Combined Analysis of Early CD4+ T Cell Counts and CMV Serostatus May Improve CMV Risk Assessment after Allogeneic Hematopoietic Cell Transplantation

The incidence and severity of viral complications after cellular therapy are highly variable. Recent publications describe relevant interactions between the human Cytomegalovirus (CMV) and host immunity in recipients of allogeneic hematopoietic cell transplantation (HCT). Although immune monitoring is routinely performed in HCT patients, validated cut-off levels correlating with transplant outcomes such as survival or CMV reactivation are mostly limited to day +100, which is later than the median time for CMV reactivation in the absence of medical prophylaxis. To address this gap in early risk assessment, we applied an unsupervised machine learning technique based on clustering of day +30 CD4+ helper T cell count data, and identified relevant cut-off levels within the diverse spectrum of early CD4+ reconstitution. These clusters were stratified for CMV recipient serostatus to identify early risk groups that predict clinical HCT outcome. Indeed, the new risk groups predicted subsequent clinical events such as NRM, OS, and high CMV peak titers better than the most established predictor, i.e., the positive CMV recipient serostatus (R+). More specifically, patients from the R+/low CD4+ subgroup strongly associated with high CMV peak titers and increased 3-year NRM (subdistribution hazard ratio (SHR) 10.1, 95% CI 1.38–73.8, p = 0.023), while patients from the R-/very high CD4+ subgroup showed comparable NRM risks (SHR 9.57, 95% CI 1.12–81.9, p = 0.039) without such an association. In short, our study established novel cut-off levels for early CD4+ T cells via unsupervised learning and supports the integration of host cellular immunity into clinical risk-assessment after HCT in the context of CMV reactivation.

Reactivation of EBV and CMV in Severe COVID-19—Epiphenomena or Trigger of Hyperinflammation in Need of Treatment? A Large Case Series of Critically ill Patients

Background Reactivation of viruses such as Epstein-Barr virus (EBV) and cytomegalovirus (CMV) are common in critically ill patients and have been described in patients with severe COVID-19. However, it is unclear whether these reactivations are associated with increased mortality and whether targeted treatments are beneficial. Methods In a retrospective single-center cohort study, patients with severe COVID-19 treated on our intensive care unit (ICU) were screened for EBV and CMV reactivation as detected by polymerase chain reaction. If present, patient characteristics, temporal connections to severe acute respiratory syndrome coronavirus 2 diagnosis and corticosteroid use, the use of targeted treatments as well as the course of disease and outcome were analyzed. As control group, non-COVID-19 patients with sepsis, treated within the same time period on our ICU, served as control group to compare incidences of viral reactivation. Results In 19 (16%) of 117 patients with severe COVID-19 treated on our ICU EBV reactivations were identified, comparable 18 (14%) of 126 in the non-COVID-19 control group ( P = .672). Similarly, in 11 (9%) of 117 patients CMV reactivations were identified, comparable to the 16 (13%) of 126 in the non-COVID-19 sepsis patients ( P = .296). The majority of EBV (58%) and CMV reactivations (55%) were detected in patients under systemic corticosteroid treatment. 7 (37%) of 19 patients with EBV reactivation survived the ICU stay, 2 (29%) of 7 patients with rituximab treatment and 5 (42%) of 12 patients without treatment ( P = .568). Five (50%) of 10 patients with CMV reactivation survived the ICU stay, 5 (83%) of 6 patients with ganciclovir treatment and 0 of 4 patients without treatment ( P = .048). Follow-up analysis in these patients showed that the initiation of treatment lead to decrease in viral load. Conclusion Critically ill patients with COVID-19 are at a high risk for EBV and CMV reactivations. Whether these reactivations are a cause of hyperinflammation and require targeted treatment remains uncertain. However, in patients with clinical deterioration or signs of hyperinflammation targeted treatment might be beneficial and warrants further studying.

Letermovir Prophylaxis and Cytomegalovirus Reactivation in Adult Hematopoietic Cell Transplant Recipients with and without Acute Graft Versus Host Disease

Cytomegalovirus (CMV) is the most clinically significant infection after allogeneic hematopoietic-cell transplantation (allo-HCT) and is associated with increased mortality. The risk for CMV reactivation increases with graft versus host disease (GVHD). GVHD contributes to significant morbidity and mortality and is treated with immunosuppressive therapies that can further increase CMV infection risk. Prophylaxis with letermovir, an oral antiviral approved to prevent CMV, has been shown to decrease the incidence of CMV infection post-allo-HCT in patients at high risk of CMV reactivation, but there is a lack of data confirming this benefit in patients with GVHD. In this single-center, retrospective study, we assessed the incidence of clinically significant CMV infection (CS-CMVi) in allo-HCT patients who received letermovir prophylaxis (n = 119) and who developed aGVHD compared to a control group (n = 143) who did not receive letermovir. Among aGVHD patients, letermovir prophylaxis decreased CS-CMVi in patients with aGVHD (HR 0.08 [95% CI 0.03–0.27], p < 0.001), reduced non-relapsed mortality (p = 0.04) and improved overall survival (p = 0.04). This data suggests that letermovir prophylaxis improves outcomes by preventing CS-CMVi in patients with aGVHD.

