Chemical optimization of siRNA for safe and efficient silencing of placental sFLT1

Targeted lipid nanoparticles to prevent trans-placental passage in the ex vivo human placental cotyledon perfusion model

Medication use during pregnancy poses risks to both the mother and the fetus. These risks include an elevated potential for fetotoxicity due to placental drug transport. Nanomedicines offer a promising solution by potentially preventing trans-placental passage. Targeted nanomedicines could enhance safety and efficacy in treating maternal or placental pathophysiology. Our study investigates placental transfer kinetics of targeted lipid nanoparticles (LNPs) in an ex vivo human placenta cotyledon perfusion model. We collected human placentas for dual-side ex vivo placental perfusions. Targeted LNPs with a fluorescence tag were introduced into the maternal circuit of each placenta. To establish if there was trans-placental passage of LNPs to the fetal circuit, we collected samples from maternal and fetal circuits throughout the six hours of the perfusion. We determined the fluorescence signal using a multi-mode microplate reader and Multiphoton microscopy to localize the LNPs in the placenta tissue. Data from perfused placenta tissue showed no significant transfer of the fluorescently labeled LNPs across the placental barrier to the fetal circuit. Localization of targeted LNPs in tissue samples is mainly observed in the maternal blood space of the placenta. Our results suggest that targeted LNPs present a promising strategic approach to prevent trans-placental passage to the fetus. Our future perspectives involve investigating the efficacy of targeted LNPs as well as loading targeted LNPs with nucleic acid-based therapeutics to investigate their therapeutic potential.

Heme oxygenase/carbon monoxide system affects the placenta and preeclampsia

Preeclampsia affects 2% to 8% of pregnancies worldwide and results in significantly high maternal and perinatal morbidity and mortality, with delivery being the only definitive treatment. It is not a single disorder, but rather a manifestation of an insult(s) to the uteroplacental unit -whether maternal, fetal, and/or placental. Multiple etiologies have been implicated, including uteroplacental ischemia, maternal infection and/or inflammation, maternal obesity, sleep disorders, hydatidiform mole, maternal intestinal dysbiosis, autoimmune disorders, fetal diseases, breakdown of maternal-fetal immune tolerance, placental aging, and endocrine disorders. Early- and late-onset preeclampsia are associated with different etiologies: early-onset preeclampsia develops because of poor placentation, while late-onset preeclampsia occurs in women with latent maternal endothelial dysfunction. In preeclamptic placentas, acquired, genetic, and immune risk factors may result in impaired trophoblast invasion and spiral artery remodeling, which affects uteroplacental perfusion. The resulting placental hypoxia affects the heme oxygenase system-a known stress response pathway affected by hypoxia that is important during normal pregnancy and may offer a therapeutic approach in preeclampsia. This review will address the effect of the heme oxygenase/carbon monoxide system on the placenta and preeclampsia.

Single-dose administration of therapeutic divalent siRNA targeting MECP2 prevents lethality for one year in an MECP2 duplication mouse model

MECP2 duplication syndrome (MDS) is a rare X-linked neurodevelopmental disorder caused by duplications of the dosage-sensitive methyl-CpG-binding protein 2 (MECP2) gene. Developing effective therapies for MDS is particularly challenging due to the variability in MECP2 expression among patients and the potential risk of inducing Rett syndrome through excessive pharmacological intervention. Reducing dosage to optimize silencing levels often compromises durability and necessitates increased dosing frequency. We present here a series of fully chemically modified small interfering RNAs (siRNAs) designed for both isoform-selective and total MECP2 silencing. Among these, we identify six lead siRNA candidates across two distinct chemical scaffolds, achieving targeted total MECP2 expression reductions ranging from 25% to 75%, sustained for at least four months following a single administration. The efficacy and safety of human ortholog silencing were evaluated using two mouse models with distinct levels of human MECP2 transgene expression. In the severe duplication model, a single dose of the total isoform-silencing siRNA fully rescued early mortality and behavioral impairments. Additionally, we show that the isoform-selective targeting strategy may be safer in mild cases of MDS where exaggerated pharmacology may lead to Rett Syndrome. Overall, this study introduces a series of preclinical candidates with the capacity to address the varying levels of MECP2 duplication encountered in clinical settings. Furthermore, it establishes a target selection strategy that may be applied to other dosage-sensitive gene imbalances.

