Abstract: In the era of preemptive antiviral therapy, cytomegalovirus (CMV) still remains the cause of major health complications, profound defects in immune reconstitution, and significant morbidity in post-transplant recovery of immune-compromised HCT recipients. Substituting antivirals with a vaccine that harnesses the native immune response to CMV may improve outcomes for HCT recipients. Modified Vaccinia Ankara (MVA), a vaccinia virus being investigated as a smallpox vaccine by the Defense Department, is a safe and robust delivery system to treat or prevent a wide range of diseases including HIV and cancer. Replication-defective MVA is safe, well tolerated and strongly immunogenic when given to HCT recipients or AIDS patients. We developed a multiple-antigen recombinant MVA with genes encoding 3 immunodominant CMV proteins: UL83 (pp65), UL123 (IE1-exon4), and UL122 (IE2-exon5) (CMV-MVA-Triplex), and established its pre-clinical safety and immunogenicity using humanized HLA transgenic mouse models and human PBMC from CMV-seropositive healthy volunteers and HCT recipients. Defining safety, persistence of the virus, maximum tolerated dose and immunogenicity of CMV-MVA-Triplex in healthy volunteers is a critical first step in its clinical development for HCT recipients as required by the FDA. In a Phase I trial (NCT01941056), these endpoints were evaluated in 24 healthy volunteers (age: 18-60), with or without prior immunity to CMV and vaccinia. Three escalating dose levels (DL) were administered intramuscularly (DL1=10xE7; DL2=5x10E7; DL3=5x10E8 pfu/dose) in 8 subjects/DL, with a booster injection 28 days later, and follow up for 1 year. As of July 2015, all 24 planned volunteers were enrolled, vaccinated and followed for at least 4 months. Vaccinations at all DL were well-tolerated, with only a few expected injection reactions and no SAE or dose limiting toxicities. Immunogenicity of the vaccine was evaluated by measuring the levels of the CD137 T-cell surface marker representing functional activation of PBL harvested from vaccinees and stimulated 24 hours with full-length pp65, IE-1 and IE2 overlapping peptide libraries, or direct measurement of CMV-specific T-cells using HLA multimers. CMV-MVA-Triplex induced robust expansion of pp65-, IE1- and IE2-specific CD8 and CD4 T-cells in vaccinated CMV-seropositives, at each DL (Cf. plot showing geometric mean with upper lower/limits of the pp65 T-cell levels for DL2 cohort). HLA multimers identified CMV-specific T-cells whose expansion closely followed CD137-activated CMV-specific T-cells in vaccinees with common HLA alleles which have a corresponding known CMV-CTL epitope (data to be presented). A statistical analysis performed using generalized estimated equations indicated that the post-vaccination levels of pp65-, IE1- or IE2-specific CD8 and CD4 T-cells were significantly increased, with p-values ranging from 3x10-5 to 0.025. For example, the pre-/post-vaccination median pp65-reactive CD4+ CD137+ T-cells rose from 1.3 to 4.4 cells/µL (p=3x10-5); and pp65-reactive CD8+ CD137+ T-cells rose from a median of 0.22 to 3.1 cells/µL (p=0.003). Importantly, robust immunity was detected in CMV-seronegatives (as shown in the plot for UPN 14 and 18), as well as in subjects who had received smallpox vaccinations. Elevated frequencies of CMV-specific CD4 and CD8 T cells for all 3 antigens plateaued after day 56, but in most cases remained elevated up to one year post-vaccination (data to be presented). Circulating MVA vector in blood was assessed by real-time PCR post-injection and showed only minimal residual vector DNA [10-30 gc/mL] in just 2 vaccinees in the DL3 cohort that disappeared within 3 months. These results provide evidence that CMV-seropositive HCT recipients, whether they receive stem cell product from CMV-seropositive or -seronegative donors could respond to CMV-MVA-Triplex by generating protective CMV-specific immunity. CMV-MVA-Triplex is the first vaccine against CMV that uses a recombinant MVA incorporating multiple CMV antigens, developed for HCT recipients, who are at risk for CMV reactivation. The safety and marked immunogenicity of CMV-MVA-Triplex in this Phase I trial, warrant testing of the vaccine in the HCT setting. A Phase 2 multicenter, placebo-controlled trial to assess CMV-MVA-Triplex in CMV seropositive recipients, receiving HCT from matched related or unrelated donors will start in Fall 2015. Figure 1. Figure 1. Figure 2. Figure 2. Disclosures Diamond: Helocyte, Inc.: Consultancy, Equity Ownership, Membership on an entity's Board of Directors or advisory committees, Patents & Royalties.

