Allogeneic hematopoietic stem cell transplantation (allo-HSCT) profoundly reshapes the gut microbiome (GM), yet age-related differences in this process remain incompletely understood. In this study, we analyzed stool samples from a cohort of pediatric and adult patients collected before allo-HSCT and at neutrophil engraftment to assess GM dynamics. We observed a significant reduction in alpha diversity post-HSCT across both age groups, with young patients displaying notably lower biodiversity. While GM composition varies among age ranges before transplantation, these distinctions largely disappeared at neutrophil engraftment, indicating a convergence toward a more uniform “transplant-specific” signature. This shift entailed a loss of health-associated, butyrate-producing taxa and a rise in potentially opportunistic bacteria (e.g., Enterococcaceae, Staphylococcaceae). Low pre-allo-HSCT GM diversity correlated with an increased risk of clinically significant acute graft-versus-host disease, overwhelming the age differences, underscoring the clinical relevance of maintaining a balanced microbiome before transplantation. Overall, our findings highlight the importance of age in shaping the pre-transplant GM and reveal how allo-HSCT-driven factors homogenize microbial communities among age ranges, offering insights for future microbiome-targeted interventions to improve transplant outcomes.

Clonal hematopoiesis of indeterminate potential (CHIP) refers to the phenomenon where a hematopoietic stem cell acquires fitness-increasing mutation(s), resulting in its clonal expansion. CHIP is frequently observed in multiple myeloma (MM) patients, and it is associated with a worse outcome. High-throughput amplicon-based single-cell DNA sequencing was performed on circulating CD34+ cells collected from twelve MM patients before autologous stem cell transplantation (ASCT). Moreover, in four MM patients, longitudinal samples either before or post-ASCT were collected. Single-cell sequencing and data analysis were assessed using the MissionBio Tapestri® platform, with a targeted panel of 20 leukemia-associated genes. We detected CHIP pathogenic mutations in 6/12 patients (50%) at the time of transplant. The most frequently mutated genes were TET2, EZH2, KIT, DNMT3A, and ASXL1. In two patients, we observed co-occurring mutations involving an epigenetic modifier (i.e., DNMT3A) and/or a gene involved in splicing machinery (i.e., SF3B1) and/or a tyrosine kinase receptor (i.e., KIT) in the same clone. Longitudinal analysis of paired samples revealed a positive selection of mutant high-fitness clones over time, regardless of their affinity with a major or minor sub-clone. Copy number analysis of the panel of all genes did not show any numerical alterations present in stem cell compartment. Moreover, we observed a tendency of CHIP-positive patients to achieve a suboptimal response to therapy compared to those without. A sub-clone dynamic of high-fitness mutations over time was confirmed.

Plasma metabolomics analysis was performed on 44 patients with relapsed/refractory B-cell non-Hodgkin lymphoma (r/r/BNHL) infused with approved CD19 chimeric antigen receptor (CAR) T-cell products at the time of pre-lymphodepletion (PLD) and at day +1 (D1), D7, and D30 after CAR T-cell infusion. At the PLD time point, a metabolic profile characterized by high lipoproteins and lactate and low glucose contributed to poor outcome prediction in association with high lactate dehydrogenase levels. At D1, higher plasma levels of lipid metabolism products and lower glucose and glycoproteins levels were observed in tisa-cel-compared to axi-cel-treated patients. At D30, discriminant analysis found two clusters in a subgroup of patients, one with complete response lasting 1 year after therapy, and another who relapsed within 1 year (relapsed >D30). This latter showed a higher content of N-GlycA, a known biomarker of systemic inflammation that is also correlated with C-reactive protein in our case setting of relapsing patients. Our data show complex metabolomic changes that track the evolution of the disease and drug activity in the first 30 days of CAR T-cell therapy. Conceivably, a pro-inflammatory drift may be linked to a forthcoming disease relapse in CAR T patients.

