PSMA-Targeted Nanotheranostics for Imaging and Radiotherapy of Prostate Cancer.

Targeted nanotheranostic systems offer significant benefits due to the integration of diagnostic and therapeutic functionality, promoting personalized medicine. In recent years, prostate-specific membrane antigen (PSMA) has emerged as an ideal theranostic target, fueling multiple new drug approvals and changing the standard of care in prostate cancer (PCa). PSMA-targeted nanosystems such as self-assembled nanoparticles (NPs), liposomal structures, water-soluble polymers, dendrimers, and other macromolecules are under development for PCa theranostics due to their multifunctional sensing and therapeutic capabilities. Herein, we discuss the significance and up-to-date development of "PSMA-targeted nanocarrier systems for radioligand imaging and therapy of PCa". The review also highlights critical parameters for designing nanostructured radiopharmaceuticals for PCa, including radionuclides and their chelators, PSMA-targeting ligands, and the EPR effect. Finally, prospects and potential for clinical translation is discussed.

Intravital Microscopy Reveals Endothelial Transcytosis Contributing to Significant Tumor Accumulation of Albumin Nanoparticles.

The principle of enhanced permeability and retention (EPR) effect has been used to design anti-cancer nanomedicines over decades. However, it is being challenged due to the poor clinical outcome of nanoparticles and controversial physiological foundation. Herein, we use a near-infrared-II (1000-1700 nm, NIR-II) fluorescence probe BPBBT to investigate the pathway for the entry of human serum albumin-bound nanoparticles (BPBBT-HSA NPs) into tumor compared with BPBBT micelles with phospholipid-poly (ethylene glycol) of the similar particle size about 110 nm. The plasma elimination half-life of BPBBT micelles was 2.8-fold of that of BPBBT-HSA NPs. However, the area under the BPBBT concentration in tumor-time curve to 48 h post-injection (AUCtumor0→48h) of BPBBT-HSA NPs was 7.2-fold of that of BPBBT micelles. The intravital NIR-II fluorescence microscopy revealed that BPBBT-HSA NPs but not BPBBT micelles were transported from the tumor vasculature into tumor parenchyma with high efficiency, and endocytosed by the tumor cells within 3 h post-injection in vivo. This effect was blocked by cross-linking BPBBT-HSA NPs to denature HSA, resulting in the AUCtumor0→48h decreased to 22% of that of BPBBT-HSA NPs. Our results demonstrated that the active process of endothelial transcytosis is the dominant pathway for albumin-bound nanoparticles' entry into tumor.

Prostate-Specific Membrane Antigen Targeted Deep Tumor Penetration of Polymer Nanocarriers.

Tumoral uptake of large-size nanoparticles is mediated by the enhanced permeability and retention (EPR) effect, with variable accumulation and heterogenous tumor tissue penetration depending on the tumor phenotype. The performance of nanocarriers via specific targeting has the potential to improve imaging contrast and therapeutic efficacy in vivo with increased deep tissue penetration. To address this hypothesis, we designed and synthesized prostate cancer-targeting starPEG nanocarriers (40 kDa, 15 nm), [89Zr]PEG-(DFB)3(ACUPA)1 and [89Zr]PEG-(DFB)1(ACUPA)3, with one or three prostate-specific membrane antigen (PSMA)-targeting ACUPA ligands. The in vitro PSMA binding affinity and in vivo pharmacokinetics of the targeted nanocarriers were compared with a nontargeted starPEG, [89Zr]PEG-(DFB)4, in PSMA+ PC3-Pip and PSMA- PC3-Flu cells, and xenografts. Increasing the number of ACUPA ligands improved the in vitro binding affinity of PEG-derived polymers to PC3-Pip cells. While both PSMA-targeted nanocarriers significantly improved tissue penetration in PC3-Pip tumors, the multivalent [89Zr]PEG-(DFB)1(ACUPA)3 showed a remarkably higher PC3-Pip/blood ratio and background clearance. In contrast, the nontargeted [89Zr]PEG-(DFB)4 showed low EPR-mediated accumulation with poor tumor tissue penetration. Overall, ACUPA conjugated targeted starPEGs significantly improve tumor retention with deep tumor tissue penetration in low EPR PC3-Pip xenografts. These data suggest that PSMA targeting with multivalent ACUPA ligands may be a generally applicable strategy to increase nanocarrier delivery to prostate cancer. These targeted multivalent nanocarriers with high tumor binding and low healthy tissue retention could be employed in imaging and therapeutic applications.

