A randomized, double-blind, placebo-controlled phase II study to assess the efficacy and safety of mapatumumab with sorafenib in patients with advanced hepatocellular carcinoma.

BACKGROUND: This randomized, double-blind, placebo-controlled, phase II study evaluated the efficacy and safety of mapatumumab (a human agonistic monoclonal antibody against tumor necrosis factor-related apoptosis-inducing ligand receptor 1) in combination with sorafenib in patients with advanced hepatocellular carcinoma (HCC). PATIENTS AND METHODS: Patients with advanced HCC (stratified by Barcelona Clinic Liver Cancer stage and Eastern Cooperative Oncology Group performance status) were randomized 1:1 to receive sorafenib (400 mg, twice daily per 21-day cycle) and either placebo (placebo-sorafenib arm) or mapatumumab (30 mg/kg on day 1 per 21-day cycle; mapatumumab-sorafenib arm). The primary end point was time to (radiologic) progression (TTP), assessed by blinded independent central review. Key secondary end points included progression-free survival, overall survival, and objective response. RESULTS: In total, 101 patients were randomized (placebo-sorafenib arm: N = 51; mapatumumab-sorafenib arm: N = 50). There was no significant difference in median TTP between both arms [5.6 versus 4.1 months, respectively; adjusted hazard ratio (one-sided 90% confidence interval) 1.192 (0-1.737)]. No mapatumumab-related benefit was identified when TTP was evaluated in the stratified subgroups. The addition of mapatumumab to sorafenib did not demonstrate improvement in the secondary efficacy end points. The reported frequency of adverse events (AEs) and serious AEs was comparable in both treatment arms. CONCLUSIONS: The addition of mapatumumab to sorafenib did not improve TTP or other efficacy end points, nor did it substantially change the toxicity profile of sorafenib in patients with advanced HCC. Based on these results, further development of the combination of mapatumumab and sorafenib in HCC is not planned.

Phase I and pharmacological study of pazopanib in combination with oral topotecan in patients with advanced solid tumours.

BACKGROUND: This phase I study evaluated the safety, tolerability, maximum tolerated dose (MTD) and pharmacokinetics of two dosing schedules of oral topotecan in combination with pazopanib in patients with advanced solid tumours. METHODS: Stage I of this study was to determine whether there was an impact of pazopanib on topotecan exposure. In stage II, the MTD and safety profile of oral topotecan given weekly on days 1, 8 and 15 in a 28-day cycle; or daily-times-five on days 1-5 in a 21-day cycle, both in combination with daily pazopanib, were explored. RESULTS: In total, 67 patients were enroled. Pazopanib co-administration caused a substantial increase in exposure to total topotecan (1.7-fold) compared with topotecan alone, which is considered clinically relevant. Topotecan had no effect on pazopanib concentrations. Safety findings were consistent with the known profile of both agents. There were three drug-related deaths, liver failure, tumour haemorrhage and myelosuppression. Two patients experienced dose-limiting toxicities (DLTs; hand-foot syndrome, myelosuppression and diarrhoea) on the weekly topotecan schedule and four patients experienced DLTs (myelosuppression) on the daily-times-five topotecan schedule. When combined with pazopanib, 800 mg daily, the recommended doses for oral topotecan are: 8 mg weekly and 2.5 mg daily-times-five. Seven of eight patients with partial response had platinum-resistant ovarian cancer. In addition, 54% of patients had stable disease with 22% stable for 6 months. CONCLUSIONS: Total topotecan exposure is 1.7-fold higher when co-administered with pazopanib. Both schedules of administration were tolerated and would permit further evaluation, especially the weekly schedule.

A phase II trial of gemcitabine, irinotecan and panitumumab in advanced cholangiocarcinoma.

