Panellists advising regulators in the USA have said that plans by Amgen and ImClone Systems to tailor their colorectal cancer drugs to be used with specific genetic profiles may require larger clinical studies to gather sufficient data.

The US Food and Drug Administration's Oncologic Drugs Advisory Committee has been discussing the KRAS gene as a specific example of a predictive biomarker in selecting patients with metastatic colorectal cancer for treatment with anti-epidermal growth factor receptor (EGFr) antibodies, namely Amgen’s Vectibix (panitumumab) and ImClone’s Erbitux (cetuximab). The hearing is particularly interesting because it (indirectly) involves the two firms asking the FDA to actually reduce the number of patients who may be prescribed their products.

Specifically, studies have shown that Vectibix and Erbitux do not work in patients with a mutated KRAS gene (around 40% of colon cancer patients) which plays a key role in the EGFR chain of events involved in cancer growth. Amgen and ImClone believe they have sufficient data to show the drugs are most effective in patients with a normal KRAS gene and that the FDA should approve label modifications to the products to include this information.

Such a move would be a significant development in the future of personalised medicine. However the FDA panellists said that analysing data from earlier studies can lead to false conclusions or misinterpretation and additional analyses may be required to better screen individuals for gene mutations.

The committee members also suggested that larger clinical studies could be needed to determine other biochemical factors that may affect drug efficacy. They added that companies must have a well-structured plan to review their earlier data.

Commenting on the meeting, Amgen said that “there was an important discussion on the level of evidence required to bring forth a predictive biomarker and make this type of information widely available to treating physicians and patients”. The firm added that biomarkers like KRAS “deliver on the promise of personalised medicine for complex diseases like cancer”, saying that “we look forward to our continued dialogue with FDA on how best to address both KRAS and future biomarker data in our clinical trials”.