Profiling SARS-CoV-2 HLA-I peptidome reveals T cell epitopes from out-of-frame ORFs.

T cell-mediated immunity plays an important role in controlling SARS-CoV-2 infection, but the repertoire of naturally processed and presented viral epitopes on class I human leukocyte antigen (HLA-I) remains uncharacterized. Here, we report the first HLA-I immunopeptidome of SARS-CoV-2 in two cell lines at different times post infection using mass spectrometry. We found HLA-I peptides derived not only from canonical open reading frames (ORFs) but also from internal out-of-frame ORFs in spike and nucleocapsid not captured by current vaccines. Some peptides from out-of-frame ORFs elicited T cell responses in a humanized mouse model and individuals with COVID-19 that exceeded responses to canonical peptides, including some of the strongest epitopes reported to date. Whole-proteome analysis of infected cells revealed that early expressed viral proteins contribute more to HLA-I presentation and immunogenicity. These biological insights, as well as the discovery of out-of-frame ORF epitopes, will facilitate selection of peptides for immune monitoring and vaccine development.

Intraventricular CARv3-TEAM-E T Cells in Recurrent Glioblastoma.

In this first-in-human, investigator-initiated, open-label study, three participants with recurrent glioblastoma were treated with CARv3-TEAM-E T cells, which are chimeric antigen receptor (CAR) T cells engineered to target the epidermal growth factor receptor (EGFR) variant III tumor-specific antigen, as well as the wild-type EGFR protein, through secretion of a T-cell-engaging antibody molecule (TEAM). Treatment with CARv3-TEAM-E T cells did not result in adverse events greater than grade 3 or dose-limiting toxic effects. Radiographic tumor regression was dramatic and rapid, occurring within days after receipt of a single intraventricular infusion, but the responses were transient in two of the three participants. (Funded by Gateway for Cancer Research and others; INCIPIENT ClinicalTrials.gov number, NCT05660369.).

Phase 1 study of CAR-37 T cells in patients with relapsed or refractory CD37+ lymphoid malignancies.

ABSTRACT: We report a first-in-human clinical trial using chimeric antigen receptor (CAR) T cells targeting CD37, an antigen highly expressed in B- and T-cell malignancies. Five patients with relapsed or refractory CD37+ lymphoid malignancies were enrolled and infused with autologous CAR-37 T cells. CAR-37 T cells expanded in the peripheral blood of all patients and, at peak, comprised >94% of the total lymphocytes in 4 of 5 patients. Tumor responses were observed in 4 of 5 patients with 3 complete responses, 1 mixed response, and 1 patient whose disease progressed rapidly and with relative loss of CD37 expression. Three patients experienced prolonged and severe pancytopenia, and in 2 of these patients, efforts to ablate CAR-37 T cells, which were engineered to coexpress truncated epidermal growth factor receptor, with cetuximab were unsuccessful. Hematopoiesis was restored in these 2 patients after allogeneic hematopoietic stem cell transplantation. No other severe, nonhematopoietic toxicities occurred. We investigated the mechanisms of profound pancytopenia and did not observe activation of CAR-37 T cells in response to hematopoietic stem cells in vitro or hematotoxicity in humanized models. Patients with pancytopenia had sustained high levels of interleukin-18 (IL-18) with low levels of IL-18 binding protein in their peripheral blood. IL-18 levels were significantly higher in CAR-37-treated patients than in both cytopenic and noncytopenic cohorts of CAR-19-treated patients. In conclusion, CAR-37 T cells exhibited antitumor activity, with significant CAR expansion and cytokine production. CAR-37 T cells may be an effective therapy in hematologic malignancies as a bridge to hematopoietic stem cell transplant. This trial was registered at www.ClinicalTrials.gov as #NCT04136275.

Fractionated vs single-dose gemtuzumab ozogamicin with determinants of benefit in older patients with AML: the UK NCRI AML18 trial.