Unveiling sequence-agnostic mixed-chemical modification patterns for splice-switching oligonucleotides using the NATURA platform

Chemical optimization of ribose has significantly advanced nucleic acid therapeutics (NATs) by improving the stability, specificity, and safety of therapies like small interfering RNAs, CRISPR-Cas9 guide RNAs, and GAPmers. Recent research has extended this approach to splice-switching oligonucleotides (SSOs), which target splicing events. Our study identifies a set of mixed-modification patterns-combining 2'-O-Methyl, 2'-MethOxyEthyl, 2'-Locked Nucleic Acid, and 2'-Constrained Ethyl ribose moieties (2'OMe, 2'MOE, LNA, and cET)-that enhance SSO potency. We term this strategy lateral mixed positional configuration, which improves SSO efficacy across various sequences and could reduce the trial-and-error process in SSO development. This advancement is supported by NAT Unlabeled Reporter Assay (NATURA), a novel platform for high-throughput quantification of NATs' functional delivery and potency. NATURA uses a reporter gene system and a comprehensive sequence library to test modifications and delivery methods, validated in a transgenic mouse model. This approach aims to accelerate NAT development and address challenges in delivering these therapies to patients.

To conjugate or not to conjugate? evaluating the potential use of cell-penetrating peptides for conjugation or complexation with oligonucleotides by surface plasmon resonance

Oligonucleotides represent a class of molecules that exhibit remarkable therapeutic potential due to their unparalleled target specificity, yet they suffer from limited cellular uptake and lack of tissue selectivity. Extensive research is conducted with cell-penetrating peptides (CPPs) as delivery excipients due to their ability to translocate across cellular membranes and deliver cargo into cells. This study aims to investigate an innovative approach to rapidly, and with small amounts of compound, analyze and compare complexation of CPPs to oligonucleotides. The study applies surface plasmon resonance (SPR) to evaluate a comprehensive library of CPPs regarding their interaction with a double-stranded oligonucleotide to assess their potential as complexing molecules or whether the CPP should be chemically linked to the negatively charged oligonucleotide to ensure proximity. Specifically, a small interfering RNA (siRNA) was immobilized on a biotinylated chip, and solutions of 66 CPPs were subsequently injected to determine their binding stoichiometry with the siRNA. The most influential molecular properties of the CPPs were determined to be the positive charge-to-length ratio, the total number of positive charges, and the overall hydrophobicity of the CPP. These findings demonstrate the effectiveness and utility of SPR as a high throughput screening tool for selecting peptide/oligonucleotide pairs intended for complexation or conjugation.

The absorption, distribution, metabolism and elimination characteristics of small interfering RNA therapeutics and the opportunity to predict disposition in pregnant women

Small interfering RNA (siRNA) therapeutics represent an emerging class of pharmacotherapy with the potential to address previously hard-to-treat diseases. Currently approved siRNA therapeutics include lipid nanoparticle-encapsulated siRNA and tri-N-acetylated galactosamine-conjugated siRNA. These siRNA therapeutics exhibit distinct pharmacokinetic characteristics and unique absorption, distribution, metabolism, and elimination (ADME) properties. As a new drug modality, limited clinical data are available for siRNA therapeutics in specific populations, including pediatrics, geriatrics, individuals with renal or hepatic impairment, and pregnant women, making dosing challenging. In this Minireview, a mechanistic overview of the ADME properties of the 5 currently approved siRNA therapeutics is presented. A concise overview of the clinical data available for therapeutic siRNAs in special populations, focusing on the potential impact of physiologic changes during pregnancy on siRNA disposition, is provided. The utility of physiologically based pharmacokinetic (PBPK) modeling as a tool to elucidate the characteristics and disposition of siRNA therapeutics in pregnant women is explored. Additionally, opportunities to integrate known physiologic alterations induced by pregnancy into PBPK models that incorporate siRNA ADME mechanisms to predict the effects of pregnancy on siRNA disposition are discussed. Clinical data regarding the use of therapeutic siRNA in special populations remain limited. Data for precise parameterization of maternal-fetal siRNA PBPK models are lacking presently and underscore the need for further research in this area. Addressing this gap in knowledge will not only enhance our understanding of siRNA pharmacokinetics during pregnancy but also advance the possible development of siRNA therapeutics to treat pregnancy-related conditions. SIGNIFICANCE STATEMENT: This Minireview proposes a framework on how small interfering RNA (siRNA) disposition can be predicted in pregnancy based on mechanistic absorption, distribution, metabolism, and elimination (ADME) information using physiologically-based pharmacokinetic (PBPK) modeling. The mechanistic ADME information and available clinical data in special populations of currently Food and Drug Administration-approved siRNA therapeutics are summarized. Additionally, how physiological changes during pregnancy may affect siRNA disposition is reviewed, and the opportunities to use PBPK modeling to predict siRNA disposition in pregnant women is explored.

