Complex sentence: Tiazesim (Altinil) is not a TCA, but is a bicyclic antidepressant that is closely related structurally and pharmacologically, though, similarly to many TCAs, is no longer marketed.
Split into simpler sentences: Tiazesim (Altinil) is not a TCA, but is a bicyclic antidepressant that is closely related structurally and pharmacologically. Similarly to many TCAs, is no longer marketed.