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Adverse Reactions (ARs)
Laboratory Abnormalities

LUNSUMIO® [IV] or LUNSUMIO VELO™ safety profiles1,4

LUNSUMIO [IV] ARs LUNSUMIO VELO ARs
Adverse reactions (≥10%) in patients with relapsed or refractory follicular lymphoma who received LUNSUMIO [IV] (n=90)
Adverse reactions* All Grades (%) Grade 3 or 4 (%)
Cytokine release syndrome 44 2.2
Fatigue† 42 0
Pyrexia 29 1.1‡
Edema† 17 1.1
Chills 13 1.1‡
Rash† 39 4.4‡
Pruritus 21 0
Dry skin 16 0
Skin exfoliation 10 0
Headache† 32 1.1‡
Peripheral neuropathy† 20 0
Dizziness† 12 0
Musculoskeletal pain† 28 1.1‡
Arthralgia 11 0
Cough† 22 0
Dyspnea† 11 1.1‡
Diarrhea 17 0
Nausea 17 0
Abdominal pain† 12 1.1‡
Upper respiratory tract infection† 14 2.2‡
Urinary tract infection† 10 1.1‡
Insomnia 12 0
Adverse reactions (≥10%) in patients with relapsed or refractory follicular lymphoma who received LUNSUMIO VELO (n=94)
Adverse reactions* All Grades (%) Grade 3 or 4 (%)
Cytokine release syndrome 30 2.1
Injection site reactions§ 69 0
Fatigue† 39 0
Edema† 13 0
Pyrexia 11 1.1
Chills 11 0
Rash† 35 3.2
Dry skin 11 0
Headache 17 0
Peripheral neuropathy† 11 0
Dizziness† 10 0
Musculoskeletal pain† 20 0
Arthralgia 13 0
Cough 13 0
Dyspnea 11 0
Diarrhea 20 0
Nausea 14 0
Constipation 14 0
Abdominal pain 13 0
COVID-19‖¶ 27 4.3
Upper respiratory tract infection† 15 2.1
Pneumonia† 13 4.3
Insomnia 15 0

Fatal adverse reactions occurred in 4.3% of patients from COVID-19 (3.2%) and HLH (1.1%).1

*Adverse reactions were graded based on CTCAE Version 4.0, with the exception of CRS, which was graded per ASTCT 2019 criteria.
†Includes grouped terms as defined by the FDA. Definitions can be found in the LUNSUMIO [IV] or LUNSUMIO VELO Prescribing Information.
‡Only Grade 3 adverse reactions occurred.
§Injection site reactions includes injection site reaction, injection site discharge, injection site erythema, injection site edema, injection site pain, injection site pruritus, and injection site rash.
‖Adverse reaction with fatal outcome.
Grade 5 COVID-19 occurred in 3.2% of patients.

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Laboratory abnormalities1,4

LUNSUMIO [IV] LUNSUMIO VELO
Select laboratory abnormalities (≥20%) that worsened from baseline in patients with relapsed or refractory follicular lymphoma who received LUNSUMIO [IV] (n=90)#
Laboratory abnormality All Grades (%) Grade 3 or 4 (%)
Lymphocyte count decreased 100 98
Hemoglobin decreased 68 12
Neutrophils decreased 58 40
Platelets decreased 46 10
Phosphate decreased 78 46
Glucose increased 42 42
Aspartate aminotransferase increased 39 4.4
Gamma-glutamyl transferase increased 34 9
Magnesium decreased 34 0
Potassium decreased 33 6
Alanine aminotransferase increased 32 7
Uric acid increased 22 22
Select laboratory abnormalities (≥20%) that worsened from baseline in patients with relapsed or refractory follicular lymphoma who received LUNSUMIO VELO (n=94)**
Laboratory abnormality All Grades (%) Grade 3 or 4 (%)
Lymphocyte count decreased 84 69
Hemoglobin decreased 60 10
Neutrophils decreased 50 26
Platelets decreased 33 6.4
Phosphate decreased 48 11
Alanine aminotransferase increased 34 1.1
Gamma-glutamyl transferase increased 31 1.1
Uric acid increased 28 28
Aspartate aminotransferase increased 28 2.1
Potassium decreased 27 0
Magnesium decreased 25 2.1

#The denominator used to calculate the rate varied from 72 to 90 based on the number of patients with a baseline value and at least one post-treatment value.
**The denominator used to calculate the rate varied from 85 to 94 based on the number of patients with a baseline value and at least one post-treatment value.

