Biomedical subjects
Publications and source records attributed to G G Chabot.
Screening methods for the detection of anticancer activity are of crucial importance in order to find solid tumor-specific agents. A review of past screening methods is followed by a description of present methodologies targetted toward the discovery of such agents. Finally, we discuss primary and secondary in vivo evaluation in experimental chemotherapy.
Because of encouraging response rates published with recombinant interleukin-2 (rIL-2) alone in metastatic malignant melanoma (MMM), dacarbazine (DTIC) and rIL-2 were sequentially combined to evaluate efficacy, toxicity, pharmacokinetics, and immunologic interaction. Thirty-two patients aged 18 to 67 years have received 127 courses of treatment. The dose of DTIC was 1.0 g/m2 as a 24-hour infusion every 28 days on day 1. Recombinant interleukin-2 (2.0, 3.0, 4.0, or 5.0 x 10(6) Cetus units/m2) was administered as a 30-minute infusion on days 15 through 19 and 22 through 26 of each 28-day cycle. Seven of 32 patients (22%) who received therapy had a remission, one complete and six partial. The complete response was in a lung mass. Partial responses were seen in lymph nodes, liver, and lung. The median duration of response was 4.7 months. One patient is in persistent partial remission of the liver for greater than 2 years. One patient had residual mediastinal disease resected after partial response and remains without evidence of disease for 18+ months. This regimen was generally well tolerated, did not create overlapping toxicity, and produced encouraging responses in visceral sites. This provides a framework for future combinations of chemotherapy with rIL-2 alone or in combination with other biologic response modifiers in an outpatient setting.
In an effort to improve the treatment of metastatic malignant melanoma, we evaluated the sequential administration of the chemotherapeutic agent dacarbazine (DTIC) and the biological response modifier interleukin-2 (rIL-2) in a phase I-II study. Since the combination of biological response modifiers and chemotherapeutic agents could alter drug disposition, we evaluated the pharmacokinetics of DTIC and its major metabolite, 5-amino-imidazole 4-carboxamide (AIC), before and after rIL-2 administration. DTIC (1 g/m2, 24-h i.v. infusion) was given on day 1 and rIL-2 (2-4 million Cetus units/m2, 30-min i.v. injection), on days 15-19 and 22-26 of each course of therapy. The second DTIC dose was given on day 29, i.e., 3 days after the last rIL-2 administration. DTIC and AIC were assayed by reversed-phase HPLC. DTIC plasma levels showed a significant decrease after rIL-2 administration as compared with DTIC values obtained in the same patients before rIL-2 administration. DTIC area under the curve (AUC) values obtained after rIL-2 were lower than those obtained on day 1 before rIL-2 administration (P = 0.02). After rIL-2, the total body clearance (ClT) was increased (P = 0.04), as was the volume of distribution at steady state (Vss; P = 0.02). The decrease in AUC after rIL-2 administration became more pronounced as the rIL-2 dose was increased (P = 0.03). No significant difference was detected in the elimination phase of DTIC when half-lives obtained before and after rIL-2 administration were compared; the mean half-lives were 0.7 and 2.8 h for the alpha- and beta-phases, respectively. The model-independent mean residence time was 3.4 h. The plasma AUC for the metabolite AIC did not charge after rIL-2 administration. AIC biphasic plasma elimination was also similar after rIL-2 administration, with alpha- and beta-half-lives of 0.7 and 11.4 h, respectively. Urinary excretion of DTIC and AIC did not differ after rIL-2 administration; the overall DTIC excretion was 39% of the dose over 48 h, and AIC urinary excretion was 25% of the DTIC dose. The observed decrease in the DTIC plasma AUC after rIL-2 administration appears to be due to an increase in the volume of distribution, since other factors such as half-lives, urinary excretion, and metabolism were not significantly altered. The clinical consequences of the rIL-2-DTIC interaction remain difficult to assess based on presently available data, but this drug interaction should be taken into consideration in the development of future chemo-immunotherapy regimens that include high-dose rIL-2.
To evaluate the role of amphotericin B (AmB) in the biochemical modulation of antineoplastic agents, AmB was administered as a continuous infusion over a period of 52 to 120 h to 14 patients (26 courses) with advanced carcinomas. Continuous infusion amphotericin B (CI-AmB) was delivered at a rate of 0.5 to 0.8 mg/kg/d (19-31 mg/m2/d). The AmB plateau levels assayed by HPLC ranged from 0.7 to 1.9 micrograms/mL and were directly related to the infusion rate. The AmB plasma disposition was biphasic, with mean half-lives of 17 h for the first phase and 11 d for the terminal phase, and a mean residence time of 12 d. Biochemical modulation of antineoplastic agents (lomustine, doxorubicin, cyclophosphamide) by CI-AmB was not demonstrated clinically. Acute toxicities of fever and chills were noted in only 3 of the 26 courses. Reversible renal toxicity was observed in 23 courses. Therapeutic antifungal plasma levels were rapidly reached and maintained for the duration of infusion, with a reduction of acute toxicities associated with shorter infusions. These observations provide impetus for further clinical investigation of CI-AmB.
