Effects of genetic variation in the P2RX7 gene on pharmacodynamics of a P2X₇ receptor antagonist: a prospective genotyping approach

Abstract

WHAT IS ALREADY KNOWN ABOUT THIS SUBJECT • Analysis of allelic variation in large populations has identified numerous single nucleotide polymorphisms (SNPs) in the P2RX7 gene. In vitro transfection has demonstrated SNP‐dependent alterations (gain or loss) of P2X7 receptor function, as measured by ATP‐induced ethidium uptake and interleukin‐1β production. WHAT THIS STUDY ADDS • We provide definitive evidence of SNP‐dependent alteration in P2X7 receptor pharmacodynamics to a specific antagonist (GSK1370319A) in a small sample of prospectively genotyped subjects. These effects on drug response underline the importance of genetic stratification in drug development of P2X7 receptor antagonists. AIMS To investigate the effects of two single nucleotide polymorphisms (SNPs) in the human P2X7 receptor gene (P2RX7) – 1068G>A (A348T) and 1513A>C (E496A) – on P2X7 receptor function, using a specific receptor antagonist (GSK1370319A) and prospective genetic stratification. METHODS Lipopolysaccharide‐ and ATP‐stimulated interleukin‐1β production was determined in the presence or absence of GSK1370319A in blood culture from 32 prospectively genotyped subjects. RESULTS There was approximately 6.7‐fold difference (P < 0.0001) in IC50 for inhibition of ATP‐stimulated interleukin‐1β release by GSK1370319A between individuals with the homozygous gain‐ (1068A) and loss‐of‐function (1513C) genotypes (expressing the 348T, 496E and 348A, 496A alleles, respectively). CONCLUSIONS Leukocyte P2X7 receptors had significantly altered pharmacodynamic responses to a specific antagonist (GSK1370319A), directly related to SNP genotype.

The potential of P2X7 receptors as a therapeutic target, including inflammation and tumour progression

“…As mentioned above, a major challenge is to understand which polymorphic variations of the P2X7R have relevance to which disease and to fit patients with different polymorphisms to the P2X7R antagonist that would have the greatest efficacy for that variant. For example, the responses of human leukocytes to GSK1370319A were significantly altered, directly related to the SNP genotype, there being a 6.7-fold difference in the inhibition of ATP-stimulated IL-1β release by GSK1370319A between individuals with the homozygous gain- and loss-of-function genotypes [ 223 ]. A correlation was found between some gain-of-function and loss-of-function P2X7R SNPs, transfected into HEK-293 cells, and the expression of the channel protein.…”

The P2X7 Receptor Channel: Recent Developments and the Use of P2X7 Antagonists in Models of Disease

“…Furthermore, P2X7 variants, including SNPs and splice isoforms, are likely to play a role in the differential activity of these compounds both between and within species. For example, N-[(2,4-dichlorophenyl)methyl]-1-methyl-5-oxo-l-prolinamide (GSK1370319A) has an almost 7-fold higher IC 50 value for ATP-induced IL-1b in human blood cultures from individuals with the A348T gain-of-function SNP than those from individuals with the E496A loss-of-function SNP (McHugh et al, 2012). Thus, given that human P2X7 is highly polymorphic (see section VIII), this has ramifications for the future use of P2X7 antagonists in treating human disorders.…”

“…However, the possibility remains that the efficacy of these P2X7 antagonists is dependent on P2RX7 genotype, as indicated in other in vitro studies using GSK1370319A (McHugh et al, 2012). Thus, it may be essential to stratify clinical data by P2RX7 genotype to detect therapeutic benefits of P2X7 blockade.…”

What is the point of large-scale collections of human induced pluripotent stem cells?

“…We now know that minor genetic variations in the drug target may also lead to inter-individual variation in drug responses. A recent study showed that an exploratory new drug differed by 10 fold in affinity for its target, the P2X7 ion-channel, solely depending on two polymorphisms in the protein 19 , and a single polymorphism in the TNF-alpha 1 receptor can predict an adverse effect of TNF antagonist treatment 20 . Polymorphisms may be unrelated to known disease but determine which patients do and do not respond to a drug.…”