Summary of the technology
Novel Glycogen synthase kinase 3 (GSK-3) inhibitors were developed. These inhibitors are substrate competitors that interact specifically with the GSK-3 substrate binding site.
GSK-3, like other protein kinases, has a common structurally conserved catalytic domain that comprises the ATP-binding loop. The great majority of reported inhibitors developed to date are ATP-competitive compounds; however, such inhibitors demonstrate limited specificity, as the ATP-binding pocket is highly conserved among protein kinases. In contrast, the substrate binding site is more specific, and thus targeting inhibitors toward this domain yields more specific compounds. The strategy is based on exploiting the unique recognition motif of GSK-3 which comprises a phosphorylated residue and using molecular and computational analyses.
Project ID : 10-2011-132
Novel Glycogen synthase kinase 3 (GSK-3) inhibitors were developed. These inhibitors are substrate competitors that interact specifically with the GSK-3 substrate binding site. The strategy is based on exploiting the unique GSK-3-substrate’s binding motifs as extracted from molecular and computational analyses.
GSK3 is emerging as a prominent drug target in the CNS. Recent studies demonstrated the involvement of GSK-3 in synaptic regulation and cognitive functions and showed that hyperactive GSK- 3 has deleterious effects on neurogenesis, brain pathology and behavior. Extensive studies were performed in Alzheimer's disease model where abnormal increases in GSK3 levels and activity are associated with neuronal death, paired helical filament tau formation and decline in cognitive performance. Abnormal activity of GSK3 is also implicated in stroke, schizophrenia and bipolar disorder. Thus pharmaceutical companies are investing in finding selective inhibitors of GSK3.
The Need and Potential Application
GSK-3, like other protein kinases, has a common structurally conserved catalytic domain that comprises the ATP-binding loop. The great majority of reported inhibitors developed to date are ATPcompetitive compounds; however, such inhibitors demonstrate limited specificity, as the ATP-binding pocket is highly conserved among protein kinases. In contrast, the substrate binding site is more specific, and thus targeting inhibitors toward this binding site yields more specific compounds.
Potential applications in treatment of CNS diseases include:
Alzheimer’s disease Bipolar disorders
Huntington disease Parkinson's disease
Progressive Supranuclear Palsy
Former developed GSK-3 inhibitors aimed at the ATP binding site of the enzyme, demonstrated significant side effects caused by nonspecific inhibition. Most programs were discontinued due to lack of specificity. Our novel inhibitors are the first substrate competitive inhibitors that target substrate binding of GSK-3 enabling specific mechanism of inhibition not common to all kinases.
Specific inhibitors have the potential as drugs with less side effects that will enable long time treatment.
Our biochemical and computational analyses provide in depth understanding of the molecular interactions of the substrates and inhibitors with the enzyme.
The lead peptide is bioavailable via nasal and i.p administration, an important advantage for drugs aimed to reach the brain by either avoiding impact on peripheral tissues, or swallowing problems as compared to oral administration
Stage of Development
L803-mts, the original and well characterized compound and two recently developed L803-mts derivatives, L807-mts and L806-mts were developed and demonstrated improved inhibitory activities in vitro and in cellular systems. IC50 values of the new inhibitors were within or below 1uM.
Results in the Alzheimer’s disease animal mouse model 5xFAD demonstrated that nasal L803-mts or L807-mts treatment reduced beta amyloid pathology and improved cognitive deficits as indicated by the fear conditioning test.
L8930mts improved depressive behavior as demonstrated by the forced swimming test, a widely accepted preclinical animal model of anti-depressive drug activity.
L803-mts prevented paralysis progression in the experimental autoimmune encephalomyelitis (EAE) model of multiple sclerosis model of Pharmacokinetic and safety analyses were conducted for L803-mts.
Patents protecting GSK-3 peptide inhibitor L803-mts are granted in the US (US Patents 6,780,625;
7,157,422; 7,348,308; 7,446,092; 7,833,974) and under exanimation in Europe and Israel.
New peptide derivatives patent applications were submitted worldwide (PCT/IB2012/050376 and PCT/IB2012/050373) – priority Jan 2011.
- Kaidanovich-Beilin O, Milman A, Weizman A, Pick HG, Eldar-Finkelman H. (2004) Rapid Antidepressive-Like Activity of Specific Glycogen Synthase Kinase-3 Inhibitor and Its Effect on b-Catenin in Mouse Hippocampus. Biol Psychiatry 55:781–784
- Shapira M, Licht A, Milman A, Pick CG, Shohami E, and Eldar-Finkelmana H (2007) Role of glycogen synthase kinase-3β in early depressive behavior induced by mild traumatic brain injury. Mol. Cell. Neurosci. 34: 571–577
- Chen, G., Bower, K. A., Ma, C., Fang, S., Thiele, C. J., and Luo, J. (2004). Glycogen synthase kinase 3beta (GSK3beta) mediates 6-hydroxydopamine-induced neuronal death. Faseb J 18, 1162-1164.
- Licht-Murava, A., Plotkin, B., Eisenstein, M., Eldar-Finkelman, H. 2011, Elucidating substrate and Inhibitor binding sites on the surface of GSK-3beta and the refinement of a competitive inhibitor. J. Mol. Biol. 408:366-378
- Eldar-Finkelman, H., Martinez a. GSK-3 inhibitors: Preclinical and clinical focus at the CNS. Frontiers
Molecular Neuroscience in press