Plate design recommendations for kD determination and the screening of prototype formulations. (A) “Low risk”: 8 formulations (marked by blue to yellow), based on a horizontally arranged concentration series (2, 4, 6, 8, and 10-mg/mL API), and 6 replicates of each concentration are positioned vertically (=240 sample wells, elapsed time (well B3 → M22): 5 h). Control samples are optionally placed at the end positions. Total net amount API: 44 mg. (B) “High quantity”: 20 formulations (marked by blue to gray), based on a horizontally arranged concentration series (2, 5, and 10-mg/mL API), and 5 replicates of each concentration are positioned vertically (=300 sample wells, elapsed time (well B2 → O21): 6.25 h). Placebo samples are not placed on the microtiter plate. Total net amount API: 50 mg.