An isozyme-selective inhibitor of protein kinase Cβ (PKCβ). Inhibits both the PKCβI (IC₅₀ = 4.7 nM) and PKCβII (IC₅₀ = 5.9 nM) isozymes. LY-333,531 is 76- and 61-fold more selective for inhibition of PKCβI and PKCβII over PKCα.