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AE=adverse event; AR=adverse reaction; ASTCT=American Society for Transplantation and Cellular Therapy; CRS=cytokine release syndrome; CTCAE=Common Terminology Criteria for Adverse Events; FDA=Food and Drug Administration; FL=follicular lymphoma; IV=intravenous.

Important Safety Information & Indication

Indication

LUNSUMIO (mosunetuzumab-axgb) or LUNSUMIO VELO is indicated for the treatment of adult patients with relapsed or refractory follicular lymphoma after two or more lines of systemic therapy.

This indication is approved under accelerated approval based on response rate. Continued approval for this indication may be contingent upon verification and description of clinical benefit in a confirmatory trial(s).

BOXED WARNING

Cytokine release syndrome (CRS), including serious or life-threatening reactions, can occur in patients receiving LUNSUMIO or LUNSUMIO VELO. Initiate treatment with the LUNSUMIO or LUNSUMIO VELO step-up dosing schedule to reduce the risk of CRS. Withhold LUNSUMIO or LUNSUMIO VELO until CRS resolves or permanently discontinue based on severity.

Warnings and Precautions

Cytokine Release Syndrome (CRS)

LUNSUMIO or LUNSUMIO VELO can cause CRS, including serious or life-threatening reactions.

CRS occurred in 39% of patients who received LUNSUMIO at the recommended dosage in the clinical trial (N=218), with Grade 1 CRS occurring in 28%, Grade 2 in 15%, Grade 3 in 2%, and Grade 4 in 0.5% of patients. Among 86 patients who experienced CRS, CRS recurred in 28%. Most cases of CRS occurred following doses of 1 mg on Cycle 1 Day 1 (15%), 2 mg on Cycle 1 Day 8 (5%), and 60 mg on Cycle 1 Day 15 (33%). Five percent of patients experienced CRS after receiving 60 mg on Cycle 2 Day 1 with 1% of patients experiencing CRS following subsequent doses of LUNSUMIO.

The median time to onset of CRS from the start of administration of LUNSUMIO in Cycle 1 Day 1 was 5 hours (range: 1 hour to 3 days), Cycle 1 Day 8 was 28 hours (range: 5 hours to 3 days), Cycle 1 Day 15 was 25 hours (range: 0.1 hours to 16 days), and Cycle 2 Day 1 was 46 hours (range: 12 hours to 3 days). The median duration of CRS was 3 days (range: 1 to 29 days).

Clinical signs and symptoms of CRS occurring in patients receiving LUNSUMIO included, but were not limited to, fever, chills, hypotension, tachycardia, hypoxia, and headache. Concurrent neurologic adverse reactions occurred in 6% of patients and included, but were not limited to, headache, confusional state, and anxiety.

CRS occurred in 30% of patients who received LUNSUMIO VELO at the recommended dosage in the clinical trial (N=94), with Grade 1 CRS occurring in 20%, Grade 2 in 7%, and Grade 3 in 2.1%. Among 28 patients who experienced CRS, CRS recurred in 14% of patients. CRS occurred most commonly after the first two doses: 19% of patients experienced CRS after the Cycle 1 Day 1 dose, 13% after the Cycle 1 Day 8 dose, and 2.1% after the Cycle 1 Day 15 dose.

The median time to CRS onset from the start of LUNSUMIO VELO administration was 17 hours (range: 7 to 33 hours) with the Cycle 1 Day 1 dose, and 62 hours (range: 30 to 113 hours) with the Cycle 1 Day 8 dose. CRS resolved in all patients, after a median duration of 2 days (range: 1 to 15 days).

Clinical signs and symptoms of CRS occurring in patients receiving LUNSUMIO VELO included fever, hypoxia, chills, tachycardia, and headache. Concurrent neurologic adverse reactions occurred in 5% of patients and included but were not limited to headache, dizziness, lethargy, memory impairment, and peripheral neuropathy.