An Updated Review on EPR-Based Solid Tumor Targeting Nanocarriers for Cancer Treatment.

The enhanced permeability and retention (EPR) effect in cancer treatment is one of the key mechanisms that enables drug accumulation at the tumor site. However, despite a plethora of virus/inorganic/organic-based nanocarriers designed to rely on the EPR effect to effectively target tumors, most have failed in the clinic. It seems that the non-compliance of research activities with clinical trials, goals unrelated to the EPR effect, and lack of awareness of the impact of solid tumor structure and interactions on the performance of drug nanocarriers have intensified this dissatisfaction. As such, the asymmetric growth and structural complexity of solid tumors, physicochemical properties of drug nanocarriers, EPR analytical combination tools, and EPR description goals should be considered to improve EPR-based cancer therapeutics. This review provides valuable insights into the limitations of the EPR effect in therapeutic efficacy and reports crucial perspectives on how the EPR effect can be modulated to improve the therapeutic effects of nanomedicine.

Advocation and advancements of EPR effect theory in drug delivery science: A commentary.

To honor the contributions of Professor Hiroshi Maeda to the progress of targeted drug delivery research, a brief review of enhanced permeability and retention (EPR) effect theory proposed by him as the physiology-based principal mechanism of intra-tumoral accumulation of large molecules and small particles is presented. Under historical and practical backgrounds in developments of various drug delivery systems including macromolecular conjugates, the concept of EPR effect was advocated in mid1980s and has cultivated new cancer chemotherapeutic modalities until recently. Namely, nanoplatforms such as polymer conjugates, liposomes, polymeric micelles, and nanoparticles have been studied as a promising fusion area for nanotechnology and medicine. Modulation of EPR effect by chemical and/or mechanical approaches to achieve tumor vascular and tissue modification would further lead to sophistication of cancer chemotherapy employing nanomedicines.

Novel Nanoparticle-Based Cancer Treatment, Effectively Inhibits Lung Metastases and Improves Survival in a Murine Breast Cancer Model.

Sarah Nanoparticles (SaNPs) are unique multicore iron oxide-based nanoparticles, developed for the treatment of advanced cancer, following standard care, through the selective delivery of thermal energy to malignant cells upon exposure to an alternating magnetic field. For their therapeutic effect, SaNPs need to accumulate in the tumor. Since the potential accumulation and associated toxicity in normal tissues are an important risk consideration, biodistribution and toxicity were assessed in naïve BALB/c mice. Therapeutic efficacy and the effect on survival were investigated in the 4T1 murine model of metastatic breast cancer. Toxicity evaluation at various timepoints did not reveal any abnormal clinical signs, evidence of alterations in organ function, nor histopathologic adverse target organ toxicity, even after a follow up period of 25 weeks, confirming the safety of SaNP use. The biodistribution evaluation, following SaNP administration, indicated that SaNPs accumulate mainly in the liver and spleen. A comprehensive pharmacokinetics evaluation, demonstrated that the total percentage of SaNPs that accumulated in the blood and vital organs was ~78%, 46%, and 36% after 4, 13, and 25 weeks, respectively, suggesting a time-dependent clearance from the body. Efficacy studies in mice bearing 4T1 metastatic tumors revealed a 49.6% and 70% reduction in the number of lung metastases and their relative size, respectively, in treated vs. control mice, accompanied by a decrease in tumor cell viability in response to treatment. Moreover, SaNP treatment followed by alternating magnetic field exposure significantly improved the survival rate of treated mice compared to the controls. The median survival time was 29 ± 3.8 days in the treated group vs. 21.6 ± 4.9 days in the control, p-value 0.029. These assessments open new avenues for generating SaNPs and alternating magnetic field application as a potential novel therapeutic modality for metastatic cancer patients.

