Design, Synthesis, and Evaluation of (2-Aminocyclopropyl)phenyl Derivatives as Novel Positron Emission Tomography Imaging Agents for Lysine-Specific Demethylase 1 in the Brain

LSD1 in drug discovery: From biological function to clinical application

Lysine-specific demethylase 1 (LSD1) is a flavin adenine dinucleotide (FAD) dependent monoamine oxidase (MAO) that erases the mono-, and dimethylation of histone 3 lysine 4 (H3K4), resulting in the suppression of target gene transcriptions. Besides, it can also demethylate some nonhistone substrates to regulate their biological functions. As reported, LSD1 is widely upregulated and plays a key role in several kinds of cancers, pharmacological or genetic ablation of LSD1 in cancer cells suppresses cell aggressiveness by several distinct mechanisms. Therefore, numerous LSD1 inhibitors, including covalent and noncovalent, have been developed and several of them have entered clinical trials. Herein, we systemically reviewed and discussed the biological function of LSD1 in tumors, lymphocytes as well as LSD1-targeting inhibitors in clinical trials, hoping to benefit the field of LSD1 and its inhibitors.

A Quinquennial Review of Potent LSD1 Inhibitors Explored for the Treatment of Different Cancers, with Special Focus on SAR Studies

Cancer bears a significant share of global mortality. The enzyme Lysine Specific Demethylase 1 (LSD1, also known as KDM1A), since its discovery in 2004, has captured the attention of cancer researchers due to its overexpression in several cancers like acute myeloid leukaemia (AML), solid tumours, etc. The Lysine Specific Demethylase (LSD1) downregulation is reported to have an effect on cancer proliferation, migration, and invasion. Therefore, research to discover safer and more potent LSD1 inhibitors can pave the way for the development of better cancer therapeutics. These efforts have resulted in the synthesis of many types of derivatives containing diverse structural nuclei. The present manuscript describes the role of Lysine Specific Demethylase 1 (LSD1) in carcinogenesis, reviews the LSD1 inhibitors explored in the past five years and discusses their comprehensive structural activity characteristics apart from the thorough description of LSD1. Besides, the potential challenges, opportunities, and future perspectives in the development of LSD1 inhibitors are also discussed. The review suggests that tranylcypromine derivatives are the most promising potent LSD1 inhibitors, followed by triazole and pyrimidine derivatives with IC₅₀ values in the nanomolar and sub-micromolar range. A number of potent LSD1 inhibitors derived from natural sources like resveratrol, protoberberine alkaloids, curcumin, etc. are also discussed. The structural-activity relationships discussed in the manuscript can be exploited to design potent and relatively safer LSD1 inhibitors as anticancer agents.

Investigating the Therapeutic Potential of LSD1 Enzyme Activity-Specific Inhibition by TAK-418 for Social and Memory Deficits in Rodent Disease Models

Inhibition of lysine-specific demethylase 1 (LSD1) enzyme activity is a promising approach to treat diseases associated with epigenetic dysregulation, such as neurodevelopmental disorders. However, this concept has not been fully validated because genetic LSD1 deletion causes embryonic lethality and conventional LSD1 inhibitors cause thrombocytopenia via the dissociation of LSD1-cofactor complex. To characterize the therapeutic potential of LSD1 enzyme inhibition, we used TAK-418 and T-448, the LSD1 enzyme activity-specific inhibitors with minimal impact on the LSD1-cofactor complex. TAK-418 and T-448, by inhibiting brain LSD1 enzyme activity, consistently improved social deficits in animal models of neurodevelopmental disorders without causing thrombocytopenia. Moreover, TAK-418 improved memory deficits caused by aging or amyloid precursor protein overexpression. In contrast, TAK-418 did not improve memory deficits caused by miR-137 overexpression. Thus, miR-137 modulation may be involved in memory improvement by LSD1 inhibition. TAK-418 warrants further investigation as a novel therapeutic agent for diseases with epigenetic dysregulation.

Annual review of lysine-specific demethylase 1 (LSD1/KDM1A) inhibitors in 2021

Lysine-specific demethylase 1 (LSD1/KDM1A) has emerged as a promising epigenetic target for disease treatment. Several LSD1 inhibitors have advanced into clinical trials. Following our last annual review on LSD1 inhibitors in 2020 (Eur. J. Med. Chem. 2021, 214, 113254), in this review we aim to update LSD1 inhibitors including natural products, synthetic compounds and cyclic peptides reported during 2021. Design strategies, structure-activity relationships, binding model analysis and modes of action are highlighted. In particular, two FDA-approved antihypertensive drugs raloxifene and fenoldopam were repurposed as reversible LSD1 inhibitors. The clinical candidate TAK-418 for treating neurodevelopmental disorders and PET imaging agent [¹⁸F]30 for LSD1 were identified. Moreover, dual inhibitors targeting both LSD1 and HDAC6 or tubulin displayed enhanced anti-cancer effects than single agents. These compounds further enrich the structural types of LSD1 inhibitors.

Design, Synthesis, and Evaluation of [18F]T-914 as a Novel Positron-Emission Tomography Tracer for Lysine-Specific Demethylase 1

Histone methylation is associated with the pathophysiology of neurodevelopmental disorders. Lysine-specific demethylase 1 (LSD1) catalyzes histone demethylation in a flavin adenine dinucleotide (FAD)-dependent manner. Thus, inhibiting LSD1 enzyme activity could offer a novel way to treat neurodevelopmental disorders. Assessing LSD1 target engagement using positron-emission tomography (PET) imaging could aid in developing therapeutic LSD1 inhibitors. In this study, PET probes based on 4-(2-aminocyclopropyl)benzamide derivatives that bind irreversibly to FAD found in LSD1 were examined. By optimizing the profiles of brain penetrance and brain-penetrant metabolites, T-914 (1g) was identified as a suitable PET tracer candidate. PET studies in nonhuman primates demonstrated that [¹⁸F]1g had heterogeneous brain uptake, which corresponded to known LSD1 expression levels. Moreover, brain uptake of [¹⁸F]1g was reduced by coadministration of unlabeled 1g, demonstrating blockable binding. These data suggest that [¹⁸F]1g warrants further investigation as a potential PET tracer candidate for assessing target engagement of LSD1.