Comparative Analysis of SMN2 Splicing Activity and Protein Production Following In Vitro Treatment with the Generic Risdiplam Drug Vapromin® and the Reference Drug Evrysdi®

Background/Objectives: Risdiplam is a low-molecular-weight small-molecule modifier of SMN2 pre-mRNA splicing that was developed for spinal muscular atrophy (SMA) therapy and approved for the treatment of SMA as Evrysdi® (Roche, Basel, Switzerland). Vapromin® is a generic drug produced by JSC GENERIUM. In order to evaluate its biological activity and compare different batches of the reference drug and generic risdiplam, we performed comprehensive in vitro procedures. It is important to emphasize that this study did not assess the bioequivalence of the medicinal products for the purpose of comparing the biopharmaceutical quality of the generic and reference products. Instead, this study was designed specifically to compare their biological activity using cells derived from SMA patients and a reporter cell line. Methods: The biological activity of generic risdiplam was compared with that of the reference drug by assessing increases in SMN protein production and the relative transcription level of SMN2 mRNA in fibroblasts from SMA donors. Additionally, Exon 7 inclusion efficiency was evaluated using a constructed reporter cell line. Results: Using primary dermal fibroblasts from SMA probands, we demonstrated a concentration-dependent relationship between risdiplam concentration and SMN2 FL and SMN2 Δ7 transcript levels. At a risdiplam concentration of 0.18 μM, the relative SMN2 full-length transcript levels reached a maximum, with a mean 2.5-fold increase observed for both Evrysdi® (Roche, Basel, Switzerland) and Vapromin®. In primary fibroblasts derived from three SMA patients, the 2 SD quality range for Evrysdi® (Roche, Basel, Switzerland) was 98.0–106.7% (σ(log RP) = 0.0092), and the activities of all Vapromin® batches fell within this range. Using the reporter cell line, the quality range for Evrysdi® (Roche, Basel, Switzerland) was 88.32–117.3% (σ = 0.0309), and the Vapromin® values also fell within this range. Conclusions: This study experimentally confirmed that the in vitro biological activity of the generic drug Vapromin® is comparable to that of Evrysdi® (Roche, Basel, Switzerland). Further research should be conducted to confirm bioequivalence between the two products.