Reduced toxicity and superior therapeutic activity of a mitomycin C lipid-based prodrug incorporated in pegylated liposomes.

PURPOSE: A lipid-based prodrug of mitomycin C [MMC; 2,3-(distearoyloxy)propane-1-dithio-4'-benzyloxycarbonyl-MMC] was designed for liposome formulation. The purpose of this study was to examine the in vitro cytotoxicity, pharmacokinetics, in vivo toxicity, and in vivo antitumor activity of this new lipid-based prodrug formulated in polyethylene glycol-coated (pegylated) liposomes. EXPERIMENTAL DESIGN: MMC was released from the MMC lipid-based prodrug (MLP) by thiolytic-induced cleavage with a variety of thiol-containing reducing agents. MLP was incorporated with nearly 100% efficiency in cholesterol-free pegylated liposomes with hydrogenated phosphatidylcholine as the main component and a mean vesicle size of approximately 90 nm. This formulation was used for in vitro and in vivo tests in rodents. RESULTS: In vitro, the cytotoxic activity of pegylated liposomal MLP (PL-MLP) was drastically reduced compared with free MMC. However, in the presence of reducing agents, such as cysteine or N-acetyl-cysteine, its activity increased to nearly comparable levels to those of free MMC. Intravenous administration of PL-MLP in rats resulted in a slow clearance indicating stable prodrug retention in liposomes and long circulation time kinetics, with a pharmacokinetic profile substantially different from that of free MMC. In vivo, PL-MLP was approximately 3-fold less toxic than free MMC. The therapeutic index and absolute antitumor efficacy of PL-MLP were superior to that of free MMC in the three tumor models tested. In addition, PL-MLP was significantly more active than a formulation of doxorubicin in pegylated liposomes (DOXIL) in the M109R tumor model, a mouse tumor cell line with a multidrug-resistant phenotype. CONCLUSIONS: Delivery of MLP in pegylated liposomes is a potential approach for effective treatment of multidrug-resistant tumors while significantly buffering the toxicity of MMC.

Tumor-inhibitory antibiotic uptake facilitated by leukoregulin: a new approach to drug delivery.

The uptake of tumor-inhibitory antibiotics by human K562 erythroleukemia cells was examined in the presence of leukoregulin to determine if the lymphokine's ability to increase the plasma membrane permeability of tumor cells facilitates concurrent entry of pharmacologically active molecules. K562 cells were exposed to 0.25-2.0 micrograms of doxorubicin/mL for up to 60 minutes at 37 degrees C. Commencing within 15 minutes, leukoregulin increased the entry of doxorubicin approximately twofold and the uptake of mitomycin, mithramycin, and propidium iodide twofold to tenfold. This finding indicates the potential biotherapeutic value of leukoregulin in promoting the selective entry of pharmacologically active molecules into leukoregulin-sensitive target cells.

Disposition characteristics of mitomycin C-dextran conjugate in normal and tumor-bearing muscles of rabbits.

Disposition characteristics of the macromolecular prodrug of mitomycin C (MMC), mitomycin C-dextran conjugate (MMC-D), in normal and tumor (VX2 carcinoma)-bearing rabbit thigh muscles were studied using the in situ vascular perfusion technique. Three types of cationic MMC-D (MMC-Dcat) and two types of anionic MMC-D (MMC-Dan) with different carrier molecular weights were used. After bolus arterial injection in normal muscles, 83-96% of injected MMC-D was recovered in the venous outflow regardless of the carrier size or charge, whereas less than 60% of MMC was recovered in the same system. By applying statistical moment analysis to the outflow pattern of these drugs, pharmacokinetic parameters representing their disposition characteristics were obtained. Smaller intrinsic clearance (CLint) and distribution volume (V) were noted for MMC-D than for MMC, indicating low extravascular diffusion of MMC-D. In the tumor-bearing muscle, blood contamination from other parts of the body increased and a shortage of flow recovery due to the neovascularization of the tumors occurred. The disposition parameters of MMC-Dcat with a molecular weight of 500,000 (T-500) indicated some tissue distribution and sequestration in the tumor preparation. After constant infusion of [14C]MMC-D (T-500) for 4 h, tissue radioactivity concentrations were determined in various tissues. A higher radioactivity was observed in the viable region of the tumor and the lymph node compared with the normal muscle tissue and the necrotic region of the tumors. 131I-Labeled human serum albumin also gave similar results. In conclusion, higher tumor localization of antitumor agents may be made possible by the application of macromolecular prodrugs.

