Randomized, double-blind trial of F14512, a polyamine-vectorized anticancer drug, compared with etoposide phosphate, in dogs with naturally occurring lymphoma

Purpose: F14512 is an epipodophyllotoxin derivative from etoposide, combined with a spermine moiety introduced as a cell delivery vector. The objective of this study was to compare the safety and antitumor activity of F14512 and etoposide phosphate in dogs with spontaneous non-Hodgkin lymphoma (NHL) and to investigate the potential benefit of F14512 in P-glycoprotein (Pgp) overexpressing lymphomas.

Experimental Design: Forty-eight client-owned dogs with intermediate to high-grade NHL were enrolled into a randomized, double-blind trial of F14512 versus etoposide phosphate. Endpoints included safety and therapeutic efficacy.

Results: Twenty-five dogs were randomized to receive F14512 and 23 dogs to receive etoposide phosphate. All adverse events (AEs) were reversible, and no treatment-related death was reported. Hematologic AEs were more severe with F14512 and gastrointestinal AEs were more frequent with etoposide phosphate. F14512 exhibited similar response rate and progression-free survival (PFS) as etoposide phosphate in the global treated population. Subgroup analysis of dogs with Pgp-overexpressing NHL showed a significant improvement in PFS in dogs treated with F14512 compared with etoposide phosphate.

Conclusion: F14512 showed strong therapeutic efficacy against spontaneous NHL and exhibited a clinical benefice in Pgp-overexpressing lymphoma superior to etoposide phosphate. The results clearly justify the evaluation of F14512 in human clinical trials.

eIF4A inhibition circumvents uncontrolled DNA replication mediated by 4E-BP1 loss in pancreatic cancer

Pancreatic ductal adenocarcinoma (PDAC) relies on hyperactivated protein synthesis. Consistently, human and mouse PDAC lose expression of the translational repressor and mTOR target 4E-BP1. Using genome-wide polysome profiling, we here explore mRNAs whose translational efficiencies depend on the mTOR/4E-BP1 axis in pancreatic cancer cells. We identified a functional enrichment for mRNAs encoding DNA replication and repair proteins, including RRM2 and CDC6. Consequently, 4E-BP1 depletion favors DNA repair and renders DNA replication insensitive to mTOR inhibitors, in correlation with a sustained protein expression of CDC6 and RRM2, which is inversely correlated with 4E-BP1 expression in PDAC patient samples. DNA damage and pancreatic lesions induced by an experimental pancreatitis model uncover that 4E-BP1/2-deleted mice display an increased acinar cell proliferation and a better recovery than WT animals. Targeting translation, independently of 4E-BP1 status, using eIF4A RNA helicase inhibitors (silvestrol derivatives) selectively modulates translation and limits CDC6 expression and DNA replication, leading to reduced PDAC tumor growth. In summary, 4E-BP1 expression loss during PDAC development induces selective changes in translation of mRNA encoding DNA replication and repair protein. Importantly, targeting protein synthesis by eIF4A inhibitors circumvents PDAC resistance to mTOR inhibition.

Phase I dose-escalation study of F14512, a polyamine-vectorized topoisomerase II inhibitor, in patients with platinum-refractory or resistant ovarian cancer

Purpose To determine the maximum tolerated dose (MTD) of F14512, a topoisomerase II inhibitor designed to target cancer cells through the polyamine transport system, (three-hour daily infusion given for 3 consecutive days every 3 weeks) in platinum-refractory or resistant ovarian cancer. Other objectives were safety, pharmacokinetics (PK), PK/pharmacodynamics relationship, and efficacy. Methods This was an open-label, dose-escalation, multicenter phase I study. Results Eleven patients were enrolled and were treated at dose levels (DLs) of 10 and 5 mg/m²/day. All patients received the 3 injections per cycle as per study protocol (median, 1 cycle (Ferlay et al. Int J Cancer 136:E359–386, 2015; Siegel et al. CA Cancer J Clin 65:5–29, 2015; Oronsky et al. Med Oncol 34:103, 2017; Barret et al. Cancer Res 68:9845–9853, 2008; Ballot et al. Apoptosis 17:364–376, 2012; Brel et al. Biochem Pharmacol 82:1843–1852, 2011; Gentry et al. Biochemistry 50:3240–3249, 2011; Kruczynski et al. Investig New Drugs 29:9–21, 2011; Chelouah et al. PLoS One 6:e23597, 2011)) with no dose reductions. At DL 10 mg/m²/day, 6 dose-limiting toxicities (DLTs) were reported (3/4 evaluable patients: 2 grade 3 febrile neutropenia, 1 grade 4 neutropenia lasting at least 7 days, 1 grade 3 nausea, 1 decreased appetite, and 1 grade 3 asthenia). At dose 5 mg/m²/day, 2 DLTs were reported (2/6 treated patients: 2 grade 3 febrile neutropenia). Both DLs were defined as MTD. Stable disease was reported as best overall response in 2 (40%) patients having both received 9 cycles, one at each DL. 90.9% of patients experienced grade 4 neutropenia, but for only one (9.1%) it was reported as a serious adverse event. Conclusion Although there was some encouraging efficacy signal, grade 4 neutropenia led to complications and it was decided to stop the study. A DL below 5 mg/m²/day was not tested as this would not allow reaching the minimum serum concentration needed for the pharmacological activity of the drug.

Actinic keratosis modelling in mice: A translational study

Background

Actinic keratoses (AK) are pre-malignant cutaneous lesions caused by prolonged exposure to ultraviolet radiation. As AKs lesions are generally accepted to be the initial lesions in a disease continuum that progresses to squamous cell carcinoma (SCC), AK lesions have to be treated. They are also the second most common reason for visits to the dermatologist. Several treatments are available but their efficacy still needs to be improved. The UV-B-induced KA lesion mouse model is used in preclinical studies to assess the efficacy of novel molecules, even though it is often more representative of advanced AK or SCC.

Objectives

Here we report on a translational study, comparing the various stages of AK development in humans and in the UV-B irradiated mouse model, as well as the optimization of photograph acquisition of AK lesions on mouse skin.

Methods

Human and mouse skin lesions were analysed by histology and immunohistochemistry. Mouse lesions were also assessed using a digital dermatoscope.

Results

An histological and phenotypic analysis, including p53, Ki67 and CD3 expression detection, performed on human and mouse AK lesions, shows that overall AK modelling in mice is relevant in the clinical situation. Some differences are observed, such as disorganization of keratinocytes of the basal layer and a number of atypical nuclei which are more numerous in human AK, whereas much more pronounced acanthosis is observed in skin lesion in mice. Thanks to this translational study, we are able to select appropriate experimental conditions for establishing either early or advanced stage AK or an SCC model. Furthermore, we optimized photograph acquisition of AK lesions on mouse skin by using a digital dermatoscope which is also used in clinics and allows reproducible photograph acquisition for further reliable assessment of mouse lesions. Use of this camera is illustrated through a pharmacological study assessing the activity of CARAC^®.

Conclusion

These data demonstrate that this mouse model of UV-B-induced skin lesions is predictive for the identification of novel therapeutic treatments for both early and advanced stages of the disease.

The DNA-Binding Polyamine Moiety in the Vectorized DNA Topoisomerase II Inhibitor F14512 Alters Reparability of the Consequent Enzyme-Linked DNA Double-Strand Breaks

Poisons of topoisomerase II (TOP2) kill cancer cells by preventing religation of intermediate DNA breaks during the enzymatic process and thus by accumulating enzyme-drug-DNA complexes called TOP2 cleavage-complex (TOP2cc). F14512 is a highly cytotoxic polyamine-vectorized TOP2 inhibitor derived from etoposide and currently in clinical trials. It was shown in vitro that F14512 has acquired DNA-binding properties and that the stability of TOP2cc was strongly increased. Paradoxically, at equitoxic concentrations in cells, F14512 induced less DNA breaks than etoposide. Here, we directly compared etoposide and F14512 for their rates of TOP2cc production and resolution in human cells. We report that targeting of TOP2α and not TOP2β impacts cell killing by F14512, contrary to etoposide that kills cells through targeting both isoforms. Then, we show that despite being more cytotoxic, F14512 is less efficient than etoposide at producing TOP2α cleavage-complex (TOP2αcc) in cells. Finally, we report that compared with TOP2αcc mediated by etoposide, those generated by F14512 persist longer in the genome, are not dependent on TDP2 for cleaning break ends from TOP2α, are channeled to a larger extent to resection-based repair processes relying on CtIP and BRCA1 and promote RAD51 recruitment to damaged chromatin. In addition to the addressing of F14512 to the polyamine transport system, the properties uncovered here would be particularly valuable for a therapeutic usage of this new anticancer compound. More generally, the concept of increasing drug cytotoxicity by switching the repair mode of the induced DNA lesions via addition of a DNA-binding moiety deserves further developments. Mol Cancer Ther; 16(10); 2166-77. ©2017 AACR.

