Post-transplantation cyclophosphamide for tolerance induction in HLA-haploidentical bone marrow transplantation

Post-transplant cyclophosphamide or cell selection in haploidentical allogeneic hematopoietic cell transplantation?

BACKGROUND

One major limitation for broader applicability of allogeneic hematopoietic cell transplantation (allo-HCT) in the past was the lack of HLA-matched histocompatible donors. Preclinical mouse studies using T-cell depleted haploidentical grafts led to an increased interest in the use of ex vivo T-cell depleted (TCD) haploidentical allo-HCT. TCD grafts through negative (T-cell depletion) or positive (CD34+ cell selection) techniques have been investigated to reduce the risk of graft-versus-host disease (GVHD) given the known implications of alloreactive T cells. A more practical approach to deplete alloreactive T cells in vivo using high doses of cyclophosphamide after allografting has proved to be feasible in overcoming the HLA barrier. Such approach has extended allo-HCT feasibility to patients for whom donors could not be found in the past. Nowadays, haploidentical donors represent a common donor source for patients in need of an allo-HCT. The broad application of haploidentical donors became possible by understanding the importance of depleting alloreactive donor T cells to facilitate engraftment and reduce incidence and severity of GVHD. These techniques involve ex vivo graft manipulation or in vivo utilization of pharmacologic agents, notably post-transplant cyclophosphamide (PTCy).

DISCUSSION

While acknowledging that no randomized controlled prospective studies have been yet conducted comparing TCD versus PTCy in haploidentical allo-HCT recipients, there are two advantages that would favor the PTCy, namely ease of application and lower cost. However, emerging data on adverse events associated with PTCy including, but not limited to cardiac associated toxicities or increased incidence of post-allograft infections, and others, are important to recognize.

Post-transplantation cyclophosphamide and cyclosporine A versus methotrexate and cyclosporine A for graft-versus-host disease prophylaxis after allogeneic peripheral stem cell transplantation in adult acute myeloid leukemia patients

BACKGROUND

Different prophylactic protocols are available for preventing graft-versus-host disease (GVHD) after matched sibling donor (MSD) allogeneic hematopoietic cell transplantation (allo-HCT). This study aimed to compare the effectiveness of post-transplantation cyclophosphamide plus cyclosporine A (PT-CY/CSA) versus methotrexate plus CSA (MTX/CSA) as GVHD prophylaxis protocols in adult acute myeloid leukemia (AML) patients who received peripheral blood stem cells (PBSC) from fully matched donors.

METHODS

The 1-year outcomes of 89 patients treated with PT-CY/CSA and 90 patients treated with MTX/CSA who had MSD allo-HCT for AML using unmanipulated mobilized PBSC were examined and compared.

RESULTS

The cumulative incidence of acute GVHD at 100 days was considerably lower in the PT-CY/CSA group (4% vs 19.3%, p = 0.002), however there were no statistically significant difference in the cumulative incidence of chronic GVHD at 1-year (19.6% vs 37.4%, p = 0.053). Significant delays in neutrophil and platelet engraftments were reported in the PT-CY/CSA group (17 vs 12 days) and (13 vs 12 days), respectively (p < 0.001). The cumulative incidences of relapse (19.1% vs 13.7%, p = 0.470), overall survival (79.1% vs 77.3%, p = 0.986), non-relapse mortality (16.5% vs 16.8%, p = 0.837), and the GVHD and relapse-free survival (GRFS) (53.7% vs 46.6%, p = 0.478) did not differ statistically at 1-year.

CONCLUSION

PT-CY/CSA demonstrated a significant decrease in the rate of acute GVHD. However, it was associated with engraftment delay.

A Tender Reduced-Intensity Conditioning for the Unfit: A Novel 4 Gy Total Body Irradiation-Based Conditioning Followed by Two-Step Haploidentical Stem Cell Transplant, Results of a Prospective Trial

Allogeneic hematopoietic stem cell transplant (HSCT) remains the only potentially curative treatment for many hematologic malignancies (HM). We previously developed a two-step approach that separates the lymphoid and myeloid portions of the graft, allowing a consistent T cell dosing and sparing the stem cells from the effect of post-transplant cyclophosphamide (CY). The two-step approach demonstrated safety and efficacy in patients treated with myeloablative and reduced-intensity conditioning. Here, we extended our two-step platform to older and less fit patients and explored the effects of using a high dose of T cells on disease relapse and transplant outcomes. Thirty-four patients with HM were treated. Median age was 68 years old and included a minority population constituting 32%. Eighty-two percent had a hematopoietic cell transplantation comorbidity index score ≥3. Ninety-one percent were haploidentical, and the rest were matched-related donor HSCT. Following administration of fludarabine and 2 Gy total body irradiation (TBI) (13 patients) or 4 Gy TBI (21 patients) conditioning regimen, a fixed dose of 2 × 108/kg CD3+ T cells was given, followed 2 days later by CY, then infusion of CD34-selected stem cells. Overall survival (OS) was 70% at 1 year and 48% at 3 years. The cumulative incidence (CI) of non-relapse mortality (NRM) and relapse were 22% and 33% at 3 years. However, the CI of relapse was much lower for patients treated with 4 Gy TBI versus those treated with 2 Gy TBI (11% versus 54%, P = .045), while NRM was similar (23% versus 15%, P = .399). This contributed to a high OS of 64% in patients who received 4 Gy TBI-based conditioning at 3 years, with median OS not reached, although this was not statistically significant (P = .68). The median time to neutrophil and platelet recovery was 12 and 17 days, respectively. The CI of grade II acute graft-versus-host-disease (aGVHD) was 22% and 26% at 100 days and 6 months, respectively. The CI of chronic GVHD (cGVHD) was 7.5% at 3 years. There was no grade III or IV aGVHD, no severe cGVHD, and no deaths attributable to GVHD. In conclusion, the two-step approach HSCT demonstrated a low disease relapse rate and high survival in patients treated with 4 Gy TBI-based conditioning, despite a generally older and more medically compromised patient population.

Current Approaches for the Prevention and Treatment of Acute and Chronic GVHD

Whereas aGVHD has strong inflammatory components, cGVHD displays autoimmune and fibrotic features; incidence and risk factors are similar but not identical; indeed, the aGVHD is the main risk factor for cGVHD. Calcineurin Inhibitors (CNI) with either Methotrexate (MTX) or Mycophenolate (MMF) still represent the standard prophylaxis in HLA-matched allogeneic stem cell transplantation (HSCT); other strategies focused on ATG, Post-Transplant Cyclophosphamide (PTCy), Abatacept and graft manipulation. Despite the high rate, first-line treatment for aGVHD is represented by corticosteroids, and Ruxolitinib is the standard second-line therapy; investigational approaches include Microbiota transplant and the infusion of Mesenchymal stem cells. GVHD is a pleiotropic disease involving any anatomical district; also, Ruxolitinib represents the standard for steroid-refractory cGVHD in this setting. It is a pleiotropic disease involving any anatomical district; also, Ruxolitinib represents the standard for steroid-refractory cGVHD in this setting. Extracorporeal Photopheresis (ECP) is still an option used for steroid refractoriness or to achieve a steroid-sparing. For Ruxolitinib-refractory cGVHD, Belumosudil and Axatilimab represent the most promising agents. Bronchiolitis obliterans syndrome (BOS) still represents a challenge; among the compounds targeting non-immune effectors, Alvelestat, a Neutrophil elastase inhibitor, seems promising in BOS. Finally, in both aGVHD and cGVHD, the association of biological markers with specific disease manifestations could help refine risk stratification and the availability of reliable biomarkers for specific treatments.

Sinusoidal Obstruction Syndrome/Veno-Occlusive Disease after Unmanipulated Haploidentical Hematopoietic Stem Cell Transplantation with Post-Transplantation Cyclophosphamide: A Study on Behalf of the Spanish Hematopoietic Stem Cell Transplantation and Cellular Therapy Group (GETH)

Sinusoidal obstruction syndrome/veno-occlusive disease (SOS/VOD) is a life-threatening complication after both autologous and allogeneic hematopoietic stem cell transplantation (HSCT). However, its characterization after haploidentical HSCT (haplo-HSCT) with post-transplantation cyclophosphamide (PT-Cy) is scarce. This study aimed to describe characteristics and outcomes of patients with SOS/VOD after haplo-HSCT with PT-Cy. We conducted a retrospective study of 797 patients undergoing a haplo-HSCT with PT-Cy between 2007 and 2019 in 9 centers in Spain. SOS/VOD was defined according to modified Seattle, Baltimore, or revised European Society for Blood and Marrow Transplantation (EBMT) criteria. Severity was graded retrospectively according to revised EBMT severity criteria into 4 categories: mild, moderate, severe, and very severe. From a total of 797 haplo-HSCTs performed, 46 patients (5.77%) were diagnosed with SOS/VOD at a median of 19 days (range, 4 to 84 days) after transplantation. Based on revised EBMT severity criteria, the SOS/VOD cases were classified as mild (n = 4; 8.7%), moderate (n = 10; 21.7%), severe (n = 12; 26.1%), and very severe (n = 20; 43.5%). Overall, 30 patients (65%) achieved SOS/VOD complete response, 25 (83%) of whom were treated with defibrotide. Twenty patients (43%) died before day +100 post-HSCT. Death was attributed to SOS/VOD in 11 patients, and 5 patients died of other causes without resolution of SOS/VOD. The incidence of SOS/VOD after haplo-HSCT with PT-Cy was comparable to those reported after HLA-identical HSCT series. Most of the patients developed very severe SOS/VOD according to revised EBMT severity criteria. Despite a promising SOS/VOD complete response (CR) rate (65%), 100-day mortality remained high (43%), indicating that further improvement in the management of this potentially fatal complication is needed.

Graft Versus Host Disease Prophylaxis in Matched Donor Stem Cell Transplantation: Post-transplantation Cyclophosphamide Combinations Versus Methotrexate/Tacrolimus

BACKGROUND

The use of post-transplant cyclophosphamide (PTCy) is highly effective in preventing graft versus host disease (GVHD) for haploidentical allogeneic hematopoietic stem cell transplantation (allo-HSCT). There is limited data on the role of PTCy as GVHD prophylaxis in matched-sibling and fully matched-unrelated donor (MSD/MUD) allo-HSCT.

