Panitumumab

Panitumumab is a fully human monoclonal antibody and an antineoplastic agent used to treat selected patients with metastatic colorectal cancer. It belongs to the class of epidermal growth factor receptor (EGFR) inhibitors. EGFR is a cell-surface protein involved in signalling pathways that regulate cell growth, survival, and proliferation. Panitumumab binds to EGFR and blocks the interaction between the receptor and its natural ligands, reducing downstream signalling that may support tumour growth. Its clinical benefit depends partly on the molecular characteristics of the cancer, particularly the RAS gene status. Tumours with certain RAS mutations may continue to signal independently of EGFR, making treatment with panitumumab ineffective. The medicine is administered by intravenous infusion under the supervision of healthcare professionals experienced in cancer treatment. It may be used alone or in combination with selected chemotherapy regimens, depending on the indication, previous treatment, tumour characteristics, and applicable prescribing information. Panitumumab is not suitable for every patient with colorectal cancer, and molecular testing is essential before treatment selection. Important safety considerations include skin toxicity, electrolyte disturbances, infusion-related reactions, and potentially serious pulmonary complications. Treatment requires ongoing assessment of tolerability, laboratory results, and disease response.

Panitumumab was developed as a fully human immunoglobulin G2 (IgG2) monoclonal antibody targeting EGFR, with the aim of inhibiting growth signalling in selected cancers. The United States Food and Drug Administration (FDA) granted its initial approval on 27 September 2006 for patients with EGFR-expressing metastatic colorectal cancer that had progressed after specified chemotherapy regimens. Subsequent clinical research, including the PRIME and ASPECCT phase III trials, helped clarify its role in patients with appropriate tumour molecular profiles and in comparison with other EGFR-targeted treatment. Expanded indications incorporated RAS mutation testing because activating mutations in KRAS or NRAS can predict a lack of benefit from EGFR inhibition in colorectal cancer. The European Commission granted marketing authorisation for panitumumab in the European Union on 3 December 2007, initially under conditional authorisation, which became full authorisation in January 2015. Current US prescribing information also includes panitumumab in combination with sotorasib for selected adults with KRAS G12C-mutated metastatic colorectal cancer after prior chemotherapy. Approved indications differ between jurisdictions and may change as new evidence is evaluated. Clinicians should consult the applicable national prescribing information before selecting treatment.

Panitumumab is used in adults with metastatic colorectal cancer when the tumour's molecular profile and treatment history meet the relevant approved indication. For RAS wild-type disease, it may be used with FOLFOX chemotherapy as first-line treatment and as monotherapy after progression following chemotherapy containing a fluoropyrimidine, oxaliplatin, and irinotecan. Under the European indication, it may also be combined with FOLFIRI in selected first- or second-line settings. In the United States, panitumumab is additionally indicated with sotorasib for adults with KRAS G12C-mutated metastatic colorectal cancer who have received prior fluoropyrimidine-, oxaliplatin-, and irinotecan-based chemotherapy. This combination is a distinct molecularly selected indication and should not be confused with panitumumab monotherapy for RAS wild-type disease. Tumour testing must be performed using an appropriately validated method before treatment selection. Panitumumab is not a general treatment for all colorectal cancers and is not routinely used for cancers arising in other organs. The choice between monotherapy and combination treatment depends on tumour genetics, previous treatment, clinical condition, treatment goals, and local regulatory guidance.

Panitumumab is administered by intravenous infusion under the supervision of a healthcare professional experienced in cancer treatment. For approved indications involving metastatic colorectal cancer, the usual recommended dose is 6 mg/kg of body weight every 14 days. The infusion duration depends on the total dose and the applicable product information; in current US prescribing information, doses up to 1,000 mg are generally infused over 60 minutes, while higher doses are infused over 90 minutes. When used with sotorasib for KRAS G12C-mutated disease, panitumumab follows the specified combination regimen, and sotorasib dosing must be managed according to its own prescribing information. Treatment generally continues until disease progression or unacceptable toxicity, with modifications or temporary interruption when clinically indicated. Severe skin reactions may require withholding treatment, reducing subsequent doses, or discontinuation according to the approved protocol. The dose should be calculated using the patient's current body weight and verified before each infusion. Treatment should only begin after the required molecular testing confirms eligibility. Infusion monitoring and management of adverse effects should follow the specific product label and institutional oncology protocols.

