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

VIROLOGICAL OUTCOME IN NAÏVE AND SWITCH PATIENTS RECEIVING TDF/DDI AS THEIR 2NRTI BACKBONE

HIV Med 2006; 7(Suppl. 1):12 (abstract no. P6)

Elizabeth Hart, Amar Javaid and Edmund Wilkins
North Manchester General Hospital, Manchester, UK

AIMS: To look at outcomes following the use of didanosine (ddI) and tenofovir (TDF) as a 2NRTI backbone in patients naïve to treatment or switching to this combination with a viral load (VL) <50 copies/ml without previous ARV failure.

METHODS: Data were retrieved from pharmacy lists, databases, and case notes. Virological failure (VF) was defined as two consecutive VLs >400 copies/ml following <50 copies/ml or failure to achieve <50 copies/ml by 3 months (naïve group only). Statistical analysis was by chi-squared and student t-tests.

RESULTS: Thirty-nine patients were identified: 24 naïve (21 NNRTI, 3 PI/r) and 15 switch (11 NNRTI, 4 PI/r). 14/24 (58%) naïve patients failed treatment of whom eight were VF. Those with a baseline VL >10⁵ were more likely to fail treatment (91% versus 31% <10⁵: P<0.005). 7/8 patients who had VF had genotypic resistance testing. All had significant RT mutations (7 NNRTI, 2 K65R). 67% (10) of switch patients maintained a VL <50 copies/ml (median follow-up 23 months) with only three demonstrating VF. Treatment failure occurred earlier in naïve patients than those switching to TDF/ddI (mean 98 day versus 539 days: P<0.005) Of 10 naïve and 10 switch patients achieving/maintaining a VL <50 copies/ml, 13 (65%) had their 2NRTI backbone changed because of concerns over TDF/ddI efficacy. All of these patients remain with a VL <50 copies/ml (median follow-up 6 months). None of the patients on PI/r-TDF/ddI who developed VF had PI mutations.

CONCLUSION: As in other studies, the 2NRTI backbone of TDF/ddI has been shown to produce unacceptably high rates of VF in naïve patients, associated with high baseline VL and NNRTI and K65R resistance. However, patients switching with an undetectable VL and no likely previous ARV failure or drug resistance may remain successfully suppressed for a prolonged period on TDF/ ddI.

2006-03-29
P6

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