ClinicalTrials.gov record NCT07548450

Mosunetuzumab in Combination With Pirtobrutinib in Patients With Relapsed or Refractory Waldenstrom Macroglobulinemia (MPOWER)

Record copied from ClinicalTrials.gov: Oct 10, 2026AI summaries generated: Sep 28, 2026

A Phase II Study of Mosunetuzumab in Combination With Pirtobrutinib in Patients With Relapsed or Refractory Waldenstrom Macroglobulinemia (MPOWER)

StatusNot yet recruitingThe study has been registered but has not started enrolling. Sites and contacts may not be listed yet.
Study typeInterventionalA study in which researchers assign participants to one or more interventions, such as a drug, procedure, device, behavioural programme or other approach, to measure their effects.
PhasePhase 2A study that tests whether a treatment has the intended effect and continues to check safety, usually in a larger group than phase 1.
Age18 years old and older
SexAll
LocationUnited States
AI summaryWhat this study is about, in plain languageShow ▾Hide ▴

AI-written from the registry record, not the study's own wording. May contain errors or omissions. Check the registry text on this page and the original record ↗ before acting on it.

This is a Phase II, non-randomized study testing the combination of oral pirtobrutinib and subcutaneous mosunetuzumab in people with relapsed or refractory Waldenstrom Macroglobulinemia. The study uses two dosing strategies (mosunetuzumab starting in cycle 2 or cycle 3) and will measure safety, tolerability, and response.

What it is studying. The study is testing the safety and tolerability of mosunetuzumab given with pirtobrutinib and is measuring how well the combination controls disease, including rates of very good partial response or better.

What the researchers hope to learn. Determine a recommended Phase 2 dose (RP2D) based on dose-limiting toxicities; evaluate response rates (including VGPR and CR), conversion of responses over treatment cycles, duration of response, progression-free survival, and overall survival.

What this study is about

The study's own summary, as published on ClinicalTrials.gov. Underlined terms have a short explanation.

The purpose of this clinical trial it to test the safety and tolerability of the study drugs mosunetuzumab in combination with pirtobrutinib in patients with relapsed or refractory Waldenstrom's Macroglobulinemia.

Interventions being studied

Being studied in this trial does not mean the treatment or procedure is approved or available for this condition.

Drug
  • Pirtobrutinib
  • Mosunetuzumab

Eligibility

The criteria exactly as listed on ClinicalTrials.gov. Only the study team can say whether they apply to you.