METHODS

Our single-center retrospective study aims to compare outcomes of PTCy alone or in combination with mycophenolate mofetil and tacrolimus (PTCy/MMF/TAC) relative to methotrexate and tacrolimus (MTX/TAC). The primary endpoint of our study was GVHD-free, relapse free survival (GRFS). Secondary endpoints were overall survival (OS), disease free survival (DFS), and incidence of severe acute and chronic GVHD. We identified 74 adult patients who underwent MSD/MUD allo-HSCT at our institution from 2015 to 2023.

RESULTS

Within our cohort, 33.8% (n = 25) received MTX/TAC, while 54.0% (n = 40) received PTCy/MMF/TAC, and 12.2% (n = 9) received PTCy alone. Patients receiving PTCY had the longest time to neutrophil engraftment relative to MTX/TAC (15 days vs. 12 days, P = .010). PTCy/MMF/TAC was associated with improved GRFS relative to MTX/TAC (hazard ratio [HR] = HR 0.42, 95% CI 0.19-0.93, P = .031), which persisted when controlling for age. Incidence of chronic GVHD was lower in the PTCy/MMF/TAC group compared to MTX/TAC (1-year 9.0% vs. 30.1%, HR 0.19, 95% CI 0.06-0.59, P = .005). However, OS and DFS were comparable across all groups.

CONCLUSIONS

Our results demonstrate decreased rates of severe chronic GVHD resulting in improved GRFS when using PTCy/TAC/MTX as GVHD prophylaxis compared to MTX/TAC in MSD/MUD.

Real-Life Management of FLT3-Mutated AML: Single-Centre Experience over 24 Years

We analyzed 140 patients with a median age of 51 years; 21% had WBC ≥ 100 × 109/L, and 52% had an NPM1 co-mutation. Until 2018, 101 patients received chemotherapy; thereafter, 39 received 3+7+midostaurin. The overall CR rate was 64%, higher in NPM1 mutant patients (73%). Univariate analysis showed that NPM1 mutation (p = 0.032) and WBC < 100 × 109/L (p = 0.013) positively influenced the response, with a trend for FLT3i administration (p = 0.052). Multivariate analysis confirmed WBC count as an independent prognostic factor (p = 0.017). In CR1, 41/90 patients underwent allogeneic and 18 autologous transplantation. The median EFS was 1.1 vs. 1.6 years in autografted and allografted patients, respectively (p = 0.9). The one-year non-relapse mortality was 0.00% for autologous and 28% for allogeneic transplants (p = 0.007); CIR at 1 and 3 years was higher in autologous transplants (39% vs. 15% and 57% vs. 21%, p = 0.004). The median survival was not reached in the FLT3i group. Overall, 69 patients received stem cell transplantation (18 autologous, 51 allogeneic). Post-transplant FLT3i was resumed in eight patients, all alive after a median of 65 months. Allogeneic transplantation is crucial in FLT3-mutated AML, but the next challenge will be to identify which patients can benefit from transplants in CR1 and in which to intensify post-transplant therapy.

Haploidentical transplantation in primary refractory/relapsed secondary vs de novo AML: from the ALWP/EBMT

ABSTRACT

We compared the outcomes of haploidentical stem cell transplantation (haplo-HSCT) with posttransplant cyclophosphamide (PTCy) in 719 patients with primary refractory (PR) or first relapse (Rel) secondary acute myeloid leukemia (sAML; n = 129) vs those with de novo AML (n = 590), who received HSCT between 2010 and 2022. A higher percentage of patients with sAML vs de novo AML had PR disease (73.6% vs 58.6%; P = .002). In 81.4% of patients with sAML , the antecedent hematological disorder was myelodysplastic syndrome. Engraftment was 83.5% vs 88.4% in sAML and de novo AML, respectively (P = .13). In multivariate analysis, haplo-HSCT outcomes did not differ significantly between the groups: nonrelapse mortality hazard ratio (HR), 1.38 (95% confidence interval [CI], 0.96-1.98; P = .083), relapse incidence HR, 0.68 (95% CI, 0.4.7.-1.00; P = .051). The HRs for leukemia-free survival, overall survival, and graft-versus-host disease (GVHD)-free, and GVHD and relapse-free survival were 0.99 (95% CI, 0.76-1.28; P = .94), 0.99 (95% CI, 0.77-1.29; P = .97), and 0.99 (95% CI, 0.77-1.27; P = .94), respectively. We conclude that outcomes of haplo-HSCT with PTCy are not different for PR/Rel sAML in comparison with PR/Rel de novo AML, a finding of major clinical importance.

Reduced Dose of Post-Transplant Cyclophosphamide with Tacrolimus for the Prevention of Graft-versus-Host Disease in HLA-Matched Donor Peripheral Blood Stem Cell Transplants: A Prospective Pilot Study

PTCY 50 mg/kg/day on days +3/+4 is an excellent strategy to prevent GVHD. However, its use is associated with adverse outcomes such as delayed engraftment, increased risk of infection, and cardiac complications. This pilot study evaluates the efficacy and toxicity of a reduced dose of PTCY (40 mg/kg/day) combined with tacrolimus in 22 peripheral blood HLA-matched alloHSCT patients. At day +100, the cumulative incidences of grade II-IV and III-IV acute GVHD were 18.2% and 4.5%, respectively. No grade IV acute GVHD or steroid-refractory disease was observed. The cumulative incidences of all-grade and moderate-severe chronic GVHD at 1-year were 11.4% and 6.4%, respectively. No patient died from transplant-related complications. Two-year OS and RFS were 77.1% and 58.3%, respectively. All patients engrafted, with neutrophil and platelet recovery occurring at a median of 15 (IQR 14-16) and 16 days (IQR 12-23), respectively. The cumulative incidences of bloodstream bacterial infections, polyomavirus BK hemorrhagic cystitis, HHV6 reactivation, CMV reactivation, and fungal infections were 13.6%, 9.1%, 9.1%, 4.6%, and 6%, respectively. Only one early cardiac event was observed. These results suggest that PTCY 40 mg/kg/day on a +3/+4 schedule provides adequate immunosuppression to allow for engraftment and prevent clinically significant GVHD with a low toxicity profile.

Post-transplant cyclophosphamide, calcineurin inhibitor, and mycophenolate mofetil compared to anti-thymocyte globulin, calcineurin inhibitor, and methotrexate combinations as graft-versus-host disease prophylaxis post allogeneic stem cell transplantation from sibling and unrelated donors in patients with acute myeloid leukemia: a study on behalf of the Acute Leukemia Working Party of the European Society for Blood and Marrow Transplantation

Post-transplant cyclophosphamide plus calcineurin inhibitor (CNI)(tacrolimus or cyclosporine A) plus mycophenolate mofetil (PTCy/TAC or CSA/MMF) and anti-thymocyte globulin plus CNI (tacrolimus or cyclosporine A) plus methotrexate (ATG/TAC or CSA/MTX) are common graft-versus-host disease (GVHD) prophylaxis regimens. We compared the two regimens in patients with acute myeloid leukemia (AML) undergoing allogeneic transplantation from matched siblings or unrelated donors. 402 received PTCy/TAC or CSA/MMF and 5648 received ATG/TAC or CSA/MTX. Patients in the PTCy-based group were younger (48.7 vs. 51.5 years, p = 0.024) and there was a higher frequency of patient cytomegalovirus seropositivity and female donor to male patient combination in this group (77.8% vs. 71.8%, p = 0.009 and 18.4% vs. 14.4%, p = 0.029, respectively). More patients in the PTCy-based group received reduced-intensity conditioning (51.5% vs. 41%, p < 0.0001). No differences were observed in the incidence of acute GVHD grade II-IV and III-IV (21.2% vs. 20.4%, p = 0.92 and 8.1% vs. 6%, p = 0.1) or 2-year total and extensive chronic GVHD (33.7% vs. 30%, p = 0.09 and 10.7% vs. 11.2%, p = 0.81) between the groups. In the multivariate analysis, all transplant outcomes did not differ between the groups. PTCy/CNI/MMF and ATG/CNI/MTX are alternative regimens for GVHD prophylaxis in AML patients.

Calcineurin inhibition rescues alloantigen-specific central memory T cell subsets that promote chronic GVHD

Calcineurin inhibitors (CNIs) constitute the backbone of modern acute graft-versus-host disease (aGVHD) prophylaxis regimens but have limited efficacy in the prevention and treatment of chronic GVHD (cGVHD). We investigated the effect of CNIs on immune tolerance after stem cell transplantation with discovery-based single-cell gene expression and T cell receptor (TCR) assays of clonal immunity in tandem with traditional protein-based approaches and preclinical modeling. While cyclosporin and tacrolimus suppressed the clonal expansion of CD8+ T cells during GVHD, alloreactive CD4+ T cell clusters were preferentially expanded. Moreover, CNIs mediated reversible dose-dependent suppression of T cell activation and all stages of donor T cell exhaustion. Critically, CNIs promoted the expansion of both polyclonal and TCR-specific alloreactive central memory CD4+ T cells (TCM) with high self-renewal capacity that mediated cGVHD following drug withdrawal. In contrast to posttransplant cyclophosphamide (PT-Cy), CSA was ineffective in eliminating IL-17A-secreting alloreactive T cell clones that play an important role in the pathogenesis of cGVHD. Collectively, we have shown that, although CNIs attenuate aGVHD, they paradoxically rescue alloantigen-specific TCM, especially within the CD4+ compartment in lymphoid and GVHD target tissues, thus predisposing patients to cGVHD. These data provide further evidence to caution against CNI-based immune suppression without concurrent approaches that eliminate alloreactive T cell clones.

