Acute myeloid leukemia is a malignant disorder characterized by the rapid, uncontrolled proliferation of malignant clonal hematopoietic stem cells that accumulate as immature, undifferentiated cells (blasts) in the bone marrow and circulation.

APG-115 is a potent and orally active small-molecule MDM2 inhibitor, it binds to MDM2 protein and shows potent cell growth inhibitory activity in vitro with low nanomolar potencies in a subset of human cancer cell lines. APG-115 has demonstrated its strong antitumor activities with either daily or less frequent dosing-schedules in the acute leukemia xenograft models.

This is a phase 1b, open-label, three-stages study that will initially evaluate the safety and PK/PD profile of APG-115 as a single agent, followed by a combination of APG-115 + azacytidine or cytarabine in R/R AML or MDS subjects.

Patients will continue treatment for maximally 6 cycles or until progression of disease or unacceptable toxicity is observed or administrative discontinuation whichever occurs first. Patients who continue to be benefit after 6 cycles' treatment will receive additional cycles of treatment until progression of disease, unacceptable toxicity is observed or administrative discontinuation. (As long as it is proven safe).

Stage 1: This will be a 3+3 dose escalation to determine the DLTs and MTD/RP2D of APG-115 given according to the different dose levels once daily from Days 1 to 7 every 28 days.

Stage 2: After stage 1 of APG-115 single agent dose escalation first cycle is completed, stage 2 can be initiated with the combination regimen. This will be a 3+3 dose escalation to determine the MTD/RP2D and DLTs of APG-115 + AZA(arm A)/Cytarabine (arm B)combination.

Stage 3: dose expansion of the combination regimes.

Inclusion Criteria:

1. Patients with a diagnosis of histologically confirmed relapsed or refractory (R/R) acute myeloid leukemia by WHO classification or relapsed/progressed high/very high risk MDS (score≥4.5) according to IPSS-R risk stratification
2. Age >/= 18 years.
3. Adequate organ function
4. Subject must have a projected life expectancy of at least 12 weeks.
5. ECOG performance status of 0-1.
6. Patient must have the ability to understand the requirements of the study and signed informed consent. A signed informed consent by the patient or his legally authorized representative is required prior to their enrollment on the protocol.
7. Subject has a white blood cell count< 50 × 109/L. Note: Hydroxyurea is permitted to meet this criterion.

Exclusion Criteria:

1. Subject has acute promyelocytic leukemia.

2. Patients must not have had leukemia biotherapy 4 weeks prior to starting investigational drug, or less than 5 half-lives small molecular targeted drug therapy, or 28 days any anti-cancer therapy (whichever is longer)

3. Uncontrolled intercurrent illness including, but not limited to active uncontrolled infection, symptomatic congestive heart failure (NYHA Class III or IV), unstable angina pectoris, clinically significant cardiac arrhythmia, or psychiatric illness/social situations that would limit compliance with study requirements.

4. Active infection requiring systemic antibiotic/antifungal medication, known clinically active hepatitis B or C, or HIV infection.

5. Participants who have received allogeneic HSCT, or autologous HSCT within 12 months.

6. Patients with active, uncontrolled CNS leukemia will not be eligible.

7. Any prior systemic MDM2-p53 inhibitor treatment

8. Any other condition or circumstance that would, in the opinion of the investigator, make the patient unsuitable for participation in the study.

9. Subject has a history of other malignancies within 2 years prior to study entry, with the exception of:

   • Adequately treated in situ carcinoma of the cervix uteri or carcinoma in situ of breast;
   • Basal cell carcinoma of the skin or localized squamous cell carcinoma of the skin;
   • Previous malignancy confined and surgically resected (or treated with other modalities) with curative intention: requires discussion with sponsor.