A Phase 2, Multicenter, Open-label Study of MEDI-551 in Adults With Relapsed or Refractory Chronic Lymphocytic Leukemia (CLL)

ORR, defined as the proportion of participants with complete response (CR) or partial response (PR) out of total number of participants. Responses were assessed by using National Cancer Institute - Working Group guidelines on CLL.

An adverse event (AE) was any untoward medical occurrence attributed to study drug in a participant who received study drug (MEDI-551). A serious adverse event (SAE) was an AE resulting in any of the following outcomes or deemed significant for any other reason: death; initial or prolonged inpatient hospitalization; life-threatening experience; persistent or significant disability/incapacity; congenital anomaly. Treatment-emergent are events between administration of study drug and Day 90 that were absent before treatment or that worsened relative to pre-treatment state. An AESIs was one of scientific and medical interest specific to understanding of study product and may have required close monitoring and rapid communication by investigator to the sponsor. Treatment emergent AESIs were collected from the time of dosing through Day 90 after the last dose of study drug.Hepatic function abnormality and infusion reactions resulting in discontinuation were considered as AESIs.

An abnormal laboratory finding which required an action or intervention by the investigator, or a finding judged by the investigator to represent a change beyond the range of normal physiologic fluctuation were reported as an adverse event. Laboratory evaluations (haematology, serum chemistry and urinalysis) of blood and urine samples were performed.

AEs observed in participants with clinically significant ECG abnormalities were assessed.

Complete response was as per IWG was the complete disappearance of all detectable clinical evidence of disease and disease-related symptoms if present before therapy.

The MRD-negative CR rate was defined as the percentage of participants who achieved CR and became MRD-negative as determined by flow cytometry. CR as per International Working Group (IWG) was complete disappearance of all detectable clinical evidence of disease and disease-related symptoms if present before therapy.

Time to response was evaluated using the Kaplan-Meier method.

TTP was defined as the time from onset of treatment with study drug until first evidence/diagnosis of progressive disease or - in the absence of any diagnosis of progressive disease - until the participant´s death.

PFS was measured from the start of treatment with study drug until the first documentation of disease progression or death due to any cause, whichever occurred first. Kaplan-Meier method was used for evaluation.

OS was determined as the time from the start of treatment with study drug until death due to any cause. For participants who were alive at the end of the study or lost to follow-up, OS was censored on the last date when the participant was known be alive. Kaplan-Meier method was used for evaluation.

A participant was considered ADA-positive across the study if they had a positive reading at any time point during the study.

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