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Background Imipenem/relebactam (IMI/REL) is a combination of Imipenem with Relebactam, an inhibitor of class A and C β-lactamases and has been approved in the US and EU, but not in Latin America. This report evaluates the in vitro activity of IMI/REL and comparators against Latin America (LATAM) Enterobacterales and P. aeruginosa (PSA) and the frequency of carbapenemase encoding genes (CEG) among gram-negative bacilli (GNB) isolated through the SMART Program (2017-2020). Methods 21606 nonconsecutive GNB isolates were collected in 10 LATAM countries. MICs for amikacin (AK), ceftazidime-avibactam (C-A), ceftolozane/tazobactam (C/T) and IMI/REL were determined by broth microdilution and interpreted by CLSI; a subset of Enterobacterales and P. aeruginosa carbapenem resistant was selected for characterization of carbapenemase encoding genes by PCR followed by DNA sequencing. Results Escherichia coli (N=9872; EC) tested susceptible to > 96% of all antibiotics analyzed; for P. aeruginosa (N=4528), C/T and C-A had the best susceptibility rates (85.7 and 86.6% respectively); for Enterobacter cloacae (N=1091; ECL) and Klebsiella pneumoniae (N=6115; KPN), we note that only IMI/REL and C-A were ≥ 95%. Profile of 2845 carbapenem resistant isolates was analysed and the main isolated agent in most countries was KPN, corresponding to 55% (1470), except in Mexico, Panama and Venezuela where PSA was the main carbapenemase producer. The blakpc-2, 3 were found in KPN 76.7, 79.2, 53.3, 52.1 and 85.3% in Argentina, Brazil, Colombia, Ecuador and Puerto Rico, respectively; Guatemala, Mexico, Venezuela presented blaNDM-1 in 74.3, 44.1 and 51.4%. Among ECL blakpc-2 (35.7%-Brazil, 48.2%-Colombia) and blaNDM-1(45.7%-Mexico) were most frequent, blaVIM-24 (16.6%) and blaIMP-18 (38.8%) were observed in Venezuela and Puerto Rico and in the latter, we observed first time reported blakpc-45 in 27.7 %. PSA expressed blakpc-2 (33.33%- Colombia), Chile and Venezuela blaVIM-2 (44.3%, 58.8%); blaspm-1 occurred only in Brazil (6.9%). Most common carbapenemase-producing bacteria in LATAM (n=2845) Antimicrobial susceptibility of Enterobacterales and P. aeruginosa (full data analysis=21606) Most Frequent CEG detected among carbapenemase producing isolates in Latin American countries (Genotypical sample analyzed n=2845) Conclusion The frequency of CEG is a threat in LATAM, mostly in Enterobacterales, whereas PSA as expected, has a lower frequency, but still a concern. In LATAM, IMI/REL has shown relevant activity against CEG producers, showing it is an option for treatment infections caused by MDR strains. Disclosures Gustavo Mizuno, PharmD, MSD Brazil: Employee Thales Polis, MD, MSD Brazil: Employee Jacqueline Ferrari, MD, MSD Brazil: Employee Jacqueline Pavia, MD, MSD COLOMBIA: EMPLOYEE Elisa Beirão, MD, MSD BRAZIL: Grant/Research Support Ana C. Gales, MD, MSD BRAZIL: Grant/Research Support Felipe Tuon, MD, MSD BRAZIL: Grant/Research Support Alexandre Alcantara, PharmD, MSD BRAZIL: EMPLOYEE Paula M. Batista, PharmD, MSD BRAZIL: EMPLOYEE.

Background Pseudomonas aeruginosa (Pa) is a common cause of nosocomial pneumonia; resistance among traditionally used empiric agents is observed frequently. To improve patient outcomes, a heightened focus has been placed on evaluating the adequacy of recommended dosing regimens, particularly of beta-lactams. The Phase 3 study ASPECT-NP demonstrated the efficacy and safety of 3 g of ceftolozane/tazobactam (C/T) infused every 8 h for 8 to 14 days for treatment of adults with Hospital-Acquired Pneumonia/Ventilator-Associated Pneumonia (HAP/VAP). We assessed the Probability of Target Attainment (PTA) of the C/T 3g dosage regimen in patients with HAP/VAP due to Pa, with an additional focus on carbapenem-resistant Pa, from Latin America. Methods Non duplicate Pa isolates from a respiratory source were collected as part of the SMART surveillance program from 36 sites in 10 Latin American countries during 2017-2020. MICs were determined by broth microdilution and interpreted by CLSI criteria. C and T concentration-time profiles were simulated in plasma and ELF following administration of the approved 3g (2g/1g) C/T dose (or equivalent dose adjusted based on renal function) administered by 1-hour infusion every 8 hours. PTA in plasma and ELF was calculated using the PK/PD target of 30% fT > MIC for C. T does not contribute to the antipseudomonal activity of C and therefore was not considered. Results A total of 2,757 P. aeruginosa were collected, of which 1208 (43.8%) were carbapenem nonsusceptible. C/T susceptiblity was 87.7% against all Pa and 73.4% among carbapenem nonsusceptible strains. At C/T doses of 2g/1g (CrCL > 50mL/min); 1g/0.5g (30mL/min≤ CrCL≤ 50mL/min), and 500mg/250mg (15mL/min≤ CrCL≤29mL/min), steady-state ceftolozane plasma and ELF PTA was 100% and > 99%, respectively, for isolates with an MIC at the Pa susceptiblity breakpoint of 4 µg/mL. Ceftolozane plasma and ELF PTA remained above 90% up to an MIC of 16 µg/mL and 8 µg/mL, respectively. Conclusion The regulatory approved pneumonia dosage regimen of C/T 3g (administered over 1 hour) every 8 hours (or equivalent dose adjusted based on renal function) resulted in high plasma and ELF PTAs sufficient to cover the vast majority of circulating P. aeruginosa present in Latin America, including carbapenem resistant strains. Disclosures Aline Okuma, PharmD, MSD Brazil: Employee Thales Polis, MD, MSD Brazil: Employee Jacqueline Pavia, MD, MSD COLOMBIA: EMPLOYEE Gustavo Mizuno, PharmD, MSD Brazil: Employee Jacqueline Ferrari, MD, MSD Brazil: Employee Charles A. DeRyke, PharmD, Merck & Co., Inc. Merck Research Laboratories: Stocks/Bonds.