Gene therapy in preeclampsia: the dawn of a new era

Preeclampsia is a severe complication of pregnancy, affecting an estimated 4 million women annually. It is one of the leading causes of maternal and fetal mortality worldwide, and it has life-long consequences. The maternal multisystemic symptoms are driven by poor placentation, which causes syncytiotrophoblastic stress and the release of factors into the maternal bloodstream. Amongst them, the soluble fms-like tyrosine kinase-1 (sFLT-1) triggers extensive endothelial dysfunction by acting as a decoy receptor for the vascular endothelial growth factor (VEGF) and the placental growth factor (PGF). Current interventions aim to mitigate hypertension and seizures, but the only definite treatment remains induced delivery. Thus, there is a pressing need for novel therapies to remedy this situation. Notably, CBP-4888, a siRNA drug delivered subcutaneously to knock down sFLT1 expression in the placenta, has recently obtained Fast Track approval from the Food and Drug Administration (FDA) and is undergoing a phase 1 clinical trial. Such advance highlights a growing interest and significant potential in gene therapy to manage preeclampsia. This review summarizes the advances and prospects of gene therapy in treating placental dysfunction and illustrates crucial challenges and considerations for these emerging treatments.

Non-Viral RNA Delivery During Pregnancy: Opportunities and Challenges

During pregnancy, the risk of maternal and fetal adversities increases due to physiological changes, genetic predispositions, environmental factors, and infections. Unfortunately, treatment options are severely limited because many essential interventions are unsafe, inaccessible, or lacking in sufficient scientific data to support their use. One potential solution to this challenge may lie in emerging RNA therapeutics for gene therapy, protein replacement, maternal vaccination, fetal gene editing, and other prenatal treatment applications. In this review, the current landscape of RNA platforms and non-viral RNA delivery technologies that are under active development for administration during pregnancy is explored. Advancements of pregnancy-specific RNA drugs against SARS-CoV-2, Zika, influenza, preeclampsia, and for in-utero gene editing are discussed. Finally, this study highlights bottlenecks that are impeding translation efforts of RNA therapies, including the lack of accurate cell-based and animal models of human pregnancy and concerns related to toxicity and immunogenicity during pregnancy. Overcoming these challenges will facilitate the rapid development of this new class of pregnancy-safe drugs.

Placental Drug Delivery to Treat Pre-Eclampsia and Fetal Growth Restriction

Pre-eclampsia and fetal growth restriction (FGR) continue to cause unacceptably high levels of morbidity and mortality, despite significant pharmaceutical and technological advances in other disease areas. The recent pandemic has also impacted obstetric care, as COVID-19 infection increases the risk of poor pregnancy outcomes. This review explores the reasons why it lacks effective drug treatments for the placental dysfunction that underlies many common obstetric conditions and describes how nanomedicines and targeted drug delivery approaches may provide the solution to the current drug drought. The ever-increasing range of biocompatible nanoparticle formulations available is now making it possible to selectively deliver drugs to uterine and placental tissues and dramatically limit fetal drug transfer. Formulations that are refractory to placental uptake offer the possibility of retaining drugs within the maternal circulation, allowing pregnant individuals to take medicines previously considered too harmful to the developing baby. Liposomes, ionizable lipid nanoparticles, polymeric nanoparticles, and adenoviral vectors have all been used to create efficacious drug delivery systems for use in pregnancy, although each approach offers distinct advantages and limitations. It is imperative that recent advances continue to be built upon and that there is an overdue investment of intellectual and financial capital in this field.

Near Sequence Homology Does Not Guarantee siRNA Cross-Species Efficacy

Small interfering RNAs (siRNAs) represent a novel class of drugs capable of potent and sustained modulation of genes across various tissues. Preclinical development of siRNAs necessitates assessing efficacy and toxicity in animal models. While identifying therapeutic leads with cross-species activity can expedite development, it may compromise efficacy and be infeasible for certain gene targets. Here, we investigate whether deriving species-active siRNAs from potent human-targeting leads-an approach termed mismatch conversion-can yield potent compounds. We systematically altered potent siRNAs targeting human genes associated with diseases-SOD1 (ALS), JAK1 (inflammation), and HTT (HD)-to generate species-matching variants with full complementarity to their target in NHPs, mice, rats, sheep, and dogs. Variants potency and efficacy were measured in corresponding cell lines. We demonstrate that sequence, position, and number of mismatches significantly influence the ability to generate potent species-active compounds via mismatch conversion. Across tested sequences, mismatch conversion strategy ability to identify a species-active lead varied from 0% to 70%. For SOD1, lead compounds identified from species-focus screening in mouse and dog cells were more potent than leads obtained from mismatch conversion. Thus, a focused screening of therapeutic lead and model compounds may represent a more reliable strategy for the clinical advancement of siRNAs.

