definiens: means, with respect to any Primary Development Compound and the related Backup Compounds, the period commencing on the date of CONFIDENTIAL TREATMENT REQUESTED designation by DS of a Primary Development Compound, and continuing until sixty ( 60 ) days following the date of receipt by the JRC of the Toxicology Studies Results with respect to such Primary Development Compound, or up to twe (: 2- ) subsequently evaluated Backup Compounds provided that DS has designated such Backup Compounds prior to the start of the first Toxicology Study ; provided that the DS Option Period shall end no later than tweflty s * ( U ) months after November 30, 2010 with respect to any Primary Development Compound and the related Backup Compounds whose DS Target is an Initial DS Target and shall end no later than t\venty six ( U ) months after the end of the Research Collaboration Period with respect to any Primary Development Compound and the related Backup Compounds whose DS Target is a New DS Target or a replacement to an Initial DS Target or a New DS Target designated pursuant to Section 3.5.2