after joining the study, you will undergo a series of baseline examinations that include medical history review, physical examination, blood tests, and imaging studies to document the current status of your lung cancer.

the purpose of these assessments is to provide reference data for later comparisons during the trial.

based on the baseline information, you will be assigned by a computer system to one of three groups: the combination group, the monotherapy group, or the placebo group.

the assignment is random and you will not know which group you belong to.

if you are placed in the combination group, you will receive pembrolizumab 790 mg administered by subcutaneous injection and mRNA-4157 1 mg administered by intramuscular injection on the same day.

if you are placed in the monotherapy group, you will receive only mRNA-4157 1 mg by intramuscular injection.

if you are placed in the placebo group, you will receive injections that look identical to the active drugs but contain no active substance.

you will continue to receive the assigned injections according to the study schedule.

each cycle will include the same dosage as the first dose: 790 mg of pembrolizumab subcutaneously for participants in the combination group and 1 mg of mRNA-4157 intramuscularly for participants in the combination or monotherapy groups.

the interval between cycles is defined by the trial protocol and will be explained to you by the study staff.

at scheduled intervals you will attend clinic visits for clinical evaluation, repeat blood tests, and imaging studies to monitor the status of your disease.

quality‑of‑life questionnaires will be completed to assess any changes in your well‑being.

during each visit you will be asked about any new symptoms or side effects.

all reported events will be recorded and evaluated by the study physicians.

if a serious adverse event occurs, the investigator may decide to discontinue the study medication for safety reasons.

treatment will stop after the pre‑defined number of cycles, or earlier if disease progression, unacceptable toxicity, or withdrawal from the study occurs.

you will be informed of the reason for treatment discontinuation.

after the end of treatment you will continue to attend periodic visits for up to several years.

these visits aim to assess disease‑free survival, overall survival, and any late side effects.

the schedule of follow‑up visits is determined by the study protocol.