A Study of ARV-393 in Relapsed/Refractory Non-Hodgkin Lymphoma.

Inclusion Criteria:

• For Part A and B: Have relapsed/refractory NHL and >=2 prior systemic therapies, (including rituximab), and be ineligible for known therapies with demonstratedclinical benefit per investigator assessment or, histologically confirmed AITL thathas recurred or progressed following institutional standard of care therapy.

• For Part C and D: Have R/R DLBCL, not otherwise specified [NOS (DLBCL, NOS)] orlarge B-cell lymphoma (LBCL) arising from follicular lymphoma and have received twoor more lines of systemic therapy.

• Have at least one bi dimensionally measurable lesion >1.5-centimeter (cm) in largestdimension for nodal or >1.0 cm for extranodal lesion.

• Eastern Cooperative Oncology Group (ECOG) performance status (PS) of 0 or 1 (NOTE:For Part A only - ECOG PS of 2 is allowed for participants with secondary CNSlymphoma).

• Adequate bone marrow function

• Adequate kidney function

• Adequate Liver Function

Exclusion Criteria:

• Current or past history of peripheral eosinophilia, hypereosinophilic syndrome (HES), organ-specific eosinophilic disorder, or drug reaction with eosinophilia andsystemic symptoms (DRESS), except for peripheral eosinophilia due to disease understudy. Participants with current or prior eosinophilia requiring systemic steroidtreatment are excluded regardless of etiology.

• Prior allogeneic stem cell transplant (SCT) or solid organ transplantation.

• Prior treatment with chimeric antigen receptor (CAR) T-cell therapy within 60 daysprior to Cycle 1 Day 1 (C1D1) or any prior treatment with a BCL6-targeted therapy

• Any other active malignancy within 3 years prior to enrollment, except foradequately treated basal cell or squamous cell skin cancer, melanoma in situ orcarcinoma in situ of the breast or cervix, and prostate cancer with activesurveillance.

• Any of the following in the previous 6 months:

• Myocardial infarction, long QT syndrome or family history of long QT syndrome,or Torsade de Pointes;

• Clinically important atrial or ventricular arrhythmias;

• Serious conduction system abnormalities, 3rd degree atrioventricular (AVblock), unstable angina, coronary/peripheral artery bypass graft, symptomaticcongestive heart failure (CHF), New York Heart Association Class III or IV;

• Cerebrovascular accident, transient ischemic attack, symptomatic pulmonaryembolism, and/or other clinically significant episode of thromboembolicdisease;

• Active inflammatory gastrointestinal (GI) disease, chronic diarrhea, previousgastric resection, or lap band surgery.

• Uncontrolled hypertension despite optimal medical treatment

• History of myocarditis.

• In ability to comply with listed prohibited treatments.

• Standard 12-lead electrocardiogram (ECG) that demonstrates clinically relevantabnormalities that may affect participant safety or interpretation of study results.

• Cardiac ejection fraction <45%.