L-Canavanine potentiates the cytotoxicity of doxorubicin and cisplatin in arginine deprived human cancer cells

Raptinal: a powerful tool for rapid induction of apoptotic cell death

Chemical inducers of apoptosis have been utilized for decades as tools to uncover steps of the apoptotic cascade and to treat various diseases, most notably cancer. While there are several useful compounds available, limitations in potency, universality, or speed of cell death of these pro-apoptotic agents have meant that no single compound is suitable for all (or most) purposes. Raptinal is a recently described small molecule that induces intrinsic pathway apoptosis rapidly and reliably, and consequently, has been utilized in cell culture and whole organisms for a wide range of biological studies. Its distinct mechanism of action complements the current arsenal of cytotoxic compounds, making it useful as a probe for the apoptosis pathway and other cellular processes. The rapid induction of cell death by Raptinal and its widespread commercial availability make it the pro-apoptotic agent of choice for many applications.

Dendrimer Platforms for Targeted Doxorubicin Delivery-Physicochemical Properties in Context of Biological Responses

The unique structure of G4.0 PAMAM dendrimers allows a drug to be enclosed in internal spaces or immobilized on the surface. In the conducted research, the conditions for the formation of the active G4.0 PAMAM complex with doxorubicin hydrochloride (DOX) were optimized. The physicochemical properties of the system were monitored using dynamic light scattering (DLS), circular dichroism (CD), and fluorescence spectroscopy. The Quartz Crystal Microbalance with Dissipation Monitoring (QCM-D) method was chosen to determine the preferential conditions for the complex formation. The highest binding efficiency of the drug to the cationic dendrimer was observed under basic conditions when the DOX molecule was deprotonated. The decrease in the zeta potential of the complex confirms that DOX immobilizes through electrostatic interaction with the carrier's surface amine groups. The binding constants were determined from the fluorescence quenching of the DOX molecule in the presence of G4.0 PAMAM. The two-fold way of binding doxorubicin in the structure of dendrimers was visible in the Isothermal calorimetry (ITC) isotherm. Fluorescence spectra and release curves identified the reversible binding of DOX to the nanocarrier. Among the selected cancer cells, the most promising anticancer activity of the G4.0-DOX complex was observed in A375 malignant melanoma cells. Moreover, the preferred intracellular location of the complexes concerning the free drug was found, which is essential from a therapeutic point of view.

Assessment of the anti-cancer potential of Ephedra foeminea leaf extract on MDA-MB-231, MCF-7, 4 T1, and MCF-10 breast cancer cell lines: Cytotoxic, apoptotic and oxidative assays

Ephedra foeminea is traditionally used to treat breast cancer in several Arab countries. Scientific studies have reported different effects of this plant on some cancer cell lines. The current study determined the anti-cancer potential of the methanolic extract of Ephedra foeminea against four different types of breast cancer cell lines in-vitro. The extract was prepared by maceration and phytoconstituents were identified by LC-MS analysis. The IC50 value was determined against MDA-MB-231, MCF-7, 4 T1, and MCF-10 cell lines using the MTT assay. Further investigations were carried out using IC50 concentration of the extract (40.09 µg/ml) to determine live/dead cells by acridine orange/ethidium bromide staining. The effect on the expression of reactive oxygen species (ROS) was evaluated by flow cytometry. The results were analyzed using one-way ANOVA followed by Tukey's test. The LC-MS analysis revealed the presence of 34 and 30 phytoconstituents in positive and negative modes respectively. The Ephedra foeminea extract was most effective against 4 T1 cells in a dose-dependent manner (P < 0.001) with an IC50 value of 40.09 µg/ml and showed negligible effect against MCF-10 cells. It increased apoptosis in 77.84 % of 4 T1 cells, as determined by acridine orange/ethidium bromide staining. The extract also increased the ROS expression in the 39.57 % of 4 T1 cells. The study results showed that Ephedra foeminea extract possesses an anti-cancer effect against 4 T1 cells by increasing the expression of ROS and inducing apoptosis in the 4 T1 cells. The result suggests Ephedra foemenia methanolic extract possesses a reasonable anti-cancer effect due to its effect on apoptosis and oxidative pathways. The results confirm the traditional belief that Ephedra is effective against breast cancerز.

