A-943931 is a selective histamine H4 receptor antagonist with human and rat Ki values of 4.6 and 3.8 nM respectively. It inhibits the scratching response in mice and exhibits anti-pruritic activity.

H4 receptor (human):4.6 nM (Ki), H4 receptor (rat):3.8 nM (Ki)

In the mouse zymosan-induced peritonitis model, A-943931 demonstrated significant anti-inflammatory activity through either subcutaneous or intraperitoneal administration, with ED₅₀ values of 34 µmol/kg and 33 µmol/kg, respectively [2].
In rat models of inflammatory pain and neuropathic pain, A-943931 (10, 30, and 100 µmol/kg, intraperitoneal injection) exhibited marked analgesic effects [2].