Lunsumio (Mosunetuzumab)
Bispecific CD20-directed CD3 T-cell engager for relapsed or refractory follicular lymphoma
Lunsumio (mosunetuzumab) is a first-in-class bispecific antibody approved for the treatment of adults with relapsed or refractory follicular lymphoma after at least two prior systemic therapies. It works by simultaneously binding to CD20 on malignant B-cells and CD3 on T-cells, creating a bridge that redirects the patient’s own immune system to attack and destroy cancerous cells. Lunsumio is administered as a subcutaneous injection in a hospital or clinic setting under medical supervision, with a fixed-duration treatment course of up to 17 cycles.
Quick Facts: Lunsumio
Key Takeaways
- Lunsumio is a bispecific antibody that redirects T-cells to destroy CD20-positive cancerous B-cells in follicular lymphoma.
- It is indicated for adults who have had at least two prior systemic therapies where the cancer did not respond or has returned.
- Treatment is given as a subcutaneous injection over a fixed course of up to 17 three-week cycles (approximately 12 months).
- Cytokine release syndrome (CRS) is the most significant risk; pre-medications and hospital monitoring are required during the first cycle.
- In clinical trials, approximately 80% of patients achieved an overall response, with about 60% achieving complete responses.
What Is Lunsumio and What Is It Used For?
Lunsumio contains the active substance mosunetuzumab, which belongs to a novel class of anticancer agents known as bispecific T-cell engagers. It was developed by Roche and received conditional marketing authorization from the European Medicines Agency (EMA) in June 2022 and accelerated approval from the U.S. Food and Drug Administration (FDA) in December 2022 for the treatment of relapsed or refractory follicular lymphoma (FL).
Follicular lymphoma is the most common type of indolent (slow-growing) non-Hodgkin lymphoma, accounting for approximately 20–25% of all non-Hodgkin lymphoma cases worldwide. It arises from malignant transformation of B-lymphocytes within the germinal centers of lymph nodes. While FL typically responds well to initial treatment, most patients eventually relapse, and the disease becomes increasingly difficult to treat with each subsequent line of therapy. After two or more prior treatments, patients have limited options and a poorer prognosis.
This is where Lunsumio fills a critical unmet need. As a bispecific antibody, it has a unique mechanism of action: one arm of the antibody binds to CD20, a protein expressed on the surface of both normal and malignant B-cells, while the other arm binds to CD3, a receptor found on T-cells. By simultaneously binding to both cell types, mosunetuzumab forms a physical bridge between the patient’s own T-cells and the cancerous B-cells, activating the T-cells to release cytotoxic molecules that destroy the cancer cells.
How Does Lunsumio Differ from Other Lymphoma Treatments?
Unlike traditional monoclonal antibodies such as rituximab (which bind only to CD20 and rely on indirect immune mechanisms), Lunsumio directly engages and activates T-cells, which are among the most potent effector cells of the immune system. This bispecific mechanism can overcome resistance to prior anti-CD20 therapies, making it particularly valuable for patients whose lymphoma has stopped responding to rituximab-based regimens.
Additionally, Lunsumio offers a fixed-duration treatment course of approximately 12 months, in contrast to some other immunotherapies that require indefinite treatment or complex cell-manufacturing processes (as with CAR-T cell therapy). The subcutaneous formulation also allows for more convenient administration compared to intravenous alternatives.
Clinical Evidence
The approval of Lunsumio was based on the pivotal GO29781 trial, a single-arm, open-label, multicenter study that enrolled patients with relapsed or refractory follicular lymphoma who had received at least two prior systemic therapies, including an anti-CD20 antibody and an alkylating agent. Results demonstrated an overall response rate of approximately 80%, with complete response rates of approximately 60%. These results are notable given that the study population had been heavily pretreated, with a median of three prior lines of therapy.
What Should You Know Before Taking Lunsumio?
Lunsumio is a powerful immunotherapy that requires careful patient selection and monitoring. Before treatment begins, your healthcare team will conduct a thorough medical evaluation to ensure the drug is appropriate for you. Understanding the contraindications, warnings, and precautions is essential for safe treatment.
