Non-myeloablative Research Articles

Effect of ABO Mismatch and RBC Alloimmunization on the Outcome of Hematopoietic Cell Transplantation for Sickle Cell Disease

BackgroundHematopoietic cell transplantation (HCT) remains the only well-established curative option for sickle cell disease (SCD) patients. Nonmyeloablative (NMA) conditioning has been used to improve the outcomes and reduce toxicities in adult SCD patients. However, Recipient/Donor (R/D) ABO incompatibility and alloimmunization could be significant impediments to successful outcomes when transplanting SCD patients due to risks of hemolysis, delayed engraftment, poor graft function and graft failure (GF). Herein, we report our experience with allogeneic HSCT for SCD and the effects of RBC groups mismatch and alloimmunization on the outcome of transplanted patients. MethodsWe conducted a retrospective analysis of all SCD patients (age >14 year) that underwent HSCT from January 2015 to February 2022 at our center. All patients received Intravenous alemtuzumab (1 mg/kg divided over 5 days on days -7 to -3) and 300 cGy TBI on day -2 or -1 for conditioning. Pre-transplant preparation consisted of hydroxyurea at maximum tolerated dose for 2-3 months and one session of exchange transfusion. Peripherally mobilized CD34 stem cells targeting 10 × 106 /kg of recipient weight were used. For graft versus host disease (GVHD) prophylaxis sirolimus was started on day -1 and continued for one year with tapering if lymphoid chimerism was > 50%. For Patients with major ABO incompatibility, we administered 2 doses of rituximab (375 mg/m2) and 3 sessions of plasmapheresis before starting the conditioning regimen targeting an isoheamagglutinin titer < 1/32. The primary objective was to determine the impact of RBC groups mismatch and alloimmunization on the outcome of transplanted patients. The secondary objective was to assess the impact of GF on overall survival (OS). Logistic regression was done to evaluate predictors for GF. Kaplan-Meier method was used for survival analysis. ResultsA total of 194 patients were included with a median age of 26 years. The median baseline Hgb and HbS were 93 g/L and 71.3%, respectively. Indications of stem cell transplantations were most commonly due to recurrent vaso-occlusive crisis in 52.5% of patients, CNS events in 19.6%, and acute chest syndrome in 17%. After a median follow up of 28.8 months (5-83), sixteen patients (8%) experienced graft failure (3 with primary GF and 13 with secondary GF). On univariate analysis, ABO minor incompatibility and RBC alloantibodies against donor non-ABO antigens were predictive for GF.On multivariate analysis RBC alloantibodies against donor non-ABO antigens (OR, 8.29; 95% CI, 2.01 to 34.05, P=0.0033) was the only factor predictive of GF. None of the 16 patients with major ABO incompatibility developed GF. Two-years OS for all patients was 95%. The 2 years OS for patients without GF was 98% compared to 74% in patients with GF, (P<0.0001). ConclusionIn our SCD transplanted patients, RBC alloantibodies against donor non- ABO antigens were an independent risk factor for GF. Patients with GF had an inferior survival and strategies for decreasing GF risk are needed.

Outcomes of Patients with Myeloid Malignancies and Cardiovascular Disease Undergoing Allogeneic Stem Cell Transplantation

Introduction/Background: Reduced-intensity conditioning (RIC) and nonmyeloablative (NMA) regimens have enabled patients with cardiovascular disease (CVD) to undergo allogeneic stem cell transplantation (allo-HSCT). However, little is known about long-term outcomes, including cardiovascular (CV) complications. Methods: We retrospectively studied 99 consecutive patients with acute myeloid leukemia (AML) or myelodysplastic syndrome (MDS) who underwent allo-HSCT between September 1, 2013, and November 30, 2020. Overall survival (OS), progression-free survival (PFS), nonrelapse mortality (NRM), cumulative incidence of relapse, and cumulative incidence of acute and chronic graft-versus-host disease (GvHD) were compared in patients with and without CV risk factors or disease. Results: Preexisting CVD was present in 34 of 99 patients (34%). CVD patients more commonly had reduced-intensity conditioning (91% vs. 60%, p = 0.001) and unrelated donors (56% vs. 35%, p = 0.04). Early adverse cardiac events occurred more frequently in the CVD versus no-CVD group (38% vs. 14%), particularly arrhythmias (21% vs. 5%; p = 0.04). CVD patients tended to have poorer OS and PFS outcomes (HR = 1.98, [1.00, 3.92]; HR = 1.89, [0.96–3.72], respectively). OS rate at 1, 2, and 3 years for CVD versus no-CVD patients was 66% versus 72%, 55% versus 64%, and 46% versus 62%, respectively. Causes of death in the CVD and no-CVD groups were infections (53% vs. 28%), relapsed disease (32% vs. 52%), and CV events (10% vs. 3%). Conclusion: Based on these data, predictive models to identify patients with CVD with higher risk of post-allo-HSCT complications and mortality and strategies to mitigate these risks should be developed.

A first-in-human study of CRISPR/Cas9-engineered tumor infiltrating lymphocytes (TILs) product GT316 as monotherapy in advanced solid tumors.

2549 Background: A next-generation TIL product GT316 was engineered with CRISPR/Cas9 to genetically disrupt two key immunoregulatory targets identified from a genome-wide CRISPR screening platform and demonstrated significantly enhanced anti-tumor efficacy and persistence in pre-clinical animal studies with ameliorated TIL exhaustion profile. A first-in-human trial was initiated to evaluate the preliminary safety and efficacy of GT316 in advanced solid tumors. Methods: The first-in-class study is to enroll patients (pts) with advanced treatment-refractory solid tumors, especially gynecological tumors. Once the optimal biological dose (OBD) is identified, a monotherapy expansion phase will be initiated for pts with various solid tumors. Enrolled pts were preconditioned with a nonmyeloablative (NMA) lymphodepletion regimen and treated by infusion of the GMP-grade G316 product followed by IL-2 administration. Results: As of January 22, 2024, the dose escalation study enrolled 4 pts, all of whom were female with a median age of 58 years with 1 to 9 prior lines of systemic treatment. The median number of infused TIL cells was 1.0E+10. All pts experienced TRAEs with the majority being grade 1 or 2. Grade 3/4 TRAEs included lymphocyte count decreased, white blood cell count decreased, monocyte count decreased and neutrophil count decreased, which were related to the NMA regimen. No dose-limiting toxicities (DLTs) or TIL-related grade≥3 TRAEs were observed. Median time on study was 33.4 wks (8–35 wks). One pt with treatment-refractory cervical cancer experienced a confirmed complete response (CR) after 4 wks and the duration of response is 32 wks by now (RECIST 1.1). One ovarian cancer pt with 9 lines of previous systemic therapies experienced a confirmed partial response (PR) after 4 wks and the duration of response is 22 wks by now (RECIST 1.1). Response data will be continuously collected. The other two ovarian cancer pts experienced stable disease (SD) and progressive disease (PD), respectively. Despite varying doses of TILs (3.2E+09 to 1.90E+10) and IL-2 (up to 3.0E+05 IU/kg), all pts receiving GT316 showed robust TIL expansion post-infusion, which is positively correlated with administrated IL-2 doses. Enhanced IFN-γ secretion could be detected in the serum of the CR and PR pts compared to the SD and PD pts, indicating potential tumor antigen-specific response. Conclusions: The first-in-human study of GT316, a CRISPR/Cas9-dual KO anti-exhaustion TIL product, demonstrates good tolerability with encouraging preliminary anti-tumor efficacy as a monotherapy in pts with advanced solid cancers. The infusion of GT316 was associated with robust TIL expansion and IFN-γ secretion. Updated data with additional follow-up will be continuously collected, and OBD will be determined based on the overall data of safety and preliminary efficiency. Clinical trial information: NCT06145802 .

