17(R),18(S)-epoxyeicosatetraenoic acid, a potent eicosapentaenoic acid (EPA) derived regulator of cardiomyocyte contraction: structure-activity relationships and stable analogues.

17(R),18(S)-epoxyeicosatetraenoic acid [17(R),18(S)-EETeTr], a cytochrome P450 epoxygenase metabolite of eicosapentaenoic acid (EPA), exerts negative chronotropic effects and protects neonatal rat cardiomyocytes against Ca(2+)-overload with EC(50) ≈ 1-2 nM. Structure-activity studies revealed that a cis-Δ(11,12)- or Δ(14,15)-olefin and a 17(R),18(S)-epoxide are minimal structural elements for antiarrhythmic activity whereas antagonist activity was often associated with the combination of a Δ(14,15)-olefin and a 17(S),18(R)-epoxide. Compared with natural material, the agonist and antagonist analogues are chemically and metabolically more robust and several show promise as templates for future development of clinical candidates.