Abstract: The incidence of IFIs during VEN-HMA therapy is low, and the used antifungal prophylaxis approach did not influence the risk of IFIs. The risk of IFIs is higher in nonresponders and those who were treated in the r/r AML setting.

Abstract: CMV recipient seropositivity (R+) and CMVi are independent risk factors for increased mortality after alloHCT. Preemptive therapy (PET) was standard of care until LTV approval by the FDA in November 2017 for CMVi prevention in CMV R+ alloHCT patients (pts). In a registration trial, LTV led to a significant reduction in clinically significant CMVi (CS-CMVi) defined as CMVi requiring PET in both high-risk (HR) or low-risk (LR) recipients. In the HR-group, defined as mismatched related / unrelated donor with at least one mismatch in one of the four HLA-gene loci of HLA-A, -B, -C or -DRB1, haploidentical donor, umbilical cord source or grade ≥2 acute graft-versus-host disease (aGVHD) at randomization, the impact of LTV on CS-CMVi was more robust. Small studies have confirmed the positive impact of LTV on CS-CMVi. Here, we compared the natural history of CMVi and CS-CMVi between the pre-LTV and LTV era in the first 100 days after HR-alloHCT. We also explored the impact on non-relapse mortality (NRM), overall survival (OS), disease free survival (DFS), and incidence of aGVHD between the two eras. In this IRB approved retrospective study, we identified 450 consecutive HR-alloHCT pts who underwent their first HCT from 1/1/2016 to 12/31/2020 at our center. Pre-LTV era was from 1/1/2016 to 2/28/2018 and LTV era was from 3/1/2018 onwards when prophylaxis became standard of care (SOC) for all R+ alloHCT at our institution. In the HR-alloHCT, the uptake of the new SOC was consistent in all HR-R+ pts beginning LTV prophylaxis on day +7 post-HCT. We defined R+ HR-alloHCT pts at high-risk for CMVi or CS-CMVi as described above except for aGVHD (not recorded at time of institution of LTV). CMVi was defined as first time viral load (VL) of & gt;500 genomic copies/ml (gc/ml). CS-CMVi was defined as a VL & gt;500 gc/ml (910 IU/ml) on two consecutive tests done atleast 48 hours apart, that triggered PET (ganciclovir, valganciclovir, foscarnet, cidofovir), or had identification of CMV end organ disease . The incidence of CMVi and CS-CMVi in R+ allo-HCT was compared by LTV era using Gray test. Kaplan-Meier curves and log-rank tests were used for OS and DFS by LTV era. NRM, relapse, acute and chronic GVHD were compared using cumulative incidence curves and Gray test. All tests were 2-sided at 0.05 level. Of the 450 HR-alloHCT pts, 146 were R+ in pre-LTV vs. 246 R+ in LTV era. R+ patient, their eligible underlying disease, and HCT characteristics are shown in Table 1. There was a significant reduction in both CMVi and CS-CMVi in LTV era vs pre-LTV era (24.1% vs 45.2%, and 22.3% vs 44.5% respectively; p & lt;0.001 for both outcomes) in the first 100 days. Compared to pre LTV era, LTV era was associated with significantly reduced CS-CMVi among R+ pts (HR=0.39, 95%CI: 0.26-0.58, p & lt;0.001) in the multivariable Fine and Gray model adjusted for primary diagnosis, donor type and acute GVHD. CMVi was also reduced in the multivariable model (HR=0.41 and 95%CI: 0.28-0.61, p & lt;0.001). Although there were no significant differences in OS, DFS, NRM, relapse, and chronic GVHD between the two eras at 6, 12, and 18 months post-HCT in R+ pts, a trend towards improved OS and DFS in LTV era was noted (p=0.06 and p=0.07) in this patient population. There was a significantly lower rate of grade III-IV acute GVHD in the LTV era (9.2% vs 17.8% at day 100, p=0.012 with HR = 0.49). No case of CMV disease was identified in the first 100 days. LTV has substantially reduced CS-CMVi in the first 100 days post-HCT in HR-R+ pts and resultant burden from PET. We identified a significant reduction in grade III - IV aGVHD in LTV era suggesting that with reduced CMVi, LTV may have a salutary impact on development of aGVHD; this is in agreement with studies showing bidirectional relationship between CMVi and onset of aGVHD. We did not observe a significant difference in OS, DFS, NRM amongst the two eras but there was trend towards higher OS and DFS in LTV era that requires further assessment in a larger multicenter cohort. Lastly, significant burden persists from CS-CMVi in this patient population during the first 100 days of alloHCT that underscores the need of efforts to identify other novel methods to mitigate it. One of the limitations in the LTV era is identifying the clinical scenarios surrounding the CMVi and CS-CMVi that may relate to compliance, absorption from gastrointestinal tract, and affordability or coverage of LTV after discharge from hospital. Figure 1 Figure 1. Disclosures Dadwal: Astellas: Speakers Bureau; Aseptiscope: Consultancy; AlloVir: Research Funding; Shire/Takeda: Research Funding; Merck: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding, Speakers Bureau; Janssen: Other: Investigator; Karius: Other: Investigator. Marcucci: Novartis: Other: Speaker and advisory scientific board meetings; Agios: Other: Speaker and advisory scientific board meetings; Abbvie: Other: Speaker and advisory scientific board meetings. Taplitz: Merck: Membership on an entity's Board of Directors or advisory committees. Artz: Radiology Partners: Other: Spouse has equity interest in Radiology Partners, a private radiology physician practice. Stein: Amgen: Consultancy, Speakers Bureau; Celgene: Speakers Bureau; Stemline: Speakers Bureau. 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. Al Malki: Neximmune: Consultancy; Jazz Pharmaceuticals, Inc.: Consultancy; CareDx: Consultancy; Rigel Pharma: Consultancy; Hansa Biopharma: Consultancy.

