An Updated Review of Food and Drug Administration Warning and Untitled Letters for Clinical Outcome Assessment Claims Between 2013 and 2021

Objectives: We aimed to ascertain the frequency and types of Food and Drug Administration (FDA)-identified clinical outcome assessment (COA) violations in US pharmaceutical promotional materials from 2013 to 2021 by updating the review by Symonds et al (covering the period 2006-2012 for patient-reported outcomes [PRO] measures), expanding to infringements across all types of COAs, and grouping by efficacy or overall patient experience.Methods: Warning letters (WLs) and untitled letters (ULs) issued by the FDA's Office of Prescription Drug Promotion were reviewed for COA violations and classified by their type: (1) COA measure not fit for purpose, (2) issue with study design or interpretation of results, and (3) inadequate statistical analysis.Results: From 2013 to 2021, the FDA issued 22 WLs and 65 ULs. Year 2013 showed the highest number of letters issued (n = 24). Of the total 87 letters reviewed, 22 (25%) contained a COA violation, consisting of 6 WLs (27%) and 16 ULs (25%), including 20 (23%) with a PRO-related violation. The most common violations cited "study design or interpretation of results" (21 of 22 [95%]).Conclusions: Overall, the absolute number of WLs and ULs issued declined when comparing 2006 to 2012 with 2013 to 2021. Despite the overall reduction, this review still identified 25% of letters citing COA infringements (23% with PRO issues), which was similar to the prior review (19% PRO infringements). This may be due to increased FDA attention to patient-focused drug development.