Inclusion Criteria:

        Inclusion Criteria for Dose Escalation and Dose Expansion Part:

          1. Patients with histologically confirmed diagnosis of locally advanced/metastatic HER2
             negative breast cancer, epithelial ovarian cancer, castration-resistant prostate
             cancer (CRPC) or pancreatic cancer. BRCA1 and BRCA2 mutation status is not required
             for enrollment in the Dose Escalation part, but enrichment with deleterious/pathogenic
             BRCA carriers will be attempted.

          2. Patients must have progressive disease defined by RECIST 1.1 following standard
             therapy or be unsuitable for standard therapy. For CRPC patients, disease progression
             at study entry is defined as one or more of the following three criteria (according to
             PCWG2):

               -  PSA progression defined by a minimum of three rising PSA levels with an interval
                  of ≥ 1 week between each determination. The PSA value at the Screening visit
                  should be ≥ 2.0 ng/ml (µg/L). If the third PSA value is less than second PSA, a
                  fourth PSA must be repeated and if the value is higher than second it must be
                  considered as progressive disease;

               -  Soft tissue/visceral disease progression defined by RECIST 1.1;

               -  Bone disease progression defined by two or more new lesions on bone scan.

          3. Male or female patients with age ≥ 18 years.

          4. Eastern Cooperative Oncology Group (ECOG) performance status (PS) ≤ 2.

          5. Life expectancy of at least 3 months.

          6. Signed and dated IEC or IRB-approved Informed Consent.

          7. At least 4 weeks must have elapsed or, in absence of toxicity, 5 half-lives, since
             completion of prior cancer therapy (at least 6 weeks for nitrosureas, mitomycin C and
             liposomal doxorubicin) before Cycle 1 Day 1.

          8. Prior platinum therapy is allowed provided that criteria for platinum refractory
             disease are not met (see exclusion criterion n.3).

          9. Prior treatment with PARP inhibitors is allowed in the Dose Escalation Part and
             required in two Cohorts of the Dose Expansion Part (HER2 neg breast cancer and
             epithelial ovarian cancer with prior therapy with a PARP inhibitor). It is not allowed
             in the other cohorts of patients enrolled in the Dose Expansion.

         10. Resolution of all acute toxic effects (excluding alopecia) of any prior anticancer
             therapy to NCI CTC (Version 5.0) Grade ≤ 1 or to the baseline laboratory values as
             defined in Inclusion Criterion Number 11.

         11. Adequate hematological profile, renal and hepatic functions.

         12. All patients must agree before enrollment to undergo germline BRCA1 and BRCA2 testing
             on blood. The test will be performed in a centralized laboratory selected by the
             sponsor. Availability of an ad hoc blood sample is mandatory for central germline BRCA
             analysis both in dose escalation and in dose expansion.

         13. Patients must use effective contraception or abstinence. Female patients of
             childbearing potential must agree to use effective contraception or abstinence during
             the period of therapy and in the following 90 days after discontinuation of study
             treatment. Male patients must be surgically sterile or must agree to use effective
             contraception or abstinence during the period of therapy and in the following 90 days
             after discontinuation of study treatment.

         14. Capability to swallow capsules intact (without chewing, crushing, or opening).

         15. Willingness and ability to comply with scheduled visits, treatment plan, laboratory
             tests and other study indications or procedures.

             Inclusion Criteria specific for Dose Expansion Part:

         16. Patients must have deleterious/pathogenic germline BRCA1 or BRCA2 mutation confirmed
             by the centralized laboratory selected by the Sponsor.

         17. Measurable disease by Response Evaluation Criteria in Solid Tumors version 1.1
             (RECIST) except for CRPC patient who can have non-measurable disease.

         18. Patients must have received the following previous treatment:

               -  HER2 negative breast cancer: no more than 3 prior chemotherapy regimens for
                  locally advanced and/or metastatic disease (no limit on prior hormonal therapies
                  or targeted anticancer therapies). At least 1 line of taxane or anthracycline
                  based chemotherapy, if not contraindicated, in adjuvant/neoadjuvant or metastatic
                  setting. If HR (Hormone Receptor) positive, at least 1 line of prior endocrine
                  therapy.