Abstract: Cytomegalovirus reactivation commonly referred to as CMV infection (CMVi) is a frequent event after allogeneic hematopoietic cell transplantation (HCT), with studies associating CMVi within the first 100 days post-HCT with higher risk of non-relapse mortality (NRM) and decreased overall survival (OS). In addition, understanding the impact of CMVi on resource utilization during the primary HCT admission is critical. Together, this knowledge of epidemiology and resource utilization may be used to inform preventive strategies to minimize CMVi, e.g., use of antiviral agent letermovir. After receiving IRB approval, we retrospectively reviewed institutional electronic medical records and CMVi database from 824 patients who underwent their first allogeneic HCT between 2011 and 2016 at City of Hope (pre-letermovir era). Patients were censored at death, disease relapse or lost to follow up. Data collected: demographics, HCT indication, conditioning regimen, CMV serostatus of the donor and recipient (D/R), length of stay (LOS) for primary HCT admission (all allo HCT were performed as inpatient), readmission rates in first 100 days, and use of supportive care. CMV viral load of & gt;250 genomic copies/ml constituted a diagnosis of CMVi. CMV viral load surveillance in MUD recipients began at engraftment or day +21 post-HCT, whichever occurred earlier. For Haplo and cord blood (CB) HCT, CMV viral load surveillance started on day +14. The primary endpoint of the study was LOS for HCT admission. Supportive care use, transfusions, growth factors and antiviral usage were secondary endpoints. The differences in resource utilization between different groups were examined by CMVi during the primary HCT admission period, using Wilcoxon test or chi-square test whenever appropriate. Median age of patients at the time of HCT was 52 years (range: 1-78), with 57% of patients being male. The most common diagnoses included: AML (39%), ALL (21%) and MDS/MPN (17%). Patients underwent MUD (n=627, 76%), Haplo (n=102, 12%), or CB-HCT (n=95, 12%), and 44% of patients received myeloablative conditioning regimen. Majority of the patients were CMV seropositive (83.7%). Graft source was peripheral blood stem cells in 75% of the recipients. Most commonly used graft-versus-host disease prophylaxis consisted of post-transplant cyclophosphamide (100%), Tacrolimus/sirolimus (83%), and cyclosporine/cellcept (78%) in Haplo, MUD, and CB-HCT recipients, respectively. During the primary HCT admission, rate of CMVi was 7%, 36% and 28% in all of MUD, Haplo, and CB-HCT, respectively (compared to 25%, 71.6%, and 50.5% in MUD, Haplo and CB-HCT respectively in the first 100 days after HCT). Rate of CMVi in CMV+ recipients was 8.2% in MUD, 41.6% Haplo and 34.2% in CB-HCT (Table 1). Majority of patients with CMVi received antiviral therapy (85.8%), with Haplo and CB-HCT more likely to be treated than MUD (p=0.023). LOS was longer among CMVi patients compared to no CMVi patients in each donor type, median of 59 vs. 36 days for the overall cohort (p & lt;0.01). The difference in LOS by CMVi remained significant (p & lt;0.001) in the multivariable regression model including donor type, graft source, primary diagnosis and conditioning intensity (Table 2). Filgastrim use was higher among CMVi patients than no CMVi patients in MUD (p & lt;0.001), but not in Haplo or CB-HCT (p & gt;0.2). Transfusion of packed red blood cells (PRBC) and platelet units were significantly higher among CMVi recipients of MUD and Haplo (p & lt;0.02), but not CB-HCT (p & gt;0.82). There was no significant difference in hospital readmission by CMVi across donor type in the first 100 days (p & gt;0.5). In conclusion, the rate of CMVi during primary HCT admission was high, particularly in the Haplo and Cord HCT ( & gt;50% of the CMVi occurring within 100 days of HCT). Given the relatively high CMV viral load cut-off values and later CMV surveillance initiation, the rate could, in fact, have been underestimated in our cohort. CMVi during primary HCT admission was associated with significantly higher health care resource utilization; longer hospital LOS and supportive care utilization (CMV specific antiviral usage, transfusion and growth factors use). Prophylactic strategies to prevent early CMVi in alloHCT should be considered to decrease NRM and improve value based care delivery. Disclosures Dadwal: Shire/ Takeda: Research Funding; Karius: Research Funding; Astellas: Speakers Bureau; Janssen: Other: Advisory board meeting; Ansun Biopharma: Research Funding; Chimerix: Research Funding; Gilead: Research Funding; Merck: Consultancy, Honoraria, Other: Advisory board meeting, Research Funding, Speakers Bureau. Pullarkat:Dova: Consultancy, Honoraria; Amgen: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Novartis: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Jazz Pharmaceuticals: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Pfizer: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Genetech: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; AbbVie, Inc.: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Servier: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau. Stein:Stemline: Consultancy, Speakers Bureau; Amgen: Consultancy, Speakers Bureau. Taplitz:Merck: Other: Immunocompromised Advisory Group. Al Malki:Neximmune: Consultancy; Rigel Pharma: Consultancy; Jazz Pharmacuticals, Inc: Consultancy. Nakamura:NapaJen Pharma: Consultancy; Magenta Therapeutics: Other: Advisory board meeting; Alexion: Other: Support on a meeting presentation; Kyowa-Kirin: Other: Support on a meeting presentation; Celgene: Other: Support on seminar; Viracor: Consultancy; Merck: Other: advisory board meeting; Kadmon Corporation: Other: Advisory board meeting.

Abstract: In the current post-pandemic era, recipients of an allogeneic hematopoietic stem cell transplant (HCT) deserve special attention. In these vulnerable patients, vaccine effectiveness is reduced by post-transplant immune-suppressive therapy; consequently, severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) disease (COVID-19) is often associated with elevated morbidity and mortality. Characterizing SARS-CoV-2 adaptive immunity transfer from immune donors to HCT recipients in the context of immunosuppression will help identify optimal timing and vaccination strategies that can provide adequate protection to HCT recipients against infection with evolving SARS-CoV-2 variants. We performed a prospective observational study (NCT04666025 at ClinicalTrials.gov ) to longitudinally monitor the transfer of SARS-CoV-2-specific antiviral immunity from HCT donors, who were either vaccinated or had a history of COVID-19, to their recipients via T-cell replete graft. Levels, function, and quality of SARS-CoV-2-specific immune responses were longitudinally analyzed up to 6 months post-HCT in 14 matched unrelated donor/recipients and four haploidentical donor/recipient pairs. A markedly skewed donor-derived SARS-CoV-2 CD4 T-cell response was measurable in 15 (83%) recipients. It showed a polarized Th1 functional profile, with the prevalence of central memory phenotype subsets. SARS-CoV-2-specific IFN-γ was detectable throughout the observation period, including early post-transplant (day +30). Functionally experienced SARS-CoV-2 Th1-type T cells promptly expanded in two recipients at the time of post-HCT vaccination and in two others who were infected and survived post-transplant COVID-19 infection. Our data suggest that donor-derived SARS-CoV-2 T-cell responses are functional in immunosuppressed recipients and may play a critical role in post-HCT vaccine response and protection from the fatal disease. Clinical trial registration clinicaltrials.gov, identifier NCT04666025.

