Abstract: Introduction:Recently there has been a renewal of therapeutic tools for the treatment of lymphoid neoplasms to increase the antitumor efficacy and reduce the toxicity generated by conventional chemotherapies, which adds to the intrinsic immunological dysfunction of the disease itself. To date, few data are published about infection risk of these new drugs, and the need for infectious prophylaxis is unknown. The aim of the study is to analyze the infectious complications in patients with LPD treated with monoclonal antibodies (obinutuzumab, ofatumumab, brentuximab, nivolumab and pembrolizumab), BTK inhibitors (ibrutinib, acalabrutinib) and PI3K inhibitors (idelalisib). Methods: Multicenter retrospective study in patients with LPD treated with targeted therapies (single agents or combination) in 18 Hematology centers in Spain, from the time of their commercial availability to March 2020. Patients in clinical trials were excluded as well as patients with active infections at the beginning of treatment. Results:During the study period, 380 patients were included.Baseline characteristics of the entire cohort are shown in Table 1.Median follow-up was 17.3 months (range 0-103), the longest follow-up corresponding to CLL patients (24 months, range 0-98) and the shortest to LBCL (5 months, range 0-25). Median exposure to target drugs was 8 months (range 0-72).Ibrutinib was administered to 219 patients(1 FL, 147 CLL, 27 MCL, 10 DLBCL, 1 TL and 32 WM, 1 HL),Brentuximab to 49(31 HL, 14 TL and 4 DLBCL) andIdelalisibto 35 patients (16 affected by chronic lymphocytic leukemia - CLL, 15 FL and 1 DLBCL, 1 WM, 1MCL, 1HL).Obinutuzumabcombinations were used in 10 (6 CLL, 3 FL, 1 MCL) and 5 HL patients (of which 4/5 underwent previous BMT) receivedNivolumab. A total number of 237 infectious events occurred in 148/380 patients (38.9%), 39% of which were grade 3 and 54/148 (36.4%) experienced 2 or more infective episodes: of those 54, 21 (38%) had underwent 3 or more lines of therapy and 28 (51%) had hypogammaglobulinemia. Hospitalization was required in 59.2% events. A bacterial cause of infection was reported in 40% of cases, and viral in 16%, including 11/237 (4,6%) SARS-CoV-2 infection. Invasive fungal infection (IFI) occurred in 3.3% (8/237). Noteworthy, no case of PJP was identified. Lung was the most frequent site of infection in 24% of cases (57/237) while the upper respiratory tract was involved in 17% of events (41/237). Urinary tract infections were diagnosed in 10% (24/237). Other sites involved were skin and soft tissue 7%, gastrointestinal tract 5,4%, bloodstream infections 3% and catheter related infections 2,5%. Considering drugs individually, 86 patients that receivedIbrutinib(39.2 %)experienced a total of 137 infectious episodes: 30% bacterial, 19% viral, 5% fungal and 45% clinical and image-based infections; the 17(34.6%of those who received Brentuximab, experienced a total of 16 infectious episodes: 56% bacterial, 37.5% viral infections and one catheter-related sepsis. Of those who receivedIdelalisib,18 (51.4%)experienced a total of 28 episodes: 42% bacterial, 14% viral and 7% fungal. Four patients treated withObinutuzumabcombinations (40%) experienced one infection during treatment (25% bacterial and 75% viral). Only one patient treated withNivolumabexperienced more than three infections, he was also under corticosteroid treatment. Focusing on IFI (Table 2): 7/8 infections were identified in CLL patients, 6 out 7 being on ibrutinib treatment and 1/7 on Idelalisib.Aspergilluswas the fungus most frequently isolated. The targeted drug was discontinued temporarily in 4 patients and indefinitely in 3. Twenty three (6%) patients died due to infection in our series. Conclusions: 1. We identified 38.7% infections in our LPD patients treated with targeted drugs, with a median drug-exposure time of 8 months (range 0-72), with a non-negligible incidence of bacterial infections. 2. The highest rates of infection were found in patients treated with with Idelalisib and Ibrutinib (51.4% and 39.2% respectively). 3. IFI (3.3%) occurred with low frequency, mostly in CLL patients during ibrutinib treatment, leading to its temporal discontinuation in most of the cases. 4. No case of PJP was identified in our cohort. 5. An analysis to determine risk factors for infection and the optimal monitoring and prophylaxis for these patients is ongoing. Disclosures Hernandez-Rivas: Janssen:Membership on an entity's Board of Directors or advisory committees;Abbvie:Membership on an entity's Board of Directors or advisory committees;Roche:Membership on an entity's Board of Directors or advisory committees;AstraZeneca:Membership on an entity's Board of Directors or advisory committees;Gilead:Membership on an entity's Board of Directors or advisory committees;Celgene/BMS:Membership on an entity's Board of Directors or advisory committees;Rovi:Membership on an entity's Board of Directors or advisory committees.Lopez-Guillermo:novartis:Consultancy;celgene:Consultancy, Research Funding;roche:Consultancy, Research Funding;gilead:Consultancy, Research Funding.

