DLTs were defined as: All Grade 5 toxicities, Grade 4 thrombocytopenia, neutropenia or anemia and Grade 3/4 febrile neutropenia and hemorrhage associated with thrombocytopenia, all non-hematological toxicities of grade ≥3 (with exceptions per protocol), Grade 4 tumor lysis syndrome (TLS), Grade 4 infusion-related reaction (IRR), and any liver toxicity of elevated alanine aminotransferase (ALT) or aspartate aminotransferase (AST) ≥3 times or greater above the upper limit of normal (ULN) with serum total bilirubin of ≥2 times the upper limit of normal, without findings of cholestasis and in the absence of alternative etiologies. DLTs were graded for severity according to National Cancer Institute Common Terminology Criteria for Adverse Events (NCI-CTCAE) v5.0.

Dose-Determining Analysis Set (DDS) included all FAS participants (all enrolled participants who received at least 1 dose of trial drug [GEN3014 or daratumumab SC]) in the Dose Escalation part who met the minimum exposure criterion and had sufficient safety evaluations or experienced a DLT during the first 28 days of dosing (ie, in Cycle 1).

An AE was any untoward medical occurrence in a participant or clinical trial participant, temporally associated with the use of a medicinal product, whether or not considered related to the medicinal product. An AE was any unfavorable and unintended sign (including an abnormal laboratory finding), symptom, or disease (new or exacerbated) temporally associated with the use of a medicinal product. An SAE was defined as an AE that met 1 of the following criteria: fatal or life-threatening, resulted in persistent or significant disability/incapacity, a congenital anomaly/birth defect, was medically significant (jeopardized the participant or may have required medical or surgical intervention to prevent one of the outcomes listed above), required inpatient hospitalization or prolongation of existing hospitalization. A summary of all Serious Adverse Events and Other Adverse Events (nonserious) regardless of causality is located in the 'Reported Adverse Events' Section.

Safety Analysis Set included all enrolled participants who received at least 1 dose of trial drug (GEN3014 or daratumumab SC). In the RRMM Dose Escalation: GEN3014 0.2/0.6 mg/kg arm, the participant underwent intraparticipant dose escalation in Cycle 1. As pre-specified, safety data were collected and are reported combined for both 0.2 and 0.6 mg/kg dose levels in this arm.

ORR was defined as the percentage of participants with a partial response (PR) or better based on International Myeloma Working Group (IMWG) criteria for RRMM participants and based on Lugano criteria for DLBCL participants. Per IMWG criteria, PR was defined as ≥50% reduction of serum M-protein plus reduction in 24-h urinary M-protein by ≥90% or to <200 mg per 24 h. In addition to these criteria, if present at baseline, a ≥50% reduction in the size (sum of the product of the diameters [SPD]) of soft tissue plasmacytomas was also required. Per Lugano criteria, PR was defined as ≥50% decrease in SPD of up to 6 target measurable nodes and extranodal sites, absent/normal, regressed, but no increase in non-measurable lesions, spleen regressed >50% in length beyond normal (13 centimeters [cm]), and no new lesions.

Full Analysis set included all enrolled participants who received at least 1 dose of trial drug (GEN3014 or daratumumab SC).

ORR was defined as the percentage of participants with a PR or better based on IMWG criteria. Per IMWG criteria, PR was defined as ≥50% reduction of serum M-protein plus reduction in 24-h urinary M-protein by ≥90% or to <200 mg per 24 h. In addition to these criteria, if present at baseline, a ≥50% reduction in the size (SPD) of soft tissue plasmacytomas was also required.

Full Analysis set included all enrolled participants who received at least 1 dose of trial drug (GEN3014 or daratumumab SC).

Venous blood samples were collected for analyzing concentrations of GEN3014. For the RRMM Dose Escalation 0.2/0.6 mg/kg arm, the participant underwent intraparticipant dose escalation in Cycle 1, where the participant received 0.2 mg/kg during the first week and 0.6 mg/kg from second week and beyond. Therefore, pharmacokinetic (PK) parameters were additionally calculated for Cycle 1 Day 8 dosing only in the RRMM Dose Escalation 0.2/0.6 mg/kg arm to account for the change in dosing over Cycle 1 in this arm.

