The precise mechanism by which HEXALEN exerts its cytotoxic effect is unknown, although a number of theoretical possibilities have been studied. Structurally, HEXALEN resembles the alkylating agent triethylenemelamine, yet in vitro tests for alkylating activity of HEXALEN and its metabolitics have been negative. HEXALEN has been demonstrated to be efficacious for certain ovarian tumors resistant to classical alkylating agents. Metabolism of altretamine is a requirement of cytotoxicity. Synthetic monohydroxymethylmelamines, and products of altretamine metabolism, in vitro and in vivo, can form covalent adducts with tissue macromolecules including DNA, but the relevance of these reactions to antitumor activity is unknown.

HEXALEN is well-absorbed following oral administration in humans, but undergoes rapid and extensive demethylation in the liver, producing variation in altretamine plasma levels. The principal metabolites are pentamethylmelamine and tetramethylmelamine.

Pharmacokinetic studies were performed in a limited number of patients and should be considered preliminary. After oral administration of HEXALEN to 11 patients with advanced ovarian cancer in doses of 120-300 mg/m², peak plasma levels (as measured by gas-chromatographic assay) were reached between 0.5 and 3 hours, varying from 0.2 to 20.8 mg/l. Half-life of the ß-phase of elimination ranged from 4.7 to 10.2 hours. Altretamine and metabolites show binding to plasma proteins. The free fractions of altretamine, pentamethylmelamine and tetramethylmelamine are 6%, 25% and 50% respectively.

Following oral administration of ¹⁴C-ring-labeled altretamine (4 mg/kg), urinary recovery of radioactivity was 61% at 24 hours and 90% at 72 hours. Human uninary metabolites were N-demethylated homologues of altretamine with <1% unmetabolized altretamine excreted at 24 hours.

After intraperitoneal administration of ¹⁴C-ring-labeled altretamine to mice, tissue distribution was rapid in all organs, reaching a maximum at 30 minutes. The excretory organs (liver and kidney) and the small intestine showed high concentrations of radioactivity, whereas relatively low concentrations were found in other organs, including the brain.

There have been no formal pharmacokinetic studies in patients with compromised hepatic and/or renal function, though HEXALEN has been administered both concurrently and following nephrotoxic drugs such as cisplatin.

HEXALEN has been administered in 4 divided doses, with meals and at bedtime, though there is no pharmacokinetic data on this schedule nor information from formal interaction studies about the effect of food on its bioavailability or pharmacokinetics.

In two studies in patients with persistent or recurrent ovarian cancer following first-line treatment with cisplatin and/or alkylating agent-based combinations, HEXALEN was administered as a single agent for 14 or 21 days of a 28 day cycle. In the 51 patients with measurable or evaluable disease, there were 6 clinical complete responses, 1 pathologic complete response, and 2 partial responses for an overall response rate of 18%. The duration of these responses ranged from 2 months in a patient with a palpable pelvic mass to 36 months in a patient who achieved a pathologic complete response. In some patients, tumor regression was associated with improvement in symptoms and performance status.

Bookmark this page: