Ideally, new FDA-regulated products should be tested in populations that are similar to those that would eventually use the product after approval. However, ensuring the diversity of clinical trial populations has been an ongoing challenge.
The FDA has released a draft guidance entitled “Enhancing the Diversity of Clinical Trial Populations — Eligibility Criteria, Enrollment Practices, and Trial Designs Guidance for Industry” addressing this concern. Note that this is a draft guidance, released for comment purposes only right now. But it may have some ideas you can incorporate into investigator-initiated protocols to make it easier for you to find an appropriate study population. It may also give you an idea of methods industry sponsors may incorporate into future protocols.