A Study to Evaluate ALN-4324 in Overweight to Obese Healthy Volunteers and in Overweight to Obese Patients With T2DM

The purpose of this study is to: * evaluate the safety and tolerability of single ascending doses of ALN-4324 in healthy volunteers and to characterize the single-dose PK of ALN-4324 * evaluate the efficacy, safety, tolerability, and pharmacodynamics (PD) of multiple doses of ALN-4324 in adult overweight to obese patients with T2DM

Inclusion Criteria: Part A: * Has a body mass index (BMI) of ≥27 kg/m\^2 and \<40 kg/m\^2 Part B: * Is an adult patient with a confirmed diagnosis of T2DM * Has a hemoglobin A1c (HbA1c) ≥7% to \<10.5% * Has a BMI of ≥25 kg/m\^2 and \<45 kg/m\^2 * Is on a stable dose of either metformin or metformin and a sodium-glucose cotransporter 2 inhibitor (SGLT2i) Exclusion Criteria: Part A: * Has known human immunodeficiency virus (HIV) infection; or known current or chronic hepatitis C virus or hepatitis B virus infection Part B: * Receiving therapies for chronic weight management or antidiabetic medications other than metformin and SGLT2i Note: other protocol defined inclusion/exclusion criteria apply