Discovery of novel 2-phenylamino-4-prolylpyrimidine derivatives as TRK/ALK dual inhibitors with promising antitumor effects

Recent advances in the discovery of tropomyosin receptor kinases TRKs inhibitors: A mini review

The tropomyosin receptor tyrosine kinases (TRKs) control the cell proliferation mainly in the nervous system and are encoded by NTRK genes. Fusion and mutation of NTRK genes were detected in various types of cancers. Many small molecules TRK inhibitors have been discovered during the last two decades and some of them have entered clinical trials. Moreover, two of these inhibitors; larotrectinib and entrectinib; were approved by FDA for the treatment of TRK-fusion positive solid tumors. However, mutation of TRK enzymes resulted in resistance to both drugs. Therefore, next generation TRK inhibitors were discovered to overcome the acquired drug resistance. Additionally, the off-target and on-target adverse effects on the brain initiated the need for selective TRK subtype inhibitors. Indeed, some molecules were recently reported as selective TRKA or TRKC inhibitors with minimal CNS side effects. The current review highlighted the efforts done during the last three years in the design and discovery of novel TRK inhibitors.

Design, synthesis and anti-tumor efficacy of novel phenyl thiazole/triazole derivatives as selective TrkA inhibitors

Aiming to develop novel tropomyosin receptor kinase A (TrkA) inhibitors, a scaffold hopping strategy was utilized by transforming the fused indazole of Entrectinib to phenyl triazole/thiazole skeleton to obtain compounds 7a-7 h and 13a-13 h. In the light of MTT assay, phenyl triazole derivatives 7a-7 h exhibited moderate anti-proliferative activities against KM-12 cells with the IC₅₀ values of 1.78-17.51 μM, while phenyl thiazole derivatives 13a-13 h showed the weaker efficacy. Further structure-guided optimizations by combining the phenyl triazole skeleton with 3,5‑difluorophenyl and 3-carbamoyl-4-piperazinylaniline moiety led to compounds 19a-19d and 20. Eventually, 19c bearing (2-(4-methylpiperazin-1-yl)phenyl)(morpholino)methanone moiety exhibited excellent anti-proliferative activity on TrkA-positive KM-12 cells with IC₅₀ value of 0.17 μM. Meanwhile, compound 19c showed the inhibitory potency on TrkA with IC₅₀ value of 1.6 nM, and displayed higher selectivity on TrkA over TrkB (IC₅₀ = 12.3 nM) and TrkC (IC₅₀ = 18.4 nM). The dedicated wound healing and colony formation assay indicated that the optimal compound 19c could suppress migration and significantly inhibit KM-12 cell colony formation in a dose-dependent manner. In addition, 19c could weakly induce apoptosis of KM-12 cell in immunofluorescent staining analysis. Taken together, the above results suggest 19c as a novel TrkA inhibitor worthy of further profiling.

Discovery of Next-Generation Tropomyosin Receptor Kinase Inhibitors for Combating Multiple Resistance Associated with Protein Mutation

Tropomyosin receptor kinase (TRK) inhibition is an effective therapeutic approach for treatment of a variety of cancers. Despite the use of first-generation TRK inhibitor (TRKI) larotrectinib (1) resulting in significant therapeutic response in patients, acquired resistance develops invariably. The emergence of secondary mutations occurring at the solvent-front, xDFG, and gatekeeper regions of TRK represents a common mechanism for acquired resistance. However, xDFG mutations remain insensitive to second-generation macrocyclic TRKIs selitrectinib (3) and repotrectinib (4) designed to overcome the resistance mediated by solvent-front and gatekeeper mutations. Here, we report the structure-based drug design and discovery of a next-generation TRKI. The structure-activity relationship studies culminated in the identification of a promising drug candidate 8 that showed excellent in vitro potency on a panel of TRK mutants, especially TRKA^G667C in the xDFG motif, and improved in vivo efficacy than 1 and 3 in TRK wild-type and mutant fusion-driven tumor xenograft models, respectively.