  Generalizability and transportability methods have been proposed to address
the external validity bias of randomized clinical trials that results from
differences in the distribution of treatment effect modifiers between trial and
target populations. However, such studies present many challenges. We review
and summarize state-of-the-art methodological considerations. We additionally
provide investigators with a step-by-step guide to address these challenges,
illustrated through a published case study. When conducted with rigor, such
studies may play an integral role in regulatory decisions by providing key
real-world evidence.

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