Synthesis and characterization of novel isoform-selective IP6K1 inhibitors

Abstract

Inositol hexakisphosphate kinases (IP6Ks) have been increasingly studied as therapeutically interesting enzymes. IP6K isoform specific knock-outs have been used to successfully explore inositol pyrophosphate physiology and related pathologies. A pan-IP6K inhibitor, N2-(m-trifluorobenzyl)-N6-(p-nitrobenzyl) purine (TNP), has been used to confirm phenotypes observed in genetic knock-out experiments; however, it suffers by having modest potency and poor solubility making it difficult to handle for in vitro applications in the absence of DMSO. Moreover, TNP's pan-IP6K inhibitory profile does not inform which IP6K isoform is responsible for which phenotypes. In this report we describe a series of purine-based isoform specific IP6K1 inhibitors. The lead compound was identified after multiple rounds of SAR and has been found to selectively inhibit IP6K1 over IP6K2 or IP6K3 using biochemical and biophysical approaches. It also boasts increased solubility and IP6K1 potency over TNP. These new compounds are useful tools for additional assay development and exploration of IP6K1 specific biology.

Keywords: Inositol hexakisphosphate kinase; Inositol pyrophosphate; Kinases; Selective enzyme inhibitors; Structure activity relationships.

Figure 1.

Biosynthesis of inositol pyrophosphates

Scheme 1.

Preparation of N2- and N6- substituted purine analogs 2–25. Reagents and reaction conditions: (a) R¹-NH₂, DIPEA, nBuOH, 110°C (b) R²-NH₂, DIPEA, DMSO, 110°C.