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Infliximab Similar to Methotrexate in Infection Rate Among Rheumatoid Arthritis Patients: Presented at ACR

By Ed Susman

SAN ANTONIO, TX -- October 21 2004 -- Patients taking the recommended dose of infliximab plus methotrexate have comparable risk of infection as those taking methotrexate alone, researchers said at the 68th Annual Scientific Meeting of the American College of Rheumatology.

David Yocum, MD, professor of medicine at the University of Arizona College of Medicine, Tuscon, Arizona, cautioned, however, that starting patients on high dose infliximab is associated with infection.

"The effects of a drug on the immune system are always a concern of researchers and clinicians," Dr. Yocum said here October 19th.

"We found that when patients received infliximab at the suggested dosing of 3 mg/kg, the infection rate was similar to placebo," he said. "However, at the higher induction and maintenance dosing of 10 mg/kg we saw a notably higher rate of serious infections. This confirms that infliximab is quite safe at recommended dosing levels and can be used confidently with careful monitoring."

Dr. Yocum and colleagues conducted a multinational, double-blind study, enrolling 1082 patients in 12 countries. The year-long study sought to determine the risk of serious infections for patients using infliximab plus methotrexate compared to placebo.

Investigators randomized patients into 3 evenly divided groups; 363 patients in group 1 received placebo; 360 patients in group 2 received 3 mg/kg infliximab; and 361 patients in group 3 were given 10 mg/kg infliximab. Dosing was done at weeks 0, 2, 6, and 14. All of the patients also received methotrexate for the study period.

They gave group 1 patients placebo for the first 22 weeks, then received 3 mg/kg every 8 weeks up through week 54. Clinicians administered a dose of 3 mg/kg of infliximab to group 2, giving 3 mg/kg of infliximab at the outset and at week 2 and 6, followed by a similar dose every 8 weeks until week 22. They then increased the dose in increments of 1.5 mg/kg every 8 weeks, if patients needed it. About 3.6% of patients in group 1 and in group 2 suffered infections.

For group 3, Dr. Yocum's team administered a dose of 10 mg/kg at baseline, and at weeks 2 and 6, followed by every 8 weeks for the duration of the study. In this group 8.3% of patients had infections.

Dr. Yocum said that patients receiving infliximab at the recommended induction and maintenance protocol of 3 mg/kg experienced a comparable risk of serious infection as those patients in the placebo group, though some patients required an increase in dose of infliximab during the second part of the study. "If the dose was increased gradually, there was no risk of infection," he said.

Serious infections occurred during the first 22 weeks in 1.7%, 1.7%, and 5.3% of patients, respectively. The relative risk of serious infection relative to placebo was 1.00 (P =.99), 3.29 (P =.008), and 2.13 (P =.09), respectively.

At week 54, rates of serious infection were 3.6%, 3.6%, and 8.3%, which included pneumonia, active tuberculosis, abscess, pyelonephritis, and sepsis. The 3 groups had similar incidences of other adverse events.

At week 22, ACR 20 responses were achieved in 26%, 58%, and 61% of patients, respectively (P <.001), which was maintained through week 54.

They noted that "the efficacy of infliximab and types of serious infections observed in this study were similar to those reported in previous clinical trials."

The study was supported by Centocor, Inc.


[Presentation title: The Safety and Efficacy of Infliximab in RA: 1-year Results of a Large, Randomized, Placebo-Controlled Trial in Patients With Various Comorbidities and Background Treatments As Encountered in Clinical Practice. Abstract 1761]

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