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: Background: Patients who undergo allogeneic hematopoietic cell transplantation (allo-HCT) are at high risk of reactivation or de novo infection with double-stranded (ds) DNA viruses such as cytomegalovirus (CMV), Epstein-Barr virus (EBV), human herpesvirus 6 (HHV-6), adenovirus (AdV), BK virus (BKV), and JC virus (JCV). After allo-HCT, up to 90% patients develop detectable viremia by PCR. EMR data collected between 2018 and April 1, 2021, from over 1400 high-risk allo-HCT patients at 21 US centers suggest that 40-50% develop clinically significant viral infection or disease associated with ≥1 of these dsDNA viruses within 200 days of transplant. Multiple studies demonstrate increased morbidity and mortality associated with viremia, with or without end-organ disease. Prophylactic and preemptive therapies have substantial side effects and can lead to the development of resistance, especially in CMV. HCT donor-derived virus-specific T-cells have shown promise in preventing single virus infections in prior clinical trials but were infeasible for wide-scale use. There is an urgent unmet medical need for preventive strategies targeting multiple viruses in patients undergoing high-risk allo-HCT. Methods: We are conducting a clinical trial (NCT04693637) to evaluate the safety and efficacy of posoleucel (ALVR105, Viralym-M) for preventing clinically significant viral infections due to CMV, EBV, HHV-6, AdV, BKV, and JCV in high-risk allo-HCT recipients. Posoleucel is an ex-vivo expanded, partially HLA-matched, off-the-shelf, multivirus-specific T cell investigational product generated from healthy, third-party donors targeting CMV, EBV, HHV-6, AdV, BKV, and JCV. In the open-label portion of the study, patients receive up to seven infusions of 4×10 7 cells of posoleucel administered once every 14 days. High-risk patients are those who received a graft from a sibling or unrelated donor with ≥1 HLA mismatch; from a haploidentical donor; from umbilical cord blood or with T-cell-depletion; as well as patients with lymphocytes & lt;180/mm 3 or CD4 T cells & lt;50/mm 3 at enrollment. Patients must be engrafted and within 15-49 days of allo-HCT. Those with grade ≥3 GVHD as well as those requiring steroids ( & gt;0.5 mg/kg/day prednisone equivalent) at enrollment are ineligible. Patients are tested weekly for viremia using quantitative PCR assays and are monitored every other week for adverse events. The primary endpoint is the number of clinically significant viral infections or episodes of end-organ disease due to CMV, EBV, HHV6, AdV, BKV, or JCV by week 14. Results: Data are available for 12 of 25 planned participants thus far (Table 1). No patient developed a clinically significant infection within 14 weeks, the primary study endpoint. Over the entire study duration, defined as the primary 14-week treatment period plus the additional 12-week follow-up, 11 (92%) patients have remained free of any clinically significant viral infections, the key secondary endpoint. One patient, a 49-year-old female haploidentical transplant recipient, developed clinically significant AdV viremia after receiving over a month of high-dose methylprednisolone exceeding 0.5 mg/kg/day for recurrent aGVHD. This patient was administered IV cidofovir in week 15 of the study. During the primary study efficacy period one participant received 2 doses of valganciclovir following transient CMV viremia deemed not to be clinically significant by the principal investigator. Posoleucel has been well tolerated to date, with no drug-related serious adverse events, new-onset acute GVHD, or cytokine release syndrome. Safety and efficacy data from the entire open-label cohort will be presented. Conclusions: Preliminary results in this open-label cohort show that in high-risk allo-HCT patients receiving off-the-shelf posoleucel, clinically significant viral infections or disease from the 6 targeted dsDNA viruses were uncommon. No clinically significant infections were observed among participants treated in accordance with the protocol. These results, combined with the favorable safety and tolerability profile of posoleucel, support its continued evaluation in high-risk allo-HCT recipients for the prevention of CMV, EBV, HHV6, AdV, BK virus, or JC virus infection and disease. Figure 1 Figure 1. Disclosures Dadwal: Shire/Takeda: Research Funding; Astellas: Speakers Bureau; Merck: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding, Speakers Bureau; AlloVir: Research Funding; Aseptiscope: Consultancy; Janssen: Other: Investigator; Karius: Other: Investigator. Shuster: Bristol Myers Squibb: Consultancy, Speakers Bureau; Novartis: Consultancy, Speakers Bureau; Genentech: Consultancy, Speakers Bureau; Intellisphere: Consultancy, Speakers Bureau; Amgen: Consultancy, Current equity holder in publicly-traded company; Rafael: Research Funding; Celgene: Consultancy, Current equity holder in publicly-traded company; Incyte: Research Funding; Beigene: Consultancy; Seattle Genetics: Consultancy, Speakers Bureau; Actinium: Research Funding; GSK: Research Funding; Pharmcyclics: Consultancy, Research Funding, Speakers Bureau; Epizyme: Consultancy, Speakers Bureau; AbbVie: Consultancy, Speakers Bureau; AlloVir: Research Funding; Janssen: Consultancy, Speakers Bureau; Astellas: Consultancy, Research Funding, Speakers Bureau; MorphSys: Consultancy, Research Funding, Speakers Bureau; Takeda: Consultancy, Research Funding, Speakers Bureau. Myers: Novartis: Consultancy, Speakers Bureau; AlloVir: Research Funding; Eliana: Consultancy, Membership on an entity's Board of Directors or advisory committees. Boundy: AlloVir: Current Employment, Current equity holder in publicly-traded company. Warren: AlloVir: Consultancy. Stoner: AlloVir: Current Employment, Current equity holder in publicly-traded company. Hill: Octapharma: Consultancy; OptumHealth: Consultancy; CRISPR therapeutics: Consultancy; CLS Behring: Consultancy; Allogene therapeutics: Consultancy; Gilead: Consultancy, Research Funding; Allovir: Consultancy, Research Funding; Amplyx: Consultancy; Takeda: Consultancy, Research Funding; Karius: Research Funding.

