Showing papers on "Doxorubicin published in 1987"

Chemotherapy with or without Radiation Therapy in Limited Small-Cell Carcinoma of the Lung

Abstract: We conducted a prospective, randomized study to clarify the role of radiotherapy of the primary tumor in limited small-cell cancer of the lung. After stratification for sex and for performance score based on the ability to ambulate, patients were randomly assigned to receive initial radiotherapy plus chemotherapy, delayed radiotherapy plus chemotherapy, or chemotherapy alone. The chemotherapy consisted of cyclophosphamide, etoposide (VP-16-213), and vincristine, with doxorubicin subsequently replacing etoposide in alternate cycles 7 through 18. Chemotherapy was given every three weeks for 18 months. The radiotherapy comprised 4000 rad in four weeks, followed by a 1000-rad "boost" directed against residual disease. All patients received prophylactic whole-brain radiation. The patients enrolled totaled 426, and 399 were evaluable. There was a statistically significant difference in the frequency of complete responses in favor of the two radiotherapy regimens (P = 0.0013). Failure-free survival was also longer with these two regimens (P less than 0.001), as was the interval before treatment failure in the chest (P less than 0.001) and overall survival (P = 0.0099). As expected, toxic effects--chiefly neutropenia--were also increased. The addition of radiotherapy of the primary tumor to combination chemotherapy improved both complete-response rates and survival, with increased but acceptable toxicity.

Late intensification chemotherapy with autologous bone marrow transplantation in selected small-cell carcinoma of the lung: a randomized study.

Abstract: A multicentric randomized prospective trial was conducted to test whether late intensification chemotherapy would increase the remission rate, the relapse-free survival, and the survival of small-cell lung cancer patients responding to induction chemotherapy. Autologous bone marrow transplantation was used as support to reduce the duration of the aplasia induced by very high-dose chemotherapy. As induction chemotherapy, 101 patients received, during a period of 5 months, a total dosage of 120 mg/m2 methotrexate, 4.5 mg/m2 vincristine, 1,800 mg/m2 cyclophosphamide, 180 mg/m2 doxorubicin, 160 mg/m2 cisplatin, 750 mg/m2 VP-16-213, and 30 Gy prophylactic cranial irradiation. Forty-five patients, selected for their sensitivity to this induction treatment, were randomized to a last cycle of chemotherapy that combined cyclophosphamide, BCNU, and VP-16-213 either at a conventional dosage of 750 mg/m2 intravenously (IV), 60 mg/m2 IV, and 600 mg/m2 orally or alternatively at a very high dosage of 6 g/m2 IV, 300 mg/...

A Monoclonal Antibody--Pseudomonas Toxin Conjugate that Specifically Kills Multidrug-Resistant Cells

Abstract: One form of multidrug resistance is due to the expression of a 170-kDa energy-dependent drug efflux pump called P-glycoprotein in the plasma membranes of human cancer cells. We have prepared conjugates of Pseudomonas toxin with the anti-P-glycoprotein monoclonal antibody MRK-16. These anti-P-glycoprotein-toxin conjugates specifically kill multidrug-resistant human KB cells. Similar conjugates could be useful in cancer therapy to reduce or eliminate multidrug-resistant tumor populations in tumors intrinsically resistant to chemotherapy or in populations that become resistant during combination chemotherapy.

A comparison of two doses of adriamycin in the primary chemotherapy of disseminated breast carcinoma.

Abstract: Forty-eight patients with advanced breast carcinoma who had not received prior chemotherapy (minimum follow up 21 months) were randomised to receive either adriamycin 70 mg m-2 i.v. 3-weekly for 8 cycles (Regimen A) or adriamycin 35 mg m-2 i.v. 3-weekly for 16 courses (Regimen B). Objective responses were seen in 14/24 (58%) patients with regimen A (4 complete) and 6/24 (25%) with regimen B (1 complete) (P less than 0.02). The median duration of response was 14 months with regimen A and 6.5 months with regimen B. The median duration of survival was 20 months and 8 months respectively (P less than 0.01). The toxicity was similar with each regimen. There was no evidence of deterioration in left ventricular ejection fraction nor congestive heart failure in any patient. It is concluded that when given at 3-weekly intervals adriamycin is a more effective treatment for advanced breast cancer at higher rather than lower dosage.

