Inhibition of vascular endothelial growth factor-A (VEGF) signaling is a promising therapeutic approach that aims to stabilize the progression of solid malignancies by abrogating tumor-induced angiogenesis. This may be accomplished by inhibiting the kinase activity of VEGF receptor-2 (KDR), which has a key role in mediating VEGF-induced responses. The novel indole-ether quinazoline AZD2171 is a highly potent (IC50 < 1 nmol/L) ATP-competitive inhibitor of recombinant KDR tyrosine kinase in vitro. Concordant with this activity, in human umbilical vein endothelial cells, AZD2171 inhibited VEGF-stimulated proliferation and KDR phosphorylation with IC50 values of 0.4 and 0.5 nmol/L, respectively. In a fibroblast/endothelial cell coculture model of vessel sprouting, AZD2171 also reduced vessel area, length, and branching at subnanomolar concentrations. Once-daily oral administration of AZD2171 ablated experimental (VEGF-induced) angiogenesis in vivo and inhibited endochondral ossification in bone or corpora luteal development in ovary; physiologic processes that are highly dependent upon neovascularization. The growth of established human tumor xenografts (colon, lung, prostate, breast, and ovary) in athymic mice was inhibited dose-dependently by AZD2171, with chronic administration of 1.5 mg per kg per day producing statistically significant inhibition in all models. A histologic analysis of Calu-6 lung tumors treated with AZD2171 revealed a reduction in microvessel density within 52 hours that became progressively greater with the duration of treatment. These changes are indicative of vascular regression within tumors. Collectively, the data obtained with AZD2171 are consistent with potent inhibition of VEGF signaling, angiogenesis, neovascular survival, and tumor growth. AZD2171 is being developed clinically as a once-daily oral therapy for the treatment of cancer.

The effects of L-NG-nitro arginine (L-NOARG) on a-chymotrypsin-resistant, non-adrenergic, noncholinergic (NANC) relaxations of guinea-pig tracheal smooth muscle have been examined. L-NOARG (1-100pM), but not D-NOARG (100pM), inhibited the NANC relaxations in a concentration-related manner. The effects of L-NOARG were partially reversed by L-arginine but not D-arginine. L-NOARG was without effect on acetylcholine-induced contractile responses of the trachea or on relaxations produced by vasoactive intestinal peptide, sodium nitroprusside or isoprenaline. These results suggest that an endogenous nitrate may contribute to NANC relaxations of tracheal smooth muscle.Introduction In many species, including man and guinea-pig, electrically induced relaxations of tracheal smooth muscle have a non-adrenergic, non-cholinergic (NANC) component (Barnes, 1986). The identity of the neurotransmitter which mediates this effect is unknown and may vary with the species studied. In the guinea-pig, vasoactive intestinal peptide (VIP) and peptide histidine isoleucine (PHI) are strong candidates for at least part of this NANC relaxant response. Ellis &

Purpose: Vascular endothelial growth factor (VEGF) plays a key role in tumor angiogenesis and acts as a radiation survival factor for endothelial cells. ZD6474 (N-(4-bromo-2-fluorophenyl)-6-methoxy-7-[(1-methylpiperidin-4-yl)methoxy]-quinazolin-4-amine) is a potent VEGF receptor 2 (KDR) tyrosine kinase inhibitor (TKI) that has additional activity versus the epidermal growth factor receptor. This study was designed to determine the efficacy of combining ZD6474 and radiotherapy in vivo.Experimental Design: The Calu-6 (non-small-cell lung cancer) tumor model was selected because it was found to be unresponsive to treatment with a selective epidermal growth factor receptor TKI but responds significantly to treatment with selective VEGF receptor TKIs. Tumor-bearing mice received either vehicle or ZD6474 (50 mg/kg, by mouth, once daily) for the duration of the experiment, with or without radiotherapy (3 ؋ 2 Gy, days 1-3). Two combination schedules were examined: (a) ZD6474 given before each dose of radiation (concurrent schedule); and (b) ZD6474 given 30 minutes after the last dose of radiotherapy (sequential schedule).Results: The growth delay induced using the concurrent schedule was greater than that induced by ZD6474 or radiation treatment alone (22 ؎ 1 versus 9 ؎ 1 and 17 ؎ 2 days, respectively; P ‫؍‬ 0.03 versus radiation alone). When administered sequentially, the growth delay was markedly enhanced (36 ؎ 1 days; P < 0.001 versus radiation alone or the concurrent schedule). Intravenous administration of Hoechst 33342 showed a trend toward reduced tumor perfusion after ZD6474 treatment, and a pairwise comparison (versus control) was significant after three doses of ZD6474 (P ‫؍‬ 0.05 by one-tailed t test). Thus, impaired reoxygenation between fractions in the concurrent protocol may be the causal basis for the schedule dependency of the radiopotentiation observed.Conclusions: ZD6474 may be a successful adjuvant to clinical radiotherapy, and scheduling of the treatments could be important to ensure optimal efficacy.

Continued androgen receptor (AR) expression and signaling is a key driver in castration-resistant prostate cancer (CRPC) after classical androgen ablation therapies have failed, and therefore remains a target for the treatment of progressive disease. Here, we describe the biological characterization of AZD3514, an orally bioavailable drug that inhibits androgen-dependent and -independent AR signaling. AZD3514 modulates AR signaling through two distinct mechanisms, an inhibition of ligand-driven nuclear translocation of AR and a downregulation of receptor levels, both of which were observed in vitro and in vivo. AZD3514 inhibited testosterone-driven seminal vesicle development in juvenile male rats and the growth of androgen-dependent Dunning R3327H prostate tumors in adult rats. Furthermore, this class of compound showed antitumor activity in the HID28 mouse model of CRPC in vivo. AZD3514 is currently in phase I clinical evaluation.