Recently approved to treat relapsed or refractory Philadelphia chromosome–negative precursor B-cell acute lymphoblastic leukemia, blinatumomab also seems to knock out minimal residual disease in the bone marrow of patients who achieve remission after treatment.

A novel immunotherapeutic given to adults with acute lymphoblastic leukemia (ALL) before relapse showed promising results in a phase II trial presented in December at the American Society of Hematology Annual Meeting in San Francisco, CA.

The trial assessed Amgen's blinatumomab (Blincyto), a bispecific T-cell engager that directs T cells to kill malignant B cells. The agent was approved in December to treat relapsed or refractory Philadelphia chromosome–negative precursor B-cell ALL.

Researchers wanted to see if the drug would also be effective in treating patients who are in remission but have trace amounts of disease in their bone marrow, putting them at high risk for disease recurrence.

The 113 trial participants were deemed to be at high risk for recurrence based on a PCR test that detected a small amount of residual disease. (Conventional cytology is typically used to examine bone marrow smears.)

The participants received continual infusion of blinatumomab for 4 weeks, followed by a 2-week break. Responders could receive up to four cycles of treatment or have a stem cell transplant after the first cycle. At the end of the trial, no minimal residual disease was detected in 78% of participants.

“If positive long-term results are confirmed, [blinatumomab] may really change the standard of care of ALL in the future,” says first author Nicola Gökbuget, MD, coordinator of the German ALL study group and an investigator at the University Hospital Frankfurt, Germany.

Most side effects—mild to moderate flu-like symptoms—related to the activation of the immune system, although some patients had neurologic symptoms. Two patients died during the trial.

It appears that the drug “tips the balance in favor of the immune system over the tumor cell,” says Catherine Bollard, MD, a professor of pediatrics at George Washington University, who moderated the press conference at which the trial results were presented.

Bollard says she was surprised by the drug's effectiveness as a single agent, but that it makes sense in the context of what scientists are learning about the relationship between cancer and the immune system. Cancer needs many different strategies to override the immune system, she says, but blocking any one of them may be enough to give the immune system the advantage.

Gökbuget says the first part of the trial was very promising, but she's restraining her enthusiasm until after follow up. “We want to see whether the achievement of a molecular response will result in a better long-term outcome,” she explains.

Researchers will also need to confirm the effectiveness of PCR detection before applying for federal approval to prescribe the drug this way, Gökbuget says.

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