Activation and antitumor activity of CPT-11 in plasma esterase-deficient mice

Purpose: To examine the antitumor activity and the pharmacokinetics of CPT-11 (irinotecan, 7-ethyl-10-[4-(1-piperidino)-1-piperidino] carbonyloxycamptothecin) in a plasma esterase-deficient scid mouse model, bearing human tumor xenografts. Experimental design: Plasma carboxylesterase (CE)-deficient mice were bred with scid animals to develop a strain that would allow growth of human tumor xenografts. Following xenotransplantation, the effect of the plasma esterase on antitumor activity following CPT-11 administration was assessed. In addition, detailed pharmacokinetic studies examining plasma and biliary disposition of CPT-11 and its metabolites were performed. Results: In mice lacking plasma carboxylesterase, the mean SN-38 systemic exposures were approximately fourfold less than that observed in control animals. Consistent with the pharmacokinetic data, four to fivefold more CPT-11 was required to induce regressions in human Rh30 xenografts grown in esterase-deficient scid mice, as opposed to those grown in scid animals. Additionally, the route of elimination of CPT-11, SN-38, and SN-38 glucuronide (SN-38G) was principally in the bile. Conclusions: The pharmacokinetic profile for CPT-11 and its metabolites in the esterase-deficient mice more closely reflects that seen in humans. Hence, these mice may represent a more accurate model for antitumor studies with this drug and other agents metabolized by CEs.     

Co-treatment with therapeutic neural stem cells expressing carboxyl esterase and CPT-11 inhibit growth of primary and metastatic lung cancers in mice

In this study, neural stem cells (NSCs)-derived enzyme/prodrug therapy (NDEPT) was used to treat primary lung cancer or metastatic lung cancer in the brain. To confirm the anti-tumor effect of NSCs expressing carboxyl esterase (CE), A549 lung cancer cells were treated with HB1.F3.CE cells and CPT-11. A significant decrease in the viability/proliferation of lung cancer cells was observed compared to negative controls or cells treated with CPT-11 alone. To produce a mouse model of primary lung cancer or lung cancer metastasis to the brain, A549 cells were implanted in the dorsal area of the mouse or right hemisphere. CM-DiI pre-stained stem cells were implanted near the primary lung cancer tumor mass or in the contralateral brain. Two days after stem cells injection, mice were inoculated with CPT-11 (13.5 kg/mouse/day) via intraperitoneal injection. In the primary lung cancer mouse models, tumor mass was 80% lower in response to HB1.F3.CE in conjunction with CPT-11, while it was only reduced by 40% in the group treated with CPT-11 alone. Additionally, therapeutic efficacy of co-treatment with stem cells and CPT-11 was confirmed by detection of apoptosis and necrosis in primary and metastatic lung cancer tissues. By secreting VEGF, tumor cells modulate Erk1/2 and Akt signaling and migration of stem cells. This further increased tumor-selectivity of stem cell/prodrug co-therapy. Overall, these results indicate that NSCs expressing the therapeutic gene may be a powerful tool for treatment of primary lung cancer or metastasis of lung cancer to the brain.     

Pharmacokinetic study of CPT-11, SN-38 and SN-38 glucuronide in the ascites,plasma and bile after intraperitoneal administration of CPT-11

We studied the pharmacokinetics of CPT-11 with intraperitoneal administration in a patient with a PTCD tube. The patient had advanced gastric cancer with peritoneal metastasis. CPT-11 was administrated in a dose of 40 mg and the intraperitoneal, plasma and bile levels of CPT-11, SN-38 and SN-38 glucuronide (SN-38 GLU) were measured periodically. The results showed that the periodical concentration pattern of CPT-11, SN-38 and SN-38 GLU in the bile was closely related to that of CPT-11 in the abdominal cavity.     

Experimental study on CPT-11 intraperitoneal chemotherapy--metabolism of CPT-11 in malignant ascites

The metabolism of CPT-11 in malignant ascites of gastric cancer patients with peritoneal seedings was studied in advance of the intraperitoneal chemotherapy of CPT-11 in humans. Malignant ascites and blood were drawn from gastric cancer patients. CPT-11 solution (20 mg/ml; 0.2 ml) was added into 3.8 ml ascites or plasma under 37 degrees C and CPT-11, SN-38 and SN-38GLU concentrations were measured with HPLC at times of 5, 30 and 60 minutes after addition of CPT-11. The change from CPT-11 to SN-38 was minimal not only in plasma, but also in malignant ascites. SN-38 GLU concentration was below the limit of measurement. This study showed that in malignant ascites, the enzymes such as carboxyesterase that convert CPT-11 to SN-38 were not present or minimal.     