PK Analysis Set=all participants exposed to GEN3014 who had 1+ PK sample collected with a valid bioanalytical result. Overall number of participants analyzed = number of participants evaluable for the outcome measure. Number analyzed=participants evaluable at the specified timepoint.

Venous blood samples were collected for analyzing concentrations of GEN3014. For the RRMM Dose Escalation 0.2/0.6 mg/kg arm, the participant underwent intraparticipant dose escalation in Cycle 1, where the participant received 0.2 mg/kg during the first week and 0.6 mg/kg from second week and beyond. Therefore, PK parameters were additionally calculated for Cycle 1 Day 8 dosing in the RRMM Dose Escalation 0.2/0.6 mg/kg arm to account for the change in dosing over Cycle 1 in this arm.

PK Analysis Set=all participants exposed to GEN3014 with 1+ PK sample with a valid bioanalytical result. Overall number of participants analyzed= participants evaluable for the outcome measure. Number analyzed=participants evaluable at specified timepoint.

Venous blood samples were collected for analyzing concentrations of GEN3014. For the RRMM Dose Escalation 0.2/0.6 mg/kg arm, the participant underwent intraparticipant dose escalation in Cycle 1, where the participant received 0.2 mg/kg during the first week and 0.6 mg/kg from second week and beyond. Therefore, PK parameters were additionally calculated for Cycle 1 Day 8 dosing only in the RRMM Dose Escalation 0.2/0.6 mg/kg arm to account for the change in dosing over Cycle 1 in this arm.

PK Analysis Set=all participants exposed to GEN3014 with 1+ PK sample with a valid bioanalytical result. Overall number of participants analyzed=participants evaluable for the outcome measure. Number analyzed= participants evaluable at the specified timepoint.

Venous blood samples were collected for analyzing concentrations of GEN3014. For the RRMM Dose Escalation 0.2/0.6 mg/kg arm, the participant underwent intraparticipant dose escalation in Cycle 1, where the participant received 0.2 mg/kg during the first week and 0.6 mg/kg from second week and beyond. Therefore, PK parameters were additionally calculated for Cycle 1 Day 8 dosing only in the RRMM Dose Escalation 0.2/0.6 mg/kg arm to account for the change in dosing over Cycle 1 in this arm.

PK Analysis Set=all participants exposed to GEN3014 with 1+ PK sample with a valid bioanalytical result. Overall number of participants analyzed=participants evaluable for the outcome measure. Number analyzed= participants evaluable at specified timepoint.

Venous blood samples were drawn for analysis of ADAs to GEN3014.

Immunogenicity Analysis Set=all enrolled participants who received at least 1 dose of trial drug, had a baseline and at least 1 evaluable on-treatment ADA sample.

ORR was defined as the percentage of participants with a PR or better. The response in RRMM Cohorts was assessed following IMWG criteria 2016. Per IMWG criteria, PR was defined as ≥50% reduction of serum M-protein plus reduction in 24-h urinary M-protein by ≥90% or to <200 mg per 24 h. In addition to these criteria, if present at baseline, a ≥50% reduction in the size (SPD) of soft tissue plasmacytomas was also required.

Full Analysis set included all enrolled participants who received at least 1 dose of trial drug (GEN3014 or daratumumab SC). Overall number of participants analyzed = participants evaluable for the outcome measure.

CBR was defined as the percentage of participants with a best overall response of minimal response (MR), partial response (PR), very good partial response (VGPR), complete response (CR) or stringent complete response (sCR) as determined by the investigator per IMWG response criteria for RRMM participants. MR=≥25% but ≤49% reduction of serum M-protein, reduction of 24-h urine by 50%-89% and if present at baseline, ≥50% reduction in the size (SPD) of soft tissue plasmacytomas. PR=≥50% reduction of serum M-protein, reduction in 24-h urinary M-protein by ≥90% or to <200mg/24h and if present at baseline,≥50% reduction in SPD of soft tissue plasmacytomas. VGPR=Serum+urine M-protein detectable by IFE but not electrophoresis or ≥90% reduction in serum M-protein+urine M-protein level <100mg/24h. CR=Negative IFE on serum/urine + disappearance of soft tissue plasmacytomas and ≤5% plasma cells in bone marrow aspirates. sCR=CR+normal FLC ratio, absence of clonal cells in bone marrow biopsy by IHC.