Significant impact of antibiotic exposure on GI-GVHD, NRM, and GRFS following allogeneic HCT with non-myeloablative Flu-TBI conditioning

Background Acute gastro-intestinal graft-versus-host disease (GI-GVHD) and non-relapse mortality (NRM) after allogeneic HCT are closely related to loss of microbial diversity and intestinal dominance by single taxa resulting from the use of antibiotics, dietary changes, and mucosal barrier injury. There is a paucity of data on the impact of use of antibiotics in HCT after Flu-TBI-based non-myeloablative (NMA) conditioning where there is absence of mucositis and limited malnutrition. Methods We did a retrospective single-center analysis of patients receiving Flu-TBI-based NMA HCT for a high-grade myeloid malignancy, mostly AML, and MDS, or acute lymphoblastic leukemia (ALL). We analyzed the impact of pre-engraftment antibiotic exposure, prophylactic ciprofloxacin, and or treatment with broad-spectrum cephalosporin/carbapenem, on HCT outcomes, with a focus on the incidence of acute GI-GVHD by day 180 and NRM at 1 year. Results A total of 150 patients were evaluable with a median age of 62 years. Antibiotics were used in 90 patients; 60 prophylactic use only and 30 therapeutic use with or without previous prophylaxis. Antibiotic use resulted in a significant higher incidence of GI-GVHD Stage 1–4; 29% (26/90) versus 5% (3/60) in those not receiving antibiotics (OR 8.1 (95% CI 2.3–28.3), p = 0.001). Use of antibiotics resulted in higher 1-year NRM (19% (17/90) versus 10% (6/60), HR 2.3, p = 0.06), and decreased 2-year GRFS (42% (38/90) versus 55% (33/60), HR 1.7, p = 0.04), but did not impact RFS or OS. Conclusions Use of antibiotics was related to the occurrence of GI-GVHD, NRM, and GRFS in patients receiving truly NMA HCT. Therefore, in the absence of mucositis and low incidence of bacteremia, antibiotics can and should be used restrictively in this setting.

Graft Failure Incidence, Risk Factors, and Outcomes in Patients Undergoing Non-Myeloablative Allogeneic Hematopoietic Cell Transplantation Using Post-Transplant Cyclophosphamide

Graft failure (GF) is a major complication of allogeneic hematopoietic cell transplantation (alloHCT) that results in significant morbidity and mortality. Post-transplant cyclophosphamide (PTCy)-based graft-versus-host disease (GVHD) prophylaxis has emerged as an effective regimen across the spectrum of donor-match settings, but few studies have investigated the characteristics of GF in the setting of PTCy-based GVHD prophylaxis. The objective was to detail the incidence, clinical features, risk factors, and outcomes for patients with primary graft failure (PGF) and secondary graft failure (SGF). In this retrospective study at a single institution, 958 consecutive patients undergoing first nonmyeloablative (NMA) alloHCT with PTCy-based GVHD prophylaxis were analyzed. PGF was defined as a failure to achieve an ANC ≥ 500 cells/m3 by day 30 of transplant in the absence of residual disease. SGF was defined as complete loss of donor chimerism after initial engraftment. The incidences of PGF and SGF were 3.8% (n = 37) and 1.8% (n = 17), respectively. Neither PGF nor SGF were associated with HLA disparity. In a multivariate analysis, risk factors for PGF in this cohort included age ≥ 65 (OR 2.4, 95% CI 1.2 to 4.8, P = .0120), an underlying diagnosis of MDS, MPN, or MDS/MPN overlap (OR 2.8, 95% CI 1.4 to 5.7, P = .0050), post-transplant viremia with HHV-6 (OR 2.9, 95% CI 1.5 to 5.7, P = .0030), and low CD34+ dose (OR 0.7, 95% CI 0.5 to 0.9, P = .0080). Patients with PGF had poor overall survival, driven primarily by a high rate of nonrelapse mortality (59% at 36 months). SGF was associated with use of a bone marrow graft source and a diagnosis of Hodgkin lymphoma. Patients with SGF had excellent clinical outcomes with only one of seventeen patients experiencing relapse and relapse-related mortality. The incidence of PGF and SGF in patients receiving NMA conditioning and PTCy is low and is not impacted by HLA disparities between donors and recipients. PGF is more common in recipients with age ≥ 65, a diagnosis of MDS, MPN, or MDS/MPN-overlap, post-transplant HHV-6 viremia, and low CD34+ cell dose. Low total nucleated cell dose is also a risk factor for PGF in patients receiving a bone marrow graft source. Patients who experience PGF have poor outcomes due to high rates of nonrelapse mortality, whereas patients who experience SGF have excellent long-term outcomes.

Favorable outcome of non-myeloablative allogeneic transplantation in adult patients with severe sickle cell disease: A single center experience of 200 patients.

Allogeneic hematopoietic stem cell transplant (HSCT) for adults with severe sickle cell disease (SCD) is potentially curative but not commonly utilized therapy due to complications such as graft failure (GF) and organ toxicity. Herein, we are reporting our long-term outcome data of non-myeloablative (NMA) HSCT in adults with severe SCD with emphasis on factors predicting event free survival (EFS). Adults with severe SCD undergoing NMA match-related donor allogeneic HSCT from 2015 to 2021 with at least 12 months of follow-up were included. A total of 200 patients were included with a median age of 26 years (14-43) and 56% were male. The median infused CD34 dose was 13.7 (5.07-25.8), respectively. Median absolute neutrophil count engraftment was 19 (13-39) days with 51% of patients receiving GCSF to expedite recovery. A total of 17 patients experienced GF; 3 as primary and 14 as secondary within a median time of 204 days (40-905). A 76% successfully discontinued sirolimus at the last follow-up. Median follow-up for the cohort is 29.2 (2.1-71.4) months. Estimated 3-year EFS and OS were 88.2% (81.9-92.5) and 94.6% (89.2-97.3). At multivariable analysis, minor ABC incompatibility hazard ratio (HR) 4 (1.3-12.1; 0.014) and allo-antibody against non-ABO donor antigens HR 4.3 (1.3-14.1; 0.016) were significant for EFS. No clonal evolution or myeloid malignancies were seen. This largest single-center report of NMA HSCT in adults with severe SCD further delineated its feasibility, potential toxicities, and fertility outcomes. GF remains a major impediment and appears dependent on ABO matching and non-ABO antibodies.

