This study is looking at a new drug called ALN-KHK to understand how safe it is and how it works in the body. The study has two parts. In Part A, the study is for healthy people who are overweight. In Part B, it's for people who are obese with Type 2 Diabetes (T2DM). They will test both single doses and multiple doses of the drug.

Eligibility: To join, you need to have a stable thyroid (hormone that helps control your body's energy), and your body mass index (BMI) must be in a certain range. BMI is a number that tells us if you are underweight, normal weight, overweight, or obese. In Part A, your BMI should be between 27 and 34.9. For Part B, your BMI should be between 30 and 39.9, and you should have T2DM with a specific blood sugar level (HbA1c between 7.5% and less than 10%).

• The study will check how safe the drug is and how it affects the body.
• You cannot join if you've taken another study drug in the last 30 days.
• Part A is for non-diabetics, while Part B is specifically for those with Type 2 Diabetes.