HLA Matching Research Articles

What makes a good Samaritan: age, HLA matching, or both?

What makes a good Samaritan: age, HLA matching, or both?

441.5: Potential of 250 new nautical mile concentric circle allocation system for improving the donor/recipient HLA matching.

441.5: Potential of 250 new nautical mile concentric circle allocation system for improving the donor/recipient HLA matching.

The Consequences of HLA Screening in the Prevention of Graft-Versus-Host Disease in Living Donor Liver Transplantation.

To study the effects of routine HLA screening and the policy of avoiding donor-dominant one-way HLA match to prevent graft-versus-host disease (GVHD) after living donor liver transplantation (LDLT). The records of potential living liver donors and recipients who attended our center between 2007 and 2018 were reviewed retrospectively. Of the 149 patients who underwent LDLT and survived longer than 3 months, two developed GVHD despite our strict policy. The first patient presented with grade II GVHD limited to the skin. She was treated successfully by briefly discontinuing immunosuppression and switching to everolimus. In the second case, the policy had been relaxed due to the availability of a single donor for ABO-incompatible transplantation without any intervention to decrease anti-A antibody levels (special case: A2 to O). Nevertheless, the patient presented with grade I GVHD limited to skin and was treated successfully by adding oral methylprednisolone to tacrolimus and mycophenolate mofetil. To the best of our information, this is the second reported case who recovered from GVHD after LDLT from a donor, homozygous at HLA A, B and DR and a recipient, heterozygous for all. Sixteen potential donors (1.2% of all candidates) of 14 recipients were disqualified solely on the basis of the HLA results; five of these patients died due to unavailability of another donor. The results support the policy of avoiding HLA combinations that preclude immune recognition of graft lymphocytes as foreign to decrease the risk of GVHD after LDLT.

First successful ovarian cortex allotransplant to a Turner syndrome patient requiring immunosuppression: wide implications

ObjectiveTo determine whether we can safely and successfully transplant an ovary tissue allograft from a non-identical donor to her Turner syndrome sister. DesignTransplantation of cryopreserved ovary tissue, as well as fresh transplantation of ovarian tissue between identical twins, is now well established with numerous reported successful cases. However there have not yet been any ovary transplants between non-identical women requiring immunosuppression (ovary allotransplant). This could be a much more common indication for ovary tissue transplantation if safe and reliable immunosuppression were available. SubjectsA 20 year old amenorrheic woman with non-mosaic 45-XO Turner syndrome requested ovary tissue transplantation from her fertile 22 year old 46-XX sister. They were an HLA match but were ABO incompatible, a well known contra-indication to solid tissue or organ transplantation. The Turner syndrome sister strongly preferred to be able to become pregnant naturally without donor egg IVF, and to avoid HRT (hormone replacement therapy). In her religious group, that would also be important for finding a marital match. Despite the poor prognosis associated with ABO incompatibility, an ovary from her 22 year old non-identical fertile sister was transplanted to her employing the immunosuppression protocol now used for kidney transplant patients in our centers at Washington University and Johns Hopkins. Main Outcome MeasuresPost-operatively at 5 months she developed normal monthly menstrual ovarian function, and she became spontaneously pregnant with a normal baby girl. The relation between her post-op FSH and AMH levels continues to support the theory that tissue pressure controls primordial follicle recruitment. The fact that ABO incompatibility did not prevent success suggests that diffusion and not revascularization may be all that is required for successful long term ovarian cortex transplant survival with spontaneous pregnancy. ResultsOvary allotransplantation with safe immunosuppression allows natural conception, and also normal hormone function obviates the need for HRT. Orthotopic placement of the graft and surgical technique is critical for natural conception and a higher pregnancy rate. ConclusionAllotransplantation requiring safe immunosuppression, if successful, may be a much more commonly used indication for ovary transplantation in the future than frozen ovary grafts or grafts between identical twins.

