Daratumumab 1800 mg co-formulated with rHuPH20 (2000 U/mL) and administered subcutaneously once weekly for Cycles 1 and 2, once every 2 weeks for Cycles 3 to 6, and then once every 4 weeks. Daratumumab will be administered either as monotherapy or in combination with INCB001158.

A TEAE was defined as an AE that was reported for the first time or the worsening of a pre-existing event after the first dose of study treatment.

CR: negative immunofixation on serum/urine, disappearance of soft tissue plasmacytomas, <5% bone marrow plasma cells (PCs). VGPR: serum/urine M-component detectable by immunofixation but not on electrophoresis, or ≥90% reduction in serum M-protein (SMP) plus urine M-protein (UMP) <100 milligrams (mg)/24 hours. PR: ≥50% reduction of SMP and reduction in 24-hour UMP by ≥90% or to <200 mg/24 hours. SMP and UMP not measurable: decrease of ≥50% in the difference between involved and uninvolved FLC levels is required in place of the M-protein criteria. SMP and UMP not measurable, and serum free light assay is not measurable: ≥50% reduction in bone marrow PCs is required in place of M-protein, if Baseline bone marrow PC percentage was ≥30%. If present at Baseline, a ≥50% reduction in the size of soft tissue plasmacytomas is required.

CR: negative immunofixation on serum/urine, disappearance of soft tissue plasmacytomas, <5% bone marrow plasma cells (PCs). VGPR: serum/urine M-component detectable by immunofixation but not on electrophoresis, or ≥90% reduction in serum M-protein (SMP) plus urine M-protein (UMP) <100 milligrams (mg)/24 hours. PR: ≥50% reduction of SMP and reduction in 24-hour UMP by ≥90% or to <200 mg/24 hours. SMP and UMP not measurable: decrease of ≥50% in the difference between involved and uninvolved FLC levels is required in place of the M-protein criteria. SMP and UMP not measurable, and serum free light assay is not measurable: ≥50% reduction in bone marrow PCs is required in place of M-protein, if Baseline bone marrow PC percentage was ≥30%. If present at Baseline, a ≥50% reduction in the size of soft tissue plasmacytomas is required.

CR: negative immunofixation on serum/urine, disappearance of soft tissue plasmacytomas, <5% bone marrow plasma cells (PCs). VGPR: serum/urine M-component detectable by immunofixation but not on electrophoresis, or ≥90% reduction in serum M-protein (SMP) plus urine M-protein (UMP) <100 milligrams (mg)/24 hours. PR: ≥50% reduction of SMP and reduction in 24-hour UMP by ≥90% or to <200 mg/24 hours. SMP and UMP not measurable: decrease of ≥50% in the difference between involved and uninvolved FLC levels is required in place of the M-protein criteria. SMP and UMP not measurable, and serum free light assay is not measurable: ≥50% reduction in bone marrow PCs is required in place of M-protein, if Baseline bone marrow PC percentage was ≥30%. If present at Baseline, a ≥50% reduction in the size of soft tissue plasmacytomas is required.

CR: negative immunofixation on serum/urine, disappearance of soft tissue plasmacytomas, <5% bone marrow plasma cells (PCs). VGPR: serum/urine M-component detectable by immunofixation but not on electrophoresis, or ≥90% reduction in serum M-protein (SMP) plus urine M-protein (UMP) <100 milligrams (mg)/24 hours. PR: ≥50% reduction of SMP and reduction in 24-hour UMP by ≥90% or to <200 mg/24 hours. SMP and UMP not measurable: decrease of ≥50% in the difference between involved and uninvolved FLC levels is required in place of the M-protein criteria. SMP and UMP not measurable, and serum free light assay is not measurable: ≥50% reduction in bone marrow PCs is required in place of M-protein, if Baseline bone marrow PC percentage was ≥30%. If present at Baseline, a ≥50% reduction in the size of soft tissue plasmacytomas is required.

Progressive disease: increase of 25% from the lowest response value in any one of the following: (a) serum M-component (absolute increase must be ≥0.5 grams per deciliter [g/dL]); (b) urine M-component (absolute increase must be ≥200 mg/24 hours); (c) only in participants without measurable serum and urine M-protein levels: the difference between involved and uninvolved FLC levels (absolute increase must be > 10 mg/dL); (d) only in participants without measurable serum and urine M-protein levels and without measurable disease by FLC levels, bone marrow plasma cell (PC) percentage (absolute percentage must be ≥10%); (d) bone marrow PC percentage: the absolute percentage must be > 10%; (e) definite development of new bone lesions or soft tissue plasmacytomas or definite increase in the size of existing bone lesions or soft tissue plasmacytomas; (f) development of hypercalcemia (corrected serum calcium > 11.5 mg/dL) that can be attributed solely to the PC proliferative disorder.

