Clinical pharmacology of siRNA therapeutics: current status and future prospects

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.

Baculovirus Expressing Tumor Growth Factor-β1 (TGFβ1) Nanoshuttle Augments Therapeutic Effects for Vascular Wound Healing: Design and In Vitro Analysis

One of the major challenges in vascular tissue regeneration is effective wound healing that can be resolved by an innovative targeted nanoshuttle that delivers growth factors to blood vessels. This study investigates the production and efficacy of transforming growth factor-β1 (TGFβ1) gene delivery using poly(lactic-co-glycolic acid) (PLGA) baculovirus (BV) nanoshuttles (NSs). They exhibited an encapsulation efficiency of 86.23% ± 0.65% and a negative zeta potential of -29.57 ± 1.27 mV. In vitro studies in human umbilical vein endothelial cells (HUVECs) revealed that a 12 h incubation period optimized virus transduction. The safety and superior intracellular uptake of NSs and BVs in HUVECs were observed. The NSs carrying 100 and 400 MOI exhibited the highest cell proliferation rates in HUVECs. These sustained-release NSs significantly improved vascular cell migration and wound closure compared to free TGFβ1 carrying BV and can be a groundbreaking find in regenerative medicine, cardiovascular diseases, and chronic ulcer conditions.

Pyroptosis in lung cancer: The emerging role of non-coding RNAs

Lung cancer remains an intractable malignancy worldwide, prompting novel therapeutic modalities. Pyroptosis, a lethal form of programmed cell death featured by inflammation, has been involved in cancer progression and treatment response. Simultaneously, non-coding RNA has been shown to have important roles in coordinating pattern formation and oncogenic pathways, including long non-coding RNA (lncRNAs), microRNA (miRNAs), circular RNA (circRNAs), and small interfering RNA (siRNAs). Recent studies have revealed that ncRNAs can promote or inhibit pyroptosis by interacting with key molecular players such as NLRP3, GSDMD, and various transcription factors. This dual role of ncRNAs offers a unique therapeutic potential to manipulate pyroptosis pathways, providing opportunities for innovative cancer treatments. In this review, we integrate current research findings to propose novel strategies for leveraging ncRNA-mediated pyroptosis as a therapeutic intervention in lung cancer. We explore the potential of ncRNAs as biomarkers for predicting patient response to treatment and as targets for overcoming resistance to conventional therapies.

Deconstructing Regenerative Medicine: From Mechanistic Studies of Cell Therapy to Novel Bioinspired RNA Drugs

All Food and Drug Administration-approved noncoding RNA (ncRNA) drugs (n≈20) target known disease-causing molecular pathways by mechanisms such as antisense. In a fortuitous evolution of work on regenerative medicine, my coworkers and I inverted the RNA drug discovery process: first we identified natural disease-modifying ncRNAs, then used them as templates for new synthetic RNA drugs. Mechanism was probed only after bioactivity had been demonstrated. The journey began with the development of cardiosphere-derived cells (CDCs) for cardiac regeneration. While testing CDCs in a first-in-human trial, we discovered they worked indirectly: ncRNAs within CDC-secreted extracellular vesicles mediate the therapeutic benefits. The vast majority of such ncRNAs are fragments of unknown function. We chose several abundant ncRNA species from CDC-secreted extracellular vesicles, synthesized and screened each of them in vitro and in vivo. Those with exceptional disease-modifying bioactivity inspired new chemical entities that conform to the structural conventions of the Food and Drug Administration-approved ncRNA armamentarium. This discovery arc-Cell-Derived RNA from Extracellular vesicles for bioinspired Drug develOpment, or CREDO-has yielded various promising lead compounds, each of which works via a unique, and often novel, mechanism. The process relies on emergent insights to shape therapeutic development. The initial focus of our inquiry-CDCs-are now themselves in phase 3 testing for Duchenne muscular dystrophy and its associated cardiomyopathy. But the intravenous delivery strategy and the repetitive dosing protocol for CDCs, which have proven key to clinical success, both arose from systematic mechanistic inquiry. Meanwhile, emergent insights have led to multiple cell-free therapeutic candidates: CDC-secreted extracellular vesicles are in preclinical development for ventricular arrhythmias, while the CREDO-conceived RNA drugs are in translation for diseases ranging from myocarditis to scleroderma.

