Early virologic nonresponse to tenofovir, abacavir, and lamivudine in HIV-infected antiretroviral-naive subjects.
BACKGROUND
Antiretroviral combinations that reduce the number of pills and dosing frequency have the potential to simplify therapy. We compared 2 regimens dosed as 2 pills once daily.


METHODS
This was a randomized, open-label, multicenter study of tenofovir disoproxil fumarate versus efavirenz, both administered once daily with the abacavir/lamivudine fixed-dose combination in treatment-naive human immunodeficiency virus type 1 (HIV-1)-infected subjects. After reports of early nonresponse, an unplanned interim analysis was performed. Virologic nonresponse was defined as (1) a <2.0-log(10) copies/mL decrease in HIV-1 RNA level by week 8, (2) an HIV-1 RNA rebound of > or =1.0 log(10) copies/mL above the nadir, or (3) for subjects with 2 consecutive HIV-1 RNA measurements <50 copies/mL, a subsequent increase to >400 copies/mL on 2 consecutive occasions.


RESULTS
We randomized 340 subjects. Median baseline HIV-1 RNA level and CD4+ cell count were 4.7 log(10) copies/mL and 251 cells/mm3, respectively; 194 subjects with HIV-1 RNA data from > or =8 weeks were included in the interim analysis. Virologic nonresponse occurred in 50 (49%) of 102 subjects in the tenofovir disoproxil fumarate arm, compared with 5 (5%) of 92 of subjects in the efavirenz arm (P<.001). Within 12 weeks, viral genotypes for nonresponders in the tenofovir disoproxil fumarate arm showed M184V or I/M/V mixtures in 40 (98%) of 41 subjects and K65R and M184V or mixtures in 22 (54%) of 41 subjects. The protocol was immediately amended to modify the tenofovir disoproxil fumarate arm. The efavirenz arm continued unchanged; after 48 weeks, 120 (71%) of 169 subjects achieved HIV-1 RNA levels <50 copies/mL.


CONCLUSIONS
The tenofovir disoproxil fumarate/abacavir/lamivudine regimen resulted in an unexpected and unacceptably high rate of nonresponse and incidence of K65R and M184V/I. This 3-drug regimen should not be used.
Gallant
Joel E
JE
Division of Infectious Diseases, Johns Hopkins University School of Medicine, Baltimore, MD 21287, USA. jgallant@jhmi.edu
Rodriguez
Allan E
AE
Weinberg
Winkler G
WG
Young
Benjamin
B
Berger
Daniel S
DS
Lim
Michael L
ML
Liao
Qiming
Q
Ross
Lisa
L
Johnson
Judy
J
Shaefer
Mark S
MS
D000225:Adenine / Q000031:analogs & derivatives* / Q000627:therapeutic use; D000293:Adolescent; D000328:Adult; D000368:Aged; D019380:Anti-HIV Agents / Q000627:therapeutic use*; D018791:CD4 Lymphocyte Count; D015224:Dideoxynucleosides / Q000627:therapeutic use*; D024882:Drug Resistance, Viral / Q000235:genetics; D004359:Drug Therapy, Combination; D005260:Female; D015658:HIV Infections / Q000188:drug therapy* / Q000821:virology; D015497:HIV-1 / Q000187:drug effects* / Q000235:genetics; D006801:Humans; D019259:Lamivudine / Q000627:therapeutic use*; D008297:Male; D008875:Middle Aged; D009154:Mutation; D063065:Organophosphonates / Q000627:therapeutic use*; D012367:RNA, Viral / Q000097:blood; D018894:Reverse Transcriptase Inhibitors / Q000627:therapeutic use*; D000068698:Tenofovir; D013997:Time Factors; D017211:Treatment Failure; D000099227:Abacavir
D000225:Adenine; D019380:Anti-HIV Agents; D015224:Dideoxynucleosides; D019259:Lamivudine; D063065:Organophosphonates; D012367:RNA, Viral; D018894:Reverse Transcriptase Inhibitors; D000068698:Tenofovir; D000099227:Abacavir