Generating Selective Leads for Mer Kinase Inhibitors—Example of a Comprehensive Lead-Generation Strategy

Abstract

Mer is a member of the TAM (Tyro3, Axl, Mer) kinase family that has been associated with cancer progression, metastasis, and drug resistance. Their essential function in immune homeostasis has prompted an interest in their role as modulators of antitumor immune response in the tumor microenvironment. Here we illustrate the outcomes of an extensive lead-generation campaign for identification of Mer inhibitors, focusing on the results from concurrent, orthogonal high-throughput screening approaches. Data mining, HT (high-throughput), and DECL (DNA-encoded chemical library) screens offered means to evaluate large numbers of compounds. We discuss campaign strategy and screening outcomes, and exemplify series resulting from prioritization of hits that were identified. Concurrent execution of HT and DECL screening successfully yielded a large number of potent, selective, and novel starting points, covering a range of selectivity profiles across the TAM family members and modes of kinase binding, and offered excellent start points for lead development.

Optimization of an Imidazo[1,2-a]pyridine Series to Afford Highly Selective Type I1/2 Dual Mer/Axl Kinase Inhibitors with In Vivo Efficacy

“…The latter yielded promising oxadiazole-based hit compounds (Figure 1) offering novelty and selectivity. 18 Chromane 1 had lower Mer potency (pIC 50 = 7.6) in a biochemical assay than imidazo [1,2-a]pyridine 2 (pIC 50 = 8.3), and this was rationalized when we obtained a crystal structure of 2 bound to the ATP binding site of Mer kinase (Figure 2). The imidazo [1,2-a]pyridine forms a clear hydrogen-bonding interaction with Met674 at the hinge region of the binding site, and the weaker hydrogen-bonding potential of the ether results in a less favorable interaction.…”

“…We performed a comprehensive screening campaign comprising a high-throughput screen (HTS) for TAM-selective leads and a complementary DNA-encoded library (DEL) screen against Mer kinase. The latter yielded promising oxadiazole-based hit compounds (Figure ) offering novelty and selectivity . Chromane 1 had lower Mer potency (pIC 50 = 7.6) in a biochemical assay than imidazo­[1,2- a ]­pyridine 2 (pIC 50 = 8.3), and this was rationalized when we obtained a crystal structure of 2 bound to the ATP binding site of Mer kinase (Figure ).…”

“…Our aim was to discover such a compound and explore its potential in cancer immunotherapy. In this paper, we describe the optimization of a key series that emerged from a comprehensive lead generation campaign 18 to give an in vivo probe compound, which demonstrated efficacy in preclinical models.…”

“…Biochemical assays for Mer, Axl, Tyro3, and Flt3 were performed using a Rapidfire liquid chromatography−mass spectrometry (LC−MS) method as previously described. 18 COS-7 Cell Assays. The pAxl ELISA assay was performed in a pcDNA Axl-FLAG transiently transfected Cos-7 (monkey: African green) cell line.…”

Pharmacological inhibition of MERTK induces in vivo retinal degeneration: a multimodal imaging ocular safety assessment

“…Biochemical assays for Mer, Axl, Tyro3 and Flt3 were performed using a Rapidfire LCMS method as previously described (Nissink et al 2021 ). Cellular assays for pMer, pAxl, pTyro3, pFLT3 were performed in transiently transfected Cos-7 (Monkey: African green) cell lines as previously described.…”