Initiate therapy according to LUNSUMIO or LUNSUMIO VELO step-up dosing schedule to reduce the risk of CRS. Administer pretreatment medications to reduce the risk of CRS, ensure adequate hydration, and monitor patients following administration of LUNSUMIO or LUNSUMIO VELO accordingly.

At the first sign of CRS, immediately evaluate patients for hospitalization, manage per current practice guidelines, and administer supportive care; withhold or permanently discontinue LUNSUMIO or LUNSUMIO VELO based on severity.

Patients who experience CRS (or other adverse reactions that impair consciousness) should be evaluated and advised not to drive and to refrain from operating heavy or potentially dangerous machinery until resolution.

Neurologic Toxicity, including Immune Effector Cell-Associated Neurotoxicity Syndrome (ICANS)

LUNSUMIO or LUNSUMIO VELO can cause serious and life-threatening neurologic toxicity, including ICANS.

Neurologic toxicity occurred in 39% of patients who received LUNSUMIO at the recommended dosage in the clinical trial, with Grade 3 neurologic toxicity occurring in 3% of patients. The most frequent neurologic toxicities were headache (21%), peripheral neuropathy (13%), dizziness (11%), and mental status changes (6%, including confusional state, disturbance in attention, cognitive disorder, delirium, encephalopathy, and somnolence). ICANS was reported in 1% of patients (Grade 1: 0.5%, Grade 2: 0.5%) who received LUNSUMIO at the recommended dosage in the clinical trial.

Neurologic toxicity occurred in 53% of patients who received LUNSUMIO VELO at the recommended dosage in the clinical trial, with Grade 3 neurologic toxicity occurring in 1.1% of patients. The most frequent neurologic toxicities were headache (17%), insomnia (15%), dizziness (10%), and mental status changes (7%, including confusion and lethargy). ICANS or suspected ICANS was reported in 3.1% of patients (all Grade 1) who received LUNSUMIO VELO at the recommended dosage in the clinical trial.

Across a broader clinical trial population, ICANS or suspected ICANS occurred in 2.2% (21/949) of patients who received LUNSUMIO or LUNSUMIO VELO. The most frequent manifestations included confusional state and lethargy. Twenty patients had Grade 1-2 events and 1 patient had a Grade 3 event. The majority of cases (75%) occurred during the first cycle of treatment. The median time to onset was 17 days (range: 1 to 48 days). In total, 88% of cases resolved after a median duration of 3 days (range: 1 to 20 days).

Coadministration of LUNSUMIO or LUNSUMIO VELO with other products that cause dizziness or mental status changes may increase the risk of neurologic toxicity.

Monitor patients for signs and symptoms of neurologic toxicity during treatment. At the first sign of neurologic toxicity, including ICANS, immediately evaluate the patient, consider neurology evaluation as appropriate, and provide supportive therapy based on severity; withhold or permanently discontinue LUNSUMIO or LUNSUMIO VELO based on severity and follow management recommendations.

Patients who experience neurologic toxicity such as tremors, dizziness, insomnia, severe neurotoxicity, or any other adverse reactions that impair consciousness should be evaluated, including potential neurology evaluation, and patients at increased risk should be advised not to drive and to refrain from operating heavy or potentially dangerous machinery until resolution.

Infections

LUNSUMIO or LUNSUMIO VELO can cause serious or fatal infections.

Among patients who received LUNSUMIO at the recommended dosage in the clinical trial, serious infections, including opportunistic infections, occurred in 17%, with Grade 3 or 4 infections in 14% and fatal infections in 0.9% of patients. The most common Grade 3 or greater infections were pneumonia, sepsis, and upper respiratory infection.

Among patients who received LUNSUMIO VELO at the recommended dosage in the clinical trial, serious infections, including opportunistic infections, occurred in 17%, with Grade 3 or 4 infections in 16%, and fatal infections in 3.2% of patients. The most common Grade 3 or greater infections were pneumonia, sepsis, and COVID-19.