Letermovir Is Effective for Prevention of Cytomegalovirus Reactivation in HLA-Haploidentical Peripheral Blood Stem Cell Transplantation with Post-Transplant Cyclophosphamide

[Introduction] Cytomegalovirus (CMV) infection is a common viral infection in recipients of allogeneic hematopoietic stem cell transplantation (allo-SCT). Early CMV reactivation after allo-SCT is associated with worse non-relapse mortality (NRM) and overall survival (OS). Recently, T-cell replete HLA-haploidentical SCT using post-transplant cyclophosphamide (PTCy-haplo SCT) has been developed and spread rapidly worldwide. Rationale of this strategy is assumed to be selective and cytotoxic depletion of alloreactive T cells which are responsible for graft-versus-host disease (GVHD), while preserving non-alloreactive T cells which can contribute to fight infections. However, recent studies showed that PTCy-haplo SCT was associated with the increased incidence of CMV infection. Letermovir (LET), a novel anti-CMV agent, which inhibits the CMV DNA terminase complex, was approved for the prevention of CMV reactivation in allo-SCT recipients in 2018 in some countries including Japan based on the result of a phase 3 trial. Our facility performs LET prophylaxis in allo-SCT recipient if either donor or recipient is seropositive CMV. Although LET is effective for the prevention of CMV reactivation in allo-SCT recipients, the clinical effectiveness of LET prophylaxis in PTCy-haplo SCT is not well elucidated. Based on these things, we retrospectively evaluated the efficacy of LET prophylaxis in PTCy-haplo SCT. [Methods] We retrospectively analyzed consecutive 99 recipients who received PTCy-haplo SCT at Hokkaido University Hospital from March 2013 to March 2021. We compared the cumulative incidence of CMV reactivation between the LET prophylaxis group (LET group, 33 patients) and LET non-prophylaxis group (non-LET group, 66 patients). LET was initiated on the day 0 at a dosage of 480mg daily. All patients were monitored for CMV reactivation by using the anti-CMV pp65 monoclonal antibody HRP-C7 assay at least once a week from the time of engraftment. CMV reactivation was defined as the detection of CMV antigen positive cells per 50000 white blood cells, whereas CMV disease was defined by organ dysfunction attributable to CMV. [Results] As baseline patient's characteristics were summarized in Table1, there were no difference between LET and non-LET group in terms of age, sex, underlying disease, disease risk at transplantation, prior transplantation, conditioning intensity, and CMV serostatus. All patients received peripheral blood stem cell transplantation. GVHD prophylaxis consisted of Cy (40-50 mg/kg on day 3 and 4), tacrolimus (from day 5), and mycophenolate mofetil (from day 5). The cumulative incidence of CMV reactivation at 150 days after transplantation in LET group was significantly lower than that in non-LET group (30.3% versus 69.7%; P &lt;.001, Figure1A). Importantly, CMV disease were occurred in three patients without LET prophylaxis (gastritis, enteritis, and retinitis), but not in the patients with LET prophylaxis. The cumulative incidence of NRM at 1 year was similar between the patients with and without LET prophylaxis (17.6% versus 9.2%; P=0.366, Figure1B), as was OS at 1 year (71.5% versus 69.4%; P=0.801, Figure1C). Neutrophil engraftment was achieved in 32 patients (97%) at a median of 15 days in LET group and 64 patients (97%) at a median of 14.5 days in non-LET group (P=0.243). Furthermore, platelet engraftment was achieved in 26 patients (79%) at a median of 34 days in LET group and 57 patients (86%) at a median of 31 days in non-LET group (P=0.282). These findings suggest that LET does not affect engraftment. Interestingly, the length of hospitalization in the LET group was significantly shorter than that in non-LET group (the median, 59.5 days versus 71 days; P=0.0488), suggesting that LET suppresses CMV reactivation leading to early discharge. [Conclusion] To our best knowledge, this is the largest retrospective study about the efficacy of LET in PTCy-Haplo SCT. LET is effective for prevention of CMV reactivation in PTCy-haplo SCT. Further studies focused on the long term effect of LET prophylaxis in PTCy-haplo SCT, such as the incidence of relapse and chronic GVHD, is warranted. Figure 1 Figure 1. Disclosures Nakagawa: AbbVie GK: Research Funding; Takeda Pharmaceutical Company: Research Funding. Teshima: Gentium/Jazz Pharmaceuticals: Consultancy; Merck Sharp & Dohme: Membership on an entity's Board of Directors or advisory committees; Pfizer Inc.: Honoraria; Nippon Shinyaku Co., Ltd.: Research Funding; CHUGAI PHARMACEUTICAL CO., LTD.: Research Funding; Fuji pharma CO.,Ltd: Research Funding; Takeda Pharmaceutical Company: Honoraria, Membership on an entity's Board of Directors or advisory committees; Novartis International AG: Membership on an entity's Board of Directors or advisory committees, Other, Research Funding; TEIJIN PHARMA Limited: Research Funding; Astellas Pharma Inc.: Research Funding; Bristol Myers Squibb: Honoraria; Janssen Pharmaceutical K.K.: Other; Kyowa Kirin Co.,Ltd.: Honoraria, Research Funding; Sanofi S.A.: Research Funding.

