Determining topical product bioequivalence with stimulated Raman scattering microscopy

• Published in: Journal of controlled release Vol. 367; pp. 864 - 876
• Main Authors: Iliopoulos, Fotis, Tu, Dandan, Pence, Isaac J., Li, Xiaolei, Ghosh, Priyanka, Luke, Markham C., Raney, Sam G., Rantou, Elena, Evans, Conor L.
• Format: Journal Article
• Language: English
• Published: Netherlands Elsevier B.V 01.03.2024
• Subjects: Administration, Cutaneous; Bioequivalence; Biological Availability; Cutaneous pharmacokinetics; Drugs, Generic - chemistry; Generic drug; Humans; Noninvasive; Nonlinear Optical Microscopy; Skin - metabolism; Stimulated Raman microscope; Therapeutic Equivalency; Topical product; Stimulated Raman microscope; Cutaneous pharmacokinetics; Topical product; Generic drug; Bioequivalence; Noninvasive
• ISSN: 0168-3659; 1873-4995
• DOI: 10.1016/j.jconrel.2024.02.010

Generic drugs are essential for affordable medicine and improving accessibility to treatments. Bioequivalence (BE) is typically demonstrated by assessing a generic product's pharmacokinetics (PK) relative to a reference-listed drug (RLD). Accurately estimating cutaneous PK (cPK) at or near the site of action can be challenging for locally acting topical products. Certain cPK approaches are available for assessing local bioavailability (BA) in the skin. Stimulated Raman scattering (SRS) microscopy has unique capabilities enabling continuous, high spatial and temporal resolution and quantitative imaging of drugs within the skin. In this paper, we developed an approach based on SRS and a polymer-based standard reference for the evaluation of topical product BA and BE in human skin ex vivo. BE assessment of tazarotene-containing formulations was achieved using cPK parameters obtained within different skin microstructures. The establishment of BE between the RLD and an approved generic product was successfully demonstrated. Interestingly, within the constraints of the current study design the results suggest similar BA between the tested gel formulation and the reference cream formulation, despite the differences in the formulation/dosage form. Another formulation containing polyethylene glycol as the vehicle was demonstrated to be not bioequivalent to the RLD. Compared to using the SRS approach without a standard reference, the developed approach enabled more consistent and reproducible results, which is crucial in BE assessment. The abundant information from the developed approach can help to systematically identify key areas of study design that will enable a better comparison of topical products and support an assessment of BE. Stimulated Raman scattering (SRS) microscopy enables bioequivalence (BE) assessment of pharmacokinetics parameters obtained within different skin microstructures. The developed polymer standard reference normalizes the SRS intensity and enables more consistent results. [Display omitted] •Develop a method based on a stimulated Raman microscope to monitor drug in ex vivo human skin.•Develop a stable standard reference to remove the effects of signal fluctuations for monitoring drugs with high specificity.•Quantify the drug and assess the cutaneous bioequivalence of topical formulations using the developed method.•Demonstrate bioequivalence of an approved generic drug and corresponding RLD within different microstructures in the skin.•Demonstrate that the lab-made formulation with PEG, a distinct vehicle from the RLD cream, is not bioequivalent to the RLD.