This page shows what was measured, who it was measured in, and what that does not settle.
What Casimersen does in the body
Duchenne Muscular Dystrophy (exon 45 skipping)
Casimersen masks exon 45 so the cell leaves it out of the dystrophin instructions, which realigns the reading frame for boys whose deletion sits next to it. The trial biopsied muscle at 48 weeks and found more dystrophin in the treated group than in the placebo group. It also found that the placebo group had more dystrophin than at its own baseline, which is a useful reminder of how much noise there is at these levels.
What happened in people
Dystrophin rose from 0.93 to 1.74 percent of normal in treated patients at week 48
✎ Source-linked record
Where this came from
A person wrote this into the record with the study named beside it. No reviewer has signed it off.
The recorded finding that sits closest to something a person would notice. Written into the record, not signed off, and it carries no population or interval.
AMONDYS 45 (casimersen) US prescribing information, DailyMed (https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?setid=e9e5fd44-eeda-4580-bba1-a734828bbcc3) · a recorded source, not a stored snapshot
Muntoni et al., Efficacy and Safety of Golodirsen and Casimersen versus Placebo (ESSENCE): phase 3 topline results, MDA 2026 (https://www.mdaconference.org/a… · a recorded source, not a stored snapshot
It remains the only approved option for exon-45-amenable patients, which shapes how families weigh a missed endpoint
Where it acts
Skeletal muscle fibre nucleus
Kind of result
The kind of result is not recorded
Supervision
Professional supervision is normally required. It is a prescription or clinician-administered medicine where it is approved.
What the registries record it as
The substance registry classes this as nucleicacid.
FDA substance registry · X8UHF7SX0R · read 2026-08-29
Where each sentence above came from
No recorded sentence describes the change this makes in a way that stands on its own. The page opens with what it is taken for instead, and the recorded explanation follows below.
Shown as the opening line on this page.
A limit recorded against this substance. Not signed off as a reviewed claim.
The four opening statements run to 101 words.
Words this page uses
Four words worth knowing first
Chosen from what this page shows, with each one explained before the word it depends on.
Protein
A protein is a folded chain your body builds to do a specific job.
A picture of it, and where the picture fails
A protein is like a tool bent into one shape for one task.
Where that stops being true. A tool keeps its shape. A protein can change shape and stop working.
What people get wrong. Protein in food and a protein in the body are related but not the same thing.
A polymer of amino acids folded into a defined structure that determines its function.
Gene
A gene is a stretch of instructions for building one protein.
A picture of it, and where the picture fails
A gene is like one page of a building plan.
Where that stops being true. A page is read the same way every time. A gene can be read more or less often.
What people get wrong. Having a gene is often read as having a trait. Whether it is used matters as much.
A segment of DNA that encodes a functional product, usually a protein.
Messenger RNA
Messenger RNA is a working copy of one gene, carried to where proteins are built.
A picture of it, and where the picture fails
It is like a photocopy of one plan page, taken to the workshop.
Where that stops being true. A photocopy lasts. This copy is destroyed soon after use, on purpose.
What people get wrong. It is often thought to change the gene. It is a copy, and it does not alter the original.
A single-stranded transcript of a gene that ribosomes translate into a protein.
Small interfering RNA
A small interfering RNA is a short piece that makes a cell destroy one working copy.
A picture of it, and where the picture fails
It is like a note telling the workshop to shred one plan page.
Where that stops being true. A note is read once. This keeps working for months after one injection.
What people get wrong. It is often described as gene editing. It leaves the gene untouched.
A short double-stranded RNA that directs the RNA-induced silencing complex to cleave a complementary transcript.
What happened in people◇Read from sources, not yet reviewed
What happened in people
Each card is one study: the exact question it asked, who was in it, and whether it showed what it set out to show.
Change from baseline in muscle dystrophin protein at week 48, casimersen versus placebo
✓ The study showed what it set out to show
Who was studied
ESSENCE interim biopsy analysis (NCT02500381)
How many people
43
Study design
Phase 3 interim
Compared against
Not recorded for this study
Kind of result
A number that stands in for health
What was found
p=0.004 between groups
Repeated elsewhere
Unreplicated
What this does not prove. Meeting one endpoint in one population does not carry to other goals or other people.
The limits of this study, and where it came from
Main limit. Placebo-arm dystrophin also rose by 0.22 percentage points, with standard deviations larger than the means in both arms
How far it carries. This study is recorded from the curated record, not from the registry match.
