Table 1.

PhenoSense Susceptibility Results for Each of the Six Antiretroviral Drug Classes Prior to the Start of Ibalizumab and Following Virologic Rebound after a Missed Ibalizumab Infusion

Drug Class	June 2009 (fold- resistant)	June 2009 Interpretation	March 2010 (fold- resistant)	March 2010 Interpretation	Clinical Cutoffs
Nucleoside RT inhibitors (NRTIs)
Abacavir	20	R	12	R	4.5-6.5
Didanosine	4.9	R	4.1	R	1.3-2.2
Emtricitabine	>300	R	8.7	R	>3.5
Lamivudine	>300	R	6.3	R	>3.5
Stavudine	>300	R	13	R	>1.7
Zidovudine	>300	R	11	R	>1.9
Tenofovir	8.4	R	444	R	1.4-4.0
Non-nucleoside RT inhibitors (NNRTIs)
Efavirenz	5.9	R	>300	R	>3.0
Etravirine	0.7	S	5.7	I	2.9-10
Nevirapine	72	R	>300	R	>4.5
Protease inhibitors (PIs)
Atazanavir	107	R	58	R	>5.2
Darunavir	151	R	155	R	10-90
Fosamprenavir	143	R	>300	R	4-11
Indinavir	28	R	26	R	>10
Lopinavir	65	R	126	R	9-55
Nelfinavir	45	R	43	R	>3.0
Saquinavir	35	R	31	R	2.3-12
Tipranavir	12	R	9.8	R	2.0-8.0
Integrase inhibitors
Raltegravir	>200	R	9.9	R	1.5
Fusion inhibitors
Enfuvirtide	2.1	S	40	R	>9.0
CCR5 inhibitors
Maraviroc	R5+/X4+	R	R5+/X4+	R	R5+/X4+

Genotypic susceptibility data for the NRTIs, NNRTIs, and PIs can be found in Table 1 of the Supplementary Materials. Integrase inhibitor susceptibility testing in 2008 and 2009 demonstrated four Raltegravir-resistance mutations: L74M, T97A, Y143C, and S230R. Phenotypic susceptibility testing in 2007 revealed 152-fold decreased Enfuvirtide susceptibility. The presence of CXCR4 tropic virus (X4+) indicates intrinsic nonresponsiveness to Maraviroc and other CCR5 inhibitors