Effect of Phenobarbital on Cyclophosphamide Cytotoxic Activity and Pharmacokinetics in Mice

The interaction between cyclophosphamide (CPA) and phenobarbital (PB) was investigated in B6D2F, mice, checking both the antileukemic and immunosuppressive activity together with the serum levels of CPA and its metabolites. A reduced cytotoxic activity of CPA has been observed when PB is given for 2 days before CPA and an interval of at least 6 hours elapses between the last treatment of PB and the administration of CPA. On the contrary, when PB is given simultaneously with CPA for 2 or 4 consecutive days, an increased antileukemic activity of CPA occurs. In the experimental condition where PB decreases the activity of CPA, serum levels of CPA, assayed by means of a new specific gas-chromatographic method, and of its NBP-alkylating metabolites, indicate that this effect may be explained on a pure pharmacokinetic basis. However, for the situation where an increased effect of CPA was observed under the influence of PB, pharmacokinetic data did not provide a clear explanation.

Pharmacokinetics of anticancer agents in patients with impaired liver function

This report reviews published information on the clinical pharmacokinetics of antitumour agents in patients with liver dysfunction, associated with primary liver disease or liver metastases. Information was available for anthracyclines and their related compounds, antimetabolites, cyclophosphamide, vinca alkaloids, taxanes and epipodophyllotoxins. Changes in the pharmacokinetic profile or metabolism in patients with mild or severe hepatobiliary dysfunction are described and the relationships between serum levels, parameters employed for measuring hepatic function and toxic or therapeutic effects are examined. Current knowledge of the pharmacokinetics of antineoplastic agents in liver disease is far from complete, mostly obtained in small numbers of non-homogeneous patients often presenting only moderate liver dysfunction, and empirical guidelines for dose assessment are still largely applied in clinical practice. Because of the complex pathophysiological mechanisms of liver insufficiency in cancer patients, there is still doubt whether endogenous markers are useful. Although caution in treating cancer patients with liver insufficiency is compulsory, for most compounds there seems no need to recommend dose reductions for moderate impairment. However, for the tubulin acting agents, vincristine, vinblastine and possibly for paclitaxel and docetaxel, there is strong evidence that dose adjustment is mandatory in order to avoid excessive neutropenia and neurotoxicity.

Pharmacokinetics of HD-MTX in infants, children, and adolescents with non-B acute lymphoblastic leukemia

A retrospective pharmacokinetic analysis was done of methotrexate serum levels after high-dose treatment (HD-MTX, four cycles at two-week intervals of 5 g/sq.1m. over 24 h i.v.) in children with non-B acute lymphoblastic leukemia (ALL) with the specific aim of seeking differences in patients of different ages, including infants under one year. A total of 122 children (seven infants aged 3 months-1 year, 26 children aged 1-3 years, 68 children aged 3-10 years and 21 adolescents aged 10-15 years) with normal liver and renal function, receiving consolidation therapy at the Pediatric Clinic of Monza between May 1988 and April 1992, were enrolled in this study. MTX was given as an intravenous infusion in 24 h and serum concentrations were measured up to at least 72 h after the start of infusion by an enzyme immunoassay (TDX Abbot, Dallas, TX) in order to modulate folinic acid rescue. Pharmacokinetic analysis of MTX levels according to a two-compartment open model indicated that, compared to all children up to 10 years old, in adolescents older than 10 years the drug reached higher concentrations in serum and was cleared at a lower rate. Steady-state levels and AUC were from 60% higher to more than double and the total clearance of the compound, expressed either per square meter surface area or per kg body weight, in each cycle was significantly lower in adolescents > 10 years of age, sometimes being only one-third of the clearance in infants (0.2 vs. 0.6 1/h/kg and 6.6 vs. 10.7 1/h/sq.m). The relationship between each age and systemic clearance was highly significant as measured by regression analysis. Methotrexate systemic clearance progressively decreased as a function of age. Subsequent treatments did not induce changes in MTX pharmacokinetics. These data suggest that the better tolerance of HD-MTX in children may have a pharmacokinetic basis. The faster elimination of MTX in infants, who usually show the worst prognosis, suggests that full doses could be safely used in order to maximize the antileukemic effect without a high risk of toxicity.

Do anticancer agents reach the tumor target in the human brain?

The development of effective chemotherapy for tumors of the central nervous system (CNS) is complicated in that the blood-brain barrier (BBB) hampers the penetration of most drugs into the brain and cerebrospinal fluid (CSF). This review summarizes the main reports on the distribution to CNS tumors and peritumoral normal brain of antitumor agents such as epipodophyllotoxins, cis-diamminedichloroplatinum(II), some nitrosoureas, bleomycin, vinblastine, and other clinically used antitumor agents as well as that of some experimental compounds with specific physicochemical properties. Drug levels were measured at surgical resection or in autopsy samples taken from patients who presented with different primary brain tumors or with brain metastases from extracerebral tumors. The observations made in each study were summarized in some detail, and the main points were then evaluated comparatively so as to highlight common aspects in the pharmacokinetic patterns of antitumor agents in human CNS tumors. Independently of their physicochemical properties, most antitumor agents appear to accumulate to a greater extent and to persist longer in intracerebral tumors than in the normal peritumoral brain. From in vitro cytotoxicity assays, it appears that epipodophyllotoxins, platinum compounds, bleomycin, and nitrosoureas reach potentially active therapeutic concentrations at the tumor target. However, all drugs have difficulty in reaching brain tissue adjacent to the tumor, as the intact BBB hampers their penetration. Plasma and CSF drug concentrations usually give little useful indication of the absolute quantity of drugs in brain tumors. To obtain a clear understanding of the CNS distribution of antitumor agents, one must determine whether the compound being measured is actually responsible for the observed activity and must consider the role of metabolites in the effect of the parent drug.

