An RNA aptamer restores defective bone growth in FGFR3-related skeletal dysplasia in mice.

Achondroplasia is the most prevalent genetic form of dwarfism in humans and is caused by activating mutations in FGFR3 tyrosine kinase. The clinical need for a safe and effective inhibitor of FGFR3 is unmet, leaving achondroplasia currently incurable. Here, we evaluated RBM-007, an RNA aptamer previously developed to neutralize the FGFR3 ligand FGF2, for its activity against FGFR3. In cultured rat chondrocytes or mouse embryonal tibia organ culture, RBM-007 rescued the proliferation arrest, degradation of cartilaginous extracellular matrix, premature senescence, and impaired hypertrophic differentiation induced by FGFR3 signaling. In cartilage xenografts derived from induced pluripotent stem cells from individuals with achondroplasia, RBM-007 rescued impaired chondrocyte differentiation and maturation. When delivered by subcutaneous injection, RBM-007 restored defective skeletal growth in a mouse model of achondroplasia. We thus demonstrate a ligand-trap concept of targeting the cartilage FGFR3 and delineate a potential therapeutic approach for achondroplasia and other FGFR3-related skeletal dysplasias.

Anti-Angiogenic and Anti-Scarring Dual Action of an Anti-Fibroblast Growth Factor 2 Aptamer in Animal Models of Retinal Disease.

Currently approved therapies for age-related macular degeneration (AMD) are inhibitors against vascular endothelial growth factor (VEGF), which is a major contributor to the pathogenesis of neovascular AMD (nAMD). Intravitreal injections of anti-VEGF drugs have shown dramatic visual benefits for AMD patients. However, a significant portion of AMD patients exhibit an incomplete response to therapy and, over the extended management course, can lose vision, with the formation of submacular fibrosis as one risk factor. We investigated a novel target for AMD treatments, fibroblast growth factor 2 (FGF2), which has been implicated in the pathophysiology of both angiogenesis and fibrosis in a variety of tissue and organ systems. The anti-FGF2 aptamer, RBM-007, was examined for treatment of nAMD in animal models. In in vivo studies conducted in mice and rats, RBM-007 was able to inhibit FGF2-induced angiogenesis, laser-induced choroidal neovascularization (CNV), and CNV with fibrosis. Pharmacokinetic studies of RBM-007 in the rabbit vitreous revealed high and relatively long-lasting profiles that are superior to other approved anti-VEGF drugs. The anti-angiogenic and anti-scarring dual action of RBM-007 holds promise as an additive or alternative therapy to anti-VEGF treatments for nAMD.

A Chymase Inhibitory RNA Aptamer Improves Cardiac Function and Survival after Myocardial Infarction.

We have reported that mast cell chymase, an angiotensin II-generating enzyme, is important in cardiovascular tissues. Recently, we developed a new chymase-specific inhibitory RNA aptamer, HA28, and we evaluated the effects of HA28 on cardiac function and the mortality rate after myocardial infarction. Echocardiographic parameters, such as the left ventricular ejection fraction, fractional shortening, and the ratio of early to late ventricular filling velocities, were significantly improved by treatment with HA28 after myocardial infarction. The mortality rate was significantly reduced in the HA28-treated group. Cardiac chymase activity and chymase gene expression were significantly higher in the vehicle-treated myocardial infarction group, and these were markedly suppressed in the HA28-treated myocardial infarction group. The present study provides the first evidence that a single-stranded RNA aptamer that is a chymase-specific inhibitor is very effective in the treatment of acute heart failure caused by myocardial infarction. Chymase may be a new therapeutic target in post-myocardial infarction pathophysiology.

The FGF2 aptamer inhibits the growth of FGF2-FGFR pathway driven lung cancer cells.

