definiens: means the Compound known as ACH - I095 ( also known as GS-9525 ) . means September 2,2009 . means the period beginning on the Amendment # 3 Effective Date and .. continuing until the earliest of ( a ) [COMPANY] 's exercise of its opt - in right pursuant to Section 2A.2, ( b ) forty - five ( 45 ) days after [COMPANY] 's receipt ofa POC Notice, ( c ) forty - five ( 45 ) days after [COMPANY] 's receipt of a POC Failure Notice . means Compounds other than ACH - I095 . " 2 . Further Amendment of Exhibit 1.2 . Exhibit 1.2, as previously amended, is hereby amended by inserting the following sentence at the end thereof : " Notwithstanding the foregoing, Compounds shall exclude compounds that have not been conceived, made or identified by either Party prior to the Amendment # 3 Effective Date . " 1 USIDOCS 7280927vl 3 . Amendment of Exhibit 1.3 . Exhibit 1.3 is hereby restated in its entirety to read as follows : . Proof of Concept " means : Demonstration of at least a mean one ( 1 ) log ! 0 decrease from baseline in plasma HCV RNA at the end of dosing of at least one dose group in a clinical study of suitable design ( which design with respect to ACH-1095 shall be reasonably determined by [COMPANY] . and which design with respect to any Other Compound shall be approved by the Research Committee ) plus a safety . profile consistent with advancement to the next stage of clinical testing