Concentrations of VP16 and VM26 in human brain tumors

VP16 and VM26 were determined by high pressure liquid chromatography in intracerebral tumors, adjacent normal brain tissue, plasma and CSF samples from 24 patients given the two drugs before surgical resection of the tumor. The drugs were administered at doses of 100-150 mg/m2 as a 1-hour i.v. infusion, between 1.5 and 12 hours before surgery. Concentrations of VP16 ranged between 1.05 and 3.28 micrograms/g in tumors in the series of patients who received the drug 1.5-3 hours before surgery and between less than 0.05 and 1.12 micrograms/g in four patients who received the drug 9-13 hours before surgery. Tumor concentrations of VM26 also varied, ranging from less than 0.05 to 1.68 micrograms/g between 1.5 and 12 hours before surgery. VP16 and VM26 in the apparently normal brain tissue surrounding the tumor were low or undetectable except in one patient who had received radiotherapy, in whom we found 3.1 micrograms/g.

Doxorubicin toxicity and pharmacokinetics in old and young rats

Doxorubicin (Dx) toxicity was compared in old (24 months) and young (6 weeks) Crl:CD(SD) BR male rats, and a clear age-related increase was found. The mortality of all animals receiving a single i.v. Dx dose was followed for 270 days. Old rats died after doses of 2.5 mg/kg, while young animals died after doses two times higher, 5 mg/kg. In old rats body weight loss started 10 to 15 days after Dx, compared to 50 to 80 days for young animals. In young and old rats pharmacokinetic and metabolic studies of Dx were conducted in vivo and in the liver perfusion model. Peak levels of Dx and areas under the time/concentration curves (AUC) in serum and in several tissues of old rats were 1.5 to 2 times higher than in young rats. Concentrations of Dx metabolites in serum and tissues (doxorubicinol, Dxol, and doxorubicinone, Dxone) in young and old rats were not noteworthy. However, higher percentages of Dxone than Dxol were found in both groups in vivo and in vitro. Old livers appeared to produce more Dxone as a percentage, particularly in the bile, which was higher. Urinary elimination of Dx markedly slowed with age; only small amounts of the metabolites were eliminated in urine. In vivo and in vitro availability of Dx and its metabolites is discussed in view of their possible role in the greater toxicity observed in 24-month-old rats.

Hepatobiliary metabolism and urinary excretion of 4-demethoxydaunorubicin as compared to daunorubicin in rats

The hepatic metabolism and biliary excretion of 4-demethoxydaunorubicin (4DDM) was studied in Crl: CD(SD) BR rats by the liver perfusion technique. In the same strains of rats urinary excretion was investigated in vivo. Daunorubicin (DM) was always included for comparison. The drugs and their metabolites were determined in the perfusion medium, in the bile and liver and in the urine by high-performance liquid chromatography with fluorimetric detection. Compared to its analogue DM, 4DDM markedly differed in the metabolic and excretory profile. The cumulative biliary and urinary excretion of 4DDM and the metabolites was quantitatively lower than that of DM (18% vs 36% of the dose) and was consistent with prolonged persistence of 4DDM in plasma in vivo. The extensive carbonyl reduction of 4DDM and DM observed in previous in vivo pharmacokinetic studies was also evident in this study. 13-hydroxy metabolites, daunorubicinol (DMol) and 4-demethoxydaunorubicinol (4DDMol), either as such or after glycosidic cleavage, i.e. 4DDMol aglycone, were present in appreciable amounts in the perfusion medium, bile, liver and urine. In the hepatobiliary system, however, the 13-hydroxy derivative of DM amounted to a much lower fraction than the DM aglycone (17% vs 50% of the total dose), 80% of the total 4DDM dose was accounted for by 4DDMol aglycone. In urine uncleaved DMol or 4DDMol represented more than 75% of the total amount excreted for both drugs. Conjugation, a major step in the excretion of aglycones, seems to play a minor role in the biliary and urinary excretion of 4DDM and 4DDMol.