Abstract 4185: Randomized double-blind clinical study of F14512, a new polyamine-vectorized anticancer drug and Etoposide in naturally occurring canine lymphoma

F14512 is a new topoisomerase II inhibitor containing a spermine moiety that facilitates selective uptake by tumor cells and increases topoisomerase II poisoning. F14512 is currently in Phase I/II clinical trials in patients with acute myeloid leukemia. The aim of this study is to investigate the potential of F14512 in a new clinical indication and to compare its clinical efficacy with the reference topoisomerase II inhibitor Etoposide. Because of the many similarities between human and dog lymphomas, we are seeking to determine the tolerance, efficacy, PK/PD relationship of F14512 in this indication and potential biomarkers that could be translated into human trials.

Firstly, we successfully initiated two Phase 1 dose-escalation trials with 23 and 27 dogs with naturally occurring lymphomas using F14512 and Etoposide, respectively, with endpoints including safety, therapeutic efficacy and biomarker studies. Secondly, we initiated a randomized double blind study with two groups of 24 dogs with naturally occurring lymphomas in order to compare the clinical efficacy of F14512 and Etoposide in both newly diagnosed and relapsing cases.

The Phase 1 trial demonstrated that F14512 could be safely administered to dogs with lymphoma resulting in strong therapeutic efficacy with a response rate of 91% (21/23) with 10 complete responses, 11 partial responses, one stable disease and one progressive disease. Phosphorylation of histone H2AX was studied as a potential pharmacodynamic biomarker of F14512. Etoposide displayed modest therapeutic efficacy with a response rate of 19% (5/27) with 1 complete response, 4 partial responses, and 6 stable diseases. The comparative clinical study was then initiated with both compounds administered at the recommended dose identified in the Phase 1 trial. Inclusion of all the dogs from the randomized double blind comparative study will be finalized at the beginning of 2016 and the results of the study will be disclosed at the AACR 2016 meeting.

This work shows that naturally occurring cancers in dogs can be of great interest in translational research in order to support preclinical and clinical development of new compounds.

Citation Format: Bruno Gomes, François Serres, Juliette Hordeaux, Zacharie Segaoula, Emmanuel Bouchaert, Séverine Wadoux, Laurent Marescaux, Franck Floch, Pierre Boyé, Kevin Geeraert, Ingrid Bemelmans, Thierry Marchal, Corinne Fournel, Grégoire Zorza, Pierre Ferré, Aurélie Pétain, Nicolas Guilbaud, Dominique Tierny. Randomized double-blind clinical study of F14512, a new polyamine-vectorized anticancer drug and Etoposide in naturally occurring canine lymphoma. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 4185.

F14512, a polyamine-vectorized inhibitor of topoisomerase II, exhibits a marked anti-tumor activity in ovarian cancer

Epithelial ovarian cancer is the fourth cause of death among cancer-bearing women and frequently associated with carboplatin resistance, underlining the need for more efficient and targeted therapies. F14512 is an epipodophylotoxin-core linked to a spermine chain which enters cells via the polyamine transport system (PTS). Here, we investigate this novel concept of vectorization in ovarian cancer. We compared the effects of etoposide and F14512 on a panel of five carboplatin-sensitive or resistant ovarian cancer models. We assessed the incorporation of F17073, a spermine-linked fluorescent probe, in these cells and in 18 clinical samples. We then showed that F14512 exhibits a high anti-proliferative and pro-apoptotic activity, particularly in cells with high levels of F17073 incorporation. Consistently, F14512 significantly inhibited tumor growth compared to etoposide, in a cisplatin-resistant A2780R subcutaneous model, at a dose of 1.25 mg/kg. In addition, ex vivo analysis indicated that 15 out of 18 patients presented a higher F17073 incorporation into tumor cells compared to normal cells. Overall, our data suggest that F14512, a targeted drug with a potent anti-tumor efficacy, constitutes a potential new therapy for highly PTS-positive and platinum-resistant ovarian cancer-bearing patients.

Abstract 2428: Translational study of F14512, a novel vectorised epipodophyllotoxin, which demonstrates a marked activity on ovarian cancer models from patients

Epithelial ovarian cancer is the fourth cause of death among cancer-bearing women, frequently associated with carboplatin resistance, underlining the need of more efficient and targeted therapies. F14512 is a novel concept of drug vectorization that we propose here to investigate in ovarian cancer models. F14512 is an epipodophyllotoxin-core linked to a spermine chain, which enters selectively tumor cells via the polyamine transport system (PTS), currently in clinical phase II evaluation in AML. We compared the effects of F14512 versus etoposide against OVCAR-3, IGROV-1, SKOV-3, A2780S and A2780R cancer cell lines. Using the F17073 PTS fluorescent probe, we determined the PTS activity of these cells and of 18 clinical samples. As results, F14512 displayed strong anti-proliferative and pro-apoptotic activities in carboplatin-resistant models, being increased in cell lines with high levels of PTS. Consistently, at a dose of 1.25 mg/kg, F14512 significantly inhibited tumor growth in cisplatin-resistant SKOV-3 xenograft model. Interestingly, ex vivo analysis indicated that 15 patients sample out of 18 presented a higher F17073 fluorescent probe incorporation into CD326-positive tumor cells as compared to normal cells, even in the case of 2 platinum-refractory patients. Therefore, F14512 is a targeted drug with a potent anti-tumor efficacy regardless the status of cisplatin resistance. The high PTS activity detected in fresh clinical samples highlights the potential of F14512 as a new therapy for PTS-positive and platinum resistant ovarian cancer patients.

Citation Format: Benoît Thibault, Gregoire Zorza, Samuel Meignan, Nicolas Guilbaud, Christian Bailly, Jean-Pierre Delord, Bettina Couderc, Anna Kruczynski, Pierre Ferre, Jean-Philippe Annereau. Translational study of F14512, a novel vectorised epipodophyllotoxin, which demonstrates a marked activity on ovarian cancer models from patients. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 2428. doi:10.1158/1538-7445.AM2015-2428

Phase I Clinical Pharmacology Study of F14512, a New Polyamine-Vectorized Anticancer Drug, in Naturally Occurring Canine Lymphoma

PURPOSE

F14512 is a new topoisomerase II inhibitor containing a spermine moiety that facilitates selective uptake by tumor cells and increases topoisomerase II poisoning. F14512 is currently in a phase I/II clinical trial in patients with acute myeloid leukemia. The aim of this study was to investigate F14512 potential in a new clinical indication. Because of the many similarities between human and dog lymphomas, we sought to determine the tolerance, efficacy, pharmacokinetic/pharmacodynamic (PK/PD) relationship of F14512 in this indication, and potential biomarkers that could be translated into human trials.

EXPERIMENTAL DESIGN

Twenty-three dogs with stage III-IV naturally occurring lymphomas were enrolled in the phase I dose-escalation trial, which consisted of three cycles of F14512 i.v. injections. Endpoints included safety and therapeutic efficacy. Serial blood samples and tumor biopsies were obtained for PK/PD and biomarker studies.

RESULTS

Five dose levels were evaluated to determine the recommended dose. F14512 was well tolerated, with the expected dose-dependent hematologic toxicity. F14512 induced an early decrease of tumoral lymph node cells, and a high response rate of 91% (21/23) with 10 complete responses, 11 partial responses, 1 stable disease, and 1 progressive disease. Phosphorylation of histone H2AX was studied as a potential PD biomarker of F14512.

CONCLUSIONS

This trial demonstrated that F14512 can be safely administered to dogs with lymphoma resulting in strong therapeutic efficacy. Additional evaluation of F14512 is needed to compare its efficacy with standards of care in dogs, and to translate biomarker and efficacy findings into clinical trials in humans.

Abstract 1219: Patient-derived tumor models of resistant metastatic melanoma

Despite recent advances in the therapy of metastatic melanoma, patients have a poor prognosis and die from their disease, with a 5-year survival rate of less than 20%. Metastatic melanoma remains mainly chemoresistant, therefore novel therapeutic strategies to overcome primary or acquired resistance are required. In order to more reliably predict clinical activity of novel compounds in melanoma patients, we have established a series of patient-derived tumor xenograft models (PDTX). Surgically resected tumors samples were obtained from patients with metastatic melanoma before or after treatment. Twenty-three samples from 9 patients and representative of various stages of disease progression were implanted onto immunocompromised NSG mice. A high take rate of 56% (13/23 samples) was observed, corresponding to the samples from 8/9 patients. Tumor take was independent of tumor size, histologic parameters and B-RAF status. The first tumor generation (graft) harbouring the patient-derived sample (G1), as well as the subsequent generations were characterized for each PDTX. The pattern of expression of the melanoma differentiation markers S100, melanosome, tyrosinase and melan-A were maintained over the serial transplantations. These models also closely recapitulated the heterogeneity of patient tumors in terms of cell morphology over the first generations (G1-G5), but this heterogeneity tended to decrease with the number of generations. One of these primary PDTXs, MEL-11 exhibited metastatic spread in axillary lymph nodes. Furthermore 2 other primary melanoma PDTXs, MEL-1 and MEL-3, established from primary refractory patient metastatic melanoma retained complete resistance to temozolomide and vemurafenib, the two reference drugs for melanoma. The MEL-3 model was selected to assess the anti-melanoma activity of F-RK-4, a novel multi-kinases inhibitor (including inhibition of mutated B-RAF). Multiple i.p. administrations of F-RK-4 resulted in a significant antitumor activity, as reflected by a tumor growth inhibition of 50%. Overall these results suggest that these patient-derived melanoma xenografts represent a useful preclinical tool to identify novel anti-melanoma therapeutics.

