In Search of Advanced Tumor Diagnostics and Treatment: Achievements and Perspectives of Carbonic Anhydrase IX Targeted Delivery

Antibody-drug conjugates and radioconjugates targeting carbonic anhydrase IX and XII in hypoxic tumors: Bench to clinical applications

Treating hypoxic tumors is challenging due to their aggressive nature, resistance to standard treatments, often leading to poor outcomes. Hypoxic tumors create a unique environment that reduces the effectiveness of traditional treatments such as chemotherapy and radiotherapy. Human carbonic anhydrases (hCA IX and hCA XII) are involved in tumors survival and metabolism by regulating pH homeostasis, ferroptosis, metastatization, and other processes. Developing drugs that specifically target these enzymes has been demonstrated to disrupt the tumor survival mechanisms, leading to significant antitumor effects. This review discusses recent developments on antibody-drug conjugates (ADCs) and radioconjugates targeting hCA IX and hCA XII in hypoxic tumors. New approaches based on small molecule inhibitors and monoclonal antibodies such as girentuximab provided encouraging results in preclinical research and clinical trials. These advances highlight the potential of hCA-targeted therapies to improve cancer treatment for hypoxic tumors.

Comparison of carbonic anhydrase-IX-targeted trifunctional radioligands between linear- and branched-chain arrangements

Background

Carbonic anhydrase-IX (CA-IX) is overexpressed in tumors due to hypoxic conditions and considered an attractive biomarker for tumor-targeting radioligands. The introduction of an albumin binder (ALB) to radioligands can delay their renal clearance, resulting in increased radioactivity delivered to tumors and decreased renal uptake of radioligands. In this study, we designed novel CA-IX-targeted trifunctional radioligands consisting of imidazothiadiazole sulfonamide (IS) as a CA-IX-targeted ligand, DOTA as a chelator with four free carboxylic groups, and lysine-conjugated 4-(p-iodophenyl)butyric acid (Lys-IPBA) as ALB, with IS-[111In]In-DOTADG-ALB in a linear-chain arrangement and [111In]In-DOTAGA-ALB-IS in a branched-chain arrangement. Fundamental properties of IS-[111In]In-DOTADG-ALB and [111In]In-DOTAGA-ALB-IS were evaluated by in vitro and in vivo assays.

Methods

IS-DOTADG-ALB and DOTAGA-ALB-IS were synthesized and radiolabeled with [111In]InCl3. The stability of IS-[111In]In-DOTADG-ALB and [111In]In-DOTAGA-ALB-IS was evaluated by HPLC analysis after incubation in murine plasma. A cell saturation binding assay using CA-IX-positive HT-29 cells and albumin-binding assay were performed for IS-[111In]In-DOTADG-ALB and [111In]In-DOTAGA-ALB-IS to evaluate their capacity to bind CA-IX and albumin. Biodistribution assays of IS-[111In]In-DOTADG-ALB and [111In]In-DOTAGA-ALB-IS were performed using HT-29 tumor-bearing mice to evaluate their pharmacokinetics.

Results

IS-[111In]In-DOTADG-ALB and [111In]In-DOTAGA-ALB-IS were successfully synthesized by ligand substitution reaction from their corresponding precursors. IS-[111In]In-DOTADG-ALB and [111In]In-DOTAGA-ALB-IS exhibited similar stabilities in murine plasma and affinities to CA-IX, although the affinities to albumin were higher for [111In]In-DOTAGA-ALB-IS compared with IS-[111In]In-DOTADG-ALB. In the biodistribution assays, [111In]In-DOTAGA-ALB-IS showed higher blood retention and tumor accumulation and lower renal uptake than IS-[111In]In-DOTADG-ALB, reflecting their albumin-binding affinities.

Conclusion

These data suggest that the branched-chain arrangement of DOTAGA-ALB-IS may be useful for the design of CA-IX-targeted radioligands consisting of an IS ligand, DOTA, and Lys-IPBA.

Correlation of Preclinical In Vivo Imaging Modalities and Immunohistochemistry for Tumor Hypoxia and Vasculature

BACKGROUND/AIM

Tumors exhibit impaired blood flow and hypoxic areas, which can reduce the effectiveness of treatments. Characterizing these tumor features can inform treatment decisions, including the use of vasculature modulation therapies. Imaging provides insight into these characteristics, with techniques varying between clinical and preclinical settings.