Mitochondria-Targeted Lipid Nanoparticles Loaded with Rotenone as a New Approach for the Treatment of Oncological Diseases

This research is based on the concept that mitochondria are a promising target for anticancer therapy, including thatassociated with the use of oxidative phosphorylation blockers (mitochondrial poisons). Liposomes based on L-α-phosphatidylcholine (PC) and cholesterol (Chol) modified with cationic surfactants with triphenylphosphonium (TPPB-n, where n = 10, 12, 14, and 16) and imidazolium (IA-n(OH), where n = 10, 12, 14, and 16) head groups were obtained. The physicochemical characteristics of liposomes at different surfactant/lipid molar ratios were determined by dynamic/electrophoretic light scattering, transmission electron microscopy, and spectrophotometry. The hydrodynamic diameter of all the systems was within 120 nm with a polydispersity index of no more than 0.24 even after 2 months of storage. It was shown that cationization of liposomes leads to an increase in the internalization of nanocontainers in pancreatic carcinoma (PANC-1) and duodenal adenocarcinoma (HuTu 80) cells compared with unmodified liposomes. Also, using confocal microscopy, it was shown that liposomes modified with TPPB-14 and IA-14(OH) statistically better colocalize with the mitochondria of tumor cells compared with unmodified ones. At the next stage, the mitochondrial poison rotenone (ROT) was loaded into cationic liposomes. It was shown that the optimal loading concentration of ROT is 0.1 mg/mL. The Korsmeyer-Peppas and Higuchi kinetic models were used to describe the release mechanism of ROT from liposomes in vitro. A significant reduction in the IC50 value for the modified liposomes compared with free ROT was shown and, importantly, a higher degree of selectivity for the HuTu 80 cell line compared with the normal cells (SI value is 307 and 113 for PC/Chol/TPPB-14/ROT and PC/Chol/IA-14(OH)/ROT, respectively) occurred. It was shown that the treatment of HuTu 80 cells with ROT-loaded cationic liposomal formulations leads to a dose-dependent decrease in the mitochondrial membrane potential.

Bixin and Fuxoxanthin Alone and in Combination with Cisplatin Regulate ABCC1 and ABCC2 Transcription in A549 Lung Cancer Cells

Background

The ATP-Binding Cassette (ABC) transporter has long been studied to confer drug resistance in human tumors and play important role in metabolic processes and cellular signaling. The overexpression of ABCB1, ABCC1, ABCC2, ABCC3, and ABCG2 leads to decreased sensitivity of lung cancer to cisplatin. At the transcription level, the expression of ABC transporters is highly regulated and requires the complex interplay of factors involved in differentiation and development, cell survival and apoptosis upon intrinsic and environmental stress. The p53 regulation of drug-resistance genes is also complex yet not well understood. Previously, we demonstrated the synergistic interaction between bixin or fucoxanthin with cisplatin in A549 lung cancer cells.

Objectives

Current study aims to identify whether carotenoids enhancing therapeutic effect of Cisplatin due to the ability to reverse drug resistance associated proteins, such as ABC transporter and regulating the tumor suppressor corresponding gene, p53.

Methods

Real-Time Quantitative-Polymerase Chain Reaction (RT-qPCR) was performed to estimate the expression level of ABCC1 and ABCC2, and p53 of A549 cell lines in response to carotenoids alone and in combination with cisplatin.

Results and Conclusion

The administration of bixin or fucoxanthin decreases the expression of ABCC1 and ABCC2. Both carotenoids, either alone or in combination with cisplatin, upregulated p53 gene expression indicating the mechanism of proliferation inhibition and apoptosis occurs via the p53 caspase-independent pathway.

Integrated multi-omic data reveal the potential molecular mechanisms of the nutrition and flavor in Liancheng white duck meat