Reduced Cytokine Release Syndrome and Improved Outcomes with Earlier Immunosuppressive Therapy in Haploidentical Stem Cell Transplantation

The optimal timing of immunosuppression and post-transplantation cyclophosphamide (PTCy) in haploidentical hematopoietic stem cell transplantation (haplo-HSCT) is unknown. However, cytokine release syndrome (CRS) following haplo-HSCT is associated with worse transplantation outcomes, and the incidence of CRS may be affected by the timing of immunosuppression and PTCy. In this study, we compared CRS and other transplantation outcomes in 2 cohorts receiving different immunosuppression and PTCy schedules following haplo-HSCT. This was a retrospective cohort study of 91 patients who underwent haplo-HSCT at the Intermountain Health Blood and Marrow Transplant Program. The original or standard haplo-HSCT GVHD prophylaxis regimen included PTCy on days +3 and +4, with mycophenolate mofetil (MMF) and tacrolimus starting on day +5. The modified regimen adopted in November 2020 changed PTCy to days +3 and +5, with earlier introduction of tacrolimus and MMF, on day -1 and day 0, respectively. Grade ≥1 CRS occurred in 32% of patients in the modified regimen, in 82% of patients in the standard regimen (P <.0001), and 65% overall. Likewise, grade ≥2 CRS was lower with the modified regimen (16% versus 57%; P = .0002). The mean duration of CRS symptoms was longer with the standard regimen (3.14 days versus 1.44 days; P = .0003). The incidence of acute graft-versus-host disease grade III-IV or extensive chronic GVHD (cGVHD) at 1 year was lower in the modified regimen (6% versus 32%; P = .0068). No differences between the standard and modified regimens were seen in overall survival, relapse, or GVHD-free relapse-free survival (GRFS), although there appeared to be a trend toward improved GRFS with the modified regimen. Post hoc analysis comparing GRFS in patients with CRS and those without CRS found that CRS was associated with lower GRFS at 1 year (36% versus 63%; P = .0138). The duration of broad-spectrum antibiotic therapy was decreased by 7.5 days (P = .0017) and the time to hospital discharge was reduced by 7.1 days (P = .0241) with the modified regimen. This is the first analysis to evaluate and find a difference in CRS with early initiation of immunosuppressive therapy in haplo-HSCT. Our results suggest that this modified GVHD regimen benefits patients by reducing CRS and high-grade GVHD compared to the standard PTCy-based GVHD prophylaxis regimen in haplo-HSCT. Additionally, this novel regimen did not appear to negatively impact outcomes.

Allogeneic Hematopoietic Cell Transplantation in Advanced Systemic Mastocytosis: A retrospective analysis of the DRST and GREM registries

We identified 71 patients with AdvSM (aggressive SM [ASM], SM with an associated hematologic neoplasm [SM-AHN, e.g., acute myeloid leukemia, SM-AML], mast cell leukemia [MCL]) in two national registries (DRST/GREM) who received an allogeneic hematopoietic cell transplantation (alloHCT) performed in Germany from 1999-2021. Median overall survival (OS) of ASM/SM-AHN (n = 30, 45%), SM-AML (n = 28, 39%) and MCL ± AHN (n = 13, 19%) was 9.0, 3.3 and 0.9 years (P = 0.007). Improved median OS was associated with response of SM (17/41, 41%; HR 0.4 [0.2-0.9], P = 0.035) and/or of AHN (26/43, 60%, HR 0.3 [0.1-0.7], P = 0.004) prior to alloHCT. Adverse predictors for OS included absence of KIT D816V (10/61, 16%, HR 2.9 [1.2-6.5], P < 0.001) and a complex karyotype (9/60, 15%, HR 4.2 [1.8-10.0], P = 0.016). HLA-match, conditioning type or transplantation at centers reporting above-average alloHCTs (≥7) had no impact on OS. Taking into account competing events at years 1, 3 and 5, relapse-related mortality and non-relapse mortality rate were 15%/23%, 20%/30% and 23%/35%, respectively. Irrespective of subtype, subsequent treatment response was achieved in 13/30 (43%) patients and was highest on midostaurin/avapritinib (7/9, 78%). We conclude that outcome of alloHCT in AdvSM is more affected by disease phenotype and treatment response prior to transplant than by transplant characteristics.

Incidence and Role of Recipient-Specific Antibodies in Allogeneic Hematopoietic Cell Transplantation from Mismatched Related Donors

High titer of donor-specific antibodies (DSAs) increases the risk of graft rejection after mismatched related hematopoietic cell transplantation (HCT). There are no data regarding the incidence of anti-HLA recipient-specific antibodies (RSAs) and their role after transplantation. Here we aimed to identify the incidence of RSAs in a mismatched related hematopoietic cell donor population and their possible impact on immune-mediated complications, such as acute graft-versus-host disease (aGVHD), and complications resulting from endothelial injury, such as transplantation-associated thrombotic microangiopathy (TA-TMA) and veno-occlusive disease (VOD). We prospectively analyzed the incidence of anti-HLA antibodies in 28 mismatched related pairs of recipients and their donors who underwent HCT at our center between 2020 and 2022. In positive samples screened for anti-HLA class I and/or II antibodies, the specificity of the HLA antibodies was analyzed. All recipients had a hematologic malignancy and received a myeloablative conditioning regimen and immunosuppression consisting of post-transplantation cyclophosphamide, tacrolimus, and mycophenolate mofetil. Patients were tested for TA-TMA and aGVHD development during routine post-transplantation visits up to 100 days post-transplantation. We used modified Jodele criteria for TA-TMA diagnosis, and based aGVHD grading on the MAGIC criteria. VOD was assessed using the European Society for Blood and Marrow Transplantation. Anti-HLA antibodies were detected in 12 donors (43%) and in 9 recipients (32%). There were no significant differences between donors and recipients according to age (median, 42 years [range, 17 to 69 years] versus 39 years [range, 8 to 68 years]), sex, or pregnancy history. No transfusion history was noted in the donor group (P < .05). RSA antibodies were present more often than DSAs and were detected in 9 out of 12 (75%) anti-HLA-positive donors and in only 2 out of 9 (22%) recipients, respectively (P < .05). During the follow-up, 11 patients (39%) developed aGVHD, including grade I-II in 9 (32%) and grade III-IV in 2 (7%). Twelve patients (43%) met the criteria for TA-TMA, and only 1 patient (3.5%) was diagnosed with VOD by day 100 post-HCT. RSAs were detected significantly more often in the TA-TMA group; among 12 patients diagnosed with TA-TMA, 7 (58%) had RSAs (P < .05). We did not find a correlation between RSAs and aGVHD. The patient with VOD did not have an RSA-positive donor. There was no difference in membrane attack complex (MAC) concentration in the RSA-positive group on day 30 and day 60 post-HCT; however, there was a trend toward higher MAC concentration in the RSA-positive group on day 100 (median, 912 ng/mL [range, 788 to 1120 ng/mL] versus 616 ng/mL [range, 352 to 1244 ng/mL]; P = .055). Patients with RSA suffered more often from platelet and red blood cell decreases or transfusion refractoriness, and increased lactate dehydrogenase activity was observed in all RSA-positive cases. The donor immune status and the presence of RSA may be associated with higher rates of TA-TMA in mismatched HCT recipients. Antibody-mediated complement activation might be an additional factor influencing TA-TMA occurrence.

Haploidentical transplant with posttransplant cyclophosphamide vs matched related and unrelated donor transplant in acute myeloid leukemia and myelodysplastic neoplasm

Hematopoietic cell transplantation from haploidentical donors (haploHCT) has facilitated treatment of AML and MDS by increasing donor availability and became more feasible since the introduction of post-transplant cyclophosphamide (ptCY). In our single-center retrospective analysis including 213 patients with AML or MDS, we compare the outcome of haploHCT (n = 40) with ptCY with HCT from HLA-identical MRD (n = 105) and MUD (n = 68). At 2 years after transplantation, overall survival (OS) after haploHCT was not significantly different (0.59; 95% confidence interval 0.44-0.79) compared to MRD (0.77; 0.67-0.88) and MUD transplantation (0.72; 0.64-0.82, p = 0.51). While progression-free survival (PFS) was also not significantly different (haploHCT: 0.60; 0.46-0.78, MRD: 0.55; 0.44-0.69, MUD: 0.64; 0.55-0.74, p = 0.64), non-relapse mortality (NRM) was significantly higher after haploHCT (0.18; 0.08-0.33) vs. MRD (0.029; 0.005-0.09) and MUD (0.06; 0.02-0.12, p < 0.05). Higher NRM was mainly caused by a higher rate of fatal infections, while deaths related to GvHD or other non-relapse reasons were rare in all groups. As most fatal infections occurred early and were bacterial related, one potential risk factor among many was identified in the significantly longer time to neutrophil engraftment after haploHCT with a median of 16 days (interquartile range; 14.8-20.0) vs. 12 days (10.0-13.0) for MRD and 11 days (10.0-13.0) for MUD (p = 0.01).

The two-step approach to allogeneic hematopoietic stem cell transplantation

Allogeneic hematopoietic stem cell transplantation (HSCT) provides the only potentially curative option for multiple hematological conditions. However, allogeneic HSCT outcomes rely on an optimal balance of effective immune recovery, minimal graft-versus-host disease (GVHD), and lasting control of disease. The quest to attain this balance has proven challenging over the past few decades. The two-step approach to HSCT was conceptualized and pioneered at Thomas Jefferson University in 2005 and remains the main platform for allografting at our institution. Following administration of the transplant conditioning regimen, patients receive a fixed dose of donor CD3+ cells (HSCT step one-DLI) as the lymphoid portion of the graft on day -6 with the aim of optimizing and controlling T cell dosing. Cyclophosphamide (CY) is administered after the DLI (days -3 and -2) to induce donor-recipient bidirectional tolerance. On day 0, a CD34-selected stem cell graft is given as the myeloid portion of the graft (step two). In this two-step approach, the stem cell graft is infused after CY tolerization, which avoids exposure of the stem cells to an alkylating agent, allowing rapid count recovery. Here, the two-step platform is described with a focus on key results from studies over the past two decades. Finally, this review details lessons learned and current strategies to optimize the graft-versus-tumor effect and limit transplant-related toxicities.

