This is a two-part study, intended to investigate the safety, tolerability, characteristics of PK and PD of single SC dose of SRSD384 alone in overweight or obese participants (Part A) and in combination with tirzepatide in overweight or obese participants with T2DM (Part B).

Inclusion Criteria:

• Able to comprehend and willing to sign an informed consent form (ICF) and to abide by the study restrictions;
• Males or females;
• Body mass index (BMI) between 27.0 and 40.0 kg/m2, inclusive;
• Male subjects are not allowed to donate sperm, and female subjects are not allowed to donate eggs from the time the ICF is signed until at least 3 months after the last follow-up.

Exclusion Criteria:

• Obesity attributable, in the investigator's opinion, to medication use, endocrinologic or monogenic disorders;
• Having a significant medical history or clinical manifestations related to any allergic, dermatological, hepatic, renal, hematological, pulmonary, cardiovascular, gastrointestinal, neurological, respiratory, endocrine (other than overweight or obesity), or psychiatric conditions that are severe or unstable (determined by the investigator or medically qualified designee);
• Evidence of active cancer within 2 years prior to screening (non-melanoma skin cancer, localized prostate cancer treated with curative intent, or other in situ carcinoma that does not require systemic therapy and is considered cured for at least 1 year is allowed);
• Acute febrile illness within 7 days prior to randomization or evidence of active infection
• Any major surgery within 3 months prior to screening or plan to have any major surgery during the study;
• History of clinically significant hypersensitivity, intolerance, or allergy to any oligonucleotide or GalNAc as determined by the investigator;
• Receipt of an investigational drug within 30 days or 5 half-lives of that drug, whichever is longer, prior to dose administration in this study;
• Have previously completed or withdrawn from this study or any other study investigating SRSD384 and have previously received SRSD384.