Improving In Vivo Tumor Accumulation and Efficacy of Platinum Antitumor Agents by Electronic Tuning of the Kinetic Lability.

The impact of kinetic lability or reactivity on in vitro cytotoxicity, stability in plasma, in vivo tumor and tissue accumulation, and antitumor efficacy of functional platinum(II) (Pt) anticancer agents containing a O˄O ß-diketonate leaving ligand remain largely unexplored. To investigate this, we synthesized Pt complexes [(NH3 )2 Pt(L1-H)]NO3 and [(DACH)Pt(L1-H)]NO3 (L1=4,4,4-trifluoro-1-ferrocenylbutane-1,3-dione, DACH=1R,2R-cyclohexane-1,2-diamine) containing an electron deficient [L1-H]- O˄O leaving ligand and [(NH3 )2 Pt(L2-H)]NO3 and [(DACH)Pt(L2-H)]NO3 (L2=1-ferrocenylbutane-1,3-dione) containing an electron-rich [L2-H]- O˄O leaving ligand. While all four complexes have comparable lipophilicity, the presence of the electron-withdrawing CF3 group was found to dramatically enhance the reactivity of these complexes toward nucleophilic biomolecules. In vitro cellular assays revealed that the more reactive complexes have higher cellular uptake and higher anticancer potency as compared to their less reactive analogs. But the scenario is opposite in vivo, where the less reactive complex showed improved tissue and tumor accumulation and better anticancer efficacy in mice bearing ovarian xenograft when compared to its more reactive analog. Finally, in addition to demonstrating the profound but contrasting impact of kinetic lability on in vitro and in vivo antitumor potencies, we also described the impact of kinetic lability on the mechanism of action of this class of promising antitumor agents.

Necrosis-Inducing High-Valent Oxo-Rhenium(V) Complexes with Potent Antitumor Activity: Synthesis, Aquation Chemistry, Cisplatin Cross-Resistance Profile, and Mechanism of Action.

Chemotherapy with the cytotoxic platinum (Pt) drugs cisplatin, carboplatin, and oxaliplatin is the mainstay of anticancer therapy in the clinic. The antitumor activity of Pt drugs originates from their ability to induce apoptosis via covalent adduct formation with nuclear DNA. While the phenomenal clinical success is highly encouraging, resistance and adverse toxic side effects limit the wider applicability of Pt drugs. To circumvent these limitations, we embarked on an effort to explore the antitumor potential of a new class of oxo-rhenium(V) complexes of the type [(N∧N)(EG)Re(O)Cl] (where EG = ethylene glycolate and N∧N = bipyridine, Bpy (1); phenanthroline, Phen (2); 3,4,7,8-tetramethyl-phenanthroline, Me4Phen (3)). Investigation of speciation chemistry in aqueous media revealed the formation of [(N∧N)Re(O)(OH)3] as the biologically active species. Complex 3 was found to be the most potent among the three, with IC50 values ranging from 0.1 to 0.4 µM against a panel of cancer cells, which is 5-70-fold lower when compared with cisplatin. The higher potency of 3 is attributed to its higher lipophilicity, which enhanced cellular uptake. Importantly, complex 3 efficiently overcomes cisplatin resistance in ovarian, lung, and prostate cancer cells. In addition to reporting the aquation chemistry and identifying the active species in aqueous media, we performed in-depth in vitro mechanistic studies, which revealed that complex 3 preferentially accumulates in mitochondria, depletes mitochondrial membrane potential, and upregulates intracellular reactive oxygen species (ROS), leading to ER stress-mediated necrosis-mediated cancer cell death.

TCA cycle tailoring facilitates optimal growth of proton-pumping NADH dehydrogenase-dependent Escherichia coli.

