Inclusion Criteria (Part B):

          -  18+ yrs (US), 21+ yrs (Singapore)

          -  Ability to give informed consent

          -  Histologically/cytologically confirmed advanced or metastatic tumors, that are
             unresectable solid malignancies, and that are are refractory, intolerant or not
             suitable to available treatment

          -  Objective and radiologically confirmed disease progression at screening

          -  Measurable disease by RECIST v1.1

          -  ECOG (Eastern Cooperative Oncology Group) 0-2

          -  Life expectancy ≥3 months

          -  Organ function:

               -  Absolute neutrophil count ≥1.0×10^9/L

               -  Platelets ≥100×10^9/L (w/o transfusions w/in 21 days)

               -  Hemoglobin ≥9 g/dL

               -  PT (prothrombin time) and PTT (partial thromboplastin time) w/in ≤1.5× ULN

               -  International normalised ration (INR) ≤1.5× ULN

               -  Total bilirubin ≤1.5× ULN

               -  Transaminases (AST and/or alanine aminotransferase) ≤2.5× ULN (<5× ULN with liver
                  metastases)

               -  Creatinine clearance ≥60 mL/min

               -  Total calcium (corrected for serum albumin) within normal limits

               -  Magnesium ≥ lower limit of normal (LLN)

               -  Normal urinalysis

          -  Patients must have a T-score greater than -1 to be eligible, however, patients with
             osteopenia (T-score of -1 to -2.5 at L/R total hip, L/R femoral neck or lumbar spine
             [L1-L4]) are eligible to participate and will receive calcium and vitamin D
             supplements during the study. Patients with osteoporosis (T-score of < -2.5) must be
             excluded.

          -  Capable of swallowing study medication or has caregiver responsible for administering
             study drug

          -  Negative serum pregnancy test

          -  Dose Expansion - Group 1 and Group 2a only (patients with MSS [microsatellite
             stable]-colorectal cancer [CRC]): Is refractory, intolerant or not suitable for
             treatment with fluoropyrimidine, oxaliplatin, or irinotecan.

          -  Dose Expansion - Group 1 patients: MSS-CRC with confirmed presence of at least one of
             the four different recurrent gene fusions involving RSPO2 or RSPO3 (Fusions A-D).

          -  Dose Expansion - Group 2a patients: Has MSS-CRC with confirmed absence of all four
             different recurrent gene fusions involving RSPO2 or RSPO3 (Fusions A-D).

          -  Dose Expansion - Groups 2b and 2c only (patients with MSS-ovarian and MSS-endometrial
             cancer): Has advanced or metastatic disease for which further conventional therapy,
             e.g. platinum-based chemotherapy, is not suitable. Has MSS tumour as determined by IHC
             (immunohistochemistry), PCR (polymerase chain reaction) or NGS (next generation
             sequencing).

          -  Dose Expansion: All patients must have sufficient archival tumour tissue available, or
             if no archival tumour tissue or tumour ribonucleic acid (RNA) sample is available, the
             patient must have tumour sites that allow conduction of biopsies.

          -  Dose Expansion: Pre-dose and post-dose tumour biopsies are mandatory unless tumour is
             inaccessible or deemed unsafe for procedure by principal investigator.

        Exclusion Criteria (Part B):

          -  Male patient with sexual partner(s) of childbearing potential unwilling to use
             contraception. Sexually active male patients must use a condom during intercourse
             during the study and for 12 weeks after the end of treatment. Condom must also be used
             by vasectomised males.

          -  Female of childbearing potential, unless birth control is used during study and for 12
             weeks after end of treatment.

          -  Pregnant or nursing (lactating) female.

          -  Dose Escalation: Current or anti-cancer therapy within 4 weeks pre-study or with Grade
             ≤1 side effects not resolved within 4 weeks pre-study.

          -  Dose Expansion: Has received previous treatment with pembrolizumab or other immune
             checkpoint inhibitors.

          -  Is receiving any concomitant anti-cancer therapy.

          -  Has used other investigational products within 4 weeks or 5 half-lives (whichever is
             longer) prior to first dose of study drug.

          -  Has evidence of other malignancy not in remission or history of other malignancy
             within last 3 yrs (exceptions: treated basal or skin squamous cell carcinoma or in
             situ cancer of cervix)

          -  Has central nervous system metastases, unless treated with surgery, whole brain
             radiation or stereotactic radiosurgery, and stable disease ≥8 weeks without steroid
             use for ≥4 weeks prior to first dose of study drug.