The Usefulness of Determining Plasma and Tissue Concentrations of Phosphorodiamidate Morpholino Oligonucleotides to Estimate Their Efficacy in Duchenne Muscular Dystrophy Patients

Currently, four kinds of phosphorodiamidate morpholino oligomers (PMOs), such as viltolarsen, have been approved for the treatment of Duchenne muscular dystrophy (DMD); however, it is unclear whether human efficacy can be estimated using plasma concentrations. This study summarizes the tissue distribution of viltolarsen in mice and cynomolgus monkeys and evaluates the relationship between exposure and efficacy based on exon skipping. In the tissue distribution studies, all muscles in DMD-model mice showed higher concentrations of viltolarsen than those in wild-type mice and cynomolgus monkeys, and the concentrations in skeletal muscle were correlated with the exon-skipping efficiency in mice and cynomolgus monkeys. In addition, a highly sensitive bioanalytical method using liquid chromatography with tandem mass spectrometry shows promise for determining plasma concentrations up to a later time point, and the tissue (muscle)/plasma concentration ratio (Kp) in DMD-model mice was shown to be useful for predicting changes in pharmacodynamic (PD) markers in humans. Our results suggest that pharmacokinetic (PK)/PD analysis can be conducted by using the human PK profile or Kp values and skipping efficiency in DMD-model mice. This information will be useful for the efficient and effective development of PMOs as therapeutic agents. SIGNIFICANCE STATEMENT: We evaluated the relationship between the plasma or tissue concentrations and the efficiency of exon skipping for viltolarsen as an example phosphorodiamidate morpholino oligomers in the skeletal and cardiac muscle of mice and cynomolgus monkeys for pharmacokinetic/pharmacodynamic (PK/PD) analysis. The results suggest that PK/PD analysis can be conducted by using the human PK profile or tissue (muscle)/plasma concentration ratios and skipping efficiency in DMD-model mice.

Application of Model-Informed Drug Development in Dose Selection and Optimization for siRNA Therapies

The application of model-informed drug development (MIDD) has revolutionized drug development and regulatory decision making, transforming the process into one that is more efficient, effective, and patient centered. A critical application of MIDD is to facilitate dose selection and optimization, which play a pivotal role in improving efficacy, safety, and tolerability profiles of a candidate drug. With the surge of interest in small interfering RNA (siRNA) drugs as a promising class of therapeutics, their applications in various disease areas have been extensively studied preclinically. However, dosing selection and optimization experience for siRNA in humans is limited. Unique challenges exist for the dose evaluation of siRNA due to the temporal discordance between pharmacokinetic and pharmacodynamic profiles, as well as limited available clinical experience and considerable interindividual variability. This review highlights the pivotal role of MIDD in facilitating dose selection and optimization for siRNA therapeutics. Based on past experiences with approved siRNA products, MIDD has demonstrated its ability to aid in dose selection for clinical trials and enabling optimal dosing for the general patient population. In addition, MIDD presents an opportunity for dose individualization based on patient characteristics, enhancing the precision and effectiveness of siRNA therapeutics. In conclusion, the integration of MIDD offers substantial advantages in navigating the complex challenges of dose selection and optimization in siRNA drug development, which in turn accelerates the development process, supports regulatory decision making, and ultimately improves the clinical outcomes of siRNA-based therapies, fostering advancements in precision medicine across a diverse range of diseases.

Treatment with siRNAs is commonly associated with GPX4 up-regulation and target knockdown-independent sensitization to ferroptosis

Small interfering RNAs (siRNAs) are widely used in biomedical research and in clinical trials. Here, we demonstrate that siRNA treatment is commonly associated with significant sensitization to ferroptosis, independently of the target protein knockdown. Genetically targeting mitochondrial antiviral-signaling protein (MAVS) reversed the siRNA-mediated sensitizing effect, but no activation of canonical MAVS signaling, which involves phosphorylation of IkBα and interferon regulatory transcription factor 3 (IRF3), was observed. In contrast, MAVS mediated a noncanonical signal resulting in a prominent increase in mitochondrial ROS levels, and increase in the BACH1/pNRF2 transcription factor ratio and GPX4 up-regulation, which was associated with a 50% decrease in intracellular glutathione levels. We conclude that siRNAs commonly sensitize to ferroptosis and may severely compromise the conclusions drawn from silencing approaches in biomedical research. Finally, as ferroptosis contributes to a variety of pathophysiological processes, we cannot exclude side effects in human siRNA-based therapeutical concepts that should be clinically tested.

Controlled siRNA Release of Nanopolyplex for Effective Targeted Anticancer Therapy in Animal Model

Introduction

Spatiotemporally controlled release of siRNA for anti-tumor therapy poses significant challenges. Near-infrared (NIR) light, known for its exceptional tissue penetration and minimal tissue invasiveness, holds promise as a viable exogenous stimulus for inducing controlled siRNA release in vivo. However, the majority of light-responsive chemical bonds exhibit absorption wavelengths in the ultraviolet (UV) or short-wavelength visible light range.

