Young children with polyarticular juvenile idiopathic arthritis (pJIA) maintained effective vaccination against diphtheria and tetanus even after starting treatment with Orencia (abatecept) for up to two years, according to a study.
These results come from a substudy of a Phase 3 clinical trial (NCT01844518), which evaluated the efficacy and safety of subcutaneous (under-the-skin) treatment with Orencia in children with active pJIA.
The study, “Maintenance of antibody response to diphtheria/tetanus vaccine in patients aged 2–5 years with polyarticular-course juvenile idiopathic arthritis receiving subcutaneous abatacept,” was published in the journal Pediatric Rheumatology.
Patients with pJIA are often on immunosuppressive medications that put them at higher risk for infections that can be prevented with vaccines, such as diphtheria and tetanus. Because the immune system of very young children is actively developing, their responses to the vaccines may be compromised due to such therapies.
Orencia — marketed by Bristol Myers Squibb — works by blocking the activation of T-cells, an essential component of the immune system responsible for mounting a widespread immune response. Preventing T-cells from becoming fully activated is intended to decrease the likelihood they will mistake one’s own cells as “foreign.”
So far, Orencia has proven effective and well tolerated as a subcutaneous medication among children ages 2–17 and as either a subcutaneous or intravenous (into-the-vein) medication among patients ages 6–17. However, no studies have investigated the effects of Orencia on vaccination in very young children with JIA.
The study, funded by Bristol Myers Squibb, analyzed 29 children ages 2–5, with active pJIA and inadequate response or intolerance to at least one disease-modifying anti-rheumatic drug. Most (19) were on Orencia for more than one year, one child was on treatment between six and 12 months, and the remaining nine for two to six months.
They received weekly subcutaneous Orencia for four months, with dosage based on body weight — 50 mg for those weighing 10–24 kg (22–53 pounds), and 87.5 mg for children between 25 and 49 kg (55–108 pounds). Those who achieved 30% improvement at four months, as measured by JIA-American college of Rheumatology criteria, could continue on Orencia for 20 more months. To achieve this goal, JIA patients need to have clinical benefits in at least three variables, including disease activity, overall well-being (assessed by patients or caregivers), functional ability, number of joints with active disease/limited range of motion, and inflammation.
Results showed that all children had protective antibodies to tetanus after two or more months on Orencia. Of the 29 children, 26 (86.7%) also had protective antibodies against diphtheria. The remaining three patients had anti-diphtheria antibodies that bordered the lower end of the protection threshold.
In addition, using methotrexate and/or low-dose corticosteroids while taking Orencia had no effect on antibody levels. No unexpected side effects, including cases of diphtheria or tetanus, occurred during the two-year period.
“These results show that [sucutaneous Orencia] does not prevent the maintenance of protective antibody levels against tetanus and diphtheria, even if the booster dose was not administered recently,” the scientists wrote.
While encouraging, the team said these results should be interpreted with caution. Because vaccinations occurred before the trial, it was impossible to know whether the three children with borderline protective antibodies had ever had protective levels following vaccination, nor to know the rate at which these levels decreased.
In addition, the group of participants was small and homogeneous, with all children being white, which limits the application of the findings to other populations.
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