Unveiling the Role of New Molecules in Acute Myeloid Leukemia: Insights into Disease Pathogenesis and Therapeutic Potential

Abstract

This review article explores the current landscape of acute myeloid leukemia treatment, including novel target molecules and recent advancements in cell therapy and immunotherapy focused on T cell activity. Advances in treatment have been promising in recent years, driven by the development of therapies targeting new molecular and genetic therapeutic targets. These findings allowed for the approval of several target therapies by the European and American drug agencies in the last 5 years. However, mortality remains very high, particularly in relapsed or refractory (R/R) patients. In recent years, the development of immunotherapy has expanded this field, leading to the introduction of new drugs and treatments.

1. Introduction

Acute myeloid leukemia (AML) is the most common acute leukemia in adulthood. It accounts for approximately 1% of all cancers worldwide, with higher age-adjusted incidence rates observed in developed regions such as Western Europe and Australasia. In recent years, an increase in the number of cases of AML has been observed, probably due to improved diagnostic techniques and due to the aging of the population [1].

In fact, while in 1990, AML accounted for 18% of all leukemia cases worldwide, in 2017, this percentage increased to 23.1% of all acute leukemia cases [1,2]. The annual incidence rate of AML in Europe is estimated to be approximately three–four cases per 100,000 individuals, which is equivalent to about one case per 25,000 individuals [3]. In the United States, the AML incidence rate is around 4.2 cases per 100,000 people per year and AML is more common in older adults, with a median age at diagnosis of 68 years [1,3].

Since the development of the first anthracycline as a treatment for acute leukemia, daunorubicin (initially discovered as an antibiotic in 1964) [4], and following its widespread use in combination with cytarabine in the 1980s, the standard treatment of AML in children and adults up to the age of 50–60 years has been based on intensive chemotherapy regimens ± allogeneic hematopoietic stem cell transplantation. This discovery improved patient survival from as low as 5% to 20–30% [5]. Recent advancements in understanding the molecular underpinnings of AML have supported the development of novel therapies aimed at the specific genetic mutations and pathways involved. Key signaling pathways and targets of available drugs are illustrated in Figure 1. Due to the rapid development in understanding the genetic heterogeneity of AML and the advances in biological techniques for its characterization, in 2022, two new classifications were published: the update of the World Health Organization (WHO) myeloid classification [5] and the International Consensus Classification (ICC) [6].

2. FLT3 Tyrosine Kinase Inhibitors (ITK)

Mutations in the FLT3 gene occur in about one-third of patients with newly diagnosed (ND) AML. The frequency of internal tandem duplication [ITD] ranges from 10 to 30%, and the frequency of tyrosine kinase domain [TKD] ranges from 2 to 8%; their presence is associated with shorter overall survival (OS) [7] Both FLT3-ITD and TKD mutations lead to constitutive activation and upregulation of the downstream signaling cascades including the RAS, MEK, PI3/AKT, and STAT5 pathways, which promote cellular proliferation, suppress differentiation, and inhibit apoptosis of leukemic cells [8]. FLT3-ITD mutations are associated with leukocytosis, lower response rates, and increased relapse risk, which correlate with shorter event-free survival (EFS) and OS in patients receiving intensive chemotherapy (IC) [9,10].

2.1. Midostaurin

Midostaurin is a first-generation oral multi-kinase tyrosine kinase inhibitor acting against several receptors including FLT3, platelet-derived growth factor receptors, cyclin-dependent kinase 1, src, c-kit, and vascular endothelial growth factor receptor. This molecule was approved by the Food and Drug Administration (FDA) and the European Medicines Agency (EMA) for the treatment of adult patients with ND-AML who are FLT3 mutation-positive (FLT3m, either ITD or TKD) in combination with standard frontline induction and consolidation chemotherapy [11,12].

The approval was based on the multicenter randomized, double-blind, placebo-controlled phase 3 trial RATIFY. It was combined with IC therapy in younger (age < 60) patients with ND-AML and FLT3-ITD and/or TKD mutations [13]. Midostaurin was administered 50 mg orally on D8–D21 every 28 days at induction and consolidation therapy. Complete remission (CR) rates were similar in both groups: midostaurin vs. placebo (CR: 58.9% vs. 53.5%). However, midostaurin improved OS compared to the placebo with a median OS of 74.7 months for the midostaurin arm (range, 31.5 months–not reached) as compared to 25.6 months for the placebo arm (range, 18.6–42.9 months). In addition, a reduced risk of remission failure, relapse, or death was observed in the midostaurin group compared to the placebo. Furthermore, the benefit of midostaurin was observed across all FLT3 mutations. This suggests that midostaurin combined with IC confers deeper remission rates. Also, a phase 2 trial showed that midostaurin can be safely given in combination with IC in older patients (aged between 60 and 70) [14].

Regarding maintenance therapy, the lack of re-randomization prior to maintenance treatment in the RATIFY trial led the FDA to not to include it in the approval. In fact, the results from a post hoc subset analysis of the RATIFY trial [15] showed no difference in the leukemia-free survival (LFS) and OS between the treatment arms during the 12 cycles of maintenance, although it does appear that it may delay the time to relapse [12,15]. The RADIUS trial is a randomized, open-label, phase 2 trial (NCT01883362) that investigated if the addition of midostaurin to the standard of care (SOC) after allogeneic stem cell transplantation could reduce the risk of relapse in patients with FLT3-ITD AML. The study showed the benefits in LFS as being 8.2 months in the midostaurin group and 3.0 months in the placebo group (p = 0.002). The median LFS was 26.7 months in the midostaurin group and 15.5 months in the placebo group (p = 0.01). However, there was no significative difference in the 4-year OS rate (51.4% in the midostaurin group and 44.3% in the placebo group) or in the CR rate (58.9% in the midostaurin group and 53.5% in the placebo group) [16]. This improvement in LFS led the EMA to approve maintenance therapy too.

2.2. Quizartinib

Quizartinib is a second-generation tyrosine kinase inhibitor with a selective inhibition for FLT3 kinase activity, preventing autophosphorylation of the receptor, thereby inhibiting downstream FLT3 receptor signaling and blocking FLT3-ITD-dependent cell proliferation. Recently, the FDA and the EMA approved quizartinib in frontline therapy, combined with standard induction and consolidation and as maintenance monotherapy following consolidation chemotherapy for FLT3-ITD ND-AML. It was evaluated in the QuANTUM-First Study [17], a randomized phase 3 trial of IC combined with quizartinib compared to standard frontline chemotherapy in patients with ND-AML and an FLT3-ITD mutation. Quizartinib at a dose 40 mg daily was added in the experimental arm to standard IC (D8–D21 of induction and D6–D19 of consolidation). Patients in the quizartinib group continued taking the drug for up to 3 years as maintenance therapy. This resulted in a significant OS benefit compared to the placebo (median OS: 31.9 vs. 15.1 months). Patients had similar rates of CR and complete response with incomplete recovery (CRi), but in those patients achieving CR, the minimal residual disease (MRD) negativity rates were higher. In contrast to the study that led to the approval of midostaurin, this study included patients over 60 years of age, although post hoc analyses [17] showed that the survival benefit was limited to patients younger than 60 years (higher risk of early mortality in older patients).

Furthermore, preliminary data from the QUIWI study [18] showed results of 273 patients randomized to the quizartinib arm vs. the placebo arm. The median age was 57 years, and the median follow-up was 17 months. Median EFS was 16.6 months with quizartinib vs. 10.6 months with the placebo (p = 0.062). Regarding OS, 50 out of 180 patients died in the quizartinib arm and 45 out of 93 patients in the placebo group. Median OS was not reached with quizartinib, while it was 15 months with the placebo (p = 0.004). The 2-year OS was 63.5% with quizartinib vs. 47% with the placebo. LFS was not reached with quizartinib, and it was 15.4 months with the placebo (p = 0.050). There was no difference in the CR/CRi rate or MRD between both arms (76.7% vs. 76.4% and 41.5% vs. 41.6%).

The combination of quizartinib, decitabine, and venetoclax was analyzed in phase 1/2 trial NCT03661307 [19,20] among a small group of patients with ND-AML unfit for intensive therapy with excellent CR/CRi rates (100% in ND).

Several recruiting trials are exploring the addition of quizartinib to azacytidine and venetoclax, as the VEN-A-QUI study (NCT0468776) [21]. This is a phase 1–2 trial based on the combination of three drugs: low-dose cytarabine (LDAC) or azacitidine + venetoclax + quizartinib, for patients not fit for IC with ND-AML and an FLT3-ITD mutation or wild-type (WT). The phase 2 included 61 patients (30 LDAC and 31 AZA), with 12 of them FLT3-ITD+. The median age of the LDAC arm was 75.5 years, and for the AZA arm, it was 74 years. Overall, CR + CRi + CRh was observed in 26 patients (43%), partial response (PR) in 8 (13%) patients, morphological leukemia-free state (MLFS) in 7 (11%) patients, and induction death in 10 (16%) patients and (CR + CRh + CRi + MLFS was 54%). There were no differences in CR + CRi + CRh between the arms (LDAC 40% vs. AZA 45%), but induction death was more frequent in LDAC (20%) vs. AZA (13%). Due to substantial myelotoxicity, a protocol amendment reduced VEN to 7 days after achieving a response (CR + CRh + CRi + MLFS). The median follow-up at data cut-off (February 2023) was 14.4 months. The median OS was not reached (NR) without significant differences between LDAC and AZA (11.6 months vs. median NR). Median EFS was similar between LDAC (6.5 months) and AZA (8.0 months). FLT3-ITD+ patients had better OS and EFS than the wild-type (median NR vs. 11.9 months, p = 0.04 and NR vs. 4.3 months, p = 0.09, respectively). The authors conclude that this is a feasible scheme with VEN reduction, but complete data are needed to clarify the potential benefit of the triplet.

