311. Disorders of Platelet Number or Function: Heparin-Induced Thrombocytopenia and Immune Thrombocytopenia

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José Miguel Alvarez Blanco, Ana Sierra Salazar, Juan Rangel-Patiño, et al. 

Authors Conclusion from the Abstract: The search for an accessory spleen in patients with refractory immune cytopenias with risk factors (absence of Howell Jolly bodies and or complete response to steroids as first-line therapy) is useful. Accessory splenectomy is a safe and effective therapeutic strategy in the treatment of these patients.

Sanjay Khandelwal, Lubica Rauova, Ayiesha Barnes, et al.

Authors Conclusion from the Abstract: Together, these studies demonstrate an independent role for complement activation in regulating the binding and procoagulant effects of HIT ULICs and identify new non-anticoagulant therapeutic targets that could improve clinical outcomes in this otherwise potentially devastating thrombotic disorder.

Maria Selvadurai, Christine Lee, James Yeung, et al.

Authors Conclusion from the Abstract: These studies demonstrate that HIT antibodies in combination with soluble platelet agonists greatly expand the procoagulant platelet surface, which may contribute to the high thrombotic risk seen in HIT. Targeting platelet activation may thus represent a novel strategy for the treatment of HIT. Furthermore, this flow cytometry-based procoagulant platelet assay may represent a novel diagnostic strategy for rapid and accurate identification of patients with pathological platelet-activating HIT antibodies.

21 Indeterminate Serotonin Release Assays Are Associated with a High Mortality Rate  according to ASH clinically relevant abstract

Shawn Jindal, Christopher Leyton, Fred Cohen, et al.

Authors Conclusion from the Abstract: This is the largest study to date looking at patients with indeterminate SRA testing results, in which platelets exhibit high levels of serotonin release at both low and high heparin concentrations. Our data suggest 1) the majority of patients with indeterminate SRAs likely did not have HIT, 2) as evidenced by the low 4T scores and heparin-PF4 antibody levels, an indeterminate SRA suggests thrombocytopenia related to in-vivo platelet activation, and 3) an indeterminate SRA is associated with increased mortality.

SRA results warrant a case-by-case assessment of the clinical picture in order to avoid unnecessary cessation of heparin products. Further studies exploring the mechanism leading to high serotonin release at both low and high heparin concentrations, causing an “indeterminate” SRA result, are warranted.

David J. Kuter, Merlin Efraim, Jiri Mayer, et al. 

Authors Conclusion from the Abstract: Oral rilzabrutinib treatment achieved clinically significant platelet responses (≥50×109/L) in patients with heavily pretreated ITP irrespective of splenectomy or lack of response to prior ITP therapy, and maintained responses for the majority of the time. In addition, most patients (67%) achieved a clinically meaningful response (platelet counts ≥30×109/L). In patients treated beyond 6 months in the LTE, responses remained consistently reliable (median 100% of weeks). Rilzabrutinib was well tolerated with only grade 1/2 treatment-related TEAEs overall, with only 2 related grade 1 event observed in the LTE period. A continued study is warranted to further demonstrate the magnitude and durability of rilzabrutinib’s clinical benefit.

Catherine M. Broome, Alexander Röth, David J. Kuter, et al

Authors Conclusion from the Abstract: Sutimlimab therapy results in a rapid and durable response in plt count in a subset of patients with chronic ITP who had inadequate responses to multiple prior therapies. The response is sustained after more than 1 year of therapy with an acceptable safety profile. This is continued clinical evidence that the complement pathway plays a role in thrombocytopenia in a subset of patients with ITP. These sustained responses suggest ≥1 additional pathophysiologic explanation for the clinical heterogeneity of ITP and provide a strong platform for continued evaluation of CP inhibition in ITP treatment.