In vitro studies of deferasirox derivatives as potential organelle-targeting traceable anti-cancer therapeutics

Strategic design and development of a siderophore mimic: pioneering anticancer therapy via ROS generation and ferroptosis

We designed a tris-catecholate-based siderophore mimic, H6-T-CATL, to selectively chelate iron(III) from mitochondrial cytochromes and other iron-containing proteins within cellular matrices. This strategic sequestration aims to trigger apoptosis or ferroptosis in cancer cells through the glutathione (GSH)-dependent release of reduced iron and subsequent ROS-mediated cytotoxicity. Synthesis of H6-T-CATL involved precise peptide coupling reactions. Using the Fe(III)-porphyrin model (Fe-TPP-Cl), akin to cytochrome c, we studied H6-T-CATL's ability to extract iron(III), yielding a binding constant (Krel) of 1014 for the resulting iron(III) complex (FeIII-T-CATL)3-. This complex readily underwent GSH-mediated reduction to release bioavailable iron(II), which catalyzed Fenton-like reactions generating hydroxyl radicals (˙OH), confirmed by spectroscopic analyses. Our research underscores the potential of H6-T-CATL to induce cancer cell death by depleting iron(III) from cellular metalloproteins, releasing pro-apoptotic iron(II). Evaluation across various cancer types, including normal cells, demonstrated H6-T-CATL's cytotoxicity through ROS production, mitochondrial dysfunction, and activation of ferroptosis and DNA damage pathways. These findings propose a novel mechanism for cancer therapy, leveraging endogenous iron stores within cells. H6-T-CATL emerges as a promising next-generation anticancer agent, exploiting iron metabolism vulnerabilities to induce selective cancer cell death through ferroptosis induction.

Design, synthesis and evaluation of novel deferasirox derivatives with high antifungal potency in vitro and in vivo

Here we designed and synthesized 58 deferasirox derivatives with the aim of discovering novel antifungal agents. Most compounds exhibited moderate to excellent in vitro antifungal activities against Cryptococcus neoformans H99 with MIC values ranging from 0.25 μg/mL to 16 μg/mL, including ten compounds with MIC values less than 1 μg/mL that were further screened against an additional six pathogenic fungi. This class of compounds showed high potency against Candida glabrata with MIC values ranging from <0.125 μg/mL to 1 μg/mL. We identified that compound 54 has high potency against 14 strains of Candida glabrata spp. and Cryptococcus spp. with MIC values ranging from <0.125 μg/mL to 1 μg/mL. In addition, compound 54 significantly reduced the CFU in a mouse model of disseminated infection with Cryptococcus neoformans H99 at a dose of 10 mg/kg, which is comparable to FLC. Further investigations on compound 54 are currently in progress.

Targeting iron to contrast cancer progression

An altered metabolism of iron fuels cancer growth, invasion, metastasis, and recurrence. Ongoing research in cancer biology is delineating a complex iron-trafficking program involving both malignant cells and their support network of cancer stem cells, immune cells, and other stromal components in the tumor microenvironment. Iron-binding strategies in anticancer drug discovery are being pursued in clinical trials and in multiple programs at various levels of development. Polypharmacological mechanisms of action, combined with emerging iron-associated biomarkers and companion diagnostics, are poised to offer new therapeutic options. By targeting a fundamental player in cancer progression, iron-binding drug candidates (either alone or in combination therapy) have the potential to impact a broad range of cancer types and to address the major clinical problems of recurrence and resistance to therapy.

The design of small-molecule prodrugs and activatable phototherapeutics for cancer therapy

Cancer remains as one of the most significant health problems, with approximately 19 million people diagnosed worldwide each year. Chemotherapy is a routinely used method to treat cancer patients. However, current treatment options lack the appropriate selectivity for cancer cells, are prone to resistance mechanisms, and are plagued with dose-limiting toxicities. As such, researchers have devoted their attention to developing prodrug-based strategies that have the potential to overcome these limitations. This tutorial review highlights recently developed prodrug strategies for cancer therapy. Prodrug examples that provide an integrated diagnostic (fluorescent, photoacoustic, and magnetic resonance imaging) response, which are referred to as theranostics, are also discussed. Owing to the non-invasive nature of light (and X-rays), we have discussed external excitation prodrug strategies as well as examples of activatable photosensitizers that enhance the precision of photodynamic therapy/photothermal therapy. Activatable photosensitizers/photothermal agents can be seen as analogous to prodrugs, with their phototherapeutic properties at a specific wavelength activated in the presence of disease-related biomarkers. We discuss each design strategy and illustrate the importance of targeting biomarkers specific to the tumour microenvironment and biomarkers that are known to be overexpressed within cancer cells. Moreover, we discuss the advantages of each approach and highlight their inherent limitations. We hope in doing so, the reader will appreciate the current challenges and available opportunities in the field and inspire subsequent generations to pursue this crucial area of cancer research.

