Adoptively transferred CD19 chimeric antigen receptor (CAR) T-cells have led to impressive clinical outcomes in B-cell malignancies. Beyond induction of remission, the persistence of CAR-T cells is required to prevent relapse and provide long-term disease control. To improve CAR-T cell function and persistence, we developed a composite costimulatory domain of a B-cell signaling moiety, CD79A/CD40, to induce a nuclear translocating signal, NF-κB, to synergize with other T-cell signals and improve CAR-T cell function. CD79A/CD40 incorporating CD19CAR-T cells (CD19.79a.40z) exhibited higher NF-κB and p38 activity upon CD19 antigen exposure compared with the CD28 or 4-1BB incorporating CD19CAR-T cells (CD19.28z and CD19.BBz). Notably, we found that CD19.79a.40z CAR-T cells continued to suppress CD19⁺ target cells throughout the co-culture assay, whereas a tendency for tumor growth was observed with CD19.28z CAR-T cells. Moreover, CD19.79a.40z CAR-T cells exhibited robust T-cell proliferation after culturing with CD19⁺ target cells regardless of exogenous interleukin-2. In terms of in vivo efficiency, CD19.79a.40z demonstrated superior anti-tumor activity and in vivo CAR-T cell proliferation compared with CD19.28z and CD19.BBz CD19CAR-T cells in Raji-inoculated mice. Taken together, our data demonstrate that the CD79A/CD40 costimulatory domain endows CAR-T cells with enhanced proliferative capacity and improved anti-tumor efficacy in a murine model.

The outcomes of 7/8 allele-matched unrelated bone marrow transplantation (7/8 UBMT) and umbilical cord blood transplantation (UCBT) have been improving. We retrospectively analyzed adults with acute leukemia who underwent their first 7/8 UBMT or UCBT in Japan. Between January 2008 and December 2017, of the 4,150 patients recorded, 488 underwent 7/8 UBMT and 3,662 underwent UCBT. Only 32 patients with 7/8 UBMT had graft-versus-host-disease (GVHD) high-risk human leukocyte antigen mismatch pairs. Overall survival at 3 years was 54% and 46% for 7/8 UBMT and UCBT, respectively, which was not significant in the multivariate analysis (hazard ratio [HR]: 1.01; 95% confidence interval [CI]: 0.88-1.17; p = 0.89). The 7/8 UBMT and UCBT showed a similar non-relapse mortality rate (HR: 1.16; 95% CI: 0.96-1.45; p = 0.16) and relapse rate (HR: 0.85; 95% CI: 0.71-1.02; p = 0.08). However, UCBT showed a lower risk of Grade II-IV acute GVHD (HR: 0.76; 95% CI: 0.65-0.88; p < 0.001) and chronic GVHD (HR: 0.77; 95% CI: 0.66-0.91; p = 0.002) compared with 7/8 UBMT. In stratified analyses combining disease risk with conditioning intensity, 7/8 UBMT showed superior overall survival to UCBT in standard risk and myeloablative conditioning (HR: 0.72; 95% CI: 0.56-0.93; p = 0.014). Both 7/8 UBMT and UCBT are appropriate alternative donor sources. We can select the source on the basis of disease risk, patient tolerability, or concerns regarding GVHD.

Despite the remarkable initial efficacy of CD19 chimeric Ag receptor T (CAR-T) cell therapy, a high incidence of relapse has been observed. To further increase treatment efficacy and reduce the rate of escape of Ag-negative cells, we need to develop CAR-T cells that target other Ags. Given its restricted expression pattern, CD37 was considered a preferred novel target for immunotherapy in hematopoietic malignancies. Therefore, we designed a CD37-targeting CAR-T (CD37CAR-T) using the single-chain variable fragment of a humanized anti-CD37 Ab, transmembrane and intracellular domains of CD28, and CD3ζ signaling domains. High levels of CD37 expression were confirmed in B cells from human peripheral blood and bone marrow B cell precursors at late developmental stages; by contrast, more limited expression of CD37 was observed in early precursor B cells. Furthermore, we found that human CD37CAR-T cells with longer spacer lengths exhibited high gene transduction efficacy but reduced capacity to proliferate; this may be due to overactivation and fratricide. Spacer length optimization resulted in a modest transduction efficiency together with robust capacity to proliferate. CD37CAR-T cells with optimized spacer length efficiently targeted various CD37⁺ human tumor cell lines but had no impact on normal leukocytes both in vitro and in vivo. CD37CAR-T cells effectively eradicated Raji cells in xenograft model. Collectively, these results suggested that spacer-optimized CD37CAR-T cells could target CD37-high neoplastic B cells both in vitro and in vivo, with only limited interactions with their normal leukocyte lineages, thereby providing an additional promising therapeutic intervention for patients with B cell malignancies. Key Points Novel anti–CD37CAR-T cells were developed to target another B cell Ag. Shorter spacer length CAR mediated the attenuated signaling rather than longer spacer CAR. Optimizing the spacer length minimized fratricide to maintain the antitumor effect.

Previous Japanese studies have shown that bone marrow transplantation (BMT) is associated with better survival compared with peripheral blood stem cell transplantation (PBSCT) from a matched related donor (MRD). PBSCT recipients have shown higher incidences of severe graft-versus-host disease (GVHD) and nonrelapse mortality (NRM) compared with BMT recipients. In recent years, the efficacy and safety of antithymocyte globulin (ATG) for PBSCT recipients has been evaluated worldwide. In the present study, we aimed to compare BMT and PBSCT recipients to identify current improvements and unmet needs among MRD PBSCT recipients. In addition, we evaluated the impact of ATG administration on the outcomes of PBSCT recipients. We retrospectively analyzed patients age ≥16 years with acute leukemia, myelodysplastic syndrome, or chronic myelogenous leukemia who underwent their first BMT or PBSCT from an MRD between 2009 and 2018 in Japan. A total of 3599 transplantations were performed (BMT, n = 1218; PBSCT without ATG [PBSCT-ATG(-)], n = 2288; PBSCT with ATG [PBSCT-ATG(+)], n = 93). The PBSCT-ATG(-) group had a higher NRM (hazard ratio [HR], 1.30; 95% confidence interval [CI], 1.08 to 1.57; P = .005) and lower overall survival (OS) (HR, 1.16; 95% CI, 1.04 to 1.30; P = .011) compared with the BMT group. Furthermore, the PBSCT-ATG(-) group had higher incidences of grade III-IV, stage 2-4 gut, high-risk, and steroid-refractory acute GVHD compared with the BMT group. Acute GVHD had a negative impact on NRM and OS. The PBSCT-ATG(-) group also was associated with an elevated risk of chronic GVHD (HR, 1.89; 95% CI, 1.24 to 2.57; P < .001) and extensive chronic GVHD (HR, 1.44; 95% CI, 1.23 to 1.68; P < .001). The incidences of acute GVHD, chronic GVHD, and NRM and chronic GVHD-free relapse-free survival rates were comparable between the PBSCT-ATG(+) and BMT groups. The OS of patients with acute GVHD was similar in the 3 donor groups. Patients treated with reduced-intensity conditioning in the PBSCT-ATG(+) group had a higher relapse rate and lower OS rate compared with those in the BMT group. In this Japanese cohort, standard calcineurin inhibitor-based GVHD prophylaxis was not sufficient for recipients of MRD PBSCT because of the high incidence of severe acute GVHD. Prophylactic ATG was found to be a promising strategy against GVHD.