Abstract: Background: In November 2020, the U.S. Food and Drug Administration (FDA) issued emergency use authorization (EUA) for monoclonal antibody (mAb) therapy in patients with mild to moderate COVID-19 who are at high risk for disease progression. These mAbs reduce the risk of hospitalization in the general population. However, its efficacy and safety in immunocompromised hematology patients are not known. Methods: From November 9th, 2020, until February 28th, 2021, all adult hematology patients with mild to moderate COVID-19 disease who received monoclonal antibodies within 10 days of symptoms onset were included. Patients who were asymptomatic, had severe or critical COVID-19 disease, or were hospitalized at the time of COVID-19 diagnosis were excluded. Baseline demographic, clinical outcomes, and hematologic-related data were extracted. All statistical analysis was performed using SAS statistical software. Results: Thirty-eight hematology patients with mild to moderate COVID-19 disease who received mAb therapy under EUA were included in this study. Thirty (79%) patients received bamlanivimab and 8 (21%) casirivimab-imdevimab. Baseline characteristics prior to mAB administration include: 53% female, median age of 51 years (range: 21-80), with 18% above 65 years old. Twenty-eight (74%) patients received cellular therapy: 18 (47%) had undergone allogeneic hematopoietic cell transplantation (HCT), 9 (24%) autologous HCT, and 1 (3%) chimeric antigen receptor T-cell (CAR T) therapy. Among the 17 patients who had COVID-19 disease after HCT, the median time to COVID-19 diagnosis was 22.8 months (range: 2.6-274.4) from HCT to COVID-19 diagnosis. Twelve out of 17 (71%) alloHCT patients were being managed for active graft-vs-host disease (GvHD) at the time of COVID-19 diagnosis (chronic GVHD: n=11 [mild: 4, moderate: 4, severe: 3], acute GVHD (grade 2): n=1). Ten (59%) alloHCT patients were on immunosuppressant therapy at the time of COVID-19 diagnosis. Fifteen (39%) patients were on active treatment for their hematologic malignancy (HM) at the time of COVID-19 diagnosis with a mean of 3 previous lines of treatment (range: 1-6). Additional patient characteristics are shown in T able 1. mAb therapy under EUA was well tolerated in this patient population with only 1 (3%) patient having experienced an adverse reaction characterized as headache. Four (11%) patients were hospitalized due to COVID-19, and 2 (5%) progressed to severe disease. All four patients had received bamlanivimab. The median time for hospitalization from diagnosis of COVID-19 to admission date was 8 days (range: 1-20) while median time from mAB infusion to hospitalization was 7.5 days (range: 0-17). One patient (3%) died within 30 days of COVID-19 diagnosis; the cause of death was COVID-19 disease. Most patients (n=34, 89%) ultimately tested negative for SARS-CoV-2 by PCR after mAb infusion. 34% of patients (n=13) cleared the virus within 2 weeks of receiving mAb infsuion. The median time to clearance of viral shedding was 25.5 days (range: 7-138). After mAb infusion, most patients (10/15; 67%) who were previously on active treatment for HM prior to diagnosis of COVID-19 resumed therapy for their HM with a median delay of 21.5 days (range: 12-42). We observed a significant difference in hospitalization was amongst patients who received a HCT vs. non-HCT (0%, 0/26 and 36%, 4/11 respectively; p & lt;0.01). None of the other patient characteristics, which included: gender, ethnicity, age, BMI, smoking, obesity, chronic kidney disease, diabetes mellitus, hypertension, coronary vascular disease, and lung disease, were associated with significantly increased rate of hospitalization. Conclusion: This study demonstrates that SARS-COV2 specific mAb use in malignant hematology patients under EUA was safe and may reduce hospitalization as reported in the literature amongst those at high risk for disease progression. Thus, the access to SARS-COV2 mAb in this population who is at increased risk for complications from SARS-COV2 infection is critical in reducing progression to severe COVID-19 disease and hospitalization. Figure 1 Figure 1. Disclosures Ali: Incyte: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; CTI BioPharma: Membership on an entity's Board of Directors or advisory committees; BMS: Speakers Bureau. Aribi: Seagen: Consultancy. Artz: Radiology Partners: Other: Spouse has equity interest in Radiology Partners, a private radiology physician practice. Koller: Novartis: Consultancy. Nikolaenko: Rafael Pharmaceuticals: Research Funding; Pfizer: Research Funding. Shouse: Beigene: Honoraria; Kite Pharma: Speakers Bureau. Stein: Amgen: Consultancy, Speakers Bureau; Celgene: Speakers Bureau; Stemline: Speakers Bureau. Marcucci: Abbvie: Other: Speaker and advisory scientific board meetings; Novartis: Other: Speaker and advisory scientific board meetings; Agios: Other: Speaker and advisory scientific board meetings. Forman: Mustang Bio: Consultancy, Current holder of individual stocks in a privately-held company; Lixte Biotechnology: Consultancy, Current holder of individual stocks in a privately-held company; Allogene: Consultancy. Dadwal: AlloVir: Research Funding; Merck: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding, Speakers Bureau; Astellas: Speakers Bureau; Shire/Takeda: Research Funding; Aseptiscope: Consultancy; Janssen: Other: Investigator; Karius: Other: Investigator. Al Malki: CareDx: Consultancy; Rigel Pharma: Consultancy; Jazz Pharmaceuticals, Inc.: Consultancy; Neximmune: Consultancy; Hansa Biopharma: Consultancy.