The combination of CPX-351 and quizartinib is also being explored in the study NCT04128748, and no data have been posted yet.

Quizartinib has also been evaluated in the relapsed refractory landscape. The phase 3 Quantum-R study [22] randomized patients to receive quizartinib at a dose of 60 mg daily vs. several salvage chemotherapy regimens in patients with FLT3m R/R AML. OS was longer in the quizartinib group (6.2 vs. 4.7 months). CR/CRi rates were higher in the quizartinib arm (48% vs. 27%). Also, more patients in the quizartinib arm went on to allogeneic stem cell transplant (HSCT) (32% vs. 11%) and patients who underwent HSCT had significantly longer OS than those that did not, 12.2 vs. 4.4 months.

2.3. Sorafenib

Sorafenib is a first-generation type 2 multi-kinase FLT3 inhibitor that was evaluated in the randomized, double blind, placebo-controlled phase 2 SORAML trial [23] (NCT00893373), in combination with IC followed by 12 months of maintenance in ND-AML patients. The CR rates were similar between arms, but sorafenib improved EFS (3-year EFS: 40% vs. 22%) and reduced the incidence of relapse (3-year cumulative incidence of relapse: 34% vs. 49%). However, no significant difference in OS was observed. Furthermore, an increased toxicity with the addition of sorafenib was observed.

A phase 2 double-blind, placebo-controlled study (ACTRN12611001112954) evaluated the effect of adding sorafenib to 7 + 3 induction therapy and found no benefit in terms of EFS and OS in patients with FLT3-mutated ND-AML [23].

On the other hand, there is a retrospective study that evaluated the outcomes of 183 patients with FLT3 ITD treated with different IC with or without sorafenib, showing that the combination with sorafenib resulted in higher EFS and OS [24].

A phase 1 study was carried out with sorafenib in post-transplant maintenance with promising results [25]. The 1-year LFS was 85%, and 1-year OS was 95% after HSCT. For patients in first or second complete remission before HSCT, the 1-year LFS was 95% and the 1-year OS was 100%.

The SORAMIN trial [26] included 83 adult patients with FLT3-ITD-mutated AML post-HSCT. This is a phase 2, placebo-controlled study to explore the role of maintenance with sorafenib versus the placebo. Relapse-free survival was longer in the sorafenib arm (NR vs. 30.9 m).

A phase 2 trial was developed for patients with R/R ITD-mutated AML [27] (NCT01254890), combining sorafenib with AZA. The overall response was 46% (27% CR with incomplete count recovery (CRi), 16% CR, and 3% partial response), and the median duration of response was 2.3 months (range, 1–14.3 months). Six patients proceeded to HSCT, including two non-responders.

2.4. Gilteritinib

This drug is a second-generation selective inhibitor of FLT3. It has been approved by the FDA and the EMA as a monotherapy in patients with R/R AML with TKD or ITD mutations, based on the phase 3 ADMIRAL trial [28]. Thirty-four percent of patients treated with gilteritinib attained a CR or CRh vs. 15.3% of patients assigned to salvage therapy (LDAC, azacitidine, mitoxantrone/etoposide/cytarabine or fludarabine/cytarabine/idarubicin, and granulocyte colony-stimulating factor). Patients with FLT3-ITD-mutated AML achieved a CR rate of 20.5% vs. 9.7% when treated with salvage chemotherapy. After a median follow-up of 17.8 months, gilteritinib improved median OS compared to the control arm (9.3 vs. 5.6 months, p-value < 0.001). However, the median EFS was not significantly different (2.8 vs. 0.7 months). Gilteritinib also demonstrated improvement of the OS compared with salvage chemotherapy in the subgroup of patients with co-mutations in NPM1 and DNMT3A (median OS 10.8 vs. 5.0 months).

Promising results have been reported in the phase 1b multicenter, open-label study NCT03625505 with the combination of gilteritinib plus venetoclax [29] in patients with R/R FLT3m AML with a composite CR of 75% (CR 18%); the morphologic leukemia-free state rate was 36%, and it was similar among patients with or without prior FLT3 inhibitor therapy (80% vs. 67%, respectively). The observed OS was 10 months. Also, FLT3 molecular response (<10⁻²) was achieved in 60% of evaluable patients.

Moving to triplet combination, the phase 1/2 trial (NCT04140487) evaluated the use of venetoclax plus a hypomethylating agent and gilteritinib [30] with the R/R cohort showing a CR/CRh rate of 37% and 43%, respectively.

There are several studies with gilteritinib in the frontline setting, focusing on the combination of it with other molecules.

A phase 1 trial [31] combined gilteritinib with standard 7 + 3 IC followed by high-dose cytarabine maintenance and 2 years of gilteritinib maintenance. Composite CR (CRc = CR + CRi + CR with incomplete platelet recovery) was 89% for patients with FLT-3m AML with a median OS of 45 months.

The phase 3 trial LACEWING trial, aiming to compare gilteritinib in combination with azacitidine vs. azacitidine monotherapy [32] in ND-AML for non-fit patients, could not demonstrate improvement in the OS for the experimental arm over the control arm (combination arm 9.82 vs. 8.87 for azacitidine), and, as a result, the trial was concluded. Of note, higher response rates were observed in the experimental arm (58.1% vs. 26.5%; p < 0.001).

The NCT03836209 [33] is a trial where gilteritinib in combination with IC is being compared with midostaurin plus IC in ND-AML. Given the interest and potential of combinations without chemotherapy, the triplet of venetoclax plus hypomethylating therapy and gilteritinib was also studied in a phase 1/2 NCT04140487 trial [30] in ND-AML patients, where the CR/CRi rate was 96% (CR, 90% and CRi, 6%). With a median follow-up of 19.3 months, the median relapse-free survival (RFS) and OS were not reached at 18 months. The rates of RFS and OS were 71% and 72%. Currently, a phase 1/2 trial (VICEROY study) is evaluating this triplet, with the goal of further optimizing this regimen in patients with ND FLT3 AML (NCT05520567) [19,34]. Also, the phase 2 MyeloMATCH trial (NCT06317649) is currently on active recruitment until the end of 2025 and will compare the treatment of azacitidine and venetoclax to the combination treatment of azacitidine, venetoclax, and gilteritinib in older and unfit patients with ND-AML and FLT3 mutations (FLT3-ITD or D835).

The MORPHO trial [35] evaluated post-HSCT gilteritinib, where 356 patients were randomized to gilteritinib vs. the placebo. No difference was observed between both arms in the 2-year RFS. However, there was a benefit for patients with detectable MRD, who were treated with gilteritinib, having a significantly decreased risk of relapse (p = 0.0065) compared to those who received placebo.

3. IDH Inhibitors

Currently, we know that isocitrate dehydrogenase (IDH) mutations occur in 15–20% of patients with AML [36]. This is why these mutations have been considered a therapeutic target for many years, with the consequent development of several drugs.

3.1. Ivosidenib (IDH1 Inhibitor)

Ivosidenib was approved by the FDA and the EMA in the frontline setting for unfit patients, combined with azacitidine. This authorization is due to the phase 3 AGILE trial [33] that evaluated the addition of ivosidenib to azacitidine versus azacitidine monotherapy in patients with IDH1-mutated AML who are older than 75 or have comorbidities. The median OS was higher in patients who received ivosidenib (24 months vs. 7.9 months). The combination has not been directly compared to the actual standard of care VEN + hypomethylating agent [37].

It was also approved by the FDA in monotherapy as frontline treatment (and also in relapsed and refractory (R/R)) AML. The approval is based on a multicenter clinical trial (study AG120-C-001, NCT02074839) [38] that included 34 adult patients with IDH1-mutated ND-AML. The median age was 76.5 years, and CR and CR with partial hematologic recovery (CRh) rate were 30.3% and 42.4%, respectively. Of those patients in CR + CRh, 61.5% and 77.8% remained in remission at 1 year. The median follow-up was 23.5 months, with a median OS of 12.6 months. Also, of the 63.6% transfusion-dependent patients, 42.9% became transfusion-independent.

In the R/R landscape, ivosidenib demonstrated efficacy in the same terms of CR, CRh, and transfusion independence in the open-label, single-arm, multicenter clinical trial study AG120-C-001, NCT02074839. Here, 174 patients diagnosed with R/R AML with an IDH1 mutation were included. CR was achieved in 24.7% of patients, and 12% of the 174 patients underwent HSCT following ivosidenib treatment [39].

Ivosidenib, as well as enasidenib, was tested in a phase 1 trial in combination with standard chemotherapy 7 + 3 [40]. The CR/CRi/CRp rates were 77% with the addition of ivosidenib and 74% with enasidenib. There were low rates of adverse events related to differentiation syndrome or QT prolongation and good tolerance of the combination. In this direction, HOVON 150 is the phase 3 trial that will evaluate the benefit of adding IDH inhibitors (either enasidenib or ivosidenib) to 7 + 3 chemotherapy in first-line LMA and myelodysplastic syndrome with blast excess type 2 (NCT03839771).

The FDA also gave its approval for R/R myelodysplastic syndromes (MDSs) with IDH1 mutation, based on trial AG120-C-001 (NCT02074839), an open-label, single-arm, multicenter trial of 18 adult patients with relapsed or refractory MDS with an IDH1 mutation. The CR rate was 38.9%. Among nine patients with RBC- and/or platelet transfusion-dependent at baseline, 67% became RBC- and platelet transfusion-independent during any 56-day post-baseline period [41].