BACKGROUND: Current data suggest that chemotherapy combinations may be superior to single agents in biliary tract cancer. The epidermal growth factor receptor (EGFR) pathway appears to be associated with tumor stage, prognosis and response to therapy. This trial was designed to evaluate the tolerability and efficacy of the combination of panitumumab, a monoclonal anti-EGFR antibody, with gemcitabine and irinotecan. PATIENTS AND METHODS: Patients with advanced (unresectable or metastatic) cholangiocarcinoma, ECOG PS 0-2, and adequate organ function were treated with panitumumab (9 mg/kg) on day 1, and gemcitabine (1000 mg/m(2)) and irinotecan (100 mg/m(2)) on days 1 and 8 of a 21-day cycle. The primary objective was to evaluate the 5-month progression-free survival (PFS). Secondary objectives included overall response rate (ORR) and overall survival (OS). Mutational analyses of EGFR, KRAS and BRAF were carried out when feasible. RESULTS: Thirty-five patients received a median of 7 (0-30) cycles. The most common grade 3/4 toxic effects were neutropenia (10 patients, 29%), thrombocytopenia (10 patients, 29%), skin rash (13 patients, 37%) and dehydration (9 patients, 26%). Two patients had CR, 9 had partial response (PR), and 15 had SD for a disease-control rate of 74% (by RECIST) in 28 assessable patients. Two patients went on to have surgical resection. The 5-month PFS was 69%. The median PFS was 9.7 months and the median OS was 12.9 months. In 17 testable samples, no EGFR or BRAF mutations were identified; there were 7 KRAS mutations, with no difference in OS by KRAS status. CONCLUSIONS: This study showed encouraging efficacy of this regimen with good tolerability. Further study in this area is warranted. Clinical Trials Number: The trial was registered with the National Cancer Institute (www.clinicaltrials.gov identifier NCT00948935).

A phase I and pharmacologic study of the MDR converter GF120918 in combination with doxorubicin in patients with advanced solid tumors.

BACKGROUND: Resistance to chemotherapy can partly be explained by the activity of membrane bound P-glycoprotein. Competitive inhibition of P-glycoprotein, by multidrug resistance (MDR) converters, may overcome this MDR. Previously studied MDR converters either have serious intrinsic side effects or considerably influence the pharmacokinetics of cytotoxic agents at concentrations theoretically required to convert MDR. GF120918 is a third-generation MDR converter with high affinity for P-glycoprotein and can be given orally. We performed a phase 1 study with escalating doses of GF120918 in combination with doxorubicin. PATIENTS AND METHODS: The study group comprised 46 patients with advanced solid tumors. Doxorubicin was administered on day 1 (cycle 1), GF120918 on days 22-24 (cycle 2), and on days 29-33 with doxorubicin administered on day 31 (cycle 3). Pharmacokinetics of both GF120918 and doxorubicin were studied. The starting daily dose of GF120918 was 50 mg and was to be increased in subsequent cohorts until a steady state plasma level of 100 ng/ml was reached. The starting dose of doxorubicin was 50 mg/m2 and was to be increased after reaching the target dose level of GF120918. RESULTS: In 37 of the 46 patients, full pharmacokinetic data from the three scheduled cycles were obtained. Pharmacokinetics of GF120918 showed a less than linear increase in Cmax with increasing doses, with considerable interpatient variation. The target steady-state plasma level for GF120918 was exceeded in 12 out of 19 patients who received 400 mg GF120918 alone twice daily and in 12 of 17 patients who received 400 mg GF120918 twice daily in combination with doxorubicin. GF120918 pharmacokinetics were not influenced by coadministration of doxorubicin. The doxorubicin AUC was only marginally influenced by GF120918 and only at the highest dose levels. In these patients there was a significant increase in the AUC of doxorubicinol in cycle 3 as compared to cycle 1. Hematologic toxicity mainly consisted of neutropenia and was more severe in cycle 3 than in cycle 1 (13 vs 5 patients with grade 4 neutropenia, P=0.003). Neutropenic fever was the dose-limiting toxicity at a doxorubicin dose of 75 mg/m2 with 400 mg GF120918 twice daily. The toxicity of GF120918 was limited to somnolence in eight patients and occasional gastrointestinal complaints. CONCLUSION: GF120918 is an MDR converter with only minimal side effects at a dose level yielding concentrations able to convert the action of P-glycoprotein in vitro. A doxorubicin dose of 60 mg/m2 on day 3 in combination with 400 mg GF120918 twice daily on days 1-5 is an acceptable regimen for further clinical trials.

