A Phase 3, Double-Blind, Multicenter Study to Evaluate the Efficacy and Safety of CAEL-101 and Plasma Cell Dyscrasia Treatment Versus Placebo and Plasma Cell Dyscrasia Treatment in Plasma Cell Dyscrasia Treatment-Naïve Patients with Mayo Stage IIIb AL Amyloidosis

AL (or light chain) amyloidosis begins in the bone marrow where abnormal proteins misfold and
create free light chains that cannot be broken down. These free light chains bind together to
form amyloid fibrils that build up in the extracellular space of organs, affecting the
kidneys, heart, liver, spleen, nervous system and digestive tract.

The primary purpose of this study is to determine whether CAEL-101, a monoclonal antibody
that removes AL amyloid deposits from tissues and organs, improves overall survival and it is
safe and well tolerated in patients with stage IIIb AL amyloidosis.

Key Inclusion Criteria:

- AL amyloidosis stage IIIb based on the European Modification of the 2004 Standard Mayo
Clinic Staging (NT-proBNP > 8,500 ng/L) at the time of Screening

- Measurable hematologic disease at Screening as defined by at least one of the
following:

1. Involved/uninvolved free light chain difference (dFLC) > 4 mg/dL or

2. Involved free light chain (iFLC) > 4 mg/dL with abnormal Kappa/Lambda ratio or

3. Serum protein electrophoresis (SPEP) m-spike > 0.5 g/dL

- Histopathological diagnosis of amyloidosis based on polarizing light microscopy of
green bi-refringent material in Congo red stained tissue specimens AND confirmation of
AL derived amyloid deposits by at least one of the following:

1. Immunohistochemistry/Immunofluorescence or

2. Mass spectrometry or

3. Characteristic electron microscopy appearance/Immunoelectron microscopy

- Cardiac involvement as defined by:

1. Documented clinical signs and symptoms supportive of a diagnosis of heart failure
in the setting of a confirmed diagnosis of AL amyloidosis in the absence of an
alternative explanation for heart failure AND

2. At least one of the following:

i. Endomyocardial biopsy demonstrating AL cardiac amyloidosis or ii. Echocardiogram
demonstrating a mean left ventricular wall thickness (calculated as [IVSd+LPWd]/2) of
> 12 mm at diastole in the absence of other causes (e.g., severe hypertension, aortic
stenosis), which would adequately explain the degree of wall thickening or iii.
Cardiac magnetic resonance imaging (MRI) with gadolinium contrast agent diagnostic of
cardiac amyloidosis

- Planned first-line treatment for plasma cell dyscrasia is
cyclophosphamide-bortezomib-dexamethasone (CyBorD)-based regimen administered as SoC

- Women of childbearing potential (WOCBP) must have a negative pregnancy test during
Screening and must agree to use highly effective contraception from Screening to at
least 5 months following the last study drug administration or 12 months following the
last dose of her PCD therapy, whichever is longer

- Men must be surgically sterile or must agree to use highly effective contraception and
refrain from donating sperm from Screening to at least 5 months following the last
study drug administration or 12 months following the last dose of their PCD therapy,
whichever is longer

Key Exclusion Criteria:

- Have any other form of amyloidosis other than AL amyloidosis

- Received prior therapy for AL amyloidosis or multiple myeloma. A maximum exposure of 2
weeks of a CyBorD-based PCD treatment after Screening laboratory samples are obtained
and prior to randomization is allowed

- Has POEMS (plasma cell dyscrasia with polyneuropathy, organomegaly, endocrinopathy,
monoclonal protein and skin changes) syndrome or multiple myeloma defined as clonal
bone marrow plasma cells > 10% from a bone marrow biopsy (performed ≤ 3 months prior
to signing the ICF) or biopsy-proven (performed ≤ 3 months prior to signing the ICF)
bony or extramedullary plasmacytoma AND one or more of the following CRAB features:

a. Evidence of end organ damage that can be attributed to the underlying plasma cell
proliferative disorder (e.g., multiple myeloma and POEMS syndrome), specifically: i.
Hypercalcemia: serum calcium > 0.25 mmol/L (> 1 mg/dL) higher than the ULN or > 2.75
mmol/L (> 11 mg/dL) OR ii. Renal insufficiency: creatinine clearance < 40 mL per
minute or serum creatinine > 177 mol/L (> 2 mg/dL) OR iii. Anemia: hemoglobin value of
> 20 g/L below the lowest limit of normal, or a hemoglobin value < 100 g/L OR iv. Bone
lesions: one or more osteolytic lesion on imaging tests (performed ≤ 3 months prior to
signing the ICF): skeletal radiography, CT, or PET/CT, or MRI. If bone marrow has <
10% clonal plasma cells, more than one bone lesion is required to distinguish from
solitary plasmacytoma with minimal marrow involvement OR b. Any one of the following
biomarkers of malignancy: i. 60% or greater clonal plasma cells on bone marrow
examination OR ii. More than one focal lesion on MRI that is at least 5mm or greater
in size

- Have supine systolic blood pressure < 90 mmHg or symptomatic orthostatic hypotension,
defined as a decrease in systolic blood pressure upon standing of > 30 mmHg despite
medical management (e.g., midodrine, fludrocortisones) in the absence of volume
depletion