Pharmacokinetic drug interactions of commonly used anticancer drugs

With the use of combination chemotherapy as well as a wide range of symptomatic therapies (e.g. analgesics and antiemetics) for the treatment of patients with cancer, the field of oncology practises polypharmacy to an extreme degree. The risk for a drug interaction under these conditions is high, and the pharmacological characteristics of the anti-cancer drugs, such as steep dose-response curves, low therapeutic indices and severe toxicities, suggest that even small changes in the pharmacokinetic profile of the affected drug could significantly alter its toxicity or efficacy. In this review, drug interactions which quantitatively affect the absorption, distribution, biotransformation or excretion of the commonly used anticancer drugs are described. Most of the significant drug interactions involving this class of drugs occur at the level of biotransformation and excretion. For example, the renal excretion of methotrexate by glomerular filtration and tubular secretion is affected by a number of weak organic acids, such as probenecid, salicylates and penicillin, which compete for tubular secretion, resulting in delayed clearance of methotrexate. The best described example of an interaction at the level of biotransformation is the effect of allopurinol on the catabolism of 6-mercaptopurine. By inhibiting xanthine oxidase, allopurinol blocks the first-pass metabolism of 6-mercaptopurine following its oral administration, leading to a 4- to 5-fold increase in plasma concentrations. Known drug interactions may potentially be used to enhance the antitumour activity of a drug--for instance, the administration of tetrahydrouridine (a cytidine deaminase inhibitor) with cytarabine in an attempt to block its rapid inactivation to uridine arabinoside. Overall, little information is available concerning the pharmacokinetic interactions of anticancer drugs with each other and with other classes of drugs in man, in part because the high incidence of toxicity and treatment failure, and empirical dosing methods, obscure the recognition of possible interactions. Awareness on the part of the clinician and more extensive pharmacokinetic investigation will be needed to recognise, document and avoid potentially harmful pharmacokinetic drug interactions involving this class of drugs.

Intraperitoneal bleomycin for ventriculoperitoneal spread of a hypothalamic astrocytoma

A pediatric patient is presented in whom malignant ascites developed after ventriculoperitoneal shunt placement for a suprasellar astrocytoma. Paracentesis followed by intraperitoneal bleomycin resulted in decreased fluid re-accumulation with minimal side effects. A review of the literature shows that intracavitary chemotherapy, including bleomycin, can result in safe, effective relief of malignant effusion associated with adult tumors. We have demonstrated that such treatment is also applicable to the pediatric population. In this case, the effectiveness of intracavitary bleomycin may be related to its direct action against brain glioma cells. The need for effective treatment of malignant effusions in pediatric patients is growing because of their increased survival time with tumor. We propose that intracavitary bleomycin may provide relief from this potential complication of childhood solid tumors.

Intraperitoneal bleomycin. Pharmacokinetics and results of a phase II trial

Bleomycin was administered in a phase II trial to 10 patients with malignant ascites. Complete responses to intraperitoneal bleomycin were observed in 6/10 patients (60%). Pharmacokinetics of serum and intraperitoneal bleomycin showed peak levels at 15 minutes with a peritoneal fluid half-life of 4.2 +/- 0.1 hours and a serum half-life of 5.0 +/- 1.2 hours. There was a 400-fold difference in concentration when bleomycin was administered intra-abdominally. Toxicities with intraperitoneal bleomycin were minimal. This phase II trial confirms the efficacy of intraperitoneal bleomycin; further trials appear warranted.

Intraperitoneal bleomycin. Pharmacokinetics and results of a phase II trial

Bleomycin was administered in a phase II trial to 10 patients with malignant ascites. Complete responses to intraperitoneal bleomycin were observed in 6/10 patients (60%). Pharmacokinetics of serum and intraperitoneal bleomycin showed peak levels at 15 minutes with a peritoneal fluid half-life of 4.2 +/- 0.1 hours and a serum half-life of 5.0 +/- 1.2 hours. There was a 400-fold difference in concentration when bleomycin was administered intra-abdominally. Toxicities with intraperitoneal bleomycin were minimal. This phase II trial confirms the efficacy of intraperitoneal bleomycin; further trials appear warranted.