Inclusion criteria

  • Subjects aged ≥ 18 years with documented diagnosis of WM with the definition of measurable disease
  • Subjects who are able to comply with the study protocol.
  • Subjects with relapsed or refractory WM who have received at least one prior line of therapy.
  • Must have received prior treatment with covalent BTK inhibitor or have declined such treatment.
  • Prior autologous stem cell transplant is permitted if completed ≥ 100 days prior to treatment.
  • Prior allogeneic transplants are not permitted.
  • Subjects must have an indication for treatment per IWWM
  • ECOG Performance Status ≤ 2
  • Adequate organ function as defined as:
  • Hematologic:
  • Absolute neutrophil count ≥ 1000/mm3 independent of G-CSF support, unless there is documented bone marrow involvement or splenomegaly with ensuing cytopenia in which case ANC of 750 cells/mm3 (0.75 x 10\^9/L) is permissible. Also, there should be no evidence of myelodysplasia or hypoplastic bone marrow.
  • Platelet count ≥75,000 cells/mm3 (≥75 x 10\^9/L) independent of transfusion support unless there is documented bone marrow involvement in which case platelet count of 50,000 cells/mm3 (50 x 10\^9/L) is permissible. Patients must be responsive to transfusion support if given for thrombocytopenia and patients refractory to transfusion support are not eligible. Also, there should be no evidence of myelodysplasia or hypoplastic bone marrow.
  • Hemoglobin of ≥ 8.5 g/dL (≥ 85 g/L) independent of transfusion support unless there is documented bone marrow involvement or splenomegaly with ensuing cytopenia in which case hemoglobin of 7 g/dL (70 g/L) is permissible. Patients must be responsive to transfusion support if given for anemia and patients refractory to transfusion support are not eligible. Also, there should be no evidence of myelodysplasia or hypoplastic bone marrow.
  • Coagulation: Activated partial thromboplastin time (aPTT) or partial thromboplastin time (PTT) and prothrombin (PT) or (international normalized ratio (INR) not greater than 1.5 x ULN.
  • Hepatic:
  • Total Bilirubin ≤ 1.5x institutional upper limit of normal (ULN) or ≤3 x ULN with document liver involvement and/ or Gilbert's disease
  • AST(SGOT)/ALT(SGPT) ≤ 3 × institutional ULN
  • Participants with liver metastases will be allowed to enroll with AST and ALT levels ≤ 5 x ULN.
  • Renal:
  • Estimated creatinine clearance ≥ 50 mL/min by Cockcroft-Gault formula.
  • Participants must adhere to the following sex and contraceptive/barrier requirements:
  • If participant is of childbearing potential, they must have a negative pregnancy test
  • For participants of non-childbearing potential: The post-menopausal status will be defined as having been amenorrheic for 12 months without an alternative medical cause (or having undergone surgical sterilization (bilateral oophorectomy of hysterectomy). The following age-specific requirements apply:
  • < 50 years of age:
  • Amenorrheic for ≥ 12 months following cessation of exogenous hormonal treatments; and
  • Luteinizing hormone and follicle-stimulating hormone levels in the post-menopausal range for the institution
  • -≥ 50 years of age:
  • Amenorrheic for 12 months or more following cessation of all exogenous hormonal treatments; or
  • Had radiation-induced menopause with last menses >1 year ago; or
  • Had chemotherapy-induced menopause with last menses >1 year ago
  • Luteinizing hormone and follicle-stimulating hormone levels in the post-menopausal range for the institution
  • Participants of childbearing potential and participants with a sexual partner of childbearing potential must agree to use a highly effective method of contraception and lactation requirements as described in Sections 5.4.1 and 5.4.2.
  • Able to swallow oral tablets.
  • Clinically significant adverse effects from any prior oncologic treatment (e.g. prior surgery, radiotherapy, or other antineoplastic therapy) must have recovered to grade 1 or have been determined to be clinically stable per the Investigator.
  • Subject or their legal representative is able to provide informed consent and willing to sign an approved consent form that conforms to federal and institutional guidelines.

