Kenneth K. Chan

Warfarin STEREOCHEMICAL ASPECTS OF ITS METABOLISM AND THE INTERACTION WITH PHENYLBUTAZONE

An examination of the metabolic fate of the R and the S isomers of warfarin revealed that the two isomers were metabolized by different routes. R warfarin was oxidized to 6-hydroxywarfarin and was reduced to the (R,S) warfarin alcohol. In contrast, S warfarin was oxidized to 7-hydroxywarfarin and was reduced to the (S,S) warfarin alcohol. S warfarin was also oxidized to 6-hydroxywarfarin. These observations suggested that interactions between warfarin and other drugs might be manifest stereo-specifically, i.e., have a different effect on the isomers of warfarin, so a series of experiments were conducted with each isomer of warfarin, before and after phenylbutazone. The plasma clearance of S warfarin was slowed from 3.1 to 1.1% per h in one subject and from 2.3 to 1.6% per h in another. In contrast, the clearance of R warfarin was increased from 1.5 to 3.0% per h and from 0.9 to 1.6% per h in two subjects after phenylbutazone. The rate of clearance of racemic warfarin was unaffected by phenylbutazone; the depression of the rate of clearance of the S isomer masked the stimulation of the clearance of the R isomer. Since S warfarin is five times more potent an anticoagulant than R warfarin, it is concluded that inhibition of the metabolism of S warfarin provides one mechanism for the augmented anticoagulation which follows phenylbutazone.

Cardiotoxicity of Histone Deacetylase Inhibitor Depsipeptide in Patients with Metastatic Neuroendocrine Tumors

Purpose: This phase II study was undertaken to assess objective response and toxicity of histone deacetylase inhibitor depsipeptide in patients with neuroendocrine tumors. Experimental Design: A total of 15 patients with metastatic neuroendocrine tumors received a 4-hour i.v. infusion of depsipeptide at 14 mg/m2 on days 1, 8, and 15 every 28 days. Tumor response was assessed at 8-week intervals using Response Evaluation Criteria in Solid Tumors. Most patients were chemo-naïve (n = 12) but receiving long-acting octreotide for carcinoid syndrome (n = 11). All patients had Eastern Cooperative Oncology Group performance status of 0 to 1. Results: The study was terminated prematurely due to an unexpected high number of serious cardiac adverse events so the objective response rate could not be determined. A total of 77 doses of depsipeptide with a median of four doses (range, 2-13) per patient were administered. The most common adverse events included nausea (86%), anorexia (73%), vomiting (66%), and fatigue (73%). A sudden death attributed to possible fatal ventricular arrhythmia occurred within 24 hours after the fifth dose of depsipeptide. Furthermore, asymptomatic grade 2 ventricular tachycardia (n = 2) and prolonged QTc (n = 3) probably related to depsipeptide were observed. Plasma depsipeptide levels measured in a subset of patients failed to reveal differences among patients with or without cardiac adverse events. Conclusions: Depsipeptide was associated with a high number of potentially serious cardiac adverse events in patients with metastatic neuroendocrine tumor. As sudden death possibly associated with depsipeptide was observed in this trial, the risks for potentially life-threatening arrhythmia associated with this agent need to be comprehensively evaluated.

Phase I and pharmacologic study of liposomal daunorubicin (DaunoXome).

SummaryWe have completed a phase I and pharmacology study of liposomally-encapsulated daunorubicin (DaunoXome). Of 32 patients entered, 30 were evaluable. No toxicity was encountered at the initial doseescalation steps from 10 to 60 mg/m2. At 80 mg/m2, two patients manifested grade 2 neutropenia. At least grade 3 neutropenia occurred in all patients receiving 120 mg/m2. Alopecia and subjective intolerance were mild. Cardiotoxicity was not observed except for an episode of arrhythmia in a patient with lung cancer and prior radiation. Only one minor objective response was observed in this population of refractory solid tumors. Pharmacokinetics differed from those of the free drug with no detection of daunorubicinol. We recommend future phase II studies with a dose of 100 mg/m2 in previously treated and 120 mg/m2 of DaunoXome in previously untreated patients with solid tumors.

