Has received prior systemic anticancer treatment, including investigational agents, within 5 half-lives or 4 weeks prior to the first dose of study treatment (whichever is shorter). Has received Traditional Chinese Medication within 7 days prior to study treatment.

Participants who have received major surgery (defined as requiring general anesthesia and >24-hour inparticipant hospitalization) within 4 weeks prior to the first dose of study treatment. Participant must have recovered adequately from complications from the intervention prior to starting study treatment.

Has received prior radiotherapy within 2 weeks of start of study treatment or have had a history of radiation pneumonitis.

Note: Participants must have recovered from all radiation-related toxicities and not require corticosteroids. A 1-week washout is permitted for palliative radiation (≤2 weeks of radiotherapy) to non-CNS disease.

Has had an allogeneic tissue/solid organ transplant.

Has a diagnosis of immunodeficiency or is receiving chronic systemic steroid therapy (in dosing exceeding 10 mg daily of prednisone equivalent) or any other form of immunosuppressive therapy within 7 days prior the first dose of study drug.

Has known active CNS metastases and/or carcinomatous meningitis. Participants with previously treated brain metastases may participate provided they are radiologically stable (ie, without evidence of progression) for at least 4 weeks as confirmed by repeat imaging performed during the study screening, are clinically stable and have not required steroid treatment for at least 14 days before the first dose of study treatment.

Has clinically uncontrolled pericardial effusion, pleural effusion, or ascites at screening.

Has a history of (non-infectious) pneumonitis / interstitial lung disease that required steroids or has current pneumonitis / interstitial lung disease.

Active viral infection requiring systemic therapy during the screening period.

Hypertension that cannot be well-controlled with medical treatment. Not well-controlled is defined as systolic blood pressure >150 mmHg or diastolic blood pressure >95 mmHg (adjustment of hypertensive medication prior to study initiation is permitted, but the mean of the most recent three consecutive blood pressure records prior to study entry must be ≤150/95 mmHg \[with at least 2- minute interval between each measurement\]).

Cardiovascular disease of clinical significance: Including New York Heart Association \[NYHA\] Class II-IV, congestive heart failure, second-degree or higher heart block, myocardial infarction within the past 3 months, unstable arrhythmia or unstable angina, marked QT interval prolongation (12-lead ECG showing baseline-corrected QTc interval >480 ms), cerebral infarction within 3 months, or having received PTCA or CABG within 6 months.

Participants with active or chronic corneal disorders, with other active ocular conditions requiring ongoing therapy or with any clinically significant corneal disease that prevents adequate monitoring of drug-induced keratopathy.

Participants with any active infection that requires systemic anti-infective therapy judged by the investigators.

Has a known additional malignancy that is progressing or has required active treatment within the past 3 years.

Note: Participants with basal cell carcinoma of the skin, squamous cell carcinoma of the skin, or carcinoma in situ, excluding carcinoma in situ of the bladder, that have undergone potentially curative therapy are not excluded. Participants with low-risk early-stage prostate cancer (T1-T2a, Gleason score ≤6, and PSA <10 ng/mL) either treated with definitive intent or untreated in active surveillance with stable disease are not excluded.

Grade 2 or higher peripheral neuropathy. Other toxicities caused by prior anti-tumor therapy has not recovered to ≤ grade 1 (per CTCAE 5.0) (except for alopecia, pigmentation, and other events judged by the Investigator to be tolerable) or the level specified by the inclusion/exclusion criteria in this study.

Note: Participants with endocrine-related AEs Grade ≤2 requiring treatment or hormone replacement may be eligible.

Received any prior immunotherapy and was discontinued from that treatment due to a Grade 3 or higher irAE (except endocrine disorders that can be treated with replacement therapy) or was discontinued from that treatment due to Grade 2 myocarditis or recurrent Grade 2 pneumonitis.

Known severe hypersensitivity or delayed hypersensitivity (≥Grade 3) reactions to the same class and/or any components of BC3195 or pembrolizumab.

Participants who received strong CYP3A4 inhibitors or strong CYP3A4 inducers within 14 days, before the first dose of the study treatment (refer to Appendix 7 for a list of strong CYP3A4 inhibitors and inducers).

Has received a live or live-attenuated vaccine within 30 days prior to the first dose of study intervention, or planned to receive live or live-attenuated vaccine during the screening. Administration of killed vaccines are allowed.

Has a history or current evidence of any condition, therapy, or laboratory abnormality, or other circumstance that might confound the results of the study or interfere with the participant's participation for the full duration of the study, such that it is not in the best interest of the participant to participate, in the opinion of the treating investigator.

Pregnant or breastfeeding or planning to become pregnant; a positive blood pregnancy test within 7 days prior to the first dose of study treatment.

Participants with poor compliance, who are unwilling to or unable to follow study procedures.

Has received radiation therapy to the lung that is >30 Gy within 6 months of the first dose of study treatment for participants with NSCLC.