Combretastatin A4 Phosphate Research Articles

Fosbretabulin tromethamine in the treatment of thyroid cancer

ABSTRACTIntroduction: Anaplastic thyroid carcinoma [ATC] is a rare, highly aggressive neoplasm with a disease-specific mortality of nearly 100%. Available treatment options include surgery, radiotherapy, chemotherapy or their combination and, more often recently, participation in clinical trials, as recommended by all available guidelines. However, despite of many attempts with the use of new targeted drugs, to date no remarkable progress in the improvement in patients’ survival has been made. Fosbretabulin (combretastatin A4 phosphate, CA4P) is a vascular disrupting agent, and a new drug that targets tumor neovasculature leading to an acute, reversible reduction in tumor blood flow and tumor central necrosis. Its activity against ATC was evaluated in the FACT trial.Areas covered: Published results of preclinical, phase I and II studies, and other reports evaluating the mechanism of action, efficacy and safety of fosbretabulin alone or combination with other drugs in ATC are evaluated.Expert Opinion: Disappointing results of previous randomized studies, referred to ATC treatment, force us to draw conclusions. Among the reasons leading to the failure of FACT study was an insufficient number of enrolled patients. Since available guidelines emphasized the necessity to treat ATC under clinical trials, inclusion criteria should be reconsidered to make the recruitment process much easier and faster in future.

Combretastatin A4 disodium phosphate-induced myocardial injury.

Histopathological and electrocardiographic features of myocardial lesions induced by combretastatin A4 disodium phosphate (CA4DP) were evaluated, and the relation between myocardial lesions and vascular changes and the direct toxic effect of CA4DP on cardiomyocytes were discussed. We induced myocardial lesions by administration of CA4DP to rats and evaluated myocardial damage by histopathologic examination and electrocardiography. We evaluated blood pressure (BP) of CA4DP-treated rats and effects of CA4DP on cellular impedance-based contractility of human induced pluripotent stem cell-derived cardiomyocytes (hiPS-CMs). The results revealed multifocal myocardial necrosis with a predilection for the interventricular septum and subendocardial regions of the apex of the left ventricular wall, injury of capillaries, morphological change of the ST junction, and QT interval prolongation. The histopathological profile of myocardial lesions suggested that CA4DP induced a lack of myocardial blood flow. CA4DP increased the diastolic BP and showed direct effects on hiPS-CMs. These results suggest that CA4DP induces dysfunction of small arteries and capillaries and has direct toxicity in cardiomyocytes. Therefore, it is thought that CA4DP induced capillary and myocardial injury due to collapse of the microcirculation in the myocardium. Moreover, the direct toxic effect of CA4DP on cardiomyocytes induced myocardial lesions in a coordinated manner.

Combination of vascular disrupting agents and nanomedicines for solid tumor therapy

