The developmental pathway for human megakaryocytes remains unclear, and the definition of pure unipotent megakaryocyte progenitor is still controversial. Using single-cell transcriptome analysis, we have identified a cluster of cells within immature hematopoietic stem- and progenitor-cell populations that specifically expresses genes related to the megakaryocyte lineage. We used CD41 as a positive marker to identify these cells within the CD34CD38IL-3RαCD45RA common myeloid progenitor (CMP) population. These cells lacked erythroid and granulocyte-macrophage potential but exhibited robust differentiation into the megakaryocyte lineage at a high frequency, both in vivo and in vitro. The efficiency and expansion potential of these cells exceeded those of conventional bipotent megakaryocyte/erythrocyte progenitors. Accordingly, the CD41 CMP was defined as a unipotent megakaryocyte progenitor (MegP) that is likely to represent the major pathway for human megakaryopoiesis, independent of canonical megakaryocyte-erythroid lineage bifurcation. In the bone marrow of patients with essential thrombocythemia, the MegP population was significantly expanded in the context of a high burden of Janus kinase 2 mutations. Thus, the prospectively isolatable and functionally homogeneous human MegP will be useful for the elucidation of the mechanisms underlying normal and malignant human hematopoiesis.
Infertility associated with ovarian failure is a serious late complication for female survivors of allogeneic hematopoietic stem cell transplantation (SCT). Although pretransplant conditioning regimen has been appreciated as a cause of ovarian failure, increased application of reduced-intensity conditioning allowed us to revisit other factors possibly affecting ovarian function after allogeneic SCT. We have addressed whether donor T-cell-mediated graft-versus-host disease (GVHD) could be causally related to female infertility in mice. Histological evaluation of the ovaries after SCT demonstrated donor T-cell infiltration in close proximity to apoptotic granulosa cells in the ovarian follicles, resulting in impaired follicular hormone production and maturation of ovarian follicles. Mating experiments showed that female recipients of allogeneic SCT deliver significantly fewer newborns than recipients of syngeneic SCT. GVHD-mediated ovary insufficiency and infertility were independent of conditioning. Pharmacologic GVHD prophylaxis protected the ovary from GVHD and preserved fertility. These results demonstrate for the first time that GVHD targets the ovary and impairs ovarian function and fertility and has important clinical implications in young female transplant recipients with nonmalignant diseases, in whom minimally toxic regimens are used.
Human interleukin-3 receptor alpha (IL-3Ra, CD123), which promotes the proliferation and differentiation of hematopoietic cells, is highly expressed in myeloid malignancies, including acute myeloid leukemia (AML) and myelodysplastic syndrome (MDS). We newly generated KHK2823, a non-fucosylated fully human IgG1 monoclonal antibody against human IL-3Ra, by utilizing the POTELLIGENT® technology. Here, we describe the in vitro and in vivo preclinical efficacy and safety of KHK2823, as well as its pharmacodynamic (PD) profile. At first, we explored that KHK2823 bound to various hematological malignant cells and leukemic stem cells. The cells from AML and MDS bone marrows were found to be bound by KHK2823. A significant part of bone marrow cells derived from B-cell acute lymphoblastic leukemia (B-ALL) patients was also bound by KHK2823. KHK2823 bound to soluble human IL-3Ra protein with a sub-nanomolar dissociation constant (KD), and recognized CD34+ CD38+ (leukemic blast) and/or CD34+ CD38- (leukemic stem cell) cells in patients with AML/MDS, as well as AML cell lines, thereby obtaining a high antibody-dependent cellular cytotoxic activity without complement-dependent cytotoxicity. Interestingly, KHK2823 did not interfere with the binding of IL-3 to IL-3R. The lack of a receptor-ligand interaction may conserve the IL-3 