Citation Format: Bruno Gomes, Céline ROBICHON, Arnaud Pillon, Jean-Philippe Annereau, Sandrine Pourtau, Jean-Christophe Blanchet, Aline Stennevin, Karim Bedjeguelal, Philippe Rochaix, Ignacio Garrido-Stowhas, Laurence Lamant, Nicolas Meyer, Nicolas Guilbaud, Christian Bailly, Anna Kruczynski. Patient-derived tumor models of resistant metastatic melanoma. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 1219. doi:10.1158/1538-7445.AM2014-1219

Activity of the polyamine-vectorized anti-cancer drug F14512 against pediatric glioma and neuroblastoma cell lines

The poor prognosis of children with high-grade glioma (HGG) and high-risk neuroblastoma, despite multidisciplinary therapeutic approaches, demands new treatments for these indications. F14512 is a topoisomerase II inhibitor containing a spermine moiety that facilitates selective uptake by tumor cells via the Polyamine Transport System (PTS) and increases topoisomerase II poisoning. Here, F14512 was evaluated in pediatric HGG and neuroblastoma cell lines. PTS activity and specificity were evaluated using a fluorescent spermine-coupled probe. The cytotoxicity of F14512, alone or in combination with ionizing radiation and chemotherapeutic agents, was investigated in vitro. The antitumor activity of F14512 was assessed in vivo using a liver-metastatic model of neuroblastoma. An active PTS was evidenced in all tested cell lines, providing a specific and rapid transfer of spermine-coupled compounds into cell nuclei. Competition experiments confirmed the essential role of PTS in the cell uptake and cytotoxicity of F14512. This cytotoxicity appeared greater in neuroblastoma cells compared with HGG cells but appeared independent of PTS activity levels. In vivo evaluation confirmed a marked and prolonged antitumoral effect in neuroblastoma cells. The combinations of F14512 with cisplatin and carboplatin were often found to be synergistic, and we demonstrated the significant radiosensitizing potential of F14512 in the MYCN-amplified Kelly cell line. Thus, F14512 appears more effective than etoposide in pediatric tumor cell lines, with greater efficacy in neuroblastoma cells compared with HGG cells. The synergistic effects observed with platinum compounds and the radiosensitizing effect could lead to a clinical development of the drug in pediatric oncology.

Abstract 5565: Tumor targeting and enhanced efficacy of novel polyamine-cytotoxic conjugates

Rapidly proliferating cancer cells have a higher demand on polyamines resulting in an over-activated Polyamines Transport System (PTS)1. Polyamines entry can be exploited as a selective anticancer drug delivery system. We synthesized polyamines-epipodophylotoxin conjugates with improved physico-chemical and pharmacological properties. As proof of concept, we demonstrated that the conjugation of epipodophylotoxin with spermine changes the pharmacological profile of the cytotoxic moiety by increasing the solubility, enhances the cellular distribution through the PTS, and increases the capacity to inhibit topoisomerase II due to stronger DNA interaction, as compared to the closest structurally related compound etoposide. Among several conjugates, F145122 was selected as a drug candidate and is currently undergoing a phase 1/2 clinical evaluation in acute myeloid leukaemia (AML).

Based on this clinically validated objective to target cancer cells with the PTS, we set up a chemical platform of conjugation of polyamine moieties. We extended our approach to 3 natural products of interest in oncology: (i) an inhibitor of elongation phase in protein translation, a modulator of redox cell regulation and an inhibitor of polyADP-ribose polymerase. This approach led to the synthesis of novel spermine-pancratistatine, -artemisinine and -PARPi conjugates and their biochemical and biological characterization in terms of protein synthesis, PARP inhibition, ROS induction, anti-proliferative effects on cancer cells and their capacity to be imported via the PTS. Cell internalisation through the PTS was measured by differential cytotoxicity on PTS+ vs. PTS− cells, or by competition with a fluorescent probe. We also evaluated selected compounds in vivo and investigated whether their modified properties translate into a higher level of antitumor activity associated with an enlarged therapeutic index in a PTS+ tumor model. For the PARP inhibitor-spermine conjugates, an increase in cellular uptake was confirmed, without impairing the cytotoxic properties.

The dedicated polyamine conjugation platform presented here can be adapted to many cytotoxic scaffolds to enhance their solubility, preferential incorporation into cancer cells through the PTS, and their pharmacological activity in vitro and in vivo. The design of polyamine-vectorized cytotoxic agents will be presented.

1 Delcros J.G. et al., Biochem. J., 1993, 269

2 PCT Int. Appl. WO2005/100363 (Pierre Fabre Medicament); Barret J.-M. et al., Cancer Res. 2008, 68, 9845

Citation Format: Frédéric Liéby-Muller, Jean-Philippe Annereau, Viviane Brel, Frédéric Marion, Yves Guminski, Florence Redoules, Nathalie de Saint Jores, Karine André, Anna Kruczynski, Christian Bailly, Nicolas Guilbaud. Tumor targeting and enhanced efficacy of novel polyamine-cytotoxic conjugates. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 5565. doi:10.1158/1538-7445.AM2013-5565

Abstract 988: F14512, a novel vectorized topoiserase II inhibitor, bypasses MDR1 mediated resistance

F14512 is a novel polyamine-vectorized topoisomerase II inhibitor currently in phase 1/2 clinical trial in acute myeloid leukemia (AML). Since ABCB1 (also called P-glycoprotein or MDR1) has been reported to be expressed at high levels in patients with resistant leukaemia cells, and constitutes a pejorative marker of therapy, we decided to investigate whether F14512 could be exported by ABCB1 or other ABC transporters susceptible to confer drug resistance to chemotherapy, such as MRP1. In addition, we established a F14512-resistant cell line to study the mechanism of resistance to the drug.

With membrane preparation enriched in functional MDR1, we found that F14512 was unable to stimulate the ATPase activity of this transporter. Using a cellular assay over expressing MDR1 transporter by recombinant transfection of MDCKII cells, F14512 was detectable, but the intracellular level was unchanged regardless of the MDR1 status or in presence of MDR1 competitors. Consistently, iterative selection of a F14512-resistant A-549 cell line with 36 cycles of F14512 at cytotoxic doses (0.5 EC50) over 9 months, led to only moderate shift of resistance (9 fold). In the resulting selected A-549 subclones, MDR1, MRP1 and ABCG2 were detectable at the basal level.

The ability of F14512 to bypass MDR1 was finally assessed in a vinorelbine-resistant P388 model overexpressing high level of functional ABCB1 as indicated with the positive rhodamine export assay and cross resistance to MDR1 substrate. Moreover, F14512 displays strong antileukemic activity in MDR1-positive P388 cells in vitro and additional in vivo measurements are in progress.

In conclusion, the data concur to show that the antitumor activity of the targeted cytotoxic agent F14512 is not impacted by the MDR1 status of cancer cells. MDR1 clearly does not affect the potency of F14512 and this characteristic augurs well for the ongoing development of the drug in AML patients.

Citation Format: Jean Philippe Annereau, Viviane Brel, William Riquet, Laurent Créancier, Isabelle Vandenberghe, Emmanuel Fournier, Céline Robichon, Aline Stennevin, Vanessa Offrete, Laurence Lacastaigneratte, Bruno Gomes, Anna Kruczynski, Christian Bailly, Nicolas Guilbaud. F14512, a novel vectorized topoiserase II inhibitor, bypasses MDR1 mediated resistance. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 988. doi:10.1158/1538-7445.AM2013-988

CD10 expression by melanoma cells is associated with aggressive behavior in vitro and predicts rapid metastatic progression in humans

BACKGROUND

No biological or molecular marker of primary melanoma tumor cells has been shown to predict clinical outcome in melanoma.

OBJECTIVE

To determine whether CD10, CD133, nestin and CD20 may evaluate the prognosis of melanoma.

