Assessment of prescribability and switchability by using multiple bioequivalence assessment approaches

Background: In the drug development process, an assessment of bioequivalence is an integral part. For the evaluation of generics against the comparator, average bioequivalence approach is the gold standard method. In the recent past, there were many discussions on whether we have the adequate tool to evaluate generics and thereby drug interchangeability (prescribability and switchability) issue is addressed as average bioequivalence approach just considers population mean. Hence, the alternative approaches like population bioequivalence and individual bioequivalence assessment approaches arise as different variances like inter/ intra-subject variance and subject-by-formulation variance along with population mean are considered. Objectives: Methoxsalen, in combination with long-wave UVA radiation, is used in the symptomatic management certain psoriasis. The study was aimed to establish the bioequivalence (BE) of a newly developed methoxsalen capsule (MTX test) with that of a reference methoxsalen capsule (MTX reference) using multiple BE methods (i.e., average [ABE], population [PBE], and individual [IBE]) by utilizing a new LC–MS/MS method. Methods: This is an open-label, randomized, balanced, two-treatment, three-period, three-sequence, crossover, single-dose (20 mg, 2 × 10 mg capsules), comparative, oral BE study conducted in 52 healthy, adult males under fasting conditions. Along with various pharmacokinetic (PK) parameters ABE, PBE, and IBE were also determined in the single study. Results: : A non-compartmental model best described the concentration–time data of both MTX test and reference. Both the formulations demonstrated nearly similar values of BE parameters (i.e., AUCo–t, AUC0–∞, Cmax, Tmax, and t1/2). For MTX test, the observed Cmax, AUC0–t, and AUC0–∞ were 125.16±81.53 ng/mL, 313.73±260.86 ng h/mL, and 321.25±271.85 ng h/mL, respectively. For MTX reference, the values were 127.63±71.60 ng/mL, 329.11±252.91 ng h/mL, and 335.48±264.54 ng h/mL, respectively. The bioanalytical method was validated over the concentration range 0.100–100.00ng/mL and the coefficient of determination (r2) was ≥ 0.9991. The sensitivity of the method was 0.100 ng/mL with the accuracy and precision values of 115% and 10.54%, respectively. Conclusion: A single dose of MTX test met the ABE criteria of 80.00% –125.00% for Cmax, AUCo–t, and AUC0–∞, against MTX reference. The study outcome by PBE and IBE approaches proved that MTX Test was bio-inequivalent to MTX reference. Using multiple BE assessment methods in a single BE study is a novel approach and may overcome shortcomings of conventional bioequivalence assessment methods.