Posttransplant cyclophosphamide vs tacrolimus-based GVHD prophylaxis: lower incidence of relapse and chronic GVHD

The ability of posttransplant cyclophosphamide (PTCY) to facilitate haploidentical transplantation has spurred interest in whether PTCY can improve clinical outcomes in patients with HLA-matched unrelated donors undergoing peripheral blood stem cell transplantation (PBSCT). We investigated our institutional experience using PTCY-based graft-versus-host disease (GVHD) prophylaxis compared with conventional tacrolimus-based regimens. We compared overall survival, progression-free survival (PFS), relapse, nonrelapse mortality, and acute and chronic GVHD in 107 adult patients receiving a PTCY-based regimen vs 463 patients receiving tacrolimus-based regimens for GVHD prophylaxis. The 2 cohorts were well balanced for baseline characteristics except that more patients in the PTCY cohort having received 7-of-8-matched PBSCT. There was no difference in acute GVHD. All-grade chronic GVHD and moderate-to-severe chronic GVHD were substantially reduced in patients receiving PTCY compared with in those receiving tacrolimus-based regimens (2-year moderate-to-severe chronic GVHD: 12% vs 36%; P < .0001). Recipients of PTCY-based regimens also had a lower incidence of relapse compared with recipients of tacrolimus-based regimens (25% vs 34% at 2-years; P = .027), primarily in patients who received reduced intensity conditioning. This led to improved PFS in the PTCY cohort (64% vs 54% at 2 years; P = .02). In multivariable analysis, the hazard ratio was 0.59 (P = .015) for PFS and the subdistribution hazard ratio was 0.27 (P < .0001) for moderate-to-severe chronic GVHD and 0.59 (P = .015) for relapse. Our results suggest that PTCY prophylaxis is associated with lower rates of relapse and chronic GVHD in patients who receive HLA-matched unrelated donor PBSCT.

Tocilizumab for Cytokine Release Syndrome Management After Haploidentical Hematopoietic Cell Transplantation With Post-Transplantation Cyclophosphamide-Based Graft-Versus-Host Disease Prophylaxis

Cytokine release syndrome (CRS) is a common complication after haploidentical hematopoietic cell transplantation (HaploHCT). Severe CRS after haploHCT leads to higher risk of non-relapse mortality (NRM) and worse overall survival (OS). Tocilizumab (TOCI) is an interleukin-6 receptor inhibitor and is commonly used as first-line for CRS management after chimeric antigen receptor T cell therapy, but the impact of TOCI administration for CRS management on Haplo HCT outcomes is not known. In this single center retrospective analysis, we compared HCT outcomes in patients treated with or without TOCI for CRS management after HaploHCT with post-transplantation cyclophosphamide- (PTCy-) based graft-versus-host disease (GvHD) prophylaxis. Of the 115 patients eligible patients who underwent HaploHCT at City of Hope between 2019 to 2021 and developed CRS, we identified 11 patients who received tocilizumab for CRS management (TOCI). These patients were matched with 21 patients who developed CRS but did not receive tocilizumab (NO-TOCI) based on age at the time of HCT (≤64 years or >65 years or older), conditioning intensity (myeloablative versus reduced-intensity/nonmyeloablative), and CRS grading (1, 2, versus 3-4). Instead of 22 controls, we chose 21 patients because there was only 1 control matched with 1 TOCI treatment patient in 1 stratum. With only 11 patients in receiving tocilizumab for CRS treatment, matching with 21 patients who developed CRS but did not receive tocilizumab, we had 80% power to detect big differences (hazard ratio [HR] = 3.4 or higher) in transplantation outcomes using a 2-sided 0.05 test. The power would be reduced to about 20% to 30% if the difference was moderate (HR = 2.0) using the same test. No CRS-related deaths were recorded in either group. Median time to neutrophil engraftment was 21 days (range 16-43) in TOCI and 18 days (range 14-23) in NO-TOCI group (HR = 0.55; 95% confidence interval [CI] = 0.28-1.06, P = .08). Median time to platelet engraftment was 34 days (range 20-81) in TOCI and 28 days (range 12-94) in NO-TOCI group (HR = 0.56; 95% CI = 0.25-1.22, P = .19). Cumulative incidences of day 100 acute GvHD grades II-IV (P = .97) and grades III-IV (P = .47) were similar between the 2 groups. However, cumulative incidence of chronic GvHD at 1 year was significantly higher in patients receiving TOCI (64% versus 24%; P = .05). Rates of NRM (P = .66), relapse (P = .83), disease-free survival (P = .86), and overall survival (P = .73) were similar at 1 year after HCT between the 2 groups. Tocilizumab administration for CRS management after HaploHCT appears to be safe with no short-term adverse effect and no effect on relapse rate. However, the significantly higher cumulative incidence of chronic GvHD, negates the high efficacy of PTCy on GvHD prophylaxis in this patient population. Therefore using tocilizumab for CRS management in the HaploHCT population with PTCy maybe kept only for patients with severe CRS. The impact on such approach on long term outcome in HaploHCT with PTCy will need to be evaluated in a larger retrospective study or a prospective manner.

Clinical Features of Acute Kidney Injury in the Early Post-Transplantation Period Following Reduced-Intensity Conditioning Allogeneic Hematopoietic Stem Cell Transplantation

Allogeneic hematopoietic stem cell transplantation (HCT) is a potentially curative therapy for patients with hematologic malignancies but is associated with acute kidney injury (AKI). To date, few studies have examined risk factors for AKI at engraftment, or the relationship between AKI and clinical outcomes. This study examined the incidence and risk factors for periengraftment AKI, as well as the association between AKI and overall survival (OS) and nonrelapse mortality (NRM). We conducted a retrospective analysis of adult patients undergoing reduced-intensity conditioning (RIC) allogeneic HCT at the Dana-Farber Cancer Institute between 2012 and 2019. Periengraftment (day 0 to day 30) AKI incidence and severity were defined using modified KDIGO (Kidney Disease: Improving Global Outcomes) criteria. Factors associated with periengraftment AKI risk were examined using Cox regression analysis. The impact of periengraftment AKI on OS and NRM (defined as death without recurrent disease after HCT), was evaluated using Cox regression and the Fine and Gray competing risks model, respectively. Kidney recovery, defined as a return of serum creatinine (SCr) to within 25% of baseline or liberation from kidney replacement therapy (KRT), was examined at day 90 post-HCT. Periengraftment AKI occurred in 330 of 987 patients (33.4%) at a median of 13 days (interquartile range, 4 to 30 days) post-transplantation. Factors associated with a higher multivariable-adjusted risk of AKI were supratherapeutic rapamycin (hazard ratio [HR], 1.56; 95% confidence interval [CI], 1.20 to 2.03; P < .001), fludarabine/melphalan conditioning (HR, 1.35, 95% CI, 1.01 to 1.81; P = .05, compared to fludarabine/busulfan and fludarabine, cyclophosphamide, and total body irradiation), HCT Comorbidity Index ≥4 (HR, 1.43; 95% CI, 1.14 to 1.79; P = .002), albumin <3.4 g/dL (HR, 2.04; 95% CI, 1.33 to 3.12; P = .001), hemoglobin ≤12 (HR, 1.96; 95% CI, 1.38 to 2.78; P < .001), supratherapeutic tacrolimus (HR, 1.45; 95% CI, 1.07 to 1.95; P = .02), and baseline SCr >1.1 mg/dL (HR, 1.87; 95% CI, 1.48 to 2.35; P < .001). Periengraftment AKI was associated with worse OS (HR, 1.40; 95% CI, 1.16 to 1.71; P < .001) and NRM (subdistribution HR, 2.10; 95% CI, 1.52 to 2.89; P < .001). Kidney recovery occurred in 18%, 15%, and 30% of patients with stage 1, stage 2, and stage 3 AKI without KRT, respectively, and 4 of 16 patients (25%) were liberated from KRT. Periengraftment AKI is common among RIC allogeneic HCT recipients. We identified several important risk factors for periengraftment AKI. Its association with worse OS and NRM underscores the importance of timely recognition and management.

Poor graft function after haploidentical stem cell transplantation with post-transplant cyclophosphamide

This is a retrospective cohort study of consecutive adult patients who received a haploidentical-SCT (haplo-SCT) with post-transplant cyclophosphamide (PT-Cy) in a single centre. Poor graft function (PGF) was defined as the occurrence of either persistent neutropenia (ANC < 0.5 × 10⁹/µL) with poor response to granulocyte colony-stimulating factors (G-CSF) and/or thrombocytopenia (platelets < 20 × 10⁹/L) with transfusion dependence, with complete donor chimerism and without concurrent severe GVHD or underlying disease relapse, during the first 12 months after transplantation. Forty-four (27.5%) out of 161 patients were diagnosed with PGF. Previous CMV reactivation was significantly more frequent in patients with PGF (88.6% versus 73.5%, p = 0.04) and the number of reactivations was also higher in these patients. Besides, early CMV reactivations in the first 6 months post-SCT were also significantly more frequent among patients with PGF (88.6% versus 71.8% p = 0.025). Thirty-two percent of patients with PGF were treated with increasing doses of thrombopoietin-receptor agonists (TRA) and 7 patients were treated with a donor CD34 + selected boost. In total, 93.2% of patients reached adequate peripheral blood counts in a median time of 101 days (range 11-475) after diagnosis. PGF is a frequent complication after haplo-SCT with PT-Cy. CMV reactivation might be the most relevant factor associated to its development. Even when most patients recover peripheral counts with support therapy, there is a group of patients with persistent cytopenias who can effectively be treated with TRA and/or a boost of CD34 + selective cells.

Post-transplant cyclophosphamide and early mixed donor Chimerism in myeloid malignancies; a single-center experience

BACKGROUND

Allogeneic hematopoietic stem cell transplantation (allo-HSCT) remains the only curative option for high-risk myeloid malignancies. Post-transplant cyclophosphamide (PT-Cy) has proven to be effective for graft versus host disease (GVHD) prophylaxis. Given that graft-versus-tumor (GVT) effect plays a major role in reducing the risk of disease relapse, the application of PT-Cy must balance the risk of relapse. Mixed chimerism (MC) refers to a state of concurrent presence of recipient and donor cells post allo-HSCT which may precede relapse disease.

