The data met the protocol-specified criteria for futility of the investigational treatment.

Phase III, multicenter, randomized study with two arms (1:1 ratio) enrolling patients with AML relapsed/refractory after 2, 3, or 4 prior induction regimens:

Experimental arm: DFP-10917 14-day continuous intravenous (IV) infusion at a dose of 6 mg/m²/day followed by a 14-day resting period per 28-day cycles.

Control arm: Non-Intensive Reinduction (LoDAC, Azacitidine, Decitabine, Venetoclax Combination Regimens) or Intensive Reinduction (High and Intermediate Dose Cytarabine Regimens), depending on the patient's prior induction treatment.

Study to compare the rate of complete response (CR) and duration of CR, in patients with relapsed or refractory AML to two, three, or four prior induction regimens that may have included intensive chemotherapy (e.g., "7+3" cytarabine and daunorubicin), epigenetic therapy (i.e., azacitidine or decitabine), or targeted therapy (e.g., FLT-3, IDH-1/2, BCL-2, monoclonal antibody), who will receive DFP-10917 versus non-intensive reinduction (LoDAC, azacitidine, decitabine, venetoclax + LoDAC or azacitidine or decitabine) or intensive reinduction (high and intermediate dose cytarabine regimens) as a second, third, or fourth salvage treatment.

Experimental Arm DFP-10917 Dose: 6 mg/m²/day administered by continuous infusion for 14 days followed by a 14-day resting period per 28-day treatment cycle. If a patient experiences a significant treatment-related AE, the patient may undergo one dose reduction of DFP-10917 to 4 mg/m²/day x 14 days for subsequent treatment cycles

Control arm: Non-Intensive Reinduction (LoDAC, Azacitidine, Decitabine, Venetoclax + LoDAC or Azacitidine or Decitabine) or Intensive Reinduction (High and Intermediate Dose Cytarabine Regimens), depending on the patient's prior induction treatment as well as the patient's clinical condition and comorbidities. Control treatment is to be selected only from among the following. Institutional practice for administering these treatments are permitted, but the dose and days of drug administration should be followed as below.

Non-Intensive Reinduction:

• LoDAC: 20 mg Cytarabine administered by subcutaneous (SC) injection, twice daily (BID) for 10 days, plus best supportive care per 28-day treatment cycle
• Azacitidine: 75 mg/m²/day administered by SC for 7 consecutive days (or 5+2), plus best supportive care per 28-day treatment cycle
• Decitabine: administered as continuous intravenous (CIV) infusion 20 mg/m² x 5 days plus best supportive care per 28 day treatment cycle
• Venetoclax + LoDAC or Azacitidine or Decitabine: In combination with LoDAC, Venetoclax will be administered via a daily ramp-up to a final 600 mg once daily dose. During the ramp-up, patients are to receive TLS prophylaxis and may be hospitalized for monitoring. Cytarabine will be administered subcutaneously at a dose of 20 mg/m² once daily on Days 1-10 of each 28-day cycle beginning Cycle 1 Day 1. In combination with Azacitidine or Decitabine, Venetoclax will be administered via a daily ramp-up to a final 400 mg once daily dose. Azacitidine will be administered intravenously or subcutaneously at a dose of 75 mg/m² on Days 1-7 of each 28-day cycle beginning on Cycle 1 Day 1. Decitabine will be administered via IV at a dose of 20 mg/m² on Days 1-5 or 1-10, as per institutional practice, of each 28-day cycle beginning Cycle 1 Day 1.

Intensive Reinduction:

• High DAC = cytarabine at doses of 1-2 g/m²/day for up to 5 days, with a maximum total dose 10 g/m² per course
• FLAG = Days 1-5: fludarabine 30 mg/m² IV over 30 minutes, Days 1-5: cytarabine 1 2 grm/m² over 4 hours daily x 5, and granulocyte colony-stimulating factor 5 mcg/kg or 300 mcg/m² until Polymorphonuclear Neutrophil (PMN) recovery, with or without idarubicin Days 1-3 at 8 mg/m² IV daily x 3 (FLAG-Ida)
• MEC = Days 1-6: mitoxantrone 6 mg/m² IV bolus, etoposide 80 mg/m² IV over 1 hour, and cytarabine 1 grm/m² IV over 6 hrs (Etoposide may be deleted per institutional guidelines, i.e., HAM regimen)
• CLAG/M or Ida = cladribine 5 mg/m² on Days 1-5, cytarabine 2 g/m² on Days 1-5, granulocyte-colony stimulating factor 300 μg on Days 0-5 (G-CSF starts 24 hr prior to chemotherapy), and mitoxantrone 10 mg/m² on Days 1-3 or Idarubicin 10 mg/m² on Days 1-3
• Intermediate DAC = cytarabine 20 mg/m² IV daily x 5

The selection of control arm treatment will be determined by the investigator depending on the patient's prior initial induction and salvage treatment regimen(s), as well as the patient's clinical condition and comorbidities. The investigator will select the patient's control treatment from among the non-intensive or intensive regimens prior to study treatment randomization in order to balance treatment allocation between the experimental and control treatment arms.