Full Analysis set included all enrolled participants who received at least 1 dose of trial drug (GEN3014 or daratumumab SC). Overall number of participants analyzed = participants evaluable for the outcome measure. As pre-specified, data for CBR was only collected and derived for RRMM participants.

DOR was defined as time from first response (PR or better) to timing of disease progression or death (due to any cause), whichever came first.

Full Analysis set=all enrolled participants who received at least 1 dose of trial drug (GEN3014 or daratumumab SC). Overall number of participants analyzed=participants evaluable for the outcome measure with a response.

TTR was defined as the time from date of first dose, or date of randomization for participants in the Expansion Part B, to time of first response (PR or better).

Full Analysis set=all enrolled participants who received at least 1 dose of trial drug (GEN3014 or daratumumab SC). Overall number of participants analyzed=participants evaluable for the outcome measure with a response.

PFS was defined as the time from the date of first dose, or date of randomization for participants in the Expansion Part B, to the date of progression or death (due to any cause), whichever came first.

Full Analysis set=all enrolled participants who received at least 1 dose of trial drug (GEN3014 or daratumumab SC). Overall number of participants analyzed=participants evaluable for the outcome measure.

OS was defined as the time from the date of first dose, or date of randomization for participants in the Expansion Part B, to the date of death due to any cause.

Full Analysis set=all enrolled participants who received at least 1 dose of trial drug (GEN3014 or daratumumab SC). Overall number of participants analyzed=participants evaluable for the outcome measure.

An AE was any untoward medical occurrence in a participant or clinical trial participant, temporally associated with the use of a medicinal product, whether or not considered related to the medicinal product. An AE was any unfavorable and unintended sign (including an abnormal laboratory finding), symptom, or disease (new or exacerbated) temporally associated with the use of a medicinal product. An SAE was defined as an AE that met 1 of the following criteria: fatal or life-threatening, resulted in persistent or significant disability/incapacity, a congenital anomaly/birth defect, was medically significant (jeopardized the participant or may have required medical or surgical intervention to prevent one of the outcomes listed above), required inpatient hospitalization or prolongation of existing hospitalization. A summary of all Serious Adverse Events and Other Adverse Events (nonserious) regardless of causality is located in the 'Reported Adverse Events' Section.

Safety Analysis Set included all enrolled participants who received at least 1 dose of trial drug (GEN3014 or daratumumab SC).

Based on Investigator Assessment per IMWG 2016 Criteria, VGPR was defined as serum and urine M-protein detectable by immunofixation (IFE) but not on electrophoresis or ≥90% reduction in serum M-protein plus urine M-protein level <100 mg per 24 h. Data are reported for the percentage of participants with a VGPR or better.

Full Analysis set included all enrolled participants who received at least 1 dose of trial drug (GEN3014 or daratumumab SC). Overall number of participants analyzed = participants evaluable for the outcome measure.

CR was defined as negative IFE on the serum and urine and disappearance of any soft tissue plasmacytomas and ≤5% plasma cells in bone marrow aspirates based on Investigator assessment per IMWG response criteria. Data are reported for the percentage of participants with CR or better.

Full Analysis set included all enrolled participants who received at least 1 dose of trial drug (GEN3014 or daratumumab SC). Overall number of participants analyzed=participants evaluable for the outcome measure.

TTNT for participants in the Expansion Part B was defined as the time from randomization to the start of subsequent anti-cancer therapy. Participants who withdrew consent or were lost to follow up or died due to causes other than disease progression were censored at their last disease assessment.

Full Analysis set included all enrolled participants who received at least 1 dose of trial drug (GEN3014 or daratumumab SC).

Venous blood samples were drawn for analysis of ADAs to GEN3014 and daratumumab. In the GEN3014 arm, participants were tested for anti-GEN3014-antibodies; in the daratumumab arm, participants were tested for anti-daratumumab-antibodies.

The Immunogenicity Analysis Set included all enrolled participants who received at least 1 dose of trial drug and had baseline ADA, and at least 1 evaluable on-treatment ADA sample. Overall number of participants analysed = participants evaluable for the OM.