Bladder wall penetration of intravesical mitomycin C in dogs.

We examined the kinetics of penetration of mitomycin C (MMC) in the dog bladder wall after intravesical instillation of 20 mg/40 ml, a dose used in patients. Bladder tissues were harvested and concentration-depth profiles were established by analysis of thin tissue slices cut parallel to the urothelial surface of the bladder. Tissue concentrations after a dwell time of 5-7 min were similar to those after 30-120 min. In tissues harvested 60 and 75 min after removal of the dose, MMC was not detected in 5 of 6 samples and was less than 1 micrograms/g at the mucosa in the remaining sample, suggesting a rapid "washout" of the drug. The rapid equilibrium between the drug in urine and bladder tissue indicates that the duration of exposure of the bladder wall tissue was approximately equal to the dwell time of intravesical therapy. Tissue concentrations declined log-linearly with respect to the depth of penetration. The concentration immediately underneath the urothelium (C0) showed considerable intra- and interanimal variability. Bladder distention appeared to increase C0 by several fold. C0 ranged from 2 to 275 micrograms/g wet tissue weight, with a median value of 24 micrograms/g, or 11 micrograms/g when two animals with distended bladders were excluded. MMC concentrations in 3 different sites of the same bladder varied up to 5-fold. Within the capillary-perfused mucosa and muscularis (between 50 and 2000 microns from the urothelial surface), concentrations decreased by 50% for each 500-microns distance. The median concentration at 2000 microns was 1 microgram/g (n = 24). At 2000-3000 microns, tissue concentrations in most (18 of 24) specimens either declined to an asymptotic value or were lower than the detection limit of 0.1 microgram/g. Concentrations in the bladder contents were 200-500 micrograms/ml, the average tissue concentration from 50 to 3000 microns was 10 micrograms/g, and plasma concentrations were less than 0.1 microgram/ml. This supports the therapeutic advantage of intravesical therapy of high local drug concentrations while minimizing systemic exposure. A comparison of the urine concentration and C0 indicated a 30-fold decline in concentration across the urothelium. This suggests the importance of the urothelium as a barrier to MMC absorption. A separate study in our laboratories showed that 16 micrograms/ml of MMC was needed to produce a 90% inhibition of the labeling index of explants of human bladder cancers located in the urothelium (Ta tumor, TNM classification), 25 micrograms/ml in the lamina propria (T1 tumors), and 43 micrograms/ml in the muscle layer (T2 tumors).(ABSTRACT TRUNCATED AT 400 WORDS)

Early postoperative intraperitoneal chemotherapy as an adjuvant therapy to surgery for peritoneal carcinomatosis from gastrointestinal cancer: pharmacological studies.

Gastrointestinal malignancy may spread to peritoneal surfaces in the absence of lymphatic or hematogenous metastases. To treat peritoneal carcinomatosis, a uniformly lethal disease process, extensive cytoreductive surgery and i.p. chemotherapy were combined. Early postoperative i.p. chemotherapy was instilled in the first few days after the surgical procedure in an attempt to treat anatomic sites that would be sealed off by postoperative adhesions. Mitomycin C was given on the first postoperative day at two doses, 10 and 12 mg/m2. 5-Fluorouracil was given on postoperative days 2-5 at 15 and 20 mg/kg, respectively. Median area under the curve ratio i.p./i.v. was 117 for 5-fluorouracil and 21.6 for mitomycin C. Elevated intraportal levels of drug were observed for i.p. 5-fluorouracil but not for mitomycin C. The marked pharmacokinetic advantage of postoperative i.p. suggests that this treatment strategy should be considered in a clinical trial in patients at risk for progression of peritoneal carcinomatosis.

Correlation between drug uptake and selective toxicity of porfiromycin to hypoxic EMT6 cells.

