A Study of TAK-951 in Healthy Adults

Feeling sick in the stomach (nausea) or throwing up (vomiting) are among the most common symptoms during treatment with medicines. It is hoped that a medicine called TAK-951 may help people to not feel sick in the stomach or throw up. The main aim of this study is to learn about side effects of TAK-951 when given as a single or multiple doses to healthy adults. Side effects are medical problems thought to be caused by the study treatment. Another aim is to learn how a healthy adult's body processes TAK-951 (this is called pharmacokinetics or PK). In this study, participants will receive either TAK-951 or placebo. The placebo looks like TAK-951 but does not have any medicine in it. Both TAK-951 and placebo will be given as an injection directly under the skin. This is called subcutaneous or subcutaneous (SC). The study will be conducted in 3 parts: * In Part 1, participants will be given one SC injection of either TAK-951 or placebo. * In Part 2, participants will receive up to three daily SC injections of either TAK-951 or placebo of the same dose * In Part 3, participants will receive one SC injection of either TAK-951 or placebo and another SC injection up to 1 week later. Participants will be checked for their health either 28 days after the last injection (Parts 1 and 2) or 14 days after the last injection (Part 3).