Higher risk of resistance using lopinavir/r monotherapy
Simon Collins, HIV i-Base
In the last presentation at the workshop, Constance Delaugerre presented an analysis of resistance results from the MONARK trial (Kaltera monotherapy).
In the study, 136 treatment naive patients were randomised to either lopinavir/r monotherapy (n=83) or lopinavir/r + AZT/3TC (n-53). Baseline genotypes were available for 131 patients, 36% of which were non-B (CRF02 was most common).
As previously reported, low level viremia occured significantly more frequently in patients on lopinavir/r monotherapy arm. This was to a level that required genotyping in 32/83 and 7/53 of the monotherapy and triple therapy arms respectively.
18/32 monotherapy sequences showed protease changes compared to baseline, including 5/18 with major PI-associated mutations: 46I+63P at week 40, 76V at week 44. 13V+46I+76V at week 62, 10F+82A at week 76, and 76V at week 90.
These changes were detected at low levels of viremia, with latest median viral load (within 4 weeks of the test) of 2.9 logs (2.8-3.1). There was no relationship between baseline viral load and risk of viral rebound or of particular mutations. However, all patients who developed 76V had CRF02 virus.
Mean fold change in sensitivity to lopinavir in 4/5 samples available for phenotyping showed mean increase in IC50 of 1.64-fold (1.13 2.69).
4/7 patients in the triple therapy arm showed changes in protease but none of these included major PI mutations.
All patients who developed major PI mutations added AZT+3TC and resuppressed virus. It will be important to know whether these patients maintain suppression in the long-term.
Delaugerre c, Flandre P, Chaix MI et al. Protease gene mutations in a trials comparing first-line lopinavir/ritonavir monotherapy to lopinavir/ritonavir + zidovudine/lamivudine (MONARK Trial). XVI International HIV Drug Resistance Workshop, 12-16 June 2007, Barbados. Abstract 75. Published as part of Antiviral Therapy (Volume 12 Issue 5). Antiviral Therapy. 2007;12:S65. Antiviral Therapy. 2007;12:S84.