12th Annual Conference of the British HIV Association 29 March–1 April 2006, Brighton, UK

THE INHIBITORY QUOTIENT (IQ) OF RITONAVIR-BOOSTED PROTEASE INHIBITORS (PI/R): CORRELATION WITH VIROLOGICAL RESPONSE.

HIV Med 2006 Mar 29-Apr 1 (Suppl 1);12:12 (abstract no. P5)

Laura Waters¹, Alan Winston¹, Nimesh Patel¹, David Back², Saye Khoo², Steve Bulbeck¹, Anton Pozniak¹, Mark Nelson¹, Graeme Moyle¹, Brian Gazzard¹ and Marta Boffito^1
1St Stephens Centre, Chelsea and Westminster Hospital, London, ²Department of Pharmacology, University of Liverpool, Liverpool, UK

AIMS: IQ is a measure of plasma drug exposure corrected for resistance; we compared methods based on genotype (GIQ), virtual phenotype (VIQ) and population-adjusted or normalised IQ (NIQ) in terms of predicting virological response in experienced HIV-positive subjects.

METHODS: In a prospective study of therapeutic drug monitoring (TDM), individuals commencing a PI/r-based antiretroviral (ARV) regimen underwent measurement of trough PI concentration (C_trough). Week 4 C_trough was adjusted for (a) total/significant genotypic PI mutations (sigGIQ/totGIQ), (b) virtual phenotypic fold-change (VIQ), and (c) VIQ corrected for 80% clinical cut-off and population C_trough (NIQ). Associations between IQ and time-weighted change in HIV-RNA up to 48 weeks were assessed with linear regression modelling and z-transformation used to compare different PIs.

RESULTS: 53 treatment-experienced patients commencing a new PI/r-based regimen between June 2004 and August 2005 were included. Baseline viral load (VL) was undetectable (<50 copies/ml) in 18 (34%) subjects and a mean of 3.68 log₁₀ copies/ml in the remainder. Median time-weighted change in log HIV-RNA was 1.82 log copies/ml. In a multivariate analysis only baseline HIV-RNA and NIQ were significantly associated with time-weighted change in HIV-RNA (P<0.001 and 0.021, respectively); C_trough, FC, sigGIQ, totGIQ and VIQ showed no significant association.

CONCLUSION: NIQ may be a useful tool in predicting response to boosted-PI based regimens in ARV-exposed subjects.

2006-03-29
P5

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