Mechanisms affecting peplomycin sensitivity of Chinese hamster cell lines

Chinese hamster lung cell line V79 was ca. 13 times more resistant to peplomycin (PEP), and 6 times more resistant to bleomycin (BLM)-A2 than Chinese hamster ovary (CHO) cell line. The natural resistance of V79 cells to PEP or BLM was attributed to higher levels of BLM hydrolase activity and lower cellular uptake of the antibiotic. The sensitivity to PEP of a mutant clone CHO/O-2 T-1 was similar to that of CHO. A hybrid clone of CHO/O-2 T-1 X V79 showed an intermediate sensitivity to PEP between those of both parental cell lines, suggesting that the gene responsible for the natural resistance to PEP appears codominantly in the hybrid. The BLM hydrolase activity of the hybrid was also found intermediate between those of both parental cells. Mutant clones CHO/O-2 T-5 and CHO/O-2 T-6 were 8.3-9.0 times more sensitive to PEP than CHO cells. Hybrid clones CHO/O-2 T-5 X V79 and CHO/O-2 T-6 X V79 displayed PEP sensitivity similar to that of V79, suggesting that the gene responsible for the PEP supersensitivity (PEPss) behaves recessively in the hybrids. Both PEPss clones showed levels of BLM hydrolase and cellular uptake of [3H]PEP similar to the parental CHO cells, suggesting that the PEPss is due to neither BLM hydrolase nor cellular uptake of the antibiotic. Increased PEP-induced DNA cleavage and decreased DNA repair in the PEPss clones were demonstrated by alkaline sucrose density gradient sedimentation method. The results suggest that the PEPss of these mutant clones is attributed to decreased DNA-repairing activity and/or increased DNA-breaking activity.

Use of 111In-bleomycin for combining radiotherapy and chemotherapy on glioma-bearing mice

Mice bearing transplanted glioma received 0.9% NaCl, 0.1 mg of BLM, or 200-250 microCi of 111In-BLM (0.1 mg BLM) daily for 5 days intraperitoneally. After therapy, tumor sizes were in the order NaCl greater than BLM greater than 111In-BLM. On the 11th day after the first injection, tumor size (mm3) in the 111In-BLM group was 1,220; in the BLM group, it was 2,310 (P less than .025). After intratumor injection of a total dose of 0.1 mg of BLM/gm tumor weight, or of 1 mCi/gm tumor weight of 111In-BLM (carried by 0.1 mg of BLM/gm tumor weight), the tumor size decreased in the 111In-BLM group more than in the BLM group. On the 5th day after the 2nd dose therapy, the tumor size in the 111In-BLM group was 2,020; in the BLM group it was 4,220 (P less than .05). Host weights for these two groups were similar. The necrotic area in the tumor was much greater in the 111In-BLM group than in the BLM group. These results suggest the use for radiotherapy and chemotherapy.

Lidocaine potentiation of bleomycin A2 cytotoxicity and DNA strand breakage in L1210 and human A-253 cells

The survival of cultured L1210 cells exposed to bleomycin A2 (BLM A2) was markedly decreased by coincubation with the local anesthetic lidocaine. The potentiation occurred with concentrations of lidocaine that were nontoxic and was dependent upon both the concentration of lidocaine and BLM A2. A 1000-fold decrease in survival was seen with a 1-h exposure to 8 mM lidocaine and 10 microM BLM A2 compared to incubation with 10 microM BLM A2 alone. Prior exposure to lidocaine did not markedly alter BLM A2 cytotoxicity, while treatment with lidocaine immediately after BLM A2 exposure did, suggesting that increased cellular content of BLM A2 was not the mechanism of enhancement. Furthermore, lidocaine reduced the total amount of cell-associated radioactivity seen after incubation with [3H]BLM A2. The enhancement in L1210 cell cytotoxicity with lidocaine was not specific for the C- and N-terminal moieties of the BLM molecule. Other DNA-interacting antitumor agents, such as etoposide and mitomycin C, did not exhibit biologically significant alterations in their cytotoxicity when coincubated with lidocaine, although cis-diamminedichloroplatinum was significantly more toxic in the presence of lidocaine. The potentiation of BLM A2 cytotoxicity was not unique to murine tumor cells, since it was also seen with cultured human head and neck carcinoma (A-253) cells. Lidocaine did not increase directly BLM A2-induced breakage of DNA in vitro as measured by loss of form I pAT 153 DNA, but it did increase BLM A2-induced DNA strand breaks in intact L1210 cells coincubated with lidocaine and BLM A2. Exposure of L1210 cells to lidocaine after BLM A2 treatment also greatly increased DNA breakage consistent with possible inhibition of DNA repair. In addition, a modest reduction in the in vitro inactivation of BLM A2 by BLM hydrolase was found with lidocaine. We propose that inhibition of BLM metabolism and repair of BLM-induced DNA damage by lidocaine may have a role in the enhanced cytotoxicity.

A pharmacokinetic evaluation of IM administration of bleomycin oil suspension

Bleomycin oil suspension was given IM twice daily to four patients, and bleomycin saline solution infused to three patients with cervical carcinoma. The serum levels of bleomycin were followed for 12 h by radioimmunoassay. Both regimens revealed comparable side effects. Only minor responses were seen. Bleomycin oil suspension produced prolonged levels of bleomycin in serum.