BACKGROUNDPredicting immune effector cell-associated neurotoxicity syndrome (ICANS) in patients infused with CAR T cells is still a conundrum. This complication, thought to be consequent to CAR T cell activation, arises a few days after infusion, when circulating CAR T cells are scarce and specific CAR T cell-derived biomarkers are lacking.METHODSCAR+ extracellular vesicle (CAR+EV) release was assessed in human CD19.CAR T cells cocultured with CD19+ target cells. A prospective cohort of 100 patients with B cell lymphoma infused with approved CD19.CAR T cell products was assessed for plasma CAR+EVs as biomarkers of in vivo CD19.CAR T cell activation. Human induced pluripotent stem cell-derived (iPSC-derived) neural cells were used as a model for CAR+EV-induced neurotoxicity.RESULTSIn vitro release of CAR+EVs occurs within 1 hour after target engagement. Plasma CAR+EVs are detectable 1 hour after infusion. A concentration greater than 132.8 CAR+EVs/μL at hour +1 or greater than 224.5 CAR+EVs/μL at day +1 predicted ICANS in advance of 4 days, with a sensitivity and a specificity outperforming other ICANS predictors. ENO2+ nanoparticles were released by iPSC-derived neural cells upon CAR+EV exposure and were increased in plasma of patients with ICANS.CONCLUSIONPlasma CAR+EVs are an immediate signal of CD19.CAR T cell activation, are suitable predictors of neurotoxicity, and may be involved in ICANS pathogenesis.TRIAL REGISTRATIONNCT04892433, NCT05807789.FUNDINGLife Science Hub-Advanced Therapies (financed by Health Ministry as part of the National Plan for Complementary Investments to the National Recovery and Resilience Plan [NRRP]: E.3 Innovative health ecosystem for APC fees and immunomonitoring).

Introduction: Immune effector cell-associated neurotoxicity syndrome (ICANS) is a life-threatening adverse effect of anti-CD19 chimeric antigen receptor (CAR) T-cell therapy that usually occurs within 5–7 days after cell infusion. Although several clinical and biochemical parameters have been associated with ICANS, it is still a matter of debate how to predict its onset at the patient level. We here tested the hypothesis that CAR-T cell derived extracellular vesicles (EV) carrying the engineered CAR protein and produced early after CAR-T cell activation can be used as predictive biomarker of ICANS. Purposely, we measured plasma CAR+ EV in lymphoma patients underwent anti-CD19 CAR-T cell therapy. Methods: Seventy-one patients with aggressive r/r B-cell lymphomas were admitted to the advanced cell therapy unit of IRCCS AOU of Bologna (NCT04892433) for anti-CD19 CAR-T cell infusion. Included patients received tisa-cel (n = 27), axi-cel (n = 34), or brexu-cel (n = 10) after a median number of 3 prior lines of treatment (2–11); median age was 62 years (19–76) and no patients had CNS disease at the time of CAR-T cell infusion. Twenty out of 71 patients (28%) had ICANS of any grade: 5 patients (7%) ICANS grade 1, 7 patients (10%) ICANS grade 2 and 8 patients (11%) ICANS grade ≥3 (3 patients ICANS grade 3, 3 patients ICANS grade 4 and 2 patients ICANS grade 5 with diffuse cerebral edema). ICANS was classified according to Lee et al. The median time from CAR-T cell infusion to ICANS onset was 5 days (3–12). Available plasma samples at day +1 after CAR-T cell infusion were analyzed for CAR+ EV by FACS analysis. Data analysis was performed with Prism software v9.1.3 (GraphPad). Results: CAR+ EV were already detectable +1 day after CAR-T cell infusion in 58 patients. The median onset of ICANS was at day +5 (3–12). Patients with ICANS of any grade showed higher CAR+ EV level compared to no-ICANS ones (p < 0.0001). CAR+ EV anticipated the median ICANS onset of 2 to 11 days. CAR+ EV ROC analysis showed that a concentration >187.5 CAR+ EV/μl at day +1 after infusion predicts ICANS onset with sensitivity of 100% and specificity of 83.33% (p < 0.0001). Conclusions: These findings lead us to hypothesize that the plasma level of CAR+ EV mirrors target engagement by CAR-T cells, and their massive release is related to ICANS. Thus, CAR+ EV level could be considered a putative early predictor of ICANS onset; further analyses in larger cohorts are warranted to confirm this finding. Keywords: Cellular therapies, Diagnostic and Prognostic Biomarkers Conflicts of interests pertinent to the abstract. P. L. Zinzani Consultant or advisory role: Secura Bio, Celltrion, Gilead, Janssen-Cilag, BMS, Servier, Sandoz, MSD, AstraZeneca, Takeda, Roche, EUSA Pharma, Kyowa Kirin, Novartis, ADC Therapeutics, Incyte, BeiGene Other remuneration: Speakers bureau: Celltrion, Gilead, Janssen-Cilag, BMS, Servier, MSD, AstraZeneca, Takeda, Roche, EUSA Pharma, Kyowa Kirin, Novartis, Incyte, BeiGene F. Bonifazi Consultant or advisory role: Novartis, Gilead

