An adverse event (AE) was defined as any untoward medical occurrence associated with the use of a drug in humans, whether or not considered drug related. An AE could therefore have been any unfavorable and unintended sign (including an abnormal laboratory finding), symptom, or disease (new or exacerbated) temporally associated with the use of study drug/treatment. A TEAE was defined as any AE either reported for the first time or the worsening of a pre-existing event after the first dose of study drug until 30 days after the last dose of study drug.

An adverse event (AE) was defined as any untoward medical occurrence associated with the use of a drug in humans, whether or not considered drug related. A TEAE was defined as any AE either reported for the first time or the worsening of a pre-existing event after the first dose of study drug until 30 days after the last dose of study drug. The severity of AEs was assessed using Common Terminology Criteria for Adverse Events (CTCAE) version 5.0 Grades 1 through 5. Grade 1: mild; asymptomatic or mild symptoms; clinical or diagnostic observations only; treatment not indicated. Grade 2: moderate; minimal, local, or noninvasive treatment indicated; limiting age-appropriate activities of daily living. Grade 3: severe or medically significant but not immediately life-threatening; hospitalization or prolongation of hospitalization indicated; disabling; limiting self-care activities of daily living. Grade 4: life-threatening consequences; urgent treatment indicated. Grade 5: fatal.

A DLT was defined as the occurrence of any protocol-defined toxicity occurring during the first treatment cycle, from Cycle 1 Day 1 up to and including Cycle 1 Day 28 (per regimen cycle schedule), except those with a clear alternative explanation (e.g., disease progression) or transient (≤72 hours) abnormal laboratory values without associated clinically significant signs or symptoms based on investigator determination. The DLT-Evaluable Population included all non-backfill participants eligible for dose escalation who met the criteria outlined in the Analysis Population field.

The MTD was defined as the dose at which the observed DLT rate was closest to the target DLT rate of 28% using an isotonical method that took the assumption of a monotonic dose-toxicity relationship into account. Per the protocol, the stopping rule was either (a) reaching a certain number of participants at one dose level under the early stopping rule or (b) reaching the pre-defined maximum sample size. Dose escalation was to be considered complete only when one of these conditions was met. After completion, the MTD was to be defined as the dose level closest to the target DLT rate. The MTD could not be concluded until the stopping rule was met.

The RDE was defined as a pharmacodynamically active dose. The RDE was determined in an independent fashion by evaluation of all available data (i.e., safety, pharmacokinetic, and pharmacodynamic data) from the respective dose-escalation stage of the study for further investigation in the expansion cohort, including safety (e.g., low-grade but chronic toxicities, dose reduction, dose interruption, or missed doses of zilurgisertib and/or ruxolitinib). The RDE(s) could not exceed the MTD in each treatment group