OBJECTIVE

We investigated the impact of PT-Cy on early MC (EMC) and disease relapse in patients with a myeloid malignancy post allo-HSCT.

STUDY DESIGN

This retrospective single-center study included patients that underwent allo-HSCT between 2015 and 2021. Patient and disease characteristics were collected from the electronic health records. EMC was defined as <95% donor cells at day 90-120 post allo-HSCT.

RESULTS

A total of 144 patient that received an allo-HSCT were included in the study. One hundred and eight (75%) patients received PT-Cy as part of the GVHD prophylaxis regimen. The majority underwent allo-HSCT for acute myeloid leukemia (62%) or myelodysplastic syndrome (31%). Sixty-five percent received allo-HSCT from a matched unrelated donor transplant and 65% received a myeloablative conditioning regimen. A lower rate of chronic GVHD (p = 0.03) and a higher rate of EMC (p = 0.04) were observed in patients that received PT-Cy. PT-Cy was not associated with overall survival (OS) and relapse-free survival (RFS). Multivariable analysis identified measurable residual disease status (p = 0.003), hematopoietic cell transplantation-specific comorbidity index (p = 0.012) and chronic GVHD (p = 0.006) as independent prognostic variables for OS. AML-adverse risk (p = 0.004) and EMC (p = 0.018) were independently prognostic for RFS. While EMC overall was not significantly associated with higher risk of relapse, EMC was associated with shorter RFS within adverse-risk AML patients.

CONCLUSION

Our study shows that PT-Cy was associated with an increased risk of EMC. The predictive value of EMC for relapse remains unclear and may depend on the underlying disease, which should be validated in a larger cohort.

Effect of Hematopoietic Stem Cell Transplantation and Post-Transplantation Cyclophosphamide on the Microglia Phenotype in Rats with Experimental Allergic Encephalomyelitis

Microglia are the resident immune cells of the central nervous system, playing a role in the inflammatory process development and resolution, presenting two main phenotypes, pro-inflammatory M1, and anti-inflammatory M2. Therapies affecting the microglia phenotype may be beneficial in treating inflammatory neurodegenerative diseases. In our experiments, we used the animal multiple sclerosis model, experimental allergic encephalomyelitis (EAE). Rats were treated during the pre- or symptomatic phase of the disease with cyclophosphamide, followed by hematopoietic stem cell transplantation, and with/without post-transplantation cyclophosphamide. Our study aimed to analyze the microglia phenotype in animals subjected to this treatment. The number of M1 cells in the spinal cord, and inducible nitric oxide synthase (iNOS) levels in the brain were similar in all experimental groups. The differences were observed in M2 cells number and arginase 1 (Arg1) levels, which were decreased in EAE animals, and increased after treatment in the symptomatic phase of EAE, and in the pre-symptomatic phase, but only with post-transplantation cyclophosphamide. Analysis of gene expression in the brain showed decreased iNOS expression in EAE animals treated in the symptomatic phase of EAE and no differences in Arg1 expression. Results indicate that treatment applied to experimental animals influences the microglia phenotype, promoting differentiation towards M2 cells.

Outcome of COVID-19 in allogeneic stem cell transplant recipients: Results from the EPICOVIDEHA registry

Background

The outcome of COVID-19 in allogeneic hematopoietic stem cell transplantation (HSCT) recipients is almost uniformely considered poor. The aim of present study was to retrospectively analyse the outcome and risk factors for mortality in a large series of patients who developed COVID-19 infection after an allogeneic HSCT.

Methods

This multicenter retrospective study promoted by the European Hematology Association - Infections in Hematology Study Working Group, included 326 adult HSCT patients who had COVID-19 between January 2020 and March 2022.

Results

The median time from HSCT to the diagnosis of COVID-19 was 268 days (IQR 86-713; range 0-185 days). COVID-19 severity was mild in 21% of the patients, severe in 39% and critical in 16% of the patients. In multivariable analysis factors associated with a higher risk of mortality were, age above 50 years, presence of 3 or more comorbidities, active hematologic disease at time of COVID-19 infection, development of COVID-19 within 12 months of HSCT, and severe/critical infections. Overall mortality rate was 21% (n=68): COVID-19 was the main or secondary cause of death in 16% of the patients (n=53).

Conclusions

Mortality in HSCT recipients who develop COVID-19 is high and largely dependent on age, comorbidities, active hematologic disease, timing from transplant and severity of the infection.

A Calcineurin Inhibitor Free Graft Versus Host Disease Prophylaxis for Patients Undergoing Matched Related and Matched Unrelated Donor Allogeneic Hematopoietic Cell Transplant

Post-transplantation cyclophosphamide (PTCy) and calcineurin inhibitor (CNI)-based graft versus host disease (GVHD) prophylaxis has been associated with lower rates of acute and chronic GVHD compared with the traditional prophylaxis of CNI and methotrexate (MTX) in matched related donor (MRD) and matched unrelated donor (MUD) allogeneic hematopoietic cell transplantation (allo-HCT). The combination of PTCy with sirolimus (PTCy-Siro) as CNI-free GVHD prophylaxis has shown promising results, with cumulative rates of grade II-IV acute and chronic GVHD in the range of 15% to 27% and 20% to 27%, respectively, in patients undergoing MRD, MUD, and haploidentical allo-HCT. We report a single-center, nonrandomized comparison of patients undergoing matched donor allo-HCT receiving PTCy-Siro with those receiving the standard GVHD prophylaxis of tacrolimus and methotrexate (Tac-MTX). One hundred and sixteen consecutive patients who had undergone an MRD or MUD allo-HCT between January 2018 and January 2021 and received either PTCy-Siro (n = 29) or Tac-MTX (n = 87) as GVHD prophylaxis regimens were eligible for inclusion. Patients receiving PTCy-Siro had a significantly shorter median time to immunosuppression withdrawal than patients receiving Tac-MTX (138 days [range, 37 to 312 days] versus 232 days [range, 66 to 1120 days]; P < .001). There was no significant difference between the 2 arms in the incidence of grade II-IV acute GVHD, grade III-IV acute GVHD, steroid-refractory acute GVHD, or clinical infections. At a median follow-up of 1.1 years (range, 0 to 1.8 years), patients receiving PTCy-Siro were significantly less likely to have chronic GVHD, with 2-year freedom from GVHD of 75% (95% confidence interval [CI], 58% to 98%) versus 20% (95% CI, 10% to 40%) for those receiving Tac-MTX (P = .005).

Mafosfamide, a cyclophosphamide analog, causes a proinflammatory response and increased permeability on endothelial cells in vitro

Post-transplantation cyclophosphamide (PTCy) has decreased GVHD incidence. Endothelial damage in allo-HCT is caused by multiple factors, including conditioning treatments and some immunosupressants, and underlies HCT-complications as GVHD. Nevertheless, the specific impact of PTCy on the endothelium remains unclear. We evaluated the effect of mafosfamide (MAF), an active Cy analog, on endothelial cells (ECs) vs. cyclosporine A (CSA), with known damaging endothelial effect. ECs were exposed to MAF and CSA to explore changes in endothelial damage markers: (i) surface VCAM-1, (ii) leukocyte adhesion on ECs, (iii) VE-cadherin expression, (iv) production of VWF, and (v) activation of intracellular signaling proteins (p38MAPK, Akt). Results obtained (expressed in folds vs. controls) indicate that both compounds increased VCAM-1 expression (3.1 ± 0.3 and 2.8 ± 0.6, respectively, p < 0.01), with higher leukocyte adhesion (5.5 ± 0.6, p < 0.05, and 2.8 ± 0.4, respectively). VE-cadherin decreased with MAF (0.8 ± 0.1, p < 0.01), whereas no effect was observed with CSA. Production of VWF augmented with CSA (1.4 ± 0.1, p < 0.01), but diminished with MAF (0.9 ± 0.1, p < 0.05). p38MAPK activation occurred with both compounds, being more intense and faster with CSA. Both drugs activated Akt, with superior MAF effect at longer exposure. Therefore, the cyclophosphamide analog MAF is not exempt from a proinflammatory effect on the endothelium, though without modifying the subendothelial characteristics.

The Role of NK Cells and Their Exosomes in Graft Versus Host Disease and Graft Versus Leukemia

Natural killer (NK) cells are one of the innate immune cells that play an important role in preventing and controlling tumors and viral diseases, but their role in hematopoietic stem cell transplantation (HCT) is not yet fully understood. However, according to some research, these cells can prevent infections and tumor relapse without causing graft versus host disease (GVHD). In addition to NK cells, several studies are about the anti-leukemia effects of NK cell-derived exosomes that can highlight their roles in graft-versus-leukemia (GVL). In this paper, we intend to investigate the results of various articles on the role of NK cells in allogeneic hematopoietic cell transplantation and also their exosomes in GVL. Also, we have discussed the antiviral effects of these cells in post-HCT cytomegalovirus infection.

Transplantation in CML in the TKI era: who, when, and how?

Molecular therapy with tyrosine kinase inhibitors (TKIs) has significantly reduced the indication for allogeneic hematopoietic stem cell transplantation (allo-HSCT) in chronic myeloid leukemia (CML). Treatment-free remission can be obtained in about 50% of patients with an optimal response. However, cure rates up to 90% are restricted to patients receiving HSCT. Timing is essential since HSCT in the early stages of the disease has the best outcome. Patients in a more advanced phase (AdP) than chronic-phase (chP) CML undergo HSCT with suboptimal outcomes, and the gap between chP and AdP disease is widening. First-line therapy should start with first- or second-generation (G) TKIs. Patients failing treatment (BCR-ABL1 transcripts of greater than 10% at 3 and 6 months and greater than 1% at 12 months) should be switched to second-line TKIs, and HSCT should be considered. Patients not responding to 2G-TKI therapy as well as patients in an accelerated phase (AP) or blast crisis (BC) are candidates for HSCT. Therapy resistant BCR-ABL1 mutations, high-risk additional cytogenetic abnormalities, and molecular signs of leukemia progression should trigger the indication for HSCT. Patients who, despite dose adjustments, do not tolerate or develop severe adverse events, including vascular events, to multiple TKIs are also candidates for HSCT. In AdP CML, TKIs do not show long-lasting results, and the outcome of HSCT is less optimal without pretransplant therapy. In these patients the induction of chP2 with TKIs, either alone (AP) or in combination with intensive chemotherapy (BC), followed by HSCT should be pursued.

