Trial Outcomes & Findings for INCB000928 Administered as a Monotherapy or in Combination With Ruxolitinib in Participants With Anemia Due to Myeloproliferative Disorders (NCT NCT04455841)

Following a strategic decision (not based on safety concerns) to close study enrollment, the dose-expansion phase (Phase 2) was not conducted.

This study was conducted in 25 study centers in Canada, France, Italy, Japan, the United Kingdom, and the United States. Data collected through a cut off date of 12 June 2025 have been reported.

INCB000928 Administered as a Monotherapy or in Combination With Ruxolitinib in Participants With Anemia Due to Myeloproliferative Disorders

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

Anemia response was defined as (a) a hemoglobin (Hgb) increase of 1.5 grams per deciliter (g/dL) relative to baseline for any "rolling" 12-week period (84 days with each assessment that met this requirement) during the first 24 weeks of treatment if transfusion independent (TI) at baseline; or (b) transfusion independence for any "rolling" 12-week period (absence of any red blood cell \[RBC\] transfusion over any 84-day period) during the first 24 weeks of treatment if transfusion dependent (TD) at baseline.

Duration of anemia response was defined as (a) the interval from the first onset of anemia response to the earliest date of loss of anemia response that persisted for at least 4 weeks or death from any cause (for TI participants at baseline); or (b) the duration of the RBC-TI period for participants who achieved RBC-TI for at least 12 consecutive weeks during the first 24 weeks of treatment (for TD participants at baseline).

Mean change from baseline was assessed as the largest increase from baseline in the mean Hgb values over any rolling 12-week treatment period during the first 24 weeks of treatment. Change from baseline was calculated as the post-baseline value minus the baseline value.

The rate of RBC transfusion was defined as the average number of RBC units per participant-month during the treatment period.

Splenic volume response rate was defined as the percentage of participants achieving a ≥35% reduction in spleen volume at Week 24 relative to baseline as measured by magnetic resonance imaging or computed tomography scan.

Spleen length response was defined as the percentage of participants achieving a ≥50% reduction in spleen length at any visit relative to baseline as measured by palpation.

ORR was defined as the percentage of participants with complete response (CR) or partial response (PR) (including the morphologic effects of the combination of zilurgisertib with ruxolitinib on bone marrow) according to Tefferi et al (2013) definitions.

PFS was defined as the interval from the first dose of study treatment until the first documented progression or death according to Tefferi et al (2013) definitions.

LFS was defined as the interval from the first dose of study treatment until the first documented leukemia transformation or death from any cause.

Cmax was defined as the maximum concentration of zilurgisertib.

tmax was defined as the time to the maximum concentration of zilurgisertib.

AUC0-t was defined as the area under the plasma concentration-time curve from time 0 to the last quantifiable measurable plasma concentration of zilurgisertib.

Percentage change was calculated as the (\[post-baseline value minus the baseline value\] / \[baseline value\]) \* 100.

Change from Baseline (CFB) was calculated as the post-Baseline value minus the Baseline value.

Change from Baseline was calculated as the post-Baseline value minus the Baseline value.