In vitro pharmacology of cryptophycin 52 (LY355703) in human tumor cell lines

Purpose: Cryptophycin 52 (LY355703) is a new member of the cryptophycin family of antitumor agents that is currently undergoing clinical evaluation for cancer chemotherapy. The mechanism of action of the cryptophycin class of compounds is associated with an action on microtubules. This report details the pharmacological profile of this new clinical compound in a panel of human tumor cell lines. Methods: Antiproliferative effects of cryptophycin 52 were measured indirectly by detection of the metabolic reduction of alamarBlue^®. Cytoxicity was assessed by enzymatic dye activation (calcein AM) combined with dye exclusion (ethidium homodimer) and by clonogenicity assay. Cell cycle effects were evaluated using flow cytometry and fluorescence microscopy. Results: Both antiproliferative and cytotoxic effects of cryptophycin 52 were concentration- and time-dependent. IC₅₀ values for antiproliferative activity in both solid and hematologic tumor cell lines were in the low picomolar range, and without exception, were significantly below values for the antimitotic agents paclitaxel and vinblastine. Flow cytometry and microscopic examination of tumor cells treated with cryptophycin 52 indicated that they accumulated in the mitotic phase of the cell cycle. Cryptophycin 52 was tested for its sensitivity to multidrug-resistance in several paired cell lines in which a sensitive parental line was matched with a multidrug-resistant derivative line. The resistant lines have been shown to over express Pgp and/or MRP multidrug-resistance transport factors. Compared to other antimitotic agents (paclitaxel, vinblastine, vincristine), the potency of cryptophycin 52 was shown to be minimally affected in multidrug-resistant cells compared to their sensitive parental lines. Conclusion: Cryptophycin 52 has potent antimitotic, antiproliferative and cytotoxic activity in in vitro human tumor cell models. It is significantly more potent and less sensitive to multidrug resistance mechanisms than other antimitotic antitumor agents currently used in cancer therapy. These characteristics may translate into therapeutic advantages for the clinical use of cryptophycin 52 in cancer chemotherapy.     

The novel antimicrotubule agent cryptophycin 52 (LY355703) induces apoptosis via multiple pathways in human prostate cancer cells.

We assessed the ability of cryptophycin 52 (LY355703), a novel antimicrotubule, to induce growth arrest and apoptosis in prostate cancer cell lines and investigated potential molecular mechanisms of death. LNCaP (androgen-dependent) and DU-145 (androgen-independent) cells accumulated in G(2)-M phase of the cell cycle and progressively acquired sub-G(0)-G(1) DNA content after 48 h of exposure to cryptophycin 52 (1-10 pM). Induction of apoptosis was confirmed by DNA ladder formation and detection of cytoplasmic nucleosomes. PC-3 (androgen-independent) cells were less responsive to cryptophycin 52-induced death. Apoptosis was associated with proteolytic processing and activation of the caspase-3-like subfamily proteins caspase-3 and caspase-7 and cleavage of the caspase substrate poly(ADP-ribose) polymerase. The pan-caspase inhibitor BOC-Asp(OMe)-fluoromethylketone effectively reduced cryptophycin 52-induced caspase-3-like protease activity and apoptosis in DU-145 cells. In contrast, BOC-Asp(OMe)-fluoromethylketone did not inhibit apoptosis induction in LNCaP cells by cryptophycin 52, even though both cryptophycin 52-induced caspase-3-like activity and staurosporine-induced death were blocked under identical conditions. Cryptophycin 52 induced phosphorylation of c-raf1 and bcl-2 and/or bcl-x(L) to comparable levels in all cell lines studied, and LNCaP cells overexpressing bcl-2 were more resistant to cryptophycin 52-induced apoptosis. Up-regulation of p53, bax, and p21 expression was induced in wild-type p53-expressing LNCaP cells only after cryptophycin 52 exposure. A sustained increase in c-Jun NH(2)-terminal kinase phosphorylation was also observed, the levels of which strongly correlated with apoptosis. We conclude that apoptosis induced by cryptophycin 52 in prostate cancer cells is androgen status independent, cell type specific for caspase requirement, modulated by the bcl-2 family, linked to but not dependent on p53, and strongly correlated with c-Jun NH(2)-terminal kinase phosphorylation. Cryptophycin 52-induced apoptosis in prostate cancer cells is therefore associated with multiple cell line-specific alterations in apoptosis-associated proteins and pathways.     