IMPORTANCE: Energy generation pathways are a potential avenue for the development of novel antibiotics. However, bacteria possess remarkable resilience due to the compensatory pathways, which presents a challenge in this direction. NADH, the primary reducing equivalent, can transfer electrons to two distinct types of NADH dehydrogenases. Type I NADH dehydrogenase is an enzyme complex comprising multiple subunits and can generate proton motive force (PMF). Type II NADH dehydrogenase does not pump protons but plays a crucial role in maintaining the turnover of NAD+. To study the adaptive rewiring of energy metabolism, we evolved an Escherichia coli mutant lacking type II NADH dehydrogenase. We discovered that by modifying the flux through the tricarboxylic acid (TCA) cycle, E. coli could mitigate the growth impairment observed in the absence of type II NADH dehydrogenase. This research provides valuable insights into the intricate mechanisms employed by bacteria to compensate for disruptions in energy metabolism.

Development of a Highly In Vivo Efficacious Dual Antitumor and Antiangiogenic Organoiridium Complex as a Potential Anti-Lung Cancer Agent.

While the phenomenal clinical success of blockbuster platinum (Pt) drugs is highly encouraging, the inherent and acquired resistance and dose-limiting side effects severely limit their clinical application. To find a better alternative with translational potential, we synthesized a library of six organo-IrIII half-sandwich [(η5-CpX)Ir(N∧N)Cl]+-type complexes. In vitro screening identified two lead candidates [(η5-CpXPh)Ir(Ph2Phen)Cl]+ (5, CpXPh = tetramethyl-phenyl-cyclopentadienyl and Ph2Phen = 4,7-diphenyl-1,10-phenanthroline) and [(η5-CpXBiPh)Ir(Ph2Phen)Cl]+ (6, CpXBiPh = tetramethyl-biphenyl-cyclopentadienyl) with nanomolar IC50 values. Both 5 and 6 efficiently overcame Pt resistance and presented excellent cancer cell selectivity in vitro. Potent antiangiogenic properties of 6 were demonstrated in the zebrafish model. Satisfyingly, 6 and its nanoliposome Lipo-6 presented considerably higher in vivo antitumor efficacy as compared to cisplatin, as well as earlier reported IrIII half-sandwich complexes in mice bearing the A549 non-small lung cancer xenograft. In particular, complex 6 is the first example of this class that exerted dual in vivo antiangiogenic and antitumor properties.

The Power of Kinetic Inertness in Improving Platinum Anticancer Therapy by Circumventing Resistance and Ameliorating Nephrotoxicity.

Even in the modern era of precision medicine and immunotherapy, chemotherapy with platinum (Pt) drugs remains among the most commonly prescribed medications against a variety of cancers. Unfortunately, the broad applicability of these blockbuster Pt drugs is severely limited by intrinsic and/or acquired resistance, and high systemic toxicity. Considering the strong interconnection between kinetic lability and undesired shortcomings of clinical Pt drugs, we rationally designed kinetically inert organometallic Pt based anticancer agents with a novel mechanism of action. Using a combination of in vitro and in vivo assays, we demonstrated that the development of a remarkably efficacious but kinetically inert Pt anticancer agent is feasible. Along with exerting promising antitumor efficacy in Pt-sensitive as well as Pt-resistant tumors in vivo, our best candidate has the ability to mitigate the nephrotoxicity issue associated with cisplatin. In addition to demonstrating, for the first time, the power of kinetic inertness in improving the therapeutic benefits of Pt based anticancer therapy, we describe the detailed mechanism of action of our best kinetically inert antitumor agent. This study will certainly pave the way for designing the next generation of anticancer drugs for effective treatment of various cancers.

Platinum glycoconjugates: "Sweet bullets" for targeted cancer therapy?

Cancer, which is characterized by uncontrolled proliferation of abnormal cells, is a leading cause of morbidity and mortality worldwide. Cytotoxic chemotherapy, especially with platinum drugs, remains the mainstay of cancer treatment in the clinical setting. Despite phenomenal success, small-molecule chemotherapeutic drugs suffer from some serious drawbacks. Lack of cancer selectivity and the ensuing side effects mar the therapeutic potential of these drugs. Glycoconjugation has emerged as an attractive strategy for imparting selectivity and improving pharmacokinetics of cytotoxic agents. In this review, we provide an overview of the glycoconjugation strategy and then illustrate the application of this strategy with the help of some concrete examples of platinum based glycoconjugates. At the end we discuss a few important aspects of these glycoconjugates which merit further investigations.