Controversies and expectations for the prevention of GVHD: A biological and clinical perspective

Severe acute and chronic graft versus host disease (GVHD) remains a major cause of morbidity and mortality after allogeneic hematopoietic cell transplantation. Historically, cord blood and matched sibling transplantation has been associated with the lowest rates of GVHD. Newer methods have modified the lymphocyte components to minimize alloimmunity, including: anti-thymocyte globulin, post-transplant cyclophosphamide, alpha/beta T cell depletion, and abatacept. These agents have shown promise in reducing severe GVHD, however, can be associated with increased risks of relapse, graft failure, infections, and delayed immune reconstitution. Nonetheless, these GVHD prophylaxis strategies have permitted expansion of donor sources, especially critical for those of non-Caucasian decent who previously lacked transplant options. This review will focus on the biologic mechanisms driving GVHD, the method by which each agent impacts these activated pathways, and the clinical consequences of these modern prophylaxis approaches. In addition, emerging novel targeted strategies will be described. These GVHD prophylaxis approaches have revolutionized our ability to increase access to transplant and have provided important insights into the biology of GVHD and immune reconstitution.

Lower dose of ATG combined with basiliximab for haploidentical hematopoietic stem cell transplantation is associated with effective control of GVHD and less CMV viremia

Currently, the graft-versus-host disease (GVHD) prophylaxis consists of an immunosuppressive therapy mainly based on antithymocyte globulin (ATG) or post-transplant cyclophosphamide (PTCy). GVHD remains a major complication and limitation to successful allogeneic haploidentical hematopoietic stem cell transplantation (haplo-HSCT). We modified the ATG-based GVHD prophylaxis with the addition of basiliximab in the setting of haplo-HSCT and attempted to explore the appropriate dosages. We conducted a retrospective analysis of 239 patients with intermediate- or high-risk hematologic malignancies who received haplo-HSCT with unmanipulated peripheral blood stem cells combined or not with bone marrow. All patients received the same GVHD prophylaxis consisting of the combination of methotrexate, cyclosporine or tacrolimus, mycofenolate-mofetil, and basiliximab with different doses of ATG (5-9mg/kg). With a median time of 11 days (range, 7-40 days), the rate of neutrophil engraftment was 96.65%. The 100-day cumulative incidences (CIs) of grade II-IV and III-IV aGVHD were 15.8 ± 2.5% and 5.0 ± 1.5%, while the 2-year CIs of total cGVHD and extensive cGVHD were 9.8 ± 2.2% and 4.1 ± 1.5%, respectively. The 3-year CIs of treatment-related mortality (TRM), relapse, overall survival (OS), and disease-free survival (DFS) were 14.6 ± 2.6%, 28.1 ± 3.4%, 60.9 ± 3.4%, 57.3 ± 3.4%, respectively. Furthermore, the impact of the reduction of the ATG dose to 6 mg/kg or less in combination with basiliximab on GVHD prevention and transplant outcomes among patients was analyzed. Compared to higher dose of ATG(>6mg/kg), lower dose of ATG (≤6mg/kg) was associated with a significant reduced risk of CMV viremia (52.38% vs 79.35%, P<0.001), while the incidences of aGVHD and cGVHD were similar between the two dose levels. No significant effect was found with regard to the risk of relapse, TRM, and OS. ATG combined with basiliximab could prevent GVHD efficiently and safely. The optimal scheme of using this combined regimen of ATG and basiliximab is that administration of lower dose ATG (≤6mg/kg), which seems to be more appropriate for balancing infection control and GVHD prophylaxis.

Association between gene polymorphisms in the cyclophosphamide metabolism pathway with complications after haploidentical hematopoietic stem cell transplantation

Allogeneic hematopoietic stem cell transplantation (allo-HSCT) is a curative treatment for patients with hematologic malignances. Haploidentical HSCT (Haplo-HSCT) is an alternative option for patients who do not have an HLA-matched donor. The use of post-transplantation high dose cyclophosphamide (PT-Cy) is commonly employed for graft-versus-host disease (GVHD) prophylaxis in haplo-HSCT. Cyclophosphamide (Cy) is an alkylating agent with antineoplastic and immunosuppressive activity, whose bioactivation requires the activity of polymorphic enzymes in the liver to produce phosphoramide mustard, which is a DNA alkylating agent. To identify polymorphisms in the genes of Cy metabolism and correlate them with post-HSCT complications [GVHD, sinusoidal obstruction syndrome (SOS), hemorrhagic cystitis (HC) and transplant-related mortality (TRM)], we designed a custom next-generation sequencing panel with Cy metabolism enzymes. We analyzed 182 patients treated with haplo-HSCT with PT-Cy from 2007 to 2019, detecting 40 variants in 11 Cy metabolism genes. Polymorphisms in CYP2B6, a major enzyme involved in Cy activation, were associated with decreased activity of this enzyme and a higher risk of Graf-versus-host disease (GVHD). Variants in other activation enzymes (CYP2A6, CYP2C8, CYP2C9, CYP2C19) lead to decreased enzyme activity and were associated with GVHD. Polymorphisms in detoxification genes such as glutathione S-transferases decreased the ability to detoxify cyclophosphamide metabolites due to lower enzyme activity, which leads to increased amounts of toxic metabolites and the development of III-IV acute GVHD. GSMT1*0 a single nucleotide polymorphism previously recognized as a risk factor for SOS was associated with a higher risk of SOS. We conclude that polymorphisms of genes involved in the metabolism of cyclophosphamide in our series are associated with severe grades of GVHD and toxicities (SOS and TRM) after haplo-HSCT and could be used to improve the clinical management of transplanted patients.

Outcomes of two-step haploidentical allogeneic stem cell transplantation in elderly patients with hematologic malignancies

Allogeneic hematopoietic stem cell transplantation (allo-SCT) remains the best curative option for the majority of patients with hematologic malignancies (HM); however, many elderly patients are excluded from transplant and outcome data in this population is still limited. The novel two-step graft engineering approach has been the main platform for allo-SCT at Thomas Jefferson University since 2006. Following administration of the preparative regimen, we infuse donor lymphocytes, followed by cyclophosphamide to induce bidirectional tolerance, then infusion of CD34-selected cells. A total of 76 patients ≥ 65 years old with HM underwent haploidentical (haplo) allo-SCT on the two-step transplant platform between 2007 and 2021. The median time to neutrophil engraftment was 11 days and platelet engraftment was 18 days. With a median follow up of 44 months, the 3-year overall survival (OS) and progression-free survival (PFS) were 36.3% and 35.6%, respectively. The cumulative incidences of non-relapse mortality (NRM) and relapse at 3 years were 43.5% and 21.0% at 3 years, respectively. The cumulative incidence of grade III-IV acute graft-versus-host-disease (GVHD) was 11.1% at 6 months, and chronic GVHD requiring treatment was 15.1% at 2 years. The two-step haplo allo-SCT is a novel alternative platform for high-risk older HM patients, achieving fast engraftment, low relapse rates and promising survival.

Shikonin impairs T lymphocyte proliferation and thymopoiesis while it may increase myeloid-derived suppressor cells to alleviate immune responses

Shikonin (SHK) has multifaceted physiological functions, including antitumor, anti-inflammatory, and antimicrobial effects. Recently, SHK has been shown to affect immune responses; however, its detailed immune modulatory function in vivo remains unclear. In this study, we demonstrated that SHK not only inhibited T cell proliferation in vitro, but also intensively inhibited thymopoiesis and eliminated CD4/CD8 double-positive thymic progenitor cells in vivo. Treatment of mice with SHK resulted in immune profile alterations, which promoted myelosis in the bone marrow and increased inhibitory immune cells in central immune organs. A decrease in T cells and B cells was observed in the spleen. Using a murine allogenic skin transplantation model, we revealed that short-term treatment of recipients with SHK significantly inhibited skin graft rejection, in which the levels of myeloid-derived suppressor cells (MDSC) were markedly increased. Taken together, our study suggests that SHK can efficiently eliminate proliferating T cells and inhibit thymopoiesis while promoting the generation of MDSC, indicating its potential role in alleviating immune responses in allogeneic organ/cell transplantation.

Debating the Future of Sickle Cell Disease Curative Therapy: Haploidentical Hematopoietic Stem Cell Transplantation vs. Gene Therapy

Hematopoietic stem cell transplantation (HSCT) is a well-established curative therapy for patients with sickle cell disease (SCD) when using a human leukocyte antigen (HLA)-matched sibling donor. Most patients with SCD do not have a matched sibling donor, thereby significantly limiting the accessibility of this curative option to most patients. HLA-haploidentical HSCT with post-transplant cyclophosphamide expands the donor pool, with current approaches now demonstrating high overall survival, reduced toxicity, and an effective reduction in acute and chronic graft-vs.-host disease (GvHD). Alternatively, autologous genetic therapies appear promising and have the potential to overcome significant barriers associated with allogeneic HSCT, such as donor availability and GvHD. Here the authors each take a viewpoint and discuss what will be the future of curative options for patients with SCD outside of a matched sibling transplantation, specifically haploidentical HSCT vs. gene therapy.

Donor specific HLA antibody in hematopoietic stem cell transplantation: Implications for donor selection

Advances in hematopoietic stem cell transplant (HSCT) have led to changes in the approach to donor selection. Many of these new approaches result in greater HLA loci mismatching, either through the selection of haploidentical donors or permissive HLA mismatches. Although these approaches increase the potential of transplant for many patients by expanding the number of acceptable donor HLA genotypes, they add the potential barrier of donor-specific HLA antibodies (DSA). DSA presents a unique challenge in HSCT, as it can limit engraftment and lead to graft failure. However, transient reduction of HLA antibodies through desensitization treatments can limit the risk of graft failure and facilitate engraftment. Thus, the consideration of DSA in donor selection and the management of DSA prior to transplant are playing an increasingly important role in HSCT. In this review, we will discuss studies addressing the role of HLA antibodies in HSCT, the reported impact of desensitization on DSA levels, and the implications for selecting donors for patients with DSA. We found that there is a clear consensus that moderate strength DSA should be avoided, while desensitization strategies are reported to be effective in most cases at reducing DSA to amenable levels. There is limited information regarding the impact of specific characteristics of DSA, such as HLA loci or overall level of sensitization, which could further aid in donor selection for sensitized HSCT candidates.

