Optimizing Antiretroviral Therapy in HIV-Infected Children and Adolescents

• 2. The parameters of PK analysis (Cmin, Cmax, AUC)- at 6 weeeks.
• 1. Variations in CYP2C19, CYP3A4, CYP3A5, and MDR-1 genes in a study cohort - at two years.

• 1.CD4+cell count - at 6 weeks.
• 2.HIV-1 RNA - at 6 weeks
• 3.Toxicities (CBC, LFTs, Albumin, Creatinine, Blood Urea Nitrogen, Amylase, Lipase, Cholesterol, Triglycerides, Glucose) - at 6 weeks.

The proposal is aimed at the development of a dosing regimen of existing protease inhibitors (PIs) in human immunodeficiency virus (HIV)-infected children that takes into account genetic variability in drug metabolism and transport, and resistance of the dominant viral strain. The long-term goal of the research investigation is to improve dosing of protease inhibitors (PIs) in HIV-infected children, leading to improved outcome and decreased adverse drug reactions.

Although, the use of protease inhibitors (PI) containing highly active antiretroviral therapy (HAART) has led to a remarkable improvement in the prognosis and outcome of HIV infection, only 45% to 70% of treatment-naïve patients who commence HAART achieve complete virological suppression. The emergence of HIV resistance to antiretroviral drugs is one of the main obstacles to the successful long-term suppression of HIV replication. Poor adherence and unfavorable pharmacokinetics (PK) caused by altered absorption, genetic variations in metabolism and drug-drug interactions frequently lead to antiretroviral drug concentrations below the inhibitory concentration for 50% of the viral quasispecies (IC50) and loss of viral suppression.

Enzymes of the cytochrome (CYP) P450 (CYP2C19, CYP3A4, CYP3A5) family located in the liver and small intestine are responsible for the metabolism of PIs. The absence of expression of certain enzymes from this family was recently correlated with a genetic polymorphism, which may have a major role in variation of cytochrome P450-mediated drug metabolism. Results of these studies suggest significant differences in the distribution of the polymorphism associated alleles between ethnic groups, in particular between Caucasians and African Americans. Detection of cytochrome P450 variant alleles and more detailed data on their allelic frequency in various ethnic groups is critical to assess their impact on PK of antiretroviral agents, in particular PIs.

This research proposal is aimed at the development of a novel multidisciplinary approach to optimize HAART in HIV infected children. It is increasingly clear that inter-individual variation in drug metabolism and responsiveness has a strong genetic component. The metabolic pathways leading to drug clearance, bio-availability, and cellular responses are complex, and only beginning to be understood. Key to our understanding of inter-individual responses is identification of the genetic polymorphisms that contribute to this variability, the relative contribution of different genes/SNPs, and the possible interactions between the corresponding protein products or pathways. We propose to develop a dosing regimen of PIs in HIV-infected children that takes into account genetic variability in drug metabolism and transport, and resistance of the dominant viral strain (as determined by virtual phenotype).

In order to do so, the protocol address the following Specific Aims:

• Specific Aim 1: Determine the prevalence of genetic variations in CYP2C19, CYP3A4, CYP3A5, and MDR-1 genes in a cohort of children and adolescents with HIV infection.
• Specific Aim 2: Evaluate the relationship of this genetic variability to the pharmacokinetic parameters (Cmin, Cmax, AUC) and toxicity (graded by the Division of AIDS [DAIDS] classification) of protease inhibitors in pediatric patients with HIV infection.
• Specific Aim 3: Evaluate the impact of dose adjustment of protease inhibitors based on pharmacogenetic profile and virtual inhibitory quotient (VIQ) on clinical outcome (measured by HIV-RNA viral load and CD4+ cell count changes) and toxicity (graded by the DAIDS classification) in pediatric patients with HIV infection.

• Drug: Nelfinavir
  Adjust the dose of Nelfinavir to meet target therapeutic concentraions
  Other Name: Viracept
• Drug: Lopinavir/ritonavir
  Adjust the dose of Lopinavir/ritonavir to meet target therapeutic concentrations
  Other Name: Kaletra
• Drug: Ritonavir
  Adjust the dose of Ritonavir to meet target therapeutic concentrations
  Other Name: Norvir
• Drug: Amprenavir
  Adjust the dose of Amprenavir to meet target therapeutic concentrations
  Other Name: Agenerase
• Drug: Indinavir
  Adjust the dose of Indinavir to meet target therapeutic concentrations
  Other Name: Crixivan
• Drug: Saquinavir
  Adjust the dose of Saquinavir to meet target therapaeutic concentrations
  Other Name: Invirase-HGC
• Drug: Fosamprenavir
  Adjust the dose of Fosamprenavir to meet target therapeutic concentraions
  Other Name: Lexiva
• Drug: Atazanavir
  Adjust the doe of Atazanavir to meet target therapeutic concentrations
  Other Name: Reyataz
• Drug: Tipranavir
  Adjust the dose of Tipranavir to meet target therapeutic concentrations
  Other Name: Aptivus
• Drug: Dose adjustment
  Adjust the dose off the drug to meet target therapeutic concentration
  Other Names:

  • Amprenavir
  • Fosamprenavir
  • Kaletra
  • Ritonavir
  • Saquinavir
  • Nelfinavir
  • Tiprnavir
  • Atazanavir
  • Indinavir

Inclusion criteria:

• Evidence of HIV infection confirmed by positive culture or PCR on at least two occasions, or a positive ELISA and a confirmatory Western Blot. At least one of these tests must be done in an ACTG certified laboratory which is approved to perform the assay for protocol testing
• Age 4-21 years
• Current use of HAART regimen (NRTI or/and NNRTI based) containing a PI
• HIV-RNA levels above 1,000 copies/mL (Stage II)
• Signed informed consent and, if indicated, signed informed assent or waiver of assent.

Exclusion criteria:

• Grade 3-4 DAIDS defined toxicity
• Use of cimetidine (used as the internal standard for the HPLC-MS/MS assay)
• Any active opportunistic infection
• Any of the following laboratory findings at entry: absolute neutrophil count <750 cells/mm3; platelet count <75,000 cells/mm3; AST >3 times upper limit of age adjusted normal values; ALT >3 times upper limit of age adjusted normal values; serum creatinine >1.2mg/dL.
• Patients on dual PI regimen (except when second PI is given for boosting) at the time of enrollment