A bispecific ligand-directed toxin (BLT) called DT2219ARL consisting of two scFv ligands recognizing CD19 and CD22 and catalytic DT390 was genetically enhanced for superior in vivo anti-leukemia activity. Genetic alterations included reverse orienting VH-VL domains and adding aggregation reducing/stabilizing linkers. In vivo, these improvements resulted in previously unseen long-term tumor-free survivors measured in a bioluminescent xenograft imaging model in which the progression of human Raji Burkitt's lymphoma could be tracked in real time and in a Daudi model as well. Studies showed DT2219ARL was potent (IC50s 0.06-0.2 nM range) and selectively blockable. Imaging studies indicated the highly invasive nature of this B cell malignancy model and showed it likely induced pre-terminal hind limb paralysis because of metastasis to spinal regions prevented by DT2219ARL. DT2219ARL represents a new class of bispecific biological that can be continually improved by genetic mutation.
Bibliographical noteFunding Information:
This work was supported in part by the US Public Health Service Grants RO1-CA36725 and RO1-CA082154 awarded by the NCI and the NIAID, DHHS and Children's Cancer Research Fund, the Lion's Children's Cancer Fund, and the William Lawrence and Blanche Hughes Fund.
- Anti-CD19 sFv
- Anti-CD22 sFv
- Diphtheria toxin
- Scid model