Abstract: Immune thrombotic thrombocytopenic purpura (iTTP) is a thrombotic microangiopathy caused by anti-ADAMTS13 antibodies. Caplacizumab is approved for adults with an acute episode of iTTP in conjunction with plasma exchange (PEX) and immunosuppression. The objective of this study was to analyze and compare the safety and efficacy of caplacizumab vs the standard of care and assess the effect of the concomitant use of rituximab. A retrospective study from the Spanish TTP Registry of patients treated with caplacizumab vs those who did not receive it was conducted. A total of 155 patients with iTTP (77 caplacizumab, 78 no caplacizumab) were included. Patients initially treated with caplacizumab had fewer exacerbations (4.5% vs 20.5%; P  & lt; .05) and less refractoriness (4.5% vs 14.1%; P  & lt; .05) than those who were not treated. Time to clinical response was shorter when caplacizumab was used as initial treatment vs caplacizumab used after refractoriness or exacerbation. The multivariate analysis showed that its use in the first 3 days after PEX was associated with a lower number of PEX (odds ratio, 7.5; CI, 2.3-12.7; P  & lt; .05) and days of hospitalization (odds ratio, 11.2; CI, 5.6-16.9; P  & lt; .001) compared with standard therapy. There was no difference in time to clinical remission in patients treated with caplacizumab compared with the use of rituximab. No severe adverse event was described in the caplacizumab group. In summary, caplacizumab reduced exacerbations and refractoriness compared with standard of care regimens. When administered within the first 3 days after PEX, it also provided a faster clinical response, reducing hospitalization time and the need for PEX.

Abstract: Introduction: The BCL-2 inhibitor venetoclax (Ven) has been approved on monotherapy or combined with rituximab in relapsed/refractory CLL patients (pts) and combined with obinutuzumab in previously untreated CLL pts. However, evidence from clinical trials can be difficult to generalize to real-world patient populations. The VENARES study assesses the real-world use of Ven following approval to inform of subpopulations underrepresented in clinical trials. Methods: This is Spanish non-interventional retrospective, multicenter post-marketing observational study. The main objective was to evaluate the effectiveness of Ven in adult CLL pts by the overall response rate (ORR) at 9 months (mo) after the first Ven dose administration. Secondary objective was to evaluate the effectiveness for the Ven monotherapy and the Ven combined with rituximab subpopulations. Consecutive adult pts with diagnosis of CLL who have initiated Ven at least 9 mo before the inclusion in the study were included. Data of pts are retrospectively reviewed until the date of last follow-up or death. Results: 125 pts diagnosed with CLL and who met the eligibility criteria were analyzed. The median age was 72 years (67 - 77) with 76.8% being older than 65 years. Most patients were male (68.8%), had a concurrent disease (65.6%). ECOG PS was recorded in 76 pts: 40 pts (32%) had PS 0, 30 pts (24%) PS 1 and 6 pts (4.8%) PS 2. Pts had received a median of 4 prior lines of therapy (range 1-13 lines). At baseline, among the 92 pts with known Binet stage, 31 (33.7%) had stage C and 38 (41.3%) had stage B; bulky nodes ≥ 5 cm were present in 20 of 87 pts; 49 pts (39.2%) had an absolute lymphocyte count ≥ 25 x 10 9/L and 33 of 54 pts (61%) baseline beta-2 microglobulin value above of 3500 ng/mL. In total, 29 of 90 patients (32%) assessed had Cr 17p deletion, 28 of 86 patients (32%) tested had TP53 mutations, and 46 of 56 patients (82%) who were tested had unmutated immunoglobulin heavy-chain variable (IGHV) status. Ven was administered as monotherapy in 71 pts (57.6%), combined with rituximab in 36 pts (28.8%), combined with obinutuzumab in 5 pts (4%) and combined with other drugs in 13 pts (10.4%). 