Off-Label Rituximab Proves Its Mettle in Adult ITP

For adult patients with persistent or chronic immune thrombocytopenia (ITP), off-label treatment with rituximab proved a safe and effective management option, according to results of a prospective, multicenter registry study published recently in Blood. ITP is an autoimmune disease in which a patient’s immune system destroys platelets, leaving the person with too few platelets in the blood.

Rituximab, an anti- CD20 chimeric monoclonal antibody, attaches to the B-cells that help cause the platelet destruction seen in ITP, ultimately destroying them. It has been an off-label second- or third-line ITP treatment for more than a decade. Despite this, the safety profile of rituximab in ITP clinical practice had not been established. Little was known about the predictive factors for sustained response, and the optimal therapeutic regimen for the drug in ITP treatment had not been defined, the authors, led by Mehdi Khellaf, MD,explained.

In the current study, Dr. Khellaf, of the Centre Hospitalier Universitaire Henri-Mondor in Creteil, France, and colleagues assessed response and predictive factors of sustained response in 248 adults who had previously received corticosteroids or intravenous immunoglobulin (IVIg) as first-line treatment for ITP.

Two rituximab protocols were used:

  • A “lymphoma-like” regimen of four weekly doses of 375 mg/m2 in 173 patients
  • A “rheumatoid arthritis (RA)-like” regimen of fixed 1-g doses on days 1 and 15 in 72 patients.

Three patients received a regimen of a single infusion.

At a median follow-up of two years, there was a cumulative incidence of 2.3 infections per 100 patient years, Dr. Khellaf et al reported. Three patients died of infection after rituximab infusions, the authors noted, but the role of rituximab in these deaths was “questionable.”

In total, 152 patients (61%) showed an overall initial response – defined as a platelet count ≥30×109/L and at least twice their baseline value. Ninety-six patients (39% of the total population) showed a lasting response at 24 months, including 76 with complete response, the researchers reported.

Dr. Khellaf and colleagues noted that “on multivariate analysis, the probability of sustained response at one year was significantly associated with ITP duration <1 year (p=0.02) and previous transient complete response to corticosteroids (p=0.05).”

The results indicate a positive future for rituximab in ITP treatment, co-author Bertrand Godeau, MD,also from the Creteil institution, told ASH Clinical News.

Comparing regimens with respect to safety, Dr. Godeau commented, “There is really no lower adverse event incidence of the RA-like regimen, meaning the tolerance between the two regimens was similar.”

First-line treatment of ITP includes observation, corticosteroid therapy, IVIg, or anti-D immunoglobulin (anti-D). This is followed by surgical removal of the spleen if first-line treatment is unsuccessful. “We consider that rituximab is a second- or third-line treatment for ITP before splenectomy,” Dr. Godeau said. “Even if the long-term response is modest, our study confirms that, two years after rituximab infusions, about 40 percent of the patients have a response.”

“The findings of this large prospective registry of patients with ITP treated with rituximab in ‘real life’ show that the safety profile is acceptable and confirm that the treatment leads to an overall response rate of 39 percent at two years,” Dr. Khellaf and co-authors concluded. “With its benefit/ risk ratio, off-label rituximab may remain a valid option, particularly for young patients with persistent ITP and a previous transient complete response to corticosteroids because this subgroup has a high probability of sustained response.”


Reference

    Khellaf M, Charles-Nelson A, Fain O, et al. Safety and efficacy of rituximab in adult immune thrombocytopenia: results from a prospective registry including 248 patients. Blood. 2014 October 7. [Epub ahead of print]

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