Drugs › Antisense oligonucleotide
Brand name · Casimersen
Amondys 45: adverse event reports filed with FDA
764 reports list it as a suspect or interacting product, 2021–2026. Class: Antisense oligonucleotide.
- 764
- reports as suspect product
- 0% of all reports · about 150 a year
- 174
- reports, 12 months to June 2026
- 92 in the 12 months before
- 15.3%
- marked serious by the reporter
- 39.7% across the class
- 0.9%
- record death among outcomes, as reported
- 7 reports · not verified by FDA
764 adverse event reports received by FDA list the brand name Amondys 45 (casimersen) as a suspect or interacting product, from June 2021 to June 2026. A further 53 reports list it only as a concomitant medication, and those are not counted in the figures on this page.
In the 12 months to June 2026, 174 reports listed it, up 89% from 92 in the 12 months before. FDA releases FAERS data quarterly, so the newest months are incomplete and grow in later releases. Over its reporting history that is about 150 reports a year and 0% of the 20,646,523 reports in the database, and 7.3% of the reports for the antisense oligonucleotide class. How many people take it is not in the data, so a count is not a rate of occurrence.
The MedDRA terms listed most often are product dose omission issue (32.7%), no adverse event (21.7%) and poor venous access (12.8%). A report can list several reactions, so shares add to more than 100%; 90 different terms appear across these reports. Product dose omission issue is recorded in 32.7% of these reports, about the same share as in the median antisense oligonucleotide drug (30.5%).
15.3% of the reports are marked serious by the reporter (39.7% across the class); 0.9% record death among the outcomes and 12.8% record hospitalisation, as reported. 83.8% of the reports came from other health professionals, and the largest patient age group is 12 to 17 (30.2%). FDA states that "a causal relationship cannot be established between product and reactions listed in a report" and that for any given report "there is no certainty that a suspected drug caused the event."
Reports by month, five years
Reports by the month FDA received them. FDA releases FAERS data quarterly, so the newest months are incomplete and grow in later releases.
By year received
2026 covers reports received through June 2026 only.
Reactions recorded in the reports
share of Amondys 45 reports recording the termmedian drug in antisense oligonucleotide
- Product dose omission issuea dose was missed32.7%250
- No adverse eventno adverse event was reported21.7%166
- Poor venous access12.8%98
- Device issuea problem with the device9.9%76
- Malaisegeneral feeling of being unwell4.8%37
- Pyrexiafever4.2%32
- Covid-19COVID-19 infection3.7%28
- Influenzaflu2.2%17
- Pneumonialung infection2%15
- Illness1.8%14
- Falla fall1.7%13
- Coughcough1.6%12
- Exposure to SARS-CoV-21.6%12
- Dehydrationdehydration1.4%11
- Device dislocationthe device moved out of position1.2%9
- Underdoseless than the intended dose1.2%9
- Catheter site pain1%8
- Nauseafeeling sick1%8
- Infusion site extravasationinfusion fluid leaked into surrounding tissue0.9%7
- Painpain, site not specified0.9%7
- Therapy cessation0.9%7
- Device occlusionthe device blocked0.8%6
- Diarrhoealoose or frequent stools0.8%6
- Heart rate increaseda fast heart rate reading0.8%6
- Lower limb fracture0.8%6
- Oropharyngeal painsore throat0.8%6
- Sepsisa severe body-wide response to infection0.8%6
- Vomitingbeing sick0.8%6
Top 30 of 90 MedDRA preferred terms recorded across these reports, with a plain-language gloss where one is available. One report can record several terms. The hollow bar is the median share across the 3 drugs in the antisense oligonucleotide class; it describes the reports, not the patients. FDA states that adverse event reports "represent a small percentage of total usage numbers of a product", that "common products may have a higher number of adverse events due to the higher total number of people using the product", and that the data "by themselves are not an indicator of the safety profile of the drug or biologic."
Outcomes recorded
Outcome flags as the reporter set them; a report can carry several, and "other serious" is FDA's own category for serious reports outside the named outcomes. Grey bar: all 10,452 reports in the class. FDA has not verified any outcome and states that the reports "cannot be used to estimate the incidence of these events."
Patients and reporters
Patient age
Patient sex
Who reported
Age and sex as stated in the report; the reporter's qualification is the primary source recorded by FDA. 99.9% of reports give the United States as the country of the event or reporter.
Reason for use recorded
| Indication as recorded (MedDRA) | Reports | Share |
|---|---|---|
| Duchenne muscular dystrophy | 401 | 52.5% |
| Muscular dystrophy | 16 | 2.1% |
The indication field is filled in by the reporter and is often blank; shares are of all 764 reports.