Abstract: The gut microbiota plays an important role in maintaining intestinal homeostasis by regulating the maturation of the mucosal immune system, which constitutes an immune barrier for the integrity of the intestinal tract. In recent years, the role of the human GI microbiota in graft-versus-host disease (GVHD) and other outcomes after allogeneic hematopoietic cell transplantation (HCT) has been increasingly evaluated in observational studies. However, there have been limited interventional trials specifically designed to alter the microbiota of HCT recipients. CBM588 (clostridium butyricum MIYAIRI 588) is a novel Live Biotherapeutic Product (LBP) that produces short chain organic acids, mainly butyric acid, which plays a key role in the maintenance of colonic homeostasis by regulating fluid and electrolyte uptake, epithelial cell growth, and inflammatory responses. In this pilot trial (NCT03922035) we sought to determine the safety, feasibility, biologic activities, and preliminary efficacy of CBM588 in HCT recipients. Patients age ≥18 years, scheduled to undergo HCT from an 8/8 or 7/8 matched related/unrelated donor with reduced intensity conditioning (RIC) were eligible. Following the patient safety lead-in (SLI; n=6), 30 patients were randomized (1:1 ratio) to receive either standard peri-transplant supportive care alone (control arm) or with CBM588 (treatment arm, open label) at the fixed dose of 160 mg orally (2x/day) from day -8 or hospital admission until day +28 or discharge (figure 1). Patients received prophylactic antibiotics per intuitional SOPs. Study objectives were to evaluate the safety/feasibility of CBM588 (Primary), and to compare the incidence and severity of adverse events (AE), HCT outcomes including GVHD, and gut microbiome diversity between the Treatment and Control arms. Feasibility was defined as the ability to consume CDM588 for 14 days during the SLI phase. For microbiome analysis, we isolated DNA from weekly collected stool samples, and amplified the V4 region of the bacterial 16S rRNA gene from each total DNA sample. Between April, 2018 and January, 2020, we enrolled 36 patients (20 were female) at the median age of 66 years (range: 34-77). The indication for HCT was Leukemias (n=22), MDS (n=5), lymphoma (n=3), myeloma (n=3), or other (n=3). All but one patient received fludarabine/melphalan-based RIC and tacrolimus/sirolimus-based GVHD prophylaxis. Graft source was peripheral blood stem cell from a matched related (n=13) or unrelated (n=23) donor (Table 1). One patient assigned to the Treatment arm declined to receive CBM588 before the first dose; but remained on the study with clinical data/biospecimen collections and safety/feasibility/biologic endpoints were analyzed as treated for this patient. All the other patients who were assigned to the treatment arm (n=21, including the patients in SLI segment) were able to take the prescribed study drug; with the median 52 doses (range: 0-55), and 19 of 21 subjects (90.5%) consumed at least 14 days of the study drug. There were no serious adverse events (SAE) related to CBM588. The overall AEs and infection- or GI-specific AEs were similar between the Treatment and Control arms. All but one patient (who died of sepsis in the Control arm - on day 8) engrafted with a median of 15 days for neutrophils. The 100-day non-relapse mortality (NRM) was 0% in the Treatment and 6.7% in the Control arm. According to the intent-to-treat principle, acute GVHD (grade 2-4) was observed in 4 of 15 patients in the Treatment arm and 5 of 15 in the Control arm. The lower GI GVHD was seen in 2 patients in the Treatment and 4 in the control arm. As treated analyses showed the overall grade 2-4 GVHD in 3 of 14 (21.4%) with the use of CBM588 and 6 of 16 (37.5%) without CBM588 (one case of lower GI GVHD with CBM, 5 cases without; (Table 2). The Shannon Diversity Index was similar between the two groups at each time point tested. (Figure 1). However, had favorable microbial profile was detected as the pathogens Enterobacteriaceae, Clostridium baratii, and Clostridiodes difficile were reduced in the treatment group. (Figure 2) In summary, our data demonstrate the feasibility and safety of CBM588 administration during the peri-transplant period, which was associated with an intended biologic impact on the gut microbiome, and an early favorable sign of GI-GVHD