title: Analysis of single-nucleotide polymorphisms (SNPs) in human CYP3A4 and CYP3A5 genes: potential implications for the metabolism of HIV drugs.
abstract: BACKGROUND
  Drug metabolism via the cytochrome P450 (CYP450) system has emerged as an important determinant in the occurrence of several drug interactions (adverse drug reactions, reduced pharmacological effect, drug toxicities). In particular, CYP3A4 and CYP3A5 (interacting with more than 60% of licensed drugs) exhibit the most individual variations of gene expression, mostly caused by single nucleotide polymorphisms (SNPs) within the regulatory region of the CYP3A4 and CYP3A5 genes which might affect the level of enzyme production.In this study, we sought to improve the performance of sensitive screening for CYP3A polymorphism detection in twenty HIV-1 infected patients undergoing lopinavir/ritonavir (LPV/r) monotherapy.
  
  
  METHODS
  The study was performed by an effective, easy and inexpensive home-made Polymerase Chain Reaction Direct Sequencing approach for analyzing CYP3A4 and CYP3A5 genes which can detect both reported and unreported genetic variants potentially associated with altered or decreased functions of CYP3A4 and CYP3A5 proteins. Proportions and tests of association were used.
  
  
  RESULTS
  Among the genetic variants considered, CYP3A4*1B (expression of altered function) was only found in 3 patients (15%) and CYP3A5*3 (expression of splicing defect) in 3 other patients (15%). CYP3A5*3 did not appear to be associated with decreased efficacy of LPV/r in any patient, since none of the patients carrying this variant showed virological rebound during LPV/r treatment or low levels of TDM. In contrast, low-level virological rebound was observed in one patient and a low TDM level was found in another; both were carrying CYP3A4*1B.
  
  
  CONCLUSIONS
  Our method exhibited an overall efficiency of 100% (DNA amplification and sequencing in our group of patients). This may contribute to producing innovative results for better understanding the inter-genotypic variability in gene coding for CYP3A, and investigating SNPs as biological markers of individual response to drugs requiring metabolism via the cytochrome P450 system.
authors.forename: Giulia
authors.initials: G
authors.lastname: Berno
authors.forename: Mauro
authors.initials: M
authors.lastname: Zaccarelli
authors.forename: Caterina
authors.initials: C
authors.lastname: Gori
authors.forename: Massimo
authors.initials: M
authors.lastname: Tempestilli
authors.forename: Andrea
authors.initials: A
authors.lastname: Antinori
authors.forename: Carlo Federico
authors.initials: CF
authors.lastname: Perno
authors.forename: Leopoldo Paolo
authors.initials: LP
authors.lastname: Pucillo
authors.affiliation: Clinical Biochemistry and Pharmacology Laboratory, National Institute for Infectious Diseases "L, Spallanzani", Via Portuense 292, Rome, 00149, Italy. roberta.darrigo@inmi.it.
authors.forename: Roberta
authors.initials: R
authors.lastname: D'Arrigo
mesh_terms: D000328:Adult; D000483:Alleles; D019380:Anti-HIV Agents / Q000493:pharmacokinetics* / Q000627:therapeutic use; D018791:CD4 Lymphocyte Count; D051544:Cytochrome P-450 CYP3A / Q000235:genetics*; D005260:Female; D005787:Gene Frequency; D015658:HIV Infections / Q000188:drug therapy / Q000235:genetics* / Q000276:immunology / Q000821:virology; D006801:Humans; D061466:Lopinavir / Q000493:pharmacokinetics / Q000627:therapeutic use; D008297:Male; D008875:Middle Aged; D010597:Pharmacogenetics; D020641:Polymorphism, Single Nucleotide; D016896:Treatment Outcome; D019562:Viral Load
chemical_list: D019380:Anti-HIV Agents; D061466:Lopinavir; C510164:CYP3A5 protein, human; D051544:Cytochrome P-450 CYP3A; C510163:CYP3A4 protein, human