Adenosine Kinase Inhibitors. 5. Synthesis, Enzyme Inhibition, and Analgesic Activity of Diaryl-erythro-furanosyltubercidin Analogues

Abstract

Adenosine is an endogenous neuromodulator that when produced in the central and the peripheral nervous systems has anticonvulsant, anti-inflammatory, and analgesic properties. However, efforts to use adenosine receptor agonists are plagued by dose-limiting cardiovascular side effects. As an alternative, we explored the use of adenosine kinase inhibitors (AKIs) as potential antiseizure agents and demonstrated an adenosine receptor mediated therapeutic effect in the absence of overt cardiovascular side effects. These activities were associated with elevation of extracellular adenosine concentrations due to inhibition of AK in a site and event specific manner. Several tubercidin based AKIs, including the ribo- and lyxo-furanosyltubercidin analogues as well as the newly discovered erythro-furanosyltubercidin analogues, designed to prevent 5'-O-phosphorylation and associated toxicities, were tested for their analgesic activity in the rat formalin paw model. Described herein are the synthesis, enzyme inhibition structure-activity relationships (SARs) of erythro-furanosyltubercidin analogues, and SARs of analgesic activity of various classes of AKIs. Also reported is the characterization of a lead AKI, 19d (GP3966), an orally bioavailable compound (F% = 60% in dog) which exhibits broad-spectrum analgesic activities (ED50 < or = 4 mg/kg, per os) that are reversible with an adenosine receptor antagonist (theophylline).

Adenosine Kinase: Exploitation for Therapeutic Gain

“…Since cytotoxicity was found to be due to phosphorylation at the 59-position of the ribose base, l-xylofuranosyl analogs of tubercidin were synthesized, which could no longer be phosphorylated due to their altered stereochemical orientation; the lead compound GP790 of those a-llyxofuranosyl nucleosides displayed prominent antiinflammatory activity in a rat paw swelling model (Ugarkar et al, 2003). Likewise, erythrofuranosyltubercidin analogs were resistant to phosphorylation, and the orally bioavailable lead compound GP3966 was shown to exhibit broad-spectrum analgesic properties in dogs (Boyer et al, 2005). Diaryltubercidins such as GP3269 were orally active in the rat formalin paw model; however, the utility of this compound class was limited due to poor water solubility.…”

Mechanism of dual specificity kinase activity of DYRK1A

“…Iodotubercidin was previously characterized as a specific inhibitor of DYRK2 and Haspin with excellent selectivity in a screen against a panel of 98 kinases [29]. However, the use of 5-iodotubercidin as a DYRK inhibitor in cellular assays or animal experiments is compromised by its high activity as an inhibitor of adenylate kinase (IC 50 = 9 nM [45]). …”

Adenosine kinase and ribokinase – the RK family of proteins

“…Although these compounds have shown positive effects in several animal models of pain, seizure, and ischemia [158 -161], their pharmacological utility is largely compromised due to short plasma half-lives, poor bio-availability, lack of target selectivity, and the potential to form cytotoxic metabolites [161,162]. In an effort to optimize these AK inhibitors for better in vivo properties, a large series of 5'NH 2 dAdo and 5IT derivatives were synthesized and tested [161,163,164]. As a result of rounds of structure-activity relationship studies, a number of diaryltubercidin analogues were identified as potent inhibitors of AK.…”

“…As a result of rounds of structure-activity relationship studies, a number of diaryltubercidin analogues were identified as potent inhibitors of AK. Compounds such as GP790 and GP3966, for example, showed inhibition of human recombinant AK at low nanomolar concentrations [161,163,164]. When tested for anticonvulsant, anti-inflammatory, and analgesic properties in animal models, these compounds showed high efficacy with relatively mild adverse effects [161,163,164].…”