Overview

The purpose of this study is to:

• evaluate the safety, tolerability, pharmacokinetics (PK) and pharmacodynamics (PD) of single ascending doses of ALN-6400 in healthy volunteers
• evaluate the efficacy, safety, tolerability and PD of multiple doses of ALN-6400 in adult patients with HHT

Eligibility

Inclusion Criteria -

Part A:

• Is a healthy adult volunteer

Part B:

• Is an adult patient with a clinical diagnosis of HHT

Exclusion Criteria -

Part A:

• Has alanine aminotransferase (ALT) or aspartate aminotransferase (AST) \> upper limit of normal (ULN)
• Has known human immunodeficiency virus (HIV) infection; or known current or chronic hepatitis C virus or hepatitis B virus infection
• Has an estimated glomerular filtration (eGFR) of \<90 mL/min/1.73m\^2 at screening

Part B:

• Has ALT or AST \>2×ULN
• Has total bilirubin \>1.5×ULN
• Has eGFR of \<30 mL/min/1.73m\^2 at screening

Parts A and B:

• Is not willing to comply with the contraceptive requirements during the study period

Note: other protocol defined inclusion / exclusion criteria apply