83 of 125 patients included were evaluable for the primary objective of the study: the ORR at 9 mo was 84.3% (70 patients): CR/CRi in 44 (53%) pts, PR/nPR in 26 pts (31.3%), SD in 9 pts (10.8%) and PD in 4 pts (4.8%). By treatment, in the evaluable patients, ORR at 9 months were 79.2% (38 of 48 patients) in the Ven monotherapy group, with 45% of CR/CRi, and 92.3% (24 of 26 patients) in the Ven combined with rituximab, with 61% CR/Cri. The median duration of PFS was not reached at the time of the analysis (1-June-2021). Kaplan-Meier estimates of the probability of PFS at 24 mo was 75.4% (95% CI, 58.2 - 86.3). Disease progression occurred in 21 pts. Assessment of minimal residual disease (MRD) was available for 32 patients (25.6%) on the basis of peripheral-blood samples, bone marrow or both. Best undetectable MRD was reached in fourteen patients (43.8%). uMRD was more common in pts treated with Ven combined with R (83.3%, 5 of 6 pts) than in pts treated with Ven monotherapy (33.3%, 7 of 21 pts). Adverse events (AEs) were reported during Ven therapy in all 125 patients, 93 of these pts reported AEs related to Ven. Related to Ven, 67 patients (53.6%) experienced at least one AE: 52 pts (41.6%) had neutropenia being grade 3 and 4 in 22 (42.3%) and 9 (17.3%) pts, respectively. 9 pts (7.2%) had febrile neutropenia. Thrombocytopenia and anemia were less common occurring in 5.6% and 2.4%, respectively. Tumor lysis syndrome (TLS) occurred in 4 of 125 pts during ramp-up (3 laboratory and 1 clinical), 2 of them were related to Ven both lab TLS. None of the pts discontinued therapy due to TLS. Richter transformation was observed in 6 pts (4.8%). Other common AEs was diarrhea (10.4%), but most cases were mild. Conclusions: Our first real-world data show that Ven monotherapy or combined with rituximab is effective in highly pre-treated CLL patients, ORR at 9 mo was 84.3% in all population and PFS estimate at 24 mo was 75.4% with similar outcomes to those in the pivotal clinical trials. The safety profile of Ven was consistent with prior experience of Ven in monotherapy or combined with rituximab and no new safety signals were detected. Disclosures Baltasar: Janssen, Abbvie: Consultancy. Terol: Roche: Membership on an entity's Board of Directors or advisory committees, Other: Travel; BMS: Consultancy; Roche: Consultancy; Gilead: Consultancy, Membership on an entity's Board of Directors or advisory committees, Other: Travel, Research Funding; Abbvie: Consultancy, Membership on an entity's Board of Directors or advisory committees, Other: Travel; Janssen: Membership on an entity's Board of Directors or advisory committees, Other: Travel, Research Funding; Takeda: Membership on an entity's Board of Directors or advisory committees, Other: Travel; Hospital Clinico Valencia: Current Employment. Moreno: Janssen, Abbvie: Research Funding; Abbvie, Janssen, AstraZeneca: Speakers Bureau; Abbvie, Janssen, AstraZeneca, Beigene: Membership on an entity's Board of Directors or advisory committees. Osorio: Janssen, Abbvie, Roche: Consultancy. De la Cruz: Abbvie: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Beigene: Membership on an entity's Board of Directors or advisory committees; EUSA Pharma: Membership on an entity's Board of Directors or advisory committees; JANSSEN: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Kyowa Kirkin: