A PRO strategy should start with the end in mind, so that it can be both scientifically robust and implemented practically. If you haven’t considered a PRO strategy early in the product development cycle, significant benefits can still be obtained in any phase.
Ideally, your PRO strategy will be initiated as early as possible in the product development cycle, e.g. when a compound is identified for a Phase II trial. However, determining the burden of illness and identifying potential impact of the product can be initiated as early as Phase I of product development to assess the viability of the compound as a new product and to inform the decision about whether to proceed with related studies.
Finally, it is important to recognise that this should be an iterative process, liable to be adapted as new developments or information arise.