Zidovudine therapy and HIV type 1 mutations in children with symptomatic HIV type 1 infection: effect of switching to didanosine or zidovudine plus didanosine therapy. Italian Multicenter Study Group on HIV Mutations in Children

Baseline resistance to nucleoside reverse transcriptase inhibitors fails to predict virologic response to combination therapy in children (PACTG 338)

BACKGROUND

The association between baseline drug resistance mutations and subsequent increase in viral failure has not been established for HIV-infected children. We evaluated drug resistance mutations at 39 codon sites (21 protease inhibitor (PI) resistant codons and 18 nucleoside reverse transcriptase inhibitor (NRTI) resistant codons) for 92 clinically stable NRTI-experienced, PI-naive HIV-infected children 2 to 17 years of age who were initiating new therapy with ritonavir plus zidovudine (ZDV) and lamivudine or plus stavudine. The association between baseline drug resistance mutations and subsequent viral failure after 12 and 24 weeks of highly active antiretroviral therapy (HAART) was studied.

RESULTS

There were few primary PI associated mutations in this PI-naïve population, but 84% had NRTI mutations--codons 215 (66%), 41 (42%), 67 (37%), 210 (33%) and 70 (32%). None of the specific baseline drug resistance mutations were associated with a higher rate of virologic failure after 12 or 24 weeks of HAART. Median week 12 viral load decreased as the total number of NRTI mutations at baseline increased (P = 0.006). Specifically, a higher level of baseline ZDV resistance mutation was associated with a decrease in viral failure after 12 weeks on a ZDV-containing HAART regimen (P = 0.017).

CONCLUSION

No increase was seen in the rate of viral failure after HAART associated with the presence of resistance mutations at baseline. This paradoxical result may be due to adherence, replicative capacity, or ZDV hypersusceptibility to the new regimen.

Update on didanosine

Didanosine (ddl) has been a cornerstone of HIV management since it was made available in October 1991. Didanosine was originally introduced as an alternative to zidovudine (ZDV) for patients who were intolerant of ZDV or experienced disease progression during ZDV monotherapy. Didanosine is now used extensively as an integral component of multidrug combination regimens in both adults and children with HIV infection, and is now available for once-daily administration in the United States, Canada, and Europe. The recently approved Videx EC is an enteric-coated didanosine capsule dosed as one capsule, once daily. This paper provides an update of recently published studies on the use of ddl in combination anti-HIV therapy. In particular, these studies examine the rationale for the use of ddl as first-line anti-HIV therapy, and describe newer findings concerning its long-term efficacy, side effects, compliance, resistance, and once-daily use. The increased survival of HIV-infected patients is largely attributed to the introduction of the triple combination drug therapy but is probably also due to the long-term clinical efficacy of ddl.

Antiretroviral drug resistance among HIV-1 infected children failing treatment

High levels of HIV-1 replication occur following perinatal infection and antiretroviral drugs may not fully suppress viral load during the early years of childhood. Adherence to treatment may also be difficult among children. These two factors will contribute to development of drug resistance but limited paediatric data are available. This study has, therefore, evaluated the prevalence of drug resistance among children and assessed the contribution of adherence to failing therapy. Samples from 26 children who had experienced virological failure to antiretroviral therapy were tested for drug resistance using the Visible Genetics TRUGENE trade mark HIV-1 genotyping assay. HIV-1 subtype was determined using a peptide-based EIA and drug adherence determined by physician assessment. Twenty-four children were black African, 23 of whom were infected with a non-B subtype. HIV RNA sequence data was obtained for 21 of the 26 children; at treatment failure resistance mutations were detected in the protease gene of 7 (33%) and the reverse transcriptase gene of 19 (90%). A lower proportion of children had evidence of drug resistance at nadir and no resistance mutations were detected prior to treatment. Genotypic resistance was common in those treated with lamivudine (10/11, 91%), nevirapine (6/8, 75%), and zidovudine (7/11, 64%). The prevalence of mutations was lower among those receiving other nucleoside reverse transcriptase inhibitors and protease inhibitors. In 50% of children, drug adherence was >90%. Antiretroviral drug resistance was common among this group of children failing therapy, the majority of whom were infected with non-B subtypes of HIV-1. As adherence to treatment was low in 50%, this was likely to be an important contributory factor.

