Simon Collins, HIV i-Base

Taylor and colleagues from Birmingham Heartlands Hospital presented results from a pilot study that switched 20 patients to four weeks lopinavir/r monotherapy on day 0 of a planned treatment interruption. [1]

This protective strategy was designed to reduce the risk of resistance while drug levels dropped, as many regimens combine individual drugs with different plasma and intracellular half-lives, and is complicated in the case of NNRTIs by genetic polymorphisms related to higher exposure and slower clearance. This strategy was previously discussed in a paper in AIDS as probably the safest way to stop treatment. [2]

Twelve of the regimens in this study were judged likely to risk functional monotherapy: 8 for NNRTIs and 4 for tenofovir or FTC.

Viral suppression was maintained in most patients, thoughout the period of monotherapy (14/17 with results), and three patients with detectable viral load at baseline experienced significant viral declines on lopinavir/r.

Lopinavir levels remained above the minimum target of 1000ng/mL, except in two patients with suspected non-adherence and viral load rebounded by week 8 in all 12 patients who discontinued lopinavir/r at week 4.

The importance of this approach was highlighed by 6/12 patients on ‘unbalanced’ regimens having residual drug concentrations of their initial ARVs more than one week after stopping those combinations.

References

1. Taylor S et al. Kaletra single agent therapy as a universal ART stopping strategy: the STOP 2 study. 10th International Workshop on Clinical Pharmacology of HIV Therapy, 15-17 April 2009, Amsterdam. Poster abstract P-17.
2. Taylor S, Boffito M, Khoo S, Smit E, Back D. Stopping antiretroviral therapy. AIDS 2007; 21:1673-1682. (20 August 2007). doi: 10.1097/QAD.0b013e3281c61394.
http://journals.lww.com/aidsonline/Fulltext/2007/08200/Stopping_antiretroviral_therapy.1.aspx