3.2. Enasidenib

Enasidenib is a selective inhibitor targeting the mutant isocitrate dehydrogenase 2 (IDH2) enzymes. It was approved for the treatment of R/R AML with IDH2 mutations by the FDA due to the results in the study AG221-C-001 (NCT01915498). This open-label, single-arm, multicenter, clinical trial included patients with IDH2-mutated AML who were treated orally with 100 mg of enasidenib in monotherapy daily [42,43]. CR and CRh rates, CR/CRh duration, and conversion from transfusion dependence to transfusion independence were the basis of approval.

After a median follow-up time of 6.6 months, 23% of patients achieved CR or CRh lasting a median of 8.2 months. The median time to first response was 1.9 months, and the median time to best response of CR/CRh was 3.7 months. Of the 157 patients who required transfusions at the initiation of the trial, 34% no longer required transfusions during at least one 56-day period on enasidenib. Of the 42 patients who did not require transfusions at the start of the trial, 76% maintained transfusion independence.

In a randomized nonblinded phase 3 trial, enasidenib improved EFS (median, 4.9 vs. 2.6 months), ORR (40.5% vs. 9.9%; p < 0.001), and red blood cell transfusion independence (31.7% vs. 9.3%). However, it did not show improvement in OS compared with conventional treatment among patients <60 years with R/R disease after 2–3 previous lines [44].

The drug has demonstrated its efficacy in inducing differentiation and remission, with CR rates of approximately 20.6% and overall response rates (ORRs) of 40.3% [45,46] but as the OS did not improve, the EMA decided that the results of the study did not allow it to conclude that the drug was sufficiently effective in the treatment of R/R AML with an IDH2 mutation [47].

However, it is worth mentioning that the ELN (European Leukemia Net)highlights possible benefit from its use in R/R patients [4].

3.3. Olutasidenib

Olutasidenib is an IDH1 inhibitor in monotherapy that was approved by the FDA on 1 December 2022 for the treatment of adult patients with R/R AML with an IDH1 mutation. This approval is based on an interim analysis from the phase 2 part of the open-label, single-arm, multicenter clinical trial 2102-HEM-101 [48]. It included 147 evaluable adult patients with R/R IDH1 AML, treated with 150 mg tablets of olutasidenib, as a monotherapy, twice daily in continuous 28-day cycles until disease progression. The median number of prior therapies was two, including patients with a previous HSCT. The primary endpoint was CR and CRh (CR with partial hematologic recovery) using modified response criteria of the International Working Group in AML [6].

The reported CR plus CRh rate was 35% with an ORR 48% with a median time to re-sponse of 1.9 months and a median duration of CR/CRh of 25.9 months (compared with 8.2 months seen with ivosidenib [39]. The composite CR (CR + CRh + CRi) (CRi equivalent to CR with incomplete blood count recovery) was 45%. Interestingly, the ORR observed in patients with previous venetoclax treatment was 50% with a CR rate of 25%. The median OS was 11.6 months for the overall study population (compared to 8.8 months with ivosidenib [39] but was not reached for those who achieved CR/CRh.

The 18-month survival in CR/CRh responders was 78% with olutasidenib and 50% with ivosidenib. Red blood cell independence and platelet transfusion independence were achieved in 88% and 100% of responders with CR/CRh. Responders who did not achieve CR/CRh also demonstrated RBC (53%) and platelet (58%) transfusion independence (TI).

Febrile neutropenia and anemia were the most common adverse events followed by thrombocytopenia and neutropenia. Differential syndrome (DS) occurred in 14% of patients, and 9% was grade 3 or higher. QT prolongation was reported in 8% of patients, most of them with grades 1 and 2.

In addition, a post hoc analysis of nine patients previously treated with ivosidenib showed a complete remission with olutasidenib combined with azacitidine during the phase 1/2 study (not the pivotal phase 2 cohort) [49].

It was also studied in naïve patients with IDH1-mutated AML, as a monotherapy or in combination with azacitidine. The overall response was 25% in patients that received monotherapy and 77% (CR 54%) in patients that received the combination therapy. Of the 59 patients with AML who were transfusion-dependent at baseline, 36% achieved 56-day transfusion independence [48,50] The results are promising, particularly with combination treatments. However, comparative studies are necessary, especially involving the combination of azacitidine and venetoclax, which has shown notable positive outcomes in this patient subgroup. Olutasidenib has been studied in combination with azacitidine in the R/R setting of IDH-1-mutated AML with an ORR of 46% (12/26 patients) (41% for monotherapy), and CR + CRh rates were 32% and 15%, respectively, and there was a median OS for the combination of 12.1 months (NCT02719574) [48].

Table 1. IDH inhibitors: advantages and disadvantages.

Feature	Ivosidenib (IDH1)	Enasidenib (IDH2)	Olutasidenib (IDH1)
Target mutation	IDH1	IDH2	IDH1
Indication	AML, cholangiocarcinoma	AML	Relapsed/refractory AML
Advantages	- Effective for IDH1-mutant AML - Long-lasting remission - FDA-approved for two cancers	- Effective for IDH2-mutant AML - Extends survival in difficult cases	- Newest IDH1 inhibitor - High remission rates in AML
Disadvantages	- Resistance development - Differentiation syndrome	- Resistance development - Differentiation syndrome	- Limited long-term data - Differentiation syndrome
Side effects	- QT prolongation	- Gilbert syndrome, high bilirubin (jaundice)	- Liver toxicity, nausea

Abbreviations: AML, acute myeloid leukemia; IDH, isocitrate dehydrogenase.

illustrates the main characteristics of the three IDH inhibitors.

4. BCL-2 Inhibitors

4.1. Venetoclax

Venetoclax (BCL-2 Inhibitor) + Hypomethylating Therapy

Venetoclax is a BCL-2 inhibitor, approved by the FDA and the EMA for use in combination with hypomethylating therapy (HMA) as a frontline for ND-AML in elderly patients or those ineligible for IC, based on the results of the VIALE-A study [37]. Specifically, the ORR for venetoclax combined with azacitidine was approximately 76.9%, with a median OS of 14.7 months compared to 9.6 months with azacitidine alone. The CR rate was 36.7% with a composite CR + CRi rate of 66.4%. However, the response to the venetoclax and HMA combination is heterogeneous, with decreased response rates in several subgroups.

For example, it is poor in high-risk TP53-mutated AML and monocytic differentiation [51,52].

4.2. Venetoclax (BCL-2 Inhibitor) + LDAC

Although the VIALE-C trial failed to demonstrate OS improvement, the FDA approved the combination of LDAC plus venetoclax due to a post hoc analysis with 6 months of additional follow-up, where an OS advantage was achieved between LDAC plus venetoclax vs. LDAC (8.4 vs. 4.1 months) [53].

There are various phase 3 trials with the combination of venetoclax + intensive induction chemotherapy currently enrolling, like NCT04628026, that compares venetoclax plus IC vs. the placebo and IC.

A recent phase 2 study, ChiCTR2000041509, reported the outcomes of 33 young AML patients who received venetoclax in combination with daunorubicin and cytarabine [54] showing a composite CR rate of 91% at 1 year (100% in the favorable-risk subgroup, 83% for the intermediate-risk subgroup, and 75% for the adverse-risk subgroup).

Another trial combining venetoclax with FLAG-IDA [55] included 68 patients with ND-AML [17] and R/R AML [56]. In the ND cohort, the ORR was 97% and the CR rate was 69% and CRc was 90%. The MRD negativity rate was high among patients in CR (96% in the ND cohort and 69% in the R/R group). However, myelosuppression was significant and prolonged neutropenia was observed.

Venetoclax was also tested in association with CLIA (NCT02115295), cladribine, idarubicin, and cytarabine. It shows similar results [57] to the FLAG-IDA combination platform, both with more prolonged neutropenia and around a 40% rate of infection.

Over the last few years, there has been increasing interest in non-chemotherapy drug combinations for frontline fit patients. In this context, clinical trials are ongoing. One example is the SZ-AML01 study [58] that evaluated the combination of decitabine and venetoclax as a frontline therapy for young patients (<60 years old) diagnosed with adverse-risk AML. The CR rate was 81% (34 of 42 patients) with an estimated 12-month OS rate of 82%. Most were consolidated with HSCT (36 of 42; 86%). These results are promising, but long-term follow-up is needed as well as randomized trials.

An ongoing phase 2 trial for young patients with ND-AML (excluding favorable-risk AML) randomized to AZA/VEN versus 7 + 3 (NCT04801797) is still recruiting, and no results have been published yet.

Several retrospective studies reviewed outcomes in patients treated with HMA/VEN in the front-line, followed by a transplant [59,60,61]. A single-center study [61] found no difference in RFS, OS, or graft-versus-host disease between the HMA/VEN group vs. standard therapy. It is important to note that all these studies are retrospective and have few participants preventing researchers from drawing any conclusions.

5. CPX-351 (Liposomal Daunorubicin and Cytarabine)

CPX-351 is a liposomal formulation of daunorubicin and cytarabine, approved by both the FDA and the EMA for ND therapy-related AML (TR-AML) or AML with myelodysplasia-related changes (MR-AML) as a frontline therapy. In the phase 3 trial CLTR0310-301 [62], 309 patients aged 60–75 were randomized to receive either CPX351 or 7 + 3. CPX-351 was associated with higher ORRs compared with 7 + 3 (47.7% vs. 33.3%, respectively), and high CR rates (37.3% vs. 25.6%). A longer follow-up [63] reported an OS benefit for CPX-351 compared with 3 + 7 (median OS 9.33 vs. 5.95 months, 18% vs. 8% at 5 years), especially with patients who underwent HSCT (52% vs. 23%).