Cryptophycin-induced hyperphosphorylation of Bcl-2, cell cycle arrest and growth inhibition in human H460 NSCLC cells

Bcl-2 has been described as a factor that can protect from apoptosis. The protective effect of Bcl-2 may be lost if the protein is phosphorylated. Bcl-2 phosphorylation can be induced by agents that affect microtubule depolymerization or prevent microtubule assembly. In 13 human tumor cell lines there was a high degree of heterogeneity in Bcl-2 protein expression. Human H460 non-small-cell lung carcinoma (NSCLC) cells expressed high levels of Bcl-2 and were selected for study. Western blot analysis for Bcl-2 phosphorylation was carried out after 4 h and 24 h of exposure to cryptophycin 52, cryptophycin 55, paclitaxel or vinblastine. Cryptophycin 52 and cryptophycin 55 were very potent inducers of Bcl-2 phosphorylation. After 4 h of exposure, Bcl-2 phosphorylation was evident with 0.05 nM cryptophycin 52, 0.25 nM cryptophycin 55, 5 nM vinblastine and 50 nM paclitaxel. The hyperphosphorylated form of Bcl-2 was evident after 24 h exposure of H460 cells to 0.25 nM cryptophycin 52 or cryptophycin 55 and 50 nM vinblastine or paclitaxel. The effects of the compounds on the cell cycle paralleled those on Bcl-2 phosphorylation. In H460 cells 90% cell killing was obtained with 0.13 nM cryptophycin 52, 0.2 nM cryptophycin 55, 20 nM paclitaxel and > 100 nM vinblastine after 24 h of exposure as determined by colony formation. In Bcl-2-negative Calu-6 NSCLC cells, 90% cell killing was obtained with 0.03 nM cryptophycin 52, 0.1 nM cryptophycin 55, 11 nM paclitaxel and 0.5 nM vinblastine using the same experimental design. Thus, cryptophycins are potent inducers of Bcl-2 phosphorylation. The cryptophycins were more potent cytotoxic agents in Bcl-2-negative Calu-6 cells than in Bcl-2-positive H460 cells indicating that pathways triggered by Bcl-2 phosphorylation are involved in cryptophycin-induced lethality.     

Phase 2 study of cryptophycin 52 (LY355703) in patients previously treated with platinum based chemotherapy for advanced non-small cell lung cancer

BACKGROUND: Cryptophycin 52 is a novel antitubulin drug with in vitro and in vivo activity in non-small cell lung cancer. Based upon promising Phase 1 data, a multicenter trial was performed to evaluate the drug in previously treated non-small cell lung cancer (NSCLC). METHODS: Patients with Stage IIIb (pleural effusion) or Stage IV NSCLC and performance status 0-1 with adequate organ function who had received at least one and no more than two prior chemotherapy regimens (one of which must have contained a platinum agent) were eligible. Cryptophycin 52 was administered at a dose of 1.5 mg/m(2) day 1 and 8 every 3 weeks. Patients were reassessed every two cycles. RESULTS: Twenty-six patients were enrolled of whom 25 are evaluable for toxicity and response. There were no responders, toxicity was predominantly neurologic in the form of peripheral neuropathy and constipation. After the first 12 patients were enrolled, the dose was lowered to 1.125 mg/m(2) day 1 and 8. Toxicity was substantially reduced with this maneuver. Median survival was 4.1 months. The median number of cycles was two, however ten patients received four or more courses of therapy. CONCLUSION: Cryptophycin 52 failed to produce measurable responses utilizing this schedule. In 40% of patients there was evidence of disease stabilization. Toxicity at 1.5 mg/m(2) was unacceptable. Since activity and toxicity may be dose and schedule dependent, other schedules of cryptophycin 52 should be considered.     

Catalytic activity of an in vivo tumor targeted anti-CEA scFv::carboxypeptidase G2 fusion protein

Antibody-directed enzyme prodrug therapy (ADEPT) targets an enzyme selectively to a tumor where it converts a relatively non-toxic prodrug to a potent cytotoxic drug. Previous clinical work using antibody-enzyme chemical conjugates has been limited by the moderate efficiency of tumor targeting of these molecules. To address this a recombinant fusion protein composed of MFE-23, an anti-carcinoembryonic antigen (CEA) single chain Fv (scFv) antibody, fused to the amino-terminus of the enzyme carboxypeptidase G2 (CPG2) has been constructed to achieve ADEPT in CEA-producing tumors. MFE-23::CPG2 fusion protein was overexpressed in Escherichia coli and purified using CEA affinity chromatography. Efficacy of MFE-23::CPG2 delivery to tumors in vivo was assessed by measuring catalytic activity after intravenous injection of purified MFE-23::CPG2 into nude mice bearing CEA-positive LS174T human colon adenocarcinoma xenografts. Recombinant MFE-23::CPG2 cleared rapidly from circulation and catalytic activity in extracted tissues showed tumor to plasma ratios of 1.5:1 (6 hr), 10:1 (24 hr), 19:1 (48 hr) and 12:1 (72 hr). (125)I-MFE-23::CPG2 was retained in kidney, liver and spleen but MFE-23::CPG2 catalytic activity was not, resulting in excellent tumor to normal tissue enzyme ratios 48 hr after injection. These were 371:1 (tumor to liver), 450:1 (tumor to lung), 562:1 (tumor to kidney), 1,477:1 (tumor to colon) and 1,618:1 (tumor to spleen). Favorable tumor : normal tissue ratios occurred at early time points when there was still 21% (24 hr) and 9.5% (48 hr) of the injected activity present per gram of tumor tissue. The high tumor concentrations and selective tumor retention of active enzyme delivered by MFE-23::CPG2 establish that this recombinant fusion protein has potential to give improved clinical efficiency for ADEPT.     

