Glymphatic-assisted perivascular brain delivery of intrathecal small gold nanoparticles

Nanoparticles are ultrafine particulate matter having considerable potential for treatment of central nervous system (CNS) disorders. Despite their tiny size, the blood-brain barrier (BBB) restricts their access to the CNS. Their direct cerebrospinal fluid (CSF) administration bypasses the BBB endothelium, but still fails to give adequate brain uptake. We present a novel approach for efficient CNS delivery of ¹¹¹In-radiolabelled gold nanoparticles (AuNPs; 10-15 nm) via intra-cisterna magna administration, with tracking by SPECT imaging. To accelerate CSF brain influx, we administered AuNPs intracisternally in conjunction with systemic hypertonic saline, which dramatically increased the parenchymal AuNP uptake, especially in deep brain regions. AuNPs entered the CNS along periarterial spaces as visualized by MRI of gadolinium-labelled AuNPs and were cleared from brain within 24 h and excreted through the kidneys. Thus, the glymphatic-assisted perivascular network augment by systemic hypertonic saline is a pathway for highly efficient brain-wide distribution of small AuNPs.

New 4-Aminoproline-Based Small Molecule Cyclopeptidomimetics as Potential Modulators of α4β1 Integrin

Integrin α₄β₁ belongs to the leukocyte integrin family and represents a therapeutic target of relevant interest given its primary role in mediating inflammation, autoimmune pathologies and cancer-related diseases. The focus of the present work is the design, synthesis and characterization of new peptidomimetic compounds that are potentially able to recognize α₄β₁ integrin and interfere with its function. To this aim, a collection of seven new cyclic peptidomimetics possessing both a 4-aminoproline (Amp) core scaffold grafted onto key α₄β₁-recognizing sequences and the (2-methylphenyl)ureido-phenylacetyl (MPUPA) appendage, was designed, with the support of molecular modeling studies. The new compounds were synthesized through SPPS procedures followed by in-solution cyclization maneuvers. The biological evaluation of the new cyclic ligands in cell adhesion assays on Jurkat cells revealed promising submicromolar agonist activity in one compound, namely, the c[Amp(MPUPA)Val-Asp-Leu] cyclopeptide. Further investigations will be necessary to complete the characterization of this class of compounds.

Advances in Development of Radiometal Labeled Amino Acid-Based Compounds for Cancer Imaging and Diagnostics

Radiolabeled biomolecules targeted at tumor-specific enzymes, receptors, and transporters in cancer cells represent an intensively investigated and promising class of molecular tools for the cancer diagnosis and therapy. High specificity of such biomolecules is a prerequisite for the treatment with a lower burden to normal cells and for the effective and targeted imaging and diagnosis. Undoubtedly, early detection is a key factor in efficient dealing with many severe tumor types. This review provides an overview and critical evaluation of novel approaches in the designing of target-specific probes labeled with metal radionuclides for the diagnosis of most common death-causing cancers, published mainly within the last three years. Advances are discussed such traditional peptide radiolabeling approaches, and click and nanoparticle chemistry. The progress of radiolabeled peptide based ligands as potential radiopharmaceuticals is illustrated via novel structure and application studies, showing how the molecular modifications reflect their binding selectivity to significant onco-receptors, toxicity, and, by that, practical utilization. The most impressive outputs in categories of newly developed structures, as well as imaging and diagnosis approaches, and the most intensively studied oncological diseases in this context, are emphasized in order to show future perspectives of radiometal labeled amino acid-based compounds in nuclear medicine.

Efficacy of a Selective Binder of αVβ3 Integrin Linked to the Tyrosine Kinase Inhibitor Sunitinib in Ovarian Carcinoma Preclinical Models

Ovarian carcinoma, the most lethal gynecological cancer, is characterized by late diagnosis, with drug resistance limiting the efficacy of platinum-based therapy. Since some integrins are upregulated in cancer, including ovarian carcinoma, they represent a potential target for drug delivery. Receptor tyrosine kinases are also deregulated in cancer and their expression has been associated with drug resistance. Here, the antitumor effects of three conjugates possessing a selective binder of the extracellular portion of integrin α_Vβ₃ covalently linked to the tyrosine kinase inhibitor sunitinib were investigated in cisplatin-sensitive and -resistant ovarian carcinoma cells expressing both tyrosine kinase VEGFR2 and α_Vβ₃ at different levels. We found that one of the three compounds was active in inhibiting the growth of both drug-sensitive and -resistant cells in the micromolar range with a slightly increased potency in resistant cells as compared to sunitinib. The same compound markedly impaired cell migratory and invasive abilities and reduced paxillin phosphorylation. Antitumor activity studies in IGROV-1/Pt1 cells xenografted in nude mice revealed a striking activity of this conjugate versus sunitinib. Taken together, our results support the interest of integrin-targeted sunitinib conjugates for the treatment of drug-resistant tumors.

