Posted: Thursday, June 24, 2021
Hui Zhang, MD, PhD, of Guangzhou Women and Children’s Medical Center, China, and colleagues presented their interim analysis of a small phase I trial evaluating the safety and antitumor responses of anti-C–type lectin-like molecule-1 (CLL1)-based chimeric antigen receptor (CAR) T cells in the treatment of pediatric relapsed or refractory acute myeloid leukemia (AML), during the 2021 American Society of Clinical Oncology (ASCO) Annual Meeting (Abstract 10000). These investigators concluded that 10 of 11 patients responded to this therapy within 1 month, suggesting this immunotherapy warrants further study in this patient population.
Second-generation CLL1 or CLL1-CD33 dual CAR T cells were administered to 11 pediatric patients with resistant AML at a single dose of 0.3 to 1 x 106/kg after lymphodepleting conditioning with cyclophosphamide and fludarabine. The extracellular single-chain variable fragment was derived from a murine CLL1 monoclonal antibody produced by hybridoma technology.
Before and during CAR T-cell infusion, grade 3 to 4 hematologic adverse events were observed in all patients, although there were no recorded dose-limiting toxicities. Additionally, grade 1 to 3 cytokine-release syndrome was observed, but no events resulted in death. Fortunately, after the guideline-directed intervention, all adverse events were resolved.
In vivo, the anti-CLL1 CAR T cells efficiently expanded, with the median expansion peaking time at day 8. A response was observed in 10 patients after 1 month of therapy, with CLL1-positive AML blast elimination. Among the responding patients, five achieved a complete response and measurable residual disease negativity, three reached a complete response with measurable residual disease positivity, one achieved a partial response, and one had stable disease.
Disclosure: Dr. Zhang reported no conflicts of interest. For full disclosures of the other study authors, visit coi.asco.org.