In Part 2, the participants will receive dose of daratumumab as determined in part 1 (16 mg/kg) of the study. Participants will receive 8 full infusions at weekly intervals followed by biweekly (every 2 weeks) infusions for 16 additional weeks and monthly infusions until disease progression or unmanageable toxicity, whichever comes first. Predose was dropped at some point in Part 2. A predose infusion of 10 mg daratumumab will be administered on the day before the first full infusion in select cohorts.

Pre-dose: Participants (part 1) will receive methylprednisolone 80 mg intravenous (IV) injection 30 minutes to 2 hours before treatment. Participants (part 2) will receive 100 mg methylprednisolone IV 60 minutes to 2 hours before treatment; if a patient experiences no significant infusion-related reactions, the dose of methylprednisolone may be decreased to 50 mg after Visit 4.

Post-dose: All participants (part 1) will receive 40 mg methylprednisolone orally on the first and the second day after all full infusions. During Part 2, all participants will receive 20-25 mg methylprednisolone orally or equivalent on the first and second days after all full-dose infusions.

Participants (Part 2) will receive 20 mg dexamethasone intravenous (IV) injection pre-dose, on the first and second days after every full-dose infusions.

Time to first response was defined as the time from the date of first dose of daratumumab to the date of initial documentation of a response (PR or better). Time to best response was defined as the time between the date of first dose of daratumumab and the date of the initial evaluation of the best response (PR or better) to treatment. Kaplan-Meier method was used to estimate the distribution of time to response and time to best response.

TTP was defined as the number of days from the date of first infusion (Day 1) to the date of first record of disease progression. Disease progression (IMWG criteria): increase of 25 percent (%) from lowest response level in Serum M-component and/or (the absolute increase must be >=0.5 g/dL); urine M-component and/or (the absolute increase must be >=200 mg/24 hour; only in participants without measurable serum and urine M-protein levels: the difference between involved and uninvolved free light chain levels (absolute increase must be >10 mg/dL); Development of hypercalcemia (corrected serum calcium >11.5 mg/dL or 2.65 mmol/L) that can be attributed solely to the plasma cell proliferative disorder. Median TTP was estimated by using the Kaplan-Meier method.

Duration of response was calculated from the date of initial documentation of a response (PR or better) to the date of first documented evidence of progressive disease, as defined in the International Myeloma Working Group (IMWG) criteria.

Progression free survival (PFS) was defined as the time between the date of first dose of daratumumab and either disease progression or death, whichever occurs first.

Time to first response was defined as the time from the date of first dose of daratumumab to the date of initial documentation of a response (PR or better). Time to best response was defined as the time between the date of first dose of daratumumab and the date of the initial evaluation of the best response (PR or better) to treatment. Time to VGPR (very good partial response) was defined as the time from the date of first dose of daratumumab to the date of initial documentation of VGPR response. The Kaplan-Meier method was used to estimate time to response.

Overall Survival (OS) was defined as the number of days from administration of the first infusion (Day 1) to date of death. Median Overall Survival was estimated by using the Kaplan-Meier method.

Participants were administered with 7 full IV infusion of 4 mg/kg daratumumab once weekly, along with this participants also received methylprednisolone 80 mg IV injection before first 2 infusions and 40 mg methylprednisolone orally for 2 days after all full infusions. First 2 infusions were separated by 3 week washout period.

Participants were administered with 7 full IV infusion of 8 mg/kg daratumumab once weekly, along with this participants also received methylprednisolone 80 mg IV injection before first 2 infusions and 40 mg methylprednisolone orally for 2 days after all full infusions. First 2 infusions were separated by 3 week washout period.

Participants were administered with 7 full IV infusion of 16 mg/kg daratumumab once weekly, along with this participants also received methylprednisolone 80 mg IV injection before first 2 infusions and 40 mg methylprednisolone orally for 2 days after all full infusions. First 2 infusions were separated by 3 week washout period.

Participants were administered with 7 full IV infusion of 24 mg/kg daratumumab once weekly, along with this participants also received methylprednisolone 80 mg IV injection before first 2 infusions and 40 mg methylprednisolone orally for 2 days after all full infusions. First 2 infusions were separated by 3 week washout period.