In context
| Measure | Amondys 45 | Antisense oligonucleotide | All reports |
|---|---|---|---|
| Reports as suspect product | 764 | 10,452 | 20,646,523 |
| Share of that pool | — | 7.3% | 0% |
| Reports, latest 12 months | 174 | — | 1,332,454 |
| Marked serious | 15.3% | 39.7% | 57.4% |
| Death recorded among outcomes, per 1,000 reports | 9 | 79 | 91 |
| Hospitalisation recorded, per 1,000 reports | 128 | 253 | 213 |
| Consumer-filed share | 12.8% | 48.8% | 45.8% |
| Top term, share of reports | Product dose omission issue 32.7% | median 30.5% | 1.4% |
Shares are of reports, not of patients treated. The number of people taking a product is not in the data, so none of these figures is a rate, and differences between columns reflect who takes a product, who reports and how long it has been sold. FDA states that adverse event reports "represent a small percentage of total usage numbers of a product", that "common products may have a higher number of adverse events due to the higher total number of people using the product", and that the data "by themselves are not an indicator of the safety profile of the drug or biologic."
Other drugs in the antisense oligonucleotide class
| Drug | Name type | Reports | Latest 12 months | Marked serious |
|---|---|---|---|---|
| Spinraza | brand | 7,451 | 591 | 49% |
| Exondys 51 | brand | 2,237 | 458 | 17.1% |
Ordered by report count for navigation only. FDA states that adverse event reports "represent a small percentage of total usage numbers of a product", that "common products may have a higher number of adverse events due to the higher total number of people using the product", and that the data "by themselves are not an indicator of the safety profile of the drug or biologic." A brand and its generic are separate rows because reporters name them separately.
Questions about Amondys 45 reports
How many adverse event reports has FDA received for Amondys 45?
764 reports list Amondys 45 as a suspect or interacting product in the openFDA FAERS release of 28 Sep 2026, covering reports received through June 2026. 174 of them arrived in the latest 12 months. Another 53 list it only as a concomitant medication.
What reactions are recorded in Amondys 45 reports?
product dose omission issue (32.7%), no adverse event (21.7%), poor venous access (12.8%), device issue (9.9%) and intentional dose omission (9.7%). These are MedDRA preferred terms coded from what the reporter described; a report can list several, and a term's presence is not a finding that Amondys 45 was responsible.
How serious are the reports?
15.3% are marked serious by the reporter. Among the outcomes recorded, 0.9% of reports include death and 12.8% include hospitalisation. FDA has not verified these outcomes and states that the reports "cannot be used to estimate the incidence" of the events.
Who files these reports?
other health professional (83.8%), consumer or non-health professional (12.8%) and pharmacist (2.5%). Most reports reach FDA through the manufacturer, which must forward reports it receives.
Are reports for Amondys 45 rising?
174 reports in the 12 months to June 2026, up 89% from 92 in the 12 months before. FDA releases FAERS data quarterly, so the newest months are incomplete and grow in later releases. Counts also move with how many people take a product, its time on the market and publicity.
Do these reports show that Amondys 45 was responsible for these reactions?
No. FDA states that "a causal relationship cannot be established between product and reactions listed in a report" and that for any given report "there is no certainty that a suspected drug caused the event." The reaction may relate to the condition being treated, to other medicines, or to something else.
Is this a list of the side effects of Amondys 45?
No. It is a count of what was reported to FDA. The adverse reactions observed in clinical studies are printed on the FDA-approved label, which a pharmacist or clinician can go through with you.
How do I report an adverse event?
Consumers and health professionals can report to FDA through MedWatch (Form FDA 3500 online, or 1-800-FDA-1088), or to the manufacturer, which must pass reports on. See the guide on how to report.
Where this comes from. Counts are built from the openFDA Drug Adverse Event (FAERS) bulk export released 28 Sep 2026, which holds reports FDA received through 30 Jun 2026. Drug names are as reported, resolved to the brand or generic name on the FDA label where openFDA's harmonisation matched them; classes are the pharmacologic class (EPC) from the label and the National Drug Code Directory of 17 Sep 2026. A report counts here when it lists Amondys 45 as a suspect or interacting product; reports listing it only as a concomitant medication (53) are excluded. No report narrative, lot number, patient detail or reporter identity is published. See the methodology and sources; FDA's record is authoritative, and corrections are handled within five working days.
Drug data (FAERS) through 30 Jun 2026; device data (MAUDE) through 31 Aug 2026. Not medical advice.