AUY922 treatment reduces GVHD in mice undergoing haploidentical allogeneic HSCT. Lethally irradiated BDF1 recipients (11.5 Gy) received B6/SJL mouse–derived TCD-BM (5 × 10⁶) with or without spleen cells (1 × 10⁷). Recipients were treated with 14 doses of AUY922 from day 0 to day 27 (A-C) or 12 doses of AUY922 from day 5 to day 27 (D-F) after transplantation, with phosphate-buffered saline treatment as control (Con). (A,D) Survival and clinical score were monitored over time. (B-C,E-F) Tissues were collected from day 28 to day 35 after transplantation. (B,E) Images were obtained with an Olympus BX41 microscope (magnification ×200; hematoxylin-eosin stain). (C,F) Graphs show the histologic score of GVHD. (G) B6/SJL-derived TCD-BM (5 × 10⁶) with or without CD4⁺ T cells (1 × 10⁶) were transferred into lethally irradiated (8 Gy) BALB/c mice. Fourteen doses of AUY922 (50 mg/kg) were administered to these recipients from day 0 to day 27 after transplantation. Survival rate and clinical score were monitored over time. Error bars indicate mean ± standard deviation. Data are representative of 2 to 3 independent experiments. *P < .05; **P < .01; ***P < .001.