Effect of Verapamil and Other Agents on the Distribution of Anthracyclines and on Reversal of Drug Resistance

Abstract: We studied the intracellular distribution of drugs within anthracycline-sensitive and -resistant cells by computer-assisted digitized video fluorescence microscopy. We found that the antitumor antibiotic, daunorubicin, distributes differently in anthracycline-sensitive and -resistant human leukemia cells (HL-60). Verapamil and other agents known to circumvent resistance in pleiotropic drug-resistant cell lines were able to change the pattern of distribution of daunorubicin in the anthracycline-resistant HL-60 cells back to the distribution found in anthracycline-sensitive HL-60 cells. To investigate the biochemical basis for this effect, we studied the distribution of daunorubicin and doxorubicin in a hydrophobic/hydrophilic (membrane/cytoplasmic) environment using the two-compartment cell-free system of Folch. Our results demonstrate that various unrelated drugs known to overcome resistance will also change the distribution of the anthracyclines in the hydrophobic/hydrophilic compartments. Our data allow the hypothesis that various unrelated agents known to circumvent resistance may act by altering the hydrophobic/hydrophilic solubility of anthracyclines in the resistant cell.

Multidrug resistance in ovarian cancer

Abstract: The development of acquired resistance has limited the effectiveness of chemotherapy in the treatment of ovarian cancer. Experimental model systems were developed to study the mechanisms associated with primary resistance to chemotherapeutic agents and broad cross-resistance (multidrug resistance) which is characteristic of human ovarian cancer. Doxorubicin-resistant cell lines developed in vitro by exposure of a sensitive cell line to increasing concentrations of doxorubicin develop resistance on the basis of a decrease in drug accumulation and have increased expression of the mdr-1 gene. This gene encodes for a membrane glycoprotein and leads to a decreased drug accumulation in drug resistant cell lines. Cell lines established from patients refractory to doxorubicin-containing combinations, however, do not demonstrate a decrease in drug accumulation. Studies are in progress on the measurement of mdr-1 levels in tumors of patients undergoing treatment to determine whether agents, such as verapamil may be useful in the treatment of drug resistant gynecologic cancers. Human ovarian cancer cell lines from drug resistant patients also has been demonstrated to increase levels of glutathione. Lowering of glutathione levels with buthionine sulfoximine (BSO), which irreversibly inhibits the enzyme gamma-glutamyl cysteine synthetase, leads to a marked potentiation of the cytotoxicity of melphalan both in vitro and in vivo in a nude mouse model of human ovarian cancer. Based on those studies, BSO is undergoing toxicologic evaluation before initiation of clinical trials in drug resistant patients. Our studies demonstrate that drug resistance in human ovarian cancer is likely due to interaction of multiple factors. However, biochemical intervention in some of the key steps leading to drug resistance has been demonstrated experimentally feasible and indicates that pharmacologic reversal of drug resistance is a clinical possibility.

Chemotherapy for advanced or recurrent gynecologic cancer.

Abstract: Studies of chemotherapy in advanced or recurrent gynecologic cancer have focussed on ovarian, cervical, and endometrial carcinoma. For celomic epithelial carcinomas of the ovary, a large number of cytotoxic agents have been shown to be active. Dramatic improvement in frequency of response with lesser improvement in survival has been noted with the use of cisplatin-based combination chemotherapy as compared to single alkylating agents. More recent studies have evaluated alternative ways to employ cisplatin: higher dose schedules, intraperitoneal administration, and platinum compounds with a potentially better therapeutic index. None has yet been shown superior to a combination of relatively low-dose cisplatin plus an alkylating agent with or without doxorubicin. Cisplatin remains the best studied and most active single agent in patients with squamous cell carcinoma of the cervix. While a number of other agents have demonstrated moderate activity, no combination of drugs has as yet proved superior to single-agent cisplatin. In endometrial carcinoma, progestins and doxorubicin are the most active agents. Tamoxifen, cisplatin, and hexamethylmelamine appear to have moderate activity. No combination has yet been shown to be superior to single agents. Information on chemotherapy for less common gynecologic malignancies is largely anecdotal. Two observations are of note. Cisplatin-based combination chemotherapy is highly active against germ-cell neoplasms of the ovary. Cisplatin also has definite activity against mixed mesodermal sarcoma of the uterus.

