Figure 2: Quality analysis of purified human BCMA protein, Fc-tagged. A. Human BCMA, Fc-tagged on SDS-PAGE under reducing condition. B. ELISA plate pre-coated by 2 μg/ml (100 μl/well) Human BAFF, hFc tagged protein can bind Human BCMA, Fc- tagged protein in a linear range of 0.03-15.625 ng/ml. C. ELISA plate pre-coated by 2 μg/ml (100 μl/well) Human BCMA, Fc-tagged protein can bind Anti-BCMA (huC11D5.3) (Its variable region was used to construct scFv portion of CAR-T Idecabtagene vicleucel (bb2121). ) in a linear range of 3.71-22.29 ng/ml.
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Development of anti-BCMA therapeutic mAbs for CAR-T application
Our pre-selected lead mAb molecules have been successfully used by different pharmaceutical companies for their drug development. Here is one of our case studies for the anti-BCMA therapeutic lead mAb molecule development (Figure 1).
We have prepared a large amount of human BCMA recombinant proteins as the antigen for immunization. The purities and activities of the proteins were validated by SDS-PAGE and different binding assays (Figure 2) before immunization.
After immunization, around 3~5 X10^8 B cell pools were isolated from the immunized rabbit and quickly frozen in liquid nitrogen as our B-cell seed library for human BCMA target. From 4ml of rabbit whole blood, we identified 70 ELISA positive B cell clones, out of which 13 worked for the flow application and were picked up for the downstream mAb cloning and sequencing. After Cand epitope comparison, 5 new clones were identified with unique CDR sequences comparing to the Bluebird anti-BCMA huC11D5.3 clone (Figure 3 & 4). All of them have shown comparable tumor cell killing efficacy with the Bluebird anti-BCMA huC11D5.3 clone in the CAR-T application after humanization (Figure 5). One has been picked up for an Investigator Initiated trial (IIT). The preliminary data is encouraging at this moment.