A Study of Daratumumab-Based Therapies in Participants With Amyloid Light Chain (AL) Amyloidosis

Inclusion Criteria:

• Cohort 1: Cardiac involvement (amyloid light chain [AL] amyloidosis Mayo CardiacStage II and Stage IIIa) with or without other organ(s) involved; Cohort 2: One ormore organs impacted by systemic AL amyloidosis according to consensus guidelines

• Eastern Cooperative Oncology Group (ECOG) Performance Status score of 0, 1 or 2

• A female participant of childbearing potential must have a negative serum or urinetest at screening and within 72 hours of the first dose of study treatment and mustagree to further serum or urine pregnancy tests during the study

• A male participant must agree not to donate sperm for the purpose of reproductionduring the study and for a minimum of 6 months after receiving the last dose ofcyclophosphamide or 100 days after discontinuation of daratumumab, whichever islonger

• Cohort 2 only: self-identified racial and ethnic minorities, including Black orAfrican American

• Measurable disease at screening defined by one of the following:

Difference between iFLC and uninvolved FLC (dFLC) >= 40mg/L per central laboratory Serum involved free light chain (iFLC) >= 40 mg/L with an abnormal kappa:lambda ratio Serum M-protein >= 0.5 g/dL

Exclusion Criteria:

• Prior therapy for systemic AL amyloidosis or multiple myeloma including medicationsthat target cluster of differentiation 38 (CD38), with the exception of 160milligrams(mg) dexamethasone or equivalent corticosteroid maximum exposure prior torandomization/enrollment

• Previous or current diagnosis of symptomatic multiple myeloma, including thepresence of lytic bone disease, plasmacytomas, >=60% plasma cells in the bonemarrow, or hypercalcemia related to myeloma.

• Participant received any of the following therapies:

1. treatment with an investigational drug or used an invasive investigationalmedical device within 14 days or at least 5 half-lives, whichever is less;

2. vaccinated with an investigational vaccine (except for COVID-19) live,attenuated or replicating viral vector vaccines less than (<) 4 weeks prior torandomization/enrollment. Participants who are taking strong Cytochrome P450 3A4(CYP3A4) inducers must discontinue their use at least 5 half-lives prior tothe first dose of bortezomib

• Stem cell transplantation -Planned stem cell transplant during the first 9 cycles ofprotocol therapy are excluded. Stem cell collection during the first 9 cycles ofprotocol therapy is permitted

• Grade 2 sensory or Grade 1 painful peripheral neuropathy