The Liancheng white (LW) duck is one of the most valued Chinese indigenous poultry breeds. Its meat is rich in nutrients and has distinct flavors, but the molecular mechanisms behind them are unknown. To address this issue, we measured and compared multi-omic data (genome, transcriptome, and metabolome) of breast meat from LW ducks and the Mianyang Shelduck (MS) ducks. We found that the LW duck has distinct breed-specific genetic features, including numerous mutant genes with differential expressions associated with amino acid metabolism and transport activities. The metabolome driven by genetic materials was also seen to differ between the two breeds. For example, several amino acids that are beneficial for human health, such as L-Arginine, L-Ornithine, and L-lysine, were found in considerably higher concentrations in LW muscle than in MS duck muscle (p < 0.05). SLC7A6, a mutant gene, was substantially upregulated in the LW group (p < 0.05), which may lead to excessive L-arginine and L-ornithine accumulation in LW duck meat through transport regulation. Further, guanosine monophosphate (GMP), an umami-tasting molecule, was considerably higher in LW muscle (p < 0.05), while L-Aspartic acid was significantly abundant in MS duck meat (p < 0.05), showing that the LW duck has a different umami formation. Overall, this study contributed to our understanding of the molecular mechanisms driving the enriched nutrients and distinct umami of LW duck meat, which will provide a useful reference for duck breeding.

Bixin and fucoxanthin sensitize human lung cancer and cervical cancer cell to cisplatin in vitro

Objective

Cisplatin is a conventional anticancer drug that generates reactive oxygen species and causes apoptosis. However, many cancer cells develop alterations in the ATP binding cassette transporter responsible for the uptake and efflux process, which leads to resistance. Many natural products have shown potential to compete with ATP binding cassette transporter and may sensitize resistant cells to cisplatin. Studies have shown pro-oxidant effect of carotenoids that promote apoptosis of cancer cells. Bixin and fucoxanthin are well-known carotenoids with known antioxidant properties, however their bioactivity in lung cancer cells, clinically known to develop resistance due to ATP binding cassette transporter, has been minimally studied. This study is the first to investigate the potential of bixin and fucoxanthin to sensitize human lung cancer cell line, A549 and cervical cancer cell line, HeLa, to cisplatin. Drug combination method developed by Chou and Talalay theorem was employed.

Result

Employing the best combination ratio, this study shows selective sensitization of cancer cells to cisplatin after bixin and fucoxanthin treatment. Further study on the mechanism of action in specific types of cancer cells is warranted. It may improve cisplatin sensitivity in tumors and rational use of cancer drugs.

Graphical Abstract

Supplementary Information

The online version contains supplementary material available at 10.1186/s13104-021-05866-4.

Identifying new compounds with potential pharmaceutical and physiological activity in Areca catechu and Areca triandra via a non-targeted metabolomic approach

INTRODUCTION

The fruits of Areca catechu, also called areca nuts, are widely used as popular masticatory and traditional herbal medicine in Asia. Besides arecoline and related alkaloids, limited information is available about further primary and secondary metabolites and their potential biological activities.

OBJECTIVE

Here we aimed to further enhance our knowledge on phytochemical profiles of A. catechu and Areca triandra fruits. We intended to comprehensively identify metabolites in A. catechu and A. triandra fruits.

METHODOLOGY

Metabolites were identified by ultra-performance liquid chromatography triple-quadrupole tandem mass spectrometry (UPLC-MS/MS). The occurrence of 12 selected bioactive compounds in 4 different developmental stages of A. catechu and A. triandra was quantified by LC-MS/MS.

RESULTS

A total of 791 metabolites was identified. Of these, 115 metabolites could successfully be mapped to 44 Kyoto Encyclopedia of Genes and Genomes metabolic pathways, and 154 metabolites occurred at significantly different levels in A. catechu compared to A. triandra. Several components with known biological activities were identified for the first time in A. catechu and A. triandra. The abundance of many of these new components was similar in A. catechu and A. triandra, but significantly different between the pericarp and the seeds of A. catechu fruits.

CONCLUSIONS

Metabolic profiles indicate that fruits of the Areca species compared here have similar primary and secondary metabolites. Our findings provide new insights into A. catechu and A. triandra as valuable sources for traditional medicine and they pave the way for further studies to potentially improve the underlying pharmaceutical and physiological effects.

