Acetyl-CoA
carboxylase (ACC) inhibitors offer significant potential
for the treatment of type 2 diabetes mellitus (T2DM), hepatic steatosis,
and cancer. However, the identification of tool compounds suitable
to test the hypothesis in human trials has been challenging. An advanced
series of spirocyclic ketone-containing ACC inhibitors recently reported
by Pfizer were metabolized in vivo by ketone reduction, which complicated
human pharmacology projections. We disclose that this metabolic reduction
can be greatly attenuated through introduction of steric hindrance
adjacent to the ketone carbonyl. Incorporation of weakly basic functionality
improved solubility and led to the identification of 9 as a clinical candidate for the treatment of T2DM. Phase I clinical
studies demonstrated dose-proportional increases in exposure, single-dose
inhibition of de novo lipogenesis (DNL), and changes in indirect calorimetry
consistent with increased whole-body fatty acid oxidation. This demonstration
of target engagement validates the use of compound 9 to
evaluate the role of DNL in human disease.
The synthesis of 4',6'-dihydrospiro[piperidine-4,5'-pyrazolo[3,4-c]pyridin]-7'(2'H)-one-based acetyl-CoA carboxylase inhibitors is reported. The hitherto unknown N-2 tert-butyl pyrazolospirolactam core was synthesized from ethyl 3-amino-1H-pyrazole-4-carboxylate in a streamlined 10-step synthesis requiring only one chromatography procedure. The described synthetic strategy provides pyrazolo-fused spirolactams from halogenated benzylic arenes and cyclic carboxylates. Key steps include a regioselective pyrazole alkylation providing the N-2 tert-butyl pyrazole and a Curtius rearrangement under both conventional and flow conditions to install the hindered amine via a stable and isolable isocyanate. Finally, a Parham-type cyclization was used to furnish the desired spirolactam. An analogous route provided efficient access to the related N-1 isopropyl lactam series. Elaboration of the lactam cores via amidation enabled synthesis of novel ACC inhibitors and the identification of potent analogues.
Acetyl-CoA carboxylase (ACC) catalyzes the rate-determining step in de novo lipogenesis and plays a crucial role in the regulation of fatty acid oxidation. Alterations in lipid metabolism are believed to contribute to insulin resistance; thus inhibition of ACC offers a promising option for intervention in type 2 diabetes mellitus. Herein we disclose a series of ACC inhibitors based on a spirocyclic pyrazololactam core. The lactam series has improved chemical and metabolic stability relative to our previously reported pyrazoloketone series, while retaining potent inhibition of ACC1 and ACC2. Optimization of the pyrazole and amide substituents led to quinoline amide 21, which was advanced to preclinical development.
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