Pharmacokinetics and relative bioavailability of carboxyamido-triazole with respect to food and time of administration: use of a single model for simultaneous determination of changing parameters

EFFECTIVE TRANSSCLERAL DELIVERY OF TWO RETINAL ANTI-ANGIOGENIC MOLECULES

PURPOSE

To evaluate the human transscleral diffusion and intravitreal delivery of carboxyamido-triazole (CAI) and 2-Methoxyestradiol (2ME2).

METHODS

The transscleral diffusion of two retinal antiangiogenic molecules, CAI and 2ME2, was measured in vitro to assess their potential transscleral delivery. Varying concentrations and different solvents of CAI and 2ME2 were placed in the upper compartment of a two-chamber acrylic perfusion apparatus, on the episcleral side of the sclera obtained from human donor eyes. Samples were taken from the lower compartment (uveal side) for up to 24 hours and measured by high performance liquid chromatography.

RESULTS

All three solutions that contained CAI efficiently diffused through the sclera with permeability constants that ranged from 2.8 to 5.5 x 10 cm/s. The scleral permeability constant derived for 2ME2 was 9.96 x 10 cm/s. The permeability constants obtained for both CAI and 2ME2 are similar to each other as well as to permeability constants measured for other small molecules such as fluorescein and dexamethasone fluorescein.

CONCLUSION

Both CAI and 2ME2 traverse the sclera efficiently. These data combined with the reported inhibition of posterior segment neovascularization observed with these two molecules demonstrates that CAI and 2ME2 are good candidate molecules to treat posterior segment neovascularization by local delivery.

The blocking of capacitative calcium entry by 2-aminoethyl diphenylborate (2-APB) and carboxyamidotriazole (CAI) inhibits proliferation in Hep G2 and Huh-7 human hepatoma cells

Calcium entry is a component of the processes regulating the proliferative phenotype of some types of cancer. In non-excitable cells, capacitative calcium entry (CCE) and non-capacitative calcium entry (NCCE) are thought to be the main pathways of Ca2+ influx into cells. Thus, blocking calcium entry may prevent normal and pathological cell proliferation and there is evidence to suggest that molecules blocking calcium entry also have antiproliferative properties. Carboxyamidotriazole (CAI), a novel inhibitor of the non-voltage-dependent calcium entry has been shown to have such properties in model systems in vitro and in vivo. We used Hep G2 and Huh-7 human hepatoma cells to investigate the effects of calcium entry blockers on cell proliferation. CAI (10 microM) and 2-APB (20 microM) completely blocked CCE in thapsigargin-treated Huh-7, and CAI and 2-APB inhibited cell proliferation with IC50 of 4.5 and 43 microM, respectively. The plateau phase of the [Ca2+]i increases triggered by 10% FCS were abolished in the absence of external Ca2+ and in the presence of CAI or 2-APB. We, therefore, suggest that CCE is the main pathway involved in regulation of the processes leading to cell proliferation.

Phase II trial of carboxyamidotriazole in patients with relapsed epithelial ovarian cancer

PURPOSE

Carboxyamidotriazole (CAI) is a cytostatic inhibitor of nonvoltage-operated calcium channels and calcium channel-mediated signaling pathways. It inhibits angiogenesis, tumor growth, invasion, and metastasis. We hypothesized that CAI would promote disease stabilization lasting >/= 6 months in patients with relapsed ovarian cancer.

PATIENTS AND METHODS

Patients with epithelial ovarian cancer, good end-organ function, measurable disease, and three or fewer prior regimens were eligible. Oral CAI was given daily using a pharmacokinetic-dosing approach to maintain plasma concentrations between 2 and 4 microg/mL. Radiographic imaging to assess response was performed every 8 weeks. Positive outcome included stabilization or improvement of disease lasting >/= 6 months. Plasma vascular endothelial growth factor (VEGF), interleukin (IL)-8, and matrix metalloproteinase (MMP)-2 were measured.