Abstract: Preventing viral infections at an early stage is a key strategy of successfully improving transplant outcomes. Preemptive therapy and prophylaxis using antiviral agents have been used successfully to prevent clinically significant viral infections in hematopoietic cell transplant (HCT) recipients. Major progress has been made over the past decades in preventing viral infections through a better understanding of the biology and risk factors as well as the introduction of novel antiviral agents and advances in immunotherapies. High quality evidence exists for the effective prevention for herpes simplex virus (HSV), varicella zoster virus (VZV), and cytomegalovirus (CMV) infection and disease. Fewer data are available on the effective prevention of human herpesvirus 6 (HHV-6), Epstein-Barr virus (EBV), Adenovirus (ADV) and BK virus infections. To highlight the spectrum of clinical practice, here we review high-risk situations that we handle with a high degree of uniformity, and cases that feature differences in approaches, reflecting distinct HCT practices such as ex-vivo T cell depletion.

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: This study reports the incidence of chronic graft versus host disease (GvHD) in allogeneic hematopoietic stem cell transplant (alloHCT) recipients who received SARS-CoV2 vaccination. The overall rates of new and worsening chronic GvHD combined were 14%, with median time from vaccination to GVHD being approximately three to four weeks. A majority of the cases were of mild to moderate severity and primarily localized to either the skin, mouth, or joints. Prior chronic GVHD and recent transplant were associated with higher GVHD rates following COVID-19 vaccination. More prospective studies are needed to provide a definitive mechanism for the impact of SARS-CoV2 vaccination on alloHCT patients.

Abstract: Objectives: The addition of pertuzumab, to trastuzumab-based chemotherapy is currently considered first-line therapy for locally advanced and metastatic disease HER2 positive breast cancer and has also been suggested for use in the adjuvant setting. Over the past 12 months, we have observed an increase in the incidence of severe skin infections in patients receiving chemotherapy with pertuzumab and trastuzumab. We report the natural history of what we believe is a previously unrecognized toxicity of these regimens. Methods: Shortly after the FDA approval of pertuzumab, our clinical team appreciated an increase in invasive skin infections. We discussed this concern and identified new cases at our weekly research meeting, keeping a log of cases as they were identified. Infection control reviewed the individual patient and hospital data during this time period. Results: Eleven women were identified to have severe skin and/or nail infections; 6 after cycle 1; 2 after cycle 2, 1 after cycle 3 and 2 after cycle 6. The median age was 51 (Range 46-64); 9 received pertuzumab, trastuzumab, carboplatin, and docetaxel (PTCH) and 2 pertuzumab, trastuzumab, and docetaxel. Folliculitis of the scalp, abdomen, and/or buttocks were observed in 4 patients. Abscesses were observed in 5 patients, 4 of whom required incision and drainage. Severe paronychial infections involving one to 16 digits were observed in 3 (including one who also had folliculitis). 1 pt required surgical removal of 2 nails. Quantitative immunoglobulins were found to be low in 2 of 8 women tested; 1 patient had a total protein of 4.7 but did not have an assessment of quantitative immunoglobulins. All patients were initially treated with oral antibiotics, but 3 required hospitalization. Cultures were obtained on 6 patients, Staph aureus was identified in 2 and methicillin resistant Staph (MRSA) in 4. All patients resolved their infections and 9 of 10 were able to complete six cycles of chemotherapy. Infection control could identify no increase in Staph infections at our institution. Patients were treated at different locations and received different lot numbers of drug. Conclusions: We believe this is the first report of a substantial incidence of invasive skin and nail infections with the addition of pertuzumab to trastuzumab-based regimens not reported in the product label. Low levels of quantitative immunoglobulin in select patients suggest a possible mechanism. Citation Format: Joanne E Mortimer, Yuan Yuan, Daphne Stewart, Samuel Chung, Laura Kruper, Louise C Wong, Mary Mendelsohn, Carolyn Behrendt, Sanjeet Dadwal, Bernard Tegtmeier. Skin infections associated with the addition of pertuzumab to trastuzumab-containing chemotherapy [abstract]. In: Proceedings of the Thirty-Seventh Annual CTRC-AACR San Antonio Breast Cancer Symposium: 2014 Dec 9-13; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2015;75(9 Suppl):Abstract nr P4-15-21.