Studies on the biology, histology and cytogenetics of two sublines of a murine ovarian reticular cell sarcoma : Biology of M5 and R16 murine tumor

Two sublines of the ovarian reticular cell sarcoma M5 in C57BL mice respond differently to cyclophosphamide and other alkylating agents. The subline R16, which is resistant to cyclophosphamide, was obtained by treating M5 mice repeatedly with this compound and subsequently transplanting the regrowing tumor for 16 passages. The R16 subline shows biological characteristics perfectly superimposable to those of the parent line and histologically resembles an undifferentiated mesenchymal neoplasia with numerous atypical nuclei and karyokinetic figures with large necrotic areas. The cytogenetic examination of the distribution in the chromosomal number of R16 indicates that this subline may be considered a clone of the parent line with a modal class of 35 chromosomes (34-37) versus a class of 34 (31-37) in the M5 tumor line. The presence of metacentric chromosomes characterizes the modal class of the two lines, 23 in the R16, and 25 in the M5 tumor lines.

Prostaglandin and thromboxane synthesis by M5076 ovarian reticulosarcoma during growth: effects of a thromboxane synthetase inhibitor

The five stable metabolites [prostaglandin F2 alpha (PGF2 alpha), prostaglandin D2 (PGD2), prostaglandin E2 (PGE2), thromboxane B2 (TXB2), and 6-ketoprostaglandin F1 alpha (6-keto-PGF1 alpha)] of arachidonic acid (AA) via the cyclooxygenase pathway were measured by high-resolution gas chromatography-mass spectrometry in M5076 ovarian reticulosarcoma (M5) homogenates at various times after tumor implantation (Days 15, 18, 21, and 24). Vegetating tumor showed an active AA overall metabolism, which significantly increased during tumor growth. Synthesis of selected products (TXB2, PGD2, and PGE2) increased markedly over time (up to 10.6, 3.5, and 0.9 micrograms/g, respectively). The overall metabolic profile was TXB2 much greater than PGD2 greater than PGF2 alpha greater than 6-keto-PGF1 alpha greater than PGE2 on Day 15 and TXB2 much greater than PGD2 much greater than PGF2 alpha greater than 6-keto-PGF1 alpha on Day 24. TXB2 was also by far the most abundant product of in vitro-cultured M5 cells. Chronic treatment of M5-bearing mice with dazmegrel (UK-38,485), a selective thromboxane synthetase inhibitor (100 mg/kg p.o. daily, from Day 7 to killing), resulted in incomplete TXB2 synthesis inhibition, AA metabolism diversion toward the other prostaglandins, and no effects of tumor growth and metastasis. More frequent dazmegrel treatment (100 mg/kg p.o. every 8 h from Day 1 to killing) resulted in complete TXB2 synthetase inhibition, AA metabolism diversion, and increased tumor growth and metastasis. These data do not support the hypothesis of thromboxane synthetase inhibitors reducing tumor growth. However, since TXB2 suppression was accompanied by the production of other products possibly interfering in tumor growth, no conclusions on the effective role of TXA2 in malignancy can be drawn.

Antitumoral Activity of the Oxazaphosphorine Derivative, Mafosfamide-Cyclohexylamine Salt (ASTA 7557) on a Murine Ovarian Reticular Cell Sarcoma and its Subline Resistant to Cyclophosphamide

The antitumor activity of mafosfamide (MFA), and its parent compound cyclophosphamide (CTX), was investigated against an ovarian reticular cell sarcoma growing i.m. in C57BI/6 mice (M5), which is very sensitive to CTX, and against a subline of this tumor (R16) resistant to CTX. MFA is the prototype of a class of oxazaphosphorines which do not require metabolic activation since under physiologic conditions they undergo rapid spontaneous hydrolyzation to the activated 4-hydroxyoxazaphosphorine and retain a spectrum of activity very similar to the parent compound. After a single dose (300 mg/kg × 1) or repeated low doses (100 mg/kg × 6) the antitumoral activity of MFA on the M5 tumor appeared comparable to or only slightly lower than CTX; the highest T/C value for median survival times was 167% in MFA-treated mice vs. 176% in the CTX group. MFA showed no activity against the R16 subline, thus indicating cross-resistance between the two drugs. Marked thickening of the glissonian capsule with compression of the lobular area of the liver, observed on i.p. administration of MFA, did not result in histopathologic abnormalities of the hepatic parenchyma. The therapeutic efficacy of MFA was similar with the i.p. and the i.v. route. MFA may represent a good candidate to replace CTX in cases in which a compound acting per se, and not through metabolites, is preferred.

Comparative metabolism of daunorubicin and 4-demethoxydaunorubicin in mice and rabbits

In the present study, the biodisposition of 4-demethoxydaunorubicin (4DDM) and its 13-dihydrometabolite was compared with daunorubicin (DM) and its metabolite in rabbit serum, and the results were considered in the light of this DM analog's pharmacokinetic behavior in mice. In rabbit serum, the levels of the 13-OH derivative of both DM and 4DDM (daunorubicinol and 4-demethoxydaunorubicinol) were higher than in mice. In vitro metabolic studies with mouse and rabbit cytosol indicated that the hepatic metabolism was quantitatively important for both analogs (70%-90% for DM and 4DDM was reduced to the 13-OH metabolite), but the rabbit had a much higher specific capacity to metabolize these compounds. DM seemed a better substrate for cytoplasmic aldoketoreductase, the enzyme affinity in rabbits being three times higher than for 4DDM. Cytotoxicity studies in vitro showed that 4-demethoxydaunorubicinol, unlike daunorubicinol, was as cytotoxic as the parent compound, and this suggests this metabolic step does not inactivate 4DDM but contributes to its high and long-lasting biological activity in vivo.

