Key Inclusion Criteria:

          -  Measurable disease per RECIST v1.1.

          -  Life expectancy greater than or equal to 12 weeks.

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

          -  Adequate cardiovascular, hematological, liver, and renal function.

          -  Histologically or cytologically confirmed diagnosis of advanced and/or metastatic
             solid tumors with at least one tumor lesion with location accessible to safely biopsy
             per clinical judgment of the Investigator.

          -  Prior anti-cancer therapy is allowed as long as any treatment related toxicity is
             resolved to an appropriate level.

          -  Females of childbearing potential and men who are not surgically sterile must agree to
             use medically-accepted method of birth control during the study and for at least 3
             months after last dose of treatment.

          -  [Females] Negative serum pregnancy test within 7 days prior to initiating study
             treatment in premenopausal women and women less than 12 months after menopause.

          -  [Males] Agreement to refrain from donating or banking sperm during the treatment
             period and for at least 3 months after last dose of study treatment.

        Key Exclusion Criteria:

          -  Radiotherapy ≤ 14 days prior to first dose of study drug (palliative radiation or
             stereotactic radiosurgery within 7 days prior to start of study treatment).

          -  Treated with systemic anti-cancer therapy or an investigational agent within 2 weeks
             prior to start of study drug treatment (within 4 weeks for immunotherapy and tyrosine
             kinase inhibitor therapy).

          -  Major surgery ≤ 30 days prior to first dose of study drug, or has not recovered to at
             least Grade 1 from adverse effects from such procedure, or anticipation of the need
             for major surgery during study treatment.

          -  Active autoimmune disease requiring systemic treatment within the past 3 months or
             have a documented history of clinically severe autoimmune disease that requires
             systemic steroids or immunosuppressive agents.

          -  Primary central nervous system (CNS) disease or leptomeningeal disease; known CNS
             metastases unless treated, are asymptomatic, are without evidence of radiological
             progression for at least 8 weeks, and have had no requirement for steroids or enzyme
             inducing anticonvulsants in the last 14 days prior to Screening.

          -  Abnormal pulmonary function within the previous 6 months, including pneumonitis,
             active pneumonitis, interstitial lung disease requiring the use of steroids,
             idiopathic pulmonary fibrosis, confirmed pleural effusion, severe dyspnea at rest or
             requiring supplementary oxygen therapy.

          -  Parenteral antibiotics within 14 days of the first dose of study drug.

          -  History of allogenic or solid organ transplant.

          -  Known human immunodeficiency virus (HIV) infection or active infection with hepatitis
             C.

          -  Known uncontrolled hepatitis B virus (HBV) infection.

          -  Clinically significant bleeding within 2 weeks prior to initial THOR-707 dose (e.g.,
             gastrointestinal bleeding, intracranial hemorrhage).

          -  Prior diagnosis of deep vein thrombosis or pulmonary embolism within 3 months.

          -  Severe or unstable cardiac condition within 6 months prior to starting study
             treatment, such as congestive heart failure (New York Heart Association Class III or
             IV), cardiac bypass surgery or coronary artery stent placement, angioplasty, cardiac
             ejection fraction below the lower limit of normal, unstable angina, medically
             uncontrolled hypertension (e.g. ≥160 mm Hg systolic or ≥100 mm Hg diastolic),
             uncontrolled cardiac arrhythmia requiring medication (≥ grade 2, according to NCI
             CTCAE v5.0), or myocardial infarction.

          -  History of non-pharmacologically induced prolonged corrected QT interval determined
             using Fridericia's formula (QTcF) > 450 milliseconds (msec) in males or > 470 msec in
             females.

          -  Known hypersensitivity or contraindications to THOR-707, PEG, pegylated drugs,
             checkpoint inhibitor, or anti-EGFR antibody for applicable cohorts.

          -  Active second malignancy, or history of previous malignancy that would impact the
             assessment of any study endpoints. Subjects with non-melanomatous skin cancer or
             cervical cancer that has been curatively surgically resected are eligible.

          -  Any serious medical condition (including pre-existing autoimmune disease or
             inflammatory disorder), laboratory abnormality, psychiatric condition, or any other
             significant or unstable concurrent medical illness that in the opinion of the
             Investigator would preclude protocol therapy or would make the subject inappropriate
             for the study.

          -  Is pregnant or breastfeeding, or expecting to conceive or father children within the
             projected duration of the trial, starting with the screening visit through 3 months
             after the last dose of study treatment.

          -  Concurrent therapy with any other investigational agent, vaccine, or device.
             Concomitant participation in observational studies is acceptable after Sponsor
             approval.