Iberdomide Versus Observation Off Therapy After Idecabtagene Vicleucel CAR-T for Multiple Myeloma

PRIMARY OBJECTIVES: I. To establish and confirm the safety and dose of iberdomide as maintenance after idecabtagene vicleucel (ide-cel) CAR-T. (Safety run-in) II. To assess whether iberdomide maintenance therapy after idecabtagene vicleucel CAR-T cell therapy increases progression-free survival (PFS) relative to observation without additional therapy. (Randomized phase II) SECONDARY OBJECTIVES: I. To demonstrate anti-tumor activity, defined as conversion from non-minimal residual disease (MRD) complete response (CR)/stringent CR (sCR) status to MRD-negative CR/sCR, as well as improvement in PFS in the safety run-in cohort. (Safety run-in) II. To estimate the rate of conversion from MRD-positive at baseline to MRD-negative at any time point post-initiation of iberdomide maintenance or observation without additional therapy. (Key secondary objective; Randomized phase II) III. To estimate overall survival (OS) distribution post-initiation of iberdomide maintenance or observation without additional therapy. (Key secondary objective; Randomized phase II) IV. To estimate the minimal residual disease (MRD)-negativity rate at pre-registration and at one year post-initiation of iberdomide maintenance or observation without additional therapy. (Randomized phase II) V. To estimate rate of deepening hematological response among patients with measurable multiple myeloma (MM) post-initiation of iberdomide maintenance or observation without additional therapy. (Randomized phase II) VI. To evaluate the safety profile of iberdomide maintenance. (Randomized phase II) VII. To evaluate the peripheral blood immunophenotype before and during iberdomide maintenance or observation without additional therapy. (Randomized phase II) VIII. To evaluate persistence of CAR-T cells with iberdomide maintenance or observation without additional therapy. (Randomized phase II) CORRELATIVE SCIENCE OBJECTIVES: I. To estimate the minimal residual disease (MRD)-negativity rate at start of maintenance and at one year post-initiation of maintenance or observation. II. To estimate the sustained MRD-negativity rate. III. To estimate the rate of conversion from MRD-positive to MRD-negative. (Key objective) IV. To evaluate the peripheral blood immunophenotype before and during maintenance therapy or observation. V. To evaluate the persistence of CAR-T cells. VI. To evaluate B-cell maturation antigen (BCMA) protein expression by immunohistochemistry on myeloma cells from patients that have relapsed/recurrent disease. OUTLINE: Patients are randomized to 1 of 2 groups. GROUP 1: Patients undergo disease monitoring at monthly clinic visits until disease progression. Patients also undergo bone marrow aspiration and biopsy throughout the trial, undergo collection of blood samples at screening and on study, and undergo positron emission tomography (PET)/computed tomography (CT) and/or skeletal survey x-ray, CT, or magnetic resonance imaging (MRI) at screening and then as clinically indicated. GROUP 2: Patients receive iberdomide orally (PO) once daily (QD) on days 1-21 of each cycle. Cycles repeat every 28 days in the absence of disease progression or unacceptable toxicity. Patients also undergo bone marrow aspiration and biopsy throughout the trial, undergo collection of blood samples at screening and on study, and undergo PET/CT and/or skeletal survey x-ray, CT, or MRI at screening and then as clinically indicated. After completion of study treatment, patients are followed up within 30 days, then every 3-6 months until 4 years following registration.