BESPONSA Powder for concentrate for solution for infusion Ref.[8985] Active ingredients: Inotuzumab ozogamicin

Pharmacotherapeutic group: Antineoplastic agents, other Antineoplastic agent, monoclonal antibodies
ATC code: L01XC26

Mechanism of action

Inotuzumab ozogamicin is an ADC composed of a CD22-directed monoclonal antibody that is covalently linked to N-acetyl-gamma-calicheamicin dimethylhydrazide. Inotuzumab is a humanised immunoglobulin class G subtype 4 (IgG4) antibody that specifically recognises human CD22. The small molecule, N-acetyl-gamma-calicheamicin, is a cytotoxic product.

N-acetyl-gamma-calicheamicin is covalently attached to the antibody via an acid-cleavable linker. Nonclinical data suggest that the anticancer activity of BESPONSA is due to the binding of the ADC to CD22-expressing tumour cells, followed by internalisation of the ADC-CD22 complex, and the intracellular release of N-acetyl-gamma-calicheamicin dimethylhydrazide via hydrolytic cleavage of the linker. Activation of N-acetyl-gamma-calicheamicin dimethylhydrazide induces double-stranded DNA breaks, subsequently inducing cell cycle arrest and apoptotic cell death.

Clinical efficacy and safety

Patients with relapsed or refractory ALL who have received 1 or 2 prior treatment regimens for ALL – Study 1

The safety and efficacy of BESPONSA in patients with relapsed or refractory CD22-positive ALL were evaluated in an open-label, international, multicentre, Phase 3 study (Study 1) in which patients were randomised to receive BESPONSA (N=164 [164 received treatment) or Investigator’s choice of chemotherapy (N=162 [143 received treatment]), specifically fludarabine plus cytarabine plus granulocyte colony-stimulating factor (FLAG) (N=102 [93 received treatment]), mitoxantrone/cytarabine (MXN/Ara-C) (N=38 [33 received treatment]), or high dose cytarabine (HIDAC) (N=22 [17 received treatment]).

Eligible patients were ≥18 years of age with Philadelphia chromosome negative (Ph-) or Ph+ relapsed or refractory B-cell CD22-positive precursor ALL.

CD22 expression was assessed using flow cytometry based on bone marrow aspirate. In patients with an inadequate bone marrow aspirate sample, a peripheral blood sample was tested. Alternatively, CD22 expression was assessed using immunohistochemistry in patients with an inadequate bone marrow aspirate and insufficient circulating blasts.

In the clinical study, the sensitivity of some local tests was lower than the central laboratory test. Therefore only validated tests with demonstrated high sensitivity should be used.

All patients were required to have ≥5% bone marrow blasts and to have received 1 or 2 prior induction chemotherapy regimens for ALL. Patients with Ph+ B-cell precursor ALL were required to have failed treatment with at least 1 second or third generation TKI and standard chemotherapy. Table 1 (see section 4.2) shows the dosing regimen used to treat patients.

The co-primary endpoints were CR/CRi, assessed by a blinded independent endpoint adjudication committee (EAC), and overall survival (OS). The secondary endpoints included MRD negativity, duration of remission (DoR), HSCT rate, and progression-free survival (PFS). The primary analysis of CR/CRi and MRD negativity was conducted in the initial 218 randomised patients and the analysis of OS, PFS, DoR, and HSCT rate was conducted in all 326 randomised patients.

Among all 326 randomised patients (ITT population), 215 (66%) patients had received 1 prior treatment regimen and 108 (33%) patients had received 2 prior treatment regimens for ALL. The median age was 47 years (range: 18-79 years), 206 (63%) patients had a duration of first remission <12 months, and 55 (17%) patients had undergone an HSCT prior to receiving BESPONSA or Investigator’s choice of chemotherapy. The 2 treatment groups were generally balanced with respect to the baseline demographics and disease characteristics. A total of 276 (85%) patients had Ph- ALL. Of the 49 (15%) patients with Ph+ ALL, 4 patients did not receive a prior TKI, 28 patients received 1 prior TKI, and 17 patients received 2 prior TKIs. Dasatinib was the most commonly received TKI (42 patients) followed by imatinib (24 patients).

Baseline characteristics were similar in the initial 218 patients randomised.

Of the 326 patients (ITT population), 253 patients had samples that were evaluable for CD22 testing by both local and central laboratory. By central and local laboratory tests, 231/253 (91.3%) patients and 130/253 (51.4%) patients, respectively, had ≥70% CD22-positive leukaemic blasts at baseline.

Table 6 shows the efficacy results from this study.

