An inverted terminal repeat (ITR) is a palindromic DNA sequence located at both ends of the genome of certain viruses — most notably adeno-associated virus (AAV) — that forms a hairpin structure essential for genome replication, packaging, and integration. In AAV vector design, the ITRs are the only viral sequences retained in the recombinant vector, flanking the therapeutic transgene and enabling its encapsidation into the capsid. The integrity and correct configuration of ITRs are CQAs in AAV manufacturing, as truncated or modified ITRs can compromise vector potency and transduction efficiency.
