Immunotherapeutic strategies in neuroblastoma: Antitumoral activity of deglycosylated ricin A conjugated anti-CD2 antibodies and anti-CD3xanti-GD2 bispecific antibodies

Background. The antigen GD2 is selectively expressed on the surface of neur oblastoma cells, and is detected by the monoclonal antibody BW704. In this study, we describe the antitumoral capacity of the immunotoxin BW704dgA (BW 704 conjugated to deglycosylated ricin A), and of anti-CD3xanti-GD2 bispeci fic antibodies that are capable of redirecting cytotoxic T cells towards ne uroblastoma cells. We further investigate the in vivo activity of BW704dgA immunotoxins in a human neuroblastoma model in SCID mice. Procedure. BW704d gA immunotoxins were injected i.p. as a single dose (48 mug/mouse) on day 4 or divided into three doses on day 4, 5, and 6 after i.v. inoculation of t he human neuroblastoma cell line IMR5-75. Results, The mean survival time ( MST) of BW704dgA treated animals was significantly increased (MST 49 days) compared to the control animals treated with irrelevant immunotoxin, unconj ugated BW704, or control buffer (MST 33 to 39 days, P < 0.0001), without di fferences in the application schedules. Anti-CD3xanti-NP antibodies and NP- conjugated GD2-antibodies (BW704-NP) were used in a cytotoxicity assay with cytotoxic T-cells as effecters, and tracer labeled neuroblastoma cell line IMR5 as target cells. Anti-CD3xanti-NP antibodies, together with BW704-NP, showed increased cytotoxic activity compared to the incubation with CD3xan ti-NP antibodies alone or with unconjugated anti-GD2. Additionally, a dose- dependent effect of NP-conjugated anti-GD2-antibodies upon the lysis of the target cells could be demonstrated. In this report, we describe two immuno therapeutic approaches using GD2 binding BW704 antibodies, modified as immu notoxin and a bispecific antibody, for the targeting and elimination of neu roblastoma cells. Conclusions. We envisage a combined immunotherapeutic reg imen consisting of BW704dgA mediated stem cell purging, followed by a syste mic treatment with anti-CD3xanti-CD2 bispecific antibodies in neuroblastoma . Med. Pediatr. Oncol. 36:185-189, 2001. (C) 2001 Wiley-Liss, Inc.