Handling of biological samples in the determination of the anti-neoplastic drug mitomycin C

PLGA nanoparticle formulation of RK-33: an RNA helicase inhibitor against DDX3

BACKGROUND

The DDX3 helicase inhibitor RK-33 is a newly developed anticancer agent that showed promising results in preclinical research (Bol et al. EMBO Mol Med, 7(5):648-649, 2015). However, due to the physicochemical and pharmacological characteristics of RK-33, we initiated development of alternative formulations of RK-33 by preparing sustained release nanoparticles that can be administered intravenously.

METHODS

In this study, RK-33 was encapsulated in poly(lactic-co-glycolic acid) (PLGA), one of the most well-developed biodegradable polymers, using the emulsion solvent evaporation method.

RESULTS

Hydrodynamic diameter of RK-33-PLGA nanoparticles was about 245 nm with a negative charge, and RK-33-PLGA nanoparticles had a payload of 1.4 % RK-33. RK-33 was released from the PLGA nanoparticles over 7 days (90 ± 5.7 % released by day 7) and exhibited cytotoxicity to human breast carcinoma MCF-7 cells in a time-dependent manner. Moreover, RK-33-PLGA nanoparticles were well tolerated, and systemic retention of RK-33 was markedly improved in normal mice.

CONCLUSIONS

PLGA nanoparticles have a potential as a parenteral formulation of RK-33.

Validation and use of microdialysis for determination of pharmacokinetic properties of the chemotherapeutic agent mitomycin C - an experimental study

BACKGROUND

Mitomycin C is a chemotherapeutic agent used in the treatment of peritoneal surface malignancies, administered as hyperthermic intraperitoneal chemotherapy after cytoreductive surgery. Pharmacokinetic studies have been based on analyses of blood, urine and abdominal perfusate, but actual tissue concentrations of the drug have never been determined. Microdialysis is an established method for continuous monitoring of low-molecular substances in tissues, and in the present study microdialysis of mitomycin C was studied in vitro and in vivo.

METHODS

Using in vitro microdialysis, relative recovery was determined when varying drug concentration, temperature and perfusion flow rate. In vivo microdialysis was performed in rats to verify long-term stability of relative recovery in four compartments (vein, peritoneum, extraperitoneal space and hind leg muscle). Subsequently, intravenous and intraperitoneal bolus infusion experiments were performed and pharmacokinetic parameters were calculated.

RESULTS

In vitro, compatibility of mitomycin C and microdialysis equipment was demonstrated, and relative recovery was stable over an adequate concentration range, moderately increased by raising medium temperature and increased when flow rate was reduced, all according to theory. In vivo, stable relative recovery was observed over seven hours. Mitomycin C exhibited fast and even distribution in rat tissues, and equal bioavailability was achieved by intravenous and intraperitoneal infusion. The half-life of mitomycin C calculated after intravenous infusion was 40 minutes.

CONCLUSIONS

Mitomycin C concentration can be reliable monitored in vivo using microdialysis, suggesting that this technique can be used in pharmacokinetic studies of this drug during hyperthermic intraperitoneal chemotherapy.

Pharmacokinetics of the peritoneal-plasma barrier after systemic mitomycin C administration

The peritoneal plasma barrier (PPB) is a pharmacologic entity of importance for treatment planning in patients with malignant tumors confined to the abdominal cavity. We have examined the pharmacokinetics of the PPB by sampling abdominal fluid following intravenous mitomycin C (MMC) administration. The study included 15 cycles of treatment in seven patients with peritoneal carcinomatosis from colorectal cancer. Five patients were studied twice and one patient was studied three times for a total of 15 cycles. Patients were treated with intraperitoneal 5-fluorouracil (5-FU) at 20 mg/m2 in 11 of fluid. Between 250 and 500 ml of ascites remained after the 23 hour intraperitoneal dwell. On day 3, MMC (12 mg/m2) was administered intravenously as a 2-hour continuous infusion in 200 ml of dextrose solution. The concentration of MMC was determined in plasma, peritoneal fluid, and urine by high performance liquid chromatolography (HPLC) at frequent intervals for 8 hours. The area under the curve (AUC) for plasma as related to peritoneal fluid was three times greater for plasma in one cycle, two times greater for plasma in three cycles, 1.5 times greater for plasma in five cycles, and the same in six cycles. AUC ratios showed a correlation with the extent of peritoneal stripping at the prior surgical procedure 6 weeks to 14 weeks previously. We conclude that malignant ascites may be less exposed to chemotherapy than systemic tumor nodules when the intravenous route of drug administration is used. This inadequacy is even more pronounced in patients who have had extensive abdominal surgery.

