Lemtrada: adverse event reports filed with FDA

5,969

reports as suspect product

0% of all reports · about 471 a year

49

reports, 12 months to June 2026

142 in the 12 months before

69.4%

marked serious by the reporter

86% across the class

3.6%

record death among outcomes, as reported

216 reports · not verified by FDA

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 Lemtrada reports recording the termmedian drug in cd52-directed cytolytic antibody

1. Headachehead pain12.1%723
2. Fatiguetiredness11.9%709
3. Pyrexiafever8.6%514
4. Rashskin rash8.1%482
5. Multiple sclerosis relapsea flare of multiple sclerosis5.8%347
6. Dyspnoeashortness of breath5.7%343
7. Nauseafeeling sick5.4%320
8. Astheniaweakness or lack of energy5.2%310
9. Painpain, site not specified4.6%276
10. Urinary tract infectionbladder or urinary infection4.5%266
11. Platelet count decreasedlow platelet count4.2%250
12. Malaisegeneral feeling of being unwell4.1%246
13. Immune thrombocytopenic purpura4%238
14. Muscular weaknessmuscle weakness4%237
15. Chest discomfortchest discomfort3.8%225
16. Coughcough3.7%220
17. Gait disturbancedifficulty walking3.6%215
18. Condition aggravatedthe condition being treated got worse3.5%206
19. Leukopenialow white blood cells3.5%206
20. Lymphopenia3.1%188
21. Pruritusitching3%182
22. Lymphocyte count decreased3%180
23. Thrombocytopenialow platelets3%178
24. Vomitingbeing sick3%177
25. Hypoaesthesianumbness2.9%173
26. Dizzinesslight-headedness or unsteadiness2.8%170
27. Contusiona bruise2.7%164
28. Urticariahives2.7%161
29. White blood cell count decreasedlow white cell count2.7%161
30. Feeling abnormalfeeling odd or not right2.6%158

Top 30 of 1,186 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 cd52-directed cytolytic antibody 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 17,330 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

Age and sex as stated in the report; the reporter's qualification is the primary source recorded by FDA. 56.4% of reports give the United States as the country of the event or reporter.

Reason for use recorded

The indication field is filled in by the reporter and is often blank; shares are of all 5,969 reports.

Drugs most often listed in the same reports

Other products listed in reports where Lemtrada is a suspect product, whatever their own role. Co-listing means the two were recorded together; it says nothing about either product's part in the event. Only the 2,500 most-reported names are counted here.

In context

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 cd52-directed cytolytic antibody class

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.

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 Lemtrada as a suspect or interacting product; reports listing it only as a concomitant medication (252) 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.