Monitor patients for signs and symptoms of infection prior to and during treatment with LUNSUMIO or LUNSUMIO VELO and treat appropriately. LUNSUMIO or LUNSUMIO VELO should not be administered in the presence of active infection. Caution should be exercised when considering the use of LUNSUMIO or LUNSUMIO VELO in patients with a history of recurring or chronic infections (eg, chronic, active Epstein-Barr Virus), with underlying conditions that may predispose to infections, or who have had significant prior immunosuppressive treatment. Administer prophylactic antimicrobials according to guidelines. Withhold LUNSUMIO or LUNSUMIO VELO or consider permanent discontinuation of LUNSUMIO or LUNSUMIO VELO based on severity.

Hemophagocytic Lymphohistiocytosis (HLH)

LUNSUMIO or LUNSUMIO VELO can cause fatal or serious HLH. HLH is a potentially life-threatening, hyperinflammatory syndrome that is independent of CRS. Common manifestations include fever, elevated ferritin, hemophagocytosis, cytopenias, coagulopathy, hepatitis, and splenomegaly.

Across a broader clinical trial population, HLH occurred in 0.5% (7/1536) of patients. Most cases (5/7) were identified within the first 28 days following initiation of LUNSUMIO or LUNSUMIO VELO, with 3 cases preceded by diagnosed or suspected CRS. Of the 7 cases of HLH, 6 had fatal outcomes, with 2 deaths from HLH alone and 4 deaths with concurrent unresolved HLH. Of the 7 cases of HLH, 4 occurred in the context of concurrent EBV and/or CMV infection.

Monitor for clinical signs and symptoms of HLH. Consider HLH when the presentation of CRS is atypical or prolonged, or when there are features of macrophage activation. For suspected HLH, interrupt LUNSUMIO or LUNSUMIO VELO and treat promptly for HLH per current practice guidelines.

Cytopenias

LUNSUMIO or LUNSUMIO VELO can cause serious or severe cytopenias, including lymphopenia, neutropenia, anemia, and thrombocytopenia.

Among patients who received LUNSUMIO at the recommended dosage in the clinical trial, Grade 3 or 4 decreased lymphocytes occurred in 92%, decreased neutrophils in 38%, decreased hemoglobin in 19%, and decreased platelets in 12% of patients. Grade 4 decreased lymphocytes occurred in 71%, decreased neutrophils in 19%, and decreased platelets in 5% of patients. Febrile neutropenia occurred in 2% of patients.

Among patients who received LUNSUMIO VELO at the recommended dosage in the clinical trial, Grade 3 or 4 decreased lymphocytes occurred in 69%, decreased neutrophils occurred in 26%, decreased hemoglobin in 10%, and decreased platelets in 10% of patients. Grade 4 decreased neutrophils occurred in 13% and decreased platelets in 6% of patients. Grade 4 decreased lymphocytes occurred in 22%, decreased neutrophils in 9%, and decreased platelets in 3.2% of patients. Febrile neutropenia occurred in 2.1% of patients.

Monitor complete blood counts throughout treatment. Based on the severity of cytopenias, temporarily withhold or permanently discontinue LUNSUMIO or LUNSUMIO VELO. Consider prophylactic granulocyte colony-stimulating factor administration as applicable.

Tumor Flare

LUNSUMIO or LUNSUMIO VELO can cause serious or severe tumor flare.

Among patients who received LUNSUMIO at the recommended dosage in the clinical trial, tumor flare occurred in 4%. Among patients who received LUNSUMIO VELO at the recommended dosage in the clinical trial, tumor flare occurred in 1.1% of patients. Manifestations included new or worsening pleural effusions, localized pain and swelling at the sites of lymphoma lesions, and tumor inflammation.

Patients with bulky tumors or disease located in close proximity to airways or a vital organ should be monitored closely during initial therapy. Monitor for signs and symptoms of compression or obstruction due to mass effect secondary to tumor flare. If compression or obstruction develops, institute standard treatment of these complications.

Risk of Medication Errors with Incorrect Product Use

Mosunetuzumab-axgb is available in two formulations: as an injection for intravenous use (LUNSUMIO) and as an injection for subcutaneous use (LUNSUMIO VELO). Check the product labels to ensure that the correct formulation is being prescribed, dispensed, and administered to the patient. Do not substitute LUNSUMIO for or with LUNSUMIO VELO.