signal, which plays an important role in normal hematopoiesis. In a tumor model xenografting the human AML cell line MOLM-13 on nude rats, KHK2823 significantly suppressed the tumor growth at doses of 0.1 and 1 mg/kg (Figure 1). The PD and toxicity profiles of KHK2823 were assessed in cynomolgus monkeys administered at doses ranging from 0.1 to 100 mg/kg by i.v. infusion, once weekly for 4 weeks. KHK2823 was generally well tolerated in monkeys, even at 100 mg/kg. The number of IL-3Ra-positive cells in the peripheral blood of cynomolgus monkeys decreased in all groups receiving KHK2823, which suggest KHK2823 could exert its depletion activity of IL-3Ra-positive cells in human (Figure 2). Currently, the safety and tolerability of KHK2823 is being investigated in patients with AML or MDS in a Phase 1 study (NCT02181699, https://clinicaltrials.gov/ct2/show/NCT02181699). This is the first non-randomized, open-label, dose escalation clinical study to investigate the safety, PK, immunogenicity and PD of repeated doses of KHK2823. In summary, KHK2823 was confirmed to bind to AML, MDS and B-ALL cells as the IL-3Ra in accordance with other publications. KHK2823 was also found to eliminate AML cells in vitro and also suppressed the AML tumor growth in the in vivo model. In addition, the number of IL-3Ra-positive cells in cynomolgus monkeys decreased following i.v. infusion of 0.1mg/kg KHK2823 with a tolerable safety profile, even at a dose of 100 mg/kg. Taken together, KHK2823 may therefore be a promising anti-IL-3Ra therapeutic drug for the treatment of AML. Figure 1. Antitumor activity of KHK2823 in a tumor xenograft nude rat model Figure 1. Antitumor activity of KHK2823 in a tumor xenograft nude rat model Figure 2. PD profile of KHK2823 in cynomolgus monkeys Figure 2. PD profile of KHK2823 in cynomolgus monkeys Disclosures Akiyama: Kyowa Hakko Kirin Co., Ltd.: Employment. Takayanagi:Kyowa Hakko Kirin Co., Ltd.: Employment. Maekawa:Kyowa Hakko Kirin Co., Ltd.: Employment. Shimabe:Kyowa Hakko Kirin Co., Ltd.: Employment. Nishikawa:Kyowa Hakko Kirin Co., Ltd.: Employment. Yamawaki:Kyowa Hakko Kirin Co., Ltd: Employment. Iijima:Kyowa Hakko Kirin Co., Ltd: Employment. Hiura:Kyowa Hakko Kirin Co., Ltd.: Employment. Takahashi:Kyowa Hakko Kirin Co., Ltd.: Employment. Akashi:Asahi Kasei: Research Funding, Speakers Bureau; Chugai: Research Funding, Speakers Bureau; Bristol-Myers Squibb: Research Funding, Speakers Bureau; Novartis Pharma K.K.: Consultancy, Research Funding, Speakers Bureau; Kyowa Hakko Kirin Co., Ltd.: Consultancy, Research Funding, Speakers Bureau; Celgene: Research Funding, Speakers Bureau; Shionogi: Research Funding, Speakers Bureau; Astellas: Research Funding, Speakers Bureau. Tawara:Kyowa Hakko Kirin Co., Ltd: Employment.
Herein we describe four patients with acquired hemophilia A (AHA) caused by factor VIII (FVIII) inhibitor and histories of dipeptidyl peptidase-4 inhibitor (DPP4-I) treatment for diabetes mellitus (DM). Drug exposure can cause a breakdown of immune tolerance to FVIII associated with CD4 T cells, resulting in the induction of autoantibodies against FVIII. In patient 1 in the present series, FVIII inhibitor disappeared after DPP4-I treatment. The DPP4-I treatment was stopped faster in patient 1 than it was in patient 2, whose FVIII inhibitor titer was higher than patient 1’s. Two patients died: patient 3 due to brain infarction after recurrence associated with the development of sigmoid colon rupture, and patient 4 due to multiple organ failure associated with Clostridium difficile colitis. DPP4-I treatment may create an ideal environment for the induction of new antibodies and AHA onset associated with tumor necrosis factor-α reduction. These are the first reported cases of the potential development and/or prolonging of AHA after DDP4-I treatment for DM, and they suggest possible disease associations. Electronic supplementary material The online version of this article (10.1007/s13300-019-0609-3) contains supplementary material, which is available to authorized users.
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