Selective haematological cancer eradication with preserved haematopoiesis.

Haematopoietic stem cell (HSC) transplantation (HSCT) is the only curative treatment for a broad range of haematological malignancies, but the standard of care relies on untargeted chemotherapies and limited possibilities to treat malignant cells after HSCT without affecting the transplanted healthy cells1. Antigen-specific cell-depleting therapies hold the promise of much more targeted elimination of diseased cells, as witnessed in the past decade by the revolution of clinical practice for B cell malignancies2. However, target selection is complex and limited to antigens expressed on subsets of haematopoietic cells, resulting in a fragmented therapy landscape with high development costs2-5. Here we demonstrate that an antibody-drug conjugate (ADC) targeting the pan-haematopoietic marker CD45 enables the antigen-specific depletion of the entire haematopoietic system, including HSCs. Pairing this ADC with the transplantation of human HSCs engineered to be shielded from the CD45-targeting ADC enables the selective eradication of leukaemic cells with preserved haematopoiesis. The combination of CD45-targeting ADCs and engineered HSCs creates an almost universal strategy to replace a diseased haematopoietic system, irrespective of disease aetiology or originating cell type. We propose that this approach could have broad implications beyond haematological malignancies.

Antibody response to mRNA SARS-CoV-2 vaccination in 182 patients after allogeneic hematopoietic cell transplantation.

INTRODUCTION: Patients after allogeneic stem cell transplantation are at high risk for infection-related complications, and vaccination efficacy might be impaired depending on the immune reconstitution. In this study, we evaluate their response to mRNA vaccines against SARS-CoV-2. METHODS: During routine follow-up visits, patients were asked about their vaccination status and if they had a previous infection with SARS-CoV-2. In fully vaccinated patients, the antibody titer was measured using the Roche Elecsys Anti-SARS-CoV-2 S test. A titer of <1 U/L was considered as negative, titers of ≥250 U/ml as a high antibody titer, and a titer of 50-249 U/ml as a low antibody titer. Patient characteristics were evaluated by chart review to identify risk factors for poor vaccination response. RESULTS: The majority of patients developed a high antibody titer (138 out 182 patients, 75.8%). Risk factors for a low antibody titer were immunosuppressive therapy, a lymphocyte count <0.9 G/L, ongoing treatment for the underlying malignancy, and active graft-versus-host disease (GvHD). Donor type, underlying disease, a previous SARS-CoV-2 infection, and sex did not significantly influence the response to the vaccination. DISCUSSION: While patients undergoing allogeneic stem cell transplantation have been excluded from the initial registration trials, our real-world experience with a large patient cohort confirms the data of previous studies, showing that most patients do have a good response to mRNA vaccines against SARS-CoV-2. Nevertheless, a significant proportion of patients shows an inadequate vaccination, which can be improved after a third vaccination in most cases despite immunosuppressive therapy.

Dasatinib for treatment of CAR T-cell therapy-related complications.

Cytokine release syndrome (CRS) and immune effector cell-associated neurotoxicity syndrome (ICANS) are severe, potentially life-threatening side effects of chimeric antigen receptor T-cell (CAR T) therapy caused by the release of cytokines by proliferating and activated CAR T-cells. Current mainstay treatment includes interleukin-1 and interleukin-6 (IL-6) blockade and steroids. The use of steroids is still controversial, since they may have the potential to irreversibly damage CAR T-cells and thus increase the risk of relapse. Therefore, additional treatment options need to be explored. We report the successful treatment of a patient with a grade 3 CRS and grade 4 ICANS refractory to IL-6 blockade and steroids with the tyrosine kinase inhibitor dasatinib. The use of dasatinib for treatment of CAR T-cell therapy-related severe complications warrants further studies.