Medical Technology

Low-Dose Rituximab Can Keep RA Activity Low in Responders

Rituximab doses of 200 mg or less decreased disease activity in patients suffering from Rheumatoidarthritis in a manner similar to the usual dose of 1,000 mg over more than three years of follow-up, according to results of an extension study in the Netherlands.

Nathan den Broeder

We could not formally prove statistically that the lower doses were less efficient than the higher dose,” study leader Nathan den Broeder MSc, a PhD candidate at St. Maarten Clinic and the Radboud Institute for Health Sciences in Nijmegen, the Netherlands, spoke at the virtual annual meeting of the American College of Rheumatology. “We concluded at this time that only 6 percent of patients required to switch to a different biologic or targeted antirheumatic drug and that mean disease activity was very low,” he said of the patients treated with 500 and 200 mg doses of the drug rituximab.

The extension study covered the 118 patients who were part of the REDO trial. It was conducted from the beginning of the trial in 2017-2018 until April 2021. They were randomized to three treatment arms: the standard 1,000 mg dose (24 patients), a 500-mg dose (n = 48) and the 200 mg dose (n = 46). The average follow-up time was 3.2 years.

The study evaluated the disease activity in 28 joints with C-reactive protein (DAS28CRP) and found that scores varied between 2.2-2.3. Seven patients in the study group switched to a different DMARD He stated.

“On average, we observed DAS28-CRP 0.15 points lower per 1,000 mg rituximab used over the past year,” Mr. den Broeder told reporters in an interview. “For context, this can be compared to an error in measurement of around 0.6. A DAS28-CRP reduction of 1.2 is a great response to a drug. This means that we can almost get a better effect than the measurement error comparison of the highest dose with the lowest.

After one year, the median annual rituximab dosage was 978 mg, with an interquartile range of 704-1,425 mg. 40% of patients took 500 mg every 6.2 months, and 29 percent took 1,000mg each 6.4 months.

“It’s important to remember, though, this is the context of patients being given doses based on disease activity,” Mr. den Broeder stated. “That is, we try one dose; when the patient responds well, we will try the lower dose; if not, we may back to a higher dosage. We could expect somewhat greater variations in the event that all patients be moved to a lower dose, regardless of whether that is effective for them.”

The results were obtained without the use of glucocorticoids (GCs) the researcher said. The use of comedication in the extension study sample was 0.38 GC injections per year for each patient and the beginning or increase of oral GC took place at a rate of only 0.05 per patient-year.

“As the result of this research, we are now implementing an strategy of reducing the dosage of rituximab in the clinical setting and at our clinic,” Mr. den Broeder said. Patients with RA receive a 1,000 mg dose for six months. If they respond well, they are then transferred to a 500 mg dose. After six months, patients suffering from RA are moved to the 200 mg dose if they’ve been able to respond well. He said this will allow patients to have fewer side adverse effects. “We are hoping to reduce the cost of treatment and we will also see immediate results that the infusion time for patients can be reduced.”

Future research concerns include the evaluation of the 200 mg subcutaneous injection. “Another thing to think about is are lower doses possible?” he said.

Maya Buch, MD is a professor of rheumatology and musculoskeletal disorders at the University of Manchester (England). She was also the director of Experimental Medicine at The Centre for Musculoskeletal Research. She asked if researchers utilized CD19 to measure B-cell or immunoglobulin levels to determine dose increment.

Mr. den Broeder stated that CD19 was not utilized in clinical practice but was utilized in the initial trial. However, it was not found to have any predictive ability as immunoglobulin levels were determined in patients with multiple infections. “Sporadically it is possible that an lower dose may have been initiated due to this, but not consistently,” he said.

Mr. den Broeder did not have any relevant relationships to disclose. Dr. Buch reported financial relationships with AbbVie, Eli Lilly, Gilead Sciences, Merck-Serono, Pfizer, Roche, Sanofi and UCB.

This article was originally published on MDedge.com. It is part of the Medscape Professional Network.

Content Source: https://www.medscape.com/viewarticle/963360?src=rss

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