               -  Epithelial ovarian cancer: no more than 4 prior regimens for locally
                  advanced/metastatic disease including at least 1 line of platinum based
                  hemotherapy;

               -  CRPC: no more than 4 prior regimens; must have received at least 1 prior NHA
                  (e.g. abiraterone or enzalutamide) and a taxane. Ongoing androgen deprivation
                  therapy with a GnRH analogue or orchiectomy (i.e., surgical or medical
                  castration) is mandatory.

               -  Pancreatic cancer: no more than 2 prior regimens. Patients may have received
                  prior radiotherapies (not considered as a regimen).

         19. Patients with controlled, asymptomatic CNS involvement, which has been stable for the
             previous 4 weeks, are eligible. The use of seizure prophylaxis is allowed as long as
             patients are taking non-enzyme-inducing anti-epileptic drugs (non-EIAEDs).

        Exclusion Criteria:

          1. Current enrollment in another therapeutic clinical trial.

          2. Prior malignancy except for any of the following:

               -  Prior BRCA-associated cancer as long as there is no current evidence of the prior
                  cancer;

               -  Carcinoma in situ or non-melanoma skin cancer;

               -  A cancer diagnosed and definitively treated ≥ 5 years before enrolment with no
                  subsequent evidence of recurrence;

          3. Patients with prior platinum therapy exposure who had evidence of disease progression
             during platinum treatment (refractory disease) and patients whose disease relapsed
             within 6 months of the last dose of prior adjuvant or neo-adjuvant platinum therapy.

          4. Patients who have received prior PARP inhibitors should be excluded in the Dose
             Expansion part except for the cohorts of HER2 negative breast cancer patients with
             prior PARP inhibitors and epithelial ovarian cancer patients with prior PARP
             inhibitors.

          5. Patients with known symptomatic brain metastases or leptomeningeal involvement.
             Patients with asymptomatic brain metastases or leptomeningeal involvement are excluded
             in the Dose Escalation Part only.

          6. Treatment with systemic immune modulators such as corticosteroids at
             prednisone-equivalent dose of >10 mg/day, cyclosporine and tacrolimus or radiotherapy
             within 28 days before Cycle 1 Day 1.

          7. Prior high-dose chemotherapy with bone marrow or stem cell transplant.

          8. Major surgery, other than diagnostic surgery, within 4 weeks prior to treatment.

          9. Any of the following in the past 6 months: myocardial infarction, unstable angina,
             coronary/peripheral artery bypass graft, symptomatic congestive heart failure,
             cerebrovascular accident or transient ischemic attack, pulmonary embolism, deep vein
             thrombosis.

         10. Pregnancy or breast-feeding women.

         11. Known active infections (bacterial, fungal, viral including HIV positivity).

         12. Active gastrointestinal disease (e.g., documented gastrointestinal ulcer, Crohn's
             disease, ulcerative colitis, or short gut syndrome) or other syndromes that would
             impact on drug absorption.

         13. Patients with QTc interval ≥ 480 milliseconds or with risk factors for torsade de
             pointes (e.g., heart failure, uncontrolled hypokalemia, family history of long QT
             syndrome) or receiving treatment with concomitant medications known to prolong the
             QT/QTc interval that cannot be replaced with another treatment.

         14. Patients receiving treatment with concomitant medications known to be CYP2D6 and
             CYP2C19 sensitive substrates that cannot be replaced with another treatment.

         15. Other severe acute or chronic medical or psychiatric condition (including history of
             seizure disorder) or laboratory abnormality that may increase the risk associated with
             study participation or study drug administration or may interfere with the
             interpretation of study results and, in the judgment of the Investigator, would make
             the patient inappropriate for entry into this study or could compromise protocol
             objectives in the opinion of the Investigator and/or the Sponsor.