Optimization of a Pyrimidinone Series for Selective Inhibition of Ca²⁺/Calmodulin-Stimulated Adenylyl Cyclase 1 Activity for the Treatment of Chronic Pain

Abstract

Adenylyl cyclase type 1 (AC1) is involved in signaling for chronic pain sensitization in the central nervous system and is an emerging target for the treatment of chronic pain. AC1 and a closely related isoform AC8 are also implicated to have roles in learning and memory signaling processes. Our team has carried out cellular screening for inhibitors of AC1 yielding a pyrazolyl-pyrimidinone scaffold with low micromolar potency against AC1 and selectivity versus AC8. Structure–activity relationship (SAR) studies led to analogues with cellular IC50 values as low as 0.25 μM, selectivity versus AC8 and other AC isoforms as well as other common neurological targets. A representative analogue displayed modest antiallodynic effects in a mouse model of inflammatory pain. This series represents the most potent and selective inhibitors of Ca2+/calmodulin-stimulated AC1 activity to date with improved drug-like physicochemical properties making them potential lead compounds for the treatment of inflammatory pain.

Protein-protein interaction-based high throughput screening for adenylyl cyclase 1 inhibitors: Design, implementation, and discovery of a novel chemotype

“…We selected 13 dithiophene analogs including 15 for cellular testing against inhibition of Ca 2+ /CaM-stimulated AC1 and/or AC8 activity. This scaffold contains a central thiophene ring linked to an aromatic ring (furan) via an amide, which directly overlaps with the benzamide series ( Scott et al, 2022 ). The central thiophene is also linked to a central carbon bound to the second aromatic ring (usually thiophene), with a variation of different heterocycles (piperazine, piperidine, morpholine, or pyridine).…”

“…Through development of a novel fluorescence polarization assay, screening of over 21,000 compounds for inhibition of AC1 and/or AC8, and validation of activity in novel NanoBiT assays, we have discovered a novel dithiophene scaffold. Interestingly, the dithiophene scaffold shares structural similarities with the AC1 inhibitor benzamide series ( Scott et al, 2022 ). Unlike the benzamide series, however, many compounds among this small dithiophene set were not selective for AC1 over AC8.…”

“…Frontiers in Pharmacology frontiersin.org Lastly, we observed that compound 15 shared some structural overlap with a benzamide series of compounds that are known inhibitors of AC1 activity with selectivity vs. AC8 (Scott et al, 2022). We selected 13 dithiophene analogs including 15 for cellular testing against inhibition of Ca 2+ /CaM-stimulated AC1 and/or AC8 activity.…”

“…Moreover, chronic inflammatory pain stimuli increases AC1 activity in mice, while AC1 KO mice had significantly less chronic pain ( Wei et al, 2002 ; Vadakkan et al, 2006 ; Corder et al, 2013 ). Studies have also reported that pharmacologic inhibition of AC1 also elicits a reduction in responses to inflammatory pain stimuli ( Wang et al, 2011 ; Brust et al, 2017 ; Kaur et al, 2019 ; Scott et al, 2022 ). The combination of these findings support AC1 as a promising target for treating chronic inflammatory pain conditions; however, they also emphasize the importance of selectively targeting AC1 over other AC isoforms, most notably AC8, which is co-localized in the same neuronal tissues ( Defer et al, 2000 ).…”

Ca2+-stimulated adenylyl cyclases as therapeutic targets for psychiatric and neurodevelopmental disorders

“…The oxadiazole-based AC10065 at micromolar concentrations can suppress both ADCY1 and ADCY8 (Kaur et al, 2019). New drug screening followed by structure optimization has revealed several pyrimidinonebased compounds that show selectivity of ADCY1 over other ADCYs with an IC50 at the sub-micromolar level (Scott et al, 2022). As these newly identified ADCY1 inhibitors show moderate therapeutic efficacy in an inflammatory pain model (Scott et al, 2022), further optimization may be needed.…”