Protein isoform-centric therapeutics: expanding targets and increasing specificity

Most protein-coding genes produce multiple protein isoforms; however, these isoforms are commonly neglected in drug discovery. The expression of protein isoforms can be specific to a disease, tissue and/or developmental stage, and this specific expression can be harnessed to achieve greater drug specificity than pan-targeting of all gene products and to enable improved treatments for diseases caused by aberrant protein isoform production. In recent years, several protein isoform-centric therapeutics have been developed. Here, we collate these studies and clinical trials to highlight three distinct but overlapping modes of action for protein isoform-centric drugs: isoform switching, isoform introduction or depletion, and modulation of isoform activity. In addition, we discuss how protein isoforms can be used clinically as targets for cell type-specific drug delivery and immunotherapy, diagnostic biomarkers and sources of cancer neoantigens. Collectively, we emphasize the value of a focus on isoforms as a route to discovering drugs with greater specificity and fewer adverse effects. This approach could enable the targeting of proteins for which pan-inhibition of all isoforms is toxic and poorly tolerated.

Identification of selective and non-selective C9ORF72 targeting in vivo active siRNAs

A hexanucleotide (G4C2) repeat expansion (HRE) within intron one of C9ORF72 is the leading genetic cause of amyotrophic lateral sclerosis (ALS) and frontotemporal dementia (FTD). C9ORF72 haploinsufficiency, formation of RNA foci, and production of dipeptide repeat (DPR) proteins have been proposed as mechanisms of disease. Here, we report the first example of disease-modifying siRNAs for C9ORF72 driven ALS/FTD. Using a combination of reporter assay and primary cortical neurons derived from a C9-ALS/FTD mouse model, we screened a panel of more than 150 fully chemically stabilized siRNAs targeting different C9ORF72 transcriptional variants. We demonstrate the lack of correlation between siRNA efficacy in reporter assay versus native environment; repeat-containing C9ORF72 mRNA variants are found to preferentially localize to the nucleus, and thus C9ORF72 mRNA accessibility and intracellular localization have a dominant impact on functional RNAi. Using a C9-ALS/FTD mouse model, we demonstrate that divalent siRNAs targeting C9ORF72 mRNA variants specifically or non-selectively reduce the expression of C9ORF72 mRNA and significantly reduce DPR proteins. Interestingly, siRNA silencing all C9ORF72 mRNA transcripts was more effective in removing intranuclear mRNA aggregates than targeting only HRE-containing C9ORF72 mRNA transcripts. Combined, these data support RNAi-based degradation of C9ORF72 as a potential therapeutic paradigm.

Pharmacotherapeutic options for the treatment of hypertension in pregnancy

INTRODUCTION

Hypertensive disorders of pregnancy affect approximately one in 10 pregnancies and are associated with increased risk of adverse fetal, neonatal and maternal outcomes. There is strong evidence that effective treatment of hypertension (blood pressure ≥ 140/90 mmHg), and enhanced monitoring throughout pregnancy reduces these risks.

AREAS COVERED

This article provides a contemporaneous review of treatment of hypertension in pregnancy with antihypertensive agents. We completed a systematic search and review of all meta-analyses and systematic reviews of studies comparing antihypertensives for treatment of pregnancy hypertension in the last five years. We provide a clinically focused summary of when to treat hypertension in pregnancy and which antihypertensive agents can be offered. Special scenarios reviewed include treatment-resistant hypertension and pre-pregnancy antihypertensive optimization.

EXPERT OPINION

Several antihypertensives are considered safe and are known to be effective for treatment of hypertension in pregnancy. Given the current uncertainty as to which antihypertensive(s) are superior for treatment of hypertension in pregnancy, women should be counselled and offered a range of antihypertensive options in keeping with evidence on clinical effectiveness, local context and availability of antihypertensive(s), potential side effect profile, and women's preference. Further research is required to help guide clinical decision making, and move toward personalized treatment.

