Background: Dual blockade of PD-1 and CTLA-4 has shown improved overall survival (OS) in combination with a short course of chemotherapy. KN046 is a novel bispecific antibody that blocks both PD-L1 interaction with PD-1/CD80 and CTLA-4 interaction with CD80/CD86. We hypothesized that KN046 could be combined with a full course of chemotherapy and build more durable clinical benefit. Methods: This study enrolled systemic treatment naive, stage IV NSCLC patients (pts). Eligible pts received KN046 plus platinum doublet chemotherapy until progressive disease, unacceptable toxicity, withdrawal of informed consent or death. Efficacy evaluation was performed by investigators per RECIST 1.1. Safety and tolerability were assessed per NCI-CTCAE v5.0. Results: As of the Jan. 19, 2021, 87 pts [Cohort 1 (n = 51), Cohort 2 (n = 36)] have been enrolled with 83 pts having tumor PD-L1 expression data (PD-L1 ≥1%: 55.4%; PD-L1 < 1%: 44.6%). 33.3% pts remained on the study treatment and 66.7% pts discontinued treatment due to disease progression (27.6%), TEAE (13.8%), death (9.2%) and other reasons (16%). The median treatment duration of KN046 was 21 weeks (range: 1.6̃68.7 weeks). Treatment related TEAE (TRAE) occurred in 92% pts. 25.3% pts experienced Grade≥3 TRAE [diarrhoea (5.7%), alanine aminotransferase increased (4.6%), infusion related reaction (3.4%), rash (3.4%), aspartate aminotransferase increased, dermatitis allergic and immune-mediated pneumonitis (2.3%, respectively), anaphylactoid reaction, autoimmune hepatitis, back pain, bilirubin conjugated increased, hypertension, neutrophil count decreased, platelet count decreased, pneumonitis, rash maculo-papular, septic shock and white blood cell count decreased (1.1%, respectively). In 81 efficacy evaluable pts, the overall objective response rate (ORR) was 50.6% (95% CI: 39.3%,61.9%) and disease control rate (DCR) was 87.7% (95% CI: 78.5%-93.9%). The ORR and DCR in pts with non-squamous NSCLC (n = 48) were 45.8% (95% CI: 31.4%, 60.8%) and 89.6% (95% CI: 77.3%, 96.5%). The ORR and DCR in pts with squamous NSCLC (n = 33) were 57.6% (95% CI: 39.2%, 74.5%) and 84.8% (95% CI: 68.1%, 94.9). Progression free survival (PFS) and OS events have occurred in 53% and 18% patients. Median PFS was 5.9 (95%CI: 5.3, 8.7) months. Median OS was not reached. OS rate at 12 and 15 months were both 74.9%. Similar OS curves have been observed in PD-L1 ≥1% and PD-L1 < 1% pts. In PD-L1 ≥1% patients, median PFS was 6.7 months (10.8 months for PD-L1 ≥1% squamous NSCLC pts). Conclusions: KN046 combined with platinum doublet chemotherapy is tolerated and has shown promising clinical benefit as IL treatment for stage IV NSCLC particularly in PD-L1≥1% tumors and squamous histology. Pivotal Phase III trial in advanced unresectable or metastatic squamous NSCLC is currently ongoing. Clinical trial information: NCT04054531