Sponsor's clinical development strategy adjustment

The purpose of this study is to evaluate the safety, RP2D and PK/pharmacodynamic profile of ES101 monotherapy in patients with advanced NSCLC and to further evaluate the antitumor efficacy of ES101 in advanced malignant thoracic tumors, including NSCLC and SCLC.

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.