61 | A PIVOTAL STUDY OF SHR2554, AN ORAL INHIBITOR AGAINST ENHANCER OF ZESTE HOMOLOG 2 (EZH2), IN RELAPSED OR REFRACTORY (R/R) PERIPHERAL T‐CELL LYMPHOMA (PTCL)

Y. Song and Z. Li equally contributing authors. Introduction: Inhibition of EZH2, a key histone methyltransferase, represents a rational therapeutic strategy for lymphomas. SHR2554 is an oral, small-molecule inhibitor exhibiting potent selectivity for wild-type and mutant EZH2. Here, we reported the findings from a single-arm pivotal study of SHR2554 in patients (pts) with r/r PTCL (NCT03603951). Methods: Pts with centrally confirmed r/r PTCL who had received prior chemotherapy and at least one additional class of approved medications were given SHR2554 at 350 mg twice daily. The primary endpoint was ORR per independent review committee (IRC), assessed with CT/MRI and PET-CT according to Lugano 2014 criteria. The predefined target for primary endpoint was that the lower boundary of the 95% CI for ORR should exceed 15%. Results: 67 pts were enrolled and treated with SHR2554, including 37 (55.2%) diagnosed with angioimmunoblastic T-cell lymphoma (AITL), 14 (20.9%) with PTCL-not otherwise specified (PTCL-NOS), 7 (10.4%) with anaplastic large-cell lymphoma, anaplastic lymphoma kinase-negative (ALCL, ALK-), 4 (6.0%) with extranodal NK/T-cell lymphoma, nasal type (ENKTL-NT), 2 (3.0%) with ALCL, ALK-positive (ALCL, ALK+), 1 (1.5%) with monomorphic epitheliotropic intestinal T-cell lymphoma (MEITL), and 2 (3.0%) with other subtypes. Median number of prior lines of therapy was 2 (range, 1–9). All pts had received chemotherapy; moreover, all had been treated with tucidinostat or brentuximab vedotin (tucidinostat, 59 [88.1%]; brentuximab vedotin, 21 [31.3%]; both, 13 [19.4%]). As of Dec 20, 2024, 22 (32.8%) pts achieved a complete response and 21 (31.3%) achieved a partial response, resulting in an IRC-assessed ORR of 64.2% (95% CI: 51.5–75.5). Benefit was observed across all subtypes (AITL, 70.3% [26/37]; PTCL-NOS, 57.1% [8/14]; ENKTL-NT, 50.0% [2/4]; ALCL, ALK-, 42.9% [3/7]; ALCL, ALK+, 50.0% [1/2]; MEITL, 100% [1/1]; others, 100% [2/2]). Responses were still ongoing in 51.2% (22/43) of the responders, and estimated median DoR was 18.7 months (95% CI: 6.3-not reached [NR]). 40 (59.7%) pts experienced disease progression or died, and median PFS was 10.0 months (95% CI: 3.7–15.7). There were 20 (29.9%) deaths, and estimated median OS was 16.9 months (95% CI: 15.2–19.0). Grade ≥ 3 TEAEs were reported in 41 (61.2%) pts, with the most common being decreased platelet count (28.4%), decreased neutrophil count (26.9%), decreased white blood cell count (25.4%), and anemia (23.9%). Only 4 (6.0%) pts had treatment-related adverse events leading to treatment discontinuation. No treatment-related deaths occurred. Conclusions: The pivotal study met its primary endpoint, demonstrating that SHR2554 is efficacious and has a manageable safety profile in pts with r/r PTCL. Our findings position SHR2554 as a new potential therapeutic option for this challenging-to-treat population. A randomized controlled phase 3 study comparing SHR2554 with standard therapy for r/r PTCL is currently underway (NCT06122389). Research funding declaration: Jiangsu Hengrui Pharmaceuticals Encore Abstract: EHA 2025 Keywords: aggressive T-cell non-Hodgkin lymphoma; molecular targeted therapies Potential sources of conflict of interest: Y. Li Employment or leadership position: Jiangsu Hengrui Pharmaceuticals J. Shen Employment or leadership position: Jiangsu Hengrui Pharmaceuticals Z. Xiao Employment or leadership position: Jiangsu Hengrui Pharmaceuticals W. Shi Employment or leadership position: Jiangsu Hengrui Pharmaceuticals