Generic name
Mosunetuzumab: adverse event reports filed with FDA
577 reports list it as a suspect or interacting product, 2018–2026.
- 577
- reports as suspect product
- 0% of all reports · about 72 a year
- 88
- reports, 12 months to June 2026
- 66 in the 12 months before
- 95.8%
- marked serious by the reporter
- 57.4% across all reports
- 18.9%
- record death among outcomes, as reported
- 109 reports · not verified by FDA
577 adverse event reports received by FDA list mosunetuzumab, a generic name as a suspect or interacting product, from July 2018 to June 2026. A further 17 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, 88 reports listed it, up 33% from 66 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 72 reports a year and 0% of the 20,646,523 reports in the database. How many people take it is not in the data, so a count is not a rate of occurrence.
Reporters most often recorded cytokine release syndrome (20.1%), disease progression (15.3%) and neutropenia (11.3%). A report can list several reactions, so shares add to more than 100%; 137 different terms appear across these reports. Cytokine release syndrome is recorded in 20.1% of these reports, against 0.1% of all reports in the database.
95.8% of the reports are marked serious by the reporter; 18.9% record death among the outcomes and 58.8% record hospitalisation, as reported. 86.7% of the reports came from physicians, and the largest patient age group is 65 to 74 (30.8%). 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 Mosunetuzumab reports recording the termall reports in the database
- Cytokine release syndrome20.1%116
- Disease progressionthe disease advanced15.3%88
- Neutropenialow neutrophils, a type of white blood cell11.3%65
- Covid-19COVID-19 infection10.1%58
- Deaththe patient died; cause not stated by this term6.8%39
- COVID-19 pneumonia6.4%37
- Off label useused for a purpose or in a way not on the label5.5%32
- Pneumonialung infection5.5%32
- Disorientation5.4%31
- Neurological symptom5.4%31
- Vasogenic cerebral oedema5.4%31
- Diffuse large B-cell lymphoma recurrent4.9%28
- Pyrexiafever4%23
- Upper respiratory tract infectiona cold or similar infection3.5%20
- Infectionan infection, type not specified3.1%18
- Thrombocytopenialow platelets3.1%18
- Hypogammaglobulinaemia2.9%17
- Pneumonitis2.6%15
- Injection site reactiona reaction where the injection was given2.3%13
- Alanine aminotransferase increasedraised liver enzyme (ALT)2.1%12
- Febrile neutropeniafever with low white blood cells2.1%12
- Follicular lymphoma2.1%12
- Inflammatory marker increased2.1%12
- Anaemialow red blood cells1.9%11
- Tumour lysis syndrome1.9%11
- Infusion related reactiona reaction during or soon after an infusion1.7%10
- Respiratory failurethe lungs could not supply enough oxygen1.7%10
Top 30 of 137 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 share of all reports in the database; 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 20,646,523 reports. 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. 26.7% of reports give the United States as the country of the event or reporter.
Reason for use recorded
| Indication as recorded (MedDRA) | Reports | Share |
|---|---|---|
| Follicular lymphoma | 189 | 32.8% |
| B-cell lymphoma | 153 | 26.5% |
| Non-hodgkin's lymphoma | 49 | 8.5% |
| Diffuse large b-cell lymphoma | 47 | 8.1% |
| Diffuse large b-cell lymphoma stage iv | 22 | 3.8% |
| Non-hodgkin's lymphoma unspecified histology indolent | 20 | 3.5% |
The indication field is filled in by the reporter and is often blank; shares are of all 577 reports.
In context
| Measure | Mosunetuzumab | All reports |
|---|---|---|
| Reports as suspect product | 577 | 20,646,523 |
| Share of that pool | — | 0% |
| Reports, latest 12 months | 88 | 1,332,454 |
| Marked serious | 95.8% | 57.4% |
| Death recorded among outcomes, per 1,000 reports | 189 | 91 |
| Hospitalisation recorded, per 1,000 reports | 588 | 213 |
| Consumer-filed share | 2.4% | 45.8% |
| Top term, share of reports | Cytokine release syndrome 20.1% | 0.1% |
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."
Questions about Mosunetuzumab reports
How many adverse event reports has FDA received for Mosunetuzumab?
577 reports list Mosunetuzumab as a suspect or interacting product in the openFDA FAERS release of 28 Sep 2026, covering reports received through June 2026. 88 of them arrived in the latest 12 months. Another 17 list it only as a concomitant medication.
What reactions are recorded in Mosunetuzumab reports?
cytokine release syndrome (20.1%), disease progression (15.3%), neutropenia (11.3%), covid-19 (10.1%) and death (6.8%). 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 Mosunetuzumab was responsible.
How serious are the reports?
95.8% are marked serious by the reporter. Among the outcomes recorded, 18.9% of reports include death and 58.8% 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?
physician (86.7%), other health professional (9.7%) and consumer or non-health professional (2.4%). Most reports reach FDA through the manufacturer, which must forward reports it receives.
Are reports for Mosunetuzumab rising?
88 reports in the 12 months to June 2026, up 33% from 66 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 Mosunetuzumab 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 Mosunetuzumab?
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 Mosunetuzumab as a suspect or interacting product; reports listing it only as a concomitant medication (17) 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.