Distribution of adriamycin in cancer patients. Tissue uptakes, plasma concentration after IV and hepatic IA administration

Twenty patients with solid tumors received 30 mg/M2 of adriamycin. Various tissue samples were intra‐operatively obtained from 18 patients, about 1.5–5 hours after an intravenous (IV) bolus dose. Normal liver showed the highest levels of adriamycin uptake (2.3–19.8 μg/g); lymph nodes were second; muscle and bone marrow, next; fat and skin had the lowest adriamycin uptake (0.04–0.40 μg/g). Tumor tissue, excluding that with much necrosis and hemorrhaging, had adriamycin concentrations which approximated those of the liver (1.1–9.2 μg/g). Six patients, all with hepatic malignancies, had prolonged plasma concentration studies after IV administration; 5 also had adriamycin administered directly into the hepatic artery catheter. Adriamycin‐plasma‐time courses were similar, whether the drug was administered by bolus directly into the hepatic artery or peripheral vein. The concentration of metabolites after hepatic intraarterial administration was definitely higher than that after IV administration. Patients with hepatic dysfunction had delayed plasma clearance and secondarily elevated levels approximately 160 and 300 minutes after administration.

Path model of multidimensional compliance with cancer therapy.

Patients newly diagnosed with hematologic malignancies were followed for a 6-month treatment period to assess compliance with three regimen requirements for cancer therapy: anti-neoplastic medication self-administered intermittently, supportive medication self-administered daily, and monthly clinic appointments. The effect on compliance of three intervention packages (some combination of education, shaping of pill-taking behavior, and home restructuring) and the extent that patient satisfaction, knowledge, and uncertainty about illness-related events mediated the effects of the interventions were also examined. Blood levels of the drugs and self-report measures indicated that compliance with daily pill taking was higher for each intervention group compared to a control group. Similar results were obtained for compliance with clinic appointments. No improvement in intermittent self-medication was found. Although each intervention package increased patient knowledge and satisfaction, path analyses demonstrated that knowledge did not affect any aspect of compliance, whereas satisfaction was associated with increased appointment keeping only. Daily pill taking was influenced directly by the behavioral components of the interventions. Uncertainty did not influence compliance but was associated with depression, which was negatively correlated with intermittent self-medication.

Carbon-13 nuclear magnetic resonance studies of coumarin and related compounds

Fourier-transform ^(13)C NMR spectra of nine coumarinoid compounds of medicinal interest are reported. All of the carbon resonances are assigned with the aid of various spectral techniques and stable isotopic labeling. The substituent effects on the chemical shifts in several systems are also discussed.

Preclinical pharmacokinetics and stability of isophosphoramide mustard

Stability and preclinical pharmacokinetics of isophosphoramide mustard (IPM), an active metabolite of ifosphamide, were investigated using analytical methods developed in this laboratory. For stability evaluation of IPM we used a rapid, high-pressure liquid chromatographic (HPLC) method by which IPM is analyzed directly from aqueous solutions without derivatization on a 10-μm C-18 reversed-phase column with theophylline as the internal standard. IPM in sodium phosphate buffers was found to undergo pH-dependent first-order degradations. At pH 7.4 and 38° C, the IPM solution showed a half-life of 45 min. A gas chromatographic-mass spectrometry (GC/MS) method for the analysis of IPM in plasma was also developed. This method utilized solid-phase extraction with deuterium-labeled IPM as the internal standard. The routine detection limit for the assay was 50 ng/ml with within-run and between-run coefficients of variation of 6% and 11%, respectively. By this method, stability of IPM in plasma and in RPMI 1640 tissue culture medium was evaluated, and its pharmacokinetics in the Sprague-Dawley rat following i.v. administration at 40 mg/kg were investigated. IPM was found to be more stable in these media, with half-lives in the range of 100 min. IPM plasma pharmacokinetics were found to decline monoexponentially with terminal halflives ranging from 6.8 to 18.7 min and total clearance between 6.0 and 18.3 ml/min. Plasma protein binding of IPM was found to be 55%, and the partition ratio between plasma and red blood cells of 4.9 to 1, respectively. Cytotoxicity of IPM to L1210 cells was evaluated, and the results indicated that the IC50 with 1-h and 4-h exposure was 33 and 15 μm, respectively. Based on these data, IPM plasma levels in the rat declined below the IC50 in about 1 h at this dose. More frequent dosing or infusion may be necessary to maintain adequate drug levels for antitumor activity when IPM is administered directly.