CR obtained by CPT-11 and CDDP combination-therapy in a small-cell lung-cancer patient through effective pharmaceutical care

We encountered a 64-year-old UGT1A1*28 heterotype patient who received CPT-11 and CDDP chemotherapy for Stage III A small-cell lung-cancer and developed grade 4 neutropenia as assessed by CTCAE v3.0 in Pharmaceutical Management. The therapeutic effect was good; 4 courses of chemotherapy could be safely administered at 1/3 of the applied dose of CPT-11, and CR was obtained. In this period, we participated in selecting antibiotics to neutropenia and CPT-11 closing regimen as pharmacists. Additionally, we carefully monitored patients about their bowel pattern and hematotoxicity, and collected information about gene searching for the patient and the Hospital Ethics Committee. The analysis of the gene polymorphism of CPT-11 is useful to predict the occurrence of serious side effects, but this judgment cannot easily be made clinically. In the event of a marked decrease in the neutrophil count of a patient during the first courses of treatment with CPT-11, we believe that it is important to consider gene polymorphism, to closely monitor the symptoms and laboratory parameters, and to give a smaller dose of the drug.     

Inhibition of spontaneous and experimental metastasis by a new derivative of camptothecin,CPT-11, in mice

Summary The antimetastatic effect of a new water-soluble derivative of camptothecin, 7-ethyl-10-(4-(1-piperidino)-1-piperidino) carbonyloxy-camptothecin (CPT-11), were examined in several metastatic murine tumor systems. Intravenous (i.v.) injection of CPT-11 into BALB/c mice inhibited lung metastasis by i.v. inoculated, metastatic colonic adenocarcinoma 26 (C26) cells, C26NL-17, in BALB/c mice. This treatment was also effective in C57BL/6 mice against lung metastasis by i.v. inoculated B16-F10 and B16-BL6 cells, highly metastatic variants of the B16 melanoma. Furthermore, intraperitoneal (i.p.) injection of CPT-11 significantly inhibited the growth of C26NL-22 cells, a highly metastatic variant of C26, inoculated subcutaneously (s.c.) into the left front footpads of BALB/c mice. Also, i.p. or i.v. injection of CPT-11 effectively inhibited the growth of 3LL tumors inoculated s.c. into the hind footpads of C57BL/6 mice. Moreover, following s.c. inoculation of either C26NL-22 or 3LL cells, combined surgical excision of the primary tumor and either i.p. or i. v. CPT-11 injections given before or after surgery markedly inhibited the formation of pulmonary metastases. These results show that a new derivative of camptothecin, CPT-11, has a potent inhibitory effect against both spontaneous and experimental lung metastasis.     

Intracellular distribution of CPT-11 in CPT-11-resistant cells with confocal laser scanning microscopy.

CPT-11, 7-ethyl-10-[4-(1-piperidino)-1-piperidino]carbonyloxy camptothecin, is a well-known DNA topoisomerase I inhibitor. SN-38 is a metabolite of this compound. Both emit fluorescence when activated by a laser beam. With a confocal laser scanning microscope (CLSM), we determined the intracellular distribution of CPT-11 and SN-38 and the chronological changes in drug-treated PC-7, a cell line of human non-small cell lung cancer, and its CPT-11 resistant variant, PC-7/CPT cells. There were many more granules in the cytoplasm in PC-7/CPT than in the parent cell line (PC-7). The granule formation of the resistant cell could indicate a different drug metabolism in the cytoplasm from that of the parent cell. This technique would provide a new way of investigating the mechanism of resistance of cancer cells to anticancer drugs.     

