A uniquely efficacious type of CFTR corrector with complementary mode of action.

Three distinct pharmacological corrector types (I, II, III) with different binding sites and additive behavior only partially rescue the F508del-cystic fibrosis transmembrane conductance regulator (CFTR) folding and trafficking defect observed in cystic fibrosis. We describe uniquely effective, macrocyclic CFTR correctors that were additive to the known corrector types, exerting a complementary "type IV" corrector mechanism. Macrocycles achieved wild-type-like folding efficiency of F508del-CFTR at the endoplasmic reticulum and normalized CFTR currents in reconstituted patient-derived bronchial epithelium. Using photo-activatable macrocycles, docking studies and site-directed mutagenesis a highly probable binding site and pose for type IV correctors was identified in a cavity between lasso helix-1 (Lh1) and transmembrane helix-1 of membrane spanning domain (MSD)-1, distinct from the known corrector binding sites. Since only F508del-CFTR fragments spanning from Lh1 until MSD2 responded to type IV correctors, these likely promote cotranslational assembly of Lh1, MSD1, and MSD2. Previously corrector-resistant CFTR folding mutants were also robustly rescued, suggesting substantial therapeutic potential for type IV correctors.

Pose, duplicate, then elaborate: Steps towards increased affinity for inhibitors targeting the specificity surface of the Pim-1 kinase.

In this study, fragment-sized hits binding to Pim-1 kinase with initially modest affinity were further optimized by combining computational, synthetic and crystallographic expertise, eventually resulting in potent ligands with affinities in the nanomolar range that address rarely-targeted regions of Pim-1 kinase. Starting from a set of crystallographically validated, chemically distinct fragments that bind to Pim-1 kinase but lack typical nucleotide mimetic structures, a library of extended fragments was built by exhaustive in silico reactions. After docking, minimization, clustering, visual inspection of the top-ranked compounds, and evaluation of ease of synthetic accessibility, either the original compound or a close derivative was synthesized and tested against Pim-1. For compounds showing the highest degree of Pim-1 inhibition the binding mode was determined crystallographically. Following a structure-guided approach, these were further optimized in a subsequent design cycle improving the compound's initial affinity by several orders of magnitude while synthesizing only a comparatively modest number of derivatives. The combination of computational and experimental approaches resulted in the development of a reasonably potent, novel molecular scaffold for inhibition of Pim-1 that targets specific surface regions, such as the interaction with R122 and P123 of the hinge region, which has been less frequently investigated in similar studies.