Potent Ruthenium-Ferrocene Bimetallic Antitumor Antiangiogenic Agent That Circumvents Platinum Resistance: From Synthesis and Mechanistic Studies to In Vivo Evaluation in Zebrafish.

Emergence of resistance in cancer cells and dose-limiting side effects severely limit the widespread use of platinum (Pt) anticancer drugs. Multi-action hybrid anticancer agents that are constructed by merging two or more pharmacophores offer the prospect of circumventing issues of Pt drugs. Herein, we report the design, synthesis, and in-depth biological evaluation of a ruthenium-ferrocene (Ru-Fc) bimetallic agent [(η6-p-cymene)Ru(1,1,1-trifluoro-4-oxo-4-ferrocenyl-but-2-en-2-olate)Cl] and its five analogues. Along with aquation/anation chemistry, we evaluated the in vitro antitumor potency, Pt cross-resistance profile, and in vivo antiangiogenic properties. A structure activity analysis was performed to understand the impact of Fc, CF3, and p-cymene groups on the anticancer potency of the Ru-Fc hybrid. Finally, in addition to assessing cellular uptake and intracellular distribution, we demonstrated that the Ru-Fc hybrid binds to nucleophilic biomolecules and produces reactive oxygen species, which causes mitochondrial dysfunction and induces ER stress, leading to poly(ADP-ribose) polymerase-mediated necroptotic cell death.

A BOPHY based fluorescent probe for Hg2+via NTe2 chelation.

A BOPHY-based organotellurium-containing probe was synthesized and characterized via single crystal XRD for the selective and sensitive detection of Hg2+ over other metal ions. The probe detects Hg2+ in less than 1 s with a 2.5-fold enhancement in fluorescent intensity. Due to the chalcogenophilicity of mercury, Hg2+ was facilely trapped in the NTe2 chelating cavity of the probe. The probe can detect Hg2+ in the nanomolar range (62 nM) and it showed reversibility with S2- ions. The sensitivity of the probe for the detection of Hg2+ was confirmed in living HeLa cells.

A Rationally Designed Bimetallic Platinum (II)-Ferrocene Antitumor Agent Induces Non-Apoptotic Cell Death and Exerts in Vivo Efficacy.

Despite phenomenal clinical success, the efficacy of platinum anticancer drugs is often compromised due to inherent and acquired drug resistant phenotypes in cancers. To circumvent this issue, we designed two heterobimetallic platinum (II)-ferrocene hybrids that display multi-pronged anticancer action. In cancer cells, our best compound, 2, platinates DNA, produces reactive oxygen species, and has nucleus, mitochondria, and endoplasmic reticulum as potential targets. The multi-modal mechanism of action of these hybrid agents lead to non-apoptotic cell death induction which enables circumventing apoptosis resistance and significant improvement in platinum cross resistance profile. Finally, in addition to describing detail mechanistic insights, we also assessed its stability in plasma and demonstrate anticancer efficacy in an in vivo A2780 xenograft model. Strikingly, compared to oxaliplatin, our compound displays better tolerability, safety profile and efficacy in vivo.

Challenges and opportunities in the development of metal-based anticancer theranostic agents.

