Vectibix, a new drug for colorectal cancer

The FDA ( Food and Drug Administration ) has approved Vectibix ( Panitumumab ) for the treatment of patients with colorectal cancer that has metastasized following standard chemotherapy.

Vectibix, a monoclonal antibody that binds to a protein called epidermal growth factor receptor ( EGFR ) on some cancer cells.

FDA has approved Vectibix on the basis of the results of a randomized, controlled clinical trial of 463 patients with metastatic cancer of the colon and the rectum after undergoing treatment with chemotherapy drugs, fluoropyrimidine, Oxaliplatin and Irinotecan.

The mean time to disease progression or death in patients receiving Vectibix was 96 days versus 60 days in patients receiving the best standard supportive care.
In addition, 8 percent of the patients on Vectibix experienced a tumor shrinkage that in some cases exceeded 50 percent of the pre-treatment size of the tumor.

The most serious adverse events in the studies of Vectibix included pulmonary fibrosis, severe skin rash complicated by infections, infusion reactions, abdominal pain, nausea, vomiting and constipation.

Dermatologic toxicities, related to Vectibix blockade of EGF binding and subsequent inhibition of EGF receptor-mediated signaling pathways, included but were not limited to dermatitis acneiform, pruritus, erythema, rash, skin exfoliation, paronychia, dry skin, and skin fissures.
Dermatologic toxicities were reported in 89 percent of patients treated with Vectibix and were severe in 12 percent of patients.
Severe dermatologic toxicities were complicated by infection, including sepsis, septic death, and abscesses requiring incisions and drainage. Vectibix may need to be withheld or discontinued for severe dermatologic toxicities.

Severe infusion reactions occurred with Vectibix in approximately 1 percent of patients. Severe infusion reactions were identified as anaphylactic reactions, bronchospasm, fever, chills, and hypotension. Although fatal infusion reactions have not been reported with Vectibix, they have occurred with other monoclonal antibody products. Severe infusion reactions require stopping the infusion and possibly permanently discontinuing Vectibix, depending on the severity and/or persistence of the reaction.

The most common adverse events associated with the drug included skin rash, fatigue, abdominal pain, nausea, and diarrhea.

In the United States, it is estimated that 150,000 new cases of colon cancer will be diagnosed and 55,000 deaths will occur from colon and rectal cancer in 2006. Approximately 70 percent of all colorectal carcinomas test positive for EGFR.

Source: FDA, 2006