METHODS

The differential expression of these molecules was assessed in pairs of cell lines. We evaluated, by both immunohistochemical staining and RT-qPCR, their expression in a cohort of 32 patients (68 samples) with a history of metastatic melanoma, divided into two groups according to their clinical outcome profile.

RESULTS

CD10 over expression in cancer cell lines was associated with more aggressive behavior in vitro. A CD10-positive staining was more frequent in patients in the "rapidly progressive" group than those in the "long survivor" group (23/35 versus 2/18, p<10(-4)). CD10 expression was associated with a lower median overall survival (1.15 year - IQR: [0.50-2.58] versus 4.27 - IQR: [1.66-6.33]; p=10(-4)). The Odds Ratio of displaying a "rapidly progressive" melanoma when tumor cells expressed CD10 was 15 (95% confidence interval: [3-78]). After adjusting for confounding factors, CD10 expression in melanoma tumor cells remained associated with an increased risk of death and more rapid disease progression (p=6×10(-4); HR=3.71).

CONCLUSION

CD10 may predict clinical outcome in melanoma patients.

The nonlysosomal β-glucosidase GBA2 promotes endoplasmic reticulum stress and impairs tumorigenicity of human melanoma cells

Glycosphingolipids, which are abundant at the surface of melanoma cells, play crucial roles in tumor progression. We investigated whether a newly described glycosphingolipid hydrolase, encoded by the GBA2 gene, can modulate human melanoma cell growth and death. GBA2 expression was quantified on melanoma cells by RT-qPCR. The antiproliferative effects of GBA2 were assessed in tumor cells expressing inducible GBA2 and in established melanoma xenografts. As a control an inducible catalytically inactive GBA2 mutant was generated. Sphingolipid levels were monitored by mass spectrometry; unfolded protein response (UPR) and apoptosis were assessed by Western blot and flow cytometry analyses, respectively. We report that GBA2 is down-regulated in melanoma; inducible expression of GBA2 affects endogenous sphingolipid metabolism by promoting glucosylceramide degradation (decrease by 78%) and ceramide generation; this is followed by a UPR that causes apoptosis, subsequent decreased anchorage-independent cell growth, and reduced in vivo tumor growth (by 40%); and all these events are abrogated when expressing a catalytically inactive GBA2. This study documents for the first time the antitumor activity of GBA2 and provides evidence for the role of nonlysosomal glucosylceramide breakdown as a source of bioactive ceramide and a mechanistic link between glycolipid catabolism and the UPR/death response of melanoma cells.

Melanoma chemotherapy leads to the selection of ABCB5-expressing cells

Metastatic melanoma is the most aggressive skin cancer. Recently, phenotypically distinct subpopulations of tumor cells were identified. Among them, ABCB5-expressing cells were proposed to display an enhanced tumorigenicity with stem cell-like properties. In addition, ABCB5⁺ cells are thought to participate to chemoresistance through a potential efflux function of ABCB5. Nevertheless, the fate of these cells upon drugs that are used in melanoma chemotherapy remains to be clarified. Here we explored the effect of anti-melanoma treatments on the ABCB5-expressing cells. Using a melanoma xenograft model (WM266-4), we observed in vivo that ABCB5-expressing cells are enriched after a temozolomide treatment that induces a significant tumor regression. These results were further confirmed in a preliminary study conducted on clinical samples from patients that received dacarbazine. In vitro, we showed that ABCB5-expressing cells selectively survive when exposed to dacarbazine, the reference treatment of metastatic melanoma, but also to vemurafenib, a new inhibitor of the mutated kinase V600E BRAF and other various chemotherapeutic drugs. Our results show that anti-melanoma chemotherapy might participate to the chemoresistance acquisition by selecting tumor cell subpopulations expressing ABCB5. This is of particular importance in understanding the relapses observed after anti-melanoma treatments and reinforces the interest of ABCB5 and ABCB5-expressing cells as potential therapeutic targets in melanoma.

Abstract A51: Antiproliferative activity of F14512, a novel polyamine-vectorized drug, on multidrug resistant cancer cells

F14512 is a novel vectorized topoisomerase II inhibitor currently in phase I clinical study in AML. Briefly, F14512 combines a polyamine (spermine) chain with an epipodophyllotoxin warhead. An enhanced antitumor effect associated with a large therapeutic index results from this specific targeting of cancer cells through polyamine transport system. One of the most important limitations in chemotherapeutic treatment is acquired or innate drug resistance. To investigate this phenomenon for F14152, we selected A549 NSCLC cell lines upon F14512 treatment by increasing doses selection, and characterized the profile of resistance in term of ABC transporter expression and modification of topoisomerase II expression. As results, resistant cell lines were selected after 46 passages and 32 treatment of F14512 with doses ranging 0.25 to 4 IC50 of inhibition of proliferation, over a period of 9 months. As key observation, the intense selection pressure led solely to a moderated shift of EC50 of proliferation, not mediated through MDR1 nor MRP1, but more likely attributable to reduction of topoisomerase II expression. Moreover, we demonstrated that F14512 retains significant antiproliferative activity of F14512 on cell line overexpressing MDR1: CEM selected in vinblastine, A-549 in vinflunine, and P388 in vinorelbine, with a striking enhanced impact on the later model. According to these first investigations, we conclude that MDR1 would not be involved in the resistance mechanism against F14512. We are investigating hypotheses potentially explaining the collateral sensitivity to this novel polyamine derivative on MDR1 expressing P-388 cells.

Abstract 1925: Trifluoromethylated artemisinin dimers demonstrate a potent anti-cancer activity in vitro and in vivo

Beside their widely recognised efficacy as antimalaric drugs, artemisinin derivatives are also known for their cytotoxic properties since the early nineties. More recently, artemisinin dimers (ADs) were shown to possess an increased potential as anti-cancer agents due to their ability to inhibit cancer cells proliferation in the low nanomolar range. Taking advantage of an original chemistry, we synthesized a new series of trifluoromethylated artemisnin dimers which proved to be particularly potent depending on the size and nature of the linker. Different mode of linkage were performed by either carbon 16 or carbon 10 and were tested in vitro and in vivo. Best combination was found in a hybrid linking position delivering non-symmetrical C10-C16 ADs. One of the lead compound of this series, F98458 demonstrated a moderate (but statiscally significative) anti-tumor activity in mice against a human melanoma xenograft that is, to our knowledge, the first demonstration of in vivo antitumor properties of ADs in preclinical models. Many efforts to understand the molecular origin of the cytotoxic effect of monomeric artemisinin derivatives have been undertaken. One of the aims of this study was to investigate the mechanism of action of ADs in comparison with artemisinin: the antimalaric drug artesunate, a representative monomeric derivative of artemisinin, is known to induce DNA damage and ROS generation while our ADs did not under the same experimental conditions. Moreover ADs did not induce apoptosis (caspase 3/7, annexin V), leading us to investigate cell death related to senescence and autophagy. We have also synthesized partially reduced ADs possessing only one endoperoxide functionality. These compounds did show the same potency than non reduced ADs, underlaying that a tight molecular recognition is involved in its biological response. All these observations suggest that monomeric artemisinin derivatives such as artesunate and ADs possess distinct modes of action. The high in vitro potency associated with the in vivo response led us to synthesize affinity probes in order to identify the molecular target of ADs which could provide fundamental informations for further developpement of these compounds as anti-cancer agents. This work currently underway will also be discussed.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 1925. doi:1538-7445.AM2012-1925

Abstract 2747: Synergistic antileukemic activity of F14512 in combination with AraC

New antileukemic agents are urgently needed to achieve improvement of the survival of patients suffering from Acute Myelogenous Leukemia (AML). F14512 combines an epipodophyllotoxin core with a spermine moiety that targets cells with a high demand for polyamines such as cancer cells. F14512 exhibits a high level of in vivo anti-tumor activity in a series of experimental murine and human solid tumor models and has entered into clinical phase one. In this study, we investigated the in vivo antileukemic activity of F14512 against cell line or primary human AML models and evaluated its potential in combination with the reference antileukemic agent, AraC. HL60 cells or AML cells collected from different patients were engrafted onto NSG mice. Using flow cytometry and q-PCR analysis, we demonstrated that multiple administrations of F14512 for 3 weeks resulted in an extensive reduction of AML cell number in the bone marrow and blood of treated mice. We also showed in vitro and in vivo synergistic activity of F14512 in combination with AraC in HL-60 and primary AML models when both compounds were used at suboptimal doses. The mechanisms triggering primary leukemic cell death were investigated and our results indicated that senescence could be involved. Collectively, these results demonstrate that F14512 exhibits a marked in vivo antileukemic activity, supporting the Phase I clinical trials of this novel promising drug candidate.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 2747. doi:1538-7445.AM2012-2747

Optical imaging of disseminated leukemia models in mice with near-infrared probe conjugated to a monoclonal antibody

BACKGROUND

The assessment of anticancer agents to treat leukemia needs to have animal models closer to the human pathology such as implantation in immunodeficient mice of leukemic cells from patient samples. A sensitive and early detection of tumor cells in these orthotopic models is a prerequisite for monitoring engraftment of leukemic cells and their dissemination in mice. Therefore, we developed a fluorescent antibody based strategy to detect leukemic foci in mice bearing patient-derived leukemic cells using fluorescence reflectance imaging (FRI) to determine when to start treatments with novel antitumor agents.