Integrin-targeted AmpRGD sunitinib liposomes as integrated antiangiogenic tools

We report here the preparation, physico-chemical characterization, and biological evaluation of a new liposome formulation as a tool for tumor angiogenesis inhibition. Liposomes are loaded with sunitinib, a tyrosine kinase inhibitor, and decorated with cyclo-aminoprolineRGD units (cAmpRGD), efficient and selective ligands for integrin α_Vβ₃. The RGD units play multiple roles since they target the nanovehicles at the integrin α_Vβ₃-overexpressing cells (e.g. activated endothelial cells), favor their active cell internalization, providing drug accumulation in the cytoplasm, and likely take part in the angiogenesis inhibition by interfering in the α_Vβ₃-VEGFR2 cross-talk. Both in vitro and in vivo studies show a better efficacy of this integrated antiangiogenic tool with respect to the free sunitinib and untargeted sunitinib-loaded liposomes. This system could allow a lower administration of the drug and, by increasing the vector specificity, reduce side-effects in a prolonged antiangiogenic therapy.

Cell-targeted c(AmpRGD)-sunitinib molecular conjugates impair tumor growth of melanoma

Drug resistance and off-organ toxicity remain unsolved issues in chemotherapy of advanced-stage melanoma patients. Thus, the creation of new molecular conjugates able to combine a selective accumulation, high ability of internalization and signaling pathway inhibition, are highly requested. Recently, we reported a new class of molecular conjugates, compounds 1-3, where the anti-α_Vβ₃ integrin peptidomimetic c(AmpRGD), which is a selective ligand for α_Vβ₃ integrin, was covalently bound to the tyrosine kinase inhibitor sunitinib. Here, we report that these c(AmpRGD)-sunitinib conjugates and, in particular, compound 3, are selectively internalized by human melanoma cells through α_Vβ₃ receptor-mediated endocytosis. Compound 3 is more effective than sunitinib in reducing in vitro melanoma cells proliferation, cloning efficiency, migration, and invasion. More interestingly, compound 3 is able to significantly reduce the growth of xenografted melanoma tumor developed in immune-compromised mice, more efficiently than an equimolar dose of sunitinib. Indeed, its targeting ability was demonstrated by the selective localization at the tumor level with respect to healthy tissues. Thus, c(AmpRGD)-sunitinib conjugates such as compound 3 could serve as intriguing multiple-target agents to selectively reach melanoma cells and interfere with the progression of the disease.

Synthesis of Novel c(AmpRGD)-Sunitinib Dual Conjugates as Molecular Tools Targeting the αvβ3 Integrin/VEGFR2 Couple and Impairing Tumor-Associated Angiogenesis

On the basis of a previously discovered anti-α_Vβ₃ integrin peptidomimetic (c(AmpRGD)) and the clinically approved antiangiogenic kinase inhibitor sunitinib, three novel dual conjugates were synthesized (compounds 1-3), featuring the covalent and robust linkage between these two active modules. In all conjugates, the ligand binding competence toward α_Vβ₃ (using both isolated receptors and α_Vβ₃-overexpressing endothelial progenitor EP cells) and the kinase inhibitory activity (toward both isolated kinases and EPCs) remained almost untouched and comparable to the activity of the single active units. Compounds 1-3 showed interesting antiangiogenesis properties in an in vitro tubulogenic assay; furthermore, dimeric-RGD conjugate 3 strongly inhibited in vivo angiogenesis in Matrigel plug assays in FVB mice. These results offer proof-of-concept of how the covalent conjugation of two angiogenesis-related small modules may result in novel and stable molecules, which impair tumor-related angiogenesis with equal or even superior ability as compared to the single modules or their simple combinations.