Biosimilar Studies: Three-Arm Design

Authored by: Seung-Ho Kang

Encyclopedia of Biopharmaceutical Statistics

Print publication date:  August  2018
Online publication date:  August  2018

Print ISBN: 9781498733953
eBook ISBN: 9781351110273
Adobe ISBN:


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One of the most commonly used designs for assessing the degree of biosimilarity between a biosimilar product and a reference product is the two-arm parallel design, with which biosimilarity is assessed using the difference between two population means. A problem with this method is that the variability of a reference product among different batches cannot be taken into account accurately. This problem is overcome when using the three-arm parallel design, in which one arm is used for the biosimilar product and the other two arms are for the reference product. A relative distance is employed to evaluate the degree of biosimilarity. The distance between the biosimilar product and the reference product, defined as the absolute mean difference between the two products, becomes the numerator of the relative distance. The distance between the reference products from two different batches becomes the denominator of the relative distance. If the relative distance is less than a pre-specified margin, the two products are claimed to be biosimilar. Statistical tests based on a ratio estimator method were developed to assess the degree of biosimilarity when using the relative distance in the three-arm parallel design.

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