Impact of variability on the choice of biosimilarity limits in assessing follow-on biologics

Adaptive Seamless Design for Establishing Pharmacokinetic and Efficacy Equivalence in Developing Biosimilars

BACKGROUND

Recently, numerous pharmaceutical sponsors have expressed a great deal of interest in the development of biosimilars, which requires clinical trials to demonstrate that the pharmacokinetic (PK) and clinical efficacy are equivalent. Pharmacodynamics (PD) may be used in evaluating efficacy if there are relevant PD markers available. However, in their absence, it is necessary to design the associated clinical trials to include efficacy measures as the primary endpoint.

METHODS

In this study, we propose a novel adaptive seamless PK and efficacy design with an efficient framework to remedy the risk of misspecification of efficacy parameters and to discontinue the trial evaluating the efficacy for futility based on the PK evaluation. Here, we consider the clinical development of biosimilars including their evaluation in patients rather than healthy volunteers under a situation where both PK and efficacy parameters are required to demonstrate equivalence. The original idea of the proposed method was to organize a clinical trial that includes the statistical analysis of PK as an interim analysis, with sample size recalculation of the efficacy data.

RESULTS

Our simulation study indicated that the proposed design would allow trials to be more efficient than with the classical design.

CONCLUSIONS

This proposal provides appealing advantages, such as a shorter time period, additional cost savings, and a smaller number of patients required.

A Calibrated Power Prior Approach to Borrow Information from Historical Data with Application to Biosimilar Clinical Trials

A biosimilar refers to a follow-on biologic intended to be approved for marketing based on biosimilarity to an existing patented biological product (i.e., the reference product). To develop a biosimilar product, it is essential to demonstrate biosimilarity between the follow-on biologic and the reference product, typically through two-arm randomization trials. We propose a Bayesian adaptive design for trials to evaluate biosimilar products. To take advantage of the abundant historical data on the efficacy of the reference product that is typically available at the time a biosimilar product is developed, we propose the calibrated power prior, which allows our design to adaptively borrow information from the historical data according to the congruence between the historical data and the new data collected from the current trial. We propose a new measure, the Bayesian biosimilarity index, to measure the similarity between the biosimilar and the reference product. During the trial, we evaluate the Bayesian biosimilarity index in a group sequential fashion based on the accumulating interim data, and stop the trial early once there is enough information to conclude or reject the similarity. Extensive simulation studies show that the proposed design has higher power than traditional designs. We applied the proposed design to a biosimilar trial for treating rheumatoid arthritis.

Avoiding ambiguity with the Type I error rate in noninferiority trials

This review article sets out to examine the Type I error rates used in noninferiority trials. Most papers regarding noninferiority trials only state Type I error rate without mentioning clearly which Type I error rate is evaluated. Therefore, the Type I error rate in one paper is often different from the Type I error rate in another paper, which can confuse readers and makes it difficult to understand papers. Which Type I error rate should be evaluated is related directly to which paradigm is employed in the analysis of noninferiority trial, and to how the historical data are treated. This article reviews the characteristics of the within-trial Type I error rate and the unconditional across-trial Type I error rate which have frequently been examined in noninferiority trials. The conditional across-trial Type I error rate is also briefly discussed. In noninferiority trials comparing a new treatment with an active control without a placebo arm, it is argued that the within-trial Type I error rate should be controlled in order to obtain approval of the new treatment from the regulatory agencies. I hope that this article can help readers understand the difference between two paradigms employed in noninferiority trials.

Sample size calculations for the development of biosimilar products

The most widely used design for a Phase III comparative study for demonstrating the biosimilarity between a biosimilar product and a renovator biological product is the equivalence trial, whose aim is to show that the difference between two population means of a primary endpoint is less than a prespecified equivalence margin. A well-known sample size formula for the equivalence trial is given by [Formula: see text] Since this formula is obtained based on the approximate power rather than the exact power, we investigate in this article the accuracy of the sample size formula. We conclude that the sample size formula is very conservative. Specifically, we show that the exact power based on the sample size calculated from the formula to have power [Formula: see text] is actually [Formula: see text] under some conditions. Therefore, the use of the sample size formula may cause a huge extra cost to biotechnology companies. We propose that the sample size should be calculated based on the exact power precisely and numerically. The R code to calculate the sample size numerically is provided in this article.

Keeping a critical eye on the science and the regulation of oral drug absorption: a review

This review starts with an introduction on the theoretical aspects of biopharmaceutics and developments in this field from mid-1950s to late 1970s. It critically addresses issues related to fundamental processes in oral drug absorption such as the complex interplay between drugs and the gastrointestinal system. Special emphasis is placed on drug dissolution and permeability phenomena as well as on the mathematical modeling of oral drug absorption. The review ends with regulatory aspects of oral drug absorption focusing on bioequivalence studies and the US Food and Drug Administration and European Medicines Agency guidelines dealing with Biopharmaceutics Classification System and Biopharmaceutic Drug Disposition Classification System.