Design, Synthesis, and Cellular Characterization of a New Class of IPMK Kinase Inhibitors.

The kinase activity of human inositol phosphate multikinase (IPMK) is required for the synthesis of higher-order inositol phosphate signaling molecules, regulation of gene expression, and control of the cell cycle. Here, we report a novel series of highly potent IPMK inhibitors. The first-generation IPMK inhibitor (UNC7437) decreased cellular proliferation and tritiated inositol phosphate levels in metabolically labeled human U251-MG glioblastoma cells.

Discovery of Novel TYRO3/MERTK Dual Inhibitors.

The TAM (TYRO3, AXL, MERTK) family of receptor tyrosine kinases has roles in oncogenesis and innate immunity, but the relative importance of the family members can differ in different contexts and between tumor types or individual tumors. Dual TYRO3 and MERTK inhibition may be advantageous for treatment of diseases or in tumors that are dependent on their coordinated action. Here, we report the discovery of the first potent dual TYRO3/MERTK inhibitor, UNC9435 ().

Exploiting structural variability in the kinase back-pocket to modulate polypharmacology of TAM inhibitors.

TAM kinases play dual roles in tumor cells and the innate immune system. While they have redundant functions, the TAM kinases are differentially required in specific contexts. Therefore, inhibition of specific TAM kinases or pairs of TAM kinases will be desirable in different tumor types.

UNC9426, a Potent and Orally Bioavailable TYRO3-Specific Inhibitor.

TYRO3 plays a critical role in platelet aggregation as a platelet response amplifier. Selective inhibition of TYRO3 may provide therapeutic benefits for treating thrombosis and related diseases without increasing bleeding risk. We employed a structure-based approach and discovered a novel and potent TYRO3 inhibitor UNC9426 () with an excellent Ambit selectivity score ( (1.

Potent and selective SETDB1 covalent negative allosteric modulator reduces methyltransferase activity in cells.

A promising drug target, SETDB1, is a dual methyl-lysine (Kme) reader and methyltransferase implicated in cancer and neurodegenerative disease progression. To help understand the role of the triple Tudor domain (3TD) of SETDB1, its Kme reader, we first identify a low micromolar potency small molecule ligand, UNC6535, which occupies simultaneously both the TD2 and TD3 reader binding sites. Further optimization leads to the discovery of UNC10013, a covalent 3TD ligand targeting Cys385 of SETDB1.

Potent and Selective SETDB1 Covalent Negative Allosteric Modulator Reduces Methyltransferase Activity in Cells.

A promising drug target, SETDB1, is a dual Kme reader and methyltransferase, which has been implicated in cancer and neurodegenerative disease progression. To help understand the role of the triple Tudor domain (3TD) of SETDB1, its Kme reader, we first identified a low micromolar small molecule ligand, UNC6535, which occupies simultaneously both the TD2 and TD3 reader binding sites. Further optimization led to the discovery of UNC10013, the first covalent 3TD ligand targeting Cys385 of SETDB1.

Discovery of a cell-active chikungunya virus nsP2 protease inhibitor using a covalent fragment-based screening approach.

Unlabelled: Chikungunya virus (CHIKV) is a mosquito-borne alphavirus that has been responsible for numerous large-scale outbreaks in the last twenty years. Currently, there are no FDA-approved therapeutics for any alphavirus infection. CHIKV non-structural protein 2 (nsP2), which contains a cysteine protease domain, is essential for viral replication, making it an attractive target for a drug discovery campaign.

Discovery of Novel Macrocyclic MERTK/AXL Dual Inhibitors.

MERTK and AXL are members of the TAM (TYRO3, AXL, MERTK) family of receptor tyrosine kinases that are aberrantly expressed and have been implicated as therapeutic targets in a wide variety of human tumors. Dual MERTK and AXL inhibition could provide antitumor action mediated by both direct tumor cell killing and modulation of the innate immune response in some tumors such as nonsmall cell lung cancer. We utilized our knowledge of MERTK inhibitors and a structure-based drug design approach to discover a novel class of macrocyclic dual MERTK/AXL inhibitors.