Graft versus host disease (GVHD) is a major complication of allogeneic hematopoietic stem cell transplantation (HSCT). Rabbit anti-T lymphocyte globulin (ATLG) in addition to calcineurin inhibitors and antimetabolites is a suitable strategy to prevent GVHD in several transplant settings. Randomized studies already demonstrated its efficacy in terms of GVHD prevention, although the effect on relapse remains the major concern for a wider use. Tailoring of ATLG dose on host characteristics is expected to minimize its side effects (immunological reconstitution, relapse, and infections). Here, day -6 to day +15 pharmacokinetics of active ATLG serum level was first assayed in an explorative cohort of 23 patients by testing the ability of the polyclonal serum to bind antigens on human leukocytes. Significantly lower levels of serum active ATLG were found in the patients who developed GVHD (ATLG_AUCCD45: 241.52 ± 152.16 vs. 766.63 +/- 283.52 (μg*day)/ml, p = 1.46e-5). Consistent results were obtained when the ATLG binding capacity was assessed on CD3+ and CD3+/CD4+ T lymphocytes (ATLG_AUCCD3: 335.83 ± 208.15 vs. 903.54 ± 378.78 (μg*day)/ml, p = 1.92e-4; ATLG_AUCCD4: 317.75 ± 170.70 vs. 910.54 ± 353.35 (μg*day)/ml, p = 3.78e-5. Concomitantly, at pre-infusion time points, increased concentrations of CD69+ extracellular vesicles (EVs) were found in patients who developed GVHD (mean fold 9.01 ± 1.33; p = 2.12e-5). Consistent results were obtained in a validation cohort of 12 additional ATLG-treated HSCT patients. Serum CD69+ EVs were mainly represented in the nano (i.e. 100 nm in diameter) EV compartment and expressed the leukocyte marker CD45, the EV markers CD9 and CD63, and CD103, a marker of tissue-resident memory T cells. The latter are expected to set up a host pro-inflammatory cell compartment that can survive in the recipient for years after conditioning regimen and contribute to GVHD pathogenesis. In summary, high levels of CD69+ EVs are significantly correlated with an increased risk of GVHD, and they may be proposed as a tool to tailor ATLG dose for personalized GVHD prevention.

Figure S2. Immunofluorescence analyses of 2 representative donor alloreactive NK cell clones expressing the KIR for which there is no class I ligand in the recipient as their only inhibitory receptor for self.

Disease relapse represents by far the most frequent cause of hematopoietic cell transplantation (HCT) failure. Patients with acute leukemia suffering relapse after HCT have limited conventional treatment options with little possibility of cure and represent, de facto, suitable candidates for the evaluation of novel cellular and biological-based therapies. Donor lymphocyte infusions (DLI) has been one of the first cellular therapies adopted to treat post HCT relapse of acute leukemia patients and still now, it is widely adopted in preemptive and prophylactic settings, with renewed interest for manipulated cellular products such as NK-DLI. The acquisition of novel biological insights into pathobiology of leukemia relapse are translating into the clinic, with novel combinations of target therapies and novel agents, helping delineate new therapeutical landscapes. Hypomethylating agents alone or in combination with novel drugs demonstrated their efficacy in pre-clinical models and controlled trials. FLT3 inhibitors represent an essential therapeutical instrument incorporated in post-transplant maintenance strategies. The Holy grail of allogeneic transplantation lies in the separation of graft-vs.-host disease from graft vs. tumor effects and after more than five decades, is still the most ambitious goal to reach and many ways to accomplish are on their way.

PURPOSE OF REVIEW:Several studies showed that age alone should not be used as an arbitrary parameter to exclude patients from allogeneic hematopoietic cell transplantation (HCT). The accessibility to allogeneic HCT programs for older patients with hematological diseases is growing up constantly. The Center for International Blood and Marrow Transplant Research has recently shown that over 30% of allogeneic HCT recipients are at least 60 years old and that nearly 4% are aged 70 or more. Historically, the use of allogeneic HCT among elderly patients has been limited by age restrictions, reflecting physicians' concerns regarding prohibitive transplant-related mortality and HCT-associated morbidity. RECENT FINDINGS:The introduction of reduced intensity/toxicity conditioning regimens has allowed transplant Centers to carry out allogeneic HCT on patients previously considered not ideal candidates. The integration of specific risk scores could lead to better capture mental and physical frailties of older patients. Older adults less frequently have available medically fit siblings, able to donate, so, unrelated donors, familial haploidentical donors or umbilical cord blood grafts could potentially abrogate such a difficulty, allowing the curative potential of allogeneic HCT. SUMMARY:The appropriate assessing of allogeneic HCT feasibility for elderly patients should be the resonate application of different clinical and biological principles.

