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).

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.