Participants were administered with 8 full IV infusions of 8 mg/kg daratumumab once weekly for 8 weeks, then every 2 weeks (q2w) for 16 weeks, then every 4 weeks (q4w) until the participant experienced disease progression or unmanageable toxicity whichever came first, along with this participants also received methylprednisolone 100 mg IV before treatment and 20-25 mg methylprednisolone orally for 2 days after all full infusions.

Participants were administered with 8 full IV infusions of 16 mg/kg daratumumab once weekly for 7 weeks, then every 2 weeks (q2w) for 14 weeks, then every 4 weeks (q4w) until the participant experienced disease progression or unmanageable toxicity whichever came first, along with this participants also received methylprednisolone 100 mg IV before treatment and 20-25 mg methylprednisolone orally for 2 days after all full infusions. First 2 infusions were separated by 3 week washout period.

Total of all reporting groups

Participants were administered with 7 full IV infusion of 4 mg/kg daratumumab once weekly, along with this participants also received methylprednisolone 80 mg IV injection before first 2 infusions and 40 mg methylprednisolone orally for 2 days after all full infusions. First 2 infusions were separated by 3 week washout period.

Participants were administered with 7 full IV infusion of 8 mg/kg daratumumab once weekly, along with this participants also received methylprednisolone 80 mg IV injection before first 2 infusions and 40 mg methylprednisolone orally for 2 days after all full infusions. First 2 infusions were separated by 3 week washout period.

Participants were administered with 8 full IV infusions of 16 mg/kg daratumumab every 2 week (q2w) for 14 weeks, then every 4 weeks (q4w), along with this participants also received methylprednisolone 80 mg IV injection before first 2 infusions and 40 mg methylprednisolone orally for 2 days after all full infusions. First 2 infusions were separated by 3 week washout period.

Participants were administered with 7 full IV infusion of 24 mg/kg daratumumab once weekly, along with this participants also received methylprednisolone 80 mg IV injection before first 2 infusions and 40 mg methylprednisolone orally for 2 days after all full infusions. First 2 infusions were separated by 3 week washout period.

Participants were administered with 8 full IV infusions of 8 mg/kg daratumumab once weekly for 8 weeks, then every 2 weeks (q2w) for 16 weeks, then every 4 weeks (q4w) until the participant experienced disease progression or unmanageable toxicity whichever came first, along with this participants also received methylprednisolone 100 mg IV before treatment and 20-25 mg methylprednisolone orally for 2 days after all full infusions.

Participants were administered with 8 full IV infusions of 16 mg/kg daratumumab once weekly for 7 weeks, then every 2 weeks (q2w) for 14 weeks, then every 4 weeks (q4w) until the participant experienced disease progression or unmanageable toxicity whichever came first, along with this participants also received methylprednisolone 100 mg IV before treatment and 20-25 mg methylprednisolone orally for 2 days after all full infusions. First 2 infusions were separated by 3 week washout period.

Overall response defined as percentage of participants who achieved stringent complete response (sCR), complete response (CR), very good partial response (VGPR) or partial response (PR). Per IMWG criteria, sCR: is defined as normal free light chain (FLC) ratio, and absence of clonal plasma cells (PCs) by immunohistochemistry, immunofluorescence or 2- to 4-color flow cytometry; CR: Negative immunofixation on the serum and urine and disappearance of any soft tissue plasmacytomas and < 5 % plasma cells in bone marrow; VGPR: Serum and urine M-protein detectable by immunofixation but not on electrophoresis or >= 90% reduction in serum M-protein plus urine M-protein level < 100mg/24 hours; PR: >= 50 % reduction of serum M-protein and reduction in 24 hour urinary M-protein by >= 90% or to <200 mg/24 hours; if the serum and urine M-protein are not measurable, a decrease of >=50% in the difference between involved and uninvolved FLC levels is required in place of the M-protein criteria.

All-Treated Analysis Set included all enrolled participants who received at least 1 dose of study drug. For Part 1, only participants treated with >= 4 mg/kg daratumumab were used for efficacy analyses and less than (<) 4 mg/kg doses were considered under the therapeutic levels.

Time to first response was defined as the time from the date of first dose of daratumumab to the date of initial documentation of a response (PR or better). Time to best response was defined as the time between the date of first dose of daratumumab and the date of the initial evaluation of the best response (PR or better) to treatment. Kaplan-Meier method was used to estimate the distribution of time to response and time to best response.

