Neutral sphingomyelinase 2 inhibitors based on the pyrazolo[1,5-a]pyrimidin-3-amine scaffold

Area of Science:

• Medicinal Chemistry
• Pharmacology
• Enzyme Inhibition

Background:

• Neutral sphingomyelinase 2 (nSMase2) is a key enzyme regulating ceramide production and is implicated in various diseases.
• Current nSMase2 inhibitors, like PDDC, are valuable tools but new scaffolds are sought for improved therapeutics.
• Larotrectinib identified the pyrazolo[1,5-a]pyrimidine ring as a potential nSMase2 inhibitory scaffold.

Purpose of the Study:

• To explore the pyrazolo[1,5-a]pyrimidine scaffold as a replacement for the imidazo[1,2-b]pyridazine core in nSMase2 inhibitors.
• To synthesize and evaluate novel pyrazolo[1,5-a]pyrimidine derivatives for their nSMase2 inhibitory activity.
• To identify potent, metabolically stable, and orally bioavailable nSMase2 inhibitors.

Main Methods:

• Synthesis of a series of pyrazolo[1,5-a]pyrimidin-3-amine derivatives.
• In vitro testing of synthesized compounds for human nSMase2 inhibitory potency.
• Evaluation of lead compounds for metabolic stability in liver microsomes and oral bioavailability.
• Assessment of brain-to-plasma ratio for selected compounds.

Main Results:

• Several synthesized pyrazolo[1,5-a]pyrimidine compounds demonstrated superior nSMase2 inhibitory potency compared to PDDC.
• Compound 11j (N,N-dimethyl-5-morpholinopyrazolo[1,5-a]pyrimidin-3-amine) exhibited significant nSMase2 inhibition.
• Compound 11j displayed favorable metabolic stability in liver microsomes and good oral availability.
• 11j possessed a promising brain-to-plasma ratio, indicating potential for central nervous system penetration.

Conclusions:

• The pyrazolo[1,5-a]pyrimidine scaffold is a viable and effective core for developing novel nSMase2 inhibitors.
• Compound 11j represents a promising lead candidate for further therapeutic development targeting nSMase2-related diseases.
• This study highlights the potential of pyrazolo[1,5-a]pyrimidines in modulating ceramide homeostasis.