The Ezh2-specific inhibitor GSK126 is unable to control GVHD in mice. (A-B) Spleen mononuclear cells (3 × 10⁷) were isolated from B6/SJL mice and transplanted into unirradiated BDF1 recipient mice. On days 4, 5, and 6, various doses of GSK126 (0, 30, 37.5, and 42.5 mg/kg/day intraperitoneally) were injected into these recipient mice. Donor T cells were recovered on day 7 after transplantation. Graphs show the donor T-cell number (A) and the fraction of interferon γ (IFN-γ)–expressing donor T cells (B). (C-D) Lethally irradiated (11.5 Gy) BDF1 recipient mice received B6/SJL TCD-BM (5 × 10⁶) or TCD-BM plus spleen-cell (1 × 10⁷) transplants (C), and lethally irradiated (10 Gy) B6/SJL recipient mice received C3H.SW TCD-BM (5 × 10⁶) or TCD-BM plus CD8⁺ T-cell (2 × 10⁶) transplants (D). GSK126 (37.5 mg/kg) was administered to the mice for 12 doses from day 0 to day 27 after transplantation. Survival was monitored over time. (E) Sublethally irradiated (6.5 Gy) BDF1 recipient mice received B6 lymph node–cell (1 × 10⁶) transplants, followed by UNC1999 treatment daily for 10 doses (50 mg/kg) from the day of transplantation or 5 doses (100 mg/kg) from day 5 after transplantation. Survival was monitored over time. (F) Lethally irradiated BDF1 recipient mice received B6/SJL TCD-BM (5 × 10⁶) plus spleen cells (1 × 10⁷) transplants. EPZ6438 (1, 10, or 30 mg/kg) was administered for 12 doses from day 0 to 27 after transplantation. Survival was monitored over time. (G) B6 mouse–derived CD4⁺ and CD8⁺ naïve T cells were stimulated with anti-CD3 antibody (3 μg/mL), anti-CD28 antibody (2 μg/mL), and recombinant murine interleukin-2 (5 ng/mL). One day later, different doses of GSK126 were used to treat the cells for another 2 days. The expressions of Ezh2 and H3K27me3 were measured. Error bars indicate mean ± standard deviation. Results are representative of 2 to 3 independent experiments. *P < .05. TBI, total-body irradiation.