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[P2–051]: IN VITRO CHARACTERIZATION OF TAK‐071: A NOVEL MUSCARINIC M 1 RECEPTOR‐POSITIVE ALLOSTERIC MODULATOR WITH LOW COOPERATIVITY
Author(s) -
Kimura Haruhide,
Shimizu Yuji,
Suzuki Atsushi,
Kurimoto Emi,
Mandai Takao,
Yamada Masami,
Sako Yuu
Publication year - 2017
Publication title -
alzheimer's and dementia
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 6.713
H-Index - 118
eISSN - 1552-5279
pISSN - 1552-5260
DOI - 10.1016/j.jalz.2017.06.700
Subject(s) - muscarinic acetylcholine receptor , chemistry , depolarization , allosteric regulation , receptor , membrane potential , neuroscience , biophysics , biology , biochemistry
Background: Muscarinic M1 receptor (M1R) is a promising target for CNS disorders with cholinergic deficits such as Alzheimer’s disease. We previously reported that the cooperativity (a-value) was a key to lower the risk of diarrhea by M1R positive allosteric modulators (M1PAMs). In this study, we characterized in vitro profiles of TAK-071, a novel M1R selective PAM with a low a-value and compared with that of T-662, an M1PAM with a high a-value. Methods:PAM parameters were assessed by using in vitro binding and functional analysis in Chinese hamster ovary cells stably expressing human M1R. Evaluation of mouse ileum contraction was conducted under the conditions to assess spontaneous activity or electric field stimulation (EFS)-induced activity by using the in vitro Magnus method. Electrophysiological experiments were performed by using current clamp recordings in slices of mouse medial prefrontal cortex. Results:TAK-071 had an inflection point (IP)-value of 2.7 nM, and showed an a-value of 199 for humanM1R with more than 3700-fold selectivity over other muscarinic receptor subtypes. T-662 also had potent M1PAM activity with an IP-value of 2.1 nM, and showed an a-value of 1786. In the in vitro Magnus method, T-662, but not TAK-071, strengthened spontaneous ileum contraction in a concentration-dependent manner, and augmented EFS-induced ileum contraction. Tonic activation of M1Rs is known to produce neuronal excitability through three actions; depolarizing the resting membrane potential, suppressing the after hyperpolarization that follows the spike, and revealing the afterdepolarization (ADP) that can initiate repetitive firing. Among then, T-662 induced all three actions, while TAK-071 selectively induced ADP in layer 5 pyramidal neurons. Conclusions: We searched M1PAMs with low a-value and discovered TAK-071. TAK-071 induced ADP in layer 5 pyramidal neurons, while it did not cause mouse ileum contraction in vitro. Thus, TAK-071may have a promising therapeutic potential for CNS disorders without causing diarrhea. TAK-071 is currently in clinical development (ClinicalTrials. gov, Identifier: NCT02769065). total number of participants 297