MATERIALS AND METHODS

To investigate changes in different tumor regions over time, R2* values from blood oxygen-level dependent MRI (BOLD-MRI), blood flow from power Doppler ultrasound, and oxygen saturation from photoacoustic ultrasound were analyzed and compared to CD31+ and pimonidazole tissue staining. To aid in preclinical translation, the fluorescence of a hypoxia probe was also compared to ultrasound techniques.

RESULTS

The imaging techniques detected tumor heterogeneity and an overall decrease in blood flow and oxygen levels over time. The analysis found varying correlations between regions, indicating an indirect relationship between imaging outcomes, which is influenced by external factors. Regional analysis allowed for more accurate results, as areas less affected by various factors were examined separately from highly impacted regions, aiding in their identification.

CONCLUSION

Examining tumor regions with multiple imaging techniques allowed for better understanding and identification of modality-specific limitations, as certain techniques may incorrectly suggest that tumors are more vascularized and less hypoxic than they are.

An asiatic acid derived trisulfamate acts as a nanomolar inhibitor of human carbonic anhydrase VA

This investigation delves into the inhibitory capabilities of a specific set of triterpenoic acids on diverse isoforms of human carbonic anhydrase (hCA). Oleanolic acid (1), maslinic acid (2), betulinic acid (3), platanic acid (4), and asiatic acid (5) were chosen as representative triterpenoids for evaluation. The synthesis involved acetylation of parent triterpenoic acids 1-5, followed by sequential reactions with oxalyl chloride and benzylamine, de-acetylation of the amides, and subsequent treatment with sodium hydride and sulfamoyl chloride, leading to the formation of final compounds 21-25. Inhibition assays against hCAs I, II, VA, and IX demonstrated noteworthy outcomes. A derivative of betulinic acid, compound 23, exhibited a Ki value of 88.1 nM for hCA VA, and a derivative of asiatic acid, compound 25, displayed an even lower Ki value of 36.2 nM for the same isoform. Notably, the latter compound displayed enhanced inhibitory activity against hCA VA when compared to the benchmark compound acetazolamide (AAZ), which had a Ki value of 63.0 nM. Thus, this compound surpasses the inhibitory potency and isoform selectivity of the standard compound acetazolamide (AAZ). In conclusion, the research offers insights into the inhibitory potential of selected triterpenoic acids across diverse hCA isoforms, emphasizing the pivotal role of structural attributes in determining isoform-specific inhibitory activity. The identification of compound 25 as a robust and selective hCA VA inhibitor prompts further exploration of its therapeutic applications.

Clinical Advances and Perspectives in Targeted Radionuclide Therapy

Targeted radionuclide therapy has become increasingly prominent as a nuclear medicine subspecialty. For many decades, treatment with radionuclides has been mainly restricted to the use of iodine-131 in thyroid disorders. Currently, radiopharmaceuticals, consisting of a radionuclide coupled to a vector that binds to a desired biological target with high specificity, are being developed. The objective is to be as selective as possible at the tumor level, while limiting the dose received at the healthy tissue level. In recent years, a better understanding of molecular mechanisms of cancer, as well as the appearance of innovative targeting agents (antibodies, peptides, and small molecules) and the availability of new radioisotopes, have enabled considerable advances in the field of vectorized internal radiotherapy with a better therapeutic efficacy, radiation safety and personalized treatments. For instance, targeting the tumor microenvironment, instead of the cancer cells, now appears particularly attractive. Several radiopharmaceuticals for therapeutic targeting have shown clinical value in several types of tumors and have been or will soon be approved and authorized for clinical use. Following their clinical and commercial success, research in that domain is particularly growing, with the clinical pipeline appearing as a promising target. This review aims to provide an overview of current research on targeting radionuclide therapy.

IN SILICO STUDY OF NOVEL SULFONAMIDE DERIVATIVES BEARING A 1, 2, 4-TRIAZOLE MOIETY ACT AS CARBONIC ANHYDRASE INHIBITORS WITH PROMISING ANTI-CANCER ACTIVITY

OBJECTIVE

Aim: To evaluate the theoretical binding affinities of four synthetic compounds that target the carbonic anhydrase IX enzyme in solid tumors.

