The dose threshold for nanoparticle tumour delivery.

Nanoparticle delivery to solid tumours over the past ten years has stagnated at a median of 0.7% of the injected dose. Varying nanoparticle designs and strategies have yielded only minor improvements. Here we discovered a dose threshold for improving nanoparticle tumour delivery: 1 trillion nanoparticles in mice. Doses above this threshold overwhelmed Kupffer cell uptake rates, nonlinearly decreased liver clearance, prolonged circulation and increased nanoparticle tumour delivery. This enabled up to 12% tumour delivery efficiency and delivery to 93% of cells in tumours, and also improved the therapeutic efficacy of Caelyx/Doxil. This threshold was robust across different nanoparticle types, tumour models and studies across ten years of the literature. Our results have implications for human translation and highlight a simple, but powerful, principle for designing nanoparticle cancer treatments.

Porphyrin-lipid stabilized paclitaxel nanoemulsion for combined photodynamic therapy and chemotherapy.

BACKGROUND: Porphyrin-lipids are versatile building blocks that enable cancer theranostics and have been applied to create several multimodal nanoparticle platforms, including liposome-like porphysome (aqueous-core), porphyrin nanodroplet (liquefied gas-core), and ultrasmall porphyrin lipoproteins. Here, we used porphyrin-lipid to stabilize the water/oil interface to create porphyrin-lipid nanoemulsions with paclitaxel loaded in the oil core (PLNE-PTX), facilitating combination photodynamic therapy (PDT) and chemotherapy in one platform. RESULTS: PTX (3.1 wt%) and porphyrin (18.3 wt%) were loaded efficiently into PLNE-PTX, forming spherical core-shell nanoemulsions with a diameter of 120 nm. PLNE-PTX demonstrated stability in systemic delivery, resulting in high tumor accumulation (~ 5.4 ID %/g) in KB-tumor bearing mice. PLNE-PTX combination therapy inhibited tumor growth (78%) in an additive manner, compared with monotherapy PDT (44%) or chemotherapy (46%) 16 days post-treatment. Furthermore, a fourfold reduced PTX dose (1.8 mg PTX/kg) in PLNE-PTX combination therapy platform demonstrated superior therapeutic efficacy to Taxol at a dose of 7.2 mg PTX/kg, which can reduce side effects. Moreover, the intrinsic fluorescence of PLNE-PTX enabled real-time tracking of nanoparticles to the tumor, which can help inform treatment planning. CONCLUSION: PLNE-PTX combining PDT and chemotherapy in a single platform enables superior anti-tumor effects and holds potential to reduce side effects associated with monotherapy chemotherapy. The inherent imaging modality of PLNE-PTX enables real-time tracking and permits spatial and temporal regulation to improve cancer treatment.

Nanoparticle-mediated Photodynamic Therapy as a Method to Ablate Oral Cavity Squamous Cell Carcinoma in Preclinical Models.