Bone marrow aspirate was to be collected for MRD analysis.

Bone marrow aspirate was to be collected for MRD analysis.

Overall survival was defined as the time from the first dose of study drug to death from any cause until study completion.

In Phase 1, participants received oral INCB001158 100 mg BID in 28-day cycles starting at Cycle 1, and 1800 mg subcutaneous daratumumab, administered once weekly for Cycles 1 and 2, once every 2 weeks for Cycles 3 to 6, and once every 4 weeks thereafter. Treatment continued until disease progression, unacceptable toxicity, or discontinuation from study treatment for any other reason.

In Phase 1, participants received oral INCB001158 100 mg BID in 28-day cycles starting at Cycle 1, and 1800 mg subcutaneous daratumumab, administered once weekly for Cycles 1 and 2, once every 2 weeks for Cycles 3 to 6, and once every 4 weeks thereafter. Treatment continued until disease progression, unacceptable toxicity, or discontinuation from study treatment for any other reason.

In Part 1 of Phase 2, participants received daratumumb 1800 mg subcutaneous daratumumab, administered once weekly for Cycles 1 and 2 (28-day cycles), once every 2 weeks for Cycles 3 to 6, and once every 4 weeks thereafter. At the time of confirmed disease progression, participants crossed over to Part 2 of Phase 2 to receive oral INCB001158 100 mg BID starting at Cycle 1, and 1800 mg subcutaneous daratumumab, administered once weekly for Cycles 1 and 2, once every 2 weeks for Cycles 3 to 6, and once every 4 weeks thereafter. Treatment in Phase 2 continued for as long as participants were receiving clinical benefit and did not met any criteria for study withdrawal.

In Part 1 of Phase 2, participants received oral INCB001158 100 mg BID in 28-day cycles starting at Cycle 1. At the time of confirmed disease progression, participants crossed over to Part 2 of Part 2 to receive oral INCB001158 100 mg BID starting at Cycle 1, and 1800 mg subcutaneous daratumumab, administered once weekly for Cycles 1 and 2, once every 2 weeks for Cycles 3 to 6, and once every 4 weeks thereafter. Treatment in Phase 2 continued for as long as participants were receiving clinical benefit and did not met any criteria for study withdrawal.

In Part 1 of Phase 2, participants received oral INCB001158 100 mg BID in 28-day cycles starting at Cycle 1. At the time of confirmed disease progression, participants crossed over to Part 2 of Part 2 to receive oral INCB001158 100 mg BID starting at Cycle 1, and 1800 mg subcutaneous daratumumab, administered once weekly for Cycles 1 and 2, once every 2 weeks for Cycles 3 to 6, and once every 4 weeks thereafter. Treatment in Phase 2 continued for as long as participants were receiving clinical benefit and did not met any criteria for study withdrawal.

In Part 1 of Phase 2, participants received oral INCB001158 100 mg BID in 28-day cycles starting at Cycle 1. At the time of confirmed disease progression, participants crossed over to Part 2 of Part 2 to receive oral INCB001158 100 mg BID starting at Cycle 1, and 1800 mg subcutaneous daratumumab, administered once weekly for Cycles 1 and 2, once every 2 weeks for Cycles 3 to 6, and once every 4 weeks thereafter. Treatment in Phase 2 continued for as long as participants were receiving clinical benefit and did not met any criteria for study withdrawal.

In Part 1 of Phase 2, participants received oral INCB001158 100 mg BID in 28-day cycles starting at Cycle 1. At the time of confirmed disease progression, participants crossed over to Part 2 of Part 2 to receive oral INCB001158 100 mg BID starting at Cycle 1, and 1800 mg subcutaneous daratumumab, administered once weekly for Cycles 1 and 2, once every 2 weeks for Cycles 3 to 6, and once every 4 weeks thereafter. Treatment in Phase 2 continued for as long as participants were receiving clinical benefit and did not met any criteria for study withdrawal.

In Part 1 of Phase 2, participants received oral INCB001158 100 mg BID in 28-day cycles starting at Cycle 1. At the time of confirmed disease progression, participants crossed over to Part 2 of Part 2 to receive oral INCB001158 100 mg BID starting at Cycle 1, and 1800 mg subcutaneous daratumumab, administered once weekly for Cycles 1 and 2, once every 2 weeks for Cycles 3 to 6, and once every 4 weeks thereafter. Treatment in Phase 2 continued for as long as participants were receiving clinical benefit and did not met any criteria for study withdrawal.