PATIENTS AND METHODS

Materials and Methods: To accurately depict the molecular structure, we utilized the Chem Draw Professional 12.0 program. We downloaded the carbonic anhydrase IX enzyme (29.25 KDa) (PDB code: 4YWP) from the Protein Data Bank into the Molecular Operating Environment software. Then, the S-score and rmsd were calculated for the proposed compounds.

RESULTS

Results: The theoretically synthesized compounds demonstrated good binding affinities with the receptor active pockets Sa, Sb, and Sd, with S-scores of -7.6491, -8.3789, and -8.3218, respectively. Substitutions improve compound orientation. The substituted triazoles ring increases flexibility and receptor interaction. In addition, the benzyl chloride derivatives play an important role in the interaction, with varying effects dependent on the groups substituted at position 4 of the benzene ring.

CONCLUSION

Conclusions: The synthesized compounds Sb with para Br substitution (S-score = -8.37) and Sd with para Cl substitution (S-score = -8.32) are considered the best ones as they exhibit a high affinity for the receptor.

A photo-responsive fluorescent amphiphile for target-specific and image-guided drug delivery applications

Multifunctional drug delivery systems are the centerpiece of effective chemotherapeutic strategies. Herein, we report the synthesis of an acetazolamide-linked cyanine-3-based NIR-responsive fluorescent macrocyclic amphiphile that self-assembled into spherical nanostructures in the aqueous medium via a J-aggregation pattern. The amphiphile shows various favorable properties of lipids. The photocleavage of the strained dioxacycloundecine ring induces spherical to nanotubular self-assembly with concomitant release of an encapsulated anticancer drug, doxorubicin (Dox), in a controlled manner. The CA-IX targeted amphiphile also showed lower cytotoxicity, effective cellular uptake, and Dox delivery to the model carcinoma cells.

A pH-responsive crosslinker platform for antibody-drug conjugate (ADC) targeting delivery

We report a new 1-6 self-immolative, traceless crosslinker derived from the natural product gallic acid. The linker acts through a pH-dependent mechanism for drug release. This 5-(hydroxymethyl)pyrogallol orthoester derivative (HMPO) was stable for 24 hours at pH values of 7.4 and 6.6 and in plasma, releasing molecules bound to the hydroxymethyl moiety under acid-dependent stimuli at pH 5.5. The linker was non-toxic and was used for the conjugation of Doxorubicin (Doxo) or Combretastatin A4 with Cetuximab. The ADCs formed showed their pH responsivity reducing cell viability of A431 and A549 cancer cells better than Cetuximab alone.

A combination strategy of structure-based virtual screening, MM-GBSA, cross docking, molecular dynamics and metadynamics simulations used to investigate natural compounds as potent and specific inhibitors of tumor linked human carbonic anhydrase IX

Cancer remains a serious health concern representing one of the leading causes of deaths worldwide. The enzyme human carbonic anhydrase IX (hCA IX) is found to be over-expressed in many cancer types and its selective inhibition over its cytosolic off-target isoform, human carbonic anhydrase II (hCA II), represents a potential area of research in the development of novel anticancer compounds. This work is concerned with the use of various in silico tools for the identification of natural product based molecules that can selectively inhibit hCA IX over hCA II. MM-GBSA assisted structure-based virtual screening against hCA IX was performed for nearly 225,000 natural products imported from the ZINC15 database. The obtained hits were checked for their potency by considering acetazolamide, the bound inhibitor of hCA IX, as the reference molecule, and 121 molecules were identified as potent hCA IX inhibitors. After ensuring their potency, cross-docking, followed by MM-GBSA calculations of the hits with hCA II, was performed, and their selectivity was assessed by considering the hCA IX selective compound SLC-0111 as the reference molecule, and 50 natural products were identified as potent as well as selective hCA IX inhibitors. Molecules with the quinoline scaffold showed the highest selectivity, and their selectivity was attributed to the strong electrostatic interactions of the zinc binding group (ZBG) with the active site Zn(II) ion. Furthermore, the stability of the binding modes of the top hCA IX selective hits was ensured by performing molecular dynamics (MD) simulations, which clearly proved that one of the short-listed molecules is truly selective, as it does not interact with the active site Zn(II) ion of hCA II, but interacts strongly with this ion in hCA IX. Bonding pose metadynamics studies revealed that the ligand moves to a more stable binding site from the one predicted by the docking studies and shows stronger interaction with the protein and Zn(II) at this binding site. The ligand is not likely to have issues with bioavailability. As a result, this ligand can be taken for bioassay testing and subsequently used as a feasible therapeutic treatment for a variety of cancer types. Communicated by Ramaswamy H. Sarma.

