GALK1 and classic galactosemia: However, independently of the molecular mechanism, the observation that GAL1 deletion completely inhibited the galactose-dependent UPR activation (Fig. 3) and galactose toxicity in these models (supplementary material Fig. S1) (Douglas and Hawthorne, 1964; Ross et al., 2004; Masuda et al., 2008) represents further evidence that the inhibition of galactokinase is a good strategy to treat classic galactosemia.