Novel DYRK1A Inhibitor Rescues Learning and Memory Deficits in a Mouse Model of Down Syndrome

Design, synthesis, and structure-activity relationship studies of 6H-benzo[b]indeno[1,2-d]thiophen-6-one derivatives as DYRK1A/CLK1/CLK4/haspin inhibitors

A series of sulfur-containing tetracycles was designed and evaluated for their ability to inhibit protein kinase DYRK1A, a target known to have several potential therapeutic applications including cancers, Down syndrome or Alzheimer's disease. Our medicinal chemistry strategy relied on the design of new compounds using ring contraction/isosteric replacement and constrained analogy of known DYRK1A inhibitors, thus resulting in their DYRK1A inhibitory activity enhancement. Whereas a good inhibitory effect of targeted DYRK1A protein was observed for 5-hydroxy compounds 4i-k (IC50 = 35-116 nM) and the 5-methoxy derivative 4e (IC50 = 52 nM), a fairly good selectivity towards its known DYRK1B off-target was observed for 4k. In addition, the most active compound 4k, having an ATP-competitive mechanism of action, proved to be also a potent inhibitor of CLK1/CLK4 (IC50 = 20 and 26 nM) and, to a lesser extent, of haspin (IC50 = 76 nM) kinases. In silico docking studies within the DYRK1A, CLK1/CLK4 and haspin ATP binding sites were carried out to understand the interactions of our tetracyclic derivatives 4 with these targets. Antiproliferative activities on U87/U373 glioblastoma cell lines of the most potent compound 4k showed a moderate effect (IC50 values between 33 and 46 μM). Microsomal stabilities of the designed compounds 4a-m were also investigated, showing great disparities, depending on benzo[b]thiophene ring 5-substitution.

Psychoplastogenic DYRK1A Inhibitors with Therapeutic Effects Relevant to Alzheimer's Disease

Tauopathy, neuronal atrophy, and psychological impairments are hallmarks of neurodegenerative diseases, such as Alzheimer's disease, that currently lack efficacious clinical treatments capable of rectifying these issues. To address these unmet needs, we used rational drug design to combine the pharmacophores of DYRK1A inhibitors and isoDMTs to develop psychoplastogenic DYRK1A inhibitors. Using this approach, we discovered a nonhallucinogenic compound capable of promoting cortical neuron growth and suppressing tau hyperphosphorylation while also having the potential to mitigate the biological and psychological symptoms of dementia. Together, our results suggest that hybridization of the DYRK1A and psychoplastogen pharmacophores represents a promising strategy for identifying compounds that might address the cognitive as well as the behavioral and psychological symptoms of dementia.

Leucettinib-21, a DYRK1A Kinase Inhibitor as Clinical Drug Candidate for Alzheimer's Disease and Down Syndrome

Alzheimer's disease (AD) and Down syndrome (DS) share a common therapeutic target, the dual-specificity, tyrosine phosphorylation activated kinase 1A (DYRK1A). Abnormally active DYRK1A is responsible for cognitive disorders (memory, learning, spatial localization) observed in both conditions. In DS, DYRK1A is overexpressed due to the presence of the DYRK1A gene on chromosome 21. In AD, calcium-activated calpains cleave full-length DYRK1A (FL-DYRK1A) into a more stable and more active, low molecular weight, kinase (LMW-DYRK1A). Genetic and pharmacological experiments carried out with animal models of AD and DS strongly support the idea that pharmacological inhibitors of DYRK1A might be able to correct memory/learning disorders in people with AD and DS. Starting from a marine sponge natural product, Leucettamine B, Perha Pharmaceuticals has optimized, through classical medicinal chemistry, and extensively characterized a small molecule drug candidate, Leucettinib-21. Regulatory preclinical safety studies in rats and minipigs have been completed and formulation of Leucettinib-21 has been optimized as immediate-release tablets. Leucettinib-21 is now undergoing a phase 1 clinical trial (120 participants, including 12 adults with DS and 12 patients with AD). The therapeutic potential of DYRK1A inhibitors in AD and DS is presented.

Chemical, Biochemical, Cellular, and Physiological Characterization of Leucettinib-21, a Down Syndrome and Alzheimer's Disease Drug Candidate

Leucettinibs are substituted 2-aminoimidazolin-4-ones (inspired by the marine sponge natural product Leucettamine B) developed as pharmacological inhibitors of DYRK1A (dual-specificity, tyrosine phosphorylation-regulated kinase 1A), a therapeutic target for indications such as Down syndrome and Alzheimer's disease. Leucettinib-21 was selected as a drug candidate following extensive structure/activity studies and multiparametric evaluations. We here report its physicochemical properties (X-ray powder diffraction, differential scanning calorimetry, stability, solubility, crystal structure) and drug-like profile. Leucettinib-21's selectivity (analyzed by radiometric, fluorescence, interaction, thermal shift, residence time assays) reveals DYRK1A as the first target but also some "off-targets" which may contribute to the drug's biological effects. Leucettinib-21 was cocrystallized with CLK1 and modeled in the DYRK1A structure. Leucettinib-21 inhibits DYRK1A in cells (demonstrated by direct catalytic activity and phosphorylation levels of Thr286-cyclin D1 or Thr212-Tau). Leucettinib-21 corrects memory disorders in the Down syndrome mouse model Ts65Dn and is now entering safety/tolerance phase 1 clinical trials.