Population pharmacokinetic and dynamic analysis of the topoisomerase I inhibitor lurtotecan in phase II studies.

Population pharmacokinetic-dynamic analysis was prospectively integrated in a broad phase II program of lurtotecan (GI147211), a novel camptothecin derived topoisomerase I inhibitor, to determine the population pharmacokinetic profile in a larger population, to estimate individual pharmacokinetic parameters and to investigate relationships with clinical outcome. A sparse sampling method was applied during course one, which involved two sampling time-points. A Bayesian algorithm was used to estimate individual pharmacokinetic parameters, in particular total plasma clearance (CL) and volume of distribution. In total, samples were collected of 109 (63%) of 173 patients. Pharmacokinetic-dynamic evaluation could be carried out successfully in 85 (78%) of the sampled patients. CL of lurtotecan showed substantial variability (mean 87 +/- 28 L/h) and was of the same magnitude as in the phase I studies where full pharmacokinetic curves were used. Residual variability in the population estimate of CL was 9.9%. No significant relationships were observed between exposure parameters and toxicity nor likelihood of tumor response, however the latter relationship may well have been obscured by the heterogeneity of the studied population. Prospective implementation of large scale population pharmacokinetic-dynamic analysis is feasible and important to establish whether interpatient variability in drug exposure is a major determinant of toxicity or activity.

Androgen antagonists: Potential role in prostate cancer prevention.

This article summarizes discussions of the importance of androgens and androgen antagonists in the genesis of prostate cancer. These discussions occurred at a recent symposium on prostate cancer chemoprevention sponsored by the National Cancer Institute. Considerable information exists indicating the importance of androgens in the development of prostate cancer. Trials in breast cancer indicate that estrogen antagonists prevent breast cancer-suggesting, by analogy, that the blockade of androgen action might prevent the emergence of prostate cancer. The 5alpha-reductase inhibitors block the intracellular metabolism of testosterone and inhibit the growth of the prostate. Limited data suggest that 5alpha-reductase inhibitors reduces prostate-specific antigen in men with localized and advanced, primary or recurrent prostate cancer. An ongoing national trial of 18,000 men over 50 years of age has completed accrual and will evaluate whether a standard dose of finasteride will prevent the development of prostate cancer. The toxicity profile of finasteride (Proscar, Merck & Co., West Point, PA), the only approved 5alpha-reductase inhibitor, is favorable leading to its evaluation as a potential chemopreventive agent for prostate cancer. Anti-androgens such as bicalutamide (Casodex, AstraZeneca, Wilmington, DE) are active in the treatment of prostate cancer and comparable, in some trials, to testicular androgen suppression. These data suggest that antiandrogens may be active in the prevention of prostate cancer; however, the toxicity of antiandrogens (gynecomastia, gastrointestinal toxicity) poses concerns for application in prevention studies. Opportunities for study of factors predictive or associated with the development of prostate cancer and new agents that may interrupt this process offer numerous leads that may reduce the incidence of prostate cancer.

Antiplatelet effects of MK-852, a platelet fibrinogen receptor antagonist, in healthy volunteers.