Addition of gemtuzumab ozogamicin (GO) to induction chemotherapy improves outcomes in older patients with acute myeloid leukemia (AML), but it is uncertain whether a fractionated schedule provides additional benefit to a single dose. We randomized 852 older adults (median age, 68-years) with AML/high-risk myelodysplasia to GO on day 1 (GO1) or on days 1 and 4 (GO2) of course 1 induction. The median follow-up period was 50.2 months. Although complete remission (CR) rates after course 1 did not significantly differ between arms (GO2, 63%; GO1, 57%; odds ratio [OR], 0.78; P = .08), there were significantly more patients who achieved CR with a measurable residual disease (MRD)<0.1% (50% vs 41%; OR, 0.72; P = .027). This differential MRD reduction with GO2 varied across molecular subtypes, being greatest for IDH mutations. The 5-year overall survival (OS) was 29% for patients in the GO2 arm and 24% for those in the GO1 arm (hazard ratio [HR], 0.89; P = .14). In a sensitivity analysis excluding patients found to have adverse cytogenetics or TP53 mutations, the 5-year OS was 33% for GO2 and 26% for GO1 (HR, 0.83; P = .045). In total, 228 (27%) patients received an allogeneic transplantation in first remission. Posttransplant OS was superior in the GO2 arm (HR, 0.67; P = .033); furthermore, the survival advantage from GO2 in the sensitivity analysis was lost when data of patients were censored at transplantation. In conclusion, GO2 was associated with a greater reduction in MRD and improved survival in older adults with nonadverse risk genetics. This benefit from GO2 was dependent on allogeneic transplantation to translate the better leukemia clearance into improved survival. This trial was registered at www.isrctn.com as #ISRCTN 31682779.

Safety and efficacy of tisagenlecleucel in primary CNS lymphoma: a phase 1/2 clinical trial.

CD19-directed chimerical antigen receptor T-cell (CAR-T) products have gained US Food and Drug Administration approval for systemic large B-cell lymphoma. Because of concerns about potential immune cell-associated neurotoxicity syndrome (ICANS), patients with primary central nervous system (CNS) lymphoma (PCNSL) were excluded from all pivotal CAR-T studies. We conducted a phase 1/2 clinical trial of tisagenlecleucel in a highly refractory patients with PCNSL and significant unmet medical need. Here, we present results of 12 relapsed patients with PCNSL who were treated with tisagenlecleucel and followed for a median time of 12.2 months (range, 3.64-23.5). Grade 1 cytokine release syndrome was observed in 7/12 patients (58.3%), low-grade ICANS in 5/12 (41.6%) patients, and only 1 patient experienced grade 3 ICANS. Seven of 12 patients (58.3%) demonstrated response, including a complete response in 6/12 patients (50%). There were no treatment-related deaths. Three patients had ongoing complete remission at data cutoff. Tisagenlecleucel expanded in the peripheral blood and trafficked to the CNS. Exploratory analysis identified T-cell, CAR T, and macrophage gene signatures in cerebrospinal fluid following infusion when compared with baseline. Overall, tisagenlecleucel was well tolerated and resulted in a sustained remission in 3/7 (42.9%) of initial responders. These data suggest that tisagenlecleucel is safe and effective in this highly refractory patient population. This trial was registered at www.clinicaltrials.gov as #NCT02445248.

A proactive financial navigation intervention in patients with newly diagnosed gastric and gastroesophageal junction adenocarcinoma.

PURPOSE: Many cancer patients and caregivers experience financial hardship, leading to poor outcomes. Gastric and gastroesophageal junction (GEJ) cancer patients are particularly at risk for financial hardship given the intensity of treatment. This pilot randomized study among gastric/GEJ cancer patients and caregivers tested a proactive financial navigation (FN) intervention to obtain a signal of efficacy to inform a larger, more rigorous randomized study. METHODS: We tested a 3-month proactive FN intervention among gastric/GEJ cancer patients and caregivers compared to usual care. Caregiver participation was optional. The primary endpoint was incidence of financial hardship, defined as follows: accrual of debt, income decline of ≥ 20%, or taking loans to pay for treatment. Data from participant surveys and documentation by partner organizations delivering the FN intervention was analyzed and outcomes were compared between study arms. RESULTS: Nineteen patients and 12 caregivers consented. Primary FN resources provided included insurance navigation, budget planning, and help with out-of-pocket medical expenses. Usual care patients were more likely to experience financial hardship (50% vs 40%) and declines in quality of life (37.5% vs 0%) compared to intervention patients. Caregivers in both arms reported increased financial stress and poorer quality of life over the study period. CONCLUSIONS: Proactive financial navigation has potentially positive impacts on financial hardship and quality of life for cancer patients and more large-scale randomized interventions should be conducted to rigorously explore the impact of similar interventions. Interventions that have the potential to lessen caregiver financial stress and burden need further exploration. TRIAL REGISTRATION: TRN: NCT03986502, June 14, 2019.

