Barbara Heckman

Early Initiation of Lopinavir/Ritonavir in Infants Less Than 6 Weeks of Age: Pharmacokinetics and 24 Week Safety and Efficacy

Background: With increasing recognition of the benefits of early antiretroviral therapy initiation in perinatally HIV-infected infants, data are needed regarding the pharmacokinetics (PK), safety, and efficacy of recommended first-line protease inhibitors such as lopinavir/ritonavir (LPV/r). Methods: A prospective, phase I/II, open-label, dose-finding trial evaluated LPV/r at a dose of 300/75 mg/m2 twice daily plus 2 nucleoside analogs in HIV-1-infected infants ≥14 days to <6 weeks of age. Intensive 12-hour PK evaluations were performed after 2 weeks of LPV/r therapy, and doses were modified to maintain LPV predose concentrations >1 μg/mL and area under the curve (AUC) <170 μg hr/mL. Results: Ten infants enrolled [median age 5.7 (range, 3.6–5.9) weeks] with median HIV-1 RNA of 6.0 (range, 4.7–7.2) log10 copies/mL; all completed 24 weeks of follow-up. Nine completed the intensive PK evaluation at a median LPV dose of 267 (range, 246–305) mg/m2 q12 hours; median measures were AUC = 36.6 (range, 27.9–62.6) μg hr/mL; predose concentration = 2.2 (range, 0.99–4.9) μg/mL; maximum concentration = 4.76 (range, 2.84–7.28) μg/mL and apparent clearance (L/h/m2) = 6.75 (range, 2.79–12.83). Adverse events were limited to transient grade 3 neutropenia in 3 subjects. By week 24, 2 of 10 subjects had experienced a protocol-defined virologic failure. Conclusions: Although the LPV AUC in this population was significantly lower than that observed in infants ages 6 weeks to 6 months, LPV/r-based antiretroviral therapy in doses of 300/75 mg/m2 BID was well tolerated and resulted in virologic control in 8 of 10 infants by 24 weeks. Additional investigation is needed to understand the long-term implications of the lower LPV exposure in this age group.

Phase I/II, open-label trial of safety and immunogenicity of meningococcal (groups A, C, Y, and W-135) polysaccharide diphtheria toxoid conjugate vaccine in human immunodeficiency virus-infected adolescents.

Background: Quadrivalent meningococcal polysaccharide conjugate vaccine (MCV4) is routinely recommended for healthy youth in the United States, but there are no data about its use in HIV-infected people. Methods: P1065 is a Phase I/II trial of MCV4 safety and immunogenicity in HIV-infected children and youth performed at 27 US sites of the IMPAACT network. All youth (11–24 years old) received 1 dose of open-label MCV4 at entry. Standardized questionnaires were used to evaluate safety. Baseline protective immunity was defined as rabbit serum bactericidal antibody (rSBA) titer ≥1:128. Immunogenic response was defined as a ≥4-fold rise in rSBA against each meningococcal serogroup. Multivariable logistic regression analysis was used to evaluate the association of demographic and clinical characteristics on immunogenic response to serogroup C. Results: Among 319 subjects who received MCV4, 10 (3.1%) reported immediate adverse events which were local and mild, and 7 (2.2%) experienced Grade ≥3 adverse events, unrelated to vaccine. The 305 subjects with serologic data had a median age of 17 years and were 59% male, 50% Black, and 38% Latino. Subjects were stratified by entry CD4%: 12%, CD4 <15%; 40%, 15% to 24%; and 48%, ≥25%. Baseline protective immunity varied by serogroup: A, 41%; C, 11%; W-135, 15%; Y, 35% The immunogenic response rates to serogroups A, C, W-135, and Y were 68%, 52%, 73%, and 63%, respectively. In multivariable logistic regression models, lower entry CD4%, higher entry viral load, and CDC Class B/C diagnosis were associated with significantly lower odds of response to serogroup C. Conclusion: Many HIV-infected youth naturally acquire meningococcal immunity. MCV4 is safe and immunogenic in HIV-infected youth, but response rates are lower than in healthy youth, particularly for those with more advanced HIV clinical, immunologic, and virologic status.

