An Open Label Dose Finding Study of PTT-4256 in Patients With Solid Tumours (RAISIC-1).

Inclusion Criteria:

1. ≥ 18 years of age at the time of consent.

2. Participant has given written informed consent to participate in the study and isable and willing to adhere to the study protocol.

3. Participant has cytologically or histologically confirmed solid malignancy and haslocally advanced or metastatic disease. Melanoma, non-small cell lung cancer, renalcell carcinoma, metastatic castrate-resistant prostate cancer, cervix cancer, triplenegative breast cancer, colorectal cancer, gastric cancer are preferred solidtumours.

4. Participant must require systemic treatment for their tumour and either:

5. be refractory to,

6. have progressed on,

7. be intolerant to, or

8. be not otherwise a candidate - in the opinion of the Investigator - for any ofthe currently available standard treatments.

9. Participant has measurable disease per RECIST v1.1. Participants with non-measurabledisease per RECIST v1.1 might be considered eligible upon discussion with theSponsor.

10. Participant has an Eastern Cooperative Oncology Group (ECOG) performance status of 0to 1.

11. Participant has an estimated life expectancy of at least 3 months in the opinion ofthe Investigator.

12. Adequate haematological (blood or platelet transfusion not allowed within 7 daysprior to Screening), liver, and renal function defined below (repeat measurement ofborderline values permitted):

• Haemoglobin ≥ 8.5 g/dL,

• Absolute neutrophil count (ANC) ≥ 1.5 × 109/L,

• Platelet count ≥ 90 x 109/L,

• Total bilirubin ≤ 1.5 institutional upper limit of normal (ULN), (or where ≤ 2 × ULN with known hepatobiliary metastases or Gilbert's syndrome),

• Aspartate transaminase (AST) and Alanine transaminase (ALT) ≤ 2.5 × ULN (or ≤ 5 ×ULN if liver metastases are present),

• Estimated glomerular filtration rate (eGFR) > 30 mL/min/1.73 m2 (calculatedusing Cockcroft-Gault).

9. Females:

10. must not be pregnant or lactating, and must use acceptable, highly effectivecontraception from Screening until 90 days after last IMP administration.Effective forms of contraception are defined in Section 7.3.2,

11. Females with same-sex partners (abstinence from penile-vaginal intercourse) orwho are abstinent from heterosexual intercourse are not required to usecontraception when this is their preferred and usual lifestyle,

12. Women of childbearing potential (WOCBP) must have a negative pregnancy test atScreening and Day 1 and be willing to have additional pregnancy tests asrequired throughout the study. WOCBP must not donate ova from signing informedconsent until at least 90 days after the last IMP administration.

13. Women of non-childbearing potential (WONCBP) must be postmenopausal for ≥12months or ≥ 60 years of age at the time of consent (postmenopausal status is tobe confirmed through testing of follicle-stimulating hormone (FSH) levels ≥ 40IU/L (except for participants on hormone replacement therapy) at Screening foramenorrhoeic female participants).

14. Males:

15. must be surgically sterile (> 6 months since vasectomy with confirmation of noviable sperm),

16. or if engaged in sexual relations (intercourse) with a WOCBP, either hispartner must be surgically sterile (eg, hysterectomy, bilateral salpingectomy,bilateral oophorectomy), or an acceptable, highly effective contraceptivemethod must be used from Screening until 90 days after last IMP administration,

17. Males with same-sex partners (abstinence from penile-vaginal intercourse) orwho are abstinent from heterosexual intercourse are not required to usecontraception when this is their preferred and usual lifestyle,

18. Males must not donate sperm from the first dose of IMP until at least 90 daysafter the last dose of IMP

Exclusion Criteria:

1. Inability or unwillingness to adhere to the study protocol, including studyprocedures and oral intake of the IP.

2. Active primary central nervous system (CNS) malignancy, active CNS metastases orleptomeningeal disease. Participants with previously treated primary CNS malignancyor CNS metastases are eligible to participate if:

3. they have stable and controlled neurological symptoms without deterioration;

4. they have stable disease as assessed by imaging (preferably contrast-enhancedMRI) for at least 28 days prior to first IMP administration;

5. they have no evidence of new or enlarging brain metastases; and

6. they are not using corticosteroids for at least 7 days prior to first IMPadministration.

7. Unresolved or unstable serious toxic side effects of prior chemotherapy orradiotherapy, ie, ≥ Grade 2 per CTCAE v5.0 except fatigue, alopecia, infertility, orthose relating to palliative radiotherapy within 6 weeks prior to first IMPadministration. Participants with residual AEs > Grade 1 considered not clinicallysignificant may be considered eligible on a case-by-case basis, in discussion withthe Sponsor.