Induction of apoptosis by cryptophycin 1, a new antimicrotubule agent

The ability of cryptophycin 1, a new potent cytotoxic antimicrotubule agent, to initiate apoptosis was studied. Treatment of cells with cryptophycin 1 (50 pM) rapidly caused morphological changes consistent with the induction of apoptosis. DNA strand breakage and fragmentation of the DNA into oligonucleosome-sized fragments was observed, and this coincided with the loss of cellular DNA. Activation of the cysteine protease CPP32 (caspase 3, YAMA, apopain), a member of the ICE/CED-3-like protease family of apoptosis effectors, was consistent with the execution of cell death by a coordinated sequence of events. Low concentrations of cryptophycin 1 caused mitotic arrest with the formation of abnormal mitotic spindles without affecting interphase microtubule structures. Unlike other microtubule active agents, cryptophycin-induced mitotic arrest persisted for only a brief period before the onset of apoptosis. There was no evidence of release from G₂/M cell cycle arrest. Our results show that low concentrations of cryptophycin 1 (50 pM) initiated cell death consistent with apoptosis. These data suggest that the cytotoxic effects of cryptophycin 1 are due in part to its ability to initiate apoptosis rapidly. Int. J. Cancer 73:440–448, 1997. © 1997 Wiley-Liss, Inc.     

Direct comparison of liposomal doxorubicin with or without polyethylene glycol coating in C-26 tumor-bearing mice: is surface coating with polyethylene glycol beneficial?

Sterically stabilized liposome is characterized by a surface coating of polyethylene glycol (PEG) or other polymers that can reduce opsonization of the liposome by plasma proteins. It has a higher plasma area under the concentration-time curve (AUC), which is believed to correlate with better therapeutic efficacy. However, the presence of large molecules on the liposomal surface may reduce the interactions of liposomes with cells and hinder entry of liposomes into the tumor tissue. Using a stable liposomal system composed of distearoyl phosphatidylcholine/cholesterol, we examined the effect of PEG (Mr 2000) on the pharmacokinetics and on the efficacy of liposomal doxorubicin with C-26 syngeneic tumor model in BALB/c mice. The plasma AUC of liposomal doxorubicin with 6 mol-% PEG-modified distearoyl phosphatidylethanolamine (PEG-DSPE) was approximately twice that of liposomal doxorubicin without PEG at various dosages, regardless of whether the mice were tumor-bearing. Paradoxically, the group of mice treated with liposomal doxorubicin without PEG had higher tumor doxorubicin concentrations. The 72-h tumor AUC was 1.44 times that of liposomal doxorubicin with 6% PEG-DSPE. The tumor-accumulation efficiency (AUC(Tumor)/AUC(Plasma)) of liposomal doxorubicin without PEG was 0.87, and this was more than twice that of the liposomal doxorubicin with 6% PEG-DSPE (0.31). At a dose of 10 mg/kg, although both liposomal groups were better than the free drug group in terms of clinically relevant parameters, including toxicity, tumor shrinkage, and survival, there was no difference between the two liposomal drug groups. In this stable liposome system, surface coating with PEG offered no benefit for liposomal doxorubicin in the C-26 tumor model. To enhance the therapeutic index of liposomal doxorubicin, simply increasing plasma AUC by surface coating with PEG may not be satisfactory.     

