Real-world data of thrombotic microangiopathy management: The key role of ADAMTS13 activity and complement testing

ADAMTS13 (A Disintegrin and Metalloprotease with ThromboSpondin type 1 motifs) activity is a key tool in differential diagnosis of thrombotic microangiopathies (TMAs). Due to the lack of availability of ADAMTS13 testing, PLASMIC/PLASIC scores have been suggested to predict ADAMTS13 deficiency. The importance of differentiating TTP from other complement-mediated TMAs is highlighted by the need to urgently start plasma exchange and utility of treatments such as caplacizumab or eculuzimab. Therefore, we aimed to evaluate ADAMTS13 activity, PLASMIC/PLASIC scores, and complement testing in guiding management of a real-world TMA cohort. We enrolled consecutive TMA patients with samples referred to our Center (01/2018–2020). If ADAMTS13 ​> ​10%, soluble C5b-9 was measured. Among 80 TMA patients, ADAMTS13 activity was ≤10% in 50 patients, while 28 had a relapsing disease. PLASMIC/PLASIC were excellent predictors of ADAMTS13 deficiency, especially in patients without secondary causes. Soluble C5b-9 levels were elevated (median 525 ​ng/ml, range 313–913 ​ng/ml) in 7 patients without secondary causes and ADAMTS13 ​> ​10% (hemolytic uremic syndrome/HUS). Two were shiga-toxin associated; while 5 atypical HUS. Only 1/5 patients received eculizumab and achieved TMA resolution implemented by guidance based on soluble C5b-9 levels. In transplant-associated TMA, 8/16 patients not responding to first-line treatment received eculizumab due to elevated C5b-9 levels (median 353 ​ng/ml, range 281–1252 ​ng/ml) and achieved TMA resolution. In conclusion, our real-world data confirm that ADAMTS13, complement testing, and PLASMIC/PLASIC are valuable tools in diagnosis and management of TMAs, but also highlight the unmet need of using available markers and treatments in clinical practice. © 202

Real-life experience with the combination of polatuzumab vedotin, rituximab, and bendamustine in aggressive B-cell lymphomas

Transplant-ineligible relapsed/refractory (rr) diffuse large B-cell lymphoma (DLBCL) patients represent an unmet medical need. Polatuzumab vedotin (Pola), an anti-CD79b antibody-drug-conjugate (ADG), with bendamustine- rituximab(BR) has recently gained approval for these patients, both in the USA and Europe, based on the GO29365 phase IIb trial. Real-life data with Pola are extremely limited. We report the outcomes of 61 Greek patients, who received Pola-(B)R mainly within a compassionate use program. Treatment was given for up to six 21-day cycles. Bendamustine was omitted in three cases due to previous short-lived responses. Fourty-nine rrDLBCL(efficacy cohort-EC) and 58 rr aggressive B-NHL (safety cohort-SC) patients received at least 1 Pola-BR cycle. Twenty-one (43%) patients of the EC responded with 12/49 (25%) CR and 9/49 (18%) PR as best response. Median progression–free survival, overall survival and duration of response were 4.0, 8.5, and 8.5 months respectively, while 55% of patients experienced a grade ≥3 adverse event, mainly hematologic. Treatment discontinuations and death during treatment were mainly due to disease progression. Twenty-two (41%) patients received further treatment; 11/22 are still alive, including one after CAR-T cells, and two after stem cell transplantation. Our data confirm that Pola-BR is a promising treatment for rrDLBCL patients, inducing an adequate response rate with acceptable toxicity. Pola-BR could be used as bridging therapy before further consolidative treatments. © 2021 John Wiley & Sons Ltd

The Apcmin mouse has altered hematopoietic stem cell function and provides a model for MPD/MDS

Apc, a negative regulator of the canonical Wnt signaling pathway, is a bona-fide tumor suppressor whose loss of function results in intestinal polyposis. APC is located in a commonly deleted region on human chromosome 5q, associated with myelodysplastic syndrome (MDS), suggesting that haploinsufficiency of APC contributes to the MDS phenotype. Analysis of the hematopoietic system of mice with the Apcmin allele that results in a premature stop codon and loss of function showed no abnormality in steady state hematopoiesis. Bone marrow derived from Apcmin mice showed enhanced repopulation potential, indicating a cell intrinsic gain of function in the long-term hematopoietic stem cell (HSC) population. However, Apcmin bone marrow was unable to repopulate secondary recipients because of loss of the quiescent HSC population. Apcmin mice developed a MDS/myeloproliferative phenotype. Our data indicate that Wnt activation through haploinsufficiency of Apc causes insidious loss of HSC function that is only evident in serial transplantation strategies. These data provide a cautionary note for HSC-expansion strategies through Wnt pathway activation, provide evidence that cell extrinsic factors can contribute to the development of myeloid disease, and indicate that loss of function of APC may contribute to the phenotype observed in patients with MDS and del(5q)

Lenalidomide as a disease-modifying agent in patients with del(5q) myelodysplastic syndromes:linking mechanism of action to clinical outcomes

Deletion of the long arm of chromosome 5, del(5q), is the most prevalent cytogenetic abnormality in patients with myelodysplastic syndromes (MDS). In isolation, it is traditionally associated with favorable prognosis compared with other subtypes of MDS. However, owing to the inherent heterogeneity of the disease, prognosis for patients with del(5q) MDS is highly variable depending on the presence of factors such as additional chromosomal abnormalities, >5 % blasts in the bone marrow (BM), or transfusion dependence. Over recent years, the immunomodulatory drug lenalidomide has demonstrated remarkable efficacy in patients with del(5q) MDS. Advances in the understanding of the pathogenesis of the disease have suggested that lenalidomide targets aberrant signaling pathways caused by haplosufficiency of specific genes in a commonly deleted region on chromosome 5 (e.g., SPARC, RPS14, Cdc25C, and PP2A). As a result, the agent specifically targets del(5q) clones while also promoting erythropoiesis and repopulation of the bone marrow in normal cells. This review discusses recent developments in the understanding of the mechanism of action of lenalidomide, and how this underlies favorable outcomes in patients with del(5q) MDS. In addition, we discuss how improved understanding of the mechanism of disease will facilitate clinicians’ ability to predict/monitor response and identify patients at risk of relapse

Myelodysplasia is in the niche : novel concepts and emerging therapies

Myelodysplastic syndromes (MDSs) represent clonal disorders mainly of the elderly that are characterized by ineffective hematopoiesis and an increased risk of transformation into acute myeloid leukemia. The pathogenesis of MDS is thought to evolve from accumulation and selection of specific genetic or epigenetic events. Emerging evidence indicates that MDS is not solely a hematopoietic disease but rather affects the entire bone marrow microenvironment, including bone metabolism. Many of these cells, in particular mesenchymal stem and progenitor cells (MSPCs) and osteoblasts, express a number of adhesion molecules and secreted factors that regulate blood regeneration throughout life by contributing to hematopoietic stem and progenitor cell (HSPC) maintenance, self-renewal and differentiation. Several endocrine factors, such as erythropoietin, parathyroid hormone and estrogens, as well as deranged iron metabolism modulate these processes. Thus, interactions between MSPC and HSPC contribute to the pathogenesis of MDS and associated pathologies. A detailed understanding of these mechanisms may help to define novel targets for diagnosis and possibly therapy. In this review, we will discuss the scientific rationale of "osteohematology" as an emerging research field in MDS and outline clinical implications