Membership on an entity's Board of Directors or advisory committees; Roche: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Takeda: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau. de la Serna: AbbVie, AstraZeneca, Roche: Speakers Bureau; ABBVIE, ASTRAZENECA,ROCHE: Research Funding; AbbVie, AstraZeneca, Beigene, Gilead, GSK, Janssen, Jazzpharma, Novartis, Roche: Consultancy. Arguiñano: Takeda, Sanofi, Janssen, BMS-Celgene, Abbvie: Speakers Bureau; Takeda, Sanofi, Janssen, BMS-Celgene, Abbvie: Consultancy. Loscertales: Janssen, Abbvie, Roche, Gilead: Speakers Bureau; Janssen, Abbvie, Astra-Zeneca, Beigene, Roche, Gilead: Consultancy. García: Janssen, Roche, Gilead, Celgene: Consultancy; Janssen, AbbVie: Research Funding; Janssen, Roche, Gilead, AbbVie, Celgene: Other: medical meetings funding. Pérez Persona: BMS/Celgene: Consultancy, Other: Support for attending meetings and/or travel, Speakers Bureau; Amgen: Consultancy, Other: Support for attending meetings and/or travel, Speakers Bureau; Takeda: Speakers Bureau; AbbVie: Other: Support for attending meetings and/or travel, Speakers Bureau; Sanofi: Consultancy, Speakers Bureau; AstraZeneca: Speakers Bureau; GSK: Consultancy; Incyte: Consultancy. Pérez-Encinas: Janssen: Consultancy. Caballero: Celgene, Janssen, Novartis, Abbvie: Speakers Bureau; Celgene, Janssen, Amgen: Consultancy. Ruiz-Zorrilla: Abbvie: Current Employment. Moreno: abbvie: Current Employment. Ferrà: Janssen, Roche, Gilead, Takeda, Abbvie: Consultancy; Janssen, Roche, Gilead, AbbVie: Other: medical meetings funding.

Abstract: Background: Chimeric Antigen Receptor-modified T cell (CAR-T) therapies have revolutionized cancer immunotherapy, especially in hematological malignancies. Although great results have been achieved during the last years, long-term efficacy is still compromised in some cases and factors behind CAR-T cell disfunction are not fully understood. Recent studies have shown that the control of CAR expression influences CAR-T fitness and antitumoral efficacy 1. Therefore, we hypothesized that CAR density on the membrane of CAR-T cells could directly affect CAR-T cell function. In this study we perform a functional and genomic analysis of FACS-isolated subpopulations of CAR-T cells with different CAR densities (CAR High and CAR Low). Methodology: Second generation CAR-T cells with 4-1BB costimulatory domain targeting BCMA were generated by lentiviral transduction of αCD3/αCD28 activated T cells that were expanded for 12-14 days in the presence of IL-7/IL-15. Phenotypic analyses were performed by flow cytometry before and after coculture with MM cells. Cytotoxic activity and cytokine production were measured by standard procedures. In vivo antitumoral efficacy was evaluated in xenogeneic tumor models in NSG mice. Transcriptomic (RNA-seq) and epigenetic (ATAC-seq) analysis were performed following stablished protocols 2. Single cell analysis was performed using the Chromium Single Cell Immune Profiling solution from 10x Genomic that allows simultaneous analysis of gene expression and paired T-cell receptors from a single cell. Gene Regulatory Network (GRN) analysis was performed using SimiC, a novel computational method that infers regulatory dissimilarities 3. Results: RNA-seq and ATAC-seq analysis revealed completely different profiles between CAR High- and CAR Low-T cells in both CD4 +and CD8 + cell subsets, with & gt;3500 differentially expressed genes (2086 for CD4 + and 1553 for CD8 +) that were related with increased tonic signaling, T cell activation and proliferation in CAR High-T cells. Functional studies at resting state (before antigen