Risdiplam is an orally administered small molecule used for the treatment of spinal muscular atrophy (SMA), a rare genetic disorder caused by mutations in the SMN1 gene leading to reduced levels of survival motor neuron (SMN) protein. Risdiplam works by modifying pre-mRNA splicing of the SMN2 gene, enhancing the production of functional SMN protein.
It is the first oral therapy approved for SMA and is marketed under the brand name Evrysdi®.
Indications include:
• Treatment of spinal muscular atrophy (SMA) in patients 2 months of age and older
• Approved for all types of SMA (types 1, 2, and 3), including presymptomatic patients
Parent: Risdiplam
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Parent: Risdiplam
Impurities in risdiplam arise from its complex multi-step synthesis, involving heterocyclic ring construction, functional group substitutions, and chiral resolution, as well as from degradation under thermal, photolytic, or oxidative conditions. Given its use in pediatric and long-term therapy, impurity levels must strictly comply with ICH Q3A/B, FDA, and EMA guidelines.
Process-Related Impurities
• Residual starting materials such as aryl halides, amines, or boronic acids
• By-products from Suzuki coupling, amide bond formation, or regioisomeric substitutions
• Residual solvents like dimethylacetamide (DMAc), acetonitrile, or ethyl acetate
Degradation Impurities
• Oxidation products of the aromatic rings or nitrogen-containing groups
• Hydrolysis products of amide or ether linkages
• Photodegradation products (light-sensitive groups present in the structure)
• Chiral impurities resulting from racemization or incomplete stereoselective synthesis
Elemental Impurities
• Trace metals such as palladium, copper, iron, or nickel from catalytic reactions
• Controlled under ICH Q3D, with strict limits due to chronic oral exposure in children
Analytical Techniques for Impurity Detection
• High-Performance Liquid Chromatography (HPLC) – for assay and related substance profiling
• LC-MS/MS (Liquid Chromatography–Tandem Mass Spectrometry) – for structural elucidation of low-level impurities and degradants
• Chiral HPLC – to detect enantiomeric impurities
• Gas Chromatography (GC) – for residual solvent detection
• ICP-MS – for elemental impurities
• Photostability and forced degradation studies – to ensure product stability
Risdiplam is used to treat spinal muscular atrophy (SMA) by increasing SMN protein levels through modulation of SMN2 pre-mRNA splicing.
It is taken orally once daily, in liquid form, and can be administered at home.
• Fever
• Diarrhea
• Rash
• Mouth ulcers
• Joint or muscle pain
• Upper respiratory infections
Yes, it is approved for patients as young as 2 months old, and dosing is weight-based.
Risdiplam is light-sensitive and should be stored in its original container, refrigerated, and protected from light. Once opened, it has a limited shelf life (as per label instructions).
