CD99 and neoplasm: A human monospecific bivalent single-chain fragment variable (scFv) diabody (dAbd C7 in development at Diatheva) targeting CD99 by recognizing a different epitope was developed [135] and characterized recently, with encouraging results similar to those obtained with murine antibodies [98] but with the advantage of preventing a potential human anti-mouse antibody (HAMA) response and enhanced penetration into the tumor mass.