encounter) corroborated that CAR High-T cells presented increased tonic signaling, that lead to a higher basal activation and a more differentiated phenotype with skewed presence of CCR7 +/CD45RA +/CXCR3 + T SCM cells. After antigen-driven activation, increased cytotoxicity and cytokine production was observed in CAR High-T cells, that also presented higher percentage of terminally differentiated effector cells (CCR7 -/CD45RA +), along with increased exhaustion (PD1 +/LAG3 +/TIGIT +). This effect was also observed in the infusion products of CARTBCMA-HCB-01 clinical trial for patients with R/R MM (NCT04309981), where products enriched in CAR High-T cells presented increased cytotoxic activity. Although no significant differences were observed in the antitumoral efficacy in vivo, CAR Low-T cells presented increased persistence, suggesting that higher CAR levels could reduce long-term efficacy. Further characterization of CAR-T cells at single cell level (scRNA-seq) showed enrichment of CAR High-T cells in activated CD4 + and exhausted CD8 + cell clusters. The analysis of regulatory dissimilarities driven by different CAR densities with SimiC revealed an increased activity of the regulon associated to NR4A1 transcription factor (a well-known TF driving T cell exhaustion 4) in CAR High-T cells, providing mechanistic insights of the regulatory networks behind differential functionality of CAR High-T cells. Finally, to evaluate the impact of CAR density in the clinical outcome of CAR-T therapies, we developed a gene signature associated to increased CAR density, that was applied to transcriptomic data available from public studies 5. We score the infusion products of several clinical trials testing CTL019 (NCT01029366, NCT01747486 and NCT02640209) and we observed an enrichment on CAR High signature in the products from non-responder patients. Conclusions: Our data demonstrate that CAR density on the membrane of engineered T cells plays important roles in CAR-T activity with a significant impact on clinical outcome. Moreover, the comprehension of regulatory mechanisms driven by CAR densities at the single cell level offer an important tool for the identification of key regulatory factors that could be modulated for the development of improved therapies. Figure 1 Figure 1. Disclosures Rodríguez-Otero: Oncopeptides: Honoraria, Membership on an entity's Board of Directors or advisory committees; Kite: Honoraria, Membership on an entity's Board of Directors or advisory committees; Amgen: Honoraria, Membership on an entity's Board of Directors or advisory committees; Regeneron: Membership on an entity's Board of Directors or advisory committees; Abbvie: Honoraria, Membership on an entity's Board of Directors or advisory committees; Sanofi: Honoraria, Membership on an entity's Board of Directors or advisory committees; GlaxoSmithKline: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees; Janssen: Honoraria, Membership on an entity's Board of Directors or advisory committees; BMS/Celgene: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Other: Travel and other expenses. Paiva: Bristol-Myers Squibb-Celgene, Janssen, and Sanofi: Consultancy; Adaptive, Amgen, Bristol-Myers Squibb-Celgene, Janssen, Kite Pharma, Sanofi and Takeda: Honoraria; Celgene, EngMab, Roche, Sanofi, Takeda: Research Funding. San-Miguel: AbbVie, Amgen, Bristol-Myers Squibb, Celgene, GlaxoSmithKline, Janssen, Karyopharm, Merck Sharpe & Dohme, Novartis, Regeneron, Roche, Sanofi, SecuraBio, Takeda: Consultancy, Other: Advisory board. Prósper: Oryzon: Honoraria; Janssen: Honoraria; BMS-Celgene: Honoraria, Research Funding.