PENTA guidelines for the use of antiretroviral therapy in paediatric HIV infection. Pediatric European Network for Treatment of AIDS

OBJECTIVE

To produce European Guidelines for the use of antiretroviral therapy (ART) in HIV-infected children.

DESIGN

Systematic literature review using Medline, the major antiretroviral conference reports, and IDSA recommendations on guideline production.

SETTING

Pediatric European Network for Treatment of AIDS (PENTA) Steering Committee.

OUTCOME MEASURE

Guidelines have been produced for the use of antiretroviral therapy in HIV-infected children in Europe. Recommendations on when to start ART and which ART to start, with dosages and a summary of the relevant literature, have been produced.

CONCLUSIONS

These guidelines are aimed at assisting paediatricians in Europe with ART prescribing, and provide a more cautious approach to starting therapy than current paediatric USA guidelines.

Didanosine: an updated review of its use in HIV infection

Didanosine, like zidovudine, stavudine and lamivudine, is a nucleoside analogue reverse transcriptase inhibitor (NRTI). In the target cell for HIV, didanosine is converted to its active moiety, dideoxyadenosine-5'-triphosphate (ddATP), which inhibits HIV reverse transcriptase and terminates viral DNA growth. It is now well established that didanosine therapy produces beneficial effects on virological and immunological markers of HIV disease and improves clinical outcome in adults or children with HIV infection. In numerous clinical trials, pronounced and sustained decreases in plasma HIV RNA levels and increases in CD4+ cell counts occurred in previously untreated or antiretroviral therapy-experienced patients treated with didanosine in combination with at least 1 other antiretroviral drug; zidovudine, stavudine, lamivudine, nevirapine, nelfinavir and hydroxyurea (hydroxycarbamide) are among the drugs that have been given in combination with didanosine. Of note, HIV RNA levels decreased to below the limits of detection in some patients receiving triple or dual therapy with didanosine-containing regimens. In double-blind, placebo-controlled trials, triple therapy with didanosine, zidovudine and nevirapine was significantly more effective than dual therapy with various combinations of these agents in improving surrogate disease markers in treatment-naive patients and in delaying disease progression or death in treatment-experienced patients with advanced disease. Improvements in virological and immunological markers were greater with didanosine-containing triple regimens than with dual therapy or monotherapy in comparative trials. Triple therapy with didanosine, stavudine and indinavir showed efficacy similar to that of various other triple therapy regimens in nonblind comparative trials. Comparator regimens included combinations of stavudine, lamivudine plus indinavir, zidovudine, lamivudine plus indinavir and didanosine, stavudine and nevirapine. Combination therapy with didanosine plus hydroxyurea as dual therapy or with a third agent produced marked and sustained decreases in HIV RNA levels in the plasma and in lymph nodes. Combination therapy with didanosine and zidovudine delays disease progression and prolongs survival in patients with intermediate or advanced HIV infection. In large, randomised, double-blind, clinical trials, dual therapy with didanosine plus zidovudine was significantly more effective than zidovudine monotherapy in preventing disease progression and prolonging survival in previously untreated or antiretroviral therapy-experienced patients with intermediate or advanced HIV infection. Pancreatitis and peripheral neuropathy are serious adverse effects of didanosine. These effects are dose-related and usually reversible after discontinuation of treatment. Nausea, vomiting, diarrhoea and/or abdominal pain have been reported in patients receiving treatment with the drug.

CONCLUSIONS

Didanosine is an effective and generally well tolerated drug in previously untreated and antiretroviral therapy-experienced patients with HIV infection. Given once or twice daily, it has an important role as a component of triple combination regimens for the treatment of patients with symptomatic or asymptomatic HIV infection.