Improved Ultrafiltration Method to Measure Drug Release from Nanomedicines Utilizing a Stable Isotope Tracer

Advanced bioanalytical techniques for pharmacokinetic studies of nanocarrier drug delivery systems

Significant investment in nanocarrier drug delivery systems (Nano-DDSs) has yielded only a limited number of successfully marketed nanomedicines, highlighting a low rate of clinical translation. A primary contributing factor is the lack of foundational understanding of in vivo processes. Comprehensive knowledge of the pharmacokinetics of Nano-DDSs is essential for developing more efficacious nanomedicines and accurately evaluating their safety and associated risks. However, the complexity of Nano-DDSs has impeded thorough and systematic pharmacokinetic studies. Key components of pharmacokinetic investigations on Nano-DDSs include the analysis of the released drug, the encapsulated drug, and the nanomaterial, which present a higher level of complexity compared to traditional small-molecule drugs. Establishing an appropriate approach for monitoring the pharmacokinetics of Nano-DDSs is crucial for facilitating the clinical translation of nanomedicines. This review provides an overview of advanced bioanalytical methodologies employed in studying the pharmacokinetics of anticancer organic Nano-DDSs over the past five years. We hope that this review will enhance the understanding of the pharmacokinetics of Nano-DDSs and support the advancement of nanomedicines.

Current state of nanomedicine drug products: An industry perspective

Nanomedicine drug products have reached an unprecedented high in terms of global commercial acceptance and media exposure with the approvals of the mRNA COVID-19 vaccines in 2021. In this paper, we examine the current state of the art for nanomedicine technologies as applied for pharmaceutical products and compare those trends with results from a recent IQ Consortium industry survey on nanomedicine drug products. We find that 1) industry companies continue to push the envelope in terms of new technologies for characterizing their specific drug products, 2) new analytical technologies continue to be utilized by industry to characterize the increasingly complex nanomedicine drug products and 3) alignment and communication are key between industry and regulatory authorities to better understand the regulatory filings that are being submitted. There are many CMC challenges that a company must overcome to successfully file a nanomedicine drug product. In 2022, the FDA Guidance on Drug Products containing Nanomaterials was published, and it provides a roadmap for submission of a nanomedicine drug product. We propose that our paper serves as a complimentary guide providing knowledge on specific CMC issues such as quality attributes, physicochemical characterization methods, excipients, and stability.

Advancements in Nanoparticle Characterization

Nanotechnology for drug delivery has made significant advancements over the last two decades. Innovations have been made in cancer research and development, including chemotherapies, imaging agents, and vaccine strategies, as well as other therapeutic areas, e.g., the recent commercialization of mRNA lipid nanoparticles as vaccines against the SARS-CoV-2 virus. The field has also seen technological advancements to aid in addressing the complex questions posed by these novel therapies. In this latest edition of protocols and methods for nanoparticle characterization, we highlight both old and new methodologies for defining physicochemical properties, present both in vitro and in vivo methods to test for a variety of immunotoxicities, and describe assays used for pharmacological studies to assess drug release and tissue distribution.

Assessment of Temperature-Dependent Drug Release of Solubilizing Nanoformulations Using the SITUA

The evaluation of temperature-dependent drug release for solubilizing nanoformulations uses a modification of the stable isotope ultrafiltration assay (SITUA). This method is specific to parenterally administered solubilizing nanomedicines and can be used to assess drug release from the total dosage form for regulatory purposes of lot release. The principle upon which this method is based is the relationship between drug solubility and temperature in a plasma simulating media, 4.5% human serum albumin, that allows for discrimination of passing and failing lots based upon the release characteristics.

Development and validation of HPLC method for simultaneous estimation of erlotinib and niclosamide from liposomes optimized by screening design

The emerging drug resistance to the approved first-line drug therapy leads to clinical failure in cancer. Drug repurposing studies lead to the identification of many old drugs to be used for cancer treatment. Combining the repurposed drugs (niclosamide) with first-line therapy agents like erlotinib HCl showed improved efficacy by inhibiting erlotinib HCl acquired resistance. But there is a need to develop a sensitive, accurate, and excellent analytical method and drug delivery system for successfully delivering drug combinations. In the current study, an HPLC method was developed and validated for the simultaneous estimation of niclosamide and erlotinib HCl. The retention time of niclosamide and erlotinib hydrochloride was 6.48 and 7.65 min at 333 nm. The developed method was rapid and sensitive to separating the two drugs with reasonable accuracy, precision, robustness, and ruggedness. A Plackett-Burman (PBD) screening design was used to identify the critical parameters affecting liposomal formulation development using particle size, size distribution, zeta potential, and entrapment efficiency as the response. Lipid concentration, drug concentration, hydration temperature, and media volume were critical parameters affecting the particle size, polydispersity index (PDI), ZP, and %EE of the liposomes. The optimized NCM-ERL liposomes showed the particle size (126.05 ± 2.1), PDI (0.498 ± 0.1), ZP (-16.2 ± 0.3), and %EE of NCM and ERL (50.04 ± 2.8 and 05.42 ± 1.3). In vitro release studies indicated the controlled release of the drugs loaded liposomes (87.06 ± 9.93% and 42.33 ± 0.89% in 24 h).

