VECTIBIX® (panitumumab) Injection
Panitumumab is an epidermal growth factor receptor (EGFR) antagonist for intravenous use. Panitumumab is a human IgG2 kappa monoclonal antibody with an approximate molecular weight of 147 kDa that is produced in genetically engineered mammalian (Chinese hamster ovary) cells.
Vectibix (panitumumab) Injection for intravenous use is a sterile, colorless solution with a pH range of 5.6 to 6.0, which may contain a small amount of visible translucent-to-white, amorphous, proteinaceous particles. Each single-dose 5 mL vial contains 100 mg of panitumumab, 34 mg sodium acetate, 29 mg sodium chloride, and Water for Injection, USP. Each single-dose 20 mL vial contains 400 mg of panitumumab, 136 mg sodium acetate, 117 mg sodium chloride, and Water for Injection, USP.
Indications and usage
Vectibix is an epidermal growth factor receptor (EGFR) antagonist indicated for the treatment of wild-type RAS (defined as wild-type in both KRAS and NRAS as determined by an FDA-approved test for this use) metastatic colorectal cancer (mCRC):
- In combination with FOLFOX for first-line treatment.
- As monotherapy following disease progression after prior treatment with fluoropyrimidine, oxaliplatin, and irinotecan-containing chemotherapy.
Limitation of Use: Vectibix is not indicated for the treatment of patients with RAS-mutant mCRC or for whom RAS mutation status is unknown.
Mechanism of Action
The EGFR is a transmembrane glycoprotein that is a member of a subfamily of type I receptor tyrosine kinases, including EGFR, HER2, HER3, and HER4. EGFR is constitutively expressed in normal epithelial tissues, including the skin and hair follicle. EGFR is overexpressed in certain human cancers, including colon and rectum cancers. Interaction of EGFR with its normal ligands (e.g., EGF, transforming growth factor-alpha) leads to phosphorylation and activation of a series of intracellular proteins, which in turn regulate transcription of genes involved with cellular growth and survival, motility, and proliferation.
KRAS (Kirsten rat sarcoma 2 viral oncogene homologue) and NRAS (Neuroblastoma RAS viral oncogene homologue) are highly related members of the RAS oncogene family. Signal transduction through the EGFR can result in activation of the wild-type KRAS and NRAS proteins; however, in cells with activating RAS somatic mutations, the RAS-mutant proteins are continuously active and appear independent of EGFR regulation.
Panitumumab binds specifically to EGFR on both normal and tumor cells, and competitively inhibits the binding of ligands for EGFR. Nonclinical studies show that binding of panitumumab to the EGFR prevents ligand-induced receptor autophosphorylation and activation of receptor-associated kinases, resulting in inhibition of cell growth, induction of apoptosis, decreased proinflammatory cytokine and vascular growth factor production, and internalization of the EGFR. In vitro assays and in vivo animal studies demonstrate that panitumumab inhibits the growth and survival of selected human tumor cell lines expressing EGFR.
Dosage and administration
Patient Selection: Prior to initiation of treatment with Vectibix, assess RAS mutational status in colorectal tumors and confirm the absence of a RAS mutation in exon 2 (codons 12 and 13), exon 3 (codons 59 and 61), and exon 4 (codons 117 and 146) of both KRAS and NRAS. Information on FDA-approved tests for the detection of RAS mutations in patients with metastatic colorectal cancer is available at: http://www.fda.gov/CompanionDiagnostics.
Recommended Dose: The recommended dose of Vectibix is 6 mg/kg, administered as an intravenous infusion over 60 minutes, every 14 days. If the first infusion is tolerated, administer subsequent infusions over 30 to 60 minutes. Administer doses higher than 1000 mg over 90 minutes
Appropriate medical resources for the treatment of severe infusion reactions should be available during Vectibix infusions
Warnings and precautions
Dermatologic and Soft Tissue Toxicity: In Study 20020408, dermatologic toxicities occurred in 90% of patients and were severe (NCI-CTC grade 3 and higher) in 15% of patients with mCRC receiving Vectibix. The clinical manifestations included, but were not limited to, acneiform dermatitis, pruritus, erythema, rash, skin exfoliation, paronychia, dry skin, and skin fissures.
Monitor patients who develop dermatologic or soft tissue toxicities while receiving Vectibix for the development of inflammatory or infectious sequelae. Life-threatening and fatal infectious complications including necrotizing fasciitis, abscesses, and sepsis have been observed in patients treated with Vectibix.