Table 6. Study 1: Efficacy results in patients ≥18 years of age with relapsed or refractory B-cell precursor ALL who received 1 or 2 prior treatment regimens for ALL:

Abbreviations: ALL=acute lymphoblastic leukaemia; ANC=absolute neutrophil counts; Ara-C=cytarabine; CI=confidence interval; CR=complete remission; CRi=complete remission with incomplete haematological recovery; DoR=duration of remission; EAC=Endpoint Adjudication Committee; FLAG=fludarabine + cytarabine + granulocyte colony-stimulating factor; HIDAC=high dose cytarabine; HSCT=haematopoietic stem cell transplant; ITT=intent-to-treat; MRD=minimal residual disease; MXN=mitoxantrone; N/n=number of patients; OS=overall survival; PFS=progression-free survival.

^a CR, per EAC, was defined as <5% blasts in the bone marrow and the absence of peripheral blood leukaemic blasts, full recovery of peripheral blood counts (platelets ≥100 × 10⁹/L and ANC ≥1 × 10⁹/L) and resolution of any extramedullary disease.
^b CRi, per EAC, was defined as <5% blasts in the bone marrow and the absence of peripheral blood leukaemic blasts, partial recovery of peripheral blood counts (platelets <100 × 10⁹/L and/or ANC <1 × 10⁹/L) and resolution of any extramedullary disease.
^c MRD negativity was defined by flow cytometry as leukaemic cells comprising <1 × 10^-4 (<0.01%) of bone marrow nucleated cells.
^d Rate was defined as number of patients who achieved MRD negativity divided by the total number of patients who achieved CR/CRi per EAC.
^e PFS was defined as the time from date of randomisation to earliest date of the following events: death, progressive disease (including objective progression, relapse from CR/CRi, treatment discontinuation due to global deterioration of health status), and start of new induction therapy or post-therapy HSCT without achieving CR/CRi.
^f In the standard definition of PFS, defined as the time from date of randomisation to earliest date of the following events: death, progressive disease (including objective progression and relapse from CR/CRi), the HR was 0.568 (2-sided p-value=0.0002) and median PFS was 5.6 months and 3.7 months in the BESPONSA and Investigator’s choice of chemotherapy arm, respectively.
^g Duration of remission was defined as the time since first response of CR a or CRi b per Investigator’s assessment to the date of a PFS event or censoring date if no PFS event was documented. Analysis was based on the ITT population with patients without remission being given a duration of zero and considered an event.

Among the initial 218 randomised patients, 64/88 (73%) and 21/88 (24%) of responding patients per EAC achieved a CR/CRi in Cycles 1 and 2, respectively, in the BESPONSA arm. No additional patients achieved CR/CRi after Cycle 3 in the BESPONSA arm.

CR/CRi and MRD negativity findings in the initial 218 randomised patients were consistent with those seen in all 326 randomised patients.

Among all 326 randomised patients, the survival probability at 24 months was 22.8% in the BESPONSA arm and 10% in the Investigator’s choice of chemotherapy arm.

A total of 79/164 (48.2%) patients in the BESPONSA arm and 36/162 (22.2%) patients in the Investigator’s choice of chemotherapy arm had a follow-up HSCT. This included 70 and 18 patients in the BESPONSA and Investigator’s choice of chemotherapy arm, respectively, who proceeded directly to HSCT. In those patients who proceeded directly to HSCT, there was a median gap of 4.8 weeks (range: 1-19 weeks) between the last dose of inotuzumab ozogamicin and HSCT. The OS improvement for BESPONSA versus Investigator’s choice of chemotherapy arm was seen in patients who underwent HSCT. Although there was a higher frequency of early deaths post-HSCT (at Day 100) in the BESPONSA arm, there was evidence of a late survival benefit for BESPONSA. In patients who underwent a follow-up HSCT, the median OS was 11.9 months (95% CI: 9.2, 20.6) for BESPONSA versus 19.8 months (95% CI: 14.6, 26.7) for Investigator’s choice of chemotherapy. At month 24, the survival probability was 38.0% (95% CI: 27.4, 48.5) versus 35.5% (95% CI: 20.1, 51.3) for BESPONSA and Investigator’s choice of chemotherapy, respectively. Furthermore, at month 24, the survival probability was 38.0% (95% CI: 27.4, 48.5) for patients who underwent a follow-up HSCT compared to 8.0% (95% CI: 3.3, 15.3) for patients who did not undergo a follow-up HSCT in the BESPONSA arm.

