ABI-007, an albumin-bound, 130-nm particle form of paclitaxel, was developed to avoid Cremophor/ethanol-associated toxicities in Cremophor-based paclitaxel (Taxol) and to exploit albumin receptor-mediated endothelial transport. We studied the antitumor activity, intratumoral paclitaxel accumulation, and endothelial transport for ABI-007 and Cremophor-based paclitaxel. Antitumor activity and mortality were assessed in nude mice bearing human tumor xenografts [lung (H522), breast (MX-1), ovarian (SK-OV-3), prostate (PC-3), and colon (HT29)] treated with ABI-007 or Cremophor-based paclitaxel. Intratumoral paclitaxel concentrations (MX-1-tumored mice) were compared for radiolabeled ABI-007 and Cremophor-based paclitaxel. In vitro endothelial transcytosis and Cremophor inhibition of paclitaxel binding to cells and albumin was compared for ABI-007 and Cremophor-based paclitaxel. Both ABI-007 and Cremophor-based paclitaxel caused tumor regression and prolonged survival; the order of sensitivity was lung > breast ffi ovary > prostate > colon. The LD 50 and maximum tolerated dose for ABI-007 and Cremophor-based paclitaxel were 47 and 30 mg/kg/d and 30 and 13.4 mg/kg/d, respectively. At equitoxic dose, the ABI-007-treated groups showed more complete regressions, longer time to recurrence, longer doubling time, and prolonged survival. At equal dose, tumor paclitaxel area under the curve was 33% higher for ABI-007 versus Cremophorbased paclitaxel, indicating more effective intratumoral accumulation of ABI-007. Endothelial binding and transcytosis of paclitaxel were markedly higher for ABI-007 versus Cremophorbased paclitaxel, and this difference was abrogated by a known inhibitor of endothelial gp60 receptor/caveolar transport. In addition, Cremophor was found to inhibit binding of paclitaxel to endothelial cells and albumin. Enhanced endothelial cell binding and transcytosis for ABI-007 and inhibition by Cremophor in Cremophor-based paclitaxel may account in part for the greater efficacy and intratumor delivery of ABI-007.Paclitaxel is a naturally occurring complex diterpenoid product extracted from the bark of the western yew, Taxus brevifolia (1). The unique mechanism of paclitaxel of stabilizing tubulin polymer and promoting microtubule assembly effectively inhibits mitosis, motility, and intracellular transport within cancerous cells and results in antineoplastic activity against a wide variety of malignancies (2 -4). Paclitaxel is widely used for the treatment of breast, lung, and advanced ovarian cancers (5).Because paclitaxel has very little aqueous solubility, Cremophor-based paclitaxel uses a Cremophor EL/ethanol vehicle. The amount of Cremophor EL necessary to deliver the requisite doses of paclitaxel is significantly higher than that given with any other marketed drug containing Cremophor EL, reaching plasma concentrations up to 0.4% and remaining >0.1% for 24 hours following a dose of 175 mg/m 2 (6). The Cremophor EL -containing paclitaxel formulation causes severe allergic, hypersensitivity, and anaph...

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While engaged in therapeutic intervention against a number of proliferative diseases, we have discovered the 2-aminopyrido[2, 3-d]pyrimidin-7(8H)-ones as a novel class of potent, broadly active tyrosine kinase (TK) inhibitors. An efficient route was developed that enabled the synthesis of a wide variety of analogues with substitution on several positions of the template. From the lead structure 2, a series of analogues bearing variable substituents at the C-2 position and methyl or ethyl at N-8 was made. Compounds of this series were competitive with ATP and displayed submicromolar to low nanomolar potency against a panel of TKs, including receptor (platelet-derived growth factor, PDGFr; fibroblast growth factor, FGFr; epidermal growth factor, EGFr) and nonreceptor (c-Src) classes. One of the more thoroughly evaluated members was 63 with IC50 values of 0.079 microM (PDGFr), 0.043 microM (bFGFr), 0.044 microM (EGFr), and 0.009 microM (c-Src). In cellular studies, 63 inhibited PDGF-mediated receptor autophosphorylation in a number of cell lines at IC50 values of 0.026-0.002 microM and proliferation of two PDGF-dependent lines at 0.3 microM. It also caused inhibition of soft agar colony formation in three cell lines that overexpress the c-Src TK, with IC50 values of 0.33-1.8 microM. In in vivo studies against a panel of seven xenograft tumor models with known and/or inferred dependence on the EGFr, PDGFr, and c-Src TKs, compound 63 produced a tumor growth delay of 10.6 days against the relatively refractory SK-OV-3 ovarian xenograft and also displayed activity against the HT-29 tumor. In rat oral bioavailability studies, compound 63 plasma concentrations declined in a biexponential manner, and systemic plasma clearance was high relative to liver blood flow. Finally, in rat metabolism studies, HPLC chromatography identified two metabolites of 63, which were proved by mass spectrometry and synthesis to be the primary amine (58) and N-oxide (66). Because of the excellent potency of 63 against selected TKs, in vitro and in vivo studies are underway for this compound in additional tumor models dependent upon PDGFr, FGFr, and c-Src to assess its potential for advancement to clinical trials.

In a 2-yr carcinogenicity bioassay, 0, 2, 4, or 8 mg furan/kg body weight (BW) was administered to male and female Fischer (F344) rats and resulted in an 86-100% incidence of cholangiocarcinomas with occasional metastasis. In a separate but concurrent study, male F344 rats dosed with 30 mg furan/kg BW for 90 days developed marked cholangiofibrosis and cholangiohepatitis and, when subsequently maintained without further treatment for an additional 6, 12, or 18 months, the cholangiofibrosis progressed to yield a 100% incidence of cholangiocarcinomas. Transplantation of 21 primary cholangiocarcinomas into syngeneic recipients resulted in growth from 4 donors. The 4 transplanted lines were successfully transferred through 8 serial passages and resulted in metastases in the recipients. The progressive growth of these proliferative hepatocholangial lesions over time, their transplantability, and the development of metastases in some of the cases provide biological evidence of the malignant potential of the furan-induced liver changes.

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