Preparation of Enzymatically Highly Active Pegylated-D-Amino Acid Oxidase and Its Application to Antitumor Therapy.

BACKGROUND: D-Amino acid oxidase (DAO) is an H2O2-generating enzyme, and tumor growth suppression by selective delivery of porcine DAO in tumors via the cytotoxic action of H2O2 has been reported. DAO isolated from Fusariumspp. (fDAO) shows much higher enzyme activity than porcine DAO, although the application of fDAO for antitumor treatment has not yet been determined. OBJECTIVE: The purpose of this study was to prepare enzymatically highly active pegylated-fDAO, and to determine whether it accumulates in tumors and exerts a potent antitumor effect in tumor- bearing mice. METHODS: Polyethylene glycol (PEG; Mw. 2000) was conjugated to fDAO to form PEGylated fDAO (PEG-fDAO). PEG-fDAO was intravenously administered into S180 tumor-bearing mice, and the body distribution and antitumor activity of PEG-fDAO was determined. RESULTS: The enzyme activity of PEG-fDAO was 26.1 U/mg, which was comparable to that of fDAO. Intravenously administered PEG-fDAO accumulated in tumors with less distribution in normal tissue except in the plasma. Enzyme activity in the tumor was 60-120 mU/g-tissue over 7-20 h after i.v. injection of 0.1 mg of PEG-fDAO. To generate the H2O2 in the tumor tissue, PEG-fDAO was intravenously administered, and then, D-phenylalanine was intraperitoneally administered after a lag time. No remarkable tumor suppression effect was observed under conditions used in this study, compared to the non-treated group. CONCLUSION: The results suggest that PEG-fDAO maintained high enzymatic activity after pegylation. Treatment with PEG-fDAO conferred high enzyme activity on tumor tissue; 3-6 fold higher than that of previously reported pDAO; however, high enzyme activity in the plasma limited repeated treatment owing to lethal toxicity, which seemingly led to poor therapeutic outcome. Overall, the use of PEG-fDAO is promising for antitumor therapy, although the suppression of DAO activity in the plasma would also be required rather than only the increase in DAO activity in the tumor for an antitumor effect.

Prostate-specific membrane antigen (PSMA)-targeted photodynamic therapy enhances the delivery of PSMA-targeted magnetic nanoparticles to PSMA-expressing prostate tumors.

Enhanced vascular permeability in tumors plays an essential role in nanoparticle delivery. Prostate-specific membrane antigen (PSMA) is overexpressed on the epithelium of aggressive prostate cancers (PCs). Here, we evaluated the feasibility of increasing the delivery of PSMA-targeted magnetic nanoparticles (MNPs) to tumors by enhancing vascular permeability in PSMA(+) PC tumors with PSMA-targeted photodynamic therapy (PDT). Method: PSMA(+) PC3 PIP tumor-bearing mice were given a low-molecular-weight PSMA-targeted photosensitizer and treated with fluorescence image-guided PDT, 4 h after. The mice were then given a PSMA-targeted MNP immediately after PDT and monitored with fluorescence imaging and T2-weighted magnetic resonance imaging (T2-W MRI) 18 h, 42 h, and 66 h after MNP administration. Untreated PSMA(+) PC3 PIP tumor-bearing mice were used as negative controls. Results: An 8-fold increase in the delivery of the PSMA-targeted MNPs was detected using T2-W MRI in the pretreated tumors 42 h after PDT, compared to untreated tumors. Additionally, T2-W MRIs revealed enhanced peripheral intra-tumoral delivery of the PSMA-targeted MNPs. That finding is in keeping with two-photon microscopy, which revealed higher vascular densities at the tumor periphery. Conclusion: These results suggest that PSMA-targeted PDT enhances the delivery of PSMA-targeted MNPs to PSMA(+) tumors by enhancing the vascular permeability of the tumors.