Form and route. Intravenous infusion of an uncharged phosphorodiamidate morpholino oligomer
Interval reported. Not recorded in this summary
Written into the record, not signed off as a reviewed claim.
AMONDYS 45 (casimersen) US prescribing information, DailyMed (https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?setid=e9e5fd44-eeda-4580-bba1-a734828bbcc3) · a recorded source, not a stored snapshot
Muntoni et al., Efficacy and Safety of Golodirsen and Casimersen versus Placebo (ESSENCE): phase 3 topline results, MDA 2026 (https://www.mdaconference.org/a… · a recorded source, not a stored snapshot
Change from baseline in 4-step ascend velocity at week 96 versus placebo
✗ The study did not show it
Who was studied
ESSENCE final analysis (NCT02500381)
How many people
212
Study design
Phase 3
Compared against
Not recorded for this study
Kind of result
A number that stands in for health
What was found
p=0.309 (LSM difference 0.06 steps/s, 95 percent CI -0.05 to 0.16)
Repeated elsewhere
Failed to Replicate
What this does not prove. A study that did not show an effect does not show that no effect exists anywhere.
The limits of this study, and where it came from
Main limit. No limitation is recorded for this study.
How far it carries. This study is recorded from the curated record, not from the registry match.
Form and route. Intravenous infusion of an uncharged phosphorodiamidate morpholino oligomer
Interval reported. Not recorded in this summary
Written into the record, not signed off as a reviewed claim.
AMONDYS 45 (casimersen) US prescribing information, DailyMed (https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?setid=e9e5fd44-eeda-4580-bba1-a734828bbcc3) · a recorded source, not a stored snapshot
Muntoni et al., Efficacy and Safety of Golodirsen and Casimersen versus Placebo (ESSENCE): phase 3 topline results, MDA 2026 (https://www.mdaconference.org/a… · a recorded source, not a stored snapshot
RNAWiki holds 2 written-up human studies for this substance, each with the question it asked.
How we know it
Each card names the study, the number of people and what the study set out to measure.
What this does not prove
These summaries were written by a person and have not been signed off as reviewed claims.
Why it matters
A study that failed is as informative as one that worked, and both are here.
What we still do not know
No reviewed claim exists, so no exact population, effect size or interval is published yet.
What it changes in the body◇Read from sources, not yet reviewed
The path through the body
From what a person takes to what changes. A solid line is a step measured in people. A dashed line is a step nobody has measured that way.
Start
Casimersen
What a person takes: Intravenous infusion of an uncharged phosphorodiamidate morpholino oligomer.
The measurement behind this step
Single-dose vials diluted into saline and infused weekly over 35 to 60 minutes. No carrier system; sustained venous access is usual.
Getting in
Weekly intravenous infusion
Delivered into a vein once a week, without interruption.
╌╌Described, with no measurement named. No measurement is named for this step, so it is drawn as an unconfirmed link.
The measurement behind this step
Uncharged 22-mer PMO in isotonic phosphate-buffered saline. Rapid renal clearance; muscle uptake is a small fraction of the administered dose.
AMONDYS 45 (casimersen) US prescribing information, DailyMed (https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?setid=e9e5fd44-eeda-4580-bba1-a734828bbcc3) · a recorded source, not a stored snapshot
Muntoni et al., Efficacy and Safety of Golodirsen and Casimersen versus Placebo (ESSENCE): phase 3 topline results, MDA 2026 (https://www.mdaconference.org/a… · a recorded source, not a stored snapshot
Some of the drug crosses into muscle cells and reaches the nucleus.
╌╌Described, with no measurement named. No measurement is named for this step, so it is drawn as an unconfirmed link.
The measurement behind this step
Neutral phosphorodiamidate backbone resists nucleases but forfeits the protein-binding uptake pathway used by charged phosphorothioates.
AMONDYS 45 (casimersen) US prescribing information, DailyMed (https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?setid=e9e5fd44-eeda-4580-bba1-a734828bbcc3) · a recorded source, not a stored snapshot
Muntoni et al., Efficacy and Safety of Golodirsen and Casimersen versus Placebo (ESSENCE): phase 3 topline results, MDA 2026 (https://www.mdaconference.org/a… · a recorded source, not a stored snapshot
It pairs with exon 45 and hides the signals that tell the cell to include it.
╌╌Described, with no measurement named. No measurement is named for this step, so it is drawn as an unconfirmed link.