Principle, application and challenges of development siRNA-based therapeutics against bacterial and viral infections: a comprehensive review

While significant progress has been made in understanding and applying gene silencing mechanisms and the treatment of human diseases, there have been still several obstacles in therapeutic use. For the first time, ONPATTRO, as the first small interfering RNA (siRNA) based drug was invented in 2018 for treatment of hTTR with polyneuropathy. Additionally, four other siRNA based drugs naming Givosiran, Inclisiran, Lumasiran, and Vutrisiran have been approved by the US Food and Drug Administration and the European Medicines Agency for clinical use by hitherto. In this review, we have discussed the key and promising advances in the development of siRNA-based drugs in preclinical and clinical stages, the impact of these molecules in bacterial and viral infection diseases, delivery system issues, the impact of administration methods, limitations of siRNA application and how to overcome them and a glimpse into future developments.

Phosphatidylcholine head group chemistry alters the extrahepatic accumulation of lipid-conjugated siRNA

Small interfering RNAs (siRNAs) are revolutionizing the treatment of liver-associated indications. Yet, robust delivery to extrahepatic tissues remains a challenge. Conjugating lipids (e.g., docosanoic acid [DCA]) to siRNA supports extrahepatic delivery, but tissue accumulation remains lower than that achieved in liver by approved siRNA therapeutics. Early evidence suggests that functionalizing DCA with a head group (e.g., phosphatidylcholine [PC]) may enhance delivery to certain tissues. Here, we report the first systematic evaluation of the effect of PC head group chemistry on the extrahepatic distribution of DCA-conjugated siRNAs. We show that functionalizing DCA with a PC head group enhances siRNA accumulation in heart, muscle, lung, pancreas, duodenum, urinary bladder, and fat. Varying the size of the linker between the phosphate and choline moiety of the PC head group altered the extrahepatic accumulation of siRNA, with the optimal linker length being different for different tissues. Increasing PC head group valency also improved extrahepatic accumulation in a tissue-specific manner. This study demonstrates the structural impact of the PC moiety on the biodistribution of lipid-conjugated siRNA and introduces multiple novel PC variants for the chemical optimization of DCA-conjugated siRNA. These chemical variants can be used in the context of other lipids to increase the repertoire of conjugates for the extrahepatic distribution of siRNAs.

RNAi-based drug design: considerations and future directions

More than 25 years after its discovery, the post-transcriptional gene regulation mechanism termed RNAi is now transforming pharmaceutical development, proved by the recent FDA approval of multiple small interfering RNA (siRNA) drugs that target the liver. Synthetic siRNAs that trigger RNAi have the potential to specifically silence virtually any therapeutic target with unprecedented potency and durability. Bringing this innovative class of medicines to patients, however, has been riddled with substantial challenges, with delivery issues at the forefront. Several classes of siRNA drug are under clinical evaluation, but their utility in treating extrahepatic diseases remains limited, demanding continued innovation. In this Review, we discuss principal considerations and future directions in the design of therapeutic siRNAs, with a particular emphasis on chemistry, the application of informatics, delivery strategies and the importance of careful target selection, which together influence therapeutic success.

Chemical modification patterns for microRNA therapeutic mimics: a structure-activity relationship (SAR) case-study on miR-200c

microRNA (miRNA) mimics are an emerging class of oligonucleotide therapeutics, with a few compounds already in clinical stages. Synthetic miRNAs are able to restore downregulated levels of intrinsic miRNAs, allowing for parallel regulation of multiple genes involved in a particular disease. In this work, we examined the influence of chemical modifications patterns in miR-200c mimics, assessing the regulation of a selection of target messenger RNAs (mRNA) and, subsequently, of the whole transcriptome in A549 cells. We have probed 37 mimics and provided an initial set of instructions for designing miRNA mimics with potency and selectivity similar to an unmodified miRNA duplex. Additionally, we have examined the stability of selected mimics in serum. Finally, the selected two modification patterns were translated to two other miRNAs, miR-34a and miR-155. To differing degrees, these designs acted on target mRNAs in a similar manner to the unmodified mimic. Here, for the first time, we describe a structured overview of 'miRNA mimics modification templates' that are chemically stabilised and optimised for use in an in vitro set up and highlight the need of further sequence specific optimization when mimics are to be used beyond in vitro tool experiments.

