Identification and structural analysis of a selective tropomyosin receptor kinase C (TRKC) inhibitor.

Tropomyosin receptor kinases (TRKs) are a family of TRKA, TRKB and TRKC isoforms. It has been widely reported that TRKs are implicated in a variety of tumors with several Pan-TRK inhibitors currently being used or evaluated in clinical treatment. However, off-target adverse events frequently occur in the clinical use of Pan-TRK inhibitors, which result in poor patient compliance, even drug discontinuation. Although a subtype-selectivity TRK inhibitor may avert the potential off-target adverse events and can act as a more powerful tool compound in the biochemical studies on TRKs, the high sequence similarities of TRKs hinder the development of subtype-selectivity TRK inhibitors. For example, no selective TRKC inhibitor has been reported. Herein, a selective TRKC inhibitor (L13) was disclosed, with potent TRKC inhibitory activity and 107.5-/34.9-fold selectivity over TRKA/B (IC50 TRKA/B/C = 1400 nM, 454 nM, 13 nM, respectively). Extensive molecular dynamics simulations illustrated that key interactions of L13 with the residues and diversely conserved water molecules in the ribose regions of different TRKs may be the structural basis of selectivity. This will provide inspiring insights into the development of subtype-selectivity TRK inhibitors. Moreover, L13 could serve as a tool compound to investigate the distinct biological functions of TRKC and a starting point for further research on drugs specifically targeting TRKC.

Discovery of a Potent FLT3 Inhibitor (LT-850-166) with the Capacity of Overcoming a Variety of FLT3 Mutations.

Secondary mutations of FLT3 have become the main mechanism of FLT3 inhibitor resistance that presents a significant clinical challenge. Herein, a series of pyrazole-3-amine derivatives were synthesized and optimized to overcome the common secondary resistance mutations of FLT3. The structure-activity relationship and molecular dynamics simulation studies illustrated that the ribose region of FLT3 could be occupied to help address the obstacle of secondary mutations. Among those derivatives, compound 67 exhibited potent and selective inhibitory activities against FLT3-ITD-positive acute myeloid leukemia (AML) cells and possessed equivalent potency against transformed BaF3 cells with a variety of secondary mutations. Besides, cellular mechanism assays demonstrated that 67 strongly inhibited phosphorylation of FLT3 and its downstream signaling factors, as well as induced cell cycle arrest and apoptosis in MV4-11 cells. In the MV4-11 xenograft models, 67 exhibited potent antitumor potency without obvious toxicity. Taken together, these results demonstrated that 67 might be a drug candidate for the treatment of FLT3-ITD-positive AML.