after joining the study, a written consent form is signed to confirm understanding of the trial requirements.

baseline health information and medical history are recorded.

initial examinations include physical measurements, laboratory tests, and endoscopic evaluation of the colon.

the modified mayo score, which measures ulcerative colitis activity, is calculated.

participants are assigned, by a computer system, to receive either mk-8690 or a placebo without knowing which one is administered.

the assignment is double‑blind, meaning neither the participant nor the study staff knows the group assignment.

the study drug is given by subcutaneous injection, which means the medication is injected into the tissue under the skin.

the injection contains a solution with a concentration of 00 % (v/v) of mk-8690 for participants in the active group; the placebo injection contains no active substance.

the specific schedule (how often the injection is given) and the total duration are defined by the study protocol and continue until the assessment at week 12.

participants attend scheduled clinic visits for safety checks, laboratory tests, and symptom review.

any adverse events, which are unwanted medical occurrences, are recorded at each visit.

the study staff may perform additional endoscopic examinations as required by the protocol.

if the protocol includes an interim evaluation, participants may undergo a brief assessment of disease activity before the final visit.

at the end of the 12‑week treatment period, a comprehensive evaluation is performed.

the primary outcome is the proportion of participants achieving clinical remission according to the modified mayo score.

secondary outcomes include clinical response, endoscopic improvement, and safety measures such as adverse events.

after the final assessment, participants may have a post‑study follow‑up visit to ensure continued safety.

study medication is discontinued, and participants receive standard medical care as directed by their own physicians.