Inclusion Criteria:

          -  Subjects must fulfill all the following inclusion criteria relevant to their tumor
             type to be eligible for participation in the study:

        Malignant Melanoma

          1. Histopathologically confirmed diagnosis of advanced, unresectable or metastatic
             malignant melanoma.

          2. Subjects must have progressed on treatment with an anti-PD1/Ligand 1 (L1) monoclonal
             antibody (mAb) administered either as monotherapy, or in combination with other
             checkpoint inhibitors or other therapies. PD-1 treatment progression is defined by
             meeting all of the following criteria:

               1. Has received at least 2 doses of an approved anti-PD-1/L1 mAb.

               2. Has demonstrated disease progression (PD) after PD-1/L1 as defined by RECIST
                  Version 1.1. The initial evidence of PD is to be confirmed by a second assessment
                  no less than four weeks from the date of the first documented PD, in the absence
                  of rapid clinical progression.1

               3. Progressive disease has been documented within 12 weeks from the last dose of
                  anti-PD-1/L1 mAb.1

             i. This determination is made by the investigator. Once PD is confirmed, the initial
             date of PD documentation will be considered the date of PD.

             Pancreatic Cancer

          3. Histologically confirmed (previously obtained biopsied) metastatic unresectable
             pancreatic adenocarcinoma, including with intraductal papillary mucinous neoplasm.

          4. Subjects with one or more prior treatments for their pancreatic cancer.

          5. If subjects have high microsatellite instability (MSI-H) or mismatch-repair deficiency
             (dMMR) phenotype they must have been previously treated with anti-PD1 and demonstrated
             either PD or disease stabilization.

             Ovarian Cancer

          6. Histologically proven diagnosis of high grade serous, high grade endometroid or clear
             cell ovarian cancer, fallopian tube or primary peritoneal carcinoma.

          7. Recurrent platinum-resistant disease, defined as PD within 6 months (182 days) of the
             last receipt of platinum-based chemotherapy OR greater than 6 months from completion
             of most recent platinum-based chemotherapy, but not suitable for further platinum
             therapy.

             Sarcoma

          8. Histologically confirmed diagnosis of leiomyosarcoma, poorly differentiated or
             dedifferentiated liposarcoma, undifferentiated pleomorphic sarcoma, malignant fibers
             histiocytoma, synovial sarcoma, Ewing's sarcoma, osteosarcoma, or dedifferentiated or
             mesenchymal chondrosarcoma.

          9. All cases should be classified histologically as being intermediate- or high grade.
             For soft-tissue sarcomas, this would correspond to Grade 2 or 3 according to the
             FNCLCC (Fédération Nationale des Centres de Lutte Contre le Cancer) grading system.

         10. Locally advanced/unresectable or metastatic disease not amenable to curative surgical
             resection.

         11. Receipt of at least 1 systemic line of therapy for advanced disease. For subjects
             diagnosed with diseases for which no standard therapy exists (e.g. dedifferentiated
             chondrosarcoma), this requirement is waived.

         12. Subjects may have received up to 3 previous lines of systemic anti-cancer therapy for
             advanced disease. Systemic therapy administered with neoadjuvant or adjuvant intent is
             not considered a therapy for advanced disease.

             All Subjects

         13. Be willing and able to provide written informed consent for the trial.

         14. Be ≥18 years of age on day of signing informed consent.

         15. For subjects with tumor types other than malignant melanoma, ovarian cancer or
             pancreatic cancer with histologically or cytologically confirmed advanced or
             metastatic solid tumors who have PD after treatment with at least 1 available therapy
             for metastatic disease that is known to confer clinical benefit, or are intolerant to
             treatment, or refuse standard treatment.

         16. For the dose-escalation phase (Part A), tumor vasculature, stroma and/or tumor cells
             are marker positive for ETBR, as determined by IHC staining >25%. Subjects who do not
             satisfy this criterion may be enrolled in the dose expansion phase (Part B).

         17. Has a life expectancy of >3 months.

         18. All subjects must have an archived tumor tissue biopsy sample obtained within 24
             months of Screening that is suitable for performing IHC and biomarker analyses.