Size-shrinkable and protein kinase Cα-recognizable nanoparticles for deep tumor penetration and cellular internalization.

In the present study, the three functions, including enhanced permeability and retention (EPR) effect, deep penetration within tumor, and receptor-mediated endocytosis, were integrated into a single platform in order to improve antitumor efficiency. A novel nanoparticle (dendrigraft poly-L-lysine@glycyrrhetinic acid@cyclohexane dicarboxylic anhydride@doxorubicin@ hyaluronic acid composite) has been successfully developed and was denoted as DGL-GA-CDA-DOX-HA. The transmission electron microscope (TEM), dynamic light scattering (DLS), polymer dispersity index (PDI), fourier transform infrared spectrometer (FTIR), and zeta potentials were used to characterize the physicochemical properties of the nanoparticles. According to the results of TEM and DLS, the DGL-GA-CDA-DOX-HA nanoparticles could be rapidly degraded with a size shrink from 182.5 nm to 47.7 nm by hyaluronidase (HAase) added in the medium. The loading amount of DOX reached 252.03 ± 36.38 mg/g for DGL-GA-CDA-DOX nanoparticles. When the nanoparticles were in a medium with HAase at pH 5.0, the drug quickly released. However, when the nanoparticles were exposed to a medium without HAase at pH 5.0, or a neutral medium containing HAase, drug release slowed down. The modification of GA on nanoparticles significantly enhanced their affinity and cytotoxicity to hepatocellular carcinoma HepG2 cells. The study showed that the penetrability of DGL-GA-CDA-DOX and DGL-GA-CDA DOX-HA nanoparticles pre-degraded by HAase in vitro multicellular tumor spheroids were always better than that of DGL-GA-CDA-DOX-HA nanoparticles untreated by HAase. The imaging in vivo and ex vivo exhibited that DGL-GA-CDA-DOX-HA nanoparticles could preferentially accumulate in the tumor site. Correspondingly, the DGL-GA-CDA-DOX-HA displayed the preferable antitumor efficiency to other experimental groups in H22 tumor-bearing mice, with a tumor inhibition rate of 71.6%. In short, these results suggested that DGL-GA-CDA-DOX-HA nanoparticles could promote therapeutic effects by modulating particle size and GA receptor-mediated endocytosis.

Corrigendum to 'quantitative determination of 64Cu-liposome accumulation at inflammatory and infectious sites: Potential for future theranostic system': [journal of controlled release 327 (2020) 737-746].

BACKGROUND: Therapeutic interventions for infectious and inflammatory diseases are becoming increasingly challenging in terms of therapeutic resistance and side-effects. Theranostic systems to ameliorate diagnosis and therapy are therefore highly warranted. The pathophysiological changes in inflammatory lesions provide an attractive basis for extravasation and accumulation of PEGylated liposomes. The objective of this study was to provide direct quantitative information on the theranostic potential of radiolabeled liposome for accumulation in inflammatory models using position emission tomography (PET). METHOD: Preclinical murine models of inflammation (turpentine and LPS), infection (Staphylococcus aureus) and collagen-induced arthritis (CIA) was established and monitored using bioluminescence imaging (BLI). Across all models PET imaging using radiolabeled PEGylated liposomes (64Cu-liposomes) were performed and evaluated in terms of accumulation properties in inflammatory and infectious lesions. RESULTS: BLI demonstrated that the inflammatory and infectious models were successfully established and provided information on lesion pathology. Activity of 64Cu-liposomes were increased in inflammatory and infectious lesions between early (10-min or 3-h) and late (24-h) PET scans, which validates that a continuous extravasation and accumulation of long circulation PEGylated liposomes occurs. CONCLUSION: The theranostic potential of long circulating PEGylated radiolabeled liposomes was shown in multiple preclinical models. Impressive accumulation was seen in both inflammatory and infectious lesions. These results are encouraging towards advancing PEGylated liposomes as imaging and drug delivery systems in inflammatory and infectious diseases.