Haploidentical versus Cord Blood Transplantation in Pediatric AML. A Retrospective Outcome Analysis on Behalf of the Pediatric Subcommittee of GETH (Grupo Español de Trasplante Hematopoyético)

Haploidentical stem cell transplantation (Haplo-SCT) and cord blood transplantation (CBT) are both effective alternative treatments in patients suffering from acute myeloid leukemia (AML) and lacking a matched HLA donor. In the last years, many centers have abandoned CBT procedures mostly due to concern about poorer immune recovery compared with Haplo-SCT. We conducted a retrospective multicenter study comparing the outcomes using both alternative approaches in AML. A total of 122 transplants (86 Haplo-SCTs and 36 CBTs) from 12 Spanish centers were collected from 2007 to 2021. Median age at hematopoietic stem cell transplantation (HSCT) was 7 years (0.4-20). Thirty-nine patients (31.9%) showed positive minimal residual disease (MRD) at HSCT and a previous HSCT was performed in 37 patients (30.3%). The median infused cellularity was 14.4 × 106/kg CD34+ cells (6.0-22.07) for Haplo-SCT and 4.74 × 105/kg CD34+ cells (0.8-9.4) for CBT. Median time to neutrophil engraftment was 14 days (7-44) for Haplo-SCT and 17 days (8-29) for CBT (P = .03). The median time to platelet engraftment was 14 days (6-70) for Haplo-SCT and 43 days (10-151) for CBT (P < .001). Graft rejection was observed in 13 Haplo-SCTs (15%) and in 6 CBTs (16%). The cumulative incidence of acute graft versus host disease (GvHD) grades II-IV was 54% and 51% for Haplo-SCT and CBT, respectively (P = .50). The cumulative incidence of severe acute GvHD (grades III-IV) was 22% for Haplo-SCT and 25% for CBT (P = .90). There was a tendency to a higher risk of chronic GvHD in the Haplo-SCT group being the cumulative incidence of 30% for Haplo-SCT and 12% for CBT (P = .09). The cumulative incidence of relapse was 28% and 20% for Haplo-SCT and CBT, respectively (P = .60). We did not observe statistically significant differences in outcome measures between Haplo-SCT and CBT procedures: 5-year overall survival (OS) was 64% versus 57% (P = .50), 5-year disease-free survival (DFS) 58% versus 57% (P = .80), GvHD-free and relapse-free survival (GFRFS) 41% versus 54% (P = .30), and cumulative incidence of transplant-related mortality (TRM) 14% versus 15% (P = .80), respectively. In the multivariate analysis, MRD positivity and a disease status >CR1 at the time of HSCT were significantly associated with poorer outcomes (P < .05). In conclusion, our study supports that both haploidentical and cord blood transplantation show comparable outcomes in pediatric AML patients. We obtained comparable survival rates, although CBT showed a trend to lower rates of chronic GvHD and higher GFRFS, demonstrating that it should still be considered a valuable option, particularly for pediatric patients.

Unsupervised Clustering Analysis of Regimen and HLA Characteristics in Pediatric Umbilical Cord Blood Transplantation

HLA matching is a critical factor in allogeneic unrelated hematopoietic cell transplantation (HCT) because of its impact on post-transplantation survival and quality of life. Umbilical cord blood transplantation (UCBT) offers unique advantages, but determining the optimal approach to graft selection and immunosuppression remains challenging. Unsupervised clustering, a machine learning technique, has potential for analyzing transplantation outcomes, but its application in investigating leukemia outcomes has been limited. This study aimed to identify optimal combinations of HLA/ killer immunoglobulin receptor (KIR) donor-patient pairing, conditioning, and immunosuppressive regimens in pediatric patients with acute lymphoblastic leukemia (ALL) or acute myeloblastic leukemia (AML) undergoing UCBT. Outcome data for single, unmanipulated UCBT in pediatric AML (n = 708) and ALL (n = 1034) patients from the Eurocord/EBMT registry were analyzed using unsupervised clustering. Resulting clusters were used to inform post hoc competing risks and Kaplan-Meier analyses. In AML, single HLA-C mismatches with other loci fully matched (7/8) were associated with poorer relapse-free survival (RFS) (P = .039), but a second mismatch at any other locus counteracted this effect. In ALL, total body irradiation (TBI) effectively prevented relapse mortality (P = .007). KIR/HLA-C match status affected RFS in AML (P = .039) but not in ALL (P = .8). Administration of antithymocyte globulin (ATG) substantially increased relapse, with no relapses occurring in the 85 patients who did not receive ATG. Our unsupervised clustering analyses generate several key statistical and mechanistic hypotheses regarding the relationships between HLA matching, conditioning regimens, immunosuppressive therapies, and transplantation outcomes in pediatric AML and ALL patients. HLA-C and KIR combinations significantly impact RFS in pediatric AML but not in ALL. ATG use in fully matched pediatric patients is associated with late-stage relapse. TBI regimens appear to be beneficial in ALL, with efficacy largely independent of histocompatibility variables. These findings reflect the distinct genetic and biological profiles of AML and ALL.