Distribution of lung adenocarcinoma-associated antigens in human tissues and sera defined by monoclonal antibodies KM-52 and KM-93

Two monoclonal antibodies to human lung adenocarcinoma, KM-52 and KM-93, were generated by the novel immunizing procedure using mice rendered tolerant to the normal human lung (N. Hanai et al., Cancer Res., 46: 4438-4443, 1986). KM-93 recognized sialylated carbohydrate epitope on the antigen different from CA19-9 and DU-PAN-2, while KM-52 recognized the protein antigen. Both antigens were different from carcinoembryonic antigen, alpha-fetoprotein, and beta 2-microglobulin. Distribution of KA-52 and KA-93, the antigens recognized by KM-52 and KM-93, respectively, in various tissues and sera was investigated. In immunoperoxidase staining, KM-93 reacted strongly and frequently with tumor cells of lung adenocarcinoma and partially with those of lung squamous cell carcinoma, large cell carcinoma, and small cell carcinoma. In normal adult and fetal tissues, KA-93 was expressed on the surface of a small number of cells of the lung, pancreas, liver, kidney, and bone marrow. KM-52 reacted selectively with tumor cells of adenocarcinoma among four different histological types of lung carcinoma. In normal adult and fetal tissues, KA-52 was distributed on a small number of cells of the lung, stomach, intestine, and pancreas. Of the two monoclonal antibodies, KM-93 could be used in detecting the antigen in sera of patients with lung cancer. The KA-93 level in sera was determined by the sandwich-type enzyme-linked immunosorbent assay. Serum with a high KA-93 level was found in 34 of 70 patients with lung adenocarcinoma (48.6%), one of 67 healthy adults (1.5%), and none of 32 patients with benign diseases (0%). Combined detection by KA-93 with KA-32, a new tumor marker of lung squamous cell carcinoma (N. Hanai et al., Cancer Res., 46: 5206-5210, 1986), elevated the positive percentage in patients with lung squamous cell carcinoma (52.7%) and with lung adenocarcinoma (59.5%). These results suggested that KM-52 and KM-93 would be potential monoclonal antibodies in immunohistological diagnosis and serum diagnosis of lung adenocarcinoma, respectively.     

Tyrosine-317 of p52(Shc) mediates androgen-stimulated proliferation signals in human prostate cancer cells

The involvement of tyrosine phosphorylation signaling pathways in steroid-induced cell proliferation has received much attention. However, the adaptor molecule that mediates this interaction remains to be identified. In this communication, we identify p52(Shc) as the mediator between tyrosine phosphorylation signaling and steroid signaling in steroid-responsive cell proliferation. Although the different LNCaP prostate cancer cells, C-33, C-51 and C-81, express similar levels of functional androgen receptor (AR), they exhibit different levels of androgen sensitivity. C-33 cell proliferation is highly responsive to the presence of androgens, whereas C-51 cell proliferation is comparatively less responsive to androgens. In contrast, C-81 cell proliferation is independent of androgens. In these cells, tyrosine phosphorylation levels of both p52(Shc) and ErbB-2 were greatest in C-81 cells, comparatively less in C-51 cells and weaker in C-33 cells. The levels and activity of protein tyrosine phosphatase, cellular prostatic acid phosphatase, decreased correspondingly in those cells. In both androgen-independent, rapidly growing C-81 and ErbB-2 cDNA-transfected C-33 cells, p52(Shc) was hyperphosphorylated at Tyr317 (Y317). Conversely, p52(Shc) tyrophosphorylation was decreased in prostatic acid phosphatase cDNA-transfected stable subclones of C-81 cells, which restore androgen-sensitive proliferation and leads to slow growth rates. In C-33 cells, androgen-stimulated cell proliferation correlated with tyrophosphorylation of ErbB-2 and increased phosphorylation of p52(Shc) at Y317, but not at Y239, differing from phosphorylation patterns associated with epidermal growth factor (EGF) stimulation. Furthermore, overexpression of a mutant of p52(Shc), that is Y317F, blocks Y317 phosphorylation of endogenous p52(Shc) and abolishes androgen-stimulated proliferation, but not EGF-stimulated proliferation. Thus, Y317 of p52(Shc) serves as an important regulatory site that allows tyrosine phosphorylation pathways to moderate androgen sensitivity in human prostate cancer cells.     

Intracerebral penetration and tissue distribution of 2,5-diaziridinyl 3,6-bis(carboethoxyamino) 1,4-benzoquinone (AZQ,NSC-182986)

[¹⁴C]AZQ (2–4 mg/m², 100–200 mCi) was administered at varying times to five patients undergoing surgical resection of intracerebral tumors. Plasma, cerebrospinal fluid (CSF), edematous brain, and tumor specimens were obtained during surgery and the concentration of AZQ was determined radiochemically and chromatographically. Total [¹⁴C]AZQ equivalent concentration in tumor for two patients was determined to be 47.5% and 85% of concurrent plasma concentration which was similar to that found in normal brain (60.4% and 75.5% respectively). Only 18–45% of the total radioactivity in tumor tissue and 30–56% in plasma were accounted for by unchanged AZQ. These findings suggest that AZQ may be metabolized to a certain extent. Tissue samples from various organs were obtained during autopsy in a patient who expired ten days after AZQ administration. The highest AZQ concentration was found in the liver, followed by the kidney. Comparable amounts were found in normal brain and brain tumor (22 ng/ g vs. 31 ng/ g respectively). These results indicate that AZQ penetrates readily into the normal brain and brain tumor with a tendency to persist.     