Around 10 million fatalities were recorded worldwide in 2020 due to cancer and statistical projections estimate the number to increase by 60% in 2040. With such a substantial rise in the global cancer burden, the disease will continue to impose a huge socio-economic burden on society. Currently, the most widely used clinical treatment modality is cytotoxic chemotherapy using platinum drugs which is used to treat variety of cancers. Despite its clinical success, critical challenges like resistance, off-target side effects and cancer variability often reduce its overall therapeutic efficiency. These challenges require faster diagnosis, simultaneous therapy and a more personalized approach toward cancer management. To this end, small-molecule 'theranostic' agents have presented a viable solution combining diagnosis and therapy into a single platform. In this review, we present a summary of recent efforts in the design and optimization of metal-based small-molecule 'theranostic' anticancer agents. Importantly, we highlight the advantages of a theranostic candidate over the purely therapeutic or diagnostic agent in terms of evaluation of its biological properties.

X-rays Actuate Anticancer Drugs: Opening New Vistas in Prodrug Therapy.

Chemotherapy is the primary treatment modality employed in the clinic for the treatment of cancer. Despite proven clinical success, adverse side effects are one of the drawbacks of this approach. The prodrug strategy has emerged as an alternative approach with the aim of alleviating these drawbacks. Prodrug activation is typically achieved by either endogenous or exogenous triggers. Exogenous triggers like light are appealing as they are independent of inherent patient and/or cancer-type variations. However, tissue penetration depth remains the Achilles' heel of this approach. In this context, usage of X-rays as the external trigger with infinite tissue penetration depth opens up exciting prospects in prodrug activation strategies.

Interaction of the C2 Ig-like Domain of Cardiac Myosin Binding Protein-C with F-actin.

Cardiac muscle contraction depends on interactions between thick (myosin) and thin (actin) filaments (TFs). TFs are regulated by intracellular Ca2+ levels. Under activating conditions Ca2+ binds to the troponin complex and displaces tropomyosin from myosin binding sites on the TF surface to allow actomyosin interactions. Recent studies have shown that in addition to Ca2+, the first four N-terminal domains (NTDs) of cardiac myosin binding protein C (cMyBP-C) (e.g. C0, C1, M and C2), are potent modulators of the TF activity, but the mechanism of their collective action is poorly understood. Previously, we showed that C1 activates the TF at low Ca2+ and C0 stabilizes binding of C1 to the TF, but the ability of C2 to bind and/or affect the TF remains unknown. Here we obtained 7.5 Å resolution cryo-EM reconstruction of C2-decorated actin filaments to demonstrate that C2 binds to actin in a single structural mode that does not activate the TF unlike the polymorphic binding of C0 and C1 to actin. Comparison of amino acid sequences of C2 with either C0 or C1 shows low levels of identity between the residues involved in interactions with the TF but high levels of conservation for residues involved in Ig fold stabilization. This provides a structural basis for strikingly different interactions of structurally homologous C0, C1 and C2 with the TF. Our detailed analysis of the interaction of C2 with the actin filament provides crucial information required to model the collective action of cMyBP-C NTDs on the cardiac TF.

Light-induced synthesis of protein conjugates and its application in photoradiosynthesis of 89Zr-radiolabeled monoclonal antibodies.

Efficient methods to functionalize proteins are essential for the development of many diagnostic and therapeutic compounds, such as fluorescent probes for immunohistochemistry, zirconium-89 radiolabeled mAbs (89Zr-mAbs) for positron emission tomography and antibody-drug conjugates (ADCs). This protocol describes a step-by-step procedure for the light-induced functionalization of proteins with compounds bearing the photochemically active aryl azide group. As an illustration of the potential utility of our approach, this protocol focuses on the synthesis of 89Zr-mAbs using photoactivatable derivatives of the metal ion binding chelate desferrioxamine B (DFO). The light-induced synthesis of 89Zr-mAbs is a unique, one-pot process involving simultaneous radiolabeling and protein conjugation. The photoradiochemical synthesis of purified 89Zr-mAbs, starting from unmodified proteins, [89Zr][Zr(C2O4)4]4- (89Zr-oxalate), and a photoactivatable DFO derivative, can be performed in <90 min. The method can be easily adapted to prepare other radiolabeled proteins, ADCs or fluorescently tagged proteins by using drug molecules or fluorophores functionalized with photoactive moieties.