incidence and HCT outcomes in this older population who underwent RIC HCT. Figure 1 Figure 1. Disclosures Dadwal: Astellas: Speakers Bureau; Aseptiscope: Consultancy; Shire/Takeda: Research Funding; AlloVir: Research Funding; Merck: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding, Speakers Bureau; Janssen: Other: Investigator; Karius: Other: Investigator. Pullarkat: AbbVie, Amgen, Genentech, Jazz Pharmaceuticals, Novartis, Pfizer, and Servier: Membership on an entity's Board of Directors or advisory committees; Amgen, Dova, and Novartis: Consultancy, Honoraria. Al Malki: CareDx: Consultancy; Neximmune: Consultancy; Hansa Biopharma: Consultancy; Rigel Pharma: Consultancy; Jazz Pharmaceuticals, Inc.: Consultancy. Ali: Incyte: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; BMS: Speakers Bureau; CTI BioPharma: Membership on an entity's Board of Directors or advisory committees. Artz: Radiology Partners: Other: Spouse has equity interest in Radiology Partners, a private radiology physician practice. Stein: Amgen: Consultancy, Speakers Bureau; Celgene: Speakers Bureau; Stemline: Speakers Bureau. Budde: Roche: Consultancy; BeiGene: Consultancy; IGM Biosciences: Research Funding; Merck, Inc: Research Funding; Gilead: Consultancy; AstraZeneca: Research Funding; Mustang Bio, Inc: Research Funding; Novartis: Consultancy; Amgen: Research Funding. Popplewell: Hoffman La Roche: Other: Food; Pfizer: Other: Travel; Novartis: Other: Travel. Marcucci: Novartis: Other: Speaker and advisory scientific board meetings; Agios: Other: Speaker and advisory scientific board meetings; Abbvie: Other: Speaker and advisory scientific board meetings. Forman: 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; Allogene: Consultancy.

Abstract: The prevalence of vancomycin-resistance Enterococci colonization (VRE-C) in patients undergoing allogeneic hematopoietic cell transplantation (aHCT) is between 23-40%. Pre-HCT VRE-C is shown to be associated with high risks of VRE bloodstream infection (VRE-BSI), non-relapse mortality (NRM) and lower overall survival. Recent studies investigating the association between VRE-C and risk of acute graft-versus-host disease (aGVHD) after aHCT has demonstrated conflicting results, possibly due to the heterogeneous transplant conditioning and GVHD prophylactic regimens. Here, we sought to examine the VRE-C prevalence and determine its impact on aHCT outcomes, in patients receiving tacrolimus and sirolimus (T/S) as aGVHD prophylaxis. To explore the association between pre-HCT VRE-C and transplant outcomes, we retrospectively reviewed medical records of a cohort of 1074 consecutive patients who underwent aHCT at City of Hope from 2014 to 2017. Patients with stool culture screening within 30 days pre-aHCT (n=862) were identified from the microbiology database and were grouped as VRE-C and non-colonized (VRE-NC). Data was not available on VRE-C in 185 patients and they were not included in analysis. Overall survival (OS) and progression-free survival (PFS) were examined by Kaplan-Meier curves and log-rank tests. Non-relapse mortality (NRM), VRE-BSI, and GVHD rates of the 2 groups were compared by cumulative incidence rates and Gray's test. Multivariate analyses were performed when adjusting for prognostic factors. Two-sided P value of ≤0.05 was considered significant. Of the 862 evaluated patients, 68 had VRE-C (7.9% prevalence). Median age of patients in VRE-C and VRE-NC groups were 53 and 55 years, respectively. Gender distribution, transplant indications, stem cell source, proportion of unrelated donors, GVHD prophylaxis with T/S and other clinical variables including intensity of conditioning regimen and HCT-CI were similar between the two groups (Table 1) . Karnofsky performance status (KPS) of 90-100 and 70-80 were seen in 40% and 53% of patients with VRE-C compared to 47% and 48% of VRE-NC patients (p=0.12). Overall, VRE-BSI episodes were rare (n=7) with 4 patients in VRE-C (6.1%) and 3 patients in VRE-NC (0.4 %); p 〈 0.001. All 3 patients in the VRE-NC group developed bacteremia within the first 100 days (range 2-97) but VRE-BSI was not the eventual cause of death. The median onset of VRE-BSI in the VRE-C group (n=4) was only 6 days (range: 2-12) with 1 surviving patient and 3 who died of non VRE-BSI related causes. No statistical significance was detected in rates of non-VRE BSI (24.1% in VRE-C