Inclusion Criteria:

1. Histologically or pathologically confirmed diagnosis of AML based on WHO classification that has relapsed after, or is refractory to, two, three, or four prior induction regimens that may have included intensive chemotherapy (e.g., "7+3" cytarabine and daunorubicin), epigenetic therapy (i.e., azacitidine or decitabine), or targeted therapy (e.g., FLT-3, IDH-1/2, BCL-2, monoclonal antibody).

   (Relapse is defined as reemergence of ≥5% leukemia blasts in bone marrow or ≥1% blasts in peripheral blood ≥90 days after first CR or CR without complete platelet recovery (CRp). Refractory AML is defined as persistent disease ≥28 days after initiation of intensive induction therapy (up to two induction cycles) or relapse <90 days after first CR or CRp. Refractory disease for patients undergoing hypomethylating agent induction is defined as lack of remission following at least 2 cycles of epigenetic therapy without reduction in bone marrow blast status.)

   Patients with a history of IPSS-R high or very high risk MDS that transformed to AML during treatment with hypomethylating drugs and then relapse following or are refractory to a subsequent AML induction regimen may be enrolled as Second Salvage AML patients. Additionally, patients with a history of MPN in accelerated phase (MPN-AP) or high-risk primary myelofibrosis (PMF) that transformed to AML during treatment with hypomethylating drugs and then relapse following or are refractory to a subsequent AML induction regimen may be enrolled as Second Salvage AML patients.

2. Aged ≥ 18 years.

3. ECOG Performance Status of 0, 1 or 2.

4. Adequate clinical laboratory values (i.e., plasma creatinine <2.5 x upper limit of normal (ULN) for the institution, bilirubin <2.5 x ULN, alanine transaminase (ALT) and aspartate transaminase (AST) ≤2.5 x ULN).

5. Absence of active central nervous system (CNS) involvement by leukemia. Patients with previously diagnosed CNS leukemia are eligible if the CNS leukemia is under control and intrathecal treatment may continue throughout the study.

6. Absence of uncontrolled intercurrent illnesses, including uncontrolled infections, cardiac conditions, or other organ dysfunctions.

7. Signed informed consent prior to the start of any study specific procedures.

8. Women of child-bearing potential must have a negative serum or urine pregnancy test.

9. Male and female patients must agree to use acceptable contraceptive methods for the duration of the study and for at least one month after the last drug administration.

Exclusion Criteria:

1. The interval from prior treatment to time of study drug administration is < 2 weeks for cytotoxic agents or < 5 half-lives for noncytotoxic agents. Exceptions: Use of hydroxyurea is allowed before the start of study and is to be discontinued prior to the initiation of study treatment. At the investigator's discretion, for patients with significant leukocytosis that develops during the early treatment cycles, hydroxyurea may be administered. The hydroxyurea should be discontinued as soon as clinically appropriate.

2. Any >grade 1 persistent clinically significant toxicities from prior chemotherapy.

3. Inadequate Cardiac (left ventricular ejection fraction ≤40%) function.

4. White blood cell (WBC) count >15,000/μL (Note: Patients considered for possible venetoclax-containing regimen must have WBC ≤10k/μL prior to initiating venetoclax treatment).

5. For patients with prior hematopoietic stem cell transplant (HSCT):

   1. Less than 3 months since HSCT
   2. Acute Graft versus Host Disease (GvHD) >Grade 1
   3. Chronic GvHD >Grade 1

6. Any concomitant condition that in the opinion of the investigator could compromise the objectives of this study and the patient's compliance.

7. A pregnant or lactating woman.

8. Current malignancies of another type. Exceptions: Patients may participate if they have previously treated and currently controlled prostate cancer, or adequately treated in situ cervical cancer or basal cell skin cancer, or other malignancies with no evidence of disease for 2 years or more.

9. Patient has acute promyelocytic leukemia (APL).

10. Patients with known HIV, active HBV or active HCV infection (note: testing for these infections is not required). For patients with evidence of chronic hepatitis B virus (HBV) infection, the HBV viral load must be undetectable on suppressive therapy, if indicated. Patients with a history of hepatitis C virus (HCV) infection must have been treated and cured. For patients with HCV infection who are currently on treatment, they are eligible if they have an undetectable HCV viral load.

11. Documented or known clinically significant bleeding disorder.