Toxin-Based Therapeutic Approaches

Shapira, Assaf; Benhar, Itai

Targeting CD22 and CD19: RFB4-dgA and HD37-dgA CD22 and CD19 are cell surface glycoproteins expressed on normal and malignant B cells [306] [307] [308] [309] . For targeting B-cell lymphoma cells, the anti CD22 monoclonal antibody RFB4 [190, 310] and the anti CD19 monoclonal antibody HD37 [311] were conjugated to dgA. In a Phase I clinical trial with the immunotoxin RFB4-dgA (IMTOX-22), five of 24 evaluable patients with B-cell lymphoma showed a partial response and one showed a complete response. Similar results were obtained when the drug was administrated as a continuous infusion instead of intermittent bolus [67, 312] . Partial and complete responses were also obtained in a Phase I trial on patients with non-Hodgkin's B-cell lymphoma treated with the immunotoxin HD37-dgA (IMTOX-19) [69] . Vascular leak syndrome (VLS) was a common dose-related toxicity in these studies.