The IND System, or Investigational New Drug system, is a regulatory process in the United States that allows pharmaceutical companies to test new drugs in humans. Before a drug can be tested, companies must submit an IND application to the Food and Drug Administration (FDA), which includes data on the drug's safety, manufacturing, and proposed clinical trial plans. Once the IND is approved, the drug can enter clinical trials, which are conducted in phases to assess its safety and effectiveness. The IND system ensures that new drugs are thoroughly evaluated before they reach the market, protecting public health while encouraging medical innovation.