Inclusion Criteria:

          1. Provision of fully informed consent prior to any study specific procedures.

          2. Histologically confirmed SCLC with documented MYC family (MYC, MYCN, MYCL)
             amplification or CDKN2A mutation combined with TP53 mutation.

          3. Patients must be ≥20 years of age.

          4. Small cell lung cancer that has progressed during or after first-line therapy.

               -  The 1st line regimen must have contained platinum based regimen.

               -  Refractory to first-line chemotherapy or relapse within 6 months since the last
                  dose of first-line chemotherapy

               -  If the patient correspond to sensitive relapse (relapse more than 6 months since
                  the last dose of first-line chemotherapy), she/he should get second-line
                  treatment.

          5. Previous radiotherapy is allowed.

          6. Provision of tumor sample (from either archival or fresh biopsy)

          7. Patients are willing and able to comply with the protocol for the duration of the
             study including undergoing treatment and scheduled visits and examinations.

          8. ECOG performance status 0-2

          9. Patients must have a life expectancy ≥ 3 months from proposed first dose date.

         10. Patients must have acceptable bone marrow, liver and renal function measured within 14
             days prior to administration of study treatment as defined below:

               -  Haemoglobin ≥9.0 g/dL

               -  Absolute neutrophil count (ANC) ≥ 1.5 x 109/L

               -  White blood cells (WBC) > 3 x 109/L

               -  Platelet count ≥100 x 109/L

               -  Total bilirubin ≤ 1.5 x institutional upper limit of normal (ULN)

               -  AST (SGOT)/ALT (SGPT) ≤ 2.5 x institutional upper limit of normal unless liver
                  metastases are present in which case it must be ≤ 5x ULN

               -  Serum creatinine ≤1.5 x institutional ULN and a calculated creatinine clearance
                  (CrCl) ≥45 mL/min by the Cockcroft-gault method:

             CrCl = (140-age) x (weight/kg) x (0.85 if female)

         11. At least one measurable lesion that can be accurately assessed by imaging or physical
             examination at baseline and follow up visits.

         12. Negative urine or serum pregnancy test within 28 days of study treatment, confirmed
             prior to treatment on day 1, if woman of childbearing potential

         13. Female patients who are not of childbearing potential and fertile female patients of
             childbearing potential who agree to use adequate contraceptive measures, who are not
             breastfeeding.

         14. Fertile male patients willing to use at least one medically acceptable form of birth
             control, and must not donate sperm, for the duration of the study, and for 2 weeks
             after treatment stops

        Exclusion Criteria:

          1. More than two prior chemotherapy regimen for the treatment of small cell lung cancer

          2. Any previous treatment with P53 inhibitors (small molecules)

          3. Patients with second primary cancer, except: adequately treated non-melanoma skin
             cancer, curatively treated in-situ cancer of the cervix, or other solid tumours
             curatively treated with no evidence of disease for >2 years.

          4. Patients unable to swallow orally administered medication.

          5. Treatment with any investigational product during the last 14 days before the
             enrollment (or a longer period depending on the defined characteristics of the agents
             used).

          6. Patients receiving any systemic chemotherapy, radiotherapy (except for palliative
             reasons), within 3 weeks from the last dose prior to study treatment (or a longer
             period depending on the defined characteristics of the agents used). The patient can
             receive a stable dose of bisphosphonates or denosumab for bone metastases, before and
             during the study as long as these were started at least 4 weeks prior to treatment.

          7. Concomitant use of known sensitive CYP3A4 substrates or CYP3A4 substrates with a
             narrow therapeutic index, or to be moderate to strong CYP3A4 inhibitor/inducer which
             cannot be discontinued to weeks prior to Day 1 of dosing and withheld throughout the
             study until 2 weeks after the last dose of study drug, Co-administration of aprepitant
             or fosaprepitant during this study is prohibitedRefer to the Section 5.9.2 and
             Appendix H for listing of all prohibited medications.

          8. With the exception of alopecia, any ongoing toxicities (>CTCAE grade 1) caused by
             previous cancer therapy.

          9. Intestinal obstruction or CTCAE grade 3 or grade 4 upper GI bleeding within 4 weeks
             before the enrollment.

         10. Resting ECG with measurable QTcB > 480 msec on 2 or more time points within a 24 hour
             period or family history of long QT syndrome.

         11. Patients with cardiac problem as follows: unstable angina pectoris, congestive heart
             failure, acute myocardial infarction, conduction abnormality not controlled with
             pacemaker or medication, significant ventricular or supraventricular arrhythmias
             (patients with chronic rate controlled atrial fibrillation in the absence of other
             cardiac abnormalities are eligible).

         12. Female patients who are breast-feeding or child-bearing

         13. Any evidence of severe or uncontrolled systemic disease, active infection, active
             bleeding diatheses or renal transplant, including any patient known to have human
             immunodeficiency virus (HIV), active hepatitis B or active hepatitis C

         14. Major surgical procedures ≤28 days of beginning study treatment, or minor surgical
             procedures ≤7 days

         15. Known central nervous system (CNS) disease other than neurologically stable,treated
             brain metastases - defined as metastasis having no evidence of progression or
             haemorrhage for at least 2 weeks after treatment