Pharmacokinetics and Safety of Single-Dose Tenofovir Disoproxil Fumarate and Emtricitabine in HIV-1-Infected Pregnant Women and Their Infants

ABSTRACT Tenofovir (TFV) is effective in preventing simian immunodeficiency virus (SIV) transmission in a macaque model, is available as the oral agent tenofovir disoproxil fumarate (TDF), and may be useful in the prevention of mother-to-child transmission of human immunodeficiency virus (HIV). We conducted a trial of TDF and TDF-emtricitabine (FTC) in HIV-infected pregnant women and their infants. Women received a single dose of either 600 mg TDF, 900 mg TDF, or 900 mg TDF-600 mg FTC at labor onset or prior to a cesarean section. Infants received no drug or a single dose of TDF at 4 mg/kg of body weight or of TDF at 4 mg/kg plus FTC at 3 mg/kg as soon as possible after birth. All regimens were safe and well tolerated. Maternal areas under the serum concentration-time curve (AUC) and concentrations at the end of sampling after 24 h (C24) were similar between the two doses of TDF; the maximum concentrations of the drugs in serum (Cmax) and cord blood concentrations were higher in women delivering via cesarean section than in those who delivered vaginally (P = 0.04 and 0.046, respectively). The median ratio of the TFV concentration in cord blood to that in the maternal plasma at delivery was 0.73 (range, 0.26 to 1.95). Without TDF administration, infants had a median TFV concentration of 12 ng/ml 12 h after birth. Following administration of a single dose of TDF at 4 mg/kg, infant TFV concentrations fell below the targeted level, 50 ng/ml, by 24 h postdose. In HIV-infected pregnant women and their infants, 600 mg of TDF is acceptable as a single dose during labor. Low concentrations at birth support infant dosing as soon after birth as possible. Rapidly decreasing TFV levels in infants suggest that multiple or higher doses of TDF will be necessary to maintain concentrations that are effective for viral suppression.

Long-term outcomes for HIV-infected infants less than 6 months of age at initiation of lopinavir/ritonavir combination antiretroviral therapy

Objective:To investigate the longitudinal pharmacokinetics, safety and efficacy of lopinavir/ritonavir (LPV/r) in HIV-infected infants initiating combination antiretroviral therapy (cART) between 2 weeks and 6 months of age. Method:A prospective, open-label, multicenter Phase I/II study of LPV/r-based cART at a dose of 300/75 mg/m2/dose LPV/r twice daily. Intensive pharmacokinetic sampling at 12 months of age and quarterly predose LPV concentrations were collected and safety, virologic and immunologic responses were monitored every 4–12 weeks up to 252 weeks. Results:Thirty-one HIV-infected infants enrolled into two age cohorts, 14 days to <6 weeks and 6 weeks to <6 months; 29 completed ≥48 weeks of follow-up (median = 123 weeks, range 4–252). At 12 months of age, median LPV area under the curve was comparable for both age cohorts and similar to older children and adults. At week 48, 22 of 31 patients (71%) had HIV-1 RNA <400 copies/ml and 11 of 15 (73%) had <50 copies/ml; 29 of 31 achieved HIV-1 RNA <400 copies/ml on study treatment and 19 (66%) remained durably suppressed until the end of study; viral suppression correlated with a higher percentage of predose time points exceeding the LPV target of 1 μg/ml (92 vs. 71%, P = 0.002). Conclusion:LPV/r at 300/75 mg/m2/dose as part of a cART regimen resulted in viral suppression through 96 weeks of treatment in >65% of young infants. Due to initially low LPV exposure in infants <6 weeks of age, frequent dose adjustment for weight gain is advisable and consideration should be given to studying a higher dose for very young infants.