Patient-reported discrimination among limited-resourced cancer survivors: a brief report.

PURPOSE: Healthcare discrimination has been associated with health disparities including lower cancer screenings, higher medical mistrust, and strained patient-provider relationships. Our study sought to understand patient-reported discrimination among cancer survivors with limited resources living in the United States. DESIGN AND METHODS: We used cross-sectional survey data distributed by the Patient Advocate Foundation (PAF) in 12/2020 and 07/2021. Respondents reported source and reason of healthcare discrimination. Age, sex, race and ethnicity, annual household income, Rural-Urban Commuting Area (RUCA), Area Deprivation Index (ADI), employment status, cancer type, and number of comorbidities were independent variables of interest. The association between these variables and patient-reported healthcare discrimination was estimated using risk ratios (RRs) and 95% confidence intervals (CIs) from a multivariable modified Poisson regression model with robust standard errors. FINDINGS: A total of 587 cancer survivors were included in our analysis. Most respondents were female (72%) and aged ≥56 (62%); while 33% were Black, Indigenous, or Person of Color. Overall, 23% reported receipt of discrimination, with the majority reporting doctor, nurse, or healthcare provider as the source (58%). Most common reasons for discrimination included disease status (42%), income/ability to pay (36%), and race and ethnicity (17%). In the adjusted model, retired survivors were 62% less likely to report discrimination compared to those employed (RR 0.38; 95% CI 0.23-0.64). Additionally, survivors with ≥3 comorbidities were 86% more likely to report discrimination compared to those survivors with no non-cancer comorbidities (RR 1.86; 95% CI 1.26-2.72). IMPLICATIONS: Cancer survivors with limited resources reported substantial discrimination most often from a healthcare provider and most commonly for disease status and income. Discrimination should be mitigated to provide equitable and high-quality cancer care.

Differential T-Cell Immunity to Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) in mRNA-1273- and BNT162b2-Vaccinated Individuals.

COVID-19 breakthrough cases among vaccinated individuals demonstrate the value of measuring long-term immunity to SARS-CoV-2 and its variants. We demonstrate that anti-spike T-cell responses and IgG antibody levels are maintained but decrease over time and are lower in BNT162b2- versus mRNA-1273-vaccinated individuals. T-cell responses to the variants are relatively unaffected.

Extending and Strengthening Routine DHIS2 Surveillance Systems for COVID-19 Responses in Sierra Leone, Sri Lanka, and Uganda.

The COVID-19 pandemic challenged countries to protect their populations from this emerging disease. One aspect of that challenge was to rapidly modify national surveillance systems or create new systems that would effectively detect new cases of COVID-19. Fifty-five countries leveraged past investments in District Health Information Software version 2 (DHIS2) to quickly adapt their national public health surveillance systems for COVID-19 case reporting and response activities. We provide background on DHIS2 and describe case studies from Sierra Leone, Sri Lanka, and Uganda to illustrate how the DHIS2 platform, its community of practice, long-term capacity building, and local autonomy enabled countries to establish an effective COVID-19 response. With these case studies, we provide valuable insights and recommendations for strategies that can be used for national electronic disease surveillance platforms to detect new and emerging pathogens and respond to public health emergencies.

Public Health Actions to Control Measles Among Afghan Evacuees During Operation Allies Welcome - United States, September-November 2021.

On August 29, 2021, the United States government oversaw the emergent establishment of Operation Allies Welcome (OAW), led by the U.S. Department of Homeland Security (DHS) and implemented by the U.S. Department of Defense (DoD) and U.S. Department of State (DoS), to safely resettle U.S. citizens and Afghan nationals from Afghanistan to the United States. Evacuees were temporarily housed at several overseas locations in Europe and Asia* before being transported via military and charter flights through two U.S. international airports, and onward to eight U.S. military bases,† with hotel A used for isolation and quarantine of persons with or exposed to certain infectious diseases.§ On August 30, CDC issued an Epi-X notice encouraging public health officials to maintain vigilance for measles among Afghan evacuees because of an ongoing measles outbreak in Afghanistan (25,988 clinical cases reported nationwide during January-November 2021) (1) and low routine measles vaccination coverage (66% and 43% for the first and second doses, respectively, in 2020) (2).

Determinants of telemedicine adoption among financially distressed patients with cancer during the COVID-19 pandemic: insights from a nationwide study.