Letermovir Prophylaxis Versus Pre-Emptive Therapy for Cytomegalovirus after Hematopoietic Stem-Cell Transplantation

Introduction Cytomegalovirus (CMV) infection is one of the most common complication after allogeneic hematopoietic stem-cell transplantation (HSCT) still associated with significant morbidity and mortality. Although pre-emptive therapy (PET) are routinely used in treatment of CMV after SCT, their prophylactic use is limited by clinically unacceptable myelosuppression and nephrotoxicity. Letermovir, available since 2019 in Italy, is the first antiviral agent approved by FDA and EMA which is indicated for the prophylaxis of CMV infection in CMV seropositive (R+) patients undergoing SCT. Presently, cost and drug interactions are the main disadvantages of Letermovir use. We performed a single-center observational retrospective study to evaluate the efficacy of primary Letermovir prophylaxis for CMV infection among high-risk patients (R+) receiving HSCT from serological negative donor (D-). Methods We evaluated a cohort of R+/D- patients transplanted from January 2017 to December 2020 (86/235 transplanted patients): among those eligible for Letermovir prophylaxis (N=70), 29 patients (transplanted after 2019) received Letermovir until day +100, whereas 41 patients (the historical control group transplanted before 2019) received CMV PET only in case of increased viral load (CMV reactivation). Patients unable to take oral therapy at day +7 from HSCT or assuming drugs for concomitant clinical conditions bringing about major pharmacokinetic interaction were excluded (N=16). We compared day +100 and day +200 cumulative incidence of clinically significant CMV infection (CS-CMVi), defined according to drug registration trial: Letermovir discontinuation before day +100, CMV reactivation (CMV-DNAemia leading to PET), CMV tissue invasive disease, disease relapse and death from any causes. Survival functions between groups were estimated by the Kaplan-Meier method and compared using log-rank test. Moreover, the overall survival (OS), disease free survival (DFS), non-relapse mortality (NRM) and cumulative incidence of II-IV grade acute graft-versus-host disease (aGVHD) was compared in the two cohorts. Finally, we analyzed the number of accesses in day hospital from initial discharge to day +180, as an indirect cost-effectiveness evaluation of letermovir prophylaxis. Results No severe adverse events related to the therapy were observed in the letermovir group. Letermovir prophylaxis started at a median of 11 days (range, 5-27) after HSCT. The median duration of Letermovir administration was 89 days (range, 40-113). The only early stop was due to patient death, not related to CMV or drug toxicity. CS-CMVi at day +100 occurred in 13.8% vs 61.0% in letermovir and historical group, respectively (p &lt;0.001). Of note, none of the events in letermovir group was related to CMV reactivation whereas 24/25 in the historical group were. A trend toward lower CS-CMVi in the letermovir group was observed also at day +180 (44,8% vs 65,9%, p =0.080), with 6 late reactivations in patients who received prophylaxis. Moreover, at follow-up one patient in the experimental group and 3 in the control group developed CMV disease. Of note, in vivo T-cell depletion was used in 86% of patients in letermovir and 83% in historical group, and most of the CMV reactivations occurred after development of aGVHD: in 83% and 54% of patients, respectively. No differences in OS and DFS were observed between the two cohorts. Finally, a trend toward lower number of day hospital admissions was shown in patients who received letermovir prophylaxis (median 2 admissions, IQR 0-8, vs median 4.5, IQR 0-16), suggesting higher quality of life and costs reduction. Conclusions Our real-life experience demonstrated the efficacy of Letermovir in reducing the incidence of CMV reactivation. Longer follow-up is needed to clarify advantages in terms of disease-free and overall survival. Further studies are needed to investigate the role of prophylaxis beyond day 100 in high risk patients, such as those who receive a T-depleted transplant or who develop aGVHD. The role of Letermovir prophylaxis on immuno-reconstitution and its cost-effectiveness remains to be evaluated. Disclosures Marco: Jazz: Consultancy; Insight,: Consultancy; Janssen: Consultancy. Ferrero: EUSA Pharma: Consultancy, Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Janssen: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding, Speakers Bureau; Gilead: Research Funding, Speakers Bureau; Morphosys: Research Funding; Incyte: Membership on an entity's Board of Directors or advisory committees; Clinigen: Membership on an entity's Board of Directors or advisory committees; Servier: Speakers Bureau.

