Shigeo Yanai

Antitumor Effect of Arterial Administration of a Medium-Chain Triglyceride Solution of an Angiogenesis Inhibitor, TNP-470, in Rabbits Bearing VX-2 Carcinoma

Using rabbits bearing VX-2 carcinoma on the inner side of the leg, we examined the antitumor activity of a medium-chain triglyceride (MCT) solution of an angiogenesis inhibitor, TNP-470 (AGM-1470, 6-O-(N-chloroacetylcarbamoyl)-fumagillol), following administration into the femoral artery feeding the tumor. The MCT solution of TNP-470 (1 and 5 mg) strongly suppressed tumor growth following a single intra-arterial (i. a.) injection 2 or 3 weeks after tumor inoculation. Moreover, remarkable regression of well-developed tumors, those 4 weeks after inoculation, was obtained by i.a. injection of the MCT solution containing 20 mg of TNP-470 without any influence on body weight. The antitumor effects were potentiated by coad-ministration of doxorubicin or mitomycin C (MMC) in the solution or microspheres containing MMC. In a shell-less chorioallantoic membrane (CAM) assay, angiogenesis was inhibited when a droplet of the MCT solution containing 25 µg of TNP-470 was placed on the CAM for 2 days, suggesting that the prolonged antitumor effect resulted from the inhibition of tumor neovascularization by sustained drug release from the preparation. These results indicate that i. a. injection of the MCT solution of TNP-470 is promising for treating well-developed tumors.

Insulin fragments as a carrier for peptide delivery across the blood-brain barrier.

The possibility of using insulin (INS), which is transported into the brain by receptor-mediated transcytosis, as a peptide carrier for delivery across the blood-brain barrier (BBB) was investigated. After mice received an i.v. injection of horseradish peroxidase (HRP, M.W., 40,000) conjugated with INS, the HRP activity in the brain was higher than that after HRP injection. Since INS-HRP lowered the blood glucose level, we prepared insulin fragments by chemical and enzymatic procedures in an effort to find a carrier with no hypoglycemic activity. Seven fragments were synthesized taking the binding regions into consideration, but none showed any receptor binding affinity in cultures of bovine brain micro vessel endothelial cells (BMEC). However, the fragment (F007) obtained by trypsin digestion showed high affinity and scarcely any hypoglycemic activity in mice even at a dose ten times the effective dose of insulin. These results suggest that this fragment may be useful as a carrier to transport therapeutic peptides across the BBB.

Iontophoretic pulsatile transdermal delivery of human parathyroid hormone (1-34).

Iontophoretic pulsatile transdermal delivery of hPTH(1–34) was examined in Sprague‐Dawley (SD) rats, hairless rats and beagle dogs. Application for 60 min (200 μ 0.1 mA cm−2) showed current‐responsive increases in serum hPTH(1–34) levels in all the animals. In SD rats, the area under the curves of serum hPTH(1–34) levels (AUCs) were proportional to the doses (40, 120, 200, 400 and 1000 μg) and current densities (0.05, 0.1 and 0.15 mA cm−2) applied. The absorption rates per 200‐μg dose, calculated by a deconvolution method, were 6.7, 2.4 and 3.7 μg h−1 for SD rats, hairless rats and beagle dogs, respectively. These values correlated well with the ratios of the skin porosity to the dermal thickness reported for these animals, which are believed to represent the reciprocal of the electrical resistance of the aqueous channels formed by the hair follicles. From this correlation, we suggested that absorption of hPTH(1–34) occurs mainly via the hair‐follicle route, and that the absorption rate in man might be intermediate between those in hairless rats and beagle dogs. Three‐fold repetitions of 30 min current with various rest intervals produced current‐responsive triple pulses in serum hPTH(1–34) levels in SD rats. Seven‐fold repetitions of current also produced similar current‐responsive pulsatile serum hPTH(1–34) levels. However, peak serum hPTH(1–34) levels tended to decrease gradually after the fourth current application, possibly due to consumption of the electrodes, suggesting that three‐fold repetitions of current might be optimal. These findings suggest that this iontophoretic administration system could create a repeated‐pulsatile pattern of serum hPTH(1–34) levels without the necessity for frequent injections, and may be useful for the treatment of osteoporosis with hPTH(1–34).

Optimal formulation of an angiogenesis inhibitor, TNP-470, for arterial injection determined by in vitro drug release and stability, and in vivo antitumor activity

TNP-470 (6-O-(N-chloroacetylcarbamoyl)fumagillol, AGM-1470) is an angiogenesis inhibitor, a new type of anticancer drug which prevents tumor neovascularization, thereby blocking the nutrient supply to tumors. In this study, we sought the optimal formulation of TNP-470 for arterial injection in order to achieve strong anticancer activity due to the tumor-selective targeting of the drug, by investigating in vitro release and stability and in vivo rabbit VX-2 antitumor activity. We found that a medium-chain triglyceride (MCT) solution containing TNP-470 facilitated the 2-week sustained release of TNP-470 in vitro and fairly good long-term stability of the agent, although it was very labile in aqueous solution. In a rabbit VX-2 tumor model, 3 weeks after inoculation on the inner side of the leg, the antitumor activities of various formulations of TNP-470 were evaluated by administration into the femoral artery feeding the tumor. Compared with Lipiodol solution or PLGA microspheres containing TNP-470, the MCT solution containing TNP-470 exerted stronger and more persistent antitumor activity accompanied by tumor regression for 3 weeks subsequently. The release sustainability of TNP-470 in the in vitro release test was suggested to be an important factor in the antitumor activity of each formulation. From these results, we conclude that the MCT solution is the most promising formulation of TNP-470 as an arterial injection for treatment of cancers.

Anticancer Effects of an Angiogenesis Inhibitor (TNP-470) After Arterial Injection in Rabbits Bearing VX-2 Carcinoma

TNP-470, an angiogenesis inhibitor, is a new type of anticancer drug that inhibits tumor neovascularization which is critical to tumor growth. Chemoembolization using TNP-470 microspheres prepared with a biodegradable polymer provided striking regression of the tumor, but growth was again observed 1 week after injection. TNP-470 dissolved in Lipiodol (a liquid lymphography agent) or MIGLYOL 812 (medium-chain triglycerides) caused persistent suppression of the tumor growth for 2 or 3 weeks after a single intraarterial injection due to sustained drug release from the preparation. Coadministration of TNP-470 and a conventional chemotherapeutic agent resulted in enhanced antitumor effects.