Single-base tiled screen unveils design principles of PspCas13b for potent and off-target-free RNA silencing.

The development of precise RNA-editing tools is essential for the advancement of RNA therapeutics. CRISPR (clustered regularly interspaced short palindromic repeats) PspCas13b is a programmable RNA nuclease predicted to offer superior specificity because of its 30-nucleotide spacer sequence. However, its design principles and its on-target, off-target and collateral activities remain poorly characterized. Here, we present single-base tiled screening and computational analyses that identify key design principles for potent and highly selective RNA recognition and cleavage in human cells. We show that the de novo design of spacers containing guanosine bases at precise positions can greatly enhance the catalytic activity of inefficient CRISPR RNAs (crRNAs). These validated design principles (integrated into an online tool, https://cas13target.azurewebsites.net/ ) can predict highly effective crRNAs with ~90% accuracy. Furthermore, the comprehensive spacer-target mutagenesis revealed that PspCas13b can tolerate only up to four mismatches and requires ~26-nucleotide base pairing with the target to activate its nuclease domains, highlighting its superior specificity compared to other RNA or DNA interference tools. On the basis of this targeting resolution, we predict an extremely low probability of PspCas13b having off-target effects on other cellular transcripts. Proteomic analysis validated this prediction and showed that, unlike other Cas13 orthologs, PspCas13b exhibits potent on-target activity and lacks collateral effects.

Degraders upgraded: the rise of PROTACs in hematological malignancies.

ABSTRACT: Targeted protein degradation (TPD) is a revolutionary approach to targeted therapy in hematological malignancies that potentially circumvents many constraints of existing small-molecule inhibitors. Heterobifunctional proteolysis-targeting chimeras (PROTACs) are the leading TPD drug class, with numerous agents now in clinical trials for a range of blood cancers. PROTACs harness the cell-intrinsic protein recycling infrastructure, the ubiquitin-proteasome system, to completely degrade target proteins. Distinct from targeted small-molecule inhibitor therapies, PROTACs can eliminate critical but conventionally "undruggable" targets, overcome resistance mechanisms to small-molecule therapies, and can improve tissue specificity and off-target toxicity. Orally bioavailable, PROTACs are not dependent on the occupancy-driven pharmacology inherent to inhibitory therapeutics, facilitating substoichiometric dosing that does not require an active or allosteric target binding site. Preliminary clinical data demonstrate promising therapeutic activity in heavily pretreated populations and novel technology platforms are poised to exploit a myriad of permutations of PROTAC molecular design to enhance efficacy and targeting specificity. As the field rapidly progresses and various non-PROTAC TPD drug candidates emerge, this review explores the scientific and preclinical foundations of PROTACs and presents them within common clinical contexts. Additionally, we examine the latest findings from ongoing active PROTAC clinical trials.

Reprogrammed CRISPR-Cas13b suppresses SARS-CoV-2 replication and circumvents its mutational escape through mismatch tolerance.

The recent dramatic appearance of variants of concern of SARS-coronavirus-2 (SARS-CoV-2) highlights the need for innovative approaches that simultaneously suppress viral replication and circumvent viral escape from host immunity and antiviral therapeutics. Here, we employ genome-wide computational prediction and single-nucleotide resolution screening to reprogram CRISPR-Cas13b against SARS-CoV-2 genomic and subgenomic RNAs. Reprogrammed Cas13b effectors targeting accessible regions of Spike and Nucleocapsid transcripts achieved >98% silencing efficiency in virus-free models. Further, optimized and multiplexed Cas13b CRISPR RNAs (crRNAs) suppress viral replication in mammalian cells infected with replication-competent SARS-CoV-2, including the recently emerging dominant variant of concern B.1.1.7. The comprehensive mutagenesis of guide-target interaction demonstrated that single-nucleotide mismatches does not impair the capacity of a potent single crRNA to simultaneously suppress ancestral and mutated SARS-CoV-2 strains in infected mammalian cells, including the Spike D614G mutant. The specificity, efficiency and rapid deployment properties of reprogrammed Cas13b described here provide a molecular blueprint for antiviral drug development to suppress and prevent a wide range of SARS-CoV-2 mutants, and is readily adaptable to other emerging pathogenic viruses.

Cytarabine-based induction immunochemotherapy in the front-line treatment of older patients with mantle cell lymphoma.

The role of cytarabine-based induction and autologous stem cell transplantation (ASCT) in front-line treatment of younger patients with mantle cell lymphoma (MCL) is well established, however the utility of intensive approaches in older patients remains unclear. This retrospective study compared first line treatment outcomes in patients aged 60 years or more, treated at six tertiary centres between 2000-2015. 70 patients included had a median age of 69 (60-91) and most (94%) demonstrated advanced stage disease. Treatment regimens included: R-CHOP-like (n = 39), alternating R-CHOP/R-DHAC (n = 10), R-HyperCVAD/R-MA (n = 7), R-CHOP/Cytarabine (Nordic Protocol) (n = 10) and other (n = 4). 16 patients underwent an ASCT. The median follow-up for surviving patients was 37 months. Compared to R-CHOP-like therapies, cytarabine-based regimens were associated with an improved overall response rate (ORR) of 70% vs 33% (p < 0.001) and overall survival (OS) (HR 0.541, [0.292-1.001], p = 0.05). No difference in efficacy between different cytarabine-based regimens was detected, but R-HyperCVAD/R-MA was associated with increased hospitalisation and transfusion requirements. Patients undergoing ASCT demonstrated an improved median OS (HR 0.108 [0.015-0.796], p = 0.029) but were significantly younger. These results reaffirm the use of cytarabine in MCL for selected patients aged over 60. Such regimens should be strongly considered for this population in frontline therapy.