Recurrent CMV Viremia Portends Poor Prognosis and Results in Significant Resource Utilization in Patients with Poor Graft Function Post Allogeneic Stem Cell Transplantation

Introduction Poor Graft Function (PGF) characterized by 2 or more lineage cytopenias in the setting of complete donor chimerism is a recognized complication of allogeneic stem cell transplantation (alloSCT). Recurrent CMV viremia jeopardizes blood count recovery in PGF through direct effect of the virus on bone marrow function as well as myelosuppression/organ toxicity due to widely available antivirals such as val/ganciclovir or foscarnet. Methods To assess the clinical effect and resource utilization of recurrent CMV viremia on patients with PGF we performed a retrospective analysis of alloSCT recipients at our Centre from 2018-2019. Patients were classified as having PGF based on the following parameters: 1) Donor myeloid chimerism ≥95% at last assessment, 2) 2 or more lineage cytopenias defined by Hb ≤85g/L, Neutrophils ≤1.0x10 9/L, Platelets ≤60x10 9/L, 3) cytopenias present for 10 days after D30. CMV viral loads were monitored by q PCR twice weekly with reactivation defined as the first reading quantifiable above the threshold of detection of the assay. Recurrent CMV reactivation was defined as detectable CMV after an interval of 4weeks without detectable virus, with patients who reactivated within 4 weeks of an undetectable viral load defined as prolonged persisting infection. Patients who died before D60 or who relapsed within the 1 st 100 days or those who had a prior alloSCT were excluded. Baseline factors in the CMV seropositive PGF group were evaluated by Chi Squared and Kruskall-Wallis test for categorical and continuous variables respectively to establish any associations with recurrent or persisting CMV. Survival analysis of PGF patients was performed by the Kaplan Meier method with patients stratified by the following: Recurrent CMV/Prolonged persisting infection (RP-CMV), Single CMV reactivation (S-CMV), No CMV reactivations (N-CMV) and CMV sero-negativity (S-NCMV). A descriptive analysis of the number of hospital admissions in addition to the initial alloSCT admission (extra admissions) and total hospital days was also performed. Results There were 155 eligible patients of which 38 (24%) fulfilled criteria for PGF. The median follow-up of the cohort was 26 months (95%CI:23.1-28). The median overall survival (OS) of the cohort was not reached with an estimated 2 year OS of 73%. The 2 year OS of PGF patients was 59% compared to 78% in the non PGF group. There were no significant baseline associations found with RP-CMV (Table 1). Figure 1 demonstrates the survival of patients by nature of CMV reactivation. The 2 year OS by CMV reactivation was as follows: RP-CMV 25%, S-CMV 68%, N-CMV 70%, SN-CMV 87%. On univariate analysis, RP-CMV was significantly associated with mortality [HR 5.41; 95%CI 1.80-16.28; P=0.003]. This association remained significant when including Age and grade III-IV GVHD in multivariate analysis: RPCMV [HR 7.57; 95%CI 2.20-25.9;P=0.0013=], Age [HR 1.03; 95% CI 0.99-1.08; P=0.16] and GVHD [HR 2.91; 95%CI 0.87-9.75; P=0.08]. RP-CMV was not a risk factor for mortality within the NPGF population [HR 0.75; 95%CI 0.29-01.97; P=0.56]. Those with RP-CMV experienced an increase in their CMV viral load within a median of 4 days range (2-86) after achievement of an undetectable result. Those with PGF and RP-CMV had an average of 1.4 extra admissions with an average length of stay of 80 days, those with S-CMV reactivation had an average of 1.6 extra admissions with an average length of stay of 35 days, and those with N-CMV had an average of 1 extra admission with an average length of stay of 17 days. Those with SN-CMV had an average of 1 extra admission with an average length of stay of 23 days. CMV reactivation and CMV therapy contributed to 13/17 (76%) total readmissions for those with RP-CMV compared to 5/13 (38%) readmissions for those with S-CMV. Conclusion Patients with PGF and RP-CMV are at high risk of mortality as well as more lengthy hospital admissions of which CMV reactivation and CMV therapy is a potential contributor. Targeted use of novel therapies to prevent CMV reactivation in patients with PGF may improve both bone marrow function and survival leading to less resource utilization. Figure 1 Figure 1. Disclosures Chee: Novartis: Honoraria, Membership on an entity's Board of Directors or advisory committees. Koldej: CRISPR Therapeutics: Research Funding. Ritchie: BMS: Research Funding; Takeda: Research Funding; CRISPR Therapeutics: Research Funding; Amgen Inc: Honoraria, Research Funding; CSL: Honoraria; Novartis: Honoraria.