Event Abstract Back to Event Combination of vascular disrupting agents and nanomedicines for solid tumor therapy Xuesi Chen1*, Zhaohui Tang1* and Wantong Song1* 1 Changchun Institute of Applied Chemistry, CAS, Key Laboratory of Polymer Ecomaterials, China Introduction: Nanosized anticancer drug delivery systems hold great promise for safe, simple and effective therapies against malignant solid tumors. Due to the enhanced permeability and retention (EPR) effect of solid tumor tissues, nanoparticles can passively accumulate in tumors, and this resulted in more than ten nanocarrier-based drugs been marketed for the treatment of cancers. However, a main barrier for further improving the therapeutic efficiency of nanomedicines lies in the poor permeability of solid tumors. Especially in the tumor central regions, low penetration of nanoparticles results in low contact probability of drugs to reach a majority of tumor cells and limited therapeutic outcomes. Aiming at this problem, in this study, we proposed a novel strategy for enhancing the treatment efficacy of nanomedicines within the central regions of solid tumor by combining nanomedicines with vascular disrupting agents (VDAs). As shown in Figure 1, nanomedicines mainly act on the tumor periphery, while VDAs eradicate tumor cells in the central regions of a solid tumor. Therefore, the combination is expected to eradicate the entire tumor. Materials and Methods: A typical small-molecule VDA, combretastatin A4 disodium phosphate (CA4P), which is in phase I/II clinical trials was applied here. Cis-diamminedichloroplatinum loaded nanoparticles (CDDP-NPs) prepared from CDDP and poly(L-glutamic acid)-g-methoxy poly(ethylene glycol) (PLG-g-mPEG), which was previously reported and optimized by us was applied here as the model nanomedicine. For in vivo studies, Balb/C mice bearing murine colon carcinoma C26 tumors was applied. Results and Discussion: The effect of CA4P, CDDP-NPs and the combination on tumor necrosis after a single intravenous injection was compared by H-E staining. As shown in Figure 2, in contrast to CDDP-NPs or CA4P alone, the combination of CDDP-NPs+CA4P caused necrosis in both the central and peripheral regions, and resulted in a necrosis rate of 92.8±3.0%. In the following in vivo anticancer efficacy test, the combination group exhibited significant tumor growth suppression without significant bodyweight loss. Conclusion: Our work supports the notion that coadministration of nanomedicines plus vascular disrupting agents will serve as a promising strategy for the treatment of solid tumors with high efficacy and low side effects.

Reverse micelles-in-microspheres with sustained release of water-soluble combretastatin A4 phosphate for S180 tumor treatment.

Combretastatin A4 phosphate (CA4P), the water-soluble phosphate pro-drug of combretastatin A4 (CA4), acts as a novel vascular disrupting agent (VDA). It strongly inhibits tubulin polymerization and selectively exerts action against tumor blood vessels. However, its quite short half-life (∼30 min) results in a short action time and consequently limits its application. Therefore, it is beneficial to develop a sustained-release preparation of CA4P for relatively long action duration. On the other hand, conventional PLGA microspheres display poor encapsulation capability for water-soluble small molecules due to rapid diffusion outside. Hence, we developed CA4P-loaded microspheres (CA4P-MS) composed of methoxy poly(ethylene glycol)-b-polylactide (PELA) reverse micelles and PLGA with a nano-in-micro sea-island structure. The CA4P encapsulation efficiency of CA4P-MS reached 92.88%. More interestingly, sustained drug release was achieved, which contributed to the prolonged inhibition effect on S180 tumor during a 30-day period with one-time subcutaneous administration. In conclusion, our study established a biodegradable polymer based platform to construct microspheres for water-soluble small molecular compounds with sustained release and a long-lasting action.

Stimulation of Eryptosis by Combretastatin A4 Phosphate Disodium (CA4P)

Background/Aims: Combretastatin A4 phosphate disodium (CA4P) is utilized for the treatment of malignancy. The substance has previously been shown to trigger suicidal cell death or apoptosis. Similar to apoptosis of nucleated cells, erythrocytes may enter suicidal death or eryptosis, characterized by cell shrinkage and cell membrane scrambling with phosphatidylserine translocation to the erythrocyte surface. Stimulators of eryptosis include increase of cytosolic Ca²⁺ activity ([Ca²⁺]_i), ceramide, oxidative stress and ATP depletion. The present study explored, whether CA4P induces eryptosis and, if so, to gain insight into mechanisms involved. Methods: Flow cytometry has been employed to estimate phosphatidylserine exposure at the cell surface from annexin-V-binding, cell volume from forward scatter, [Ca²⁺]_i from Fluo3-fluorescence, reactive oxygen species (ROS) abundance from DCF fluorescence, glutathione (GSH) abundance from CMF fluorescence and ceramide abundance from fluorescent antibodies. In addition cytosolic ATP levels were quantified utilizing a luciferin-luciferase-based assay and hemolysis was estimated from hemoglobin concentration in the supernatant. Results: A 48 hours exposure of human erythrocytes to CA4P (≥ 50 µM) significantly increased the percentage of annexin-V-binding cells and significantly decreased forward scatter. CA4P did not appreciably increase hemolysis. Hundred µM CA4P significantly increased Fluo3-fluorescence. The effect of CA4P (100 µM) on annexin-V-binding was significantly blunted, but not abolished, by removal of extracellular Ca²⁺. CA4P (≥ 50 µM) significantly decreased GSH abundance and ATP levels but did not significantly increase ROS or ceramide. Conclusions: CA4P triggers cell shrinkage and phospholipid scrambling of the erythrocyte cell membrane, an effect at least in part due to entry of extracellular Ca²⁺ and energy depletion.

