Off-Label Use of Anakinra in Inflammatory Conditions in Neonates and Infants Up to 3 Months of Age: A Case Series and a Review of the Literature.

Background: Anakinra is an interleukin-1 receptor antagonist (IL-1Ra). Since IL-1 has been shown to play a key role in the etiology of different autoinflammatory diseases, blocking its pathway has become an important therapeutic target, even in neonates.

Aims: We aimed to report our experience in using anakinra to treat specific neonatal inflammatory conditions.

Methods: We described the clinical management with anakinra of five cases of neonates or infants up to 3 months of age admitted to the neonatal intensive care unit (NICU) of Bambino Gesù Children's Hospital IRCCS in Rome (Italy) from 2020 onwards. Medical history and clinical data concerning NICU hospitalization were collected from the electronic medical records. Furthermore, we performed a literature review of off-label anakinra in the first 3 months of life, up to 5 April 2024. We excluded from this review cases of cryopyrin-associated periodic syndrome, deficiency of the interleukin-1 receptor antagonist, and mevalonate kinase deficiency, for which anakinra is a known treatment.

Results: We reported three off-label cardiorespiratory reasons to use IL-1Ra from our series: (i) chronic lung disease with pulmonary hypertension, (ii) interstitial lung disease with pulmonary hypertension to facilitate the weaning from respiratory support, and (iii) post-surgical polyserositis if effusions accumulate despite drainage. In all our patients, the drug was administered at a dosage of 10 mg/kg/day. The route of administration was chosen based on the patient's clinical characteristics, with the subcutaneous and intravenous routes being comparable in efficacy. The duration of therapy was modulated based on the patient's clinical response, with a minimum duration of 4 months. A total of 308 retrieved articles were screened, and then full texts of records deemed eligible for inclusion were assessed. Based on the literature search and our five cases, a total of 17 infants were treated with anakinra outside its approved indications. The major off-label use was for hemophagocytic lymphohistiocytosis/macrophage activation syndrome, followed by multisystem inflammatory syndrome in children and Kawasaki disease, as in two of our cases.

Conclusions: According to the results of our case series and review of the literature, the off-label use of anakinra in neonates with inflammatory conditions refractory to first-line therapy could be considered. Prospective, multicenter research is necessary to determine whether anakinra is a safe treatment option for these infants to prevent early inflammatory illnesses and in which situations it could enhance clinical results.