         19. Eastern Cooperative Oncology Group (ECOG) Performance Status of 0 or 1.

         20. A female subject is eligible to participate if she is not pregnant, not breastfeeding,
             and at least one of the following conditions applies:

             a. Not a woman of childbearing potential (WOCBP), where a WOCBP is defined as: i. Not
             surgically sterile i.e. bilateral tubal ligation, bilateral oophorectomy, or complete
             hysterectomy, or ii. Not post-menopausal, defined as amenorrhea for ≥ 2 years without
             an alternative medical cause.

             Note: Women with amenorrhea for < 2 years and who are not surgically sterile i.e.
             tubal ligation, bilateral oophorectomy, or complete hysterectomy will only be
             considered not to be of reproductive potential if they have a documented follicle
             stimulating hormone (FSH) value in the postmenopausal range.

             b. A WOCBP who agrees to follow contraceptive guidance from the date of informed
             consent and for at least 150 days after the last dose of study treatment.

         21. A male subject must agree to use contraception from the date of informed consent and
             for at least 120 days after the last dose of study treatment AND must refrain from
             donating sperm during this period.

         22. Has measurable disease per RECIST Version 1.1, defined as at least one lesion that can
             be accurately measured by CT scan or MRI. Minimum measurement must be ≥10 mm as
             assessed by the Investigator. Lesions situated in a previously irradiated area are
             considered measurable if progression has been demonstrated in such lesions.

         23. Has adequate organ function, as defined in table below. Specimens must be collected
             within 3 days prior to the start of study treatment.

        System Laboratory Value Hematological Absolute neutrophil count (ANC) ≥1500/µL or ≥1500/mm3
        Platelets ≥100 000/µL or ≥100 000/mm3 Hemoglobin ≥90.0 g/L or ≥5.6 mmol/L1 Renal Creatinine
        OR Measured or calculated2 creatinine clearance (GFR can also be used in place of
        creatinine or CrCl) ≤1.5 ×ULN OR ≥30 mL/min for subject with creatinine levels >1.5 ×
        institutional ULN Hepatic Total bilirubin ≤1.5 ×ULN OR direct bilirubin ≤ULN for subjects
        with total bilirubin levels >1.5 × ULN AST (SGOT) and ALT (SGPT) ≤2.5 × ULN (≤5 × ULN for
        subjects with liver metastases)

        Coagulation International normalized ratio (INR) OR prothrombin time (PT) Activated partial
        thromboplastin time (aPTT) ≤1.5 × ULN unless subject is receiving anticoagulant therapy
        provided PT or aPTT is within therapeutic range of intended use of anticoagulants ALT
        (SGPT) = alanine aminotransferase (serum glutamic pyruvic transaminase); AST (SGOT) =
        aspartate aminotransferase (serum glutamic oxaloacetic transaminase); GFR = glomerular
        filtration rate; ULN = upper limit of normal.

        1 Criteria must be met without erythropoietin dependency and without packed red blood cell
        (pRBC) transfusion within last 2 weeks.

        1. 2 Creatinine clearance (CrCl) will be calculated by the central laboratory using the
        Cockcroft-Gault equation.

        24. Capable of understanding and complying with protocol requirements.

        Exclusion Criteria:

        Subjects will be excluded if they fulfill any of the following exclusion criteria:

        Pregnancy Exclusion

          1. A WOCBP who has a positive urine pregnancy test (e.g. within 72 hours) prior to
             treatment. If the urine test is positive or cannot be confirmed as negative, a
             negative serum pregnancy test will be required.

          2. Is breastfeeding or expecting to conceive or father children within the projected
             duration of the study, from the day date of informed consent through to 150 days after
             the last dose of study treatment for females, and 120 days after the last dose of
             study treatment for males.

             Prior/Concomitant Therapy

          3. Has received prior therapy with an anti-PD-1, anti-PD-L1, or anti PD L2 agent or with
             an agent directed to another stimulatory or co-inhibitory T-cell receptor (e.g.,
             CTLA-4, OX 40, CD137) and was discontinued from that treatment due to a Grade 3 or
             higher immune-related adverse event (irAE).

          4. Has received prior systemic anti-cancer therapy including investigational agents
             within 4 weeks prior to treatment.

             Note: Subjects must have recovered from all AEs due to previous therapies to ≤Grade 1
             severity or baseline. Subjects with ≤Grade 2 neuropathy may be eligible at
             Investigator's discretion.

             Note: If subject received major surgery, they must have recovered adequately from the
             toxicity and/or complications from the surgery prior to starting study treatment, as
             determined by the Investigator.

