Complex sentence: Taking place between August 2009 and October 2010,20 007 participants were enrolled in its first phase of recruitment (Phase A) and a new wave of recruitment (Phase B) will enroll an additional 17 000 participants by March 2013.
Split into simpler sentences: Taking place between August 2009 and October 2010,20 007 participants were enrolled in its first phase of recruitment (Phase A). A new wave of recruitment (Phase B) will enroll an additional 17 000 participants by March 2013.