Synthesis and Evaluation of 131I-Skyrin as a Necrosis Avid Agent for Potential Targeted Radionuclide Therapy of Solid Tumors.

An innovative anticancer approach targeted to necrotic tissues, which serves as a noncancerous and generic anchor, may present a breakthrough. Necrosis avid agents with a flat conjugate aromatic structure selectively accumulate in necrotic tissues, but they easily form aggregates that undesirably distribute to normal tissues. In this study, skyrin, a dianthraquinone compound with smaller and distorted π-cores and thus decreased aggregates as compared with hypericin (Hyp), was designed to target necrosis for tumor therapy. Aggregation studies of skyrin by UV/vis spectroscopy showed a smaller self-association constant with skyrin than with Hyp. Skyrin was labeled by iodine-131 with a radiochemical purity of 98% and exhibited good stability in rat serum for 72 h. In vitro cell uptake studies showed significant difference in the uptake of 131I-skyrin by necrotic cells compared to normal cells (P < 0.05). Compared in rats with liver and muscle necrosis, radiobiodistribution, whole-body autoradiography, and SPECT/CT studies revealed higher accumulation of 131I-skyrin in necrotic liver and muscle (p < 0.05), but lower uptake in normal organs, relative to that of 131I-Hyp. In mice bearing H22 tumor xenografts treated with combretastatin A4 disodium phosphate, the highest uptake of 131I-skyrin was found in necrotic tumor. In conclusion, 131I-skyrin appears a promising agent with reduced accumulation in nontarget organs for targeted radionuclide therapy of solid tumors.

Concentration-Induced J-Aggregate Formation Causes a Biphasic Change in the Release of trans-Combretastatin A4 Disodium Phosphate from Archaeosomes and the Subsequent Cytotoxicity on Mammary Cancer Cells.

Combretastatin A4 disodium phosphate (CA4P) is a fluorescent, water-soluble prodrug able to induce vascular shutdown within tumors at doses less than one-tenth of the maximum tolerated dose. As a continued effort to develop efficient liposomal CA4P to treat solid tumor, we herein investigate the physical and spectroscopic properties of CA4P in aqueous solution and the mechanism of CA4P release from archaeal tetraether liposomes (archaeosomes). We found that cis-CA4P can be photoisomerized to trans-CA4P. This photoisomerization results in an increase in fluorescence intensity. Both cis- and trans-CA4P undergo fluorescence intensity self-quenching after they reach a critical concentration Cq (∼0.15-0.25 mM). Moreover, both cis- and trans-CA4P in buffer exhibit a red shift in their excitation spectrum and an increase in excitation spectrum band sharpness with increasing concentration, which can be attributed to the formation of J-aggregates. The onset of the dramatic change in excitation maximum occurs at concentrations close to Cq, suggesting that the self-quenching arises from extensive J-aggregate formation and that, when CA4P concentration exceeds Cq, J-aggregate formation begins to increase sharply. Our data also suggest that the extent of J-aggregate formation plays a critical role in CA4P release from tetraether archaeosomes and in the subsequent cytotoxicity on cultured human breast cancer MCF-7 cells. The drug leakage and cytotoxicity rate constants vary with the initial CA4P concentration entrapped inside archaeosomes in a biphasic manner, reaching a local maximum at 0.25-0.50 mM. A mechanism based on the concept of J-aggregate formation has been proposed to explain the biphasic changes in drug release and cytotoxicity with increasing drug concentration. Tetraether archaeosomes are extraordinarily stable and relatively nontoxic to animals; thus, they are promising nano drug carriers. The results obtained from this study pave the way for future development of archaeosomal CA4P to treat solid tumors.

