Synthesis and evaluation of in vivo anti‐hypothermic effect of all stereoisomers of the thyrotropin‐releasing hormone mimetic: Rovatirelin Hydrate

Abstract

We discovered the orally active thyrotropin‐releasing hormone (TRH) mimetic: (4S,5S)‐5‐methyl‐N‐{(2S)‐1‐[(2R)‐2‐methylpyrrolidin‐1‐yl]‐1‐oxo‐3‐(1,3‐thiazol‐4‐yl)propan‐2‐yl}‐2‐oxo‐1,3‐oxazolidine‐4‐carboxamide 1 (rovatirelin). The central nervous system (CNS) effect of rovatirelin after intravenous (iv) administration is 100‐fold higher than that of TRH. As 1 has four asymmetric carbons in its molecule, there are 16 stereoisomers. We synthesized and evaluated the anti‐hypothermic effect of all stereoisomers of 1, which has the (4S),(5S),(2S),(2R) configuration from the N‐terminus to the C‐terminus, in order to clarify the structure−activity relationship (SAR) of stereoisomers. The (4R),(5R),(2R),(2S)‐isomer 16 did not show any anti‐hypothermic effect. Only the (4S),(5S),(2S),(2S)‐isomer 10, which has the (2S)‐2‐methylpyrrolidine moiety at the C‐terminus showed the anti‐hypothermic effect similar to 1. Stereoisomers, which have the (5R) configuration of the oxazolidinone at the N‐terminus and the (2R) configuration at the middle‐part, showed a much lower anti‐hypothermic effect than that of 1. On the other hand, stereoisomers, which have the (4R) configuration of the oxazolidinone at the N‐terminus or the (2S) configuration of the C‐terminus, have little influence on the anti‐hypothermic effect.

Synthesis and Evaluation of <i>in Vivo</i> Anti-hypothermic Effect of the N- and C-Terminus Modified Thyrotropin-Releasing Hormone Mimetic: [(4<i>S</i>,5<i>S</i>)-(5-Methyl-2-oxooxazolidine-4-yl)carbonyl]-[3-(thiazol-4-yl)-L-alanyl]-L-prolinamide

“…TRH mimetics 54-59 were synthesized based on our previous method 34) (Chart 4). The C-terminus fragments 40-43 were coupled with N-Boc-3-(thiazol-4-yl)-L-alanine 44 44,45) to afford N-Boc dipeptide 45, 46 Physicochemical Properties and Anti-hypothermic Effects of TRH Mimetics The physicochemical properties were estimated by c log P, which is the log of the octanol/ water partition coefficient, calculated using ChemBioDraw Ultra. TRH and TRH analogues promote the secretion of catecholamine against reserpine in the brain and increase body a) c log P was calculated using ChemBioDraw Ultra 14.0. b) Administration doses of TRH, 1 or TRH mimetics were 50, 5.0 or 10 µmol/kg, respectively.…”

“…Moreover, the anti-hypothermic effect of each compound was calculated as the ΔAUC 0-7h of each compound and saline. 34,46) The anti-hypothermic effects (ΔAUC 0-7h ) of TRH mimetics are shown with the lipophilicity (c log P) and administration doses in Table 1. Rectal temperature-time graphs of TRH mimetics and the detailed calculation method of anti-hypothermic effects are given in the Supplementary Materials (Figure S1-S16).…”

New Efforts to Demonstrate the Successful Use of TRH as a Therapeutic Agent

“…By testing the proven ability of TRH to antagonize reserpine-induced hypothermia, the efficacy of different designed and synthesized analogs has been studied in vivo by oral and intravenous delivery. Kobayashi et al [ 22 ] successfully obtained TRH stereoisomers with characteristics superior to those of the native peptide and some of its known analogs, for use in the clinic. They tested different analogs in mice with hypothermia using subcutaneous injections of reserpine, trying to mimic TRH’s central action in increasing the mice’s temperatures [ 22 , 23 ].…”

“…Kobayashi et al [ 22 ] successfully obtained TRH stereoisomers with characteristics superior to those of the native peptide and some of its known analogs, for use in the clinic. They tested different analogs in mice with hypothermia using subcutaneous injections of reserpine, trying to mimic TRH’s central action in increasing the mice’s temperatures [ 22 , 23 ]. This central effect of TRH has previously been described, when administration of the peptide reversed ethanol-induced hypothermia in mice [ 36 ].…”

“…The findings of Kobayashi et al [ 22 ] support that the potency of reversing the reserpine hypothermic role of TRH may successfully be 100 times more potent when using some of the new tested TRH analogs in mice subcutaneously injected with reserpine that show a colonic temperature of 30 °C or less [ 22 ]. Another advantage of some TRH mimetics is that they do not have endocrine effects, which is relevant because hypothalamic PVN TRH directs the functioning of the thyroid axis and ultimately increases serum T 3 and T 4 levels.…”