Disposition of amsacrine and its analogue 9-([2-methoxy-4-[(methylsulfonyl)amino]phenyl]amino)-N,5-dimethyl-4- acridinecarboxamide (CI-921) in plasma, liver, and Lewis lung tumors in mice

9-([2-Methoxy-4-[(methylsulfonyl)amino]phenyl]amino)-N,5-dimethyl-4- acridinecarboxamide (CI-921), an analogue of the clinical antileukemia drug amsacrine with improved solid tumor activity in mice, is currently being evaluated in patients. In order to determine whether CI-921 possesses any advantages over amsacrine in terms of tissue delivery, the pharmacokinetics of amsacrine and CI-921 were determined following i.v. injection in male B6D2F1 mice. Plasma kinetics in normal mice were measured following administration of 14.4, 28.9, and 57.7 mumol/kg. The kinetics in s.c. Lewis lung tumors, and in plasma and livers of normal and tumor-bearing mice were measured following administration of 57.7 mumol/kg. CI-921 and amsacrine were quantitated by high-performance liquid chromatography after extraction from plasma and from liver and tumor homogenates. In experiments with appropriate 3H-labeled compounds, both total and covalently bound radioactivity (determined after precipitation and washing with acetonitrile) were measured in plasma and in liver homogenates. Over this dose range, nonlinear kinetics were observed in plasma for unchanged CI-921 and amsacrine, and a reasonable fit was obtained with Michaelis-Menten kinetics to a one-compartment model for CI-921 (Km 3.7 mumol/liter; Vmax 18 mumol/h/kg; V ss 3.3 liter/kg) and a two-compartment model for amsacrine (Km 3.6 mumol/liter; Vmax 76 mumol/h/kg; Vss 4.8 liter/kg). The area under the concentration-time curve (AUC) for plasma following a dose of 57.7 mumol/kg was 31 mumol.h/liter for CI-921 and 6.3 mumol.h/liter for amsacrine. However, equilibrium dialysis measurements indicated high plasma protein binding with free drug fractions for CI-921 and amsacrine of 0.63 and 6.7%, respectively. In the liver, unchanged drug concentrations and total radioactivity for both compounds were approximately 10-fold those in plasma, and the tissue half-life of CI-921 was approximately 4-fold longer for CI-921 than for amsacrine. Plasma and liver kinetics in mice with s.c. Lewis lung tumors were similar to those in normal mice. Tumor half-lives of unchanged CI-921 and amsacrine were 3.9 and 2.7 h, respectively, considerably longer than those for plasma (1.2 and 0.30 h respectively) or liver (1.2 and 0.28 h, respectively). Tumor AUC values for CI-921 and amsacrine were 68 and 37 mumol.h/liter, respectively, as compared to the calculated AUC values for free drug in plasma of 0.19 and 0.42 mumol.h/liter, respectively. It is concluded that the uptake into tumors from the plasma free drug fraction is more efficient for CI-921 than for amsacrine.     

Pharmacokinetics of nitrosoureas: levels of 1,3-bis-(2-chloroethyl)-1-nitrosourea (BCNU) in organs of normal and Walker 256/B carcinoma bearing rats after i.v. bolus

The disappearance of 1,3-bis(2-chlorethyl)-1-nitrosourea (BCNU) from plasma, liver, kidney, lung, brain, spleen, tumor tissue and epididymal adipose tissue of Walker 256/B carcinoma-bearing rats and healthy animals was measured by differential pulse polarography after i.v. bolus of the drug. Only BCNU, not its decomposition products, was detected by the polarographic assay. Levels of BCNU in liver of tumor-bearing animals were significantly lower (about 10 times) than those on healthy rats. A bi-exponential fit was used to calculate the kinetics of BCNU in plasma, kidney, lung and brain, but no difference could be found between healthy and Walker tumor-bearing rats. BCNU disappeared faster from adipose tissue of tumor-bearing animals than from normals.     

Metabolic activation of R,S-1-(tetrahydro-2-furanyl)-5-fluorouracil (ftorafur) to 5-fluorouracil by soluble enzymes

There are two major R,S-1-(tetrahydro-2-furanyl)-5-fluorouracil (ftorafur) activation pathways to 5-fluorouracil, one that is mediated by microsomal cytochrome P-450 oxidation at C-5' of the tetrahydrofuran moiety and one that is mediated by soluble enzymes. This report demonstrates that the soluble enzyme pathway proceeds via enzymatic cleavage (possibly hydrolytic) of the N-1--C-2' bond to yield 5-fluorouracil and 4-hydroxybutanal, which is immediately further metabolized to gamma-butyrolactone or gamma-hydroxybutyric acid. The soluble activation pathway was present in liver, small intestine, and brain. Because of the limited distribution of cytochrome P-450 in body tissues and because of the lack of redistribution of 5-fluorouracil via the systemic circulation after ftorafur administration, we propose that the soluble enzyme pathway is at least in part responsible for organ toxicity and possibly antitumor effect. Distinction of the microsomal (C-5') and the soluble enzyme (C-2') activation pathways can be exploited in the design of more selective prodrug analogues.     