A New Water-Soluble Thermosensitive Star-Like Copolymer as a Promising Carrier of the Chemotherapeutic Drug Doxorubicin

A new water-soluble thermosensitive star-like copolymer, dextran-graft-poly-N-iso-propilacrylamide (D-g-PNIPAM), was created and characterized by various techniques (size-exclusion chromatography, differential scanning calorimetry, Fourier-transform infrared (FTIR) spectroscopy, and dynamic light scattering (DLS) spectroscopy). The viability of cancer cell lines (human transformed cervix epithelial cells, HeLa) as a model for cancer cells was studied using MTT and Live/Dead assays after incubation with a D-g-PNIPAM copolymer as a carrier for the drug doxorubicin (Dox) as well as a D-g-PNIPAM + Dox mixture as a function of the concentration. FTIR spectroscopy clearly indicated the complex formation of Dox with the D-g-PNIPAM copolymer. The size distribution of particles in Hank’s solution was determined by the DLS technique at different temperatures. The in vitro uptake of the studied D-g-PNIPAM + Dox nanoparticles into cancer cells was demonstrated by confocal laser scanning microscopy. It was found that D-g-PNIPAM + Dox nanoparticles in contrast to Dox alone showed higher toxicity toward cancer cells. All of the aforementioned facts indicate a possibility of further preclinical studies of the water-soluble D-g-PNIPAM particles’ behavior in animal tumor models in vivo as promising carriers of anticancer agents.

Uncovering the Effect of Passage Number on HT29 Cell Line Based on the Cell Metabolomic Approach

The passage number is an important factor when designing the cell line-based experiment. Although HT29 cells were widely used in the laboratory for colorectal cancer studies, the impact of cell passage number on the HT29 cells was still unknown. In this study, phenotypic assay and metabolomic approach were applied to analyze the systemic effects of passage numbers (passage 4, 10, and 16) on the HT29 cells. The results showed that the increased cell passage number affected the cell cycle distribution and also decreased the proliferation and migration ability of HT29 cells. The metabolomic analysis coupled with heatmap and hierarchical cluster analysis showed obvious metabolome difference among the cells with different passage numbers, which was related with 61 differential metabolites. Three metabolic pathways were determined as the key pathways, and arginine participated in two of them. In addition, it was found that arginine supplementation could inhibit the proliferation ability of HT29 cells in vitro, and a synergistic effect existed between arginine and cisplatin. In conclusion, this study not only revealed the influence of passage numbers on the HT29 cell but also provided an important reference that arginine has the potential role to be developed as the cisplatin therapeutic adjuvant.

An In Vitro Study on the Interactions of Pycnogenol® with Cisplatin in Human Cervical Cancer Cells

Objectives

In the treatment of cancer, it is intended to increase the anticancer effect and decrease cytotoxicity using various plant-derived phenolic compounds with chemotherapeutic drugs. Pycnogenol^® (PYC), a phenolic compound, has been the subject of many studies. Since the mechanisms of the interactions of PYC with cisplatin need to be clarified, we aimed to determine the effects of PYC on cisplatin cytotoxicity in human cervix cancer cells (HeLa) and to evaluate the genotoxicity of PYC.

Materials and Methods

The cytotoxicity of cisplatin and PYC was measured by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay in HeLa cells for 24 h and 48 h. The effect of PYC against oxidative DNA damage was evaluated using the comet assay.

Results

The IC₅₀ values of cisplatin were 22.4 μM and 12.3 μM for 24 h and 48 h, respectively. The IC₅₀ values of PYC were 261 μM and 213 μM for 24 h and 48 h, respectively. For 24 h exposure, PYC significantly reduced the IC₅₀ value of cisplatin at the selected concentrations (15.6-500 μM). For 48 h exposure, PYC did not change the cytotoxicity of cisplatin at concentrations between 15.6 and 125 μM, but significantly reduced it at concentrations of 250 μM and 500 μM. PYC alone did not induce DNA damage at concentrations of 10 μM or 25 μM; however, it significantly induced DNA damage at higher concentrations (50-100 μM). It also significantly reduced H₂O₂-induced DNA damage at all concentrations studied (10-100 μM).

Conclusion

Our results suggest that PYC may increase the cisplatin cytotoxicity in HeLa cells at nongenotoxic doses. The results might contribute to the anticancer effect of cisplatin with PYC in cervical carcinoma, but in order to confirm this result further in vitro studies with cancer cell lines and in vivo studies are needed.