Flavone acetic acid (FAA) is a novel antitumor agent with broad solid-tumor activity. However, this drug has shown a steep dose-response curve in preclinical trials, with a narrow sublethal window of efficacy. To investigate this threshold behavior, we studied various aspects of FAA pharmacology in mice after i.v. administration. Mice bearing advanced-stage s.c. colon 38 adenocarcinoma were treated at four dose levels (39, 65, 108 and 180 mg/kg), and only the highest dose produced significant antitumor activity, showing a steep dose-response curve. Using an HPLC assay, FAA pharmacokinetics in both plasma and tumors were found to be dose-dependent. As the dose increased, there was a decrease in both total body clearance and volume of distribution at steady state. The increase in tumor area under the curve (AUC) was more pronounced than the corresponding increase in plasma AUC, showing a better tumor exposure to FAA at high doses. The distribution of FAA in normal tissues showed a short-term retention in the liver and kidneys; low concentrations were observed in the heart, spleen, and brain, with some retention in the latter. The highest FAA concentrations were found in the gastrointestinal (GI) tract, mainly in the duodenum, suggesting an important biliary excretion of the drug. Various possible causes of FAA nonlinear pharmacokinetics were investigated. Serum protein binding was high (79%) and remained constant up to 100 micrograms/ml, but decreased thereafter at higher FAA concentrations, e.g., 76% at 500 micrograms/ml and 64% at 1,000 micrograms/ml. Urinary and biliary clearances were dose-dependent and decreased 5- and 9-fold, from the 39- to the 180-mg/kg dose levels, respectively. A direct assessment of FAA enterohepatic circulation using intercannulated mice showed that 27% of the plasma AUC was accounted for by enterohepatic circulation. FAA acyl glucuronide was identified as the major metabolite in mice and was found to contribute to the nonlinear pharmacokinetics due to its facile hydrolysis under physiological conditions, regenerating FAA. In conclusion, the steep FAA dose-response curve was found to be caused by dose-dependent pharmacokinetics in mice. The nonlinear pharmacokinetics of this drug was attributed to a dose-dependent decrease in both urinary and biliary clearances, concentration-dependent serum protein binding, enterohepatic circulation, and the instability of FAA acyl glucuronide under physiological conditions forming a futile cycle.(ABSTRACT TRUNCATED AT 400 WORDS)
Flavone acetic acid (FAA; LM 975; NSC 347512) is a new anticancer agent with unprecedented, broad antitumor activity in murine models. Although FAA is very effective in vivo against solid tumors, including colon 38 adenocarcinoma, it was not cytotoxic in vitro against colon 38 cells and human colon adenocarcinoma cells HCT116 at pharmacologically achievable concentrations and exposure times. For example, a concentration of 300 micrograms/ml for a 10-day exposure time was required to obtain less than 1 log cell kill. After the administration of an effective FAA dose (180 mg/kg, i.v.) to mice, plasma cytotoxicity against HCT116 cells attained a 2 log cell kill between 0.5 and 2 h, which decreased to 1 log cell kill at 4 h. No cytotoxicity was observed 6, 12 or 21 h after drug administration. The controls used comprised mouse plasma containing FAA concentrations similar to those assayed in the above plasma samples from in-vivo-dosed mice. These spiked plasma were not cytotoxic, indicating that other cytotoxic species, formed in vivo, were responsible for the increased cytotoxicity. Mouse hepatocytes co-cultured with HCT116 cells increased FAA cytotoxicity to 1 log cell kill at 30-100 micrograms/ml. The addition of phenobarbital-induced mouse liver supernatant S-9000xg also markedly increased FAA cytotoxicity to a 2 log cell kill at 300 micrograms/ml. We conclude that FAA can be activated both in vivo and in vitro to cytotoxic species that are more active than the parent compound.