Contraindications
You must not receive Lunsumio if you have a known hypersensitivity (allergy) to mosunetuzumab or to any of the excipients in the formulation, including L-histidine, L-methionine, acetic acid, sucrose, and polysorbat 20 (E432). Allergic reactions to the drug can range from mild skin reactions to severe, potentially life-threatening anaphylaxis.
Warnings and Precautions
Talk to your doctor or nurse before receiving Lunsumio if any of the following apply to you:
- Heart, lung, or kidney problems: Pre-existing conditions in these organs can increase the risk of complications from cytokine release syndrome (CRS) and tumor lysis syndrome.
- Active or chronic infections: Lunsumio affects B-cells, which play a role in fighting infections. A current or recurring infection may worsen during treatment.
- Vaccination plans: Live vaccines should be avoided during treatment and for a period afterward, as Lunsumio can impair your immune response to vaccines. Discuss any planned vaccinations with your healthcare team before starting treatment.
- Large tumor burden: Patients with a high volume of cancer may be at increased risk for tumor lysis syndrome, a potentially dangerous condition caused by the rapid breakdown of cancer cells.
Your doctor will monitor you closely during treatment, particularly during the first cycle when the risk of CRS is highest. You may receive pre-medications including corticosteroids (such as dexamethasone or methylprednisolone), paracetamol (acetaminophen), and an antihistamine (such as diphenhydramine) 30 to 60 minutes before each injection to reduce the risk of adverse reactions.
Pregnancy and Breastfeeding
Lunsumio may cause harm to an unborn child. It is important to inform your doctor before and during treatment if you are pregnant, think you may be pregnant, or plan to become pregnant. You should not use Lunsumio during pregnancy unless you and your doctor have determined that the potential benefit outweighs the risks to the fetus.
Women of childbearing potential must use effective contraception during treatment with Lunsumio and for at least 3 months after the last dose. Discuss appropriate contraceptive methods with your healthcare provider.
You must not breastfeed during treatment and for at least 3 months after your last dose. It is not known whether mosunetuzumab passes into breast milk or what effects it may have on the nursing infant or milk production.
Driving and Operating Machinery
Lunsumio can significantly affect your ability to drive, cycle, or operate machinery. Due to the potential symptoms of immune effector cell-associated neurotoxicity syndrome (ICANS), which may include confusion, disorientation, altered mental state, and impaired memory, you should exercise extreme caution. If you are experiencing any neurological symptoms, do not drive or operate heavy or potentially dangerous machinery and contact your healthcare team immediately.
Children and Adolescents
Lunsumio is not approved for use in children or adolescents under 18 years of age. There is insufficient data on the safety and efficacy of mosunetuzumab in pediatric populations, and it should not be administered to patients below the approved age range.
How Does Lunsumio Interact with Other Drugs?
As a monoclonal antibody, mosunetuzumab is not metabolized by cytochrome P450 enzymes in the same way as small-molecule drugs. However, its mechanism of action — activating T-cells and inducing cytokine release — can indirectly affect drug metabolism. Elevated cytokine levels, particularly interleukin-6 (IL-6), are known to suppress CYP450 enzyme activity, which could alter the plasma concentrations of concomitant medications that are CYP450 substrates.
This is particularly relevant during the first treatment cycle when cytokine release syndrome (CRS) is most likely to occur. Patients receiving medications with a narrow therapeutic index — where small changes in blood levels can lead to toxicity or treatment failure — should be monitored closely.
Major Considerations
| Drug / Drug Class | Type of Interaction | Clinical Significance |
|---|---|---|
| Warfarin and other narrow therapeutic index drugs | CRS-mediated CYP450 suppression may alter drug levels | Monitor INR and drug levels closely, especially during Cycle 1 |
| Live vaccines | Impaired immune response due to B-cell depletion | Avoid live vaccines during treatment and for a period after last dose |
| Immunosuppressive agents | Potential for additive immunosuppression | Increased risk of severe infections; use with caution |
| Anti-seizure medications (e.g., phenytoin, carbamazepine) | CYP450-mediated level changes during CRS episodes | Monitor serum levels during early treatment cycles |
| Corticosteroids (pre-medication) | Used as pre-medication to mitigate CRS | Required before Lunsumio doses; beneficial interaction |
It is critical that you tell your doctor about all medications you are currently taking, including prescription drugs, over-the-counter medications, and herbal supplements. Your healthcare team will evaluate your medication list and adjust dosing or monitoring as needed, particularly during the initial treatment cycles when the risk of CRS-related cytokine elevation is highest.