In Vivo Imaging of Prostate Cancer Tumors and Metastasis Using Non-Specific Fluorescent Nanoparticles in Mice.

With the growing interest in the use of nanoparticles (NPs) in nanomedicine, there is a crucial need for imaging and targeted therapies to determine NP distribution in the body after systemic administration, and to achieve strong accumulation in tumors with low background in other tissues. Accumulation of NPs in tumors results from different mechanisms, and appears extremely heterogeneous in mice models and rather limited in humans. Developing new tumor models in mice, with their low spontaneous NP accumulation, is thus necessary for screening imaging probes and for testing new targeting strategies. In the present work, accumulation of LipImageTM 815, a non-specific nanosized fluorescent imaging agent, was compared in subcutaneous, orthotopic and metastatic tumors of RM1 cells (murine prostate cancer cell line) by in vivo and ex vivo fluorescence imaging techniques. LipImageTM 815 mainly accumulated in liver at 24 h but also in orthotopic tumors. Limited accumulation occurred in subcutaneous tumors, and very low fluorescence was detected in metastasis. Altogether, these different tumor models in mice offered a wide range of NP accumulation levels, and a panel of in vivo models that may be useful to further challenge NP targeting properties.

Targeting Strategies for the Combination Treatment of Cancer Using Drug Delivery Systems.

Cancer cells have characteristics of acquired and intrinsic resistances to chemotherapy treatment-due to the hostile tumor microenvironment-that create a significant challenge for effective therapeutic regimens. Multidrug resistance, collateral toxicity to normal cells, and detrimental systemic side effects present significant obstacles, necessitating alternative and safer treatment strategies. Traditional administration of chemotherapeutics has demonstrated minimal success due to the non-specificity of action, uptake and rapid clearance by the immune system, and subsequent metabolic alteration and poor tumor penetration. Nanomedicine can provide a more effective approach to targeting cancer by focusing on the vascular, tissue, and cellular characteristics that are unique to solid tumors. Targeted methods of treatment using nanoparticles can decrease the likelihood of resistant clonal populations of cancerous cells. Dual encapsulation of chemotherapeutic drug allows simultaneous targeting of more than one characteristic of the tumor. Several first-generation, non-targeted nanomedicines have received clinical approval starting with Doxil® in 1995. However, more than two decades later, second-generation or targeted nanomedicines have yet to be approved for treatment despite promising results in pre-clinical studies. This review highlights recent studies using targeted nanoparticles for cancer treatment focusing on approaches that target either the tumor vasculature (referred to as 'vascular targeting'), the tumor microenvironment ('tissue targeting') or the individual cancer cells ('cellular targeting'). Recent studies combining these different targeting methods are also discussed in this review. Finally, this review summarizes some of the reasons for the lack of clinical success in the field of targeted nanomedicines.

Quantitative Evaluation of the Enhanced Permeability and Retention (EPR) Effect.

Quantitative evaluation of nanoparticle delivery to a tumor site can be invaluable for cross-platform comparison, a consideration not currently taken into account by many in the field of cancer nanomedicine (Dawidczyk et al., Front Chem 2:69, 2014). Standardization of measured parameters and experimental design will facilitate nanoparticle design and understanding in the field. Here, we present a broadly applicable in vivo protocol for preclinical trials of nanomedicines, including pharmacokinetic modeling and recommendations for parameters to be reported for nanoparticle evaluation. The proposed protocol is simple and not prohibitively mouse-heavy, using procedures that are not overly complicated or difficult to learn, yet is a powerful way to analyze the effectiveness of new cancer nanomedicines against standard or more developed ones.

Radiation effects on the tumor microenvironment: Implications for nanomedicine delivery.

