SAN DIEGO – Lower-than-usual doses of rituximab may be sufficient in patients with acquired thrombotic thrombocytopenic purpura (TTP), results of a recent pilot safety and efficacy study suggest.
Patients receiving just 100 mg/week for 4 weeks had rates of relapse and exacerbation that were favorable, compared with historical controls, according to investigator, of Beth Israel Deaconess Medical Center and Harvard Medical School, both in Boston. He presented the findings at the annual meeting of the American Society of Hematology.
However, the low-dose treatment was not without side effects, according to Dr. Zwicker, who described one case of acute respiratory failure out of the 19 patients enrolled in the ART () study.
“The likely benefit is cost savings, rather than less toxicity,” Dr. Zwicker said of the low-dose rituximab regimen.
Out of 19 patients enrolled in ART, 18 were eligible to receive the study treatment, which included low-dose rituximab plus standard plasma exchange and corticosteroids.
Following this initial therapy, all patients had a response, defined as a platelet count 150,000/mcL or greater for 2 consecutive days, with a median time to response of 5 days.
There were two exacerbations (12%) at 30 days after stopping plasma exchange and no cases of refractory TTP, which compared favorably to historical controls, Dr. Zwicker said.
The rate of relapse at 2 years was 28%, which again compared favorably with a historical control data repository in which the rate of relapse at 2 years was 51%.
One patient in the study suffered a case of acute respiratory failure requiring intubation during the third rituximab infusion and was ultimately placed on extracorporeal membrane oxygenation.
“The patient did survive, but this is just a reminder that there are potential side effects, even with lower doses of rituximab,” Dr. Zwicker said.
A few other serious adverse events – including central line infection and bacteremia in one patient – were more likely related to the plasma exchange, he added.
These results with low-dose rituximab are consistent with findings that rituximab 375 mg/m2 for four doses reduces the incidence of exacerbation and refractory disease and prevents or delays relapses, according to Dr. Zwicker and his coinvestigators, including, of Washington University, St. Louis, who initiated the study.
The typical TTP regimen of rituximab 375 mg/m2 for four weekly doses is borrowed from protocols for B-cell lymphomas; however, the B-cell mass in nonmalignant disease is likely to be much less than in lymphoproliferative disorders, Dr. Zwicker told attendees.
“The benefit, principally, of lower-dose rituximab is saving of thousands upon thousands of dollars,” Dr. Zwicker said.
This is not the only data set to suggest a potential role for lower-dose rituximab, he added, noting that a recently published retrospective analysis showed “fairly similar” treatment-free survival rates for standard rituximab and a reduced-dose regimen. There also are case series in other autoimmune cytopenias, namely idiopathic thrombocytopenic purpura and pure red cell aplasia, that provide evidence in support of low-dose rituximab, he added.
Dr. Zwicker reported research funding with Incyte and Quercegen, and consultancy with Parexel. Dr. Sadler reported consultancy with Ablynx.
SOURCE: Zwicker JI et al. ASH 2018, .