What Is the Correct Dosage of Lunsumio?
Lunsumio must be administered under the supervision of a healthcare professional experienced in the treatment of cancer. The drug is given as a subcutaneous (under the skin) injection, which is prepared by drawing the required volume of Lunsumio solution from its vial into a syringe.
Adults
The dosing schedule follows a carefully designed step-up protocol during the first cycle to minimize the risk of cytokine release syndrome:
Cycle 1 (21 days) — Step-up Dosing
- Day 1: 5 mg subcutaneous injection
- Day 8: 45 mg subcutaneous injection
- Day 15: 45 mg subcutaneous injection
Cycles 2 to 17 (each 21 days)
- Day 1: 45 mg subcutaneous injection
A full treatment course lasts up to approximately 12 months.
| Treatment Cycle | Day | Dose | Notes |
|---|---|---|---|
| Cycle 1 | Day 1 | 5 mg | Initial step-up dose; CRS monitoring required |
| Cycle 1 | Day 8 | 45 mg | Second step-up dose; CRS monitoring required |
| Cycle 1 | Day 15 | 45 mg | Third dose of Cycle 1 |
| Cycles 2–17 | Day 1 | 45 mg | Single dose per cycle; every 21 days |
Pre-medication
Before each Lunsumio injection, you may receive pre-medications 30 to 60 minutes in advance to reduce the risk of cytokine release syndrome and other infusion-related reactions. These typically include:
- Corticosteroids: Dexametason or methylprednisolone
- Analgesic/antipyretic: Paracetamol (acetaminophen)
- Antihistamine: Diphenhydramine or equivalent
Children
Lunsumio is not approved for use in patients under 18 years of age. No pediatric dosing recommendations exist. Safety and efficacy have not been established in this age group.
Elderly
No dose adjustment is required based on age alone. In clinical trials, patients over 65 years of age showed similar efficacy and safety profiles compared to younger adults. However, elderly patients may have reduced organ function and should be monitored appropriately for adverse effects, particularly CRS and infections.
Missed Dose
If you miss a scheduled appointment, contact your healthcare team immediately to reschedule. It is very important that you do not miss a dose, as the step-up dosing schedule in Cycle 1 is designed to gradually increase your body’s exposure to the drug and reduce the risk of severe adverse reactions. Your doctor will advise you on the appropriate next steps based on how long the delay has been.
Overdose
There is limited data on overdose with Lunsumio. In the event of an overdose, the patient should be closely monitored for signs of cytokine release syndrome, neurotoxicity, and other adverse reactions. Treatment is supportive and symptomatic, with management of CRS following established protocols including corticosteroids and, if necessary, tocilizumab (an IL-6 receptor antagonist). There is no specific antidote for mosunetuzumab.
What Are the Side Effects of Lunsumio?
Like all medicines, Lunsumio can cause side effects, although not everyone experiences them. Some side effects can be serious and require immediate medical attention. The following section provides a comprehensive overview of known adverse effects organized by frequency, based on data from the pivotal clinical trials and post-marketing surveillance.
Serious Side Effects
Tell your doctor immediately if you experience any symptoms of the following serious conditions:
Cytokine Release Syndrome (CRS)
CRS is the most clinically significant adverse effect of Lunsumio. It occurs when T-cell activation by the drug triggers a massive release of inflammatory cytokines. CRS is most common during the first treatment cycle, particularly after the first and second doses. Symptoms include fever (38°C or higher), chills, difficulty breathing, dizziness, rapid or irregular heartbeat, confusion, weakness, fainting, and blurred vision. Most CRS events are Grade 1–2 (mild to moderate) and resolve within a few days. Pre-medications significantly reduce the risk and severity of CRS.