The measurement behind this step
Watson-Crick pairing to a 22-nucleotide site in DMD exon 45, occluding exonic splicing enhancer elements and blocking exon definition.
AMONDYS 45 (casimersen) US prescribing information, DailyMed (https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?setid=e9e5fd44-eeda-4580-bba1-a734828bbcc3) · a recorded source, not a stored snapshot
Muntoni et al., Efficacy and Safety of Golodirsen and Casimersen versus Placebo (ESSENCE): phase 3 topline results, MDA 2026 (https://www.mdaconference.org/a… · a recorded source, not a stored snapshot
The neighbouring exons are joined, which realigns the rest of the instructions.
──Measured in people. Written by a person from the study named beside the step. Not signed off as a reviewed claim.
The measurement behind this step
Exclusion of exon 45 creates an in-frame junction in patients with deletions such as 46-47, 46-48 or 44, allowing translation of an internally truncated dystrophin.
AMONDYS 45 (casimersen) US prescribing information, DailyMed (https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?setid=e9e5fd44-eeda-4580-bba1-a734828bbcc3) · a recorded source, not a stored snapshot
Muntoni et al., Efficacy and Safety of Golodirsen and Casimersen versus Placebo (ESSENCE): phase 3 topline results, MDA 2026 (https://www.mdaconference.org/a… · a recorded source, not a stored snapshot
Truncated dystrophin at the sarcolemma, around 1.7 percent of normal
A shortened dystrophin appears at the muscle membrane in small amounts, measurably more than in untreated muscle.
╌╌Described, with no measurement named. No measurement is named for this step, so it is drawn as an unconfirmed link.
The measurement behind this step
Mean week-48 western blot value 1.74 percent of healthy muscle, with a between-group difference of 0.59 percentage points. Whether this reconstitutes enough dystrophin-glycoprotein complex to change fibre mechanics is untested.
AMONDYS 45 (casimersen) US prescribing information, DailyMed (https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?setid=e9e5fd44-eeda-4580-bba1-a734828bbcc3) · a recorded source, not a stored snapshot
Muntoni et al., Efficacy and Safety of Golodirsen and Casimersen versus Placebo (ESSENCE): phase 3 topline results, MDA 2026 (https://www.mdaconference.org/a… · a recorded source, not a stored snapshot
No suggested links are held for this record, so nothing is hidden from this path.
What we know
The record describes 5 steps from taking it to an effect in a person.
How we know it
Each step names the study behind it in the technical detail beside it.
What this does not prove
A change inside the body is a reason to look. It is not a result in a person.
Why it matters
A reader can see exactly where the chain stops being measured in people.
What we still do not know
No reviewed claim binds any of these steps to a named population.
What is missing or unclear◇Read from sources, not yet reviewed
Were people like you studied?
RNAWiki cannot tell whether a study fits you. It can show who was in it, and where the result stops carrying.
Who was studied
People similar to this profile were included.
Boys and young men with an exon-45-amenable DMD deletion, by weekly intravenous infusion, on top of corticosteroids.
Who is missing from the studies
Which groups were under-represented in the studies has not been recorded for this substance. Pregnancy, breastfeeding, children, older adults, and people with liver or kidney conditions are commonly excluded from trials; nothing here says whether they were.
What the label states about particular groups
On pediatric, the label states: “AMONDYS 45 is indicated for the treatment of DMD in patients who have a confirmed mutation of the DMD gene that is amenable to exon 45 skipping, including pediatric patients [see Clinical Studies ( 14 )].”
US prescribing information · e9e5fd44-eeda-4580-bba1-a734828bbcc3 · read 2026-08-30
On older people, the label states: “DMD is largely a disease of children and young adults; therefore, there is no experience with AMONDYS 45 in geriatric DMD patients.”
US prescribing information · e9e5fd44-eeda-4580-bba1-a734828bbcc3 · read 2026-08-30
On people who are pregnant, the label states: “Risk Summary There are no human or animal data available to assess the use of AMONDYS 45 during pregnancy.”
US prescribing information · e9e5fd44-eeda-4580-bba1-a734828bbcc3 · read 2026-08-30
On people who are breastfeeding, the label states: “Risk Summary There are no human or animal data to assess the effect of AMONDYS 45 on milk production, the presence of casimersen in milk, or the effects of AMONDYS 45 on the breastfed infant.”