Markedly Reduced Levels of Anthracycline-induced DNA Strand Breaks in Resistant P388 Leukemia Cells and Isolated Nuclei

Abstract: DNA single-strand and double-strand breaks produced by doxorubicin and two anthracycline derivatives (4-demethoxy-daunorubicin and 4′-deoxy-4′-iododoxorubicin) were measured in doxorubicin-sensitive and -resistant P388 leukemia cell lines, using filter elution methods, and compared with cellular drug accumulation to account for major differences in their cytotoxic activities and cross-resistance. The increased cytotoxic potency of the two derivatives reflects at least in part the enhanced drug accumulation by cells that results from their increased lipophilicity. However, the level of protein-linked DNA breaks was not directly related to cellular accumulation of drug analogues. It is possible that enhanced cytotoxicity may also be the consequence of the greatly enhanced ability of analogues to cause DNA strand breaks. The resistant line showed only a modest degree of resistance to both anthracycline derivatives compared with the high degree of resistance to doxorubicin. Although for all the anthracyclines tested drug accumulation was reduced in the resistant line, this did not correlate with the degree of resistance. A differential sensitivity of resistant and parental cell lines to DNA cleavage activity was consistently found for all three drugs tested. However, in contrast to a lack of effect of doxorubicin, the derivatives caused appreciable DNA strand breakage in resistant cells. The enhanced ability of these analogues to break DNA in resistant cells is consistent with the slight cross-resistance with doxorubicin. DNA double-strand breaks produced in isolated nuclei from these cells paralleled the pattern found in whole cells, thus indicating that a nuclear alteration, presumably involving DNA topoisomerases, is associated with anthracycline resistance. Our findings strongly support the hypothesis that anthracycline resistance in these cell variants may be mediated by multiple mechanisms, involving alterations of plasma membrane and changes of nuclear enzymatic activities responsible for DNA strand breaks.

Cross-sensitivity to topoisomerase II inhibitors in cytotoxic drug-hypersensitive Chinese hamster ovary cell lines.

Abstract: We have isolated a Chinese hamster ovary cell line, designated ADR-1, which exhibits hypersensitivity to a range of drugs which are thought to inhibit the action of the enzyme topoisomerase II. These include anthracyclines, other classes of intercalating agents, and the epipodophyllotoxin, etoposide. No significant sensitivity to radiation, or to mono- and bifunctional alkylating agents was seen, although mild cross-sensitivity to the radiomimetic agent bleomycin was observed. We have monitored the level of DNA strand breaks induced by topoisomerase II inhibitors in ADR-1 cells using alkaline elution. At equimolar Adriamycin (doxorubicin) doses, more protein-associated DNA strand breaks are induced in ADR-1 cells than in wild-type cells. This enhanced level of drug-induced strand breaks does not appear to be a function of increased drug uptake as both lines accumulate similar levels of radiolabeled daunomycin. Both the rate of repair of strand breaks and the final percentage of strand breaks rejoined was equivalent in the 2 cell lines. These results are consistent with an enhancement in the level of topoisomerase II-dependent DNA breakage in ADR-1 cells following exposure to topoisomerase II inhibitors. We have previously reported the isolation of 2 bleomycin-sensitive Chinese hamster ovary cell lines, BLM-1 and BLM-2 (C. N. Robson et al., Cancer Res. 45:5304-5309, 1985). While BLM-1 exhibited cross-sensitivity only to Adriamycin, BLM-2 was shown to be hypersensitive not only to Adriamycin out also to certain alkylating agents and to ionizing radiation. In this paper, we show that both BLM-1 and BLM-2 also exhibit mild cross-sensitivity to a range of topoisomerase II inhibitors. These results indicate that intercalating agents and epipodophyllotoxins exert their cytotoxicity via common mechanisms and suggest that the maintenance of normal levels of cellular resistance to these agents requires the products of several different genes.

Chemotherapy with estrogenic recruitment and surgery in locally advanced breast cancer: clinical and cytokinetic results