Liposome-Mediated Chemotherapeutic Delivery Is Synergistically Enhanced by Ternary Lipid Compositions and Cationic Lipids

Most small molecule chemotherapeutics must cross one or more cellular membrane barriers to reach their biochemical targets. Owing to the relatively low solubility of chemotherapeutics in the lipid membrane environment, high doses are often required to achieve a therapeutic effect. The resulting systemic toxicity has motivated efforts to improve the efficiency of chemotherapeutic delivery to the cellular interior. Toward this end, liposomes containing lipids with cationic head groups have been shown to permeabilize cellular membranes, resulting in the more efficient release of encapsulated drugs into the cytoplasm. However, the high concentrations of cationic lipids required to achieve efficient delivery remain a key limitation, frequently resulting in toxicity. Toward overcoming this limitation, here, we investigate the ability of ternary lipid mixtures to enhance liposomal delivery. Specifically, we investigate the delivery of the chemotherapeutic, doxorubicin, using ternary liposomes that are homogeneous at physiological temperature but have the potential to undergo membrane phase separation upon contact with the cell surface. This approach, which relies upon the ability of membrane phase boundaries to promote drug release, provides a novel method for reducing the overall concentration of cationic lipids required for efficient delivery. Our results show that this approach improves the performance of doxorubicin by up to 5-fold in comparison to the delivery of the same drug by conventional liposomes. These data demonstrate that ternary lipid compositions and cationic lipids can be combined synergistically to substantially improve the efficiency of chemotherapeutic delivery in vitro.

Canavanine-Induced Decrease in Nitric Oxide Synthesis Alters Activity of Antioxidant System but Does Not Impact S-Nitrosoglutathione Catabolism in Tomato Roots

Canavanine (CAN) is a nonproteinogenic amino acid synthesized in legumes. In mammalians, as arginine analogue, it is an inhibitor of nitric oxide synthase (NOS) activity. The aim of this study was to investigate the impact of CAN-induced nitric oxide level limitation on the antioxidant system and S-nitrosoglutathione (GSNO) metabolism in roots of tomato seedlings. Treatment with CAN (10 or 50 µM) for 24-72 h led to restriction in root growth. Arginine-dependent NOS-like activity was almost completely inhibited, demonstrating direct effect of CAN action. CAN increased total antioxidant capacity and the level of sulphydryl groups. Catalase (CAT) and superoxide dismutase (SOD) activity decreased in CAN exposed roots. CAN supplementation resulted in the decrease of transcript levels of genes coding CAT (with the exception of CAT1). Genes coding SOD (except MnSOD and CuSOD) were upregulated by CAN short treatment; prolonged exposition to 50-µM CAN resulted in downregulation of FeSOD, CuSOD, and SODP-2. Activity of glutathione reductase dropped down after short-term (10-µM CAN) supplementation, while glutathione peroxidase activity was not affected. Transcript levels of glutathione reductase genes declined in response to CAN. Genes coding glutathione peroxidase were upregulated by 50-µM CAN, while 10-µM CAN downregulated GSHPx1. Inhibition of NOS-like activity by CAN resulted in lower GSNO accumulation in root tips. Activity of GSNO reductase was decreased by short-term supplementation with CAN. In contrast, GSNO reductase protein abundance was higher, while transcript levels were slightly altered in roots exposed to CAN. This is the first report on identification of differentially nitrated proteins in response to supplementation with nonproteinogenic amino acid. Among nitrated proteins differentially modified by CAN, seed storage proteins (after short-term CAN treatment) and components of the cellular redox system (after prolonged CAN supplementation) were identified. The findings demonstrate that due to inhibition of NOS-like activity, CAN leads to modification in antioxidant system. Limitation in GSNO level is due to lower nitric oxide formation, while GSNO catabolism is less affected. We demonstrated that monodehydroascorbate reductase, activity of which is inhibited in roots of CAN-treated plants, is the protein preferentially modified by tyrosine nitration.

Loading of doxorubicin and thymoquinone with F2 gel nanofibers improves the antitumor activity and ameliorates doxorubicin-associated nephrotoxicity

AIMS

This study aimed to elucidate the benefits of nanoformulation of doxorubicin (DOX) and thymoquinone (TQ) loaded with nanofibers of poly-N-acetyl glucosamine (pGlcNAc), which is known as F2 gel, over their conventional free forms. Moreover, evaluate the role of TQ in improving chemotherapeutic effect and ameliorating nephrotoxicity of DOX.

