What type of application must drug manufacturers file before conducting clinical trials?

The Investigational New Drug Application (INDA) is the application that drug manufacturers must submit to the FDA before starting clinical trials. This application is crucial because it provides the FDA with the necessary information to assess the safety and efficacy of the drug for initial human trials. The INDA contains data from preclinical studies, including animal testing and any available information on pharmacology, toxicology, and manufacturing.

Submitting an INDA ensures that the drug manufacturer has conducted thorough preliminary research and is ready to move forward with clinical trials that evaluate the drug's effects in humans. It is the first step in a critical pathway that leads to the eventual approval of a new drug.

The other options are related to different stages of the drug approval process. A New Drug Application (NDA) is submitted after clinical trials are completed, once a manufacturer wants to obtain permission to market the drug. A Prescriber Authorization Request would be related to specific prescriptive authorities and is not a standard requirement for starting clinical trials. Reassessment of Drug Efficacy is typically not a form of application but rather an ongoing process that may occur after a drug is already on the market. Thus, the INDA is the essential application required prior to initiating clinical trials.