[Fundamental studies on arterial infusion chemotherapy for cervical cancer--with reference to the histological finding in infiltrating cancer and localization of the drugs in tissues]

Preoperative arterial infusion of peplomycin was carried out on 15 cases of Stage I or II cancer of the cervix, and the value of arterial infusion chemotherapy with peplomycin and its efficacy as a preoperative therapy in cervical cancer were evaluated by analysis of (1) histological changes, (2) localization of the drug in tissue, and (3) tissue concentration of the drug in the completely resected tissues, with the following results: The chief histological change was a regression of cancer nests accompanied by degeneration and necrosis of cancer cells. This change was clearer at the head of infiltrating cancers than at their superficial layer or center. Peplomycin was localized with high activity at the disintegrated part of cancer nests, i.e., its activity was closely correlated to the severity of histological change. Time-course changes in its localization suggested the vessel wall----stroma----cancer as the route of its transport. The tissue concentration of peplomycin was maintained high over a long time. Particularly in the portio vaginalis, the time course decline of the concentration was gentle. From the above findings, arterial infusion of peplomycin was considered to be an effective method of chemotherapy for cervical cancer, and worth being tried as a preoperative therapy too.

Origin and cytotoxic properties of base propenals derived from DNA

Base propenals arise from DNA by a Fe(II)-bleomycin-mediated reaction which leads to strand scission. These compounds undergo addition-elimination reactions with thiols and other nucleophilic groups under physiological conditions and form an addition product with glutathione. Thymine- and adenine-N1-propenals inhibit DNA synthesis in HeLa cells; both compounds are cytotoxic [50% inhibiting concentration (IC50) = 1 to 2 microM]. A structurally related nucleoside, thymidine-N3-propenal, designed as a metabolic pathway inhibitor, inhibits growth of HeLa, L1210 leukemia, Lewis lung carcinoma, B16 melanoma, and DLD-1 human colon carcinoma cells in culture (IC50 = 1 to 6 microM). A single injection of this compound, administered on the first day following transplant of L1210 leukemia cells, increased the mean survival time of mice by 50% (T/C = 154). Thymidine-N3-propenal selectively blocks DNA synthesis in HeLa cells and inhibits thymidine kinase (Ki = 5.1 microM) and DNA polymerase-alpha. We suggest that base propenals, rather than damaged DNA, account for some of the cytotoxic effects of bleomycin and that nucleoside propenals represent a novel class of site-directed inhibitors.

[Combination chemotherapy with cis-dichlorodiammineplatinum (11) (CDDP) and bleomycin BLM in advanced esophageal carcinoma]

Five patients with advanced carcinoma of the esophagus were treated with a combination chemotherapy employing CDDP and BLM. One cycle of chemotherapy consisted of CDDP, 50 mg/m2, on day 1 and BLM, 15 mg/patient on days, 1, 7 and 14. Two partial remission and 2 minor responses were obtained. Overall response rates, ths, were 80%. The most adverse effect was nausea. No significant elevation in the serum creatinine or BUN was recognized. Furthermore, the method of CDDP administration was studied on the serum level by 15 minutes' infusion and by 24 hours continuous infusion. The CDDP levels in the serum and tissue were determined by flameless atomic absorption spectrophotometry. The CDDP level in the serum by 15 minutes' infusion was higher than that by 24 hours continuous infusion. These results suggest that combination chemotherapy with CDDP and BLM may be a useful method for the treatment of advanced esophageal carcinoma.

Bleomycin may be activated for DNA cleavage by NADPH-cytochrome P-450 reductase

In the presence of NADPH and O2, NADPH-cytochrome P-450 reductase was found to activate Fe(III)-bleomycin A2 for DNA strand scission. Consistent with observations made previously when cccDNA was incubated in the presence of bleomycin and Fe(II) + O2 or Fe(III) + C6H5IO, degradation of DNA by NADPH-cytochrome P-450 reductase activated Fe(III)-bleomycin A2 produced both single- and double-strand nicks with concomitant formation of malondialdehyde (precursors). Cu(II)-bleomycin A2 also produced nicks in SV40 DNA following activation with NADPH-cytochrome P-450 reductase, but these were not accompanied by the formation of malondialdehyde (precursors). These findings confirm the activity of copper bleomycin in DNA strand scission and indicate that it degrades DNA in a fashion that differs mechanistically from that of iron bleomycin. The present findings also-establish the most facile pathways for enzymatic activation of Fe(III)-bleomycin and Cu(II)-bleomycin, provide data concerning the nature of the activated metallobleomycins, and extend the analogy between the chemistry of cytochrome P-450 and bleomycin.