Improved Gvhd-Relapse Free Survival of Ex Vivo αβtcr/CD19 Depleted Allo-Sct Combined with In Vivo T Cell Depletion with ATG When Compared to T Cell Replete Transplantations with or without the Addition of ATG

Introduction The aim of allogeneic stem cell transplantation (allo-SCT) is to reach graft-versus-host disease, relapse free survival (GRFS). To reduce the incidence of graft-versus-host disease (GVHD), we have developed an allo-SCT platform combining ex vivo αβTCR/CD19 depletion with in vivo T-cell depletion through administration of antithymoglobulin (ATG). Here we compare GRFS to historical cohorts of T-cell replete allo-SCT. Methods Adults with hematological malignancies and transplanted between 2011 and 2022 were included in this retrospective analysis. Written informed consent was obtained in accordance with the JACIE guidelines. Clinical data was extracted from the EBMT registry. 3 cohorts were identified. Cohort A: Allo-SCT of unmanipulated peripheral blood derived mononuclear cells (PBMCs) of matched related donors (MRD) after non-myeloablative (NMA) or myeloablative (MA) conditioning without ATG. Cohort B: Allo-SCT of unmanipulated PBMCs of 10/10 or 9/10 matched unrelated donors (MUD) after NMA or MA conditioning with ATG. Patients in cohorts A &amp; B received dual immunosuppression with cyclosporin (CsA) and mycophenolic acid (MMF). Cohort C: Allo-SCT of αβTCR/CD19 depleted PBMCs of MRD and MUD (10/10 and 9/10) after ATG and a myeloablative conditioning as previously described[1]. Patients in cohort C received 28 days of MMF. Cumulative incidence (CI) of GVHD was defined as time to onset of GVHD, with relapse and death as competing events. Overall survival (OS) was defined as time to death from any cause. CI of relapse was defined as time to relapse, with death as a competing event. Non-relapse mortality (NRM) was defined as time to death, without relapse or progression. Event free survival (EFS) was defined as the time to relapse, graft failure or death. GRFS was defined as the time to relapse, aGVHD 3-4 or extensive cGVHD, graft failure or death. CI of CMV and EBV reactivations were calculated with relapse and death as competing events. Results 341 patients were included (cohort A: N=63; cohort B: N=150; cohort C: N=128) (table 1). In T cell replete allo-SCT (A&amp;B) ATG was administered to recipients of MUD and MA conditioning was administered to patients &amp;lt; 40 years with acute leukemia. In cohort C, all patients received ATG and an MA conditioning, regardless of age or underlying malignancy. This explains differences donor types and intensity of conditioning between the cohorts (table 1). Other clinical characteristics were comparable. Two year OS (A=66.7%; B=58.7%; C=63.8%) and EFS (A=57.1%; B=52%; C=55.7%) was comparable between the cohorts. Two year CI of relapse was also comparable (A=30%; B=23%; C=28%). Two year NRM appeared higher in B, but this difference did not reach significance (A= 9.8%; B=24%; C=15%). The CI of aGVHD grade 2-4 and 3-4 at day 100 was significantly higher in T cell replete allo-SCT with MUD (2-4; A=23%; B=37%; C=20% (p=0.002); 3-4: A=5%; B=16%; C=4.7% (p=0.043)). The incidence of extensive cGVHD was significantly higher in T cell replete allo-SCT of MRD. (A= 25%; B=13%; C= 2.3% (p=&amp;lt; 0.001)). The low incidence of grade 3-4 aGVHD and extensive cGVHD without an increase in relapse or NRM, translated into a superior 2 year GRFS in patients receiving ATG combined with an αβTCR/CD19 allograft (C=55.6%) as compared to T cell replete allo-HSCT of MRD (A=38.1%) and MUD (B=40.8%) (Figure 1, p=0.04). This difference remained significant in a multivariate analysis. Conclusion We demonstrate that αβTCR/CD19 depletion combined with ATG, with a myeloablative conditioning and a very short course of immunosuppression results in very low incidences of life-threatening GVHD and an improved GRFS as compared to T cell replete allo-SCT for adult patients up to the age of 70. This is likely to positively impact the long term quality of life in survivors of allo-SCT[2]. In addition, this platform provides a window for additional early post allo-interventions to further improve the control of underlying hematological malignancies. 1. de Witte, M.A., et al., alphabeta T-cell graft depletion for allogeneic HSCT in adults with hematological malignancies. Blood Adv, 2021. 5(1): p. 240-249. 2. Oerlemans, S., et al. Relapse and severe Graft-versus-Host Disease have a negative impact on long-term symptoms and quality of life of patients three years after allogeneic haematopoietic stem cell transplantation. Annual meeting EBMT 2022.

Favorable Fertility Outcome in a Large Cohort of Sickle Cell Disease Patients Undergoing Allogeneic Hematopoietic Stem Cell Transplantation

Introduction: Fertility preservation is an important consideration for individuals with sickle cell disease (SCD) who may face reproductive challenges. While SCD itself does not directly affect fertility, certain complications and its treatment such as hematopoietic cell transplantation (HCT) can impact the reproductive health in SCD patients. HCT is a potential curative therapy for SCD, however, one of the negative outcomes is the premature gonadal failure and infertility. Both male and female patients have different risk factors that may impact the fertility post-transplant. Therefore, these patients should undergo fertility preservation counselling pre transplant. In this study, we report the fertility outcome of large transplant cohort undergoing Non-myeloablative (NMA) conditioning regimen. Methods: We retrospectively collected the data for all SCD patients who were ≥ 14 years old and who underwent allogeneic HCT in our center from 2015 until 2022 with a minimum of 1 year follow up post-transplant. All patients received hydroxyurea for 2 to 3 months pre- transplant at maximum tolerated dose. The conditioning regimen was alemtuzumab 1 mg /kg divided over 5 days from day - 7 to day -3 and Total Body Irradation 200 cGy on day -2 (with testicular shielding for male patients). Graft versus host disease prophylaxis with sirolimus started from day -1 and continued for at least 1 year post-transplant. We started the fertility program in October 2019 where all patients get counselled for fertility preservation methods. Male patients undergo sperm cryopreservation after holding hydroxyurea for 3 months and female patients were referred to a specialized oncology fertility clinic for either oocyte cryopreservation or treatment with Gonadotropin-releasing hormone (GnRH) agonists pre transplant. Primary objective of the study was to assess post-transplant fertility (defined by either ability to conceive for married patients, or development of azoospermia for male patient or secondary amenorrhea for female patients). Secondary objectives were to assess pre transplant fertility, assess the success of different fertility preservations methods and finally to assess for risk factors (pre- transplant and transplant) that affect the fertility potential. Results: We identified a total of 200 SCD patients who underwent HCT. Out of these 200 patients, 107 (54%) were included in our fertility program. The median post-transplant follow up was 3.5 years (1 - 7.5). One hundred and twelve patients (56%) were male, and eighty eight (44%) were female patients. All patients were on hydroxyurea pre transplant with average dose 1000 mg and a duration of less than 2 years in 47 (23.5%) patients, 2 to 5 years in 94 (47%) patients and more than 5 years in 59 (39.5%) patients. Other baseline characteristics are shown in table 1. In the pre-transplant fertility assessment; 58 patients were married and 48 (82%) of them had children pre transplant. 36 male patients attempted sperm cryopreservation and were successful in 33 (91%). 39 female patients received Leuprolide (GNRH agonists) pre-transplant with no complications and 6 female patients attempted oocyte cryopreservation and all were successful. One patient developed cerebral venous thrombosis during the oocyte cryopreservation course. For the post-transplant fertility assessment; out of 57 married patients 26 (45%) were able to conceive. From these 26 pregnancies; 20 ended with successful live-births, 1 ended with abortion and 5 are still pregnant. 6 patients were able to conceive twice and one patient had one twin babies. For male patients 74 did semen analysis at minimum 1 year post-transplant; 35 (47%) had azoospermia and 39 (53%) had viable sperms. Majority recovered spermatogenesis after 1 year (24 patients), at 2 years (9 patients) and after 3 years (3 patients). Three male patients had Azoospermia at one year but was able to conceive successfully without repeating the test. For female patients 71 (80.7%) were able to regain menses and 17 (19.3%) developed secondary amenorrhea. Table 2 shows the pre and post-transplant fertility measures outcome. In conclusion In this study, we have shown the fertility outcomes of male and female patients with SCD undergoing NMA conditioning HCT can be preserved in a significant proportion of patients. All adult patients should be counselled for fertility preservation methods before undergoing curative allogeneic HCT.