MAIN METHODS

The drugs were loaded into F2 gel followed by measurement of physicochemical characterization. Next, MCF-7 and HEPG2 cells were treated with the prepared formulations and assessed for apoptosis alongside with cellular proliferation. Furthermore, we experimentally induced Heps liver carcinoma in mice and at the end of the treatment, mice were sacrificed and serum samples were used to assess nephrotoxicity markers; blood urea nitrogen (BUN) and creatinine. Additionally, renal tissue was used for determination of oxidative markers and antioxidant enzymes; whereas, tumor tissue was utilized to measure nuclear factor kappa B (NF-κB) and caspase 3.

KEY FINDINGS

Nanoformulation showed dramatic increase in apoptosis, caspase 3, and antioxidant enzymes; in contrast to, dramatic fall in cell viability, tumor volume, oxidative and nephrotoxicity markers, and NF-κB compared to corresponding free therapies. Combined therapy was superior in conserving the measured parameters compared to other treated groups.

SIGNIFICANCE

F2 gel loaded with DOX and TQ revealed enhanced antitumor activity with minimal toxicity. Moreover, using TQ as an adjuvant with DOX could augment its cytotoxicity and ameliorate nephrotoxicity.

Doxorubicin-Wrapped Zinc Oxide Nanoclusters for the Therapy of Colorectal Adenocarcinoma

Doxorubicin (DOX)-wrapped zinc oxide nanoclusters (ZnO NCs) were developed for the therapy of colorectal cancer. DOX was coated onto the agglomerates of ZnO nanoparticles using a facile coating process. DOX-ZnO NCs with a hydrodynamic size of 170 nm, narrow size distribution, and positive zeta potential were fabricated. The aggregated shape of developed DOX-ZnO NCs was observed by transmission electron microscopy (TEM) imaging. The result of Fourier-transform infrared (FT-IR) analysis suggested the interaction between DOX and ZnO in DOX-ZnO NCs. The existence of DOX in the outer surface of DOX-ZnO NCs was further identified by X-ray powder diffractometer (XRD) and X-ray photoelectron spectroscopy (XPS) analyses. Cellular uptake efficiency and antiproliferation efficacy of developed DOX-ZnO NCs were tested in Caco-2 (human colorectal adenocarcinoma) cells. The cellular accumulated amount of DOX-ZnO NCs was 3.19-fold higher than that of free DOX (p < 0.05). The DOX-ZnO NCs group also exhibited improved antiproliferation potentials, compared with the DOX and ZnO groups, in Caco-2 cells at 0.5 and 1 μg/mL DOX concentrations. All these findings imply that developed DOX-ZnO NCs can be efficient hybrid nanoformulations for the therapy of colorectal cancers.

Deciphering molecular mechanisms of arginine deiminase-based therapy - Comparative response analysis in paired human primary and recurrent glioblastomas

Arginine auxotrophy constitutes the Achilles' heel for several tumors, among them glioblastoma multiforme (GBM). Hence, arginine-depleting enzymes such as arginine deiminase (ADI) from Streptococcus pyogenes are promising for treatment of primary and maybe even refractory GBM. Based on our previous study in which ADI-susceptibility was shown on a panel of patient-derived GBM cell lines, we here aimed at deciphering underlying molecular mechanisms of ADI-mediated growth inhibition. We found that ADI (35 mU/mL) initially induces a cellular stress-response that is characterized by upregulation of genes primarily belonging to the heat-shock protein family. In addition to autophagocytosis, we show for the first time that senescence constitutes another cellular response mechanism upon ADI-treatment and that this bacterial enzyme is able to act as radiosensitizer (¼ cases). Long-term treatment schedules revealed no resistance development, with treated cells showing morphological signs of cell stress. Next, several combination strategies were employed to optimize ADI-based treatment. Simultaneous and sequential S. pyogenes ADI-based combinations included substances acting at different molecular pathways (curcumin, resveratrol, quinacrine, and sorafenib, 2 × 72 h treatment). Adding drugs to GBM cell lines (n = 4, including a matched pair of primary and recurrent GBM in one case) accelerated and potentiated ADI-mediated cytotoxicity. Autophagy was identified as the main cause of tumor growth inhibition. Of note, residual cells again showed classical signs of senescence in most combinations. Our results suggest an alternative treatment regimen for this fatal cancer type which circumvents many of the traditional barriers. Using the metabolic defect in GBM thus warrants further (pre-) clinical evaluation.