Hirotaka Kashiwagi

Novel nonsecosteroidal vitamin D3 carboxylic acid analogs for osteoporosis, and SAR analysis.

Novel vitamin D(3) analogs with carboxylic acid were explored, focusing on a nonsecosteroidal analog, LG190178, with a bisphenyl skeleton. From X-ray analysis of these analogs with vitamin D receptor (VDR), the carboxyl groups had very unique hydrogen bonding interactions in VDR and mimicked 1α-hydroxy group and/or 3β-hydroxy group of 1α,25-dihydroxyvitamin D(3). A highly potent analog, 6a, with good in vitro activity and pharmacokinetic profiles was identified from an SAR study. Compound 6a showed significant prevention of bone loss in a rat osteoporosis model by oral administration.

A series of nonsecosteroidal vitamin D receptor agonists for osteoporosis therapy.

In an extension of our study on gamma hydroxy carboxylic acid analogs, we explored a series of nonsecosteroidal vitamin D receptor (VDR) agonists in which 1,3-diol of 1,25(OH)2D3 had been replaced by aryl acetic acid. These analogs showed very potent activity in vitro compared with 1,25(OH)2D3. An X-ray analysis of 8d showed that the inserted phenyl ring well mimicked the folded methylene linker of the gamma hydroxy carboxylic acid moiety but the carboxylic acid of 8d interacted with VDR in a different manner from gamma hydroxy carboxylic acids. Through our in vivo screening in an osteoporosis rat model using immature rats, we identified a potent active vitamin D3 analog, compound 7e. In mature rats of the same model, compound 7e also showed good PK profiling and excellent ability to prevent bone mineral density loss without severe hypercalcemia. Our nonsecosteroidal VDR agonist 7e (CH5036249) could be a possible new drug candidate for treating osteoporosis in human.

Systematic SAR study of the side chain of nonsecosteroidal vitamin D3 analogs

A series of nonsecosteroidal vitamin D(3) analogs with carboxylic acid were explored. Through our systematic SAR studies on the side chain moiety, compound 6b was identified as the optimal compound showing excellent vitamin D receptor (VDR) agonistic activity. Compound 6b had the diethyl group in the terminal which was bound by (E)-olefin linker to the bisphenyl core. Calculating the volume of the side chain showed that the diethyl group in 6b filled the hydrophobic region of VDR with the ideal packing coefficient based on the 55% rule, and that this resulted in the most potent in vitro activity.

Discovery of a potent and highly selective transforming growth factor β receptor-associated kinase 1 (TAK1) inhibitor by structure based drug design (SBDD).

A novel thienopyrimidinone analog was discovered as a potent and highly selective TAK1 inhibitor using the SBDD approach. TAK1 plays a key role in inflammatory and immune signaling, so TAK1 is considered to be an attractive molecular target for the treatment of human diseases (inflammatory disease, cancer, etc.). After the hit compound had been obtained, our modifications successfully increased TAK1 inhibitory activity and solubility, but metabolic stability was still unsatisfactory. To improve metabolic stability, we conducted metabolic identification. Although the obtained metabolite was fortunately a potent TAK1 inhibitor, its kinase selectivity was low. Subsequently, to achieve high kinase selectivity, we used SBDD to follow two strategies: one targeting unique amino acid residues in TAK1, especially the combination of Ser111 and Asn114; the other decreasing the interaction with Tyr106 at the hinge position in TAK1. As expected, our designed compound showed an excellent kinase selectivity profile in both an in-house and a commercially available panel assay of over 420 kinases and also retained its potent TAK1 inhibitory activity (TAK1 IC50=11nM).

Effects of fluorines on nonsecosteroidal vitamin D receptor agonists

From our research of nonsecosteroidal vitamin D(3) derivatives with gamma hydroxy carboxylic acid, we identified compound 6, with two CF(3) groups in the side chain, as a most potent vitamin D receptor (VDR) agonist that shows superagonistic activity in VDRE reporter gene assay, MG-63 osteocalcin production assay and HL-60 cell differentiation assay. Compound 6 demonstrated that fluorination is as effective in the case of our nonsecosteroidal scaffold as in the case of secosteroidal VD(3) analogs. X-ray analysis of the VDR with compound 6 revealed all of the six fluorine atoms of the hexafluoropropanol (HFP) moiety in the side chain effectively interacting with the VDR by both steric (van der Waals) and electrostatic (hydrogen bond, NH-F and CH-F) interactions. The HFP moiety of 6 effectively interacts with helix 12 (H12) of the VDR and stabilizes the position and the orientation of H12, which could result in stabilizing the coactivator and enhancing the VDR agonistic activity.

Facile Construction of the 7,8‐Olefin Linkage in Vitamin D3: A Practical Synthesis Benefiting the Vitamin D3 Analog Study

Abstract A facile procedure for construction of the 7,8‐olefin linkage in vitamin D3 is described. Treatment of a mixture of A‐ring phosphine oxide and CD‐ring ketone in THF with lithium hexamethyldisilazide (LHMDS) at −20°C followed by gradual heating to 50°C gives the key intermediate of vitamin D3 analogs in excellent yield. This simplified procedure makes possible small‐scale synthesis benefiting the vitamin D3 analog study.

Identification of a selective inhibitor of transforming growth factor β-activated kinase 1 by biosensor-based screening of focused libraries

Transforming growth factor-β activated kinase 1 (TAK1), a member of the mitogen-activated protein kinase kinase kinase family, plays an essential role in mediating signals from various pro-inflammatory cytokines and therefore may be a good target for developing anti-inflammation agents. Herein, we report our efforts to identify TAK1 inhibitors with a good selectivity profile with which to initiate medicinal chemistry. Instead of resorting to a high-throughput screening campaign, we performed biosensor-based biophysical screening for a limited number of compounds by taking advantage of existing knowledge on kinase inhibitors. Rather than focusing on one specific inhibition mode, we searched for three different types, Type I (ATP-competitive, DFG-in), Type II (DFG-out), and Type III binders (non-ATP competitive) in parallel, and succeeded in identifying candidates in all three categories efficiently and rapidly. Finally, the biosensor-based binding kinetics for the active and inactive forms of TAK1 were measured to prioritize the Type I and Type II inhibitors. The effort resulted in the identification of a new TAK1-selective Type I compound with a thienopyrimidine scaffold that served as a good starting point for medicinal chemistry.