US prescribing information · e9e5fd44-eeda-4580-bba1-a734828bbcc3 · read 2026-08-30
Where the result stopped carrying
ESSENCE missed its primary functional endpoint at 96 weeks
The single-drug arm was pooled with golodirsen for the primary comparison, so a casimersen-specific functional estimate was never the trial primary
This is a scope explorer, not a diagnosis engine.
It shows who was studied so you can see whether people similar to you were included.
RNAWiki cannot tell whether a study fits you. It can show who was in it.
What it would be like to take◇Read from sources, not yet reviewed
Why it might seem to do nothing
A real effect and a noticed effect are different things. These are the recorded reasons the two come apart.
It was studied in different people
The people in the studies were not much like the reader.
On this record: Which groups were under-represented in the studies has not been recorded for this substance. Pregnancy, breastfeeding, children, older adults, and people with liver or kidney conditions are commonly excluded from trials; nothing here says whether they were.
The evidence may simply be wrong
Small early studies often do not hold up.
On this record: RNAWiki has not yet published a reviewed conclusion for this use.
Other reasons RNAWiki checked and found nothing for (11)
It was studied for a different goal
The studies measured something else entirely. Nothing in this record points to this reason.
A different form was studied
The studied form is not the form on the shelf. Nothing in this record points to this reason.
There was nothing to correct
Where a level is already normal, topping it up may change nothing. Nothing in this record points to this reason.
Something else had to happen too
In the studies it was paired with training, a diet or another treatment. Nothing in this record points to this reason.
The change is too small to feel
A real change can still sit below what a person notices. Nothing in this record points to this reason.
Day-to-day swing hides it
Sleep, food, stress and time of day move most numbers more than this would. Nothing in this record points to this reason.
Not enough time yet
The studies ran longer than the person has waited. Nothing in this record points to this reason.
It was not taken as studied
Missed days change the result, and studies count them. Nothing in this record points to this reason.
Something else changed at the same time
Two changes at once cannot be told apart afterwards. Nothing in this record points to this reason.
The product may not be what it says
Contents of a sold product are not always what the label states. Nothing in this record points to this reason.
No recorded reason
RNAWiki has nothing stored that would explain it. Nothing in this record points to this reason.
None of these is a reason to take more. Taking more is not a step this page ever suggests.
What it would be like to take◇Read from sources, not yet reviewed
What taking it involves
The recorded facts about getting hold of it and using it. Nothing here is a suggestion about what you should do.
How it is supplied
Not established
❝ Quoted from a source
Where this came from
Copied from a source RNAWiki stored, with the source named.
Read from the recorded approval status.
No source is stored against this line.
Form and route
Intravenous infusion of an uncharged phosphorodiamidate morpholino oligomer
✎ Source-linked record
Where this came from
A person wrote this into the record with the study named beside it. No reviewer has signed it off.
The form and route recorded on this substance.
No source is stored against this line.
Who oversees it
Professional supervision is normally required. It is a prescription or clinician-administered medicine where it is approved.
❝ Quoted from a source
Where this came from
Copied from a source RNAWiki stored, with the source named.
The identity record classes it as ASO (Antisense Oligonucleotide).
No source is stored against this line.
What is in the pack
Single-dose vials diluted into saline and infused weekly over 35 to 60 minutes. No carrier system; sustained venous access is usual.
✎ Source-linked record
Where this came from
A person wrote this into the record with the study named beside it. No reviewer has signed it off.
Recorded notes on how this is sold and what that means for what is in the pack.
No source is stored against this line.
Where it is registered
Regulatory records are listed in the technical disclosure at the foot of this page.
# Counted from records
Where this came from
A count of rows RNAWiki holds. It describes our records, not your body.
Register entries are stored per jurisdiction and shown with their dates.
No source is stored against this line.
Why people stop
Not recorded.
∅ Nothing recorded
Where this came from
RNAWiki holds nothing here and says so rather than guessing.
No record of why people stopped taking it is stored for this substance.
No source is stored against this line.
What it would be like to take◇Read from sources, not yet reviewed
What can go wrong
Sorted by where each line came from. A regulator's label and a report somebody sent in are not the same kind of fact.
·Worth asking a clinician aboutWritten into the record from the studies named on this page
Renal toxicity is a labelled warning based on nonclinical findings with other PMOs, monitored by serum cystatin C and urine protein-to-creatinine ratio. Hypersensitivity reactions labelled. Common adverse reactions include upper respiratory tract infection, cough, pyrexia, headache, arthralgia and oropharyngeal pain.
