Clinical Overview (CLO)

A Clinical Overview (CLO) is a succinct discussion and interpretation of the findings from clinical studies together with any other relevant information. The purpose of the CLO is to provide a critical analysis of the clinical data in the Common Technical Document (Module 2.5). In other words, the CLO should primarily present the conclusions and implications of those data, and should not recapitulate them.


The CLO presents the strengths and limitations of the development program and study results, analyses the benefits and risks of the medicinal product in its intended use, and describes how the study results support critical parts of the product labeling/prescribing information. In addition, any particular efficacy or safety issues encountered in development and any unresolved issues, with plans to resolve them, should be included.


The CLO is not updated systematically, but an addendum may be prepared to support the update of Prescribing Information (eg, due to post-marketing safety issue) or as a follow-up post-marketing commitment/measure.


Writing the CLO is a collaborative effort involving many functions. The large number of sources, dossier size, and data complexity as well as the timelines and the simultaneous development of several CTD documents. It is therefore crucial to determine the key messages as early as possible.


The Medical Writer can play a key role in the document development process, by ensuring that the data are well structured, the key messages are brought forward clearly, it is a high-level summary, and ensuring consistency with other CTD documents that are developed in parallel.


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