Inotuzumab ozogamicin is a novel antibody-drug conjugate that targets CD22, a common antigen on pre-B acute lymphoblastic leukemia cells.
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.
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: email@example.com).
Received April 24, 2018
Accepted January 11, 2019