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In the last years, natural killer (NK) cell-based immunotherapy has emerged as a promising therapeutic approach for solid tumors and hematological malignancies. NK cells are innate lymphocytes with an array of functional competences, including anti-cancer, anti-viral, and anti-graft-vs.-host disease potential. The intriguing idea of harnessing such potent innate immune system effectors for cancer treatment led to the development of clinical trials based on the adoptive therapy of NK cells or on the use of monoclonal antibodies targeting the main NK cell immune checkpoints. Indeed, checkpoint immunotherapy that targets inhibitory receptors of T cells, reversing their functional blocking, marked a breakthrough in anticancer therapy, opening new approaches for cancer immunotherapy and resulted in extensive research on immune checkpoints. However, the clinical efficacy of T cell-based immunotherapy presents a series of limitations, including the inability of T cells to recognize and kill HLA-I tumor cells. For these reasons, new strategies for cancer immunotherapy are now focusing on NK cells. Blockade with NK cell checkpoint inhibitors that reverse their functional block may overcome the limitations of T cell-based immunotherapy, mainly against HLA-I tumor targets. Here, we discuss recent anti-tumor approaches based on mAb-mediated blocking of immune checkpoints (either restricted to NK cells or shared with T cells), used either as a single agent or in combination with other compounds, that have demonstrated promising clinical responses in both solid tumors and hematological malignancies.

Acute myeloid leukemia (AML), especially therapy-related (t-AML) or secondary AML (s-AML), presents complex therapeutic challenges. CPX-351, a liposomal formulation of cytarabine and daunorubicin, has demonstrated superior outcomes compared to standard 7 + 3 chemotherapy. However, optimal post-remission strategies are debated. This retrospective study evaluates the feasibility and efficacy of intermediate-dose ARA-C (IDAC), total dose of 8–9 g/m², following CPX-351 in 47 patients from three Italian centers. Median patient age was 69, with 64% having AML with myelodysplasia-related changes (MRC-AML). Based on the 2017 European LeukemiaNet (ELN) risk stratification, 8 patients were classified as favorable, 20 as intermediate, and 19 as adverse. The median overall survival (OS) was 21 months (IC95% 17–43), with 85% alive at 12 months and 48.4% at 24 months. Event-free survival (EFS) was 14.9 months (IC95% 11.7–28.2). Multivariate analyses identified adverse-risk ELN-2017 and MRD-positivity after CPX-351 as negative predictors for OS. IDAC was well tolerated, with manageable toxicities: neutropenic fever (27, grade 1–3) and mucositis (4, grade 2–3). Importantly, 70% of patients achieved stable or improved measurable residual disease (MRD) after consolidation. The study underscores IDAC as a viable consolidation strategy, especially for patients unable to receive further CPX-351 or awaiting transplant. Despite its retrospective nature and limited sample size, the findings suggest that IDAC may offer improved outcomes, including lower costs, compared to CPX-351.

Background L-asparaginase (L-ASP) is a key component of acute lymphoblastic leukemia (ALL) treatment, but its use in clinical practice raises challenges to clinicians due to a relatively high incidence of drug-related adverse events, mainly in adult patients. In the past years the use of ASP in adult population has been mainly limited due to a poor knowledge of its safety profile and to an approximate management of ASP-related toxicity. Recently the development of pediatric-inspired treatment protocols for adult ALL has led to a wider use of ASP and since 2010 in Italy three national treatment protocols including Pegylated asparaginase (Peg-ASP) have been sequentially developed for adolescents, young adults and adults with Philadelphia-negative (Ph-) ALL. Methods With the aim to better understand the approach adopted in Italian centers for the management and prevention of Peg-ASP toxicity in adult ALL and to provide practical, consensus-based recommendations, a board of 6 Italian clinicians, with known expertise in adult ALL, designed 41 consensus statements on current challenges on the management of Peg-ASP associated toxicity. A group of 19 clinical experts in the field then rated these statements using the 5-point Likert-type scale (1 = strongly disagree; 5 = strongly agree). Results The main Peg-ASP related issues identified by the board included: 1) clinician’s attitudes; 2) toxicity profile; 3) hypersensitivity reactions; 4) hepatic toxicity; 5) hepatic and/or metabolic toxicity; 6) hemorrhagic/thrombotic toxicity; 7) pancreatitis; 8) metabolic toxicity management and prevention; 9) activity levels monitoring. Overall, participants agreed on most statements, except those addressing the potential contraindications to the treatment with Peg-ASP, such as patients with a diagnosis of chronic liver disease or the subsequent administrations of the drug in patients who had previously developed chemical pancreatitis or severe metabolic toxicity. Participants agreed that adult patients with ALL should receive Peg-Asp because this drug is essential to improve treatment results. Conclusions The panel agreed that a critical evaluation of specific risk factors for each patient is crucial in order to reduce the risk of adverse events and specific advices in the management of Peg-ASP toxicities are reported.