Role of Conventional Karyotyping in Multiple Myeloma in the Era of Modern Treatment and FISH Analysis.

BACKGROUND: The Revised International Staging System (R-ISS) has been widely adopted to prognosticate multiple myeloma. As a result, the continued utility of conventional metaphase karyotyping has been called into question. PATIENTS AND METHODS: A multi-center study for newly diagnosed patients with multiple myeloma who received novel agent(s) at induction was conducted. Conventional metaphase karyotype information was categorized based on ploidy. We evaluated the impact of ploidy on overall survival (OS) including multivariate analysis, taking into account the R-ISS stages, transplant status, age, and novel agent(s) used at induction. We also evaluated if it is possible to identify high-risk (HR) patients with conventional karyotyping when a fluorescence in situ hybridization analysis is not available. Results were validated in an independent cohort. RESULTS: There were 308 patients evaluable. Ploidy significantly affected the OS of patients with R-ISS stage II, with non-hyperdiploid patients doing the worst. In the multivariate analysis, ploidy was significantly associated with OS. R-ISS stage II patients with or without non-hyperdiploid karyotype had significantly different survival. We replaced HR fluorescence in situ hybridization abnormalities with HR metaphase karyotypic abnormalities (non-hyperdiploid karyotype). When compared with R-ISS, there was a high level of concordance in HR patients identified using HR karyotypic abnormalities. These results were validated with an independent cohort of 375 patients. CONCLUSION: Conventional metaphase karyotyping is an independent prognostic factor even in the setting of R-ISS.

Atraumatic splenic rupture following IVIg for parvovirus B19 pure red cell aplasia post renal transplant.

Parvovirus B19 (PB19) associated pure red cell aplasia (PRCA) is an uncommon but well described complication of immunosuppression post solid organ transplantation. We report a unique case of a renal transplant patient with PB19 associated PRCA who developed a spontaneous splenic rupture after receiving IVIg for persistent anemia. He subsequently required splenectomy. Within the spleen we subsequently identified PB19 affected cells.

Mechanisms of Platelet Dysfunction in Patients with Implantable Devices.

As treatment options in modern medicine continue to expand, physicians globally have witnessed a veritable explosion in the utility of therapeutic devices. Particularly within the spheres of cardiology and critical care medicine, a plethora of devices are now available with an ever-increasing range of clinical indications. Additionally, the advent of transcatheter-mounted devices has enabled patients unsuitable for more invasive procedures to benefit from intervention, thereby greatly expanding the cohort of device-eligible patients. However, despite advances in design and materials, as well as pharmacological prophylaxis, hemostatic complications continue to plague device recipients, contributing to morbidity and mortality. Elucidating the complex interplay between components of the hemostatic system and cardiac devices has been the subject of much recent research, with greater focus on the coagulation cascade and device-induced perturbations. However, less is known about impact of mechanical surfaces on platelets and the resultant clinical complications, both hemorrhagic and thrombotic. This review will focus on exploring the pathobiology of platelet-surface interactions, contextualized within the wider hemostatic system, with a focus on the increasingly utilized technologies of transcatheter aortic-valve implantation, ventricular assist devices, and extracorporeal membrane oxygenation.

Rivaroxaban in treatment refractory heparin-induced thrombocytopenia.

Following orthopaedic surgery, a 56-year-old woman developed heparin-induced thrombocytopenia (HIT), complicated by extensive proximal deep vein thrombosis. The patient did not respond to multiple conventional therapies; however, a prompt treatment response occurred after starting rivaroxaban at standard dosing. This case represents the first documentation of efficacy for rivaroxaban in the setting of treatment refractory HIT and strengthens the limited existing evidence for this agent in HIT.

Estimation of central aortic blood pressure: a systematic meta-analysis of available techniques.