A Novel and Cost-Efficient Measurable Residual Disease (MRD) Detection Assay Using a Single Molecule Molecular Inversion Probe-Based Next Generation Sequencing (NGS) Assay Predicts Overall Survival in Patients with Acute Myeloid Leukemia Undergoing Allogeneic Stem Cell Transplantation

Introduction Relapse remains the main reason for poor outcomes of patients (pts) with acute myeloid leukemia (AML). Allogeneic hematopoietic stem cell transplantation (HSCT) is the preferred post-remission treatment in pts at high risk of relapse. The presence of measurable residual disease (MRD) after intensive frontline treatment or before or after HSCT has emerged as an important predictor of relapse. Various methods are used for MRD detection, including flow cytometry and molecular assays detecting individual gene mutations (mut) such as NPM1mut. Next generation sequencing (NGS)-based assays covering multiple genes commonly mutated in AML may allow sensitive MRD detection in a broad range of pts with diverse genetic characteristics. Methods We established a targeted, error corrected NGS MRD assay utilizing single-molecule molecular inversion probes (smMIPs). The smMIP protocol uses a hybridization-capture approach to selectively enrich and amplify both DNA strands of 92 regions in 32 genes in a single reaction. Unique molecular identifiers (UMIs) facilitate computational correction of sequencing errors to enable reliable detection of variants ≥0.5% variant allele frequency (VAF), with the additional advantage of relatively low reagent and sequencing costs of &amp;lt; $100 per sample. The smMIP assay was used to evaluate MRD status on pre-HSCT bone marrow samples from 98 AML pts who received an HSCT in first (n=83) or second (n=15) complete remission with or without count recovery. Median age at HSCT was 59 (range 20-75) years, 42% were female; 70% had de novo AML, 19% had an antecedent myeloid neoplasm and 11% had AML post cytotoxic therapy. European LeukemiaNet (ELN)-2022 risk groups at diagnosis were favorable in 11%, intermediate in 33%, adverse in 20% and unknown in 22%. All pts had received intensive induction chemotherapy. Twenty-nine percent received a myeloablative conditioning regimen (MAC), while 23% received reduced intensity conditioning (RIC) and 48% a non-myeloablative (NMA) conditioning regimen. Donors were matched related (18%), haploidentical (6%), or matched (55%) or mismatched (21%) unrelated. The median follow-up for pts alive was 34.8 months. Results Overall, we detected 190 variants in 71 (72%) of 98 pre-HSCT remission samples. The most commonly affected genes were DNMT3A (in 37% of pts), TET2 (21%), PPM1D (12%), IDH2 (10%) and TP53 (5%). Twenty-nine percent of pts had only variants affecting the clonal hematopoiesis-related genes DNMT3A, TET2 or ASXL1 (‘DTA‘), while 44% of patients had ≥1 variant involving a non-DTA gene. MRD-positive pts, defined as those with ≥1 non-DTA variant, had similar baseline and HSCT-related characteristics (includingage, sex, ELN risk group, de novo vs. secondary AML) compared to pts without non-DTA variants. Overall survival (OS) was significantly inferior in NGS MRD-positive pts compared to those with no non-DTA variant (Figure A, 5-year OS, 49% vs. 85%, P=.011). MRD-positive pts also had a non-significant higher cumulative incidence of relapse at 5 years (46% vs. 24%, P=.14), while non-relapse mortality was similar in both groups (P=.72). We next performed multivariable analyses, considering variables associated with OS at an univariable P&amp;lt;.10 (MRD status, patient sex, therapy-related AML, conditioning intensity), and using stepwise backward variable selection to identify factors significantly associated with OS (Figure B). In the final multivariable model, pre-HSCT MRD detection remained associated with inferior OS (hazard ratio 2.51; 95% confidence interval, 1.07 - 5.91; P=.035). Female sex associated with favorable OS, while myeloablative conditioning (MAC) showed a borderline significant association with superior OS. Of note, we did not detect an interaction between conditioning intensity and detection of MRD with regard to OS, i.e. the prognostic association of MRD detection was not different between pts receiving myeloablative or less-intensive conditioning. However, this analysis was limited by the small patient number. Conclusion Detection of MRD by targeted NGS using the smMIPs approach provides prognostic information in pts undergoing allogeneic HSCT, including those without established molecular markers such as NPM1mut. This method is applicable to a large proportion of AML pts and is cost-efficient for broad clinical use. S.M.K. and T.H., and M.J. and K.H.M. contributed equally to this abstract.

Myeloablative or reduced-intensity/non-myeloablative hematopoietic cell transplantation for Philadelphia-positive acute lymphoblastic leukemia in adults older than 40years old - a secondary analysis of a CIBMTR database.

Few studies have addressed the role of reduced-intensity conditioning (RIC) and non-myeloablative (NMA) regimens in older adults with Philadelphia acute lymphoblastic leukemia (Ph + ALL). The objective of this current study was to compare the outcomes of RIC/NMA versus TBI-based myeloablative (MAC) regimens in Ph + ALL patients older than 40years old who underwent hematopoietic cell transplantation (HCT) in CR1. We used a freely available database from the CIBMTR. Transplants were performed between 2013 and 2017. With a median follow-up of 37.6months, we have included 629 patients. We used propensity score weighting. Three-year OSs were 64% in the TBI-MAC group and 66% in the RIC/NMA group. OS was not different (HR = 0.92; p = 0.69). Three-year relapse incidences were 21.6% and 27.6% in the TBI-MAC and RIC/NMA groups. RIC/NMA was not associated with an increase in relapse rate (HR 1.02; p = 0.91). Three-year NRMs were 24.3% in the TBI-MAC group and 20.3% in the RIC/NMA group. RIC/NMA was not associated with superior NRM (HR 0.88; p = 0.57). In summary, we have shown that RIC/NMA regimens achieve outcomes comparable to TBI-based MACin Ph+ ALL older patients in CR1 who may tolerate a TBI-based MAC regimen.

