Efficacy and Safety of Nemtabrutinib (MK-1026) in Participants With Hematologic Malignancies (MK-1026-003)

Part 1: Number of participants experiencing dose-limiting toxicities (DLTs)

DLTs will be defined as toxicities observed during the first 2 cycles (8 weeks) of Part 1 and include: Grade ≥3 nonhematologic toxicity (except Grade 3 nausea, vomiting, diarrhea, rash, fatigue, and uncontrolled hypertension which will not be considered a DLT unless lasting ≥72 hours despite optimal supportive care); Grade 4 hematologic toxicity lasting \>7 days (except Grade 3 lymphocytosis, Grade 4 platelet count decreased of any duration, or Grade 3 platelet count decreased if associated with bleeding); any Grade 3 or Grade 4 nonhematologic laboratory abnormality if values result in drug-induced liver injury, or medical intervention is required, or the abnormality leads to hospitalization, or the abnormality persists for \>1 week (with exceptions); missing \>25% of nemtabrutinib doses as a result of drug-related adverse events (AEs) during the first 2 cycles (8 weeks); Grade 5 toxicity.

Part 1: Number of participants experiencing adverse events (AEs)

An AE is any untoward medical occurrence in a participant, temporally associated with the use of study treatment, whether or not considered related to the study treatment. The number of participants experiencing AEs will be reported for Part 1.

Part 1: Number of participants discontinuing study treatment due to AEs

An AE is any untoward medical occurrence in a participant, temporally associated with the use of study treatment, whether or not considered related to the study treatment. The number of participants discontinuing study treatment due to an AE will be reported for Part 1.

Part 2: Objective Response Rate (ORR) per International Workshop on Chronic Lymphocytic Leukemia (iwCLL) criteria 2018 as assessed by independent central review (ICR)

ORR per iwCLL 2018 criteria is defined as the percentage of participants achieving a complete response (CR), complete response with incomplete bone marrow recovery (CRi), nodular partial response (nPR), or partial response (PR). CR is defined as meeting the following criteria: no lymph nodes \>1.5 cm, spleen size \<13 cm, liver normal; no constitutional symptoms, normal lymphocyte count, platelets ≥100 x 10\^9/L; hemoglobin ≥11 g/dL; and normocellular marrow (no CLL cells or B lymphoid nodules). CRi is defined as meeting CR criteria but with hypocellular bone marrow. nPR is defined as having features of CR but with lymphoid nodules in the marrow. PR is defined as ≥50% decrease in ≥2 of the following: lymph nodes, liver and/or spleen size, lymphocytes PLUS ≥1 of the following met: platelets ≥100 x 10\^9/L or ≥50% increase from screening, hemoglobin \>11 g/dL or ≥50% increase from screening, CLL cells or B lymphoid nodules in marrow.

Part 1: Area Under the Curve (AUC) of Nemtabrutinib

Blood samples will be obtained at designated time points during Part 1 for the assessment of nemtabrutinib AUC (Day 1 of Cycles 1 and 2: Pre-dose, 2, 4, 6, 8, and 24 hours post-dose; Day 1 of Cycle 3: pre-dose and 2, 4, and 6 hours post-dose \[up to \~57 days\]). Each cycle is 28 days.

Part 1: Minimum Concentration (Cmin) of Nemtabrutinib

Blood samples will be obtained at designated time points during Part 1 for the assessment of nemtabrutinib Cmin (Day 1 of Cycles 1 and 2: Pre-dose, 2, 4, 6, 8, and 24 hours post-dose; Day 1 of Cycle 3: pre-dose and 2, 4, and 6 hours post-dose \[up to \~57 days\]). Each cycle is 28 days.

Part 1: Maximum Concentration (Cmax) of Nemtabrutinib

Blood samples will be obtained at designated time points during Part 1 for the assessment of nemtabrutinib Cmax (Day 1 of Cycles 1 and 2: Pre-dose, 2, 4, 6, 8, and 24 hours post-dose; Day 1 of Cycle 3: pre-dose and 2, 4, and 6 hours post-dose \[up to \~57 days\]). Each cycle is 28 days.

Part 1: ORR per iwCLL criteria 2018 as assessed by ICR

ORR per iwCLL 2018 criteria is defined as the percentage of participants achieving a CR, CRi, nPR, or PR. CR is defined as meeting the following criteria: no lymph nodes \>1.5 cm, spleen size \<13 cm, liver normal; no constitutional symptoms, normal lymphocyte count, platelets ≥100 x 10\^9/L; hemoglobin ≥11 g/dL; and normocellular marrow (no CLL cells or B lymphoid nodules). CRi is defined as meeting CR criteria but with hypocellular bone marrow. nPR is defined as having features of CR but with lymphoid nodules in the marrow. PR is defined as ≥50% decrease in ≥2 of the following: lymph nodes, liver and/or spleen size, lymphocytes PLUS ≥1 of the following met: platelets ≥100 x 10\^9/L or ≥50% increase from screening, hemoglobin \>11 g/dL or ≥50% increase from screening, CLL cells or B lymphoid nodules in marrow.