PURPOSE: Telemedicine use during the COVID-19 pandemic among financially distressed patients with cancer, with respect to the determinants of adoption and patterns of utilization, has yet to be delineated. We sought to systematically characterize telemedicine utilization in financially distressed patients with cancer during the COVID-19 pandemic. METHODS: We conducted a cross-sectional analysis of nationwide survey data assessing telemedicine use in patients with cancer during the COVID-19 pandemic collected by Patient Advocate Foundation (PAF) in December 2020. Patients were characterized as financially distressed by self-reporting limited financial resources to manage out-of-pocket costs, psychological distress, and/or adaptive coping behaviors. Primary study outcome was telemedicine utilization during the pandemic. Secondary outcomes were telemedicine utilization volume and modality preferences. Multivariable and Poisson regression analyses were used to identify factors associated with telemedicine use. RESULTS: A convenience sample of 627 patients with cancer responded to the PAF survey. Telemedicine adoption during the pandemic was reported by 67% of patients, with most (63%) preferring video visits. Younger age (19-35 age compared to ≥ 75 age) (OR, 6.07; 95% CI, 1.47-25.1) and more comorbidities (≥ 3 comorbidities compared to cancer only) (OR, 1.79; 95% CI, 1.13-2.65) were factors associated with telemedicine adoption. Younger age (19-35 years) (incidence rate ratios [IRR], 1.78; 95% CI, 24-115%) and higher comorbidities (≥ 3) (IRR; 1.36; 95% CI, 20-55%) were factors associated with higher utilization volume. As area deprivation index increased by 10 units, the number of visits decreased by 3% (IRR 1.03, 95% CI, 1.03-1.05). CONCLUSIONS: The rapid adoption of telemedicine may exacerbate existing inequities, particularly among vulnerable financially distressed patients with cancer. Policy-level interventions are needed for the equitable and efficient provision of this service.

Quantifying treatment preferences and their association with financial toxicity in women with breast cancer.

BACKGROUND: The objective of the current study was to understand treatment preferences and their association with financial toxicity in Patient Advocate Foundation clients with breast cancer. METHODS: This choice-based conjoint analysis used data from a nationwide sample of women with breast cancer who received assistance from the Patient Advocate Foundation. Choice sets created from 13 attributes of 3 levels each elicited patient preferences and trade-offs. Latent class analysis segmented respondents into distinct preference archetypes. The Comprehensive Score for Financial Toxicity (COST) tool captured financial toxicity. Adjusted generalized linear models estimated COST score differences by preference archetype. RESULTS: Of 220 respondents (for a response rate of 10%), the median age was 58 years (interquartile range, 49-66 years); 28% of respondents were Black, indigenous, or people of color; and approximately 60% had household incomes <$40,000. The majority of respondents were diagnosed with early-stage cancer (91%), 38% had recurrent disease, and 61% were receiving treatment. Treatment choice was most affected by preferences related to affordability and impact on activities of daily living. Two distinct treatment preference archetypes emerged. The "cost-prioritizing group" (75% of respondents) was most concerned about affordability, impact on activities of daily living, and burdening care partners. The "functional independence-prioritizing group" (25% of respondents) was most concerned about their ability to work, physical side effects, and interference with life events. COST scores were found to be similar between the archetypes in adjusted models (cost-prioritizing group COST score, 12 [95% confidence interval, 9-14]; and functional independence-prioritizing COST score, 11 [95% confidence interval, 9-13]). CONCLUSIONS: Patients with breast cancer prioritized affordability or maintaining functional independence when making treatment decisions. Because of this variability, preference evaluation during treatment decision making could optimize patients' treatment experiences.

Tisagenlecleucel CAR T-cell therapy in secondary CNS lymphoma.

Chimeric antigen receptor (CAR) T cells targeting CD19 have emerged as a leading engineered T-cell therapy for relapsed/refractory B-cell non-Hodgkin lymphoma. The phase 1/2 clinical trials that led to US Food and Drug Administration approval excluded patients with central nervous system (CNS) involvement, due to strict eligibility criteria. Here, we report on our institutional experience with 8 secondary CNS lymphoma patients treated with commercial tisagenlecleucel. No patient experienced greater than grade 1 neurotoxicity, and no patient required tocilizumab or steroids for CAR T-cell-mediated toxicities. Biomarker analysis suggested CAR T-cell expansion, despite the absence of systemic disease, and early response assessments demonstrated activity of IV infused CAR T cells within the CNS space.