Real-world evidence from several studies also demonstrated that is useful among patients <60 years [64,65]. On the other hand, a retrospective comparison evaluated the outcomes of 217 patients who received CPX351 vs. 437 patients who received hypomethylating therapy (HMA) + venetoclax [66]. The OS rates were comparable between the two groups (13 months for CPX351 vs. 11 months for HMA + venetoclax). However, higher rates of infections were seen among patients treated with CPX351 vs. HMA + venetoclax (51% versus 20%, p < 0.00005). Randomized clinical trials to determine which patients could benefit from this therapy are needed.

However, the benefit was especially high in those patients who underwent a transplant [63] (OS 52% vs. 23%).

There is a retrospective comparison study which evaluated the outcomes of 217 patients who received CPX351 vs. 437 patients who received hypomethylating therapy (HMA) + venetoclax [66], with the OS rates being comparable between both groups (13 months for CPX351 vs. 11 months for HMA + venetoclax), but higher rates of infections were seen among patients treated with CPX351. A recent phase 1b trial evaluated lower-intensity CPX-351 combined with venetoclax in 35 adults with AML not fit for IC. Among all, 17 achieved CR after cycle 1, proving it is a suitable option for patients considered not eligible for IC [67]. Further randomized trials are needed.

6. CD 33-Targeted Therapy with Gentuzumab Ozogamicin

Gentuzumab ozogamicin (GO) is a conjugate antibody drug linked to a cytotoxic agent calicheamicin that targets CD33. GO was approved by the FDA and the EMA for the treatment of newly diagnosed CD-33 or core-binding factor (CBF) AML in combination with frontline IC. The approval of GO was based on the phase 3 EORTC-GIMEMA AML-19 trial [56], where a total of 237 patients were randomized to receive GO or best support care (BSC). Eligible patients had ND-AML and were older than 75 years of age or 61 to 75 years of age with a performance status greater than 2. Treatment consisted of induction with GO 6 mg/m² on day 1 and GO 3 mg/m² on day 8. After induction, if no disease progression or important adverse events were observed, patients received continuation therapy as outpatients with up to eight courses of treatment with GO 2 mg/m² on day 1, every 4 weeks. BSC included standard supportive care measures and hydroxyurea or other anti-metabolites for palliative purposes. The median OS was 4.9 months in the GO group and 3.6 months in the BSC group (p = 0.005); the 1-year OS rate was 24.3% with GO and 9.7% with BSC. The OS benefit with GO was consistent across most subgroups, especially in patients with high CD33 expression status, in those with favorable/intermediate cytogenetic risk profile, and in women. The study demonstrated that GO significantly improved OS in older patients with AML who were not eligible for HSCT.

The ALFA-0701 trial [68,69] showed that patients (aged 50–70) receiving GO plus chemotherapy had a higher EFS compared to those receiving chemotherapy alone (17.3 months vs. 9.5 months) but without differences in OS or ORRs [69]. In an individual patient meta-analysis of randomized control trials, improved survival was seen among patients treated with GO plus IC [70], although the benefit was confined to patients with favorable and intermediate cytogenetics (6-year OS of 76% versus 55% and 39% versus 34%, respectively). Furthermore, a post hoc analysis of the ALFA0701 trial demonstrated a benefit for the addition of GO in favorable- and intermediate-risk groups per ELN 2017 risk criteria [71]. Patients with activating signaling mutations, which were associated with higher CD33 expression levels, showed significant benefit from GO.

The drug was previously removed from the market in 2010 due to toxicities observed in the SWOG-S0106 trial [72]. This phase 3 trial was terminated due to an increased risk of veno-occlusive disease, hepatotoxicity, and early death in patients treated with GO. After that, the ALFA0701 trial demonstrated equal benefits with less associated toxicity using a fractionated dose of 3mg/m₂ in three separate administrations (days 1, 4, and 7 of induction) [68], that were also confirmed in a larger metanalysis [70]. Given these data, GO was re-approved in 2017 at a lower, fractionated dose in combination with induction chemotherapy (3 + 7) and as a monotherapy in patients unfit to receive IC.

7. Hypomethylating Therapy

7.1. Onureg, Oral Azacytidine (CC-486)

Both the FDA and the EMA have approved azacitidine tablets (CC-486 or Onureg) for patients with AML who have the disease under control after an initial treatment but are not able to proceed to HSCT.

The results were shown in the phase 3 QUAZAR study [73], a multicenter, randomized, double-blind, placebo-controlled trial, where 472 patients that achieved CR or Cri with intensive induction chemotherapy, were included. The study randomized subjects 1:1 to receive Onureg 300 mg or a placebo orally on days 1 to 14 of each 28-day cycle. The results included a median OS of 24.7 months in the Onureg arm and 14.8 months in the placebo arm (p < 0.001). Adverse events led to discontinuation of the trial regimen in 13% of the patients in the CC-486 group, with gastrointestinal events being the main cause. An ad hoc analysis showed improved OS irrespective of MRD status at first remission and a conversion to MRD negativity in 25% of patients receiving CC-486. The use of CC-486 may be limited to a few patients who are considered fit for IC but not for HSCT.

7.2. Decitabine

The ASCERTAIN phase 3 study [74] is a randomized two-period, two-sequence, two-treatment, crossover study design which included patients with AML not eligible for IC. They were randomized 1:1 to either Sequence A: DEC-C (35 mg DEC/100 mg cedazuridine) in Cycle 1 followed by IV-DEC at 20 mg/m² in Cycle 2 or Sequence B: IV-DEC in Cycle 1 followed by DEC-C in Cycle 2 to compare pharmaco-kinetics. All patients received DEC-C from Cycle 3 until treatment discontinuation. This demonstrates that daily (5 days) dosing of the oral formula of DEC-C resulted in an equivalent decitabine exposure to IV-DEC at 20 mg/m² over 5 days. Pharmacodynamic data showed similar demethylation rates (≤1.1% difference). Also, safety findings and clinical activity (response rates and OS) are consistent with published data from IV-DEC, suggesting that DEC-C has the potential to be an oral alternative to the standard IV-DEC daily × 5 regimen.

There is an ongoing phase 2 trial NCT04746235 [75] investigating the possible benefits of venetoclax and ASTX727 in treating patients with R/R AML or elderly patients with newly diagnosed acute myeloid leukemia who are not eligible for IC. Concerning the ND-AML setting, 42 patients were enrolled with a median age of 79 years. By ELN (European Leukemia Net) 2022, 6 (14%) were favorable, 3 (7%) were intermediate, and 33 (79%) were adverse and 9 (21%) had complex cytogenetics and 6 (14%) had TP53 mutations. The ORR was 67% with 36% CR and 26% CRi. At a median follow-up of 12.8 months, the median OS was 12.7 months, and for those who achieved CR/Cri, the median RFS was 9.8 months. The median duration of response (DOR) was 13.2. Regarding genetics, they made three genetic groups (group 1: TP53 WT, K/NRAS WT, and no FLT3-ITD; group 2: TP53 WT, K/NRAS mut, or FLT3-ITD-positive; and group 3: TP53 mut). The median OS in group 1 (n = 24), group 2 (n = 12), and group 3 (n = 6) was 16.2, 9.1, and 1.4 months, respectively. For those who achieved CR/CRi, the median RFS in group 1 (n = 17), group 2 (n = 7), and group 3 (n = 2) was 13.2, 8.1, and 9.8 months, respectively. So, it could be a combination to consider for the future, but more randomized studies are required.

Several interesting studies are in progress, such as the case of a phase 1b trial with active recruitment whose objective is to evaluate a maintenance treatment in patients with controlled acute leukemia, with oral decitabine in monotherapy, in combination with venetoclax, gilteritinib, enasidenib, or ivosidenib (NCT05010772). Another phase 1/2 trial is combining ASTX727, venetoclax, and gilteritinib for the treatment of ND and RR FLT3m AML or high-risk myelodysplastic syndrome, NCT05010122.

7.3. ASTX727 or Decitabine/Cedazuridine

A phase 2 trial, NCT04746235 [75], is currently underway to evaluate the potential benefits of venetoclax and ASTX727 in patients with relapsed or refractory AML, as well as in elderly patients with newly diagnosed AML who are ineligible for intensive chemotherapy. The median age in the R/R cohort was 72.9 years old. Here, the overall response rate was 45%. The median follow-up was 5 months, and the median survival was 7.2 (range, 0.8–7.3) months for the R/R cohort. The authors concluded that this could be an option either for elderly patients with ND leukemia or for R/R patients, especially those with older ages.

8. Revumenib SNDX-5613 (Menin Inhibitor)

This drug targets the menin–KMT2A interaction, which is crucial for leukemogenesis, especially in KMT2A-rearranged (KMT2Ar) or NPM1-mutant (NPM1m) AML [76]. Revumenib is being evaluated in the phase 1/2 trial AUGMENT-101 [77] that is still recruiting patients with KMT2Ar or NPM1m R/R AML and ALL. Data from the interim analysis showed that the primary endpoint was achieved in the subgroup of KMT2A-rearranged AML. Patients received revumenib in monotherapy (95 mg/m² if <40 kg) in 28-day cycles until unacceptable toxicity, lack of at least morphological leukemia-free state (MLFS) by the end of cycle 4, or progressive disease. In adults with AML (n = 51), the largest KMT2Ar subgroup, CR + CRh, was 28% and the ORR was 59%. Regarding adverse events, 16% of patients experienced a grade 2 differentiation syndrome, resolved with hydroxyurea and steroids. Considering these data, in March 2024, the FDA granted priority review for the new drug application of revumenib for the treatment of adult and pediatric patients with R/R KMT2A-rearranged acute leukemia.

Furthermore, the final AUGMENT-101 pivotal trial cohort of patients with R/R NPM1m AML also completed enrollment and data are expected at the end of this year.

Several trials are ongoing to explore the combination with other drugs. The phase 1/2 trial combining revumenib with decitabine/cedazuridine and venetoclax (SAVE was presented at ASH (American Society of Hematology)2023 (NCT05360160) [78] with only eight patients with KMT2Ar-, NPM1m-, or NUP98-rearranged R/R AML. The ORR was 100%.

