The US Food and Drug Administration (FDA) on Friday finalized guidance for sponsors who wish to request a waiver of an in vivo bioavailability (BA) and/or bioequivalence (BE) study requirements for immediate release (IR) solid oral dosage forms based on an approach termed the Biopharmaceutics Classification System (BCS).

The guidance, finalized from a 2015 draft, explains what is necessary for sponsors of investigational new drugs (INDs) and applicants of new drug applications (NDAs), abbreviated new drug applications (ANDAs) and supplements who wish to request a waiver.

FDA says these recommendations are intended to apply to waivers requested during the IND period and the NDA stage or for ANDAs, i.e.: "(1) subsequent in vivo BA or BE studies of formulations after the initial establishment of the in vivo BA of IR solid oral dosage forms during the IND period, and (2) in vivo BE studies of IR solid oral dosage forms in NDAs, ANDAs, and supplements to these applications."

The BCS, FDA explains, is a scientific framework for classifying drug substances based on their aqueous solubility and intestinal permeability.

"When combined with the dissolution of the drug product, the BCS takes into account three major factors that govern the rate and extent of drug absorption from IR solid oral dosage forms: (1) dissolution, (2) solubility, and (3) intestinal permeability," the guidance notes. "According to the BCS, drug substances are classified as follows: Class 1: High Solubility – High Permeability Class 2: Low Solubility – High Permeability Class 3: High Solubility – Low Permeability Class 4: Low Solubility – Low Permeability."

In terms of changes between the draft and final guidance, FDA noted: "While many positive comments were received on the published draft guidance, several requests were made for additional clarification regarding the biowaivers for BCS class 3 drug substances, and specific issues pertaining to dissolution and permeability categories. In response, this guidance includes biowaiver extension to BCS class 3 drug products, and additional modifications, such as criteria for high permeability and high solubility."

Waiver of In Vivo Bioavailability and Bioequivalence Studies for Immediate-Release Solid Oral Dosage Forms Based on a Biopharmaceutics Classification System Guidance for Industry