Abstract
Purpose :
There is a lack of successful treatment options that prevent photoreceptor cell death. We have shown that reprogramming photoreceptor metabolism via activation of PKM2 is a novel therapeutic strategy for neuroprotection. The low aqueous solubility and structural features of current PKM2 activators limit their ability to be translated to the bedside. The goal of this study was to develop the next generation of small molecule PKM2 activators, with improved solubility and in vivo potency for ocular delivery.
Methods :
To address the structural limitations of current PKM2 activators, medicinal chemistry efforts focused on a pyridazinoindolone heterocyclic core with a range of functional groups. 49 novel analogues were developed, and solubility of the compounds was tested at pH 7.4. The ability to activate PKM2 was tested with human recombinant PKM2 enzyme, in vitro in 661W cells, and in vivo in rat retina via intravitreal (IVT) injection, oral gavage, or intraperitoneal injection (IP), using a continuous, enzyme-coupled assay that measures the depletion of NADH via absorbance at 340 nm.
Results :
All compounds showed nanomolar potency with recombinant PKM2 and in vitro in 661W cells. MCTI-566 was identified as a highly soluble PKM2 activator with aqueous solubility of 385 μg/mL and an AC50 = 83 ± 9 nM. When injected intravitreally, MCTI-566 retained PKM activation as compared to tool compound and known selective PKM2 activator, ML-265. Interestingly, a single oral dose of ML-265 (50 mg/kg) produces similar PKM activation in the retina as a single intravitreal injection of ML-265 (1 mM) and retains 100% increased PKM activation after 1 week. Likewise, a single IP dose (50 mg/kg) of MCTI-566 produced similar PKM activation in the retina as compared to a single IVT injection of ML-265 (1 mM) and retained 100% increased PKM activation in the retina after 1 week.
Conclusions :
This study developed the next generation of PKM2 activators with improved aqueous solubility while maintaining nanomolar potency. Successful commercial development of MCTI-566 would be transformative for ophthalmology, as a novel PKM2 activator could potentially be the first therapeutic to stop photoreceptor death and improve vision in currently untreatable eye conditions. Future studies will assess ocular and systemic toxicity and in vivo efficacy.
This abstract was presented at the 2022 ARVO Annual Meeting, held in Denver, CO, May 1-4, 2022, and virtually.