CHARLOTTE, N.C. – Scores on a novel AGS scale improved, and skin and liver complications resolved in children with AGS who received treatment with baricitinib, according to results presented at the annual meeting of the Child Neurology Society.
AGS is caused by various heritable disorders of the innate immunity that result in excessive interferon production. AGS characteristically manifests as an early-onset encephalopathy that causes intellectual and physical disability, but patients may have a wide range of clinical phenotypes. The disease may involve the skin, liver, lungs, heart, and other organs, as well as the brain.
A multisystem disorder
“The neurologic features, while they are the most compelling for us, are really only the tip of the iceberg,” said, program director of the leukodystrophy center, and the Jacob A. Kamens Endowed Chair in Neurologic Disorders and Translational Neurotherapeutics at Children’s Hospital of Philadelphia. “Nearly every single organ system in the body is affected, from either direct interferon injury or from a secondary vasculopathy related to the interferonopathy.”
Dr. Vanderver presented results from the compassionate use study, which assessed whether the JAK inhibitor baricitinib () may decrease interferon signaling in AGS and limit the morbidity of the disease.
The phase 1, open-label trial “included compassionate use of baricitinib in AGS under the argument that these children did not have time to wait for approval of the drug,” said Dr. Vanderver. In 2018, the Food and Drug Administration approved baricitinib for moderate to severe rheumatoid arthritis in adults with an inadequate response to methotrexate.
The phase 1 trial in AGS included 35 patients with mutation-defined AGS and evidence of inflammatory disease that could be targeted by JAK inhibition. The trial population was 36% female. The average age of disease onset was 0.8 years, and patients’ average age at treatment was 6.1 years. The investigators assessed safety and laboratory data every 3 months and conducted clinical assessments every 6 months.
The heterogeneity of AGS phenotypes within families and across genotypes makes treatment trials in this disorder a challenge, Dr. Vanderver said. Outcome measures may have ceiling or floor effects that fail to capture the range of severity of AGS symptoms. Dr. Vanderver and colleagues developed a novel AGS scale to capture the scope of neurologic function in patients with AGS
When the researchers applied the AGS scale to a historical cohort of patients, most had stable scores about 6 months after disease onset. “After the first 6 months of the disease, the disease tends to be much more static, as the children have sustained significant neurologic injury,” Dr. Vanderver said.
They applied the novel AGS scale post hoc as an exploratory endpoint in the phase 1 trial. In addition, parents recorded information in a diary about skin involvement, irritability, seizures, and fever. “Over time, we see a reduction, although not always a statistically significant reduction, in symptom burden,” Dr. Vanderver said. The AGS clinical diary scores reflect “what the parents were telling us – that they felt like their children were feeling better during treatment,” she said.
Several patients had skin conditions that improved with treatment. One patient with dermatitis or eczema had the skin abnormality resolve within 3 days. A patient with full-body panniculitis began healing for the first time after about a month of treatment. Seasonal variations and dose adjustments led to fluctuations in some of the skin conditions. Nevertheless, the results suggested significant improvement in skin manifestations in patients with AGS, Dr. Vanderver said.
Patients generally had stable AGS scale scores in the year before treatment, although a couple of patients who were closer to disease onset had precipitous decline in neurologic function, she said. “We had a statistically significant increase in that scale of neurologic function in our patients during the period of the study, even in patients who had sometimes had years of disease duration,” said Dr. Vanderver.
Dr. Vanderver cautioned that she does not want to overstate the changes in function. Patients with AGS may have less potential for recuperation, compared with patients with other conditions. “A child with significant disruptive CNS disease may not recuperate normal functioning,” Dr. Vanderver said, “but it can be clinically meaningful to families if children start having better head control, smile, communicate, even if they might not regain all their motor milestones.”
In addition, a small subset of patients who had potentially life threatening liver complications from the disease experienced rapid normalization and improvement of liver function. “This blockade can be important not just for neurologic function but also to maintain normal physiologic homeostasis of other organs that are affected by the interferonopathy,” Dr. Vanderver said.
Interferon signaling scores decreased in the days after starting treatment and subsequently leveled out.
Serious adverse events that occurred during the trial, such as hospitalizations, were attributable to AGS. One child died from unrecognized pulmonary hypertension, which is now known to be a complication of AGS but was not at the time.