In this article, we will discuss Pralatrexate (Mechanism of Action). So, let’s get started.
Mechanism of Action
Pralatrexate is a folate analogue metabolic inhibitor that competitively inhibits dihydrofolate reductase. It is also a competitive inhibitor for polyglutamylation by the enzyme folylpolyglutamyl synthetase. This inhibition results in the depletion of thymidine and other biological molecules the synthesis of which depends on single carbon transfer.
Pharmacokinetics
Absorption
The pharmacokinetics of pralatrexate administered as a single agent at a dose of 30 mg/m2 administered as an intravenous push over 3-5 minutes once weekly for 6 weeks in 7-week cycles have been evaluated in 10 patients with PTCL. The total systemic clearance of pralatrexate diastereomers was 417 mL/min (S-diastereomer) and 191 mL/min (R-diastereomer). The terminal elimination half-life of pralatrexate was 12-18 hours (coefficient of variance (CV) = 62-120%). Pralatrexate total systemic exposure (AUC) and maximum plasma concentration (Cmax) increased proportionally with dose (dose range 30-325 mg/m2, including pharmacokinetics data from high dose solid tumor clinical studies). The pharmacokinetics of pralatrexate did not change significantly over multiple treatment cycles, and no accumulation of pralatrexate was observed.
Distribution
Pralatrexate diastereomers showed a steady-state volume of distribution of 105 L (S-diastereomer) and 37 L (R-diastereomer). In vitro studies indicate that pralatrexate is approximately 67% bound to plasma proteins. In in vitro studies using MDR1-MDCK and Caco-2 cell systems, pralatrexate was not a substrate for P-glycoprotein (Pgp)-mediated transport nor did it inhibit Pgp-mediated transport.
Metabolism
In vitro studies using human hepatocytes, liver microsomes and S9 fractions, and recombinant human CYP450 isozymes showed that pralatrexate is not significantly metabolized by the phase I hepatic CYP450 isozymes or phase II hepatic glucuronidases. In vitro studies indicated that pralatrexate has low potential to induce or inhibit the activity of CYP450 isozymes.
Excretion
A mass balance study has not been performed. The mean fraction of unchanged pralatrexate diastereomers excreted in urine following a pralatrexate dose of 30 mg/m2 administered as an intravenous push over 3-5 minutes was 31 (S-diastereomer) (CV = 47%) and 38% (R-diastereomer) (CV = 45%), respectively