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Notes: Abstract  To define a maximum tolerable dose, chloroquinoxaline sulfonamide (CQS) was given as a 1-h infusion every 28 days to cancer patients for whom no effective standard therapy was available. Doses were escalated in cohorts of at least three patients each. Plasma for characterization of the pharmacokinetics of free and total CQS was obtained during and after the initial infusion and, when possible, during and after subsequent infusions of CQS if the dose had been reduced. A total of 101 courses of CQS in 55 patients were evaluated. Dose levels ranged from 18 to 3,700 mg/m2. The dose-limiting toxicity was hypoglycemia, first recognized at the 3,700-mg/m2 dose. When dose-limiting hypoglycemia was recognized, patients were entered at successively lower doses, with close monitoring of plasma glucose and insulin concentrations being done in 26 patients. Grade 1–3 hypoglycemia occurred within 4 h of the termination of CQS infusion and cleared by 24 h. Symptomatic hypoglycemia was more frequent at doses of CQS above 1,000 mg/m2. Concomitant administration of 5% glucose did not ameliorate the hypoglycemia associated with CQS doses of 〉1,000 mg/m2. The total calorie intake, percentage of ideal body weight, or percentage of weight lost did not explain the incidence or severity of hypoglycemia in 12 patients in whom these data were obtained. Cardiac tachyarrhythmias occurred in 7 patients who received CQS at doses of ≥1, 000 mg/m2, and tachyarrhythmia was associated with hypoglycemia in 3 patients. Other toxicities were sporadic, but the frequency of toxicity was higher at CQS doses of ≥1, 000 mg/m2. These toxicities included fever, rash, lightheadedness, leukopenia, thrombocytopenia, alopecia, diarrhea, nausea, and vomiting. All toxicities were reversible. Mean peak plasma [CQS] and AUC increased with dose, with a suggestion that peak plasma [CQS] plateaued at higher doses. The decline in plasma [CQS] was fitted to a three-compartment, open linear model. The terminal half-life ranged from 28 to 206 h. Total body clearance ranged from 44 to 881 ml/h with no evidence of saturation. Urinary excretion of the parent compound in 24 h averaged 〈5%. CQS not bound to plasma protein (free CQS) comprised 1%–17% of total plasma CQS and was not related to dose. A relationship was defined between the magnitude of hypoglycemia and CQS pharmacokinetic parameters. The percentage of decrease in plasma [glucose], i.e., (predose [glucose]-nadir [glucose]/predose [glucose])×100, correlated with both free and total peak plasma [CQS]. The relationship was described by the Hill equation: Effect=(Emax) (peak) H/(peak 50)H+(peak) H, where the maximal effect (Emax) equals the maximal possible percentage of decrease in plasma [glucose] equals 100%, peak 50 is the peak total [CQS] at which E is half-maximal (326 mg/l), and H is the Hill constant, a measure of the sigmoidicity of the relationship (1.06). The relationship fit the data precisely with a mean absolute error (MAE) of 10.42 and was unbiased with a mean error (ME) of −0.06. The recommended phase II dose of CQS is 1, 000 mg/m2. Because the magnitude of hypoglycemia after CQS administration is related to peak plasma [CQS], repetitive CQS doses of ≤1,000 mg/m2 would probably be tolerated better than single large doses of equivalent intensity.

Notes: Abstract  A phase I trial of all-trans-retinoic acid (ATRA) was conducted to establish the maximum tolerable dose (MTD) of ATRA given once daily to patients with solid tumors. Cancer patients for whom no standard therapy was available were treated with ATRA once daily. Doses were escalated in cohorts of at least three patients. The pharmacokinetics of ATRA were assessed on day 1 for all patients and weekly for 31 patients who received doses of ≥110 mg/m2 per day. Patients were followed for toxicity and response. Correlations of toxicity frequency and grade with pharmacokinetic parameters were sought. In addition, correlation of changes in ATRA pharmacokinetics with the concentration of ATRA metabolites in plasma were sought. A total of 49 patients received ATRA at doses ranging from 45 to 309 mg/m2 per day. Hypertriglyceridemia was dose-limiting at 269 mg/m2 per day. Other frequent toxicities included mucocutaneous dryness and headache. With chronic dosing, plasma ATRA concentrations fell in 59% of patients. Stable, low, or variable [ATRA] were seen in 16%, 6%, and 16% of patients respectively. Age, gender, smoking, or concurrent medication did not correlate with the pharmacokinetic pattern. Severe toxicities tended to occur with initial peak [ATRA] of ≥0.5 μg/ml (1.7 μM), and the toxicity frequency did not change if [ATRA] decreased with continued dosing. No consistent change in 4-oxo-ATRA or retinoid glucuronide concentrations was observed with decreases in plasma [ATRA]. The recommended once-daily ATRA dose is 215 mg/m2, although significant interpatient variability is observed in toxicity and plasma retinoid concentrations. Although not statistically significant, more frequent and severe toxicity tended to occur in patients with higher plasma peak ATRA concentrations. Other factors, such as responses at target tissues, may be at least as important as the plasma ATRA concentration in predicting toxicity and/or response.