SA51, a medium potency inhibitor of protein tyrosine phosphatase 1B (PTP1B), was identified to be a potent inhibitor of $I{kappa}B$ kinase ${eta}$ ($IKK{eta}$). Consistent with this, SA51 prevented lipopolysaccharide (LPS)-induced breakdown of $I{kappa}B{alpha}$ in macrophages. The effects of SA51 in mice were compared with those of structurally related compounds, SA18 and SA32, which were previously reported as inhibitors of both enzymes - less potent against $IKK{eta}$ but more potent against PTP1B compared to SA51. SA51 improved glucose tolerance and lipid parameters in mice, consistent with the results reported for $IKK{eta}^{+/-}$ mice. In contrast, SA18 and SA32 showed anti-obesity effects without anti-diabetic effects. Collectively, the effects of SA51 could be due largely to the inhibition of $IKK{eta}$, whereas SA18 and SA32 may be more likely to inhibit PTP1B, consistent with their relative in vitro inhibitory effects.