Embryo-Fetal Toxicity

Based on its mechanism of action, LUNSUMIO or LUNSUMIO VELO may cause fetal harm when administered to a pregnant woman. Advise pregnant women of the potential risk to the fetus. Verify pregnancy status in females of reproductive potential prior to initiating LUNSUMIO or LUNSUMIO VELO. Advise females of reproductive potential to use effective contraception during treatment with LUNSUMIO or LUNSUMIO VELO and for 3 months after the last dose.

Most Common Adverse Reactions

The most common (≥20%) adverse reactions of LUNSUMIO are CRS (44%), fatigue (42%), rash (39%), headache (32%), pyrexia (29%), musculoskeletal pain (28%), cough (22%), pruritus (21%), and peripheral neuropathy (20%).

The most common (≥20%) adverse reactions of LUNSUMIO VELO are injection site reactions (69%), fatigue (39%), rash (35%), CRS (30%), COVID-19 infection (27%), musculoskeletal pain (20%), and diarrhea (20%).

The most common Grade 3 to 4 laboratory abnormalities (≥10%) with LUNSUMIO are decreased lymphocyte count (92%), decreased phosphate (41%), increased glucose (40%), decreased neutrophil count (38%), decreased hemoglobin (19%), increased uric acid (15%), and decreased platelets (12%).

The most common Grade 3 to 4 laboratory abnormalities (≥15%) with LUNSUMIO VELO are decreased lymphocyte count (69%), decreased neutrophil count (26%), and increased uric acid (28%). Grade 4 laboratory abnormalities in >5% included lymphocyte count decreased (22%) and neutrophil count decreased (9%).

Drug Interactions

LUNSUMIO or LUNSUMIO VELO causes release of cytokines that may suppress activity of CYP450 enzymes, resulting in increased exposure of CYP450 substrates. Increased exposure of CYP450 substrates is more likely to occur after the first dose of LUNSUMIO or LUNSUMIO VELO on Cycle 1 Day 1 and up to 14 days after the 60 mg dose of LUNSUMIO on Cycle 2 Day 1 or the 45 mg dose of LUNSUMIO VELO on Cycle 1 Day 8 and during and after CRS. Monitor for toxicity or concentrations of drugs that are CYP450 substrates where minimal concentration changes may lead to serious adverse reactions. Consult the concomitant CYP450 substrate drug prescribing information for recommended dosage modification.

Use in Specific Populations

Lactation

There is no information regarding the presence of mosunetuzumab-axgb in human milk, the effect on the breastfed child, or milk production. Because human IgG is present in human milk, and there is potential for mosunetuzumab-axgb absorption leading to B-cell depletion, advise women not to breastfeed during treatment with LUNSUMIO or LUNSUMIO VELO for 3 months after the last dose.

You may report side effects to the FDA at 1-800-FDA-1088 or www.fda.gov/medwatch. You may also report side effects to Genentech at 1-888-835-2555.

Please see the LUNSUMIO full Prescribing Information and LUNSUMIO VELO full Prescribing Information for additional Important Safety Information, including BOXED WARNING.

    • LUNSUMIO VELO. Prescribing Information. Genentech, Inc.

      LUNSUMIO VELO. Prescribing Information. Genentech, Inc.

    • Referenced with permission from the NCCN Clinical Practice Guidelines in Oncology (NCCN Guidelines®) for B-cell Lymphomas V.1.2026. © National Comprehensive Cancer Network, Inc. 2025. All rights reserved. Accessed December 22, 2025. To view the most recent and complete version of the guideline, go online to NCCN.org.

      Referenced with permission from the NCCN Clinical Practice Guidelines in Oncology (NCCN Guidelines®) for B-cell Lymphomas V.1.2026. © National Comprehensive Cancer Network, Inc. 2025. All rights reserved. Accessed December 22, 2025. To view the most recent and complete version of the guideline, go online to NCCN.org.

    • Rivas-Delgado A, Magnano L, Moreno-Velazquez M, et al. Response duration and survival shorten after each relapse in patients with follicular lymphoma treated in the rituximab era. Br J Haematol. 2019;184(5):753-759. doi:10.1111/bjh.15708.

