Synthesis, high-throughput screening and pharmacological characterization of β–lactam derivatives as TRPM8 antagonists

Abstract

The mammalian transient receptor potential melastatin channel 8 (TRPM8), highly expressed in trigeminal and dorsal root ganglia, mediates the cooling sensation and plays an important role in the cold hypersensitivity characteristic of some types of neuropathic pain, as well as in cancer. Consequently, the identification of selective and potent ligands for TRPM8 is of great interest. Here, a series of compounds, having a β-lactam central scaffold, were prepared to explore the pharmacophore requirements for TRPM8 modulation. Structure-activity studies indicate that the minimal requirements for potent β-lactam-based TRPM8 blockers are hydrophobic groups (benzyl preferentially or tBu) on R1, R2, R3 and R5 and a short N-alkyl chain (≤3 carbons). The best compounds in the focused library (41 and 45) showed IC50 values of 46 nM and 83 nM, respectively, in electrophysiology assays. These compounds selectively blocked all modalities of TRPM8 activation, i.e. menthol, voltage, and temperature. Molecular modelling studies using a homology model of TRPM8 identified two putative binding sites, involving networks of hydrophobic interactions, and suggesting a negative allosteric modulation through the stabilization of the closed state. Thus, these β-lactams provide a novel pharmacophore scaffold to evolve TRPM8 allosteric modulators to treat TRPM8 channel dysfunction.

Highly functionalized β-lactams and 2-ketopiperazines as TRPM8 antagonists with antiallodynic activity

“…However, in the case of distereoisomeric mixtures (ab), the exact contribution to the activity of each individual isomer cannot be assessed. As previously described for the first generation of β-lactam TRPM8 antagonists 37 , the phenyl group at position 4 is important for Ca 2+ entrance inhibition, since the 4-CH 3 derivative 39a was one order of magnitude less active than the 4-Bn analogue 29a.…”

“…As previously described for Phe-Asp conjugates 37 , the preparation of chloroacetyl derivatives 10 and 11 started by a Mitsunobu reaction between Ns-L-Phe-OBn (3) and the corresponding Z-phenylalaninol derivative (4 or 5) to give compounds 6 and 7 (Scheme 1). Then, the removal of the nosyl group afforded NH derivatives 8 and 9 that, finally, were reacted with chloroacetyl chloride to give key intermediates 10 and 11 (Scheme 1).…”

“…1) was more potent than the longer Glu analogue 2 (n = 3, Fig. 1), while all the three benzyl and the Boc hydrophobic moieties are important for activity 37 .…”

“…In this context, we have recently described a series of compounds derived from Phe and Asp/Glu amino acid conjugates and having a monocyclic β-lactam central core, which were able to potently and selectively inhibit the activation of TRPM8 by menthol, cool and voltage 37 . Among this series, the shorter Asp derivative 1 (n = 2, Fig.…”

Impact of suggestion on the human experimental model of cold hyperalgesia after topical application of high‐concentration menthol [40%]

“…The topical application of menthol has been characterized and evaluated thoroughly as a human experimental model of pain and hyperalgesia (Klein et al., ; Mahn et al., ; Andersen et al., , ). Menthol induces cold and mechanical hyperalgesia (Klein et al., ) and activates the transient receptor potential (TRP) melastin 8 (TRPM8; de la Torre‐Martinez et al., ) channel leading to activation and sensitization of afferent nociceptive neurons (Klein et al., ).…”