Increased Lipophilicity of Halogenated Ruthenium(II) Polypyridyl Complexes Leads to Decreased Phototoxicity in†vitro when Used as Photosensitizers for Photodynamic Therapy.

In the fight against cancer, photodynamic therapy is generating great interest thanks to its ability to selectively kill cancer cells without harming healthy tissues. In this field, ruthenium(II) polypyridyl complexes, and more specifically, complexes with dipyrido[3,2-a:2',3'-c]phenazine (dppz) as a ligand are of particular interest due to their DNA-binding and photocleaving properties. However, ruthenium(II) polypyridyl complexes can sometimes suffer from low lipophilicity, which hampers cellular internalisation through passive diffusion. In this study, four new [Ru(dppz-X2 )3 ]2+ complexes (X=H, F, Cl, Br, I) were synthesized and their lipophilicity (logP), cytotoxicity and phototoxicity on cancerous and noncancerous cell lines were assessed. This study shows that, counterintuitively, the phototoxicity of these complexes decreases as their lipophilicity increases; this could be due solely to the atomic radius of the halogen substituents.

Structural basis for active single and double ring complexes in human mitochondrial Hsp60-Hsp10 chaperonin.

mHsp60-mHsp10 assists the folding of mitochondrial matrix proteins without the negative ATP binding inter-ring cooperativity of GroEL-GroES. Here we report the crystal structure of an ATP (ADP:BeF3-bound) ground-state mimic double-ring mHsp6014-(mHsp107)2 football complex, and the cryo-EM structures of the ADP-bound successor mHsp6014-(mHsp107)2 complex, and a single-ring mHsp607-mHsp107 half-football. The structures explain the nucleotide dependence of mHsp60 ring formation, and reveal an inter-ring nucleotide symmetry consistent with the absence of negative cooperativity. In the ground-state a two-fold symmetric H-bond and a salt bridge stitch the double-rings together, whereas only the H-bond remains as the equatorial gap increases in an ADP football poised to split into half-footballs. Refolding assays demonstrate obligate single- and double-ring mHsp60 variants are active, and complementation analysis in bacteria shows the single-ring variant is as efficient as wild-type mHsp60. Our work provides a structural basis for active single- and double-ring complexes coexisting in the mHsp60-mHsp10 chaperonin reaction cycle.

A Ru(II) polypyridyl complex bearing aldehyde functions as a versatile synthetic precursor for long-wavelength absorbing photodynamic therapy photosensitizers.

The use of Photodynamic Therapy (PDT) for the treatment of several kinds of cancer as well as bacterial, fungal or viral infections has received increasing attention during the last decade. However, the currently clinically approved photosensitizers (PSs) have several drawbacks, including photobleaching, slow clearance from the organism and poor water solubility. To overcome these shortcomings, many efforts have been made in the development of new types of PSs, such as Ru(II) polypyridyl complexes. Nevertheless, most studied Ru(II) polypyridyl complexes have a low absorbance in the spectral therapeutic window. In this work, we show that, by carefully selecting substituents on the polypyridyl complex, it is possible to prepare a complex absorbing at a much higher wavelength. Specifically, we report on the synthesis as well as in-depth experimental and theoretical characterisation of a Ru(II) polypyridyl complex (complex 3) combining a shift in absorbance towards the spectral therapeutic window with a high 1O2 production. To overcome the absence or poor selectivity of most approved PSs into targeted cells/bacteria, they can be linked to targeting moieties. In this line, compound 3 was designed with reactive aldehyde groups, which can be used as a highly versatile synthetic precursor for further conjugation. As a proof of concept, 3 was reacted with benzylamine and the stability of the resulting conjugate 4 was investigated in DMSO, PBS and cell media. 4 showed an impressive ability to act as a PDT PS with no measurable dark cytotoxicity and photocytotoxicity in the low micromolar range against cancerous HeLa cells from 450 nm up to 540 nm.