Mitomycin C and its methylated analogue porfiromycin (Por) have significant potential as adjuncts to regimens presently used for treating solid tumors because of their preferential toxicity to cells existing in an hypoxic environment. An understanding of the factors producing the differential activity of these drugs under aerobic and hypoxic conditions would facilitate the development of new agents of this class. Previous studies have focused on the enzymes that reductively activate the mitomycins and on the interaction of these drugs with DNA; none of these studies has fully explained the differences in cytotoxicity observed under hypoxic and aerobic conditions. The present investigation demonstrates that the rate of Por uptake is directly correlated with cytotoxicity under both aerobic and hypoxic conditions. Uptake of Por into hypoxic cells is more rapid than into aerobic cells at equal drug concentrations. Hypoxic cells also accumulate drug in concentrations well in excess of those in the extracellular medium; this is apparently a reflection of drug sequestration in these cells. This sequestration of Por, which affects the rate and extent of uptake in hypoxic cells, does not take place in aerobic cells. The failure of aerobic cells to sequester drug is evidenced by the very rapid efflux of Por from these cells upon removal of extracellular Por and by the fact that aerobic cells attain a state of equilibrium between the intracellular and extracellular drug concentrations. The findings demonstrate that differences in the uptake and retention of Por are associated with the preferential toxicity of Por to hypoxic cells.

Disposition of anticancer drugs after bolus arterial administration in a tissue-isolated tumor perfusion system.

Disposition characteristics of various anticancer drugs in a tissue-isolated tumor preparation were studied in Walker 256 carcinosarcoma-bearing rats using an in situ single-pass vascular perfusion technique. Three anticancer drugs, 5-fluorouracil, mitomycin C, and Adriamycin, and two lipophilic prodrugs of mitomycin C were tested in the tumor preparation perfused with Tyrode's solution containing 4.7% bovine serum albumin. After bolus arterial injection of test drugs, their outflow concentration-time curves were analyzed based on statistical moment theory. In each tumor preparation, the injection of drug was paired with that of vascular reference substance, Evans' blue-labeled bovine serum albumin, and disposition parameters of the drug were corrected with those of vascular reference substance. From the mean transit time values of vascular reference substance, the average vascular volume of the tumor preparation was calculated to be 0.063 ml/g, which decreased with tumor growth. All drugs showed significant extraction by the tumor tissue, depending on their physicochemical properties. Distribution volumes of tested drugs were from 1.53 to 3.33 times larger than the vascular volume. Calculated intrinsic clearance values for the protein-unbound fractions increased as the lipophilicity of the drug increased. The potential increase in tumor uptake was observed in lipophilic prodrugs of mitomycin C. The present experimental system is thus suggested to be useful for analyzing drug disposition in tumor tissue.

Intrapleural cisplatin and mitomycin for malignant mesothelioma following pleurectomy: pharmacokinetic studies.

PURPOSE: Intrapleural cisplatin-based chemotherapy has been used in the treatment of patients with malignant pleural mesothelioma and malignant pleural effusions, but the pharmacokinetics of this form of chemotherapy have not been previously evaluated. We performed pharmacokinetic studies on 12 patients who received both intrapleural cisplatin and mitomycin immediately following pleurectomy/decortication for malignant pleural mesothelioma. PATIENTS AND METHODS: Simultaneous pleural fluid and plasma samples were collected at 15 and 30 minutes, and at 1, 2, 3, 4, and 24 hours after administration of the intrapleural chemotherapy (cisplatin 100 mg/m2 and mitomycin 8 mg/m2), and after cisplatin (total and free) and mitomycin levels were measured. The mean peak levels, the areas under the concentration-time curve (AUC) and the drug half-lives (t1/2s) in plasma and pleural fluid were compared using the paired t test. Differences were considered significant if P less than or equal to .05. RESULTS: Systemic absorption was rapid, with peak plasma levels being reached within 1 hour of administration of the intrapleural chemotherapy. Peak plasma levels measured after intrapleural chemotherapy approximated those reportedly attained during systemic administration of these drugs at similar doses. However, the mean peak cisplatin and mitomycin levels, and their mean AUCs, were significantly higher in the pleural fluid than in the plasma. There was a three- to fivefold advantage (on a logarithmic scale) for pleural to plasma AUCs for both cisplatin and mitomycin. The mean t1/2s for cisplatin and mitomycin were significantly longer in the plasma than in the pleural fluid. CONCLUSIONS: The pharmacokinetics of intrapleural cisplatin-based chemotherapy are analogous to those of intraperitoneal chemotherapy. Our findings show that intrapleural cisplatin-based chemotherapy has a distinct local pharmacologic advantage, but also produces significant and sustained drug plasma levels.