METHODS

Two mAbs against the CD44 human myeloid marker or the CD45 human leukocyte marker were labeled with Alexa Fluor 750 and administered to leukemia-bearing mice after having verified the immunoreactivity in vitro. Bioluminescent leukemic cells (HL60-Luc) were used to compare the colocalization of the fluorescent mAb with these cells. The impact of the labeled antibodies on disease progression was further determined. Finally, the fluorescent hCD45 mAb was tested in mice engrafted with human leukemic cells.

RESULTS

The probe labeling did not modify the immunoreactivity of the mAbs. There was a satisfactory correlation between bioluminescence imaging (BLI) and FRI and low doses of mAb were sufficient to detect leukemic foci. However, anti-hCD44 mAb had a strong impact on the tumor proliferation contrary to anti-hCD45 mAb. The use of anti-hCD45 mAb allowed the detection of leukemic patient cells engrafted onto NOD/SCID mice.

CONCLUSIONS

A mAb labeled with a near infrared fluorochrome is useful to detect leukemic foci in disseminated models provided that its potential impact on tumor proliferation has been thoroughly documented.

Abstract B37: F14512, a polyamine-vectorized anticancer drug, triggers senescence cell death mechanism

Drugs specifically vectorized to cancer cells may offer a reinforced activity, resulting in an improved therapeutic index. In this context, F14512 exploits the Polyamines Transport System (PTS) to accumulate into cells and exhibits an enhanced anti-proliferative activity on a large panel of tumor cell lines as compared to etoposide. At the molecular level, the spermine tail of F14512 contributes to enhance the water solubility of the drug, and reinforces the activity of the drug toward its primary molecular target, topoisomerase II. This observation has encouraged the set up of a phase 1 clinical study with F14512 in patients with relapsed or refractory acute myeloid leukemia (AML).

In order to determine how these molecular properties translate at the cellular level, we have compared the kinetic of cell cycle modulation associated with the inhibition of cell proliferation. F14512 proved to be &gt;30-fold more cytotoxic than etoposide against A549 non-small cell lung cancer cells and triggers less but unrecoverable DNA damages and does not lead to a marked accumulation in the S-phase of the cell cycle, unlike etoposide. Interestingly, A549 cells treated with F14512 were less prone to undergo apoptosis (neither caspases-dependent, nor caspases-independent pathways) or autophagy but preferentially entered into senescence. Drug-induced senescence was characterized qualitatively and quantitatively by an increased -galactosidase activity, both by cytochemical staining and by flow cytometry. A morphological analysis by electron microscopy revealed the presence of numerous multi-lamellar and vesicular bodies and large electron-lucent vacuoles in F14512-treated cell samples. The mechanism of drug-induced cell death is thus distinct for F14512 as compared to etoposide, and this difference may account for their distinct pharmacological profiles and the superior activity of F14512 in vivo. The identification of such response markers for senescence are currently pursued on in vivo MX-1 models by following a transcriptomic analysis focused on cell death cascades including apoptosis and senescence. This study suggests that senescence markers should be considered as potential pharmacodynamic biomarkers of F14512 antitumor response, applicable in clinical trial.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the AACR-NCI-EORTC International Conference: Molecular Targets and Cancer Therapeutics; 2011 Nov 12-16; San Francisco, CA. Philadelphia (PA): AACR; Mol Cancer Ther 2011;10(11 Suppl):Abstract nr B37.

Abstract A214: F14512, a novel targeted cytotoxic agent exhibits a marked antileukemic activity, alone and in combination with AraC

Chemotherapy remains mainly used for the treatment of Acute Myelogenous Leukemia (AML). However, in the past 3 decades limited progress has been achieved in improving the long-term disease-free survival. Therefore the development of more effective drugs for AML represents a high level of priority. F14512 combines an epipodophyllotoxin core targeting topoisomerase II with a spermine moiety introduced as a cell delivery vector. In fact the polyamine moiety facilitates F14512 selective uptake by tumor cells via the polyamine transport system, a machinery frequently overactivated in cancer cells. In this study, we report the in vivo antileukemic activity of F14512 against human AML models, established from patient samples. AML cells, collected from 3 different patients, were established onto NSG mice (LAM-2, LAM-7 and LAM-18). These 3 AML samples exhibited a normal karyotype, with FLT3-ITD, NPM1 and DNMTA3 mutations which proved stable over serial transplantations in vivo. After multiple i.v. administrations of F14512, 3 times a week for 3 weeks, an extensive reduction of AML cell number (98–99%) was observed in LAM-2 and LAM-7 - bearing mice. This antileukemic activity was recorded on the basis of flow cytometry, q-PCR and histology assessments. The effects of F14512 on LAM-18 bearing mice were marginal with an inhibition of AML cell growth of 42%. We also show in vitro and in vivo synergistic effects of F14512 in combination with AraC, one of the frontline chemotherapeutic agents for AML. These results were obtained using the HL-60 cell line. The activity of F14512 in combination with AraC will be further investigated in patient AML models. Collectively, these results demonstrate that F14512 exhibits a marked in vivo antileukemic activity, supporting its clinical development. Phase I clinical trials in onco-hematology are on going with this novel promising drug candidate.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the AACR-NCI-EORTC International Conference: Molecular Targets and Cancer Therapeutics; 2011 Nov 12-16; San Francisco, CA. Philadelphia (PA): AACR; Mol Cancer Ther 2011;10(11 Suppl):Abstract nr A214.

An integrated Drosophila model system reveals unique properties for F14512, a novel polyamine-containing anticancer drug that targets topoisomerase II

F14512 is a novel anti-tumor molecule based on an epipodophyllotoxin core coupled to a cancer-cell vectoring spermine moiety. This polyamine linkage is assumed to ensure the preferential uptake of F14512 by cancer cells, strong interaction with DNA and potent inhibition of topoisomerase II (Topo II). The antitumor activity of F14512 in human tumor models is significantly higher than that of other epipodophyllotoxins in spite of a lower induction of DNA breakage. Hence, the demonstrated superiority of F14512 over other Topo II poisons might not result solely from its preferential uptake by cancer cells, but could also be due to unique effects on Topo II interactions with DNA. To further dissect the mechanism of action of F14512, we used Drosophila melanogaster mutants whose genetic background leads to an easily scored phenotype that is sensitive to changes in Topo II activity and/or localization. F14512 has antiproliferative properties in Drosophila cells and stabilizes ternary Topo II/DNA cleavable complexes at unique sites located in moderately repeated sequences, suggesting that the drug specifically targets a select and limited subset of genomic sequences. Feeding F14512 to developing mutant Drosophila larvae led to the recovery of flies expressing a striking phenotype, "Eye wide shut," where one eye is replaced by a first thoracic segment. Other recovered F14512-induced gain- and loss-of-function phenotypes similarly correspond to precise genetic dysfunctions. These complex in vivo results obtained in a whole developing organism can be reconciled with known genetic anomalies and constitute a remarkable instance of specific alterations of gene expression by ingestion of a drug. "Drosophila-based anticancer pharmacology" hence reveals unique properties for F14512, demonstrating the usefulness of an assay system that provides a low-cost, rapid and effective complement to mammalian models and permits the elucidation of fundamental mechanisms of action of candidate drugs of therapeutic interest in humans.

99mTc-HYNIC-spermine for imaging polyamine transport system-positive tumours: preclinical evaluation

PURPOSE

F14512 exploiting the polyamine transport system (PTS) for tumour cell delivery has been described as a potent antitumour agent. The optimal use of this compound will require a probe to identify tumour cells expressing a highly active PTS that might be more sensitive to the treatment. The aim of this study was to design and characterize a scintigraphic probe to evaluate its uptake in cancer cells expressing the PTS.

METHODS

Three polyamines coupled to a hydrazinonicotinamide (HYNIC) moiety were synthesized and labelled with 99mTc. Their radiochemical purity was determined by HPLC. The plasma stability of the 99mTc-HYNIC-spermine probe and its capacity to accumulate into PTS-active cells were also evaluated. In vitro internalization was tested using murine melanoma B16/F10 cells and human lung carcinoma A549 cells. Biodistribution was determined in healthy mice and tumour uptake was studied in B16/F10 tumour-bearing mice. A HL-60-Luc human leukaemia model was used to confront single photon emission computed tomography (SPECT) images obtained with the 99mTc-labelled probe with those obtained by bioluminescence.