In Phase 1, participants received oral INCB001158 100 mg BID in 28-day cycles starting at Cycle 1, and 1800 mg subcutaneous daratumumab, administered once weekly for Cycles 1 and 2, once every 2 weeks for Cycles 3 to 6, and once every 4 weeks thereafter. Treatment continued until disease progression, unacceptable toxicity, or discontinuation from study treatment for any other reason.

In Phase 1, participants received oral INCB001158 100 mg BID in 28-day cycles starting at Cycle 1, and 1800 mg subcutaneous daratumumab, administered once weekly for Cycles 1 and 2, once every 2 weeks for Cycles 3 to 6, and once every 4 weeks thereafter. Treatment continued until disease progression, unacceptable toxicity, or discontinuation from study treatment for any other reason.

In Part 1 of Phase 2, participants received daratumumb 1800 mg subcutaneous daratumumab, administered once weekly for Cycles 1 and 2 (28-day cycles), once every 2 weeks for Cycles 3 to 6, and once every 4 weeks thereafter. At the time of confirmed disease progression, participants crossed over to Part 2 of Phase 2 to receive oral INCB001158 100 mg BID starting at Cycle 1, and 1800 mg subcutaneous daratumumab, administered once weekly for Cycles 1 and 2, once every 2 weeks for Cycles 3 to 6, and once every 4 weeks thereafter. Treatment in Phase 2 continued for as long as participants were receiving clinical benefit and did not met any criteria for study withdrawal.

In Part 1 of Phase 2, participants received oral INCB001158 100 mg BID in 28-day cycles starting at Cycle 1. At the time of confirmed disease progression, participants crossed over to Part 2 of Part 2 to receive oral INCB001158 100 mg BID starting at Cycle 1, and 1800 mg subcutaneous daratumumab, administered once weekly for Cycles 1 and 2, once every 2 weeks for Cycles 3 to 6, and once every 4 weeks thereafter. Treatment in Phase 2 continued for as long as participants were receiving clinical benefit and did not met any criteria for study withdrawal.

In Part 1 of Phase 2, participants received oral INCB001158 100 mg BID in 28-day cycles starting at Cycle 1. At the time of confirmed disease progression, participants crossed over to Part 2 of Part 2 to receive oral INCB001158 100 mg BID starting at Cycle 1, and 1800 mg subcutaneous daratumumab, administered once weekly for Cycles 1 and 2, once every 2 weeks for Cycles 3 to 6, and once every 4 weeks thereafter. Treatment in Phase 2 continued for as long as participants were receiving clinical benefit and did not met any criteria for study withdrawal.

In Phase 1, participants received oral INCB001158 100 mg BID in 28-day cycles starting at Cycle 1, and 1800 mg subcutaneous daratumumab, administered once weekly for Cycles 1 and 2, once every 2 weeks for Cycles 3 to 6, and once every 4 weeks thereafter. Treatment continued until disease progression, unacceptable toxicity, or discontinuation from study treatment for any other reason.

In Part 1 of Phase 2, participants received daratumumb 1800 mg subcutaneous daratumumab, administered once weekly for Cycles 1 and 2 (28-day cycles), once every 2 weeks for Cycles 3 to 6, and once every 4 weeks thereafter. At the time of confirmed disease progression, participants crossed over to Part 2 of Phase 2 to receive oral INCB001158 100 mg BID starting at Cycle 1, and 1800 mg subcutaneous daratumumab, administered once weekly for Cycles 1 and 2, once every 2 weeks for Cycles 3 to 6, and once every 4 weeks thereafter. Treatment in Phase 2 continued for as long as participants were receiving clinical benefit and did not met any criteria for study withdrawal.

In Part 1 of Phase 2, participants received oral INCB001158 100 mg BID in 28-day cycles starting at Cycle 1. At the time of confirmed disease progression, participants crossed over to Part 2 of Part 2 to receive oral INCB001158 100 mg BID starting at Cycle 1, and 1800 mg subcutaneous daratumumab, administered once weekly for Cycles 1 and 2, once every 2 weeks for Cycles 3 to 6, and once every 4 weeks thereafter. Treatment in Phase 2 continued for as long as participants were receiving clinical benefit and did not met any criteria for study withdrawal.