O-304 (ATX-304)

O-304 (ATX-304) is a small-molecule AMPK (AMP-activated protein kinase) activator developed by Betagenon AB. Unlike AICAR, which activates AMPK indirectly through conversion to the AMP-mimetic ZMP, O-304 has been characterized as a direct AMPK activator that inhibits dephosphorylation of the activating Thr172 residue on the AMPK alpha subunit. This mechanism preserves AMPK in its active phosphorylated state regardless of AMP/ATP ratios. O-304 has advanced into Phase 2 clinical trials for type 2 diabetes, where researchers investigated its effects on glucose homeostasis, insulin sensitivity, and cardiovascular parameters. The compound is orally bioavailable and has been studied for its ability to activate AMPK in multiple tissues including skeletal muscle, liver, and adipose tissue. O-304 represents a pharmacological approach to AMPK activation distinct from the nucleoside analog mechanism of AICAR.

O-304 has been investigated for its direct activation of AMPK through inhibition of Thr172 dephosphorylation. AMPK is normally activated when AMP/ADP levels rise relative to ATP, causing conformational changes that protect Thr172 from phosphatase PP2C. Researchers observed that O-304 independently protects Thr172 from dephosphorylation, maintaining AMPK in its active state regardless of cellular energy charge. Studies suggest that this mechanism activates downstream AMPK substrates including ACC (reducing malonyl-CoA and promoting fatty acid oxidation), ULK1 (promoting autophagy), and PGC-1α (promoting mitochondrial biogenesis). In clinical studies, researchers observed that O-304 administration was associated with changes in fasting glucose, insulin sensitivity markers, and blood pressure parameters. The compound’s ability to activate AMPK independently of AMP accumulation distinguishes it from exercise mimetics like AICAR and may engage different downstream signaling kinetics.

Phase 2 Clinical Trial

Steneberg et al. (2018) investigated O-304 in preclinical models and a Phase 2a clinical trial in patients with type 2 diabetes. Researchers observed that O-304 improved glucose homeostasis and insulin sensitivity, and in preclinical models, reduced micro- and macrovascular complications [1].

AMPK Activation Mechanism

Steneberg et al. characterized O-304’s mechanism as protection of AMPK Thr172 from dephosphorylation, demonstrating that the compound maintains AMPK activity independent of AMP/ATP ratios [1].

AMPK Biology

Hardie et al. (2012) reviewed AMPK as a cellular energy sensor and drug target, describing the signaling networks activated by AMPK and the therapeutic rationale for pharmacological AMPK activation [2].