Orthogonal and complementary measurements of properties of drug products containing nanomaterials

Quality control of pharmaceutical and biopharmaceutical products, and verification of their safety and efficacy, depends on reliable measurements of critical quality attributes (CQAs). The task becomes particularly challenging for drug products and vaccines containing nanomaterials, where multiple complex CQAs must be identified and monitored. To reduce (i) the risk of measurement bias and (ii) the uncertainty in decision-making during product development, the combination of orthogonal and complementary analytical techniques are generally recommended by regulators. However, despite frequent reference to "orthogonal" and "complementary" in guidance documents, neither term is clearly defined. How does one determine if two analytical methods are orthogonal or complementary to one another? Definitions are needed to design a robust characterization strategy aligned to regulatory needs. Definitions for "orthogonal" and "complementary" are proposed that are compatible with existing metrological terminology and are applicable to complex measurement problems. Orthogonal methods target the quantitative evaluation of the true value of a product attribute to address unknown bias or interference. Complementary measurements include a broader scope of methods that reinforce each other to support a common decision. Examples of the application of these terms are presented, with a focus on measurement of physical properties of nano-enabled drug products, including liposomes and polymeric nanoparticles for cancer treatment, lipid-based nanoparticles (LNPs) and virus-like particles for nucleic acid delivery. The proposed framework represents a first step in advancing the assessment of the orthogonality and complementarity of two measurements and it can potentially serve as the basis for a future international standard. This framework may help product developers to implement more efficient product characterization strategies, accelerate the introduction of novel medicines to the clinic and be applicable to other therapeutics beyond nanomaterial-containing pharmaceuticals.

Current hurdles to the translation of nanomedicines from bench to the clinic

The field of nanomedicine has significantly influenced research areas such as drug delivery, diagnostics, theranostics, and regenerative medicine; however, the further development of this field will face significant challenges at the regulatory level if related guidance remains unclear and unconsolidated. This review describes those features and pathways crucial to the clinical translation of nanomedicine and highlights considerations for early-stage product development. These include identifying those critical quality attributes of the drug product essential for activity and safety, appropriate analytical methods (physical, chemical, biological) for characterization, important process parameters, and adequate pre-clinical models. Additional concerns include the evaluation of batch-to-batch consistency and considerations regarding scaling up that will ensure a successful reproducible manufacturing process. Furthermore, we advise close collaboration with regulatory agencies from the early stages of development to assure an aligned position to accelerate the development of future nanomedicines.

Facile Separation of PEGylated Liposomes Enabled by Anti-PEG scFv

PEGylated nanocarriers have gained increasing attention due to reduced toxicity and enhanced circulation compared with free drugs. According to guidances of drug regulatory departments worldwide, it is crucial to determine free and liposomal drug concentrations; however, the conventional used separation methods including dialysis, ultrafiltration, and solid-phase extraction (SPE) have drawbacks of time-consuming, drug leakage, environmental pollution or error bias of trace level drug. Here we developed a facile PEG-scFv-based separation method combined with HPLC to quantify free doxorubicin (DOX) and liposomal DOX in plasma. Anti-PEG single chain variable fragment antibody (PEG-scFv) was adopted to sediment PEGylated liposomes by simple incubation and low speed centrifugation. Compared to SPE, it demonstrated sufficient accuracy and sensitivity to evaluate free and liposomal DOX with intact liposomes. Therefore, it can serve as an alternative approach of SPE, which is suitable for quality assessment and pharmacokinetics evaluation of PEGylated liposomal drugs and possible other PEGylated nanocarriers.