Hematopoietic Stem Cells and Regeneration

Hematopoietic stem cell (HSC) regeneration is the remarkable process by which extremely rare, normally inactive cells of the bone marrow can replace an entire organ if called to do so by injury or harnessed by transplantation. HSC research is arguably the first quantitative single-cell science and the foundation of adult stem cell biology. Bone marrow transplant is the oldest and most refined technique of regenerative medicine. Here we review the intertwined history of the discovery of HSCs and bone marrow transplant, the molecular and cellular mechanisms of HSC self-renewal, and the use of HSCs and their derivatives for cell therapy.

Feasibility and Efficacy of Partially Replacing Post-Transplantation Cyclophosphamide with Bendamustine in Pediatric and Young Adult Patients Undergoing Haploidentical Bone Marrow Transplantation

Post-transplantation cyclophosphamide (PT-CY) is the most widely applied graft-versus-host disease (GVHD) prophylaxis regimen in T-cell replete haploidentical bone marrow transplantation (haplo-BMT). Although PT-CY has met with great success in the haplo-BMT arena by suppressing GVHD, patients without acute GVHD have high relapse rates. One strategy to reduce relapse rates being explored by others is a dosage reduction of PT-CY. We have taken a different approach in evaluating whether partially replacing PT-CY with post-transplantation bendamustine (PT-BEN) would be advantageous, an idea based on our preclinical research identifying several beneficial immunomodulatory properties of BEN. We therefore initiated and completed a Phase Ia trial to evaluate the progressive substitution of PT-CY with PT-BEN (ClinicalTrials.gov identifier NCT02996773). We compared outcomes between 13 patients with high-risk hematologic malignancies who received PT-CY/BEN and 31 contemporaneous haplo-BMT recipients treated with the same myeloablative conditioning regimens but receiving only PT-CY. We found that partial replacement of PT-CY with PT-BEN (PT-CY/BEN) on day +4 was well tolerated and associated with significantly earlier trilineage engraftment. We also report favorable trends toward significant improvements on univariate and multivariate analyses with PT-CY/BEN compared with PT-CY with respect to rates of chronic GVHD (hazard ratio [HR], .08; 95% confidence interval [CI], .005 to 1.11; P = .06), and GVHD-free relapse-free survival (GRFS) (HR, .22; 95% CI, .05 to .86; P = .039). Our human trial has now transitioned to Phase Ib, which will further evaluate the safety and potential benefits of PT-CY/BEN. Herein we also expand our pediatric, adolescent, and young adult experience to 31 patients, demonstrating overall survival, progression-free survival, and GRFS at 3 years of 85.6%, 76.1%, and 58.2%, respectively, in a largely racial/ethnic minority cohort. PT-CY/BEN appears to be a promising treatment option that requires further evaluation.

Antigen receptor-engineered Tregs inhibit CNS autoimmunity in cell therapy using non-redundant immune mechanisms in mice

CD4⁺FOXP3⁺ Tregs are currently explored to develop cell therapies against immune‐mediated disorders, with an increasing focus on antigen receptor‐engineered Tregs. Deciphering their mode of action is necessary to identify the strengths and limits of this approach. Here, we addressed this issue in an autoimmune disease of the CNS, EAE. Following disease induction, autoreactive Tregs upregulated LAG‐3 and CTLA‐4 in LNs, while IL‐10 and amphiregulin (AREG) were increased in CNS Tregs. Using genetic approaches, we demonstrated that IL‐10, CTLA‐4, and LAG‐3 were nonredundantly required for the protective function of antigen receptor‐engineered Tregs against EAE in cell therapy whereas AREG was dispensable. Treg‐derived IL‐10 and CTLA‐4 were both required to suppress acute autoreactive CD4⁺ T‐cell activation, which correlated with disease control. These molecules also affected the accumulation in the recipients of engineered Tregs themselves, underlying complex roles for these molecules. Noteworthy, despite the persistence of the transferred Tregs and their protective effect, autoreactive T cells eventually accumulated in the spleen of treated mice. In conclusion, this study highlights the remarkable power of antigen receptor‐engineered Tregs to appropriately provide multiple suppressive factors nonredundantly necessary to prevent autoimmune attacks.

Impact of donor kinship on non-T-cell depleted haploidentical stem cell transplantation with post transplantation cyclophosphamide for acute leukemia: From the ALWP of the EBMT

Non-T-cell depleted haploidentical hematopoietic cell transplantation (Haplo-HCT) is a unique transplantation setting in which several donors are available. We assessed the impact of donor kinship on outcome of Haplo-HCT with post-transplantation cyclophosphamide in a cohort of 717 acute leukemia patients. We compared sibling with parent donors in patients ≤45 years, and child with sibling donors in patients >45 years. Donor kinship was not associated with worse outcomes in multivariate analysis. For patients ≤45 years, the hazard ratio (HR) for leukemia-free survival (LFS), overall survival (OS), relapse incidence (RI), and chronic graft-versus-host disease (cGVHD) was 0.87 (p = 0.75), 1.19 (p = 0.7), 0.52 (p = 0.19), and 0.99 (p = 0.97) for parents versus siblings, respectively, and for patients >45 years the HR was 0.93 (p = 0.8), 0.98 (p = 0.94), 1.3 (p = 0.53), and 0.98 (p = 0.95) for children versus siblings, respectively. Univariate incidence of acute GVHD grade II-IV was significantly higher in patients transplanted from siblings versus children (p = 0.002). Factors associated with inferior outcome were advanced disease and earlier transplant. In patients ≤45 years, acute lymphocytic leukemia and peripheral blood stem cell graft were additional prognostic factors for OS. We did not find a significant impact of donor kinship on transplantation outcome when analyzing by age group (≤45 and >45 years).

Short treatment of peripheral blood cells product with Fas ligand using closed automated cell processing system significantly reduces immune cell reactivity of the graft in vitro and in vivo

Mobilized peripheral blood cells (MPBCs) graft and peripheral blood cells apheresis are used for bone marrow transplantation and for treatment of graft versus host disease (GvHD). We demonstrate that a short treatment of MPBCs with Fas ligand (FasL, CD95L) for 2 h using a closed automated cell processing system selectively induces apoptosis of specific donor T cells, B cells and antigen presenting cells, but, critically, not CD34⁺ hematopoietic stem cells and progenitors, all of which may contribute to an increased likelihood of graft survival and functionality and reduced GvHD. Treated cells secreted lower levels of interferon-gamma as compared with control, untreated, cells. Moreover, FasL treatment of immune cells increased signals, which led to their phagocytosis by activated macrophages. FasL treated immune cells also reduced the ability of activated macrophages to secrete pro-inflammatory cytokines. Most importantly, FasL ex vivo treated MPBCs prior to transplantation in NOD-SCID NSG mice prevented GvHD and improved stem cell transplantation in vivo. In conclusion, MPBCs, as well as other blood cell products, treated with FasL by automated manufacturing (AM), may be used as potential treatments for conditions where the immune system is over-responding to both self and non-self-antigens.

Post-Transplantation Cyclophosphamide-Based Graft- versus-Host Disease Prophylaxis with Nonmyeloablative Conditioning for Blood or Marrow Transplantation for Myelofibrosis

We describe outcomes after post-transplantation cyclophosphamide and nonmyeloablative conditioning-based allogeneic blood or marrow transplantation for myelofibrosis using matched or mismatched related or unrelated donors. The conditioning regimen consisted of fludarabine, cyclophosphamide, and total body irradiation. Forty-two patients were included, with a median age of 63 years, of whom 19% had Dynamic International Prognostic Scoring System (DIPSS)-plus intermediate-1 risk, 60% had intermediate-2 risk, and 21% had high-risk disease, and 60% had at least 1 high-risk somatic mutation. More than 90% of patients engrafted neutrophils, at a median of 19.5 days, and 7% experienced graft failure. At 1 year and 3 years, respectively, overall survival was 65% and 60%, relapse-free survival was 65% and 31%, relapse was 5% and 40%, and nonrelapse mortality was 30% and 30%. Acute graft-versus-host disease grade 3-4 was seen in 17% of patients at 1 year, and chronic graft-versus-host disease requiring systemic therapy in occurred in 12% patients. Spleen size ≥17 cm or prior splenectomy was associated with inferior relapse-free survival (hazard ratio [HR], 3.50; 95% confidence interval [CI], 1.18 to 10.37; P = .02) and higher relapse rate (subdistribution HR [SDHR] not calculable; P = .01). Age >60 years (SDHR, 0.26; 95% CI, 0.08 to 0.80, P = .02) and receipt of peripheral blood grafts (SDHR, 0.34; 95% CI, 0.11 to 0.99; P = .05) were associated with a lower risk of relapse. In our limited sample, the presence of a high-risk mutation was not statistically significantly associated with an inferior outcome, although ASXL1 was suggestive of inferior survival (SDHR, 2.36; 95% CI, 0.85 to 6.6; P = .09). Overall, this approach shows outcomes comparable those of to previously reported approaches and underscores the importance of spleen size in the evaluation of transplantation candidates.