Flavone acetic acid (FAA), a new drug with broad activity against transplanted solid tumors of mice, induces nonrepairable DNA single strand breaks that correlate with therapeutic efficacy. To test the hypothesis that the inability of the cells to repair single strand breaks is associated with a disruption of tumor energy metabolism, in vivo 31P nuclear magnetic resonance (NMR) spectra were acquired from s.c. implanted Glasgow osteogenic sarcomas in C57BL/6 x DBA/2 F1 mice both before and after treatment with FAA i.v. at 100, 150, or 200 mg/kg and from a control (no treatment) group (n = 4 in each group). While FAA produced a dose-dependent decrease in both the nucleoside triphosphates level and pH, only treatment with an efficacious dose of 200 mg/kg resulted in both a reduction in pH and a complete loss of nucleoside triphosphates from the NMR spectrum at 4 h with no recovery until 48 h and little recovery out to 72 h. The ATP concentration determined by high pressure liquid chromatography in a parallel set of experiments was 5.59 +/- 1.16 (SE) mumol/g (wet weight) in control tumors (n = 9) and 0.24 +/- 0.12 mumol/g (wet weight) at 4 h after 200 mg/kg FAA (n = 7). To examine the possibility that the loss of ATP and decreased pH are associated with a reduction in tumor blood flow, we used 2H NMR to monitor the washout of D2O injected directly into the tumor both before and 4 h after treatment with 200 mg/kg FAA. The pretreatment tumor blood flow of 12.4 +/- 1.7 ml/min/100 g was reduced to 1.9 +/- 0.5 ml/min/100 g at 4 h after treatment (n = 3). The FAA-induced reduction of both tumor blood flow and ATP may play an important role in its mechanism of action and should be considered in the combination of FAA with other drugs or therapeutic modalities. In addition, because 31P NMR can be used clinically, it should provide a nonambiguous early indicator of activity for clinical trials of FAA.
Acodazole (NSC 305884) was examined in a Phase I trial evaluating a 1-h infusion repeated every 21 days in 37 patients with advanced carcinomas. Cardiac toxicity was dose-limiting at 1370 mg/m2, manifested as multiple premature ventricular contractions, QTc interval prolongation, and decreasing heart rate. Other toxicities included mild to moderate nausea and vomiting and local reaction near the i.v. injection site requiring the use of central venous catheters. Antineoplastic activity was not observed. Acodazole levels assayed by high-performance liquid chromatography disclosed a peak plasma level of 19 +/- 4 (SEM) micrograms/ml for 1370 mg/m2. Acodazole plasma levels decreased in a triphasic manner over a 100-fold range. The volume of distribution at steady state was 238 +/- 18 liter/m2 suggesting extensive tissue binding. The total body clearance was 13.6 +/- 0.9 liter/h/m2; the percentage of urinary excretion was 29 +/- 2% for 48 h. To evaluate cardiac toxicity, acodazole was administered to five dogs at 2262 mg/m2 (1-h infusion) which provided plasma concentrations similar to those achieved at 1370 mg/m2 in humans. Consistent findings in dogs were drug-related prolongation of QTc intervals, and reduction in heart rate, left ventricular dP/dt, and mean blood pressures. Clinical development of acodazole requires studies to further elucidate and alleviate this cardiac toxicity.
Flavone acetic acid (FAA) is a new antitumor agent with broad activity against transplantable solid tumors of mice but with only scant or no activity against leukemias and lymphomas. The technique of alkaline elution was used to study DNA lesions in s.c. implanted Glasgow osteogenic sarcoma in C57BL/6 x DBA/2 F1 mice treated i.v. with FAA. At efficacious dosages (235 and 200 mg/kg), FAA produced extensive single strand breakage. Formation of single strand breaks was dependent on time of assay after exposure to FAA with only minimal damage occurring prior to 5 h posttreatment. Apparently Glasgow osteogenic sarcoma had no capacity to repair single strand breaks for at least 45 h after drug administration. Thus, FAA differs in its mechanism from other scission agents (e.g., VP-16). Neither interstrand cross-links nor DNA-protein cross-links were detected. DNA single strand breaks did not occur in the bone marrow cells or in the unresponsive P388 leukemia cells at dosages causing extensive DNA damage in solid tumor cells.