Photodynamic therapy (PDT) is a tissue ablation technique able to selectively target tumor cells by activating the cytotoxicity of photosensitizer dyes with light. PDT is nonsurgical and tissue sparing, two advantages for treatments in anatomically complex disease sites such as the oral cavity. We have previously developed PORPHYSOME (PS) nanoparticles assembled from chlorin photosensitizer-containing building blocks (∼94,000 photosensitizers per particle) and capable of potent PDT. In this study, we demonstrate the selective uptake and curative tumor ablation of PS-enabled PDT in three preclinical models of oral cavity squamous cell carcinoma (OCSCC): biologically relevant subcutaneous Cal-33 (cell line) and MOC22 (syngeneic) mouse models, and an anatomically relevant orthotopic VX-2 rabbit model. Tumors selectively uptake PS (10 mg/kg, i.v.) with 6-to 40-fold greater concentration versus muscle 24 hours post-injection. Single PS nanoparticle-mediated PDT (PS-PDT) treatment (100 J/cm2, 100 mW/cm2) of Cal-33 tumors yielded significant apoptosis in 65.7% of tumor cells. Survival studies following PS-PDT treatments demonstrated 90% (36/40) overall response rate across all three tumor models. Complete tumor response was achieved in 65% of Cal-33 and 91% of MOC22 tumor mouse models 14 days after PS-PDT, and partial responses obtained in 25% and 9% of Cal-33 and MOC22 tumors, respectively. In buccal VX-2 rabbit tumors, combined surface and interstitial PS-PDT (200 J total) yielded complete responses in only 60% of rabbits 6 weeks after a single treatment whereas three repeated weekly treatments with PS-PDT (200 J/week) achieved complete ablation in 100% of tumors. PS-PDT treatments were well tolerated by animals with no treatment-associated toxicities and excellent cosmetic outcomes. SIGNIFICANCE: PS-PDT is a safe and repeatable treatment modality for OCSCC ablation. PS demonstrated tumor selective uptake and PS-PDT treatments achieved reproducible efficacy and effectiveness in multiple tumor models superior to other clinically tested photosensitizer drugs. Cosmetic and functional outcomes were excellent, and no clinically significant treatment-associated toxicities were detected. These results are enabling of window of opportunity trials for fluorescence-guided PS-PDT in patients with early-stage OCSCC scheduled for surgery.

Guidelines for the experimental design of pharmacokinetic studies with nanomaterials in preclinical animal models.

A shared feature in the value proposition of every nanomaterial-based drug delivery systems is the desirable improvement in the disposition (or ADME) and pharmacokinetic profiles of the encapsulated drug being delivered. Remarkable progress has been made towards understanding the complex and multifactorial relationships between pharmacokinetic profiles and nanomaterial physicochemical properties, biological interactions, species physiology, etc. These advances have fuelled the rational design of numerous nanomaterials with long-circulation times and improved tissue accumulation (e.g., in tumours). Unfortunately, a central weakness in many of these research efforts has been the inconsistent and insufficient characterisation of the pharmacokinetic profiles of nanomaterials in scientific reporting-a problem affecting the majoirty of of contemporary nanomaterials literature and innovative nanomaterials in early stages of preclinical development especially. Given the significant role of pharmacokinetic assessments to serve as guideposts for deciding whether to continue with the preclinical development and clinical translation of drug delivery systems, the prevalence of poor pharmacokinetic characterisations in nanomaterials research is particularly alarming. A conspicuous problem in many reports is the inappropriate selection of experimental designs and methodologies for studying nanomaterial pharmacokinetics, the consequences of which are increased uncertainty over the accurate interpretation of reported pharmacokinetic data and diminished experimental reproducibility throughout the field. Thus, there is renewed interest in the establishment of consistent and comprehensive strategies for designing preclinical experiments to assess the pharmacokinetics of nanomaterials with diverse physicochemical properties. Towards this end, herein are proposed simple guidelines for the experimental design of pharmacokinetic studies with nanomaterials drawn from the best research practices, principle strategies, and important considerations used in industry for collecting pharmacokinetic data in preclinical animal models. Specifically, key experimental design factors in these studies are identified and examined in the context of nanomaterials for optimality, including blood sampling strategy and technique, sample allocation and sampling time window, test species selection, experimental sources of pharmacokinetic variability, etc. Methods for noninvasive imaging-derived pharmacokinetic assessments of theranostic nanomaterials are also explored with particular focus on emission tomography imaging modalities. Taken together, this review will provide nanomaterial researchers with practical knowledge and pragmatic recommendations for selecting the best designs and methodologies for assessing the pharmacokinetic profiles of their nanomaterials, and hopefully maximise the chances of translational success of these innovative products into humans.

Photodynamic therapy enables tumor-specific ablation in preclinical models of thyroid cancer.

