Abstract CT039: Alectinib in children and adolescents with solid or CNS tumors harboring ALK-fusions: Data from the iMATRIX Alectinib Phase I/II open-label, multi-center study

Abstract Background Alectinib is a central nervous system (CNS)-penetrant, oral, inhibitor of ALK-fusion proteins that has demonstrated durable responses in adults with ALK-positive non-small cell lung cancer. In children and adolescents there remains a significant unmet clinical need for patients with tumors harboring ALK-fusions, including infantile high grade gliomas and inflammatory myofibroblastic tumors at diagnosis and relapse. Here we present updated safety and efficacy data from the iMATRIX Alectinib phase I-II study (NCT04774718). Methods Patients with ALK fusion-positive solid or CNS tumors for whom prior treatment has proven to be ineffective or for whom there is no satisfactory treatment available, less than 18 years of age, were eligible. Patients were recruited to the Part 1, safety run-in to confirm the recommended phase 2 dose and monitor drug pharmacokinetics. Investigators reported responses according to RANO (CNS tumors), RECIST (solid tumors) or INRC (neuroblastoma) criteria with a data cut off of June 12, 2023. Results In total 8 patients at a median age of 11 years (range 6 months - 17 years), diagnosed with inflammatory myofibroblastic tumor (n=2), high grade glioma (n=3), renal cell carcinoma (n=2), and anaplastic large cell lymphoma (n=1, protocol deviation) were enrolled. Among 7 patients evaluable for efficacy, 6 had not received prior systemic therapy. ALK fusion partners were KIF5C in 2 patients and TPM3, CLTC, PLEKHA7, DCTN1 and HNRNPA3 in 1 patient each. Median treatment duration was 12 months (range 1-21). No Dose Limiting Toxicities were reported. Seven patients experienced a related Adverse Event (AE) including 2 patients with Grade ≥ 3 related AE. There were no AE-related deaths, and no new safety signals detected. Investigators reported Best Overall Responses as follows: in 4 patients (57.1%; 1 CR, 3 PR), 2 patients (28.6%) with Stable Disease and 1 patient had not undergone a tumor assessment at the time of data cut off. Conclusions Alectinib was generally well tolerated in pediatric patients with ALK-fusion positive solid or CNS tumors. In this hard-to-treat population, efficacy results are promising with the majority of patients experiencing a response, demonstrating a favorable benefit-risk profile. Citation Format: Francois Doz, Michela Casanova, Kyung-Nam Koh, Karsten Nysom, Adela Canete, Hyoung Jin Kang, Matthias Karajannis, Darren Hargrave, Nadege Corradini, Yeming Wu, Thorsten Ruf, Johannes Noe, Gabriele Manzella, Tao Xu, Nastya Kassir, Yachun Tai, Francis Mussai, Clare Devlin, Amar Gajjar. Alectinib in children and adolescents with solid or CNS tumors harboring ALK-fusions: Data from the iMATRIX Alectinib Phase I/II open-label, multi-center study [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 2 (Late-Breaking, Clinical Trial, and Invited Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(7_Suppl):Abstract nr CT039.