\[Introduction\]
At present, CAR-T cell therapy targeting CD19 has achieved remarkable efficacy in the treatment of r/r B-NHL. However, at the same time, CAR-T cell treatment has a high incidence of cytokine release syndrome (CRS), immune cell-associated neurotoxicity syndrome (ICANS) and other toxicities. TCR-T is another adoptive T cell therapy, which recognizes the surface and intracellular antigens of target cells presented by major histocompatibility complex (MHC) molecules and engage CD3 signaling machinery, triggering a wide range of TCR-CD3 signaling to kill tumors. TCR-T is characterized by high affinity with target antigen, low toxicity, but difficulty in preparation.
Here, the researchers connected the murine TCR constant regions α and β with the light chain and heavy chain of the murine FMC63 single-chain variable fragment (scFv) respectively to construct a human leukocyte antigen (HLA)-independent antibody TCR chimera, called synthetic T cell receptor and antigen receptor (STAR). Then, researchers introduced an additional interchain disulfide bond by making cysteine mutations within TCRα/β constant regions, and employed hydrophobic substitutions to the TCR-α chain transmembrane domain to improve the receptor's stability on plasma membrane.
Further, the team disrupted the endogenous TRAC locus by CRISPR/cas9, and then knocked in the CD19-STAR construct to this locus, and transcription of CD19-STAR triggered by the TRAC endogenous promoter. TRAC locus knockout can prevent endogenous TCR assembly, and avoid the harm caused by graft-versus host disease (GVHD) as well as random insertion. This specific integration of "two in one" technology can give rise to highly efficient expression of CD19-STAR chimeric molecule on T cell surface, and the subsequent assembly of complete TCR signaling structure.
The molecular structure of STAR in this study: the variable region of TCRα/β chain is replaced with the heavy chain and light chain of FMC63 antibody respectively, the intracellular region of α/β chain is connected with an OX40 costimulatory molecule respectively.
STAR integrates the advantages of TCR and CAR, and is close to the natural TCR-antigen action mode with high affinity, high sensitivity, and low T cell exhaustion. Compared with TCR-T, it is easier to obtain and prepare. The researchers confirmed that the CD19-STAR-T cells, by in vitro and in vivo assays, had lower cytokine release but more efficient anti-tumor activities when compared to canonical CAR-T cells. In this study, we would like to evaluate the safety and efficacy of autologous TRAC locus-inserted CD19-STAR-T cell in r/r patients with r/r B-NHL . The completion of this trial will provide a research foundation for potential universal allogeneic adoptive T cell therapy.
\[Study design\]
Phase 1 (dose escalation)
In phase 1, 9 to 18 subjects will be enrolled. Subjects will receive 3 doses of CD19-STAR-T cell therapy (1 × 10\^6 cells/kg, 3 × 10\^6 cells/kg, 1 × 10\^7 cells/kg) from low dose to high dose according to the "3 + 3" principle:
1. Three patients were enrolled in the lowest dose group.
2. Subsequent patients were enrolled according to the following rules:
1. If the incidence of dose limiting toxicity (DLT) was 0/3, 3 patients were enrolled in the next high-dose group.
2. If the incidence of DLT was 1/3, 3 patients were enrolled at the same dose; If the incidence of DLT was 1/3 + 0/3, 3 patients were enrolled in the next high-dose group. If the incidence of DLT was 1/3 + 1/3, this dose was defined as maximum tolerated dose (MTD); If the incidence of DLT was 1/3 + 2/3 or 1/3 + 3/3, the previous dose was MTD.
3. If the incidence of DLT was 2/3 or 3/3, the previous dose was MTD.
To ensure the safety of the subjects, the first subject in each dose group was observed for at least 28 days after the cell infusion. If no DLT occurred, the remaining two subjects could be enrolled and treated at the same dose level. The safety data of all subjects in each dose group until day 28 should be reviewed and tolerated before proceeding to the next dose group trial. No dose escalation was allowed for the same subject during the trial. If a subject drop out during the observation period due to non-DLT reasons, new subjects should be enrolled to make up for the number of subjects who drop out.
Phase 2 (expansion cohort)
In phase 2, 10 to 20 subjects will be enrolled and receive CD19-STAR-T cell infusion at dose of RP2D, which will be determined based on the MTD, occurrence of DLT, the obtained efficacy results, pharmacokinetics / pharmacodynamics and other data according to the phase 1.
\[Objectives\]
The primary objectives of the phase 1 were to evaluate the tolerability, safety, and determine recommended phase 2 dose (RP2D). The primary purpose of the phase 2 study was to evaluate the efficacy.
