Polycation-siRNA nanoparticles can disassemble at the kidney glomerular basement membrane

Abstract

Despite being engineered to avoid renal clearance, many cationic polymer (polycation)-based siRNA nanoparticles that are used for systemic delivery are rapidly eliminated from the circulation. Here, we show that a component of the renal filtration barrier-the glomerular basement membrane (GBM)-can disassemble cationic cyclodextrin-containing polymer (CDP)-based siRNA nanoparticles and, thereby, facilitate their rapid elimination from circulation. Using confocal and electron microscopies, positron emission tomography, and compartment modeling, we demonstrate that siRNA nanoparticles, but not free siRNA, accumulate and disassemble in the GBM. We also confirm that the siRNA nanoparticles do not disassemble in blood plasma in vitro and in vivo. This clearance mechanism may affect any nanoparticles that assemble primarily by electrostatic interactions between cationic delivery components and anionic nucleic acids (or other therapeutic entities). pharmacokinetics | glomerulusA major challenge with the use of small interfering RNA (siRNA) in mammals is their delivery to intracellular locations in specific tissues (1). The two most investigated approaches to siRNA delivery involve the combination of siRNA with cationic lipids (lipoplexes, liposomes, micelles) or cationic polymers (polyplexes) (2). Polymer-based siRNA delivery vehicles can be tuned to be nonimmunogenic, nononcogenic, nontoxic, and targeted (3). A targeted nanoparticle formulation of siRNA (not chemically modified) with a cationic, cyclodextrin-containing polymer (CDP)-based delivery vehicle (clinical version denoted CALAA-01) was shown to accumulate in human tumors and deliver functional siRNA from a systemic, i.v. infusion (4). This first-in-human study demonstrated the clinical potential for cationic polymerbased siRNA delivery systems.Like most cationic polymer-based siRNA delivery systems (5-9), the siRNA/CDP nanoparticle is rapidly eliminated from circulation (shown in mice, monkeys, and humans) (10-12). In fact, polymer complexation often does not extend the circulation time of siRNA. The rapid clearance of these siRNA nanoparticles is puzzling because they are engineered to be above the size cutoff for single-pass clearance via renal filtration (13). In understanding the mechanism behind the rapid clearance of this type of cancer therapeutic, we can efficiently seek ways to increase their circulation time and, thus, enhance their anticancer efficacy (3).We hypothesize that the paradoxical renal clearance of polycation-nucleic acid nanoparticles results from their binding and disassembly by components of the renal filtration barrier. Three key properties of such nanoparticles (diameters between 10 and 100 nm, positive zeta potentials, and electrostatically driven selfassembly) make them susceptible to this mechanism of clearance.The renal filtration barrier, located within the glomerulus of the nephron, consists of three layers that must be traversed to enter the urinary space. These three layers are the glomerular endothelial fenestrations (≈100 n...

Correlating animal and human phase Ia/Ib clinical data with CALAA-01, a targeted, polymer-based nanoparticle containing siRNA

“…2A). These findings are consistent with the preclinical data in mice (13), rats, and monkeys (SI Appendix, Fig. S2A).…”

“…The monocyte phagocytic system is thought to be primarily responsible for nanoparticle clearance (20). However, CALAA-01 is cleared mainly through the kidney due to its interaction with the renal filtration barrier (13). Therefore, PK observations of CALAA-01 may be generalizable only to other nanoparticles that are held together by electrostatic interactions between the carrier molecules (positively charged) and the siRNA (negatively charged).…”

Mathematical framework for activity-based cancer biomarkers

“…To date, pharmacokinetic models have been developed for abundance-based drugs and diagnostics-such as predicting nanoparticle (NP) targeting to tumor vasculature (11), identifying rate-limiting steps in the distribution of drugs within tumors (16)(17)(18), providing guidelines to increase NP penetration (19), and modeling NP disassembly at the glomerulus (20). Here, we establish a mathematical framework for synthetic biomarkers, a class of activity-based probes that amplify disease-derived signals into urine for easy analysis (3,(21)(22)(23)(24).…”

15 years on siRNA delivery: Beyond the State-of-the-Art on inorganic nanoparticles for RNAi therapeutics

“…To avoid renal clearance, nanocarriers chemically modified to increase the retention time of the siRNAs in the circulatory system (e.g. cationic polymers) are frequently proposed [162,163]. The interaction of siRNA with serum components may affect their delivery, some serum proteins in the bloodstream can tag the delivery vehicles for uptake via the MPS.…”

“…Therefore, the size of nanoparticles and their payload should be large enough to prevent rapid leakage in blood capillaries but at the same time small enough to escape from the scavenge of macrophages in the RES, such as the liver and spleen or being cleared out by the kidneys. Appropriately sized nanoparticles can be chemically modified to increase their retention time in the circulatory system, using cationic polymers as described [162,163] or directly engineered to target phagocytic cells to increase uptake and antigen presentation [169].…”