Lemborexant is a dual orexin receptor antagonist assigned to class II of the Biopharmaceutics Classification System (BCS). Thus, the ICH M9 Guideline excludes immediate-release (IR) solid oral dosage forms containing lemborexant from BCS-based biowaivers, irrespective of their in vitro dissolution behavior. By contrast, classification of lemborexant according to the refined Developability Classification System (rDCS) falls into class I, indicating few biopharmaceutics risks. Customized rDCS investigations identify dissolution as the main risk factor, in line with clinical data in humans which suggest that the absorption of lemborexant is limited neither by solubility nor by permeability. Instead, any risks lie in dissolution. Analysis by the rDCS coupled with biorelevant dissolution testing thus provides a way forward for manufacturers to mitigate the risks associated with changes in formulation or introduction of a generic version prior to running clinical bioequivalence (BE) studies. As a way forward regarding biowaivers for lemborexant and similar cases, where justifying BE based on the current BCS-based approach is not possible, a four-step pathway towards establishing BE virtually could be adopted as follows: (i) rDCS analysis to identify critical bioavailability attributes, (ii) comparative (biorelevant) dissolution testing, (iii) Physiologically Based Biopharmaceutics Modeling (PBBM), and (iv) virtual BE assessment.
Keywords: Absorption; Biopharmaceutics classification system (BCS); Lemborexant; Permeability; Refined developability classification system (rDCS); Solubility; Virtual bioequivalence.
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