MK-852, a cyclic heptapeptide, is a potent platelet fibrinogen receptor antagonist. When administered to normal healthy male subjects by 1- and 4-hour constant rate intravenous infusions, it provides a generally well-tolerated and reversible means of inhibition of platelet function. At infusion rates of 1 microgram/kg/min for 1 hour and 0.44 microgram/kg/min for 4 hours, respectively, MK-852 extended baseline bleeding time by greater than 2.2-fold and 2.6-fold, inhibited ADP-induced platelet aggregation by 76% and 69%, and inhibited collagen-induced platelet aggregation by 65% and 67%, respectively. The pharmacokinetics of MK-852 include an elimination half-life of approximately 2 hours, total clearance of about 150 ml/min, and volume of distribution of about 18 liters. Examination of the relationship between MK-852 whole-blood concentration in vitro and inhibition of platelet aggregation showed an EC50 of about 55 ng/ml and a Hill coefficient of 1.55. The infusions were generally well tolerated, with no study drug-related changes in blood counts or biochemical profiles.

Second-line treatment of small-cell lung cancer with the camptothecin-derivative GI147211: a study of the EORTC Early Clinical Studies Group (ECSG).

BACKGROUND: GI147211, a 10,11-ethylenedioxy substituted analogue of camptothecin (CPT), was brought into clinical development because of its higher water solubility and greater potency as compared to topotecan (TPT). The antitumor activity of GI147211 as second-line therapy in small-cell lung cancer (SCLC) was assessed after stratification of patients in refractory (no response to initial treatment or relapse within three months from last cycle) and chemosensitive (relapse more than three months from last cycle). PATIENTS AND METHODS: Sixty-seven patients were entered in the study and sixty-two were evaluable for response, twenty-eight in the refractory and thirty-four in the chemosensitive group. All patients had received 1 line of chemotherapy; radiation had also been given in 29 cases, 6 in the refractory and 23 in the chemosensitive group. GI147211 was administered at 1.2 mg/m2/day as 30-min infusion for five consecutive days every three weeks. RESULTS: The overall response rate was 16.6% (11 of 66 patients; 95% confidence interval (95% CI): 8.5%-27.5%), 10.3% (3 of 29 patients; 95% CI: 2.2%-27%) in the refractory and 21.1% (8 of 37 patients; 95% CI: 9.5%-37%) in the chemosensitive group. Only partial responses (PR) were observed with a median duration of PR of 4.8 months (5.7 months in the refractory and 5.2 in the chemosensitive group). Hematological toxicity consisted mainly of neutropenia (grades 3-4 in 25% of cycles) and thrombocytopenia (grades 3-4 in 23% of cycles); non-hematological toxicity was mild to moderate and consisted of nausea (22% of cycles), vomiting (11%), malaise (34%). CONCLUSIONS: At the dose and schedule tested GI147211 is an active new agent for second-line treatment of SCLC; the antitumor activity and toxicity profile are comparable to those observed with TPT which remains the leading CPT analogue for salvage treatment. Interest has been renewed in the clinical development of GI147211 by preclinical data with the liposomal formulation showing an increased therapeutic index.

Clinical pharmacokinetics of doxorubicin in combination with GF120918, a potent inhibitor of MDR1 P-glycoprotein.

