Real-World Efficacy and Safety of Gemtuzumab Ozogamycin (GO) and 3 + 7 regimen in fit newly diagnosed Acute Myeloid Leukemia (AML) patients. A Retrospective multicenter study of “Rete Ematologica Pugliese” (REP)

Abstract

Gemtuzumab Ozogamicin, a monoclonal antibody targeting CD33, linked to calicheamicin, is approved in combination with “3 + 7″ for the treatment of patients with de novo CD33 positive AML. The aim of study was to evaluate the outcome of patients receiving 3 + 7 plus GO as front-line therapy outside clinical trials. Between March 2020 and February 2023, 34 consecutive fit CD33+ AML patients, median age 54.5 years (range, 25–75) were treated. This study confirms the efficacy and toxicity data reported in clinical trials, highlighting the feasibility of GO based chemotherapy also in patients older than 60 years and as a bridge to allo-HSCT.

1. Introduction

Acute myeloid leukemia (AML) is a myeloid neoplasm characterized by the clonal expansion of primitive hematopoietic stem cells, with a block in differentiation, leading to ineffective normal haematopoiesis, resulting in rapid bone marrow failure [1]. AML occurs at any age, it is the most common type of acute leukemia in adults occurring mainly in the elderly, with a median age at diagnosis of 68 years [2]. The standard of care for AML has remained largely stagnant since the 1970s, with the ‘3 + 7 ’regimen with daunorubicin and cytarabine (Ara-C) remaining the most common induction therapy for fit patients [3]. Gemtuzumab ozogamicin (GO) is an antibody-drug conjugate (ADC) composed of the CD33-directed monoclonal antibody Ig G4 that is covalently linked to the cytotoxic agent N-acetyl gamma calicheamicin which binds specifically to CD33-expressing leukemia cells, where the linker is hydrolyzed and then releases calicheamicin, which enters the nucleus and binds to DNA to break the double helix chain, ultimately leading to cell death. GO spares the normal precursors, so allowing for restoration of normal hematopoiesis [4]. Mylotarg originally received accelerated FDA approval in May 2000 as a stand-alone treatment for older patients with CD33-positive AML who had experienced a relapse. Mylotarg was voluntarily withdrawn from the market after subsequent confirmatory trials failed to verify clinical benefit and demonstrated safety concerns. In 2017 GO was reapproved in combination with standard ‘3 + 7′ regimen for newly diagnosed CD33-positive AML after the French ALFA0701 trial results randomizing 280 newly diagnosed patients aged 50–70 years (median age 62 years) to receive ‘3 + 7’ with or without GO with fractionated doses (3 mg/m2 on days 1, 4, and 7). The study showed improved event-free survival (EFS) defined per protocol as failure to achieve CR or CRp in induction (17.3 months vs 9.5 months; p < 0.001) although this benefit was limited mostly to patients with favorable or intermediate cytogenetics risk. To date there are scant data on the efficacy and safety of GO plus 3 + 7 in daily clinical practice. The study aims to analyze the clinical outcome of AML patients treated with the 3 + 7 regimen and GO in a real life of Rete Ematologica Pugliese retrospective experience.

