Thanks for taking the time out from your weekend to respond again. I have indeed read your links to pharmacogenomics of the CYP450 system and the effect on drug metabolism in general, as well as drug-drug interactions due to CYP450 inhibition. I am well familiar with such genomic and drug-drug interactions. I have reviewed trial protocols that genotype CYP450 and adjust drug dosing based on those polymorphisms, and my institution is at the forefront of testing for CYP450 genotype, putting in the EMR, and adjusting drug dosing based on that outside of clinical research trials. Sorry, but your hand waving about CYP450 explaining maraviroc toxicity just isn't convincing. I hope you don't take it personally! I do appreciate the discussion as a chance to learn something. Perhaps you are saying some of the toxicity could come from drug-drug interactions or unknown toxic metabolites, and we might not ever know why, and I would agree with that. Cheers.