Relationship of 1,3-bis(2-chloroethyl)-1-nitrosourea (BCNU) and 1-(2-chloroethyl)-3-cyclohexyl-1-nitrosourea (CCNU) pharmacokinetics of uptake,distribution, and tissue/plasma partitioning in rat organs and intracerebral tumors

Summary To obtain a clearer definition of the relationship between the structure of BCNU and CCNU and their antitumor activity, we determined the uptake, distribution, and tissue/plasma partition ratios of both compounds in normal organs and intracerebral (ic) 9L tumors in rats. Greater uptake, distribution, and tissue/plasma partition ratios were obtained for parent CCNU in fat, liver, and brain, and for parent BCNU in kidney. CCNU distributes more rapidly and extensively than BCNU only in fatty tissues. BCNU distributed more extensively in kidney and liver. Rats received bolus IV injections of ¹⁴C-labeled BCNU or CCNU in increasing doses; measurments taken 30 min after injection showed that three- to fourfold more BCNU than CCNU was bound to nucleic acids in brain and ic 9L tumor tissue. Because the chloroethyl group is the alkylating moiety for both drugs, these findings implied that BCNU biotransformed to its reactive intermediate more rapidly than did CCNU.These observations, together with previous findings, indicate that one reason for the greater effectiveness of BCNU than CCNU against ic 9L tumors is its superior ability to form an intermediate that can bind to ic 9L tumor cell nucleic acids.     

Combretastatin A4 phosphate has tumor antivascular activity in rat and man as demonstrated by dynamic magnetic resonance imaging.

PURPOSE: Combretastatin A4 phosphate (CA4P) is a novel vascular targeting agent. Dynamic contrast enhanced magnetic resonance imaging (DCE-MRI) studies were performed to examine changes in parameters related to blood flow and vascular permeability in tumor and normal tissue after CA4P treatment. Materials and METHODS: Changes in kinetic DCE-MRI parameters (transfer constant [Ktrans] and area under contrast medium-time curve [AUC]) over 24 hours after treatment with CA4P were measured in 18 patients in a phase I trial and compared with those obtained in the rat P22 carcinosarcoma model, using the same imaging technique. Rats were treated with 30 mg/kg of CA4P; patients received escalating doses from 5 to 114 mg/m2. RESULTS: A similar pattern and time course of change in tumor and normal tissue parameters was seen in rats and humans. Rat tumor Ktrans was reduced by 64% 6 hours after treatment with CA4P (30 mg/kg). No significant reductions in kidney or muscle parameters were seen. Significant reductions were seen in tumor Ktrans in six of 16 patients treated at >or= 52 mg/m2, with a significant group mean reduction of 37% and 29% at 4 and 24 hours, respectively, after treatment. The mean reduction in tumor initial area under the gadolinium-diethylenetriamine pentaacetic acid concentration-time curve (AUC) was 33% and 18%, respectively, at these times. No reduction was seen in muscle Ktrans or in kidney AUC in group analysis of the clinical data. CONCLUSION: CA4P acutely reduces Ktrans in human as well as rat tumors at well-tolerated doses, with no significant changes in kidney or muscle, providing proof of principle that this drug has tumor antivascular activity in rats and humans.     

Therapeutic effect of 1 M tegafur-0.4 M 5-chloro-2,4-dihydroxypyridine-1 M potassium oxonate (S-1) on liver metastasis of xenotransplanted human colon carcinoma.

S-1 [1 M tegafur (FT)-0.4 M 5-chloro-2,4-dihydroxypyridine (CDHP)-1 M potassium oxonate (Oxo)], was developed as a new oral antineoplastic agent based on biochemical modulation of fluorouracil (5-FU) by CDHP and Oxo. The therapeutic effect of S-1 on human colon cancer xenografts (TK-13) with high metastatic potential to the liver was evaluated. Small pieces of TK-13 were sutured into the cecal wall of 52 nude mice, and the animals were randomly divided into 3 groups [control (n=17), UFT (combination of 1 M FT and 4 M uracil) (n=18) and S-1 (n=17)]. S-1 or UFT was administered orally at an equitoxic dose (S-1, 7.5 mg/kg; UFT, 17.5 mg/kg as FT) for 37 consecutive days beginning 10 days after the transplantation. S-1 showed higher tumor growth inhibition than UFT (P<0.05) and also showed a significant anti-metastatic effect on liver metastasis, while UFT did not. Liver metastasis developed in only 2 of the 17 mice (12%) in the S-1 group, whereas it developed in 9 of the 17 (53%) and 7 of the 18 (39%) in the control and UFT group, respectively. Analysis of AUC (area under the curve) revealed that S-1 yielded higher 5-FU levels in both tumor tissue (1.6 times) and plasma (2.5 times) than UFT. These results suggest that S-1 will show a higher clinical therapeutic effect against human colorectal cancer than UFT.     

