Study of Blinatumomab in Japanese Patients With Relapsed/Refractory B-precursor Acute Lymphoblastic Leukemia

Dose-limiting toxicities (DLTs) were defined as any Common Terminology Criteria for Adverse Events (CTCAE) version 4.03 grade ≥ 3 adverse event related to blinatumomab, excluding specific CTCAE grade ≥ 3 adverse events considered consistent with the current known safety profile of blinatumomab, CTCAE grade ≥ 3 fever or infection, and laboratory parameters of CTCAE grade ≥ 3 not considered clinically relevant and/or responding to routine medical management.

Hematological assessments were performed from bone marrow biopsy samples. All hematological assessments of bone marrow were reviewed in a central reference laboratory.

Hematological remissions were defined by the following criteria:

• Complete Remission (CR) is defined as ≤ 5% blasts in the bone marrow, no evidence of disease, and full recovery of peripheral blood counts: platelets > 100,000/µl and absolute neutrophil count (ANC) > 1,000/µl.
• Complete Remission With Partial Hematological Recovery (CRh*) is defined as ≤ 5% blasts in the bone marrow, no evidence of disease, and partial recovery of peripheral blood counts: platelets > 50,000/µl and ANC > 500/µl.

TEAEs are defined as those that start between the start of the first infusion of blinatumomab and 30 days after the end of the last infusion during the treatment period.

The severity of adverse events was assessed by the investigator according to the Common Terminology Criteria for Adverse Events (CTCAE) version 4.0 as follows: Grade 1 - Mild AE; Grade 2 - Moderate AE; Grade 3 - Severe AE; Grade 4 - Life-threatening or disabling AE; Grade 5 - Death.

The investigator used medical judgment to determine if there was a causal relationship (ie, related, unrelated) between an adverse event and blinatumomab.

Hematological assessments were performed from bone marrow biopsy samples. All hematological assessments of bone marrow were reviewed in a central reference laboratory.

Hematological remissions were defined by the following criteria:

• Complete Remission (CR) is defined as ≤ 5% blasts in the bone marrow, no evidence of disease, and full recovery of peripheral blood counts: platelets > 100,000/µl and absolute neutrophil count (ANC) > 1,000/µl.
• Complete Remission With Partial Hematological Recovery (CRh*) is defined as ≤ 5% blasts in the bone marrow, no evidence of disease, and partial recovery of peripheral blood counts: platelets > 50,000/µl and ANC > 500/µl

M1 remission for pediatric participants was defined as ≤ 5% blasts (M1 bone marrow) in the bone marrow and no evidence of disease.

Duration of response was calculated from the date of bone marrow aspiration when response (CR/CRh*) was detected for the first time during the first 2 cycles of treatment until the earlier of the following events:

• the date of bone marrow aspiration at which hematological relapse or progressive disease (PD) was first detected,
• the date of diagnosis on which the hematological or extra medullary relapse was documented,
• the date of death if patient died due to PD
• the date of end of induction phase if primary reason for treatment termination was hematological or extramedullary relapse.

For a responder who did not report an event and was alive during the study, the end date of duration (censoring) was based on the date of the last available bone marrow aspiration prior to the data cutoff date for the analysis. Participants with response who did not report an event and who died due to reasons other than PD, were censored on the date of death, with death treated as a competing risk.

Relapse-free survival (RFS) was defined for participants who achieved a response (CR/CRh*) during the first 2 cycles of treatment. RFS was calculated from the date of bone marrow aspiration when response was detected for the first time to the date of bone marrow aspiration at which hematological relapse was first detected or the date of diagnosis on which the hematological or extra medullary relapse was documented or the date of death due to any cause, whichever was earlier. Participants who did not experience hematological relapse and did not die were censored on the date of the last available bone marrow aspiration prior to the data cutoff date for the analysis.

Overall survival (OS) was calculated from the start date of blinatumomab infusion in the first treatment cycle. All deaths were counted as events on the date of death.

Participants still alive were censored on the last documented visit date or the date of the last phone contact when the participant was last known to have been alive. For participants who withdrew their informed consent, only information until the date of withdrawal was used in the analysis.

Best response was defined as one of the following:

CR: ≤ 5% blasts in the bone marrow (BM); No evidence of disease; Full recovery of peripheral blood counts: Platelets > 100,000/µl, and absolute neutrophil count (ANC) > 1,000/µl

CRh*: ≤ 5% blasts in BM; No evidence of disease; Partial recovery of peripheral blood counts: Platelets > 50,000/µl, and ANC > 500/µl

CRi: CR with incomplete count recovery without CRh*

Blast free hypoplastic or aplastic BM: ≤ 5 % blasts in BM; No evidence of disease; Insufficient recovery of peripheral blood counts: platelets ≤ 50,000/µl and/or ANC ≤ 500/µl

Partial Remission: BM blasts > 5 to < 25% with at least a 50% reduction from baseline

Hematological Relapse: > 5% blasts in BM or blasts in peripheral blood after documented CR/CRh* during the study

PD: An increase from baseline of ≥ 25% of BM blasts or an absolute increase of ≥ 5,000 cells/µL in the number of circulating leukemia cells.

Participants who were eligible for allogeneic HSCT were those who achieved remission (complete response or complete response with partial recovery of peripheral blood counts) after 2 cycles of blinatumomab treatment, and no further anti-leukemic medication was given before HSCT.

