On March 6, 2024, the Food and Drug Administration approved inotuzumab ozogamicin (Besponsa, Pfizer) for pediatric patients 1 year and older with relapsed or refractory CD22-positive B-cell precursor acute lymphoblastic leukemia (ALL).

Full prescribing information for Besponsa will be posted here.

Efficacy was evaluated in a multicenter, single-arm, open-label study in 53 pediatric patients 1 year and older with relapsed or refractory CD22-positive B-cell precursor ALL. Two dose levels were evaluated--an initial dose of 1.4 mg/m2/cycle in 12 patients and 1.8 mg/m2/cycle in 41 patients. Premedications included methylprednisolone 1 mg/kg (maximum of 50 mg), an antipyretic, and an antihistamine. Patients received a median of 2 cycles of therapy (range: 1 to 4 cycles).

The main efficacy outcome measures were complete remission (CR), duration of CR, and the proportion of patients with minimal residual disease (MRD) negative CR. CR was defined as < 5% blasts in the bone marrow and the absence of peripheral blood leukemia blasts, full recovery of peripheral blood counts (platelets ≥ 100 × 109 and ANC ≥1 × 109/L), and resolution of any extramedullary disease. MRD was defined by leukemic cells comprising < 1 × 10-4 (<0.01%) of bone marrow nucleated cells by flow cytometry or by PCR.

In all patients, 22/53 (42%, 95% CI: 28.1, 55.9%) achieved CR and the median duration of CR was 8.2 months (95% CI: 2.6, NE). The MRD negativity rate in patients with CR was 21/22 [95.5% (95% CI: 77.2, 99.9)] based on flow cytometry, and 19/22 [86.4% (95% CI: 65.1, 97.1] based on RQ-PCR.

The most common adverse reactions (≥20%), including laboratory abnormalities, were thrombocytopenia, pyrexia, anemia, vomiting, infection, hemorrhage, neutropenia, nausea, leukopenia, febrile neutropenia, increased transaminases, abdominal pain, and headache.

For the first cycle, the recommended inotuzumab ozogamicin dose is 1.8 mg/m2 per cycle, administered as 3 divided doses on Day 1 (0.8 mg/m2), Day 8 (0.5 mg/m2), and Day 15 (0.5 mg/m2). Cycle 1 is 3 weeks in duration but may be extended to 4 weeks if the patient achieves a complete remission or complete remission with incomplete hematologic recovery, and/or to allow recovery from toxicity. See the prescribing information for the recommended dosage after the first cycle.

This application was granted priority review and orphan drug designation. FDA expedited programs are described in the Guidance for Industry: Expedited Programs for Serious Conditions-Drugs and Biologics.

Healthcare professionals should report all serious adverse events suspected to be associated with the use of any medicine and device to FDA’s MedWatch Reporting System or by calling 1-800-FDA-1088.

For assistance with single-patient INDs for investigational oncology products, healthcare professionals may contact OCE’s Project Facilitate at 240-402-0004 or email OncProjectFacilitate@fda.hhs.gov.

Follow the Oncology Center of Excellence on X (formerly Twitter) @FDAOncology.