PepGen reported a 10 mg/kg multiple ascending dose signal for PGN-EDODM1 in Phase 2 FREEDOM2-DM1 (NCT06667453) with mean splicing correction of 46.5% described as the highest reported to date in a multiple dose study, alongside directional improvements in vHOT and hand grip strength and no serious adverse events or discontinuations. The weight is randomized Phase 2 with an estimated enrollment of 24 and RECRUITING status, well below the Phase 3 randomized double-blind placebo-controlled tier occupied by AOC 1001 with 159 patients ACTIVE_NOT_RECRUITING and DYNE-101 with a 48-week study in 111 patients, plus Mexiletine PR in 176 patients and METFORMINE VIATRIS in 203 patients. [1][2] No mechanism of action is stated for PGN-EDODM1 or any peer, so no peer passes mechanistic fit and no closely comparable precedent exists to anchor whether splicing correction predicts approval, with DMD exon-skippers flagged as mechanistically distinct. No ICER, HTA outcome, pricing or label language is stated for any DM1 program, leaving payer standards undefined, while open-label extensions for AOC 1001 with 217 patients, Mexiletine PR with 176 patients and VX-670 with 33 patients set long-term safety expectations. [3][4] With $104.8 million funding into 2028, replication with placebo-controlled effect size, durability and larger safety data remains the gating risk.
Randomized Phase 2 cohort with 46.5% splicing correction and vHOT/grip directionality but 24 patients estimated, no p-values or durability, below Phase 3 peers. [1][5]
| Indication | Myotonic dystrophy type 1 (DM1) |
| Drug | PGN-EDODM1 |
| Mechanism of Action | Oligonucleotide therapy targeting DMPK RNA splicing |
| Company | PepGen Inc. |
| Trial Phase | Phase 2 |
| Trial Acronym | FREEDOM2-DM1 |
| NCT ID | NCT06667453 |
| Category | Clinical Trial Event |
| Sub Category | Topline Results Positive |
| Therapeutic Area | Rare Diseases & Genetics |
| Mean Splicing Correction | 46.5% |
| Participants with >20% Splicing Improvement | Five of six |
| Participants with >50% Splicing Improvement | Four |
| Functional Measures Improved | video Hand Opening Time (vHOT), hand grip strength, 10-Meter Walk/Run Test (10MWRT), Timed Up and Go (TUG) |
| Cash, Cash Equivalents and Marketable Securities | $104.8 million |
| Cash Runway | Into 2028 |
| Regulatory Designations | Orphan Drug, Fast Track, CMC Development and Readiness Pilot (CDRP) program |
| Regulatory Status | Partial Clinical Hold |
| Next Dose Cohort Enrolled | 12.5 mg/kg |
| Next Data Expected | 1H 2027 (12.5 mg/kg FREEDOM2), January 2027 (FREEDOM-OLE) |
PepGen's PGN-EDODM1 Shows Positive Phase 2 Results in DM1
PepGen Inc. announced positive topline results from the 10 mg/kg multiple ascending dose cohort of its Phase 2 FREEDOM2-DM1 trial (NCT06667453) for PGN-EDODM1 in myotonic dystrophy type 1 (DM1). The data showed a mean splicing correction of 46.5%, the highest reported to date in a multiple dose study, alongside improvements in functional measures like vHOT and hand grip strength. PGN-EDODM1 was generally well tolerated, with no serious adverse events or discontinuations. The company also reported $104.8 million in cash, cash equivalents, and marketable securities as of September 30, 2026, providing funding into 2028.
- The 10 mg/kg cohort of the FREEDOM2-DM1 trial demonstrated a mean splicing correction of 46.5%, marking the highest reported to date in a multiple dose study. Five out of six participants achieved over 20% splicing improvement, with four exceeding 50% improvement by Week 13, indicating a robust molecular response to PGN-EDODM1.
- PGN-EDODM1 showed notable improvements across multiple functional measures, including video Hand Opening Time (vHOT), hand grip strength, 10-Meter Walk/Run Test (10MWRT), and Timed Up and Go (TUG). The drug was generally well tolerated at 10 mg/kg, with no treatment discontinuations, serious adverse events, or dose-limiting toxicities reported, supporting its safety profile.
- Based on positive safety data, the independent Data and Safety Monitoring Board (DSMB) recommended advancing the FREEDOM2 trial to its highest dose cohort (12.5 mg/kg), which is now fully enrolled with results expected in 1H 2027. Additionally, PGN-EDODM1 was selected for the FDA's CMC Development and Readiness Pilot (CDRP) program, aiming to accelerate manufacturing alignment for future Phase 3 and NDA submission, despite an ongoing partial clinical hold.
The Persistent Unmet Need in Myotonic Dystrophy Type 1
Current treatment for myotonic dystrophy type 1 remains limited to symptomatic intervention, with no curative or disease-modifying treatment and no therapeutic approach to prevent or reverse disease progression. Management focuses on genetic counseling, preserving function and independence, preventing cardiopulmonary complications, and symptomatic treatment of pain, myotonia, and hypersomnolence.
No disease-modifying options: Mutant DMPK mRNAs containing the trinucleotide expansion are retained in the nucleus, entrapping Muscleblind (MBNL1) protein and stabilizing CUG binding protein, Elav-like family member 1 (CELF1), causing aberrant pre-mRNA splicing and gene expression, yet most experimental approaches targeting mutant RNA by antisense oligonucleotides or small chemical compounds remain in cell-based and animal models.