Methods

To achieve NIR-controlled siRNA release, the study synthesized a UV-sensitive triblock copolymer cRGD-poly(ethylene glycol)-b-poly(aspartic acid ester-5-(2'-(dimethylamino)ethoxy)-2-nitrobenzyl alcohol)-b-polyphenylalanine, abbreviated as cRGD-PEG-PAsp(EDONB)-PPHE. This copolymer is composed of a cRGD-capped PEG block (cRGD-PEG), a poly(aspartate) block modified with cationic moieties through UV-cleavable 2-nitrobenzyl ester bonds [PAsp(EDONB)], and a hydrophobic polyphenylalanine block (PPHE). The cationic amphiphilic polymer cRGD-PEG-PAsp(EDONB)-PPHE can assemble with hydrophobic upconversion nanoparticles (UCNPs) to form a cationic micelle designated as T-UCNP, which subsequently complexes with siRNA to create the final nanopolyplex T-si/UCNP. siRNA-PLK1 was employed to prepare T-PLK1/UCNP nanopolyplex for anti-tumor therapy.

Results

T-PLK1/UCNP not only exhibited outstanding tumor cell targeting through cRGD modification but also achieved 980 nm NIR-controlled PLK1 gene silencing. This was achieved by utilizing the encapsulated UCNPs to convert NIR into UV light, facilitating the cleavage of 2-nitrobenzyl ester bonds. As a result, there was a significant suppression of tumor growth.

Conclusion

The UCNPs-encapsulated nanopolyplex T-si/UCNP, capable of co-delivering siRNA and UCNPs, enables precise NIR-controlled release of siRNA at the tumor site for cancer RNAi therapy. This nanopolyplex can enhance the controllability and safety of RNAi therapy for tumors, and it also holds the potential to serve as a platform for achieving controlled release and activation of other drugs, such as mRNA and DNA.

Types of RNA therapeutics

RNA therapy is one of the new treatments using small RNA molecules to target and regulate gene expression. It involves the application of synthetic or modified RNA molecules to inhibit the expression of disease-causing genes specifically. In other words, it silences genes and suppresses the transcription process. The main theory behind RNA therapy is that RNA molecules can prevent the translation into proteins by binding to specific messenger RNA (mRNA) molecules. By targeting disease-related mRNA molecules, RNA therapy can effectively silence or reduce the development of harmful proteins. There are different types of RNA molecules used in therapy, including small interfering RNAs (siRNAs), microRNAs (miRNAs), aptamer, ribozyme, and antisense oligonucleotides (ASOs). These molecules are designed to complement specific mRNA sequences, allowing them to bind and degrade the targeted mRNA or prevent its translation into protein. Nanotechnology is also highlighted to increase the efficacy of RNA-based drugs. In this chapter, while examining various methods of RNA therapy, we discuss the advantages and challenges of each.

PEG-modified nano liposomes co-deliver Apigenin and RAGE-siRNA to protect myocardial ischemia injury

Ischemic heart disease (IHD) is a cardiac disorder in which myocardial damage occurs as a result of myocardial ischemia and hypoxia. Evidence suggests that oxidative stress and inflammatory responses are critical in the development of myocardial ischemia. Therefore, the combination of antioxidant and anti-inflammatory applications is an effective strategy to combat ischemic heart disease. In this paper, polyethylene glycol (PEG)-modified cationic liposomes were used as carriers to deliver apigenin (Apn) with small interfering RNA (siRNA) targeting the receptor for glycosylation end products (RAGE) (siRAGE) into cardiomyocytes to prevent myocardial ischemic injury through antioxidant and anti-inflammatory effects. Our results showed that we successfully prepared cationic PEG liposomes loaded with Apn and siRAGE (P-CLP-A/R) with normal appearance and morphology, particle size and Zeta potential, and good encapsulation rate, drug loading and in vitro release degree. In vitro, P-CLP-A/R was able to prevent oxidative stress injury in H9C2 cells, downregulate the expression of RAGE, reduce the secretion of cellular inflammatory factors and inhibit apoptosis through the RAGE/NF-κB pathway; In vivo, P-CLP-A/R was able to prevent arrhythmia and myocardial pathological injury, and reduce apoptosis and the area of necrotic myocardium in rats. In conclusion, P-CLP-A/R has a protective effect on myocardial ischemic injury and is expected to be a potential drug for the prevention of ischemic heart disease in the future.

Biodrug Delivery Systems: Do mRNA Lipid Nanoparticles Come of Age?

As an appealing alternative to treat and prevent diseases ranging from cancer to COVID-19, mRNA has demonstrated significant clinical effects. Nanotechnology facilitates the successful implementation of the systemic delivery of mRNA for safe human consumption. In this manuscript, we provide an overview of current mRNA therapeutic applications and discuss key biological barriers to delivery and recent advances in the development of nonviral systems. The relevant challenges that LNPs face in achieving cost-effective and widespread clinical implementation when delivering mRNA are likewise discussed.