PRKCB and diabetic retinopathy: Ruboxistaurin, an oral PKCβ inhibitor, is currently undergoing phase 2 and phase 3 clinical testing for several cardiovascular diseases, such as diabetic retinopathy and diabetic kidney disease.32, 33 Due to be administrated orally, ruboxistaurin was gavaged for 3 days before I/R, which would be a potential limitation in acute clinical cases.