definiens: means, with respect to a Target, any Target for which ( a ) SNFX or any of its Aﬃliates hasgranted an exclusive license or an exclusive option to a license, that in either case has not expired or terminated, to a ThirdParty to Develop, Manufacture,12Exhibit 10.1CERTAIN CONFIDENTIAL INFORMATION CONTAINED IN THIS DOCUMENT, MARKED BY [ * * * ], HAS BEEN OMITTEDBECAUSE IT IS NOT MATERIAL AND WOULD LIKELY CAUSE COMPETITIVE HARM TO MERSANA THERAPEUTICS, INC . IFPUBLICLY DISCLOSEDCommercialize and otherwise Exploit a product against the Target that would conﬂict with the grant of rights with respect tosuch Target to MERSANA hereunder prior to the date Agent sends notice of Final Target Veriﬁcation ( as deﬁned herein ) toMERSANA, ( b ) SNFX has notiﬁed MERSANA that it has reserved for itself or its Aﬃliates such Target ( without, for theavoidance of doubt, any obligation to conduct Development activities with respect to such Target ) ; provided that the numberof such reserved Targets shall not exceed three ( 3 ) at any given time and SNFX will not add or substitute any reservedTargets more than one ( 1 ) time per Calendar Quarter, or ( c ) SNFX has initiated a bona ﬁde program for Development of aproduct against the Target, for which SNFX has approved a research plan, has identiﬁed an antibody - drug conjugate orother product against such Target to be used in such program, and has commenced activities to make an antibody - drugconjugate or other product against such Target, and in the case of clause ( a ), ( b ) or ( c ), SNFX has provided written noticethereof to Agent prior to the date Agent sends notice of Final Target Verification to MERSANA