From Pharmacophore to Warhead: NAD⁺-Targeting Triazoles as Mechanism-Based Sirtuin Inhibitors

Area of Science:

• Biochemistry
• Enzymology
• Medicinal Chemistry

Background:

• Sirtuins (SIRTs) are NAD+-dependent enzymes crucial in physiological and disease pathways.
• Existing NAD+-targeting SIRT inhibitors face challenges like instability and off-target effects.

Purpose of the Study:

• To discover a new class of SIRT inhibitors with improved properties.
• To elucidate the mechanism of action for these novel inhibitors.

Main Methods:

• Mechanism-based inhibition using 1,2,3-triazole compounds (SirTraps).
• X-ray crystallography, kinetics, and mass spectrometry to confirm adduct formation.
• In vitro and in cellulo studies, including NanoBRET assays for cellular target engagement.

Main Results:

• SirTraps form stalled triazolium- or triazole-ADP-ribose (ADPR) adducts with NAD+, inhibiting SIRTs without covalent modification.
• Adduct formation involves nucleophilic attack at the nicotinamide riboside moiety of NAD+.
• SirTraps exhibit potent, isoform-selective inhibition, high stability, and nanomolar cellular target engagement.

Conclusions:

• SirTraps represent a novel, stable, and tunable class of mechanism-based SIRT inhibitors.
• This inhibition strategy has potential applications beyond SIRTs, including other NAD+-dependent enzymes.
• SirTraps offer a promising platform for mechanism-driven drug discovery.