Abstract: Thirty-nine patients with locally advanced breast cancer (T3b-4, N1-3 or inflammatory carcinoma) received 3 cycles of induction chemotherapy with estrogenic recruitment before surgery. The therapeutic regimen consisted of diethylstilbestrol (DES) orally on days 1-3, 5-Fluorouracil + Doxorubicin + Cyclophosphamide on day 4 q 21 days (DES-FAC). After surgery 6 additional cycles of chemotherapy (3 DES-FAC alternating with 3 DES-CMF with Methotrexate + F and C as in FAC) were administered. The objective response rate was 71.8% with 15.4% CR, and 56.4% PR; after surgery 36/39 (92.3%) patients were rendered disease-free. So far, 13 of 26 patients in stage IIIb have relapsed (9 of 13 with inflammatory carcinomas). Three-year survival and progression-free survival are 60% and 53.5%, respectively. Twenty-three of the 39 patients were subjected to serial tumor biopsies during the first DES-FAC regimen to allow for tumor-cell kinetic studies during DES and chemotherapy. A significant estrogenic recruitment occurred in 16 patients (69.6%), irrespective of estrogen-receptor status. At surgery, 3-4 weeks after induction chemotherapy, tumor proliferative activity was significantly depressed in comparison to basal values. These results indicate that breast cancer cells can be recruited in vivo with DES and that chemotherapy following estrogenic stimulation is effective and feasible with acceptable toxicity.

Nucleolar Protein B23 Translocation after Doxorubicin Treatment in Murine Tumor Cells

Abstract: Rats bearing Novikoff hepatoma ascites cells were given i.p. injections of actinomycin D, doxorubicin, or daunorubicin. Four hours after injection, tumor cells were removed from the ascites fluid and analyzed for protein B23 translocation using an immunofluorescence technique. Bright nucleolar fluorescence was observed in untreated cells. Treatment with actinomycin D (1.25 mg/kg), doxorubicin (25 mg/kg), or daunorubicin (12.5 mg/kg) produced a uniform nucleoplasmic fluorescence. This change in immunofluorescence distribution indicated that protein B23 translocated from the nucleolus to the nucleoplasm after drug treatment. These results are an extension of previous studies with HeLa cells (Yung et al., Cancer Res. 46: 922-925, 1986). Doxorubicin-resistant and -sensitive mouse leukemia cells (P388) were cultured in medium containing various doses of doxorubicin for 4 h, and the responsive levels of the cells to doxorubicin were compared. At 50 micrograms/ml doxorubicin, 86% of the doxorubicin-sensitive cells showed uniform nucleoplasmic fluorescence, and less than 2% of the cells retained nucleolar fluorescence. At this same dose, only 9% of the resistant cells showed nucleoplasmic fluorescence, and 75% of the cells retained nucleolar fluorescence. At 100 micrograms/ml, about 26% of the resistant cells showed translocation, in contrast to 100% of the sensitive cells that showed B23 translocation. About 57% of the resistant cells showed an intermediate effect, and about 17% of the resistant cells maintained bright nucleolar fluorescence at this dose. The resistant cells also showed less responsiveness to actinomycin D. These results suggest that identification of "B23 translocation" may be used to detect drug-resistant cells and to study the efficacy of certain antitumor agents.

Prevention by Fructose-1,6-bisphosphate of Cardiac Oxidative Damage Induced in Mice by Subchronic Doxorubicin Treatment

Abstract: An experimental model of mild, subchronic doxorubicin cardiotoxicity in mice was investigated by monitoring changes of biochemical parameters related to cell response against oxidative stress in both liver and heart. A specific increase of the lactate dehydrogenase isoenzyme typical of the heart was observed for doxorubicin-treated mice. Lipid peroxidation, as evaluated by malondialdehyde determination, and catalase activity were greatly increased in heart and unaffected in liver. On the other hand, these changes can be considered as indicative of early heart damage induced by doxorubicin. Glutathione, glutathione peroxidase, and 6-phosphogluconate dehydrogenase values were not significantly altered by the treatment and glucose-6-phosphate dehydrogenase increased in both liver and heart. Administration of fructose-1,6-bisphosphate strongly reduced the increase of plasma lactate dehydrogenase, heart lipid peroxidation, and heart catalase while no effect on the diagnostically irrelevant increase of glucose-6-phosphate dehydrogenase was observed. The inhibitory effect on the onset of biochemical modification typical of early subchronic doxorubicin cardiotoxicity may be related to stimulation of ATP synthesis by fructose-1,6-bisphosphate and is therapeutically promising in view of the lack of toxicity of fructose-1,6-bisphosphate as a drug.

Amiodarone is more efficient than verapamil in reversing resistance to anthracyclines in tumour cells.