RESULTS

The 99mTc-HYNIC-spermine probe was selected for its capacity to accumulate into PTS-active cells and its stability in plasma. In vitro studies demonstrated that the probe was internalized in the cells via the PTS. In vivo measurements indicated a tumour to muscle scintigraphic ratio of 7.9±2.8. The combined bioluminescence and scintigraphic analyses with the leukaemia model demonstrated that the spermine conjugate accumulates into the tumour cells.

CONCLUSION

The 99mTc-HYNIC-spermine scintigraphic probe is potentially useful to characterize the PTS activity of tumours. Additional work is needed to determine if this novel conjugate may be useful to analyse the PTS status of patients with solid tumours.

Abstract 3518: In vitro and in vivo synergistic effects of F14512, a novel targeted cytotoxic agent in phase I clinical study, in combination with other anticancer drugs

Targeted anticancer therapies represent an increasing subject of interest in order to improve tumor cell selectivity. Extensive study suggests that the Polyamine Transport System (PTS) is an energy-dependent machinery generally hyper-activated in cancer cells with a high demand for polyamines. This system can be viewed as a suitable molecular target to deliver selectively polyamine-based molecules into cancer cells. We exploited this strategy to target a potent cytotoxic agent to PTS-positive tumor cells with F14512, a novel polyamine-epipodophyllotoxin conjugate that exhibits a high in vivo anti-tumor activity in a series of experimental murine and human tumors. F14512 has recently entered into clinical development.

This preclinical study was undertaken to investigate its potential in combination chemotherapy therapies. The in vitro cytotoxicity of F14512 against the A549 human non-small cell lung cancer cell line was investigated following simultaneous incubation with a variety of cytotoxic/cytostatic drugs. When using median effect analysis, F14512 in combination with 5-fluorouracil, camptothecin, gemcitabine or mitoxantrone showed synergistic cytotoxicity. Additive effects were demonstrated when F14512 was combined with bortezomib, doxorubicin or SAHA while antagonistic anti-proliferative effects were observed only with co-incubation of F14512 and etoposide, vinorelbine or paclitaxel.

Combinations inducing synergistic anti-proliferative activities were also investigated against the HL-60 human acute myeloid leukemia cell line, confirming the synergy with gemcitabine. Cellular effects of F14512 are characterized by a DNA damage induction, a cell cycle blockage in G2 phase and a cell death induction. Such characteristics were investigated in A549 cells treated with this combination in order to propose mechanistic explanation of this synergy.

In vivo, F14512 combined with irinotecan, gemcitabine, mitoxantrone or doxorubicin showed a gain of anti-tumor activity against P388 murine leukemia grafted intravenously. As an example, the administration of sub-optimal doses of F14512 (0.63 mg/kg, q1d4 schedule) and mitoxantrone (1.25 mg/kg, single dose) alone resulted in an increased life span of only 29% compared to untreated mice, while combined treatments improved survival of tumor bearing mice with an increase life span of 57%. Moreover, F14512 combined with doxorubicin displayed an increased antitumor activity against MX-1 human breast cancer in nude mice.F14512 appears to be a promising candidate for combination chemotherapy, especially with DNA-damaging agents and antimetabolites.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 3518. doi:10.1158/1538-7445.AM2011-3518

Abstract 3261: Novel hemisynthetic derivatives of Amaryllidaceae alkaloids exert antitumor activity on xenograft melanoma models

Alkaloids pancratistatin and narciclasine, isolated from Amaryllidaceae, have been shown to present antitumor activity on preclinical models, including melanoma. Despite extensive investigations, pancratistatin or narciclasine analogues did not succeed to provide sufficient therapeutic benefit, [1] mostly hampered by poor water solubility and systemic toxicity [1]. To overcome those limitations, we developed a chemistry program aimed at improving both their physicochemical and pharmacological properties. A literature survey suggests that any structural modification of this highly oxigenated isocarbostiryl specific scaffold would lead to a loss of activity except on position 1, difficult to achieve but interesting to explore.

A series of 40 novel 1-aminopancratistatin derivatives was synthesised starting from large quantities of narciclasine extracted from Narcissus bulbs. These novel compounds exhibit an improved pharmaceutical profile facing standard solubility, plasmatic and microsomal stability assays. Moreover, a subset of narciclasine derivatives demonstrated a significant enhancement of the antiproliferative effect with IC50 reaching the nM range, consistent with a major induction of pro-apoptotic signals, including mitochondrial depolarisation.

To explore the mode of action of these alkaloids derivatives, we tested their capacity to inhibit protein synthesis, compared their pharmacological profile with 80 anticancer compounds on 16 tumor cell lines (oncoprofile.16) and explored their impact on major cellular functions such as cellular integrity, cell cycle, topoisomerases inhibition, DNA damage and synthesis. We demonstrated thus that inhibition of DNA synthesis is a key component of their mechanism of action.

Based on the pharmacological properties, a structure-activity card can be built to select different categories of pancrastistatin derivatives depending on their ability to inhibit preferentially protein synthesis or/and DNA synthesis. Interestingly, the dimethylaminomethyl benzamide derivative F98604 exhibited a significant antiproliferative activity on the murine B16 and human A375 melanoma xenograft models associated with an increased therapeutic index as compared with the natural compound narciclasine.

In conclusion, modulation of position 1 on the narciclasine pharmacophore overcomes the solubility issue and is a key position to modify their pharmacological profiles, this opening new perspectives as anticancer agents active against melanoma.

1. A. Kornienko, A. Evidente Chem. Rev. 2008, 108, 1982

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 3261. doi:10.1158/1538-7445.AM2011-3261

Abstract 5461: Novel antitumor amino-pancratistatin derivatives inhibitors of protein and DNA synthesis

The Amaryllidaceous alkaloids pancratistatin and narciclasine are known to exert marginal antitumor properties but associated with toxicities. Despite extensive investigations, pancratistatin or analogues did not succeed to provide sufficient therapeutic benefit although a new pro-drug strategy was applied recently to narciclasine. We decided to undertake a chemistry program aimed at modifying the skeleton of this attractive pharmacophore in order to improve its therapeutic application. At first sight, literature survey suggests that any change in the structure would lead to a loss of activity but a careful examination of published data indicated that position −1 of the molecule may be of potential interest although poorly investigated. We report here the synthesis of a series of 39 novel derivatives of 1-aminopancratistatin by chemical modification of the naturally available narciclasine extracted from Narcissus bulbs. These new compounds present improved pharmaceutical properties such as higher aqueous solubility (from 300 µg/ml for narciclasine up to 2000 µg/ml) without loss of stability tested on human and murine microsomal assays (70-90% stability after 1h incubation). A sub-set of these novel derivatives demonstrated a drastic increase of the cytotoxic activity reaching nM range tested on a panel of 8 different cell lines. The higher antiproliferative activity translates towards the induction of stronger pro-apoptotic signals evidenced with Annexin V, caspase 3/7 and JC-1 assay. Besides the previously described inhibition of protein synthesis, our studies originally demonstrated that part of the mechanism of action involves inhibition of DNA synthesis as well. The contribution of these two pharmacological properties elaborates a SAR (structure - activity relationship) and segregates our new pancrastistatin derivatives into different categories depending on their ability to inhibit protein synthesis, DNA synthesis or both. Based on their differential in vitro activity profile, the compounds were selected for evaluation of their in vivo antitumor properties on murine and xenografted models. As a major result F 98604 (dimethylaminomethyl benzamide derivative of pancratistatin) exhibited significant and reproducible activity on the murine B16 sc and human A375 melanoma models in terms of tumor growth inhibition as well as increased therapeutic index. The present SAR suggests that modification of the natural pancratistatin or narciclasine pharmacophore at the position −1 open new perspectives as potential anticancer agents with novel pharmacological profiles.

Note: This abstract was not presented at the AACR 101st Annual Meeting 2010 because the presenter was unable to attend.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 5461.

A fluorescent biomarker of the polyamine transport system to select patients with AML for F14512 treatment

The polyamine transport system (PTS), hyperactive in cancer cells, can constitute a gate to deliver F14512, a novel spermine epipodophyllotoxin conjugate recently selected for clinical development in AML phase I. We investigated in vitro the high antiproliferative effect of F14512 against 13 leukemia cell lines, and demonstrated a statistically significant correlation with the level of PTS activity, using a novel fluorescent marker F96982. This labelling protocol was then adapted for clinical applications for blood, bone marrow and AML samples with CD45 gating. Within the patient samples, the PTS activity varied significantly in AML cells, as compared to normal lymphocytes. In conclusion, the identification of PTS-positive AML with F98982 probe offers new perspectives to select patients prone to respond to F14512.