Previous clinical investigations with doxorubicin indicated that modulators of P-glycoprotein dramatically decrease the systemic clearance of the drug, which complicates the interpretation of toxicity and response data. In the present study, we examined the pharmacokinetics of doxorubicin and GF120918, a novel potent P-glycoprotein inhibitor, in cancer patients in a search for more selective modulation of multidrug resistance (MDR). Seven cohorts (46 patients) received sequential treatments with doxorubicin alone by a 5 min i.v. bolus (50-75 mg/m2), oral GF120918 alone (50 mg q.d.-400 mg b.i.d.), and the combination of doxorubicin and GF120918. Serial blood and urine samples were taken during both treatment courses and analyzed for doxorubicin and its metabolite doxorubicinol by a liquid chromatographic assay. The pharmacokinetic characteristics of doxorubicin in the presence or absence of GF120918 indicate a very minor overall effect of the modulator, except at the highest combined dose level (i.e. 75 mg/m2 plus 400 mg b.i.d.). A limited number of patients experienced significantly increased exposure to doxorubicinol upon combined treatment, which was associated with concomitantly higher plasma levels of GF120918. Sigmoidal maximum-effect models revealed significant correlations (p<0.02) between the area under the curve of doxorubicinol and the percent decrease in neutrophils and platelets. Sigmoidicity factors in the fitted Hill equation were similar between both treatment courses, suggesting no pharmacodynamic potentiation of doxorubicinol myelotoxicity by GF120918. Our data indicate that GF120918 at the tested doses of combination treatment achieves plasma concentrations that reverse MDR in experimental models and it lacks the significant kinetic interaction with doxorubicin observed previously with other modulators. Hence, it may be possible in future trials to assess the contribution of a potent inhibitor of P-glycoprotein activity to the toxicity and activity of doxorubicin with the knowledge that profound plasma pharmacokinetic interactions are unlikely.

Phase I/pharmacokinetic study of the topoisomerase I inhibitor GG211 administered as a 21-day continuous infusion.

BACKGROUND: Preclinical results support a prolonged schedule of administration for topoisomerase I inhibitors, and we have previously demonstrated the safety and activity of the novel water-soluble topoisomerase I inhibitor GG211 when given as a 72-hour continuous infusion to cancer patients. PATIENTS AND METHODS: In a three-center international phase I trial, 38 patients received GG211 doses from 0.3 to 0.5 mg/m2/day by continuous intravenous infusions for seven, 14, and 21 days. Patients' median performance status was 1; nearly half had colorectal cancer, and 35 patients had prior chemotherapy. RESULTS: The first patient cohort received 0.3 mg/m2/day for seven days with no significant toxicities. Subsequent cohorts received continuous infusions for 14 and 21 days at this dose level with only mild myelosuppression noted. Dose-escalation on the 21-day schedule was then performed. No dose-limiting toxicity occurred at the 0.4 mg/m2/day dose level. Thrombocytopenia was dose-limiting with 0.5 mg/m2/day dosing but was not cumulative. Other grade 3 4 toxicities included neutropenia, nausea, vomiting, diarrhea, and fatigue. Partial responses occurred with 21-day infusion in two patients with breast and ovarian cancer at the 0.3 and 0.4 mg/m2/day dose levels, respectively. Mean GG211 lactone Css ranged from 0.17 to 0.64 ng/ml. CONCLUSION: The maximum tolerated dose of GG211 administered as a 21-day continuous infusion is 0.4 mg/m2/day with antitumor activity noted at tolerable doses.

A phase I clinical and pharmacokinetic study of the new topoisomerase inhibitor GI147211 given as a 72-h continuous infusion.

GI147211 is a novel, totally synthetic camptothecin with promising preclinical and early clinical activity. This study was designed to determine the maximum tolerated dose of Gl147211 as a 72-h infusion and to describe its pharmacokinetics and pharmacodynamics on this schedule. In a single-arm, rising-dose study in patients with advanced cancer, eight cohorts of three or more patients received 72-h infusions of Gl147211 at doses ranging from 0.25 to 2.5 mg m(-2) day(-1). Forty-four patients received a total of 124 cycles. All patients had refractory tumours and 40 had received prior chemotherapy and/or radiotherapy. Whole-blood Gl147211 lactone, total blood and total concentrations were measured during and over the 12 h following the infusion. Myelosuppression was observed at all dose levels. Neutropenia was dose limiting at 2.0 mg m(-2) day(-1) in minimally pretreated patients, while both neutropenia and thrombocytopenia were limiting at 1.5 mg m(-2) day(-1) in those more heavily pretreated. Phlebitis occurred with infusions through peripheral veins early in this study, necessitating the use of central venous access. Other toxicities included mild nausea and vomiting, fatigue, headache, central venous catheter infections and alopecia. Three partial and two minor responses lasting 8-34+ weeks were noted in patients with ovarian, colon and breast carcinomas and hepatoma. Mean steady-state concentrations of Gl147211 increased with dose over a range of 0.25-1.24 ng ml(-1). The mean terminal elimination half-life was 7.5 h, and the clearance averaged 1074 ml min(-1) m(-2) over the doses studied. The mean fractional excretion of unchanged drug in urine was 0.114. Gl147211 lactone exposure correlated with haematological toxicity. The recommended phase II doses for this regimen are 1.75 mg m(-2) day(-1) and 1.2 mg m(-2) day(-1) for minimally pretreated and heavily pretreated patients respectively. At these doses, steady-state Gl147211 concentrations within the range of those effective in vitro were achieved. Extensive phase II evaluation of this compound and further phase I trials evaluating more prolonged infusions are ongoing.

