Immune Cytopenias after Ex Vivo CD34+-Selected Allogeneic Hematopoietic Cell Transplantation

Treatment of post-allogeneic hematopoietic stem cell transplant cytopenias with sequential doses of multipotent mesenchymal stromal/stem cells

BACKGROUND AIMS

Cytopenias after allogeneic stem cell transplantation (allo-SCT) are a common complication, the underlying pathogenic mechanisms of which remain incompletely understood. Multipotent mesenchymal stromal/stem cell (MSC) therapy has been successfully employed in the treatment of immune-related disorders and can aid in the restoration of the hematopoietic niche.

METHODS

A phase II clinical trial to assess the efficacy and safety of administering four sequential doses of ex-vivo expanded bone marrow MSCs from a third-party donor to patients with persistent severe cytopenias after allo-SCT was performed.

RESULTS

The overall response rate on day 90 was 75% among the 27 evaluable patients (comprising 12 complete responses, 8 partial responses, and 7 with no response). The median time to respond was 14.5 days. Responses were observed across different profiles, including single or multiple affected lineages, primary or secondary timing, and potential immune-mediated or post-infectious pathophysiology versus idiopathic origin. With a median follow-up for surviving patients of 85 months after MSC infusion, 53% of patients are alive. Notably, no adverse events related to MSC therapy were reported.

CONCLUSIONS

In summary, the sequential infusion of third-party MSCs emerges as a viable and safe therapeutic option, exhibiting potential benefits for patients experiencing cytopenias following allo-SCT.

The many facets of immune-mediated thrombocytopenia: Principles of immunobiology and immunotherapy

Immune thrombocytopenia (ITP) is a rare autoimmune condition, due to peripheral platelet destruction through antibody-dependent cellular phagocytosis, complement-dependent cytotoxicity, cytotoxic T lymphocyte-mediated cytotoxicity, and megakaryopoiesis alteration. This condition may be idiopathic or triggered by drugs, vaccines, infections, cancers, autoimmune disorders and systemic diseases. Recent advances in our understanding of ITP immunobiology support the idea that other forms of thrombocytopenia, for instance, occurring after immunotherapy or cellular therapies, may share a common pathophysiology with possible therapeutic implications. If a decent pipeline of old and new agents is currently deployed for classical ITP, in other more complex immune-mediated thrombocytopenic disorders, clinical management is less harmonized and would deserve further prospective investigations. Here, we seek to provide a fresh overview of pathophysiology and current therapeutical algorithms for adult patients affected by this disorder with specific insights into poorly codified scenarios, including refractory ITP and post-immunotherapy/cellular therapy immune-mediated thrombocytopenia.

Allogeneic hematopoietic stem cell transplantation for inherited metabolic disorders

Allogeneic hematopoietic stem cell transplantation (HSCT) has been used to treat patients with inherited metabolic disorders (IMDs) for more than 40 years. In the first two decades, various IMDs were treated by HSCT with a wide variety of donor sources and conditioning regimens selected at the institutional level. However, HSCT was not always successful due to post-transplant complications such as graft failure. In the third decade, myeloablative conditioning with targeted busulfan-based pharmacokinetic monitoring was established as an optimal conditioning regimen, and unrelated cord blood was recognized as an excellent donor source. During the fourth decade, further improvements were made to transplant procedures, including modification of the conditioning regimen, and the survival rate after HSCT markedly improved. Simultaneously, several long-term observational studies for patients after HSCT clarified its therapeutic effects on growth and development of cognitive function, fine motor skills, and activities of daily living when compared with enzyme replacement therapy. Although immune-mediated cytopenia was newly highlighted as a problematic morbidity after HSCT for IMDs, especially in younger patients who received unrelated cord blood, a recent study with rituximab added to the conditioning raised expectations that this issue can be overcome.

Pathogenesis, risk factors and therapeutic options for autoimmune haemolytic anaemia in the post-transplant setting

Autoimmune haemolytic anaemia (AIHA) is a rare complication of allogeneic haematopoietic stem cell transplantation (HSCT), observed with an incidence of 1-5%. Paediatric age, diagnosis of non-malignant disease, lympho-depleting agents in the conditioning regimen, use of unrelated donor, graft versus host disease and infections have been associated with a higher risk of AIHA post HSCT. Post-HSCT AIHA is associated with high mortality and morbidity, and it is often very difficult to treat. Steroids and rituximab are used with a response rate around 30-50%. These and other therapeutic strategies are mainly derived from data on primary AIHA, although response rates in post-HSCT AIHA have been generally lower. Here we review the currently available data on risk factors and therapeutic options. There is a need for prospective studies in post-HSCT AIHA to guide clinicians in managing these complex patients.

Immune cytopenia after allogeneic haematopoietic stem-cell transplantation: challenges, approaches, and future directions

Immune-mediated cytopenia after allogeneic haematopoietic stem-cell transplantation is rare. The pathophysiology of immune-mediated anaemia, thrombocytopenia, and neutropenia, which occur alone or in combination with other cytopenias, is unclear and most probably a consequence of immune dysregulation. Risk factors for this complication have been identified in retrospective studies but these should be interpreted with caution and should not be generalised to this heterogeneous patient population. Diagnosis is challenging, requires awareness of such complications, and has to be differentiated from a multitude of other, and sometimes overlapping, possible complications. The clinical course of immune-mediated cytopenia is highly variable. Treatment requires an interdisciplinary approach and ranges from observation to symptomatic measures and directed therapies. Intensive immunosuppression is associated with an increased risk of infections and relapse, and current treatments are based on approaches in patients who have not undergone transplantation. Plasma cell-directed therapies, immunomodulation, and receptor-stimulating agents can be used to treat immune-mediated cytopenia.

Incidence, Risk Factors, and Outcomes of Primary Prolonged Isolated Thrombocytopenia after Haploidentical Hematopoietic Stem Cell Transplant

The aim of this study was to evaluate the incidence, risk factors, and outcomes of primary prolonged isolated thrombocytopenia (PT) after haploidentical hematopoietic stem cell transplant (haplo-HSCT). We retrospectively analyzed patients who received haplo-HSCT for various hematologic malignancies at Peking University Institute of Hematology between January 2015 and December 2016. Of the 918 patients, 93 (10.1%) developed primary PT. We designed a propensity score method-based study. For each primary PT patient control subjects (1:3) were selected using a propensity score-matching method. A total of 372 recipients were enrolled in the study: 93 in the PT group and 279 in the control group. Multivariate analysis showed that age older than 25 years (P = .002), median mononuclear cells (P = .000), median CD34⁺ counts (P = .003), history of grades II to IV acute graft-versus-host disease (GVHD; P = .000), and Epstein-Barr virus (EBV) infection after haplo-HSCT (P = .016) were independent risk factors for primary PT. Primary PT was significantly associated with higher transplant-related mortality (TRM; P < .001), inferior overall survival (P = .001), and disease-free survival (P = .005). In conclusion, the incidence of primary PT after haplo-HSCT was 10.1%. Primary PT was associated with poorer survival and higher TRM along with older age, grades II to IV acute GVHD, and EBV infection after haplo-HSCT.