BESPONSA improved OS versus Investigator’s choice of chemotherapy for all stratification factors including duration of first remission ≥12 months, Salvage 1 status, and age at randomisation <55 years. There was also a trend for better OS with BESPONSA for patients with other prognostic factors (Ph-, no prior HSCT, ≥90% leukaemic blasts CD22-positive at baseline, no baseline peripheral blasts, and baseline haemoglobin ≥10 g/dL, based on exploratory analyses). Patients with mixed-lineage leukaemia (MLL) gene rearrangements, including t (4;11), that generally have lower CD22 expression prior to treatment, had a worse OS outcome following treatment with BESPONSA or Investigator’s choice of chemotherapy.

For patient-reported outcomes, most functioning and symptom scores were in favour of BESPONSA compared to Investigator’s choice of chemotherapy. Patient-reported outcomes measured using the European Organisation for Research and Treatment of Cancer Quality of Life Core Questionnaire (EORTC QLQ-C30), were significantly better for BESPONSA by estimated mean postbaseline scores (BESPONSA and Investigator’s choice of chemotherapy, respectively) for role functioning (64.7 versus 53.4, improvement grade small), physical functioning (75.0 versus 68.1, improvement grade small), social functioning (68.1 versus 59.8, improvement grade medium), and appetite loss (17.6 versus 26.3, improvement grade small) compared to Investigator’s choice of chemotherapy. There was a trend in favour of BESPONSA, improvement grade small, for estimated mean postbaseline scores (BESPONSA and Investigator’s choice, respectively) in global health status/Quality of Life (QoL) (62.1 versus 57.8), cognitive functioning (85.3 versus 82.5), dyspnoea (14.7 versus 19.4), diarrhoea (5.9 versus 8.9), fatigue (35.0 versus 39.4). There was a trend in favour of BESPONSA for estimated mean postbaseline scores from the EuroQoL 5 Dimension (EQ-5D) questionnaire, (BESPONSA and Investigator’s choice of chemotherapy, respectively) for the EQ-5D index (0.80 versus 0.76, minimally important difference for cancer = 0.06).

Patients with relapsed or refractory ALL who have received 2 or more prior treatment regimens for ALL – Study 2

The safety and efficacy of BESPONSA were evaluated in a single-arm, open-label, multicentre Phase ½ study (Study 2). Eligible patients were ≥ 18 years of age with relapsed or refractory B-cell precursor ALL.

Of 93 screened patients, 72 patients were assigned to study drug and treated with BESPONSA. The median age was 45 years (range 20-79); 76.4% were Salvage status ≥ 2; 31.9% had received a prior HSCT and 22.2% were Ph+. The most common reasons for treatment discontinuation were: disease progression/relapse (30 [41.7%)], resistant disease (4 [5.6%]); HSCT (18 [25.0%]), and adverse events (13 [18.1%]).

In the Phase 1 portion of the study, 37 patients received BESPONSA at a total dose of 1.2 mg/m² (n=3), 1.6 mg/m² (n=12), or 1.8 mg/m 2 (n=22). The recommended BESPONSA dose was determined to be 1.8 mg/m²/cycle administered at a dose of 0.8 mg/m 2 on Day 1 and 0.5 mg/m² on Days 8 and 15 of a 28-day cycle with a dose reduction upon achieving CR/CRi.

In the Phase 2 portion of the study, patients had to have received at least 2 prior treatment regimens for ALL and patients with Ph+ B-cell ALL had to have failed treatment with at least 1 TKI. Of the 9 patients with Ph+ B-cell ALL, 1 patient had received 1 previous TKI and 1 patient had received no prior TKIs.

Table 7 shows the efficacy results from this study.

Table 7. Study 2: Efficacy results in patients ≥18 years of age with relapsed or refractory B-cell precursor ALL who received 2 or more prior treatment regimens for ALL:

Abbreviations: ALL=acute lymphoblastic leukaemia; ANC=absolute neutrophil counts; CI=confidence interval; CR=complete remission; CRi=complete remission with incomplete haematological recovery; DoR=duration of remission; HSCT=haematopoietic stem cell transplant; MRD=minimal residual disease;
N/n=number of patients; OS=overall survival; PFS=progression-free survival.
^a,b,c,d,e,f For definition, see Table 6 (with the exception that CR/CRi was not per EAC for Study 2)

In the Phase 2 portion of the study, 8/35 (22.9%) patients had a follow-up HSCT.

Paediatric population

The European Medicines Agency has deferred the obligation to submit the results of studies with BESPONSA in 1 or more subsets of the paediatric population for the treatment of relapsed or refractory ALL (see section 4.2 for information on paediatric use).