On 2014 Jul 30, Jim Woodgett commented:

This compound was not tested in vitro against GSK-3alpha. Given the virtual identity in the active (ATP binding) site of these two isoforms, it is extremely probable that these compounds also inhibit GSK-3alpha with very similar potency to GSK-3beta. The authors also measured the effect of compound 21 (in comparison to LiCl) on tau phosphorylation in brains of mice. Notably, GSK-3alpha also phosphorylates tau and the observed effects are likely a result of combined inhibition of these related kinases.

On 2014 Jul 30, Jim Woodgett commented:

This compound was not tested in vitro against GSK-3alpha. Given the virtual identity in the active (ATP binding) site of these two isoforms, it is extremely probable that these compounds also inhibit GSK-3alpha with very similar potency to GSK-3beta. The authors also measured the effect of compound 21 (in comparison to LiCl) on tau phosphorylation in brains of mice. Notably, GSK-3alpha also phosphorylates tau and the observed effects are likely a result of combined inhibition of these related kinases.