Abstract: Introduction In the first weeks of the Covid-19 pandemic when healthcare systems in many areas were overstretched, we documented that hospital mortality in multiple myeloma (MM) patients infected by Sars-Cov-2 was 50% higher than in age matched Covid-19 patients without cancer. In the following months, the pressure on healthcare systems in Spain continued although it did not reach the extreme levels of the first weeks of the pandemic. In this study, we proposed to determine if the severity of Covid-19 outcomes in MM patients has changed over the first year of the pandemic. Patients and methods The Spanish MM Collaborative Group (Pethema-GEM) conducted a survey at national level on plasma cell disorder patients infected by SARS-Cov-2 between March 2020 and February 2021. Sixty-six (69%) out of 96 contacted healthcare centers, from all 17 regions in Spain, reported 502 patients. Data on Covid-19 acute and post-acute phase outcomes (hospitalization, oxygen requirements, severity of symptoms and mortality) were reported first in May 2020 (Martinez-Lopez et al, BCJ 2021) and updated in February 2021. In this study, we compared outcome occurrence between two study periods: P1, a period of extreme stress for the healthcare system in Spain, from March to mid-June 2020; and a second period, P2, up to mid-February 2021 with a sustained but lower burden on the national health care system. Results Among the 451 patients with plasma cell disorders and a Sars-Cov-2 infection documented with an rRT-PCR positive test, 377 (84%) were MM patients, 15 SMM (3%), 40 MGUS (9%) and 19 amyloidosis (4%). The number of MM weekly reported cases was 57% (95%CI, 48-65) lower in P2 (188 cases in 35 weeks) compared to P1 (189 cases in 15 weeks), p & lt;0.001. The mean (SD) age and the proportion of men did not differ between P1 and P2, respectively 69.8 (10.9) vs 68.6 (11.0) years, p=0.6, and 53.3% vs 59.6%, p=0.2. MM patients with active or progressive disease at time of Covid-19 diagnosis were 24% in P1 and 34% in P2, p=0.05; patients on active treatment were more frequent in P1, 89%, than in P2, 79%, p=0.01. MM treatment was withheld in 78% and 82% of patients, p=0.4. Covid-19 treatment changed over time: MM inpatients received more remdesivir and corticoids in the second period (3% vs 31% p & lt;0.001, and 49% vs 73%, p & lt;0.001, respectively). In P1, 90% of the reported MM patients were hospitalized compared to 71% in P2, p & lt;0.001. Thirty-one and 41% of patients did not require oxygen support during P1 and P2, respectively; non-invasive ventilation in 19% and 14%, and mechanical ventilation in 7% and 8%, p=0.12. Overall, acute clinical Covid-19 severity was reduced from P1 to P2: 75% to 51%, p & lt;0.001: moderate/severe pneumonia was reduced from 68% to 36%, p & lt;0.001 but severe distress syndrome increased from 7% to 15%, p=0.03. However, mortality in all reported patients was 30.7% in P1 vs 26.1% in P2, p=0.3; and no differences in mortality were observed in hospitalized patients, 32.2% in P1 and 35.3% in P2, p=0.6. We performed a multivariable adjustment with the predictors identified in our previous study (BCJ 2021) and confirmed that inpatient mortality was similar in both study periods, odds ratio (OR) 0.99 (95%CI 0.59-1.66). Independently of the study period, an increased mortality was observed in men (OR 1.81, 1.08-3.05), patients over 65 (OR 2.40, 1.33-4.36), and patients with active or progressive disease (OR 2.12, 1.24-3.62). The severity of Covid-19 clinical outcomes -besides mortality, was associated with increased age but not with active or progressive disease. Conclusions Although COVID-19 clinical severity has decreased over the first year of the pandemic in multiple myeloma patients, mortality remains high with no change between the initial weeks of the pandemic and the following months. Prevention and vaccination strategies should be strengthened in this vulnerable population, particularly in patients with active or progressive disease at time of Covid-19 diagnosis. Disclosures Martínez-López: Janssen, BMS, Novartis, Incyte, Roche, GSK, Pfizer: Consultancy; Roche, Novartis, Incyte, Astellas, BMS: Research Funding. Mateos: Oncopeptides: Honoraria, Membership on an entity's Board of Directors or advisory committees; Regeneron: Honoraria, Membership on an entity's Board of Directors or advisory committees; Roche: Honoraria, Membership on an entity's Board of Directors or advisory committees; Amgen: Honoraria, Membership on an entity's Board of Directors or advisory committees; Pfizer: Honoraria, Membership on an entity's Board of Directors or advisory committees; Adaptive Biotechnologies: Honoraria, Membership on an entity's Board of Directors or advisory committees; Sea-Gen: Honoraria, Membership on an entity's Board of Directors or advisory committees; AbbVie: Honoraria; Sanofi: Honoraria, Membership on an entity's Board of Directors or advisory committees; Takeda: Honoraria, Membership on an entity's Board of Directors or advisory committees; Celgene - Bristol Myers Squibb: Honoraria, Membership on an entity's Board of Directors or advisory committees; Janssen: Honoraria, Membership on an entity's Board of Directors or advisory committees; Bluebird bio: Honoraria; GSK: Honoraria; Oncopeptides: Honoraria. López-Muñoz: Amgen: Consultancy. Sureda: GSK: Consultancy, Honoraria, Speakers Bureau; Sanofi: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Amgen: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Roche: Other: Support for attending meetings and/or travel; Mundipharma: Consultancy; Bluebird: Membership on an entity's Board of Directors or advisory committees; Janssen: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Kite, a Gilead Company: 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; MSD: Consultancy, Honoraria, Speakers Bureau; BMS/Celgene: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Other: Support for attending meetings and/or travel, Speakers Bureau; Takeda: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Other: Support for attending meetings and/or travel, Research Funding, Speakers Bureau. Rosinol: Janssen, Celgene, Amgen and Takeda: Honoraria. Lahuerta: Celgene, Takeda, Amgen, Janssen and Sanofi: Consultancy; Celgene: Other: Travel accomodations and expenses. San-Miguel: AbbVie, Amgen, Bristol-Myers Squibb, Celgene, GlaxoSmithKline, Janssen, Karyopharm, Merck Sharpe & Dohme, Novartis, Regeneron, Roche, Sanofi, SecuraBio, Takeda: Consultancy, Other: Advisory board.

Abstract: Introduction: Multidrug-resistant organisms (MDRO) are a challenge in patients undergoing stem cell transplant (SCT) which often result in an increase in mortality. To our knowledge, current literature defines only screening at the time of work-up for SCT-patients. The aims of the study were to assess the rate of MDRO colonization with weekly screening, rate of infection and the associated mortality in patients undergoing SCT. Patients and methods: Consecutive patients admitted at the SCT unit between January-18 to July-18 were reviewed in our institution. Screening consisted of rectal and perineal swab on admission and weekly until the date of discharge. In case of detection of MDRO , patients were isolated and infection control strategies were applied. Results: 41 patients were analysed, with 47 admissions, 6 patients had 2 admissions. The median duration of hospitalization was 27 days/patient (range 8-100). 168 rectal-and perineal swab were performed with a median of 3 swabs/patient (range 1-7). Patient characteristics are shown in Table 1. 36 patients (87%) spiked fever in a median of 8,5 days after admission (1-38days). 24,4% (n=10) had a positive screening: 2/10 patients at baseline and 8/10 patients (80%) were detected for the first time beyond baseline screen. Rate of MDRO colonization was 3% per week (95%CI 1.4-5.4). MDRO identified were : 4 patients with Extended-spectrum beta-lactamases producing E. Coli (ESBL-EC), Multidrug-resistant (MR) Pseudomonas aeruginosa (n=3), Vancomycin-resistant Enterococci (n=2) and 1 patient with carbapenem-resistant Citrobacter freundii. 6/10 patients developed MDRO infection (60%), all with previous MDRO positive detection: MR-Pseudomonas aeruginosa in urine culture (n=3) 2 treated with ceftolozane/tazobactam, 1 with meropenem+amikacin; ESBL-EC in urine culture (n=2) both treated with meropenem and 1 with Klebsiella pneumoniae carbapenemase in urine culture treated with ceftazidime/avibactam. The infection rate was 4,6% (95% CI 3.9-5.2). In 80% patients (n=8) antibiotic treatment was guided by positive screening, 3 patients were admitted to intensive care unit for sepsis. No mortality was associated to MDRO. In 76%of patients (n=28) screening was negative for MDRO. 24/28 (85%) spiked fever with a median of 10 days after admission (1-38days). None MDRO-infections in negative-screened patients were detected. Conclusions : Weekly screening for MDRO identified a high number of MDRO colonizations allowing to apply early strategies of infection control in high risk patients . Besides, MDRO infection occurred only in patients previously colonized, therefore, 80% of our cohort could benefit from guided treatment by the time of the febrile episode. Early identification of MDRO colonization might have helped to reduce MDRO related mortality. However, these findings should be confirmed with further studies, comparing baseline with weekly MDRO screening strategies. Disclosures No relevant conflicts of interest to declare.