The following criteria is provided for health care professionals.

Inclusion Criteria:

Participants are eligible to be included in the study only if all the following criteria apply.

1. ≥ 18 years of age at the time of signing the informed consent form (ICF).
2. Willing and able to provide written ICF.
3. Willing and able to adhere to the study visit schedule and other protocol requirements.
4. Hematooncological or pathological diagnosis of MM, MCL, FL, DLBCL, indolent lymphoma, ATL or CLL.
5. For KPG-818 dose escalations and dose expansion, subjects who have relapsed from or are refractory to ALL FDA approved therapies known to provide clinical benefit for the specific disease or have failed to their last line of therapy of the hematological malignancy, be intolerant to or are not otherwise candidates for available FDA approved standard treatment known to provide clinical benefit for the specific disease.
6. Have measurable or assessable disease.

   For Multiple Myeloma:

   • M-protein quantities ≥ 0.5 g/dL by serum protein electrophoresis (SPEP) or
   • M-protein quantities ≥ 200 mg/24-hour urine collection by urine protein electrophoresis (UPEP) or
   • Serum free light chain (FLC) levels > 100 mg/L involved light chain and an abnormal kappa/lambda (κ/λ) ratio in subjects without detectable serum or urine M-protein or
   • For subjects with immunoglobulin (Ig) class A (IgA) myeloma whose disease can only be reliably measured by quantitative Ig measurement, a serum IgA level ≥ 0.50 g/dL.

   For MCL, FL, DLBCL, indolent lymphoma, ATL, or CLL:

   • At least 1 bidimensionally measurable lesion larger than 1.5 cm in largest dimension by computed tomography (CT), positron emission tomography-CT (PET-CT), or magnetic resonance imaging (MRI) scan.

7. Eastern Cooperative Oncology Group (ECOG) performance status of 0 or 1.
8. Males and females of childbearing potential must agree to use at least two methods of contraception, as detailed in Section 6.1.3, during the study treatment and continue until 3 months after the completion of study treatment.

Exclusion Criteria Participants are excluded from the study if any of the following criteria apply.

1. Has any significant medical condition, laboratory abnormality, or psychiatric illness that would prevent the subject from participating in the study.
2. Currently enrolled in another clinical study, except observational studies.
3. Has known active central nervous system metastases and/or lymphomatous meningitis.
4. Persisting toxicities related to prior anticancer treatment > Grade 1 according to NCI-CTCAE v5.0.
5. Major surgery or significant traumatic injury within 6 weeks prior to Screening or planned major surgery during the study period.
6. Any of the following laboratory abnormalities:
   • Absolute neutrophil count (ANC) ≤ 1.5 × 109/L.
   • Hemoglobin ≤ 8 g/dL.
   • Platelet count < 75 000/μL.
   • Corrected serum calcium > 13.5 mg/dL (> 3.4 mmol/L).
   • Alanine aminotransferase (ALT) and aspartate aminotransferase (AST) ≥ 2.5 × upper limit of normal (ULN) or ≥ 5.0 × ULN if liver tumor is present.
   • Total bilirubin > 1.5 × ULN.
   • Potassium not within normal limits.
   • Estimated serum creatinine clearance of ≤ 60 mL/min or requiring dialysis.
7. Subjects with gastrointestinal disease that may significantly alter the absorption of the study drug.
8. Subjects with a prior history of malignancies, other than MM, lymphoma, or CLL, unless the subject has been free of the disease for ≥ 5 years with the exception of the following noninvasive malignancies:
   • Basal cell carcinoma of the skin.
   • Squamous cell carcinoma of the skin.
   • Carcinoma in situ.
   • Incidental histological findings of prostate cancer such as T1a or T1b using the tumor/node/metastasis classification of malignant tumors or prostate cancer that is curative.
9. Has a history of anaphylaxis or hypersensitivity to thalidomide, lenalidomide, or pomalidomide.
10. Has known or suspected hypersensitivity to the excipients contained in the formulation of investigational product (IP).
11. Has received any of the following within the last 14 days of initiating dosing:
    • Plasmapheresis
    • Radiation therapy other than local therapy for MM associated bone lesions
    • Use of any systemic myeloma/lymphoma/CLL drug therapy.
12. Has been treated with an investigational agent (ie, an agent not commercially available) within 28 days or 5 half-lives (whichever is longer) of initiating IP.
13. Prior treatment of any inhibitors of PD-1 or PD-L1 within 3 months prior to initiating dosing.
14. Has any one of the following:
    • Clinically significant abnormal ECG finding, including QTcF interval elongation (> 480 ms), at Screening.
    • Congestive heart failure (New York Heart Association Class III or IV).
    • Myocardial infarction within 12 months prior to initiating IP.
    • Unstable or poorly controlled angina pectoris, including the Prinzmetal variant of angina pectoris.
    • Peripheral neuropathy ≥ Grade 2.
    • Subject has taken a strong inhibitor or inducer of CYP3A4/5 including grapefruit, St. John's Wort or related products within 2 weeks prior to dosing and during the course of study.
15. Has current or prior use of immunosuppressive medication within 14 days prior initiating IP. The following are exceptions to this criterion:
    • Intranasal, inhaled, topical, or local steroid injections (eg, intra-articular injection)
    • Systemic corticosteroids at physiologic doses that do not exceed 10 mg/day of prednisone or equivalent
    • Steroids as premedication for hypersensitivity reactions (eg, CT scan premedication).
16. Subject known to test positive for human immunodeficiency virus, chronic or active hepatitis B, or active hepatitis C.
17. Subjects with any active or uncontrolled infection.
18. Subject is unable or unwilling to undergo protocol required thromboembolism prophylaxis.
19. Subject is a female who is pregnant, nursing, or breastfeeding.