Design, synthesis and biological evaluation of pyrazolo[3,4-b]pyridine derivatives as TRK inhibitors

ω-transaminase-catalyzed synthesis of (R)-2-(1-aminoethyl)-4-fluorophenol, a chiral intermediate of novel anti-tumor drugs

The chiral amine (R)-2-(1-aminoethyl)-4-fluorophenol has attracted increasing attentions in recent years in the field of pharmaceuticals because of its important use as a building block in the synthesis of novel anti-tumor drugs targeting tropomyosin receptor kinases. In the present study, a ω-transaminase (ωTA) library consisting of 21 (R)-enantioselective enzymes was constructed and screened for the asymmetric biosynthesis of (R)-2-(1-aminoethyl)-4-fluorophenol from its prochiral ketone. Using (R)-α-methylbenzylamine, D-alanine, or isopropylamine as amino donor, 18 ωTAs were identified with target activity and the enzyme AbTA, which was originally identified from Arthrobacter sp. KNK168, was found to be a potent candidate. The E. coli whole cells expressing AbTA could be used as catalysts. The optimal temperature and pH for the activity were 35-40 °C and pH8.0, respectively. Simple alcohols (such as ethanol, isopropanol, and methanol) and dimethyl sulfoxide were shown to be good cosolvents. High activities were detected when using ethanol and dimethyl sulfoxide at the concentrations of 5-20%. In the scaled-up reaction of 1-liter containing 13 mM ketone substrate, about 50% conversion was achieved in 24 h. 6.4 mM (R)-2-(1-aminoethyl)-4-fluorophenol was generated. After a simple and efficient process of product isolation and purification (with 98.8% recovery), 0.986 g yellowish powder of the product (R)-2-(1-aminoethyl)-4-fluorophenol with high (R)-enantiopurity (up to 100% enantiomeric excess) was obtained. This study established an overall process for the biosynthesis of the high value pharmaceutical chiral amine (R)-2-(1-aminoethyl)-4-fluorophenol by ωTA. Its applicable potential was exemplified by gram-scale production.

Design of new small molecules derived from indolin-2-one as potent TRKs inhibitors using a computer-aided drug design approach

Tropomyosin receptor kinase (TRKs) enzymes are responsible for cancers associated with the neurotrophic tyrosine kinase receptor gene fusion and are identified as effective targets for anticancer drug discovery. A series of small-molecule indolin-2-one derivatives showed remarkable biological activity against TRKs enzymatic activity. These small molecules could have an excellent profile for pharmaceutical application in the treatment of cancers caused by TRKs activity. The aim of this study is to modify the structure of these molecules to obtain new molecules with improved TRK inhibitory activity and pharmacokinetic properties favorable to the design of new drugs. Based on these series, we carried out a 3D-QSAR study. As a result, robust and reliable CoMFA and CoMSIA models are developed and applied to the design of 11 new molecules. These new molecules have a biological activity superior to the most active molecule in the starting series. The eleven designed molecules are screened using drug-likeness, ADMET proprieties, molecular docking, and MM-GBSA filters. The results of this screening identified the T1, T3, and T4 molecules as the best candidates for strong inhibition of TRKs enzymatic activity. In addition, molecular dynamics simulations are performed for TRK free and complexed with ligands T1, T3, and T4 to evaluate the stability of ligand-protein complexes over the simulation time. On the other hand, we proposed experimental synthesis routes for these newly designed molecules. Finally, the designed molecules T1, T2, and T3 have great potential to become reliable candidates for the conception of new drug inhibitors of TRKs.Communicated by Ramaswamy H. Sarma.

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.