Ziftomenib

This is another menin inhibitor that showed higher rates of CR in NPM1m AML than in KMT2Ar in the phase 1 part of the KOMET-001 trial (NCT04067336) [79]. Differentiation syndrome was reported in 20%, with 5% (n = 1) being grade 3 events. Different trials are also ongoing combing ziftomenib with other schemes or drugs. The phase 2 trial results are eagerly awaited.

9. Hedghog Inhibitor—Glasdegib

An open-label randomized study showed improved survival of glasdegib in combination with LDC [80]. In the EU, glasdegib is approved in combination with LDC for the treatment of ND (de novo or secondary) AML in adult patients who are not candidates for standard chemotherapy. In the U.S. and Canada, the drug is approved in combination with LDAC for the treatment of newly diagnosed AML in adult patients who are 75 years or older or who have comorbidities that preclude the use of intensive induction chemotherapy.

10. TP53 AML

The frequency of TP53 mutations in de novo AML ranges from 5 to 10%, increasing to approximately 30% in cases of therapy-related AML and AML with complex cytogenetics. This mutation is associated with an OS of less than 30% at 2 years [81], and only 20–30% of patients achieve complete remission after standard induction chemotherapy regimens [82]. Given the poor prognosis associated with intensive chemotherapy, there has been interest in less intensive and targeted therapeutic approaches. Pollyea et al. analyzed the outcomes of 127 AML patients with HR genetics treated with AZA + EN in front-line treatment compared to 56 patients treated with AZA alone [83]. The combination of AZA + VEN in patients with adverse genetics allowed a complete remission rate in 70% of patients versus 30% for AZA alone, with a median OS of 23 months versus 11.3 months, respectively. However, for patients with the Tp53 mutation, even if CR was achieved in 41% with AZA + VEN versus 17% with AZA alone, no benefit was observed in OS (5.2 months versus 4.9 months).

APR-246/eprenetapopt is a small molecule that targets TP53-mutated cancers, which has shown promising results against TP53-mutated MDS, and AML APR-246 reactivates mutant p53 transcription by facilitating its binding to DNA sequences, eventually inducing apoptosis [84,85,86] The first clinical trial that investigated the combination of APR-246 and AZA was a phase 2 trial (NCT03072043) in which there were 55 patients with the TP53 mutation (40 MDS and 11 AML). The overall response rate was 71% with a CR rate of 44%, and 38% achieved MRD negativity assessed by NGS [87].

The median duration of CR was 7.3 months, with a median follow-up of 10.5 months. The median OS was 10.8 months. A French phase 2 trial (NCT03588078) enrolled 52 patients (34 MDS and 18 AML) with a median age of 74 years. The ORR was 52% with a CR rate of 37% with 30% of patients with MRD negativity. The median duration of CR was 11.7 months, with a median follow-up of 9.7 months. The median OS was 12.1 months. No additional hematological toxicity was reported compared to AZA alone. However, neurological effects including ataxia, acute confusion, facial dizziness, and paresthesia were reported in 40% of patients [86]. Based on these results, a phase 3 randomized clinical trial was conducted to compare AZA alone + AZA + APR-246 in MDS (NCT03745716).

The results failed to demonstrate the superiority of the combination compared to AZA alone. However, more recently, a phase 1 trial (NCT04214860) has shown that the addition of APR-246 to VEN and AZA appears encouraging in treating TP53-mutated AML with a well-tolerated toxicity profile and promising efficacy by achieving an overall response of 64% (25/49) and CR of 38% (15/39) [88].

Magrolimab is a first-in-class investigational monoclonal antibody against CD47 and macrophage checkpoint inhibitor, which interferes with the recognition of CD47 by the SIRPα receptor on macrophages, thus blocking the “don’t eat me” signal used by cancer cells to evade phagocytosis. In a phase 1b trial, magrolimab was studied in AML patients not eligible for intensive chemotherapy with a focus on TP53-mutant patients in this large phase 1b study (n = 72 for TP53 mutation). In this study, the combination of magrolimab with azacitidine had an overall response rate of 48.6%, a CR rate of 33%, and a median OS of 10.8 months [89].

Based on these results, several phase 3 randomized clinical trials were designed to treat frontline patients: ENHANCE-2 (NCT04778397 to investigate the role of magrolimab plus AZA versus physician’s choice of VEN-AZA or intensive chemotherapy in patients with TP53 AML in previously untreated AML and ENHANCE-3 (NCT05079230) to investigate the role of magrolimab versus a placebo in combination with venetoclax and azacitidine in previously untreated patients with AML who are ineligible for intensive chemotherapy. Recently, the ENHANCE-2 study was discontinued for reasons of futility with no survival benefit compared to standard of care therapies in TP53-mutated AML after the primary endpoint of OS was not met. However, these data have not been presented and a subset analysis of this study is warranted. This negative result is compounded by the recent closure of ENHANCE for higher-risk MDS where the study was also futile for an improvement in OS versus HMA alone. As of August 2023, the FDA placed a partial clinical hold on the enrollment of new patients in the clinical trial, thereby affecting the ENHANCE-3 trial.

Sabatolimab, a novel anti-TIM3 monoclonal antibody, demonstrates antileukemic activity by directly targeting TIM-3 on the blast surface, promoting antibody-dependent phagocytosis and inhibiting the TIM-3–galectin-9 interaction, which prevents the renewal of leukemia stem cells [90].

Sabatolimab has been investigated in association with HMA in 48 patients with HR-MDS and AML who are unfit for intensive chemotherapy. The ORR was 40%, and of these, 30% achieved CR. The median duration of response was 12.6 months with a PFS (Progression Free Survival) of 27.9%. For patients with at least one genetical adverse-risk mutation, the ORR was 53.8% with a median duration of response of 12.6 months [91].

Based on these results, the STIMULUS clinical trial program was started in which randomized phase 2 and phase 3 clinical trials are investigating multiple combinations with sabatolimab based on AML, high-risk MDS, and chronic myelomonocytic leukemia. STIMULUS-AML1 (NCT04150029) is an ongoing phase 2, single-arm study of sabatolimab + AZA + VEN in adult patients with AML who are ineligible for intensive chemotherapy [92].

To date, TP53-mutated AML represents a challenging subtype with distinct clinical and molecular features. Although current treatment options for TP53-mutated AML are limited, further investigations are warranted to develop effective treatments that specifically target this genetic alteration, without further toxicities, in hopes of improving survival outcomes.

11. CD123 Target Therapy

11.1. Pivekimab Surine

CD123 is the alpha chain of the human interleukin-3 receptor (IL-3R), which is highly expressed in myeloid leukemia stem cells (LSCs) compared to normal stem cells [93]. This has raised interest in using it as a target in the treatment of AML. Pivekimab surine (PVEK) is a first-in-class antibody–drug conjugate comprising a high-affinity CD123 antibody. PVEK was first tested in monotherapy in R/R AML patients with favorable safety profiles, with low single-agent activity in the phase 1 trial NCT03386513 [94]. Dose-limiting toxicities (DLTs) were reversible, including among all veno-occlusive disease and neutropenia The recommended phase 2 dose was selected as 0.045 mg/kg once every 3 weeks. At the phase 2 dose (n = 29), the most common grade 3 or worse treatment-related adverse events were febrile neutropenia in three patients, infusion-related reactions in two patients, and anemia in two patients. Among the 68 participants in the phase 2 trial, the ORR was 21% and the composite CR rate (cCR) was 17%.

Recently, PVEK has also been studied in combination with azacitidine/venetoclax in R/R AML NCT04086264 [86] achieving an ORR of 51% and CRc 31%. The triplet has also been evaluated in a population of ND CD123+ AML patients in the same trial [95], with promising results: CR/CRc rates of 52%/66%. In patients ≥ 75 years old, the CCR rate was 76% (16/21). In those with TP53wt, both the CR and CCR rates were 88% (22/25). The rate of MRD negativity for those in CR was 73% [95]. CCR rates were high across main molecular subsets with FLT3 (ITD/TKD) at 100% (7/7), IDH1/2 at 89% (8/9), and NPM1 at 89% (8/9), as well as ELN risk groups (intermediate-risk group 80% and adverse-risk group 64%).

With these promising results, it was decided to start a clinical trial in combination with IC FLAG-IDA in ND-AML (NCT06034470), which is ongoing.

11.2. Flotetuzumab

Flotetuzumab (CD123xCD3) is a dual-affinity retargeting (DART) kind of bispecific therapy (BITE) that has been tested in a multicenter, open-label, phase 1/2 study including 88 patients with R/R AML. The CR and CR with partial hematological recovery (CRh) rate was 26.7%, with an overall response rate (CR/CRh/CR with incomplete hematological recovery) of 30%. Among patients who achieved CR/CRh, the median OS was 10.2 months, with 6- and 12-month survival rates of 75% and 50% [96]. However, high rates of cytokine release syndrome (CRS) were observed (>80% of the patients); therefore, the company behind it decided to interrupt the development of this drug and focus on a new generation BITE, named MGD024 that was created to reduce CRS rates with an actively recruiting trial (NCT05362773).

11.3. SAR443579

SAR443579 is a trifunctional natural killer (NK) cell engager targeting CD123 antigen and co-engaging NKp46 and CD16a on NK cells [89]. It facilitates the formation of a cytolytic synapse between NK cells and CD123-positive tumor cells leading to NK cell activation and tumor cell killing. There is an active trial NCT05086315 [97] where no dose-limiting toxicities were observed up to the highest dose of 6000 µg/kg QW. There were two cases of grade 1 CRS at DL4 and DL5 and no cases of immune effector cell-associated neurotoxicity syndrome. Composite CR (CR + CRi) was 12.0% (5/42 R/R AML). The authors concluded that there is a clinical benefit in its use in R/R AML with a good safety profile [97].

