section_path: Efficacy
section_name: Efficacy
paragraph_text: Efficacy
  
  Drug action is highly specific and their effects may only be detected in certain individuals. For instance, the 10 highest-grossing drugs in the US may help only 4-25% of people. Often, the activity of a drug depends on the genotype of a patient. For example, Erbitux (cetuximab) increases the survival rate of colorectal cancer patients if they carry a particular mutation in the EGFR gene. Some drugs are specifically approved for certain genotypes. Vemurafenib is such a case which is used for melanoma patients who carry a mutation in BRAF gene. The number of people who benefit from a drug determines if drug trials are worth carrying out, given that phase III trials may cost between $100 million and $700 million per drug. This is the motivation behind personalized medicine, that is, to develop drugs that are adapted to individual patients.