This is a multicenter, open-label, phase II study to evaluate the safety, tolerability, clinical activity, and pharmacokinetics of ILKN421H in combination with pembrolizumab in participants with locally advanced or metastatic NSCLC.

The study consists of 4 cohorts in participants with locally advanced or metastatic NSCLC ( squamous [sq] or non-squamous [non-sq]) without functional genomic alterations including EGFR, ALK and Ros-1, who failed systemic PD-1/L1 inhibitor treatment either alone or in combination with standard chemotherapy (post-IO) (Cohort 1 and 2), or without any prior systemic anti-cancer therapy (1L) with PDL-1 TPS ≥1% (Cohort 3 and 4). Participants will be dosed either with 1.6 mg of ILKN421H (Cohort 1 and Cohort 3) or 2.4 mg of ILKN421H (Cohort 2 and Cohort 4) in combination with 200 mg pembrolizumab. Both treatments will be administered through intravenous (i.v.) infusion every 3 weeks (Q3W) on Day 1 of each cycle with 21-day as one cycle, while ILKN421H will be dosed 4 hours after pembrolizumab. All 4 cohorts will have 3 study periods:

• Screening Period: ≤ 28 days prior to first dose of study treatment;
• Treatment period: 21-day cycles until unacceptable toxicity, lost to follow-up, disease progression, withdrawal of consent, death, or the sponsor closes the study, whichever occurs first;
• Follow-up Period: 30-day safety follow-up and a Long-Term follow-up every 6-month for survival information.

Inclusion Criteria:

To be enrolled in this study, participants must meet all the following inclusion criteria:

1. Provide written informed consent after full understanding of the study.

2. Adults at least 18 years of age.

3. ECOG performance status of 0 or 1.

4. Life expectancy ≥12 weeks.

5. At least one measurable lesion per iRECIST/RECIST 1.1 criteria, defined as:

   Lymph node lesion with short axis ≥1.5 cm or non-lymph node lesion with longest diameter ≥1 cm on CT/MRI; If the only lesion has undergone prior local treatment (radiotherapy, ablation, vascular intervention, etc.), there must be clear imaging evidence of disease progression in this lesion after local treatment.

6. Participants must have locally advanced or metastatic NSCLC, confirmed by available pathology records or current biopsy, that is advanced (non-resectable), or recurrent, for which no alternative, curative standard therapy exists. For Cohort 1 and Cohort 2, pathologically or cytologically confirmed advanced malignant locally advanced or metastatic NSCLC participants who have failed standard PD-1/L1 inhibitor alone or in combination with standard chemotherapy treatment regardless of PD-L1 expression. For Cohort 3 and Cohort 4, participants with pathologically or cytologically confirmed advanced, non-resectable locally advanced or metastatic NSCLC, who have previously untreated with any anticancer drugs expressing PD-L1 (TPS≥ 1%) as determined by an FDA-approved test.

7. Adequate organ and marrow function within 7 days before first dose, as defined below:

   1. Absolute neutrophil count (ANC) ≥1.5×10⁹/L
   2. Platelets (PLT) ≥100×10⁹/L
   3. Hemoglobin (HGB) ≥90 g/L
   4. Alanine aminotransferase (ALT) ≤2.5×ULN (≤5×ULN if known liver involvement)
   5. Aspartate aminotransferase (AST) ≤2.5×ULN (≤5×ULN if known liver involvement)
   6. Total bilirubin (TBIL) ≤1.5×ULN (≤3.0×ULN if diagnosed with Gilbert's syndrome)
   7. Serum creatinine ≤1.5×ULN or estimated glomerular filtration rate (eGFR, calculated by Cockcroft-Gault formula or 24-hour urine measurement) ≥40 mL/min
   8. International normalized ratio (INR) ≤1.5 and activated partial thromboplastin time (APTT) ≤1.5×ULN No component blood transfusion within 14 days prior to the above testing, and no supportive treatments (e.g., G-CSF, TPO, TPO receptor agonists, IL-11, EPO) within 7 days of above testing.

