Antitumor activity of anti-CD30 immunotoxin (Ber-H2/saporin) in vitro and in severe combined immunodeficiency disease mice xenografted with human CD30+ anaplastic large-cell lymphoma

Abstract

To develop a novel adjunctive therapy for CD30 (Ki-1)+ anaplastic large- cell lymphoma (ALCL), we investigated in preclinical studies the antitumor activity of an immunotoxin (IT) constructed by coupling the plant ribosome- inactivating protein saporin (SO6) to the monoclonal antibody (MoAb) Ber-H2 that is directed against the CD30 molecule, a new member of the tumor necrosis factor receptor (TNFR) superfamily. The activity of Ber-H2/SO6 IT was tested both in vitro against the CD30+ ALCL-derived cell line JB6 and in vivo using our severe combined immunodeficiency disease (SCID) mouse model of human xenografted CD30+ ALCL. In vitro, the Ber-H2/SO6 IT was selectively and highly toxic to the JB6 cell line [50% inhibiting concentration (IC50), 3.23 x 10-12 mol/L as SO6]. In vivo, a 3-day treatment with nontoxic doses of Ber-H2/SO6 (50% of LD50) induced lasting complete remissions (CR) in 80% of mice when started 24 hours after tumor transplantation. In contrast, injection of the IT at later stages of tumor growth (mice bearing subcutaneous tumors of 40- to 60-mm3 volume), induced CR in only 6 of 21 (approximately 30%) mice and significantly delayed tumor growth rate (P