Nobody counted how many people took this and were fine, so this cannot be turned into a rate.
Where this came from
AMONDYS 45 (casimersen) US prescribing information, DailyMed (https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?setid=e9e5fd44-eeda-4580-bba1-a734828bbcc3) · a recorded source, not a stored snapshot
Muntoni et al., Efficacy and Safety of Golodirsen and Casimersen versus Placebo (ESSENCE): phase 3 topline results, MDA 2026 (https://www.mdaconference.org/a… · a recorded source, not a stored snapshot
Over a long time. No completed tested study window is recorded, so long-term effects are not established by the registry record.
Groups the studies covered thinly. Which groups were under-represented in the studies has not been recorded for this substance. Pregnancy, breastfeeding, children, older adults, and people with liver or kidney conditions are commonly excluded from trials; nothing here says whether they were.
What is missing or unclear◇Read from sources, not yet reviewed
Does the exact form matter?
Evidence belongs to the exact thing that was tested. A different salt, a different mixture or a different preparation is a different question.
The form that was studied
Intravenous infusion of an uncharged phosphorodiamidate morpholino oligomer
✎ Source-linked record
Where this came from
A person wrote this into the record with the study named beside it. No reviewer has signed it off.
The form used in the studies cited on this page.
No source is stored against this line.
What is sold
No carrier system; sustained venous access is usual.
✎ Source-linked record
Where this came from
A person wrote this into the record with the study named beside it. No reviewer has signed it off.
Recorded notes on which forms are sold and how they compare.
No source is stored against this line.
What is recorded as being sold
5 products list this as an active ingredient in the United States drug directory. 5 of them contain it and nothing else.
FDA National Drug Code directory · 52416-095 · read 2026-08-29
They are sold as injection and powder, taken intravenous.
FDA National Drug Code directory · 52416-095 · read 2026-08-29
The regulator's established pharmacologic class for it is antisense oligonucleotide [epc], antisense [cs] and increased protein synthesis [pe].
FDA National Drug Code directory · 52416-095 · read 2026-08-29
1 published label names it as an active ingredient. 1 of them describe this substance alone, which is where its own label text on this page comes from.
US prescribing information · e9e5fd44-eeda-4580-bba1-a734828bbcc3 · read 2026-08-29
Those labels are classed as human prescription drug.
US prescribing information · e9e5fd44-eeda-4580-bba1-a734828bbcc3 · read 2026-08-29
AMONDYS 45 is intravenous at 3 DOSAGE FORMS AND STRENGTHS AMONDYS 45 is a clear to slightly opalescent, colorless liquid and may contain trace amounts of small, white to off-white amorphous particles and is available as: Injection: 100 mg/2 mL (50…, recorded as fda label in effect 2026-01-09 in the United States.
US prescribing information · e9e5fd44-eeda-4580-bba1-a734828bbcc3 · read 2026-08-30
Evidence carries across two names for one substance. It does not carry across a salt, a mirror form or a mixture.
What it would be like to take◇Read from sources, not yet reviewed
What you could measure
This one is decided with a clinician, so this section holds questions to ask rather than a plan to run.
Self-experiment planning is not offered for a prescription or clinician-supervised medicine. The questions below are for a clinician or pharmacist.
Questions worth asking
Which of the trials of Casimersen studied people like me?
What was measured, and for how long?
Was the result a laboratory value or a health outcome?
What would we watch for, and when would we stop?
Tracking can show whether something changed for you. It cannot show what caused it.
RNAWiki records evidence. It does not say whether this substance is right for you.
What is missing or unclear◇Read from sources, not yet reviewed
Claims that go past the evidence
Things said about this substance that sound reasonable, and the exact step that is missing between the evidence and the claim.
✗Goes past the evidence
That the measured dystrophin difference predicts slower loss of function
Why it sounds right. It follows from something real on this page: a body step, an animal result or a related finding.
The missing step. Nobody measured this in people for this use, or the study that did measure it did not show it.
What would change this
A study in people, for this exact use, measuring this exact thing, that a reviewer signs off.
RNAWiki has not yet published a reviewed conclusion for this use.
✗Goes past the evidence
That percentage-of-normal dystrophin values are comparable across the four approved exon-skipping drugs
Why it sounds right. It follows from something real on this page: a body step, an animal result or a related finding.