Pharmacokinetics of mitomycin C in patients after bolus injection and chemobolisation of the hepatic artery with Spherex starch particles

The pharmacokinetics of mitomycin C after chemobolisation of the common hepatic artery by micronized Spherex starch particles (mean particle size 30 microns) were investigated in 5 cancer patients. Bolus injection and simultaneous occlusion of the artery lead to a significantly lower systemic circulation of mitomycin C in the blood vessel system than after bolus injection without chemobolisation. The plasma concentration-time curves showed lower values in the alpha-phase in the presence of Spherex (co = 743 ng/ml) than without starch particles (co = 987 ng/ml). Accordingly, the AUC values were significantly lower too (AUC = 28.6 micrograms/ml.h with Spherex and 39.7 micrograms/ml.h without Spherex), thus leading to a lower systemic bioavailability of the drug and a higher local bioavailability in the tumor region. Elimination of mitomycin from the central compartment was similar for both administrations (t1/2 = 27 min with Spherex and 28 min without Spherex) and showed the characteristic profile of the substance. The clinical picture showed a milder toxicity with a certain loss of side effects. These results indicate a significant and desirable change in the pharmacokinetics of mitomycin C during the distribution phase into the tissue of patients.

[The effect of the vasoconstrictor glycylpressin on the bioavailability of mitomycin C]

During an intra-arterial chemotherapy of patients with liver metastases the plasma concentration-time curves of Mitomycin C (1) after occlusion of the common hepatic artery by the vasoconstricting agent Glycylpressin (2) were investigated. Vasoconstriction by 2 leads to significantly (p less than 0.01) lower blood levels of 1 in contrast to bolus injection of 1 without 2 under identical dosage regimens. This reduction of systemic availability of about 50% leads to a corresponding higher availability for the tumor region.

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.

Absence of interaction between furosemide and mitomycin C

The possible interaction between furosemide and mitomycin C (MMC) was studied in five patients. The pharmacokinetics of MMC were studied using an HPLC assay. Furosemide was administered prior to, or 120 min after MMC. Furosemide did not change the pharmacokinetics of MMC, nor did it change the amount of MMC excreted in the urine. There appears to be no interaction between the two drugs.

Relationship between clinical parameters and pharmacokinetics of mitomycin C

Although the number of reports on mitomycin C (MMC) pharmacokinetics is increasing, data on possible relations between clinical parameters and pharmacokinetics are usually lacking. The present report concerns the results of a detailed study on this subject in 35 patients receiving MMC, either as a single agent or as a part of combination chemotherapy. MMC concentrations were determined by HPLC. T1/2 beta varied from 23 to 78 min, VD from 11 to 48 l/m2, Cl tot from 12 to 42 l/h per m2, and AUC from 138 to 1221 micrograms/h per l, confirming previously reported data. Infusion time, cholestasis, and urinary pH did not influence the pharmacokinetic data. There were no relations between other clinical data and pharmacokinetics, nor between AUC and bone marrow toxicity. An interaction between MMC and furosemide could not be excluded, but there was no interaction with other comedication. Consecutive pharmacokinetics in 6 patients showed consistent results. Because renal impairment does not alter MMC pharmacokinetics and renal excretion is not a major route of elimination, it is suggested that renal impairment does not call for dose adjustment.