Different sensitivity of two Walker 256 carcinoma lines to cyclophosphamide: correlation with drug distribution, biotransformation and macromolecule binding

Two closely related lines of the same Walker 256 carcinoma in Crl-CD/COBS rats, described as behaving differently as regards tumor growth and host reaction, show different chemotherapeutic sensitivity to cyclophosphamide (CPA). Line B, which induces early cachexia with marked anorexia, is only moderately sensitive to CPA, while line A, which causes mild anorexia and only terminal cachexia, shows marked responsiveness to CPA, cure being attained in 75% of animals treated with a single dose of 120 mg/kg and in 90-100% of those given 20 mg/kg every other day. Comparative studies in both tumor lines on the distribution of CPA in vivo and on its metabolism by the liver perfusion technique showed no appreciable differences between the two lines in the pharmacokinetics of the compound, but indicate a much greater metabolizing capacity of CPA in the Walker 256/A animals. In vitro metabolic and covalent binding studies confirm that the liver of the Walker 256/A group metabolizes and covalently binds twice as much CPA as the liver of the Walker 256/B group. Conversely to Walker B, microsomal preparations of the Walker tumor line A are able to metabolize CPA to intermediates which irreversibly bind to tissue macromolecules, suggesting an in situ activation of the compound in the sensitive Walker tumor.

Prostaglandin and thromboxane synthesis by Lewis lung carcinoma during growth

The five stable metabolites [prostaglandin F2 alpha, prostaglandin D2, prostaglandin E2 (PGE2), thromboxane B2, and 6-keto-prostaglandin F1 alpha] of arachidonic acid (AA) via the cyclooxygenase pathway were measured by high-resolution gas chromatography-mass spectrometry in Lewis lung carcinoma homogenates at various times after tumor implantation (11 to 25 days). Vegetating and necrotic sections of the primary tumor and lung metastases were examined. Vegetating tumor showed a very active AA metabolism. Synthesis of PGE2, the most abundant product, markedly increased during tumor growth (up to 30 micrograms/g). A high and increasing synthetic capacity was also noted for prostaglandin D2 (up to 9 micrograms/g). Minor time differences and lower levels (up to 1.4 micrograms/g) were found for the other AA metabolites. PGE2 and prostaglandin D2 were the major products in necrotic tumor, too, but synthesis was markedly less than in vegetating tumor, and no increase was noted over time. Metastatic tissue showed a different AA metabolic profile, as compared to primary tumor and surrounding lung tissue, with PGE2 and 6-keto-prostaglandin F1 alpha being the main metabolites.

Metabolic studies of a podophyllotoxin derivative (VP16) in the isolated perfused liver

The metabolism of VP16 was studied in isolated perfused rat liver. The rate of elimination into the medium and excretion in bile were determined by h.p.l.c. with u.v. detection. With high VP16 concentrations (180 micrograms/ml medium), the elimination half-life of the compound was prolonged markedly (156 v. 45 min for lower doses), the percentage recovered in bile was more than halved and drug accumulation in the hepatic tissue was three times greater. These findings indicate saturation of metabolism and of biliary elimination during high-dose treatment. The presence of glucuronides in the bile of VP16 perfused livers indicates that VP16 undergoes conjugation with glucuronic acid. Formation of picro isomer of VP16 in the liver also occurs.

Activity and distribution of iv and oral 4-demethoxydaunorubicin in murine experimental tumors

The antitumor activity of 4-demethoxydaunorubicin ( 4DDM ) compared to its parent compound daunorubicin (DM) was investigated in C57BL/6 mice bearing a T-cell lymphoma, the EL-4, chosen because of its sensitivity to this compound. 4DDM was moderately effective against Lewis lung carcinoma and M5076 ovarian reticulosarcoma tumor systems. Against the EL-4 tumor, after either iv or oral treatment, 4DDM had a good therapeutic effect (survival time in treated mice was almost double that in untreated mice) which was comparable to that of iv doxorubicin. Serum and tissue distribution of 4DDM and its reduced metabolite 4- demethoxydaunorubicinol , given either iv or orally at therapeutic doses to EL-4-bearing mice, was then compared with iv DM using a high-performance liquid chromatography technique with fluorimetric detection. DM seemed to be cleared faster and to a greater extent by metabolism than 4DDM , with half-lives after iv treatment of 23 hrs for 4DDM versus 4.6 hrs for DM. The reduced metabolite in serum amounted to greater than 100% of the concentration of the native compound for DM and less than 20% for 4DDM . By both the iv and oral routes, 4DDM appeared to be concentrated and retained in tissues to a proportionally higher extent than DM, with drug exposure being at least twice as high with correspondingly longer half-lives in almost all tissues investigated, including the tumor. Moreover, this demethoxy analog appeared to be somewhat more selective than DM, since the relative capacity of the tumor tissue to accumulate this compound seemed higher than that of other organs (eg, heart and spleen) reported to be targets of toxicity. Oral administration gave more favorable distribution, resulting in the highest tumor to heart and spleen concentration ratio; this suggests a superiority of this route of administration.