2. Materials and methods

This is a multicentre, retrospective, real life analysis including 34 adult patients (age ≥18 years) with a diagnosis of de novo consecutive CD 33 positive non promyelocytic AML treated at 7 Italian haematology centres of “Rete Ematologica Pugliese” (REP) between March 2020 and February 2023. The diagnosis was established according to 2016 and 2022 World Health Organization (WHO) guidelines [6,7]. All patients were classified according to the 2017 European LeukemiaNet (ELN) risk stratification [8]. Patient's fitness was assessed according to Ferrara criteria [9]. Patients received GO at 3 mg/m2 / on days 1, 4, and 7, outside clinical trials in combination with 3 + 7 induction chemotherapy, as per standard schedule (intravenous daunorubicin at 60 mg/m2 on days 1–3 and intravenous cytarabine at 200 mg/m2 on Days 1–7). GO was given at the same dosage only on day 1 during consolidation. All patients received diphenhydramine and acetaminophen as premedication and ursodeoxycholic acid as prophylaxis of Veno-Occlusive Disease (VOD). Antibiotic, antiviral, and antifungal prophylaxis was performed according to internal guidelines of individual institution. Primary endpoint was: rate of complete remission (CR) + CR with incomplete hematological recovery (CRi). Secondary endpoints were: Overall Survival (OS) and Event Free Survival (EFS). Response to treatment was defined according to ELN criteria [8]: (a) complete remission (CR), defined as bone marrow blasts <5 %; absence of circulating blasts and blasts with Auer rods; absence of extramedullary disease; ANC ≥ 1.0 × 10⁹/L (1000/mL) and platelet count ≥100 × 10⁹/L (100,000/mL); (b) CR with incomplete hematologic recovery (CRi): all CR criteria except for residual neutropenia (<1.0 × 10⁹/L [1000/mL]) or thrombocytopenia ≤100 × 10⁹/L [100,000/mL]); (c) partial remission (PR): all hematologic criteria of CR; decrease of bone marrow blast percentage to 5 % to 25 %; and decrease of pretreatment bone marrow blast percentage by at least 50 %; (d) progressive disease (PD) defined as >50 % increase in marrow blasts over baseline or persistent marrow blast percentage of >70 % over at least 3 months, without at least a 100 % improvement in ANC to an absolute level (>0.5 × 10⁹/L [500/mL], and/or platelet count to >50 × 10⁹/L [50,000/mL] non transfused); >50 % increase in peripheral blasts and appearance of extramedullary disease; (e) primary refractory defined as failure to attain CR following exposure to at least 2 courses of intensive induction therapy. Patients with stable or progressive disease were defined as non-responders. Minimal residual disease (MRD) was monitored by polymerase chain reaction (PCR) (RTqPCR) for patients with a molecular marker (NPM1 mutation or CBF rearrangements) or by multiparametric flow cytometry (MFC) in those lacking a molecular marker after the first consolidation cycle. A p-value < 0.1 % was considered MRD negative for flow cytometry and < 1000 copie /10 ⁵ ABL for real time quantitative PCR. MRD monitoring was performed on BM samples according to the 2021 ELN MRD Working Party criteria [10]. The safety profile was assessed by adverse events, medical histories, physical examinations, concurrent medications, and central laboratory assessments. Toxicities were graded according to National Cancer Institute Common Toxicity Criteria, version 4.3.

Ethics statement. Patients' records were retrospectively collected for their clinical and laboratory characteristics, treatment regimens and outcome in an anonymous database. Written informed consent was obtained from all living patients. For deceased patients, the treatment of personal data was compliant with the provisions of the GDPR n.679/2016. The study was conducted in accordance with the Declaration of Helsinki and received ethical approval (prot. 291) from the Ethics Committee of the ASL Lecce, Via Miglietta, n. 5, 73,100 Lecce, Italy.

2.1. Statistical analysis

Survival was considered from the date of diagnosis to the date of death or the last follow-up; EFS was measured from the date of initiation of treatment to the date of primary refractory disease, or relapse from CR, or CRi, or death from any cause. CR duration was considered from the date of CR achievement to the date of relapse or the last follow-up. Survival, EFS and CR duration distributions were estimated using the Kaplan–Meier method and were compared using the log-rank test. All tests were 2-sided, accepting p < 0.05 as indicating a statistically significant difference and confidence intervals were calculated at 95 % level. Multivariate analysis was performed using a Cox model after the proportional hazard assumption was checked. Statistical analyses were performed using SAS version 9.3 (SAS Institute, Cary, North Carolina, USA).