Antitumor activity of a camptothecin derivative,CPT-11, against human tumor xenografts in nude mice

Summary The antitumor effects of the camptothecin (CPT) derivative CPT-11, 7-ethyl-10-[4-(1-piperidino)-l-piperidino]-carbonyloxycamptothecin, were tested on human tumor xenografts in nude mice. CPT-11 showed antitumor activity higher than that of Adriamycin, 5-fluorouracil, or futraful, with little or no reduction of body weight being observed in the mice. The growth of colon adenocarcinoma Co-4 was significantly inhibited after a single i.v. injection of CPT-11 at 25, 50, or 100 mg/kg. The single i.v. injection was also significantly effective against mammary carcinoma MX-1 and gastric adenocarcinoma St-15. All of the mice bearing MX-1 tumors were cured by the administration of CPT-11 every 4 days for a total of three treatments at a total dose of 200 mg/kg given i.v. or of 400 mg/kg given p.o. Three i.v. or oral treatments were also effective against Co-4, St-15, gastric adenocarcinoma SC-6, and squamous-cell lung carcinoma QG-56. To achieve the same efficacy attained by i.v.injection, however, oral doses 2–4 times higher than the i.v. doses were required. When the total dose was fixed at 100 mg/kg, a triple i.v. injection was most effective, followed by a single i.v. injection and, finally daily p.o. administration for 10 days. Although SN-38 (7-ethyl-10-hydroxycamptothecin), a metabolite of CPT-11, showed much stronger cytotoxic activity in vitro than did CPT-11, its antitumor effects were similar, if not inferior, to those of CPT-11 in vitro at the same dose level. CPT-11 was converted into SN-38 by human tumors, but the sensitivity of these tumors to CPT-11 in vivo was independent of their ability to produce SN-38. These results suggest that CPT-11 may be clinically effective, depending on the schedule of administration, but that its effectiveness is not related to the ability of the tumor to produce SN-38.     

Pharmacokinetics of CPT-11 in rhesus monkeys

Purpose: To examine the pharmacokinetic relationships between humans and monkeys, we studied the disposition of 7-ethyl-10-[4-(1-piperidino)-1-piperidino]carbonyloxycamptothecin (CPT-11) and its active metabolite, 7-ethyl-10-hydroxycamptothecin (SN-38), in rhesus monkeys. Methods: CPT-11 was administered to a total of six monkeys at doses of 3, 7, 15 and 25 mg/kg by intravenous infusion for 10 min and plasma concentrations and pharmacokinetic parameters of CPT-11 determined. Results: Maximum plasma concentrations at 25 mg/kg reached around 10 000 ng/ml, and dropped to 500 ng/ml in 8 h. Plasma concentrations of SN-38 remained between 2 and 10 ng/ml. Mean values of systemic clearance, mean residence time and distribution volume at steady state, the major pharmacokinetic parameters for CPT-11, were 13.3 (ml/min per kg), 192 (min) and 2553 (ml/kg), respectively. The initial plasma concentration ratio of lactone to total CPT-11, 76%, declined to about 20% within 75 min, and the final ratio was about 40% at 8 h; the initial ratio of SN-38 was 72%, dropped to 34% within 70 min and finally recovered to 55% at 8 h. Conclusion: Comparison with human data revealed that systemic clearances of CPT-11 and the maximum AUC of SN-38 were not as different between humans and monkeys as between humans and mice, but the metabolic conversion of CPT-11 into SN-38 in monkeys was significantly lower than in humans. Received: 19 December 1996 / Accepted: 9 May 1997     

Pharmacological Correlation between Total Drug Concentration and Lactones of CPT-11 and SN-38 in Patients Treated with CPT-11

The pharmacokinetics of 7-ethyl-10-[4-(1-piperidino)-1-piperidino]carbonyloxycamptothecin (CPT-11) and its active metabolite, 7-ethyl-10-hydroxycamptothecin (SN-38), were examined to establish the pharmacokinetic variability of the active lactones of CPT-11 and SN-38 in comparison with that of the total (lactone and carboxylates) plasma CPT-11 and SN-38. Twelve patients with malignancies were entered in the study. All received 100 mg/m² of CPT-11 by intravenous drip infusion over 90 min. Blood was sampled at 10 time points in heparin-containing syringes. Analysis by high-performance liquid chromatography showed that the ratio of CPT-11 lactone to total CPT-11 concentration was highest (66%) just after the end of infusion and gradually decreased to 30% at 24 h. Almost 70% of SN-38 lactone was detected after the end of infusion and this decreased to 50% within 24 h. The standard errors of percent lactone of CPT-11 or SN-38 to total drug concentration at each sampling point were less than 12%. The area under the concentration-time curve (AUC) of total CPT-11 and that of total SN-38 were significantly correlated with the AUCs of the lactone CPT-11 and those of lactone SN-38, respectively. We conclude that, for practical purposes, monitoring of total CPT-11 and SN-38 has essentially the same clinical significance as monitoring of lactone CPT-11 and SN-38.     