8. For Cohort 1 and Cohort 2, prior anti-tumor treatment-related toxicities resolved to ≤ Grade 1 (excluding Grade 2 neurotoxicity, Grade 2 hypothyroidism, any grade alopecia and pigmentation, and Grade 2 AEs that cannot resolve to ≤Grade 1 but remain stable long-term as judged by the investigator based on clinical practice; laboratory parameters refer to Inclusion Criteria 7).

9. Willing and able to comply with study schedules and all protocol requirements.

10. Women must meet one of the following criteria: postmenopausal for at least 24 consecutive months; surgically incapable of bearing children (i.e., have had a hysterectomy or bilateral oophorectomy); or utilizing a reliable form of contraception (either medication [oral, implant, or injection] or a barrier method). In general, the decision for appropriate methods to prevent pregnancy should be determined by discussions between the investigator and the participant to use a reliable form of contraceptive during the study Treatment Period and for at least 70 days following the last dose of study drug (Appendix IV). Women must have a negative serum or urine pregnancy test (minimum sensitivity 25 IU/L or equivalent units of HCG) within 72 hours prior to the start of investigational product; and Men must agree to the use of contraception during the study Treatment Period and for at least 180 days after the last dose of study drug.

Exclusion Criteria:

To be included in this study, participants must not meet any of the following exclusion criteria:

1. Known allergy to any component of the investigational drug formulation or IL-2.

2. Participation in any therapeutic clinical study and receiving treatment within 28 days prior to the first dose, excluding observational studies or survival follow-up stages of interventional studies.

3. Use of immunomodulatory drugs within 14 days or 5 half-life (whichever is longer) before the first dose, including but not limited to thymosin, IL-2, IL-15, interferon, etc.

4. Received chimeric antigen receptor T-cell (CAR-T) immunotherapy within 3 months prior to the first dose; chemotherapy (≥6 weeks for nitrosoureas and mitomycin C, ≥14 days for oral fluoropyrimidines), endocrine therapy, targeted therapy (with a washout period of 14 days or 5 half-lives, whichever is longer), immunotherapy (see exclusion criterion 3 for immunomodulatory drugs), tumor embolization, etc., within 28 days prior to the first dose; radiotherapy within 14 days before the first dose, except for palliative radiotherapy, which must be completed at least 7 days prior to the first dose; Exceptions may be allowed if, based on investigator assessment, the subject is still eligible for enrollment.

5. Major surgery within 28 days prior to the first dose or minor surgery within 7 days prior to the first dose, or having unhealed wounds, ulcers, or fractures, or requiring elective surgery during the study (except for diagnostic biopsy or insertion of vascular access devices).

6. Vaccination with live attenuated vaccines within 28 days prior to the first dose or planned during the study.

7. Use of systemic immunosuppressive agents within 28 days prior to the first dose, except for:

   1. Intranasal or localized corticosteroids (e.g., intra-articular injection);
   2. Systemic corticosteroids ≤ 10 mg/day prednisone or equivalent dose;
   3. Corticosteroids for preventing allergic reactions (e.g., pre-chemotherapy);
   4. Corticosteroids for preventing infusion reactions;

8. Known or confirmed central nervous system (CNS) metastases or carcinomatous meningitis during screening.

9. Uncontrolled third-space fluid accumulation requiring repeated drainage, such as pleural effusion, ascites, pericardial effusion, etc. (participants without the need for drainage or who have not had significant accumulation after ceasing drainage for 3 days can be included), or blood-tinged third-space fluid confirmed by diagnostic aspiration.

10. History of any other malignant tumors within 5 years prior to the first dose, except for cured early-stage malignancies (e.g., carcinoma in situ or stage I tumors), such as adequately treated basal or squamous cell carcinoma of the skin, surgically resected carcinoma in situ of the cervix or breast, early-stage papillary thyroid carcinoma, or prostate cancer with a Gleason score ≤ 6.