Effects of disodium etidronate in murine tumor models

This study was designed to elucidate the effect of ethane-1-hydroxy-1,1-diphosphonate (EHDP) in experimental rodent tumors. EHDP had no antitumor activity against the L1210 leukemia implanted i.p. and against sarcoma 180, Lewis lung carcinoma (3LL) and Walker 256/B carcinoma injected i.p., s.c. or i.m. respectively. EHDP did not interfere with the antitumor activity of commonly used conventional chemotherapeutic agents (adriamycin, cyclophosphamide, 5-fluorouracil, bis-chloroethylnitrosourea) in the L1210 and 3LL models. EHDP reduced proportionally to the dose the hypercalcemia and hypercalciuria due to the Walker 256/B carcinoma growth. In an effort to evaluate whether EHDP-treated osseous tissues were more refractory to tumor growth, cells from sarcoma 180 and 3LL carcinoma were implanted intratibially (i.t.). Growth of 3LL cells was not consistently affected by EHDP, whereas a modest, but significant, growth inhibition was consistently observed with sarcoma 180 injected i.t. Growth of sarcoma 180 implanted i.p. or s.c. was not reduced by this drug, thus suggesting that inhibition of i.t. sarcoma 180 was in fact related to alterations of osseous tissues by EHDP. Inoculation of Walker 256/B carcinoma intra-aortically resulted in osteolytic bone lesions in the hind limbs. EHDP inhibited the formation of bone metastasis under these conditions.

Pharmacokinetic studies of anticancer drugs in tumor-bearing animals

The pharmacokinetics of antitumor agents is a relatively recent area of research, as lack of proper specific methodology for monitoring drug levels has always hampered major efforts. Although the relationship among administered dose, tissue concentration, and therapeutic and/or toxic effects remains extremely complex, a series of experimental and clinical studies provides information on the pharmacokinetic behavior of most anticancer agents in different conditions. This review article describes examples selected from the work of this Institute on several points which may be relevant to the use of these compounds: (a) factors influencing pharmacokinetics, such as genetic constitution of the host, presence of the tumor, dose, route of administration and schedule, organ insufficiency, and interactions with other drugs; (b) drug distribution in host tissues in relation to toxic effects; (c) drug distribution to secondary tumors (metastases); (d) importance of active metabolites; and (e) drug distribution and binding to intracellular target sites. An analysis of these factors shows that many aspects are still very poorly understood and require considerable further study.

Distribution, metabolism, and irreversible binding of hexamethylmelamine in mice bearing ovarian carcinoma

The covalent binding of hexamethylmelamine (HMM) and its metabolites was studied in liver, tumor, blood, kidney, spleen, lung, brain, heart, and small intestine after a single IP injection of 2,4,6-14C-hexamethylmelamine (50 mg/kg) to C57Bl/6J female mice bearing 20-day-old M5076/73A ovarian cancer. Covalent binding to tissue macromolecules was measured 2, 10, and 40 h after injection of the drug. At 2 h liver and small intestine showed the highest levels of irreversibly bound metabolites, the lowest being found in brain and heart. Except in the small intestine, where a decrease was observed between 2 and 10 h, the level of covalent binding was constant up to 40 h. HMM metabolism was also studied. Tissue distribution of pentamethylmelamine (PMM), 2,2,4,6-tetramethylmelamine (TMM), and 2,4,6-trimethylmelamine (TriMM) was determined at the three times considered. At 2 h the drug was already extensively metabolized, TriMM being the major metabolite among those determined.

Intact rat liver nuclei catalyze adriamycin irreversible interactions with DNA and nuclear proteins

Male rat liver intact nuclear preparations are able to metabolize adriamycin to reactive species that irreversibly interact with nuclear DNA and proteins in the presence of reduced NADPH. This process was not inhibited by 1 mM SKF-525A, suggesting that a nuclear monooxygenase enzymatic system was not involved.

Subcellular distribution of adriamycin in the liver and tumor of 3LL-bearing mice

The apparent subcellular distribution of adriamycin (ADM) was investigated in the liver and primary or metastatic tumor tissue of C57BL/6 mice bearing i.m. 3LL. ADM was measured by a fluorimetric assay in the various cell components, nuclei (N), mitochondria (MT), microsomes (M) and soluble fraction of cytoplasm (SF), either in vitro at various times of incubation or in vivo after drug injection. In both experimental conditions more than 50% of ADM accumulated in nuclei, whereas only a proportionally low amount of drug has recovered in the other fractions. However, a progressive increase in the percentage of drug stored in M and particularly in MT was noted in vivo in both liver and tumor, reaching in MT 3 times the starting amount on a percentage basis 24 hr after drug treatment. The elimination half-life of ADM was consistently longer in MT and M than in nuclei and total liver, suggesting that M and particularly MT have a higher capacity than nuclei to retain the drug. Work is in progress to evaluate whether this higher ADM accumulation at these subcellular sites is related to higher specific affinity or more persistent binding, like covalent binding to macromolecules, possibly accounting for the mitochondrial injury usually observed after treatment with ADM.