A Phase II Randomized, Double-Blind, Placebo-Controlled, Multicenter Trial to Evaluate the Efficacy of Cmvpepvax for Preventing CMV Reactivation/Disease after Matched Related/Unrelated Donor Hematopoietic Cell Transplant

Cytomegalovirus (CMV) infection remains a major cause of morbidity/mortality after allogeneic hematopoietic cell transplantation (HCT). Preemptive antiviral therapy is associated with drug-induced toxicities, and prophylactic therapy with letermovir is associated with late reactivations and delayed antiviral immune reconstitution. Therefore, substituting antivirals with a vaccine that harnesses the native immune response to CMV may improve outcomes for HCT recipients. Our group has developed a peptide vaccine, CMVPepvax, composed of an HLA-A*0201 restricted pp65 495-503 CD8 T cell epitope, covalently linked to a universal tetanus T helper epitope and co-administered with PF-03512676 adjuvant. CMV PepVax was safe and immunogenic in a healthy volunteer study (La Rosa et al. PMID: 22402037;) and a phase Ib HCT recipient trial (Nakamura, et al. PMID: 26853648) with the latter demonstrating a promising sign of efficacy in reducing CMV viremia. In this double blind, placebo-controlled, randomized phase 2 trial (NCT02396134), HCT recipients were enrolled at four USA transplant centers. Eligible patients were CMV seropositive, HLA A*0201-positive, 18-75 years, receiving HCT from a matched related/unrelated donor. T-cell depleting agents (i.e. ATG) or recipients of ex-vivo T-cell-depleted grafts were excluded. Prophylactic antiviral therapy was not allowed. Patients were enrolled prior to day 0 of HCT and reassessed on day +28 for eligibility and randomization to the vaccine (VA) or placebo arm (PA), stratified by donor CMV serostatus. PepVax was administered subcutaneously on days +28 and +56 post-HCT. The primary endpoint of the trial was CMV viremia ≥1250 IU/m or CMV disease through 100 days post-HCT. A total of 96 patients were planned to be randomized at 1:1 ratio, providing 90% power to detect a reduction of viremia from 40% to 15%. CMVpp65-specific immune reconstitution was monitored by measuring levels of CD8 T cells binding to MHC class I pp65 495-503 and HIVgag 77-85 (as control) multimers (Immudex Dextramers), as well as CD28 and CD45 memory markers (BD Biosciences). The intensity of the fluorescent labels was measured using a Gallios flow cytometer with Kaluza software (Beckman Coulter). Enrollment started in June 2015 but was stopped in November 2017 when a planned interim analysis suggested futility for the primary efficacy endpoint. By that time, 76 subjects had been consented, of whom 61 met the day 28 eligibility criteria and were randomized to the VA (n=32) or PA (n=29). The unblinded data were released when the planned one-year follow up was completed for these 61 subjects. The two groups were overall balanced in their demographics and HCT characteristics. There was no difference in the primary endpoint of CMV reactivation/disease between VA (25.1%) and PA (13.8%, p=0.15). The incidence of preemptive therapy was similar between the two arms. PepVax was well tolerated with no increase in adverse events. Transplant outcomes were also similar between the two groups with regards to 1-year overall survival, relapse-free survival, non-relapse mortality, relapse, and acute GVHD. In subjects in VA who reached the primary endpoint (n=8), CMV viremia occurred at a median of 20 days (interquartile range: 15-23 days; range, 0-48) after the first vaccine, suggesting that there was insufficient time for the vaccine-induced T cell expansion. Significantly higher levels of long lasting pp65-specific T cells with effector memory phenotype were measured in non viremic participants in the VA compared to those in the PA; this effect was driven by differences observed late after vaccination (p = 0.004 by GEE analysis; Figure, panel A). In patients who controlled viremia, robust expansion of functional pp65-specific CD8 T cells was observed following PepVax injections (Figure, panels B-C). Our results confirm safety and immunogenicity of PepVax in CMV seropositive HCT recipients. However, the trial failed to demonstrate a clinical efficacy of PepVax in reducing CMV viremia/disease despite favorable CD8 T cell responses. Early CMV reactivation/disease detected before receipt of the second vaccine may have reduced the ability of PepVax to elicit a protective T cell response. Transfer of vaccine-induced immunity through donor CMV immunization combined with recipient booster immunization may overcome this issue and lead to faster immune reconstitution post-HCT. Figure 1 Figure 1. Disclosures Hill: Amplyx: Consultancy; OptumHealth: Consultancy; CRISPR therapeutics: Consultancy; Gilead: Consultancy, Research Funding; Allogene therapeutics: Consultancy; Octapharma: Consultancy; Allovir: Consultancy, Research Funding; Takeda: Consultancy, Research Funding; CLS Behring: Consultancy; Karius: Research Funding. Al Malki: Hansa Biopharma: Consultancy; Jazz Pharmaceuticals, Inc.: Consultancy; Neximmune: Consultancy; Rigel Pharma: Consultancy; CareDx: Consultancy. Pullarkat: Amgen, Dova, and Novartis: Consultancy, Honoraria; AbbVie, Amgen, Genentech, Jazz Pharmaceuticals, Novartis, Pfizer, and Servier: Membership on an entity's Board of Directors or advisory committees. Aribi: Seagen: Consultancy. Devine: Tmunity: Current Employment, Research Funding; Magenta Therapeutics: Current Employment, Research Funding; Sanofi: Consultancy, Research Funding; Johnsonand Johnson: Consultancy, Research Funding; Orca Bio: Consultancy, Research Funding; Be the Match: Current Employment; Vor Bio: Research Funding; Kiadis: Consultancy, Research Funding. Verneris: Novartis: Other: advisory board; jazz: Other: advisory board; Fate Therapeutics: Consultancy. Miller: Fate Therapeutics, Inc: Consultancy, Patents & Royalties, Research Funding; GT Biopharma: Consultancy, Patents & Royalties, Research Funding; Vycellix: Consultancy; ONK Therapeutics: Honoraria, Membership on an entity's Board of Directors or advisory committees; Magenta: Membership on an entity's Board of Directors or advisory committees; Sanofi: Membership on an entity's Board of Directors or advisory committees; Wugen: Membership on an entity's Board of Directors or advisory committees. Forman: Allogene: Consultancy; Lixte Biotechnology: Consultancy, Current holder of individual stocks in a privately-held company; Mustang Bio: Consultancy, Current holder of individual stocks in a privately-held company. Diamond: Pfizer Inc: Other; Helocyte Inc: Membership on an entity's Board of Directors or advisory committees, Other, Patents & Royalties.