Nonlinear pharmacokinetics of CPT-11 in rats

The pharmacokinetics of a new water-soluble derivative of camptothecin. 7-ethyl-10-[4-(1-piperidino)-1-piperidino]carbonyloxycamptothecin (CPT-11), and its major metabolite, 7-ethyl-10-hydroxycamptothecin (SN-38), was investigated after i.v. administration of 1 to 40 mg/kg of CPT-11 to rats. The plasma concentration of CPT-11 decreased biexponentially. The area under the concentration-time curve increased nonlinearly as the dose increased. SN-38 was found in the plasma, bile, urine, and feces. The SN-38 level was maintained at 0.06 to 0.08 micrograms/ml for 0.5 to 5.5 h depending on the dose, followed by exponential decay. Thirty-three to 58% of the CPT-11 was excreted without metabolism into the bile and urine for 24 h. SN-38 was mainly excreted into the bile. Analysis of the clearance has shown nonlinear pharmacokinetics which was due to metabolic processes such as the conversion of CPT-11 to SN-38.     

Liver concentration of CPT-11, SN-38 and SN-38 GLU in intraperitoneal and intravenous administration of CPT-11

Our previous mouse experiment showed intraperitoneal administration of CPT-11 was more effective not only for peritoneal seeding but for liver metastases than intravenous administration of CPT-11. We studied tissue concentrations of the liver when CPT-11 was administered intraperitoneally or intravenously for ICR mice. Mice liver was resected at 15 min, 1, 2, 4, 8 and 26 hours after intraperitoneal or intravenous administration of 40 mg/kg CPT-11. CPT-11, SN-38 and SN-38 GLU were measured with HPLC. The liver concentration of CPT-11 at 15 min after intravenous administration was higher than after intraperitoneal administration. A higher liver CPT-11 concentration was prolonged in the intraperitoneal administration group. No differences were demonstrated in the concentrations of SN-38 and SN-38 GLU between i.p. and i.v. groups.     

Intracellular roles of SN-38, a metabolite of the camptothecin derivative CPT-11, in the antitumor effect of CPT-11.

It is known that 7-ethyl-10-[4-(1-piperidino)-1-piperidino]carbonyloxycamptothecin (CPT-11), a semisynthesized derivative of camptothecin (CPT), has a potent antitumor activity in vivo, but 7-ethyl-10-hydroxycamptothecin (SN-38), a metabolite of CPT-11, shows much stronger cytotoxicity in vitro than CPT-11. In this study, we demonstrated that the relaxation of SV40 DNA plasmids by type I DNA topoisomerase prepared from P388 murine leukemia cells was inhibited by 50% by SN-38 at approximately 1 microM, although CPT-11 at 1 mM slightly inhibited the relaxation. SN-38 and CPT showed strong, time-dependent inhibitory activity against DNA synthesis of P388 cells. However, CPT-11 weakly inhibited DNA synthesis independently of time with coincident inhibition of the total thymidine uptake by the cells. By alkaline and neutral elution assays, it was demonstrated that SN-38 caused much more frequent DNA single-strand breaks in P388 cells than did CPT-11. The same content of SN-38 and a similar frequency of single-strand breaks were detected in the cells treated with SN-38 at 0.1 microM or with CPT-11 at 100 microM. Therefore, single-strand breaks by CPT-11 seem to be due to SN-38 produced from CPT-11 in cells. These results indicate that CPT-11 itself possesses a marginal antiproliferative effect but that SN-38 plays an essential role in the mechanism of action of CPT-11.     

