Improper selection of a pre-specified primary dose-response analysis delays regulatory drug approval

Dose-response analysis is one of the accepted efficacy endpoints to establish effectiveness. The purpose of this research was to inform selection of an appropriate pre-specified primary dose-response analysis to demonstrate drug efficacy in a registration trial. The power and the type I error rate of the placebo-corrected (i.e., simply adjusting the observed treatment value by subtracting the placebo mean) and the placebo-anchored (i.e., including the placebo data as dose 0 in the regression) slope analyses were assessed based on regulatory submission data for two antihypertensive drugs and simulated data from hypothetical clinical trials. In the simulated hypothetical trials, the impact of different dosing strategies (i.e., the fixed dose versus the weight-based per kilogram dose), sample size, and scenarios governing the drug exposure-response relationship (e.g., E(max), ED(50), and SD) was also evaluated. For each scenario, a total 300 replications were simulated. The placebo-anchored slope analysis is always more powerful to demonstrate effectiveness in all plausible scenarios. The difference between the placebo-anchored and the placebo-corrected analyses was maximum when the studied doses were too high. However, the dose-response analysis is not sensitive to the dosing strategies. Furthermore, the type I error rate of these two methods was also found to be comparable. The design of dose-response studies should carefully consider these results to justify the inclusion of placebo and the analysis method. The pharmaceutical industry and the regulatory agencies are equally responsible for using the appropriate methods of primary analysis and providing justification in the protocol.