A healthy live birth after mosaic blastocyst transfer in preimplantation genetic testing for GATA1-related cytopenia combined with HLA matching

BackgroundGATA1-related cytopenia (GRC) is characterized by thrombocytopaenia and/or anaemia ranging from mild to severe. Haematopoietic stem cell transplantation (HSCT) is a healing therapeutic choice for GRC patients. We identified a novel pathogenic variant (GATA1: c.1019delG) in a boy with GATA1-related cytopenia. Then we performed preimplantation genetic testing (PGT) in this GRC family. After a mosaic embryo transfered, a healthy and HLA-compatible with the proband baby was delivered.Case presentationThe proband is a 6-year-old boy who was diagnosed to have transfusion-dependent anaemia since 3 year old. Whole-exome sequencing (WES) showed that the proband has a hemizygous variant c.1019delG in GATA1, which is inherited from his mother. His parents decided to undergo PGT to have a health and HLA-compatible offspring. After whole genome amplification (WGA) of biopsied trophectoderm (TE) cells, next generation sequencing (NGS)-based PGT was preformed to analyse embryos on chromosomal aneuploidy, target mutation and HLA typing. There were 3 embryos HLA-matched to the proband. The genotypes of the 3 embryos were heterozygous variant, hemizygous variant, normal respectively. After a heterozygous, mosaic partial trisomy (chr)16, and HLA-matched embryo transfer, a healthy baby was delivered and whose HSCT is compatible with the proband.ConclusionsNGS-based PGT-HLA is a valuable procedure for the treatment of GATA1-related cytopenia caused by GATA1 variants, or other haematological disorders, oncological and immunological diseases. Furthermore, our study reconfirms that mosaic embryos transfer would bring healthy offspring.

Gene therapy for rare haematological and neurometabolic paediatric diseases

Nowadays, gene therapy hast the potential to cure an increasingly greater number of monogenic inherited disorders with absent or limited treatment options, and radically change their natural history. Hematopoietic stem cells (HSCs) represent one of the preferred targets for gene therapy, as genetic modification of multipotent cells ensures a permanent correction of the progeny. Gene-corrected HSCs and their progeny can also be used as cell vehicles to deliver molecules into the circulation and tissues, including the central nervous system or the skeleton. Major successes of this approach have been achieved in the field of monogenic blood disorders and neurometabolic diseases and several medicinal products have recently reached the stage of marketing approval by the EMA based on safety and efficacy data collected over more than 10 years of clinical trials. Gene therapy for these severe pathologies offers undeniable advantages over the sole alternative therapy of allogeneic transplantation because it can be applied to every patient, even when no matched HLA donor is available, reducing mortality and complications related to allogeneic transplantation, such as graft-versus-host disease, graft rejection, organ toxicity, and infections. Additionally, in neurometabolic diseases, gene therapy allows supra-physiological expression of the transgene, consequently producing supra-normal levels of the missing enzyme, providing a greater clinical benefit compared to allogeneic transplantation. Despite these remarkable achievements, several challenges remain for HSPC gene therapy regarding access to treatment and its sustainability for the future.

Initial data from a phase 1, first-in-human clinical trial for T-Plex, a multiplexed, enhanced T cell receptor-engineered T cell therapy (TCR-T) for solid tumors.