Phase I and pharmacokinetic study of GI147211, a water-soluble camptothecin analogue, administered for five consecutive days every three weeks.

GI1147211 is a 7-substituted 10,11-ethylenedioxy-20(S)-camptothecin analogue that inhibits the nuclear enzyme topoisomerase I. In this Phase I and pharmacological study, 24 patients with advanced solid malignancies received a total of 72 courses of GI147211 as a 30-min infusion daily for 5 consecutive days, at doses ranging from 0.3 to 1.75 mg/m2/day. Severe neutropenia precluded dose escalation above 1.5 mg/m2/day in minimally pretreated patients, and both severe neutropenia and thrombocytopenia were dose limiting in heavily pretreated patients at doses above 1.0 mg/m2/day. These doses are, therefore, recommended for subsequent Phase II evaluations of GI147211 in patients with comparable prior therapy. Nonhematological toxicities, including nausea, vomiting, fatigue, and anorexia, were mild to moderate. The disposition of GI147211 in blood was described by a linear three-compartment model, with renal elimination accounting for only 11% of drug distribution. No relationship was observed between the pharmacological exposure to GI147211 and effects on neutrophils; however, patients who developed dose-limiting myelosuppression did experience greater exposure to both the lactone and total forms of the drug. The hydrolysis kinetics of GI147211 revealed not only a shift of the drug to the inactive carboxylate form in human serum albumin but also stabilization of the lactone in erythrocytes, perhaps accounting for the observed lactone:total area under the concentration-time curve ratio of 0.27. These results indicate that GI147211 exhibits predictable toxicities and that further studies are warranted to determine the distinct role of this compound among currently available camptothecin analogues.

The bioavailability of oral GI147211 (GG211), a new topoisomerase I inhibitor.

Topoisomerase I inhibitors are new compounds of interest for cancer chemotherapy. We performed a study with GI147211, a new semisynthetic camptothecin analogue, to determine the absolute bioavailability of the drug given orally. Patients with a histologically confirmed diagnosis of a solid tumour refractory to standard forms of therapy were eligible for the study. GI147211 was given orally on day 1 and as a 30-min infusion daily on days 2-5. The treatment course was repeated every 3 weeks. In subsequent patient cohorts, the dose of the oral formulation was escalated from 1.5 mg m(-2) to 6.0 mg m(-2); the dose for i.v. administration was fixed at 1.2 mg m(-2). Plasma pharmacokinetics was performed on day 1 and 2 of the first course and on day 1 of the second course using a validated high-performance liquid chromatographic assay. Nineteen patients were entered into the study; one patient was not evaluable because the treatment course was stopped prematurely. Eighteen patients received a total of 47 treatment courses. The absolute bioavailability of GI147211 averaged 1.3 +/- 5.2%. Drug appeared quickly in plasma with a median Tmax at 0.5 h. Fasting or fed state had no significant influence on the bioavailability of GI147211. The terminal half-life after administration of oral GI147211 was 6.85 +/- 3.13 h, similar to the half-life after intravenous administration. The major toxicities were neutropenia and thrombocytopenia. Nadirs for neutropenia and thrombocytopenia occurred on day 8 and day 15 respectively. Other toxicities predominantly consisted of mild and infrequent nausea and vomiting, and fatigue. The oral administration of the drug is well tolerated. Oral administration of topoisomerase I inhibitor GI147211 results in a low bioavailability with relatively wide interpatient variation. The intravenous route of administration is advised for further development of this promising topoisomerase I inhibitor.

