Relative Contributions of the Five Major Human Cytochromes P450, 1a2, 2c9, 2c19, 2d6, and 3a4, to the Hepatic Metabolism of the Proteasome Inhibitor Bortezomib

Abstract

ABSTRACT:VELCADE (bortezomib, PS-341), reversibly inhibits the 20S proteasome and exhibits cytotoxic and antitumor activities. Pretreatment of cancer cells with bortezomib increases the chemosensitivity of these cells, suggesting that bortezomib may be used in combination chemotherapy. The relative contributions of the five major human cytochromes P450 (P450s), 1A2, 2C9, 2C19, 2D6, and 3A4 (the focus of the present study), to the metabolism of bortezomib are an important aspect of potential drug interactions. Relative activity factor (RAF), chemical inhibition, and immunoinhibition using monoclonal antibodies were three approaches employed to determine the relative contributions of the major human P450s to the net hepatic metabolism of bortezomib. RAFs for the P450 isoform-selective substrates were determined; the ratio of the rate of metabolism of bortezomib with cDNA-expressed P450s versus rate of metabolism with human liver microsomes was normalized with respect to the RAF for each P450 isoform to determine the percentage contributions of the P450s to the net hepatic metabolism of bortezomib. CYP3A4 followed by CYP2C19 were determined to be the major contributors to the metabolism of bortezomib. Chemical inhibition and immunoinhibition confirmed that CYP3A4 and CYP2C19 were the major P450s responsible for the hepatic metabolism of bortezomib. The studies were conducted with 2 M bortezomib, and the disappearance of bortezomib, rather than appearance of a specific metabolite, was quantified to determine the contributions of the P450s to the overall hepatic metabolism of bortezomib in humans.Boronic acids as protease inhibitors were first synthesized in the early 1970s and were demonstrated to act as potent transition state analogs of serine proteases (Koehler and Leinhard, 1971;Philipp and Bender, 1971;Kettner and Shenvi, 1984). Throughout the 1980s, peptide boronic acids were shown to be effective inhibitors of trypsin, chymotrypsin, ␣-lytic protease, pancreatic elastase, leukocyte elastase, thrombin, and ␤-lactamases (Kettner and Shenvi, 1984;Crompton et al., 1988) and have been explored for use as therapeutic agents in various disease states (Snow and Bachovchin, 1995;Groziak, 2001). More recently, peptidyl boronic acids were demonstrated as potent proteasome inhibitors, and antitumor and anti-inflammatory efficacy was observed both in vitro and in animal models (Adams et al., 1998). The approval of VELCADE (bortezomib, PS-341; Fig. 1), a dipeptidyl boronic acid, by the United States Food and Drug Administration in 2003 for the treatment of relapsed refractory multiple myeloma made it the first boronic acid and the first in a new class of drugs, proteasome inhibitors, to be marketed as a therapeutic agent.Bortezomib, an N-pyrazinylcarbonylated derivative of the dipeptide boronic acid Phe-Leu-B(OH) 2 , is a potent, selective, and reversible inhibitor (K i ϳ 0.62 nM) of the 26S proteasome in mammalian cells (Adams et al., 1998). The molecular mechanisms by which bortezomib exerts its effects include inhibition...

Phase I and Pharmacokinetic Study of Bortezomib in Combination with Idarubicin and Cytarabine in Patients with Acute Myelogenous Leukemia

“…We therefore sought to define the pharmacokinetics of bortezomib when given in this regimen. Because anthracyclines are metabolized by an aldoketoreductase (34) and cytarabine by cytidine deaminase (35), their pharmacokinetics are unlikely to be altered by bortezomib (36), which is hepatically metabolized by cytochrome P450 enzymes (37,38). Therefore, the pharmacokinetic studies were limited to that of bortezomib.…”

Novel Therapeutic Agents for the Management of Patients with Multiple Myeloma and Renal Impairment

“…The pharmacokinetics of bortezomib is not affected by the degree of renal impairment, and therefore dosing adjustments are not necessary for patients with renal insufficiency, including patients requiring dialysis (57). This is because the primary metabolic pathway of bortezomib, as shown in in vitro studies, is oxidative deboronation by hepatic cytochrome P450 enzymes (57)(58)(59), mainly CYP3A4, CYP2C19, and CYP1A2 (57,59,60). U.S. Food and Drug Administration (FDA) approval of the labeling regarding the use of bortezomib in patients with renal impairment was based on the findings of a U.S. National Cancer Institute-sponsored dose-escalating and pharmacologic study (61).…”

Effect of CYP2C19 and CYP3A4 gene polymorphisms on the efficacy of bortezomib-based regimens in patients with multiple myeloma

“…There was no significant effect of CYP2C19 genotype on the response to treatment. CYP3A4 is considered to be a major contributor to the metabolism of bortezomib (5). In the present study, six patients were found to carry mutations in the CYP3A4 gene.…”

“…A previous study identified the percentage of each isoform to be 69.8, 33.5, 23.4, 15.8 and 13.6%, respectively (5). CYP3A4 and CYP2C19 are considered to be the principal metabolic enzymes for the inactivation of bortezomib (5).…”