The incidence of differentiated thyroid cancer has increased significantly during the last several decades. Surgical resection is the primary treatment for thyroid cancer and is highly effective, resulting in 5-year survival rates greater than 98%. However, surgical resection can result in short- and long-term treatment-related morbidities. Additionally, as this malignancy often affects women less than 40 years of age, there is interest in more conservative treatment approaches and, an unmet need for therapeutic options that minimize the risk of surgery-related morbidities while simultaneously providing an effective cancer treatment. Photodynamic therapy (PDT) has the potential to reduce treatment-related side effects by decreasing invasiveness and limiting toxicity. Owing to multiple advantageous properties of the porphyrin-HDL nanoparticle (PLP) as a PDT agent, including preferential accumulation in tumor, biodegradability and unprecedented photosensitizer packing, we evaluate PLP-mediated PDT as a minimally invasive, tumor-specific treatment for thyroid cancer. On both a biologically relevant human papillary thyroid cancer (K1) mouse model and an anatomically relevant rabbit squamous carcinoma (VX2)-implanted rabbit thyroid model, the intrinsic fluorescence of PLP enabled tracking of tumor preferential accumulation and guided PDT. This resulted in significant and specific apoptosis in tumor tissue, but not surrounding normal tissues including trachea and recurrent laryngeal nerve (RLN). A long-term survival study further demonstrated that PLP-PDT enabled complete ablation of tumor tissue while sparing both the normal thyroid tissue and RLN from damage, thus providing a safe, minimally invasive, and effective alternative to thyroidectomy for thyroid cancer therapies.

Research tools for extrapolating the disposition and pharmacokinetics of nanomaterials from preclinical animals to humans.

A critical step in the translational science of nanomaterials from preclinical animal studies to humans is the comprehensive investigation of their disposition (or ADME) and pharmacokinetic behaviours. Disposition and pharmacokinetic data are ideally collected in different animal species (rodent and nonrodent), at different dose levels, and following multiple administrations. These data are used to assess the systemic exposure and effect to nanomaterials, primary determinants of their potential toxicity and therapeutic efficacy. At toxic doses in animal models, pharmacokinetic (termed toxicokinetic) data are related to toxicologic findings that inform the design of nonclinical toxicity studies and contribute to the determination of the maximum recommended starting dose in clinical phase 1 trials. Nanomaterials present a unique challenge for disposition and pharmacokinetic investigations owing to their prolonged circulation times, nonlinear pharmacokinetic profiles, and their extensive distribution into tissues. Predictive relationships between nanomaterial physicochemical properties and behaviours in vivo are lacking and are confounded by anatomical, physiological, and immunological differences amongst preclinical animal models and humans. These challenges are poorly understood and frequently overlooked by investigators, leading to inaccurate assumptions of disposition, pharmacokinetic, and toxicokinetics profiles across species that can have profoundly detrimental impacts for nonclinical toxicity studies and clinical phase 1 trials. Herein are highlighted two research tools for analysing and interpreting disposition and pharmacokinetic data from multiple species and for extrapolating this data accurately in humans. Empirical methodologies and mechanistic mathematical modelling approaches are discussed with emphasis placed on important considerations and caveats for representing nanomaterials, such as the importance of integrating physiological variables associated with the mononuclear phagocyte system (MPS) into extrapolation methods for nanomaterials. The application of these tools will be examined in recent examples of investigational and clinically approved nanomaterials. Finally, strategies for applying these extrapolation tools in a complementary manner to perform dose predictions and in silico toxicity assessments in humans will be explained. A greater familiarity with the available tools and prior experiences of extrapolating nanomaterial disposition and pharmacokinetics from preclinical animal models to humans will hopefully result in a more straightforward roadmap for the clinical translation of promising nanomaterials.

Mixed and Matched Metallo-Nanotexaphyrin for Customizable Biomedical Imaging.