12. CD47 Target Therapy

AK117-206, Ligofalimab

The transmembrane antigen CD47 is an immune checkpoint overexpressed by tumor cells, facilitating the evasion of the antitumor response. CD47 suppresses activity of phagocytes through its interactions with SIRPα macrophages [98,99]. Therefore, blocking this CD47-SIRPα interaction as antiCD47 antibodies do, leads to the phagocytosis of tumor cells by macrophages [98,100].

This antigen is heterogeneously expressed in AML (also in stem cells). High CD47 expression has been shown to be an independent prognostic factor for poor OS in AML patients [101,102]. It is particularly increased in AML with TP53 mutations (50%) [103]. Ligofalimab is an anti-CD47 antibody that is under investigation [98]. The last clinical trials with magrolimab (another antiCD47 antibody) for MDS or AML in combination with azacitidine, (ENHANCE and ENHANCE 2) and venetoclax (ENHANCE-3) demonstrated futility, and an increased risk of death was observed, especially due to infections, so the sponsor decided to stop the development of magrolimab in hematologic malignancies [104].

13. Other Inhibitors

13.1. Myeloid Cell Leukemia Sequence (MCL-1) Inhibitors

MCL-1 is an anti-apoptotic protein that contributes to the survival of AML cells (as well as other kinds of neoplasia). It is known that ND-AML overexpresses BCL-2 family proteins as MCL-1 and that higher levels of antiapoptotic BCL-2 proteins, including MCL-1, are related to relapse [105,106].

The MCL-1 inhibitor S64315 failed to achieve any response in the phase 1 CL1-64315-001 trial NCT02979366. In the same way, a combination trial of S64315 with azacitidine in patients with AML (ND and R/R) CL1-64315-004/NCT04629443 was discontinued due to strategic reasons, and no data were published.

In clinical trials, AZD5991 showed preclinical efficacy inducing apoptosis in AML cells [107]. However, in clinical trials, it failed to be safe, so for now, development is discontinued (NCT03218683).

13.2. IOX5 (Prolyl Hydroxylase Inhibitor)

It is well known that the inactivation of HIF-1α/HIF-2α promotes AML, so this opens an area for research to target the HIF-prolyl hydroxylases, which promote HIF-1α/HIF-2α destruction [108]. The use of a prolyl hydroxylase inhibitor (PHD) is being investigated in preclinical studies [109]. This PHD inhibition compromises AML in an HIF-1α-dependent manner to disable pro-leukemogenic pathways, reprogram metabolism, and induce apoptosis. Importantly, the concurrent inhibition of BCL-2 by venetoclax potentiates the anti-leukemic effect of PHD inhibition [110].

13.3. ROCK1 Inhibitor

ROCK1 was recently identified as an important gene for leukemic bulk and stem cells [103,111]. ROCK1 regulates cell functions, including migration, apoptosis, survival, and proliferation. GSK269962A is a molecule that targets coiled-coil protein-associated kinase-1 (ROCK1). ROCK1 could be a potential therapeutic target for AML. GSK269962A selectively inhibited cell growth and clonogenicity of AML cells, arresting AML cells in the G2 phase, and induced apoptosis by regulating multiple cell-cycle- and apoptosis-associated proteins in preclinical trials with mouse models. This could indicate its potential effectiveness in AML therapy [112].

14. CAR T Cell Therapy

A chimeric antigen receptor (CAR) is a synthetic receptor with an antigen-binding domain composed of a variable fragment chain of an antibody [113,114,115]. This domain is also linked to an intracellular signaling domain, which contains a CD3 T cell receptor (TCR) chain. Thus, CAR Ts are T cells with CAR receptors genetically modified for recognition of a specific desired antigen [116]. The concept was first described in 1987 by Kuwana et al. [117]. Autologous T cells are collected from the patient’s blood by leukapheresis (or allo-cells from a healthy donor), then activated and genetically engineered ex vivo to express the CAR on their surface. Finally, these cells are expanded in bioreactors and mostly cryopreserved [118].

The first-generation CAR Ts were not very successful because of the limited ability to awaken quiescent T cells and maintain a sustained T cell response or cytokine release [119]. Thus, second-generation CAR Ts with the addition of a co-stimulatory domain or third-generation CAR Ts with the addition of a second co-stimulatory molecule have been developed, which are able to enhance activation, proliferation, and persistence of CAR T cells [114]. In fourth-generation CAR Ts [120], CAR-inducible genes encoding various cytokines that promote activation are added, so they can be used for universal cytokine-mediated killing. Moreover, fifth-generation CAR Ts [121], also known as next-generation CAR T cells, have also been developed. They include a truncated intracellular cytokine receptor domain with a binding site for STAT3/5 transcription factors, which in preliminary studies appears to favor efficacy. The main limitation with AML is the absence of a common target for all types and the fact that several of the targets used are also expressed in normal hematopoietic cells [122]. We summarized the principal targets under investigation through CAR T therapy.

14.1. CD123

Also called human interleukin 3 receptor alpha chain (IL-3Rα), CD123 is known to be overexpressed in AML as well as CD33 [123]. It is also known to be expressed on normal hematopoietic [124]. Several clinical trials aiming to evaluate CAR Ts directed against AML are ongoing. NCT02159495 [125], is a first-in-human (FIH) phase 1 trial of a single-center trial that evaluates CD123-CAR-CD28CD3ζ-EGFR T cells in R/R AML (cohort 1) and BPDCN (cohort 2). A total of 18 patients were enrolled; only 9 were treated; 7 had an AML diagnosis, and they all had at least one prior HSCT. Lymphodepleting regimen was fludarabine 25–30 mg/m² and cyclophosphamide 300–500 mg/m² for 3 days. Regarding response, one patient had CR, and two patients achieved MLFS (but one of them improved to CR). The maximum CRS grade was 2. Another interesting trial is the NCT03190278 [126] or AMELI-01, which is a phase 1, open-label, dose-escalation trial evaluating the preliminary activity of UCART123v1.2 given at escalating doses after lymphodepletion with the addition of alemtuzumab (FCA) in patients with R/R CD123+ AML. Adding alemtuzumab to the FC regimen was associated with significantly higher UCART123v1.2 cell expansion, which correlated with improved activity and cytokine profiles. One patient in the dose 2 FCA arm achieved >90% blast reduction at day 28. One patient in the dose 2 FCA arm achieved a long-term durable MRD-negative CR (>12 months). Overall, these data support further study of UCART123v1.2 after FCA lymphodepletion in patients with R/R AML. The NCT04230265 phase 1 trial [127] evaluated the safety and tolerability of UniCAR02-T-CD123 with a recombinant antibody derivative (TM123) in R/R AML with CD123+ in more than or equal to>20% blast. The results from the 14 patients treated are available. They used standard fludarabine/cyclophosphamide lymphodepletion on days −5 to −3. TM123 administration was given over 21 days as continuous infusion via a mobile pump, and on day +1, UniCAR-T was administered. After initial mandatory hospitalization, patients continued to be treated in an outpatient setting from day +12. CRS was observed in 12 patients, mostly grade 1 or 2. Treatment-related toxicity was reversible in all patients with interruption of TM123 administration. Two patients achieved CRi, and one patient achieved MRD-positive CR. The observed side effects warrant further investigation, and an expansion cohort will be implemented at dose level 16.

AVC-201 is a CAR T designed for AML and other CD123+ hematologic diseases being tested in the phase 1 clinical trial NCT05949125 [128]. This is a CRISPR-engineered allogeneic switchable CAR T designed to target CD123-positive cells. It incorporates two platforms. The first platform consists in the transduction of a “universal” receptor that is completely biologically inert and is only activated when bound to a second biological molecule that leads the T cells to a CD123. Thus, the presence or absence of the second molecule in circulation allows for “on” and “off” control, respectively, of the therapeutic activity. The second technology platform used technology developed by Intellia Therapeutics which allows for unrelated donors to provide cells for patients. These cells are uniquely engineered via CRISPR/Cas9 to avoid GvHD and rejection via the host’s/patient’s immune system by either innate or adaptive mechanisms.

14.2. CD33

CD33 is a sialic acid-binding immunoglobulin-related lectin that works as a trans-membrane receptor on hematopoietic cells. It is an inhibitory receptor that when phosphorylated inhibits the production of pro-inflammatory cytokines. It is also known to be expressed on normal hematopoietic cells although to a lower expression. Several clinical trials targeting CD33 with CAR T cell therapy have been performed.

NCT06420063 is a current clinical study that still does not have results, but it is interesting to mention because it is using sequential dual CAR T cells targeting both CD33/CD123 (BAH244). Bispecific CARs with CD33 and CD123 single-stranded variable fragments (ScFv) have superior proliferative capability and less hematopoietic stem cell toxicity both in vitro and in vivo [129].

PRGN-3006 is an autologous ultraCAR T tested in 20 patients with AML (NCT03927261) [130]. Ten of them were treated without LD (cohort 1) and 14 with LD (cohort 2). One patient was in CRi after cycle 2 and was bridged to HSCT (CR MRD post-HSCT). Regarding adverse events, 10 patients had grade 1, 6 grade 2, and 1 grade 3 CRS.

The phase 1/2 trial NCT03126864 [131] tested VCAR33 in patients with R/R or MRD+ AML after HSCT. The CAR construct used contained a lintuzumab-derived binding domain and a CD28 co-stimulatory domain. Patients were assigned to different arms based on their disease burden: (A) ≥5% blasts in the bone marrow or (B) MRD+ defined as <5% blasts in the bone marrow with ≥0.1% CD33+ AML cells by flow cytometry. Each arm enrolled and escalated independently according to a 3 + 3 trial design, starting at 1 × 106 CAR T cells/kg. Lymphodepletion with fludarabine (total 120 mg/m²) and cyclophosphamide (total 1000 mg/m²) was given prior to VCAR33 infusion. There was no evidence of antileukemic activity in this case, and all the patients died.