Influence of adriamycin on growth kinetics of Lewis lung carcinoma and its lung metastases

Using a Gompertzian pharmacodynamic model, we have studied the changes induced by graded doses of adriamycin (AM) on the growth of intramuscular Lewis lung carcinoma (3LL) and its lung metastases in C57Bl/6 mice. An interpretation of the drug's effects on free growth of the tumor cells is given in the Appendix. Unlike other tumors (1-6), in which AM treatment induces no long-term change in growth parameters, in the 3LL model after an initial phase of inhibited growth following treatment with AM, the theoretically attainable plateau value is lowered. This is dose dependent for the primary tumor and even more so for metastases. In order to investigate whether the drug effect was irreversible or whether the host's weakened condition was a factor in the altered growth conditions, the tumor and its metastases were removed from AM-treated mice and transplanted in healthy animals in which its growth was then observed over time. For transplants of the primary intramuscular tumor no differences could be seen between treated and nontreated mice, but for the metastases the growth was markedly slowed. However, after a 'lag' period, the tumors arising from metastases returned to a growth pattern whose kinetic parameters, analyzed statistically, were not different from controls.

Interaction between heparin and adriamycin in mice bearing the Lewis lung carcinoma

The investigation was prompted by the observation that adriamycin can interact with heparin in vitro and reduces its anticoagulant activity in ex vivo tests in humans. The possible interactions between these two drugs were studied in C57Bl/6J mice bearing the Lewis Lung Carcinoma (3LL). The anticoagulant activity of heparin was temporarily reduced by concomitant treatment with adriamycin, as indicated by both activated partial thromboplastin times and blood recalcification times. In contrast, no changes were found in the kinetics of adriamycin disappearance from blood and accumulation in tissues if mice had been pretreated with heparin. Moreover, the effect of adriamycin on tumour and metastasis growth was unchanged by the association with the anticoagulant. These data indicate that the short-lived interaction between adriamycin and heparin, which can be documented by coagulation tests, does not necessarily involve a modification in the anticancer activity of the anthracycline.

Differential adriamycin distribution to blood components

The differential distribution of doxorubicin (Adriamycin = AM) and daunorubicin (Daunomycin = DM) within the blood components, after an i.v. injection of 10 or 15 mg/kg of body weight, was investigated from its metabolites and quantified by means of the TLC scanning fluorescence technique. AM accumulated in the following order (of decreasing percentages): plasma and red cells (RBC), white cells (WBC), and platelets (PT), but the absolute amount of drug that reached each cell type was related to its relative volume. In the presence of higher blood concentrations (after injection of 15 mg/kg of body weight) the RBCs accumulated much more AM than the plasma, WBC, and PT; suggesting that the RBC fraction has a greater capacity to concentrate the drug. However, if the concentration of AM is expressed per unit volume of each component, a markedly higher value was observed for PT, and this was confirmed by in vitro results obtained by incubating blood in the presence of AM. DM seemed to be distributed on a percent basis to a greater extent than AM in the RBC fraction. Both compounds were taken up by blood cells, particularly platelets, to levels in excess of the extracellular concentration.

Pharmacodynamic model describing the growth of a mammary carcinoma in the mouse under the influence of adriamycin treatment

The chemotherapeutic effects of different doses of adriamycin in (C3H x 020)F1 mice bearing mammary carcinoma have been investigated and a model of the growth of neoplastic cells under the influence of treatment is described. An estimate of cell kill and of the fraction of cells surviving after treatment is given by the efficacy constant K, which is a function of the dose level of the drug. The therapeutic value of each treatment is, however, also related to the degree of toxicity which in our model is expressed by the probability of death for each dose level.

Possible relevance of N-trifluoroacetyladriamycin (AD 41) in the antitumoral activity of N-trifluoroacetyladriamycin-14-valerate (AD 32) in tumor-bearing mice. I. Pharmacokinetic evidence

N-Trifluoroacetyladriamycin-14-valerate (AD 32) is an analog of doxorubicin whose chemico-physical characteristics are nontypical compared to the parent compound. Its most interesting feature is the lack of capacity to intercalate with DNA; thus, its mechanism of action as an antitumoral drug is still unknown. The N-trifluoroacetyl bond on the glycoside moiety is very stable and does not easily undergo enzymatic hydrolysis. Conversely, the valerate ester is split very rapidly by tissue and blood hydrolases. In this paper we present a kinetic study on AD 32, and we additionally follow the formation and disappearance of its metabolite, N-trifluoroacetyladriamycin (AD 41). Peak levels, areas under the curve, and beta-half-lives of AD 32 and AD 41 after an iv injection of 80 mg/kg of AD 32 to Lewis lung carcinoma-bearing mice are presented. The results indicated very rapid disappearance of AD 32 from blood and tissues, whereas AD 42 persisted for much longer. Moreover, all of the tissues taken into consideration were able to hydrolyze AD 32 to AD 41, suggesting that this compound plays an important role in the antitumoral activity of AD 32.