The analysis of 100-day mortality after allogeneic HSCT was assessed for all participants who received an allogeneic HSCT while in any CR following treatment with blinatumomab. 100-day mortality after allogeneic HSCT was calculated relative to the date of allogeneic HSCT.

Participants still alive alive were censored on the last documented visit date or the date of the last phone contact when the patient was last known to have been alive.

The 100-day mortality rate after allogeneic HSCT was defined as the percentage of participants having died up to 100 days after allogeneic HSCT estimated using the estimated time to death in percent calculated by Kaplan-Meier methods.

TEAEs are defined as those that start between the start of the first infusion of blinatumomab and 30 days after the end of the last infusion during the treatment period.

The severity of adverse events was assessed by the investigator according to the Common Terminology Criteria for Adverse Events (CTCAE) version 4.0 as follows: Grade 1 - Mild AE; Grade 2 - Moderate AE; Grade 3 - Severe AE; Grade 4 - Life-threatening or disabling AE; Grade 5 - Death.

The investigator used medical judgment to determine if there was a causal relationship (ie, related, unrelated) between an adverse event and blinatumomab.

The steady-state concentration (Css) of serum blinatumomab was summarized as the average of the observed concentrations collected after 5 half-lives or after 24 hours from the start of continuous IV infusion.

Cycle 1, day 2 values represent steady-state concentration after CIV with the initial dose of blinatumomab (9 µg/day for adults and 5 µg/m²/day for pediatric patients). All other time points were measured after the dose step to 28 µg/day (adults) / 15 µg/m²/day (pediatric participants).

Systemic clearance (CL) was calculated as CL = R0/Css, where R0 is the infusion rate (µg/hour or µg/m²/hour).

Antibodies to blinatumomab were detected using an electrochemiluminescence (ECL)-based assay.

The activation of immune effector cells was monitored by the measurement of peripheral blood cytokine levels including interleukin (IL)-2, IL-6, IL-10, tumor necrosis factor (TNF)-α and interferon gamma (IFN-γ) using multiplex cytometric bead assays. The lower limit of quantification (LLOQ) was 125 pg/mL and the limit of detection (LOD) was 20 pg/mL.

For calculations of mean cytokine concentrations at every time point across all participants, samples with concentrations below LLOQ were included in the calculation as ½ LLOQ (= 62.5 pg/mL); samples with values below LOD were included as ½ LOD (= 10 pg/mL).

The activation of immune effector cells was monitored by the measurement of peripheral blood cytokine levels including interleukin (IL)-2, IL-6, IL-10, tumor necrosis factor (TNF)-α and interferon gamma (IFN-γ) using multiplex cytometric bead assays. The lower limit of quantification (LLOQ) was 125 pg/mL and the limit of detection (LOD) was 20 pg/mL.

For calculations of mean cytokine concentrations at every time point across all participants, samples with concentrations below LLOQ were included in the calculation as ½ LLOQ (= 62.5 pg/mL); samples with values below LOD were included as ½ LOD (= 10 pg/mL).

The activation of immune effector cells was monitored by the measurement of peripheral blood cytokine levels including interleukin (IL)-2, IL-6, IL-10, tumor necrosis factor (TNF)-α and interferon gamma (IFN-γ) using multiplex cytometric bead assays. The lower limit of quantification (LLOQ) was 125 pg/mL and the limit of detection (LOD) was 20 pg/mL.

For calculations of mean cytokine concentrations at every time point across all participants, samples with concentrations below LLOQ were included in the calculation as ½ LLOQ (= 62.5 pg/mL); samples with values below LOD were included as ½ LOD (= 10 pg/mL).

The activation of immune effector cells was monitored by the measurement of peripheral blood cytokine levels including interleukin (IL)-2, IL-6, IL-10, tumor necrosis factor (TNF)-α and interferon gamma (IFN-γ) using multiplex cytometric bead assays. The lower limit of quantification (LLOQ) was 125 pg/mL and the limit of detection (LOD) was 20 pg/mL.

For calculations of mean cytokine concentrations at every time point across all participants, samples with concentrations below LLOQ were included in the calculation as ½ LLOQ (= 62.5 pg/mL); samples with values below LOD were included as ½ LOD (= 10 pg/mL).

The activation of immune effector cells was monitored by the measurement of peripheral blood cytokine levels including interleukin (IL)-2, IL-6, IL-10, tumor necrosis factor (TNF)-α and interferon gamma (IFN-γ) using multiplex cytometric bead assays. The lower limit of quantification (LLOQ) was 125 pg/mL and the limit of detection (LOD) was 20 pg/mL.

For calculations of mean cytokine concentrations at every time point across all participants, samples with concentrations below LLOQ were included in the calculation as ½ LLOQ (= 62.5 pg/mL); samples with values below LOD were included as ½ LOD (= 10 pg/mL).

Hematological assessments were performed from bone marrow biopsy samples. All hematological assessments of bone marrow were reviewed in a central reference laboratory.

Hematological remissions were defined by the following criteria:

• Complete Remission (CR) is defined as ≤ 5% blasts in the bone marrow, no evidence of disease, and full recovery of peripheral blood counts: platelets > 100,000/µl and absolute neutrophil count (ANC) > 1,000/µl.
• Complete Remission With Partial Hematological Recovery (CRh*) is defined as ≤ 5% blasts in the bone marrow, no evidence of disease, and partial recovery of peripheral blood counts: platelets > 50,000/µl and ANC > 500/µl.

M1 remission for pediatric participants was defined as ≤ 5% blasts (M1 bone marrow) in the bone marrow and no evidence of disease.