Co-Encapsulation of Combretastatin-A4 Phosphate and Doxorubicin in Polymersomes for Synergistic Therapy of Nasopharyngeal Epidermal Carcinoma.

In this study, we designed biodegradable polymersomes for co-delivery of an antiangiogenic drug combretastatin-A4 phosphate (CA4P) and doxorubicin (DOX) to collapse tumor neovasculature and inhibit cancer cell proliferation with the aim to achieve synergistic antitumor effects. The polymersomes co-encapsulating DOX and CA4P (Ps-DOX-CA4P) were prepared by solvent evaporation method using methoxy poly(ethylene glycol)-b-polylactide (mPEG-PLA) block copolymers as drug carriers. The resulting Ps-DOX-CA4P has vesicles shape with uniform sizes of about 50 nm and controlled co-encapsulation ratios of DOX to CA4P. More importantly, Ps-DOX-CA4P (1:10) showed strong synergistic cytotoxicity (combination index CI = 0.31) against human nasopharyngeal epidermal carcinoma (KB) cells. Furthermore, Ps-DOX-CA4P accumulated remarkably in KB tissues xenografts in nude mice. Consistent with these observations, Ps-DOX-CA4P (1:10) achieved significant antitumor potency because of fast tumor vasculature disruption and sustained tumor cells proliferation inhibition in vivo. The overall findings indicate that co-delivery of an antiangiogenic drug and a chemotherapeutic agent in polymersomes is a potentially promising strategy for cancer therapy.

Combretastatin A4 phosphate treatment induces vasculogenic mimicry formation of W256 breast carcinoma tumor in vitro and in vivo.

The purpose of this study was to investigate the effect of combretastatin A4 phosphate (CA4P) on vasculogenic mimicry (VM) channel formation in vitro and in vivo after a single-dose treatment and the underlying mechanism involved in supporting VM. In vitro model of three-dimensional cultures was used to test the effect of CA4P on the tube formation of Walker 256 cells. Western blot analysis was conducted to assess the expression of hypoxia-inducible factor (HIF)-1α and VM-associated markers. W256 tumor-bearing rat model was established to demonstrate the effect of CA4P on VM formation and tumor hypoxia by double staining and a hypoxic marker pimonidazole. Anti-tumor efficacy of CA4P treatment was evaluated by tumor growth curve. Under hypoxic conditions for 48 h in vitro, W256 cells formed VM network associated with increased expression of VM markers. Pretreatment with CA4P did not influence the amount of VM in 3-D culture as well as the expression of these key molecules. In vivo, W256 tumors showed marked intratumoral hypoxia after CA4P treatment, accompanied by increased VM formation. CA4P exhibited only a delay in tumor growth within 2 days but rapid tumor regrowth afterward. VM density was positively related to tumor volume and tumor weight at day 8. CA4P causes hypoxia which induces VM formation in W256 tumors through HIF-1α/EphA2/PI3K/matrix metalloproteinase (MMP) signaling pathway, resulting in the consequent regrowth of the damaged tumor.

Combretastatin A4-phosphate and its potential in veterinary oncology: a review.

For many years, research on anticancer therapy has focussed almost exclusively on targeting cancer cells directly, to selectively kill them or restrict their growth. But limited advances in this strategy have led researchers to shift their attention to other potential targets. Active research is now on-going on targeting tumour stroma. Vascular disrupting agents (VDAs) appear a promising class of anticancer drugs that are currently under investigation as a sole or combined therapy in human cancer patients. This article will briefly touch on the history and biology of combretastatin A4-phosphate (CA4P) as a typical example of VDAs and will concentrate on the side effects that can be expected when used in veterinary patients. Particularly, the pathogenesis of these side effects and how they may be prevented and/or treated will be discussed. The purpose of this article is to illustrate the potentials of CA4P as anticancer therapy in veterinary oncology patients.

