Inclusion Criteria:

          -  Part 1 and Part 2

               1. Written Informed Consent (mentally competent patient, able to understand and
                  willing to sign the informed consent form)

               2. Age ≥ 18 years, male or non-pregnant female

               3. Histologically confirmed unresectable metastatic cancer (adenocarcinomas and
                  squamous cell carcinomas allowed). Patients with resectable disease are excluded

               4. Able to comply with the study protocol, as per Investigator's judgment

               5. Life expectancy > 3 months according to Investigator's judgement

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

               7. Coronavirus SARS-CoV-2 (COVID-19) negative patients.

               8. Patient able and willing to undergo pre- and on/post-treatment biopsies.
                  According to the Investigator's judgement, the planned biopsies should not expose
                  the patient to substantially increased risk of complications. Every effort will
                  be made that the same lesion is biopsied on repeat biopsies. If the patient is
                  eligible according to all other criteria but declines to consent to a biopsy or
                  there are other medical reasons precluding biopsy, this will be discussed with
                  the sponsor.

               9. Measurable disease, according to Response Evaluation Criteria in Solid Tumors
                  (RECIST) v1.1. Note that lesions intended to be biopsied should not be target
                  lesions.

              10. Adequate hematologic and end organ function, defined by the following laboratory
                  results obtained prior to first dose of study drug treatment, provided no
                  anti-cancer treatment was administered within the last 7 days:

                    1. neutrophil count ≥ 1 x 109/L

                    2. platelet count ≥ 100 x 109/L; for hepatocellular carcinoma (HCC) in Part 1 ≥
                       50 x 109/L

                    3. hemoglobin ≥ 9.0 g/dL without transfusion in the previous week

                    4. creatinine ≤ 1.5 x upper limit of normal (ULN)

                    5. aspartate aminotransferase AST (SGOT) ≤ 3 x ULN (≤ 5 x ULN when HCC or
                       hepatic metastases are present)

                    6. alanine aminotransferase (ALT [SGPT]) ≤ 3 x ULN (≤ 5 x ULN when HCC or
                       hepatic metastases present)

                    7. bilirubin ≤ 1.5 x ULN (patients with known Gilbert's disease may have a
                       bilirubin ≤ 3.0 x ULN)

                    8. albumin ≥ 3.0 g/dL

                    9. international normalized ratio (INR) and partial thromboplastin time (PTT) ≤
                       1.5 x ULN

                   10. amylase and lipase ≤ 1.5 x ULN

              11. No evidence of active infection or infections requiring parenteral antibiotics,
                  and no serious infection within 4 weeks before study start.

              12. Women of child-bearing potential must have a negative pregnancy test within 72 h
                  prior to start of treatment. For women of childbearing potential: agreement to
                  remain abstinent (refrain from heterosexual intercourse) or to use contraceptive
                  methods that result in a failure rate of < 1% per year during the treatment
                  period and for at least 180 days after the last study treatment.

                  A woman is of childbearing potential if she is post-menarche, has not reached a
                  postmenopausal state (≥ 12 continuous months of amenorrhea with no identified
                  cause other than menopause), and has not undergone surgical sterilization
                  (removal of ovaries and/or uterus).

                  Examples of contraceptive methods with a failure rate of < 1% per year include
                  bilateral tubal ligation, male sterilization, hormonal contraceptives that
                  inhibit ovulation, hormone-releasing intrauterine devices and copper intrauterine
                  devices. The reliability of sexual abstinence should be evaluated in relation to
                  the duration of the clinical trial and the preferred and usual lifestyle of the
                  patient. Periodic abstinence (eg, calendar, ovulation, symptom-thermal, or post
                  ovulation methods) and withdrawal are not acceptable methods of contraception.
                  Fertile men must practice effective contraceptive methods during the study,
                  unless documentation of infertility exists.

              13. Four (4) weeks or 5 half-lives (whichever is shorter) since the last dose of
                  anti-cancer therapy before the first LYT 200 administration

              14. Continuation of bisphosphonate treatment (eg, zoledronic acid) or denosumab for
                  bone metastases, which have been stable for at least 6 months before C1D1, is
                  allowed

              15. Biliary or gastric outlet obstruction allowed, provided it is effectively drained
                  by endoscopic, operative, or interventional means

              16. Pancreatic, biliary, or enteric fistulae allowed, provided they are controlled
                  with an appropriate non-infected and patent drain (if any drains or stents are in
                  situ, patency needs to be confirmed before study start)

                  Additionally, for Part 1 only:

              17. Patients:

                    1. for whom there are no available standard of care options or

                    2. who are not eligible for available and indicated standard of care therapy.

                  Additionally, for Part 2 only:

              18. PDAC expansion cohort: 1st line metastatic patients who are either
                  gemcitabine-containing regimen naïve or at least 3 months out of having been
                  treated using a gemcitabine-containing regimen previously in a neoadjuvant or
                  adjuvant/locally advanced setting

              19. CRC and CCA expansion cohorts - patients who have received at least one prior
                  line of therapy in the metastatic setting

        Exclusion Criteria

          1. Patient unwilling or unable to follow protocol requirements

          2. Patient diagnosed with metastatic cancer of an unknown primary

          3. Prior or current illicit drug addiction (medical and recreational
             marijuana/cannabidiol [CBD]/ tetrahydrocannabinol [THC] would not be considered
             "illicit")

          4. Clinically significant, active uncontrolled bleeding, and any patients with a bleeding
             diathesis (eg, active peptic ulcer disease). Prophylactic or therapeutic use of
             anticoagulants is allowed.

