What the label lists and what reports show
Loncastuximab tesirine side effects
Loncastuximab tesirine's FDA label: “Most common (≥20%) adverse reactions, including laboratory abnormalities, are thrombocytopenia, increased gamma-glutamyltransferase, neutropenia, anemia, hyperglycemia, transaminase elevation, fatigue, hypoalbuminemia, rash, edema, nausea, and musculoskeletal …” FAERS holds 393 reports naming it through July 30, 2026; the reaction reported most often, leaving out the conditions it is used for, product-use terms and outcomes, is rash (32 reports).
- No generic listed
Check it at the source: the loncastuximab tesirine FDA label on DailyMed (effective June 12, 2026); the FDA FAERS public dashboard.
What does the patient leaflet say about side effects?
From the patient leaflet: What are the possible side effects of ZYNLONTA?ZYNLONTA may cause serious side effects, including: Fluid retention, including capillary leak syndrome (CLS ). Fluid retention has happened in people treated with ZYNLONTA, and can be serious and become life-threatening. Too much fluid buildup in your body can cause fluid to leak from blood vessels into the body's tissues. This condition is called capillary leak syndrome (CLS). Tell your healthcare provider and get emergency help right away if you develop new or worsening signs and symptoms of fluid retention including CLS: swelling or puffiness rapid weight gain chest pain trouble breathing feeling unusually weak or tired dizziness or feeling faint especially when standing up Low blood cell counts (platelets, red blood cells, and white blood cells). Low blood cell counts are common with ZYNLONTA but can also be serious or severe. […]
Source: FDA drug label, ADC Therapeutics America, Inc., effective June 12, 2026 (SPL set af54af12-3edf-4301-8bc5-0446bc813c1d), via openFDA; the full label on DailyMed
What does the label list?
From the label: adverse reactionsMost common (≥20%) adverse reactions, including laboratory abnormalities, are thrombocytopenia, increased gamma-glutamyltransferase, neutropenia, anemia, hyperglycemia, transaminase elevation, fatigue, hypoalbuminemia, rash, edema, nausea, and musculoskeletal pain.
Table 2: Adverse Reactions (≥10%) in Patients with Relapsed or Refractory DLBCL who received ZYNLONTA in LOTIS-2
| Reaction | Adverse Reaction All Grades (%) | ZYNLONTA (N=145) Grades 3 or 4 (%) |
|---|---|---|
| Fatigue Fatigue includes fatigue, asthenia, and lethargy | 38 | 1 No Grade 4 adverse reactions occurred |
| Edema Edema includes edema, face edema, generalized edema, peripheral edema, ascites,… | 28 | 3 |
| Rash Rash includes rash, rash erythematous, rash maculopapular, rash pruritic, rash… | 30 | 2 |
| Pruritus | 12 | 0 |
| Photosensitivity reaction | 10 | 2 |
| Nausea | 23 | 0 |
| Diarrhea | 17 | 2 |
| Abdominal pain Abdominal pain includes abdominal pain, abdominal discomfort, abdominal… | 14 | 3 |
| Vomiting | 13 | 0 |
| Constipation | 12 | 0 |
| Musculoskeletal pain Musculoskeletal pain includes musculoskeletal pain, musculoskeletal… | 23 | 1 |
| Decreased appetite | 15 | 0 |
| Dyspnea Dyspnea includes dyspnea, and dyspnea exertional | 13 | 1 |
| Pleural effusion | 10 | 2 |
| Upper respiratory tract infection Upper respiratory tract infection includes upper… | 10 | <1 |
Rows and numbers as the label prints them, under its own column headings (the first rows of a longer table where it runs on). A reaction in a trial table is not necessarily caused by the medicine, and trials differ from everyday use.
From the label: adverse reactions, continuedThe following clinically significant adverse reactions are described elsewhere in the labeling: Effusion and Edema [see Warnings and Precautions (5.1) ] Myelosuppression [see Warnings and Precautions (5.2)] Infections [see Warnings and Precautions (5.3) ] Hepatotoxicity, including DILI [see Warnings and Precautions(5.4) ] Cutaneous Reactions [see Warnings and Precautions (5.5) ] Most common (≥20%) adverse reactions, including laboratory abnormalities, are thrombocytopenia, increased gamma-glutamyltransferase, neutropenia, anemia, hyperglycemia, transaminase elevation, fatigue, hypoalbuminemia, rash, edema, nausea, and musculoskeletal pain. ( 6.1 ) To report SUSPECTED ADVERSE REACTIONS, contact ADC Therapeutics at 1-855-690-0340 or FDA at 1-800-FDA-1088 or www.fda.gov/medwatch. 6.1 Clinical Trials Experience Because clinical trials are conducted under widely varying conditions, adverse reaction rates observed in the clinical trials of a drug cannot be directly compared to rates in the clinical trials of another drug and may not reflect the rates observed in practice. …
Source: FDA drug label, ADC Therapeutics America, Inc., effective June 12, 2026 (SPL set af54af12-3edf-4301-8bc5-0446bc813c1d), via openFDA; the full label on DailyMed
What do FAERS reports show?
393 reports list loncastuximab tesirine among the medicines taken, each a report of something that happened, not proof the medicine caused it; 135 are coded as a death and 104 as a hospital stay. Counts follow how widely a medicine is used and watched, and they are not a measure of how risky it is. Of the 20 reactions below, 16 are named by the same term (in US spelling) in the label's adverse reactions, warnings or patient leaflet; a reaction the label does not name may still be there under another word, and a report does not show that the medicine caused it.
The 25 most reported reactions
Source: FDA Adverse Event Reporting System (FAERS) via openFDA, reports through July 30, 2026; reactions as MedDRA preferred terms
What next?
- Loncastuximab tesirine: the full record
- label, generics, price, shortages, recalls
- Report a side effect to the FDA
- MedWatch
- Side effects hub
- the most reported medicines and reactions