Post-Transplant Maintenance in AML and MDS Patients Undergoing Non-Myeloablative Peripheral Blood Stem Cell Transplant with Post-Transplant Cyclophosphamide

Disease relapse remains a major cause of mortality for patients with AML and MDS undergoing allogeneic hematopoietic stem cell transplant (HSCT). Several trials have evaluated the use of hypomethylating agents (HMA) like azacitadine or decitabine as post-transplant maintenance with its use not currently recommended. Here we review our experience with AML and MDS patients undergoing non-myeloablative (NMA) peripheral blood stem cell transplant using post-transplant cyclophosphamide (PTCy) as GVHD prophylaxis and in whom post-transplant maintenance was used. We retrospectively reviewed AML and MDS patients who had a NMA HSCT from January 2015 until December 2022. All patients received fludarabine, cyclophosphamide and TBI200 or TBI300 as conditioning regimen with tacrolimus, mycophenolate mofetil and PTCy as GVHD prophylaxis (Table 1). Sixty patients received TBI200 and 28 patients received TBI300. Median age at transplant was 65.5 years in the TBI200 group vs 69 years in the TBI300 group. Haploidentical donors were used in 59 (98%) of patients in the TBI200 group and 18 (64%) of patients in the TBI300 group. Minimal residual disease (MRD) was present 35 (58%) of patients receiving TBI200 and 12 (43%) of patients receiving TBI300. Post-transplant therapy was given in 46 (77%) of patients in the TBI200 group and 23 (82%) in the TBI300 group. The majority of patients in both groups received azacitadine. The median cycles of HMAs was 4 (range 1-12). We found no difference in OS, PFS, relapse, or NRM comparing Flu/Cy/TBI200 and Flu/Cy/TBI300 (not shown). We evaluated the use of post-transplant maintenance on survival endpoints and found no difference in endpoints. In addition, post-transplant maintenance had no effect on OS, PFS, relapse, NRM or grade II-IV aGVHD regardless of MRD status at time of transplant. While, this is a small retrospective series, it warrants further investigation into the use of post-transplant maintenance in the setting of NMA HSCT using PTCy. While the use of HMA's did not increase NRM, their efficacy and perhaps combination with other drugs needs to be more closely studied in NMA PTCy transplants to decrease relapse.

Comparison of Non-Myeloablative Conditioning Regimens Flu/Bu2, Flu/Mel 100 and Flu/TBI in Patients with AML and MDS

Allogeneic hematopoietic stem cell transplantation (HSCT) is a potentially curative treatment modality for patients with myelodysplastic syndrome (MDS) or acute myeloid leukemia (AML). Non-myeloablative (NMA) conditioning regimens are used to decrease toxicity, making HSCT more tolerable and available to older patients or patients with co-morbidities. It remains unclear as to which NMA regimen leads to superior outcomes. Methods: We retrospectively compared outcomes of 3 NMA regimens in 98 patients with AML or MDS undergoing allogeneic HSCT from January 2017 to December 2021. The 3 regimens were: Flu/Mel 100: fludarabine 40 mg/m2 days -5 to -2, melphalan 100 mg/m2 day -2; Flu/Bu2: fludarabine 30 mg/m2 days -6 to -2, busulfan 130 mg/m2 days -3 to -2; Flu/TBI: fludarabine 30 mg/m2 days -4 to -2, total body irradiation 200-300 cGY on day-1. Patients conditioned with Flu/Mel 100 or Flu/Bu2 also received rabbit anti-thymocyte globulin 4-6 mg/kg. Graft versus host disease (GVHD) prophylaxis consisted of tacrolimus and low dose methotrexate for patients receiving Flu/Mel 100 or Flu/Bu2, and sirolimus, cyclosporine and mycophenolate mofetil for patients conditioned with Flu/TBI. Continuous variables were compared between conditioning regimens using Pearson's Chi-squared test or Fisher's exact test. PFS and OS survival probability and survival times were estimated with Kaplan-Meyer(K-M) procedure. To compare survival distributions between conditioning regimens, a log-rank test was used. We report 24-month survival probabilities in months with corresponding 95% confidence intervals. Results: Patient demographics were balanced between the 3 groups including age (range 54-80), gender, disease risk and cell source (Table 1). 24-month progression free survival (PFS) was not different between the groups: Flu/Mel 100 was 70% (47%-100%), Flu/Bu2 was 49% (39%-63%), and Flu/TBI was 33% (18%-61%) (p=0.3). For Flu/Mel 100 the 24-month overall survival (OS) was 70% (47%-100%), Flu/Bu2 was 53% (42%-66%), Flu/TBI was 32% (17%-61%) which was not statistically different ( p=0.3) (Figure 1). There was no difference between the 3 groups for non-relapse mortality (NRM) ( p=0.46). The incidence of all grade acute GVHD was 70% for Flu/Mel 100, 66% for Flu/Bu2 and 76% for Flu/TBI ( p=0.70). There was no difference in the incidence of chronic GVHD between the groups; Flu/Mel 100 50%, Flu/Bu2 55%, Flu/TBI 57% (p&amp;gt;0.99). Conclusions: All three NMA regimens were found to be statistically equivalent. NRM, PFS, OS and the incidence of acute and chronic GVHD was not statistically different between the groups. A limitation of the study is the relatively small number of patients in the Flu/Mel 100 group. Further study with a larger sample size is needed to evaluate for small differences between the regimens.

Generation of Non-Alloreactive Antiviral Central Memory CD8 Human Veto T Cells for Cell Therapy

