Fig. 7: Selective targeting of PRMT5 in vitro and in vivo with PRT382 displays antileukemic activity in an aggressive model of CLL/RT.

a Cas9-mediated doxycycline-inducible knockout of PRMT5 in Mec-1 cell line confirmed via western blot (n = 3). b Knockout of PRMT5 in Mec-1 cells (from a) blocked cell proliferation. Plot represents the mean of n = 2 independent experiments. c Global symmetric dimethyl arginine (SDMA) residues via western blot (n = 3) as a marker of PRMT5 activity in HG3 and Mec-1 cell lines treated with PRT382 for 72 h. d Dose-dependent proliferative potential as measured by cell growth in CLL cell lines upon treatment with PRT382 (n = 3), EPZ015666 (n = 4), JNJ-64619178 (n = 2), LLY-283 (n = 2), and PF-06855800 (n = 2). Cell growth is plotted as fold change relative to vehicle-treated cells ±SD. Fresh culture media and PRMT5 inhibitor at indicated concentrations were supplied every 3 days for continuous exposure over 12 days. e Viable Cd19⁺Cd5⁺ cells (5 × 10⁶) Eµ-PRMT5/TCL1 spleen cells were engrafted by tail vein into immunocompetent C57/BL6J mice. Engrafted mice were randomly assigned to treatment conditions: PRT382 10 mg/kg (n = 10), EPZ015666 50 mg/kg (n = 9), or vehicle (n = 7) at 1-week post engraftment. All treatments were administered for 4 contiguous days per week. Illustration created with BioRender.com. f Engrafted mice weekly peripheral blood flow cytometry for the percentage of CLL-like (Cd5⁺Cd19⁺B220^dim) cells ±SD. PRT382 10 mg/kg (n = 10), EPZ015666 50 mg/kg (n = 9), or vehicle (0.5% methylcellulose, 0.1% Tween; n = 7). g Kaplan–Meier plot of engrafted mice survival post-enrollment. Median survival: PRT382, 77 days; EPZ015666, 51 days; vehicle, 50 days. Mantel–Cox test [PRT382 vs vehicle P < 0.0001, hazard ratio = 0.21 95% CI (0.051–0.87); PRT382 vs EPZ015666 P < 0.0001, hazard ratio=0.65 95% CI (0.26–1.6)]. h Average splenic weight at ERC ± SD. PRT382 vs vehicle P = 0.0013; PRT382 vs EPZ015666 P = 0.0004, paired two-tailed t test. PRT382 (n = 7), EPZ015666 (n = 6), vehicle (n = 6). i PRMT5 activity evaluated by immunoblot analysis of splenic B cells from engrafted mice. Vehicle (n = 2), PRT382 (n = 3), or EPZ015666 (n = 3). Cells from Eµ-TCL1 (n = 1) shown as comparison. j Representative H&E histopathology evaluation at ERC in lymph node, spleen, and liver tissues of engrafted mice (from e) treated with vehicle (n = 6), PRT382 (n = 7), or EPZ015666 (n = 8). Sinusoidal lymphocytes are highlighted with arrows. The scale bar is 33.3 µm. Source data are provided as a Source Data file.