Phase I trial and pharmacokinetics of trimelamol (N2,N4,N6-trihydroxymethyl-N2,N4,N6-trimethylmelamine)

Trimelamol is an analogue of hexamethylmelamine and pentamethylmelamine which does not require metabolic activation and is sufficiently soluble to allow parenteral administration. A Phase I trial has been performed at the Royal Marsden Hospital in which two schedules of administration have been evaluated, a single i.v. infusion repeated every 3 weeks and 3 daily doses repeated every 3 weeks. Pharmacokinetic analysis was performed at all dose levels on both schedules and a linear correlation was demonstrated between dose and area under the curve. Myelosuppression was dose limiting for single dose administration with a maximum tolerated dose of 2400 mg/m2. Median leukocyte nadirs at 1800, 2100, and 2400 mg/m2 were 3.2, 2.6, and 1.5 x 10(9)/liter. Thrombocytopenia and anemia also occurred but were not dose limiting. Doses greater than 1500 mg/m2 caused WHO grade 3 nausea and vomiting but no acute sedation. Three day administration appeared to be less myelosuppressive, giving a maximum tolerated dose of 1000 mg/m2. Median leukocyte nadirs at 800, 900, and 1000 mg/m2 daily for 3 days were 3.0, 2.3, and 1.5 x 10(9)/liter. Nonhematological toxicities were also less marked on the fractionated schedule. Antitumor effects were observed including 1 complete and 9 partial responses. Demonstration of activity in ovarian cancer has led to further evaluation in this disease using the 3-day schedule at a dose of 800 mg/m2 daily for 3 days.