PhenoSense Entry is a commercially available test for testing resistance to entry inhibitors. The assay assesses resistance to Fuzeon® (enfuvirtide), which interacts with glycoprotein gp41 of the HIV envelope.
Genotyping may be insufficient because data have shown that areas outside of the envelope impact Fuzeon® susceptibility. This may explain why a wide range of fold changes have been observed with similar mutational patterns.
Together with PhenoSenseGT, a combination phenotype and genotype drug resistance test, and PhenoSense® Integrase, PhenoSense Entry® provides the most complete picture of resistance to antiretroviral medications.
Reference: Mink, et al. " Impact of HIV-1 gp41 amino acid substitutions on susceptibility to T-20 (enfuvirtide) in vitro." Abstract 22, presented at HIV Drug Resistance Workshop, Seville, July 2002.