Inotuzumab ozogamicin for relapse prevention in a boy with Down syndrome and relapsed acute lymphoblastic leukemia.

Inotuzumab ozogamicin (InO), a CD22-directed antibody conjugated to calicheamicin, has demonstrated excellent efficacy in B-cell precursor (BCP) acute lymphoblastic leukemia (ALL). It has been used for patients with relapsed or refractory BCP-ALL as a bridge to allo-HCT. Children with Down syndrome (DS) have an increased risk of BCP-ALL and higher rates of relapse and toxicity, including treatment-related mortality. Although allo-HCT is potentially curative for relapsed or refractory ALL, post-transplant leukemic relapse rates and transplant-related mortality are dismal in patients with DS-ALL, which results in less frequent use of allo-HCT in this group than in the non-DS population. Therefore, novel and less toxic therapeutic strategies are required to improve outcomes. Here we report the case of a child with DS who was diagnosed with a second relapse of BCP-ALL and has maintained complete remission through regular single-agent InO therapy. Single-agent maintenance using InO can be a good option to avoid subsequent relapse in patients with relapsed or refractory BCP-ALL who cannot proceed to allo-HCT and require less-toxic treatments.