A Study of ES101 (PD-L1x4-1BB Bispecific Antibody) in Patients With Advanced Malignant Thoracic Tumors

Inclusion Criteria:

* Ability to understand and the willingness to sign a written informed consent form.
* Eastern Cooperative Oncology Group performance status (ECOG PS) of 0 or 1.
* At least one measurable lesion is required (RECIST v1.1)
* Phase 1b: Subjects with pathologically or cytologically confirmed recurrent or metastatic NSCLC without known EGFR mutation and ALK and ROS1 gene rearrangements.
* Phase II: Subjects with pathologically or cytologically confirmed recurrent or metastatic malignant thoracic tumours who have received 1-2 lines of systemic anti-tumour therapy, including platinum regimens, and have failed, including at least 2 cycles of chemotherapy.

Exclusion Criteria:

* Prior exposure to 4-1BB agonists.
* Receipt of any anticancer investigational product or any approved drug(s) or biological products (except hormone-replacement therapy, testosterone or oral contraceptives) within 4 weeks prior to the first dose of study drug. Previous exposure to oral fluorouracils or small molecular targeted drugs require a minimum washout period of 2 weeks or 5 half-lives prior to the first dose of study drug (whichever is longer). Previous exposure to mitomycin C or nitrosourea requires a minimum washout period of 6 weeks prior to the first dose of study drug.
* Receipt of PD-L1 therapy within 24 weeks prior to the first dose of study drug.
* Known allergies to CHO-produced antibodies, which in the opinion of the Investigator suggests an increased potential for an adverse hypersensitivity to ES101.
* Grade ≥ 3 immune-related adverse events (irAEs) or irAE that lead to discontinuation of prior immunotherapy. Some exceptions as defined per protocol apply.
* Subject has not recovered from all AEs of previous anticancer therapies to baseline or ≤ Grade 1 per CTCAE v5.0 before teh first dose of study drug. Certain exceptions as defined in protocol apply.
* Active autoimmune disease or documented history of autoimmune disease that required systemic steroids or other immunosuppressive medications. Certain exceptions as defined in protocol apply.
* Active interstitial lung disease (ILD) or pneumonitis or a history of ILD or pneumonitis requiring treatment with steroids or other immunosuppressive medications.
* Systemic anti-infectious drug treatments within 4 weeks prior to the first dose of study drug.
* Pregnant or nursing females.