Pharmacokinetics of bronchial artery infusion of mitomycin in patients with non-small cell lung cancer.

The pharmacokinetics of bronchial artery infusion of 20 mg (11.4-14.0 mg/m2) mitomycin was studied in 14 patients with non-small cell lung cancer (NSCLC). The mean elimination half-life was 34.3 min (range 6-72), and the area under the plasma concentration-time curve (AUC) was 166 ng h/ml (39-312). The mean maximum plasma drug concentration (Cmax) was 178 ng/ml (12-540) and back-extrapolated plasma drug concentration was 308 ng/ml (17-1423). The mean volume of distribution in the one-compartment model was 0.183 l/kg (0.010-0.887) and the rate constant for unchanged drug appearing in the urine was 1.91/min (0.57-7.27). There was considerable variation among individuals with respect to the pharmacokinetics of mitomycin, and the mean Cmax and AUC were lower than those reported after intravenous administration.

New findings in the pharmacokinetic, metabolic, and drug-resistance aspects of mitomycin C.

The pharmacokinetics of mitomycin C are reviewed from reports using specific and sensitive high-performance liquid chromatography (HPLC) assays. These studies demonstrate a rapid, biphasic elimination pattern for the drug: alpha half-life of 8 minutes and beta, or terminal, half-life of 48 minutes. Urinary elimination of intact drug is minimal (8% to 10% of a dose), whereas biliary drug levels may exceed those in the plasma. There was no evidence of dose dependent pharmacokinetics over a wide range of doses and patient populations, including pediatric solid tumor patients. Metabolic studies with mitomycin C have demonstrated an absolute requirement for reductive enzymatic activation of the drug to mono- and bifunctional alkylating species. The preferred DNA target for covalent attachment by mitomycin C was found to be the N2 position of guanine. Chemical metabolites of activated mitomycin C were also demonstrated to include 2, 7 diaminomitosene and its cis- and trans-1-hydroxy or 1-phosphate analogues. Also, there was no evidence for hypoxic cell selectivity for mitomycin C in several human tumor cell lines, although some animal tumors unequivocally display this phenomenon. Finally, there are new observations of the development of the multidrug-resistance phenotype in mitomycin C-treated L-1210 cells in vitro. These cells became collaterally resistant to anthracyclines and vinca alkaloids and expressed the P-glycoprotein in cell membranes. The implications of these findings for mitomycin C use in solid tumors in humans is discussed.

Mitomycin C resistant L1210 leukemia cells: association with pleiotropic drug resistance.

A mitomycin C-resistant (MMCR) strain of L1210 mouse leukemia was developed by continuous drug exposure in vitro. MMC concentrations were increased in a stepwise fashion beginning at 0.033 microM and ending at 0.34 microM. This produced a 10-fold resistant cell line over the parental line. Resistance simultaneously developed to anthracene and anthracycline DNA intercalators, to vinca alkaloids and epipodophyllotoxins but not to cisplatin, bleomycin, fluorouracil or ionizing X-rays. MMC resistance was reversed using the membrane-active agent verapamil. The level of non-protein sulfhydryls was increased 2-fold in the MMCR cells. Intracellular uptake of unchanged MMC was reduced by 40% in the MMCR cells. Cytogenetic analyses demonstrated no recognizable clonal chromosomal alterations unique to the resistant subline and no evidence of double minutes or homogeneously staining regions in the DNA. Gel renaturation analysis failed to document the presence of an amplified DNA domain. Southern blotting of parental and MMCR DNA using a cDNA probe (CHP1) for the P-glycoprotein gene also failed to demonstrate amplification or rearrangement of P-glycoprotein-related homologous sequences. However, an Mr 180,000 glycoprotein was detected in the plasma membranes from MMCR cells. This protein also specifically reacted with a monoclonal antibody (C219) to the P-glycoprotein of Ling and co-workers [Kartner et al., Nature, Lond. 316, 820 (1985)]. These results suggest a pleiotropic drug resistance pattern in the MMCR cells, associated with membrane glycoprotein alterations, enhanced non-protein sulfhydryl levels, and reduced MMC accumulation. This is a novel observation for a resistant cell line selected with an alkylating agent.