Limited functional benefit of anti-myotonic drugs: Mexiletine (150 mg 3 times daily) does not significantly change 6-minute walk distance at 6 months, with a sustained positive effect on objectively measured hand grip myotonia and hand grip relaxation time but not seen in measures reflecting participants' perceptions of their myotonia, validated scales, or 36-item Short Form Physical Component Summary and Mental Component Summary.
Tolerability and availability constraints: The most frequent adverse events with mexiletine were gastrointestinal symptoms, lethargy, and headache, with 84 adverse events with mexiletine versus 55 with placebo across four RCTs, while mexiletine has limited availability and is associated with several side effects, and lamotrigine data are limited to preliminary open-label pilot evidence requiring larger, placebo-controlled trials.
Weak trial evidence base and rare-disease design challenges: Trials were small, with participant numbers ranging from nine to 59 and a total of 392 participants across 17 RCTs, with high risk of bias, and not all patients respond to therapy, highlighting challenges in recruitment and design of robust trials in rare diseases and lack of validated clinical end points in early childhood with variable disease progression.
Complex multisystem monitoring burden: Patients may experience cataracts, myotonia, muscle weakness/atrophy, fatigue, excessive daytime sleepiness, cardiac arrhythmia, insulin resistance, dysphagia, GI dysmotility, and cognitive impairment, requiring multidisciplinary care, yet adequate follow-up varied with 90% in cardiology, 60% in neurology, 68% in ophthalmology, 53% in physiotherapy, 23% in pneumology, and 12% in rehabilitation, and respiratory management remains challenging due to adherence issues.
PGN-EDODM1's Design and Endpoints in FREEDOM2-DM1
Key trials in myotonic dystrophy type 1 (DM1) span symptomatic myotonia therapies, hypersomnia interventions, functional mobility strategies, and quantitative myotonia measurement methods, alongside preclinical delivery platforms. Designs range from small short-term cross-over RCTs to multicentre randomized trials with functional primary endpoints and reproducibility assessments.
| Study | Design and Population | Endpoints |
|---|---|---|
| OPTIMISTIC (NCT02118779) | Multi-centre, randomised trial comparing cognitive behavioural therapy (CBT) plus graded exercise therapy against standard care; 296 male and female patients aged 18 years and older with genetically proven classical or adult DM1, Checklist Individual Strength (CIS) fatigue severity score ≥ 35, able to walk independently; recruited from France, Germany, the Netherlands and the United Kingdom | Primary: score on the DM1-Activ scale, a measure of activity and participation; Secondary: 6-minute walk test, objective physical activity measured with an accelerometer, quality of life and cognitive measures, plus pain, muscular impairment and cognitive-behavioural variables |
| Metformin randomized controlled trial | Forty ambulatory adult patients recruited consecutively at the neuromuscular reference centre of Henri-Mondor Hospital; participants and investigators blinded; oral metformin or placebo three times daily, dose-escalation over 4 weeks up to 3 g/day, followed by 48 weeks at maximum dose | Primary: change in distance walked during the 6-minute walk test, from baseline to end of study; Secondary: muscle strength, myotonia, gait variables, biological parameters and quality of life |
| Drug treatment for myotonia RCTs | 17 double-blind or single-blind RCTs involving 392 participants, 219 with myotonic dystrophy type 1 and 173 with non-dystrophic myotonia; mexiletine, lamotrigine, phenytoin, imipramine, procainamide, clomipramine, nifedipine, tocainide, diazepam, quinine, diphenylhydantoin, and taurine versus placebo or active comparator | Primary: participant-reported improvement in clinical myotonia; Secondary: relaxation time, electromyographic relaxation time, adverse events, and quality of life including 36-item Short Form (SF-36) Physical and Mental Component Summary |
| Psychostimulants for hypersomnia RCTs | 6 trials (136 participants); adult outpatients aged 18 to 70 years old, followed in the short term (up to four weeks); five trials had a cross-over design; any psychostimulant versus placebo or no treatment | Primary: mean improvement in the Maintenance of Wakefulness Test; Secondary: Epworth Sleepiness Scale, Multiple Sleep Latency Test, quality of life, and risk of adverse events |
| Computerized hand grip myometry | 29 genetically confirmed DM1 patients and 17 normals; three maximum voluntary isometric contractions (MVICs) of finger flexors recorded on 2 successive days using a computerized handgrip myometer | MVIC peak force (PF) and relaxation times (RTs) at 90%, 75%, 50%, 10%, and 5% of PF; quantitative strength testing (QST) and manual muscle testing (MMT); correlation with leukocyte CTG repeat length |
| HandClench Relaxometer (HCR) | Twenty DM1 individuals and ten age-matched controls; patients returned for follow up within two months; portable device measuring grip myotonia and strength with automated command prompts | Grip myotonia duration and strength, day to day reproducibility (ICC >0.80), reaction time to relax and squeeze commands, correlation with pinch strength, hand dexterity test, and fat replacement in MRI of long finger flexor muscles |
| FORCE platform / DYNE-101 preclinical | Surrogate FORCE conjugates and DYNE-101, an antigen-binding fragment specific for human transferrin receptor 1 (TfR1) conjugated via cleavable valine-citrulline linker; tested in HSA mice, TfR1;DMSXL mice expressing human TfR1 and human DMPK RNA with >1,000 CUG repeats, patient-derived myoblasts, and cynomolgus monkeys with low monthly dosing | Reduction of DMPK RNA and nuclear foci, correction of spliceopathy, improvement of myotonia, reduction of DMPK foci in cardiomyocyte nuclei, and reduction of DMPK expression in muscle |
Frequently Asked Questions
References
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