[Mechanism of action of bleomycin at the molecular level]

On the basis of the structures of bleomycin (BLM) and its copper-complex, which were determined by us in 1978, it has become possible to discuss the mechanism of antitumor action of BLM of the molecular level. BLM is a bifunctional compound comprised of a binding site to DNA and a reaction site with DNA. The positive charge at the terminal amine interacts with negatively charged DNA by electrostatic attraction and the planar bithiazole moiety intercalates with DNA. The activated molecular oxygen at the axial site of the BLM-Fe (II) complex reacts with DNA. The mechanism of the activation of oxygen coupled with the Fe(II)-Fe(III) redox cycle is discussed. The degradation process of DNA by BLM and the bases-specific cleavage of DNA are described. Finally, the behavior of BLM in animals is described.

Bleomycin hydrolase activity in pulmonary cells

The metabolism of bleomycin (BLM) A2 by BLM hydrolase in the 105,000 X g supernatant fraction of homogenates obtained from freshly isolated and cultured pulmonary cells was assayed by high-pressure liquid chromatography. BLM A2 was converted solely to the less toxic desamido metabolite by the cytosol from isolated rabbit and bovine alveolar and interstitial macrophages, cultured rabbit and bovine pulmonary fibroblasts and cultured rabbit pulmonary artery endothelial cells. The BLM hydrolase activity in the cytosol from cultured rabbit fibroblasts had an apparent Km of 700 microM and Vmax of 33 nmol/hr/mg protein. The rate of BLM dA2 formation found with the cytosol of cultured rabbit pulmonary artery endothelial cells and pulmonary fibroblasts was 3 to 5 times greater per cell than that from the cytosol of rabbit alveolar and interstitial macrophages. Freshly isolated rabbit type II pneumocytes and bovine pulmonary artery endothelial cells grown in culture had undetectable levels of this inactivating enzyme activity. The expression of BLM hydrolase activity in rabbit pulmonary fibroblasts was stable for at least five passages in culture and was not significantly different over wide cell densities in culture. These data suggest that heterogeneity in the cellular distribution of BLM hydrolase activity exists in lungs. High levels of BLM hydrolase activity in the pulmonary endothelium or fibroblasts of some species may have an important role in determining the toxicity of BLM to the lungs.

Chemistry and mechanism of action of bleomycin

Bleomycin (BLM) is an antitumoral antibiotic active against various animal and human tumors. BLM causes a lot of biological effects characteristic of drugs which attack the DNA in cells. The nature of DNA damage consists of the release of bases and single and double-strand breaks. The Fe (II) is a necessary cofactor in the reaction of BLM with DNA. BLM is effective principally against non-dividing cells and against cells in mitotic phase, G2 and S. The various contents of BLM inactivating enzymes in tissues can explain the particular toxicity and therapeutic activity of this drug.

Subcellular distribution of spin-labeled bithiazoles and bleomycin in living KB cells: an ESR study

Spin-labeled derivatives of bithiazole and bleomycin were studied with respect to their uptake and localization in KB cells in vivo. It was found that the amidification of the C-terminal carboxylic group of bleomycinic acid was essential for the penetration of the probes in the cells and that the subcellular localization depended on the number and spacing of positively charged groups.

[Pharmacokinetics of the antitumor antibiotic bleomycetin in cancer patients given the preparation by different methods]

The pharmacokinetics of bleomycetin, a new antitumor antibiotic prepared in the USSR, was studied microbiologically. The less the extent of the main tumor in the patients, the higher the antibiotic blood levels in them. This might be associated with the adsorption capacity of the tumor tissue. The dependence of the bleomycetin kinetics on the intensity of renal clearance was shown. The characteristics of the drug distribution in the blood after intravenous, intramuscular and intrapleural administration are presented.

Delayed-release bleomycin. Comparative pharmacology of bleomycin oil suspension and bleomycin in saline

Experimental and clinical evidence indicates that bleomycin by continuous infusion is superior to intermittent administration. Continuous infusion is less convenient, however. It has been suggested that a suspension of bleomycin in sesame oil, given by IM injection, simulates a continuous infusion. The pharmacokinetics of this formulation have been compared with those of bleomycin in saline following IM injection, in six patients. The pharmacokinetic profiles of the two formulations were similar. The only difference between the profiles was the long terminal half-life at very low concentrations between 12 and 48 h after injection of the oil suspension. This difference is of unknown, but doubtful, clinical significance.

Uptake of main fractions of labelled bleomycin by solid Ehrlich ascites tumours in mice

Concentrations were studied of 58Co in the solid Ehrlich ascites tumour, blood, muscle and bone of male Swiss mice administered as complexed with total bleomycin commercially available and its isolated fractions A2, B2, demethyl A2, A1, A5, B4 and bleomycinic acid. The tumour/non-tumour ratios were determined 24 hrs after injection of the complexes. The ratios for fraction A2, B2 and total bleomycin were very close to each other. The remaining fractions showed lower values of the ratios. These results suggest that it is unlikely that any of the fractions studied are superior to total labelled bleomycin with respect to tumour scintigraphy.