HLA-B Leader Dimorphism Impacts on Outcomes of HLA-Matched Related/Unrelated Transplantation: Analysis of the Japanese Society for Transplantation and Cellular Therapy

Background: HLA-B leader encodes methionine (M) or threonine (T) at position 2 and gives rise to TT, MT, or MM genotype. HLA-B M leaders promote higher HLA-E expression than T leaders, enhancing T cell and natural killer (NK) cell recognition on HLA-E via NKG2A and NKG2C related to cytomegalovirus (CMV) recognition. The dimorphic HLA-B leader informs acute graft-versus-host disease (GVHD) risk in HLA 1 allele mismatched unrelated hematopoietic stem cell transplantation (HCT) (Petersdorf EW et al. Lancet Haematol. 2020 and Blood. 2020) and haploidentical HCT (Fuchs EJ et al. 62nd ASH Annual Meeting 2020). However, the impact of the HLA-B leader genotype in HLA-matched related/unrelated donor HCT from the viewpoints of CMV reactivation has not been elucidated fully yet. We performed this retrospective study to explore the significance of HLA-B leaders in HLA-matched related/unrelated HCT in the Japanese population. Methods: All clinical data of 10,110 patients who underwent 8/8 HLA matched related/unrelated donor bone marrow/peripheral blood HCT for acute myeloid leukemia (AML), acute lymphoblastic leukemia (ALL), and myelodysplastic syndrome (MDS) between 1996 - 2019 were provided by the Japanese Data Center for Hematopoietic Cell Transplantation. All 8 alleles at HLA-A, -B, -C, and DRB1 were matched by genotyping, and sibling pairs whose genotype were unknown but matched 8/8 for HLA antigen at a serologic level were included. Study outcomes were overall survival (OS), relapse, non-relapse mortality (NRM), grade II-IV acute GVHD, grade III-IV acute GVHD, and chronic GVHD. Multivariable models using Cox regression analysis assessed transplant outcomes associated patient age, patient sex, patient performance status, donor sex, donor age, diagnosis, disease risk index (DRI), donor source (bone marrow or peripheral blood), related/unrelated donor, myeloablative (MAC)/reduced-intensity conditioning, patient CMV serostatus and patient/donor HLA B-leader (TT, MT, MM). In subgroup analysis, we adopted results of CMV antigenemia instead of CMV serostatus to evaluate the impact of CMV reactivation for HCT outcomes. All statistical analyses were performed with EZR. Results: This study included 5,212 AML patients (51.9%), 2,995 ALL patients (29.6%) and 1,864 MDS patients (18.4%). In DRI, low risk was 501 (5.4%), intermediate risk was 5,750 (61.6%), high risk was 2,711 (29.0%) and very high risk was 378 (4.0%). Median patients age was 44 (range 0-77) years. Bone marrow was the graft source in 7,183 recipients (71.0%). Related donors were 5,378 (53.2%). MAC was used in 5,891 (70.3%) patients. The number of TT patients/donor was 7,419 (73.4%), MT patients was 2,496 (24.7%) and MM patients was 195 (1.9%). MM patients was associated with significant lower OS (hazard ratio [HR] 1.329 [95% CI, 1.053 - 1.677]); p = 0.017 and higher NRM (HR 1.391, [95% CI, 1.018 - 1.902]); p = 0.039) compared to TT patients (Table). There was no significant correlation between MM patients and grade II-IV/III-IV acute GVHD. In subset analysis for each diagnosis, MM genotype didn't affect outcomes in AML patients, whereas MDS and ALL patients with MM genotype showed lower OS (MDS: HR 1.829, [95% CI, 1.070 - 3.128]; p = 0.023), (ALL: HR 1.638, [95% CI, 1.032 - 2.599]; p = 0.037) compared to TT genotype (Table). In subgroup analysis for HLA-B leader genotype, CMV reactivated patients were significant better for OS (HR 0.467, [95% CI, 0.266 - 0.819]; p &lt; 0.001) and lower NRM (HR 0.342, [95% CI, 0.153 - 0.763], p = 0.009) only in MM patients. Conclusions: MM HLA-B leader genotype is a risk factor for worse OS and higher NRM compared to TT genotype in HLA matched related and unrelated HCT, particularly MDS and ALL patients in the study. On the other hand, CMV reactivation could be favorable for OS and NRM in MM leader patients suggesting that promoting NK cell reconstitution and education due to CMV reactivation might benefit MM leader patients. Figure 1 Figure 1. Disclosures Kanda: CHUGAI PHARMACEUTICAL Co., Ltd.: Honoraria; DAIICHI SANKYO Co., Ltd.: Honoraria, Membership on an entity's Board of Directors or advisory committees; Eisai: Research Funding; Janssen Pharmaceutical K.K.: Honoraria, Membership on an entity's Board of Directors or advisory committees; Kyowa Kirin Co., Ltd.: Honoraria; Megakaryon Co: Honoraria, Membership on an entity's Board of Directors or advisory committees; NextGeM Inc: Patents & Royalties; Novartis Pharma K.K.: Honoraria; Ono Pharma Inc.: Honoraria; Otsuka Pharmaceutical Co., Ltd.: Honoraria; Sanofi K.K.: Honoraria; Sumitomo Dainippon Pharma Co., Ltd.: Honoraria; SymBio Pharmaceuticals, Ltd.: Membership on an entity's Board of Directors or advisory committees; Takeda Pharmaceutical Company Limited: Honoraria, Membership on an entity's Board of Directors or advisory committees; TEIJIN PHARMA LIMITED.: Honoraria; Bristol-Myers Squibb Co: Honoraria; Astellas Pharma Inc.: Consultancy, Honoraria; Amgen Astellas BioPharma: Honoraria. Ichinohe: Takeda Pharmaceutical Co.: Honoraria; Kyowa Kirin Co.: Honoraria, Research Funding; FUJIFILM Wako Chemicals.: Honoraria, Research Funding; Daiichi Sankyo: Research Funding; CSL Behring: Honoraria, Research Funding; Taiho Pharmaceutical Co.: Research Funding; Sumitomo Dainippon Pharma Co.: Honoraria, Research Funding; Ono Pharmaceutical Co.: Honoraria, Research Funding; Nippon Shinyaku Co: Research Funding; Takara Bio Inc.: Research Funding; Zenyaku Kogyo Co.: Research Funding; Repertoire Genesis Inc.: Honoraria, Research Funding; Novartis Pharma K.K.: Honoraria; Celgene: Honoraria; Otsuka Pharmaceutical Co.: Research Funding; Eisai Co.: Honoraria, Research Funding; Chugai Pharmaceutical: Research Funding; Bristol-Myers Squibb: Honoraria; AbbVie Pharma: Research Funding; Astellas Pharma: Honoraria, Research Funding. Atsuta: Mochida Pharmaceutical Co., Ltd.: Speakers Bureau; Meiji Seika Pharma Co, Ltd.: Honoraria; Astellas Pharma Inc.: Speakers Bureau; AbbVie GK: Speakers Bureau; Kyowa Kirin Co., Ltd: Honoraria.