A Phase I study of caracemide evaluating a short intravenous infusion repeated every 21 days is presented. Patients were entered at 85 mg/m2 with subsequent escalation levels of 170, 425, 595, and 795 mg/m2. Mild to moderate nausea and vomiting occurred at all dose levels. An apparent allergic reaction was observed at the 425 mg/m2 level. A "burning pain" originating in the mucosal areas of the head and neck, progressing to the chest and abdomen, was noted at the 425 mg/m2 level. Because of this observation, the infusion time was extended to 4 h. At the 795 mg/m2, this toxicity precluded completion of the 4 h infusion. Pharmacokinetic evaluation disclosed blood levels of 0.74-2.31 microgram/ml at the 425 mg/m2 during the 0.5 h infusion. At the same dose for a 4 h infusion time, blood levels were 0.15-0.18 microgram/ml. At 595 mg/m2 administered as a 4 h infusion, blood levels increased to 0.33 +/- 0.14 microgram/ml. The drug was cleared rapidly from the blood compartment with a half-life of 2.5 min and a total body clearance of 11.51/min/m2. No partial or complete response was observed. However, an advanced colon carcinoma patient experienced subjective pain relief with a decrease in carcinoembryonic antigen. The dose-limiting toxicity of caracemide using the 4 h infusion was an intolerable "burning pain" with a maximum tolerated dose of 795 mg/m2. Further characterization of this dose-limiting toxicity is required prior to further clinical evaluation of caracemide.
The in-vitro effects of the antileukemic agent 5-aza-2'-deoxycytidine (5-aza-dCyd), on DNA synthesis, growth, cloning in agar, and cell cycle traverse of L1210 leukemia cells were studied. 5-Aza-dCyd at 0.1 microgram/ml for 10 hr (cytotoxic concentration) did not inhibit DNA synthesis but produced a very potent growth inhibition, and changed markedly the DNA flow cytometric histograms. A 5-h continuous exposure to the drug at concentrations ranging from 0.1 to 10 micrograms/ml caused an accumulation of cells in the S portion of the DNA histograms indicating a slowing of the progression of cells in the S phase. A longer exposure time (10 h) at the same concentrations led to a bimodal DNA distribution (peaks at G1 and G2-M) and a depletion of the S phase. When the exposure time to 5-aza-dCyd (0.1 microgram/ml) was extended to 15 and 20 h, there was a decrease in the G2-M peak and an augmentation of the G1 peak. To determine if 5-aza-dCyd produced a block in cell cycle progression, L1210 cells were treated for 10 h with colcemid and 5-aza-dCyd simultaneously for 10 h. Colcemid alone, or colcemid in combination with 5-aza-dCyd produced an accumulation of cells under a single G2-M peak. This indicates that 5-aza-dCyd did not block the progression of L1210 cells through S phase, but only produced a slowing down of this event. These results, indicating that 5-aza-dCyd does not block cell cycle progression and that its cytotoxic action is not self-limiting, are of importance for designing future clinical trials.
In an attempt to increase the peak plasma levels of 13-cis-retinoic acid (13-cis-RA) and its efficacy in vivo, a Phase I study and pharmacokinetics of weekly high-dose, oral 13-cis-RA was conducted in 23 cancer patients who were refractory to conventional treatments. At 200 mg/sq m, the mean peak plasma level of 13-cis-RA was 1.5 +/- 0.1 (SE) micrograms/ml; at 400 mg/sq m, the mean peak plasma level increased to 3.8 +/- 0.7 micrograms/ml. Further increases of the 13-cis-RA dose up to 1800 mg/sq m did not lead to proportional increases in either the mean peak plasma levels or area under the curve, indicating a saturable absorption phenomenon. The terminal half-life was highly variable (range, 2.8 to 101.3 h) and was not related to the dose given. A secondary peak plasma concentration was seen in five patients, suggesting enterohepatic circulation. The toxicities such as headache, cheilitis, dry skin, and dry eyes were frequent on the weekly schedule but were not dose-limiting. One patient had an elevation of the triglycerides of 2 to 5 times the upper limit of normal; five patients had an elevation of 1.1 to 2 times normal. No objective responses were observed to treatment with 13-cis-RA. Of 20 patients receiving an adequate trial of the drug, 18 showed progression of their cancer, and two had stable disease.
The effect of different doses of 5-aza-2'-deoxycytidine (5-aza-dCyd) or cytarabine (ara-C) on the survival time of mice with intracerebral (ic) L1210 leukemia was compared. CD2F1 mice were given ic inoculation of 10(3) L1210 cells, and chemotherapy was given as a 12-hour iv infusion at various days thereafter. Treatment on Day 6 with increasing doses of 5-aza-dCyd reached a mean maximal percent increase in lifespan (ILS) of 118% at 20 mg/kg, whereas the mean maximal ILS reached for ara-C was about 60% at 1000 mg/kg. When these equitoxic doses of each drug, as determined by body weight loss, were given on Day 3, 4, or 5, 5-aza-dCyd gave greater ILS and more 60-day survivors than ara-C. These data indicate that 5-aza-dCyd is more effective than ara-C against the ic L1210 leukemia.