Copper-based theranostic nanocatalysts for synergetic photothermal-chemodynamic therapy

Chemodynamic therapy (CDT) has aroused extensive attention as a potent therapeutic modality. However, its practical application is severely restricted by the strong acidity requirement for Fenton reaction and upregulated antioxidant defense within metastatic breast cancer. Herein, a copper-based single-site nanocatalyst functionalized with carbonic anhydrase inhibitor (CAI) was constructed for magnetic resonance/photoacoustic imaging (MRI/PA)-guided synergetic photothermal therapy (PTT) and CDT. Once reaching tumor sites, the nanocatalyst can be recognized by tumor cell membranes-overexpressed carbonic anhydrase IX (CA IX). Subsequently, the single-site Cu^II can be reduced to Cu^I by the tumor-overexpressed glutathione (GSH), which simultaneously impaired the tumor antioxidant defense system and triggered CAI release for inducing intracellular H⁺ accumulation. Further, the decreased intracellular pH can accelerate the nanocatalyst biodegradation to release more Cu^II and CAI to participate in next-cycle GSH-depletion and cytoplasm acidification, respectively, thereby continuously supplying Cu^I and H⁺ for self-cyclically amplified CDT. Upon laser irradiation, the nanocatalyst can generate local heat, which not only permits PTT but also enhances the nanocatalyst-mediated CDT. Moreover, the suppression of CA IX can hinder the tumor extracellular matrix degradation to prevent tumor metastasis. Overall, this work highlighted the great application prospect in enhancing CDT via tumor acidic/redox microenvironment remodeling, and provides an insightful paradigm for inhibiting breast cancer metastasis. STATEMENT OF SIGNIFICANCE: The practical application of chemodynamic therapy (CDT) is severely restricted by the strong acidity requirement for Fenton reaction and upregulated antioxidant defense within cancer. Herein, we developed a carbonic anhydrase inhibitor (CAI)-functionalized Cu-based nanocatalyst. Once reaching tumor sites, the Cu^II can be reduced to Cu^I by the tumor-overexpressed glutathione (GSH), which simultaneously impaired the tumor antioxidant system and triggered CAI release for inducing intracellular H⁺ accumulation. Further, the decreased intracellular pH can accelerate the nanocatalyst biodegradation to release more Cu^II and CAI to participate in next-cycle GSH-depletion and cytoplasm acidification, respectively, thus continuously supplying Cu^I and H⁺ for self-cyclically amplified CDT. Upon laser irradiation, the nanocatalyst not only permits PTT but also enhances the CDT.

High throughput acoustic microfluidic mixer controls self-assembly of protein nanoparticles with tuneable sizes

HYPOTHESIS

Protein nanoparticles have attracted increased interest due to their broad applications ranging from drug delivery and vaccines to biocatalysts and biosensors. The morphology and the size of the nanoparticles play a crucial role in determining their suitability for different applications. Yet, effectively controlling the size of the nanoparticles is still a significant challenge in their manufacture. The hypothesis of this paper is that the assembly conditions and size of protein particles can be tuned via a mechanical route by simply modifying the mixing time and strength, while keeping the chemical parameters constant.

EXPERIMENTAL

We use an acoustically actuated, high throughput, ultrafast, microfluidic mixer for the assembly of protein particles with tuneable sizes. The performance of the acoustic micro-mixer is characterized via Laser Doppler Vibrometry and image processing. The assembly of protein nanoparticles is monitored by dynamic light scattering (DLS) and transmission electron microscopy (TEM).

FINDINGS

By changing actuation parameters, the turbulence and mixing in the microchannel can be precisely varied to control the initiation of protein particle assembly while the solution conditions of assembly (pH and ionic strength) are kept constant. Importantly, mixing times as low as 6 ms can be achieved for triggering protein assembly in the microfluidic channel. In comparison to the conventional batch process of assembly, the acoustic microfluidic mixer approach produces smaller particles with a more uniform size distribution, promising a new way to manufacture protein particles with controllable quality.