Immune Effector Cell-Associated Neurotoxicity Syndrome (ICANS)
ICANS is a neurological complication associated with T-cell engaging therapies. Symptoms may appear days or weeks after dosing and can initially be subtle. They include confusion, disorientation, reduced consciousness, impaired memory, difficulty speaking or writing, inability to concentrate, and, in rare cases, hallucinations. If you notice any changes in your mental state or neurological function after receiving Lunsumio, contact your healthcare team immediately.
Hemophagocytic Lymphohistiocytosis (HLH)
HLH is a rare but serious condition in which the immune system overproduces infection-fighting cells called histiocytes and lymphocytes. Signs and symptoms can overlap with CRS and include persistent fever, enlarged liver and/or spleen, skin rash, swollen lymph nodes, easy bruising, kidney impairment, breathing difficulties, and heart problems. Your doctor will investigate for HLH if your CRS does not respond to treatment as expected or persists longer than anticipated.
Tumor Lysis Syndrome (TLS)
TLS can occur when cancer cells are destroyed rapidly, releasing their contents into the bloodstream. This can cause abnormal levels of potassium, phosphorus, uric acid, and calcium in the blood, potentially leading to kidney damage, heart rhythm abnormalities, and seizures. Symptoms include fever, chills, nausea, vomiting, confusion, shortness of breath, muscle or joint pain, and dark or cloudy urine. Before treatment, your doctor will ensure you are well-hydrated and may prescribe medication to lower uric acid levels.
Tumor Flare Reaction
When cancer is being attacked by the immune system, the tumor may temporarily swell and appear to worsen before improving. Symptoms include tender and swollen lymph nodes, chest pain, cough, difficulty breathing, and pain at the tumor site.
Infections
Because Lunsumio depletes B-cells (which play a role in the immune response), patients are at increased risk for infections. These can range from mild upper respiratory infections to serious pneumonia or urinary tract infections. Symptoms vary depending on the site of infection and may include fever, cough, chest pain, fatigue, shortness of breath, painful rash, sore throat, burning sensation during urination, and general malaise.
Side Effects by Frequency
Very Common
- Cytokine release syndrome (CRS)
- Injection site reactions (redness, swelling, pain at injection site)
- Skin rash
- Itching (pruritus)
- Dry skin
- Diarrhea
- Headache
- Fever (pyrexia)
- Chills
- Low white blood cell count (neutropenia)
- Low red blood cell count (anemia)
- Low platelet count (thrombocytopenia)
- Low levels of phosphate, potassium, or magnesium in the blood
- Elevated alanine aminotransferase (ALT) levels
Common
- Lung infection (pneumonia)
- Upper respiratory tract infection (nose, throat, sinuses)
- Urinary tract infection
- Febrile neutropenia (fever due to low neutrophil count)
- Tumor flare reaction
- Immune effector cell-associated neurotoxicity syndrome (ICANS)
- Elevated liver enzymes
Uncommon
- Tumor lysis syndrome (TLS)
- Hemophagocytic lymphohistiocytosis (HLH)
If you experience any side effects, including those not listed here, talk to your doctor, pharmacist, or nurse. Reporting suspected adverse reactions after the drug has been authorized is important, as it enables ongoing monitoring of the benefit-risk balance of the medicine. Healthcare professionals and patients are encouraged to report adverse reactions to their national medicines regulatory authority.
How Should You Store Lunsumio?
Because Lunsumio is administered in a hospital or clinical setting, storage is handled by trained healthcare professionals. However, it is useful for patients to understand the storage requirements for this biologic medicine:
- Temperature: Store in a refrigerator at 2°C to 8°C (36°F to 46°F).
- Do not freeze. Frozen product must not be used.
- Light protection: Keep the vial in its outer carton to protect from light.
- Keep out of sight and reach of children.
- Do not use after the expiry date printed on the carton and vial (Exp.). The expiry date refers to the last day of that month.
Once the solution has been drawn into a syringe for injection, it should be administered immediately. If not used immediately, the capped syringe may be stored for up to 28 days at 2°C to 8°C, or up to 24 hours at 9°C to 30°C, provided it was prepared under appropriate aseptic conditions.