Cancers, including lung cancer, are a leading cause of death worldwide. To overcome this deadly disease, multiple modality inhibitors have been developed. These include cytotoxic agents, molecular targeted small molecules, such as tyrosine kinase inhibitors, and neutralizing antibodies. An aptamer is a short single-stranded nucleic acid molecule that is selected in vitro from a large random sequence library based on its high and specific affinity to a target molecule. Aptamers can be applied to therapeutics of various types of diseases, including cancer, due to their strong and specific neutralizing activities. However, the efficacy of aptamer-based therapy for cancer cells is not well characterized. In this study, we aimed to show that the FGF2 aptamer is effective for the treatment of FGF2 dependent lung cancer cells. We previously developed PC9GR lung cancer cells, whose proliferation is dependent on EGFR and FGF2-FGFR pathways in a cell autonomous manner. Using PC9GR cells, we demonstrate that the addition of the FGF2 aptamer induces more significant inhibition of PC9GR cell proliferation than does the addition of EGFR inhibitor alone. Furthermore, the addition of the FGF2 aptamer more significantly inhibits the downstream signals and induces apoptosis to a higher extent than does the addition of EGFR inhibitor alone. Our results show that the FGF2 aptamer inhibits the growth of FGF2-FGFR pathway-dependent lung cancer cells. The findings provide preclinical evidence that aptamers can be useful for cancer treatment.

Dual Therapeutic Action of a Neutralizing Anti-FGF2 Aptamer in Bone Disease and Bone Cancer Pain.

Fibroblast growth factor 2 (FGF2) plays a crucial role in bone remodeling and disease progression. However, the potential of FGF2 antagonists for treatment of patients with bone diseases has not yet been explored. Therefore, we generated a novel RNA aptamer, APT-F2, specific for human FGF2 and characterized its properties in vitro and in vivo. APT-F2 blocked binding of FGF2 to each of its four cellular receptors, inhibited FGF2-induced downstream signaling and cells proliferation, and restored osteoblast differentiation blocked by FGF2. APT-F2P, a PEGylated form of APT-F2, effectively blocked the bone disruption in mouse and rat models of arthritis and osteoporosis. Treatment with APT-F2P also exerted a strong analgesic effect, equivalent to morphine, in a mouse model of bone cancer pain. These findings demonstrated dual therapeutic action of APT-F2P in bone diseases and pain, providing a promising approach to the treatment of bone diseases.

Selective inhibition of the kinase DYRK1A by targeting its folding process.

Autophosphorylation of amino-acid residues is part of the folding process of various protein kinases. Conventional chemical screening of mature kinases has missed inhibitors that selectively interfere with the folding process. Here we report a cell-based assay that evaluates inhibition of a kinase at a transitional state during the folding process and identify a folding intermediate-selective inhibitor of dual-specificity tyrosine-phosphorylation-regulated kinase 1A (DYRK1A), which we refer to as FINDY. FINDY suppresses intramolecular autophosphorylation of Ser97 in DYRK1A in cultured cells, leading to its degradation, but does not inhibit substrate phosphorylation catalysed by the mature kinase. FINDY also suppresses Ser97 autophosphorylation of recombinant DYRK1A, suggesting direct inhibition, and shows high selectivity for DYRK1A over other DYRK family members. In addition, FINDY rescues DYRK1A-induced developmental malformations in Xenopus laevis embryos. Our study demonstrates that transitional folding intermediates of protein kinases can be targeted by small molecules, and paves the way for developing novel types of kinase inhibitors.

Structural basis for specific inhibition of Autotaxin by a DNA aptamer.

ATX is a plasma lysophospholipase D that hydrolyzes lysophosphatidylcholine (LPC) and produces lysophosphatidic acid. To date, no ATX-inhibition-mediated treatment strategies for human diseases have been established. Here, we report anti-ATX DNA aptamers that inhibit ATX with high specificity and efficacy. We solved the crystal structure of ATX in complex with the anti-ATX aptamer RB011, at 2.0-Å resolution. RB011 binds in the vicinity of the active site through base-specific interactions, thus preventing the access of the choline moiety of LPC substrates. Using the structural information, we developed the modified anti-ATX DNA aptamer RB014, which exhibited in vivo efficacy in a bleomycin-induced pulmonary fibrosis mouse model. Our findings reveal the structural basis for the specific inhibition of ATX by the anti-ATX aptamer and highlight the therapeutic potential of anti-ATX aptamers for the treatment of human diseases, such as pulmonary fibrosis.

