Pharmacogenetics
In consenting patients, prior to the first palbociclib dose, whole blood
(5 mL) was collected for DNA extraction with a Gentra Puregene Blood Kit
(#158389, Qiagen). DNA was quantified by using Nanodrop 2000
Spectrophotometer (Thermo Fisher Scientific). Genome-wide genotyping was
performed in germline DNA with an Illumina Infinium Omni2.5Exome-8
Bead-Chip (Illumina Inc.) Selected genes included CYP3A4 ,CYP3A5 , and SULT2A1 involved in palbociclib metabolism,
and ABCB1 , ABCG2 , ABCC1 , and ABCC4 which
encode genes for known drug transporters. All available single
nucleotide polymorphisms (SNPs) from these genes with a reported minor
allelic frequency >5% (https://www.ncbi.nlm.nih.gov/snp/)
were extracted.
Associations between palbociclib Cmax and
AUC0-Tlast after single and repeated doses and genotypes
were evaluated using non-parametric Kruskal-Wallis tests, Mann-Whitney
U-tests, and linear regression. For SNPs including data from wild-type
(0), heterozygous (1), and homozygous mutant (2) patients, the
distribution of the pharmacokinetic variables was compared between 0,1,
and 2, and between 0+1 vs 2, and 0 vs 1+2. Statistical
significance was defined by a p-value P < 0.05. Strong
linkage disequilibrium (LD) between SNPs, defined as
r2>0.80, was verified using the LD matrix
tool (https://ldlink.nci.nih.gov/ ). Based on the population size,
associations were tested using a univariate analysis only. All the tests
were performed using R® software.