Graft-Vs-Host Disease (GvHD) Prophylaxis with Post-Transplant Cyclophosphamide (PTCy) and Thymoglobulin (ATG) Are More Important Determinants of Cytomegalovirus (CMV) Reactivation after Allogeneic Hematopoietic Cell Transplantation (HCT) Than Ex-Vivo T-Cell Depletion in the Era of Pre-Emptive Therapy

Background: Cytomegalovirus (CMV) is a common cause of morbidity and mortality after allogeneic hematopoietic cell transplantation (HCT) despite major advances in diagnostic techniques and antiviral prophylactic strategies. The relative impacts of donor/recipient CMV serologic status, disease-specific and transplant-related prognostic factors on the risk of CMV reactivation and survival are undefined. Methods: We studied the outcome of 199 patients (median age, 46 years; range 17-71 years) receiving allogeneic HCT at National University Cancer Institute of Singapore (NCIS) between January 2016 and December 2020. Their hematologic diseases included AML (n=92), ALL (n=46), MDS (n=19), lymphomas (n=19), MPN (n=7) and others (n=16) such as refractory myelomas and aplastic anemias. The conditioning regimens used were either myeloablative (n=80) or reduced intensity conditioning (n=119) prior to an allograft from different donor sources. T-cell depletion (TCD) was used for GVHD prophylaxis in 124 patients; and this included post-transplant cyclophosphamide (PTCy, n=31), ex-vivo T-cell receptor alpha-beta / CD45RA depletion (TCRab/CD45RA) (ex-vivo TCD, n=31) for haploidentical HCT, or thymoglobulin (ATG, n=62) for matched unrelated donor (MUD) HCT. Results: With a median follow-up duration of 15.6 months (range, 0.2-63.6 months), 136 (68.3%) patients had CMV reactivation (median onset, 27.5 days) while 6 (3.0 %) patients developed clinically significant CMV disease, such as colitis, retinitis and encephalitis. The cumulative incidences of CMV reactivation within the first 100 days among the recipients of matched unrelated donor (MUD) (n=60), mismatched related donor or unrelated donor (MMRD/MMUD) (n=60), umbilical cord blood (UCB) (n=18) and matched related donor (MRD) (n=61) HCT were 71.6 %, 61.7 %, 50.0 % and 32.7 %, respectively (p&lt;0.001). There were no statistically significant differences in overall survival (OS, p=0.830) and disease-free survival (DFS, p=0.983) at 5 years between CMV-seropositive (D+/R+ or D-/R+, n=181) and CMV-seronegative recipients (D-/R- or D+/R-, n=18). There were also no significant differences in the cumulative incidences of CMV reactivation within 100 days (p=0.879), CMV end-organ disease (p=0.522) and non-relapse mortality (NRM, p=0.202), respectively. HCT-CI score of ≥1 (p=0.005) and the use of reduced intensity conditioning regimen (p&lt;0.001) were associated with a higher NRM at 2 years. There was also a trend towards higher NRM among patients with peak CMV DNA titers of above 1000 IU/ml, but this did not reach statistical significance (p=0.188). The secondary objective of this study was to determine the risk factors associated with CMV reactivation within the first 100 days post-transplant. There was no statistically significant impact of the donor or recipient CMV serostatus (p=0.790) on the risk of CMV reactivation. In multivariable analysis, the use of any T-cell depletion (p&lt;0.001) was a significant predictor of CMV reactivation. In a subset analysis comparing the 3 different methods of TCD, the use of ATG (p=0.004) and PTCy (p=0.005) was found to be associated with an increased risk of CMV reactivation, but not in patients receiving ex-vivo TCD (p=0.184) (Figure 1). Notably, patients receiving ex-vivo TCD haploidentical HCT was not associated with a higher risk of CMV reactivation as compared to the recipients of MRD HCT without any TCD. Conclusions: Our study concluded that CMV serologic status did not affect the incidence of CMV reactivation, NRM, OS and DFS in patients undergoing allogeneic HCT. The use of PTCy and ATG for GVHD prophylaxis, remains the most important risk factor for CMV reactivation in the era of pre-emptive therapy and hence, the need for aggressive prevention strategies in this vulnerable group of patients. Figure 1 Figure 1. Disclosures No relevant conflicts of interest to declare.