Previous studies in mice demonstrated that CD8 T cells exhibit marked veto activity enhancing engraftment in several models for T cell-depleted bone marrow (TDBM) allografting. To reduce the risk of graft-versus-host disease (GVHD) associated with allogeneic CD8 veto T cells, these studies made use of naive CD8 T cells stimulated against third-party stimulators under cytokine deprivation and subsequent expansion in the presence of IL-15. More recently, it was shown that mouse CD8 veto T cells can be generated by stimulating CD8 memory T cells from ovalbumin immunized mice under cytokine deprivation, using ovalbumin as a third-party antigen. These cells also exhibited substantial enhancement of BM allografting without GVHD. In this study, we tested the hypothesis that stimulation and expansion of human CD8 memory T cells under IL-15 and IL-7 deprivation during the early phase of activation against recall viral antigens can lead to substantial loss of alloreactive T clones while retaining marked veto activity. Memory CD8 T cells were enriched by removal of CD45RA+, CD4+, and CD56+ cells from peripheral blood of cytomegalovirus (CMV)- and Epstein-Barr virus (EBV)-positive donors. In parallel, CD14+ monocytes were isolated; differentiated into mature dendritic cells (mDCs); pulsed with a library of CMV, EBV, adenovirus, and BK virus peptides; and irradiated. The CD8 T cell-enriched fraction was then cultured with the pulsed mDCs in the presence of IL-21 for 3 days, after which IL-15 and IL-7 were added. After 12 days of culture, the cells were tested by limiting dilution analysis for the frequency of alloreactive T cell clones and their veto activity. In preclinical runs using GMP reagents, we established that within 12 days of culture, a large number of highly homogenous CD8 T cells, predominantly expressing a central memory phenotype, could be harvested. These cells exhibited marked veto activity in vitro and >3-log depletion of alloreactivity. Based on these preclinical data, a phase 1-2 clinical trial was initiated to test the safety and efficacy of these antiviral CD8 central memory veto cells in the context of nonmyeloablative (NMA) T cell-depleted haploidentical hematopoietic stem cell transplantation (HSCT). In 2 validation runs and 11 clinical runs using GMP reagents, >1×1010 cells were generated from a single leukapheresis in 12 out of 13 experiments. At the end of 12 days of culture, there were 97 ± 2.5% CD3+CD8+ T cells, of which 84 ± 9.0% (range, 71.5% to 95.1%) exhibited the CD45RO+CD62L+ CM phenotype. Antiviral activity tested by intracellular expression of INF-γ and TNF-α and showed an average of 38.8 ± 19.6% positive cells on 6 hours of stimulation against the viral peptide mixture. Our results demonstrate a novel approach for depleting alloreactive T cell clones from preparations of antiviral CD8 veto cells. Based on these results, a phase 1-2 clinical trial is currently in progress to test the safety and efficacy of these veto cells in the context of NMA haploidentical T cell-depleted HSCT. Studies testing the hypothesis that these non-alloreactive CD8 T cells could potentially offer a platform for off-the-shelf veto chimeric antigen receptor T cell therapy in allogenic recipients, are warranted.

Allogeneic Hematopoietic Cell Transplantation with Non-Myeloablative Conditioning and Post-Transplant Cyclophosphamide Prophylaxis in Patients with Reduced Systolic Function

Post-transplantation cyclophosphamide (PTCy) has become standard of care for graft-versus-host disease (GVHD) prophylaxis after allogeneic hematopoietic cell transplantation (alloHCT), allowing for expanded donor options. However, there is scant literature examining outcomes of patients with reduced systolic function receiving PTCy. The present study aimed to describe our experience in performing alloHCT in patients with reduced systolic function, including their nonrelapse mortality (NRM), overall survival (OS), and cumulative incidence of early cardiac events (ECEs). We performed a retrospective descriptive analysis using the Johns Hopkins Hematologic Malignancy database. From 2017 through 2021, 1118 consecutive patients underwent alloHCT with nonmyeloablative (NMA) conditioning and PTCy. Forty-three of those patients had a pretransplantation left ventricular ejection fraction (LVEF) ≤45% measured by transthoracic echocardiography. Patients whose LVEF improved on treatment prior to transplantation were also included. These 2 cohorts were stratified into 2 groups-heart failure with reduced ejection fraction (HFrEF) and heart failure with recovered ejection fraction (HFrecEF)-and subgroup analyses compared NRM, OS, and cumulative incidence of ECEs, including arrhythmia, coronary artery disease, reduction in LVEF, and pericardial effusion, within 100 days post-transplantation. The median LVEF was 40% to 45% (range, 30% to 45%) for the 31 patients undergoing transplantation with HFrEF and 35% to 40% (range, 20% to 45%) for the 12 patients with HFrecEF. The NRM for all 43 patients was 16% (95% confidence interval [CI], 5% to 27%) at 100 days and 23% (95% CI, 11% to 36%) at 2 years. The NRM was 23% (95% CI, 8% to 38%) at 100 days and 26% (95% CI, 10% to 42%) at 2 years for the HFrEF cohort and 0 at 100 days and 18% (95% CI, 0 to 41%) at 2 years for the HFrecEf cohort. The OS at 3 years was 41% (95% CI, 26% to 62%), 40% (95% CI, 25% to 65%) and 38% (95% CI, 14% to 100%) in the combined, HFrEF, and HFrecEF cohorts, respectively. The cumulative incidence of any ECE was 37.2% (95% CI, 22% to 51.9%), including 39% of HFrEF subjects and 33% of HFrecEF subjects. Grade ≥3 toxicities were seen in 56% of patients. Reduced ejection fraction was the most common ECE. One death was attributable to a cardiac etiology. Cardiac toxicities seemed to be more frequent and severe in patients with a history of systolic dysfunction, but this did not lead to worse survival outcomes. This study adds to and extends the existing literature supporting the use of NMA conditioning and PTCy in patients with systolic dysfunction.

Reduced-Intensity Compared to Nonmyeloablative Conditioning in Patients with Non-Hodgkin Lymphoma Undergoing Allogeneic Hematopoietic Stem Cell Transplantation

Reduced-intensity conditioning (RIC) and nonmyeloablative (NMA) conditioning are preferred for patients with non-Hodgkin lymphoma (NHL) undergoing allogeneic hematopoietic stem cell transplantation (allo-HCT). Although prior studies have suggested that higher-intensity regimens in RIC-NMA conditioning are associated with inferior outcomes in patients with NHL, the optimal conditioning regimen remains unknown. We performed a retrospective single-center analysis to determine outcomes of adult patients with B cell and T cell NHL who underwent allo-HCT and received either RIC or NMA conditioning between March 2008 and December 2019. RIC regimens included fludarabine-cyclophosphamide-thiotepa-4 Gy-total body irradiation (Flu-Cy-TT-4Gy-TBI), fludarabine-melphalan (Flu-Mel), fludarabine-cyclophosphamide-4 Gy-total body irradiation (Flu-Cy-4Gy-TBI), and fludarabine-busulfan-4 (Flu-Bu-4). The NMA regimen comprised fludarabine-cyclophosphamide-2 Gy-total body irradiation (Flu-Cy-2Gy-TBI). The primary outcome was overall survival (OS); secondary outcomes included progression-free survival (PFS), nonrelapse mortality (NRM), and the incidence of acute and chronic graft-versus-host-disease (GVHD). Of 279 transplants recipients (median age, 58 years), 110 received RIC (55% Flu-Mel, 38% Flu-Cy-TT-4Gy-TBI, 6% Flu-Bu-4, 1% Flu-Cy-4Gy-TBI) and 169 received NMA conditioning with Flu-Cy-2Gy-TBI. With a median of 64 months of follow-up post-allo-HCT, there was no significant difference in OS between the NMA and RIC groups (median, not reached [NR] versus 103 months; P=.1), and this was maintained on multivariable analysis. Similarly, after adjustment for all independently significant covariates (age, Karnofsky Performance Status [KPS], Hematopoietic Cell Transplantation Comorbidity Index [HCT-CI], and disease histology), the regression analysis showed no significant difference in PFS with RIC compared to NMA conditioning (hazard ratio [HR] 1.38; 95% confidence interval [CI], .92 to 2.09; P=.24). On univariable analysis, there was no significant difference in NRM between the RIC and NMA arms (100-day estimate, 10.0% versus 1.8%; P=.5). After adjustment for age, ethnicity, KPS, HCT-CI, GVHD prophylaxis, and donor source, RIC conditioning was associated with a significantly higher incidence of NRM compared to NMA conditioning (HR, 2.61; 95% CI, 1.04 to 6.52; P=.039). On multivariable analysis, compared with the NMA arm, the RIC arm had higher rates of grade II-IV (HR, 2.25; 95% CI, 1.31 to 3.86; P=.002) and grade III-IV acute GVHD (HR, 5.62; 95% CI, 2.03 to 15.6; P < .001). The findings of this study suggest that NMA conditioning with Flu-Cy-TBI-2Gy may be considered over more intensive RIC regimens for patients with NHL undergoing allo-HCT.