Bioequivalence assessment of high-capacity polymeric micelle nanoformulation of paclitaxel and Abraxane® in rodent and non-human primate models using a stable isotope tracer assay

The in vivo fate of nanoformulated drugs is governed by the physicochemical properties of the drug and the functionality of nanocarriers. Nanoformulations such as polymeric micelles, which physically encapsulate poorly soluble drugs, release their payload into the bloodstream during systemic circulation. This results in three distinct fractions of the drug-nanomedicine: encapsulated, protein-bound, and free drug. Having a thorough understanding of the pharmacokinetic (PK) profiles of each fraction is essential to elucidate mechanisms of nanomedicine-driven changes in drug exposure and PK/PD relationships pharmacodynamic activity. Here, we present a comprehensive preclinical assessment of the poly (2-oxazoline)-based polymeric micelle of paclitaxel (PTX) (POXOL hl-PM), including bioequivalence comparison to the clinically approved paclitaxel nanomedicine, Abraxane®. Physicochemical characterization and toxicity analysis of POXOL hl-PM was conducted using standardized protocols by the Nanotechnology Characterization Laboratory (NCL). The bioequivalence of POXOL hl-PM to Abraxane® was evaluated in rats and rhesus macaques using the NCL's established stable isotope tracer ultrafiltration assay (SITUA) to delineate the plasma PK of each PTX fraction. The SITUA study revealed that POXOL hl-PM and Abraxane® had comparable PK profiles not only for total PTX but also for the distinct drug fractions, suggesting bioequivalence in given animal models. The comprehensive preclinical evaluation of POXOL hl-PM in this study showcases a series of widely applicable standardized studies by NCL for assessing nanoformulations prior to clinical investigation.

Supramolecular copolymer modified statin-loaded discoidal rHDLs for atherosclerotic anti-inflammatory therapy by cholesterol efflux and M2 macrophage polarization

Foam cells with the pro-inflammatory macrophage phenotype (M1) play an essential role in atherosclerosis progression. Either cellular cholesterol removal or drug intervention was reported to polarize M1 into the anti-inflammatory phenotype (M2) for atherosclerosis regression. These might be realized simultaneously by drug-loaded discoidal reconstituted high-density lipoproteins (d-rHDLs) with the functions of cellular cholesterol efflux and targeted drug delivery on macrophages. However, cholesterol reception can drive the remodelling of d-rHDLs, which serves to release drugs specifically in the atherosclerotic plaque but might incur premature drug leakage in blood circulation. Given that, the proposed strategy is to inhibit the remodelling behaviour of the carrier in blood circulation and responsively accelerate it under the atherosclerotic microenvironmental stimulus. Herein, atorvastatin calcium-loaded d-rHDL was modified by a PEGylated ferrocene/β-cyclodextrin supramolecular copolymer (PF/TC) to construct ROS-responsive PF/TC-AT-d-rHDL, which is expected to possess plasma stability and biosafety as well as triggered drug release by cholesterol efflux promotion. As a result, PF/TC-AT-d-rHDL could responsively dissemble into β-cyclodextrin modified AT-d-rHDL under the ROS-triggered dissociation of PF/TC, therefore exhibiting increased cholesterol efflux from the cholesterol donor and drug release through the remodelling behaviour of the carrier in vitro. Moreover, PF/TC-AT-d-rHDL enhanced cellular cholesterol removal in foam cells after response to ROS, inhibiting intracellular lipid deposition compared with other d-rHDL carriers. Interestingly, cellular drug uptake was significantly promoted upon cellular cholesterol removal by restoring the permeability and fluidity of foam cell membranes as indicated by flow cytometry and fluorescence polarization analysis, respectively. Importantly, compared with untreated foam cells, PF/TC-AT-d-rHDL obviously increased the ratio of M2/M1 by 6.3-fold, which was even higher than the effect of PF/TC-d-rHDL (3.4-fold) and free drugs (1.9-fold), revealing that PF/TC-AT-d-rHDL synergistically promoted the M2 polarization of macrophages. Accordingly, PF/TC-AT-d-rHDL boosted the secretion of anti-inflammatory cytokines and inhibited that of inflammatory cytokines. Collectively, PF/TC-AT-d-rHDL exerted synergistic M2 polarization effects on foam cells for atherosclerotic immunomodulatory therapy via responsively mediating cholesterol efflux and delivering drugs.

Quantification of Cellular Drug Biodistribution Addresses Challenges in Evaluating in vitro and in vivo Encapsulated Drug Delivery

Nanoencapsulated drug delivery to solid tumors is a promising approach to overcome pharmacokinetic limitations of therapeutic drugs. However, encapsulation leads to complex drug biodistribution and delivery making analysis of delivery efficacy challenging. As proxies, nanocarrier accumulation or total tumor drug uptake in the tumor are used to evaluate delivery. Yet, these measurements fail to assess delivery of active, released drug to the target, and thus it commonly remains unknown if drug-target occupancy has been achieved. Here, we develop an approach to evaluate the delivery of encapsulated drug to the target, where residual drug target vacancy is measured using a fluorescent drug analog. In vitro measurements reveal that burst release governs drug delivery independent of nanoparticle uptake, and highlight limitations of evaluating nanoencapsulated drug delivery in these models. In vivo, however, our approach captures successful nanoencapsulated delivery, finding that tumor stromal cells drive nanoparticle accumulation and mediate drug delivery to adjacent cancer cells. These results, and generalizable approach, provide a critical advance to evaluate delivery of encapsulated drug to the drug target - the central objective of nanotherapeutics.