Angiogenic Biomarkers in Preeclampsia

Preeclampsia contributes disproportionately to maternal and neonatal morbidity and mortality throughout the world. A critical driver of preeclampsia is angiogenic imbalance, which is often present weeks to months before overt disease. Two placenta-derived angiogenic biomarkers, soluble fms-like tyrosine kinase 1 (sFlt-1) and placental growth factor (PlGF), have proved useful as diagnostic and prognostic tests for preeclampsia. Recently, the U.S. Food and Drug Administration approved the sFlt-1/PlGF assay to aid in the prediction of preeclampsia with severe features among women with hypertensive disorders of pregnancy at 24-34 weeks of gestation. In this narrative review, we summarize the body of work leading to this approval and describe how the sFlt-1/PlGF ratio may be implemented in clinical practice as an adjunctive measure to help optimize care and to reduce adverse outcomes in preeclampsia.

Nucleic Acid Therapeutics: Successes, Milestones, and Upcoming Innovation

Nucleic acid-based therapies have become the third major drug class after small molecules and antibodies. The role of nucleic acid-based therapies has been strengthened by recent regulatory approvals and tremendous clinical success. In this review, we look at the major obstacles that have hindered the field, the historical milestones that have been achieved, and what is yet to be resolved and anticipated soon. This review provides a view of the key innovations that are expanding nucleic acid capabilities, setting the stage for the future of nucleic acid therapeutics.

Abideen M, Monopoli KR, Blanchard C, Bouix-Peter C, Portal T, Harris JE, Khvorova A, Alterman JF. Multispecies-targeting siRNAs for the modulation of JAK1 in the skin

Identifying therapeutic oligonucleotides that are cross-reactive to experimental animal species can dramatically accelerate the process of preclinical development and clinical translation. Here, we identify fully chemically-modified small interfering RNAs (siRNAs) that are cross-reactive to Janus kinase 1 (JAK1) in humans and a large variety of other species. We validated the identified siRNAs in silencing JAK1 in cell lines and skin tissues of multiple species. JAK1 is one of the four members of the JAK family of tyrosine kinases that mediate the signaling transduction of many inflammatory cytokine pathways. Dysregulation of these pathways is often involved in the pathogenesis of various immune disorders, and modulation of JAK family enzymes is an effective strategy in the clinic. Thus, this work may open up unprecedented opportunities for evaluating the modulation of JAK1 in many animal models of human inflammatory skin diseases. Further chemical engineering of the optimized JAK1 siRNAs may expand the utility of these compounds for treating immune disorders in additional tissues.

Translation of mechanistic advances in preeclampsia to the clinic: Long and winding road

As one of the leading causes of premature birth and maternal and infant mortality worldwide, preeclampsia remains a major unmet public health challenge. Preeclampsia and related hypertensive disorders of pregnancy are estimated to cause >75 000 maternal and 500 000 infant deaths globally each year. Because of rising rates of risk factors such as obesity, in vitro fertilization and advanced maternal age, the incidence of preeclampsia is going up with rates ranging from 5% to 10% of all pregnancies worldwide. A major discovery in the field was the realization that the clinical phenotypes related to preeclampsia, such as hypertension, proteinuria, and other adverse maternal/fetal events, are due to excess circulating soluble fms-like tyrosine kinase-1 (sFlt-1, also referred to as sVEGFR-1). sFlt-1 is an endogenous anti-angiogenic protein that is made by the placenta and acts by neutralizing the pro-angiogenic proteins vascular endothelial growth factor (VEGF) and placental growth factor (PlGF). During the last decade, this work has spawned a new era of molecular diagnostics for early detection of this condition. Antagonizing sFlt-1 either by reducing production or blocking its actions has shown salutary effects in animal models. Further, in early-stage human studies, the therapeutic removal of sFlt-1 from maternal circulation has shown promise in delaying disease progression and improving outcomes. Recently, the FDA approved the first molecular test for preterm preeclampsia (sFlt-1/PlGF ratio) for clinical use in the United States. Measuring serum sFlt-1/PlGF ratio in the acute hospital setting may aid short-term management, particularly regarding step-up or step-down of care, decision to transfer to settings better equipped to manage both the mother and the preterm neonate, appropriate timing of administration of steroids and magnesium sulfate, and in expectant management decisions. The test itself has the potential to save lives. Furthermore, the availability of a molecular test that correlates with adverse outcomes has set the stage for interventional clinical trials testing treatments for this disorder. In this review, we will discuss the role of circulating sFlt-1 and related factors in the pathogenesis of preeclampsia and specifically how this discovery is leading to concrete advances in the care of women with preeclampsia.

