This study is testing a new medicine called **AZD0780** to see if it can help lower "bad" cholesterol, known as **LDL-C**, in people who have or are at risk of heart disease (called **ASCVD**). ASCVD stands for Atherosclerotic Cardiovascular Disease, which includes heart attacks and strokes. The study will compare AZD0780 to a placebo (a pill with no medicine) to check its effectiveness and safety. The study lasts for about **56 weeks** in total. *Key Points:* 1. **Duration:** The study lasts for about 1 year, with medication given for 52 weeks. 2. **Participation:** Participants won't know if they receive the real medicine or a placebo. 3. **Eligibility:** Adults 18+ with high LDL-C and either a history of or risk for ASCVD can join. Participants will take a pill once daily and will need to visit the study site regularly. The study is happening in many countries, and about 2800 people will take part. Your safety and health will be monitored closely throughout the study.