Inclusion Criteria:

          1. ≥ 18 years of age.

          2. MM patients (for Arm A and Arm B): Patients with Relapsed/Refractory MM per 2016 IMWG
             criteria, previously treated with at least 1 but not more than 4 prior lines of
             therapy for MM. Refractory MM, meanwhile, is defined as disease that progresses on
             salvage therapy or progresses within 60 days of the last treatment.

             AL amyloidosis patients (for Arm C ONLY): Patients with AL amyloidosis when meeting:

             i. histochemical diagnosis based on detection by polarizing microscopy of green
             birefringent material in Congo red-stained tissue specimens, the type must have been
             confirmed unequivocally. ii. have symptomatic organ involvement as defined by Appendix
             J. Only purpura and/or carpal tunnel syndrome are not acceptable. iii. have at least
             one prior line of systemic therapy for AL. Patients who do not achieve at least a PR
             to frontline therapy in 3 months are eligible. iv. have measurable disease as defined
             by at least ONE of the following:

               -  Serum monoclonal protein ≥1.0 g/dl by protein electrophoresis.

               -  >200 mg of monoclonal protein in the urine on 24-hour electrophoresis.

               -  Serum differential FLC concentration (dFLC, difference between amyloid forming
                  [involved] and nonamyloid forming [uninvolved] free light chain [FLC]) > 5 mg/dL;
                  OR serum FLC of 7.5 mg/dL provided the κ/λ FLC ratio is abnormal (κ/λ <0.26 for
                  patients with monoclonal λ FLC, κ/λ >1.65 for patients with monoclonal κ FLC).

          3. Eastern Cooperative Oncology Group (ECOG) ≤ 2.

          4. Life expectancy ≥ 6 months.

          5. Adequate hematologic function defined as:

               1. ANC ≥1.0 x 109/L independent of growth factor support within 7 days of the first
                  dose with study drug.

               2. Hemoglobin ≥8 g/dL without transfusion or growth factor support within 7 days of
                  the first dose of study drug.

               3. Platelet count ≥ 50 x 109/L without transfusion support within 7 days of the
                  first doseof study drug (for MM patients); or platelet count ≥ 100 x 109/L or ≥
                  50 x 109/L if bone marrow involvement independent of transfusion support in
                  either (for AL amyloidosis patients).

          6. Adequate hepatic and renal function defined as:

               1. AST and ALT < 3 x ULN (upper limit of normal)

               2. Creatinine clearance >30mL/min(for MM patients); or Creatinine ≤3 mg/dL and CrCL

                  ≥25 ml/min using the Cockcroft-Gault formula (for AL amyloidosis patients)

               3. Bilirubin< 1.5 x ULN (Except if considered secondary to Gilbert's syndrome and
                  primarily indirect bilirubinemia)

          7. PT/INR ≤2 x ULN and PTT (or aPTT) ≤2 x ULN.

          8. Female subjects who are of non-reproductive potential (i.e., post-menopausal by
             historyno menses for ≥2 year; OR history of hysterectomy; OR history of bilateral
             tubal ligation;OR history of bilateral oophorectomy). Female subjects of childbearing
             potential must havea negative serum pregnancy test upon study entry.

          9. Male and female subjects who agree to use highly effective methods of birth control
             (e.g.,condoms, implants, injectables, combined oral contraceptives, some intrauterine
             devices[IUDs], sexual abstinence, or sterilized partner) during the period of therapy
             and for 90days after the last dose of study drug.

         10. Ability to complete questionnaire(s) by themselves or with assistance (For AL
             amyloidosis patients only).

        Exclusion Criteria:

          1. MM patients with newly diagnosed MM, previously untreated for MM or only had been
             treated with localized palliative treatment or steroids less than equivalent of
             dexamethasone 40 mg daily for 4 days). AL amyloidosis patients with AL amyloidosis
             have not been treated with any systemic therapy, or AL amyloidosis clinically overt
             multiple myeloma i.e. original CRAB criteria. Extent of marrow plasmacytosis is not
             prohibitive.

          2. Subject has received antineoplastic therapy within 2 weeks before the date of
             registration.

          3. Subject has previously received an allogenic stem cell transplant (regardless of
             timing).

          4. Subjects planning to undergo a stem cell transplant prior to progression of disease on
             this study, i.e., these subjects should not be enrolled in order to reduce disease
             burden prior to transplant.

          5. Prior exposure to any BCL-2-directed therapy for MM.

          6. For Arm A only: The subjects show evidence of intolerance to pomalidomide, which is
             defined as subjects discontinued due to any AEs related to prior pomalidomide
             treatment;

          7. For Arm B only: The subjects show evidence of intolerance to daratumumab or
             lenalidomide, which is defined as subjects discontinued due to any AEs related to
             prior daratumumab or lenalidomide treatment;

          8. Patients with any uncontrolled active systemic infection, including but not limited to
             :

             active hepatitis B or C virus infection, known human immunodeficiency virus (HIV)
             positive

          9. Subject has peripheral neuropathy ≥grade 3.

         10. Subject has plasma cell leukemia (>2.0*109/L circulating plasma cells by standard
             differential) or Waldenström's macroglobulinemia or POEMS syndrome (polyneuropathy,
             organomegaly, endocrinopathy, monoclonal protein, and skin changes).

         11. Plasmapheresis <35 days prior to the initiation of study drug. (Note: Subjects with
             high Mprotein values or hyper-viscosity symptoms during screening may receive
             plasmapheresis prior to initiating study drug if the previous plasmapheresis was
             performed >35 days before the plasmapheresis performed during screening (in order to
             obtain a true baseline M-protein value for efficacy evaluations).

         12. Failure to have fully recovered (i.e., ≤ Grade 1 toxicity) from the reversible effects
             of prior treatment for MM or AL amyloidosis..

         13. Unable to swallow tablets or malabsorption syndrome, disease significantly affecting
             gastrointestinal function, or resection of the stomach or small bowel, symptomatic
             inflammatory bowel disease or ulcerative colitis, or partial or complete bowel
             obstruction.

         14. Currently active, clinically significant cardiovascular disease, such as uncontrolled
             arrhythmia (including Frederica corrected QT interval (QTc) ≥470 msec ) or Class 3 or
             4 congestive heart failure as defined by the New York Heart Association Functional
             Classification; or a history of myocardial infarction, unstable angina, or acute
             coronary syndrome within 6 months prior to randomization.

         15. Major surgical procedure within ≤14 days prior to initiating study treatment, or
             anticipation of the need for major surgery during the course of the study treatment,
             radiotherapy ≤14 days prior to initiating study treatment, systemic treatment within
             14 days before the first dose of APG2575.

         16. Recent infection requiring systemic treatment that was completed≤14 days before the
             first dose of study drug.

         17. Vaccinated with live, attenuated vaccines within 4 weeks of initiation of APG2575.

         18. Subject has any concurrent or recent malignancy ≤ 1 year prior to registration with
             the exception of: basal or squamous cell skin cancer, any carcinoma in situ,. NOTE: If
             there is a history or prior malignancy, they must not be receiving other specific
             treatment for their cancer.

         19. Requires treatment with a strong cytochrome P450 (CYP) 3A inhibitor.

         20. Known bleeding disorders (e.g., von Willebrand's disease) or hemophilia.

         21. History of stroke or intracranial hemorrhage within 6 months prior to enrollment.

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