Delayed Toxicities Post-CAR-T

Inclusion Criteria: * Subject is ≥18 years of age at the time of signing the informed consent form (ICF). * Subject must understand and voluntarily sign an ICF prior to any study-related assessments/procedures being conducted. * Subject is willing and able to adhere to the study visit schedule and other protocol requirements. * All subjects must have documented diagnosis of MM and be eligible for commercial CAR-T therapy with cilta-cel. Patients planned for standard of care cilta-cel whose cell product is considered out of specification after manufacture will still be eligible to proceed with the current study protocol if proceeding with cilta-cel infusion * All patients must have ECOG Performance Status ≤ 2. Exclusion Criteria: An individual who meets any of the following criteria will be excluded from participation in this study: * Subjects with monoclonal gammopathy of undetermined significance (MGUS), smoldering multiple myeloma (SMM), primary amyloidosis (no active multiple myeloma), Waldenström's macroglobulinemia, or POEMS syndrome (plasma cell dyscrasia with polyneuropathy, organomegaly, endocrinopathy, monoclonal protein, and skin changes) * Subjects with active plasma cell leukemia (defined as either 5% of peripheral blood white blood cell count comprised of plasma/CD138+ cells or an absolute plasma cell count of 2 x 109/L) * Subjects with active Central Nervous System (CNS) involvement with multiple myeloma * Cardiac conditions including: * New York Heart Associated class 3 or 4 congestive heart failure * Myocardial infarction or coronary artery bypass graft (CABG) ≤6 months prior to enrollment * History of clinically significant ventricular arrhythmia * History of severe non-ischemic cardiomyopathy * Stroke or seizure within 6 months of enrollment * Any serious medical condition, laboratory abnormality, or psychiatric illness that would prevent the patient from signing the informed consent form * Any serious concurrent medical conditions that may make the patient non-evaluable or put the patient's safety at risk, per the discretion of the treating physician or PI * Patients with a positive PCR test for hepatitis B virus or hepatitis C virus indicating active infection. Patients with positive serologic testing indicating exposure will need confirmatory testing by PCR. * Patients who are seropositive for HIV * Prior or concurrent malignancy, except for the following: * Adequately treated basal cell or squamous cell skin cancer or in-situ carcinoma. * Non-muscle invasive bladder cancer treated within the last 24 months that is considered completely cured. * Localized prostate cancer (N0M0): * with a Gleason score of ≤6, treated within the last 24 months or untreated and under surveillance, * with a Gleason score of 3+4 that has been treated more than 6 months prior to full study screening and considered to have a very low risk of recurrence; or * any history of localized prostate cancer and receiving androgen deprivation therapy and considered to have a very low risk of recurrence per the discretion of the treating physician or PI * Non-invasive cervical cancer treated within the last 24 months that is considered completely cured. * Breast cancer: adequately treated lobular carcinoma in situ, or ductal carcinoma in situ, or history of localized breast cancer and receiving anti-hormonal agents and considered to have a very low risk of recurrence. * Any other cancer from which the subject has been disease free for \> 3 years prior to study entry, or considered cured with minimal risk of disease recurrence. * Prior treatment with CAR-T * Prior allogeneic stem cell transplant * Major cardiac surgery within 8 weeks prior to cilta-cel; all other major surgery within 4 weeks prior to cilta-cel. * Patients who are pregnant or breastfeeding * Subjects with following physical and laboratory test findings: * Absolute neutrophil count \< 1 x 109/L without growth factor support within 1 week, or absolute neutrophil count \< 0.5 x 109/L for patients with documented Duffy-null blood typing * Platelets \< 50 x 109/L without transfusion support within 1 week * Creatinine clearance \< 30 ml/min according to the Cockroft-Gault formula: * Female CrCl = \[(140 - age in years) x weight in kg x 0.85\] / \[72 x serum creatinine in mg/dl\] * Male CrCl = \[(140 - age in years) x weight in kg x 1.00\] / \[72 x serum creatinine in mg/dl\] * Total bilirubin ≥ 2 x ULN (≥ 3 x ULN if documented Gilbert's syndrome) * AST or ALT ≥ 3x ULN * Corrected serum calcium \> 13.5 mg/dL * Are also excluded: * Prisoners or subjects who are involuntarily incarcerated * Subjects who are compulsorily detained for treatment of either a psychiatric or physical (e.g., infectious disease) illness