An early phase II study of CPT-11 in gynecologic cancers. Research Group of CPT-11 in Gynecologic Cancers

An early Phase II study of CTP-11, a new derivative of Camptothecin, in gynecologic cancers was carried out by a cooperative study group of 9 institutions. Forty-six patients were enrolled, and there were 14 cases of ovarian cancers, 7 of cervical cancer, 6 of uterine body cancers and 1 of endometrial stromal sarcoma which satisfied study criteria. The response rate in ovarian cancers was 21.4%, and in cervical cancers 42.9%, among an overall rate of 21.4%. Three out of 6 patients with objective response had undergone previous chemotherapies including cisplatin, suggesting that CPT-11 was effective for patients with no response or refractory to these therapies. Leukopenia was a major adverse reaction with an incidence of 60.0% (grade 2 or more). Gastrointestinal symptoms such as nausea vomiting, anorexia and diarrhea were frequently observed (grade 2 or more; 13.3-43.3%). These were generally tolerable except in a few cases. Besides these reactions, alopecia was also observed (33.3%), but severe adverse reactions such as nephropathy were not. These results suggested that CPT-11 was effective against ovarian cancer and cervical cancer. The recommended dose regimen for a late phase II study is considered to be 100 mg/m2 once weekly and 150 mg/m2 once every 2 weeks.     

Clinical experience of second-line chemotherapy with S-1/CPT-11 for highly advanced gastric cancer

We have performed chemoradiation with S-1 and low-dose CDDP as an initial treatment for 27 patients with incurable or unresectable highly advanced gastric cancer since 2002. Twelve out of 27 patients received combination chemotherapy of S-1 and CPT-11 as the second-line chemotherapy. On this regimen, S-1 was administered orally at a dose of 80 mg-120 mg daily, and CPT-11 at a dose of 60 mg/m(2) once in 2 or 3 weeks for outpatients. Clinical effects after therapy showed a response rate of 30.0%. Considering the prognostic outcome of the regimen, the one-year survival rate of the therapy was 66.7%, and the median survival time was more than 1 year, suggesting second-line chemotherapy will be one of the beneficial regimens in gastric cancer patients. Although 4 patients showed grade 3 bone marrow suppression (33.3%), they were all able to continue the therapy, after recovering from toxicity by means of G-CSF and/ or cessation of chemotherapy. The incidence and level of toxicity accompanying subjective symptoms, however, were relatively low, and the regimen was useful as an outpatient treatment maintaining good quality of life and improving their prognosis. Treatment with an appropriate regimen at an appropriate time will enable these patients to have good quality of life and survival.     

Overcoming CPT-11 resistance by using a biscoclaurine alkaloid,cepharanthine, to modulate plasma trans-membrane potential

Irinotecan, 7-ethyl-10-[4-(I-piperidino)-1-piperidino] carbonyloxycamptothecin, (CPT-11) resistance was overcome by using a biscoclaurine alkaloid, cepharanthine, in CPT-11- and multidrug-resistant 50MT-1 cells. 50MT-1 cells were established from a mouse breast-cancer cell line, FM3A, by subjecting the cells to a low dose of CPT-11 continuously. 50MT-1 cells exhibited resistance to CPT-11 (40-fold in colony-formation assay) and to other drugs such as doxorubicin (11.7-fold) and etoposide (VP-16) (16.8-fold). The plasma trans-membrane potential was lower in 50MT-1 cells than in FM3A cells, although there were no differences in expressions of P-glycoprotein and of DNA topoisomerase-I and -II proteins. The lower membrane potential in 50MT-1 cells was augmented by co-treatment with a non-toxic dose of cepharanthine. CPT-11 resistance in 50MT-1 cells was overcome (5.0- to 1.4-fold, 6-hr exposure) by the co-treatment with cepharanthine through increasing intracellular accumulation of CPT-11. Resistance to doxorubicin and VP-16 was also overcome by cepharanthine treatment (2.5- to 0.69-fold and 4.2- to 1.4-fold respectively). We conclude that the modification of plasma trans-membrane potential by cepharanthine should be effective in overcoming CPT-11 and multidrug resistance in 50MT-1 cells. Int. J. Cancer, 72:295–300, 1997. © 1997 Wiley-Liss, Inc.     

Altered pharmacokinetics and metabolism of CPT-11 in liver dysfunction: a need for guidelines.