Development of a novel selective inhibitor of the Down syndrome-related kinase Dyrk1A.

Dyrk1A (dual-specificity tyrosine-(Y)-phosphorylation-regulated kinase 1A) is a serine/threonine kinase essential for brain development and function, and its excessive activity is considered a pathogenic factor in Down syndrome. The development of potent, selective inhibitors of Dyrk1A would help to elucidate the molecular mechanisms of normal and diseased brains, and may provide a new lead compound for molecular-targeted drug discovery. Here, we report a novel Dyrk1A inhibitor, INDY, a benzothiazole derivative showing a potent ATP-competitive inhibitory effect with IC(50) and K(i) values of 0.24 and 0.18 µM, respectively. X-ray crystallography of the Dyrk1A/INDY complex revealed the binding of INDY in the ATP pocket of the enzyme. INDY effectively reversed the aberrant tau-phosphorylation and rescued the repressed NFAT (nuclear factor of activated T cell) signalling induced by Dyrk1A overexpression. Importantly, proINDY, a prodrug of INDY, effectively recovered Xenopus embryos from head malformation induced by Dyrk1A overexpression, resulting in normally developed embryos and demonstrating the utility of proINDY in vivo.

Identification of endogenous surrogate ligands for human P2Y12 receptors by in silico and in vitro methods.

Endogenous ligands acting on a human P2Y12 receptor, one of the G-protein coupled receptors, were searched by in silico screening against our own database, which contains more than 500 animal metabolites. The in silico screening using the docking software AutoDock resulted in selection of cysteinylleukotrienes (CysLTs) and 5-phosphoribosyl 1-pyrophosphate (PRPP), with high free energy changes, in addition to the known P2Y12 ligands such as 2MeSADP and ADP. These candidates were subjected to an in vitro Ca2+ assay using the CHO cells stably expressing P2Y12-G16alpha fusion proteins. We found that CysLTE4 and PRPP acted on the P2Y12 receptor as agonists with the EC50 values of 1.3 and 7.8 nM, respectively. Furthermore, we analyzed the phylogenetic relationship of the P2Y, P2Y-like, and CysLT receptors based on sequence alignment followed by evolutionary analyses. The analyses showed that the P2Y12, P2Y13, P2Y14, GPR87, CysLT-1, and CysLT-2 receptors formed a P2Y-related receptor subfamily with common sequence motifs in the transmembrane regions.

Identification of endogenous surrogate ligands for human P2Y receptors through an in silico search.

G protein-coupled receptors (GPCRs) are distributed widely throughout the human body, and nearly 50% of current medicines act on a GPCR. GPCRs are considered to consist of seven transmembrane alpha-helices that form an alpha-helical bundle in which agonists and antagonists bind. A 3D structure of the target GPCR is indispensable for designing novel medicines acting on a GPCR. We have previously constructed the 3D structure of human P2Y(1) (hP2Y(1)) receptor, a GPCR, by homology modeling with the 3D structure of bovine rhodopsin as a template. In the present study, we have employed an in silico screening for compounds that could bind to the hP2Y(1)-receptor model using AutoDock 3.0. We selected 21 of the 30 top-ranked compounds, and by measuring intracellular Ca(2+) concentration, we identified 12 compounds that activated or blocked the hP2Y(1) receptor stably expressed in recombinant CHO cells. 5-Phosphoribosyl-1-pyrophosphate (PRPP) was found to activate the hP2Y(1) receptor with a low ED(50) value of 15 nM. The Ca(2+) assays showed it had no significant effect on P2Y(2), P2Y(6), or P2X(2) receptors, but acted as a weak agonist on the P2Y(12) receptor. This is the first study to rationally identify surrogate ligands for the P2Y-receptor family.