The biologic drug rilonacept (Arcalyst) is an effective and relatively safe treatment for systemic juvenile idiopathic arthritis (sJIA), a rare but especially serious form of arthritis in children, according to a study presented at the American College of Rheumatology’s annual meeting this week in San Diego.

Roughly 10 percent of children with juvenile idiopathic arthritis (JIA) have the systemic form, which can involve not only joint pain and swelling but also a high daily fever, a rash and anemia. Because sJIA can also cause inflammation of internal organs – including the spleen, heart, and brain – it’s a serious condition that requires aggressive treatment.

Treatment for sJIA varies depending on how severe it is (the American College of Rheumatology released new treatment guidelines in October). A non-steroidal anti-inflammatory drug (NSAID), such as ibuprofen may be tried, but if it doesn’t work well enough (which is often the case), doctors move on to disease-modifying antirheumatic drugs (DMARDs) such as methotrexate or lefunomide, or on to a biologic.

The first biologics developed for rheumatic conditions – so-called TNF inhibitors like etanercept (Enbrel) and adalimumab (Humira) – do not work particularly well on children with sJIA (compared to those with other forms of JIA). But the more recent approval of biologics that work via other chemical pathways have shown much more promise in controlling it.

In this phase 3 study – typically the last stage of a clinical trial before a drug is approved by the FDA – the researchers randomly assigned 71 children with sJIA to receive weekly injections of rilonacept for 24 weeks or four weeks of placebo injections followed by weekly injections of rilonacept for 20 weeks. Neither the researchers nor the patients knew who was receiving a placebo. A number of patients continued the drug after 24 weeks, for as long as 21 months. Participants were drawn from the Childhood Arthritis & Rheumatology Research Alliance (CARRA) – a network of pediatric rheumatology research centers across North America – which is supported in part by Arthritis Foundation research funding.

“Rilonacept was found to be effective and generally well tolerated in treating systemic JIA patients,” says lead study author Norman T. Ilowite, MD, division chief of rheumatology at Children’s Hospital at Montefiore Medical Center, in New York City.

Children who started on rilonacept from the get-go saw improvement two weeks sooner, on average, than those who started it later. At week four, 79 percent of patients in the rilonacept group showed at least a 30 percent improvement compared to 39 percent in the placebo group; 40 percent of the rilonacept group saw at least a 70 percent improvement at week four compared with 12 percent in the placebo group.

The drug was effective in patients both with and without systemic symptoms such as fever, says Dr. Ilowite, who is also a professor of pediatrics at Albert Einstein College of Medicine, in New York City.