Safety and Immunogenicity of Quadrivalent Meningococcal Conjugate Vaccine in 2 to 10 Year-Old Human Immunodeficiency Virus-Infected Children

Background: Human immunodeficiency virus (HIV)-infected children are at increased risk of meningococcal infection and poor response to quadrivalent meningococcal conjugate vaccine (MCV4), but MCV4 has not been studied in preadolescent HIV-infected children. Methods: The P1065 trial enrolled 2- to 10-year-old HIV-infected children with CD4 ≥25% to receive MCV4 at entry and at week 24. Rates of response (≥4-fold increase in rabbit serum bactericidal antibody) against each meningococcal serogroup (A, C, Y, W-135), geometric mean titers, and rates of seroprotection (rabbit serum bactericidal antibody titer ≥1:128) were determined from sera obtained at entry and weeks 4, 24, 28, and 72. Adverse events were assessed for 6 weeks after each MCV4 dose. Results: At entry, 47% of the 59 participants were male, 56% black, 31% Latino, median age was 6 years, 88% were receiving antiretroviral therapy, and 75% had viral load <400 copies/mL. There were no serious adverse events within 6 weeks after MCV4 doses; all vaccination reactions were mild. Response after a single MCV4 dose was high to serogroup A (92%) and W-135 (98%); responses improved after a second dose for serogroup C (43%–80%) (P < 0.0001) and Y (76%–84%) (P = 0.38). By week 72, seroprotection rates were 93%, 91%, 78%, and 46% for serogroups W-135, Y, A, and C, respectively. Conclusions: Two doses of MCV4 were safe and immunogenic in 2- to 10-year-old HIV-infected children. The second dose increased the proportion of children who made a response to serogroup C. Seroprotection waned substantially for serogroups A and C within 1 year of last MCV4 dose.

Pharmacokinetics of High-Dose Lopinavir-Ritonavir with and without Saquinavir or Nonnucleoside Reverse Transcriptase Inhibitors in Human Immunodeficiency Virus-Infected Pediatric and Adolescent Patients Previously Treated with Protease Inhibitors

ABSTRACT Human immunodeficiency virus (HIV)-infected children and adolescents who are failing antiretrovirals may have a better virologic response when drug exposures are increased, using higher protease inhibitor doses or ritonavir boosting. We studied the pharmacokinetics and safety of high-dose lopinavir-ritonavir (LPV/r) in treatment-experienced patients, using an LPV/r dose of 400/100 mg/m2 orally every 12 h (p.o. q12h) (without nonnucleoside reverse transcriptase inhibitor [NNRTI]), or 480/120 mg/m2 p.o. q12h (with NNRTI). We calculated the LPV inhibitory quotient (IQ), and when the IQ was <15, saquinavir (SQV) 750 mg/m2 p.o. q12h was added to the regimen. We studied 26 HIV-infected patients. The median age was 15 years (range, 7 to 17), with 11.5 prior antiretroviral medications, 197 CD4 cells/ml, viral load of 75,577 copies/ml, and a 133-fold change in LPV resistance. By treatment week 2, 14 patients had a viral-load decrease of >0.75 log10, with a median maximal decrease in viral load of −1.57 log10 copies/ml at week 8. At week 2, 19 subjects showed a median LPV area under the concentration-time curve (AUC) of 157.2 (range, 62.8 to 305.5) μg·h/ml and median LPV trough concentration (Ctrough) of 10.8 (range, 4.1 to 25.3) μg/ml. In 16 subjects with SQV added, the SQV median AUC was 33.7 (range, 4.4 to 76.5) μg·h/ml and the median SQV Ctrough was 2.1 (range, 0.2 to 4.1) μg/ml. At week 24, 18 of 26 (69%) subjects remained in the study. Between weeks 24 and 48, one subject withdrew for nonadherence and nine withdrew for persistently high virus load. In antiretroviral-experienced children and adolescents with HIV, high doses of LPV/r with or without SQV offer safe options for salvage therapy, but the modest virologic response and the challenge of adherence to a regimen with a high pill burden may limit the usefulness of this approach.