          5. Pregnant and/or lactating females

          6. Receiving any other investigational agents or participating in any other clinical
             trial involving another investigational agent for treatment of solid tumors within 4
             weeks or 5 half-lives of the administered drug (whichever is shorter) prior to Cycle
             1, Day 1 of the study, or other investigational therapy or major surgery within 4
             weeks of the date of consent, or planned surgery within 4 weeks of envisaged study
             start (this includes dental surgery).

          7. Radiation therapy within 4 weeks of the first dose of study drug, except for
             palliative radiotherapy to a limited field, such as for the treatment of bone pain or
             a focally painful tumor mass, and which does not jeopardize required measurable
             lesions for response assessment (RECIST v1.1).

          8. Patients with fungating tumor masses

          9. Patients with locally advanced PDAC without distant organ metastatic deposits

         10. Grade 4 immune-mediated toxicities with a prior checkpoint inhibitor. Grade 2 or Grade
             3 pneumonitis or any other Grade 3 checkpoint inhibitor-related toxicity that led to
             immunotherapy treatment discontinuation. Low-grade (< Grade 3) toxicities, such as
             neuropathy from prior treatments, manageable electrolyte abnormalities and
             lymphopenia, alopecia and vitiligo are allowed.

         11. History of second malignancy, except those treated with curative intent more than five
             years previously without relapse or low likelihood of recurrence (for example,
             non-melanotic skin cancer, cervical carcinoma in situ, early (or localized) prostate
             cancer, or superficial bladder cancer)

         12. Active brain or leptomeningeal metastases. Patients with brain metastases are eligible
             provided they have shown clinically and radiographically stable disease for at least 4
             weeks after definitive therapy and have not used steroids (> 10 mg/day of prednisone
             or equivalent) for at least 4 weeks prior to the first dose of study drug

         13. Evidence of severe or uncontrolled systemic diseases, congestive heart failure > New
             York Heart Association (NYHA) class 2, myocardial infarction (MI) within 6 months, or
             laboratory finding that in the view of the Investigator makes it undesirable for the
             patient to participate in the trial

         14. Any medical condition that the Investigator considers significant to compromise the
             safety of the patient or that impairs the interpretation of LYT 200 toxicity
             assessment

         15. Serious non-healing wound, active ulcer, or untreated bone fracture

         16. Uncontrolled pleural effusion, pericardial effusion, or ascites requiring recurrent
             drainage procedures. For the purposes of this study, "recurrent" is defined as greater
             than or equal to 3 drains in the last 30 days.

         17. History of severe allergic, anaphylactic, or other hypersensitivity reactions to
             chimeric or humanized antibodies or fusion proteins

         18. Significant vascular disease (eg, aortic aneurysm requiring surgical repair or recent
             arterial thrombosis) within 6 months of Cycle 1, Day 1

         19. History of pulmonary embolism, stroke or transient ischemic attack within 3 months
             prior to Cycle 1, Day 1

         20. History of abdominal fistula or gastrointestinal perforation within 6 months prior to
             Cycle 1, Day 1

         21. Active auto-immune disorder (except type I/II diabetes, hypothyroidism requiring only
             hormone replacement, vitiligo, psoriasis, or alopecia areata)

         22. Requires systemic immunosuppressive treatment, including, but not limited to
             cyclophosphamide, azathioprine, methotrexate, thalidomide, and anti-tumor necrosis
             factor (anti-TNF) agents. Patients who have received or are receiving acute, low dose
             systemic immunosuppressant medications (eg, ≤ 10 mg/day of prednisone or equivalent)
             may be enrolled. Replacement therapy (eg, thyroxine, insulin, physiologic
             corticosteroid replacement therapy [eg, ≤ 10 mg/day of prednisone equivalent] for
             adrenal or pituitary insufficiency) is not considered a form of systemic treatment.
             The use of inhaled corticosteroids and mineralocorticoids (eg, fludrocortisone),
             topical steroids, intranasal steroids, intra-articular, and ophthalmic steroids is
             allowed.

         23. Severe tumor-related pain (Grade 3, Common Terminology Criteria for Adverse Events
             [CTCAE] v.5.0) unresponsive to broad analgesic interventions (oral and/or patches)

         24. Hypercalcemia(defined as greater than or equal to Grade 3, per CTCAE v 5.0)despite use
             of bisphosphonates

         25. Any other diseases, metabolic dysfunction, physical examination finding, or clinical
             laboratory finding giving reasonable suspicion of a disease or condition that
             contraindicates the use of an investigational drug or that may affect the
             interpretation of the results or render the patient at high risk of treatment
             complications

         26. Received organ transplant(s)

         27. Patients undergoing dialysis

         28. For patients enrolled into nivolumab combination cohorts, no prior exposure to any
             anti-PD-1 or anti-PD-L1 agent in any prior lines of therapy. Additionally, patients
             diagnosed as dMMR/MSI-H are excluded.

         29. For Part 1, hormonal androgen deprivation therapy is allowed to continue for patients
             with metastatic castration-resistant prostate cancer.

         30. Any ablative therapy (Radio Frequency Ablation or Percutaneous Ethanol Injection) for
             HCC < 6 weeks prior trial entry

         31. Hepatic encephalopathy or severe liver adenoma

         32. Child-Pugh score ≥ 7