Therapeutic Effect of 1 M Tegafur-0.4 M 5-Chloro-2,4-dihydroxypyridine-1 M Potassium Oxonate (S-1) on Liver Metastasis of Xenotransplanted Human Colon Carcinoma

S-1 [1 M tegafur (FT)-0.4 M 5-chloro-2,4-dihydroxypyridine (CDHP)-1 M potassium oxonate (Oxo)], was developed as a new oral antineoplastic agent based on biochemical modulation of fluorouracil (5-FU) by CDHP and Oxo. The therapeutic effect of S-1 on human colon cancer xenografts (TK-13) with high metastatic potential to the liver was evaluated. Small pieces of TK-13 were sutured into the cecal wall of 52 nude mice, and the animals were randomly divided into 3 groups [control ( n =17), UFT (combination of 1 M FT and 4 M uracil) ( n =18) and S-1 ( n =17)]. S-1 or UFT was administered orally at an equitoxic dose (S-1, 7.5 mg/kg; UFT, 17.5 mg/kg as FT) for 37 consecutive days beginning 10 days after the transplantation. S-1 showed higher tumor growth inhibition than UFT ( P < 0.05) and also showed a significant anti-metastatic effect on liver metastasis, while UFT did not. Liver metastasis developed in only 2 of the 17 mice (12%) in the S-1 group, whereas it developed in 9 of the 17 (53%) and 7 of the 18 (39%) in the control and UFT group, respectively. Analysis of AUC (area under the curve) revealed that S-1 yielded higher 5-FU levels in both tumor tissue (1.6 times) and plasma (2.5 times) than UFT. These results suggest that S-1 will show a higher clinical therapeutic effect against human colorectal cancer than UFT.     

Antitumor Activity and Metabolism of a New Anthracycline-containing Fluorine (ME2303) in Lewis Lung Carcinoma-bearing Mice

(7-O-(2,6-Dideoxy-2-fluoro-α-L-talopyranosyl)adriamycmone-14-hemipimerate (ME2303) showed a more marked growth inhibition of Lewis lung carcinoma than adriamycin (ADM). When administered to s.c. Lewis lung carcinoma-hearing mice, ME2303 in the plasma and liver was rapidly metabolized and disappeared. However, ME2303 was incorporated into the tumor at higher concentrations and remained in the tumor for a longer period than in the plasma and liver. ME2303 was metabolized to 7-O-(2,6-dideoxy-2-fluoro-α-L-talopyranosyl) adriamycinone (M1), the product of esterolysis, and its reduced derivative at the C-13 position (M2), Larger amounts of these metabolites were found in the analyzed tissues than in plasma. The maximum concentration of Ml in the tumor was observed at 2 h posttreatment, while the maxima in the plasma and liver were observed at 15 min. On the other hand, i.v. injection of M1 into mice showed a weaker antitumor effect than ME2303 injection, though Ml levels in the plasma and tumor were almost the same as those after administration of ME2303 at the maximum tolerated doses. Some metabolites of ME2303 were found in the tumor after administration of ME2303, but not after administration of M1. ADM remained in the analyzed tissues for a long period and ADM concentrations in the tumor were much higher than in the plasma but less than in the liver. M1 reached a concentration higher than that of ADM in the tumor, opposite to the pattern observed in the liver. The conversion process from ME2303 to M1, the metabolites and their locations in the tumor may be important for the marked antitumor effect of ME2303 in vivo.     