Exclusion criteria

  • History of transformation of indolent disease to DLBCL
  • Active or history of CNS lymphoma or leptomeningeal infiltration
  • Prior treatment with a non-covalent BTK inhibitor
  • Prior treatment with CD20-directed bispecific antibody therapy
  • Receiving other investigational agents.
  • Receipt of a live, attenuated vaccine within 4 weeks before first dose of study treatment or anticipation that such a live attenuated vaccine will be required during the study
  • Patients must not receive live, attenuated vaccines (e.g., FluMistâ) while receiving study treatment or after the last dose until B-cell recovery to the normal ranges.
  • Inactivated influenza vaccination should be given during the influenza season only.
  • An approved coronavirus disease 2019 (COVID-19) vaccine (messenger RNA [mRNA], inactivated virus, and replication deficient viral vector vaccines) is allowed, as these are not considered live vaccines.
  • Receipt of systemic immunosuppressive medications (including, but not limited to, cyclophosphamide, azathioprine, methotrexate, thalidomide, and anti-tumor necrosis factor agents) with the exception of corticosteroid treatment £ 10 mg/day prednisone or equivalent within 2 weeks prior to the first dose of mosunetuzumab
  • Patients who received acute, low-dose, systemic immunosuppressant medications (e.g., single dose of dexamethasone for nausea or B-symptoms) may be enrolled in the study if deemed appropriate by the investigator.
  • The use of inhaled corticosteroids is permitted.
  • The use of mineralocorticoids for management of orthostatic hypotension is permitted.
  • The use of physiologic doses of corticosteroids for management of adrenal insufficiency is permitted.
  • History of solid organ transplantation
  • History of severe allergic or anaphylactic reaction to humanized, chimeric or murine monoclonal antibodies (MAbs) or known sensitivity or allergy to murine products
  • Known active bacterial, viral (including SARS-CoV-2), fungal, or other infection, or any major episode of infection requiring treatment with IV antibiotics within 4 weeks of Day 1 of Cycle 1
  • Known or suspected chronic active Epstein-Barr virus (EBV) infection
  • Known or suspected history of macrophage activation syndrome (MAS) / hemophagocytic lymphohistiocytosis (HLH)
  • History of confirmed progressive multifocal leukoencephalopathy (PML)
  • Current or past history of CNS disease, such as stroke, epilepsy, CNS vasculitis, or neurodegenerative disease
  • Patients with a history of stroke who have not experienced a stroke or transient ischemic attack in the past 1 year and have no significant residual neurologic deficits as judged by the investigator are allowed.
  • Patients with a history of epilepsy who have had no seizures in the past 1 year while not receiving any anti-epileptic medications are allowed.
  • Clinically significant active malabsorption syndrome or other conditions likely to affect gastrointestinal absorption of the study drug
  • History of bleeding diathesis
  • Major surgery 4 weeks prior to starting study therapy or participant has not fully recovered from major surgery.
  • The diagnosis of another malignancy which, in the opinion of the Investigator, is likely to negatively impact the participant's safety or ability to participate in the study.
  • Current evidence of uncontrolled, significant intercurrent illness including, but not limited to, the following conditions:
  • Cardiovascular disorders:
  • Congestive heart failure New York Heart Association Class III or IV, unstable angina pectoris, serious cardiac arrhythmias.
  • Unstable angina or acute coronary syndrome within 6 months prior to first dose of study therapy.
  • History of myocardial infarction within 6 months prior to first dose of study therapy
  • QTc prolongation defined as a QTcF > 470 ms.
  • Correction of suspected drug induced QTcF prolongation can be attempted at the investigator's discretion and only if clinically safe to do so with either discontinuation of the offending drug or switch to another drug not known to be associated with QTcF prolongation.
  • Correction for underlying bundle branch block (BBB) allowed.
  • Note: Patients with pacemakers are eligible if they have no history of fainting or clinically relevant arrhythmias while using the pacemaker
  • --Left ventricular ejection fraction < 40% within 12 months prior to first dose of study therapy.
  • Any other condition that would, in the Investigator's judgment, contraindicate the participant's participation in the clinical study due to safety concerns or compliance with clinical study procedures (e.g., infection/inflammation, intestinal obstruction, social/ psychological issues, etc.)
  • Evidence of other clinically significant uncontrolled condition(s) or other clinically significant active disease process which, in the opinion of the investigator, is likely to pose a risk for patient participation.
  • Known HIV infection.
  • Clinically significant history of liver disease, including viral or other hepatitis, or cirrhosis
  • -Note: Participants with a past or resolved HBV infection (defined as the presence of hepatitis B core antibody [anti-HBc] and absence of HBsAg) are eligible. Participants with positive anti-HBc and negative HBV DNA should be on prophylactic nucleo(t)side analogue therapy to prevent reactivation with serial HBV DNA PCR monitoring Participants positive for hepatitis C (HCV) antibody are eligible only if polymerase chain reaction is negative for HCV RNA.
  • Known active cytomegalovirus (CMV) infection.
  • History of autoimmune disease, including, but not limited to myocarditis, pneumonitis, myasthenia gravis, myositis, autoimmune hepatitis, systemic lupus erythematosus, rheumatoid arthritis, inflammatory bowel disease, vascular thrombosis associated with antiphospholipid syndrome, Wegener's granulomatosis, Sjögren's syndrome, Guillain-Barré syndrome, multiple sclerosis, vasculitis, or glomerulonephritis
  • Patients with a remote history of, or well-controlled, autoimmune disease with a treatment-free interval from immunosuppressive therapy for 12 months may be eligible to enroll if judged to be safe by the investigator.
  • Patients with a history of autoimmune-related hypothyroidism on a stable dose of thyroid-replacement hormone are eligible.
  • Patients with controlled Type 1 diabetes mellitus who are on an insulin regimen are eligible for the study.
  • Patients with a history of disease-related immune thrombocytopenic purpura, or autoimmune hemolytic anemia may be eligible.
  • Patients with eczema, psoriasis, lichen simplex chronicus, or vitiligo with dermatologic manifestations only (e.g., patients with psoriatic arthritis are excluded) are eligible for the study provided all of following conditions are met:
  • Rash must cover 10% of body surface area
  • Disease is well controlled at baseline and requires only low-potency topical corticosteroids
  • No occurrence of acute exacerbations of the underlying condition requiring psoralen plus ultraviolet A radiation, methotrexate, retinoids, biologic agents, oral calcineurin inhibitors, or high potency oral corticosteroids within the previous 12 months.
  • Positive SARS-CoV-2 test within 7 days prior to enrollment
  • Substance abuse within 12 months prior to screening
  • Medical, psychiatric, cognitive, or other conditions that may compromise the participant's ability to understand the participant information, give informed consent, comply with the study protocol or complete the study.
  • Known prior severe hypersensitivity to investigational product or any component in its formulations (CTCAE v 6.0 Grade ≥ 3).
  • Participants taking prohibited medications as described in Section 7.5.10.
  • Subject has received prior standard or investigational anti cancer therapy as specified below:
  • Chimeric antigen receptor T-cell therapy within 60 days prior to Day 1 of Cycle 1.
  • Radioimmunoconjugate within 12 weeks prior to Day 1 of Cycle 1.
  • Prior treatment with monoclonal antibodies, chemotherapy, or antibody-drug conjugates within 4 weeks before first mosunetuzumab administration.
  • Treatment with any anticancer agent (investigational or otherwise) within 4 weeks or 5 half-lives of the drug, whichever is shorter, prior to first dose of study treatment.
  • Radiotherapy
  • 14 days for local site radiation therapy
  • 6 weeks for prior radioisotope therapy
  • 12 weeks for 50% pelvic or total body irradiation