The discovery and synthesis of multifunctional organic building blocks for nanoparticles have remained challenging. Texaphyrin macrocycles are multifunctional, all-organic compounds that possess versatile metal-chelation capabilities and unique theranostics properties for biomedical applications. Unfortunately, there are significant difficulties associated with the synthesis of texaphyrin-based subunits capable of forming nanoparticles. Herein, the detailed synthesis of a texaphyrin-phospholipid building block is reported via a key 1,2-dinitrophenyl-phospholipid intermediate, along with stable chelation of two clinically relevant metal ions into texaphyrin-lipid without compromising their self-assembly into texaphyrin nanoparticles or nanotexaphyrin. A postinsertion methodology to quantitatively insert a variety of metal-ions into preformed nanotexaphyrins is developed and employed to synthesize a structurally stable, mixed 111 indium-manganese-nanotexaphyrin for dual modal single-photon emission computed tomography (SPECT) and magnetic resonance imaging (MRI). In vivo dual SPECT/MRI imaging of 111 In-Mn-nanotexaphyrins in an orthotopic prostatic PC3 mouse model demonstrates complementary signal enhancement in the tumor with both modalities at 22 h post intravenous administration. This result highlights the utility of hybrid metallo-nanotexaphyrins to achieve sensitive and accurate detection of tumors by accommodating multiple imaging modalities. The power of this mixed and matched metallo-nanotexaphyrin strategy can be unleashed to allow a diverse range of multifunctional biomedical imaging.

Evaluation of Novel Imaging Devices for Nanoparticle-Mediated Fluorescence-Guided Lung Tumor Therapy.

BACKGROUND: Nonsurgical and minimally invasive approaches for early-stage peripheral lung cancer are needed to avoid the known morbidity of surgical resection, particularly in high-risk patients. We previously demonstrated the utility of multifunctional porphyrin-phospholipid nanoparticles (porphysomes) for fluorescence imaging and phototherapy after preferential accumulation into tumors. The objective of this study was to demonstrate the feasibility of porphysome-mediated imaging and photothermal therapy using a newly developed fiberscope and thoracoscope. METHODS: To prepare this technology for clinical translation, we developed a porphysome-specific fiberscope (scanning fiber endoscope and porphysome-specific thoracoscope), both capable of detecting porphysome fluorescence, for image-guided transbronchial and transpleural photothermal therapy to treat endobronchial/peribronchial and subpleural tumors, respectively. These were tested in three animal models: human lung cancer xenografts (A549) in mice, orthotopic VX2 lung tumors in rabbits, and ex vivo pig lung into which A549 tumor tissue was transplanted. RESULTS: The scanning fiber endoscope, with a 1.2-mm diameter, is small enough to pass through the working channel of a conventional bronchoscope and could visualize porphysome-laden tumors located inside or close to the peripheral bronchial wall. The porphysome-specific thoracoscope system had high sensitivity for porphysome fluorescence and enabled image-guided thoracoscopic resection of porphysome-accumulating tumors close to the pleura. Porphysomes also enhanced the efficacy of scanning fiber endoscope-guided transbronchial photothermal therapy and porphysome-specific thoracoscope-guided transpleural photothermal therapy, resulting in selective and efficient tumor tissue ablation in the rabbit and pig models. CONCLUSIONS: These results support the potential for clinical translation of this novel platform to affect nonsurgical and minimally invasive treatment options for early-stage peripheral lung cancer.

Rethinking translational nanomedicine: insights from the 'bottom-up' design of the Porphysome for guiding the clinical development of imageable nanomaterials.

Progress in therapeutics and biotechnologies leveraging new insights in our understanding of cancer biology and progression have had an underwhelming clinical significance thus far. A key challenge arising from the creation of nanomedicines consolidating multiple desirable functionalities into a 'all-in-one' platform is that the layering of functionalities into a single agent introduces novel complexities that significantly impede clinical translation. An alternative design approach seeks to exploit intrinsically multi-functional building block to assemble nanomedicines from the bottom-up, yielding agents with a multiplicity of radiologic, pharmacologic, and therapeutic properties derived from a single constituent. Herein are highlighted recent developments in the formulation, multi-modal imaging, and targeting of an exemplary 'one-for-all' nanomaterial-the Pyropheophorbide Porphysome-treated from a hitherto unexplored clinical design and development perspective.