A study of the extension of the regulatory three batch stability approach to larger number of batches
*Sungwoo Choi, FDA Center for Drug Evaluation and Research  Yu-Ting Weng, FDA 

Keywords: drug stability, stability pooling test, shelf-life estimation

Drug stability plays a very important role in pharmaceutical research and development. For a newly developed drug product, stability analysis not only provides useful information regarding the degradation of the drug product, but also determines an expiration dating period of the drug product. The purpose of a stability study is to establish a retest period or shelf life and label storage instructions applicable to all future batches manufactured and packaged under similar circumstances. To determine the labeled shelf-life, the ICH stability guidelines require at least three batches, being tested to allow for a reliable estimate of batch-to-batch variability. The product shelf life is determined by the shortest of the three individual batch or by the pooled data. Before one can combine stability data from all batches, it is required to perform preliminary tests for batch similarity at the 0.25 significance level. However, there is no approach proposed for shelf life determination with lot numbers greater than three. In this presentation, we discuss the potential approaches to determine the nominal level of pooling test for large number of lots in order to proper power of “rejecting pooling” under certain deviation of slope or intercept from their mean value. On the other hand, without being pooling, we also discuss the potential approaches to determine which “less favorable” batch among the many to be used for shelf life determination.