Study description and what participation involves

The registry record has no detailed description beyond the summary above.

AI summaryWhat participation may involve, in plain languageShow ▾Hide ▴

AI-written from the registry record, not the study's own wording. May contain errors or omissions. Check the registry text on this page and the original record ↗ before acting on it.

Participants are treated in repeating 21-day cycles: they take oral pirtobrutinib (200 mg) daily on days 1–21 of each cycle and receive subcutaneous mosunetuzumab injections on day 1 of applicable cycles. The study has two dosing strategies in which mosunetuzumab begins in either cycle 2 or cycle 3; total planned treatment length is described as 18 cycles (dosing strategy 1) or 19 cycles (dosing strategy 2), with continuation determined by the participant's response (complete response, very good partial response, or minor response). Study staff will monitor safety and response to guide dosing and duration. The registry record does not list other on-study procedures, the visit schedule, or specific assessments that will be performed.

How the study is structured. Phase II interventional trial with no masking. Participants receive oral pirtobrutinib (200 mg daily on days 1–21 of 21-day cycles) and subcutaneous mosunetuzumab starting either in cycle 2 or cycle 3 depending on the dosing strategy. Assignment is non-randomized and sequential; both arms are experimental. Treatment duration and continuation depend on individual response as described in the protocol.

Questions you could ask

These questions are suggestions for a conversation with the study team or your own clinician, not advice.

  • The registry says recruitment has not started. When is it expected to open, and can I register interest now?
  • The listed sites are in United States. Is any of them reachable for me, and does the study help with travel?
  • Which of the eligibility criteria would need to be checked with tests before I could join?

More on Waldenström macroglobulinemia

Important dates

Study start
November 2026 (estimated)
Primary completion
November 2034 (estimated)
Study completion
November 2035 (estimated)
Target enrollment
25 participants (estimated)
Last updated on registry
Sep 24, 2026
Data verified
Oct 10, 2026

Sponsor and research team

The lead sponsor funds and oversees the trial. A pharmaceutical or biotech company sponsor typically means the study is testing that company's drug or device; a hospital, university, or government agency usually indicates investigator-initiated or publicly funded research.

