Afatinib in paediatric patients with recurrent/refractory ErbB-dysregulated tumours: Results of a phase I/expansion trial

Aim: This phase I/expansion study assessed the safety, pharmacokinetics and preliminary antitumor activity of afatinib in paediatric patients with cancer. Methods: The dose-finding part enroled patients (2- < 18 years) with recurrent/refractory tumours. Patients received 18 or 23 mg/m2/d afatinib orally (tablet or solution) in 28-d cycles. In the maximum tolerated dose (MTD) expansion, eligible patients (1- < 18 years) had tumours fulfilling >= 2 of the following criteria in the pre-screening: EGFR amplification; HER2 amplification; EGFR membrane staining (H-score > 150); HER2 membrane staining (H-score > 0). The primary end-points were dose-limiting toxicities (DLTs), afatinib exposure, and objective response. Results: Of 564 patients pre-screened, 536 patients had biomarker data and 63 (12%) fulfilled >= 2 EGFR/HER2 criteria required for inclusion in the expansion part. A total of 56 patients were treated (17 in the dose-finding and 39 in the expansion part). DLTs were observed in one of six MTD-evaluable patients receiving 18 mg/m(2)/d and in two of five MTD-evaluable patients receiving 23 mg/m(2)/d; 18 mg/m(2)/d was defined as the MTD. There were no new safety signals. Pharmacokinetics confirmed exposure consistent with the approved dose in adults. One partial response (-81% per Response Assessment in Neuro-Oncology) was observed in a patient with a glioneuronal tumour harbouring a CLIP2::EGFR fusion; unconfirmed partial responses were observed in two patients. In total, 25% of patients experienced objective response or stable disease (95% confidence interval: 14-38). Conclusion: Targetable EGFR/HER2 drivers are rare in paediatric cancers. Treatment with afatinib led to a durable response (> 3 years) in one patient with a glioneuronal tumour with CLIP2::EGFR fusion. (c) 2023 The Authors. Published by Elsevier Ltd.