CID 6918992

Protein binding of melphalan ranges from 50% to 90%. Serum albumin is the major binding protein, accounting for approximately 40% to 60% of the plasma protein binding, while α1-acid glycoprotein accounts for about 20% of the plasma protein binding. Approximately 30% of melphalan is covalently and irreversibly bound to plasma proteins.

Melphalan possesses cytotoxic, immunosuppressive, and myeloablative activities. Melphalan produces chromosomal aberrations _in vitro_ and _in vivo_; thus, it is considered to be potentially leukemogenic in humans. It also causes dose-limiting bone marrow suppression. The peak mean heart rate increased by 20 bpm from baseline following melphalan 100 mg/m² for two consecutive days in multiple myeloma patients undergoing autologous stem cell transplantation.

Melphalan is an alkylating agent of the bischloroethylamine type. It is believed to be taken up by tumour cells via a neutral amino acid active pathway shared by leucine. Melphalan binds at the N7 position of guanine and induces inter-strand cross-links in DNA, disrupting DNA synthesis or transcription. It can also cause DNA-protein cross-linking and induce lesions in RNA, proteins, and lipids. Melphalan is cytotoxic in resting and rapidly dividing tumour cells.

The absorption of oral melphalan is highly variable concerning both the time to the first appearance of the drug in plasma (range: 0 to 6 hours) and peak plasma concentration (Cmax). The average absolute bioavailability of melphalan ranges from 56% to 93%. High variability in bioavailability may be due to incomplete intestinal absorption, variable first-pass hepatic metabolism, or rapid hydrolysis. Tmax was one hour in patients who received single oral doses of 0.2 mg/kg to 0.25 mg/kg of melphalan. Oral administration of melphalan with a high-fat meal may reduce melphalan exposure (AUC) by 36% to 54%. Mean (± SD) Cmax and AUC0-inf were 5.8 ± 1.5 mcg/mL and 451 ± 109 mcg x min/mL, respectively, following intravenous administration of 100 mg/m2 in multiple myeloma patients.