definiens: means any of ( i ) PRO051 and PRO044, and ( ii ) comp ounds comprising an antisense oligonucleotide ( ) that are directed to exon s kipping by a mechanism intended to directly induce single exon skipping in the dystrophin gene for the treatm ent of DMD for the relevant exons of the Exon 51 Pr ogram, the Exon 44 Program, the DMD Program 3, or the DMD Program 4, as applicable, and in the case of PRO051 and PRO044, all derivatives and improvements of suc h compounds : ( a ) that are existing as of the Effect i ve Date of the Collaboration Agreement, or ( b ) that were Re searched and/or Developed by [COMPANY] under a Collaboration Program or ( c ) that were identified, further modified, optimized or otherwise Researched or Developed by [COMPANY] under the Exon 51 Program