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Rational redesign of antigen binding domain improves in vivo efficacy of the CD22-CAR

ABSTRACT: Chimeric antigen receptor (CAR) T cells targeting CD19 are highly effective against B-lineage malignancies. However, about half of patients either fail to achieve complete remission (in the case of lymphoma) or relapse (in the case of acute lymphoblastic leukemia). CD22 represents an alternative highly B-lineage-restricted target. Although CD22-targeted CAR T cells are clinically active, targeting this antigen has proven difficult relative to CD19, attributable, in part, to lower expression levels. Commonly, patients relapse or progress with reduced CD22 expression compared to pre-treatment, contrasting with the loss of CD19 expression typically observed after CD19-CAR therapy. Prior work demonstrated that an antigen-independent “tonic” signaling CD22-CAR has enhanced clinical efficacy relative to other CD22-CARs tested. However, tonic signaling has been shown to be detrimental to long-term CAR T cell function. Here, we demonstrate a balance between binding affinity and antigen-independent signaling (determined by length of the linker between fragment variable regions) in determining CAR function against CD22. We show that CAR function against both CD22Lo and WT leukemia can be augmented by boosting binding affinity without shortening the linker to induce tonic signaling, establishing rational combinatorial modification of antigen binding domain as an important approach for modulating the function of cellular therapeutics.

ORGANISM(S): Homo sapiens

PROVIDER: GSE313971 | GEO | 2025/12/17

REPOSITORIES: GEO

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Project description:Chimeric antigen receptor (CAR) T cell therapy have demonstrated remarkable success in treating B-cell malignancies that are refractory to standard therapies; however, preclinical and clinical studies have demonstrated that CAR T cell efficacy is greatly reduced against antigen-low tumors. This was exemplified in a clinical trial of CD22-directed CAR T cells where post-CAR relapses were driven by a decrease in the surface expression of the CD22 antigen. To address the poor response of CAR T cells to antigen-low tumor cells, we performed global phosphoproteomics using a SILAC/mass spectrometry approach to examine signal transduction events within CAR T cells in response to high- and low-levels of CD22 antigen. Stimulation with low levels of CD22 antigen resulted in decreased activation of several canonical T cell signaling pathways in CAR T cells, suggesting poor utilization of LAT. To overcome this inefficiency of LAT activation, we designed a bicistronic construct consisting of a clinically active 2nd generation CD22-BBz CAR along with a novel Adjunctive LAT Activating CAR incorporating the intracellular signaling domain of LAT (ALA-CART). ALA-CART cells demonstrated enhanced phosphorylation of LAT and restored downstream signaling in response to low levels of CD22. In xenograft models, ALA-CART cells completely eradicated CD22-low leukemia, significantly extending survival of mice in comparison to the clinically-active, standard CD22-BBz CAR T cells. Compared to the standard CD22-BBz CAR T cells, ALA-CART cells exhibited transcriptional differences in the resting state reflecting a less differentiated state, which corresponded to an enrichment of T stem cell memory cells and enhanced in vivo persistence. Thus, through the identification of CAR signaling deficits, we rationally designed the ALA-CART platform which improves the sensitivity and persistence of CAR T cells to target antigen-low cells, overcoming a mechanism of resistance to standard CAR therapies.

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Rational redesign of antigen binding domain improves in vivo efficacy of the CD22-CAR

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