Exaggerated hypertensive response to combretastatin A-4 phosphate in hypertensive rats: Effective pharmacological inhibition by diltiazem

Combretastatin A-4 phosphate (CA4P), a tubulin depolymerizing agent, shows promise in anti-cancer therapy and is associated with dose-dependent transient hypertension. The cardiac consequence of this hypertensive effect is unknown. This study was conducted to examine the cardiotoxic effect of CA4P on a rat model of hypertension. Hypertensive rats were created by feeding a 6% high salt (HS) diet to Dahl salt sensitive (DSS) rats for 2.5weeks. Cardiac toxicity was measured using serum troponin I levels 24h after CA4P administration. In rats fed HS diet, there was a significant increase in mean arterial blood pressure (MAP) from baseline, which was further increased by 80% following CA4P administration with peak systolic blood pressure (BP) of 247mmHg. Treatment with the calcium channel blockers, diltiazem and nicardipine, completely inhibited the hypertensive effects of CA4P. Nitroglycerin or enalapril, however, failed to completely block the hypertensive effects of CA4P. CA4P injection also significantly increased the cardiac troponin I level in hypertensive rats though pretreatment with diltiazem effectively blocked troponin I increase after CA4P administration. Based on these findings, an exaggerated hypertensive response to CA4P is associated with myocardial damage in hypertensive rats. Calcium channel blockers effectively blocked both CA4P induced hypertension and cardiac damage.

Tyrosine Kinase Inhibitors for the Therapy of Anaplastic Thyroid Cancer

Anaplastic thyroid cancer (ATC) is often incurable so new therapeutic approaches are needed. Tyrosine kinases inhibitors (such as imanitib, sunitinib or sorafenib) are under evaluation for the treatment of ATC. Other vascular disrupting agents, such as combretastatin A4 phosphate, and antiangiogenic agents, such as aplidin, PTK787/ZK222584 and human VEGF monoclonal antibodies (bevacizumab, cetuximab), have been evaluated. Small-molecule adenosine triphosphate competitive inhibitors directed intracellularly at EGFRs tyrosine kinase, such as erlotinib or gefitinib, are also studied. Furthermore, new molecules have been shown to be active against ATC, such as CLM94 and CLM3. However, more research is needed to finally identify therapies able to control and to cure this disease.

Coadministration of Vascular Disrupting Agents and Nanomedicines to Eradicate Tumors from Peripheral and Central Regions.

A strategy for enhancing the treatment efficacy of nanomedicines within the central region of solid tumors is developed by combining nanomedicines and free small-molecule vascular disrupting agents (VDAs). The nanomedicines (cis-diamminedichloroplatinum-loaded nanoparticles) primarily target cells at the tumor periphery whereas the free small-molecule VDA (combretastatin A4 disodium phosphate) efficiently kills the cancer cells within the central regions of the tumor.

Trapping effect on a small molecular drug with vascular-disrupting agent CA4P in rodent H22 hepatic tumor model: in vivo magnetic resonance imaging and postmortem inductively coupled plasma atomic emission spectroscopy

The aim of the present study is to verify the trapping effect of combretastatin A-4-phosphate (CA4P) on small molecular drugs in rodent tumors. Mice with H22 hepatocarcinoma were randomized into groups A and B. Magnetic resonance imaging (MRI) of T1WI, T2WI, and DWI was performed as baseline. Mice in group A were injected with Gd-DTPA and PBS. Mice in group B were injected with Gd-DTPA and CA4P. All mice undergo CE-T1WI at 0 h, 3 h, 6 h, 12 h, and 24 h. Enhancing efficacy of the two groups on CE-T1WI was compared with the signal-to-noise ratio (SNR) calculated. Concentrations of gadolinium measured by ICP-AES in the tumor were compared between groups. On the early CE-T1WI, tumors were equally enhanced in both groups. On the delayed CE-T1WI, the enhancing effect of group A was weaker than that of group B. The SNR and the concentration of gadolinium within the tumor of group A were lower than that of group B at 6 h, 12 h, and 24 h after administration. This study indicates that CA4P could improve the retention of Gd-DTPA in the tumor and MRI allowed dynamically monitoring trapping effects of CA4P on local retention of Gd-DTPA as a small molecular drug.