2542 Background: Solid tumors are notoriously heterogenous with highly variable antigen expression and an immunosuppressive microenvironment. HLA loss of heterozygosity (LOH) has also been identified in up to 40% of solid tumors, allowing tumor cells to evade T cell attack. To overcome these issues and a lack of potent endogenous antitumor T cells in cancer patients, TScan has developed T-Plex, a multiplexed cell therapy comprising two to three different TCR-Ts, chosen from a collection of TCR-Ts called the ImmunoBank. Product and study design details were presented at ASCO 2023 (Abstract #2554). Methods: A screening protocol (NCT05812027) pre-identifies patients with solid tumors any time during clinical care, enabling rapid enrollment into the treatment protocol (NCT05973487) upon disease progression. TCR-Ts currently in the master protocol target PRAME on HLA-A*02:01; HPV16 on HLA-A*02:01; MAGE-A1 on HLA-A*02:01, HLA-A*01:01, or HLA-C*07:02; or MAGE-C2 on HLA-B*07:02. All TCR-Ts in the ImmunoBank and master protocol are first tested as single therapies in dose levels 1 and 2 before becoming available for multiplexing in dose levels 3 and 4. Results: From September 2023 to the time of abstract submission, 140 participants with a variety of solid tumors were enrolled in the screening protocol and are in different stages of screening. To date, 65% have ≥1 HLA match, and 20% and 6% have 2 and 3 HLA matches, respectively, highlighting the advantage of including TCR-Ts targeting multiple different HLA types within the same master protocol. Of those who have completed target screening, 92% express at least one target and 65% qualify for at least one TCR-T. Intratumoral heterogeneity of target expression was observed even with the most prevalently expressed target, PRAME, supporting the rationale for multiplexed TCR-T treatment. Although HLA-LOH affects only half of HLA genes and the remaining intact HLA alleles in tumors can still be recognized by TCR-Ts, about 13% of participants had LOH of the targeted HLA allele, excluding them from TCR-T treatment. Conclusions: Initial data indicate that the combination of HLAs and targets in the ImmunoBank results in ≥1 TCR-T match for the majority of solid tumor patients evaluated to date, and many patients qualify for multiplexed TCR-T treatment. LOH testing can prevent selection and treatment with a TCR-T that would not confer benefit. The proportion of patients eligible for multiplexing is expected to increase as the ImmunoBank grows. Updated data on screened and treated patients will be presented at the meeting. Clinical trial information: NCT05973487 ; NCT05812027 .

Post-transplant cyclophosphamide-based graft-versus-host disease prophylaxis following mismatched unrelated donor peripheral blood stem cell (PBSC) transplantation.

6503 Background: Our prior prospective multi-center clinical trial (15-MMUD; NCT02793544) estimated 79% overall survival (OS) at one year in adult patients with hematological malignancies undergoing reduced intensity conditioning (RIC), receiving bone marrow (BM) grafts from HLA-mismatched unrelated donors (MMUD), and post-transplant cyclophosphamide (PTCy)-based graft- versus-host disease (GVHD) prophylaxis (Shaw et al, J Clin Oncol 2021). We sought to determine whether OS in adults receiving mobilized PBSC from MMUD would be comparable. Methods: We conducted a prospective, multi-center Phase II study (ACCESS; NCT04904588) to assess the impact of PTCy-based GVHD prophylaxis on OS following MMUD transplantation in adults and children with advanced hematological malignancies. The study included three strata: two for adults based on conditioning regimen intensity [myeloablative (MAC) or RIC] using PBSC, and one pediatric cohort using MAC and BM. Eligible donors were matched at 4-7/8 HLA-loci (HLA -A, -B, -C, and -DRB1) and &lt; 35 years. The primary endpoint was OS at one year following transplantation. We report the results of a planned interim analysis of the first 70 adult patients enrolled on the RIC PBSC stratum. Results: Thirteen sites enrolled 70 patients with the following demographics: median age of 65 years (range 24-77); 50% male; diagnoses: AML (53%), MDS (26%), ALL (7%), other heme malignancies (14%); and patient race/ethnicity: non-Hispanic white (48%). Donor characteristics included: median age 25y (range 18-35); male (44%); and HLA match level: 7/8: 67%; 6/8: 27%; 5/8: 6%. Conditioning regimens included fludarabine (flu) and melphalan (63%), flu/busulfan (20%), other (17%). OS at one year post HCT was 79% (95% confidence interval (CI): 68-87%). Secondary endpoints are provided in the table. Conclusions: Encouraging OS was observed at one year following MMUD PBSC in patients receiving RIC and PTCy. Notably, half of enrolled patients were people of color. OS was similar to our prior study using BM grafts. Rates of GVHD and other complications appear comparable to those in HLA-matched donor recipients, suggesting MMUD HCT could expand access to a potentially life-saving therapy. Accrual to both adult strata of ACCESS is complete, with over 200 patients in follow-up. Accrual to the pediatric stratum continues. Clinical trial information: NCT04904588 . [Table: see text]

#3036 The influence of first renal graft on second graft rejection and survival: the importance of revisiting histocompatibility and clinical outcomes