PLAT-08 is another clinical study, NCT05105152 [132], that tested SC-DARIC33 CD33-targeted autologous T cell product. DARIC T cells are intended to be switched from “off” to “on” in the presence of rapamycin. This therapy is unique as it uses a rapamycin-regulated mechanism to control the activation of the CAR T cells, potentially allowing for more precise management of the treatment’s effects. Recent developments in the trial have led to a significant pause in the study due to a serious adverse event classified as grade 5. This event occurred at the second dose level of the treatment, prompting the FDA to place a clinical hold on the trial while the cause of the adverse event is investigated.

The clinical trial NCT03971799 [133] analyzed CD33 CAR T cell therapy (CD33CART) in children and young adults with R/R AML. Among a total of 19 patients infused, DLT appears at dose 3 (DLT3) with grade 4 CRS. At DL4, a patient experienced prolonged grade 3 CRS and grade 3 ICANS. CR was only seen at DL4 and was achieved in two subjects, both achieving MRD-negative CR alongside myeloid aplasia. One patient underwent HSCT holding CR at day 100 after HSCT. The second patient (post- to prior-HSCTs) declined a third transplant, had a spontaneous count recovery, and remained in remission until day +119 (MRD+ relapse).

14.3. CLL-1

C-type lectin-like receptor 1 (CLL-1) regulates granulocyte and monocyte functions, particularly during inflammatory responses [127]. Also, CLL-1 has gained attention as a potential target for CAR T cell therapy in AML due to its high expression on primary AML cells (ranging between 77.5% and 90%) and leukemia stem cells (LSCs), while being minimally expressed on healthy hematopoietic stem cells (HSCs), where it is present in only about 2.5% of cases [134]. A few CAR T-based trials are running.

Zhang et al. performed a phase 1 trial ChiCTR2000041054 [135] including 30 adult patients. All of them experienced CRS (only one patient had grade 4 CRS), and one patient suffered grade 4 ICANS that improved with plasma exchange. Regarding efficacy, 12 patients achieved MRD-CR/CRi and 10 patients achieved MRD + CR/CRi. The median OS rate after transplantation was higher than for those patients who did not have a transplantation. The median OS was 348 days.

CAR T trials are also being conducted in children, some with promising results, as in the case of phase 1/2 trial NCT03222674 [136]. Seven children with R/R AML were enrolled to receive CD28/CD27-based CAR T cell therapy (four of them) and 4-1BB-based CAR T cell therapy (three of them). The ORRs were 75% and 66.7% in the CD28/CD27 and 4-1BB groups, respectively. All patients experienced grade 1 to 2 CRS, and one patient had grade 2 ICANS. The maximum CAR T cell durations were 156 and 274 days for the CD28/CD27 group and the 4-1BB group, respectively. The 1-year overall survival rate was 57.1% [136].

There is an interesting trial, NCT05995041, aiming to assess the feasibility, safety, and efficacy of universal CAR T cell targeting CCL-1, CD33, CD38, and CD123 in patients with R/R AML. The authors propose that CAR T therapy for AML is difficult to optimize because AML patients usually have suppressed bone marrow function, so it is complicated to obtain good T cells. Also, AML progression is often so rapid that there is no time for a CAR T manufacture process. They propose using universal CAR T cells as they can be supplied off-the-shelf without being customized to individual patients.

Also, the manufacture of allogeneic CAR T cells edited by CRISPR technology is being studied in patients with R/R AML (AMpLify trial, NCT06128044).

Furthermore, dual CAR Ts, in this case, anti-CLL CAR are bound to an anti-CD33 CAR T cells. Preliminary results from NCT03795779 [137] showed CR with MRD negativity in seven out of nine patients and two non-responders. Six out of seven patients in CR moved to HSCT.

14.4. CD7

CD7 is a transmembrane glycoprotein that works as a co-stimulatory receptor for T and NK cells during their development. CD7 is also expressed in blasts in about 30% of AML patients. However, the development of anti-CD7 CAR T cells may lead to therapeutic failure due to the fratricide effect [138], so CD7 removal mechanisms have to be established in the manufacture of the product.

An ongoing trial, NCT04538599, with CD7 CAR-T cells using 4-1BB co-stimulatory domain included one patient with CD7+ AML. Lymphodepletion was performed with fludarabine and cyclophosphamide + etoposide. The patient achieved CRi at day 28 and only experienced G1 CRS [139].

In NCT049388115, CD7- anti-CD7 CAR T cells were used in ten patients with CD7 + AML. Among the seven patients who achieved CR, three underwent consolidative second HSCT about 2 months after CD7 CAR T cell infusion. One patient died on day 241 due to transplant-related mortality (TRM). Among the other four patients, three relapsed on day 47, day 83, and day 115, respectively (all three patients were found to have CD7 loss), and one patient died from a lung infection. CRS appeared in 80% of patients, grades 1–3. The patients did not experienced neurotoxicity [140].

14.5. NKG2D

NKG2D is an activating receptor present on T and NK cells, which recognizes ligands that are upregulated in malignant transformation, including AML (barely expressed on healthy tissues [141].

Several trials tried NKG2D as a target. In NCT02203825, autologous NKG2D CAR T cells were used in seven AML patients, observing an OS of 4.7 months without CRS or ICANS [142].

Sallman et al. published results from NCT03018405 after infusion in 12 patients with AML, an autologous NKG2D CAR T cell (CYAD-01) [143]. Three patients had an objective response. Among responders, two patients with acute myeloid leukemia proceeded to HSCT after treatment, with durable ongoing remissions. Grade 3–4 CRS were observed [135,143].

Table 2. Clinical trial results of new therapies.