The missing step. Nobody measured this in people for this use, or the study that did measure it did not show it.
What would change this
A study in people, for this exact use, measuring this exact thing, that a reviewer signs off.
RNAWiki has not yet published a reviewed conclusion for this use.
What is missing or unclear◇Read from sources, not yet reviewed
What nobody knows yet
Open questions, each with why it is open and what would close it.
How much did people take in the studies?
The sources RNAWiki checked hold nothing for this field.
Why it matters. A result belongs to an amount. Without the amount the result floats free.
What would answer it
A stored source that records it, and a reviewer to sign it off.
Last checked 2026-09-04. Searched: The sources listed in the receipts at the foot of this page.
Missing populations
Which groups were under-represented in the studies has not been recorded.
Why it matters. Recorded by the evidence model as a gap on this record.
What would answer it
A study that measures it, and a reviewer to sign it off.
Last checked 2026-09-04. Searched: The sources listed in the receipts at the foot of this page.
Missing long-term data
No completed tested study window is recorded.
Why it matters. Recorded by the evidence model as a gap on this record.
What would answer it
A study that measures it, and a reviewer to sign it off.
Last checked 2026-09-04. Searched: The sources listed in the receipts at the foot of this page.
No reviewed conclusion
RNAWiki has not yet published a reviewed conclusion for this use.
Why it matters. Recorded by the evidence model as a gap on this record.
What would answer it
A study that measures it, and a reviewer to sign it off.
Last checked 2026-09-04. Searched: The sources listed in the receipts at the foot of this page.
Missing interaction studies
No interaction was found in the registers checked. Not finding one is not the same as showing there is none.
Why it matters. Recorded by the evidence model as a gap on this record.
What would answer it
A study that measures it, and a reviewer to sign it off.
Last checked 2026-09-04. Searched: The sources listed in the receipts at the foot of this page.
Formulation uncertainty
Several salts, forms or products of Casimersen are recorded. Results from one form may not transfer to another.
Why it matters. Recorded by the evidence model as a gap on this record.
What would answer it
A study that measures it, and a reviewer to sign it off.
Last checked 2026-09-04. Searched: The sources listed in the receipts at the foot of this page.
Mechanism not reviewed
No reviewed mechanism story exists for this substance.
Why it matters. Recorded by the evidence model as a gap on this record.
What would answer it
A study that measures it, and a reviewer to sign it off.
Last checked 2026-09-04. Searched: The sources listed in the receipts at the foot of this page.
What happened in people◇Read from sources, not yet reviewed
Check any of this yourself
Every line above traced back to the study it came from. This is the technical layer, and the vocabulary changes here.
Every line above can be traced to the study named beside it. Follow the link and read it.
Interim ESSENCE biopsies: dystrophin 0.93 to 1.74 percent of normal
In plain words
Twenty-seven treated boys were biopsied at 48 weeks. Their average dystrophin nearly doubled, and the difference from placebo was statistically significant.
No reviewed effect estimate exists for this record.
Limits
See the technical detail.
From the source
Interim results from 43 evaluable patients in Study 1 (NCT02500381), 27 on casimersen and 16 on placebo. Casimersen mean dystrophin rose from 0.93 percent (SD 1.67) to 1.74 percent (SD 1.97) of normal, change 0.81 percent (SD 0.70), p<0.001. Between-group mean difference 0.59, p=0.004.
Source
AMONDYS 45 US prescribing information, section 14, Table 2
Role in the trial
Not matched to a registered study
Identity check
no open identity hold
Audit mark
verified
Review state
Written into the record, not signed off as a reviewed claim
The placebo arm gained dystrophin too
In plain words
Boys who received no drug at all also showed more dystrophin at 48 weeks than at baseline. That is the size of the noise the treatment effect has to be read against.
What was measured
Placebo arm dystrophin change +0.22 percentage points (SD 0.49), p=0.09
Effect estimate
No reviewed effect estimate exists for this record.
Limits
See the technical detail.
From the source
The label records placebo dystrophin rising from 0.54 percent (SD 0.79) at baseline to 0.76 percent (SD 1.15) at week 48, a mean change of 0.22 percent (SD 0.49), p=0.09. The standard deviations exceed the means in both arms. Quantifying a protein at one percent of normal in a needle biopsy of a heterogeneous, fibrotic muscle is a hard measurement, and the placebo drift is the honest measure of that difficulty.
