Swedish Orphan Biovitrum AB, of Stockholm, Sweden, announced that it has returned full development rights for its immune thrombocytopenic purpura (ITP) treatment and for hemolytic disease in newborn (HDN) prophylaxis to Symphogen A/S, of Copenhagen, Denmark, co-developer of Sym001, which is currently in Phase II trials for treatment of ITP and in anti-D prophylaxis to prevent HDN.