Abstract Background and Aims Kidney retransplantation confers a robust survival benefit over dialysis and recent data has shown similar outcomes to first kidney transplant. The number of HLA mismatches is an important predictor of graft loss and sensitization and the presence of donor specific antibodies (DSA) -pre and -post transplant is a major risk factor for rejection and worst outcomes. However, the importance of HLA matching of first graft and the relevance of first donor DSAs on second graft outcomes is less known. Our aim was to identify risk factors to second graft acute rejection and graft loss, related to second and first graft features. Method We performed a retrospective, longitudinal study including all patients submitted to a 2nd kidney transplant between January 2008 and December 2021, excluding patients with more than 2 grafts or multi-organ transplant. Clinical and histocompatibility data from the first and second donor and recipient were collected. HLA antibodies were detected by solid phase assays and considered if MFI &amp;gt;2500. For subsequent kidney transplants, repeated mismatches are not allowed and unacceptable antigens are those for which the patient has pre-formed -A, -B and -DR antibodies, with MFI&amp;gt;1000. Biopsy proven acute rejection was defined according to Banff 2017 criteria. Follow-up was 31st December 2023 for functioning grafts or time to graft failure, with a mean time of 92 ± 53 months. Results We included 114 patients, 73 (64%) males, mostly Caucasians (96%), with a mean age of 43.9 ± 13 years at 2nd transplant. First kidney transplant was performed before 2010 for 99 patients (87%), with a median first graft survival of 82.5 [12.5-144] months and 19 patients (16.7%) presented primary disfunction due to surgical/vascular complications. After graft loss, 43 patients (37.7%) had their graft removed. For second transplant, 11 (9.6%) patients had a living donor. Induction therapy with thymoglobulin occurred in 94 patients (83%) and maintenance therapy with mycophenolic acid, calcineurin inhibitors and steroids was prescribed in 83 patients (73%). During follow-up, 20 patients (17.5%) presented biopsy proven acute rejection, 13 (65%) T cell mediated and 7 (35%) antibody-mediated, the majority during the first-year post-transplant (N = 17, 85%). The risk factors for second graft rejection are summarized in Table 1. Patients with a first graft nephrectomy had a higher risk of acute rejection (OR 3.9, 95% CI [1.4-10.9], p &amp;lt; 0.006) and were more susceptible to the development of second donor post-transplant DSA (58% vs 35%, p = 0.02). Death censored second allograft loss occurred in 24 patients (21%) at follow up and acute rejection was an important risk factors (OR 4.3, 95% CI [1.5-12.1], p = 0.004). First-year graft survival was 93% and a survival at follow up was 79%. On survival analysis the presence of second graft DSA was a major risk factor for graft loss, especially class 2 -DQ and -DR. First transplant total mismatch load, especially on class 1 contributed to worst graft survival. Conclusion Worst outcomes in first kidney transplant were related with an increased risk of acute rejection in second graft and 1st graft nephrectomy increases the risk of the development of 2nd graft DSA and acute rejection. First transplant mismatch load decreased second graft survival.

The degree of HLA matching determines the incidence of cytokine release syndrome and associated nonrelapse mortality in matched related and unrelated allogeneic stem cell transplantation with post-transplant cyclophosphamide

Cytokine release syndrome (CRS) occurs frequently after haplo-identical allogeneic stem cell transplantation (alloSCT) with post-transplant cyclophosphamide (PTCy), increasing nonrelapse mortality (NRM) and decreasing survival. Data on CRS in HLA-matched alloSCT are limited and effects of specific HLA-mismatches on CRS development unknown. We hypothesized that in HLA-matched alloSCT increasing degrees of HLA-mismatching influence CRS incidence, NRM and survival. Retrospective analysis of 126 HLA-matched PTCy-alloSCT patients showed that higher degrees of HLA-mismatching significantly increased CRS incidence (26%, 75% and 90% CRS with 12/12, 10/10 and 9/10 matched donors, respectively). Maximum temperature during CRS increased with higher HLA-mismatch. Specific associations between HLA-mismatches and CRS could be determined. Grade 2 CRS and CRS-induced grade 3 fever were associated with significantly increased NRM (p < 0.001 and p = 0.003, respectively) and inferior survival (p < 0.001 and p = 0.005, respectively). NRM was mainly caused by disease conditions that may be considered CRS-induced inflammatory responses (encephalopathy, cryptogenic organizing pneumonia and multi-organ failure).