Perspectives on Nanodelivery to the Brain: Prerequisites for Successful Brain Treatment

Nanocarriers (NCs) are promising tools to improve drug delivery across the blood–brain barrier (BBB) for more effective treatment of brain disorders, although there is a scarcity of clinical translation of brain-directed NCs. In order to drive the development of brain-oriented NCs toward clinical success, it is essential to understand the prerequisites for nanodelivery to be successful in brain treatment. In this Perspective, we present how pharmacokinetic/pharmacodynamic (PK/PD), formulation and nanotoxicity factors impact the therapeutic success of brain-specific nanodelivery. Properties including high loading efficiency, slow in vivo drug release, long systemic circulation, an increase in unbound brain-to-plasma concentration/exposure ratio (K_p,uu,brain), high drug potency, and minimal nanotoxicity are prerequisites that should preferably be combined to maximize the therapeutic potential of a brain-targeted NC. The PK of brain-directed NCs needs to be evaluated in a more therapeutically relevant manner, focusing on the released, unbound drug. It is more crucial to increase the K_p,uu,brain than to improve the ability of the NC to cross the BBB in its intact form. Brain-targeted NCs, which are mostly developed for treating brain tumors, including metastases, should aim to enhance drug delivery not just to tumor regions with disrupted BBB, but equally important to regions with intact BBB where the drugs themselves have problems reaching. This article provides critical insights into how a brain-targeted nanoformulation needs to be designed and optimized to achieve therapeutic success in the brain.

Distinguishing Pharmacokinetics of Marketed Nanomedicine Formulations Using a Stable Isotope Tracer Assay

The pharmacokinetics of nanomedicines are complicated by the unique dispositional characteristics of the drug carrier. Most simplistically, the carrier could be a solubilizing platform that allows administration of a hydrophobic drug. Alternatively, the carrier could be stable and release the drug in a controlled manner, allowing for distribution of the carrier to influence distribution of the encapsulated drug. A third potential dispositional mechanism is carriers that are not stably complexed to the drug, but rather bind the drug in a dynamic equilibrium, similar to the binding of unbound drug to protein; since the nanocarrier has distributional and binding characteristics unlike plasma proteins, the equilibrium binding of drug to a nanocarrier can affect pharmacokinetics in unexpected ways, diverging from classical protein binding paradigms. The recently developed stable isotope tracer ultrafiltration assay (SITUA) for nanomedicine fractionation is uniquely suited for distinguishing and comparing these carrier/drug interactions. Here we present the the encapsulated, unencapsulated, and unbound drug fraction pharmacokinetic profiles in rats for marketed nanomedicines, representing examples of controlled release (doxorubicin liposomes, Doxil; and doxorubicin HCl liposome generic), equilibrium binding (paclitaxel cremophor micelle solution, Taxol generic), and solubilizing (paclitaxel albumin nanoparticle, Abraxane; and paclitaxel polylactic acid micelle, Genexol-PM) nanomedicine formulations. The utility of the SITUA method in differentiating these unique pharmacokinetic profiles and its potential for use in establishing generic nanomedicine bioequivalence are discussed.

Hyaluronic Acid-Modified Micelles Encapsulating Gem-C12 and HNK for Glioblastoma Multiforme Chemotherapy

Glioblastoma multiforme (GBM), a prevalent brain cancer with high mortality, is resistant to the conventional single-agent chemotherapy. In this study, we employed a combination chemotherapy strategy to inhibit GBM growth and addressed its possible beneficial effects. The synergistic effect of lauroyl-gemcitabine (Gem-C₁₂) and honokiol (HNK) was first tested and optimized using U87 cells in vitro. Then, the hyaluronic acid-grafted micelles (HA-M), encapsulating the optimal mole ratio (1:1) of Gem-C₁₂ and HNK, were prepared and characterized. Cell-based studies demonstrated that HA-M could be transported into cells by a CD44 receptor-mediated endocytosis, which could penetrate deeper into tumor spheroids and enhance the cytotoxicity of payloads to glioma cells. In vivo, drug-loaded HA-M significantly increased the survival rate of mice bearing orthotopic xenograft GBM compared with the negative control (1.85-fold). Immunohistochemical analysis indicated that the enhanced efficacy of HA-M was attributed to the stronger inhibition of glioma proliferation and induction of apoptosis. Altogether, our findings showed advantages of combination chemotherapy of GBM using HA-grafted micelles.