A Study to Look at How Safe a New Medicine (NNC0491-6075) is in Healthy People and in Participants With High Levels of Fat in the Blood

The study is testing a new study medicine to treat people with high levels of fat in the blood. The main aim of the study is to see if the new study medicine is safe and how it works in the body. Participants will either get NNC0491-6075 (the new study medicine) or placebo (a "dummy medicine" without active ingredients). Which treatment participants get is decided by chance. NNC0491-6075 is a new medicine which cannot be prescribed by doctors. The study has 3 parts (Part A, Part B and Part C). In Part A, investigators look at the effect of the study medicine after a single dose in healthy participants. Participants will get the study medicine either as injection(s) under the skin or as an infusion into a vein by the study staff. In Part B, investigators look at the effect of receiving the study medicine once weekly for four weeks in participants with high levels of fat in the blood but who are otherwise healthy. Participants will get the study medicine as injections under the skin by the study staff. In Part C, investigators look at the effect of the study medicine after a single dose in healthy participants of Japanese origin. Participants will get the study medicine either as injection(s) under the skin or as an infusion into a vein by the study staff. The study will last for about 18 months in total for Part A, Part B and Part C. Participants in Part A and Part C will be in the study for about 139 days each, from screening to the final visit while in Part B they will be in the study for about 160 days from screening to the final visit.