Abstract: We have previously demonstrated that amiodarone is able to reverse resistance of rat colon cancer cells to anthracyclines. We now compare the efficiency of amiodarone to verapamil one, another antiarrhythmic agent used in experimental systems and in clinical trials to enhance the effects of anthracyclines on resistant cancer cells. Amiodarone is more efficient than verapamil when both drugs are used at the same molar concentrations. Desethylamiodarone, the main metabolite of amiodarone, is as efficient as its precursor. Optimal concentrations of amiodarone are obtained without side effects in the sera of patients treated by oral administration followed by a loading infusion of amiodarone. On the other hand, maximal tolerated levels of verapamil reported in clinical trials are less efficient than amiodarone maximal levels in the reversal of resistance to anthracyclines in our experimental model in vitro. We suggest that amiodarone, which is more efficient and less toxic than verapamil, could be substituted for verapamil in future clinical trials.

Continuous venous infusion of doxorubicin in advanced sarcomas.

Abstract: Seventeen patients with advanced sarcoma were treated with continuous venous infusion of doxorubicin for a mean of 118 days, achieving total doses up to 1097 mg/m2. Three partial responses and one minor response were obtained. Major toxic effects were stomatitis and hand-foot syndrome. There was a low incidence of leukopenia (18%) and clinical cardiotoxicity (11%). Continuous venous infusion is a safe means of administering doxorubicin, with a response rate similar to that observed with bolus doxorubicin in metastatic sarcoma.

Pharmacokinetics of 4'-deoxy-4'-iodo-doxorubicin in plasma and tissues of tumor-bearing mice compared with doxorubicin.

Abstract: It has been reported that 4′-deoxy-4′-iodo-doxorubicin (4′-deoxy-4′-I-DX) displays, on experimental tumors, a spectrum of activity comparable to that of doxorubicin, is active when administered orally, is not cardiotoxic, and is cytotoxic to doxorubicin-resistant cells. We have investigated by high-performance liquid chromatography the pharmacokinetics of this drug in comparison with doxorubicin by treating mice bearing colon 38 adenocarcinoma with equal doses of the two drugs i.v. 4′-Deoxy-4′-I-DX, unlike doxorubicin, is transformed into several metabolites. The 13-dihydro derivative is the major metabolite found; in tumor and in all the organs it accounts for 4–7% of the total fluorescent area under the curve, whereas in plasma and liver it accounts for 15 and 34%, respectively. 4′-Deoxy-4′-I-DX disappears from plasma with a terminal half-life of 5 h, which is half the terminal half-life of doxorubicin (11 h), and its efficiency of absorption after oral administration is 27%. Tissue concentrations of 4′-deoxy-4′-I-DX are initially highest in lung and spleen, whereas those of doxorubicin are highest in liver and kidney. 4′-Deoxy-4′-I-DX levels are higher than those of doxorubicin in tumor, spleen, lung, small intestine, brain, pancreas, and ovaries whereas they are similar in heart, liver, kidney, and bone marrow. The rate of elimination of the new analogue is higher than that of doxorubicin from the tumor and all the organs investigated except the liver. The area under the curve of 4′-deoxy-4′-I-DX is similar to that of doxorubicin in tumor and spleen, whereas it is three times lower in heart. This may explain the lack of cardiotoxicity of this new analogue, which is equiactive and equitoxic with doxorubicin on the experimental system tested.

Second-line chemotherapy of stage III-IV ovarian carcinoma: a randomized comparison of melphalan to melphalan and hexamethylmelamine in patients with persistent disease after doxorubicin and cisplatin.

Abstract: A total of 205 women with stage III or IV ovarian cancer who had persistent disease after initial treatment with doxorubicin and cisplatin were randomized to receive melphalan (8 mg/m2 orally for 4 days) or the combination of melphalan (6 mg/m2 for 4 days) and hexamethylmelamine (120 mg/m2 for 14 days) every 4 weeks. Only one of 64 patients with measurable disease had an objective response. The major determinants of survival after randomization were the amount of residual disease after initial chemotherapy and the type of response to initial chemotherapy. There was no overall difference in survival between the two chemotherapy regimens, but the small group of patients whose disease progressed on initial chemotherapy survived significantly longer when treated with the two-drug combination. Neither of these regimens provided effective therapy for women whose disease was not eliminated by first-line treatment. However, the superior results obtained in one subgroup with the addition of hexamethylmelamine suggest that the place of this agent in treating ovarian cancer should be carefully evaluated.

Function of the anthracycline amino group in cellular transport and cytotoxicity.

