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The receptor tyrosine kinase rearranged during transfection (RET) is an oncogenic driver activated in multiple cancers, including non-small cell lung cancer (NSCLC), medullary thyroid cancer (MTC), and papillary thyroid cancer. No approved therapies have been designed to target RET; treatment has been limited to multikinase inhibitors (MKI), which can have significant off-target toxicities and limited efficacy. BLU-667 is a highly potent and selective RET inhibitor designed to overcome these limitations. In vitro , BLU-667 demonstrated ≥10-fold increased potency over approved MKIs against oncogenic RET variants and resistance mutants. In vivo , BLU-667 potently inhibited growth of NSCLC and thyroid cancer xenografts driven by various RET mutations and fusions without inhibiting VEGFR2. In first-in-human testing, BLU-667 significantly inhibited RET signaling and induced durable clinical responses in patients with RET -altered NSCLC and MTC without notable off-target toxicity, providing clinical validation for selective RET targeting. Significance: Patients with RET -driven cancers derive limited benefit from available MKIs. BLU-667 is a potent and selective RET inhibitor that induces tumor regression in cancer models with RET mutations and fusions. BLU-667 attenuated RET signaling and produced durable clinical responses in patients with RET -altered tumors, clinically validating selective RET targeting. Cancer Discov; 8(7); 836-49. ©2018 AACR. See related commentary by Iams and Lovly, p. 797 This article is highlighted in the In This Issue feature, p. 781 ., (©2018 American Association for Cancer Research.)

One of the challenges for targeting B-Raf(V600E) with small molecule inhibitors had been achieving adequate selectivity over the wild-type protein B-Raf(WT), as inhibition of the latter has been associated with hyperplasia in normal tissues. Recent studies suggest that B-Raf inhibitors inducing the 'DFG-in/αC-helix-out' conformation (Type IIB) likely will exhibit improved selectivity for B-Raf(V600E). To explore this hypothesis, we transformed Type IIA inhibitor (1) into a series of Type IIB inhibitors (sulfonamides and sulfamides 4-6) and examined the SAR. Three selectivity indices were introduced to facilitate the analyses: the B-Raf(V600E)/B-Raf(WT) biochemical ((b)S), cellular ((c)S) selectivity, and the phospho-ERK activation ((p)A). Our data indicates that α-branched sulfonamides and sulfamides show higher selectivities than the linear derivatives. We rationalized this finding based on analysis of structural information from the literature and provided evidence for a monomeric B-Raf-inhibitor complex previously hypothesized to be responsible for the desired B-Raf(V600E) selectivity., (Copyright © 2016 Elsevier Ltd. All rights reserved.)

mTOR is a critical regulator of cellular signaling downstream of multiple growth factors. The mTOR/PI3K/AKT pathway is frequently mutated in human cancers and is thus an important oncology target. Herein we report the evolution of our program to discover ATP-competitive mTOR inhibitors that demonstrate improved pharmacokinetic properties and selectivity compared to our previous leads. Through targeted SAR and structure-guided design, new imidazopyridine and imidazopyridazine scaffolds were identified that demonstrated superior inhibition of mTOR in cellular assays, selectivity over the closely related PIKK family and improved in vivo clearance over our previously reported benzimidazole series., (Copyright © 2012. Published by Elsevier Ltd.)

Inhibition of the VEGF signaling pathway has become a valuable approach in the treatment of cancers. Guided by X-ray crystallography and molecular modeling, a series of 2-aminobenzimidazoles and 2-aminobenzoxazoles were identified as potent inhibitors of VEGFR-2 (KDR) in both enzymatic and HUVEC cellular proliferation assays. In this report we describe the synthesis and structure-activity relationship of a series of 2-aminobenzimidazoles and benzoxazoles, culminating in the identification of benzoxazole 22 as a potent and selective VEGFR-2 inhibitor displaying a good pharmacokinetic profile. Compound 22 demonstrated efficacy in both the murine matrigel model for vascular permeability (79% inhibition observed at 100 mg/kg) and the rat corneal angiogenesis model (ED(50) = 16.3 mg/kg).

Inhibition of angiogenesis is a promising and clinically validated approach for limiting tumor growth and survival. The receptor tyrosine kinase Tie-2 is expressed almost exclusively in the vascular endothelium and is required for developmental angiogenesis and vessel maturation. However, the significance of Tie-2 signaling in tumor angiogenesis is not well understood. In order to evaluate the therapeutic utility of inhibiting Tie-2 signaling, we developed a series of potent and orally bioavailable small molecule Tie-2 kinase inhibitors with selectivity over other kinases, especially those that are believed to be important for tumor angiogenesis. Our earlier work provided pyridinyl pyrimidine 6 as a potent, nonselective Tie-2 inhibitor that was designed on the basis of X-ray cocrystal structures of KDR inhibitors 34 (triazine) and 35 (nicotinamide). Lead optimization resulted in pyridinyl triazine 63, which exhibited >30-fold selectivity over a panel of kinases, good oral exposure, and in vivo inhibition of Tie-2 phosphorylation.