U-73122 is an inhibitor of PLC-dependent processes, however, the mechanism of action remains unclear.[1],[2],[3] The IC50 values for inhibition of platelet aggregation induced by collagen or thrombin are 0.6 and 5 μM, respectively.2 It also exhibits inhibitory activity against HIV-1 integrase with an IC50 value of 7 μM.[4] U-73343 is a close structural analog of U-73122 that does not inhibit PLC, making it useful as a negative control for PLC inhibition.[1]

Reference:
[1]. Smith, R.J., Sam, L.M., Justen, J.M., et al. Receptor-coupled signal transduction in human polymorphonuclear neutrophils: Effects of a novel inhibitor of phospholipase C-dependent processes on cell responsiveness. Journal of Pharmacology and Experimental Therapeutics 253, 688-697 (1990).
[2]. Bleasdale, J.E., Thakur, N.R., Gremban, R.S., et al. Selective inhibition of receptor-coupled phospholipase C-dependent processes in human platelets and polymorphonuclear neutrophils. Journal of Pharmacology and Experimental Therapeutics 255, 756-768 (1990).
[3]. Hildebrandt, J.P., Plant, T.D., and Meves, H. The effects of bradykinin on K+ currents in NG108-15 cells treated with U73122, a phospholipase C inhibitor, or neomycin. British Journal of Pharmacology 120, 841-850 (1997).
[4]. Burke, T.R., Jr., Fesen, M.R., Mazumder, A., et al. Hydroxylated aromatic inhibitors of HIV-1 integrase. Journal of Medicinal Chemistry 38, 4171-4178 (1995).