In the fiercely competitive space of Duchenne muscular dystrophy (DMD) gene therapy, Regenxbio’s latest data on RGX-202 has drawn significant attention. However, contrary to high expectations, it appears to match, rather than outperform, Sarepta’s Elevidys, which received approval in June 2023. This comes despite promising interim Phase I/II results from the AFFINITY DUCHENNE trial. The findings, as industry insiders would have it, raise questions concerning Regenxbio’s ability to deliver a differentiated clinical outcome.
The AFFINITY DUCHENNE trial focused on RGX-202’s impact on five patients, aged between 6 and 12 years. The trial spanned nine to twelve months post-treatment. The data showed “consistent, robust microdystrophin expression,” as stated in Regenxbio’s press release, an encouraging sign in the fight against DMD. Moreover, Regenxbio reported no serious adverse effects, a significant consideration in the ongoing quest for a safe and effective DMD treatment.
However, the primary endpoint of the AFFINITY DUCHENNE trial was safety, with microdystrophin expression being a biomarker endpoint. In this context, the lack of a placebo arm and high variability across patients were seen as potentially undermining the comparative efficacy of RGX-202 and Elevidys.
This comparison was drawn by analysts at BMO Capital Markets. The analysts opined that while RGX-202 did display some functional improvements over Elevidys, the efficacy difference was not significant enough to be deemed material or capable of driving differentiated clinical outcomes.
Regenxbio’s stock took a hit upon the release of this information, falling by about 16%. This reflects the high stakes in the biotech industry, with every data point potentially swinging investor sentiment and market valuation.
Interestingly, patients on the RGX-202 regimen were given immunosuppressants to reduce potential adverse effects, a practice not employed when using Elevidys. Whether this difference in treatment protocol may have influenced the trial results is a question worth pondering.
As the race for a superior DMD gene therapy continues, Regenxbio maintains that RGX-202 “continues to demonstrate evidence of positively impacting disease trajectory.” The treatment has shown improvements on the North Star Ambulatory Assessment and timed function tests, including time to stand, 10-meter walk-run, and time to climb, outperforming external natural history controls. These findings underline the potential of RGX-202, but as the BMO analysis suggests, more robust, differentiated outcomes may be needed to secure its position in the fiercely competitive DMD gene therapy landscape.
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