**3.5 Repurposed drugs for KDMs**

One of the types of KDMs, LSD1, is a member of the amine oxidase family. Consequently, it shares sequence similarity with monoamine oxidase (MAO), an important enzyme involved in the clearance of neurotransmitters from the brain [105]. As a result, approved monoamine inhibitors, such as the antidepressant tranylcypromine, can also inhibit LSD1 [89]. Notably, tranylcypromine has been reported to suppress amyloid β-induced proinflammatory responses in AD mouse models [89]. Tranylcypromine also reduces tumor growth and metastasis. Hence, its derivatives were developed to optimize the inhibition of LSD1 [90]. One of these derivatives, ORY-1001, is in phase II clinical trial for AML, relapsed, phase I clinical trial for extended-stage disease small cell lung cancer (ED SCLC), and phase I clinical trial for refractory or relapsed acute leukemia (AL). Also, other classes of MAO inhibitors, such as pargyline (anti-hypertensive drug) and phenelzine (antidepressant), inhibit LSD1 with anti-cancer effects in breast and prostate cancer, respectively [91, 92]. On the other hand, the second class of KDM, the JmjC KDM, is yet to be investigated for market drug repurposing. Nonetheless, a couple of pharmaceutical companies are taking strides to develop inhibitors against this class of KDM in hematological and solid cancers [32].
