A Phase 2, Multicenter, Randomized, Open-label Study of MEDI-551 in Adults With Relapsed or Refractory Diffuse Large B-Cell Lymphoma (DLBCL)

Objective Response Rate is defined as the proportion of participants with a best response of complete response (CR) or partial response (PR) according to the International Working Group criteria. CR is defined as disappearance of all evidence of disease. PR is defined as 50 percent (%) decrease in the sum of the product of the perpendicular diameters (SPD) of up to 6 largest dominant nodal masses and greater than or equal to (>=) 50% decrease in SPD of spleen/liver nodules.

Progression-free survival (PFS) is defined as the time from randomization until the first documentation of progressive disease (PD) or death due to any cause, whichever occurs first according to the International Working Group criteria. PD is defined as appearance of any new lesions or >= 50% increase in SPD of more than one node or >= 50% increase in longest diameter of a previously identified node or >50% increase from nadir in the SPD of any previous lesions. PFS (months) = (Date of PD/death or censoring - Date of randomization + 1) / (365.25/12).

Event-Free Survival (EFS) is defined as the time from randomization until the first documentation of EFS events which include PD, initiation of alternative antitumor treatment or death due to any cause, whichever occurs first according to the International Working Group criteria. PD is defined as appearance of any new lesions or >= 50% increase in SPD of more than one node or >= 50% increase in longest diameter of a previously identified node or >50% increase from nadir in the SPD of any previous lesions. EFS (months) = (Date of EFS or censoring - Date of randomization + 1) / (365.25/12).

Overall survival is defined as the time from randomization until death due to any cause according to the International Working Group criteria. OS (months) = (Date of death or censoring - Date of randomization + 1) / (365.25/12).

Time to Progression (TTP) is defined as the time from randomization until the first documentation of PD according to the International Working Group criteria. PD is defined as appearance of any new lesions or >= 50% increase in SPD of more than one node or >= 50% increase in longest diameter of a previously identified node or >50% increase from nadir in the SPD of any previous lesions. TTP (months) = (Date of PD or censoring - Date of randomization + 1) / (365.25/12).

Time to response (TTR) is defined as the time from randomization until the first documentation of disease response according to the International Working Group criteria. Only participants who have achieved objective response (confirmed CR or confirmed PR) assessed by investigator were evaluated for TTR. CR is defined as disappearance of all evidence of disease. PR is defined as 50% decrease in the SPD of up to 6 largest dominant nodal masses and >= 50% decrease in SPD of spleen/liver nodules. TTR (months) = (Date of first disease response - Date of randomization + 1) / (365.25/12).

Duration of Response (DR) is defined as time from start of first documented objective response (confirmed CR or confirmed PR) to first documented PD according to the International Working Group criteria. CR is defined as disappearance of all evidence of disease. PR is defined as 50% decrease in the SPD of up to 6 largest dominant nodal masses and >= 50% decrease in SPD of spleen/liver nodules. PD: appearance of any new lesions or >= 50% increase in SPD of more than one node or >= 50% increase in longest diameter of a previously identified node or > 50% increase from nadir in the SPD of any previous lesions. Only participants who have achieved objective response assessed by investigator were evaluated. DR calculated as (months) = (Date of PD or censoring - Date of first disease response + 1)/ (365.25/12).

The best overall response was calculated, based upon the disease assessments recorded during the study visits, and summarized with the number of participants for the following categories: CR, PR, stable disease (SD), PD, and unknown. Responses were assessed according to the International Working Group criteria. CR: disappearance of all evidence of disease; PR: 50% decrease in the SPD of up to 6 largest dominant nodal masses and >= 50% decrease in SPD of spleen/liver nodules; PD: appearance of any new lesions or >= 50% increase in SPD of more than one node or >= 50% increase in longest diameter of a previously identified node or >50% increase from nadir in the SPD of any previous lesions; SD: failure to attain CR/PR or PD.

Acceptable dose for MEDI-551 was evaluated based on the benefit-risk analysis.

An Adverse Event (AE) is any unfavourable and unintended signs, symptoms, or diseases temporally associated with use of study drug, whether or not considered related to study drug. Serious adverse event (SAE) is any AE that resulted in death, inpatient hospitalization or prolongation of existing hospitalization, persistent or significant disability or incapacity, life-threatening, a congenital anomaly/birth defect, or an important medical event. TEAEs are defined as AEs present at baseline that worsened in intensity after administration of study drug, or events absent at baseline that emerged after administration of study drug, up to 90 days after the end of treatment (EOT).

An abnormal laboratory finding that was judged by the investigator to be clinically significant was reported as an AE. TEAEs were defined as events present at baseline that worsened in intensity after administration of MEDI-551, or events absent at baseline that emerged after administration of MEDI-551, for the period extending to 90 days after the end of study treatment (EOT).

An abnormal laboratory findings that was judged by the investigator to be clinically significant was reported as an AE. TEAEs were defined as events present at baseline that worsened in intensity after administration of MEDI-551, or events absent at baseline that emerged after administration of MEDI-551, for the period extending to 90 days after the end of study treatment.

Vital signs included parameters such as heart rate, blood pressure, temperature, and respiratory rate. An abnormal vital signs and ECG findings that was judged by the investigator to be clinically significant was reported an AE. TEAEs were defined as events present at baseline that worsened in intensity after administration of MEDI-551, or events absent at baseline that emerged after administration of MEDI-551, for the period extending to 90 days after the end of study treatment.

A participant was considered ADA-positive across the study if they had a positive reading (titer of 50 or higher) at any time point during the study.

The mean serum concentration of MEDI-551 were observed.

Terminal elimination half-life (T1/2) is the time required for half of the drug to be eliminated from the serum.