HLA reduction of human T cells facilitates generation of immunologically multicompatible cellular products

AbstractAdoptive cellular therapies have shown enormous potential but are complicated by personalization. Because of HLA mismatch, rejection of transferred T cells frequently occurs, compromising the T-cell graft's functionality. This obstacle has led to the development of HLA knock-out (KO) T cells as universal donor cells. Whether such editing directly affects T-cell functionality remains poorly understood. In addition, HLA KO T cells are susceptible to missing self-recognition through natural killer (NK) cells and lack of canonical HLA class I expression may represent a safety hazard. Engineering of noncanonical HLA molecules could counteract NK-cell recognition, but further complicates the generation of cell products. Here, we show that HLA KO does not alter T-cell functionality in vitro and in vivo. Although HLA KO abrogates allogeneic T-cell responses, it elicits NK-cell recognition. To circumvent this problem, we demonstrate that selective editing of individual HLA class I molecules in primary human T cells is possible. Such HLA reduction not only inhibits T-cell alloreactivity and NK-cell recognition simultaneously, but also preserves the T-cell graft's canonical HLA class I expression. In the presence of allogeneic T cells and NK cells, T cells with remaining expression of a single, matched HLA class I allele show improved functionality in vivo in comparison with conventional allogeneic T cells. Since reduction to only a few, most frequent HLA haplotypes would already be compatible with large shares of patient populations, this approach significantly extends the toolbox to generate broadly applicable cellular products.

Maximizing matching, equity and survival in kidney transplantation using molecular HLA immunogenicity quantitation

HLA matching improves long-term outcomes of kidney transplantation, yet implementation challenges persist, particularly within the African American (Black) patient demographic due to donor scarcity. Consequently, kidney survival rates among Black patients significantly lag behind those of other racial groups. A refined matching scheme holds promise for improving kidney survival, with prioritized matching for Black patients potentially bolstering rates of HLA-matched transplants.To facilitate quantity, quality and equity in kidney transplants, we propose two matching algorithms based on quantification of HLA immunogenicity using the hydrophobic mismatch score (HMS) for prospective transplants. We mined the national transplant patient database (SRTR) for a diverse group of donors and recipients with known racial backgrounds. Additionally, we use novel methods to infer survival assessment in the simulated transplants generated by our matching algorithms, in the absence of actual target outcomes, utilizing modified unsupervised clustering techniques.Our allocation algorithms demonstrated the ability to match 87.7% of Black and 86.1% of White recipients under the HLA immunogenicity threshold of 10. Notably, at the lowest HMS threshold of 0, 4.4% of Black and 12.1% of White recipients were matched, a marked increase from the 1.8% and 6.6% matched under the prevailing allocation scheme. Furthermore, our allocation algorithms yielded similar or improved survival rates, as illustrated by Kaplan–Meier (KM) curves, and enhanced survival prediction accuracy, evidenced by C-indices and Integrated Brier Scores.

Abstract CT204: Efficacy of Bria-IMT regimen in inducing CNS metastasis regression

Abstract Objectives: Breast cancer metastasis to the central nervous system (CNS) often leads to severe morbidity and mortality, and while systemic treatments manage primary tumors, their impact on CNS metastases is limited. This retrospective analysis evaluates the efficacy of Bria-IMT as a monotherapy or in combination with an immune checkpoint inhibitor (ICI) on CNS tumor regression. Methods: Post-hoc analysis of a subset of advanced MBC patients with CNS metastases from previous phase 1 and 2, and ongoing randomized phase 2 trials involving SV-BR-1-GM. SV-BR-1-GM is a GM-CSF secreting, antigen-presenting immortalized breast cancer cell line. Bria-IMT (SV-BR-1-GM ~20x106 cells, intradermally 48-72 hours after cyclophosphamide 300 mg/m2, followed by interferon-alpha at the inoculation sites 2 days later) was administered q3wks. In the combination setting, an ICI was administered with each cycle. Patients A002 and 02-003 received Bria-IMT as monotherapy. Patients 06-005 and 06-007 received Bria-IMT in combination with an ICI. Results: Median pt age of 65 (range 58-70). All pts had ≥1 HLA match with SV-BR-1-GM. Significant CNS tumor regression was observed in all pts. Pt A002 (ER+/PR+, HER2-) received 6 cycles, achieving an 83% reduction in breast lesions. ~3 months after the last cycle, imaging revealed the onset of multiple brain metastases and recurrence of right breast lesions. Following 3 additional cycles, marked measurable regression in both brain metastases and breast lesions was noted. Pt 02-003 (ER-/PR-, HER2 1+ (IHC)) received 5 cycles and observed a 60% reduction (5mm -&amp;gt;2mm) in a left parietal periventricular lesion, and complete resolution (CR) of a left parietal lobe lesion. Pt 06-005 (ER+/PR-, HER2 1+(IHC)) demonstrated a 56% (9mm -&amp;gt; 4mm) reduction in the thickness of a dural lesion overlying the left anterior temporal lobe after 6 cycles of SV-BR-1-GM + ICI (pembrolizumab). After 2 additional cycles of SV-BR-1-GM + ICI (retifanlimab) and 1 cycle of SV-BR-1-GM (ICI was skipped on final cycle due to grade 2 AE), patient achieved CR of a left orbital mass observed at baseline (24mm -&amp;gt; 0m). Circulating cancer-associated macrophage-like cells (CAMLs) varied throughout the treatment, with levels ranged from a baseline of 90 to 24 by Cycle 13. Pt 06-007 (ER-/PR-, HER2 1+ (IHC)) demonstrated significant reductions in CNS lesions after 3 cycles of SV-BR-1-GM + ICI (pembrolizumab): a 67% reduction in a right frontal lobe lesion, 29% in the right parietal, 30% in the right thalamus, and 67% in the right precentral gyrus lesions. CAML levels remained low throughout treatment. Conclusions: This review consolidates evidence for the efficacy of the Bria-IMT regimen in CNS metastasis regression, both alone and with ICIs. The consistent regression seen across all breast cancer subtypes among heavily pretreated patients highlights the potential of SV-BR-1-GM in managing CNS metastasis. Ongoing trials will determine the full extent. Citation Format: Sailaja Kamaraju, Blaise Bayer, Mingjin Chang, William Williams, Charles Wiseman, Giuseppe Del Priore. Efficacy of Bria-IMT regimen in inducing CNS metastasis regression [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 2 (Late-Breaking, Clinical Trial, and Invited Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(7_Suppl):Abstract nr CT204.

