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 demonstrated clinical benefit per investigator assessment or, histologically confirmed AITL that has recurred or progressed following institutional standard of care therapy.
* For Part C and D: Have R/R DLBCL, not otherwise specified \[NOS (DLBCL, NOS)\] or large B-cell lymphoma (LBCL) arising from follicular lymphoma and have received two or more lines of systemic therapy.
* Have at least one bi dimensionally measurable lesion \>1.5-centimeter (cm) in largest dimension 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 CNS lymphoma).
* 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 and systemic symptoms (DRESS), except for peripheral eosinophilia due to disease under study. Participants with current or prior eosinophilia requiring systemic steroid treatment 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 days prior 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 for adequately treated basal cell or squamous cell skin cancer, melanoma in situ or carcinoma in situ of the breast or cervix, and prostate cancer with active surveillance.
* 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 (AV block), unstable angina, coronary/peripheral artery bypass graft, symptomatic congestive heart failure (CHF), New York Heart Association Class III or IV;
  * Cerebrovascular accident, transient ischemic attack, symptomatic pulmonary embolism, and/or other clinically significant episode of thromboembolic disease;
* Active inflammatory gastrointestinal (GI) disease, chronic diarrhea, previous gastric 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 relevant abnormalities that may affect participant safety or interpretation of study results.
* Cardiac ejection fraction \<45%.