Phase I and pharmacological study of the new topoisomerase I inhibitor GI147211, using a daily x 5 intravenous administration.

Topoisomerase I inhibitors are interesting anti-cancer agents with a novel mechanism of action. We performed a phase I study with intravenous GI147211, a new semisynthetic camptothecin analogue, using a daily x 5 schedule administered every 3 weeks, to evaluate the side-effects and pharmacokinetics of the agent. Patients with a histologically confirmed diagnosis of a solid tumour refractory to standard froms of therapy were eligible for the study. GI147211 was given as a 30 min intravenous infusion daily for 5 consecutive days, repeated every 3 weeks. In subsequent patient cohorts the dose was escalated from 0.3 to 1.5 mg m-2 day-1. Pharmacokinetics analysis was performed on days 1 and 4 of the first course using a validated high-performance liquid chromatographic assay and non-compartmental methods. A total of 19 patients were entered into the study, one patient was not evaluable for toxicity because only one drug administration was given. Eighteen patients received a total of 67 courses through four dose levels. The dose-limiting toxicities were neutropenia and thrombocytopenia at the dose of 1.5 mg m-2 day-1. Nadirs occurred on day 15 and day 15 respectively. Other toxicities were mild and infrequent and included nausea/vomiting, headache and alopecia. The maximal tolerated dose was 1.2 mg m-2 day-1. One partial response was observed in a patient with colorectal cancer. The total plasma clearance was 999+/-184 ml min-1 (range 640-1329). The volume of distribution was 190+/-461 m-2 and the terminal half-life was 3.7+/-1.2 h. The AUC increased linearly with the administered dose. A steep and significant sigmoid relationship was established between the AUC and the percent decrease of ANC. GI147211 is a new topoisomerase I inhibitor that induced dose-limiting neutropenia and thrombocytopenia in this phase I study. The recommended dose for phase II studies with this schedule is 1.2 mg m-2 x 5 every 3 weeks.

Flow cytometric assay of modulation of P-glycoprotein function in whole blood by the multidrug resistance inhibitor GG918.

We sought to develop an assay for measuring the inhibition of P-glycoprotein (Pgp) function in whole blood as an indicator of in vivo drug activity. Since the CD56(+) subset of peripheral blood lymphocytes (PBLs) has been shown to express functional Pgp, the changes in rhodamine 123 (R123) uptake by CD56(+) PBLs from GG918-treated and untreated whole blood were used as the basis for these studies. In an ex vivo study, heparin-treated whole blood was obtained from normal volunteers, and GG918 and R123 were added at various concentrations for time course analyses of dye loading. GG918 concentrations from 2.5 to 800 nm were tested in incubations ranging from 15 min to 3 h prior to R123 addition. R123 loading times ranged from 0 to 80 min. Flow cytometric analyses of the CD56(+) PBLs indicated that the resolution of Pgp inhibition was dependent on inhibitor concentration and time of R123 loading and independent of the R123 concentrations tested. In this ex vivo assay model, a dose-dependent response was seen for GG918 with a 2-fold increase in cellular R123 intensity being produced at a drug concentration of 80 nm. When this assay method was applied to blood samples from volunteers dosed p.o. with GG918, similar shifts in R123 fluorescence of the CD56(+) PBLs were observed with significant increases in R123 intensity occurring at serum concentrations as low as 40 nm. In contrast to assays in which target cell populations are enriched prior to testing, the addition of the substrate (R123) directly to the blood sample combined with the segregation of the target cells by specific immunofluorescence provides the investigator an indication of in situ activity of circulating drug. Thus, CD56(+) PBLs may prove useful as a surrogate target for monitoring multidrug resistance inhibitor activity in situ.

