(M0930-11-76) The Impact of Relative Humidity on In Vitro Permeation Test Method Performance Indicators, J_max, T_max and Amount Permeated for Molecule, TER-003

Purpose: In vitro permeation testing (IVPT) is one option in demonstrating bioavailability and bioequivalence (BA/BE) of a proposed generic topical product with its reference listed drug (RLD). The FDA Guidance recommends the validation of the IVPT method used for BA/BE studies, which includes the assessment of critical parameters defined in the IVPT method. One critical parameter the FDA highlights is the monitoring and controlling of the ambient temperature and relative humidity(RH) in the laboratory for ongoing IVPT studies; a temperature of 21°C ± 2 °C and humidity range of 50% ± 20% is recommended, if feasible. During development of the IVPT method, IVPT studies using RLD for molecule TER-003 were conducted with multiple donors over several weeks; all other parameters of the IVPT method were held constant. Over several weeks, the temperature and humidity were maintained within acceptable limits; however, maximum, and minimum humidities observed were different for each study. The current work presents some of our findings on the impact of temperature and RH maintained during an IVPT study for TER-003.

Methods: IVPT studies using RLD of TER-003 were conducted with multiple donors over several weeks. Temperature and relative humidity were monitored and controlled within the acceptable conditions 21± 2°C for temperature and 50% ± 20%, for relative humidity for the duration of the IVPT studies. As part of the IVPT method, TEWL was measured for each skin replicate prior to dosing with RLD. Throughout study, IVPT samples were collected at pre-determined timepoints and analyzed by LCMS-MS analysis. Concentration of TER-003 permeated across skin at specified timepoints were used to generate IVPT Data. Collated data from multiple replicates of each donor section was used to generate average permeation and flux profiles.

Results: The cumulative amount permeated, and flux profile were calculated for TER-003 and during week 1, which registered at a higher relative humidity (average 60% with an overall 20% shift in RH), at least 5 replicates per skin section for multiple donors, showed an average lower total amount permeated, higher T_max values, lower J_max values, and lower initial TEWL values when compared to week 2. During week 2, which registered a lower relative humidity (average RH 50% with less substantial shift in RH), at least 5 replicates per skin section for multiple donors, showed a higher total permeation, shorter T_max, higher J_max and higher TEWL values when compared to week 1. TEWL, absolute change in humidity and amount permeated for week 1 compared to week 2 is shown in Figure 1.

Conclusion: These data suggest that higher relative humidity in the laboratory relates to lower initial TEWL values for donor tissue. Moreover, higher relative humidity showed slower overall permeation, observed as larger T_max, smaller J_max, and total amount permeation for TER-003, when compared to data from a study conducted at lower relative humidity. An attempt to collect and collate additional data on other molecules (both hydrophilic and hydrophobic) and the impact on permeation due to environmental factors is underway.

References: In Vitro Permeation Test Studies for Topical Drug Products Submitted in ANDAs. Guidance for Industry, US Food and Drug Administration. (October 2022).

TEWL, Change in Relative Humidity and Amount Permeated for TER003 for Week 1 compared to Week 2