ABSTRACT
Cyclophilins are a family of peptidyl-prolyl isomerases that are implicated in a wide range of diseases including hepatitis C. Our aim was to discover through total synthesis an orally bioavailable, non-immunosuppressive cyclophilin (Cyp) inhibitor with potent anti-hepatitis C virus (HCV) activity that could serve as part of an all oral antiviral combination therapy. An initial lead 2 derived from the sanglifehrin A macrocycle was optimized using structure based design to produce a potent and orally bioavailable inhibitor 3. The macrocycle ring size was reduced by one atom, and an internal hydrogen bond drove improved permeability and drug-like properties. 3 demonstrates potent Cyp inhibition ( Kd = 5 nM), potent anti-HCV 2a activity (EC50 = 98 nM), and high oral bioavailability in rat (100%) and dog (55%). The synthetic accessibility and properties of 3 support its potential as an anti-HCV agent and for interrogating the role of Cyp inhibition in a variety of diseases.
Subject(s)
Cyclophilins/antagonists & inhibitors , Drug Design , Enzyme Inhibitors/pharmacology , Enzyme Inhibitors/pharmacokinetics , Administration, Oral , Antiviral Agents/administration & dosage , Antiviral Agents/chemistry , Antiviral Agents/pharmacokinetics , Antiviral Agents/pharmacology , Biological Availability , Cell Line , Cyclophilins/chemistry , Enzyme Inhibitors/administration & dosage , Enzyme Inhibitors/chemistry , Hepacivirus/drug effects , Lactones/administration & dosage , Lactones/chemistry , Lactones/pharmacokinetics , Lactones/pharmacology , Models, Molecular , Protein Conformation , Spiro Compounds/administration & dosage , Spiro Compounds/chemistry , Spiro Compounds/pharmacokinetics , Spiro Compounds/pharmacologyABSTRACT
Cyclophilin inhibition has been a target for the treatment of hepatitis C and other diseases, but the generation of potent, drug-like molecules through chemical synthesis has been challenging. In this study, a set of macrocyclic cyclophilin inhibitors was synthesized based on the core structure of the natural product sanglifehrin A. Initial compound optimization identified the valine-m-tyrosine-piperazic acid tripeptide (Val-m-Tyr-Pip) in the sanglifehrin core, stereocenters at C14 and C15, and the hydroxyl group of the m-tyrosine (m-Tyr) residue as key contributors to compound potency. Replacing the C18-C21 diene unit of sanglifehrin with a styryl group led to potent compounds that displayed a novel binding mode in which the styrene moiety engaged in a π-stacking interaction with Arg55 of cyclophilin A (Cyp A), and the m-Tyr residue was displaced into solvent. This observation allowed further simplifications of the scaffold to generate new lead compounds in the search for orally bioavailable cyclophilin inhibitors.