SETDB1 Triple Tudor Domain Ligand, (,)-59, Promotes Methylation of Akt1 in Cells.

Increased expression and hyperactivation of the methyltransferase SET domain bifurcated 1 (SETDB1) are commonly observed in cancer and central nervous system disorders. However, there are currently no reported SETDB1-specific methyltransferase inhibitors in the literature, suggesting that this is a challenging target. Here, we disclose that the previously reported small-molecule ligand for SETDB1's triple tudor domain, (,)-59, is unexpectedly able to increase SETDB1 methyltransferase activity both and in cells.

SETDB1 Triple Tudor Domain Ligand, ( )-59, Promotes Methylation of Akt1 in Cells.

Increased expression and hyperactivation of the methyltransferase SETDB1 are commonly observed in cancer and central nervous system disorders. However, there are currently no reported SETDB1-specific methyltransferase inhibitors in the literature, suggesting this is a challenging target. Here, we disclose that the previously reported small-molecule ligand for SETDB1's Triple Tudor Domain, ( )-59, is unexpectedly able to increase SETDB1 methyltransferase activity both and in cells.

Development of Novel IP6K Inhibitors for the Treatment of Obesity and Obesity-Induced Metabolic Dysfunctions.

Obesity and obesity-induced metabolic dysfunctions are significant risk factors for nonalcoholic fatty liver disease and cardiovascular diseases. Thus, obesity is an economic and social burden in developed countries. Blocking the synthesis of inositol pyrophosphates by inositol hexakisphosphate kinase (IP6K) has been identified as a potential therapeutic strategy for obesity and related diseases.

The Synthesis and Initial Evaluation of MerTK Targeted PET Agents.

MerTK (Mer tyrosine kinase), a receptor tyrosine kinase, is ectopically or aberrantly expressed in numerous human hematologic and solid malignancies. Although a variety of MerTK targeting therapies are being developed to enhance outcomes for patients with various cancers, the sensitivity of tumors to MerTK suppression may not be uniform due to the heterogeneity of solid tumors and different tumor stages. In this report, we develop a series of radiolabeled agents as potential MerTK PET (positron emission tomography) agents.

Development of [F]MIPS15692, a radiotracer with in vitro proof-of-concept for the imaging of MER tyrosine kinase (MERTK) in neuroinflammatory disease.

MER tyrosine kinase (MERTK) upregulation is associated with M2 polarization of microglia, which plays a vital role in neuroregeneration following damage induced by neuroinflammatory diseases such as multiple sclerosis (MS). Therefore, a radiotracer specific for MERTK could be of great utility in the clinical management of MS, for the detection and differentiation of neuroregenerative and neurodegenerative processes. This study aimed to develop an [F] ligand with high affinity and selectivity for MERTK as a potential positron emission tomography (PET) radiotracer.

UNC5293, a potent, orally available and highly MERTK-selective inhibitor.

Inhibition of MER receptor tyrosine kinase (MERTK) causes direct tumor cell killing and stimulation of the innate immune response. Therefore, MERTK has been identified as a therapeutic target in a wide variety of human tumors. Clinical trials targeting MERTK have recently been initiated, however, none of these drugs are MERTK-specific.

MerTK activity is not necessary for the proliferation of glioblastoma stem cells.

MerTK has been identified as a promising target for therapeutic intervention in glioblastoma. Genetic studies documented a range of oncogenic processes that MerTK targeting could influence, however robust pharmacological validation has been missing. The aim of this study was to assess therapeutic potential of MerTK inhibitors in glioblastoma therapy.

Inhibition of Inositol Polyphosphate Kinases by Quercetin and Related Flavonoids: A Structure-Activity Analysis.

Dietary flavonoids inhibit certain protein kinases and phospholipid kinases by competing for their ATP-binding sites. These nucleotide pockets have structural elements that are well-conserved in two human small-molecule kinases, inositol hexakisphosphate kinase (IP6K) and inositol polyphosphate multikinase (IPMK), which synthesize multifunctional inositol phosphate cell signals. Herein, we demonstrate that both kinases are inhibited by quercetin and 16 related flavonoids; IP6K is the preferred target.

