DLTs: adverse events occurring during 1st treatment cycle, unless due to disease progression/to cause obviously unrelated to investigational medicinal product (IMP) which included:hematological abnormalities: Grade(G) 4 neutropenia(N) for 7/more consecutive days, G3 to G4 N with fever (temperature greater than or equal to [>=] 38.5 degree Celsius on more than 1 occasion) or microbiologically/radiographically documented infection, G3 to G4 thrombocytopenia with clinically significant bleeding. Non-hematological abnormalities: G4 non-hematologic AE, G>=2 uveitis, G3 non-hematological AE lasting greater than (>)3 days (except G3 fatigue, allergic reaction/hypersensitivity attributed to isatuximab or REGN2810 and G3 or G4 clinically non-significant laboratory abnormality), delay in initiation of Cycle 2 >14 days due to treatment related laboratory abnormalities/AE. Any other toxicity that Investigator and Sponsor deemed to be dose-limiting, regardless of grade, was also considered as DLT.

Analysis was performed on DLT evaluable population which included participants who received the planned doses of isatuximab and REGN2810 during Cycle 1, and who completed the DLT observation period after the first IMP administration, unless they discontinued the study treatment(s) due to DLT.

An AE was defined as any untoward medical occurrence in a participant who received study drug and did not necessarily have to have a causal relationship with the treatment. Serious adverse events (SAEs) was any untoward medical occurrence that at any dose: resulted in death, was life-threatening, required inpatient hospitalization or prolongation of existing hospitalization, resulted in persistent or significant disability/incapacity, was a congenital anomaly/birth defect, was a medically important event. TEAEs were defined as AEs that developed, worsened or became serious during the TEAE period (defined as the time from the first dose of study treatment up to 30 days after the last dose of study treatment). TEAEs included both SAEs and non-SAEs.

Analysis was performed on all-treated population.

Hematological parameters assessed were anemia, white blood cell (WBC) decreased, platelet count decreased, lymphocyte count decreased and neutrophil count decreased. Abnormality criteria was based on National Cancer Institute Common Terminology Criteria for Adverse Event version 4.03 (NCI-CTCAE v 4.03), where Grade 1 = Mild; Grade 2 = Moderate; Grade 3 = Severe; Grade 4 = Potentially Life Threatening. Only those categories in which at least 1 participant had data were reported.

Analysis was performed on all-treated population. Here, overall number of participants analyzed = participants evaluable for this outcome measure.

Abnormal electrolytes parameters assessed were hyponatremia, hypokalemia, hyperkalemia, hypocalcemia, hypercalcemia, hypoalbuminemia and hyperglycemia. Abnormality criteria was based on NCI-CTCAE v 4.03, where Grade 1 = Mild; Grade 2 = Moderate; Grade 3 = Severe; Grade 4 = Potentially Life Threatening. Only those categories in which at least 1 participant had data were reported.

Analysis was performed on all-treated population. Here, overall number of participants analyzed = participants evaluable for this outcome measure.

Abnormal renal parameters assessed were creatinine clearance (CrCl), creatinine increased and hyperuricemia. Creatinine clearance was assessed in categories: >=60 - less than (<) 90 milliliters per minute per 1.73 square meter (mL/min/1.73m^2), >=30 - <60 mL/min/1.73m^2, >=15 - <30 mL/min/1.73m^2 and <15 mL/min/1.73m^2. Creatinine increased and hyperuricemia abnormality criteria was based on NCI-CTCAE v 4.03, where Grade 1 = Mild; Grade 2 = Moderate; Grade 3 = Severe; Grade 4 = Potentially Life Threatening. For all these 3 parameters, only those categories in which at least 1 participant had data were reported.

Analysis was performed on all-treated population. Here, overall number of participants analyzed = participants evaluable for this outcome measure.

Abnormal liver function parameters assessed were aspartate aminotransferase (AST) increased, alanine aminotransferase (ALT) increased, alkaline phosphatase (ALP) increased, blood bilirubin (BB) increased. Abnormality criteria was based on NCI-CTCAE v 4.03, where Grade 1 = Mild; Grade 2 = Moderate; Grade 3 = Severe; Grade 4 = Potentially Life Threatening. Only those categories in which at least 1 participant had data were reported.

Analysis was performed on all-treated population. Here, overall number of participants analyzed = participants evaluable for this outcome measure.

For participants with mCRPC, response was defined as achieving complete response (CR) or partial response (PR) as best overall response (BOR) for soft tissue assessed and confirmed by the Investigators and/or a prostate-specific antigen (PSA) decline of >=50 percent (%) from Baseline that was subsequently confirmed per Prostate Cancer Clinical Trials Working Group 3 (PCWG3) criteria. For participants with NSCLC, ORR was defined as the percentage of participants with CR or PR as BOR according to RECIST 1.1. criteria. Per RECIST 1.1. criteria, CR: disappearance of all target lesions. Any pathological lymph nodes (whether target or non-target) must had reduction in short axis to <10 millimeters (mm) and PR: at least a 30% decrease in the sum of diameters of target lesions, taking as reference the Baseline sum diameters.

Analysis was performed on all-treated population.

ADA response were categorized as treatment boosted ADA and treatment-induced ADA. Treatment boosted ADA was defined as pre-existing ADAs with a significant increase in the ADA titer during the study compared to the Baseline titer. Treatment-induced ADA was defined as ADA that developed at any time during the ADA on-study observation period in participants without pre-existing ADA (including participants without pretreatment samples).

