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Selinexor-induced thrombocytopenia results from inhibition of thrombopoietin signaling in early megakaryopoiesis

Kellie R. Machlus, Stephen K. Wu, Prakrith Vijey, Thomas S. Soussou, Zhi-Jian Liu, Eran Shacham, T. J. Unger, Trinayan Kashyap, Boris Klebanov, Martha Sola-Visner, Marsha Crochiere, Joseph E. Italiano Jr and Yosef Landesman

Key Points

  • XPO1 blockade causes thrombocytopenia by inhibiting TPO signaling and blocking the differentiation of stem cells into megakaryocytes.

  • Selinexor-induced thrombocytopenia is reversible when TPO agonists are administered in the absence of selinexor (drug holiday).

Publisher's Note: There is an Inside Blood Commentary on this article in this issue.

Abstract

Selinexor is the first oral selective inhibitor of nuclear export compound tested for cancer treatment. Selinexor has demonstrated a safety therapy profile with broad antitumor activity against solid and hematological malignancies in phases 2 and 3 clinical trials (#NCT03071276, #NCT02343042, #NCT02227251, #NCT03110562, and #NCT02606461). Although selinexor shows promising efficacy, its primary adverse effect is high-grade thrombocytopenia. Therefore, we aimed to identify the mechanism of selinexor-induced thrombocytopenia to relieve it and improve its clinical management. We determined that selinexor causes thrombocytopenia by blocking thrombopoietin (TPO) signaling and therefore differentiation of stem cells into megakaryocytes. We then used both in vitro and in vivo models and patient samples to show that selinexor-induced thrombocytopenia is indeed reversible when TPO agonists are administered in the absence of selinexor (drug holiday). In sum, these data reveal (1) the mechanism of selinexor-induced thrombocytopenia, (2) an effective way to reverse the dose-limiting thrombocytopenia, and (3) a novel role for XPO1 in megakaryopoiesis. The improved selinexor dosing regimen described herein is crucial to help reduce thrombocytopenia in selinexor patients, allowing them to continue their course of chemotherapy and have the best chance of survival. This trial was registered at www.clinicaltrials.gov as #NCT01607905.

  • Submitted November 20, 2016.
  • Accepted June 13, 2017.
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