BACKGROUND: Central aortic blood pressure (cBP) is often promoted to be a superior predictor of cardiovascular risk compared to brachial blood pressure, and brachial-central pulse pressure amplification is also suggested as prognostic. Several devices and techniques, each purporting to estimate cBP, have entered commercial use. The interchangeability of cBP measurements between devices and the influence of disease states on central to brachial pulse pressure amplification remain unclear. The useful measurement of cBP in clinical trials is dependent on clarification of these issues. METHOD: We performed a systematic meta-analysis of studies reporting cBP between 2000 and 2012. Studies were included if both central and brachial SBPs (cSBP and bSBP) were reported. Studies were categorized by technique and according to the prevalent disease state with the bSBP - cSBP difference calculated. Random-effects modeling (inverse variance weighted approach) was used to estimate the pooled mean difference associated with each technique. RESULTS: Of the 164 eligible studies, the SphygmoCor device was most commonly reported (110 studies), with direct carotid applanation second-most utilized (31 studies). In 30 included invasive cohorts, the measured cSBP did not differ significantly from the oscillometric bSBP recorded [mean difference 4.19  mmHg, 95% confidence interval (CI) -4.13 to 12.51], whereas mean differences of 12.77  mmHg (95% CI 11.93, 13.60) and 8.83  mmHg (95% CI 7.86, 9.79) were obtained with the SphygmoCor and carotid applanation estimates of cSBP, respectively (both P < 0.05). Conversely, the reported mean cSBP-to-bSBP differences measured across various disease states with SphygmoCor did not differ significantly. CONCLUSION: This meta-analysis suggests that noninvasive cBP estimation is device/technique-dependent. Consequently, caution is advisable in applying these devices and techniques across clinical studies.

Radiation dose in 320-slice multidetector cardiac CT: a single center experience of evolving dose minimization.

BACKGROUND: Minimization of radiation exposure remains an important subject that occurs in parallel with advances in scanner technology. OBJECTIVE: We report our experience of evolving radiation dose and its determinants after the introduction of 320-multidetector row cardiac CT within a single tertiary cardiology referral service. METHODS: Four cohorts of consecutive patients (total 525 scans), who underwent cardiac CT at defined time points as early as 2008, are described. These include a cohort just after scanner installation, after 2 upgrades of the operating system, and after introduction of an adaptive iterative image reconstruction algorithm. The proportions of nondiagnostic coronary artery segments and studies with nondiagnostic segments were compared between cohorts. RESULTS: Significant reductions were observed in median radiation doses in all cohorts compared with the initial cohort (P < .001). Median dose-length product fell from 944 mGy · cm (interquartile range [IQR], 567.3-1426.5 mGy · cm) to 156 mGy · cm (IQR, 99.2-265.0 mGy · cm). Although the proportion of prospectively triggered scans has increased, reductions in radiation dose have occurred independently of distribution of scan formats. In multiple regression that combined all groups, determinants of dose-length product were tube output, the number of cardiac cycles scanned, tube voltage, scan length, scan format, body mass index, phase width, and heart rate (adjusted R(2) = 0.85, P < .001). The proportion of nondiagnostic coronary artery segments was slightly increased in group 4 (2.9%; P < .01). CONCLUSION: While maintaining diagnostic quality in 320-multidetector row cardiac CT, the radiation dose has decreased substantially because of a combination of dose-reduction protocols and technical improvements. Continued minimization of radiation dose will increase the potential for cardiac CT to expand as a cardiac imaging modality.

The effect of oral anticoagulation on the prevalence and management of haematuria in a contemporary Australian patient cohort.

OBJECTIVE: • To examine the effect of oral anticoagulation (OA) on the prevalence and inpatient management of haematuria in a contemporary Australian patient cohort. PATIENTS AND METHODS: • Patients across all inpatient units who had diagnosis-related group (DRG) coding for haematuria were identified from April 2010 to September 2011. • A retrospective chart review was performed to identify the type of anticoagulation (if any), requirement for bladder irrigation or blood transfusion, length of stay (LOS) and cause of haematuria. • Patients for whom the anticoagulation status was uncertain were excluded from analysis. • Statistical significance was determined by Pearson's chi-square tests and Student's t-tests. RESULTS: • In all, 335 admissions with DRG coding for haematuria were identified from hospital records, of which 268 admissions had clear documentation of anticoagulation. There were 118 emergency admissions and 150 elective admissions for day case cystoscopy. The mean age of the patients was 66 years and the male:female ratio was 5:1. In all, 123 admissions were for patients on some form of anticoagulation (46%). • Patients were on anticoagulation in 53% of the 118 emergency admissions for gross haematuria. These comprised patients on aspirin (28%), clopidogrel (4%), warfarin (10%), combined aspirin and warfarin (1%) and combined aspirin and clopidogrel (10%). • The use of OA was a significant predictor of the need for intervention among the 118 emergency admissions (86% vs 62%, P = 0.003). • In particular, dual antiplatelet therapy in the form of aspirin and clopidogrel was associated with an increased requirement for bladder irrigation (92%) when compared with patients on other forms of anticoagulation (84%) or none at all (62%, P = 0.01). • The mean LOS for patients admitted to hospital with haematuria was 5.6 days. Patients on warfarin had a statistically significant longer LOS than the other groups (13.7 vs 4.5 days, P < 0.001). A cause for haematuria was identified in 120 of the 234 patients (51%). Of these, the most common was benign prostatic hyperplasia (21%), followed by bladder urothelial carcinoma (17%). CONCLUSION: • In our cohort of patients, about half of all admissions with haematuria were for patients on some form of OA. • OA use increased the need for intervention, especially for patients on dual antiplatelet therapy.