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Updated: Aug 19, 2025
In Vitro Tumor Cell Rechallenge For Predictive Evaluation of Chimeric Antigen Receptor T Cell Antitumor Function
Published on: February 27, 2019
Compromised antigen binding and signaling interfere with bispecific CD19 and CD79a chimeric antigen receptor function
Isabel Leung1, Megan L Templeton1, Yun Lo1
1Clinical Research Division, Fred Hutchinson Research Center, Seattle, WA.
Abstract:
Therapy with CD19-directed chimeric antigen receptor (CAR) T cells has transformed the treatment of advanced B-cell malignancies. However, loss of or low antigen expression can enable tumor escape and limit the duration of responses achieved with CAR T-cell therapy. Engineering bispecific CAR T cells that target 2 tumor antigens could overcome antigen-negative escape. We found that CD79a and b, which are heterodimeric components of the B-cell receptor, were expressed on 84.3% of lymphoma cases using immunohistochemistry, and 87.3% of CD79ab-positive tumors also coexpressed CD19. We generated 3 bispecific permutations: tandem, bicistronic, and pooled products of CD79a-CD19 or CD79b-CD19 CAR T cells and showed that bispecific CAR T cells prevented the outgrowth of antigen-negative cells in a CD19-loss lymphoma xenograft model. However, tandem and bicistronic CAR T cells were less effective than monospecific CD19 or CD79a CAR T cells for the treatment of tumors that only expressed CD19 or CD79, respectively. When compared with monospecific CAR T cells, T cells expressing a tandem CAR exhibited reduced binding of each target antigen, and T cells expressing a bicistronic CAR vector exhibited reduced phosphorylation of downstream CAR signaling molecules. Our study showed that despite added specificity, tandem and bicistronic CAR T cells exhibit different defects that impair recognition of tumor cells expressing a single antigen. Our data provide support for targeting multiple B-cell antigens to improve efficacy and identify areas for improvement in bispecific receptor designs.
Insights
Bispecific chimeric antigen receptor (CAR) T cells targeting CD79a/b and CD19 show promise against B-cell malignancies. However, tandem and bicistronic designs impair single-antigen recognition, highlighting areas for improved bispecific CAR T-cell therapy.
Area of Science:
- Immunology
- Oncology
- Biotechnology
Background:
- Chimeric antigen receptor (CAR) T-cell therapy, particularly targeting CD19, has revolutionized B-cell malignancy treatment.
- Tumor escape due to antigen loss or low expression limits CAR T-cell therapy durability.
- Bispecific CAR T cells targeting multiple antigens offer a strategy to overcome antigen-negative tumor escape.
Purpose of the Study:
- To evaluate the efficacy of bispecific CAR T cells targeting CD79a/b and CD19 in B-cell malignancies.
- To investigate the impact of different bispecific CAR T-cell designs (tandem, bicistronic) on tumor recognition and efficacy.
- To identify potential limitations and areas for improvement in bispecific CAR T-cell receptor design.
Main Methods:
- Immunohistochemistry was used to assess CD79a/b and CD19 expression in lymphoma samples.
- Bispecific CAR T cells targeting CD79a-CD19 or CD79b-CD19 were generated in tandem, bicistronic, and pooled formats.
- Efficacy was evaluated in a CD19-loss lymphoma xenograft model, with comparisons to monospecific CAR T cells.
Main Results:
- CD79a/b and CD19 were coexpressed in a significant proportion of lymphoma cases.
- Bispecific CAR T cells prevented antigen-negative tumor outgrowth in vivo.
- Tandem and bicistronic CAR T cells showed reduced efficacy against tumors expressing only a single antigen compared to monospecific CAR T cells.
- Tandem CAR T cells exhibited reduced antigen binding, while bicistronic CAR T cells showed impaired downstream signaling.
Conclusions:
- Bispecific CAR T-cell therapy targeting multiple B-cell antigens can overcome tumor escape mechanisms.
- Current tandem and bicistronic CAR T-cell designs have inherent defects that impair recognition of single-antigen-positive tumors.
- Further optimization of bispecific CAR T-cell receptor design is necessary to enhance efficacy and broaden therapeutic potential.
