294 Comparison of preclinical efficacy between CD19 CAR-T and CD3×CD19 bispecific antibody (blinatumomab)

Background

Bispecific antibodies and CAR-T have been increasingly involved in cancer therapy, especially in treating hematologic tumors, where both treatments demonstrate impressive therapeutic effect in patients with B-cell lymphomas and leukemia. However, limited research were available for comparison between the two types of therapies. Here we describe a comparison in preclinical efficacy between bispecific antibodies and CAR-T, through the demonstration of both in vitro and in vivo efficacy evaluations of CD19 CAR-T (FMC63–41BB-CD3Z) and CD3×CD19 bispecific antibodies (Blinatumomab).

Methods

To evaluate in vitro cytotoxicity, CFSE-labelled CD19 positive Raji cells were co-cultured either with CD19 CAR-T or PBMCs supplemented with gradient concentrations of Blinatumomab. The level of apoptosis in Raji cells after co-culture was analyzed using flow cytometry at 4 to 48 hours. To evaluate in vivo tumor suppression, Raji tumor-bearing mice were grouped into CD19 CAR-T or Blinatumomab groups with separate conduct: In the CD19 CAR-T group, mice were administered with CAR-T through intravenous injection (1million CAR-T/mouse). In the Blinatumomab group, hPBMCs transplant were performed, and mice were administered with Blinatumomab six times via intravenous injection (0.5 μg/mouse). Tumor volume were monitored on weekly basis, peripheral blood were analyzed for CAR-T pharmacokinetics study.

Results

For in vitro cytotoxicity, CD19 CAR-T exhibited complete cytotoxicity towards Raji tumor cells in 24 hours at effector-target ratio of 1, while Blinatumomab demonstrated complete cytotoxicity towards Raji tumor cells in 48 hours at concentration of 1ng/mL. For in vivo tumor suppression, CD19 CAR-T showed complete response rate of 100% (6/6) 7 days after administration and no relapse event in later 39 days. CAR-T were detectable until day 21, no significant body weight changes were observed. Blinatumomab showed complete response rate of 100% (6/6) 7 days after administration and the relapse rate was 66.7% (4/6) at 14 days after administration.

Conclusions

Both CD19 CAR-T and Blinatumomab demonstrated a similar in vitro tumor suppressive effect and an initial in vivo response rate. However, CAR-T showcased a greater advantage in maintaining remission due to their more sustained pharmacokinetics and better in vivo proliferation capacity.