Conversion of mitomycin C to 2,7-diaminomitosene and 10-decarbamoyl 2,7-diaminomitosene in tumour tissue in vivo.

The progress of mitomycin C (MMC) bioreduction was studied in vivo in the rat Sp 107 mammary carcinoma after intra-tumoural injection of either 100 micrograms or 1 mg. 2,7-Diaminomitosene (2,7-DM) was utilised as a primary bioreductive metabolite and 10-decarbamoyl 2,7-diaminomitosene (DC 2,7-DM) served as a secondary bioreductive metabolite, both of which were measured by high-performance liquid chromatography. 2,7-DM and DC 2,7-DM were produced rapidly, achieving close to their maximal concentrations at the earliest time point studied [5 min]. 2,7-DM was cleared rapidly from the tumour with apparent half-lives of 5 and 35 min after the low and high drug doses, respectively. DC 2,7-DM had a longer apparent half-life of 130 min at the higher dose but, as compared with 2,7-DM, was only a minor metabolite [the area under the curve (AUC) of 2,7-DM was 5.6-fold that of DC 2,7-DM]. At the lower drug dose, DC 2,7-DM was not detectable. Rapid formation and disappearance of bioreductive metabolites of MMC may account for the failure of previous studies to detect these products in vivo.

Pharmacokinetics and toxicity of mitomycin C in rodents, given alone, in combination, or after induction of microsomal drug metabolism.

The pharmacokinetics of mitomycin (MMC) was studied in Wistar rats. Up to five half-lives, the plasma concentration-time curve was biphasic. The AUC changed linearly with increasing doses between 0.5 and 7.5 mg/kg, which corresponds to 0.2 and 3 times the LD50 value in rats. Most of the drug was metabolized, and only 1%-2% and 10%-15% of the dose was eliminated unchanged by biliary and urinary excretion, respectively. The AUC of MMC at the LD50 is slightly less than that reported for the human MTD. Inoculation of MMC together with 5-fluorouracil and doxorubicin did not change the terminal half-life of MMC but decreased the total body clearance and the volume of distribution. The lack of significant influence of phenobarbital and 3-methylcholanthrene pretreatment on the terminal elimination half-life suggests that microsomal drug-metabolizing enzymes inducible by these compounds do not play a decisive role in the in vivo biotransformation of MMC.

High mitomycin C concentration in tumour tissue can be achieved by isolated liver perfusion in rats.

To enable the treatment of hepatic metastasis with higher, theoretically more effective, doses of systemically toxic anticancer drugs, an isolated liver perfusion (ILP) technique was developed in WAG/Ola rats. First, in a toxicity study the maximally tolerated dose (MTD) of mitomycin C (MMC) was determined for a 25-min ILP and for hepatic artery infusion (HAI) after the administration of a bolus dose. The MTD in the ILP setting (4.8 mg/kg) was 4 times that using HAI (1.2 mg/kg). Subsequently, in a rat colorectal hepatic-metastasis model, concentrations of MMC in tumour, liver, plasma and perfusate were measured during a 25-min ILP to investigate the expected pharmacokinetic advantage of ILP. The mean plasma level determined after ILP (1.2 as well as 4.8 mg/kg MMC) was significantly lower (P less than 0.001) than that obtained following HAI. This may explain both the absence of severe systemic toxicity and the higher MTD in ILP-treated groups. No significant difference in mean tumour and liver tissue concentrations of MMC were found when the groups treated with 1.2 mg/kg drug via HAI vs ILP were compared. The mean MMC concentration in tumour tissue was significantly higher (almost 5 times; P less than 0.05) in rats treated by ILP with the MTD (4.8 mg/kg) than in those treated via HAI with the MTD (1.2 mg/kg). ILP of MMC can be safely performed using a dose 4 times higher than the MTD in the HAI setting, leading to an almost 5-fold concentration of MMC in hepatic metastasis. ILP of MMC may therefore represent a promising therapy for metastasis confined to the liver.