The tumor microenvironment has an important influence on cancer biological and clinical behavior and radiation treatment (RT) response. However, RT also influences the tumor microenvironment in a complex and dynamic manner that can either reinforce or inhibit this response and the likelihood of long-term disease control in patients. It is increasingly evident that the interplay between RT and the tumor microenvironment can be exploited to enhance the accumulation and intra-tumoral distribution of nanoparticles, mediated by changes to the vasculature and stroma with secondary effects on hypoxia, interstitial fluid pressure (IFP), solid tissue pressure (STP), and the recruitment and activation of bone marrow-derived myeloid cells (BMDCs). The use of RT to modulate nanoparticle drug delivery offers an exciting opportunity to improve antitumor efficacy. This review explores the interplay between RT and the tumor microenvironment, and the integrated effects on nanoparticle drug delivery and efficacy.

Styrene maleic acid-encapsulated paclitaxel micelles: antitumor activity and toxicity studies following oral administration in a murine orthotopic colon cancer model.

Oral administration of paclitaxel (PTX), a broad spectrum anticancer agent, is challenged by its low uptake due to its poor bioavailability, efflux through P-glycoprotein, and gastrointestinal toxicity. We synthesized PTX nanomicelles using poly(styrene-co-maleic acid) (SMA). Oral administration of SMA-PTX micelles doubled the maximum tolerated dose (60 mg/kg vs 30 mg/kg) compared to the commercially available PTX formulation (PTX [Ebewe]). In a murine orthotopic colon cancer model, oral administration of SMA-PTX micelles at doses 30 mg/kg and 60 mg/kg reduced tumor weight by 54% and 69%, respectively, as compared to the control group, while no significant reduction in tumor weight was observed with 30 mg/kg of PTX (Ebewe). In addition, toxicity of PTX was largely reduced by its encapsulation into SMA. Furthermore, examination of the tumors demonstrated a decrease in the number of blood vessels. Thus, oral delivery of SMA-PTX micelles may provide a safe and effective strategy for the treatment of colon cancer.

Re-assessing the enhanced permeability and retention effect in peripheral arterial disease using radiolabeled long circulating nanoparticles.

As peripheral arterial disease (PAD) results in muscle ischemia and neovascularization, it has been claimed that nanoparticles can passively accumulate in ischemic tissues through the enhanced permeability and retention (EPR) effect. At this time, a quantitative evaluation of the passive targeting capabilities of nanoparticles has not been reported in PAD. Using a murine model of hindlimb ischemia, we quantitatively assessed the passive targeting capabilities of (64)Cu-labeled PEGylated reduced graphene oxide - iron oxide nanoparticles ((64)Cu-RGO-IONP-PEG) through the EPR effect using positron emission tomography (PET) imaging. Serial laser Doppler imaging was performed to monitor changes in blood perfusion upon surgical induction of ischemia. Nanoparticle accumulation was assessed at 3, 10, and 17 days post-surgery and found to be highest at 3 days post-surgery, with the ischemic hindlimb displaying an accumulation of 14.7 ± 0.5% injected dose per gram (%ID/g). Accumulation of (64)Cu-RGO-IONP-PEG was lowest at 17 days post-surgery, with the ischemic hindlimb displaying only 5.1 ± 0.5%ID/g. Furthermore, nanoparticle accumulation was confirmed by photoacoustic imaging (PA). The combination of PET and serial Doppler imaging showed that nanoparticle accumulation in the ischemic hindlimb negatively correlated with blood perfusion. Thus, we quantitatively confirmed that (64)Cu-RGO-IONP-PEG passively accumulated in ischemic tissue via the EPR effect, which is reduced as the perfusion normalizes. As (64)Cu-RGO-IONP-PEG displayed substantial accumulation in the ischemic tissue, this nanoparticle platform may function as a future theranostic agent, providing both imaging and therapeutic applications.

PEGylation as a strategy for improving nanoparticle-based drug and gene delivery.

