Inclusion Criteria:

1. Written informed consent
2. Aged at least 18 years
3. Histological or cytological confirmation of advanced malignancy not considered to be appropriate for further conventional treatment
4. Patients must use adequate contraception measures for the duration of the study and for 6 months after the study
5. Patients must have adequate organ functions
6. Ability to swallow and retain oral medication

Exclusion Criteria:

1. Prior treatment with a compound of the same mechanism of action as RXC004
2. No other anti-cancer therapy or investigational product throughout the study
3. Patients with persistent grade 2 or higher diarrhoea
4. Patients at high risk of bone fractures
5. QTc prolongation
6. Known uncontrolled intercurrent illness
7. Known severe allergies to any active or inactive ingredients

In addition for Module 2

1. Patients with any contraindication/hypersensitivity to Nivolumab of excipients
2. Patients with active or prior documented autoimmune of inflammatory disorders within the past 5 years
3. Patients with active infections, including tuberculosis, hepatitis B, hepatitis C or human immunodeficiency virus
4. Use of any live vaccines against infectious diseases (eg, influenza, varicella) within 4 weeks (28 days) of initiation of study treatment
5. Patients with body weight <40kg
6. Patients with a history of allogeneic organ transplant or active primary immunodeficiency

In addition to Module 3

Patients with Wnt ligand-dependent solid tumours, defined as:

1. Biliary tract cancers
2. Thymus cancers (thymic and thymoma WHO classification)
3. Any solid tumour with documented aberration in RNF43 and/or RSPO from central pre-screening or from a recognised panel approved by the Sponsor
4. Patients willing to have mandatory skin biopsies at baseline and on one occasion while on study treatment.