Studies on the mechanism of the cytotoxic action of the mitomycin antibiotics in hypoxic and oxygenated EMT6 cells.

The mitomycin antibiotics, because of their preferential toxicities for hypoxic cells, have significant potential as adjuncts to ionizing radiation in the treatment of solid tumors. To gain information on the mechanism by which these agents exert their cytotoxicities to hypoxic and aerobic cells, the effects of MC, POR and several of their analogs were studied in EMT6 mammary carcinoma cells. The rate of uptake of POR by these cells was directly correlated with the cytotoxicity produced by this agent under both hypoxia and aeration. At equivalent concentrations, uptake of POR into hypoxic cells was more rapid than into aerobic cells. Hypoxic cells also accumulated the antibiotic in concentrations well in excess of that present in the extracellular medium, presumably as a result of reductive activation and covalent binding of POR to cellular structures. Such activation and binding occur to a much lesser degree in aerated cells, resulting in the rapid efflux of POR from these cells when the antibiotic is removed from the extracellular environment. To gain information on the reaction of POR with DNA, mono- and bis-adducts formed in EMT6 cells exposed to this agent were measured. Three major adducts were formed. Two were mono-adducts consisting of deoxyguanosine linked at its N2-position to the C-1 of POR and of 10-decarbamoyl POR. The third was a bis-adduct in which POR was cross-linked to two deoxyguanosines at their N2-positions. More adducts were formed in hypoxia than in air, and more bis-adducts were present in hypoxic cells. Simultaneous exposure of cells to both POR and DIC reduced the total adduct level and a new unknown adduct was formed, primarily under hypoxia. Several mitomycins were evaluated for their capacity to kill EMT6 cells and to produce DNA cross-links in both hypoxia and aeration. The number of cross-links required to produce a given amount of cell kill was similar, regardless of the mitomycin employed or the degree of oxygenation. The findings support the concept that DNA is a critical target in the action of the mitomycins and that cross-linking of the DNA creates an important lesion for cytodestruction.

Mitomycin C toxicity and pharmacokinetics in mice given sulfur nucleophiles.

The sulfur nucleophiles, sodium thiosulfate (Na2S2O3) and N-acetylcysteine (NAC) given in maximally tolerated doses did not reduce the hematologic toxicity of high dose mitomycin C (MMC) in normal mice. In addition, neither sulfur nucleophile significantly altered the antileukemic activity of MMC. Pharmacokinetic studies of MMC in normal mice, demonstrated rapid plasma elimination (T1/2 beta = 0.53 hrs) and substantial drug distribution to the bone marrow which was enhanced by NAC. These results demonstrate a lack of MMC antidotal activity for Na2S2O3 and NAC.

Isolated perfusion of pancreas with mitomycin C.

The current treatment of pancreatic cancer with resection and/or radiation is considered unsatisfactory because of a high incidence of failure and a moderate incidence of complications. A sizable number of these patients present with localized or regional disease. Regional high-dose chemotherapy, such as with isolated perfusion, may offer an alternative therapy with low treatment-related morbidity and mortality and better end results in this group of patients. In an effort to develop such a treatment modality, we evaluated the pharmacokinetics and toxicity of mitomycin C (MMC) during isolated perfusion of pancreas in a canine model. From this study, it appears that a dose of 0.25 mg MMC/kg body weight is most suitable for isolated perfusion of pancreas at 39 degrees C, maintaining flow rate and pressure within physiologic range. Isolated perfusion with a dose of 0.25 mg/kg body weight has very mild short- and long-term toxicities and markedly increases drug delivery to the pancreas, duodenum, and peripancreatic lymph nodes, making it the most suitable dose for possible clinical application.