Vs. 19.2% in VRE-NC; p=0.30) and fungemia (1.5% in VRE-C vs 1.2% VRE-NC; p=0.77). At a median follow-up duration of 19.4 months (range: 2.7-48.4), similar 1-year OS was achieved in both groups (67.4% in VRE-C and 76.5% in VRE-NC; p=0.11) but 1 year PFS was significantly lower in the VRE-C cohort (55.6% Vs. 69.4%; p=0.038). Higher NRM was achieved in the VRE-C cohorts on days +100 and +365 (11.8% Vs. 7.2% and 25.1% Vs. 14.4%, respectively, p=0.041). (Figure 1) There were no differences in rates of day 100 aGVHD (grades II-IV) (Figure 2) and relapse rates at 12 months between the two groups. Conditioning regimen intensity, donor type, KPS, and primary diagnosis were significantly associated with NRM. When these variables were included in the multivariate model, VRE-C was found to be independently associated with higher NRM (HR=1.82, 95%CI: 1.12-2.93; p=0.015). In conclusion, in our cohort of patients receiving predominantly T/S-based aGVHD prophylaxis, no association was detected between VRE-C and aGVHD incidence. Higher rate of VRE-BSI in the VRE-C group is in accordance with published data, albeit lower rates of VRE-BSI was seen in our cohort. VRE-C contributed to higher NRM at days 100 and 365 post-aHCT and was an independent risk factor for poor HCT outcomes Since VRE-C is a potentially modifiable risk factor, our data supports continued efforts for specific interventional strategies (i.e. antimicrobial stewardship) to reduce drug resistant bacterial colonization, and for clinical research to reverse the impact of VRE-C, such as the use of agents, which may modulate gut microbiome. Disclosures Salhotra: Kadmon Corporation, LLC: Consultancy. Ali:Incyte Corporation: Membership on an entity's Board of Directors or advisory committees. Stein:Amgen Inc.: Speakers Bureau; Celgene: Speakers Bureau. Forman:Mustang Therapeutics: Other: Licensing Agreement, Patents & Royalties, Research Funding. Dadwal:AiCuris: Research Funding; Gilead: Research Funding; MERK: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding, Speakers Bureau; Shire: Research Funding.

Abstract: The "7+3" regimen is recommended for treatment in patients with new diagnosis of acute myeloid leukemia (AML) who are fit for intensive chemotherapy. Patients with secondary AML (sAML) [i.e. AML evolving from antecedent hematologic disorders (AHD-AML) or after previous exposure to chemo/radiation therapy for unrelated cancer (t-AML)], have inferior outcomes with "7+3" regimen. A recent phase 3 study demonstrated superior CR rates and overall survival (OS) with upfront use of CPX-351 compared to "7+3" regimen in older patients (≥60 years) with sAML (Lancet et al JCO 2018). The combination of HMA+Ven is FDA approved for upfront treatment in newly diagnosed AML patients & gt; 75 or those unfit for intensive chemotherapy based on CR+ CRi rates of 67% and median OS of 17.5 months. Herein, we compared the outcomes of older patients with sAML who received upfront treatment with either HMA+Ven or CPX-351 at our institution. Our analysis includes 47 consecutive patients with previously untreated sAML treated between 2018-2020 . Patients were treated with either HMA+Ven (n=27) or CPX-351 (n=20) based on physician preference. WHO criteria were used for the diagnosis AHD-AML and review of medical records for documenting exposure to leukemogenic agent for t-AML. Complete remission (CR) was defined by presence of & lt;5% blasts in bone marrow (BM) aspirates. CR with blood count recovery (i.e., absolute neutrophil counts & gt;1000/µL and platelets ≥100,000/µL) were defined as CRh (hematologic recovery) and CR without blood count recovery as CRi (incomplete blood count recovery). Minimal residual disease (MRD) assessment was done on day-28 BM aspirate using multiparametric flow cytometric assay with lower limit of sensitivity of 0.01%. Patients demographic and disease features are summarized in Table 1. Mean age (p=0.39), mean blast percentage in BM aspirate (P=0.82), high-risk cytogenetics (P=0.37) and high-risk molecular mutations (P=0.737) were similar in both treatment groups. Of the 27 cases of sAML in HMA+Ven group, 8 were t-AML arising after prior chemotherapy (Hodgkin's Disease n=2; paraganglioma, desmoid tumor, breast cancer, NHL, multiple myeloma, ALL: one each) while 19 were AHD-AML. In CPX-351 group, 6 cases were t-AML arising after prior chemotherapy (NHL n=2, breast