The warning letter is significant because it raps Sanofi for distributing reprints of a clinical study of the two drugs that appeared in the Journal of Clinical Oncology -- a type of promotion in which drug companies regard themselves as being on safe ground.
The FDA said the study was no good because it used secondary endpoints to make its case, not primary endpoints, and thus the data "do not generally constitute substantial evidence":
... the superiority analysis of the primary endpoint (e.g., objective response rate in the intent-to-treat population) failed to demonstrate a statistically significant difference between the two study arms. In the absence of a finding of statistical significance for the primary endpoint, any further analysis conducted on this study, including secondary endpoints and subpopulations, are all considered exploratory and do not generally constitute substantial evidence.The study, reproduced by Sanofi in a "reprint carrier," measured response duration of Taxotere, reduction in risk of death, and overall survival. But the FDA didn't like the way the primary endpoint was ignored in favor of a redicing of the stats:
... the study failed to demonstrate statistical significance on the primary endpoint and has not been replicated.Thus, the FDA ruled "This reprint carrier is false or misleading because it presents unsubstantiated superiority claims and overstates the efficacy of Taxotere."
The FDA has previously demonstrated mixed feelings about retrospective data analysis for cancer drugs.