Source
AMONDYS 45 US prescribing information, section 14, Table 2
Role in the trial
Not matched to a registered study
Identity check
no open identity hold
Audit mark
caution
Review state
Written into the record, not signed off as a reviewed claim
ESSENCE missed its functional primary endpoint
In plain words
The same trial that produced the biopsy result ran to completion. On the endpoint that mattered, how fast boys could climb four steps, there was no difference from placebo.
No reviewed effect estimate exists for this record.
Limits
This entry records a failure.
From the source
ESSENCE randomised 212 ambulatory patients across the casimersen and golodirsen arms versus placebo for 96 weeks. Primary endpoint change in 4-step ascend velocity gave a least-squares mean difference of 0.06 steps per second (95 percent CI -0.05 to 0.16, p=0.309). Secondary functional endpoints favoured treatment numerically without significance; dystrophin expression again rose significantly.
Source
Muntoni et al., ESSENCE phase 3 topline results, MDA Clinical and Scientific Conference 2026
Role in the trial
Not matched to a registered study
Identity check
no open identity hold
Audit mark
contested
Review state
Written into the record, not signed off as a reviewed claim
A 0.59 percentage point dystrophin difference is read as disease modification
In plain words
The approval assumed that a small increase in dystrophin predicts a clinical benefit. The trial that tested that assumption did not find one.
What was measured
That a 0.59 percentage point dystrophin gain slows Duchenne muscular dystrophy
Effect estimate
No reviewed effect estimate exists for this record.
Limits
See the technical detail.
From the source
Accelerated approval in February 2021 rested entirely on the interim biopsy result, with the confirmatory functional data still years away. With ESSENCE now reported, the surrogate has been reproduced and the clinical link has not been demonstrated. The label already stated that continued approval may be contingent on verification of clinical benefit.
Written into the record, not signed off as a reviewed claim
Full approval is now being sought on a trial that missed its endpoint
In plain words
Rather than withdraw, the sponsor has said it will apply to convert the conditional approval into a full one, using the failed trial plus a decade of real-world use.
What was measured
Not recorded
Effect estimate
No reviewed effect estimate exists for this record.
Limits
See the technical detail.
From the source
Following ESSENCE completion the sponsor announced it would submit supplemental applications seeking conversion of the accelerated approvals for casimersen and golodirsen to traditional approval, supported by ESSENCE data alongside published real-world evidence. Whether a missed primary endpoint plus observational data can satisfy a confirmatory requirement is an open regulatory question, not a settled one.
Source
Sarepta Therapeutics regulatory update on AMONDYS 45 and VYONDYS 53, 2026
Role in the trial
Not matched to a registered study
Identity check
no open identity hold
Audit mark
contested
Review state
Written into the record, not signed off as a reviewed claim
Where else this substance is registered
FDA substance identifier (UNII)
X8UHF7SX0R
RxNorm concept
2480100
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Trial roles classified for highlighted evidence
No registered study is classified as testing this substance.
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Safety mode resolved
The identity record classes it as ASO (Antisense Oligonucleotide).
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Canonical metadata present
slug and display name present
What is missing or unclear◇Read from sources, not yet reviewed
How this medicine reached us
Kept near the foot of the page. A historical event moves up only when it changes something about this substance today.
What the approval register records
1 approved application covers products containing this substance. The earliest was NDA213026, approved 20210225 to SAREPTA THERAPS INC.
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What is not here
7 questions this page could not answer
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What was measured, goal by goal — found nothing in the sources checked.
How close this is to real life — found nothing in the sources checked.
Felt, measured, or meaningful — found nothing in the sources checked.
How long anything takes — found nothing in the sources checked.
What it may clash with — found nothing in the sources checked.
Other ways to the same goal — found nothing in the sources checked.
What changed on this page — found nothing in the sources checked.
The record as stored
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The older medicine-wide conclusion held in this record
Written for a clinical reader, and about the medicine as a whole rather than about one indication, population and set of trials. RNAWiki does not treat it as a programme conclusion and no reviewer has signed it off in that form. It is here word for word because it is what the record holds.
A 22-mer morpholino for exon 45 skipping approved on an interim biopsy result in which treated dystrophin rose 0.81 percentage points against 0.22 in placebo; the same trial missed its functional primary endpoint five years later.
Recorded evidence blocks (8)
Q1
On the Casimersen label: indicated for what?