Studies on the comparative distribution and biliary excretion of doxorubicin and 4'-epi-doxorubicin in mice and rats

Serum and tissue distribution of doxorubicin (DX) and its stereoisomer, 4'-epidoxorubicin (4'-epiDX), after iv injection of 15 mg/kg was investigated in C57BL mice bearing 14-day intramuscular Lewis lung carcinoma. Total fluorescence was measured together with unchanged drugs, separated, and quantitated by means of thin-layer chromatography combined with a scanning fluorescence technique. In serum the disappearance of 4'-epiDX paralleled that of DX and both unchanged isomers represented < 50% of the total fluorescence measured as early as 30 minutes after drug injection. In tissues the fluorescence measured was almost completely accounted for by the native compounds, both DX and 4'-epiDX, indicating that these drugs are taken up as such by tissues. 4'-EpiDX levels were markedly lower than those of DX in tumor and spleen, whereas in heart, liver, and kidneys the concentrations of the two isomers were the same. Traces of doxorubicinol and possibly 4'-epidoxorubicinol were detected only in serum, liver, and kidneys. Comparative cumulative biliary excretion of DX and 4'-epiDX investigated in the rat indicated that a total of 40%-45% of the injected dose of both drugs was excreted either as unchanged compound or as reduced metabolite. However, the proportions were different and the presence of twice as much reduced metabolite and smaller amounts of native 4'-epiDX suggests that its metabolic rate is different from that of DX

Early phase pharmacokinetics of doxorubicin (adriamycin) in plasma of cancer patients during single- or multiple-drug therapy

Doxorubicin (Adriamycin [AM]) was measured in plasma in the early distributive phase in 26 patients with different solid tumors. Pharmacokinetic parameters were calculated during first and/or subsequent courses of AM injected iv at doses from 40 to 60 mg/m2 either alone or with other antineoplastic agents. A fluorimetric technique was employed to determine AM equivalents; the reduced metabolite Adriamycinol was quantitated by scanning fluorescence after separation in thin-layer chromatography. The following conclusions are drawn from the findings. (a) After repeated AM treatments the individual variability in pharmacokinetic parameters of the drug did not appear to be affected by the length of treatment. (b) When the same patient was given different AM doses over a certain period some degree of dose dependence was seen only in the area under the curve and extrapolated plasma drug concentration at Time 0. (c) A narrow range of AM doses gave pharmacokinetic values differing from one patient to another. (d) After repeated AM treatments, Adriamycinol levels became lower, suggesting either a reduced metabolism of the parent compound or increased excretion of the reduced metabolite.

Distribution and antitumoral activity of adriamycin combined with warfarin in mice

The distribution of adriamycin (AM) in C57Bl/6 mice bearing intramuscular Lewis lung carcinoma under the influence of combined treatment with warfarin (W) was investigated by a fluorimetric procedure. AM was injected IV at the dose of 7.5 mg/kg 14 days after tumor transplantation and W was given in the drinking water for 96 h, starting 24 h before AM.. No substantial modifications in the serum and tissue distribution of AM fluorescence were observed under combined short-term treatment with W.

Quantitative thin-layer chromatographic measurement of n-trifluoroacetyladriamycin-14-valerate (AD 32) and trifluoroacetyladriamycin (AD 41) in blood and tissues

A thin-layer chromatographic method has been developed for the detection and measurement of N-trifluoroacetyladriamycin-14-valerate (AD 32) and its major metabolite trifluoroacetyladriamycin (AD 41). The procedure gives satisfactory linearity over a large range of concentrations. The coefficient of variability is about 10% over the entire range of usable concentrations, giving good reproducibility; sensitivity is 25 ng for both AD 32 and AD 41. Analysis is specific for AD 32 and AD 41 since adriamycin or more polar metabolites can be differentiated. Recovery is high (85-90%) and the method is simple and economical to use. Pharmacokinetics of AD 32 and AD 41 are reported in blood and some tissues of mice bearing Lewis Lung carcinoma.

Distribution and antitumor activity of adriamycin given in a high-dose and a repeated low-dose schedule to mice

Experimental studies on the distribution of adriamycin (AM) under different treatment conditions and possible correlations between tissue and plasma levels and chemotherapeutic activity are discussed. C57BL/6J mice bearing im Lewis lung carcinoma and (C3H x O2O)F1 mice bearing mammary carcinoma were injected iv with AM at a single dose of 15 mg/kg or with the same total amount of drug administered in spaced doses of 3.75 mg/kg for 4 consecutive days. In the two experimental systems studied, the drug reached approximately the same value in the tumor and spleen with both types of treatment, but with the 3.75-mg/kg x 4 schedule much lower AM concentrations were observed in the heart than with the single high-dose treatment. The therapeutic activity of the two treatments also differed: the antitumor and antimetastatic effect was the same in the two tumor systems, but with the 3.75-mg/kg x 4 schedule, increased survival and somewhat lower toxicity were observed. Daunorubicin, tested in the mammary carcinoma system with the two schedules of treatment, behaves very similarly to AM in terms of both distribution and chemotherapeutic effect.