cancer n=2, T-Lymphoblastic Lymphoma and colon cancer one each) while 14 were secondary to AHD. The mean number of cycles were 3.3 (range 1-18) in HMA+Ven group and 1.45 (1-3) in CPX-351 group. Two-sample t test was used to compare continuous and normally distributed covariates, such as age and BM blasts, between HMA+Ven or CPX-351 arms. Pearson Chi-square or Fisher exact test was used to assess the associations between treatment and clinical outcomes. Kaplan-Meier method and log-rank test were used to assess OS or LFS. A P value of ≤ 0.05 was considered as statistically significant. The CR rate in patients treated on HMA+Ven group was 78% (n=21; 95% CI: 58-91%) vs 50% (n=10; 95% CI: 27-73%) in CPX-351 group (P=0.047). CRi was achieved in 52% (n=14) patients in HMA+Ven group compared to 25%(n=5) patients in CPX-351 group(p=0.064). MRD negative remission was achieved in 52% (n=14) patients in HMA+Ven group and in 25% (n=5) patients in CPX-351 group (p=0.064). In HMA+Ven group, 52% patients (n=14) achieved remission after one cycle of therapy compared to 45% (n=9) patients in CPX-351 arm (p=0.642). With a median follow-up of 6.7 months for all patients, the median leukemia free-survival (LFS) for HMA+Ven vs CPX-351 treatments is 16.2 vs NA months (P = 0.098) and the median OS is 13.2 vs NA months (P = 0.395). Ten patients in each group (37% in HMA+Ven and 50% in CPX-351; p=0.47) underwent allo-HCT. At last follow up, 14 patients (52%) have died in HMA+Ven group from: relapsed AML (n=10), sepsis (n=2), congestive heart failure (n=1) and unknown (UK) in one patient, whereas in CPX-351 group, 8 patients (40%) have died from relapsed AML in (n=5), respiratory failure (n=2) and UK causes in one patient. In patients resistant to initial therapy, the median OS is 3.5 vs 6.0 months between HMA+ Ven and CPX-351 groups (P = 0.224). Conclusion: In patients presenting with sAML, upfront treatment with HMA+Ven is feasible and associated with significantly better CR rates and a favorable trend for higher rates of negative MRD compared to CPX-351. A randomized prospective trial in patients with sAML is warranted to determine the most effective frontline regimen in this high-risk AML subgroup. Disclosures Salhotra: Celgene: Research Funding; Kadmon: Membership on an entity's Board of Directors or advisory committees. Al Malki:Rigel Pharma: Consultancy; Neximmune: Consultancy; Jazz Pharmacuticals, Inc: Consultancy. Aribi:Seattle Genetics: Consultancy. Ali:Incyte Corporation: Consultancy. Budde:Gilead Sciences: Consultancy; Merck: Research Funding; Amgen: Research Funding; Kite, a Gilead Company: Consultancy; Mustang Therapeutics: Research Funding; AstraZeneca: Research Funding; Roche: Consultancy. Dadwal:Ansun Biopharma: Research Funding; Karius: Research Funding; Shire/ Takeda: Research Funding; Gilead: Research Funding; Merck: Consultancy, Honoraria, Other: Advisory board meeting, Research Funding, Speakers Bureau; Chimerix: Research Funding; Janssen: Other: Advisory board meeting; Astellas: Speakers Bureau. Nakamura:NapaJen Pharma: Consultancy; Kadmon Corporation: Other: Advisory board meeting; Viracor: Consultancy; Magenta Therapeutics: Other: Advisory board meeting; Celgene: Other: Support on seminar; Kyowa-Kirin: Other: Support on a meeting presentation; Alexion: Other: Support on a meeting presentation; Merck: Other: advisory board meeting. Stein:Amgen: Consultancy, Speakers Bureau; Stemline: Consultancy, Speakers Bureau. Marcucci:Takeda: Other: Research Support (Investigation Initiated Clinical Trial); Merck: Other: Research Support (Investigation Initiated Clinical Trial); Iaso Bio: Membership on an entity's Board of Directors or advisory committees; Abbvie: Speakers Bureau; Novartis: Speakers Bureau; Pfizer: Other: Research Support (Investigation Initiated Clinical Trial). Pullarkat:Dova: Consultancy, Honoraria; Amgen: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Servier: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Novartis: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Jazz Pharmaceuticals: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Pfizer: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Genetech: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; AbbVie, Inc.: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau. OffLabel Disclosure: off label use of HMA+venetoclax in secondary AML