***TASK*** the task is to summarize an input biomedical literature in six sentences 
    ***INPUT*** the input is a biomedical literature 
    ***OUTPUT*** the output is the summary of an input biomedical literature in six sentences 
    ***DOCUMENTATION*** 
    ***EXAMPLES*** 
    Input: OBJECTIVE To examine the antiviral potency and tolerability profile of a single-class four drug ( quadruple ) nucleoside reverse transcriptase inhibitor ( NRTI ) regimen compared with a 2-class st and ard-of-care regimen . METHODOLOGY A three-centre , r and omized , open-label comparative pilot study of zidovudine/lamivudine/efavirenz ( triple ) versus abacavir/lamivudine/zidovudine/tenofovir ( quadruple ) therapy  in HIV-1-infected , treatment-naive individuals . Both regimens were taken without regard to food and consisted of a twice-daily regimen and 3 pills/day . The study power was based on time-weighted average changes in HIV-1 RNA load . RESULTS A total of 114 individuals ( 56 triple , 57 quadruple ) received at least one dose of medication . Patients were well matched at baseline for viral load ( mean 5.26 log10 versus 5.13 log10 , respectively ) and CD4 cell count ( median 193 versus 153 cells/mm3 , respectively ) . The two regimens performed similarly with regards to all endpoints . At week 48 , by intention-to-treat , missing = failure analysis , 68 % of triple- and 67 % of quadruple-drug treated patients had an HIV-1 RNA < 50copies/ml ( P>0.05 ) . On-treatment analysis showed 40/40 ( 100 % ) of triple- and 39/40 ( 97.5 % ) of quadruple-drug treated patients ( P=0.996 ) had responded to < 50copies/ml . No unexpected adverse events were reported . Changes in total cholesterol and triglycerides were modest but significantly favoured the quadruple therapy regimen at multiple time points . CONCLUSION This pilot study suggests a quadruple NRTI-based regimen provides similar antiviral potency , tolerability and administrative characteristics to a 2-class triple therapy regimen . These findings should be confirmed in a more fully powered study . Potent quadruple NRTI-based regimens may have advantages for some individuals with regards to salvageability , tolerability and drug interactions CONTEXT Abacavir , a nucleoside analogue , has demonstrated suppression of human immunodeficiency virus ( HIV ) replication alone and in combination therapy . However , the role of abacavir in a triple nucleoside combination regimen has not been evaluated against a st and ard protease inhibitor-containing regimen for initial antiretroviral treatment . OBJECTIVE To evaluate antiretroviral equivalence and safety of an abacavir-lamivudine-zidovudine regimen compared with an indinavir-lamivudine-zidovudine regimen . DESIGN AND SETTING A multicenter , phase 3 , r and omized , double-blind trial with an enrollment period from August 1997 to June 1998 , with follow-up through 48 weeks at 73 clinical research units in the United States , Canada , Australia , and Europe . PATIENTS Five hundred sixty-two antiretroviral-naive , HIV-infected adults with a plasma HIV RNA level of at least 10 000 copies/mL and a CD4 cell count of at least 100 x 10(6)/L. INTERVENTIONS Patients were stratified by baseline HIV RNA level and r and omly assigned to receive a combination tablet containing 150 mg of lamivudine and 300 mg of zidovudine twice daily plus either 300 mg of abacavir twice daily and indinavir placebo or 800 mg of indinavir every 8 hours daily plus abacavir placebo . After 16 weeks , patients with confirmed HIV RNA levels greater than 400 copies/mL were eligible to continue receiving r and omized treatment or receive open-label therapy . MAIN OUTCOME MEASURE Virologic suppression , defined as HIV RNA concentration of 400 copies/mL or less at week 48 . RESULTS The proportion of patients who met the end point of having an HIV RNA level of 400 copies/mL or less at week 48 was equivalent in the abacavir group ( 51 % [ 133/262 ] ) and