Therapy	Trial	Indication	Eligibility	Results
Gilteritinib + Azacitidine vs. Azacitidine	Phase 3 NCT02752035/LACEWING	- Frontline	- Non-fit - FLT3m	- CR/CRi/CRh 58.1% (GIL + AZA) vs. 26.5% (AZA) (p < 0.001) - 9.82 months (GIL + AZA) vs. 8.87 months (AZA) No difference
Gilteritinib + Venetoclax + HMA	Phase 1/2 NCT04140487	- Frontline - R/R	- Non-fit + Fit - FLT3m	- CR/CRi/CRh frontline 96% - CR/CRi/CRh R/R 37% - OS NR. 72% (18 months)
Gilteritinib + Venetoclax	Phase 1b NCT03625505	- R/R	- Non-fit + Fit	- CR + CRi + CRp + MLFS: 75% (82% ITD; 56% TKD; 67% without prior FLT3 TKI exposure and 80% with prior FLT3 TKI; CR + CRi+ CRp: 39%. - OS 10 months
Gilteritinib	Phase 3 NCT02997202/MORPHO trial	- Maintenance	- Fit adults - FLT3-ITDm	- 2-year RFS 77.2% vs. 69.9% (p > 0.05) 50.5% MRD+ pre- or post-SCT, gilteritinib decreased ROR (p = 0.0065)
Quizartinib	Phase 3 NCT02039726/Quantum-R study	- R/R	- Non-fit + Fit - FLT3-ITDm	- Quizartinib arm 48% vs. control arm 27% - OS 6.2 vs. 4.7 months
Quizartinib + Venetoclax + Decitabine	Phase 1/2 NCT03661307	- Frontline - R/R	- Non-fit in frontline - Non-fit + Fit in RR cohort. - FLT3m	- Frontline, CRc 10/10 100% (7 CR, 3 CRi) - R/R CRc 68% - OS frontline: NR (15 months) - OS R/R 7.6 months
Quizartinib + Venetoclax + Azacitidine or LDAC	Phase 1/2 NCT0468776/VEN-A-QUI	- Frontline	- Non-fit - FLT3m or WT	- Phase I: CR/CRi/CRh 44%. OS NR - Phase II: CR/CRi/CRh 43% (LDAC 40% vs. AZA 45%). OS LDAC 11.6 months vs. AZA NR
Sorafenib vs. Placebo + Induction therapy	Phase 2 NCT00893373/SORAML	- Frontline	- Fit - FLT3m or WT.	- CR/CRi/CRh 60% (sorafenib) vs. 59% (placebo) - OS 61% (sorafenib) vs. 53% (placebo) (5 years)
Sorafenib vs. Placebo + Induction therapy	Phase 2 ACTRN12611001112954/ALLG AMLM16	- Frontline	- Fit - FLT3m	- CR/Cri sorafenib, 78%/9% - CR/Cri placebo, 70%/24% - 2-year EFS 47.9% vs. 45.4% p = 0.61. - OS-2 year 67% sorafenib vs. 58% placebo. - SCT in 1º RC 2-year OS rates were 84% and 67% sorafenib vs. placebo
Sorafenib as maintenance after allo-HSCT	Phase 1 NCT01398501	- Maintenance	- Fit - FLT3-ITDm	- OS 95% (1 year). Pretransplant CR 100%.
Sorafenib as maintenance after allo-HSCT	Phase 2 DRKS00000591/SORMAIN	- Maintenance	- Fit - FLT3m	- Median RFS NR vs. 30.9 months, median OS NR both arms. Estimated OS 2-year 90.5% vs. 66.2%
Sorafenib + Azacitidine	Phase 2 NCT01254890	- R/R	- Non-fit + Fit	- ORR 46%, CR 16% - OS 6.2 months
Venetoclax + Induction therapy	Phase 2 ChiCTR2000041509	- Frontline	- Fit	- CR/CRi/CRh 91% - OS 97% (1 year)
Venetoclax + FLAG-IDA	Phase 1/2 NCT03214562	- Frontline - R/R	- Fit frontline - Non-fit + Fit in R/R	- Frontline: CRc 90%, CR 69% - R/R Ib 75%, IIB 61% - OS frontline: 94% (1 year) - OS R/R Ib 38%, IIB 68% (1 year)
Venetoclax + CLIA	Phase 2 NCT02115295	- Frontline - R/R	- Fit	- CR/CRi/CRh 94% - OS 95% (12 months)
Venetoclax + Decitabine	Phase 2 NCT04752527/SZ-AML01	- Frontline	- Fit	- CR/CRi/CRh 81% - OS 82% (12 months)
Venetoclax + Decitabine cedazuridine (ASTX727)	Phase 2 NCT04746235	- Frontline - R/R	- Non-fit frontline - Non-fit + Fit	- Frontline 62% (4 CR, 4 CRi, 1 MLFS, and 3 non-responders, total 15 pts) - R/R the ORR was 45% (total 13 patients) (2 CR, 2 CRi, 2 MLFS with 5 non-responders and 2 not evaluable) - Frontline cohort OS was 12.7 months; for those who achieved CR/Cri, the median RFS was 9.8 months. DOR 13.2 months. - Median survival R/R cohort 7.2 months
Olutasidenib ± Azacitidine	Phase 1/2 NCT02719574, IDH1-R132	- Frontline - R/R	- Non-fit frontline - Non-fit + Fit R/R cohort	- CR/CRi/CRh: frontline combination 64%; R/R combination 46% CR  +  CRh rates were 32% in frontline and 15% in R/R cohort. - Median duration OR frontline NR; median duration OR 8.5 months R/R
Revumenib SNDX–5613 (Menin inhibitor)	Phase 1/2 NCT04065399 AUGMENT-101	- R/R	- Non-fit + Fit - KMT2Ar, NPM1)	- KMT2Ar ORR 59% (CR + CRh. 28%) - NPM1m ORR 36% (CR + CRh. 21%)
Revumenib + Decitabine /Cedazuridine + Venetoclax	Phase 1/2 NCT05360160/SAVE	- R/R	- Non-fit + Fit - KMT2Ar, NPM1, NUP98r	- ORR 100%
Ziftomenib	Phase 1/2 NCT04067336/KOMET-001	- R/R	- Non-fit + Fit - KMT2A-r or NPM1m	- NPM1m CR/ORR 30%/40% vs. KMT2Ar 16.7%/33.3%. - OS NPM1m 5.1 m (dose 600 mg)
IMGN632/Pivekimab (PVEK) monotherapy	Phase 1/2 NCT03386513	- R/R	- Non-fit + Fit	- ORR 21%, cCR 17%
IMGN632/Pivekimab (PVEK) in Combination with Azacitidine/Venetoclax	Phase 1/2 NCT04086264	- Frontline - R/R	- Non-fit + Fit	- ORR 51% - CRc 31%.
SAR443579	Phase 1 NCT05086315	- R/R	- Non-fit + Fit	- CR + CRi 12%
CAR-T–CD123: CD123-CAR-CD28CD3ζ-EGFR	Phase 1 NCT02159495	- R/R	- Non-fit + Fit	- CR 2/7patients - 1 MLFS
CAR-T–CD123: UCART123v1.2	Phase 1 NCT03190278 or AMELI-01	- R/R	- Non-fit + Fit	- 1 patient FCA arm achieved >90% blast reduction at day 28. - 1 patient in FCA arm achieved long-term durable MRD-negative CR (now past 12 months)
CAR-T–CD123: UCART123v1.3 plus, TM	Phase 1 NCT04230265	- R/R	- Non-fit + Fit	- CRi 2 patients, CR MRD+ 1 patient, PR 4 patients
CAR-T–CD33: PRGN-3006	Phase 1 NCT03927261	- R/R	- Non-fit + Fit	- Cohort 2 with LD: 1 CRi bridged to allo-(CR MRD post-allo-HSCT), 1 CRh and 1 PR - Cohort 1 without LD: 1 durable SD.
CAR-T–CD33 VCAR33	Phase 1 NCT03126864	- R/R	- Non-fit + Fit	- No responses
CAR-T-CD33: CD33CART	Phase 1 NCT03971799	- R/R	- Children and young adults	- 2/24 CR
CAR-T-CLL-1	Phase 1 ChiCTR2000041054	- R/R	- Non-fit + Fit	- 12/30 MRD-CR/CRi; 10 MRD+ CR/CRi - OS 346 days
CAR-T-CLL-1 CD28/CD27and 4-1BB	Phase 1/2 NCT03222674	- R/R	- Children	- ORR 75% and 66.7% in CD28/CD27 and 4-1BB group, respectively - 1-year OS 57.1%
cCART CLL1-CD33 CAR-T	Phase 1 from NCT03795779	- R/R	- Children and adults	- CR in 7/9 patients, with MRD-negative in 6 - 2 non-responders.
CAR-T-CD7 RD13-01	Phase 1 NCT04538599	- R/R	- Non-fit + Fit	- 1/1 patient CRi at day 28
CAR-T-CD7: NS7CAR-T	Phase 1 NCT049388115	- R/R	- Non-fit + Fit	- 7/9 CR, - 6/7 MRD-
CAR-T: NKG2D-CAR T	Phase 1 NCT02203825	- R/R	- Non-fit + Fit	- OS 4.7 months
CAR-T: CYAD-01	Phase 1 NCT03018405	- R/R	- Non-fit + Fit	- 3/12 pts had an objective response. Among responders, 2/3 went to HSCT after treatment
CAR-NK- CD33	Phase 1 NCT05008575	- R/R	- Non-fit + Fit	- 6/10 CR

Abbreviations: AZA, azacitidine; CAR, chimeric antigen receptor; CR, complete response; CRc, composite complete response; CRh, complete response with partial hematologic recovery; CRi, complete response with incomplete recovery; CRp, complete response with partial platelet recovery; DOR, median duration of response; EFS, event-free survival; FCA, fludarabine and cyclophosphamide and alemtuzumab; FC, fludarabine and cyclophosphamide; FLT3m, FLT3 mutation; GIL, gilteritinib; ITDm, ITD mutation; LD, lymphodepletion; LDAC, low-dose cytarabine; MLFS, morphological leukemia-free state; NR, not reached; NPM1m, NPM1 mutation; ORR, overall response rate; OS, overall survival; PR, partial response; pts, patients; R/R, refractory/relapsed; RFS, relapse-free survival; ROR, reporting odds ratio; SCT, stem cell transplantation; SD, stable disease; versus; vs.; WT, wild-type.

summarizes the main results of clinical trials for frontline and R/R AML.

Others target have been examined as in the case of NCT06017258 [144]. Here, T cells were engineered to express a CAR specific for the tumor-associated antigen (TAA) C-type lectin domain family 12-member A (CLEC12A, CCL1, and CD371) and expressing the pro-inflammatory cytokine interleukin 18, with potential antineoplastic activity. IL-18 promotes T cell persistence and potentiates the immune response against tumor cells. CD371 is expressed on the surface of AML cells and leukemic stem cells, but it is not expressed on normal hematopoietic stem cells (HSCs) [145].

The antigen Lewis-Y (LeY) is a tumor-associated antigen of the blood-group molecule family. It is overexpressed in several tumors, including AML [138]. There are data published (NCT01716364) using an autologous CAR-T anti-LeY, with evidence of biological responses; however, disease ultimately progressed in all of the three patients included [146].

FLT3 is a membrane protein and a member of the class III receptor tyrosine kinase family that participates in normal hematopoiesis by controlling cell survival, proliferation, and differentiation [147]. Mutations of FLT3 in AML lead to the continuous activation of the FLT3 receptor, increasing survival and proliferation of leukemic cells.

Clinical trials targeting FLT3 are ongoing, and we are waiting for results from the NCT05445011 [148], NCT05432401 [149], and NCT05023707 [150] trials.

Regarding other types of cell therapy, CAR-NK cells are emerging as an option because they are capable of secreting more interleukins and they recognize HLA-I antigens that are usually expressed in healthy cells but downregulated in tumor cells. In addition, it is particularly interesting that they do not induce graft-versus-host disease and that a low rate of CRS and ICANS was observed. But one disadvantage is that their life is shorter than that of T cells [138].

Huang et al. posted results from the NCT05008575 trial. Anti-CD33 CAR-NK cells were used in ten patients, also with standard lymphodepletion. Six of them reached CR with MRD negativity at day 28. Regarding CRS, seven of them experienced G 1 CRS and one of them G 2 CRS [151].

15. Conclusions

In recent years, advances in our knowledge of the biology of AML have, in addition to allowing us to improve the prognostic classification based on genetic alterations, also allowed us to identify therapeutic targets, and with this, develop new chemotherapy-free drugs directed at these targets. Even so, the basis of standard first-line treatment continues to be chemotherapy in young adults without comorbidities, although it has been possible to add targeted therapy drugs to the standard treatment, such as FLT3 inhibitors or monoclonal antibodies such as gentuzumab ozogamycin. At relapse, gene-targeted drugs have recently been approved that lead to improved quality of life and short-term life expectancy. There are many promising drugs directed against new and old therapeutic targets. In recent years, cell therapy based on genetically modified autologous or allogeneic T or NK cells has been of particular interest. However, there is still a long way to go since both the manufacturing time and the explosiveness of this type of disease, as well as its heterogeneity, make it difficult to choose the target and to process the cell product quickly enough to administer it before fatal progression of the disease.

The outcomes remain poor in the case of patients with AML who are of an advanced age and in the case of TP53-mutated AML.