      Rivas-Delgado A, Magnano L, Moreno-Velazquez M, et al. Response duration and survival shorten after each relapse in patients with follicular lymphoma treated in the rituximab era. Br J Haematol. 2019;184(5):753-759. doi:10.1111/bjh.15708.

    • LUNSUMIO. Prescribing Information. Genentech, Inc.

      LUNSUMIO. Prescribing Information. Genentech, Inc.

    • Sun LL, Ellerman D, Mathieu M, et al. Anti-CD20/CD3 T cell-dependent bispecific antibody for the treatment of B cell malignancies. Sci Transl Med. 2015;7(287):287ra70. doi:10.1126/scitranslmed.aaa4802.

      Sun LL, Ellerman D, Mathieu M, et al. Anti-CD20/CD3 T cell-dependent bispecific antibody for the treatment of B cell malignancies. Sci Transl Med. 2015;7(287):287ra70. doi:10.1126/scitranslmed.aaa4802.

    • Ferl GZ, Reyes A, Sun LL, et al. A preclinical population pharmacokinetic model for anti-CD20/CD3 T-cell-dependent bispecific antibodies. Clin Transl Sci. 2018;11(3):296-304. doi:10.1111/cts.12535.

      Ferl GZ, Reyes A, Sun LL, et al. A preclinical population pharmacokinetic model for anti-CD20/CD3 T-cell-dependent bispecific antibodies. Clin Transl Sci. 2018;11(3):296-304. doi:10.1111/cts.12535.

    • Budde LE, Sehn LH, Matasar M, et al. Safety and efficacy of mosunetuzumab, a bispecific antibody, in patients with relapsed or refractory follicular lymphoma: a single-arm, multicentre, phase 2 study. Lancet Oncol. 2022;23(8):1055-1065. doi:10.1016/S1470-2045(22)00335-7.

      Budde LE, Sehn LH, Matasar M, et al. Safety and efficacy of mosunetuzumab, a bispecific antibody, in patients with relapsed or refractory follicular lymphoma: a single-arm, multicentre, phase 2 study. Lancet Oncol. 2022;23(8):1055-1065. doi:10.1016/S1470-2045(22)00335-7.

    • BLA Multi-disciplinary Review and Evaluation {BLA 761263, Lunsumio (Mosunetuzumab)}. US Food and Drug Administration. January 2020. Accessed March 14, 2025. https://www.accessdata.fda.gov/​drugsatfda_docs/​nda/​2023/​761263Orig1s000​MultidisciplineR.pdf.

      BLA Multi-disciplinary Review and Evaluation {BLA 761263, Lunsumio (Mosunetuzumab)}. US Food and Drug Administration. January 2020. Accessed March 14, 2025. https://www.accessdata.fda.gov/​drugsatfda_docs/​nda/​2023/​761263Orig1s000​MultidisciplineR.pdf.

    • Shadman M, Bartlett NL, Matasar M, et al. Mosunetuzumab continues to demonstrate clinically meaningful outcomes in patients with relapsed and/or refractory follicular lymphoma after ≥2 prior therapies including those with a history of POD24: 4-year follow-up of a pivotal Phase II study. Presented at: The 66th American Society of Hematology Annual Meeting. December 7-10, 2024. P4407.

      Shadman M, Bartlett NL, Matasar M, et al. Mosunetuzumab continues to demonstrate clinically meaningful outcomes in patients with relapsed and/or refractory follicular lymphoma after ≥2 prior therapies including those with a history of POD24: 4-year follow-up of a pivotal Phase II study. Presented at: The 66th American Society of Hematology Annual Meeting. December 7-10, 2024. P4407.

    • Bartlett NL, Sehn LH, Assouline S, et al. Presented at: The 66th American Society of Hematology Annual Meeting. December 7-10, 2024. P1645.

      Bartlett NL, Sehn LH, Assouline S, et al. Presented at: The 66th American Society of Hematology Annual Meeting. December 7-10, 2024. P1645.

    • Data on file. Genentech, Inc.

      Data on file. Genentech, Inc.