Abstract A08: Investigating tumor vasculature development and the effects of OXi4503 by non-invasive photoacoustic imaging

Abstract Vasculature-targeted cancer therapies, such as vascular disrupting or anti-angiogenic agents, interact directly with tumor blood vessels. Direct longitudinal assessment of vascular response, as opposed to indirect measures of tumor volume, would aid clinical translation for these targeted therapies, but novel treatment strategies require adequate biomarkers of response. OXi4503 (Combretastatin-A1 phosphate, CA1P) is a vascular disrupting agent (VDA) known to have significant antitumor effects against a wide range of pre-clinical human tumor model systems, and in the clinic. OXi4503 causes disruption of the central tumor vasculature within an hour of administration, followed by thrombosis and vessel occlusion, resulting in massive central tumor necrosis 24 hours after treatment but leaving a thin viable rim of tumor cells. Photoacoustic imaging (PAI) is a novel non-ionising and non-invasive technique, that provides 3D images of the vascular microenvironment with high spatial resolution. Structural information of blood vessel location, and potentially functional data as well, can therefore be obtained in a longitudinal manner. It is thus ideally suited to assess preclinical models of subcutaneous tumors with regard to vascular targeted therapies. We have used PAI to investigate the development of tumor blood vessels, and the effects of OXi4503 (40mg/kg) on the vasculature of 2 human colorectal xenografts grown in nude mice. Results: The human colorectal tumor cell lines SW1222 and LS174T were established as subcutaneous models in nude mice, by the injection of 5X106 tumor cells. Using PAI we were able to: Determine the extent and pattern of tumor vascularization, non-invasively, over time Differentiate between the pathophysiologies of different tumor types Follow the response to vascular targeted therapy Determine the length of time to tumor regrowth following therapy Conclusion: The data suggest that PAI could prove invaluable in providing imaging biomarkers of response to treatment for vascular targeted therapies, with potential for clinical translation. Citation Format: Sean Peter Johnson, Ollie Ogunlade, Edward Zhang, Mark Lythgoe, Paul Beard, Rosamund Barbara Pedley. Investigating tumor vasculature development and the effects of OXi4503 by non-invasive photoacoustic imaging. [abstract]. In: Abstracts: AACR Special Conference on Cellular Heterogeneity in the Tumor Microenvironment; 2014 Feb 26-Mar 1; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2015;75(1 Suppl):Abstract nr A08. doi:10.1158/1538-7445.CHTME14-A08

Treatment with a vascular disrupting agent does not increase recruitment of indium labelled human endothelial outgrowth cells in an experimental tumour model.

BackgroundThe effect of vascular disrupting agents in tumour therapy depends on both the immediate vascular shutdown, and on the following re-vascularization of the tumour. The aim of this study was to use a tumour model to investigate whether endothelial outgrowth cells (EOCs) influenced the short term treatment efficiency of combretastatin A-4 disodium phosphate (CA4P) and 5,6-dimethylxanthenone-4-acetic acid (DMXAA) by increasing EOC tumour recruitment.MethodsIn order to visualize the recruitment of EOCs to the tumours, umbilical cord blood derived human EOCs were labelled with 111Indium-tropolone in a dose of 0.37 MBq pr 3×106 cells and were injected intravenously into mice carrying a C3H mammary carcinoma on their right rear foot. DMXAA and CA4P in different concentrations and at different exposure times were used to create a hypoxic environment in the C3H mammary carcinoma in the mice. Three different mice strains with various degrees of functional immune system were used to study the homing capability of EOCs.ResultsOur data showed that approximately 4% of the total injected radioactive dose per gram of tissue was found in the tumour after treatment with CA4P and DMXAA. Regardless of the concentration and the treatment duration, CA4P did not increase EOC recruitment to the tumour in comparison to EOC recruitment in control tumours in any of the 3 mice strains studied.ConclusionOur data showed that regardless of the grade of the immune system, ranging from a fully working to a fully compromised immune system, treatment with CA4P did not increase recruitment of xenotransplanted EOCs to tumour tissue.