Haploidentical Stem Cell Transplantation for Hematological Disorders: Real-World Experience from India

Haploidentical transplant (haploSCT) has its own unique complications; hence, we studied the outcome of haploSCT from a cancer hospital in India. We retrospectively analyzed the haploSCTs performed at our center between March 2015 and mid-August 2022 using posttransplant cyclophosphamide (PTCy). Ninety-nine patients (95 malignant and 4 nonmalignant) underwent 101 haploSCTs. Myeloablative (MA), nonmyeloablative (NMA), and reduced intensity conditioning (RIC) were used in 35 (34.6%), 43 (42.5%), and 23 (22.7%) transplants, respectively. The median CD34 + was 5.9 (1.8–10) ×106/kg. The median time to neutrophil and platelet engraftment was 15 (11–32) and 15.5 (9–120) days, respectively. There were 09 (8.9%) cases of primary graft rejection. Eighteen (17.8%) patients had a relapse. Acute graft versus host disease (GVHD) was observed in 33 (32.6%) cases. Blood cultures were positive in 42 (41.5%) transplants. Common viral infections were BK (47.3%) and cytomegalovirus (CMV; 65.3%). The median follow-up was 6 (0.5–89.5) months. Forty-eight (48.4%) patients had died at the last follow-up. The main causes of the death were sepsis (27 [56.2%]), relapse (10 [22.2%]), and GVHD (04 [8.8%]). The nonrelapse mortality was 37.3%. The median overall survival (OS) was 18 ± 11.46 (0–40.77) months. The 1-year OS was 56.7%, while the 2-year OS was 49.3%. We emphasize that haploSCT offers a reasonable hope of survival for patients, although infections remain a significant challenge based on our experience.

Triple-Drug Graft-versus-Host Disease Prophylaxis after HLA-Matched Unrelated Donor Nonmyeloablative Allogenic Hematopoietic Stem Cell Transplantation

Adding sirolimus to graft-versus-host disease (GVHD) prophylaxis with cyclosporin and mycophenolate mofetil (MMF) reduced the risk of grade II-IV acute GVHD after nonmyeloablative (NMA) allogenic hematopoietic stem cell transplantation (HSCT) with an HLA-matched unrelated donor in a randomized clinical trial. We analyzed real-life data to investigate the impact of implementing the triple-drug regimen with cyclosporin, MMF and sirolimus as standard GVHD prophylaxis after NMA HSCT with an HLA-matched unrelated donor at our institution. We studied all adult patients (age ≥18 years) who underwent NMA HSCT with an HLA-matched unrelated donor at Rigshospitalet, Copenhagen University Hospital, Denmark between 2018 and 2021 and received GVHD prophylaxis with cyclosporin, MMF and sirolimus (triple-drug group [TDG]). Comparisons were made with a historical cohort who received tacrolimus and MMF as GVHD prophylaxis after HLA-matched unrelated donor NMA HSCT between 2014 and 2017 (control group [CG]). Outcomes were grade II-IV and grade III-IV acute GVHD, chronic GVHD, relapse, nonrelapse mortality (NRM) andoverall survival (OS). A total of 264 patients were included (TDG, n = 137; CG, n = 127). Median age was 66 years (interquartile range [IQR], 58 to 69 years) in the TDG and 63 years (IQR, 57 to 68 years) in the CG. Acute myeloid leukemia and myelodysplastic syndrome were the most frequent indications for HSCT in both groups (TDG, 33% and 23%, respectively; CG, 36% and 22%, respectively). The cumulative incidence at day +110 of grade II-IV GVHD was 17% (95% confidence interval [CI] 11% to 23%) in the TDG versus 29% (95% CI, 21% to 37%) in the CG (P = .02, Gray's test) and that of grade III-IV acute GVHD was 3% (95% CI, 0 to 6%) versus 5% (95% CI, 1% to 8%), respectively (P = .4, Gray's test). In a Cox regression model adjusted for age, donor age and female donor to male recipient the risk of grade II-IV acute GVHD was lower in the TDG compared to the CG (hazard ratio [HR], .51; 95% CI .30 to .86; P = .01). The 2-year OS was 77% (95% CI, 70% to 84%) in the TDG and 69% (95% CI, 61% to 77%) in the CG (P = .04), and this difference remained significant after adjustment for age and Karnofsky Performance Status (HR, .65; 95% CI, .42 to .99; P = .04). The 2-year cumulative incidences of chronic GVHD, relapse and NRM were 60% (95% CI, 51% to 69%), 21% (95% CI, 13% to 28%), and 12% (95% CI, 6% to 17%), respectively, in the TDG and 62% (95% CI, 54% to 71%), 27% (95% CI, 19% to 35%) and 14% (95% CI, 8% to 20%), respectively, in the CG. Multivariable analyses revealed no difference in the risk of chronic GVHD (HR, .91; 95% CI, .65 to 1.26; P = .56), relapse (HR, .70; 95% CI, .42 to 1.15; P = .16) or NRM (HR, .56; 95% CI, .31 to 1.05; P = .07). After changing the standard GVHD prophylaxis in patients undergoing NMA HSCT with an HLA-matched unrelated donor from tacrolimus and MMF to cyclosporin, MMF and sirolimus, we observed a reduction in the incidence of grade II-IV acute GVHD and improved 2-year OS.

Harnessing the power of tumor-infiltrating lymphocytes: A first-in-human study of GT201 as monotherapy in advanced solid tumors.

