Efficacy and safety of CAR-T therapy targeting CLL1 in patients with extramedullary diseases of acute myeloid leukemia.

Backgrounds: The incidence of extramedullary diseases (EMDs) in patients diagnosed with acute myeloid leukemia (AML) is approximately 10-20%. These patients exhibit a significantly distinct etiology, therapeutic response, and prognosis compared to patients without EMDs. CLL1 CAR-T therapy has been demonstrated satisfactory efficacy and safety in the treatment of refractory and relapsed AML patients. However, concerns have been raised regarding the potential impact of extramedullary niduses on the effectiveness of CLL1 CAR-T therapy.

Methods: A total of 47 patients were enrolled in this study, including 27 patients with isolated AML tumor bone marrow infiltration and 20 patients with both extramedullary and bone marrow infiltration of AML. CLL1 CAR-T cells were manufactured and subjected to rigorous quality control in the hematology laboratory of Tianjin First Central Hospital. The efficacy and adverse reactions were assessed following CAR-T cell infusion, while expansion of CAR-T cells, levels of cytokines releasing, and other indicators were closely monitored.

Results: Among the 20 patients with EMDs and the 27 individuals without EMDs, complete remission in bone marrow was achieved by 65.00% and 81.48% of patients, respectively. Meanwhile, among the patients with EMDs, 55.00% achieved complete remission while 10.00% achieved partial remission when assessing the efficacy of CLL1 CAR-T cells against extramedullary niduses. Although the overall survival, progression-free survival, and duration of remission period appeared to be shorter for patients with EMDs compared to those without EMDs, this difference did not reach statistical significance. The incidence rates of complications were comparable between both groups. Meanwhile, there were no significant differences observed in the levels of CAR-T cell expansion and accompanying cytokines release between patients with and without EMDs.

Conclusions: Our study findings have demonstrated the efficacy of CLL1 CAR-T therapy in the treatment of AML patients with EMDs, while also indicating manageable occurrence rates of complications within a tolerable range. The CLL1 CAR-T therapy, serving as an ideal strategy for AML patients irrespective of the presence of EMDs, effectively ameliorates the conditions of AML patients and provides them with an opportunity to undergo curative hematopoietic stem cell transplantation while significantly enhancing their prognosis.