          -  Has received prior radiation therapy within 4 weeks, or limited field radiation within
             2 weeks, prior to study drug, or with unresolved Grade ≤1 side effects .

          -  Has history of radiation to spine/pelvis bone or chemoradiation to pelvic organs.

          -  Has had major surgical procedure within 4 weeks of starting study drug. Or patient has
             not fully recovered from all surgery-related complications to Grade ≤1.

          -  Has a history of interstitial lung disease, sarcoidosis, silicosis, idiopathic
             pulmonary fibrosis, or pulmonary hypersensitivity pneumonitis.

          -  Has received bisphosphonate therapy for osteoporosis or symptomatic hypercalcaemia, or
             denosumab for osteoporosis prior to starting study drug.

          -  Has osteoporosis (T-score of < -2.5 at left or right total hip, left or right femoral
             neck, or lumbar spine [L1-L4] as determined by DEXA scan at Screening).

          -  Has a history of symptomatic vertebral fragility fractures or fragility fracture of
             hip, pelvis, wrist, or other location (fragility fracture - any fracture without
             trauma or as a result of a fall from ≤standing height).

          -  Has moderate (25%-40% decrease vertebral height) or severe (>40% decrease vertebral
             height) morphometric vertebral fractures.

          -  Has ß-CTX serum level >600 pg/mL in the morning after at least 10 hours of fasting at
             Screening. Note: If patients meet the sole exclusion criteria of ß-CTX serum level
             >600 pg/mL in the morning after at least 10 hours of fasting at screening, patient can
             begin their treatment with the bone protective treatment (denosumab with a starting
             dose of 120 mg, administered SC) as long as the patient has a ß-CTX serum level ≤1000
             pg/mL.

          -  Has thyrotropin level less than lower limit of normal (LLN).

          -  Has 25-hydroxy vitamin D levels less than 50 mmol/L (20 ng/mL).

          -  Has bone metastases.

          -  Has a history of long QT or prolonged QTc (>460 ms).

          -  Is receiving, or has received thiazolidinedione peroxisome proliferator-activated
             receptor gamma agonist (e.g. Actos® [pioglitazone] and Avandia® [rosiglitazone]) w/in
             4 wks prior to starting study drug.

          -  Has metabolic bone disease such as hyperparathyroidism, Paget's disease or
             osteomalacia.

          -  Has a known clinically significant bleeding disorder or coagulopathy.

          -  Is receiving or has received within 4 weeks prior to starting study drug, heparin,
             warfarin or similar anti-coagulants (except for patients on low molecular weight
             heparin for treatment or prophylaxis).

          -  Has severe or unstable medical conditions such as heart failure, ischemic heart
             disease, uncontrolled hypertension, uncontrolled diabetes mellitus, psychiatric
             condition, ongoing cardiac arrhythmia requiring medication (Grade ≥2, by National
             Cancer Institute [NCI] CTCAE v. 4.03).

          -  Has a known history of human immunodeficiency virus (HIV) or active bacterial, viral
             or fungal infections.

          -  Has a history of gastric bypass surgery.

          -  Has received prior treatment with an inhibitor of the Wnt-B-catenin pathway.

          -  Is unwilling or unable to comply with the protocol.

          -  Cannot start treatment with the bone protective treatment with denosumab and/or
             zoledronic acid. Cannot start treatment with the bone protective treatment with
             denosumab SC, in patients requiring this treatment at the start of the study.

          -  Dose Expansion: Patient is unable to provide tumour tissue (from archival tissue or a
             fresh biopsy or tumour RNA).

          -  Has received prophylactic administration of hematopoietic colony stimulating factors
             within 4 weeks prior to starting study drug.

          -  Is receiving active treatment with an oral or IV glucocorticoid for ≥4 weeks at a
             daily dose equivalent to ≥10 mg of oral prednisone within the 12 weeks prior to
             starting the study drug.

          -  Has recent or current active infectious disease requiring systemic antibiotics or
             antifungal or antiviral treatment within 2 weeks prior to the start of the study drug.
             Subjects receiving prophylactic antibiotics (e.g. for prevention of urinary tract
             infection or chronic obstructive pulmonary disease) are eligible.

          -  Has a serious non-healing wound.

          -  Has a history of vasculitis.

          -  Has an active autoimmune disease that has required systemic treatment in the past 2
             years. Replacement therapy is not considered a form of systemic treatment.

          -  Has received a live vaccine within 28 days prior to the start of the study drug.

        Other protocol-defined inclusion and exclusion criteria may apply.