DLT is defined as any of the following toxicities, unless assessed by the investigator to be clearly due to the underlying disease or extraneous causes: Grade (Gr) 4 nonhematologic toxicity (not laboratory); Gr 4 hematologic toxicity lasting ≥7 days, except thrombocytopenia; Gr 4 thrombocytopenia of any duration; Gr 3 thrombocytopenia associated with clinically significant bleeding; Gr 4 anemia regardless of duration; Nonhematologic AE Gr ≥3 in severity, with exceptions; Any Gr 3 or 4 nonhematologic lab abnormality if clinically significant medical intervention is required, or if leads to hospitalization, persists for \>72 hours or results in drug-induced liver injury with exceptions; Gr 3 or 4 febrile neutropenia; Prolonged delay (\>2 weeks) in initiating Cycle 2 due to treatment-related toxicity; Treatment-related toxicity resulting in study treatment discontinuation during Cycle 1 (C1); Missing \>25% of MK-6598 doses as a result of treatment-related AE during C1; Gr 5 toxicity.

An AE is any untoward medical occurrence in a clinical study participant, temporally associated with the use of study intervention, whether or not considered related to the study intervention. An AE can therefore be any unfavorable and unintended sign (including an abnormal laboratory finding), symptom, or disease (new or exacerbated) temporally associated with the use of a study intervention. The number of participants who experienced an AE will be reported.

An AE is any untoward medical occurrence in a clinical study participant, temporally associated with the use of study intervention, whether or not considered related to the study intervention. An AE can therefore be any unfavorable and unintended sign (including an abnormal laboratory finding), symptom, or disease (new or exacerbated) temporally associated with the use of a study intervention. The number of participants who discontinued study treatment due to an AE will be reported.