Use of microdialysis to study platinum anticancer agent pharmacokinetics in preclinical models

Microdialysis sampling of blood and extracellular fluid (ECF) of living tissue offers unique advantages for studying anticancer drug distribution, metabolism, and mechanisms of tumor drug resistance. We applied microdialysis sampling in a rat model to describe the pharmacokinetics of cisplatin and carboplatin simultaneously in blood and several peripheral tissues, including tumor tissue. After i.v. bolus drug administration, samples were collected every 10 min for 4-6 h using microdialysis probes implanted into the jugular vein, kidney, and either liver or subcutaneously growing breast tumor tissue in anesthetized Fisher 344 rats. Analyte concentrations are expressed as absolute extracellular concentrations obtained by correction of the data for in vivo recovery. For cisplatin, peak renal concentrations (mean, 36.7 and 80.1 micrograms/mL) always exceeded peak plasma (8.4 and 13.2 micrograms/mL) and hepatic (6.3 and 10.4 micrograms/mL) concentrations following 5 and 10 mg/kg doses, respectively. For carboplatin, doses of 20 and 30 mg/kg also resulted in high peak renal concentrations, which were similar at both dose levels (mean, 87.9 and 89.3 micrograms/mL). However, at 30 mg/kg peak hepatic carboplatin concentrations were increased significantly, resulting in a disproportionate 3.5-fold increase in mean AUC at the higher dose level. Tumor cisplatin and carboplatin AUCs were similar to that in the circulation, but variable, ranging from 52 to 109% of the corresponding plasma AUCs. Microdialysis was determined to be a reliable methodology for examining the in vivo disposition of platinum anticancer agents in multiple tissue types. Our results revealed expected large renal exposures following i.v. administration, and variable tumor exposure with dose. Significant increases in hepatic carboplatin exposure with increasing dose suggest a possible mechanism for high-dose carboplatin-induced hepatic toxicity.     

Pharmacokinetics of Bcl-2 antisense oligonucleotide (G3139) combined with doxorubicin in SCID mice bearing human breast cancer solid tumor xenografts

PURPOSE: To evaluate the pharmacokinetic (PK) properties of Bcl-2 antisense oligodeoxynucleotide G3139 when combined with the anthracycline anticancer drug doxorubicin (DOX) in a model of MDA435/LCC6 human breast cancer in severely compromised immunodeficient (SCID) mice. METHODS: An orthotopic model of MDA435/LCC6 solid breast tumors was developed by bilateral implantation of passaged cells in female SCID-RAG2 mice. The G3139 plasma profile was compared for two common routes of administration (i.v. or i.p.) in single and multiple dose treatment regimens of 5 mg/kg G3139 alone or with simultaneous DOX (5 mg/kg) administration. At selected times, plasma and major organs were assayed for [3H]G3139 using scintillation counting and DOX determined using HPLC. The molecular integrity of G3139 was analyzed using SDS-PAGE. The PKs of G3139 and DOX were evaluated using a two-compartment model. RESULTS: G3139 administered i.v. at 5 mg/kg revealed a biexponential plasma concentration-time curve with a Cmax of 99.9 microg/ml and elimination half-lives of 0.03 h and 9.8 h, respectively, which resulted in an area under the concentration-time curve (AUC) of 15.9 microg x h/ml. G3139 administered i.p. showed a plasma absorption, distribution and elimination profile typical of this route of administration, characterized by half-lives of 0.03 h, 0.2 h and 8.9 h, respectively and a Cmax of 8.6 microg/ml. Based on AUC comparisons, the bioavailability of G3139 injected i.p. was 84% compared to i.v. administration. Subtle changes were observed in G3139 PKs after three prior i.p. doses of G3139. Specifically, a six-fold slower absorption rate, lower Cmax (6.9 microg/ml), increased Tmax (0.2 h), and an AUC of 17.4 microg x h/ml were observed, consistent with concentrations approaching saturation levels in tissue sites to which G3139 distributes. Coadministration of DOX had significant effects on the PK properties of G3139, manifested by an increased Cmax (11.2 microg/ml), higher AUC (19.7 microg x h/ml), and ninefold lower plasma clearance for single-dose G3139 administration. G3139 in plasma remained largely intact (< 17% degraded in plasma over 4 h), and increased plasma protein association occurred as a function of time. G3139 was detected in both healthy and tumor tissue after i.v. and i.p. administration. The highest tissue levels of G3139 were observed in the kidneys (40 microg/g), and low levels (< 2 microg/g) were detected in lung, heart and muscle. The rate of accumulation of G3139 in organs was dependent upon G3139 levels in plasma and the presence of coadministered DOX. Significant accumulation of G3139 was observed in solid tumors, with peak levels of approximately 5 microg G3139/g tumor, and approximately a two-to threefold tumor/muscle AUC ratio. The kinetics of G3139 accumulation in tumor tissue increased with increasing circulating G3139 concentration. The tissue distribution properties of DOX were also altered in the presence of coadministered G3139: in the presence of G3139, tumor exposure to DOX increased two-to threefold without alteration in plasma DOX PKs. CONCLUSIONS: These findings indicate that drug-drug interactions between G3139 and DOX are modest and favorable in that elevated tumor DOX levels are achieved without compromising G3139 tumor uptake or significantly altering plasma drug concentrations.