Increased Tumor Progression, Increased Mortality, or Lack of Benefit in Patients with RAS-Mutant mCRC: Vectibix is not indicated for the treatment of patients with colorectal cancer that harbor somatic RAS mutations in exon 2 (codons 12 and 13), exon 3 (codons 59 and 61), and exon 4 (codons 117 and 146) of either KRAS or NRAS and hereafter is referred to as “RAS”
Electrolyte Depletion/Monitoring: Progressively decreasing serum magnesium levels leading to severe (grade 3-4) hypomagnesemia occurred in up to 7% (in Study 20080763) of patients across clinical trials. Monitor patients for hypomagnesemia and hypocalcemia prior to initiating Vectibix treatment, periodically during Vectibix treatment, and for up to 8 weeks after the completion of treatment. Other electrolyte disturbances, including hypokalemia, have also been observed. Replete magnesium and other electrolytes as appropriate.
Infusion Reactions: Infusion reactions, manifesting as fever, chills, dyspnea, bronchospasm, and hypotension, can occur following Vectibix administration. Fatal infusion reactions occurred in postmarketing experience. Terminate the infusion for severe infusion reactions
Acute Renal Failure in Combination with Chemotherapy: Severe diarrhea and dehydration, leading to acute renal failure and other complications, have been observed in patients treated with Vectibix in combination with chemotherapy
Pulmonary Fibrosis/Interstitial Lung Disease (ILD): In the event of acute onset or worsening of pulmonary symptoms, interrupt Vectibix therapy. Discontinue Vectibix therapy if ILD is confirmed.
Photosensitivity: Exposure to sunlight can exacerbate dermatologic toxicity. Advise patients to wear sunscreen and hats and limit sun exposure while receiving Vectibix.
Ocular Toxicities: Serious cases of keratitis, ulcerative keratitis, and corneal perforation have occurred with Vectibix use. Monitor for evidence of keratitis, ulcerative keratitis, or corneal perforation. Interrupt or discontinue Vectibix therapy for acute or worsening keratitis, ulcerative keratitis, or corneal perforation.
Increased Mortality and Toxicity with Vectibix in Combination with Bevacizumab and Chemotherapy: In an interim analysis of an open-label, multicenter, randomized clinical trial in the first-line setting in patients with mCRC, the addition of Vectibix to the combination of bevacizumab and chemotherapy resulted in decreased OS and increased incidence of NCI-CTC grade 3-5 (87% vs 72%) adverse reactions. NCI-CTC grade 3-4 adverse reactions occurring at a higher rate in Vectibix-treated patients included rash/acneiform dermatitis (26% vs 1%), diarrhea (23% vs 12%), dehydration (16% vs 5%), primarily occurring in patients with diarrhea, hypokalemia (10% vs 4%), stomatitis/mucositis (4% vs < 1%), and hypomagnesemia (4% vs 0).
Embryo-fetal Toxicity: Based on data from animal studies and its mechanism of action, Vectibix can cause fetal harm when administered to a pregnant woman.
Skin and subcutaneous tissue disorders: Skin necrosis, angioedema, life-threatening and fatal bullous mucocutaneous disease
Immune system disorders: Infusion reaction
Eye disorders: Keratitis/ulcerative keratitis, corneal perforation
Use in specific populations
Pregnancy: Based on data from animal studies and its mechanism of action, Vectibix can cause fetal harm when administered to pregnant women. Limited available data on the use of Vectibix in pregnant women are not sufficient to inform a risk of adverse pregnancy-related outcomes. Vectibix is a human IgG monoclonal antibody and may be transferred across the placenta during pregnancy. Reproduction studies in cynomolgus monkeys treated with 1.25 to 5 times the recommended human dose of panitumumab resulted in significant embryolethality and abortions; however, no other evidence of teratogenesis was noted in offspring. Advise pregnant women of the potential risk to the fetus.
Lactation: There are no data on the presence of panitumumab in human milk or the effects of panitumumab on the breastfed infant or on milk production. Human IgG is present in human milk, but published data suggest that breast milk antibodies do not enter the neonatal and infant circulation in substantial amounts. Because of the potential for serious adverse reactions in breastfed infants from Vectibix, advise women not to breastfeed during treatment with Vectibix and for 2 months after the final dose.
Pediatric Use: The safety and effectiveness of Vectibix have not been established in pediatric patients.
Doses up to approximately twice the recommended therapeutic dose (12 mg/kg) resulted in adverse reactions of skin toxicity, diarrhea, dehydration, and fatigue.