A preparation of soluble adapter molecules consisting of an antigen-binding moiety targeting CD123 linked to a peptide motif recognizable by UniCAR02-T, that may be used to activate UniCAR02-T. Upon administration of CD123-specific targeting module (TM) TM123, and upon co-administration of UniCAR02-T, the antigen-binding moiety of TM123 targets and binds to cancer cells expressing CD123, and the binding domain of UniCAR02-T binds to the nuclear antigen motif of TM123. This activates UniCAR02-T, and induces selective toxicity in and causes lysis of CD123-expressing tumor cells. CD123 is normally expressed on committed blood progenitor cells in the bone marrow; its overexpression is associated with both increased leukemic cell proliferation and aggressiveness.