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5-Aza-2'-deoxycytidine (5-aza-dCyd) is an effective antileukemic agent. In view of the importance for an antileukemic agent to cross effectively the blood-brain-barrier, we studied the plasma and cerebrospinal fluid (CSF) pharmacokinetics of this drug in rabbits and dogs. The 5-aza-dCyd concentrations in biological fluids were determined by bioassay and high-performance liquid chromatography. 5-Aza-dCyd was administered either as an i.v. bolus or as a continuous i.v. infusion following a loading dose. Blood and CSF samples were collected at various time intervals. After an i.v. bolus, the plasma disappearance of 5-aza-dCyd was biphasic with half-lives of 5 and 43 min in rabbits and of 5 and 75 min in dogs. The apparent volume of distribution at steady state was in the order of 800 ml/kg for both species. The total plasma clearance of the drug was 15 ml/min/kg in rabbits and 9 ml/min/kg in dogs. After a 180 min i.v. infusion, 5-aza-dCyd slow disappearance half-lives were of 39 min in rabbits and of 144 min in dogs. The 5-aza-dCyd concentrations attained in the CSF were 27 and 58% of the plateau plasma concentration in rabbits and dogs, respectively. The drug disparition from the CSF followed closely the plasma profile after an i.v. infusion with a somewhat longer half-life. These results showed that 5-aza-dCyd can cross the blood-CSF barrier effectively, producing cytotoxic concentrations in the CSF when given by i.v. infusion.
BACKGROUND: Head and neck squamous cell carcinomas (HNSCC) present variable aggressiveness and chemosensitivity. Because the glutathione (GSH) system and thymidylate synthase (TS) are involved in the resistance to the main drugs used in HNSCC (cisplatin and 5-FU), we studied these systems in tumors and normal mucosae. METHODS: Tumor samples and normal adjacent mucosae were collected from 37 untreated HNSCC patients. GSH and glutathione S-transferase (GST) activity were assayed by spectrophotometry, whereas TS activity and folates were determined by radioassays. RESULTS: Mean GSH levels were higher in tumors (15.2 +/- 8.2 nmol/mg protein) than in mucosae (8.3 +/- 4.1 nmol/mg protein) (p = 0.005, paired t test). GST activity was also higher in tumors (394 +/- 194 nmol/min/mg protein) than in mucosae (261 +/- 132 nmol/min/mg protein) (p = 0.0003). TS activity was markedly higher in tumors (9.2 +/- 21.5 pmol/min/mg protein) compared to that of mucosae (0.9 +/- 1.2 pmol/min/mg protein) (p = 0.0001). Folate levels in tumors and mucosae were similar (1.2 +/- 1.1 and 0.8 +/- 0.9 pmol/mg protein, respectively; p = 0.1, NS). In relation to clinical stage and tumor size, a statistical difference was found in GSH and GST values between tumors and mucosae for stage IV and T3/T4. The increase in tumor TS compared to that of mucosae was significant for all clinical stages, tumor sizes, and nodal involvement. CONCLUSIONS: These data enhance our understanding of the enzymatic systems involved in cisplatin and 5-fluorouracil (5-FU) resistance in HNSCC and normal mucosae and may help to elucidate tumor behavior and interpatient differences in drug sensitivity.
One of the major problems in cancer pharmacology is the prediction of the outcome of treatment in terms of both toxicity and tumor response. Indeed, why is a patient presenting a high toxicity at a standard dose? Also, why is another patient presenting a response to chemotherapy, while another does not respond, even if the same doses and drugs are used? The causes of variability in the response to chemotherapy can be classified in 2 classes, these related to the host, and those related to the tumor. Concerning the host, physiopathological parameters can influence the outcome of treatment e.g. age, sex, kidney and liver functions, plasma protein binding, concomitant treatments, and pharmacogenetics. With regard to the tumor, many factors can also influence chemotherapy e.g. tumor type, localization, volume, aggressiveness, dissemination stage, prior treatments (resistance), biological marker levels, and pharmacogenetic phenotype. Although some progress has been made in the past years concerning the clinical use of some factors responsible for the variability of pharmacological response in oncology, much remains to be done in order to adapt the treatment to a particular patient. Although pharmacogenetic phenotyping has been feasible for some anticancer drugs, this area deserves more effort in the future. Indeed, pharmacogenetic phenotyping of both the patient and the tumor will probably allow to tailor chemotherapy to an individual patient, in order to optimize the patient's chances to obtain a tumor response with minimum systemic toxicity.