Early therapies to prevent severe COVID-19 have an unclear impact on patients with hematological malignancies. The aim of this study was to assess their efficacy in this group of high-risk patients with COVID-19 in preventing hospitalizations and reducing the SARS-CoV-2 shedding. This was a single-center, retrospective, observational study conducted in the Fondazione IRCSS Policlinico San Matteo of Pavia, Northern Italy. We extracted the data of patients with hematologic malignancies and COVID-19 who received and did not receive early COVID-19 treatment between 23 December 2021, and May 2022. We used a Cox proportional hazard model to assess whether receiving any early treatment was associated with lower rates of hospitalization and reduced viral shedding. Data from 88 patients with hematologic malignancies were extracted. Among the patients, 55 (62%) received any early treatment, whereas 33 (38%) did not. Receiving any early therapy did not significantly reduce the hospitalization rate in patients with hematologic malignancies (HR 0.51; SE 0.63; p-value = 0.28), except in the vaccinated non-responders subgroup of patients with negative anti SARS-CoV-2 antibodies at the time of infection, who benefited from early therapies against SARS-CoV-2 (HR 0.07; SE 1.04; p-value = 0.001). Moreover, no difference on viral load decay was observed. In our cohort of patients with hematologic malignancies infected with SARS-CoV-2, early treatment were not effective in reducing the hospitalization rate due to COVID-19, neither in reducing its viral shedding.

Systemic mastocytosis (SM) encompasses a heterogeneous group of clonal disorders characterized by abnormal expansion of mast cells (MCs). Beyond KIT and other genes recurrently mutated in myeloid neoplasms, several genetic variants have been described as predisposing to the development of the disease and influencing its clinical phenotype. Increased copy number variants of the TPSAB1 gene were identified as a cause of nonclonal elevated tryptasemia and defined as hereditary α-tryptasemia (HαT). Moreover, HαT is enriched in patients with SM, where it can affect the incidence of mediator-related symptoms.In a multicenter data set of 444 patients with MC disorders, we aimed to investigate the clinical correlates of germline TPSAB1 copy number gains.Droplet digital PCR was performed in all cases to ascertain the presence of HαT. Clinical history along with blood values and bone marrow examination were analyzed.We confirmed a higher incidence of HαTThese findings on a large patient series support and extend previous data, and suggest that knowledge of HαT status may be useful for personalized management of patients with SM.

SARS-CoV-2 infection has a heterogeneous and largely unpredictable course, ranging from asymptomatic presentation to fatal cases. Several studies have demonstrated that patients with cancer have hi...

Clonal cytopenia of undetermined significance (CCUS) is associated with an increased risk of developing a myeloid neoplasm with myelodysplasia (MN). To identify the features of the mutant clone(s) that is associated with clinical phenotype and progression, we studied the following cohorts of individuals: 311 patients with idiopathic cytopenia of undetermined significance (ICUS), 532 community-dwelling individuals without hematologic phenotype (n = 355) or with unexplained anemia (n = 177), and 592 patients with overt MN. Ninety-two of 311 (30%) patients with ICUS carried a somatic genetic lesion that signaled CCUS. Clonal hematopoiesis (CH) was detected in 19.7% and 27.7% of nonanemic and anemic community-dwelling individuals, respectively. Different mutation patterns and variant allele frequencies (VAFs) (clone metrics parameters) were observed in the conditions studied. Recurrent mutation patterns exhibited different VAFs associated with marrow dysplasia (0.17-0.48), indicating variable clinical expressivity of mutant clones. Unsupervised clustering analysis based on mutation profiles identified 2 major clusters, characterized by isolated DNMT3A mutations (CH-like cluster) or combinatorial mutation patterns (MN-like cluster), and showing different overall survival (HR, 1.8). In patients with CCUS, the 2 clusters had different risk of progression to MN (HR, 2.7). Within the MN-like cluster, distinct subsets with different risk of progression to MN were identified based on clone metrics. These findings unveil marked variability in the clinical expressivity of myeloid driver genes and underline the limitations of morphologic dysplasia for clinical staging of mutant hematopoietic clones. Clone metrics appears to be critical for informing clinical decision-making in patients with clonal cytopenia.

