ML-265

ML-265 is widely used as an acknowledged PKM₂ (pyruvate kinase muscle isoform 2) activator^[1][2] ML-265 activates of PKM₂ in both biochemical (AC₅₀ = 92 nM) and cell-based assays with high selectivity over PKM1(pyruvate kinase muscle isoform 1), PKL and PKR. ML-265 was originally developed as a potential cancer therapy. Therefore, ML-265 represents an ideal lead molecule to explore the neuroprotective effects of pharmacologically activating PKM₂^[2]. PKM₂, which is overexpressed in many cancers, is inhibited by ROS, allowing glycolytic flux to be shuttled into the oxidative PPP for NADPH generation. The small-molecule compounds, ML-265, can positively modulate PKM₂, thereby decreasing glycolytic flux into the oxidative PPP and blunting NADPH biogenesis during ROS(fig.) ^[3].

ML-265 displayed powerful activation of recombinant human PKM₂ with a maximum activation of 249 ± 14% (best-fit value ± std. error) , the half-maximum activating concentration (AC₅₀) shows 108 ± 20 nM. To investigate the ability of ML-265 to activate PK in photoreceptors, the 661W cell line was utilized. Similar to the results observed with the recombinant enzyme, ML-265 increased PK activity in vitro (maximum activation = 515 ± 12% and AC₅₀ = 19 ± 2 nM) ^[2].

To determine the intraocular pharmacokinetic profile of intravitreally administered ML-265 in rabbits. Single, intravitreal injections (50 μL) of two different doses of ML-265 were performed in rabbits. Assuming a vitreous volume of 1.15 mL, the final concentrations in the rabbit vitreous were approximately 100 μM and 1000 μM, respectively. The aqueous humor was sampled at multiple time points after the single intravitreal injection. The distribution phase has a half-life (t1/2) of 8.3 ± 0.5 hours. The elimination phase has a t1/2 = 141.6 ± 35 hours. ML-265 has a relatively long half-life in the eye following intravitreal injection and remains active at least two weeks after injection.^[2].

References:
[1]: Walsh MJ, Brimacombe KR, Anastasiou D, et al. ML265: A potent PKM₂ activator induces tetramerization and reduces tumor formation and size in a mouse xenograft model. Probe Reports from the NIH Molecular Libraries Program [Internet]
[2] TJ Wubben, M Pawar, E Weh, et,al. Small molecule activation of metabolic enzyme pyruvate kinase muscle isozyme 2, PKM₂,circumvents photoreceptor apoptosis. Sci. Rep., 10 (2020), p. 2990, doi.org /10.1038/s41598-020-59999-w.
[3] Chakrabarti G, Gerber DE, Boothman DA. Expanding antitumor therapeutic windows by targeting cancer-specific nicotinamide adenine dinucleotide phosphate-biogenesis pathways. Clin. Pharmacol. Adv. Applications. 2015;7:57.
[4]: Xu W, Yang H, et,al. Oncometabolite 2-hydroxyglutarate is a competitive inhibitor of α-ketoglutarate-dependent dioxygenases. Cancer Cell. 2011 Jan 18;19(1):17-30. doi: 10.1016/j.ccr.2010.12.014. PMID: 21251613; PMCID: PMC3229304.