Design, synthesis, and evaluation of NO-donor containing carbonic anhydrase inhibitors to lower intraocular pressure.

The antiglaucoma drugs dorzolamide (1) and brinzolamide (2) lower intraocular pressure (IOP) by inhibiting the carbonic anhydrase (CA) enzyme to reduce aqueous humor production. The introduction of a nitric oxide (NO) donor into the alkyl side chain of dorzolamide (1) and brinzolamide (2) has led to the discovery of NO-dorzolamide 3a and NO-brinzolamide 4a, which could lower IOP through two mechanisms: CA inhibition to decrease aqueous humor secretion (reduce inflow) and NO release to increase aqueous humor drainage (increase outflow). Compounds 3a and 4a have shown improved efficacy of lowering IOP in both rabbits and monkeys compared to brinzolamide (2).

Thioether benzenesulfonamide inhibitors of carbonic anhydrases II and IV: structure-based drug design, synthesis, and biological evaluation.

A novel series of potent thioether benzenesulfonamide inhibitors of carbonic anhydrases II and IV was discovered using structure-based drug design. Synthesis, structure-activity relationship, and optimization of physicochemical properties are described. Low nanomolar potency was achieved, and selected compounds with improved thermodynamic solubility showed promising in vitro inhibition of carbonic anhydrase activity in rabbit iris ciliary body homogenate.

Evaluation of CXCR4 inhibition in the prevention and intervention model of laser-induced choroidal neovascularization.

PURPOSE. Endothelial precursor cells (EPCs) derived from hematopoietic stem cells (HSCs) have been shown to contribute to choroidal neovascularization by signaling through the SDF-1/CXCR4 axis. In a prevention and treatment/intervention modality of the laser choroidal neovascularization (CNV) model, the efficacy of CXCR4 inhibition on reducing choroidal leakage and angiogenesis was evaluated. METHODS. CNV in rats was generated by focal rupture of Bruch's membrane with an 810-nm diode laser. In the prevention mode, a CXCR4 antagonist (AMD3100) was delivered via an osmotic pump 1 day after laser induction. In the intervention mode, AMD3100 delivery commenced 14 days after laser induction. Inhibition of CXCR4 was determined through leukocyte and SDF-1 actin polymerization blood biomarker assays. Leakage was assessed by fluorescein angiography, and CNV lesion size was quantified after isolectin B4 endothelial cell staining. SU14813, an anti-VEGFR, PDGFR-beta, KIT, and FLT3 inhibitor, was also assessed in an intervention study protocol. RESULTS. Inhibition of CXCR4 was demonstrated by an increase in the number of blood leukocytes, and diminished SDF-1 induced actin polymerization in whole blood. CNV leakage and neovascularization were inhibited when the dose regimen was initiated 1 day after laser-induced CNV induction. AMD3100 did not show efficacy when administered 14 days after lasering. Treatment with SU14813 significantly decreased CNV leakage and lesion size in an intervention modality. CONCLUSIONS. Inhibition of CXCR4 may be useful in preventing neovascularization but does not appear to have an effect on already established angiogenesis. A multiple receptor tyrosine kinase (RTK) inhibitor approach shows promise for the treatment of wet age-related macular degeneration.

Nonclinical antiangiogenesis and antitumor activities of axitinib (AG-013736), an oral, potent, and selective inhibitor of vascular endothelial growth factor receptor tyrosine kinases 1, 2, 3.

PURPOSE: Axitinib (AG-013736) is a potent and selective inhibitor of vascular endothelial growth factor (VEGF) receptor tyrosine kinases 1 to 3 that is in clinical development for the treatment of solid tumors. We provide a comprehensive description of its in vitro characteristics and activities, in vivo antiangiogenesis, and antitumor efficacy and translational pharmacology data. EXPERIMENTAL DESIGN: The potency, kinase selectivity, pharmacologic activity, and antitumor efficacy of axitinib were assessed in various nonclinical models. RESULTS: Axitinib inhibits cellular autophosphorylation of VEGF receptors (VEGFR) with picomolar IC(50) values. Counterscreening across multiple kinase and protein panels shows it is selective for VEGFRs. Axitinib blocks VEGF-mediated endothelial cell survival, tube formation, and downstream signaling through endothelial nitric oxide synthase, Akt and extracellular signal-regulated kinase. Following twice daily oral administration, axitinib produces consistent and dose-dependent antitumor efficacy that is associated with blocking VEGFR-2 phosphorylation, vascular permeability, angiogenesis, and concomitant induction of tumor cell apoptosis. Axitinib in combination with chemotherapeutic or targeted agents enhances antitumor efficacy in many tumor models compared with single agent alone. Dose scheduling studies in a human pancreatic tumor xenograft model show that simultaneous administration of axitinib and gemcitabine without prolonged dose interruption or truncation of axitinib produces the greatest antitumor efficacy. The efficacious drug concentrations predicted in nonclinical studies are consistent with the range achieved in the clinic. Although axitinib inhibits platelet-derived growth factor receptors and KIT with nanomolar in vitro potencies, based on pharmacokinetic/pharmacodynamic analysis, axitinib acts primarily as a VEGFR tyrosine kinase inhibitor at the current clinical exposure. CONCLUSIONS: The selectivity, potency for VEGFRs, and robust nonclinical activity may afford broad opportunities for axitinib to improve cancer therapy.