Bortezomib

Absorption

Following intravenous administration of 1 mg/m2 and 1.3 mg/m2 doses, the mean Cmax of bortezomib were 57 and 112 ng/mL, respectively. In a twice-weekly dosing regimen, the Cmax ranged from 67 to 106 ng/mL at the dose of 1 mg/m2 and 89 to 120 ng/mL for the 1.3 mg/m2 dose. In patients with multiple myeloma, the Cmax of bortezomib followig subcutaneous administration was lower than that of intravenously-administered dose; however, the total systemic exposure of the drug was equivalent for both routes of administration. There is a wide interpatient variability in drug plasma concentrations.

Toxicity

The Lowest published toxic dose (TDLo) in mouse was 5 mg/kg/14D following intraperitoneal administration of an intermittent dose and 1.6 mg/kg/12D following subcutaneous administration of a continuous dose.
The therapeutic dose of bortezomib is individualized in each patient to prevent overdose. Fatal outcomes occurred in humans following the administration of more than twice the recommended therapeutic dose of bortezomib. The symptoms from overdose included the acute onset of symptomatic hypotension and thrombocytopenia. As there is no known antidote for bortezomib overdosage, monitoring of vital signs and appropriate supportive care should be initiated when drug overdosage is suspected. In monkeys and dogs, increased heart rate, decreased contractility, hypotension, and death were observed with the intravenous dose as low as two times the recommended clinical dose on a mg/m2 basis. A case of a slight increase in the corrected QT interval leading to death occurred in dog studies.

Description

Bortezomib (trade name Velcade) is a boronic acid that was approved by the US Food and Drug Administration in 2003 as the first drug to treat multiple myeloma, a type of white blood cell cancer. It is a proteazome blocker that is also used to treat mantle cell lymphoma. Bortezomib passed US$1 million in?sales in 2008. It has several adverse side effects, and?current research is targeting improved proteazome inhibitors.

Description

Bortezomib, a potent ubiquitin proteasome (26S) inhibitor (K_i=0.6 nM), was launched in the US as a treatment for multiple myeloma. This proteasome is required for the proteolytic degradation of the majority of cellular proteins and is present in all cells. It is required for the control of inflammatory processes, cell cycle regulation and gene expression and is a novel target in cancer treatment. Bortezomib is a N-acyl-pseudodipeptidyl boronic acid and formulated as a mannitol ester. Aldehyde containing peptides are also proteasome inhibitors, but lack chiral stability (racemization) and selectivity against other proteases including cysteine proteases. Replacement of the aldehyde moiety by a boronic acid avoids these shortcomings and provides some measure of selective proteasome inhibition relative to many other serine proteases. It is prepared by coupling the pinanediol ester of leucine boronic acid with N-tert-Bocphenylalanine utilizing O-(1H-benzotriazol-1-yl)-N,N,N′,N′-tetramethyluronium tetrafluoroborate (TBTU) as the coupling agent. The tert-Boc protecting group is then cleaved from the dipeptide and pyrazinecarboxylic acid is coupled to form the terminal amide. Hydrolysis of the boronate ester is accomplished via a two-phase transesterification procedure using isobutyl boronic acid and aqueous extraction. In a study of patients who had received at least two prior therapies and demonstrated disease progression on their most recent therapy, about twenty eight percent showed a response to bortezomib. The response lasted a median time of one year. Another trial in 54 patients with relapsed multiple myeloma showed similar responses. It is dosed intravenously at an exposure of 1.3 mg/m²/dose twice weekly for two weeks followed by a 10-day drug-holiday. At therapeutic doses, the plasma drug levels were reported to drop to near detection limits within minutes of intravenous dosing. Based upon an ex vivo proteasome activity assay using blood cells, the pharmacodynamic half-life ranged from 9 to 15 h in patients with advanced malignancies.

The Uses of Bortezomib

Bortezomib is the first proteasome inhibitor to be approved b the US FDA for multiple myeloma, a blood cancer. A reversible inhibitor of the 26S proteasome-a barrel-shaped multiprotein particle found in the nucleus and cytosol of all eukaryotic cells. T

Background

Bortezomib is a dipeptide boronic acid derivative and proteasome inhibitor used to treat multiple myeloma and mantle cell lymphoma. The 26S proteasome is a protein complex that degrades ubiquitinated proteins in the ubiquitin-proteasome pathway: reversible inhibition of the 26S proteasome, leading to cell cycle arrest and apoptosis of cancer cells, is thought to be the main mechanism of action of bortezomib. However, multiple mechanisms may be involved in the anticancer activity of bortezomib.
Bortezomib was first synthesized in 1995. In May 2003, bortezomib became the first anticancer proteasome inhibitor that was approved by the FDA under the trade name VELCADE. Phase I, II, III, and IV clinical trials are undergoing to investigate the therapeutic efficacy of bortezomib in leukemia, myasthenia gravis, systemic lupus erythematosus, rheumatoid arthritis, and solid tumours.

Indications

Bortezomib is indicated for the treatment of adults with multiple myeloma or mantle cell lymphoma.

What are the applications of Application

Bortezomib is a selective and robust 26S proteasome inhibitor and is a boronic acid dipeptide derivative

Pharmacokinetics

Bortezomib works to target the ubiquitin-proteasome pathway, an essential molecular pathway that regulates intracellular concentrations of proteins and promotes protein degradation. The ubiquitin-proteasome pathway is often dysregulated in pathological conditions, leading to aberrant pathway signalling and the formation of malignant cells. In one study, patient-derived chronic lymphocytic leukemia (CLL) cells contained 3-fold higher levels of chymotrypsin-like proteasome activity than normal lymphocytes. By reversibly inhibiting proteasome, bortezomib prevents proteasome-mediated proteolysis. Bortezomib exerts a cytotoxic effect on various cancer cell types in vitro and delays tumour growth in vivo in nonclinical tumour models. Bortezomib inhibits the proteasome activity in a dose-dependent manner. In one pharmacodynamic study, more than 75% of proteasome inhibition was observed in whole blood samples within one hour after dosing of bortezomib.

Metabolism

Bortezomib is primarily metabolized by CYP3A4, CYP2C19, and CYP1A2. CYP2D6 and CYP2C9 are also involved in drug metabolism, but to a smaller extent. Oxidative deboronation, which involves the removal of boronic acid from the parent compound, is the main metabolic pathway. Metabolites of bortezomib are pharmacologically inactive and more than 30 metabolites have been identified in human and animal studies.