Zeleciment basivarsen

An investigational infusion from Dyne Therapeutics for myotonic dystrophy type 1 (DM1), given into a vein every 8 weeks. It is the most advanced DM1 drug still on a path to approval after Novartis's del-desiran missed its Phase 3 primary endpoint in September 2026. In the ACHIEVE Phase 1/2 study, a pooled group of 25 to 26 adults saw hand myotonia (measured as video hand opening time) improve by 3.2 seconds at 6 months, against a 0.4-second worsening on placebo, with gains in walking speed, rising from a chair and grip strength holding through 12 months^[1]. A 71-person registrational cohort finished enrolling in June 2026; its topline result is due in the first quarter of 2027 and Dyne plans to file for US accelerated approval in the third quarter of 2027^[2][1]. The Phase 3 HARMONIA confirmatory trial is recruiting about 150 people at more than 35 sites^[5]. It has Breakthrough Therapy, Orphan Drug and Fast Track designations from the FDA^[1].

DM1 is caused by a stretch of DNA in the DMPK gene that repeats far too many times. The repeats are copied into an RNA message that clumps inside the cell nucleus and traps a protein called MBNL, which the cell needs to assemble many other proteins correctly. With MBNL trapped, muscle, heart and nerve cells build faulty versions of those proteins, which is what causes myotonia (muscles that cannot relax), weakness and the other features of the disease. Zeleciment basivarsen is an antisense oligonucleotide, a short strand of synthetic genetic code, designed to tag the toxic DMPK RNA for destruction so MBNL is freed. On its own an antisense strand reaches muscle poorly, so Dyne attaches it to a fragment of an antibody that grips transferrin receptor 1, a protein muscle cells use to take in iron; the cell pulls the antibody in and the drug comes with it^[1].

Through the safety cutoff of April 20, 2026, Dyne reported no drug-related serious adverse events in the ACHIEVE study and described the safety profile as favorable^[1]. The company has not published rates of individual side effects in its announcements, and the registrational cohort's safety data are still blinded, so the full picture will come with the 2027 readout and any FDA label.

Given by infusion into a vein every 8 weeks. The registrational dose chosen from the ACHIEVE study is 6.8 mg per kilogram of body weight^[1]. Earlier cohorts tested 3.4 mg/kg every 4 weeks and 5.4 mg/kg every 8 weeks.

Zeleciment basivarsen is currently in phase 3 clinical trials for Myotonic Dystrophy. It has not yet received FDA approval.

No. As of October 2026 it is investigational. Dyne plans to file for US accelerated approval in the third quarter of 2027 on the strength of the ACHIEVE registrational cohort, whose results are due in the first quarter of 2027, and has said a launch could come in the first half of 2028 if the FDA agrees.

By infusion into a vein every 8 weeks, at 6.8 mg per kilogram of body weight, the dose Dyne chose for its registrational studies.

In a pooled group of 25 to 26 adults, hand myotonia measured by video hand opening time improved by 3.2 seconds at 6 months while the placebo group worsened by 0.4 seconds, and at 12 months walking speed, rising from a chair, grip strength and a patient-reported health score all improved against a matched natural history group. Dyne notes that only 8 of the 26 received the registrational dose for the full year, and the 71-person registrational cohort that will decide the filing is still blinded.

HARMONIA (NCT07486934) is recruiting about 150 adults with DM1 at more than 35 sites worldwide. Participants are randomized to zeleciment basivarsen or placebo every 8 weeks for 48 weeks, then everyone can continue on drug in an extension. The ClinicalTrials.gov record lists the eligibility rules and site locations.

Both attach an RNA drug to an antibody that targets transferrin receptor 1 on muscle cells and both aim to destroy the toxic DMPK RNA. Dyne uses an antisense oligonucleotide linked to an antibody fragment; Novartis's del-desiran uses a small interfering RNA linked to a whole antibody. Del-desiran missed its Phase 3 primary endpoint in September 2026; zeleciment basivarsen's decisive results are due in early 2027.