Background T cells engineered to target CD19 antigen on neoplastic B cells represent the most striking example of CAR-T cell therapy. The success rate of this therapy is affected by several limitations: target antigen loss, and/or acquisition of a senescent/exhausted phenotype by CAR and non-CAR T cells. Case presentation We report on a patient affected by refractory Diffuse Large B-cell Lymphoma who was resistant to CAR T-cell therapy and to two cycles post CAR-T of pembrolizumab (PBZ) due to the evolution into a B-cell Hodgkin-like lymphoma. Owing to the CD30 expression and the Hodgkin-like phenotype, the patient was ultimately treated with Brentuximab-Vedotin and finally underwent remission. Upon PBZ treatment, 100% of circulating CAR-T + cells showed a persistent CD8 + senescent/exhausted phenotype, while an increase in the percentage of senescent cells was found in the non-CAR CD8 + T cells compartment. Conclusions PBZ is not able to reinvigorate exhausted CAR + T cells and to confer durable clinical response. We hypothesize that the phenomenon is due to the senescent phenotype of CAR + T cells, which did not allow PBZ-induced reactivation and proliferative rescue. The phenomenon, together with the loss of CAR-T target CD19 and the shift of non-CAR CD8 + T cells towards a senescent phenotype likely contributed to set up an immune landscape with poor antitumor capacity.

In chronic myeloid leukemia (CML), Aurora kinase A and Polo like kinase 1 (PLK1), two serine-threonine kinases involved in the maintenance of genomic stability by preserving a functional G2/M checkpoint, have been implicated in BCR::ABL1-independent resistance to the tyrosine kinase inhibitor (TKI) imatinib mesylate and in leukemic stem cell (LSC) persistence. It can be speculated that the observed deregulated activity of Aurora A and Plk1 enhances DNA damage, promoting the occurrence of additional genomic alterations contributing to TKI resistance and ultimately driving progression from chronic phase to blast crisis (BC). In this study, we propose a new therapeutic strategy based on the combination of Aurora kinase A or PLK1 inhibition with danusertib or volasertib, respectively, and WEE1 inhibition with AZD1775. Danusertib and volasertib used as single drugs induced apoptosis and G2/M-phase arrest, associated with accumulation of phospho-WEE1. Subsequent addition of the WEE1 inhibitor AZD1775 in combination significantly enhanced the induction of apoptotic cell death in TKI-sensitive and -resistant cell lines as compared to both danusertib and volasertib alone and to the simultaneous combination. This schedule indeed induced a significant increase of the DNA double-strand break marker γH2AX, forcing the cells through successive replication cycles ultimately resulting in apoptosis. Finally, combination of danusertib or volasertib+AZD1775 significantly reduced the clonogenic potential of CD34+ CML progenitors from BC patients. Our results may have implications for the development of innovative therapeutic approaches aimed to improve the outcomes of patients with multi-TKI-resistant or BC CML.

Recently, many reports were published supporting the clinical use of adoptively transferred natural killer (NK) cells as a therapeutic tool against cancer, including acute myeloid leukemia (AML). Our group demonstrated promising clinical response using adoptive immunotherapy with donor-derived alloreactive KIR-ligand-mismatched NK cells in AML patients. Moreover, the antileukemic effect was correlated with the dose of infused alloreactive NK cells (“functional NK cell dose”). Herein, we update the results of our previous study on a cohort of adult AML patients (median age at enrollment 64) in first morphological complete remission (CR), not eligible for allogeneic stem cell transplantation. After an extended median follow-up of 55.5 months, 8/16 evaluable patients (50%) are still off-therapy and alive disease-free. Overall survival (OS) and disease-free survival (DFS) are related with the dose of infused alloreactive NK cells (≥2 × 105/kg).

