Design of Potent mRNA Decapping Scavenger Enzyme (DcpS) Inhibitors with Improved Physicochemical Properties To Investigate the Mechanism of Therapeutic Benefit in Spinal Muscular Atrophy (SMA)

Abstract

The C-5 substituted 2,4-diaminoquinazoline RG3039 (compound 1), a member of a chemical series that was identified and optimized using an SMN2 promoter screen, prolongs survival and improves motor function in a mouse model of spinal muscular atrophy (SMA). It is a potent inhibitor of the mRNA decapping scavenger enzyme (DcpS), but the mechanism whereby DcpS inhibition leads to therapeutic benefit is unclear. Compound 1 is a dibasic lipophilic molecule that is predicted to accumulate in lysosomes. To understand if the in vivo efficacy is due to DcpS inhibition or other effects resulting from the physicochemical properties of the chemotype, we undertook structure based molecular design to identify DcpS inhibitors with improved physicochemical properties. Herein we describe the design, synthesis, and in vitro pharmacological characterization of these DcpS inhibitors along with the in vivo mouse CNS PK profile of PF-DcpSi (compound 24), one of the analogs found to be efficacious in SMA mouse model.

The Interplay between the RNA Decay and Translation Machinery in Eukaryotes

“…Following 3 0 to 5 0 decay, the m 7 G cap is removed from the remaining short oligonucleotide by the scavenger decapping enzyme DCPS (Liu et al 2008) along with FHIT/Aph1 (Taverniti and Seraphin 2015). From a biological perspective, DCPS mutations have been associated with human neurological diseases (Ng et al 2015) and DCPS inhibitors are being developed as potential therapeutics for spinal muscular atrophy (Gopalsamy et al 2017). DCPS has also been implicated in micro-RNA (miRNA) turnover (Bosse et al 2013), further illustrating the overall importance of this enzyme and impact on multiple pathways in cell biology.…”

Fluorescent Turn‐On Probes for the Development of Binding and Hydrolytic Activity Assays for mRNA Cap‐Recognizing Proteins

“…The residual cap structures are subsequently hydrolyzed by DcpS, which cleaves the pyrophosphate bond to releasem 7 GMP.I mportantly,D cpSh as been identified as am olecular target in spinal musculara trophy (SMA) and itsi nhibitors are potential therapeutics that could alleviateS MA symptoms. [20,21] C5-substitued quinazolines [20] have been reported as DcpS inhibitors, with the compound RG3039 and its analogues being among the most efficient. [21] However, it is stillu nclear how inhibition of DcpSa ffects the mechanism of disease.…”

“…[20,21] C5-substitued quinazolines [20] have been reported as DcpS inhibitors, with the compound RG3039 and its analogues being among the most efficient. [21] However, it is stillu nclear how inhibition of DcpSa ffects the mechanism of disease. DcpS specifically recognizes chemically modified cap structures, such as cap analogues with methylenebisphosphonate, [22] boranophosphate, [23] or thiophosphate, [24] which have also been shown to inhibit DcpS activity,a lbeit with lower potency.…”

In vitro and in vivo effects of 2,4 diaminoquinazoline inhibitors of the decapping scavenger enzyme DcpS: Context-specific modulation of SMN transcript levels

“…A separate report describes the synthesis of novel diaminoquinazoline compounds [ 12 ]. The inhibitory potency of compounds was performed in an assay volume of 20 μl containing 0.05 nM recombinant human DcpS, varying amounts of compound in a buffer of composition 50 mM Tris, 20 mM MgCl 2 , 60 mM (NH 4 ) 2 SO 4 , pH 7.9.…”