The Food and Drug Administration has approved the antibody drug conjugate inotuzumab ozogamicin for the treatment of adults with relapsed or refractory B-cell precursor acute lymphoblastic leukemia (ALL).

The treatment, to be marketed by Pfizer as Besponsa, won approval based on the results of the INO-VATE ALL trial, which randomized 326 patients to receive either inotuzumab ozogamicin (164 patients) or a chemotherapy regimen of the investigator’s choice (162 patients). To be considered for inclusion in the trial, patients with Philadelphia chromosome–negative or –positive relapsed or refractory B-cell precursor ALL were required to have at least 5% bone marrow blasts and have received one or two induction chemotherapy regimens.

Of the first 218 patients randomized in this international trial, 35.8% treated with inotuzumab ozogamicin saw complete remission for a median of 8 months; almost 90% of those patients achieved minimal residual disease (MDR)–negativity. In the chemotherapy arm, 17.4% saw complete remission for a median of about 5 months; of those, 31.6% achieved MDR-negativity.

Adverse events that occurred in more than 20% of patients included thrombocytopenia, neutropenia, anemia, leukopenia, fatigue, hemorrhage, pyrexia, nausea, headache, febrile neutropenia, abdominal pain, and hyperbilirubinemia, as well as increases in gamma-glutamyltransferase and transaminases. Adverse events that led to discontinuation of treatment were infection, thrombocytopenia, hyperbilirubinemia, hemorrhage, and increases in transaminases.

Preliminary results were published in August 2016 (N Engl J Med. 2016;375:740-53).

Inotuzumab ozogamicin was granted orphan drug and breakthrough status, as well as priority review, by the FDA in February 2017.

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