definiens: means any action, suit, proceeding or claim by [COMPANY] or itsSublicensees or Aﬃliates challenging the validity, patentability, scope, priority, construction, inventorship, enforceability orCytomX ’s or its Aﬃliate ’s or licensor ’s ownership of any CytomX Patent or any Collaboration Patent owned by CytomX, asapplicable, in any forum, in each case, with respect to a Product under this Agreement, but excludes any assertion byAstellas or its Sublicensees or Aﬃliates relating to validity, patentability, scope, priority, construction, non - infringement, inventorship, ownership or enforceability as a defense in any legal proceeding, administrative proceeding or arbitrationbrought by CytomX or its Aﬃliates or licensors asserting infringement against [COMPANY] or its Sublicensees or Aﬃliates withrespect to the relevant Product under this Agreement