Brand name · Belzutifan
Welireg: adverse event reports filed with FDA
932 reports list it as a suspect or interacting product, 2021–2026.
- 932
- reports as suspect product
- 0% of all reports · about 196 a year
- 474
- reports, 12 months to June 2026
- 152 in the 12 months before
- 54.8%
- marked serious by the reporter
- 57.4% across all reports
- 10.1%
- record death among outcomes, as reported
- 94 reports · not verified by FDA
932 adverse event reports received by FDA list the brand name Welireg (belzutifan) as a suspect or interacting product, from October 2021 to June 2026. A further 24 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, 474 reports listed it, up 212% from 152 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 196 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 anaemia (20%), malignant neoplasm progression (17.9%) and fatigue (9.9%). A report can list several reactions, so shares add to more than 100%; 180 different terms appear across these reports. Anaemia is recorded in 20% of these reports, against 0.9% of all reports in the database.
54.8% of the reports are marked serious by the reporter; 10.1% record death among the outcomes and 21.8% record hospitalisation, as reported. 31.3% of the reports came from consumers, and the largest patient age group is 45 to 64 (21.7%). 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 Welireg reports recording the termall reports in the database
- Anaemialow red blood cells20%186
- Malignant neoplasm progression17.9%167
- Fatiguetiredness9.9%92
- Hypoxialow oxygen8.7%81
- Deaththe patient died; cause not stated by this term6.3%59
- Haemoglobin decreasedlow haemoglobin5.5%51
- Therapy interrupted4.9%46
- Dyspnoeashortness of breath4.3%40
- Hospitalisationadmission to hospital4.3%40
- Off label useused for a purpose or in a way not on the label3.9%36
- Drug ineffectivethe medicine did not work as expected3.3%31
- Product dose omission issuea dose was missed3.2%30
- Nauseafeeling sick2.9%27
- Diarrhoealoose or frequent stools2.8%26
- Disease progressionthe disease advanced2.7%25
- Malaisegeneral feeling of being unwell2.6%24
- No adverse eventno adverse event was reported2.6%24
- Dizzinesslight-headedness or unsteadiness2.3%21
- Falla fall2.3%21
- Astheniaweakness or lack of energy2%19
- Pneumonialung infection2%19
- Arthralgiajoint pain1.9%18
- Drug interactionan interaction between medicines1.7%16
- Adverse drug reactiona harmful or unpleasant reaction reported to a medicine1.6%15
- Decreased appetitereduced appetite1.6%15
- Painpain, site not specified1.6%15
- Wound infectionan infected wound1.6%15
- Headachehead pain1.5%14
- Hospice care1.4%13
Top 30 of 180 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. 69.1% of reports give the United States as the country of the event or reporter.
Reason for use recorded
| Indication as recorded (MedDRA) | Reports | Share |
|---|---|---|
| Renal cancer | 189 | 20.3% |
| Renal cell carcinoma | 168 | 18% |
| Renal cell carcinoma stage iv | 81 | 8.7% |
| Von hippel-lindau disease | 60 | 6.4% |
| Clear cell renal cell carcinoma | 41 | 4.4% |
| Haemangioblastoma | 27 | 2.9% |
The indication field is filled in by the reporter and is often blank; shares are of all 932 reports.
In context
| Measure | Welireg | All reports |
|---|---|---|
| Reports as suspect product | 932 | 20,646,523 |
| Share of that pool | — | 0% |
| Reports, latest 12 months | 474 | 1,332,454 |
| Marked serious | 54.8% | 57.4% |
| Death recorded among outcomes, per 1,000 reports | 101 | 91 |
| Hospitalisation recorded, per 1,000 reports | 218 | 213 |
| Consumer-filed share | 31.3% | 45.8% |
| Top term, share of reports | Anaemia 20% | 0.9% |
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 Welireg reports
How many adverse event reports has FDA received for Welireg?
932 reports list Welireg as a suspect or interacting product in the openFDA FAERS release of 28 Sep 2026, covering reports received through June 2026. 474 of them arrived in the latest 12 months. Another 24 list it only as a concomitant medication.
What reactions are recorded in Welireg reports?
anaemia (20%), malignant neoplasm progression (17.9%), fatigue (9.9%), hypoxia (8.7%) and death (6.3%). 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 Welireg was responsible.
How serious are the reports?
54.8% are marked serious by the reporter. Among the outcomes recorded, 10.1% of reports include death and 21.8% 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?
consumer or non-health professional (31.3%), physician (28.9%) and not given (18.5%). Most reports reach FDA through the manufacturer, which must forward reports it receives.
Are reports for Welireg rising?
474 reports in the 12 months to June 2026, up 212% from 152 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 Welireg 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 Welireg?
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 Welireg as a suspect or interacting product; reports listing it only as a concomitant medication (24) 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.