How Broadening the Analysis of Compound Factors Allows for Predictive Solubility Solutions


The Biopharmaceutics Classification System (BCS), developed by the U.S. Food and Drug Administration to simplify and accelerate the drug development process, helps companies when they file for bioequivalence of dosage forms based on in vitro dissolution testing. The objective of the BCS system is to predict in vivo performance of drugs from in vitro measurements of solubility and permeability. The system has evolved to classify low-soluble drugs according to their permeability (BCS Class II or IV). A compound’s classification (I through IV) is indicative of its potential bioavailability.

Companies also have adopted the BCS system as a test for a compound’s oral delivery, leading decision-makers to believe that knowing a compound’s solubility (logS) and lipophilicity (logP) can guide them to the right choice of formulation.

While understandable, relying on these parameters to identify solubility solutions oversimplifies the challenge. A Thermo Fisher Scientific analysis of drugs brought to market over the past three decades shows that approved drugs do not follow clear trends when these two measures alone are considered. Additional factors can provide a more complete picture.