Protective effect of Sn-protoporphyrin against doxorubicin-induced perturbations of heme metabolism.

The administration of doxorubicin, an anti-tumor antibiotic, to rodents resulted in an increase in heme oxygenase activity and a decrease in delta-aminolevulinate (ALA) synthase activity and in cellular heme and cytochrome P450 content in liver. Sn-protoporphyrin, a potent inhibitor of heme degradation both in vitro and in vivo, when administered to rodents prior to doxorubicin, mitigates the drug-induced toxic actions which are reflected by the drug-induced decreases of both cellular heme and cytochrome P450 content. Sn-protoporphyrin thus provides a pharmacological means of protecting against the toxic effects of doxorubicin and other drugs which enhance heme oxygenase activity and thus decrease cellular heme and cytochrome P450 content in vivo.

The influence of antineoplastic chemotherapy on antipyrine metabolism in man.

When either Doxorubicin or Mitomycin-C was administered to patients, antipyrine clearance was respectively unaltered or increased. Antipyrine was administered to patients two days prior to and one day after their first course of the chemotherapeutic drug. Antipyrine clearance increased an average of 11.2% in the 5 patients that received Doxorubicin (not significant) and 15.2% in the six patients that received Mitomycin-C (P = 0.033, students t-test). The altered clearance is likely due to a rapid induction of the mixed function oxidase system by the chemotherapy as other parameters that could influence clearance were stable throughout the study (volume of distribution, weight, creatinine clearance and liver function tests). It is unlikely that the prechemotherapy antipyrine dose accounted for this change. The administration of these two antitumor antibiotics in humans may modestly increase the mixed function oxidase activity that is responsible for the metabolism of antipyrine. These findings are in direct contrast to markedly decreased mixed-function oxidase activity observed in the rodent pretreated with the same chemotherapy.

Tin-protoporphyrin inhibits heme oxygenase and prevents the decline in hepatic heme and cytochrome P-450 contents produced in nude mice by tumor transplantation.

Heme and hemeprotein perturbations are present in nude mice bearing transplanted tumors. Hepatic microsomal heme oxygenase activity is increased 50-100% in tumor bearing nu/nu mice when compared with normal controls. This elevation in activity of the rate-limiting enzyme of heme degradation is associated with a 50% depletion of microsomal heme and cytochrome P-45 concentrations in liver. The synthetic heme analogue, Sn-protoporphyrin, a potent inhibitor of heme oxygenase, lowers the activity of heme oxygenase in tumor bearing animals to below control levels. This effect is associated with a normalization of hepatic heme and cytochrome P-450 contents. These findings might have implications for protecting normal cells during tumor growth and chemotherapy.

Chemotherapy of patients with advanced soft tissue sarcoma with use of DVA (vindesine sulfate), adriamycin and cyclophosphamide (DAC).

Thirty-four patients with advanced soft tissue sarcoma were treated with a three-drug combination including vindesine sulfate (DVA), Adriamycin, and cyclophosphamide (DAC) (S9). Thirty-one patients are evaluable of whom 23 were previously untreated. Among the latter group there were six complete responses (26%) and five partial responses (22%), for a major response rate of 48%. No major responses were seen in the eight previously treated patients. The median duration of responses was 8 months. Leukopenia and peripheral neuropathy were the major complications of treatment. Gastrointestinal toxicity was mild. Adriamycin cardiotoxicity was seen in two patients. Although the overall response rate to DAC is comparable to that of other combinations, it may offer the advantages of an increased complete response rate and less gastrointestinal toxicity.