2D-ultrathin MXene/DOXjade platform for iron chelation chemo-photothermal therapy

An increased demand for iron is a hallmark of cancer cells and is thought necessary to promote high cell proliferation, tumor progression and metastasis. This makes iron metabolism an attractive therapeutic target. Unfortunately, current iron-based therapeutic strategies often lack effectiveness and can elicit off-target toxicities. We report here a dual-therapeutic prodrug, DOXjade, that allows for iron chelation chemo-photothermal cancer therapy. This prodrug takes advantage of the clinically approved iron chelator deferasirox (ExJade®) and the topoisomerase 2 inhibitor, doxorubicin (DOX). Loading DOXjade onto ultrathin 2D Ti₃C₂ MXene nanosheets produces a construct, Ti₃C₂-PVP@DOXjade, that allows the iron chelation and chemotherapeutic functions of DOXjade to be photo-activated at the tumor sites, while potentiating a robust photothermal effect with photothermal conversion efficiencies of up to 40%. Antitumor mechanistic investigations reveal that upon activation, Ti₃C₂-PVP@DOXjade serves to promote apoptotic cell death and downregulate the iron depletion-induced iron transferrin receptor (TfR). A tumor pH-responsive iron chelation/photothermal/chemotherapy antitumor effect was achieved both in vitro and in vivo. The results of this study highlight what may constitute a promising iron chelation-based phototherapeutic approach to cancer therapy.

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A conceptually novel “dual-therapeutic prodrug nanomedicine” strategy was designed for synergistic cancer therapy.

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An innovative pH responsive dual-therapeutic conjugate DOXjade was synthesized based on deferasirox and doxorubicin.

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Ti₃C₂-PVP@DOXjade with photoirradiation showed pH-responsive iron chelation/PTT/chemotherapy antitumor effect.

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This study thus serves to demonstrate a promising step forward in the development of precise cancer therapies.

Fluorescent probes for the detection of disease-associated biomarkers

Fluorescent probes have emerged as indispensable chemical tools to the field of chemical biology and medicine. The ability to detect intracellular species and monitor physiological processes has not only advanced our knowledge in biology but has provided new approaches towards disease diagnosis. In this review, we detail the design criteria and strategies for some recently reported fluorescent probes that can detect a wide range of biologically important species in cells and in vivo. In doing so, we highlight the importance of each biological species and their role in biological systems and for disease progression. We then discuss the current problems and challenges of existing technologies and provide our perspective on the future directions of the research area. Overall, we hope this review will provide inspiration for researchers and prove as useful guide for the development of the next generation of fluorescent probes.

Tuning the Solid- and Solution-State Fluorescence of the Iron-Chelator Deferasirox

Deferasirox, an FDA-approved iron chelator, has gained increasing attention for use in anticancer and antimicrobial applications. Recent efforts by our group led to the identification of this core as an easy-to-visualize aggregation-induced emission platform, or AIEgen, that provides a therapeutic effect equivalent to deferasirox (J. Am. Chem. Soc. 2021, 143, 3, 1278-1283). However, the emission wavelength of the first-generation system overlapped with that of Syto9, a green emissive dye used to indicate live cells. Here, we report a library of deferasirox derivatives with various fluorescence emission profiles designed to overcome this limitation. We propose referring to systems that show promise as both therapeutic and optical imaging agents as "illuminoceuticals". The color differences between the derivatives were observable to the unaided eye (solid- and solution-state) and were in accord with the Commission Internationale de L'Eclairage (CIE) chromaticity diagram 1913. Each fluorescent derivative successfully imaged the respective spherical and rod shapes of methicillin-resistant Staphylococcus aureus (MRSA) and Pseudomonas aeruginosa. They also displayed iron-dependent antibiotic activity. Three derivatives, ExNMe₂ (3), ExTrisT (11), and ExDCM (13), display emission features that are sufficiently distinct so as to permit the multiplex (triplex) imaging of both MRSA and P. aeruginosa via stimulated emission depletion microscopy. The present deferasirox derivatives allowed for the construction of a multi-fluorophore sensor array. This array enabled the successful discrimination between Gram-positive/Gram-negative and drug-sensitive/drug-resistant bacteria. Antibiotic sensitivity and drug-resistant mutants from clinically isolated strains could also be identified and differentiated.

Dual-factor Synergistically Activated ESIPT-based Probe: Differential Fluorescence Signals to Simultaneously Detect α-Naphthyl Acetate and Acid α-Naphthyl Acetate Esterase

α-Naphthyl acetate esterase (α-NAE) and acid α-naphthyl acetate esterase (ANAE), a class of special esterases, are important for lymphocyte typing and immunocompetence-monitoring. As such, the simultaneous detection of α-NAE and ANAE has become a target to effectively improve the accuracy in lymphocyte typing. Therefore, we developed a dual-factor synergistically activated ESIPT-based probe (HBT-NA) to detect α-NAE and ANAE sensitively, rapidly, and simultaneously in a differential manner. HBT-NA exhibits differential fluorescence signal outputs toward small changes of α-NAE and ANAE activities. HBT-NA displays a weak fluorescence signal at 392 nm over a pH range from 6.0 to 7.4. However, when it interacts with α-NAE (0-25 U) at pH = 7.4, the fluorescence intensity at 392 nm enhanced linearly within 60 s (F_392 nm/F0_392 nm = 0.042 C_α-NAE + 1.1, R² = 0.99). Furthermore, HBT-NA emits ratiometric fluorescence signals (F_505 nm/F_392 nm) for ANAE (0-25 U) at pH = 6.0 within 2.0 min, exhibiting a good linear relationship (F_505 nm/F_392 nm = 0.83C_ANAE - 1.75, R² = 0.99). The differential fluorescence signals can be used to simultaneously detect the activities of α-NAE and ANAE in solutions and complex living organisms. More importantly, based on the differential fluorescence signals toward α-NAE and ANAE, T lymphocytes and B lymphocytes could be successfully typed and differentiated among nontyped lymphocytes, facilitating the real-time evaluation of their immune functions using flow cytometry. Hence, HBT-NA could be used for the ultrasensitive detection of the enzyme activities of α-NAE and ANAE, the real-time precise typing of lymphocytes, and the monitoring of immunocompetence.