About two thirds of treatment-experienced patients with up to 3 darunavir and/or etravirine mutations will respond to those two drugs as the only active antiretrovirals in a salvage regimen, according to analysis of the DUET trials [1]. The same proportion responded if they had up to 40-fold resistance to darunavir but remained susceptible to etravirine. People with more darunavir plus etravirine resistance mutations or a higher fold-change in susceptibility to darunavir and etravirine probably need other active drugs in their salvage regimen to ensure a good response, a team of DUET researchers concluded.
http://www.natap.org/2008/IAS/IAS_14.htm