Small Molecule Targeting PPM1A Activates Autophagy for Mycobacterium tuberculosis Host-Directed Therapy

Area of Science:

• Microbiology
• Immunology
• Pharmacology

Background:

• Tuberculosis (TB), caused by Mycobacterium tuberculosis (Mtb), results in over 1.5 million global deaths annually.
• Host-directed therapies (HDT) offer a promising strategy to shorten TB treatment and combat antibiotic resistance.
• Mtb utilizes the host phosphatase PPM1A for intracellular survival.

Purpose of the Study:

• To develop a more potent inhibitor of PPM1A than the previously identified SMIP-30.
• To evaluate the efficacy of the novel inhibitor, SMIP-031, in clearing Mtb infections.
• To assess the pharmacokinetic profile and in vivo tolerability of SMIP-031.

Main Methods:

• Redesign of SMIP-30 to create SMIP-031, a more potent PPM1A inhibitor (IC50 = 180 nM).
• Assessment of SMIP-031's ability to increase S403-p62 phosphorylation and LC3B-II expression, indicating autophagy activation.
• Evaluation of Mtb clearance in infected macrophages and bacterial burden in mouse spleens following SMIP-031 treatment.
• Pharmacokinetic profiling and tolerability studies of SMIP-031 in vivo.

Main Results:

• SMIP-031 demonstrated significantly higher potency against PPM1A compared to SMIP-30.
• SMIP-031 treatment led to dose-dependent clearance of Mtb in infected macrophages via autophagy activation.
• SMIP-031 exhibited favorable oral bioavailability (74%) and was well-tolerated in mice up to 50 mg/kg.
• In vivo administration of SMIP-031 significantly reduced bacterial burden in the spleens of infected mice.

Conclusions:

• SMIP-031 is a potent, orally bioavailable PPM1A inhibitor with significant antimycobacterial activity.
• SMIP-031 represents a promising novel host-directed therapy for tuberculosis.
• Activation of autophagy by SMIP-031 is a key mechanism for Mtb clearance.