definiens: means a Ligand ( a ) that is proprietary to any Third Party ( i.e., [ as to which research to develop human therapeutic Products binding to such Ligand can not be conducted by A vidia without a license for such Ligand from a Third Party ) ) ; or ( b ) that was an Avidia Target but ceased to be an Avidia Target pursuant to Section 5.3.2 or 5.3.4 ; or ( c ) for which Avidia did not commence any research for its own benefit to develop any Product [ that binds to such a Ligand for any human therapeutic and/or prophylactic use ], but with regard to which a Third Party has entered into a written agreement with A vidia pursuant to which such Third Party will collaborate with and sponsor research at Avidia to develop Products [ that bind to such Ligand for human therapeutic and/or prophylactic use ]