Background: Combined therapy of an immune checkpoint inhibitor with a targeted anti-angiogenic agent had been proved to be effective for lung cancer. Penpulimab (AK105) was engineered to eliminate FcγR binding and antibody-dependent cell-mediated cytotoxicity (ADCC)/ antibody-dependent celluar phagocytosis (ADCP) completely, where ADCC/ADCP effects could induce T-cell apoptosis and clearance and therefore compromise anti-tumor activity. Penpulimab demonstrated a slower programmed death-1(PD-1) antigen binding off-rate, which resulted in better cellular activity and higher receptor occupancy. Penpulimab also showed numerous contacts with N58 glycosylation on the BC loop of PD-1. These structural differentiations enhance the anti-tumor activity of penpulimab and improve its safety. Anlotinib is a multi-targeted tyrosine kinase inhibitor selective for VEGF receptors 1/2/3, FGF receptors 1-4, PDGF receptors α and β, and c-kit. Anlotinib has been approved by National Medical Products Administration as the treatment for small cell lung cancer (SCLC) patients, who had progressed/relapsed on or after at least two regimens of chemotherapy. Here we report the results of one cohort which received penpulimab plus anlotinib in a Phase II study. Methods: In Cohort 4 of an open-label, multi-center, multi-cohort Phase II study evaluating the efficacy and safety of penpulimab plus anlotinib in pts with advanced head, neck or chest tumors(NCT04203719), the SCLC patients, who failed to platinum-based systemic chemotherapy treatment, received penpulimab (200 mg IV Q3W) and anlotinib (12/10 mg PO 2 weeks on/1 week off). Primary endpoint was objective response rate (ORR) per RECIST v1.1. Secondary endpoints were disease control rate (DCR), duration of response, progression-free survival (PFS) and overall survival. Results: 20 patients (median age was 61 [range:37–75] years old, Eastern Cooperative Oncology Group performance status 0/1 [5%/95%], male/female [65%/35%]) were enrolled and received combination therapy (17 received 12 mg anlotinib, 3 received 10 mg anlotinib; and all received 200 mg penpulimab). At data cut-off (Jan 25, 2021), the confirmed ORR was 50.0% (10/20, 1 complete response and 9 partial response) and DCR was 75.0% (15/20). 9 PFS events (45%) had occurred, and the median PFS was 4.7 months (95% CI: 3.6-not reached). Grade 3 treatment-related adverse events (TRAEs) occurred in 30% (6/20, 2 hypertension, 1 hypertriglyceridaemia, 1 gamma-glutamyltransferase increased, 1 palmar-plantar erythrodysaesthesia syndrome and 1 hyponatraemia) of patients, No Grade 4 or 5 TRAEs had occurred. Conclusions: Penpulimab plus anlotinib showed favorable antitumor activity and an acceptable safety profile in SCLC patients who failed to platinum-based systemic chemotherapy. This new combination therapy warrants further evaluation for the treatment of SCLC. Clinical trial information: NCT04203719