8. Concurrent active or previous history of other malignancy within the past 2 yearsbefore first IMP administration except:

9. Malignancy (other than in situ) treated with curative intent and with no knownactive disease present for ≥ 2 years before first IMP administration and feltto be at low risk of recurrence by the Investigator;

10. Adequately treated non-melanoma skin cancer or lentigo malignant with noevidence of disease;

11. Adequately treated in situ cancer without evidence of disease.

12. Received anti-cancer therapy (including chemotherapy, immunotherapy, radiationtherapy, biologic therapy, or any investigational therapy) within 28 days or 5half-lives of the therapeutic agent, whichever is shorter, prior to the first IMPadministration. Palliative adiotherapy given within 28 days prior to the first IMPadministration may be considered eligible on a case-by-case basis, in discussionwith the Sponsor.

13. Uncontrolled symptomatic malignant effusion(s) or those requiring recurrent drainagein the opinion of the Investigator.

14. Participants with clinically significant active autoimmune or chronic inflammatorydisease that is not well controlled with standard therapy in the opinion of theInvestigator.

15. Grade 3 or higher immunotherapy-induced autoimmune hepatitis.

16. Participants with:

17. symptomatic colitis of any CTCAE v5.0 Grade and aetiology within 4 weeks beforefirst dosing,

18. a history of autoimmune (including but not restricted to Crohn's disease,ulcerative colitis, and celiac's disease) or idiopathic (including but notrestricted to pseudomembranous, ischaemic and microscopic) colitis, and/or,

19. a history of drug-induced colitis of CTCAE v5.0 Grade 3 or higher.

20. History of primary immunodeficiency, bone marrow transplantation or solid organtransplantation.

21. Use of systemic immunosuppressive medication (including > 10 mg prednisolone per dayor equivalent) within 14 days prior to the first IMP administration. Note that useof immunosuppressive medications as prophylaxis in participants with contrastallergies is acceptable. Adrenal replacement corticosteroid doses ≤10 mg dailyprednisone equivalent are permitted, as are topical, inhaled, intra-articular orintra-nasal corticosteroids.

22. Participants with active Hepatitis B virus (HBV) hepatitis infection (defined ashaving a positive hepatitis B surface antigen [HBsAg] test at Screening) orHepatitis C virus (HCV) hepatitis. Participants with resolved past HBV infection (defined as having a negative HBsAg test and a positive antibody to hepatitis B coreantigen [anti-HBc] antibody test) are eligible. Participants positive for HCVantibody are eligible only if polymerase chain reaction (PCR) is negative for HCVRNA.

23. Participants with active HIV infection or known history of HIV infection.

24. Active infection requiring systemic antibacterial, antiviral or anti-fungal therapyfor ≤ 7 days of first IMP administration. Note that participants on antibacterial,anti-fungal or antiviral prophylaxis are eligible.

25. Uncontrolled or recent history of clinically significant cardiovascular disease:Symptomatic heart failure (New York Heart Association classes II-IV), unstableangina, myocardial infarction, serious/uncontrolled/unstable cardiac arrhythmia,cerebral vascular accident, coronary/peripheral artery bypass graft surgery,transient ischaemic attack, or pulmonary embolism within 4 months prior to first IMPadministration. Note that participants with small pulmonary emboli not thought toput them at higher risk may be considered eligible on a case-by-case basis, indiscussion with the Sponsor.

26. Confirmed Baseline QTcF > 450 msec for males and > 470 msec for females (triplicateECG) or history of torsades de pointes or history of congenital long QT syndrome.Note that participants with an apparent prolonged QT due to bundle branch block maybe considered eligible on a case-by-case basis, in discussion with the MM.

27. History of clinically significant interstitial lung disease, or activenon-infectious pneumonitis, or which may interfere with the detection or managementof suspected drug related pulmonary toxicity.

28. Has had or is scheduled to have major surgery < 28 days prior to the first IMPadministration. Elective surgical procedures not considered to put participants athigher risk of AEs may be allowed on a case-by-case basis, in discussion with theSponsor.

29. Any other concurrent severe and/or uncontrolled medical, surgical or psychiatricand/or social condition which, in the view of the Investigator, could compromise theparticipant's safety or ability to participate in the study and make them unsuitablefor participation.

30. Use of other investigational medicinal products within 2 weeks or at least 5half-lives (whichever is longer) before IMP administration.

31. Must not have had a live vaccine administration ≤ 28 days prior to the first dose ofthe IMP.

32. Participants with known active or suspected alcohol or drug abuse that may interferewith the study in the opinion of the Investigator.

33. Gastrointestinal conditions that may affect oral absorption of drugs in the opinionof the Investigator, including but not restricted to gastroparesis and short bowelsyndrome.