Adriamycin and methyl‐CCNU combination therapy in hepatocellular carcinoma: Clinical and pharmacokinetic aspects

Twenty‐one patients with unresectable hepatocellular carcinoma (hepatoma) were treated with Adriamycin (15–45 mg/m2 q 21 D) and methyl‐CCNU (75–150 mg/m2 q 63 D) with dosage adjusted for hepatic dysfunction. Objective response frequency was 14% with all responses occurring in patients with normal pretreatment bilirubin levels. Median survival of all patients was 87 days. Initial bilirubin levels greater than 2 mg/dl predicted for decreased survival (median 30 days vs. 115 days, P < 0.05). Only moderate hematologic toxicity was observed. Plasma profiles of Adriamycin and adriamycinol were determined during 11 courses of Adriamycin administration in seven of these patients. Despite moderately elevated transaminase levels (all cases) and bilirubin levels (three cases), plasma Adriamycin profiles in hepatoma patients were not elevated (terminal half‐life of 30 hours) and were indistinguishable from that of non‐hepatoma patients with normal liver functions. However, delayed appearance of peak levels and prolongation of terminal half‐lives were routinely observed for adriamycinol, a major metabolite of Adriamycin. This resulted in a significant increase in the CXT (concentration X time) ratio of adriamycinol/Adriamycin in hepatoma patients compared with non‐hepatoma patients (2.36 ± 2.12 vs 0.76 ± 0.31, P < 0.05). We conclude that the combination of relatively mild toxicity and normal Adriamycin disposition indicates unusual tolerance to Adriamycin therapy for patients with hepatoma and cirrhosis. As a result, severe dosage adjustments of Adriamycin may not be indicated for all such patients having only moderate hepatic dysfunction.

Phase I and pharmacologic evaluation of intraperitoneal 5-fluoro-2′-deoxyuridine

SummaryIntraperitoneal (i.p.) 5-fluoro-2′-deoxyuridine (Floxuridine, FUdR, FdUrd) was evaluated in a phase I study at a starting level of 500 mg given on 1 day in 2 I 1.5% dialysate. Escalations within patients were allowed every other cycle. A total of 23 patients (age, 32–78 years) received 108 treatment courses. Local tolerance at all dose levels was excellent, with no cases of drug-related peritonitis being observed. Nausea and vomiting increased in severity in relation to dose and was universal at >3,000 mg ×3 days. One patient each developed grade 1 mucositis as well as diarrhea at a dose of 3,000 mg×3 days and leukopenia and thrombocytopenia at 5,000 mg×3 days. Peritoneal fluid (PF) and plasma (PL) FdUrd profiles were monitored by an HPLC method in 13 subjects, with 7 being studied serially at 2–4 increment doses for up to 6 h. Profiles that exhibited apparent linear pharmacokinetics gave PF drug levels 2–4 logs higher than the PL counterparts, with the latter essentially declining in parallel to the former, indicating that the disposition of FdUrd from the peritoneal compartment is rate-determining. The mean terminal half-life for PF FdUrd was found to be 115 min and mean peritoneal clearance was 25 ml/min. The vast differences in drug levels and AUC found between the PF and the PL profiles suggests a high systemic clearance of FdUrd, which was confirmed in two patients receiving 2 g FdUrd by short i.v. infusion. A disproportionate increase in the plasma FdUrd levels and the corresponding AUC values was found with increasing dose, suggesting a disproportionate increase in the systemic partitioning of FdUrd when doses were escalated within a patient. Substantial levels of peritoneal 5-fluorouracil (FUra) were also detected in most of the subjects. Thus, FdUrd was found to have several desirable properties for i.p. administration: (1) a 2- to 4-log pharmacologic advantage, (2) the absence of local toxicities, and (3) a favorable antitumor spectrum and some evidence of antitumor effects in this phase I and pharmacology study. A 3,000-mg dose given in 2 l 1.5% dialysate for 3 consecutive days exhibited antitumor activity and produced no systemic toxicity except nausea and vomiting, which was controlled by antiemetics. This dose schedule is therefore recommended for phase II trials directed against small-volume disease in the peritoneal cavity, such as may be found in some stages of ovarian and gastrointestinal cancers. In addition, it is suitable for further exploration as a part of regimens including systemic therapy or drugs that modulate the action of fluoropyrimidines.

Quantitative thin-layer chromatography: thin-film fluorescence scanning analysis of adriamycin and metabolites in tissue.

A rapid, non-hydrolytic thin-film fluorescence scanning method is described for the quantitation of adriamycin and metabolites in tissues. Adriamycin, with daunomycin added as the internal standard, was extracted from tissue homogenate which contained 500 micrograms of oxalic acid, with ice-cold 0.5 N hydrochloric acid--85% isopropanol, separated by thin-layer chromatography, and quantitated in situ via a fluorescence scanning technique. This method has a sensitivity to 0.05 microgram per gram of tissue.