in the indinavir group ( 51 % [ 136/265 ] ) with a treatment difference of -0.6 % ( 95 % confidence interval [ CI ] , -9 % to 8 % ) . In patients with baseline HIV RNA levels greater than 100 000 copies/mL , the proportion of patients achieving less than 50 copies/mL was greater in the indinavir group than in the abacavir group with 45 % ( 45/100 ) vs 31 % ( 30/96 ) and a treatment diference of -14 % ( 95 % CI , -27 % to 0 % ) . The 2 treatments were comparable with respect to their effects on CD4 cell count . There was no difference between groups in the frequency of treatment-limiting adverse events or laboratory abnormalities . One death in the abacavir group was attributed to hypersensitivity reaction , which occurred following rechallenge with abacavir , approximately 3 weeks after initiating study treatment . CONCLUSIONS In this study of antiretroviral-naive HIV-infected adults , the triple nucleoside regimen of abacavir-lamivudine-zidovudine was equivalent to the regimen of indinavir-lamivudine-zidovudine in achieving a plasma HIV RNA level of less than 400 copies/mL at 48 weeks BACKGROUND The most effective highly active antiretroviral therapy ( HAART ) to prevent mother-to-child transmission of human immunodeficiency virus type 1 ( HIV-1 ) in pregnancy and its efficacy during breast-feeding are unknown . METHODS We r and omly assigned 560 HIV-1-infected pregnant women ( CD4 + count , > or = 200 cells per cubic millimeter ) to receive coformulated abacavir , zidovudine , and lamivudine ( the nucleoside reverse-transcriptase inhibitor [ NRTI ] group ) or lopinavir-ritonavir plus zidovudine-lamivudine ( the protease-inhibitor group ) from 26 to 34 weeks ' gestation through planned weaning by 6 months post partum . A total of 170 women with CD4 + counts of less than 200 cells per cubic millimeter received nevirapine plus zidovudine-lamivudine ( the observational group ) . Infants received single-dose nevirapine and 4 weeks of zidovudine . RESULTS The rate of virologic suppression to less than 400 copies per milliliter was high and did not differ significantly among the three groups at delivery ( 96 % in the NRTI group , 93 % in the protease-inhibitor group , and 94 % in the observational group ) or throughout the breast-feeding period ( 92 % in the NRTI group , 93 % in the protease-inhibitor group , and 95 % in the observational group ) . By 6 months of age , 8 of 709 live-born infants ( 1.1 % ) were infected ( 95 % confidence interval [ CI ] , 0.5 to 2.2 ) : 6 were infected in utero ( 4 in the NRTI group , 1 in the protease-inhibitor group , and 1 in the observational group ) , and 2 were infected during the breast-feeding period ( in the NRTI group ) . Treatment-limiting adverse events occurred in 2 % of women in the NRTI group , 2 % of women in the protease-inhibitor group , and 11 % of women in the observational group . CONCLUSIONS All regimens of HAART from pregnancy through 6 months post partum result ed in high rates of virologic suppression , with an overall rate of mother-to-child transmission of 1.1 % . ( Clinical Trials.gov number , NCT00270296 . BACKGROUND We investigated virological response and the emergence of resistance in the  Nevirapine or Abacavir ( NORA ) sub study of the Development of Antiretroviral Treatment in Africa ( DART ) trial . METHODS Six hundred symptomatic antiretroviral-naive human immunodeficiency virus (HIV)-infected adults ( CD4 cell count , < 200 cells/mm(3 ) ) from 2 Ug and an centers were r and omized to receive zidovudine-lamivudine plus abacavir or nevirapine .  