Metabolic conversion of CPT-11 is a major route of elimination of this new topoisomerase 1 inhibitor. Presently, recommendations for dose adjustments of CPT-11 in patients with liver dysfunction are lacking. We describe the case of a patient with metastatic colon cancer with liver dysfunction treated with CPT-11 at two different dose levels (100 mg/m2 and 30 mg/m2, single dose, administered as a 90-min i.v. infusion). The lactones and carboxylates of CPT-11 and SN-38 were determined by high-performance liquid chromatography. SN-38 glucuronide was determined after deglucuronidation. The procedures allowed intrapatient comparison of pharmacokinetics and metabolism of the drug. Severe side effects were encountered, which could be explained by the reduced clearance of CPT-11 and its metabolites. These included neutropenic fever with culture-proven septicemia, thrombocytopenia, somnolence, diarrhea, and signs and symptoms of transient hepatic failure. Our findings offer important data for the further development of guidelines for dose reduction of CPT-11 in patients with liver dysfunction.     

A phase II study of CPT-11, a camptothecin derivative, in patients with primary lung cancer. CPT-11 Cooperative Study Group

A Phase II study of CPT-11, a new camptothecin, was performed in patients with primary lung cancer. Patients with previously untreated non-small cell carcinomas (group A), or previously treated non-small cell carcinomas (group B), and with small cell carcinomas (group C), were enrolled in this study. CPT-11 was given at a dose of 100 mg/m2 i.v. infusion once a week for three weeks or more. Out of 153 patients enrolled, 128 (A: 67; B: 26; C: 35) were assessed to be evaluable for response by an extramural review committee. Response rates were 34.3% (23/67) for A, 0% (0/26) for B and 37.1% (13/35) for C. The response rate was 50% for previously untreated patients (4/8), and 33.3% for previously treated patients (9/27) including 2 complete responses in the group C. Major toxicities were leukopenia, nausea/vomiting, diarrhea, anorexia and alopecia. Leukopenia and diarrhea were considered to be dose limiting toxicities, but they were reversible. It was, however, suggested that some patients should be monitored carefully for severe reactions and delay in recovery. The results showed that CPT-11 was highly effective against non-small cell and small cell carcinomas of the lung.     

Progress in treatment of small-cell lung cancer: role of CPT-11

Small-cell lung cancer (SCLC) accounts for approximately 15% of all cases of lung cancer and is a particularly aggressive form of lung cancer characterised by a poor prognosis, rapid tumour growth, and early metastasis. Roughly, two-thirds of patients with SCLC present with extensive disease (ED) and one-third with limited disease (LD). Combination chemotherapy is the most effective treatment modality for SCLC, and several new agents, including carboplatin, ifosfamide, taxans, and topotecan, have been demonstrated to be active; however, there are no data on the survival benefit of these drugs. A CPT-11+ cisplatin regimen has shown improvement in overall survival over the global gold standard regimen, etoposide + cisplatin (Japanese Clinical Oncology Group: JCOG 9511), and three confirmatory randomised controlled trials are in progress to determine the reproducibility of the JCOG 9511 study. JCOG is evaluating the role of CPT-11 and a new triplet regimen containing CPT-11 in limited-stage SCLC. Strategies and the current protocols of the JCOG are presented and discussed. In the future, it will be essential to evaluate molecular target-based drugs for LD and ED SCLC with new standard combination chemotherapy regimens that include CPT-11.     

Carboplatin and CPT-11 chemotherapy in a hemodialysis patient with small-cell lung cancer

We administered a dose-down chemotherapy, which was a combination of carboplatin 100 mg/body (AUC 3.0, day 1) and CPT-11 30 mg/m2 (day 1, day 15) to the patient with a poor performance status of extensive small-cell lung cancer with renal failure. Hemodialysis was performed two hours after the chemotherapy. We measured plasma levels of total-platinum and CPT-11 and metabolic products (SN-38) after the hemodialysis. The results of pharmacokinetic study showed a high level collection of total-platinum caused by carboplatin and SN-38, and that was caused by CPT-11 in the blood. Although the grade 3 of granulocytopenia was found, the decrease in tumor marker and an improvement of the ADL were confirmed. It thought that this chemotherapeutic regimen was effective for small-cell lung cancer with renal failure undergoing hemodialysis. Further study is needed for a selection of suitable chemotherapeutic regimens, an optimal dosage of each drug and timing of hemodialysis.