Insights from the protein interaction Universe of the multifunctional "Goldilocks" kinase DYRK1A

Human Dual specificity tyrosine (Y)-Regulated Kinase 1A (DYRK1A) is encoded by a dosage-dependent gene located in the Down syndrome critical region of human chromosome 21. The known substrates of DYRK1A include proteins involved in transcription, cell cycle control, DNA repair and other processes. However, the function and regulation of this kinase is not fully understood, and the current knowledge does not fully explain the dosage-dependent function of this kinase. Several recent proteomic studies identified DYRK1A interacting proteins in several human cell lines. Interestingly, several of known protein substrates of DYRK1A were undetectable in these studies, likely due to a transient nature of the kinase-substrate interaction. It is possible that the stronger-binding DYRK1A interacting proteins, many of which are poorly characterized, are involved in regulatory functions by recruiting DYRK1A to the specific subcellular compartments or distinct signaling pathways. Better understanding of these DYRK1A-interacting proteins could help to decode the cellular processes regulated by this important protein kinase during embryonic development and in the adult organism. Here, we review the current knowledge of the biochemical and functional characterization of the DYRK1A protein-protein interaction network and discuss its involvement in human disease.

Comparative Efficacy and Selectivity of Pharmacological Inhibitors of DYRK and CLK Protein Kinases

Dual-specificity, tyrosine phosphorylation-regulated kinases (DYRKs) and cdc2-like kinases (CLKs) play a large variety of cellular functions and are involved in several diseases (cognitive disorders, diabetes, cancers, etc.). There is, thus, growing interest in pharmacological inhibitors as chemical probes and potential drug candidates. This study presents an unbiased evaluation of the kinase inhibitory activity of a library of 56 reported DYRK/CLK inhibitors on the basis of comparative, side-by-side, catalytic activity assays on a panel of 12 recombinant human kinases, enzyme kinetics (residence time and K_d), in-cell inhibition of Thr-212-Tau phosphorylation, and cytotoxicity. The 26 most active inhibitors were modeled in the crystal structure of DYRK1A. The results show a rather large diversity of potencies and selectivities among the reported inhibitors and emphasize the difficulties to avoid "off-targets" in this area of the kinome. The use of a panel of DYRKs/CLKs inhibitors is suggested to analyze the functions of these kinases in cellular processes.

DYRK1a Inhibitor Mediated Rescue of Drosophila Models of Alzheimer’s Disease-Down Syndrome Phenotypes

Alzheimer’s disease (AD) is the most common neurodegenerative disease which is becoming increasingly prevalent due to ageing populations resulting in huge social, economic, and health costs to the community. Despite the pathological processing of genes such as Amyloid Precursor Protein (APP) into Amyloid-β and Microtubule Associated Protein Tau (MAPT) gene, into hyperphosphorylated Tau tangles being known for decades, there remains no treatments to halt disease progression. One population with increased risk of AD are people with Down syndrome (DS), who have a 90% lifetime incidence of AD, due to trisomy of human chromosome 21 (HSA21) resulting in three copies of APP and other AD-associated genes, such as DYRK1A (Dual specificity tyrosine-phosphorylation-regulated kinase 1A) overexpression. This suggests that blocking DYRK1A might have therapeutic potential. However, it is still not clear to what extent DYRK1A overexpression by itself leads to AD-like phenotypes and how these compare to Tau and Amyloid-β mediated pathology. Likewise, it is still not known how effective a DYRK1A antagonist may be at preventing or improving any Tau, Amyloid-β and DYRK1a mediated phenotype. To address these outstanding questions, we characterised Drosophila models with targeted overexpression of human Tau, human Amyloid-β or the fly orthologue of DYRK1A, called minibrain (mnb). We found targeted overexpression of these AD-associated genes caused degeneration of photoreceptor neurons, shortened lifespan, as well as causing loss of locomotor performance, sleep, and memory. Treatment with the experimental DYRK1A inhibitor PST-001 decreased pathological phosphorylation of human Tau [at serine (S) 262]. PST-001 reduced degeneration caused by human Tau, Amyloid-β or mnb lengthening lifespan as well as improving locomotion, sleep and memory loss caused by expression of these AD and DS genes. This demonstrated PST-001 effectiveness as a potential new therapeutic targeting AD and DS pathology.