3. Results

In our study, a total of 34 newly consecutive CD33 positive AML patients (M/F, 17/17), were treated with GO in combination with standard 3 + 7 regimen. median age was 54.5 years (range, 25–75) with 32 %. of them older than 60 years. The characteristics of patients at the onset are summarized in Table 1. Ten patients (29.4 %) had favorable risk, 14 patients (41.2 %) intermediate risk and 10 patients (29.4 %) had high risk. Of note, these ten high-risk patients were treated with GO, while awaiting cytogenetic results. Ten patients (29.4 %) had NPM1 mutation, 2 patients (5.8 %), had inv (16), and 2 patients had t (8;21) (5.8 %), no patient had FLT3-ITD or -TKD mutation. Overall, CR+ CRi rate was 79.4 % (n = 27) after induction therapy, including 23.5 % of CRi (n = 8 (Table 2). After one (n = 12) or two (n = 14) consolidation courses,35 % of evaluated (n = 27) patients resulted MRD negative. Seven of 12 (78 %) MRD negative patients had NPM1 mutation. Overall, 16 patients (47 %) underwent to alloHSCT: 7 transplants (44 %) from an aploidentical donor; 6 (37 %) from a matched unrelated donor, and 3 (18 %) from an identical sibling donor and all but one were MRD positive before transplant. At transplant underwent 70 % of patients with high-risK, 36 % an Intermediate risk and 30 % with low risk. After a median follow-up of 13 mos, median OS was not reached, while 1-year OS was 79.4 % (Fig 1), with a trend of better survival for NPM1 mutated patients (p = 0.08) (Fig 2). No statistically significant difference was observed in patients older than 60 years of age compared with those younger (P = 0,32). Interestingly, there was no statistically significant differences between transplanted and non-transplanted patients (p = 0.4) (Fig 3). A univariate analysis of risk factors associated with OS identified MRD negativity (p = 0.01), NPM1 + mutation status (p = 0.03), as significant predictors of OS. In multivariate analysis, only MRD negativity resulted predictive of a better OS [hazard ratio (HR) = 2, 95 % CI: 0.99–4.30, p 0.05]. Notably, at last follow up 27 patients (79,4 %) were alive and in CR. Refractory/relapse rate was 26.4 % (9/34), with a median EFS not reached (Fig. 4) and no statistically significant difference observed according by risk group (P = 0,3141). Of note, in 3 patients (8.8 %) the administration of GO was suspended after induction in 2 patients and in one after the first consolidation, due to severe extra-hematological toxicity, in particular by GRAM negative sepsis (2 sepsis caused by Escherichia coli and 1 by Klebsiella Pneumoniae). Indeed, the most common grade 3–4 non-hematologic Adverse Events were sepsis (70 %) and COVID-19 Pneumonia (25 %). The most observed adverse events are reported in Table 3. There were 2 induction deaths (one cerebral hemorrhage and one Pseudomonas A. sepsis), additional 2 patients died afterwards by infections (COVID-19 pneumonia and Pseudomonas A. sepsis) and 3 patients due to recurrence of disease. Any grade hematologic and non-hematologic toxicity was 73.5 % and 76.5 % respectively. During induction phase, median time to platelet recovery to 50 × 10⁹/L and 100 10⁹/L was 30 days (range 22–82) and 35 days (range 30–99) respectively. In allo-transplanted patients two cases of grade 2 VOD were observed (5.8 %). Grade 3–4 hematological toxicity was as expected.

Table 1.

Patients’characteristics.

Characteristics	N ( %)
Median age, years (range) Age ≥ 60 years	54.5 (25–75) 11 (32)
Sex Male Female	17 (50) 17 (50)
ELN 2017 risk stratification, n ( %) Low Intermediate High	10 (29.4) 14 (41.2) 10 (29.4)
AML type, n ( %) NPM1-mutated FLT3-mutated t (8;21) Inv-16	10 (29.4) 0 (0) 2 (5.8) 2 (5.8)
Bone marrow blast % Median (range)	67.5 (25–95)
White blood cells (/µL) Median (range)	5.63 (1–229)
Hemoglobin (g/dL) Median (range)	8.3 (4–12.0)
Platelets, (/µL) Median (range)	21.5 (18–180.0)
Number of consolidation courses one two	12 (35) 14 (41)
Allogenic stem cell transplant	16 (47)

Table 2.

Results.

Results	N ( %)
CR+CRi	27 (79.4)
CR	19 (56)
CRi	8 (23.4)
PR	4 (11.8)
NV	2(5.8)
NR	1 (3)

Abbreviations: CR, Complete Remission; CRi, Complete Remission with incomplete hematologic recovery; PR, Partial remission; NV: non valuable; NR, No Response.

Fig. 1.

Overall survival (OS) of the whole population (34 cases) from the diagnosis. Median OS was not reached.

Fig. 2.

Overall survival of patients with NPM1 mutation versus patients with NPM1 wild type . There is a trend for better survival NPM1 mutated patients (p = 0.08).

Fig. 3.

Overall survival (OS) in transplanted patients versus no trasplanted patients. Median OS in allotransplanted was not reached, but there is no statically significative difference with no allotransplanted (p = 0.49).

Fig. 4.

Event Free Survival (EFS) of the whole population (34 cases).Median OS was not reached.

Table 3.

Safety.

