pf-4800567 pf-4800567 pf-4800567 is a drug developed by pfizer which acts as a selective inhibitor of the enzyme casein kinase 1 epsilon (ck1-ε), and has mainly been used in the study of the casein kinase 1 enzymes in the regulation of circadian rhythm, as well as showing potential neuroprotective effects. while this research has shown that circadian rhythm is modulated primarily by the alternate isoform ck1-δ rather than ck1-ε, both pf-4800567 and the related non-selective ck1-δ/ε inhibitor pf-670462 were found in animal studies to enhance responses to certain drugs of abuse such as methamphetamine and fentanyl, which suggests a role for ck1-ε in negative regulation of sensitivity to stimulant and opioid drugs. pf-4800567identifiers iupac name 3-(3-chloro-phenoxymethyl)-1-(tetrahydro-pyran-4-yl)-1h-pyrazolopyrimidin-4-ylamine cas number1188296-52-7pubchem cid53472153iuphar/bps8050chemspider26325201chebichebi:87237comptox dashboard (epa)dtxsid20703849 chemical and physical dataformulac17h18cln5o2molar mass359.81 g·mol−13d model (jsmol)interactive image smiles c4c(cl)cccc4occ(c1c3n)nn(c1ncn3)c2ccocc2 inchi inchi=1s/c17h18cln5o2/c18-11-2-1-3-13(8-11)25-9-14-15-16(19)20-10-21-17(15)23(22-14)12-4-6-24-7-5-12/h1-3,8,10,12h,4-7,9h2,(h2,19,20,21)key:aumdbehgjrzsoo-uhfffaoysa-n