Table 1.

Terms and definitions describing patient biopharmaceuticals (BP) treatment history

Term	Definition
Treatment-naive subject:	Subject not exposed previously to the active substance in the BP
Treatment days*	Days on which the subject received treatment with the BP
Exposure days*	Days over which the subject was exposed to the BP
Total doses	Total number of doses (administrations) of the BP received by the subject
Drug holiday	Interruption in regularly scheduled dose administrations of a BP that is intended for chronic administration on a regular schedule (e.g. weekly or monthly)
Cumulative treatment days	Total number of days on which the subject received treatment with the BP
Cumulative exposure days	Total number of days over which the subject was exposed to the BP
Time to end-point	The length of time from initial treatment to measured end-point

^*In the terminology used in clinical hemophilia literature [27] and the relevant European guidelines for clinical evaluation of therapeutic hemophila products [29,30], the accepted definition of ‘exposure days’ is equivalent to the definition of ‘treatment days’ given in Table 1.