11. Active autoimmune diseases or inflammatory diseases [including inflammatory bowel disease (e.g., ulcerative colitis or Crohn's disease), diverticulitis (excluding diverticular disease), celiac disease, systemic lupus erythematosus, sarcoidosis, Wegener's granulomatosis, Graves' disease, rheumatoid arthritis, pituitary inflammation, uveitis, etc.], or a history of such diseases within the past 2 years (participants with conditions such as vitiligo, psoriasis, alopecia, or controlled hypothyroidism or type 1 diabetes requiring only thyroid hormone replacement or insulin therapy are allowed).

12. Active or uncontrolled HBV (HBsAg positive and/or HBcAb positive with positive HBV DNA), HCV (HCV-Ab positive with positive HCV RNA), or HIV positive.

13. Active bacterial, viral, or fungal infection within 72 hours prior to the first dose (defined by persistent signs/symptoms of infection despite appropriate treatment) or requiring intravenous (i.v.) antibiotics therapy.

14. Severe or uncontrolled cardiovascular or cerebrovascular diseases requiring treatment, including but not limited to:

    1. New York Heart Association (NYHA) Class > 2 heart failure (Appendix II);
    2. Unstable angina uncontrolled by medication;
    3. Myocardial infarction within 6 months prior to the first dose;
    4. History of myocarditis;
    5. Pericardial tamponade;
    6. Uncontrolled arrhythmia (e.g., ventricular tachycardia during antiarrhythmic treatment-participants with grade I atrioventricular block or asymptomatic left bundle branch block/right bundle branch block are not excluded);
    7. QTcF > 470 msec on 12-lead ECG;
    8. Left ventricular ejection fraction (LVEF) < 50%;
    9. Uncontrolled hypertension (defined as blood pressure not at targeted level despite ≥1 month of treatment with at least two reasonable and tolerated antihypertensive medications following lifestyle modifications, or blood pressure that can only be effectively controlled with four or more antihypertensive medications) or hypotension;
    10. Stroke, cerebrovascular accident, or transient ischemic attack within 6 months prior to the first dose.

15. Known chronic obstructive pulmonary disease (COPD) with a forced expiratory volume in 1 second (FEV1) < 50% of the predicted normal value. Suspected COPD participants must undergo FEV1 testing; those with FEV1 < 50% predicted normal value must be excluded.

16. Known moderate or severe persistent asthma, a history of asthma within the past 2 years, or currently uncontrolled asthma (note: participants with intermittent asthma or mild persistent asthma under control are eligible).

17. History of interstitial lung disease (including drug-induced), pneumoconiosis, pulmonary fibrosis, or severe pulmonary dysfunction; active tuberculosis, currently receiving anti-tuberculosis treatment, or having received anti-tuberculosis treatment within the past year.

18. Significant clinical bleeding symptoms within 3 months before the first dose, including hemoptysis of any significant amount (≥ 2.5 mL per episode) within 28 days prior to the first dose.

19. History of abdominal fistula, gastrointestinal perforation, intra-abdominal abscess, or acute gastrointestinal bleeding within 6 months prior to the first dose.

20. History of deep vein thrombosis, pulmonary embolism, or other severe thromboembolic events within 3 months prior to the first dose (excluding thrombosis caused by vascular access devices or superficial venous thrombosis).

21. Hepatic encephalopathy, hepatorenal syndrome, or Child-Pugh Class B or worse cirrhosis.

22. Known history of primary immunodeficiency.

23. Known history of organ transplantation or allogeneic hematopoietic stem cell transplantation (corneal transplantation excluded).

24. Pregnant or breastfeeding women.

25. Any active severe psychiatric disorder, medical disease, or other condition that may interfere with treatment, compliance, or the ability to provide informed consent, as determined by the investigator.

26. A history of allergy to pembrolizumab.

27. A history of permanent discontinuation of pembrolizumab or similar drugs due to drug-related adverse events (AEs).

28. Potential participants may be excluded if, in the judgment of the Principal Investigator (PI), their participation would pose an unacceptable risk to their safety or significantly compromise the integrity or interpretability of the study's efficacy endpoints.