Analyzed on ADA population: all participants who signed the study IC and received at least 1 dose (even incomplete) of the study treatments, either isatuximab or REGN2810 and had at least 1 ADA non-missing results after the first dose of study treatment. Here, 'overall number of participants analyzed'= participants evaluable for this outcome measure. For this outcome measure, combined ADA analysis was planned and performed for participants with mCRPC and NSCLC.

ADA response were categorized as treatment boosted ADA and treatment-induced ADA. Treatment boosted ADA was defined as pre-existing ADAs with a significant increase in the ADA titer during the study compared to the Baseline titer. Treatment-induced ADA was defined as ADA that developed at any time during the ADA on-study observation period in participants without pre-existing ADA (including participants without pretreatment samples).

Analysis was performed on ADA population. Here, 'overall number of participants analyzed' = participants evaluable for this outcome measure. For this outcome measure, combined ADA analysis was planned and performed for participants with mCRPC and NSCLC.

Cmax was defined as the maximum observed plasma concentration. Cmax analysis was done separately for isatuximab for participants with mCRPC and NSCLC.

Analyzed on PK population which included all participants who signed the study IC and received at least 1 dose (even incomplete) of the study treatments, either isatuximab or REGN2810 and had at least 1 drug concentration after the first dose of study treatment. Here, overall number of participants analyzed = participants with available data for this outcome measure.

Cmax was defined as the maximum observed plasma concentration. Cmax analysis was done separately for REGN2810 for participants with mCRPC and NSCLC.

Analysis was performed on PK population. Here, overall number of participants analyzed = participants with available data for this outcome measure.

AUC0-168 hr was defined as the area under the plasma concentration-time curve from time zero to 168h and was calculated using the trapezoidal method over the dosing interval (i.e., 7 days) for isatuximab alone.

Analysis was performed on PK population. Here, overall number of participants analyzed = participants with available data for this outcome measure.

AUC0-504 hr was defined as the area under the plasma concentration-time curve from time zero to 504h and was calculated using the trapezoidal method over the dosing interval (i.e., 21 days) for REGN2810 alone.

Analysis was performed on PK population. Here, overall number of participants analyzed = participants with available data for this outcome measure.

Tumor burden change was defined as the best percent-change from Baseline in a sum of the diameters (longest for non-nodal lesion, short axis for nodal lesions) for all target lesions.

Analysis was performed on all-treated population.

DOR: defined as time (in months) from date of first response (PR or CR in radiographic objective response, or PSA decline >=50% for participants with mCRPC) that was subsequently confirmed to the date of first disease progression (PD) or death, whichever occurred first. PD included radiographic disease progression or unequivocal clinical progression. RECIST 1.1 criteria was used to assess radiographic PD in participants with NSCLC and PCWG3 criteria for participants with mCRPC. Per RECIST 1.1 criteria, CR: disappearance of all target lesions. Any pathological lymph nodes (whether target/non-target) must had reduction in short axis to <10 mm and PR: at least a 30% decrease in sum of diameters of target lesions, taking as reference baseline sum diameters. PD: at least a 20% increase in sum of diameters of target lesions, taking as reference smallest sum on study (Baseline sum if that was smallest), sum with an absolute increase of at least 5 mm and appearance of 1 or more new lesions.

Analysis was performed on subset of participants who had response. Here, '0' in 'overall number of participants analyzed represents that DOR could only be analyzed in participants who achieved a response. As no participant in the NSCLC cohort achieved any response, no DOR is available.

For mCRPC participants, PFS was defined as the time (in months) from first study treatment administration to the date of first documented disease progression or the date of death from any cause, whichever occurred first. Disease progression included radiographic disease progression (per PCWG3 criteria) or unequivocal clinical progression. For NSCLC participants, PFS was defined as the time from first study treatment administration to the date of first documented radiographic progression (PD) (per RECIST 1.1) or the date of death from any cause, whichever occurred first. Per RECIST 1.1 criteria, PD was defined as at least a 20% increase in the sum of diameters of target lesions, taking as reference the smallest sum on study (this included the Baseline sum if that is the smallest on study). The sum must also demonstrate an absolute increase of at least 5 mm. Appearance of 1 or more new lesions was also considered as progression. Analysis was performed using Kaplan-Meier method.

Analysis was performed on all-treated population.

Disease control: defined as percentage of participants with confirmed CR/PR/stable disease (SD), as assessed by Investigator PCWG3 modified RECIST 1.1 criteria relative to total number of participants in analysis population. Per PCWG3 modified RECIST 1.1 criteria, CR: disappearance of all target lesions. Any pathological lymph nodes (whether target/non-target) must had reduction in short axis to <10 mm, PR: at least a 30% decrease in sum of diameters of target lesions, taking as reference Baseline sum diameters and SD: neither sufficient shrinkage from the Baseline to qualify for PR nor sufficient increase to qualify for PD, taking as reference smallest sum diameters while on study. PD: at least a 20% increase in sum of diameters of target lesions, taking as reference smallest sum on study, sum with an absolute increase of diameter of at least 5 mm and appearance of 1 or more new lesions.

Analysis was performed on all-treated population. Here, '0' in 'overall number of participants analyzed represents that data for this outcome measure was not analyzed for NSCLC arm because there was insufficient data to perform the DC analysis.