FDA Expands Indication of Pfizer's Besponsa to Include Pediatric Patients with B-cell Precursor Acute Lymphoblastic Leukemia

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The FDA has approved an expanded indication for Pfizer’s antibody drug conjugate Besponsa (inotuzumab ozogamicin) to include patients 1 year of age and older with relapsed or refractory CD22-positive B-cell precursor acute lymphoblastic leukemia (B-ALL).¹ The regulatory action expands upon the initial approval of Besponsa granted in August 2017 for adults with relapsed or refractory B-cell precursor ALL.²

“Besponsa will help address a significant need for new treatment options in B-cell acute lymphoblastic leukemia, and may help more patients reach stem cell transplant, which provides the best chance for long term remission,” said Liz Barrett, former global president of Pfizer Oncology, in a 2017 press release announcing the approval. “We’re proud to build on our continued commitment to patients with hematologic malignancies, and will continue our work to find new treatments in acute lymphoblastic leukemia and other blood cancers.”²

Besponsa is comprised of a monoclonal antibody that targets CD22, which is a cell surface antigen expressed on cancer cells in most patients with B-ALL. When the agent attaches to the CD22 antigen on B-cells, it gains entry and releases the cytotoxic agent calicheamicin to cause cell death.²

The approval of the expanded indication was based on efficacy findings for Besponsa from the multicenter, single-arm, open-label, Phase II WI203581 trial (NCT02981628). Investigators enrolled patients who were at least 1 year of age and no older than 18 years of age with relapsed or refractory CD22-positive B-ALL.¹

Investigators evaluated Besponsa across two dose levels in 53 patients. Twelve patients received an initial dose of 1.4 mg/m²/cycle, which is approximately 0.78 times the recommended initial dose. A total of 41 patients received 1.8 mg/m²/cycle.

The trial’s key efficacy endpoint was complete remission (CR) rate defined as less than 5% bone marrow blasts and the absence of peripheral blood leukemic blasts, full recovery of peripheral blood counts, duration of CR, and the proportion of patients with CR and minimal residual disease (MRD) negativity. Investigators administered a median of two treatment cycles, with a range of one to four cycles.¹

Among all patients administered the drug, the CR rate was 42%, with a median CR duration of 8.2 months. Among patients who achieved a CR (n = 22), 95.5% experienced MRD negativity based on flow cytometry, whereas 86.4% of patients achieved MRD-negative status based on RQ-PCR.

In terms of safety, serious toxicities were reported in 62% of patients, with 8% experiencing fatal adverse effects (AEs), which included multiorgan failure, lung infection, sepsis, and encephalopathy. Further, 11% of patients required dose interruptions resulting from an AE and 21% reported an AE causing permanent treatment discontinuation.

The most common AEs reported by at least 5% of the patients administered Besponsa included pyrexia (all grade, 49%; grade ≥3, 4%), edema (19%; 0%), fatigue (17%; 0%), pain (15%; 2%), chills (8%; 0%), anemia (45%; 38%), febrile neutropenia (28%; 28%), vomiting (45%; 2%), nausea (32%; 0%), abdominal pain (25%; 2%), constipation (19%; 2%), stomatitis (17%; 6%), diarrhea (11%; 0%), infection (43%; 23%), hemorrhage (42%; 6%), hypotension (6%; 4%), headache (21%; 0%), rash (19%; 4%), pruritus (9%; 0%), hyperhidrosis (6%; 0%), extremity pain (19%; 2%), back pain (6%; 0%), neck pain (6%; 0%), and muscular weakness (6%; 0%).

References

1. FDA approves inotuzumab ozogamicin for pediatric patients with acute lymphoblastic leukemia. FDA. March 6, 2024. Accessed March 7, 2024. https://www.fda.gov/drugs/resources-information-approved-drugs/fda-approves-inotuzumab-ozogamicin-pediatric-patients-acute-lymphoblastic-leukemia

2. Pfizer Receives U.S. FDA Approval for BESPONSA® (inotuzumab ozogamicin). Pfizer. News release. August 17, 2017. Accessed March 7, 2024. https://www.pfizer.com/news/press-release/press-release-detail/pfizer_receives_u_s_fda_approval_for_besponsa_inotuzumab_ozogamicin