Differential distribution of antitumor agents in primary and secondary tumors

The differential distribution of a series of antineoplastic agents in metastatic tissues compared to their respective primary tumors has been investigated in one rat and two mouse experimental tumor systems, ie, the intramuscular Lewis lung carcinoma (3LL) of C57BL/6 mice, which gives rise to spontaneous lung metastases, the intratibial Sarcoma 180 (S180) of CD1 mice, which induces macroscopic metastases to the lymph nodes, and the Walker 256 carcinosarcoma of CD rats, which also metastasizes to the lymph nodes. The results described in this paper show that the concentrations of adriamycin, daunorubicin, cyclophosphamide and its alkylating metabolites, hydroxyurea, 1-methyl-1-nitrosourea, and 6-mercaptopurine are much higher in the pulmonary metastases of 3LL and/or in the lymph node metastases of S180 than the concentrations measured in the primary tumor. In the Walker 256 tumor system the distribution of adriamycin appears to follow the same pattern observed for the mouse tumors. Only for methotrexate (in the 3LL tumor) is the difference in the concentrations at the two sites not so evident. These findings are discussed in relation to the comparatively greater sensitivity of metastases to chemotherapy.

Effect of phenobarbital on cyclophosphamide metabolism in rats

1. The pharmacokinetics of cyclophosphamide and its alkylating metabolites have been studied in rats whose liver microsomal enzymes had been induced by phenobarbital pre-treatment. 2. Serum levels of cyclophosphamide were determined using a new g.l.c. method. The half-life of cyclophosphamide in blood of rats pre-treated with phenobarbital was shorter than in control rats. This change is closely related to higher rates of production of p-nitrobenzylpyridine-positive alkylating metabolites of cyclophosphamide, which in turn is followed by their more rapid disappearance from the circulation. 3. Urinary excretion reflects this situation; lower amounts of cyclophosphamide and higher concentrations of its alkylating metabolites are present in the urine of phenobarbital-treated rats. 4. Perfusion of livers isolated from phenobarbital-pre-treated rats confirmed the results in vivo. With this preparation, too, disappearance of cyclophosphamide was more rapid and formation of its alkylating metabolites was accelerated after phenobarbital treatment.

Studies on the disposition of cyclophosphamide (NSC-26271) in tumor-bearing mice by means of gas chromatography-chemical ionization-mass fragmentography

The disposition of cyclophosphamide (CP) in mice bearing Lewis lung tumor has been studied by chemical ionization-mass fragmentography using isophosphamide as the internal standard. The drugs were analyzed as their N-trifluoroacetyl derivatives in order to increase sensitivity and to avoid column adsorption and decomposition phenomena. The minimum detectable amount was 500 pg/injection. Linearity was found up to microgram amounts of the substance without any interference of endogenous compounds.

Importance of pharmacokinetic studies on cyclophosphamide (NSC-26271) in understanding its cytotoxic effect

Pharmacokinetic studies on cyclophosphamide (CP) and its alkylating metabolites produced by hepatic biotransformation have been performed in vivo in animals and in vitro in the perfused liver. CP levels were determined by a gas-chromatographic method combined with mass-spectrometry, and production of alkylating metabolites was assayed by the 4-(4-nitrobenzyl)pyridine reaction for alkylating compounds. Differenes in serum drug levels between normal rats and rats bearing Walker 256 carcinosarcoma were observed in vivo and were confirmed by the liver-perfusion technique. Pharmacokinetic parameters and enzyme kinetic data both in normal and in tumor-bearing animals will be presented. The disappearance of CP and the corresponding formation of CP metabolites was significantly modified when (a) CP was given after previous treatment with a compound which alters its biotransformation (ie, phenobarbital, an inducer of microsomal metabolism), (b) CP was given after previous treatment with CP (which inhibits microsomal metablism), or (c) CP was given with competitive substrates of aldehyde oxidase or dehydrogenase (glyceraldehyde, chloral hydrate, and disulfiram). Results obtained in animals or in the perfused liver will be discussed. The significance of this modified CP metabolism in influencing its cytotoxic effect will be discussed and correlations between drug levels and activity will be presented.

Cytotoxic Activity of in Vitro Activated Cyclophosphamide on Tumors in Primary Culture

An in vitro method for testing the cytotoxic activity of compounds active through the formation of metabolites is described, and cyclophosphamide (CPA) has been chosen as a « model » substance. A tumor primary explant, cultured in a Rose chamber, was treated for 90 min at 37 °C with CPA in the presence of microsomal enzymes (105,000 × g liver fraction) and their cofactors. At the end of the incubation, the medium was removed and changed. Appropriate controls are concurrently carried out through the procedure. The cytotoxic effect of CPA is evaluated 24 h after the treatment. Primary explants from both mammary tumors of (C3H × O20)F1 mice and human ovary tumors were sensitive to CPA under our experimental conditions. The significance of this procedure for in vitro characterization of tumor sensitivity to antineoplastic agents which requires hepatic biotransformation is emphasized.