ROCK2 inhibition suppresses cytotoxic T lymphocyte-mediated platelet destruction in primary immune thrombocytopenia.

Cytotoxic T lymphocyte (CTL)-mediated platelet destruction represents an important pathogenic mechanism in primary immune thrombocytopenia (ITP) patients. Rho-associated coiled-coil kinase 2 (ROCK2) is an emerging regulator of immune balance, but its role in pathogenic CTL activation in ITP remains undefined. Here, we demonstrated that selective ROCK2 inhibition with KD025 potently suppressed CTL-mediated platelet destruction. In vitro, KD025 treatment of CTLs from ITP patients suppressed key effector functions, reducing degranulation as measured by CD107a expression, diminishing the secretion of cytotoxic molecules such as granzyme B and perforin, and decreasing CTL-platelet conjugate formation, resulting in reduced platelet apoptosis and activation. RNA-sequencing revealed downregulation of cytotoxic and glycolytic programs, with enrichment of JAK-STAT signaling. Mechanistically, KD025 reversed the pathogenic metabolic shift in ITP CTLs by lowering glycolytic flux and restoring mitochondrial respiration, accompanied by decreased STAT3 phosphorylation. IL-6-mediated STAT3 activation largely reversed these effects, indicating a ROCK2-STAT3-dependent mechanism. In vivo, both daily KD025 administration to an active ITP mouse model and transplantation of KD025-pretreated CD8