Ultra-low dose rituximab may be considered for patients with rheumatoid arthritis already responding well to standard doses of the biologic, research suggests.

While a Dutch study was unable to demonstrate non-inferiority at six months after dosing, it found most patients maintained good disease control on the ultra low dose.

The REDO study randomised 142 patients with RA and stable low disease activity to either 1000 mg, 500 mg or 200 mg rituximab, along with usual co-medication.

Based on the change in disease activity (DAS28-CRP) from baseline, the study found 500 mg rituximab was non-inferior to 1000 mg at three months but not at six months.

Because of the predefined hierarchical test procedure, the researchers said formal conclusions about the 200mg dose could not be drawn.

However they found the mean DAS28-CRP scores remained below the threshold for low disease activity (≤2·90) for all groups during the study period.

“Moreover, the number of patients who had disease flares or changes in HAQ-DI and EQ5D score from baseline did not differ between groups,” the study authors said.

Peripheral B-cell depletion was complete in all groups at three months and use of concomitant conventional synthetic DMARDs and oral glucocorticoids remained stable during the study period.

The numbers of serious adverse events were similar in the three patient groups (10% with 1000 mg and 500 mg; 7% with 200 mg) but the infection rate was double in patients receiving the 1000 mg dose compared to the lower doses (1.24 v 0.52 and 0.55 new cases/patient-year).

Though further studies are required to demonstrate non-inferiority, the study authors concluded that dose reduction might be possible in stable patients.

“In clinical practice, a strategy with one ultra-low dose of rituximab and extra antirheumatic drugs in case of flare might be considered, weighing the risk of flare against the benefits of improved safety, shorter infusion time, and potential cost-savings.”

An accompanying Comment in The Lancet Rheumatology said the optimal timing and dosing of rituximab remained uncertain and further research was required.

Professor Janet Pope, from St Joseph’s Health Care in Ontario, Canada, also noted that the Dutch findings could not be generalised to patients with rheumatoid arthritis who were not in a low disease state.

However the study also had financial implications, she said.

“With respect to payers, the cost of treatment for rheumatoid arthritis is growing, and introduction of a 200 mg dose of rituximab (or a biosimilar drug) could lead to large cost-savings.”

“A 200 mg dose might also potentially affect the order in which treatments are used in protocols for rheumatoid arthritis.”