          5. Has received prior radiotherapy within 2 weeks of start of study treatment. Subjects
             must have recovered from all radiation-related toxicities, not currently require
             corticosteroids, and have never had radiation pneumonitis. A 1-week washout is
             permitted for palliative radiation (≤2 weeks of radiotherapy) to non-central nervous
             system (CNS) disease.

          6. Has received a live vaccine within 30 days prior to the first dose of study drug.
             Examples of live vaccines include, but are not limited to, the following: measles,
             mumps, rubella, varicella/zoster (chicken pox), yellow fever, rabies, Bacillus
             Calmette-Guérin (BCG), and typhoid vaccine. Seasonal influenza vaccines for injection
             are generally killed virus vaccines and are allowed; however, intranasal influenza
             vaccines (e.g., FluMist®) are live attenuated vaccines and are not allowed.

             Prior/Concurrent Clinical Study Experience

          7. Is currently participating in or has participated in a study of an investigational
             agent or has used an investigational device within 4 weeks prior to the first dose of
             study treatment.

             Note: Subjects who have entered the follow-up phase of an investigational study may
             participate provided it has been 4 weeks after the last dose of the previous
             investigational agent.

             Diagnostic Assessments

          8. Average Fridericia-corrected QT interval (QTcF) >460 msec for males and QTcF >480 msec
             for females as measured by electrocardiogram (ECG) at Screening.

          9. A family history of congenital long QT syndrome, Brugada syndrome or unexplained
             sudden cardiac death.

         10. Has a diagnosis of immunodeficiency or is receiving chronic systemic steroid therapy
             (in doses exceeding 10 mg daily of prednisone equivalent) or any other form of
             immunosuppressive therapy within 7 days prior the first dose of study drug.

         11. Has a known additional malignancy that is progressing or has required active treatment
             within the past 3 years.

             Note: Subjects with basal cell carcinoma of the skin, SCC of the skin, or carcinoma in
             situ (e.g., breast carcinoma, cervical cancer in situ) that have undergone potentially
             curative therapy are not excluded.

         12. Has known active CNS metastases and/or carcinomatous meningitis. Subjects with
             previously treated brain metastases may participate provided they are radiologically
             stable, i.e., without evidence of progression for at least 4 weeks by repeat imaging
             (note that the repeat imaging should be performed during study screening), clinically
             stable and without requirement of steroid treatment for at least 14 days prior to
             first dose of study treatment.

         13. Has severe hypersensitivity (≥ Grade 3) to pembrolizumab and/or any of its excipients.

         14. Has severe hypersensitivity (≥ Grade 3) to ENB-003 and/or any of its excipients

         15. Has an active autoimmune disease that has required systemic treatment in past 2 years
             (i.e., with use of disease modifying agents, corticosteroids or immunosuppressive
             drugs). Replacement therapy (e.g., thyroxine, insulin, or physiologic corticosteroid
             replacement therapy for adrenal or pituitary insufficiency) is not considered a form
             of systemic treatment and is allowed.

         16. Has a history of (non-infectious) pneumonitis that required steroids or has current
             pneumonitis.

         17. Has an active infection requiring systemic therapy.

         18. Subjects with known human immunodeficiency virus (HIV) and/or history of Hepatitis B
             or C infections or known to be positive for Hepatitis B antigen (HBcAb) or Hepatitis C
             Antibody (HCab).

         19. Has a history or current evidence of any condition, therapy, or laboratory abnormality
             that might confound the results of the study, interfere with the subject's
             participation for the full duration of the study, or it is not in the best interest of
             the subject to participate, in the opinion of the treating Investigator.

         20. Has a known psychiatric or substance abuse disorder that would interfere with the
             subject's ability to cooperate with the requirements of the study.

         21. History of myocardial infarction ≤ 6 months prior to Screening, or congestive heart
             failure requiring use of ongoing maintenance therapy for life-threatening ventricular
             arrhythmias.

         22. Has a history of Pulmonary Arterial Hypertension or Renovascular Hypertension

        Other Exclusions 23. Has had an allogenic tissue/solid organ transplant. 24. Has previously
        participated in this protocol [ENB-003-101 (MK3475-951)] i.e. a subject previously enrolled
        in Part A cannot participate in Part B.

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