4-Hydroxytamoxifen (Monohydroxytamoxifen) is a selective oestrogen receptor antagonist, with an IC ₅₀ of 3.3 nM for the [ ³ H]oestradiol binding to oestrogen receptor. 4-Hydroxytamoxifen (10, 100 nM) enables to inhibit the binding of [ ³ H]oestradiol to the human 8 S oestrogen receptor. 4-Hydroxytamoxifen activates intein-linked inactive Cas9, reduces off-target CRISPR-mediated gene editing. In human cells, conditionally active Cas9s modify target genomic sites with up to 25-fold higher specificity than wild-type Cas9.

4-Hydroxytamoxifen (0.2, 1 and 5 μg/day, p.o.) causes a dose-related decrease in uterine wet weight of immature rats. 4-Hydroxytamoxifen (6 μg/0.1 mL sesame oil/day, s.c.) effectively attenuates methamphetamine-induced nigrostriatal dopamine depletions in bothsexes of intact and gonadectomized C57BL/6 J mice. 4-Hydroxytamoxifen does not alter the dopamine content levels in the striatum.