Discovery, Synthesis, and Biological Evaluation of Novel SMN Protein Modulators

Abstract

Spinal Muscular Atrophy (SMA) is an autosomal recessive disorder affecting the expression or function of survival motor neuron protein (SMN) due to the homozygous deletion or rare point mutations in the survival motor neuron gene 1 (SMN1). The human genome includes a second nearly identical gene called SMN2 that is retained in SMA. SMN2 transcripts undergo alternative splicing with reduced levels of SMN. Up-regulation of SMN2 expression, modification of its splicing, or inhibition of proteolysis of the truncated protein derived from SMN2 have been discussed as potential therapeutic strategies for SMA. In this manuscript, we detail the discovery of a series of arylpiperidines as novel modulators of SMN protein. Systematic hit-to-lead efforts significantly improved potency and efficacy of the series in the primary and orthogonal assays. Structure property relationships including microsomal stability, cell permeability and in vivo pharmacokinetics (PK) studies were also investigated. We anticipate that a lead candidate chosen from this series may serve as a useful probe for exploring the therapeutic benefits of SMN protein up-regulation in SMA animal models, and a starting point for clinical development.

ML372 blocks SMN ubiquitination and improves spinal muscular atrophy pathology in mice

“…We previously discovered a novel arylthiazol-piperidine series as modulators of SMN protein through a campaign of quantitative high-throughput screening (qHTS) of a 210,386-compound MLSMR diversity set using cell-based SMN2-luciferase reporter assay (19). Through an extensive structure-activity relationship (SAR) investigation, more than 160 analogs of this series were synthesized and tested (schematically summarized in Supplemental Figure 1; supplemental material available online with this article; doi:10.1172/jci.insight.88427DS1).…”

“…Several potential backup series, such as the thiadiazole or the pyrimidine core, were identified as having potencies in the same range. The details of the SAR can be found in our previous publication about this series (19). ML372 was chosen for advanced studies because of its potency, efficacy, permeability, metabolic stability, and pharmacokinetic properties (Table 1).…”

“…After a systematic hit-to-lead medicinal chemistry effort on this series, a pool of lead compounds with good potency, physical properties, tolerance, and CNS penetration able to increase levels of SMN protein were identified (19). In this paper, we present a detailed characterization of one of the lead compounds, ML372, including the mechanism by which it elevates levels of SMN protein and its in vivo efficacy in a severe model of SMA, where it increases motor function and improves survival.…”

Assays for the Identification and Prioritization of Drug Candidates for Spinal Muscular Atrophy

“…The results of two of these screens have been reported, whereas hits from the others are still at the validation and development stages. 33,81,89 This reporter assay was used to identify a series of 4-arylthiazolyl piperidines in a screen at the NIH Chemical Genomics Center. 89 The lead compounds in this series have a half maximal response or EC 50 values in the nanomolar range and increase the SMN protein expression up to twofold in SMA patient fibroblasts.…”

Aplicaciones médicas de las células pluripotentes inducidas paciente-específicas

“…La atrofia muscular espinal (SMA) es una entidad autosómica recesiva que produce degeneración de las motoneuronas inferiores, debida a mutaciones en el gen de supervivencia de motoneuronas 1 (SMN1), con una incidencia poblacional de 1 en 6.000, que cursa con una expresión clínica variable de severidad diversa (51,52). En humanos, existe el gen SMN2, el cual es un gen casi idéntico al SMN1, que produce un 10% de expresión de una proteína SMN inestable; sin embargo, los pacientes con fenotipo clínico de SMA menos severo, poseen múltiples copias del gen SMN2, y se ha planteado como un gen modificador de la presentación clínica de la enfermedad (52,53).…”