The following article features coverage from the 2021 American Society of Clinical Oncology (ASCO) Annual Meeting. Click here to read more of Hematology Advisor‘s conference coverage.

In a phase 1/2 trial, 8 of 11 patients with relapsed or refractory acute myeloid leukemia (AML) achieved a complete response with chimeric antigen receptor (CAR) T-cell therapy targeting C-type lectin-like molecule-1 (CLL1).

These results were presented at the 2021 American Society of Clinical Oncology (ASCO) Annual Meeting by Hui Zhang, MD, PhD, of Guangzhou Women and Children’s Medical Center in China.

Dr Zhang noted that outcomes of childhood AML lag behind outcomes of acute lymphoblastic leukemia (ALL). Although CAR T cells have an attractive efficacy and safety profile in ALL, CAR T-cell therapy in AML has been challenging due to the lack of an ideal CAR-T target.

With this in mind, Dr Zhang and colleagues tested a CAR T-cell therapy targeting CLL1, which is highly expressed on AML blasts and leukemia stem cells but not on normal hematopoietic stem cells.

From October 2019 to January 2021, 11 pediatric AML patients from two centers were infused with a second-generation anti-CLL1 CAR T-cell therapy. Three patients received a CAR T-cell therapy targeting both CLL1 and CD33.

The CAR T cells expanded in all patients, and all patients experienced grade 1 or 2 cytokine release syndrome and severe myeloablation.

Grade 3/4 hematologic adverse events were observed before and after infusion, but no dose-limiting toxicities occurred. All 3 patients who received the anti-CLL1/CD33 CAR T cells experienced hepatic toxicity.

Eight of the 11 patients had a complete response within 1 month of infusion, including all 3 patients who received the anti-CLL1/CD33 CAR T cells.

Six patients had a complete response with minimal residual disease negativity. One patient had a partial response, 1 had stable disease, and 1 did not respond.

Six of the complete responders went on to transplant, and most were still alive and in response at the time of presentation. One patient died of graft-versus-host disease.

The patient who achieved a partial response and the patient who did not respond also went on to transplant and were still alive and in response at the time of presentation.

The 2 complete responders who did not proceed to transplant were still alive and in response as well, but the patient with stable disease had died.

“Anti-CLL1-based CAR T cell is a safe therapeutic candidate with manageable CAR T-cell-associated toxicity for children with relapsed or refractory AML,” Dr Zhang said. “It is highly effective in targeting CLL1-positive AML cells, with superior overall response rate relative to conventional and novel targeting compounds.”

Disclosures: This research was supported by Guangzhou Bio-Gene, and one of the study authors disclosed affiliations with the company. Please see the original reference for a full list of disclosures.

Read more of Hematology Advisor’s coverage of the 2021 ASCO Annual Meeting by visiting the conference page.

Reference

Zhang H, Bu C, Peng Z, et al. The efficacy and safety of anti-CLL1 based CAR T-cells in children with relapsed or refractory acute myeloid leukemia: A multicenter interim analysis. J Clin Oncol. 2021;39:(suppl 15; abstr 10000). doi:10.1200/JCO.2021.39.15_suppl.10000

This article originally appeared on Cancer Therapy Advisor