Lunsumio does not contain antimicrobial preservatives, so strict aseptic technique during preparation is essential. Any unused product or waste material should be disposed of in accordance with local requirements for cytotoxic pharmaceutical waste.
What Does Lunsumio Contain?
Active Ingredient
| Presentation | Mosunetuzumab Content | Concentration | Volume |
|---|---|---|---|
| Lunsumio 5 mg | 5 mg per vial | 10 mg/mL | 0.5 mL |
| Lunsumio 45 mg | 45 mg per vial | 45 mg/mL | 1 mL |
Inactive Ingredients (Excipients)
- L-histidine
- L-methionine
- Acetic acid
- Sucrose
- Polysorbat 20 (E432)
- Water for injections
Lunsumio is a clear and colorless to slightly brownish-yellow solution supplied in a glass vial. Each package contains one vial. The polysorbat 20 content is 0.3 mg per 5 mg vial and 0.6 mg per 45 mg vial. If you have known allergies to polysorbat, inform your healthcare provider before treatment.
Appearance and Packaging
Lunsumio is a solution for injection (sterile solution) that appears clear and colorless to slightly brownish-yellow. It is supplied in a single-use glass vial. The vial label includes a peel-off sticker designed to be transferred to the syringe after preparation for identification and traceability purposes.
Marketing Authorization Holder
Roche Registration GmbH, Emil-Barell-Strasse 1, 79639 Grenzach-Wyhlen, Germany. Lunsumio is manufactured by Roche Pharma AG at the same address. For further information about this medicine, contact your national representative of the marketing authorization holder or visit the European Medicines Agency website.
Frequently Asked Questions About Lunsumio
Medical References and Sources
This article is based on current medical research and international guidelines. All claims are supported by scientific evidence from peer-reviewed sources.
- European Medicines Agency (2022). “Lunsumio (mosunetuzumab) — EPAR Product Information.” EMA Product Page European public assessment report including full prescribing information, scientific discussion, and product characteristics.
- Budde LE, Sehn LH, Matasar M, et al. (2022). “Safety and efficacy of mosunetuzumab, a bispecific antibody, in patients with relapsed or refractory follicular lymphoma: a single-arm, multicentre, phase 2 study.” The Lancet Oncology, 23(8), 1055–1065. doi:10.1016/S1470-2045(22)00335-7 Pivotal GO29781 trial results forming the basis for regulatory approval.
- U.S. Food and Drug Administration (2022). “FDA grants accelerated approval to mosunetuzumab-axgb for relapsed or refractory follicular lymphoma.” FDA Approval Notice FDA regulatory decision and supporting clinical data summary.
- National Comprehensive Cancer Network (2025). “NCCN Clinical Practice Guidelines in Oncology: B-Cell Lymphomas, Version 1.2025.” NCCN Guidelines Comprehensive clinical practice guidelines for management of B-cell lymphomas including treatment algorithms.
- Dreyling M, Ghielmini M, Rule S, et al. (2021). “Newly diagnosed and relapsed follicular lymphoma: ESMO Clinical Practice Guidelines.” Annals of Oncology, 32(3), 298–308. doi:10.1016/j.annonc.2020.11.008 European Society for Medical Oncology guidelines for follicular lymphoma diagnosis and treatment.
- World Health Organization (2022). “WHO Classification of Tumours of Haematopoietic and Lymphoid Tissues, 5th edition.” WHO International classification standard for lymphoid malignancies.
- Lee DW, Santomasso BD, Locke FL, et al. (2019). “ASTCT Consensus Grading for Cytokine Release Syndrome and Neurologic Toxicity Associated with Immune Effector Cells.” Biology of Blood and Marrow Transplantation, 25(4), 625–638. doi:10.1016/j.bbmt.2018.12.758 Consensus grading criteria for CRS and ICANS used in clinical practice.
Evidence grading: This article uses the GRADE framework (Grading of Recommendations Assessment, Development and Evaluation) for evidence-based medicine. Evidence level 1A represents the highest quality of evidence, based on systematic reviews and meta-analyses of randomized controlled trials.