Lead sponsor
University of Utah
Collaborators
  • Genentech, Inc.
  • Eli Lilly and Company

Central study contact

If you're interested in participating, the central contact can answer general questions about the study — including eligibility requirements and how to find a recruiting site near you. Actual eligibility is determined by the site's medical team.

Participating sites (1)

Terms used on this page · explanations by MedicalUpdates.ai

relapsed or refractory
A condition that has not responded to a treatment. 'Relapsed' means it responded and then came back; 'refractory' means it did not respond in the first place.
line of therapy
Treatment a person has already had for the condition. A 'line of therapy' is one course of treatment; studies often require, or limit, the number of prior lines.
autologous stem cell transplant
A procedure that replaces blood-forming cells after high-dose treatment. 'Autologous' uses the person's own cells collected beforehand; 'allogeneic' uses cells from a donor.
ECOG Performance Status
A scale from 0 to 5 that describes how a person's condition affects daily activity. 0 means fully active; 1 means restricted in strenuous activity; 2 means able to self-care but unable to work; higher numbers mean more limitation.
Absolute neutrophil count
The number of neutrophils, a type of white blood cell that fights infection, in a blood sample. Studies often require it to be above a set level.
x ULN
The highest value of a blood test that a laboratory considers normal. Criteria such as '≤ 3 × ULN' mean the result must be no more than three times that value.
creatinine clearance
A measure of kidney function, calculated from a blood creatinine level together with age, weight and sex.
childbearing potential
Studies often ask participants who could become pregnant, or could father a child, to use contraception during the study and for a period afterwards, because the effect of the treatment on a pregnancy is unknown.
legal representative
A person who is legally allowed to make decisions, including consent to research, on behalf of someone who cannot consent for themselves.
informed consent
The process of explaining a study, including its risks and what participation involves, so that a person can decide freely whether to take part. Consent is usually documented in writing, and a participant can choose to leave the study later.
bispecific antibody
An engineered antibody that attaches to two targets at once, often linking an immune cell to a diseased cell so the immune cell can attack it.
investigational
A treatment that is being tested and has not been approved for this use. It may be approved for a different condition. Being studied does not mean it works or is available outside the study.
immunosuppressive
A medicine that reduces the activity of the immune system. Studies of autoimmune conditions often require a stable dose, a prior failure, or a washout of such medicines.
corticosteroid
Steroid medicines, such as prednisone, that reduce inflammation. Studies often require a stable dose at entry or measure whether the study treatment allows the dose to be reduced.
QTc
A recording of the heart's electrical activity. QTc is one measurement from it; some drugs are avoided if it is prolonged.
stable dose
A dose that has not changed for a defined period before the study starts. Studies may require this so that background treatment is relatively stable when study measurements begin.
baseline
Measurements taken at the start of the study, before any study treatment, so that later results can be compared with them.
enrollment
The number of participants a study plans to include, or has included. 'Estimated' means the planned number; 'actual' means the number who joined.
prior to screening
The checks done before enrolment to see whether a person qualifies, such as tests, scans or a review of medical history.
prohibited medications
A medicine that participants may not use during the study, usually because it could interfere with the study treatment or its measurement.
Chimeric antigen receptor
A treatment in which a person's own immune cells (T cells) are collected, modified in a laboratory to recognise a target, and returned to the body.
5 half-lives
The time it takes for the amount of a drug in the body to fall by half. 'Five half-lives' is often used as the point at which a previous drug has essentially left the body.
Inclusion Criteria
The conditions a person must meet to be considered for the study, for example a confirmed diagnosis, an age range or a test result.
Exclusion Criteria
The conditions that rule a person out even if they meet the inclusion criteria, for example other illnesses, certain medicines or pregnancy.

The study record on this page is reproduced from ClinicalTrials.gov, a database of the U.S. National Library of Medicine, where it was submitted by the study sponsor. MedicalUpdates.ai does not own this content, is not affiliated with or endorsed by ClinicalTrials.gov, NIH, or the U.S. Government, and does not verify the record. Plain-language notes, the glossary and the questions above are added by this site; text in the boxes marked "AI summary" was written by an AI model and may contain errors. Registry records change over time. Check the original record for the current version and discuss eligibility or participation with a qualified healthcare professional.

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