Common adverse effects of panitumumab include acne-like skin rash, dry skin, itching, redness, skin cracking, and inflammation around the nails. Rash may affect the face, scalp, chest, back, or other areas and can become painful or infected. Other frequently reported effects include diarrhoea, fatigue, nausea, abdominal discomfort, and reduced appetite. Low magnesium levels may develop during treatment and can occur alongside reductions in potassium or calcium. Some patients experience eye irritation, inflammation of the eyelids, or changes around the eyelashes. The frequency and severity of side effects vary depending on the treatment regimen, individual health status, and duration of therapy. Early skin care, moisturising products, sun protection, and prompt assessment of worsening symptoms may help manage dermatological reactions. Supportive medicines should be selected by the treating team. Patients should report persistent diarrhoea, painful skin changes, eye symptoms, or signs of infection rather than waiting until the next scheduled appointment.

Panitumumab carries an important warning for dermatological toxicity, which can be severe and may lead to infection, tissue damage, treatment interruption, or discontinuation. Serious infusion-related or hypersensitivity reactions can occur and may require immediate interruption of the infusion and emergency treatment. Electrolyte disturbances, particularly hypomagnesaemia, can become severe and may be associated with low calcium or potassium, muscle spasms, weakness, abnormal heart rhythms, or seizures. Rare but serious pulmonary complications, including interstitial lung disease, have been reported; new or worsening cough, breathlessness, or other unexplained respiratory symptoms require urgent evaluation. Severe diarrhoea and dehydration may occur, particularly when panitumumab is combined with chemotherapy. Eye inflammation and corneal complications are additional concerns in patients who develop significant ocular symptoms. Panitumumab is contraindicated in patients with a history of severe hypersensitivity to the medicine or its components and in those with interstitial pneumonitis or pulmonary fibrosis, according to the European product information. Treatment must not be used with oxaliplatin-containing chemotherapy in patients with RAS-mutant tumours or unknown RAS status. Treatment interruption, dose modification, or permanent discontinuation may be necessary depending on the nature and severity of toxicity.

Before initiating panitumumab, confirm the tumour's molecular status using a validated laboratory test appropriate to the intended indication. Testing should establish RAS wild-type status for the relevant EGFR-targeted indications or confirm KRAS G12C mutation when panitumumab is prescribed with sotorasib. Review previous treatments, allergies, pulmonary history, skin conditions, current medicines, and baseline electrolyte levels. Serum magnesium, calcium, and potassium should be assessed before treatment and monitored regularly during therapy and after completion, as electrolyte abnormalities may persist after the last dose. Patients with a history of interstitial lung disease or pulmonary fibrosis require particular attention because these conditions are contraindications under the European product information. Pregnancy-related considerations should be discussed, including potential fetal harm and the need for effective contraception during treatment and for the period specified in the applicable prescribing information. Breastfeeding advice should also follow the product label. Panitumumab is not associated with the broad range of classic metabolic drug interactions seen with many small-molecule medicines, but combination therapy can increase toxicity and must follow established protocols. Concurrent oxaliplatin use is restricted in patients with RAS-mutant or unknown-status tumours. Sotorasib must be used only in the appropriate KRAS G12C-mutated indication.

Confirm molecular eligibility before preparing or dispensing panitumumab, and ensure that the laboratory report matches the intended treatment indication. Record baseline magnesium, calcium, potassium, renal status, skin condition, and respiratory history, with particular attention to pre-existing pulmonary disease. Establish a proactive skin-care plan, including moisturising, sun protection, and early review of rash or nail inflammation. Monitor electrolytes throughout treatment and continue post-treatment monitoring for the interval specified in the product information. During infusion, observe the patient for hypersensitivity or infusion-related reactions and ensure that appropriate emergency medicines and equipment are available. Verify the dose using current body weight, confirm the correct infusion duration, and follow the manufacturer's instructions for dilution, handling, and administration. When panitumumab is combined with chemotherapy or sotorasib, review the complete regimen for indication, scheduling, overlapping toxicities, and treatment-specific precautions. Counsel patients to report severe rash, fever, worsening diarrhoea, muscle cramps, palpitations, eye pain, new cough, or breathlessness promptly. Document adverse reactions and dose modifications clearly, and coordinate care between oncology, pharmacy, nursing, and laboratory teams to support safe treatment.