Page 252 - Haematologica Vol. 110 - January 2025

LETTER TO THE EDITOR
A phase I study of MAGE-A1-targeted T1367 T-cell receptor- based cell therapy in patients with advanced multiple myeloma
Cancer/testis (C/T) antigens are genes whose expression is silenced in healthy adult tissues except for male germ cells. Because C/T antigens are expressed in various can- cers, they are potential targets for targeted therapies.1 MAGE-A1, the first identified C/T antigen, was charac- terized as the target of an autologous cytotoxic T-cell clone recognizing the melanoma cell line MZ2E.2 MAGE-A1 expression was described in biopsies from patients with multiple myeloma (MM),3 an aggressive plasma cell ma- lignancy, and was associated with poor prognosis in one study.4 Despite recent advances in the treatment of MM, such as chimeric antigen receptor (CAR )T-cell therapy and bispecific T-cell engagers (BiTE),5 MM remains incurable, and antigen loss has been described as resistance mech- anism for immunotherapies.6 Therefore, there is a high need for new treatment options and therapeutic targets. T-cell receptor (TCR) therapy represents another T-cell- based immunotherapeutic approach in cancer.7 TCR T-cell therapy allows to target intracellular proteins presented by major histocompatibility (MHC) class I molecules with a higher antigen sensitivity compared to CAR T cells.8,9 We have previously described TCR-T1367 with optimal affinity against MAGE-A1 for development of TCR-based cellular immunotherapy.10 In this study, we present the analysis of a large cohort of MM patients for MAGE-A1 expression and its association with specific clinical and disease characteristics. Furthermore, we describe TCR-1367 T-cell production in an academic setting, and present clinical data from the phase I study (EudraCT: 2017-001208-30) investigating TCR-1367 T cells in two patients.
MAGE-A1 expression was investigated by immunohisto- chemistry (IHC) in 252 formalin-fixed, paraffin-embedded histological samples from 213 patients, collected from 2012 to 2022, using the commonly used anti-MAGE-A1 antibody MA454. The study was approved by the ethical commit- tee of Charité-Universitätsmedizin Berlin (EA4/133/23). Statistical tests included Mann-Whitney test for com- paring two categories and Kruskal-Wallis test for more than two categories. Clinical and genetic characteristics of our cohort are presented in the Online Supplementary Table S1. Out of the 252 samples, 27% presented with ≥30% MAGE-A1 positive (MAGE-A1+) MM cells, 23% with a lower fraction and 50% without MAGE-A1 expression (Figure 1A). An exemplary slide of MAGE-A1 expressing MM cells is shown in Figure 1B. The fraction of MAGE-A1+ samples (≥30% of MAGE-A1+ MM cells), increased from 18% at diagnosis to 33% during relapse (Figure 1A) with a
significant increase of the mean proportion of MAGE-A1+ MM cells in all samples (15% vs. 26%; P=0.0002). For 131 patients cytogenetics and fluorescence in situ hybridiza- tion (FISH) results were available, with 59 classified as standard-risk and 72 as high-risk based on cytogenetic aberrations defined as del(17p), t(4;14), t(14;16), gain or amplification (1q21).11,12 High-risk patients presented with a slightly higher proportion of MAGE-A1+ samples (31%) compared to the standard-risk group (23%), but without significant difference in mean MAGE-A1 expression (24% vs. 18%; P=0.0788; Figure 1C).
Furthermore, we investigated the association of MAGE-A1 expression with extramedullary disease (EMD). In bone marrow (BM) samples, 22% had ≥30% MAGE-A1+ cells, compared to 55% in bone-related extramedullary myeloma (EM-B) and 46% in extraosseous extramedullary myelo- ma (EM-E) samples. The mean proportion of MAGE-A1+ MM cells in positive samples was higher in EM-B (83%; P=0.3918) and EM-E (85%; P=0.0417) samples compared to BM (68%) as shown in Figure 1D. A significant higher proportion of MAGE-A1+ MM cells in positive BM samples were found in patients with documented EMD compared to patients without EMD (82% vs. 58%; P=0.0017; Figure 1E). Analyzing 11 matched EMD and BM samples collected from the same time point and same patient we found only a weak correlation between the proportion of MAGE-A1+ cells between these samples (R2=0.3883; P=0.0405). Survival data were available for 99 newly diagnosed MM patients of which 83 were MAGE-A1-negative (<30% MAGE-A1+ MM cells) and 16 positive (≥30% MAGE-A1+ MM cells). Kaplan-Meier survival analysis revealed that MAGE-A1 expression at di- agnosis was associated with impaired overall survival (OS) resulting in 2-year survival rates of 95% for negative and 54% for positive patients (median OS not-reached for both; hazard ratio [HR]=0.21; 95% confidence interval [CI]: 0.04- 1.16; P=0.0015, log-rank test; Figure 1F).
To investigate MAGE-A1 as a therapeutic target, we applied the MAGE-A1278-286- epitope-directed TCR-T1367 sequence10 and transduced autologous T cells from patients with MM with retrovirus encoding TCR-T1367. TCR-1367 T cells were manufactured at Zellkulturlabor für Klinische Prüfung (ZKP), the GMP Facility of the Experimental and Clinical Research Center (ECRC), Charité-Universitätsmedizin Ber- lin. An overview of the manufacturing process is shown in Figure 2A. The manufacturing process was validated in three healthy donor validation runs. TCR-1367 T cells were manufactured for three patients (patients 001, 004,
Haematologica | 110 January 2025
244