Targeting chemotherapy for intrahepatic periductal lymphatic invasion by mitomycin C adsorbed to activated charcoal in hepatic hilar bile duct cancer.

A new dosage form of anticancer agent, mitomycin C adsorbed to activated charcoal (MMC-AC), was evaluated in the rabbit model of hepatic hilar bile duct cancer. The model was produced by inoculation of VX2 cells into the wall of the hepatic hilar bile duct. Histologic examination revealed that the mode of spreading of VX2 cells in the model closely resembles that of human bile duct cancer. On the other hand, selective accumulation of MMC-AC into the lymphatic vessels around the intrahepatic bile duct was observed after its injection into the hepatic hilum in rabbits. To assess the anticancer effect, 1 ml of MMC-AC was injected into the bile duct wall near the VX2 tumor. The numbers of lymphatic vessels where necrosis of VX2 cells was observed in one-third or more were 34 of 103 vessels 0.5 cm away from the tumor, 23 of 80 vessels 1.5 cm away, and 9 of 67 vessels 2.5 cm away. We believe that the injection of MMC-AC into the hepatic hilum can be effective adjuvant therapy for hepatic hilar bile duct cancer.

Behavior and resorption of mitomycin C following multiple intravesical administrations.

Although several pharmacological data of intravesical mitomycin C (MMC) are available now, data about resorption following subsequent intravesical instillations with different instillation times are lacking. We have analyzed MMC concentrations in blood plasma and urine following eight subsequent instillations, with 0.5- and 1.0-h instillation times. The relationships between urinary pH, urinary MMC concentrations, and MMC blood plasma concentrations were determined, as well as the stability of MMC in urine at pH 5-8 at 37 degrees C. An average of 40.3 and 46.4% of the total parent drug was recovered for the 0.5- and 1.0-h instillations, respectively. Blood plasma concentrations of MMC could be measured in nearly all patients and were independent of instillation times, urine concentration, or urinary pH. Resorption of MMC and recovery was stable during eight subsequent instillations. It was demonstrated that MMC can be degradated in urine at physiological conditions (pH less than 6; 37 degrees C). However, neither an influence of prolongation of the instillation time on MMC recovery from urine, nor a significant correlation between urinary pH and urinary MMC concentrations could be demonstrated. Since MMC can be degradated at pH less than 6 within 0.5 h, buffering of instillation fluids containing MMC is recommended. Reuse of instilled MMC, therefore, cannot be advised.

Disposition of a polymeric prodrug of mitomycin C, mitomycin C-dextran conjugate, in the perfused rat liver.

The disposition of a polymeric prodrug of mitomycin C (MMC), mitomycin C-dextran conjugate (MMC-D), was studied in the single-pass perfused rat liver in order to clarify the effect of physico-chemical properties, such as molecular weight and electric charge, on the hepatic uptake of MMC-D. Six types of MMC-D were used: both cationic MMC-D (MMC-Dcat) and anionic MMC-D (MMC-Dan) conjugated with dextran with molecular weights of 10,000, 70,000, and 500,000. Outflow curves were analyzed using statistical moment theory. Remarkable hepatic uptake of MMC-Dcat was observed and the uptake amount increased with an increase in molecular weight (i.e., approximately 80% of the dose was taken up by the liver during a single passage of the conjugate with a molecular weight of 500,000). Intrinsic clearance (CLint,i) and apparent distribution volume (Vi) also increased as the molecular weight increased. On the other hand, almost 100% of applied MMC-Dan was recovered in the outflow regardless of molecular weight, with almost the same moment parameters as those of the vascular reference substance (VRS), 131I-labeled human serum albumin (HSA). In a repeated application, the uptake of MMC-Dcat decreased in a stepwise manner, suggesting a saturation in the hepatic uptake of MMC-Dcat, while the uptake of MMC-Dan was unchanged. The MMC-Dcat pretreatment also affected the uptake of Evans blue (EB) bound to bovine serum albumin (BSA). These results demonstrate that molecular weight and electric charge determine the hepatic disposition of macromolecular prodrugs.