Abstract: Using a number of derivatives of doxorubicin (Adriamycin) and daunomycin, we have examined how substitution of the anthracycline amine affected net cellular accumulation and cytotoxic potency in HL-60 leukemia cells. Octanol/buffer partitioning demonstrated that each of the derivatives had an amino group titratable between pH 5 and 8, with the exception of derivatives containing a cyanomorpholino-substituted amine, which had a significantly lower pKa value. The steady state cellular drug levels for the Adriamycin and daunomycin series decreased in the following order: N,N-dimethyl-greater than morpholino-greater than parent greater than cyanomorpholino-. Thus, the net cellular accumulation of an anthracycline was found to be influenced by the basicity of the amino group; drugs with a non-basic amino group exhibited reduced uptake. Soft agar clonogenic assays showed the following order of cytotoxicity for both series: cyanomorpholino-much greater than parent greater than morpholino-approximately equal to N,N-dimethyl-. The data demonstrate an inverse correlation between uptake and potency; thus, differences in net cellular accumulation do not account for the order of anthracycline potency.

(2"-R)-4'-o-tetrahydropyranyladriamycin, a new anthracycline derivative; its effectiveness in lymphoid malignancies.

Abstract: Thirty-eight patients with adult acute lymphoblastic leukemia (ALL) or non-Hodgkin's lymphoma (NHL) were treated intravenously with (2″-R)-4′-o-Tetrahydropyranyladriamycin (THP) at a dose of 10 mg/m2 for 5 consecutive days. Seven complete and 15 partial responses were observed in 35 evaluable patients (overall response rate, 62.8%). Both antitumor activity and antitumor spectrum were similar to those for doxorubicin. Since the patients who had had chemotherapy previously, including other kinds of anthracycline, responded rather poorly to THP, cross-resistance between THP and other anthracyclines may be present. Leukopenia and thrombocytopenia were dose-limiting factors. Nausea and vomiting episodes were mild, and epilation was also minimal. Although the observation period was short and a cumulative dose was not large enough to evaluate cardiotoxicity, there were no abnormal EKG changes or clinical signs of cardiotoxicity in this study. THP is a potent antitumor agent in the treatment of lymphoid malignancies.

In vitro chemosensitivity testing using the multicellular tumor spheroid model.

Abstract: Using growth delay and clonogenic cell survival as end points, we have shown that the 3-dimensional structure of human lung tumour spheroids confers a degree of resistance to the anthracyclines doxorubicin and 4'-deoxydoxorubicin, relative to cells grown as monolayer. 4'-deoxydoxorubicin induces a longer growth delay and greater clonogenic cell kill than doxorubicin in spheroids, although it is no more cytotoxic in monolayer. Using fluorescent microscopy we have demonstrated, qualitatively, that lipophilic anthracycline analogues partition into the spheroid more rapidly and to a greater degree than doxorubicin. It is apparent that penetration is an important aspect of anthracycline drug resistance in spheroids, and the spheroid model may represent a better in vitro system for testing lipophilic analogues of cytotoxic drugs.

Antitumor activity of new derivatives of camptothecin

Abstract: With the purpose of obtaining more potent and less toxic camptothecin (CPT) analogs, we prepared many derivatives of CPT. Among them, 7-ethyl-CPT (SN 22) and 7-ethyl-10-hydroxy-CPT (SN 38) showed strong antitumor activity with less toxicity. They were, however, insoluble and when they were made soluble, their activity was markedly diminished, as a result of cleavage of the delta-lactone ring. We therefore attempted to make soluble derivatives without breaking the delta-lactone ring and obtained 7-ethyl-10-[4-(1-piperidino)-1-piperidino]-carbonyloxy-CPT (CPT-11), which showed very strong antitumor activity by i.p., i.v. or p.o. administration against the ascites type of L1210 leukemia, P388 leukemia, sarcoma 180, Meth A fibrosarcoma, B16 melanoma, Ehrlich carcinoma and MH134 hepatoma and the solid type of sarcoma 180, Meth A fibrosarcoma, Lewis lung carcinoma, C3H/HeN mammary carcinoma, Ehrlich carcinoma and MH134 hepatoma. The antileukemic activity of CPT-11 against L1210 was much higher than that of adriamycin. The acute toxicity of CPT-11 was extremely low, particularly in the case of oral administration, the LD50 being 765.3 mg/kg, 22 times greater than that of CPT-Na.