definiens: means any challenge in a legal oradministrative proceeding to the patentability, validity or enforceability of any of the Spacer Patent Rights ( or anyclaim thereof ), including by : ( a ) filing or pursuing a declaratory judgment action in which any of the Spacer PatentRights is alleged to be invalid or unenforceable ; ( b ) citing prior art against any of the Spacer Patent Rights, filing arequest for or pursuing a re - examination of any of the Spacer Patent Rights ( other than with COH ’s writtenagreement ), or becoming a party to or pursuing an interference ; or ( c ) filing or pursuing any re - examination, opposition, cancellation, nullity or other like proceedings against any of the Spacer Patent Rights ; but excluding any challengeraised as a defense against a claim, action or proceeding asserted by COH against Licensee, its Affiliates orSublicensees . In lieu of exercising its rights to terminate under this Section 7.3(a ) COH may elect upon written noticeto increase the payments due under all of Section 4 by * percent ( * % ), which election will be effective retroactively tothe date of the commencement of the Patent Challenge . Licensee acknowledges and agrees that this Section 7.3(a)is reasonable, valid and necessary for the adequate protection of COH ’s interest in and to the Spacer Patent Rights, and that would not have granted to Licensee the licenses under those Spacer Patent Rights, without this Section