Simultaneous Photoradiochemical Labeling of Antibodies for Immuno-Positron Emission Tomography.

A method for the simultaneous (one-step) photochemical conjugation and 89Zr-radiolabeling of antibodies is introduced. A photoactivatable chelate based on the functionalization of desferrioxamine B with an arylazide moiety (DFO-ArN3, [1]) was synthesized. The radiolabeled complex, 89Zr-1+, was produced and characterized. Density functional theory calculations were used to investigate the mechanism of arylazide photoactivation. 89Zr-radiolabeling experiments were also used to determine the efficiency of photochemical conjugation. A standard two-step approach gave a measured conjugation efficiency of 3.5% ± 0.4%. In contrast, the one-step process gave a higher photoradiolabeling efficiency of ∼76%. Stability measurements, cellular saturation binding assays, positron emission tomographic imaging, and biodistribution studies in mice bearing SK-OV-3 tumors confirmed the biochemical viability and tumor specificity of photoradiolabeled [89Zr]ZrDFO-azepin-trastuzumab. Experimental data support the conclusion that the combination of photochemistry and radiochemistry is a viable strategy for producing radiolabeled proteins for imaging and therapy.

A novel variant of the human mitochondrial DnaJ protein, Tid1, associates with a human disease exhibiting developmental delay and polyneuropathy.

Here, we describe a single patient from a consanguineous family, who suffers from developmental delay, intellectual disability, hypermetropia, moderate alternating esotropia, unsteady gait, and peripheral polyneuropathy. Brain MRI revealed basal ganglia disease. Exome analysis disclosed a homozygous variant, c.452G>C (p.(Arg151Thr)), in TID1, encoding a mitochondrial J-protein chaperone that is known for its function in assisting the Hsp70 chaperone, mortalin, in mediating the refolding of denatured protein and dissolving protein aggregates. Results from in vitro import assays showed that both wild type and c.452G>C (p.(Arg151Thr)) are efficiently imported into isolated mitochondria. However, the import rate of the c.452G>C (p.(Arg151Thr)) variant was less than that of the wild-type protein. In the second part of this study, we demonstrated, in vitro, that the disaggregation function of the mortalin/Tid1 team is compromised in the TID1 c.452G>C (p.(Arg151Thr)) variant, as its chaperone activity has a level similar to that of the non-functional H→Q HPD domain variant. The results shed light on the essential function played by Tid1 during neuronal development.

Photoactive chelates for radiolabelling proteins.

Photochemical reactions are an attractive foundation for the synthesis of radiolabelled antibodies, immunoglobulin fragments and other proteins/peptides. The synthesis, 68Ga-radiochemistry and photochemical reactivity of three macrocyclic chelates functionalised with an arylazide group is described. Experiments with trastuzumab confirmed that photoradiochemistry facilitates fast, one-pot synthesis of radiolabelled proteins.

Photochemical Conjugation and One-Pot Radiolabelling of Antibodies for Immuno-PET.

Monoclonal antibodies (mAbs), immunoglobulin fragments, and other proteins are important scaffolds in the development of radiopharmaceuticals for diagnostic immuno-positron emission tomography (immuno-PET) and targeted radioimmunotherapy (RIT). Conventional methods for radiolabelling proteins with metal ions such as 68 Ga, 64 Cu, 89 Zr, and 90 Y require multi-step procedures involving pre-purification, functionalisation with a chelate, and subsequent radiolabelling. Standard coupling chemistries are time-consuming, difficult to automate, and involve synthesis, isolation, and storage of an intermediate, new molecular entity (the conjugated mAb) whose biochemical properties can differ from those of the parent protein. To circumvent these issues, we developed a photoradiochemical approach that uses fast, chemoselective, light-induced protein modification under mild conditions with novel metal-ion-binding chelates derivatised with aryl azide (ArN3 ) groups. Experiments show that one-pot photochemical conjugation and radiolabelling of formulated mAbs can be achieved in <20 min.