cr665 cr665 cr665 (h-d-phe-d-phe-d-nle-d-arg-nh-4-picolyl), also known by the previous developmental code names fe-200665 and jnj-38488502, is an all d-amino acid peptide that acts as a peripherally restricted κ-opioid receptor agonist. the selectivity for fe 200665 is 1/16,900/84,600 for the human κ, μ, and δ opioid receptors, respectively. the dose of fe 200665 required to produce motor impairment (measure of cns penetration) was 548 times higher than the dose required for antinociceptive activity. it is being developed for use by cara therapeutics under the code name cr665. cr665 names iupac name (r)-2-((r)-2-((r)-2-amino-3-phenylpropanamido)-3-phenylpropanamido)-n-((r)-5-guanidino-1-oxo-1-((pyridin-4-ylmethyl)amino)pentan-2-yl)hexanamide other names cr 665; jnj 38488502 identifiers cas number 228546-92-7 y 3d model (jsmol) interactive image chemspider 32702094 pubchem cid 25030387 unii 3bx9ug06gg comptox dashboard (epa) dtxsid30177395 inchi inchi=1s/c36h49n9o4/c1-2-3-15-30(34(48)43-29(16-10-19-41-36(38)39)33(47)42-24-27-17-20-40-21-18-27)44-35(49)31(23-26-13-8-5-9-14-26)45-32(46)28(37)22-25-11-6-4-7-12-25/h4-9,11-14,17-18,20-21,28-31h,2-3,10,15-16,19,22-24,37h2,1h3,(h,42,47)(h,43,48)(h,44,49)(h,45,46)(h4,38,39,41)/t28-,29-,30-,31-/m1/s1key: dboggovkhscmnb-omrvphblsa-ninchi=1/c36h49n9o4/c1-2-3-15-30(34(48)43-29(16-10-19-41-36(38)39)33(47)42-24-27-17-20-40-21-18-27)44-35(49)31(23-26-13-8-5-9-14-26)45-32(46)28(37)22-25-11-6-4-7-12-25/h4-9,11-14,17-18,20-21,28-31h,2-3,10,15-16,19,22-24,37h2,1h3,(h,42,47)(h,43,48)(h,44,49)(h,45,46)(h4,38,39,41)/t28-,29-,30-,31-/m1/s1key: dboggovkhscmnb-omrvphblbs smiles o=c(ncc1=cc=nc=c1)(nc((nc((cc2=cc=cc=c2)nc((cc3=cc=cc=c3)n)=o)=o)cccc)=o)cccnc(n)=n properties chemical formula c36h49n9o4 molar mass 671.847 g·mol−1 except where otherwise noted, data are given for materials in their standard state (at 25 °c , 100 kpa). infobox references a small, blinded study was done in healthy humans to determine the analgesic effects. cr665 was dosed at 0.36 mg/kg i.v., and was compared to 15 mg oxycodone orally. cr665 had analgesic effects on visceral pain, but produced a hyperalgesic response in a skin pinch test.