevirapine was added, and the NRTIs were altered to include one or more new NRTI.

RESULTS: Seventy patients were enrolled. Previous PI included indinavir (44%), nelfinavir (36%), saquinavir (13%), ritonavir (6%) and amprenavir (1%). Median baseline plasma HIV RNA was 4.0 log₁₀ copies/ml. Mean baseline CD4 cell count was 380 cells/mm³. During the initial 2 weeks, 66/70 patients (94%) had _0.5 log₁₀ copies/ml decrease in HIV RNA (n=42) or a viral load value <400 copies/ml (n=24). Response during the first 2 weeks appeared to be independent of the previous PI. 54/64 patients (84%) had a decline in VL to <400 copies/ml at week 24. The regimen was well tolerated with six discontinuations prior to week 24, two of which were attributed to drug.

CONCLUSIONS: ABT-378/r is well tolerated and has antiretroviral activity among patients who experienced virological rebound following treatment with a single PI-based triple regimen.

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