A Study of Nemtabrutinib (MK-1026) Versus Comparator (Investigator's Choice of Ibrutinib or Acalabrutinib) in First Line (1L) Chronic Lymphocytic Leukemia (CLL)/ Small Lymphocytic Lymphoma (SLL) (MK-1026-011/BELLWAVE-011)

Eligibility Criteria

• * Confirmed diagnosis of CLL/SLL and active disease clearly documented to have a need to initiate therapy.
• * Has at least 1 marker of disease burden.
• * Has an Eastern Cooperative Oncology Group (ECOG) performance status of 0 to 2 within 7 days before randomization.
• * Has the ability to swallow and retain oral medication.
• * Participants who are hepatitis B surface antigen (HBsAg) positive are eligible if they have received hepatitis B virus (HBV) antiviral therapy for at least 4 weeks and have undetectable HBV deoxyribonucleic acid (DNA) viral load before randomization.
• * Participants with history of hepatitis C virus (HCV) infection are eligible if HCV ribonucleic acid (RNA) viral load is undetectable at screening.
• * Participants with human immunodeficiency virus (HIV) who meet ALL eligibility criteria.
• * Has an active hepatitis B virus/ hepatitis C virus (HBV/HCV) infection.
• * Has gastrointestinal (GI) dysfunction that may affect drug absorption.
• * Has diagnosis of Richter Transformation or active central nervous system (CNS) involvement by CLL/SLL.
• * Has had acquired immune deficiency syndrome (AIDS)-defining opportunistic infection in the past 12 months before screening.
• * Has clinically significant cardiovascular disease.
• * Has hypersensitivity to nemtabrutinib or contraindication to ibrutinib or acalabrutinib, or any of the excipients.
• * Has history of severe bleeding disorder.
• * Has history of second malignancy, unless potentially curative treatment has been completed with no evidence of malignancy for 2 years.
• * Has received any systemic anticancer therapy for CLL/SLL.
• * Is currently being treated with p-glycoprotein (P-gp) substrates with a narrow therapeutic index, cytochrome P450 3A (CYP3A) strong or moderate inducers or CYP3A strong inhibitors.
• * Received prior radiotherapy within 2 weeks of start of study intervention, or radiation-related toxicities, requiring corticosteroids.
• * Received a live or live-attenuated vaccine within 30 days before the first dose of study intervention. Administration of killed vaccines are allowed.
• * Has received an investigational agent or has used an investigational device within 4 weeks before study intervention administration.
• * Has active infection requiring systemic therapy.
• * Participants who have not adequately recovered from major surgery or have ongoing surgical complications.