Highly Selective MERTK Inhibitors Achieved by a Single Methyl Group.

Although all kinases share the same ATP binding pocket, subtle differences in the residues that form the pocket differentiate individual kinases' affinity for ATP competitive inhibitors. We have found that by introducing a single methyl group, the selectivity of our MERTK inhibitors over another target, FLT3, was increased up to 1000-fold (compound 31). Compound 19 was identified as an in vivo tool compound with subnanomolar activity against MERTK and 38-fold selectivity over FLT3 in vitro.

Use of Protein Kinase-Focused Compound Libraries for the Discovery of New Inositol Phosphate Kinase Inhibitors.

Inositol hexakisphosphate kinases (IP6Ks) regulate a myriad of cellular processes, not only through their catalytic activity (which synthesizes InsP, a multifunctional inositol pyrophosphate signaling molecule) but also through protein-protein interactions. To further study the enzymatic function and distinguish between these different mechanisms, specific inhibitors that target IP6K catalytic activity are required. Only one IP6K inhibitor is commonly used: N2-( m-(trifluoromethyl)benzyl) N6-( p-nitrobenzyl)purine (TNP).

Discovery of Macrocyclic Pyrimidines as MerTK-Specific Inhibitors.

Macrocycles have attracted significant attention in drug discovery recently. In fact, a few de novo designed macrocyclic kinase inhibitors are currently in clinical trials with good potency and selectivity for their intended target. In this study, we successfully engaged a structure-based drug design approach to discover macrocyclic pyrimidines as potent Mer tyrosine kinase (MerTK)-specific inhibitors.

Design and Synthesis of Novel Macrocyclic Mer Tyrosine Kinase Inhibitors.

Mer tyrosine kinase (MerTK) is aberrantly elevated in various tumor cells and has a normal anti-inflammatory role in the innate immune system. Inhibition of MerTK may provide dual effects against these MerTK-expressing tumors through reducing cancer cell survival and redirecting the innate immune response. Recently, we have designed novel and potent macrocyclic pyrrolopyrimidines as MerTK inhibitors using a structure-based approach.

A High-Throughput Screening-Compatible Strategy for the Identification of Inositol Pyrophosphate Kinase Inhibitors.

Pharmacological tools-'chemical probes'-that intervene in cell signaling cascades are important for complementing genetically-based experimental approaches. Probe development frequently begins with a high-throughput screen (HTS) of a chemical library. Herein, we describe the design, validation, and implementation of the first HTS-compatible strategy against any inositol phosphate kinase.

The MERTK/FLT3 inhibitor MRX-2843 overcomes resistance-conferring FLT3 mutations in acute myeloid leukemia.

FMS-like tyrosine kinase 3-targeted (FLT3-targeted) therapies have shown initial promise for the treatment of acute myeloid leukemia (AML) expressing FLT3-activating mutations; however, resistance emerges rapidly. Furthermore, limited options exist for the treatment of FLT3-independent AML, demonstrating the need for novel therapies that reduce toxicity and improve survival. MERTK receptor tyrosine kinase is overexpressed in 80% to 90% of AMLs and contributes to leukemogenesis.

Efficacy of a Mer and Flt3 tyrosine kinase small molecule inhibitor, UNC1666, in acute myeloid leukemia.

Mer and Flt3 receptor tyrosine kinases have been implicated as therapeutic targets in acute myeloid leukemia (AML). In this manuscript we describe UNC1666, a novel ATP-competitive small molecule tyrosine kinase inhibitor, which potently diminishes Mer and Flt3 phosphorylation in AML. Treatment with UNC1666 mediated biochemical and functional effects in AML cell lines expressing Mer or Flt3 internal tandem duplication (ITD), including decreased phosphorylation of Mer, Flt3 and downstream effectors Stat, Akt and Erk, induction of apoptosis in up to 98% of cells, and reduction of colony formation by greater than 90%, compared to treatment with vehicle.