Study to Evaluate the Safety and Efficacy of KITE-585 in Participants With Relapsed/Refractory Multiple Myeloma

A DLT is a KITE-585-related event with onset in the first 28 days following infusion. DLTs are defined by events and duration of events, including: * Any duration: Grade (GR) 4 cytokine release syndrome (CRS), KITE-585-related GR 5 adverse events (AE) and GR 4 nonhematologic AE with the exceptions of fever, nausea, hepatic toxicity that resolves to GR 3 or better in ≤ 72 hours, hypogammaglobulinemia, tumor lysis syndrome, acute renal toxicity requiring dialysis for ≤ 7 days, intubation for airway protection for ≤ 7 days and AE resolves to ≤ GR 1 within 2 weeks and baseline within 4 weeks * ≥ 72 hours: GR 3 CRS and GR 3 nonhematologic AE with the exceptions of fever, nausea, hepatic toxicity that resolves to GR 2 or better in ≤ 14 days, hypogammaglobulinemia and tumor lysis syndrome * ≥ 30 days: GR 4 hematologic AE with the exceptions of cytopenias attributable to ongoing or recurrent multiple myeloma

Time frame: From KITE-585 infusion until 28 days after KITE-585 infusion

Population: DLT Evaluable Set included participants in the dose escalation period who received the target dose (± 20%) and were followed for at least 28 days after the first KITE-585 infusion; or received a dose of KITE-585 lower than 20% below the target dose for that cohort and experienced a DLT during the 28-day post-first-infusion period.

DOR is defined for participants who experience an objective response and is defined as the time from the date of their first objective response (which is subsequently confirmed) to PD per IMWG Consensus Panel 1 Criteria or death from any cause, whichever is earlier. Objective response is defined in Outcome measure 2.

Time frame: From first response to the earlier date of data cutoff and first administration of other anti-cancer therapies including stem cell transplant (maximum: 17.6 months)

Population: Participants in the Safety Analysis Set who achieved a stringent CR (sCR), complete response (CR), partial response (PR), or very good PR (VGPR), as determined by IMWG Consensus Panel 1 Criteria were to be analyzed. As per changes in planned analysis, this outcome measure could not be analyzed at the data cutoff date due to an insufficient number of responders. Kite/Gilead did not collect the DOR data after the data cutoff date.

ORR: Percentage of participants who achieved a stringent CR (sCR), complete response (CR), partial response (PR), or very good PR (VGPR), as determined by IMWG Consensus Panel 1 Criteria. sCR: CR+normal free light chain (FLC) ratio, no clonal cells in BM by immunohistochemistry or immunofluorescence; CR: negative immunofixation (IFX) on serum and urine, no soft tissue plasmacytomas (STP), \<5% plasma cells in bone marrow (BM); PR: ≥50% decrease of serum M-protein + 24hr urinary M-protein decrease by ≥90% or \<200 mg/24hr. If unmeasurable serum and urine M-protein; and serum-free light assay; requires ≥ 50% decrease in the difference between involved and uninvolved FLC levels / ≥ 50% reduction in plasma cells (PC), provided baseline BM PC percentage was ≥ 30%, respectively. If present at baseline, ≥ 50% reduction in the size of STP is also required; VGPR: serum and urine M-protein detected by IFX but not electrophoresis, \>90% in serum M-protein+urine, M-protein level \<100 mg/24hr.

Time frame: From KITE-585 infusion to the earlier date of data cutoff and first administration of other anti-cancer therapies including stem cell transplant (maximum: 17.6 months)

Population: The Safety Analysis Set included all participants treated with any dose of KITE-585.

Overall survival is defined as the time from the first dose date of study drug to the date of death from any cause. Analysis was done using KM estimate. Participants who have not died by the analysis data cutoff date were censored at their last date known to be alive or cutoff date, whichever is earlier.

Time frame: From KITE-585 infusion to date of data cutoff (maximum: 17.6 months)

Population: Participants in the Safety Analysis Set were analyzed.

Clinically significant laboratory abnormalities were defined as per investigator's discretion.

Time frame: Enrollment through 24 months after treatment with KITE-585 or up to disease progression or initiation of another anti-cancer therapy, whichever occurs first (maximum: 2.9 months)

Population: Participants in the Safety Analysis Set were analyzed.

Time frame: Enrollment through 24 months after treatment with KITE-585 or up to disease progression or initiation of another anti-cancer therapy, whichever occurs first (maximum: 2.9 months)

Population: Participants in the Safety Analysis Set were analyzed.

PFS: Interval from first study drug dose date to the earlier of first documentation of definitive progressive disease (PD) per IMWG Consensus Panel 1 Criteria or death from any cause. PD: an increase of 25% from the lowest response value in 1 of the following: Serum and urine M-protein (absolute increase ≥ 0.5 g/dL and ≥ 200 mg/24 hours, respectively); In participants without measurable serum and urine M-protein levels, the difference between involved and uninvolved FLC levels (absolute increase \> 10 mg/dL); In participants without measurable serum and urine M-protein and without measurable disease by FLC levels, bone marrow PC percentage (absolute percentage ≥ 10%). Definite development of new bone lesions or STP or definite increase in the size of existing bone lesions or STPs; Development of hypercalcemia (corrected serum calcium \>11.5 mg/dL) that can be attributed solely to PC proliferative disorder. Analysis was done using Kaplan-Meier (KM) estimate.

Time frame: From KITE-585 infusion to the earlier date of data cutoff and first administration of other anti-cancer therapies including stem cell transplant (maximum: 17.6 months)

Population: Participants in the Safety Analysis Set were analyzed. Participants not meeting the criteria for PD by the analysis data cutoff date were censored at their last evaluable disease assessment date before any other anti-cancer therapies including stem cell transplant.

TTNT is defined as the length of time between the date of KITE-585 infusion to the date of initiation of the next therapy or death due to any cause, whichever is earlier.

Time frame: From KITE-585 infusion to the earlier date of data cutoff and first administration of other anti-cancer therapies including stem cell transplant (maximum: 17.6 months)

Population: Participants in the Safety Analysis Set were to be analyzed. Estimates of the proportion of participants who have not required additional treatment for progressive multiple myeloma at selected time points were to be provided. As per changes in planned analysis, this outcome measure could not be analyzed at the data cutoff date due to a lack of events. Kite/Gilead did not collect data to analyze TTNT after the data cutoff date.