Fortunately, Kojetin
et al.[
5] collaborated with other groups and identified powerful and effective NR1D1 modulators based on the GSK4112 scaffold, providing key compounds for further guidance and in-depth research on NR1D1 function
in vitro and
in vivo. SR9009 and SR9011 are typical representatives that were first synthesized and functionally tested in 2012 that have a 3- to 4-fold efficiency compared to GSK4112[
83], and have been extensively shown to pharmacologically target NR1D1. SR9009 and SR9011 undoubtedly have anti-inflammatory effects on various organs and tissues, such as the lung, retina, liver, bone and hippocampus[
7,
41,
76,
103,
104]. Moreover, SR9009 and SR9011 exert powerful metabolic effects induced by NR1D1 on processes such as glucose metabolism, lipid metabolism and cholesterol and bile acid metabolism[
83]. Solt
et al.[
83]. showed that SR9009 and SR9011 affected the circadian expression of several core clock genes in the mouse hypothalamus and dose-dependently suppressed the expression of responsive genes in the mouse liver by modulating NR1D1 activity. For example, the suppression of Srebf1, Scd1, Srebf2 and cholesterol 7α-hydroxylase expression (Cyp7a1), an increase in hexokinase 1 (HK1) and pyruvate kinase M2 (Pkm2), and a phase shift in the expression of Fasn were observed after SR9011 treatment[
83]. The strong potency of SR9009 and SR9011 in metabolic processes indicates that these agents could modulate obesity. In fact, SR9009 and SR9011 have been shown to increase energy expenditure without altering exercise behavior or food intake, inducing weight loss in diet-induced obese mice and suggesting a novel approach to weight loss[
83]. Additionally, the fundamental clock mechanism is tightly linked to metabolic control, and several examples of genetic changes in clock genes that cause metabolic abnormalities and even metabolic illnesses in mouse models exist[
105,
106]. Hence, SR9009 and SR9011 may adversely affect the biological clock of dieters by regulating circadian rhythms. Additionally, SR9009 and SR9011 have been identified as novel antitumor agents that modulate circadian regulators. Both factors have specific lethal effects on cancer cells and oncogene-induced senescent cells, such as breast cancer cells, SCLC cells and melanocytic naevi, but have no influence on normal cell survival[
71,
107,
108]. Moreover, according to Dierickx
et al.[
109], SR9009 has NR1D1-independent effects on the survival and proliferation of hepatocytes and embryonic stem cells, which has an impact on metabolism, gene expression, and mitochondrial respiration. Therefore, SR9009 cannot be used only as a surrogate for the NR1D1 effect. More attention should be focused on its independent activity, and even its conformational resolution can help to develop NR1D1-independent active molecules in the future. Despite this early promise, 10 μmol/L SR9009, SR9011 and GSK4112 have been reported to exhibit off-target binding to LXRα[
85], resulting in the limitations of using SR9009, SR9011 and GSK4112 to explore the pharmacological mechanisms of NR1D1. In an attempt to further optimize these compounds, Chang
et al.[
86] and Amir
et al.[
110] identified the novel NR1D1 agonist SR12418, which was modified from SR9009 with minimal off-target activity and significantly improved plasma exposure in mice. SR12418 inhibits Th17-driven autoimmunity
in vivo, suggesting further efficacy in autoimmune diseases.