Cholesterol Conjugates of Small Interfering RNA: Linkers and Patterns of Modification

Cholesterol siRNA conjugates attract attention because they allow the delivery of siRNA into cells without the use of transfection agents. In this study, we compared the efficacy and duration of silencing induced by cholesterol conjugates of selectively and totally modified siRNAs and their heteroduplexes of the same sequence and explored the impact of linker length between the 3' end of the sense strand of siRNA and cholesterol on the silencing activity of "light" and "heavy" modified siRNAs. All 3'-cholesterol conjugates were equally active under transfection, but the conjugate with a C3 linker was less active than those with longer linkers (C8 and C15) in a carrier-free mode. At the same time, they were significantly inferior in activity to the 5'-cholesterol conjugate. Shortening the sense strand carrying cholesterol by two nucleotides from the 3'-end did not have a significant effect on the activity of the conjugate. Replacing the antisense strand or both strands with fully modified ones had a significant effect on silencing as well as improving the duration in transfection-mediated and carrier-free modes. A significant 78% suppression of MDR1 gene expression in KB-8-5 xenograft tumors developed in mice promises an advantage from the use of fully modified siRNA cholesterol conjugates in combination chemotherapy.

Targeting RNA with synthetic oligonucleotides: Clinical success invites new challenges

Synthetic antisense oligonucleotides (ASOs) and duplex RNAs (dsRNAs) are an increasingly successful strategy for drug development. After a slow start, the pace of success has accelerated since the approval of Spinraza (nusinersen) in 2016 with several drug approvals. These accomplishments have been achieved even though oligonucleotides are large, negatively charged, and have little resemblance to traditional small-molecule drugs-a remarkable achievement of basic and applied science. The goal of this review is to summarize the foundation underlying recent progress and describe ongoing research programs that may increase the scope and impact of oligonucleotide therapeutics.

Dendritic amphiphilic siRNA: Selective albumin binding, in vivo efficacy, and low toxicity

Although an increasing number of small interfering RNA (siRNA) therapies are reaching the market, the challenge of efficient extra-hepatic delivery continues to limit their full therapeutic potential. Drug delivery vehicles and hydrophobic conjugates are being used to overcome the delivery bottleneck. Previously, we reported a novel dendritic conjugate that can be appended efficiently to oligonucleotides, allowing them to bind albumin with nanomolar affinity. Here, we explore the ability of this novel albumin-binding conjugate to improve the delivery of siRNA in vivo. We demonstrate that the conjugate binds albumin exclusively in circulation and extravasates to various organs, enabling effective gene silencing. Notably, we show that the conjugate achieves a balance between hydrophobicity and safety, as it significantly reduces the side effects associated with siRNA interactions with blood components, which are commonly observed in some hydrophobically conjugated siRNAs. In addition, it reduces siRNA monocyte uptake, which may lead to cytokine/inflammatory responses. This work showcases the potential of using this dendritic conjugate as a selective albumin binding handle for the effective and safe delivery of nucleic acid therapeutics. We envision that these properties may pave the way for new opportunities to overcome delivery hurdles of oligonucleotides in future applications.

Cholesterol-Conjugated Supramolecular Multimeric siRNAs: Effect of siRNA Length on Accumulation and Silencing In Vitro and In Vivo

Conjugation of small interfering RNA (siRNA) with lipophilic molecules is one of the most promising approaches for delivering siRNA in vivo. The rate of molecular weight-dependent siRNA renal clearance is critical for the efficiency of this process. In this study, we prepared cholesterol-containing supramolecular complexes containing from three to eight antisense strands and examined their accumulation and silencing activity in vitro and in vivo. We have shown for the first time that such complexes with 2'F, 2'OMe, and LNA modifications exhibit interfering activity both in carrier-mediated and carrier-free modes. Silencing data from a xenograft tumor model show that 4 days after intravenous injection of cholesterol-containing monomers and supramolecular trimers, the levels of MDR1 mRNA in the tumor decreased by 85% and 68%, respectively. The in vivo accumulation data demonstrated that the formation of supramolecular structures with three or four antisense strands enhanced their accumulation in the liver. After addition of two PS modifications at the ends of antisense strands, 47% and 67% reductions of Ttr mRNA levels in the liver tissue were detected 7 days after administration of monomers and supramolecular trimers, respectively. Thus, we have obtained a new type of RNAi inducer that is convenient for synthesis and provides opportunities for modifications.

