Study of DECOY20 With or Without Tislelizumab in Patients With Advanced Solid Tumors

Inclusion Criteria:

1. Males or females, age 18 years or older.

2. Histologically confirmed diagnosis of locally advanced or metastatic solid tumor.For Part 2, subjects must have one of the following locally advanced or metastatictumor types: hepatocellular carcinoma (HCC), colorectal cancer (CRC) with livermetastasis, urothelial cancer, squamous cell carcinoma of the head and neck (SCCHN),adenocarcinoma of the pancreas, non-small cell lung cancer (NSCLC), dMMR/MSI-Hightumor (Part 2c only).

3. Subject must have exhausted all available therapy or have declined treatment ortreatment is contraindicated. Subjects with tumors that have known actionablemolecular alteration such as EGFR, ALK, ROS-1, BRAF, RET, MET, and KRAS must haveprogressed on directed molecular therapy. For Part 2c, participants with a tumortype for which a CPI has been approved must have received a CPI during one or morelines of therapy.

4. Measurable disease (at least 1 measurable lesion) per Response Evaluation Criteriain Solid Tumors (RECIST) v1.1 as defined by tumor type.

5. Eastern Cooperative Oncology Group (ECOG) performance status of 0 or 1.

6. Life expectancy of at least 3 months.

7. Female subjects must be of non-childbearing potential (surgically sterile or atleast 2 years postmenopausal) or agree to use a highly effective contraceptionmethod while receiving treatment with Decoy20 and for 30 days after the last dose ofDecoy20.

8. Male subjects must utilize reliable contraceptive precautions for the duration ofDecoy20 treatment and 30 days after the last dose of Decoy20.

9. Adequate organ function as demonstrated by baseline laboratory assessment.

10. Left ventricular ejection fraction (LVEF) ≥ 45% by echocardiogram (ECHO) ormulti-gated acquisition scan (MUGA).

11. Recovered from toxicities due to prior therapies.

12. Willing and able to comply with all scheduled visits, laboratory tests, and otherstudy procedures including mandatory pre-treatment and on- treatment biopsies forsubjects enrolled to Part2.

Exclusion Criteria:

1. Pregnant or lactating females.

2. Has an active systemic (viral, bacterial, or fungal) infection or requiringtreatment.

3. Received radiotherapy within 28 days of the first dose of Decoy20. Subjects musthave recovered from all radiation-related toxicities, not require corticosteroids,and not have had radiation pneumonitis.

4. Received prior chemotherapy, targeted therapy or immunotherapy within 28 days or 5half-lives from W1D1, whichever is shorter.

5. Received systemic corticosteroid therapy > 5 mg/day of prednisone or equivalent doseof another corticosteroid within 1 week or 5 half-lives (whichever is shorter) fromthe start of study drug or is expected to require it during the course of the study (topical and inhaled steroids are permitted).

6. Has radiographically detected primary central nervous system (CNS) metastases orsymptomatic CNS involvement (including leptomeningeal carcinomatosis, cranialneuropathies or mass lesions that cause spinal cord compression). Participants withbrain metastases (either treated or deemed unnecessary to treat) that have beenstable by neuroimaging for at least 4 weeks will be eligible.

7. Clinical evidence of significant coagulopathy during Screening (e.g., deep veinthrombosis or pulmonary embolism) or history of significant uncontrolledcoagulopathy (participants with HCC must have prothrombin time (PT) < 4 secondsabove ULN or international normalized ratio [INR] < 1.7) or participants withdiagnosis of a new thrombotic event within 90 days prior to Decoy20 dosing.

8. Has an active secondary malignancy in addition to the primary, excluding low-riskneoplasms as determined by the Investigator (e.g., non-metastatic basal cell orsquamous cell skin carcinoma) and other indolent malignancies will be allowed afterdiscussion with the Sponsor).

9. Has a history of or active infection with HIV 1 or 2, a history of or activeinfection with HBV based upon HBV antigenemia or viral load, or positive read forhepatitis C virus ([HCV] viral load >15 IU/mL) at Screening. 10. Has a history ofknown genetic predisposition to HLH/MAS.

10. Has undergone splenectomy, has an active chronic liver disease, Wilson's disease,hemochromatosis, primary biliary cirrhosis, primary sclerosing cholangitis, genetichemochromatosis, history of or planned liver transplant for end-stage liver diseaseof any etiology, documented history of advanced liver fibrosis or history ofcirrhosis and/or hepatic decompensation including ascites requiring paracentesisrather than medical therapy, modified Child-Pugh B or C, clinically relevant hepaticencephalopathy within the preceding 6 months, or variceal bleeding. 12. Has receiveda vaccine within 14 days of W1D1 13. Has active autoimmune disease. 14. Has ahistory of significant CNS disease, such as stroke (past history of transientischemic attacks more than 3 months ago and controlled is allowed) or uncontrolledand unstable epilepsy. 15. Has severe pulmonary interstitial disease and/or oxygensaturation on room air < 92%. 16. Baseline Q-T correlated (QTc) interval of > 470msec for females and > 450 msec for males calculated using Fridericia's formula. 17.New York Heart Association Class III or IV cardiac disease, or myocardial ischemiaor infarction within 180 days of Screening, vaso-vagal sensitivity, unstable angina,coronary/peripheral artery bypass graft, worsening/ decompensated heart failurewithin the past 6 months, or any other clinically significant cardiac abnormalitythat, in the judgement of the Investigator, would pose a health risk to the subject.

11. Major surgical procedure within 4 weeks prior to first dose of Decoy20, oranticipation of need for a major surgical procedure, during the study. 19. Any otheracute or chronic medical or psychiatric condition that may increase the riskassociated with study participation or Decoy20 administration. 20. Has receivedinvestigational therapy within 28 days or 5 half-lives of the start of study drug.

12. Unwillingness or inability to comply with procedures required in this protocol.

13. Known allergy or hypersensitivity to Decoy20 or one of the ingredients ofDecoy20. 23. For Part 2c, participants with ongoing immune-related adverse events (irAEs) from other agents or who required permanent discontinuation of prior ICIsdue to irAEs. Participants with a prior history of Grade 3 or higher irAE except forthose with a history of an immune-related endocrinopathy which is currently treatedand clinically stable. Participants with a history of (non-infectious) Grade 2 orhigher pneumonitis that required steroids.