L-Eflornithine is an irreversible ornithine decarboxylase (ODC) inhibitor with a KD of 1.3±0.3 μM, and a Kinact of 0.15±0.03 min-1. L-Eflornithine monohydrochloride (L-DFMO monohydrochloride) is an enantiomer of Eflornithine.

Ornithine decarboxylase，ODC:(kd)1.3±0.3 µM

Treatment of human colon tumour-derived HCT116 cells with either L-Eflornithine or D- Eflornithine decreases the cellular polyamine contents in a concentration-dependent manner. The enantiomers display different potencies in vitro, with the L-enantiomer having up to a 20-fold higher affinity for the target enzyme ornithine decarboxylase. ?The L-Eflornithine also appears to be more potent in cultured T.brucei gambiense parasites.Eflornithine (D/L-DFMO) is an inhibitor of ODC, the first enzyme in eukaryotic polyamine biosynthesis.?Both enantiomers of Eflornithine (DFMO) irreversibly inactivate ODC.?Both Eflornithine enantiomers (L-Eflornithine and D-Eflornithine) suppress ODC activity in a time- and concentration-dependent manner.?The inhibitor dissociation constant (KD) values for the formation of enzyme-inhibitor complexes are 28.3±3.4, 1.3±0.3 and 2.2±0.4 μM respectively for D-Eflornithine, L-Eflornithine and Eflornithine.?The inhibitor inactivation constants (Kinact) for the irreversible step were 0.25±0.03, 0.15±0.03 and 0.15±0.03 min-1 respectively for D-Eflornithine, L-Eflornithine and Eflornithine.

The typical oral clearances of L-Eflornithine and D-Eflornithine are 17.4 and 8.23 liters/h, respectively. L-Eflornithine, being more potent, is present at significantly lower concentrations in both plasma and cerebrospinal fluid (CSF) compared to D-Eflornithine. On average, plasma concentrations of L-Eflornithine are 52% of those of the D-enantiomer.