"AMONDYS 45 is indicated for the treatment of Duchenne muscular dystrophy (DMD) in patients who have a confirmed mutation of the DMD gene that is amenable to exon 45 skipping. This indication is approved under accelerated approval based on an increase in dystrophin production in skeletal muscle observed in patients…": indications and usage on Casimersen's label. DailyMed label · e9e5fd44-eeda-4580-bba1-a734828bbcc3 · 2026-01-09
Q2
5 registered trials of Casimersen — at which phases?
"The trial was stopped to reduce the clinical trial burden on participants while ensuring continued treatment via a post-trial access program with commercially available casimersen and golodirsen. Study was not terminated due to safety concerns."; 1 of 5 registered studies
Show the evidence
TrialNCT03532542
terminated; "The trial was stopped to reduce the clinical trial burden on participants while ensuring continued treatment via a post-trial access program with commercially available casimersen and golodirsen. Study was not terminated due to safety…"
recorded 2026-09-01 · last checked 2026-09-04
Q4
Casimersen's half-life is 3.5 hours — which schedules were studied?
3.5 hours; The elimination half-life (t 1/2 ) was 3.5 hours (SD 0.4 hours).
metabolismpharmacokinetics
Metabolism Casimersen is metabolically stable in human hepatic microsomal incubations.
recorded 2026-01-09 · last checked 2026-09-04
Q5
At the median, Casimersen's trials enrolled 171 people — anything larger?
Median enrolment
171
Largest enrolment
300
Registered trials counted
5
Q6
What do 5 spontaneous reports say about Casimersen — and not say?
These are reports people sent to a regulator. They do not show the medicine caused the reaction. Nobody counted how many people took the medicine and reported nothing. The same event can be reported more than once, and many reports are incomplete. News coverage, lawsuits and new warnings change how often people report. A count is not a rate and not a risk.
Casimersen appears in spontaneous reports to regulators. Across the 2 most-reported reaction terms, 5 reaction mentions were counted: product dose omission issue 3; poor venous access 2. FAERS via Open Targets · CHEMBL4297566 · 2026-06-24
Show the evidence
product dose omission issue
3
poor venous access
2
recorded 2026-06-24 · last checked 2026-09-04
Q7
Which 2 reactions does Casimersen's label not list?
Casimersen did not inhibit CYP1A2, CYP2B6, CYP2C8, or CYP2D6 in vitro .
pharmacokinetics
Casimersen was a potential inhibitor of CYP3A4/5, CYP2C9, and CYP2C19 in vitro ; however, considering its short plasma half-life and lack of plasma accumulation with the weekly dosing regimen, clinical drug interaction with substrates for these enzymes is unlikely.
pharmacokinetics
Casimersen did not induce CYP1A2, CYP2B6, or CYP3A4 either at the mRNA or protein (activity) level.
pharmacokinetics
Casimersen was not metabolized by human hepatic microsomes and was not a substrate or strong inhibitor of the key human drug transporters tested (OAT1, OAT3, OCT2, OATP1B1, OATP1B3, MATE1, MATE2-K, P-gp, BCRP, and MRP2).
clinical_pharmacology
Casimersen did not inhibit CYP1A2, CYP2B6, CYP2C8, or CYP2D6 in vitro .
clinical_pharmacology
Casimersen was a potential inhibitor of CYP3A4/5, CYP2C9, and CYP2C19 in vitro ; however, considering its short plasma half-life and lack of plasma accumulation with the weekly dosing regimen, clinical drug interaction with substrates for these enzymes is unlikely.
2 more recorded rows
Interaction statementclinical_pharmacology
Casimersen did not induce CYP1A2, CYP2B6, or CYP3A4 either at the mRNA or protein (activity) level.
Interaction statementclinical_pharmacology
Casimersen was not metabolized by human hepatic microsomes and was not a substrate or strong inhibitor of the key human drug transporters tested (OAT1, OAT3, OCT2, OATP1B1, OATP1B3, MATE1, MATE2-K, P-gp, BCRP, and MRP2).
ChEMBL 37 — CC BY-SA 3.0 Unported · ChEMBL ATC CC BY-SA · ClinicalTrials.gov — US Government work · Open Targets 26.06 — CC0 · mixed register set; per-register licences in docs/specs/corpus-20k-sources.md · openFDA / DailyMed — US Government work
✗ required summary fields resolved: 4 required field(s) not terminal: Why people use it, Best-supported result, Biggest unanswered question, Human evidence
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✓ source coverage passed: 5 source rows
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