Inclusion Criteria:

          1. Age ≥ 18 years old

          2. Patients with relapsed/refractory T-PLL who have active disease and have received at
             least one prior therapy

          3. Patients must not have had chemotherapy or antibody therapy for 7 days prior to
             starting APG-115 and/or APG-2575. However, patients with rapidly proliferative disease
             may receive hydroxyurea or decadron until 24 hours prior to starting therapy on this
             protocol.

          4. Absolute neutrophil count (ANC) ≥ 500/mm˄3; hemoglobin ≥ 60 g/L; platelet count ≥
             30,000/mm˄3

          5. Total bilirubin ≤ 1.5 × upper limit of normal (ULN), unless related to leukemic
             involvement

          6. Aspartate aminotransferase (AST) and/or alanine aminotransferase (ALT) ≤ 3× ULN or ≤ 5
             × ULN unless related to leukemic involvement

          7. Adequate kidney function, defined as a calculated creatinine clearance ≥ 50 mL/min;
             determined via urine collection for 24-hour creatinine clearance or by the Cockcroft
             Gault formula

          8. Require laboratory TLS parameters to be within acceptable range and clinical TLS
             parameters no higher than grade 2 at study baseline, with or without TLS treatment,
             before initiation of study treatment.

          9. Known cardiac ejection fraction of ≥ 45% within the past 3 months

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

         11. Has no malignancies other than T-PLL that: 1) currently require systemic therapies; 2)
             were not previously treated with curative intention (unless the malignant disease is
             in a stable remission according to the discretion of the treating physician); 3) or
             developed signs of progression after curative treatment

         12. A negative serum pregnancy test is required within 1 week for all women of
             childbearing potential prior to enrolling in this trial. Women of childbearing
             potential and men must agree to use contraception prior to study entry and for the
             duration of study participation.

         13. 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/her legally
             authorized representative is required prior to their enrollment on the protocol.

        Exclusion Criteria:

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

          2. Patient with documented hypersensitivity to any of the components of the therapy
             program.

          3. Patient previously treated with a murine double minute 2 (MDM2) inhibitor.

          4. Known active, uncontrolled central nervous system (CNS) malignancy

          5. Patients require graft versus host therapy, or require continued treatment with
             systemic immunosuppressive agents (calcineurin inhibitors within 4 weeks prior to the
             first dose of study drug).

          6. Known history of human immunodeficiency virus (HIV) infection (HIV 1/2 antibodies)

          7. Active hepatitis B virus (HBV) or hepatitis C virus (HCV) infection that requires
             treatment or at risk for HBV reactivation. Hepatitis B virus deoxyribonucleic acid
             (DNA) and HCV ribonucleic acid (RNA) must be undetectable upon testing. At risk for
             HBV reactivation is defined as hepatitis B surface antigen positive or anti-hepatitis
             B core antibody positive. Prior test results obtained as part of standard of care that
             confirm a subject is immune and not at risk for reactivation (i.e., hepatitis B
             surface antigen negative, surface antibody positive) may be used for purposes of
             eligibility and tests do not need to be repeated. Subjects with prior positive
             serology results must have negative polymerase chain reaction results. Subjects whose
             immune status is unknown or uncertain must have results confirming immune status
             before enrollment.

          8. Failure to have recovered (Grade > 1) (except alopecia and pigmentation) from prior
             treatment (including chemotherapy, targeted therapy, immunotherapy, experimental
             agents, radiation, or surgery)

          9. Significant screening electrocardiogram (ECG) abnormalities including corrected QT
             interval (Fridericia) (QTcF) > 470 msec

         10. Patients who have any conditions or illness that, according to the opinions of the
             Investigators or the medical monitor, would compromise patient safety or interfere
             with the evaluation of safety and efficacy to the study drug(s).

         11. Patients who have used strong CYP2C8 inhibitors, or moderate or strong CYP3A4
             inhibitors or inducers within washout period of 14 days or 7 half-lives before the
             first administration of study drugs, whichever is longer.