NASHVILLE, Tennessee — , according to pharmacokinetic/pharmacodynamic (PK/PD) data from the OPERETTA 1 phase 2 clinical trial. The safety profile was similar to adult patients.
“While we believe the disease to be the same in children and adolescents, [MS] is distinguished by its very inflammatory nature, oftentimes causing two to three times the number of relapses per year as their adult-onset colleagues,” said Teri Schreiner, MD, during a presentation of the results at the annual meeting of the Consortium of Multiple Sclerosis Centers.
Approved therapies for pediatric MS include fingolimod in the United States and Europe, as well as dimethyl fumarate in Europe. “There’s a real need for high-efficacy treatment [in pediatric patients], again referring back to this disease being very inflammatory in children and adolescents. We oftentimes will use medications off label but this is clearly suboptimal as we lack safety data, and oftentimes run into difficulty with insurance approval of off-label use of medicine,” said Dr. Schreiner, who is an associate professor of neurology at University of Colorado School of Medicine, Aurora.
To determine the dose in pediatric patients that would produce comparable PK and PD to adults, the researchers dosed six patients aged 10-18 with 300 mg ocrelizumab, and 17 such patients with 600 mg ocrelizumab during a 24-week dose-exploration period, followed by a 264-week optional extension period. The cohorts were separated based on weight of less than or more than 40 kg. The mean ages were 11.2 years (mean weight, 34.9 kg) and 15.3 years (mean weight, 62.3 kg), respectively.
During the dose-exploration period, seven blood draws were performed to characterize PK. “When the PK data was analyzed, we saw that the proper cut-off point was 35 kilos. At less than 35 kilos, the appropriate dose was half of that adult dose, so 300 milligrams every 6 months, whereas above 35 kilos, the proper dose was actually 600, or the adult dose. Given the rarity of pediatric-onset MS patients less than 35 kilos, most patients will benefit from the adult dose of 600 milligrams twice yearly,” said Dr. Schreiner.
PD data were also encouraging. “The primary PD was the absence of CD-19 B cells, and that was tracked over time. While there were a few patients in both cohorts that had modest reconstitution, there was no patient in our study that crossed the retreatment threshold, and all blood samples were negative for anti-drug antibodies,” said Dr. Schreiner.
Adverse events occurred in five of six patients in the 300 mg group (83%; 4 grade 2, 1 grade 3) and 100% of patients in the 600 mg group (1 grade 1, 9 grade 2, 6 grade 3, 1 grade 4). There was one serious adverse event in the 300 mg group (16.7%) and four serious adverse events in the 600 mg group (23.5%). None led to treatment discontinuation. “This is largely consistent with what was seen in the adult studies of ocrelizumab,” said Dr. Schreiner.
Roche is now recruiting for the phase 3 OPERETTA 2 trial, which will use the 600 mg dose and compare outcomes to a fingolimod arm.