A Clinical Trial of MK-8644 in Healthy Participants and Participants With Psoriasis (MK-8644-001)

The purpose of this trial is to learn about a trial medicine called MK-8644. This trial is the first time researchers will give MK-8644 to people. This trial will help researchers learn about the safety of MK-8644 and if participants tolerate it. Tolerate means participants will receive MK-8644 in the trial unless they need to stop it due to health problems.

Inclusion Criteria: The main inclusion criteria include but are not limited to the following: * Is in good health * Has a BMI between 18 and 36 kg/m\^2, inclusive Exclusion Criteria: The main exclusion criteria include but are not limited to the following: * Has a history of clinically significant endocrine, GI, cardiovascular, hematological, hepatic, immunological, renal, respiratory, genitourinary, or major neurological (including stroke and chronic seizures) abnormalities or diseases. * Has a history of cancer. * Has a history of significant multiple and/or severe allergies. * Has positive test(s) for hepatitis B surface antigen (HBsAg), hepatitis C antibodies, tuberculosis, or HIV.