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Treatment of Recurrent Refractory Pediatric Pre-B Acute Lymphoblastic Leukemia Using Inotuzumab Ozogamicin Monotherapy Resulting in CD22 Antigen Expression Loss as a Mechanism of Therapy Resistance

Paul, Megan R. MD*; Wong, Victor MD*; Aristizabal, Paula MD, MAS*,†; Kuo, Dennis J. MD, MS*

Journal of Pediatric Hematology/Oncology: February 22, 2019 - Volume Publish Ahead of Print - Issue - p
doi: 10.1097/MPH.0000000000001440
Clinical and Laboratory Observations: PDF Only

Background: Inotuzumab ozogamicin is a novel antibody-drug conjugate that targets CD22, a common antigen on pre-B acute lymphoblastic leukemia cells.

Observations: A 7-year-old boy with pre-B acute lymphoblastic leukemia in his second relapse was given 2 cycles of inotuzumab ozogamicin. He responded morphologically with a negative bone marrow evaluation. However, he relapsed in cycle 3 of therapy with a loss of CD22 expression on his lymphoblast population.

Conclusion: To our knowledge, this is the first published case of CD22 expression loss as a mechanism of therapy resistance for inotuzumab ozogamicin.

*Department of Pediatrics, Division of Pediatric Hematology-Oncology, University of California San Diego, Peckham Center for Cancer and Blood Disorders, Rady Children’s Hospital San Diego, San Diego

Department of Populations Sciences, Disparities, and Community Outreach and Engagement, University of California San Diego, Moores Cancer Center, La Jolla, CA

The authors declare no conflict of interest.

Reprints: Dennis J. Kuo, MD, MS, 3020 Children’s Way, MC 5035, San Diego, CA 92123 (e-mail:

Received April 24, 2018

Accepted January 11, 2019

Copyright © 2019 Wolters Kluwer Health, Inc. All rights reserved.