Single Centre, Retrospective Analysis of Extracorporeal Photopheresis (ECP) Therapy in the Patients Who Are Heavily Pre-Treated for Steroid Resistant Chronic Graft-Versus-Host Disease (GVHD)

*DB and DK contributed to the work equally. Background Extracorporeal photopheresis (ECP) is a recommended second or later line of therapy for chronic GVHD (cGVHD), and is beneficial not only because of increased response but also for its lack of adverse effects, specifically systemic immune suppression, mainly from steroids. In this single centre study, we attempted to evaluate not only therapeutic efficacy of ECP, but also its steroid-sparing effect by regularly analyzing steroid dose per body weight. We also attempted to identify any predictors of response or survival after ECP, which was not well defined before. Patients and methods A total of 75 cGVHD patients (pts) who received ECP for cGVHD from 2007 to 2021 at Princess Margaret Cancer Centre were included and evaluated retrospectively. Patients and disease characteristics are as follows: median age 48.5 years (range 17-70); male 42/75 (56%); organ involvement at the time of ECP: skin (93%), oral (53%), eye (51%), gastrointestinal (25%), liver (49%), lung (57%), and musculoskeletal (n=50, 67%). Sixty-eight (91%) and 7 pts (9%) had severe and moderate grade cGVHD, respectively. Sixty-eight pts (91%) received ECP as 4 th line or beyond. They were heavily pretreated with prednisone (98%), cyclosporine (57%), tacrolimus (24%), mycophenolate mofetil (64%), azathioprine (65%), rituximab (7%), imatinib (8%), ibrunitib (3%) and ruxolitinib (1%). ECP was started twice weekly for the first 12 weeks, then twice every 2 weeks in 2012-2021, while the schedule was twice every 2 weeks from 2007-2012. If there was no response or clinical benefit noted in first 24 treatments, then ECP was discontinued. In general, we attempted to provide up to around 60 sessions based on the clinicians' discretion. The overall response rate (ORR) and clinical benefit (CB) were assessed at months 3, 6 and 12 after staring ECP. As part of standard clinical practice, NIH consensus criteria were used for grading and response assessment. CB was assessed considering clinical response as well as steroid dose reduction. Treatment failure was defined as 1) resistance to ECP requiring treatment switch, 2) non-relapse mortality (NRM), 3) relapse, 4) intolerance to ECP. Failure free survival (FFS) and overall survival (OS)were calculated from the day of ECP initiation until the endpoints of failure or death, respectively. Results ECP was started a median of 28 months (range 1-125) after development of cGVHD. ECP was performed a median of 35 times (range 6-174) with a median duration of 11 months (range 1-53). Out of 75 pts, 48 completed planned ECP successfully and 27 stopped due to no response or benefit including, of whom 14 required additional therapy, 1 stopped due to line infection, and 1 stopped due to relapse of AML. With a median 72 months of follow-up, ORR was attained in 21% (16/75), 57% (36/63) and 70% (32/46) at month 3, 6 and 12, respectively. At 6 months, ORR was observed in 47-64% across all organs assessed. No difference in ORR was noted according to the cGVHD grade; at 6 months, severe cGVHD showed similar ORR (57%) to those with moderate cGVHD (60%) (p=0.893). CB was noted in 23% (17/75), 62% (39/63), and 76% (35/46) at month 3, 6 and 12, respectively. A total of 27/75 failures (36%) and 20/75 death (27%) occurred, due to the following: ECP resistance requiring switch to other therapy (n=14, 19%), NRM (n=11, 15%), relapse of primary disease (n=1, 1%) or ECP-related complication (n=1, 1%, line infection). In the overall cohort, FFS and OS at 12 months were 68.3% and 85.9%, respectively (Figure 1). More than a half of pts stopped steroids completely within 12 months after starting ECP. The proportion of pts off steroids was 16%, 17%, 32%, and 64% at month 0, 3, 6 and 12 after starting ECP, respectively (Figure 2). Risk factor analysis did not show any predictive markers for ORR at 6 months, while prognostic factor analysis suggested the development of musculoskeletal involvement as favorable prognostic factor for FFS (p=0.003, HR 0.315 [0.147, 0.673]) even with multivariate analysis. Conclusion Our study showed that: 1) ECP is a very effective treatment for heavily pre-treated cGVHD pts who have failed other therapies; 2) More than a half of pts can stop steroids completely within 12 months after starting ECP, thus avoiding long-term toxicity risk. Further study is warranted comparing ECP with other cGVHD treatment modalities. Figure 1 Figure 1. Disclosures Patriquin: BioCryst Pharmaceuticals: Honoraria; Alexion: Consultancy, Honoraria, Speakers Bureau; AstraZeneca: Consultancy, Honoraria, Speakers Bureau; Apellis: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees; Sanofi: Honoraria. Law: Novartis: Consultancy; Actinium Pharmaceuticals: Research Funding. Lipton: Bristol Myers Squibb, Ariad, Pfizer, Novartis: Consultancy, Research Funding. Mattsson: MattssonAB medical: Current Employment, Current holder of individual stocks in a privately-held company. Kim: Paladin: Consultancy, Honoraria, Research Funding; Bristol-Meier Squibb: Research Funding; Pfizer: Honoraria; Novartis: Consultancy, Honoraria, Research Funding.

