CART Cell Therapy Targeting CD84 Alone or in Combination with CD19 for the Treatment of B-Cell Malignancies

• Published in: Blood 2024-11, Vol.144, p.1034-1034
• Main Authors: Altuna Mongelos, Ane, Perez Amill, Lorena, Val-Casals, Maria, Peña, Sergio, Armand-Ugon, Mercedes, Álamo Moreno, Jose Ramón, Correa, Juan Gonzalo, Urbano-Ispizua, Alvaro, Delgado, Julio, Santos, Claudio, Juan, Manel, Klein-Gonzalez, Nela
• Format: Article
• Language: English
• ISSN: 0006-4971
• DOI: 10.1182/blood-2024-207309

Most B-cell acute lymphoblastic leukemia (B-ALL) patients (>70%) and B-cell lymphoma patients (>50%) achieve complete remission with CD19-directed CART cell therapy (CART19). However, leukemic cells that either lack or have low levels of CD19 expression may lead to relapse. In large B-cell lymphoma (LBCL), a low or negative CD19 expression has been correlated with resistance to CART19 therapy. Moreover, it has been reported that patients with lower pre-therapy median CD19 density had increased risk of relapse after axicabtagene ciloleucel. On the other hand, loss of cell surface CD19 has been observed in more than 30% of relapses after CART19 therapy in B-ALL. Consequently, new strategies are needed in this scenario. The CD84 (SLAMF5) immunoreceptor is overexpressed in B-cell malignancies and presents a promising novel target for CART cell therapy, either alone or in combination with the CD19 antigen. We developed a second-generation CART cell targeting CD84 (CART84) (anti-CD84scFv-CD8αH-TM-4-1BB-CD3z). Its in vitro and in vivo effectiveness was evaluated against B-cell malignancies using NALM-6, a B-ALL cell line, and Ramos, a Burkitt lymphoma cell line. CART84 cells were cytotoxic towards B-ALL and aggressive B-cell lymphoma, both in vitro and in vivo. Cytokine production and proliferation assays demonstrated that CART84 specifically proliferated and secreted cytokines when co-cultured with CD84+ tumor cells. CART84 controlled disease progression and increased survival of CART-treated mice in a NSG immunodeficient B-ALL mouse model. Second, we developed a dual CART cell targeting both CD19 and CD84 antigens (CD19/CD84-DUAL1) using an “AND” strategy. The CD19/CD84 DUAL1 CART cells were cytotoxic towards CD19+/CD84+ NALM-6 cells, but also exhibited non-specific killing of CD19-/CD84+ MOLM-13 cells (a cell line derived from acute myeloid leukemia). We identified the dimerization of their hinge domains as the potential cause of this non-specific killing. To prevent dimerization, we incorporated C164S and C181S mutations in the hinge domains, resulting in the CD19/CD84 DUAL1m CART cell. The CD19/CD84 DUAL1m CART cells specifically killed NALM-6 cells expressing both antigens (CD19+/CD84+), without affecting MOLM-13 cells (CD19-/CD84+). Next, we designed two versions of CD19 and CD84 dual CART cells using an “IF BETTER” strategy while maintaining the mutations: CD19/CD84-DUAL2m (anti-CD19scFv-4-1BB-CD3z/anti-CD84scFv-4-1BB) and CD19/CD84-DUAL3m (anti-CD19scFv-