TPS2675 Background: AK119 is a humanized IgG1 monoclonal antibody (mAb) that selectively binds to and inhibits the ectonucleotidase activity of CD73, a cell surface enzyme that converts adenosine monophosphate (AMP) into adenosine. Adenosine has been shown to facilitate tumor-mediated evasion. CD73 inhibition may therefore reduce adenosine accumulation and promote anti-tumor immunity. AK104 is a recombinant humanized IgG1 bispecific antibody that simultaneously binds to programmed cell death protein 1 (PD-1) and cytotoxic T- lymphocyte-associated antigen protein 4 (CTLA-4). Preliminary data from phase I and II studies suggest that AK104 has encouraging anti-tumor activity in selected tumor types and an improved safety profile compared to the co-administration of anti-PD-1 plus anti-CTLA-4 mAbs. Preclinical studies show that CD73 inhibition synergistically increases the anti-tumor activity of PD-1 and CTLA-4 immune checkpoint inhibitors (ICIs). Published early clinical data suggests that anti-CD73 therapy in combination with ICIs produces improved clinical outcomes. Thus, AK119 plus AK104 is postulated to have synergistically enhanced anti-tumor activity compared to the administration of anti-CD73 monotherapy or ICIs alone. Methods: This is a phase 1a/1b, first-in-human, multicenter, open-label study in patients with advanced solid tumors that are refractory to standard therapies. The primary objective is to assess safety, tolerability and dose limiting toxicity; and to determine the Maximum Tolerated Dose (MTD) or Maximum Administered Dose (MAD) of AK119 in combination with AK104. Secondary objectives are to evaluate antitumor activity, PK and AK119 immunogenicity. The dose-escalation phase will evaluate 5 dose levels of AK119 (1mg/kg to 40 mg/kg Q2W IV) in combination with 6mg/kg AK104 Q2W IV using a 3+3+3 study design. Eligible pts will receive a single dose of AK119 on C0D1 of a 14-day “lead-in” period. Thereafter, from C1D1 pts will receive AK119 in combination with AK104 on a 28-day cycle, until unacceptable toxicity, confirmed progressive disease, subject withdrawal, or for a maximum of 24 months. The “lead-in” period is only applicable for dose-escalation cohorts. Any dose-escalation cohort not exceeding the MTD may be expanded to a maximum of 18 subjects with selected solid tumor types for further evaluation of safety, PK/ PD, immunogenicity, and preliminary anti-tumor activity. Cohort 1 is currently in progress with the first patient enrolled in January 2021. For the dose-expansion phase, cohorts of pts with advanced/metastatic pancreatic cancer or MSS/pMMR colorectal cancer will be enrolled. Cohorts of other tumor types may be added based on emerging pharmacodynamic and anti-tumor response data. Clinical trial information: NCT04572152.