Standardizing clinical culture specimen collection in Ethiopia: a training-of-trainers.

BACKGROUND: Proper specimen collection is central to improving patient care by ensuring optimal yield of diagnostic tests, guiding appropriate management, and targeting treatment. The purpose of this article is to describe the development and implementation of a training-of-trainers educational program designed to improve clinical culture specimen collection among healthcare personnel (HCP) in Ethiopia. METHODS: A Clinical Specimen Collection training package was created consisting of a Trainer's Manual, Reference Manual, Assessment Tools, Step-by-Step Instruction Guides (i.e., job aides), and Core Module PowerPoint Slides. RESULTS: A two-day course was used in training 16 master trainers and 47 facility-based trainers responsible for cascading trainings on clinical specimen collection to HCP at the pre-service, in-service, or national-levels. The Clinical Specimen Collection Package is offered online via The Ohio State University's CANVAS online platform. CONCLUSIONS: The training-of-trainers approach may be an effective model for development of enhanced specimen collection practices in low-resource countries.

A Pilot Study of a Comprehensive Financial Navigation Program in Patients With Cancer and Caregivers.

BACKGROUND: Few studies have engaged patients and caregivers in interventions to alleviate financial hardship. We collaborated with Consumer Education and Training Services (CENTS), Patient Advocate Foundation (PAF), and Family Reach (FR) to assess the feasibility of enrolling patient-caregiver dyads in a program that provides financial counseling, insurance navigation, and assistance with medical and cost of living expenses. METHODS: Patients with solid tumors aged ≥18 years and their primary caregiver received a financial education video, monthly contact with a CENTS counselor and PAF case manager for 6 months, and referral to FR for help with unpaid cost of living bills (eg, transportation or housing). Patient financial hardship and caregiver burden were measured using the Comprehensive Score for Financial Toxicity-Patient-Reported Outcomes (COST-PRO) and Caregiver Strain Index (CSI) measures, respectively, at baseline and follow-up. RESULTS: Thirty patients (median age, 59.5 years; 40% commercially insured) and 18 caregivers (67% spouses) consented (78% dyad participation rate). Many participants faced cancer-related financial hardships prior to enrollment, such as work change or loss (45% of patients; 39% of caregivers) and debt (64% of patients); 39% of caregivers reported high levels of financial burden at enrollment. Subjects received $11,000 in assistance (mean, $772 per household); 66% of subjects with income ≤$50,000 received cost-of-living assistance. COST-PRO and CSI scores did not change significantly. CONCLUSIONS: Patient-caregiver dyads were willing to participate in a financial navigation program that addresses various financial issues, particularly cost of living expenses in lower income participants. Future work should address financial concerns at diagnosis and determine whether doing so improves patient and caregiver outcomes.

Impact of a New Helicopter Base on Transport Time and Survival in a Rural Adult Trauma Population.

BACKGROUND: Significant disparities in access to prompt helicopter transport exist among rural trauma populations. We evaluated the impact of an additional helicopter base on transport time and mortality in a rural adult trauma population. MATERIALS AND METHODS: We performed a retrospective cohort study of adult patients with trauma transported by helicopter from scene to a level one trauma center between 2014 and 2018. A new rural helicopter base added to the trauma center's catchment area in 2016 served as the transition time for an interrupted time series analysis. Patients injured in this base's county and adjoining counties were analyzed. Baseline characteristics were compared with a Student's t-test and Pearson's chi-squared test. Cox and linear regression models evaluated the new base's effect on mortality and transport time, respectively. RESULTS: A total of 332 patients were analyzed: 120 (36.1%) transported before the addition of the new helicopter base and 212 (63.9%) transported after. Patients transported after the addition of the base had higher injury severity score (13.7 versus 10.1, P < 0.001) and were more likely to receive blood en route (19.3% versus 6.7%, P = 0.005). After the addition of the base, there was a decreased hazard ratio for mortality (hazard ratio 0.26, 95% confidence interval: 0.11-0.65, P = 0.004) with no significant change in transport time (-36.7 min, P = 0.071) for the area. CONCLUSIONS: Local helicopter transport units may confer improved survival for the injured patient. This study demonstrates the important role of helicopter transport within a regional trauma system and the impact that expanded access to rapid air transport can have on mortality.

Placement of Subcutaneous Central Venous Ports in Breast Cancer Patients: Does Side Matter?