All-Treated Analysis Set included all enrolled participants who received at least 1 dose of study drug. For Part 1, only participants treated with >= 4 mg/kg daratumumab were used for efficacy analyses and less than (<) 4 mg/kg doses were considered under the therapeutic levels.

TTP was defined as the number of days from the date of first infusion (Day 1) to the date of first record of disease progression. Disease progression (IMWG criteria): increase of 25 percent (%) from lowest response level in Serum M-component and/or (the absolute increase must be >=0.5 g/dL); urine M-component and/or (the absolute increase must be >=200 mg/24 hour; only in participants without measurable serum and urine M-protein levels: the difference between involved and uninvolved free light chain levels (absolute increase must be >10 mg/dL); Development of hypercalcemia (corrected serum calcium >11.5 mg/dL or 2.65 mmol/L) that can be attributed solely to the plasma cell proliferative disorder. Median TTP was estimated by using the Kaplan-Meier method.

All-Treated Analysis Set included all enrolled participants who received at least 1 dose of study drug.

Duration of response was calculated from the date of initial documentation of a response (PR or better) to the date of first documented evidence of progressive disease, as defined in the International Myeloma Working Group (IMWG) criteria.

Subset of All-Treated Analysis Set included those who had overall response in Part 2.

Progression free survival (PFS) was defined as the time between the date of first dose of daratumumab and either disease progression or death, whichever occurs first.

All-Treated Analysis Set included all enrolled participants who received at least 1 dose of study drug.

Time to first response was defined as the time from the date of first dose of daratumumab to the date of initial documentation of a response (PR or better). Time to best response was defined as the time between the date of first dose of daratumumab and the date of the initial evaluation of the best response (PR or better) to treatment. Time to VGPR (very good partial response) was defined as the time from the date of first dose of daratumumab to the date of initial documentation of VGPR response. The Kaplan-Meier method was used to estimate time to response.

All-Treated Analysis Set included all enrolled participants who received at least 1 dose of study drug. Here 'n' (Number of Participants Analyzed) signifies number of participants analyzed at specific time point.

Overall Survival (OS) was defined as the number of days from administration of the first infusion (Day 1) to date of death. Median Overall Survival was estimated by using the Kaplan-Meier method.

All-Treated Analysis Set included all enrolled participants who received at least 1 dose of study drug.

Participants were administered with 7 full IV infusion of 4 mg/kg daratumumab once weekly, along with this participants also received methylprednisolone 80 mg IV injection before first 2 infusions and 40 mg methylprednisolone orally for 2 days after all full infusions. First 2 infusions were separated by 3 week washout period.

Participants were administered with 7 full IV infusion of 8 mg/kg daratumumab once weekly, along with this participants also received methylprednisolone 80 mg IV injection before first 2 infusions and 40 mg methylprednisolone orally for 2 days after all full infusions. First 2 infusions were separated by 3 week washout period.

Participants were administered with 7 full IV infusion of 16 mg/kg daratumumab once weekly, along with this participants also received methylprednisolone 80 mg IV injection before first 2 infusions and 40 mg methylprednisolone orally for 2 days after all full infusions. First 2 infusions were separated by 3 week washout period.

Participants were administered with 7 full IV infusion of 24 mg/kg daratumumab once weekly, along with this participants also received methylprednisolone 80 mg IV injection before first 2 infusions and 40 mg methylprednisolone orally for 2 days after all full infusions. First 2 infusions were separated by 3 week washout period.

Participants were administered with 8 full IV infusions of 8 mg/kg daratumumab once weekly for 8 weeks, then every 2 weeks (q2w) for 16 weeks, then every 4 weeks (q4w) until the participant experienced disease progression or unmanageable toxicity whichever came first, along with this participants also received methylprednisolone 100 mg IV before treatment and 20-25 mg methylprednisolone orally for 2 days after all full infusions.

Participants were administered with 8 full IV infusions of 16 mg/kg daratumumab once weekly for 7 weeks, then every 2 weeks (q2w) for 14 weeks, then every 4 weeks (q4w) until the participant experienced disease progression or unmanageable toxicity whichever came first, along with this participants also received methylprednisolone 100 mg IV before treatment and 20-25 mg methylprednisolone orally for 2 days after all full infusions. First 2 infusions were separated by 3 week washout period.