Introduction
Pertuzumab is a recombinant humanized monoclonal antibody that targets the HER2 receptor by binding to its extracellular dimerization domain. It inhibits HER2 signaling and prevents receptor dimerization, thereby suppressing the growth and survival of HER2-positive cancer cells.
Pertuzumab is used in combination with trastuzumab and chemotherapy for the treatment of HER2-positive breast cancer, including metastatic, neoadjuvant, and adjuvant settings. Combination therapy has been shown to improve treatment outcomes and reduce the risk of disease recurrence in appropriate patients.
Uses
Pertuzumab is an antineoplastic agent used in the treatment of HER2-positive metastatic breast cancer in combination with other antineoplastic agents.
Pertuzumab is indicated for intravenous administration in combination with trastuzumab and docetaxel for the treatment of patients with HER2-positive metastatic breast cancer who have not received prior anti-HER2 therapy or chemotherapy for metastatic disease. It is also indicated in combination with trastuzumab and other chemotherapies for the neoadjuvant treatment of HER2-positive locally advanced, inflammatory, or early-stage breast cancer as part of a complete treatment regimen and as adjuvant treatment in patients with HER2-positive early-stage breast cancer at high risk of recurrence.
Pertuzumab is also indicated for subcutaneous injection - in combination with trastuzumab and hyaluronidase - in the treatment of HER2-positive breast cancers in adults.
Associated Conditions
Pharmacodynamics
Pertuzumab exerts its antineoplastic effects by binding to and inhibiting the activity of HER2, an oncogene that has been implicated in the formation of numerous cancers. As with other therapeutic monoclonal antibodies, pertuzumab has a relatively long duration of action necessitating dosing every 3 weeks. Drugs that block HER2 activity, including pertuzumab, have been implicated in the development of cardiotoxicity (specifically left ventricular dysfunction) - a baseline assessment of left ventricular ejection fraction (LVEF) should be conducted prior to beginning therapy with pertuzumab and at regular intervals throughout therapy to ensure LVEF remains within normal limits. Consider indefinite suspension of therapy if LVEF declines and does not improve.
Mechanism of Action
Human epidermal growth factor receptor-2 (HER2) is a tyrosine kinase receptor that plays an integral role in cell proliferation, differentiation, and survival. HER2 becomes active following dimerization with another HER2 receptor, another member of the HER protein family (e.g. HER3), or with a ligand - this dimer then phosphorylates and activates numerous intracellular signaling proteins, initiating signal transduction via pathways that include the Ras/mitogen-activated protein kinase pathway, the phosphatidylinositol 3' kinase (PI3K)/Akt pathway, and then Janus kinases/signal transducer and activator transcription pathway. HER2 is also a known oncogene - it is overexpressed or gene-amplified (i.e. HER2-positive) in approximately 20% of breast cancers and these cancers carry a generally poorer prognosis than HER2-negative breast cancers.
Pertuzumab targets the extracellular dimerization domain (subdomain II) of HER2, thereby inhibiting ligand-initiated intracellular signaling via the MAP kinase and PI3K pathways. Inhibition of these pathways results in inhibition of cell growth and the initiation of apoptosis, respectively. Pertuzumab also appears to mediate antibody-dependent cell-mediated cytotoxicity.
Absorption
Intravenously administered pertuzumab, given as a loading dose of 840mg followed by a maintenance dose of 420mg every 3 weeks, reaches steady-state concentration following the first maintenance dose. In its subcutaneous formulation, in combination with [hylauronidase], the absolute bioavailability of pertuzumab is approximately 0.7 and the median Tmax is 4 days. This subcutaneous formulation leverages the benefits of co-administration with hyaluronidase - this enzyme breaks down hylauronic acid, thereby decreasing the viscosity of the extracellular matrix (ECM) and allowing for greater bioavailability with subcutaneous administration.
Volume of Distribution
The average steady-state volume of distribution following intravenous administration is 3.53 - 7.5 L.
Half Life
The median half-life of pertuzumab was determined to be 18 days based on a population pharmacokinetic analysis.
Clearance
The median clearance of pertuzumab was determined to be 0.24 L/day based on a population pharmacokinetic analysis.
Toxicity
There are no data regarding overdose of pertuzumab. Single doses higher than 25 mg/kg have not been tested. Symptoms of overdose are likely to be consistent with pertuzumab's adverse effect profile, and may therefore involve significant diarrhea, alopecia, neutropenia, nausea, fatigue, rash, and/or peripheral neuropathy. Pertuzumab has been associated with the development of left ventricular dysfunction (i.e. cardiotoxicity) that may be exacerbated in instances of overdose.
Food Interactions
No interactions found.
Dosage
HER2 testing: Perform using FDA-approved tests by laboratories with demonstrated proficiency.
The initial Pertuzumab dose is 840 mg administered as a 60-minute intravenous infusion, followed every 3 weeks thereafter by 420 mg administered as a 30 to 60 minute intravenous infusion.
MBC: Administer Pertuzumab, trastuzumab, and docetaxel by intravenous infusion every 3 weeks.
Neoadjuvant: Administer Pertuzumab, trastuzumab, and chemotherapy by intravenous infusion preoperatively every 3 weeks for 3 to 6 cycles.
Adjuvant: Administer Pertuzumab, trastuzumab, and chemotherapy by intravenous infusion postoperatively every 3 weeks for a total of 1 year (up to 18 cycles).