The Role of Fecal Microbiota Transplantation in the Treatment of Acute Graft-versus-Host Disease

The number of allogeneic hematopoietic stem cell transplantations conducted worldwide is constantly rising. Together with that, the absolute number of complications after the procedure is increasing, with graft-versus-host disease (GvHD) being one of the most common. The standard treatment is steroid administration, but only 40–60% of patients will respond to the therapy and some others will be steroid-dependent. There is still no consensus regarding the best second-line option, but fecal microbiota transplantation (FMT) has shown encouraging preliminary and first clinically relevant results in recent years and seems to offer great hope for patients. The reason for treatment of steroid-resistant acute GvHD using this method derives from studies showing the significant immunomodulatory role played by the intestinal microbiota in the pathogenesis of GvHD. Depletion of commensal microbes is accountable for aggravation of the disease and is associated with decreased overall survival. In this review, we present the pathogenesis of GvHD, with special focus on the special role of the gut microbiota and its crosstalk with immune cells. Moreover, we show the results of studies and case reports to date regarding the use of FMT in the treatment of steroid-resistant acute GvHD.

HLA informs risk predictions after haploidentical stem cell transplantation with posttransplantation cyclophosphamide

Hematopoietic cell transplantation from HLA-haploidentical related donors is increasingly used to treat hematologic cancers; however, characteristics of the optimal haploidentical donor have not been established. We studied the role of donor HLA mismatching in graft-versus-host disease (GVHD), disease recurrence, and survival after haploidentical donor transplantation with posttransplantation cyclophosphamide (PTCy) for 1434 acute leukemia or myelodysplastic syndrome patients reported to the Center for International Blood and Marrow Transplant Research. The impact of mismatching in the graft-versus-host vector for HLA-A, -B, -C, -DRB1, and -DQB1 alleles, the HLA-B leader, and HLA-DPB1 T-cell epitope (TCE) were studied using multivariable regression methods. Outcome was associated with HLA (mis)matches at individual loci rather than the total number of HLA mismatches. HLA-DRB1 mismatches were associated with lower risk of disease recurrence. HLA-DRB1 mismatching with HLA-DQB1 matching correlated with improved disease-free survival. HLA-B leader matching and HLA-DPB1 TCE-nonpermissive mismatching were each associated with improved overall survival. HLA-C matching lowered chronic GVHD risk, and the level of HLA-C expression correlated with transplant-related mortality. Matching status at the HLA-B leader and HLA-DRB1, -DQB1, and -DPB1 predicted disease-free survival, as did patient and donor cytomegalovirus serostatus, patient age, and comorbidity index. A web-based tool was developed to facilitate selection of the best haploidentical-related donor by calculating disease-free survival based on these characteristics. In conclusion, HLA factors influence the success of haploidentical transplantation with PTCy. HLA-DRB1 and -DPB1 mismatching and HLA-C, -B leader, and -DQB1 matching are favorable. Consideration of HLA factors may help to optimize the selection of haploidentical related donors.

Lung Regeneration by Transplantation of Allogeneic Lung Progenitors Using a Safer Conditioning Regimen and Clinical-grade Reagents

Over the last decades, several studies demonstrated the possibility of lung regeneration through transplantation of various lung progenitor populations. Recently, we showed in mice that fetal or adult lung progenitors could potentially provide donor cells for transplantation, provided that the lung stem cell niche in the recipient is vacated of endogenous lung progenitors by adequate conditioning. Accordingly, marked lung regeneration could be attained following i.v. infusion of a single cell suspension of lung cells into recipient mice conditioned with naphthalene (NA) and 6Gy total body irradiation (TBI). As clinical translation of this approach requires the use of allogenic donors, we more recently developed a novel transplantation modality based on co-infusion of hematopoietic and lung progenitors from the same donor. Thus, by virtue of hematopoietic chimerism, which leads to immune tolerance toward donor antigens, the lung progenitors can be successfully engrafted without any need for post-transplant immune suppression. In the present study, we demonstrate that it is possible to replace NA in the conditioning regimen with Cyclophosphamide (CY), approved for the treatment of many diseases and that a lower dose of 2 GY TBI can successfully enable engraftment of donor-derived hematopoietic and lung progenitors when CY is administered in 2 doses after the stem cell infusion. Taken together, our results suggest a feasible and relatively safe protocol that could potentially be translated to clinical transplantation of lung progenitors across major MHC barriers in patients with terminal lung diseases.

Posttransplant Cyclophosphamide for Prevention of Graft-versus-Host Disease: The Prospective Randomized HOVON-96 Trial

PT-Cy after NMA matched alloHSCT will increase the proportion of patients that survive without severe GVHD.

PT-Cy could allow for implementation of early posttransplant chemo- and immunotherapy to further reduce the relapse risk after alloHSCT.

Graft-versus-host disease (GVHD) is the most important complication of allogeneic hematopoietic stem cell transplantation (alloHSCT). We performed a prospective randomized, multicenter, phase 3 trial to study whether posttransplant cyclophosphamide (PT-Cy) combined with a short course of cyclosporine A (CsA) would result in a reduction of severe GVHD and improvement of GVHD-free, relapse-free survival (GRFS) as compared with the combination of CsA and mycophenolic acid (MPA) after nonmyeloablative (NMA) matched related and unrelated peripheral blood alloHSCT. Between October 2013 and June 2018, 160 patients diagnosed with a high-risk hematological malignancy and having a matched related or at least 8 out of 8 HLA-matched unrelated donor were randomized and allocated in a 1:2 ratio to CsA/MPA or PT-Cy/CsA; a total of 151 patients were transplanted (52 vs 99 patients, respectively). The cumulative incidence of grade 2 to 4 acute GVHD at 6 months was 48% in recipients of CsA/MPA vs 30% following PT-Cy/CsA (hazard ratio [HR], 0.48; 95% confidence interval [CI], 0.29-0.82; P = .007). The 2-year cumulative incidence of extensive chronic GVHD was 48% vs 16% (HR, 0.36; 95% CI, 0.21-0.64; P < .001). The 1-year estimate of GRFS was 21% (11% to 32%) vs 45% (35% to 55%), P < .001. With a median follow-up of 56.4 months, relapse incidence, progression-free survival, and overall survival were not significantly different between the 2 treatment arms. PT-Cy combined with a short course of CsA after NMA matched alloHSCT significantly improves GRFS due to a significant reduction in severe acute and chronic GVHD.

High plasma IL-6 levels following haploidentical allogeneic hematopoietic stem cell transplantation post-transplant cyclophosphamide as predictor of early death with worse outcome

INTRODUCTION

Haploidentical hematopoietic stem cell transplantation (haplo-HSCT) can be used as an alternative procedure in the absence of HLA-compatible donors. The use of high doses of cyclophosphamide after infusion improves the prognosis and eliminates the need for T cell depletion in vivo. Among the main complications of haplo-HSCT are acute graft-versus-host disease (a-GVHD) and cytokine release syndrome (CRS). This is a systemic inflammatory response that leads to the release of inflammatory proteins, including IL-6. This syndrome has several clinical features, with mild to severe symptoms. This study aimed to compare plasma IL-6 levels in patients submitted to different HSCT types and to associate them with the presence of acute graft versus host disease (a-GVHD), CRS and survival.

METHODS

A total of 84 patients (22 haploidentical and 62 non-haploidentical) were evaluated at different times. The IL-6 levels in haplo and non-haplo-HSCT recipients were measured before transplantation and on days D7, D14, D28, D60, and D100.

RESULTS

IL-6 levels were higher in haplo-HSCT recipients than in non-haplo-HSCT recipients, remaining elevated from D14 until D100 (P = 0.006) and a cut off ≥11 pg/mL on D7, which is related to worse overall survival. In our study, we found no association with a-GVHD (P = 0.239), a common complication of this type of transplant, but we found a relationship between the increase in IL-6 and CRS (P = 0.021).

CONCLUSION

IL6 can be used as a biomarker for patients submitted to haplo-HSCT, allowing clinical interference in patients having levels of IL-6 times larger than normality values, avoiding early death in this group of patients.

Total body irradiation plus fludarabine versus thiotepa, busulfan plus fludarabine as a myeloablative conditioning for adults with acute lymphoblastic leukemia treated with haploidentical hematopoietic cell transplantation. A study by the Acute Leukemia Working Party of the EBMT

Optimal conditioning for adults with acute lymphoblastic leukemia (ALL) treated with haploidentical hematopoietic cell transplantation (haplo-HCT) and post-transplant cyclophosphamide has not been established so far. We retrospectively compared outcomes for two myeloablative regimens: fludarabine + total body irradiation (Flu-TBI, n = 117) and thiotepa + iv. busulfan + fludarabine (TBF, n = 119). Patients transplanted either in complete remission (CR) or with active disease were included in the analysis. The characteristics of both groups were comparable except for patients treated with TBF were older. In univariate analysis the incidence of non-relapse mortality (NRM) at 2 years was increased for TBF compared to Flu-TBI (31% vs. 19.5%, p = 0.03). There was a tendency towards reduced incidence of relapse after TBF (p = 0.11). Results of multivariate analysis confirmed a reduced risk of NRM using Flu-TBI (HR = 0.49, p = 0.03). In the analysis restricted to patients treated in CR1 or CR2, the use of Flu-TBI was associated with a decreased risk of NRM (HR = 0.34, p = 0.009) but an increased risk of relapse (HR = 2.59, p = 0.01) without significant effect on survival and graft-versus-host disease. We conclude that for haplo-HCT recipients with ALL, Flu-TBI may be preferable for individuals at high risk of NRM while TBF should be considered in cases at high risk of relapse.

Is It Possible to Separate the Graft-Versus-Leukemia (GVL) Effect Against B Cell Acute Lymphoblastic Leukemia From Graft-Versus-Host Disease (GVHD) After Hematopoietic Cell Transplant?

Hematopoietic cell transplant is a curative therapy for many pediatric patients with high risk acute lymphoblastic leukemia. Its therapeutic mechanism is primarily based on the generation of an alloreactive graft-versus-leukemia effect that can eliminate residual leukemia cells thus preventing relapse. However its efficacy is diminished by the concurrent emergence of harmful graft-versus-host disease disease which affects healthly tissue leading to significant morbidity and mortality. The purpose of this review is to describe the interventions that have been trialed in order to augment the beneficial graft-versus leukemia effect post-hematopoietic cell transplant while limiting the harmful consequences of graft-versus-host disease. This includes many emerging and promising strategies such as ex vivo and in vivo graft manipulation, targeted cell therapies, T-cell engagers and multiple pharmacologic interventions that stimulate specific donor effector cells.