No abstract

Tisagenlecleucel is an autologous anti-CD19 chimeric antigen receptor-T cell therapy with clinically meaningful outcomes demonstrated in patients with relapsed/refractory (r/r) B-cell lymphoma. In a previous pilot study of tisagenlecleucel in r/r follicular lymphoma (FL), 71% of patients achieved a complete response (CR). Here we report the primary, prespecified interim analysis of the ELARA phase 2 multinational trial of tisagenlecleucel in adults with r/r FL after two or more treatment lines or who relapsed after autologous stem cell transplant (no. NCT03568461). The primary endpoint was CR rate (CRR). Secondary endpoints included overall response rate (ORR), duration of response, progression-free survival, overall survival, pharmacokinetics and safety. As of 29 March 2021, 97/98 enrolled patients received tisagenlecleucel (median follow-up, 16.59 months; interquartile range, 13.8-20.21). The primary endpoint was met. In the efficacy set (n = 94), CRR was 69.1% (95% confidence interval, 58.8-78.3) and ORR 86.2% (95% confidence interval, 77.5-92.4). Within 8 weeks of infusion, rates of cytokine release syndrome were 48.5% (grade ≥3, 0%), neurological events 37.1% (grade ≥3, 3%) and immune effector cell-associated neurotoxicity syndrome (ICANS) 4.1% (grade ≥3, 1%) in the safety set (n = 97), with no treatment-related deaths. Tisagenlecleucel is safe and effective in extensively pretreated r/r FL, including in high-risk patients.

No abstract

Adult T cell leukemia (ATL) is an aggressive neoplastic disease, in which a quarter of the patients develop opportunistic infections due to cellular immunodeficiency. However, the underlying mechanism responsible for the immunosuppression has remained unclear. Recent studies have demonstrated that the leukemia cells from a subset of patients with ATL express Foxp3, a specific marker for CD25+CD4+ regulatory T (Treg) cells, which regulate the immune response by suppressing CD4+ T cell functions. However, whether there is a functional resemblance between ATL cells that have Foxp3 expression and Treg cells is still unknown. In this report, we confirmed the high expression of Foxp3 in leukemia cells from 5 of 12 ATL patients and demonstrated that ATL cells from 3 patients suppressed the proliferation of CD4+ T cells. Similarly, one of six HTLV-I-infected cell lines showed both high Foxp3 expression and suppressive activity. Like Treg cells, the suppression induced by the ATL cells from two patients and the HTLV-infected cell line appeared to be mediated by a cell-cell contact-dependent mechanism. Nevertheless, among the ATL cells that strongly expressed Foxp3, those from two of the five patients showed no apparent suppressive activity. Furthermore, retroviral transfection of Foxp3 did not confer any suppressive function on low Foxp3-expressing HTLV-I-infected cell lines. These results indicate that Foxp3 may be essential but is not sufficient for the Treg-cell-like suppressive activity of ATL cells and HTLV-I-infected cell lines.

Erythroid 5-aminolevulinate synthase (ALAS-E) catalyzes the first step of heme biosynthesis in erythroid cells. Mutation of human ALAS-E causes the disorder X-linked sideroblastic anemia. To examine the roles of heme during hematopoiesis, we disrupted the mouse ALAS-E gene. ALAS-E-null embryos showed no hemoglobinized cells and died by embryonic day 11.5, indicating that ALAS-E is the principal isozyme contributing to erythroid heme biosynthesis. In the ALAS-E-null mutant embryos, erythroid differentiation was arrested, and an abnormal hematopoietic cell fraction emerged that accumulated a large amount of iron diffusely in the cytoplasm. In contrast, we found typical ring sideroblasts that accumulated iron mostly in mitochondria in adult mice chimeric for ALAS-E-null mutant cells, indicating that the mode of iron accumulation caused by the lack of ALAS-E is different in primitive and definitive erythroid cells. These results demonstrate that ALAS-E, and hence heme supply, is necessary for differentiation and iron metabolism of erythroid cells.