Muscle Disease Drug Developer Dyne Therapeutics Stock Plunges After Updated Data From Duchenne Muscular Dystrophy

On Tuesday, Dyne Therapeutics Inc. DYN announced new clinical data from its ongoing Phase 1/2 DELIVER trial of DYNE-251 in patients with Duchenne muscular dystrophy (DMD) amenable to exon 51 skipping.

This assessment of the DELIVER trial evaluating DYNE-251 includes 6-month biomarker and functional data from 8 male patients enrolled in the 20 mg/kg (approximate PMO dose) cohort who were randomized to receive DYNE-251 or placebo once every four weeks and 12-month functional data from 6 participants in the 10 mg/kg cohort.

Also Read: Why Is Dyne Therapeutics Stock Soaring On Monday?

At a 20-mg/kg dose level, given every four weeks, DYNE-251 resulted in a mean absolute dystrophin expression of 3.71% of normal, without adjusting for muscle content.

The company noted that the expression level is more than ten times higher than in a reference clinical trial assessing the weekly standard of care treatment Sarepta Therapeutics Inc’s SRPT EXONDYS 51 (eteplirsen), where dystrophin expression was at 0.3% normal.

After controlling for patients’ muscle content, the company said that the mean absolute dystrophin expression jumped to 8.72%, which exceeds levels typically recorded in studies evaluating other investigational oligomers for DMD.

These results are in line with six-month data Dyne released in May for patients treated with the 10-mg/kg dose of DYNE-251.

Patients treated with 10 mg/kg of DYNE-251 Q4W had a mean absolute dystrophin level of 3.22% of normal and a 2.97% change (unadjusted for muscle content) from baseline at six months. 

When adjusting for muscle content, the DYNE-251 treated group reached 7.64% mean absolute dystrophin.

Dyne Therapeutics says meaningful improvements in multiple functional endpoints were observed in the 20 mg/kg and 10 mg/kg DYNE-251 Q4W groups. The 10 mg/kg cohort showed continued improvement in all reported measures from 6 to 12 months.

DYNE-251 demonstrated a favorable safety profile, and most treatment-emergent adverse events were mild or moderate.

Dyne says it is initiating registrational cohorts in the DELIVER trial and plans to provide an update on the path to registration by the end of 2024.

Price Action: DYN stock is down 31.90% at $31.39 at last check Tuesday.

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