Cyclohexane 1,3-diones and their inhibition of mutant SOD1-dependent protein aggregation and toxicity in PC12 cells

Abstract

Amyotrophic lateral sclerosis (ALS) is a fatal neurodegenerative disease characterized by the progressive loss of motor neurons. Currently, there is only one FDA-approved treatment for ALS (riluzole), and that drug only extends life, on average, by 2–3 months. Mutations in Cu/Zn superoxide dismutase (SOD1) are found in familial forms of the disease and have played an important role in the study of ALS pathophysiology. On the basis of their activity in a PC12-G93A-YFP high-throughput screening assay, several bioactive compounds have been identified and classified as cyclohexane-1,3-dione (CHD) derivatives. A concise and efficient synthetic route has been developed to provide diverse CHD analogs. The structural modification of the CHD scaffold led to the discovery of a more potent analog (26) with an EC50 of 700 nM having good pharmacokinetic properties, such as high solubility, low human and mouse metabolic potential, and relatively good plasma stability. It was also found to efficiently penetrate the blood-brain barrier. However, compound 26 did not exhibit any significant life span extension in the ALS mouse model. It was found that, although 26 was active in PC12 cells, it had poor activity in other cell types, including primary cortical neurons, indicating that it can penetrate into the brain, but is not active in neuronal cells, potentially due to poor selective cell penetration. Further structural modification of the CHD scaffold was aimed at improving global cell activity as well as maintaining potency. Two new analogs (71 and 73) were synthesized, which had significantly enhanced cortical neuronal cell permeability, as well as similar potency to that of 26 in the PC12-G93A assay. These CHD analogs are being investigated further as novel therapeutic candidates for ALS.

Recent progress in the discovery of small molecules for the treatment of amyotrophic lateral sclerosis (ALS)

“…Additionally, 14 possessed favorable PK, demonstrating high plasma stability and oral bioavailability, as well as high brain accumulation [33]. Due to its advantageous pharmacological properties, 14 was tested in SOD1 G93A transgenic mice to determine whether it was able to extend lifespan and alleviate symptoms in a mouse model of ALS.…”

“…However, this compound demonstrated no therapeutic benefit. Additional studies demonstrated that 14 exhibited poor activity in primary cortical neurons due to low penetration of neuronal cells [33]. Further SAR around this series led to new chiral CHD analogues, such as compound 15 (Fig.…”

Direct Amination of γ-Halo-β-ketoesters with Anilines

“…8 Although the same strategy was reported to give the product in 33% yield as well as self-condensation to the dihydroquinone in 22% yield, 9 we failed to get desired compound 3 with this method, as well as two other procedures, using NaH and Cs 2 CO 3 , respectively, as bases (Scheme 2). The main products under these conditions were recovered starting aniline 7 , by-product 6 , and its precursor 8 , suggesting that the electron deficiency of the aniline diminished its reactivity, strong base favored enolization of 5 , and concomitant self condensation consumed 5 .…”

Chiral Cyclohexane 1,3-Diones as Inhibitors of Mutant SOD1-Dependent Protein Aggregation for the Treatment of ALS

“…However, the most potent of the CHD derivatives did not show any significant extension of life in the ALS mouse model, despite having comparable potency in the PC-12 cell assay and favorable pharmacokinetic properties. 15 Aggregation of mutant G93A SOD1 is induced in the PC-12 assay, which produces a concomitant loss in cell viability. Cell viability is restored through treatment with compounds that reduce protein aggregation.…”