Rational design of a JAK1-selective siRNA inhibitor for the modulation of autoimmunity in the skin

Inhibition of Janus kinase (JAK) family enzymes is a popular strategy for treating inflammatory and autoimmune skin diseases. In the clinic, small molecule JAK inhibitors show distinct efficacy and safety profiles, likely reflecting variable selectivity for JAK subtypes. Absolute JAK subtype selectivity has not yet been achieved. Here, we rationally design small interfering RNAs (siRNAs) that offer sequence-specific gene silencing of JAK1, narrowing the spectrum of action on JAK-dependent cytokine signaling to maintain efficacy and improve safety. Our fully chemically modified siRNA supports efficient silencing of JAK1 expression in human skin explant and modulation of JAK1-dependent inflammatory signaling. A single injection into mouse skin enables five weeks of duration of effect. In a mouse model of vitiligo, local administration of the JAK1 siRNA significantly reduces skin infiltration of autoreactive CD8+ T cells and prevents epidermal depigmentation. This work establishes a path toward siRNA treatments as a new class of therapeutic modality for inflammatory and autoimmune skin diseases.

RNA-based medicine: from molecular mechanisms to therapy

RNA-based therapeutics have the potential to revolutionize the treatment and prevention of human diseases. While early research faced setbacks, it established the basis for breakthroughs in RNA-based drug design that culminated in the extraordinarily fast development of mRNA vaccines to combat the COVID-19 pandemic. We have now reached a pivotal moment where RNA medicines are poised to make a broad impact in the clinic. In this review, we present an overview of different RNA-based strategies to generate novel therapeutics, including antisense and RNAi-based mechanisms, mRNA-based approaches, and CRISPR-Cas-mediated genome editing. Using three rare genetic diseases as examples, we highlight the opportunities, but also the challenges to wide-ranging applications of this class of drugs.

Current Strategies for Exosome Cargo Loading and Targeting Delivery

Extracellular vesicles (EVs) such as ectosomes and exosomes have gained attention as promising natural carriers for drug delivery. Exosomes, which range from 30 to 100 nm in diameter, possess a lipid bilayer and are secreted by various cells. Due to their high biocompatibility, stability, and low immunogenicity, exosomes are favored as cargo carriers. The lipid bilayer membrane of exosomes also offers protection against cargo degradation, making them a desirable candidate for drug delivery. However, loading cargo into exosomes remains to be a challenge. Despite various strategies such as incubation, electroporation, sonication, extrusion, freeze-thaw cycling, and transfection that have been developed to facilitate cargo loading, inadequate efficiency still persists. This review offers an overview of current cargo delivery strategies using exosomes and summarizes recent approaches for loading small-molecule, nucleic acid, and protein drugs into exosomes. With insights from these studies, we provide ideas for more efficient and effective delivery of drug molecules by using exosomes.

Novel therapeutic and diagnostic approaches for preeclampsia

PURPOSE OF REVIEW

This review will summarize recent findings relating to the diagnostic approach to preeclampsia and current avenues of research aimed at modifying the underlying disease process.

RECENT FINDINGS

Growing international consensus supports a broad preeclampsia definition that incorporates maternal end-organ and uteroplacental dysfunction. Recent evidence demonstrates that this definition better identifies women and babies at risk of adverse outcomes compared to the traditional definition of hypertension and proteinuria. Multiple studies have demonstrated the usefulness and cost-effectiveness of angiogenic biomarkers such as soluble fms-like tyrosine kinase-1 and placental growth factor as a clinical adjunct to diagnose and predict severity of preeclampsia associated outcomes. Current novel therapeutic approaches to preeclampsia target pathogenic pathways (e.g. antiangiogenesis) or downstream effects such as oxidative stress and nitric oxide. Recent findings relating to these promising candidates are discussed. Multicenter clinical trials are needed to evaluate their effectiveness and ability to improve fetal and maternal outcomes.

SUMMARY

We provide an updated framework of the current approaches to define and diagnose preeclampsia. Disease modifying therapies (in particular, targeting the angiogenic pathway) are being developed for the first time and promise to revolutionize the way we manage preeclampsia.

Structural Modifications of siRNA Improve Its Performance In Vivo

The use of small interfering RNA (siRNA) in the clinic gives a wide range of possibilities for the treatment of previously incurable diseases. However, the main limitation for biomedical applications is their delivery to target cells and organs. Currently, delivery of siRNA to liver cells is a solved problem due to the bioconjugation of siRNA with N-acetylgalactosamine; other organs remain challenging for siRNA delivery to them. Despite the important role of the ligand in the composition of the bioconjugate, the structure and molecular weight of siRNA also play an important role in the delivery of siRNA. The basic principle is that siRNAs with smaller molecular weights are more efficient at entering cells, whereas siRNAs with larger molecular weights have advantages at the organism level. Here we review the relationships between siRNA structure and its biodistribution and activity to find new strategies for improving siRNA performance.