A combretastatin-mediated decrease in neutrophil concentration in peripheral blood and the impact on the anti-tumor activity of this drug in two different murine tumor models.

The vascular disrupting agent combretastatin A-4 disodium phosphate (CA4P) induces fluctuations in peripheral blood neutrophil concentration. Because neutrophils have the potential to induce both vascular damage and angiogenesis we analyzed neutrophil involvement in the anti-tumoral effects of CA4P in C3H mammary carcinomas in CDF1 mice and in SCCVII squamous cell carcinomas in C3H/HeN mice. Flow cytometry analyses of peripheral blood before and up to 144 h after CA4P administration (25 and 250 mg/kg) revealed a decrease 1 h after treatment, followed by an early (3–6 h) and a late (>72 h) increase in the granulocyte concentration. We suggest that the early increase (3–6 h) in granulocyte concentration was caused by the initial decrease at 1 h and found that the late increase was associated with tumor size, and hence independent of CA4P. No alterations in neutrophil infiltration into the C3H tumor after CA4P treatment (25 and 250 mg/kg) were found. Correspondingly, neutrophil depletion in vivo, using an anti-neutrophil antibody, followed by CA4P treatment (25 mg/kg) did not increase the necrotic fraction in C3H tumors significantly. However, by increasing the CA4P dose to 250 mg/kg we found a significant increase of 359% in necrotic fraction when compared to neutrophil-depleted mice; in mice with no neutrophil depletion CA4P induced an 89% change indicating that the presence of neutrophils reduced the effect of CA4P. In contrast, neither CA4P nor 1A8 affected the necrotic fraction in the SCCVII tumors significantly. Hence, we suggest that the initial decrease in granulocyte concentration was caused by non-tumor-specific recruitment of neutrophils and that neutrophils may attenuate CA4P-mediated anti-tumor effect in some tumor models.

Abstract 1767: Oncocidia: a small molecule dual targeting pan-anticancer theragnostic strategy

Abstract Research on imaging contrast media over the last decades has led to the discovery of small molecular necrosis-avid compounds (NACs) for potential applications in diagnosis of myocardial infarction and therapeutic assessment of tumor ablation using MRI, nuclear scintigraphy and optical imaging [1,2]. The in vivo affinity of NACs to necrosis appears to be orders of magnitude higher than in vivo antigen-antibody, ligand-receptor and biotin-avidin interactions, implying their possible superb applications. Based on a soil-to-seeds hypothesis [3], this stroma targetability has now been extended from diagnostic to theragnostic utilities by combined use of vascular disrupting agents (VDAs) to formulate a novel anticancer approach, namely a small molecule sequential dual targeting pan-anticancer theragnostic strategy or briefly OncoCiDia. The dual targeting property and conjugated iodine-131 that emits both beta and gamma radiations render solid cancers (Onco) with both tumoricidal (Ci) and diagnostic (Dia) effects, thus the acronym of OncoCiDia. Instead of directly attacking multimutant and refractory cancer cells (seeds) as elaborated in most other cancer therapies, OncoCiDia treats solid malignancies overnight by selectively destroying and radioactively sterilizing their microenvironment (soil) in two steps [3]. On day one, a VDA such as Combretastatin A4 phosphate (CA4P) is intravenously (iv) injected to specifically shut down tumoral blood vessels by disrupting the immature endothelium and to cause ischemic tumor necrosis. However, peripheral residual cancer cells always survive as the seeds for tumor re-growth, leading to cancer relapse. Thus, on day two, a NAC such as hypericin (Hyp) carrying the beta emitter iodine-131 is iv infused, which selectively accumulates at the newly generated intratumoral necrosis to create a harsh environment with crossfire radiation and lethally irradiates the adjacent viable tumor cells to prevent their repopulation. One episode of OncoCiDia exerts persistent theragnostic effects over weeks to months due to the long decay half-life of 8 days with iodine-131 and prolonged necrosis target residence of 131I-Hyp. Multicenter proof-of-principle studies and extensive preclinical investigations on the efficacy, safety, formulations and dosimetry have been conducted and the results will be demonstrated in details. Our studies suggest that OncoCiDia appears to be a novel unconventional anticancer strategy that may offer a simple, workable, affordable and generic solution for diverse cancers, and deserve further exploitation [3].

