The purpose of this study is to determine the safety, tolerability, pharmacokinetics and pharmacodynamics of a single dose of ALN-TTR01 in patients with transthyretin (TTR) mediated amyloidosis (ATTR).

Inclusion Criteria:

• Diagnosis of TTR amyloidosis
• Adequate blood counts, liver and renal function
• Women of child-bearing potential must have a negative pregnancy test, cannot be breast feeding, and must use an adequate method of birth control
• Males agree to use appropriate contraception
• Willing and able to comply with protocol-required visit schedule and visit requirements and provide written informed consent.

Exclusion Criteria:

• Known human immunodeficiency virus (HIV) positive status
• Receiving antibiotics for bacterial infection within 7 days of screening
• Known or suspected systemic viral, parasitic or fungal infection
• Receiving an investigational agent within 30 days prior to study drug administration
• Poor cardiac function
• Considered unfit for the study by the Principal Investigator
• Known sensitivity to oligonucleotides
• Employee or family member of the sponsor or the clinical study site personnel.