Coating the surface of nanoparticles with polyethylene glycol (PEG), or "PEGylation", is a commonly used approach for improving the efficiency of drug and gene delivery to target cells and tissues. Building from the success of PEGylating proteins to improve systemic circulation time and decrease immunogenicity, the impact of PEG coatings on the fate of systemically administered nanoparticle formulations has, and continues to be, widely studied. PEG coatings on nanoparticles shield the surface from aggregation, opsonization, and phagocytosis, prolonging systemic circulation time. Here, we briefly describe the history of the development of PEGylated nanoparticle formulations for systemic administration, including how factors such as PEG molecular weight, PEG surface density, nanoparticle core properties, and repeated administration impact circulation time. A less frequently discussed topic, we then describe how PEG coatings on nanoparticles have also been utilized for overcoming various biological barriers to efficient drug and gene delivery associated with other modes of administration, ranging from gastrointestinal to ocular. Finally, we describe both methods for PEGylating nanoparticles and methods for characterizing PEG surface density, a key factor in the effectiveness of the PEG surface coating for improving drug and gene delivery.

Clearance Pathways and Tumor Targeting of Imaging Nanoparticles.

A basic understanding of how imaging nanoparticles are removed from the normal organs/tissues but retained in the tumors is important for their future clinical applications in early cancer diagnosis and therapy. In this review, we discuss current understandings of clearance pathways and tumor targeting of small-molecule- and inorganic-nanoparticle-based imaging probes with an emphasis on molecular nanoprobes, a class of inorganic nanoprobes that can escape reticuloendothelial system (RES) uptake and be rapidly eliminated from the normal tissues/organs via kidneys but can still passively target the tumor with high efficiency through the enhanced permeability permeability and retention (EPR) effect. The impact of nanoparticle design (size, shape, and surface chemistry) on their excretion, pharmacokinetics, and passive tumor targeting were quantitatively discussed. Synergetic integration of effective renal clearance and EPR effect offers a promising pathway to design low-toxicity and high-contrast-enhancement imaging nanoparticles that could meet with the clinical translational requirements of regulatory agencies.

A pharmacokinetic model for quantifying the effect of vascular permeability on the choice of drug carrier: a framework for personalized nanomedicine.

Drug carriers in the ∼ 100 nm size range are of considerable interest in the field of cancer therapy because of their ability to passively accumulate in tumors. Tailoring the physicochemical properties of these carriers to individual patient requirements will help exploit their full therapeutic potential. Here, we present a pharmacokinetic model to explain how vascular physiology could be used to guide the optimal choice of specific formulation parameters. We find that in order to maximize the benefit-to-risk ratio, nanosystems should be confined to a specific particle size range. The optimal particle size range is dictated by the vascular pore size of not only the tumor tissue but also of the normal organs. Additionally, the duration of drug release is a key variable that can be used to maximize the therapeutic benefit of nanomedicine. Our model further suggests that the enhanced permeability and retention effect is not necessarily a universal outcome for every nanocarrier in every tumor model but will only be observed for nanoparticles of a specific size range. This optimal size range, in turn, is governed by the vascular physiology of the tumor and of non-target organs.

State-of-the-art in design rules for drug delivery platforms: lessons learned from FDA-approved nanomedicines.

The ability to efficiently deliver a drug to a tumor site is dependent on a wide range of physiologically imposed design constraints. Nanotechnology provides the possibility of creating delivery vehicles where these design constraints can be decoupled, allowing new approaches for reducing the unwanted side effects of systemic delivery, increasing targeting efficiency and efficacy. Here we review the design strategies of the two FDA-approved antibody-drug conjugates (Brentuximab vedotin and Trastuzumab emtansine) and the four FDA-approved nanoparticle-based drug delivery platforms (Doxil, DaunoXome, Marqibo, and Abraxane) in the context of the challenges associated with systemic targeted delivery of a drug to a solid tumor. The lessons learned from these nanomedicines provide an important insight into the key challenges associated with the development of new platforms for systemic delivery of anti-cancer drugs.