A Study to Investigate Safety and Efficacy With SAR445514 in Participants With Relapsed/Refractory Multiple Myeloma (RRMM) and Relapsed/Refractory Light-chain Amyloidosis (RRLCA)

Inclusion Criteria:

Participants must have a documented diagnosis of multiple myeloma (Part 1a, 2, and 3a) or light chain amyloidosis (Part 1b and 3b).

Participants with RRMM (Part 1, 2, and 3a)

• Participants with measurable disease for RRMM

• Participants with MM must have received at least 2 prior lines of therapy which mustinclude at least 2 consecutive cycles of a second or third generationimmunomodulator, steroid, proteasome inhibitor and anti-CD38 monoclonal antibody (MoAb).

• Participants must have documented evidence of progressive disease (PD), as per IMWG 2016 criteria.

Participants with RR LCA (Part 1b and 3b) must have received at least 1 prior line of treatment comprising at least 1 proteasome inhibitor.

• Participants with measurable disease according to ISA 2012.

• Participants must have documented evidence of progressive disease (PD), as per ISA 2012 criteria.

• One or more organ impacted by amyloidosis as per National comprehensive cancernetwork (NCCN) guidelines.

For dose escalation, body weight within 40 to 120 kg

Capable of giving signed informed consent

Exclusion Criteria:

Participants are excluded from the study if any of the following criteria apply:

Medical conditions

• Primary refractory MM defined as participants who never achieved at least a minimalresponse with any treatment during the disease course

• Second primary malignancy

Participants with RRMM (Part 1a, 2, and 3a)

• For MM participants, primary systemic LCA and plasma cell leukemia

• For MM participants, congestive heart failure (New York Heart Association [NYHA])Grade ≥II; cardiomyopathy, active ischemia, or any other uncontrolled cardiaccondition

Participants with RR LCA (Part 1b and 3b)

• For LCA participants, evidence of clinically significant cardiovascular condition,defined as one or more of the following:

1. N-terminal prohormone of brain natriuretic peptide (NT-proBNP) >8500 ng/mL

2. New York Heart Association (NYHA) classification III or IV heart failure

3. Heart failure that, in the opinion of the Investigator, is not primarilyrelated to LCA cardiomyopathy (including, but not limited to, ischemic heartdisease, uncorrected valvular disease, infections)

4. Prior event (history) in the last 6 months of acute coronary syndrome,myocardial infarction or unstable angina as well as participants who during thelast 6 months experienced a percutaneous cardiac intervention with stent and/ora coronary artery bypass

5. Hospitalization in the last 4 weeks prior to treatment related to acardiovascular event

6. Participants with prior history of arrhythmia and/or cardiac conductiondisorders for which a pacemaker or an implantable cardioverter defibrillator (ICD) is required but has not been placed. This includes, but may not belimited to, sustained ventricular tachycardia, association of anatrioventricular, or sinoatrial nodal dysfunction

• For LCA participants, a systolic blood pressure <100 mmHg or a diastolic bloodpressure <55 mmHg.

• For LCA participants: previous or current diagnosis of symptomatic MM, including thepresence of lytic bone disease, plasmacytomas, ≥60% plasma cells in the BM, orhypercalcemia.

All participants

• Uncontrolled infection within 14 days prior to study treatment.

• Known acquired immunodeficiency syndrome-related illness or known humanimmunodeficiency virus (HIV) disease requiring antiviral treatment or activehepatitis A (defined as positive hepatitis A antigen or positive IgM); HIV serologyat screening will be tested for participants in countries where it is required bylocal regulations.

• Uncontrolled or active hepatitis B virus (HBV) infection: participants with positiveB surface antigen (HBsAg) and/or HBV deoxyribonucleic acid (DNA)

• Active hepatitis C virus (HCV) infection: positive HCV ribonucleic acid (RNA) andnegative anti-HCV.

Prior/concomitant therapy

• Any anti-MM drug treatment within 14 days before study treatment

• Prior allogenic hematopoietic stem cell (HSC) transplant with activegraft-versus-host disease (GvHD) (GvHD any grade and/or being underimmunosuppressive treatment within the last 2 months prior to first IMP).

• Any major procedure within 14 days before the initiation of the study treatment

• Administration of an anti-CD38 monoclonal antibody (isatuximab or daratumumab) lessthan 90 days prior to the first administration of study treatment.

• Administration of an anti-BCMA agent (including, but not limited to, CAR T-cells,TCEs, antibody drug conjugate) less than 21 days prior to the administration ofstudy treatment.

• Unresolved toxicities from prior anticancer therapy, defined as not having resolvedto CTCAE Version 5.0 Grade 1, at the exception of residual Grade 2 peripheralneurotoxicity related to bortezomib and/or thalidomide and considered as stable.

• Participants with a contraindication to dexamethasone.

Prior/concurrent clinical study experience

• Received any other investigational drugs or prohibited therapy for this study within 28 days or 5 half-lives from study treatment, whichever is shorter

Diagnostic assessments

• Hemoglobin <8 g/dL (5.0 mmol/L)

• Platelets <50 × 10^9/L (not permissible to transfuse a participant within 1 weekprior to the screening platelet count to reach this level).

• Absolute neutrophil count (ANC) <1000 μL (1 × 10^9/L).

• Creatinine clearance <30 mL/min (Modification of Diet in Renal Disease Formula).

• Total bilirubin >1.5 × upper limit of normal (ULN) (unless the subject hasdocumented Gilbert syndrome in which case direct bilirubin should not be >2.5 ×ULN).

• Aspartate aminotransferase (AST/SGOT) or Alanine aminotransferase (ALT/SGPT) >2.5 ×ULN.

• Participants with Grade 3 or 4 hypercalcemia (corrected serum calcium of >12.5mg/dL; >3.1 mmol/L; ionized calcium >1.6 mmol/L; or requiring hospitalization) willnot be eligible unless participants recover to Grade 2 or less underanti-hypercalcemia treatment.

Other exclusions

• Individuals accommodated in an institution because of regulatory or legal order;prisoners or participants who are legally institutionalized

• Participant not suitable for participation, whatever the reason, as judged by theInvestigator

• Sensitivity to any of the study interventions, or components thereof, or drug orother allergy that, in the opinion of the Investigator, contraindicatesparticipation in the study.