Background. The Philadelphia (Ph) chromosome (chr.) is the hallmark of chronic myeloid leukemia (CML) and typically results from the reciprocal translocation t(9;22)(q34;11.2). Complex variant translocations (CVT) involving one or more additional chr. are identified in less than 5% of newly diagnosed CML. There are conflicting reports about the prognostic impact of CVT in the achievement of optimal response to tyrosine kinase inhibitor (TKI), and very few studies addressed the role of frontline treatment with imatinib or second generation (2G)-TKI in patients with CVT. Aims. To assess the response to imatinib or 2G-TKI in a large cohort of newly diagnosed CML with CVT, and to explore the impact of the different chr. translocations on outcome. Methods. This observational retrospective study was conducted in 19 hematologic centers in the framework of Campus CML, a network of Italian physicians involved in the management of CML patients. All newly diagnosed CML from 2000 to 2019 were evaluated and patients with CVT were selected for the present analysis. Karyotypes were defined according to the 2016 International System for Human Cytogenetic Nomenclature. Responses to frontline treatment were retrospectively categorized according to the 2013 ELN recommendations, as they include cytogenetic milestones. Deep molecular response (DMR, i.e. MR4or better) was defined as BCR-ABLIS ratio ≤0.01% or undetectable disease with ≥10,000 ABL copies. Patients with DMR lasting ≥2 years and at least a Q-PCR test every 6 months were defined as stable DMR responders. Failure-free survival (FFS) was calculated from the start of frontline TKI treatment to progression to advanced phase, death, or switch to other treatments for resistance. For FFS calculation, patients were censored at TKI stop for treatment-free remission (TFR) or in case of switch for intolerance only. Differences between subgroups according to the partner chr. were presented for descriptive purposes. Results. CVT were identified in 109 (3.2%) patients from a whole population of 3,361 subjects with newly diagnosed CML. Ninety-five out of 109 patients (87%) exhibited three-way translocations, with chr. 1, 4, 6, 10, 11, 12, 14, 15 and 17 representing the most common additional partners (figure). Four- and five-way translocations were identified in 13 and 1 patients, respectively. Additional chr. abnormalities (ACA) in the Ph+ cells were observed in 15/109 (13.8%) patients and were more common in older individuals (p=0.018). Overall, median age at diagnosis was 50.6 years (range 20-90). Risk distribution according to the ELTS score was 54%, 28% and 8% for L, I and H risk, respectively (10% missing). Cytogenetic result was available before the choice of frontline treatment in 45% of cases and represented a decisive factor in 28% of them (i.e. clinicians selected a 2G-TKI or high-dose imatinib, according to the available options). Frontline TKI treatment was imatinib in 80 cases (73%) and 2G-TKI (nilotinib n=22, dasatinib n=6, bosutinib n=1) in the remaining cases. The frequency of optimal response at 3, 6 and 12 months was 48%, 45% and 53%, respectively, for imatinib-treated patients, and 76%, 83% and 76%, respectively, for the 2G-TKI cohort (p The subtype of CVT had an impact on response and long-term outcome. Patients with CVT involving chr. 1, 4, 6, 11 or 12 had a higher frequency of MMR at 12 months than patients with CVT involving chr. 10, 14, 15 or 17 (75.8% vs 30.4%, respectively, p=0.001), higher frequency of stable DMR (48.7% vs 22.2%, respectively; p=0.04) and tended to have better median FFS (p=0.07), regardless of the type of frontline TKI and of the ELTS score. Conclusions. Due to its retrospective nature, this study does not allow to define which is the optimal therapy for CML harboring CVT at diagnosis. However, our data reinforce the usefulness of bone marrow karyotyping in CML. The observed differences between partner chr. may also depend on the breaking points, which are variable. Further dissection of CVT will help to identify which are associated to a poor response to TKIs. Figure Disclosures D'Adda: Incyte: Other: Advisory board; Novartis: Other: Advisory board; Pfizer: Other: Advisory board. Galimberti:Novartis: Speakers Bureau; Incyte: Honoraria. Crugnola:Celgene: Honoraria; Janssen: Honoraria; BMS: Honoraria; Novartis: Honoraria. Bocchia:Incyte: Honoraria; CELGENE: Honoraria. Krampera:Janssen: Membership on an entity's Board of Directors or advisory committees; Novartis: Membership on an entity's Board of Directors or advisory committees. Breccia:Incyte: Consultancy, Honoraria; Pfizer: Consultancy, Honoraria; Abbvie: Consultancy; Bristol-Myers Squibb/Celgene: Consultancy, Honoraria; Novartis: Consultancy, Honoraria. Saglio:Novartis: Research Funding; Ariad: Research Funding; Pfizer: Research Funding; Bristol-Myers Squibb: Research Funding; Incyte: Research Funding; Roche: Research Funding.