A Safety, Pharmacokinetic and Clinical Activity Study of NUC-7738 in Patients With Advanced Solid Tumours and Lymphoma

Inclusion Criteria: 1. Provision of signed written informed consent. 2. Solid tumour cohorts only (Phase I and Phase II; excluding NUC-7738 + pembrolizumab cohort): Histologically confirmed diagnosis of an advanced solid tumour with measurable disease as per RECIST v1.1 criteria and/or evaluable disease (evaluable: cytologically or radiologically detectable disease such as ascites, peritoneal deposits, or lesions, which do not fulfil RECIST v1.1 criteria for measurable disease) for solid tumours. 3. NUC-7738 + pembrolizumab cohort only (Phase II): Histologically confirmed diagnosis of metastatic cutaneous melanoma with measurable disease as per RECIST v1.1 criteria. Must have progressed on ≤2 prior lines of therapy for advanced/metastatic disease. In addition, patients may have been treated in the neoadjuvant/adjuvant setting. At least one prior line must have included a PD-1/PD-L1-containing regimen (either monotherapy or in combination) for which they progressed on. 4. Lymphoma cohort only (Phase II): Relapsed refractory lymphoma (high grade and low grade B-NHL, Hodgkin's Lymphoma and T-cell lymphomas), which is not amenable to standard of care, is refractory to standard of care or for which no standard of care exists. Patients must have bi-dimensionally measurable disease as per Cheson et al, 2007 criteria for lymphoma. 5. For solid tumours in single-agent Phase II cohorts only: patients should have received no more than 3 prior lines of treatment for metastatic disease. 6. Age ≥18 years (no upper age limit). 7. Eastern Cooperative Oncology Group performance status of 0 or 1. 8. Life expectancy of ≥12 weeks. 9. Adequate bone marrow, liver, and renal function. 10. Ability to comply with protocol requirements. 11. Female patients of child-bearing potential must have a negative serum pregnancy test within 3 days prior to the first NUC-7738 administration. All patients of child-bearing potential must agree to practice true abstinence or to use two forms of contraception, one of which must be a highly effective method of contraception, from the time of screening until 6 months after the last dose of study medication. 12. Phase I and Phase II dose-confirmation cohorts only: Patient must be willing to undergo a new tumour biopsy at Screening and during therapy on the study. Biopsies are mandatory for patient inclusion, except where taking a biopsy would be associated with unacceptable clinical risk due to the location of the disease. Such patients may be discussed on a case-by-case basis with the study Medical Monitor to determine their eligibility. A prior (archival) biopsy that is less than 3 months old may be substituted for a fresh tumour biopsy at Screening with agreement from the Medical Monitor. From protocol v3.4 onwards, biopsies are no longer required. 13. Patients must have been advised to take measures to avoid or minimise exposure of the skin and eyes to UV light, including avoiding sunbathing and visits to the solarium, for the duration of study participation and for a period of 4 weeks following the last dose of study medication. Exclusion Criteria: The following exclusion criteria apply to all patients. Please also refer to additional exclusion criteria for the NUC-7738 + pembrolizumab cohort below. 1. History of allergic reaction fo any of the components of NUC-7738. 2. Central nervous system or leptomeningeal metastases. Patients with brain metastases are eligible if they have no ongoing neurological symptoms, have not received corticosteroids within 7 days prior to enrolment, and show radiographic stability for at least 2 weeks. 3. Chemotherapy, radiotherapy (other than a short cycle of palliative radiotherapy for bone pain), immunotherapy, or exposure to another investigational agent within 28 days (for biological agents decision on washout period will be made on a case by base basis) of first administration of the IMP: 1. For nitrosoureas and mitomycin C within 6 weeks of first administration of NUC-7738 2. For hormone therapy within 14 days of first administration of NUC-7738 3. Corticosteroid treatment is allowed during the screening period but should be weaned to a dose of 10 mg prednisolone (or steroids equivalent) by Cycle 1 Day 1. 4. Prior toxicities from anti-cancer agents or radiotherapy, which have not regressed to Grade ≤1 severity (NCI-CTCAE v5.0), excluding neuropathy, ototoxicity and alopecia (which are excluded if ≥Grade 3). 5. Presence of any uncontrolled concomitant illness, serious illness, medical conditions, or other medical history, including laboratory results, which, in the Investigator's opinion, would be likely to interfere with their participation in the study, or with the interpretation of results, including the following: 1. Congestive heart failure (New York Heart Association Class III or Class IV). 2. Myocardial infarction within 6 months of the first dose of study medication. 3. Unstable or poorly controlled angina pectoris. 4. Complete left bundle branch, bifascicular block or other clinically significant abnormal electrocardiogram finding. 5. A history of or current risk factor for Torsades de Point (e.g., heart failure, hypokalaemia, or a family history of long QT syndrome). 6. A history of, or current diagnosis of, interstitial pneumonitis or pulmonary fibrosis. 6. Known human immunodeficiency virus positive or known active hepatitis B or C. Presence of an active bacterial or viral infection including Herpes zoster or chicken pox. 7. Any condition (e.g., known or suspected poor compliance, psychological instability, geographical location etc.) that, in the judgment of the Investigator, may affect the patient's ability to sign the informed consent and undergo study procedures. 8. Currently pregnant, lactating or breastfeeding. 9. QTc interval \>450 milliseconds for males and \>470 milliseconds for females. 10. Concomitant use of drugs known to prolong QT/QTc interval. 11. Concomitant use of strong CYP3A4 inducers or strong CYP3A4 inhibitors. The use of strong CYP3A4 inducers within 2 weeks of first receipt of study drug or the use of strong CYP3A4 inhibitors within 1 week of first receipt of study drug is also excluded. 12. Have received a live vaccination within four weeks of first planned dose of study medication. NUC-7738 + pembrolizumab cohort only 1. Any history of hypersensitivity or current contra-indication to the components of pembrolizumab (L-histidine, polysorbate 80, sucrose, sodium hydroxide, hydrochloric acid). 2. Current contra-indication to immunotherapy with checkpoint inhibitors. 3. Systemic steroid therapy or any immunosuppressive therapy (≥10 mg/day prednisone or equivalent). 4. Known neutralising antibodies against checkpoint inhibitors. 5. Patients previously exposed to checkpoint inhibitors who are not adequately treated for skin rash or have no replacement therapy for endocrinopathies. 6. Any prior toxicity attributed to checkpoint inhibitors that resulted in discontinuation of therapy. These patients should be discussed on a case-by-case basis with the Medical Monitor. 7. Active autoimmune disease or a documented history of autoimmune disease, including ulcerative colitis and Crohn's disease or any condition that requires systemic steroids. 8. Prior treatment with cell therapies.