Panitumumab — Drug Monograph

Brand names: Vectibix

Drug class: Monoclonal Antibody

Mechanism of Action

Panitumumab is a recombinant, human IgG2 monoclonal antibody that binds specifically and with high affinity to the human epidermal growth factor receptor (EGFR). Binding to EGFR inhibits the binding of endogenous ligands, such as epidermal growth factor (EGF) and transforming growth factor-alpha (TGF-α). This inhibition results in the blockade of downstream signaling pathways, including the KRAS and PI3K pathways, which are involved in cell proliferation, survival, and angiogenesis. It is effective only in tumors expressing wild-type KRAS, as mutated KRAS provides a constitutive stimulus for…

FDA Indications

• Treatment of patients with 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): As first-line therapy in combination with FOLFOX.
• Treatment of patients with 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): As monotherapy following disease progression after prior treatment with fluoropyrimidine-, oxaliplatin-, and irinotecan-containing chemotherapy.

Common Side Effects

• Acneiform dermatitis
• Pruritus
• Erythema
• Skin exfoliation
• Paronychia
• Diarrhea
• Fatigue
• Hypomagnesemia
• Hypokalemia
• Abdominal pain

Clinical Pearl

The hallmark acneiform rash is actually a positive predictive marker for efficacy; patients who develop a more severe rash often have better outcomes. Prophylaxis from Day 1 of therapy reduces severe rash: oral doxycycline or minocycline 100 mg BID, topical hydrocortisone 1%, a thick emollient moisturizer, and daily sunscreen — avoid benzoyl peroxide and other drying/anti-acne agents. Unlike Cetuximab, Panitumumab is a fully human antibody, which theoretically reduces the risk of…

Related Therapies & Mechanisms

• Bevacizumab (Avastin) — Monoclonal Antibody · CRC
• Cetuximab (Erbitux) — Monoclonal Antibody · CRC
• Ramucirumab (Cyramza) — Monoclonal Antibody · CRC
• Alemtuzumab (Campath) — Monoclonal Antibody