In Vitro and In Silico Anti-Arboviral Activities of Dihalogenated Phenolic Derivates of L-Tyrosine

Despite the serious public health problem represented by the diseases caused by dengue (DENV), Zika (ZIKV) and chikungunya (CHIKV) viruses, there are still no specific licensed antivirals available for their treatment. Here, we examined the potential anti-arbovirus activity of ten di-halogenated compounds derived from L-tyrosine with modifications in amine and carboxyl groups. The activity of compounds on VERO cell line infection and the possible mechanism of action of the most promising compounds were evaluated. Finally, molecular docking between the compounds and viral and cellular proteins was evaluated in silico with Autodock Vina®, and the molecular dynamic with Gromacs®. Only two compounds (TDC-2M-ME and TDB-2M-ME) inhibited both ZIKV and CHIKV. Within the possible mechanism, in CHIKV, the two compounds decreased the number of genome copies and in the pre-treatment strategy the infectious viral particles. In the ZIKV model, only TDB-2M-ME inhibited the viral protein and demonstrate a virucidal effect. Moreover, in the U937 cell line infected with CHIKV, both compounds inhibited the viral protein and TDB-2M-ME inhibited the viral genome too. Finally, the in silico results showed a favorable binding energy between the compounds and the helicases of both viral models, the NSP3 of CHIKV and cellular proteins DDC and β2 adrenoreceptor.

Resveratrol induces H3 and H4K16 deacetylation and H2A.X phosphorylation in Toxoplasma gondii

Objective Resveratrol (RSV) is a multitarget drug that has demonstrated activity against Toxoplasma gondii in macrophage and human foreskin fibroblast (HFF) cell line infection models. However, the mechanism of action of RSV has not yet been determined. Thus, with the aim of identifying a possible mechanism of the anti-T. gondii activity of this compound, we analyzed the effects of RSV on histones H3 and H4 lysine 16 acetylation (H4K16). We also analyzed RSV-induced DNA damage to intracellular tachyzoites by using the DNA damage marker phosphorylated histone H2A.X (γH2AX). Results RSV inhibited intracellular T. gondii tachyzoite growth at concentrations below the toxic threshold for host cells. The IC50 value after 24 h of treatment was 53 μM. RSV induced a reduction in H4K16 acetylation (H4K16ac), a marker associated with transcription, DNA replication and homologous recombination repair. A similar deacetylation effect was observed on histone H3. RSV also increased T. gondii H2A.X phosphorylation at the SQE motif (termed γH2A.X), which is a DNA damage-associated posttranslational modification. Our findings suggest a possible link between RSV and DNA damage or repair processes that is possibly associated with DNA replication stress.

697. 8 Years of Characteristics and Outcomes of Patients with MRSA Endocarditis Based on Vancomycin Minimum Inhibitory Concentration: Experience at a Tertiary Care Hospital

Background Vancomycin has been the mainstay of treatment for methicillin-resistant Staphylococcus aureus (MRSA) infective endocarditis (IE). MRSA reduced susceptibility to vancomycin is a growing threat. Data assessing the effect of vancomycin reduced susceptibility on outcomes is limited. Our study aimed to evaluate characteristics and outcomes of MRSA-related IE based on the minimum inhibitory concentration (MIC) to vancomycin Characteristics and outcomes of 51 patients with MRSA-related endocarditis according to the minimal inhibitory concentration (MIC) to vancomycin Methods IRB approval was obtained for a retrospective cohort study at a tertiary care center. Records of hospitalized adults diagnose with IE by ICD-9/ICD-10 CM codes were identified from 2011 to 2018. 51 patients had MRSA-related IE and were selected for the analysis. Demographic, microbiologic, Imaging and outcome variables were obtained. Characteristics and outcomes of patients with MRSA-related IE according to the MIC to vancomycin (≤ vs. > 1 mcg/mL) were compared Results 35.3% of patients had a MIC > 1 mcg/mL. 59% were men, mean age was 46±3 years old. 65% acquired the infection through injection drug use. Only 3.9% of patients had prosthetic valve IE. 35.3% had tricuspid valve vegetation, 25.5% mitral valve and 21.6% aortic valve vegetation. Two patients had IE possibly related to a PICC-line infection; both of these patients had a MIC to vancomycin >1 mcg/mL, suggestive of prolonged antibiotic therapy. All patients with MRSA-related IE were started empirically on vancomycin. Patients with a MIC > 1 mcg/mL were more likely to be switched to a combination of daptomycin and ceftaroline, compared to those with a MIC ≤ 1 mcg/mL (44.4% vs. 6.1%; P=0.001). 25.4% underwent valvular replacement within 6 months. 12% died within 90 days. MRSA-related IE with MIC > 1mcg/mL did not confer and an increase risk in in-hospital mortality (11.1% vs. 15.2%; P=0.67) or mortality at 90 days (11.1% vs. 12.5%; P=0.89). Conclusion In this single-center experience, we found that in 8 years 35% of patients with MRSA-related IE had MIC >1 mcg/mL. This is an alarming finding. Although our study did not reach statistic significance we didn’t found difference in valvular surgery requirement or mortality among those with MIC > 1mcg/d as compared to those with a more sensitive MRSA strain. A study with more power or a metha-analysis will be require to better answer this question. Disclosures All Authors: No reported disclosures