A phase I clinical trial assessing the safety and tolerability of combretastatin A4 phosphate injections

Combretastatin A4 phosphate (CA4P) is a prodrug that selectively destroys tumor blood vessels, and has shown efficacy as a targeted anticancer drug in both animal models and clinical trials. The aims of this single-center, open label, phase I clinical trial were to investigate the safety and tolerability of CA4P administered intravenously to patients aged 18-65 years with advanced solid tumors. Using a dose-escalation protocol, patients were assigned to five groups that received injections with 20 (n=3), 33 (n=3), 50 (n=11), 65 (n=6), or 85 (n=2) mg/m² CA4P. Patients in the 20 and 85 mg/m² groups received a single dose and the other groups received multiple doses. Adverse events (AE), cardiovascular parameters, and biochemical investigations were studied, and the maximum tolerated dose was determined. Of twenty-five patients enrolled, eight were withdrawn/excluded (not because of AE). There were no deaths. A total of 394 AE occurred in the 25 patients, with 89.3% considered related/possibly related to the drug. AE included headache and dizziness (19.8%), tumor-induced pain (14.2%), vascular vagal excitation (10.7%), and vomiting (9.4%). Ninety-five percent of AE were mild (grades 0-II), with only 5% being grade III-IV. Drug administration was associated with biphasic changes in heart rate and blood pressure, and only limited abnormalities in the laboratory investigations performed. The maximum tolerated dose was 65 mg/m². We conclude that CA4P is generally well tolerated, with the vast majority of AE that occurred being of mild severity. Further studies will establish the role of CA4P in cancer therapy.

MALDI‐MSI and label‐free LC‐ESI‐MS/MS shotgun proteomics to investigate protein induction in a murine fibrosarcoma model following treatment with a vascular disrupting agent

Tumour vasculature is notoriously sinusoidal and leaky, and is hence susceptible to vascular disruption. Microtubule destabilising drugs such as the combretastatins form the largest group of tumour vascular disrupting agents and cause selective shutdown of tumour blood flow within minutes to hours, leading to secondary tumour cell death. Targeting the tumour vasculature is a proven anticancer strategy but early treatment response biomarkers are required for personalising treatment planning. Protein induction following treatment with combretastatin A4-phosphate was examined in a mouse fibrosarcoma model (fs188), where tumour cells express only the matrix-bound isoform of vascular endothelial growth factor A (VEGF188). These tumours are relatively resistant to vascular disruption by combretastatin A4-phosphate and hence a study of protein induction following treatment could yield insights into resistance mechanisms. The distribution of a number of proteins induced following treatment were visualised by MALDI-mass spectrometry imaging. Responses identified were validated by LC-ESI-MS/MS and immunohistochemical staining. Significant changes in proteins connected with necrosis, cell structure, cell survival and stress-induced molecular chaperones were identified. Protein-protein interactions were identified using STRING 9.0 proteomic network software. These relationship pathways provided an insight into the activity of the active tumour milieu and a means of linking the identified proteins to their functional partners.