Adverse Events	N ( %)
Any grade hematological event	25 (73.5)
Any grade non hematological event	26 (76.5)
Sepsis	24 (70)
Covid 19 infection	8 (23.5)
VOD (grade 2)	3 (5.8)
Induction death	3 (5.8)

4. Discussion

Gemtuzumab ozogamicin plus standard induction chemotherapy “3 + 7″ has been reported to improve outcomes of newly diagnosed intermediate cytogenetic risk AML, showing a significant improvement in response rates and lower risk of relapse [7,8,[10], [11], [12], [13], [14]]. In line with literature, our real life study showed the efficacy of combination GO plus “3 + 7″ in a population mostly represented by intermediate AML risk (41.2 %) with a trend in survival benefit in NPM1 patients. As reported in the literature, in our study a higher MRD negativity was observed in AML patients with NMP1 mutation [15]. Notably, in multivariate analysis only MRD negativity remained predictive of a better OS, representing the crucial decision-making element for a risk adapted driven strategy, above all in intermediate risk AML, in particular regarding the opportunity to perform a transplant. In order to answer too this clinical unmet need, the Italian multicenter trial named AML1819 (NCT041685029) was designed. This trial recruits young patients (≤ 60 years of age) belonging to the ELN2017 favorable-and intermediate-risk categories, with the exception of cases FLT3 positive and relies on the addition of GO to intensive chemotherapy. Interestingly, in our real study there was no statistically significant differences between transplanted and non-transplanted patients, considering that allo-HSCT anyway represents the only therapeutic option with curative potential in high-risk AML and should be pursued as soon as possible [16,17]. In our real life experience, GO in combination with “3 + 7″ was given outside the official indications [5], since 10 patients (29.4 %) were high-risk AML, pending the results of the cytogenetics. Overall, in 8 (80 %) of them allotransplant was performed and the combination of GO + “3 + 7″, followed by consolidation as a bridge to transplant, proved to be effective and safe in line with literature [17]. Noteworthy, in allotransplanted two cases of grade 2 VOD were observed, one of two cases of VOD occurred due to an infectious complication. Both 2 cases of VOD were promptly diagnosed, treated and resolved. In our study population, the addition of GO to “3 + 7” was efficacious and well tolerated also in patients older than 60 years, representing 32 % of whole group. Nevertheless, the majority of patients experienced severe myelosuppression with similar rates to those reported in previous studies [18,19]. Infectious complications and their management represent another important issue, as they could lead to the delay or definitive suspension of treatment and an increased risk of relapse, as noted also in our group [19,20].

In conclusion our findings, though limited by the retrospective nature of the study and the small sample size, confirm in a real life setting the efficacy and toxicity data reported in clinical trials of combination of GO + “3 + 7″. Furthemore, our study suggests the feasibility of GO-based treatment given also in patients older than 60 years and as a bridge to allo-HSCT. Moreover, fitness assessment, prophylaxis, prompt management of infectious toxicities and VOD are crucial in the management of this advantageous strategy for the treatment of AML. However, this data needs to be confirmed on a larger series of patients and with a longer follow-up.

Ethics statement

Patients' records were retrospectively collected for their clinical and laboratory characteristics, treatment regimens and outcome in an anonymous database. The study was conducted in accordance with the Declaration of Helsinki and received ethical approval (prot. 291) from the Ethics Committee of the ASL Lecce, Via Miglietta, n. 5, 73,100 Lecce, Italy.

Written consent

Written informed consent was obtained from all living patients. For deceased patients, the treatment of personal data was compliant with the provisions of the GDPR n.679/2016.

CRediT authorship contribution statement

M. Dargenio: Conceptualization, Writing – original draft. C. Buquicchio: Writing – original draft. D. Pastore: Writing – original draft. L. Aprile: Writing – original draft. L. Ciuffreda: Writing – original draft. G. Greco: Writing – original draft. M. Delia: Writing – original draft. V. Federico: Writing – original draft. MP. Fina: Writing – original draft. D. Seripa: Writing – original draft. R. Matera: Writing – original draft. G. Tarantini: Writing – original draft. A. Maggi: Writing – original draft. L. Melillo: Writing – original draft. V. Pavone: Writing – original draft. P. Musto: Writing – original draft. G. Specchia: Supervision, Visualization. N. Di Renzo: Conceptualization, Writing – original draft.

Declaration of competing interest

None declared.