RESULTS

Thirty-six patients were assessable for primary end point analysis, and 38 were assessable for toxicity. Forty-four percent of patients had three prior regimens, more than 50% had four or more disease sites, and 48% had liver metastases. Thirty-three patients reached the targeted concentration range during the first cycle. Eleven patients (31%) attained the >/= 6-month outcome end point, with one partial response (8 months) and three minor responses (8, 12+, and 13 months). Median time to progression was 3.6 months (range, 1.6 to 13.3 months). CAI was well tolerated, with mostly grade 1 to 2 toxicity. Grade 3 events included fatigue (5%), vomiting (2%), neutropenic fever (2%), and neutropenia (2%). There were no grade 4 adverse events. No associations between VEGF, IL-8, and MMP-2 with CAI concentration or clinical outcome were observed.

CONCLUSION

CAI is a potential agent for additional study in the stabilization of relapsed ovarian cancer. Given a limited toxicity profile, it may have utility as a maintenance therapeutic agent for this disease.

Effects of Food on the Clinical Pharmacokinetics of Anticancer Agents

Pharmacokinetic interactions between food and orally administered drugs involve changes mainly in the absorption and metabolism of a drug, and may have clinical implications. Such interactions, in particular, may be of major clinical significance for cancer chemotherapy since the majority of anticancer agents are toxic, have a low therapeutic index and are administered long term, most often in combination with other cytotoxic agents. The purpose of this review is to compare the pharmacokinetic profiles of various anticancer drugs, including chemopreventive agents that have been examined previously in fasted and fed conditions, and to discuss the underlying basis/mechanisms of food effect in light of a drug's physicochemical and pharmacokinetic properties. Clinical pharmacokinetic parameters such as maximum concentration, area under the concentration-time curve, time to maximum concentration and half-life for each drug are compared in fasted and fed states, and specific dietary recommendations are summarised accordingly. In addition, the effects of food on the metabolite kinetics and pharmacodynamic responses, and the potential role of food effect in the modulation of oral biovariability and multidrug resistance have been extensively discussed. Overall, this comprehensive pharmacokinetic analysis indicates that a broad spectrum of food effects is seen among anticancer agents because of diverse factors regulating each drug's oral bioavailability and its interactions with food. The consideration of such effects is important, as it could lead to more rational pharmacological monitoring and possibly improve the oral chemotherapy of cancer in children, adults and the elderly.

CAI inhibits the growth of small cell lung cancer cells

The effects of carboxyamido-triazole (CAI) on small cell lung cancer (SCLC) cells were investigated. Using SCLC cell lines NCI-H209 or H345, 20 micro M CAI had little effect on basal cytosolic Ca(2+) but inhibited the ability of 10 nM bombesin (BB) or 1 nM neurotensin (NT) to elevate cytosolic Ca(2+). Also, CAI, impaired the ability of BB or NT to cause tyrosine phosphorylation of focal adhesion kinase. In contrast, CAI did not affect the ability of (125I-Tyr(4))BB or 125I-NT to bind with high affinity to NCI-H345 cells. These results indicate that CAI impairs SCLC second messenger activation, but not neuropeptide receptor binding. Using a MTT growth assay, CAI inhibited the proliferation of NCI-H209 or H345 cells in a concentration-dependent manner with little proliferation occurring using 100 micro M CAI. Also, CAI inhibited colony formation of NCI-H209 or H345 cells in a dose-dependent manner in vitro. In vivo, CAI (2 mg/day by gavage) inhibited significantly NCI-H209 xenograft proliferation in nude mice. Animals treated daily with CAI had significantly reduced CD31 immunostaining of microvessels in the tumor. Also, CAI inhibited the increase in vascular endothelial cell growth factor (VEGF) mRNA after addition of BB to SCLC cells. These results suggest that CAI inhibits the growth of SCLC cells as well as the angiogenesis of SCLC tumors in a VEGF-dependent manner.