Younger unrelated donors may be preferable over HLA match in the PTCy era: a study from the ALWP of the EBMT

AbstractThere is a paucity of information on how to select the most appropriate unrelated donor (UD) in hematopoietic stem cell transplantation (HSCT) using posttransplant cyclophosphamide (PTCy). We retrospectively analyzed the characteristics of 10/10 matched UDs (MUDs) and 9/10 mismatched UDs (MMUDs) that may affect transplant outcomes in patients with acute myeloid leukemia (AML) in first or second complete remission (CR1 or CR2). The primary end point was leukemia-free survival (LFS). Overall, 1011 patients were included with a median age of 54 years (range, 18-77). Donors had a median age of 29 years (range, 18-64); 304 (30%) were females, of which 150 (15% of the whole group) were donors to male recipients, and 621 (61%) were MUDs; 522 (52%) had negative cytomegalovirus (CMV-neg) serostatus, of which 189 (19%) were used for CMV-neg recipients. Donor age older than 30 years had a negative impact on relapse (hazard ratio [HR], 1.38; 95% confidence interval [CI], 1.06-1.8), LFS (HR, 1.4; 95% CI, 1.12-1.74), overall survival (HR 1.45; 95% CI, 1.14-1.85) and graft-versus-host disease (GVHD) free, relapse-free survival (HR, 1.29; 95% CI, 1.07-1.56). In addition, CMV-neg donors for CMV-neg recipients were associated with improved LFS (HR, 0.74; 95% CI, 0.55-0.99). The use of MMUD and female donors for male recipients did not significantly impact any transplant outcomes. For patients undergoing HSCT from a UD with PTCy for AML, donor age <30 years significantly improves survival. In this context, donor age might be prioritized over HLA match considerations. In addition, CMV-neg donors are preferable for CMV-neg recipients. However, further research is needed to validate and refine these recommendations.

(544) - Does HLA Matching in Prior Blood Transfusions Impact Lung Transplant Survival Outcomes?

(544) - Does HLA Matching in Prior Blood Transfusions Impact Lung Transplant Survival Outcomes?

Transplant Candidates of 70+ Years Have Superior Survival If Receiving Pre-Emptively a Living Donor Kidney.