Virology was performed retrospectively on stored plasma sample s at selected time points . In patients with HIV RNA levels > 1000 copies/mL , the residual activity of therapy was calculated as the reduction in HIV RNA level , compared with baseline . RESULTS Overall , HIV RNA levels were lower in the nevirapine group than in the abacavir group at 24 and 48 weeks ( P < .001 ) , although no differences were observed at weeks 4 and 12 . Virological responses were similar in the 2 treatment groups for baseline HIV RNA level < 100,000 copies/mL. The mean residual activity at week 48 was higher for abacavir in the presence of the typically observed resistance pattern of thymidine analogue mutations ( TAMs ) and M184V ( 1.47 log(10 ) copies/mL ) than for nevirapine with M184V and nonnucleoside reverse-transcriptase inhibitor mutations , whether accompanied by TAMs ( 0.96 log(10 ) copies/mL ) or not ( 1.18 log(10 ) copies/mL ) . CONCLUSIONS There was more extensive genotypic resistance in both treatment groups than is generally seen in re source -rich setting s. However , significant residual activity was observed among patients with virological failure , particularly those receiving zidovudine-lamivudine plus abacavir Objective To compare the safety/tolerability of abacavir and nevirapine in HIV-infected adults starting antiretroviral ( ARV ) therapy in Ug and a. Methods Twenty-four-week r and omized double-blind trial conducted with 600 symptomatic ARV-naive adults with CD4 < 200 cells/mm3 allocated to zidovudine/lamivudine plus 300 mg abacavir ( A ) and nevirapine placebo ( n = 300 ) or 200 mg nevirapine ( N ) and abacavir placebo ( n = 300 ) twice daily . The primary endpoint was any serious adverse event ( SAE ) definitely/probably or uncertain whether related to blinded nevirapine/abacavir . Secondary endpoints were adverse events leading to permanent discontinuation of blinded nevirapine/abacavir , and grade 4 events . Results Seventy-two per cent participants were women ; 19 % had WHO stage 4 disease ; the median age was 37 years ( range 18–66 ) ; the median baseline CD4 count was 99 cells/mm3 ( 1–199 ) . Ninety-five per cent completed 24 weeks : 4 % died and 1 % were lost to follow-up . Thirty-seven SAEs occurred on blinded drug in 36 participants . Twenty events [ 6 ( 2.0 % ) abacavir , 14 ( 4.7 % ) nevirapine participants ] were considered serious adverse reactions definitely/probably/uncertain whether related to blinded abacavir/nevirapine [ HR = 0.42 ( 95 % CI 0.16–1.09 ) P = 0.06 ] . Only 2.0 % of abacavir participants [ six patients ( 0.7–4.3 % ) ] experienced a suspected hypersensitivity reaction ( HSR ) . In total 14 ( 4.7 % ) abacavir and 30 ( 10.0 % ) nevirapine participants discontinued blinded abacavir/nevirapine ( P = 0.02 ) : because of toxicity ( 6A , 15N ; P = 0.07 , all rash/possible HSR and /or hepatotoxicity ) , anti-tuberculosis therapy ( 6A , 13N ) , or for other reasons ( 2A , 2N ) . Conclusions There was a trend towards a lower rate of serious adverse reactions in Ug and an adults with low CD4 starting ARV regimens with abacavir than with nevirapine . This suggests that abacavir could be used more widely in re source -limited setting s without major safety concerns Background Hyperlipidemia secondary to protease inhibitors ( PI ) may abate by switching to anti-HIV medications without lipid effects . Method An open-label , r and omized pilot study compared changes in fasting lipids and HIV-1 RNA in 104 HIV-infected adults with PI-associated hyperlipidemia ( fasting serum total cholesterol > 200 mg/dL ) who were r and omized either to a regimen in which their PI was replaced by abacavir 300 mg twice daily ( n = 52 ) or a regimen in which their PI was continued ( n = 52 ) for 28 weeks . All patients had undetectable viral loads ( HIV-1 RNA < 50 copies/mL ) at baseline and were naïve to abacavir and non-nucleoside reverse transcript 
    Output:
    
Switching improved serum lipids significantly .
Of the studied triple-NRTI combinations only abacavir/lamivudine/zidovudine was sufficiently potent .
Triple-NRTI maintenance after successful induction with two-class cART appeared successful in treatment-naive subjects and remains a useful option in specific circumstances , especially when other drugs are not available or drug interactions are an issue