Abstract B186: Preclinical antileukemic activity of F14512, a novel targeted cytotoxic agent

Despite advances in the therapy of acute myeloid leukemia (AML), the majority of patients die from their disease. Therefore, the lack of effective therapy mandates the development of novel compounds to improve the outcome of patients with relapsed and refractory leukemias. F14512 is a potent spermine-epipodophyllotoxin conjugate exploiting the polyamine transport system for tumor cell delivery. In this study, we report the in vivo antitumor activity of F14512 against experimental models of AML cell lines and of patient AML samples. F14512 markedly reduced the growth of HL-60 and U937 cell lines in an in vivo xenotransplantation model, resulting in a highly significant increase of survival of leukemia-bearing mice. Etoposide evaluated concurrently demonstrated only moderate in vivo activity against these models. F14512 induced in vivo apoptosis of HL-60 cells, as shown by caspase-3 activation and PARP cleavage. In an effort to mimic the human disease, we injected approximately 106 AML cells collected from a patient into NOD/SCID mice and allowed them to establish as xenografts for 8 weeks. Subsequent treatment with F14512 was carried out for 2 or 3 weeks followed by the analysis at the end of treatment and 1 week after the end of treatment. Two human AML samples were analyzed. Multiple i.v. administrations of F14512 at 0.32 mg/kg, induced an extensive reduction of the number of leukemic cells in mouse bone marrow and blood (97–99%), assessed by flow cytometry analysis, quantitative RT-PCR and histology. To identify leukemic cells expressing an active polyamine transport system, we developed a functional method based on the measurement of the cellular uptake of a nitrobenzoxadiazole fluorescent probe (F96982) combining the same spermine moiety as F14512. The level of fluorescence emitted by the probe F96982 was high in HL-60 cells as well in the 2 patient AML samples that proved to be sensitive to F14512 in vivo. Collectively, these results demonstrated that F14512 exhibits a marked in vivo antileukemic activity, supporting its clinical development. Phase I clinical trials in onco-hematology are now initiated with this novel promising drug candidate.

Citation Information: Mol Cancer Ther 2009;8(12 Suppl):B186.

Abstract CN08-03: Targeting topoisomerase II inhibitors to cancer cells via the polyamines transport system

Topoisomerases inhibitors continue to play a major role in cancer chemotherapy. A large number of drug regimens, routinely used for the management of many forms of solid tumors in particular, include a camptothecin analog targeting topoisomerase I or an anthracycline derivative targeting topoisomerase II. This is the case also for the podophyllotoxin derivative etoposide marketed more than 25 years ago and which remains prescribed for the treatment of a variety of malignancies, including leukaemia. These topoisomerases poisons form an irreplaceable class of antitumor agents, almost all derived from natural products isolated from plants or microorganisms (1). For the past 20 years, efforts have been concentrated on the discovery and conception of novel, more potent, topoisomerases inhibitors but with a limited success. Camptothecins are still unique among topoisomerase I poisons used in the clinic. Anthracyclines and podophyllotoxines remain the two most robust classes of topoisomerase II modulators. Novel compounds have been introduced into the clinical pipeline, such as the naphthyridine derivatives ARC-111 and voreloxin (SNS-595), targeting respectively topoisomerases I and II, to cite only these two novel molecules. Novel compounds interfering with the functions of these DNA manipulating enzymes are continuously reported: the alkaloids thaspine and lamellarins, the yeast-derived compound simocyclinone D-8, calothrixins, etc.

An alternative approach to the design of novel categories of topoisomerases-based antitumor agents is to maintain a known chemical archetype associated with a marked target selectivity profile (e.g. selectivity of camptothecin for toposiomerase I) but to coupled the pharmacophore with additional chemical groups susceptible to modulate target-independent properties such as cell selectivity, biodistribution, stability, pharmacokinetics, or to facilitate its handling for example. With this idea in mind, we have engineered a novel group of highly potent podophyllotoxin derivatives equipped with a cell delivery vector. Three points were considered in the design strategy: (i) improving the aqueous solubility of the molecule and its pharmaceutical and clinical use, (ii) reinforcing the drug-target interaction, so as to consolidate its DNA-damaging activity, and (iii) conferring a selectivity for tumor cells via a novel delivery strategy. The third point is obviously essential, with a general applicability to transform conventional cytotoxic agents into what we call “targeted cytotoxics”, i.e., cytotoxic molecules endowed with a pronounced selectivity for cancer cells. At the molecular level, the concept consisted to link the pharmacophore to a polyamine guide providing simultaneously the desired three properties. A suitable connector was constructed to associate the two molecular entities, without affecting their intrinsic recognition properties. Polyamines, such as spermine, are highly water-soluble molecules. As cations, they binds to nucleic acid polymers, in particular DNA through minor groove interactions. Polyamine conjugates are usually potent DNA binders. But most importantly, polyamines and in particular the naturally-occurring ones (spermine, spermidine, putrescine), are essential for cell proliferation and differentiation. Their metabolism is frequently exacerbated in tumors. Different types of cancer cells heavily rely on polyamines for growth and survival. Most importantly, an efficient polyamine transport system (PTS) has been functionally characterized in many tumors cells. Polyamine transporters, import and export systems, are poorly defined at the molecular level in human, but the PTS is now well documented functionally. This polyamine-based strategy has open novel horizons to the rational design of topoisomerase II inhibitors, acting as potent DNA damaging drugs.

Here we will present the strategy, the design and pharmacological properties of the lead compound in the series, designated F14512 (2). This compound exploits the PTS for entering and accumulating into tumor cells, functions as a potent topoisomerase II poison, triggers cell death and displays remarkable antitumor activities in vivo, in a large panel of xenografts models (2,3). This molecule is now entering clinical development. As far as we know, this is the first molecule exploiting the PTS for a tumor-selective delivery to reach clinical development in oncology. In addition, a functional screen has been set up to identify PTS(+) cancer cells, using fluorescent polyamine derivatives and cytometry assays (4). A clinical procedure has been designed to select patients with PTS(+) tumors eligible for treatment with F14512. This method is particularly well suited to identify leukemia cells expressing an active PTS. Along these lines, recently we showed that human acute myeloid leukemia (AML) animal models and human samples are sensitive to F14512, with a level of activity well superior to that of etoposide. Through this concept, we are now entering into the field of personalized medicine, with a novel generation of cell-targeted cytotoxic agents. The long history of topoisomerases inhibitors is thus revivified and novel opportunities to increase the therapeutic index of these agents can be envisioned.

Citation Information: Mol Cancer Ther 2009;8(12 Suppl):CN08-03.

Abstract A87: Synthesis and structure-activity relationships of a series of epipodophyllotoxin polyamine conjugated derivatives vectorized for active polyamine transporter system in tumor cells, leading to the selection of F14512 for clinical trials

One of the major concerns for chemotherapy is the selective targeting of drugs into highly proliferative cancer cells. Natural polyamines (spermine, spermidine, putrescine) are essential for the regulation of cellular growth and differentiation. Due to their highly proliferative nature, cancer cells have a pronounced need to import polyamines from their external environment, through the polyamine transporter system (PTS). On the basis of this biological mechanism, we vectorized the new cytotoxic anticancer compound F14512, a epipodophyllotoxin — spermine conjugate, into tumor cells.1 Here we present the synthesis and the structure-activity relationships of a new series of compounds constituted by an podophyllotoxin core tethered with a polyamine moiety with a variable spacer. Two synthetic strategies with protected polyamines, and a direct 3 steps synthesis of F14512 from natural podophyllotoxin and spermine without any protection are presented.2 This series of topoisomerase II inhibitors were checked for their cytotoxicity on A549 lung cancer cell line, displaying marked potency up to nM range. Cancer cell internalization through PTS was assessed by selective cytotoxicity on different PTS expressing cell lines, and by competition experiments. Our results displayed a potent specificity for the conjugated tetramine (spermine) compounds, which were more recognized than the triamine (spermidine) ones, while mono and diamines showed no selectivity. Lead compounds were also tested in vivo and proved potent antitumor activity. This series of new water-soluble cytotoxic compounds culminates with the selection of F14512 for clinical trials.

Citation Information: Mol Cancer Ther 2009;8(12 Suppl):A87.

