Rational Design and Optimization of a Novel Class of Macrocyclic Apoptosis Signal-Regulating Kinase 1 Inhibitors

Abstract

Structural analysis of a known apoptosis signal-regulating kinase 1 (ASK1) inhibitor bound to its kinase domain led to the design and synthesis of the novel macrocyclic inhibitor 8 (cell IC50 = 1.2 μM). The profile of this compound was optimized for CNS penetration following two independent strategies: a rational design approach leading to 19 and a parallel synthesis approach leading to 26. Both analogs are potent ASK1 inhibitors in biochemical and cellular assays (19, cell IC50 = 95 nM; 26, cell IC50 = 123 nM) and have moderate to low efflux ratio (ER) in an MDR1-MDCK assay (19, ER = 5.2; 26, ER = 1.5). In vivo PK studies revealed that inhibitor 19 had moderate CNS penetration (K puu = 0.17) and analog 26 had high CNS penetration (K puu = 1.0).

Image2SMILES: Transformer‐Based Molecular Optical Recognition Engine**

“…So manual test is feasible, but for a limited number of samples. We took ten articles [34][35][36][37][38][39][40][41][42][43] to test our method on the real data. Structures that represent reaction mechanisms were excluded, so we regarded only molecules and Markush templates.…”

“…Some examples of incorrect recognition are given in Figures 10-14. An example of incorrect recognition occurs because the functional group NMe 2 is not presented in the template dictionary (from [34]).…”

Image2SMILES: Transformer-based Molecular Optical Recognition Engine

“…So manual test is feasible, but for a limited number of samples. We took ten articles [28][29][30][31][32][33][34][35][36][37] to test our method on the real data. Structures that represent reaction mechanisms were excluded, so we regarded only molecules and Markush templates.…”

Discovery of CNS-Penetrant Apoptosis Signal-Regulating Kinase 1 (ASK1) Inhibitors

“…To gain a better understanding of the impact of modulating the ASK1 pathway in neurological disease, we have recently disclosed the identification of macrocyclic inhibitors with good potency, pharmacokinetic (PK) profile, and moderate CNS penetration following a deconstruction–cyclization strategy (analog 4 , Figure , top) . Herein we describe an alternative approach to gain access to potent and brain penetrant ASK1 inhibitors that relied on the optimization of the phenyl group in the initially deconstructed analog 5 (Figure , bottom).…”

“…Among these, the methoxy group had the biggest impact in potency and the resulting analog 8 (cell IC 50 = 90 nM) was also found to have low in vivo clearance (Cl/Cl u = 1.6/4.0 L h –1 kg –1 ) in a rat PK experiment . An initial attempt to further improve the profile of this inhibitor by implementing the previously described macrocyclization strategy led to the identification of analog 9 (cell IC 50 = 32 nM), but this compound had high in vivo clearance in a rat PK experiment (Cl/Cl u = 4.7/21 L h –1 kg –1 ) and also suffered from high efflux ratio (ER) ( 9 , Table , ER = 26) . Given the shortcomings of this macrocyclization strategy, the effort shifted toward the synthesis of analogs with reduced polar surface area (PSA) in an attempt to reduce their high ER.…”