Effective treatment of chronic pain, in particular neuropathic pain, without the side effects that often accompany currently available treatment options is an area of significant unmet medical need. A phenotypic screen of mouse gene knockouts led to the discovery that adaptor protein 2-associated kinase 1 (AAK1) is a potential therapeutic target for neuropathic pain. The synthesis and optimization of structure–activity relationships of a series of aryl amide-based AAK1 inhibitors led to the identification of 59, a brain penetrant, AAK1-selective inhibitor that proved to be a valuable tool compound. Compound 59 was evaluated in mice for the inhibition of μ2 phosphorylation. Studies conducted with 59 in pain models demonstrated that this compound was efficacious in the phase II formalin model for persistent pain and the chronic-constriction-injury-induced model for neuropathic pain in rats. These results suggest that AAK1 inhibition is a promising approach for the treatment of neuropathic pain.

Adaptor protein 2-associated kinase 1 (AAK1) is a serine/threonine kinase that was identified as a therapeutic target for the potential treatment of neuropathic pain. Inhibition of AAK1 in the central nervous system, particularly within the spinal cord, was found to be the relevant site for achieving an antinociceptive effect. We previously reported that compound 7 is a brain-penetrant, AAK1 inhibitor that showed efficacy in animal models for neuropathic pain. One approach we took to improve upon the potency of 7 involved tying the amide back into the neighboring phenyl ring to form a bicyclic heterocycle. Investigation of the structure–activity relationships (SARs) of substituents on the resultant quinazoline and quinoline ring systems led to the identification of (S)-31, a brain-penetrant, AAK1-selective inhibitor with improved enzyme and cellular potency compared to 7. The synthesis, SAR, and in vivo evaluation of a series of quinazoline and quinoline-based AAK1 inhibitors are described herein.

Candesartan cilexetil (CC) is an angiotensin II-receptor blocker (ARB). The antihypertensive effect of CC 4-16 mg/day was as great as that of other once-daily dosage regimens. Candesartan cilexetil has high first-pass metabolism and low oral bioavailability. The bioavailability of such drugs may be significantly improved if delivered through the buccal route; hence mucosal delivery is one of the alternative methods of systemic drug delivery. This study’s objective was to develop mucoadhesive buccal tablets of candesartan cilexetil using carbopol-934P, hydroxyl propyl methyl cellulose (HPMC), Eudragit RLPO, and sodium carboxy methyl cellulose (Na-CMC) as mucoadhesive polymers. Prepared CC buccal tablet formulations were evaluated for an optimized system based on physicochemical properties, ex-vivo residence time, in-vitro, and ex vivo permeation studies. The evaluation parameters of the tablets were within the acceptable Pharmacopoeial limits. However, the swelling and bio-adhesive time were increased with increasing polymer concentrations. The in-vitro release research shown that buccal tablets with sodium carboxy methyl cellulose (Na-CMC) exhibited a higher release than all other formulations and have been considered as optimized CC formulation. The release mechanism from kinetic methods suggests that the drug release follows zero-order kinetics with a diffusion mechanism. Further, in-vivo research in animal fashions is required to prove the bioavailability performance of the formulation. Keywords: Candesartan cilexetil, mucoadhesive buccal tablets, first-pass metabolism, bioavailability.