Diverse small-molecule modulators of SMN expression found by high-throughput compound screening: early leads towards a therapeutic for spinal muscular atrophy

Abstract

We have exploited the existence of a second copy of the human SMN gene (SMN2) to develop a high-throughput screening strategy to identify potential small molecule therapeutics for the genetic disease spinal muscular atrophy (SMA), which is caused by the loss of the SMN1 gene. Our screening process was designed to identify synthetic compounds that increase the total amount of full-length SMN messenger RNA and protein arising from the SMN2 gene, thereby suppressing the deleterious effects of losing SMN1. A cell-based bioassay was generated that detects SMN2 promoter activity, on which greater than 550,000 compounds was tested. This resulted in the identification of 17 distinct compounds with confirmed biological activity on the cellular primary assay, belonging to nine different structural families. Six of the nine scaffolds were chosen on the basis of their drug-like features to be tested for their ability to modulate SMN gene expression in SMA patient-derived fibroblasts. Five of the six compound classes altered SMN mRNA levels or mRNA splicing patterns in SMA patient-derived fibroblasts. Two of the compound classes, a quinazoline compound series and an indole compound, also increased SMN protein levels and nuclear gem/Cajal body numbers in patient-derived cells. In addition, these two distinct scaffolds showed additive effects when used in combination, suggesting that they may act on different molecular targets. The work described here has provided the foundation for a successful medicinal chemistry effort to further advance these compounds as potential small molecule therapeutics for SMA.

Clinical and molecular cross-sectional study of a cohort of adult type III spinal muscular atrophy patients: clues from a biomarker study

“…Some therapeutic approaches aim to increase the amount of SMN protein produced by SMN2 through promoter activation, reduction of exon 7 alternative splicing, or both. [13][14][15][16][17][18][19][20][21][22] Some of these approaches are being investigated in ongoing or planned clinical trials, and great efforts have been done to identify the most appropriate clinical outcome measures for patients affected from various severities. 23 In this view, it would be very useful to have reliable biomarkers of disease severity and response to treatment.…”

SMN transcript levels in leukocytes of SMA patients determined by absolute real-time PCR

“…Recently, evidence has been provided that SMN2 gene expression can be enhanced by pharmacological treatment in vivo and/or in vitro, using different compounds. [9][10][11][12][13][14][15][16][17] The clinical efficacy of some of these compounds has been tested also in clinical trials. [18][19][20][21] The advances in SMA clinical research highlight the need of reliable biomarkers to monitor the efficacy at the molecular level of treatments during trials, the dosage of SMN transcripts or protein in peripheral blood samples being the only one potentially available.…”

Atrofia muscular espinal: Caracterización clínica, electrofisiológica y molecular de 26 pacientes

“…Estos ensayos se han realizado con ácido valproico, fenilbutirato de sodio e hidroxiurea [19][20][21] . Específi camente las estrategias se han enfocado a aumentar la inclusión del exón 7 en el trascripto de RNA mensajero del gen SMN2 [19][20][21] , a la sobre regulación de la trascripción de SMN2 por activación del promotor 22 , a la modulación de la trascripción de la proteína SMN2 23 y a la prevención de la degradación de la proteína SMN 24 .…”