definiens: means a non - naturally occurring protein expressed from a [ single open reading frame ] that : ( a ) is capable of binding specifically to one or more Ligands ; and ( b ) consists solely of between one ( 1 ) and [ twenty ( 20 ) ] Domain(s ) ( from up to three ( 3 ) different Families ), that are covalently bound ( either directly to each other or, optionally, via linkers each of which is less than [ twenty ( 20 ) ] amino acids ), and consists of no other amino acid residues, except as expressly permitted in ( c ), ( d ) or ( e ) below ; and ( c ) optionally, has fused at [ one or both termini ] of the protein described in ( a ) and ( b ) above an amino acid sequence of less than [ twenty ( 20 ) ] amino acids ; and 4 * * * * Confidential Treatment Requested .. ( d ) optionally, has fused at [ one or both termini ] of the protein descnb ~ d In ( a ) ~d ( b ) above ( and ( c ) and/or ( e ), as applicable ) one or more other [ full length or partial ] protems [ ( other than Domains ) that confer one or more specific activities or functions ( e.g., an enzyme or a marker protein ) ], if, and only if : ( i ) [ such other protein(s ) or partial protein(s ) is not Known to confer, improve or modulate, or intended to confer, improve or modulate, any human therapeutic or prophylactic effect ], or ( ii ) [ such fusion protein is not intended for and is not developed, sold or otherwise commercialized for any human therapeutic or prophylactic use ], or ( iii ) such fusion protein is an Approved DBP Therapeutic Conjugate approved by [COMPANY] pursuant to Section 2.5 below ; and ( e ) optionally, at [ one or both termini ] of a protein described above ( Le ., a protein described in any permitted combination of ( a ), ( b ), ( c ) and ( d ) above ), a linker of less than [ twenty ( 20 ) ] amino acids that allows more rapid purification of such protein or detection of such protein in an assay ( e.g., ELISA )