Triptolide is an inhibitor of RNA polymerase I and II-dependent transcription leading predominantly to down-regulation of short-lived mRNA

Triptolide, a natural product extracted from the Chinese plant Tripterygium wilfordii, possesses antitumor properties. Despite numerous reports showing the proapoptotic capacity and the inhibition of NF-kappaB-mediated transcription by triptolide, the identity of its cellular target is still unknown. To clarify its mechanism of action, we further investigated the effect of triptolide on RNA synthesis in the human non-small cell lung cancer cell line A549. Triptolide inhibited both total RNA and mRNA de novo synthesis, with the primary action being on the latter pool. We used 44K human pan-genomic DNA microarrays and identified the genes primarily affected by a short treatment with triptolide. Among the modulated genes, up to 98% are down-regulated, encompassing a large array of oncogenes including transcription factors and cell cycle regulators. We next observed that triptolide induced a rapid depletion of RPB1, the RNA polymerase II main subunit that is considered a hallmark of a transcription elongation blockage. However, we also show that triptolide does not directly interact with the RNA polymerase II complex nor does it damage DNA. We thus conclude that triptolide is an original pharmacologic inhibitor of RNA polymerase activity, affecting indirectly the transcription machinery, leading to a rapid depletion of short-lived mRNA, including transcription factors, cell cycle regulators such as CDC25A, and the oncogenes MYC and Src. Overall, the data shed light on the effect of triptolide on transcription, along with its novel potential applications in cancers, including acute myeloid leukemia, which is in part driven by the aforementioned oncogenic factors.

A functional procedure using fresh samples to select patients with acute myeloid leukemia prior to treatment with the novel targeted cytotoxic agent F14512

11087

Background: The Polyamine Transport System (PTS) is an energy-dependent machinery generally hyper-active in cancer cells with a high demand for polyamines. This system can be viewed as a suitable molecular gate to deliver selectively polyamine-based molecules into cancer cells. We exploited this strategy to target to PTS-positive cancer cells, F14512 , a novel polyamine-epipodophyllotoxin conjugate, that exhibits significant anti-tumor activity and has been selected for further clinical development. This study was undertaken to investigate the potential of N-methyl-spermine-NBD, a proprietary fluorescent polyamine conjugate, designed to select patients with PTS-positive leukemic cells. Methods: The uptake of this probe was first measured by flow cytometry in a panel of human leukemia cell lines. The procedure was then adapted and optimized to measure N-methyl-spermine-NBD fluorescence in blood samples from healthy donors. After the selection of the optimal CD gating, median value of fluorescence of our probe was measured by flow cytometry in lymphocytes and blastes of each patient. Results: Data showed that high level of fluorescence was detected in F14512 -sensitive cancer cell lines whereas leukemia cells responding poorly to F14512 generally exhibited very low levels of PTS. We then demonstrated that human leukocytes incorporate N-methyl-spermine-NBD in a time, concentration and temperature dependent manner, confirming the active transport of polyamines in these cells. The incorporation in lymphocytes was found low and with a weak inter-individual variation. A panel of 50 fresh human acute myeloid leukemia samples showed a larger inter-individual variation and, interestingly, incorporation of the fluorescent probe was generally higher in leukemia blasts than in lymphocytes. Median values of fluorescence intensity were similar in blood and bone marrow samples, suggesting that these two sources might be used for this analysis. Conclusions: The data show that the PTS can easily be evaluated in fresh AML blasts and provides a simple means to identify patients for future enrollment in clinical trials with F14512.

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KRN951, a highly potent inhibitor of vascular endothelial growth factor receptor tyrosine kinases, has antitumor activities and affects functional vascular properties

Vascular endothelial growth factor (VEGF) plays a key role in tumor angiogenesis by stimulating the proangiogenic signaling of endothelial cells via activation of VEGF receptor (VEGFR) tyrosine kinases. Therefore, VEGFRs are an attractive therapeutic target for cancer treatment. In the present study, we show that a quinoline-urea derivative, KRN951, is a novel tyrosine kinase inhibitor for VEGFRs with antitumor angiogenesis and antigrowth activities. KRN951 potently inhibited VEGF-induced VEGFR-2 phosphorylation in endothelial cells at in vitro subnanomolar IC50 values (IC50 = 0.16 nmol/L). It also inhibited ligand-induced phosphorylation of platelet-derived growth factor receptor-beta (PDGFR-beta) and c-Kit (IC50 = 1.72 and 1.63 nmol/L, respectively). KRN951 blocked VEGF-dependent, but not VEGF-independent, activation of mitogen-activated protein kinases and proliferation of endothelial cells. In addition, it inhibited VEGF-mediated migration of human umbilical vein endothelial cells. Following p.o. administration to athymic rats, KRN951 decreased the microvessel density within tumor xenografts and attenuated VEGFR-2 phosphorylation levels in tumor endothelium. It also displayed antitumor activity against a wide variety of human tumor xenografts, including lung, breast, colon, ovarian, pancreas, and prostate cancer. Furthermore, dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI) analysis revealed that a significant reduction in tumor vascular hyperpermeability was closely associated with the antitumor activity of KRN951. These findings suggest that KRN951 is a highly potent, p.o. active antiangiogenesis and antitumor agent and that DCE-MRI would be useful in detecting early responses to KRN951 in a clinical setting. KRN951 is currently in phase I clinical development for the treatment of patients with advanced cancer.

Triterpene saponins from Eryngium campestre

Five new triterpene saponins, 3-O-alpha-l-rhamnopyranosyl-(1-->2)-beta-d-glucuronopyranosyl-22-O-beta,beta-dimethylacryloyl-A1-barrigenol (1), 3-O-alpha-l-rhamnopyranosyl-(1-->2)-beta-d-glucuronopyranosyl-22-O-angeloyl-R1-barrigenol (2), 3-O-alpha-l-rhamnopyranosyl-(1-->2)-beta-d-glucuronopyranosyl-21-O-acetyl-22-O-angeloyl-R1-barrigenol (3), 3-O-alpha-l-rhamnopyranosyl-(1-->2)-beta-d-glucuronopyranosyl-21-O-acetyl-22-O-beta,beta-dimethylacryloyl-R1-barrigenol (4), and 3-O-alpha-l-rhamnopyranosyl-(1-->2)-beta-d-glucuronopyranosyl-22-O-angeloyl-28-O-acetyl-R1-barrigenol (5), were isolated from the roots of Eryngium campestre. Their structures were established mainly by 2D NMR techniques and mass spectrometry. Compounds 1-4 and 3-O-beta-d-glucopyranosyl-(1-->2)-[alpha-l-rhamnopyranosyl-(1-->4)]-beta-d-glucuronopyranosyl-22-O-beta,beta-dimethylacryloyl-A1-barrigenol, previously isolated from the same plant, showed a weak cytotoxicity when tested against HCT 116 and HT 29 human colon cancer cells.

Tumor penetration of gefitinib (Iressa), an epidermal growth factor receptor tyrosine kinase inhibitor

The relative distribution of gefitinib-related material in nude mice bearing s.c. human tumor xenografts and in an orthotopic rat lung tumor model was investigated following oral administration (50 mg/kg) of [14C]-gefitinib. Selected tissue samples were monitored for radioactivity by liquid scintillation counting, whereas plasma and tumor extracts were assayed for gefitinib and its major metabolites (M523595 and M537194) by high-performance liquid chromatography with tandem mass spectrometric detection. Tissue distribution was also determined by whole body autoradiography. Gefitinib was extensively distributed into the tissues of tumor-bearing mice and unchanged gefitinib was shown to account for most of the tumor radioactivity. Concentrations of gefitinib in mouse s.c. tumor xenografts were similar to skin concentrations and substantially greater (up to 12-fold based on area under the concentration-time curve) than plasma. Concentrations of gefitinib-related material in an orthotopic rat lung tumor were similar to those in healthy lung tissue and were much higher than corresponding blood levels. Following treatment of breast cancer patients with oral gefitinib (Iressa) 250 mg/d for > or = 14 days, gefitinib concentrations (mean, 7.5 microg/g, 16.7 micromol/L) in breast tumor tissue were 42 times higher than plasma, confirming the preferential distribution of gefitinib from blood into tumor tissue in the clinical situation. These gefitinib tumor concentrations are considerably higher than those reportedly required in vitro to achieve complete inhibition of epidermal growth factor receptor autophosphorylation in both epidermal growth factor receptor mutant (0.2 micromol/L) and wild-type cells (2 micromol/L).

Pursaethosides A-E, triterpene saponins from Entada pursaetha

Five new triterpenoid saponins, pursaethosides A-E (1-5), were isolated from the n-BuOH extract of the seed kernels of Entada pursaetha along with the known phaseoloidin. The structures of 1-5 were elucidated mainly by spectroscopic data interpretation and chemical degradation. Pursaethosides C-E (3-5) possess as a common structural feature entagenic acid as aglycon, which is rare among triterpene saponins. Compounds 2-4 and phaesolidin were found to be not cytotoxic when tested against HCT 116 and HT-29 human colon cancer cells.

Synthesis of N,N′-disubstituted 3-aminobenzo[c] and [d]azepin-2-ones as potent and specific farnesyl transferase inhibitors

A structure-activity study was performed by synthesis on N,N'-disubstitution of 3-aminobenzo[c] and [d]azepin-2-one 2 and 3 to afford potent and specific farnesyl transferase inhibitors with low nM enzymatic and cellular activities.