Reevaluating Patient Eligibility for Inotuzumab Ozogamicin Based on CD22 Expression: Is Dim Expression Sufficient?

Salvage options for patients with relapsed B-cell acute lymphoblastic leukemia (B-ALL) include inotuzumab ozogamicin (InO), a recombinant, humanized anti-CD22 monoclonal antibody conjugated to the cytotoxic antibiotic calicheamicin. However, the benefit of InO in patients with dim CD22 expression remains unclear. We present a case of a patient with B-ALL who responded to InO despite only dim surface expression of CD22 by flow cytometry, achieving a survival benefit concordant with that reported in the literature and maintaining a good quality of life as a transfusion-independent outpatient. Our observation has broad relevance to clinicians who manage patients with B-ALL who are candidates for InO.