The adoption of pediatric-inspired regimens for the treatment of Ph-negative acute lymphoblastic leukemia (ALL) in adults has improved prognosis. However, the feasibility of these intensive regimens in older patients is limited, due to the increased incidence of therapy-related side effects, including those related to asparaginase. In this sub-analysis carried out by the Campus ALL network, 90 ALL patients aged 55 or more (median age 59 years) homogeneously treated in real-life according to the GIMEMA LAL1913 program, were analyzed to evaluate the feasibility and tolerability of pegaspargase (PEG-ASP) treatment. Among the 90 patients analyzed, 86 (96%) received PEG-ASP at least in one of the first two courses (C1-C2) of chemotherapy and were evaluated for toxicity and outcome. In detail, 51 patients received PEG-ASP in both courses and 35 in either C1 or C2. The most common adverse event was hepatic toxicity (HT), with 38% of patients experiencing any grade of HT at C1 (HT grade ≥ 3, 19%) and 23% at C2 (HT grade ≥ 3, 9%). Additionally, HT at C1 was the primary reason for withholding PEG-ASP at C2. Coagulopathy was the second most frequent toxicity (any grade of toxicity in 26% of patients at C1 and in 20% at C2). No deaths directly related to PEG-ASP therapy were reported. The CR rate after C1 and C3 was 94% and 93%, respectively. MRD negativity rate was 40% and 68%, respectively. The OS and DFS probability at 3 years was 54% and 47%, respectively. PEG-ASP administration in older ALL patients is feasible, but HT is a concern, being the major cause of PEG-ASP interruption. Therefore, a dose adjustment, according to age and concomitant comorbidities, is advisable to balance PEG-ASP efficacy with its toxicity.

Natural killer (NK) cell-based adoptive immunotherapy in leukemia patients is an emerging field of interest based on clinical evidence of efficacy and safety. Elderly acute myeloid leukemia (AML) patients have been successfully treated with NK cells from HLA-haploidentical donors, especially when high amounts of alloreactive NK cells were infused. The aim of this study was comparing two approaches to define the size of alloreactive NK cells in haploidentical donors for AML patients recruited in two clinical trials with the acronym “NK-AML” (NCT03955848), and “MRD-NK”. The standard methodology was based on the frequency of NK cell clones capable of lysing the related patient-derived cells. The alternative approach consisted of the phenotypic identification of freshly derived NK cells expressing, as inhibitory receptors, only the inhibitory KIR(s) specific for the mismatched KIR-Ligand(s) (HLA-C1, HLA-C2, HLA-Bw4). However, in KIR2DS2 + donors and HLA-C1 + patients, the unavailability of reagents staining only the inhibitory counterpart (KIR2DL2/L3) may lead to an underestimated identification of the alloreactive NK cell subset. Conversely, in the case of HLA-C1 mismatch, the alloreactive NK cell subset could be overestimated due to the ability of KIR2DL2/L3 to recognize with low-affinity also HLA-C2. Especially in this context, the additional exclusion of LIR1-expressing cells might be relevant to refine the size of the alloreactive NK cell subset. We could also associate degranulation assays, using as effector cells IL-2 activated donor peripheral blood mononuclear cells (PBMC) or NK cells upon co-culture with the related patient target cells. The donor alloreactive NK cell subset always displayed the highest functional activity, confirming its identification accuracy by flow cytometry. Despite the phenotypic limitations and considering the proposed corrective actions, a good correlation was shown by the comparison of the two investigated approaches. In addition, the characterization of receptor expression on a fraction of NK cell clones revealed expected but also few unexpected patterns. Thus, in most instances, the quantification of phenotypically defined alloreactive NK cells from PBMC can provide data similar to the analysis of lytic clones, with several advantages, such as a shorter time to achieve the results and, perhaps, higher reproducibility/feasibility in many laboratories.

Immune checkpoint inhibitors (CI) have demonstrated clinical activity in Hodgkin Lymphoma (HL) patients relapsing after autologous stem cell transplantation (ASCT), although only 20% complete response (CR) rate was observed. The efficacy of CI is strictly related to the host immune competence, which is impaired in heavily pre-treated HL patients. Here, we aimed to enhance the activity of early post-ASCT CI (nivolumab) administration with the infusion of autologous lymphocytes (ALI). Twelve patients with relapse/refractory (R/R) HL (median age 28.5 years; range 18-65), underwent lymphocyte apheresis after first line chemotherapy and then proceeded to salvage therapy. Subsequently, 9 patients with progressive disease at ASCT received early post-transplant CI supported with four ALI, whereas 3 responding patients received ALI alone, as a control cohort. No severe adverse events were recorded. HL-treated patients achieved negative PET scan CR and 8 are alive and disease-free after a median follow-up of 28 months. Four patients underwent subsequent allogeneic SCT. Phenotypic analysis of circulating cells showed a faster expansion of highly differentiated NK cells in ALI plus nivolumab-treated patients as compared to control patients. Our data show anti-tumor activity with good tolerability of ALI + CI for R/R HL and suggest that this setting may accelerate NK cell development/maturation and favor the expansion of the “adaptive” NK cell compartment in patients with HCMV seropositivity, in the absence of HCMV reactivation.