Genomic determinants of response and resistance to inotuzumab ozogamicin in B-cell ALL

Abstract

Inotuzumab ozogamicin (InO) is an antibody-drug conjugate that delivers calicheamicin to CD22-expressing cells. In a retrospective cohort of InO treated patients with B-cell acute lymphoblastic leukemia, we sought to understand the genomic determinants of response to InO. AcquiredCD22mutations were observed in 11% (3/27) of post-InO relapsed tumor samples. There were multipleCD22mutations per sample and the mechanisms of CD22 escape included protein truncation, protein destabilization, and epitope alteration. Hypermutation by error-prone DNA damage repair (alternative end-joining, mismatch repair deficiency) drove CD22 escape. Acquired loss-of-function mutations inTP53,ATMandCDKN2Awere observed, suggesting compromise of the G1/S DNA damage checkpoint as a mechanism of evading InO-induced apoptosis. In conclusion, genetic alterations modulating CD22 expression and DNA damage response influence InO efficacy. The escape strategies within and beyond antigen loss to CD22-targeted therapy elucidated in this study provide insights into improving therapeutic approaches and overcoming resistance.KEY POINTSWe identified multiple mechanisms of CD22 antigen escape from inotuzumab ozogamicin, including protein truncation, protein destabilization, and epitope alteration.Hypermutation caused by error-prone DNA damage repair was a driver of CD22 mutation and escape.VISUAL ABSTRACT