## FDA: 2×2×4 design; RSABE + ABE + σwT/σwR [Design Issues]

» All of the product-specific guidances contain a section ‘Explanation’. See also Yu et al.

OK

» » Further, can we perform crossover studies for NTI by taking extra safety measurement in to the study?
»
» You can. Whether that is necessary in healthy volunteers depends on the drug.

Yes.

» » Further, what is the BE limit for such drugs?
»
» It depends on $$\small{s_{wR}}$$ observed in the study, i.e., reference-scaling is applied. Furthermore – irrespective of passing the scaled limits – the study has to pass 80.00–125.00% as well and the upper confidence limit of $$\small{\sigma_{wT}/\sigma_{wR}}$$ has to be ≤2.5.

its common for all NTI or its varies from drug to drug?

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