Design, synthesis and biophysical evaluation of novel, tri-vector cyclophilin ligands

Abstract

Cyclophilins, protein targets linked to neurodegeneration, viral infection, and cancer, are challenged by their highly-conserved active site. Using computational calculations and chemical synthesis, Michel's team identified a first-generation of potent submicromolar inhibitors targeting the less-conserved 3 o'clock pocket, achieving initial activity against triple-negative breast cancer. The project's goal is to refine a secondgeneration of tri-vector molecules, optimizing selectivity, potency, and toxicity (Figure 1).

Chapter 2 aims to optimize the synthesis of the leading first-generation tri-vector inhibitor, a 1,3-substituted tetrazole Het-R1, and examines various substitutions. Despite the tetrazole's high electron density and low reactivity, two new tetrazole derivatives were synthesized, aiding the structure-activity relationship investigation with bulkier substituents than methyl.

Chapter 3 scrutinizes additional 1,3-substituted heterocycles with R1 substituents. Thiadiazoles emerged as promising heterocycles, yielding two final products for biophysical and pharmacokinetic profiling and indicating potential for an extended 1,3-substituted derivative library.

Chapter 4 assesses the synthesized compounds alongside a library from a Contract Research Organisation using ITC and SPR assays, aiming for potent and selective inhibitors of CypA, CypB, and CypD. Experimentation with R2 and aromatic-R3 substituents sought to optimize pharmacokinetics and enhance selectivity/toxicity concerns (Figure 1). The novel second-generation tri-vector cyclophilin inhibitors demonstrated improved binding affinity, with additional investigation into the intramolecular interaction of specific 1,3-substituted heterocycles and thiadiazole derivatives promising further insight.

The work thus yielded improved tri-vector cyclophilin inhibitors, serving as valuable probes of cyclophilin function or potential therapeutic agent foundations.