Context: Genetic/genomic instability is a hallmark of CML. SETD2, a histone methyltransferase that trimethylates histone H3 on K36 (H3K36me3), has recently demonstrated a crucial role in preserving genomic integrity by modulating DNA Mismatch Repair (MMR) and Homologous Recombination (HR) repair. By Western blotting (WB), we previously observed SETD2 and H3K36me3 loss (resulting from aberrant SETD2 turnover) in 85% of blast crisis (BC) CML patients but not in newly diagnosed chronic phase (CP) patients who will achieve optimal responses. Objectives: 1. To investigate whether SETD2 is involved in the maintenance of genetic/genomic stability in CML. 2. To assess whether SETD2 loss precedes or follows progression from CP to blast crisis BC. Materials: SETD2-proficient (LAMA84) and -deficient (KCL22) CML cell lines and primary patient samples (n=86) were studied. Results: To investigate whether SETD2/H3K36me3 loss impinges on the activation and proficiency of HR, we used UV rays to induce DNA damage in SETD2 siRNA-depleted LAMA 84 (SETD2-proficient) cells. Compared to control cells, cells silenced for SETD2 displayed a marked increase in γH2AX (a marker of DNA damage) and fewer RAD51 foci (markers of ongoing HR). Assessment of MMR proficiency is ongoing. To further confirm the role of SETD2 as a tumor suppressor implicated in maintaining genomic stability in CML, we transfected KCL22 (SETD2-deficient) cells with an ectopic SETD2 plasmid. Preliminary results showed that SETD2 re-expression induced a reduction in cell doubling time, an accumulation of cells at G1/S checkpoint and a significant reduction in clonogenic potential. Studies are ongoing to assess the effects on DNA damage repair pathways. We next wondered when during disease history SETD2/H3K36me3 loss occurs. WB analysis ofpaired (diagnosis/progression) samples from four CML patients suggested that patients who will progress still have intact and functional SETD2 at diagnosis. Additional analyses are ongoing to assess whether SETD2/H3K36me3 loss precedes, hence allows to predict, progression to BC. Conclusion: Loss of SETD2/H3K36me3 is a novel, BCR-ABL1-independent mechanism of genetic instability in CML. Further investigations are needed to establish to what extent SETD2/H3K36me3 loss contributes to (and may be predictive of) disease progression. Supported by AIRC project 23001. Genetic/genomic instability is a hallmark of CML. SETD2, a histone methyltransferase that trimethylates histone H3 on K36 (H3K36me3), has recently demonstrated a crucial role in preserving genomic integrity by modulating DNA Mismatch Repair (MMR) and Homologous Recombination (HR) repair. By Western blotting (WB), we previously observed SETD2 and H3K36me3 loss (resulting from aberrant SETD2 turnover) in 85% of blast crisis (BC) CML patients but not in newly diagnosed chronic phase (CP) patients who will achieve optimal responses. 1. To investigate whether SETD2 is involved in the maintenance of genetic/genomic stability in CML. 2. To assess whether SETD2 loss precedes or follows progression from CP to blast crisis BC. SETD2-proficient (LAMA84) and -deficient (KCL22) CML cell lines and primary patient samples (n=86) were studied. To investigate whether SETD2/H3K36me3 loss impinges on the activation and proficiency of HR, we used UV rays to induce DNA damage in SETD2 siRNA-depleted LAMA 84 (SETD2-proficient) cells. Compared to control cells, cells silenced for SETD2 displayed a marked increase in γH2AX (a marker of DNA damage) and fewer RAD51 foci (markers of ongoing HR). Assessment of MMR proficiency is ongoing. To further confirm the role of SETD2 as a tumor suppressor implicated in maintaining genomic stability in CML, we transfected KCL22 (SETD2-deficient) cells with an ectopic SETD2 plasmid. Preliminary results showed that SETD2 re-expression induced a reduction in cell doubling time, an accumulation of cells at G1/S checkpoint and a significant reduction in clonogenic potential. Studies are ongoing to assess the effects on DNA damage repair pathways. We next wondered when during disease history SETD2/H3K36me3 loss occurs. WB analysis ofpaired (diagnosis/progression) samples from four CML patients suggested that patients who will progress still have intact and functional SETD2 at diagnosis. Additional analyses are ongoing to assess whether SETD2/H3K36me3 loss precedes, hence allows to predict, progression to BC. Loss of SETD2/H3K36me3 is a novel, BCR-ABL1-independent mechanism of genetic instability in CML. Further investigations are needed to establish to what extent SETD2/H3K36me3 loss contributes to (and may be predictive of) disease progression. Supported by AIRC project 23001.