BACKGROUND: Central venous ports placed for breast cancer treatment have traditionally been placed contralateral to the disease. This is done out of concern for the possibility of an increased risk of complications with ipsilateral port placement. There have been only a few small studies evaluating complication rates between ports placed ipsilateral versus contralateral to the breast cancer. We sought to determine if there was a difference in port complications or lymphedema rates by location. METHODS: A single institution retrospective review was conducted of adult (aged >18 y) females undergoing central venous port placement for breast cancer treatment from 2012 to 2016. RESULTS: A total of 581 females were identified with a mean age of 52.9 ± 11.7 y. Ipsilateral ports were placed in 41 patients (7.1%). Ipsilateral ports were more likely to be placed via the internal jugular vein (56.1%), whereas contralateral ports were more likely to be placed in the subclavian vein (67.2%; P = 0.002). There was no difference between stage at diagnosis (P = 0.059), type of breast surgery (P = 0.999), axillary surgery (P = 0.087), or administration of radiation therapy (P = 0.684) between the groups. Ipsilateral ports were more likely to be on the right side, 73.2% versus 51.1% (P = 0.006). Port complications requiring intervention occurred in 3 patients (7.3%) with ipsilateral port and 33 patients (6.1%) with contralateral ports (P = 0.73). Lymphedema occurred in 8 patients (20%) with ipsilateral ports and 118 patients (21.9%) with contralateral ports (P = 0.639). On multivariable analysis, the type of axillary surgery (P = 0.003) was associated with upper extremity lymphedema, whereas port sidedness (P = 0.26) was not. CONCLUSIONS: There was no difference in port complications or lymphedema rates between patients who had ports placed on the ipsilateral side compared with the contralateral side for breast cancer treatment.

Impact of Referring Hospital Imaging on Mortality at a Level I Trauma Center.

BACKGROUND: Computed tomography (CT) has become a standard adjunct in the evaluation of patients with trauma. However, utility of imaging at the referring hospital remains controversial. We study the effect of CT scans at referring hospitals on in-hospital mortality at a receiving trauma center. MATERIALS AND METHODS: A retrospective cohort study was performed with adult patients with severe trauma transferred to a level I trauma center from regional nontrauma hospitals between 2012 and 2017. Baseline characteristics were compared with Student's t-test and Pearson's chi-squared testing. The primary endpoint was in-hospital mortality. Cox regression, controlling for transfer time, was used to evaluate the effect of imaging on mortality. RESULTS: Three thousand four hundred and fifteen adult patients with trauma were included: 1135 (33.2%) received a pretransfer CT scan, whereas 2280 (66.8%) did not. Patients who received a pretransfer CT scan were more likely to be older, female, white, have a higher Charlson Comorbidity Index, less severely injured, have a blunt mechanism, and be transferred by ground. There was no difference in distance (58.3 miles versus 57.0 miles, P = 0.34), but transfer times were significantly increased for those who received pretransfer scans (288 versus 213 min, P < 0.005). The adjusted model controlling for multiple variables has a hazard ratio of 0.533 (95% confidence interval 0.42-0.68, P < 0.005). CONCLUSIONS: There is a survival advantage for patients who receive pretransfer CT scans despite having significantly longer transport times. We suggest that this decreased mortality associated with pretransfer imaging may reflect improving trends in referring physician transfer decisions.

A selective inhibitor of PRMT5 with in vivo and in vitro potency in MCL models.

Protein arginine methyltransferase-5 (PRMT5) is reported to have a role in diverse cellular processes, including tumorigenesis, and its overexpression is observed in cell lines and primary patient samples derived from lymphomas, particularly mantle cell lymphoma (MCL). Here we describe the identification and characterization of a potent and selective inhibitor of PRMT5 with antiproliferative effects in both in vitro and in vivo models of MCL. EPZ015666 (GSK3235025) is an orally available inhibitor of PRMT5 enzymatic activity in biochemical assays with a half-maximal inhibitory concentration (IC50) of 22 nM and broad selectivity against a panel of other histone methyltransferases. Treatment of MCL cell lines with EPZ015666 led to inhibition of SmD3 methylation and cell death, with IC50 values in the nanomolar range. Oral dosing with EPZ015666 demonstrated dose-dependent antitumor activity in multiple MCL xenograft models. EPZ015666 represents a validated chemical probe for further study of PRMT5 biology and arginine methylation in cancer and other diseases.