2551 Background: Genetically engineered TIL has shown features such as prolonged memory that can improve therapeutic efficacy in tumor mouse models. GT201 is an engineered TIL that expresses a membrane-bound IL-15 (mbIL-15), and preclinical studies have demonstrated enhanced antitumor reactivity. A phase 1 study was initiated to evaluate the preliminary safety of GT201 and to identify Optimal Biological Dose (OBD) suitable for monotherapy expansion. Methods: The dose-escalation study (using TITE-BOIN design) intended to enroll patients (pts) with advanced treatment-refractory solid tumors. Once the OBD is identified, a monotherapy expansion phase will be opened for patients with various solid tumors. Enrolled patients were preconditioned with a nonmyeloablative (NMA) lymphodepletion regimen and treated by autologous infusion of the GMP-grade G201 cell product, followed with supportive low dose IL-2 administration. Results: As of January 17, 2023, the dose-escalation study enrolled 4 pts, all of whom were female with a median age of 52.6 years. The median number of infused TIL cells was 5.3E+09. All pts experienced TRAEs, with the majority being grade 1 or 2. The most common grade 3/4 TRAEs were lymphopenia (100%), leukopenia (25%) and neutropenia (25%), which were related to the NMA regimen. No dose-limiting toxicities (DLTs) or TIL-related grade ≥3 TRAEs were observed. Median time on study was 17 wks (6–30 wks). One pt with highly treatment-refractory cervical cancer experienced a confirmed partial response (PR) after 16 wks that was durable for 30 wks (RECIST 1.1). Two pts (cervical cancer and melanoma) experienced disease stabilization, while another malignant melanoma pt experienced progressive disease. Despite varying doses of TILs (5.0E+09 to 1.40E+10) and IL-2 (up to 3.0E+05 IU/kg), all patients receiving GT201 therapy showed robust T cell expansion post-infusion, with higher doses of IL-2 leading to more rapid TIL expansion. GT201 TILs could be detected in patients after one month post-infusion, indicating promising activation and long-term persistence of the infused TILs. Based on safety, tolerability, PKs, and preliminary efficacy, a TIL dose of 1.0E+10 and an IL-2 dose of 3.0E+05IU/kg was selected as the OBD for the study. Conclusions: The results of the first-in-human study of GT201, a mIL-15 expressed on TILs, demonstrate promising preliminary findings as a monotherapy in pts with advanced cancers. The administration of GT201 was associated with robust T cell expansion, as well as prolonged persistence of infused TILs. Results of mbIL-15 expressed TIL demonstrates that GT201 has good tolerability with encouraging preliminary antitumor activity as a monotherapy. Further investigations, including correlative biomarker analyses and updated safety and clinical outcome data, will be presented at the meeting. Clinical trial information: NCT05430360 .

Comparison of reduced intensity and nonmyeloablative conditioning for adults with acute myeloid leukemia undergoing allogeneic hematopoietic cell transplantation in first or second remission.

Reduced intensity conditioning (RIC) and nonmyeloablative (NMA) conditioning regimens have expanded use of allogeneic hematopoietic cell transplantation (HCT) in AML to include older and medically less-fit patients, but relative efficacies and toxicities remain poorly defined. Here, we analyzed outcomes from 343 adults transplanted in remission after RIC (n = 137) or NMA (n = 206) conditioning between 2006 and 2021. The characteristics of RIC and NMA HCT patients were similar except that RIC patients were younger and their time between most recent remission achievement and allografting was shorter. There were no significant differences in relapse risk, relapse-free survival (RFS), overall survival (OS), and non-relapse mortality (NRM) between RIC and NMA HCT patients, both overall (relapse: hazard ratio [HR] = 0.80, P = 0.27; RFS: HR = 0.93, P = 0.61; OS: HR = 0.93, P = 0.66; NRM: HR = 1.13, P = 0.59) and when patients were stratified by pre-HCT measurable residual disease (MRD) status. After multivariable adjustment, there was no statistically significant association between conditioning intensity and relapse (HR = 0.69, P = 0.088), RFS (HR = 0.86, P = 0.37), OS (HR = 0.89, P = 0.49), or NRM (HR = 1.37, P = 0.19). In this non-randomized cohort of adults undergoing allografting for AML in first or second remission at our center, we could not detect statistically significantdifferences in outcomes between those assigned to RIC and those assigned to NMA conditioning.

Non-Myeloablative Lymphodepleting Conditioning in Patients Undergoing Tumor Infiltrating Lymphocytes (TILs) Therapy; Past, Present, and Future

Introduction Adoptive cell therapy (ACT) using TILs is being studied in phase 2 and 3 pivotal clinical trials in patients with melanoma and other malignancies. A common feature of ACT using TILs is the administration of non-myeloablative (NMA) conditioning using cyclophosphamide and fludarabine with or without total body irradiation. This NMA lymphodepleting chemotherapy enhances the survival, persistence, and antitumor activity of the infused cells by eliminating regulatory T cells, increasing homeostatic cytokines like IL-7 and IL-15, and eliminating resident T-cells competing for these cytokines. However, an unresolved issue with ACT using TILs is the optimal intensity of NMA chemotherapy that would yield the maximal benefits with the least toxicity. This systematic review focuses on the different NMA regimens used in TILs therapy. Methods We systematically searched multiple databases, including Pubmed, Embase, and Cochrane, according to the PRISMA statement on Medline. We used MeSH terms and keywords for TILs, NMA chemotherapy, and cyclophosphamide. We included only prospective articles published in English with available full texts until July 2022. The primary database search yielded 773 articles. We excluded irrelevant, duplicates, and review articles. The final search revealed 16 articles that were explored in detail for years of publication, patients' demographics, disease site, NMA regimen, safety, and efficacy profile. Results Early studies (until 2010) A total of 165 patients (male: 100, female: 65) were enrolled across seven studies from 1991-2010, all with metastatic melanoma except 13 patients with epithelial ovarian cancer. Cy 60mg/kg and Flu 25 mg/m2 were used in two studies (Dudley et al. 2004 and Besser et al. 2009). Cy single agent at a dose of 1 g/m2 was used in two studies (Dillman et al. 1991 and Bears et al. 1992). Cy at a dose of 350 mg/m2 in combination with other agents was used in two studies (Fujita et al. 1995 and Arienti et al. 1993). Median OS was reported as nine months in one study, and 3-yr survival was reported at 100% in another study. The overall response rate (ORR) range was between 24%-51%. The most common toxicities reported were hematologic and febrile neutropenia. Recent studies (2011-2021) A total of ten studies met our inclusion criteria, in which 370 patients were included. All with metastatic melanoma except 96 patients with oral cavity SCC. The most common NMA conditioning regimen was Flu 25 mg/m2and Cy 60mg/kg, with only one study using Cy 300mg/m2(Wolf et al. 2020). The Median OS range was between 9.8-38.2 months. Goff et al. (2016) showed that adding TBI was associated with similar efficacy but a higher toxicity rate than no TBI. ORR range was between 29% and 64%. Similar to earlier studies, the most common toxicities were hematologic toxicities and febrile neutropenia.Conclusion This comprehensive systematic review summarizes NMA chemotherapy regimens used in TILs therapy. The heterogeneity of NMA chemotherapy dosing regimens, TILs technique, patient population, and IL-2 dose precludes conclusions regarding efficacy and safety. Cy 60mg/kg x 2 days and Flu 25 mg/m2 x 5 days is the most common regimen used, especially in recent studies. There is no excitement about adding TBI due to similar efficacy but more toxicity. More recently, Nissani et al. compared the Cy 60 mg/m2 to 30 mg/kg dose, both for two days with 25 mg/kg Flu for five days, and showed similar efficacy results with a better toxicity profile with the lower dose. Therefore, we expect this lower dose to be the most commonly used in future studies. Other than decreasing toxicity, using lower doses of cyclophosphamide can be logistically important due to omitting mesna and allowing outpatient administration of NMA lymphodepleting therapy, which is more convenient for patients.