Intracellular Pharmacokinetics of Once versus Twice Daily Zidovudine and Lamivudine in Adolescents

ABSTRACT Zidovudine (ZDV) and lamivudine (3TC) metabolism to triphosphates (TP) is necessary for antiviral activity. The aims of this study were to compare ZDV-TP and 3TC-TP concentrations in adolescents receiving twice daily (BID) and once daily (QD) regimens and to determine the metabolite concentrations of ZDV and 3TC during chronic therapy on a QD regimen. Human immunodeficiency virus-infected patients (12 to 24 years) taking ZDV (600 mg/day) and 3TC (300 mg/day) as part of a highly active antiretroviral therapy regimen received QD and BID regimens of ZDV and 3TC for 7 to 14 days in a crossover design. Serial blood samples were obtained over 24 h on the QD regimen. Intracellular mono-, di-, and triphosphates for ZDV and 3TC were measured. The median ratio of BID/QD for ZDV-TP predose concentrations was 1.28 (95% confidence interval [CI] = 1.00 to 2.45) and for 3TC-TP was 1.12 (95% CI = 0.81 to 1.96). The typical population estimated half-lives (± the standard error of the mean) were 9.1 ± 0.859 h for ZDV-TP and 17.7 ± 2.8 h for 3TC-TP. Most patients had detectable levels of the TP of ZDV (24 of 27) and 3TC (24 of 25) 24 h after dosing, and half-lives on a QD regimen were similar to previously reported values when the drugs were given BID. Lower, but not significantly different, concentrations of ZDV-TP were demonstrated in the QD regimen compared to the BID regimen (P = 0.056). Although findings were similar between the BID and QD groups, the lower concentrations of ZDV and the number of patients below the level of detection after 24 h suggests that ZDV should continue to be administered BID.

Clinical Response and Tolerability to and Safety of Saquinavir with Low-Dose Ritonavir in Human Immunodeficiency Virus Type 1-Infected Mothers and Their Infants

ABSTRACT Saquinavir boosted with low-dose ritonavir given with zidovudine and lamivudine was well tolerated by pregnant women and their infants. All mothers had <400 human immunodeficiency virus type 1 RNA copies/ml at delivery. Two had elevated liver transaminases and amylase. Seven infant adverse events were possibly treatment related (anemia, neutropenia, and hyperbilirubinemia).

Assessment of lopinavir pharmacokinetics with respect to developmental changes in infants and the impact on weight band-based dosing.

Improved antiretroviral therapies are needed for the treatment of HIV‐infected infants, given the rapid progression of the disease and drug resistance resulting from perinatal exposure to antiretrovirals. We examined longitudinal pharmacokinetics (PK) data from a clinical trial of lopinavir/ritonavir (LPV/r) in HIV‐infected infants in whom therapy was initiated at less than 6 months of age. A population PK analysis was performed using NONMEM to characterize changes in lopinavir (LPV) PK relating to maturational changes in infants, and to assess dosing requirements in this population. We also investigated the relationship between LPV PK and viral dynamic response. Age and ritonavir concentrations were the only covariates found to be significant. Population PK of LPV was characterized by high apparent clearance (CL/F) in young infants, which decreased with increasing age. Although younger infants had lower LPV concentrations, the viral dynamics did not correlate with initial LPV exposure. Monte Carlo simulations demonstrated that WHO weight band–based dosing recommendations predicted therapeutic LPV concentrations and provided drug exposure levels comparable to those resulting from US Food and Drug Administration (FDA)‐suggested dosing regimens.

Structured treatment interruptions (STIs) in HIV-1 infected pediatric populations increases interferon gamma production and reduces viremia.

We assessed the effect of progressively longer antiretroviral structured treatment interruptions (STIs) starting with 3 days, increasing by 2 days in length each cycle on HIV-specific immune responses. As well, we correlated these responses with control of HIV viremia. Eight individuals became viremic and reached cycle 13 with an STI of > or =27 days. HIV-specific gamma-interferon production to inactivated HIV and vaccinia vectors expressing gag, env, nef, and pol increased (>10-fold) in six of eight subjects. Median plasma RNA levels peaked @ cycle 7 and declined to levels <10(4)cp/ml after cycle 10. In a subset of five who reached cycle 17, HIV-specific IFN-gamma frequencies increased from cycle 8 to cycle 17 with evidence of improved virologic control over comparable periods off antiretroviral therapy. This allowed us to conclude that exposure to autologous virus increased HIV-specific immune responses and decreased HIV RNA were seen in those who have had >13 interruptions, with STI intervals that exceeded 27 days.