Background: The number of kidney transplant recipients over 70 years of age is increasing but detailed data on patient and graft survival in the modern era of immune suppression are few. Methods: A single-center cohort of patients of 70 years and older (n = 349) at time of kidney transplantation from 2010-2020 were followed until January 2023. Results: The median age was 73 years with a median follow-up of 4.3 years. Fifty percent of recipients of a living donor kidney (LDK, n = 143) received their graft pre-emptively. Cumulative death-censored graft survival was excellent in the LDK group and reached 98% at 5 years vs. 85% in the deceased donor kidney (DDK) group. Primary non-function (38%) and rejection (43%) were the major causes of graft loss in the first year after DDK transplantation. Rejection-related graft loss was 4.6% during follow-up. Median recipient survival was superior in the subgroup of pre-emptively transplanted LDK patients compared to non-pre-emptively LDK transplanted patients (11.1 versus 6.2 years). Non-pre-emptively transplanted patients had a significantly increased incidence of infection (HR 3.81, 1.46-9.96) and cardiovascular-related causes of death (HR 3.35, 1.16-9.71). Pre-emptive transplantation was also associated with a significantly improved graft survival in the DDK recipients but this result was confounded by significantly better HLA matching and younger donor age in this group. Conclusions: Pre-emptive LDK transplantation in patients of 70 years or older confers superior graft and recipient survival.

Abstract 1335: Generating functional CAR-NK cells for cancer immunotherapy

Abstract Chimeric Antigen Receptor-Natural Killer (CAR-NK) cells are rapidly emerging as a promising cellular therapeutic overcoming the potential life-threatening adverse events that may result from CAR-T therapy, including cytokine release syndrome (CRS), neurotoxicity and graft-versus-host disease (GVHD). Due to their intrinsic characteristics, NK cells can kill tumor cells without the requirement for recognition of antigen in the context of MHC. This removes the constraint of HLA matching and supports antigen independent cytotoxicity through NK cell intrinsic mechanisms. As such CAR-NK cells kill via both CAR-dependent and -independent mechanisms. For these reasons, they offer the advantage of being an “off-the-shelf” product; satisfying the requirement for large-scale production of cancer immunotherapies, with the potential to reach more patients at a reduced cost. The frequency of NK cells in the blood is low (~ 2-5%), therefore improving their in vitro expansion is key to generating sufficient material to offer a viable CAR-NK cell therapy. Here we outline an in-vitro method to generate, expand, and test primary human CAR-NK cells using engineered feeder cells, and go on to demonstrate the efficacy of the CAR-NK against target cancer cells. Primary human NK cells were cultured and expanded in the presence of irradiated K562 cells (iK562) modified to express 4-1BBL and membrane bound IL-21. Following initial expansion, NK cells were transduced with a clinically tested CD19-targeting CAR lentiviral vector (LV) or GFP expressing LV; as an empty vector transduced control. Following transduction, CD19 CAR-NK and GFP-NK were enriched by FACS sorting to reach &amp;gt;80% purity and further expanded in the presence of 4-1BBL/mbIL21 iK562 feeder cells. Following sufficient expansion, cytotoxicity of fresh or cryopreserved CD19 CAR-NK cells was tested in vitro in a Tumor Killing Assay (TKA) against CD19+ or CD19- target cells. As expected, CD19 CAR-NK cells showed increased on-target cytotoxicity, increased degranulation and IFNꝩ secretion compared to controls. This effect was not observed with CD19 negative cancer cells, strongly suggesting CD19 CAR engagement of the target antigen to mediate killing. Taken together these data show the generation, expansion, and enrichment of CD19 CAR-NK cells with enhanced cytotoxic activity towards CD19+ target cells. This approach provides a platform for in vitro characterization of novel CAR-constructs, allied with in-vitro safety assessment and in vivo pharmacology testing. Together, this offers the potential to further develop new and more widely available cellular therapeutics to treat cancer. Citation Format: Karina Di Gregoli, Henry Leonard, Dan Rocca, Sabrina de Munnik, Gemma Moiset, Robert Nunan, Lauren Schewitz-Bowers, Louise Brackenbury. Generating functional CAR-NK cells for cancer immunotherapy [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 1335.

Race, ethnicity, ancestry, and aspects that impact HLA data and matching for transplant.

Race, ethnicity, and ancestry are terms that are often misinterpreted and/or used interchangeably. There is lack of consensus in the scientific literature on the definition of these terms and insufficient guidelines on the proper classification, collection, and application of this data in the scientific community. However, defining groups for human populations is crucial for multiple healthcare applications and clinical research. Some examples impacted by population classification include HLA matching for stem-cell or solid organ transplant, identifying disease associations and/or adverse drug reactions, defining social determinants of health, understanding diverse representation in research studies, and identifying potential biases. This article describes aspects of race, ethnicity and ancestry information that impact the stem-cell or solid organ transplantation field with particular focus on HLA data collected from donors and recipients by donor registries or transplant centers.