Early treatment with rifaximin during epileptogenesis reverses gut alterations and reduces seizure duration in a mouse model of acquired epilepsy

The gut microbiota is altered in epilepsy and is emerging as a potential target for new therapies. We studied the effects of rifaximin, a gastrointestinal tract-specific antibiotic, on seizures and neuropathology and on alterations in the gut and its microbiota in a mouse model of temporal lobe epilepsy (TLE). Epilepsy was induced by intra-amygdala kainate injection causing status epilepticus (SE) in C57Bl6 adult male mice. Sham mice were injected with vehicle. Two cohorts of SE mice were fed a rifaximin-supplemented diet for 21 days, starting either at 24 h post-SE (early disease stage) or at day 51 post-SE (chronic disease stage). Corresponding groups of SE mice (one each disease stage) were fed a standard (control) diet. Cortical ECoG recording was done at each disease stage (24/7) for 21 days in all SE mice to measure the number and duration of spontaneous seizures during either rifaximin treatment or control diet. Then, epileptic mice ± rifaximin and respective sham mice were sacrificed and brain, gut and feces collected. Biospecimens were used for: (i) quantitative histological analysis of the gut structural and cellular components; (ii) markers of gut inflammation and intestinal barrier integrity by RTqPCR; (iii) 16S rRNA metagenomics analysis in feces. Hippocampal neuronal cell loss was assessed in epileptic mice killed in the early disease phase. Rifaximin administered for 21 days post-SE (early disease stage) reduced seizure duration (p < 0.01) and prevented hilar mossy cells loss in the hippocampus compared to epileptic mice fed a control diet. Epileptic mice fed a control diet showed a reduction of both villus height and villus height/crypt depth ratio (p < 0.01) and a decreased number of goblet cells (p < 0.01) in the duodenum, as well as increased macrophage (Iba1)-immunostaining in the jejunum (p < 0.05), compared to respective sham mice. Rifaximin's effect on seizures was associated with a reversal of gut structural and cellular changes, except for goblet cells which remained reduced. Seizure duration in epileptic mice was negatively correlated with the number of mossy cells (p < 0.01) and with villus height/crypt depth ratio (p < 0.05). Rifaximin-treated epileptic mice also showed increased tight junctions (occludin and ZO-1, p < 0.01) and decreased TNF mRNA expression (p < 0.01) in the duodenum compared to epileptic mice fed a control diet. Rifaximin administered for 21 days in chronic epileptic mice (chronic disease stage) did not change the number or duration of seizures compared to epileptic mice fed a control diet. Chronic epileptic mice fed a control diet showed an increased crypt depth (p < 0.05) and reduced villus height/crypt depth ratio (p < 0.01) compared to respective sham mice. Rifaximin treatment did not affect these intestinal changes. At both disease stages, rifaximin modified α- and β-diversity in epileptic and sham mice compared to respective mice fed a control diet. The microbiota composition in epileptic mice, as well as the effects of rifaximin at the phylum, family and genus levels, depended on the stage of the disease. During the early disease phase, the abundance of specific taxa was positively correlated with seizure duration in epileptic mice. In conclusion, gut-related alterations reflecting a dysfunctional state, occur during epilepsy development in a TLE mouse model. A short-term treatment with rifaximin during the early phase of the disease, reduced seizure duration and neuropathology, and reversed some intestinal changes, strengthening the therapeutic effects of gut-based therapies in epilepsy.

A Novel Lactobacillus brevis Fermented with a Vegetable Substrate (AL0035) Counteracts TNBS-Induced Colitis by Modulating the Gut Microbiota Composition and Intestinal Barrier

Crohn's and ulcerative colitis are common conditions associated with inflammatory bowel disease as well as intestinal flora and epithelial barrier dysfunction. A novel fermented Lactobacillus brevis (AL0035) herein assayed in a trinitro benzene sulfonic acid (TNBS)-induced colitis mice model after oral administration significantly counteracted the body weight loss and improves the disease activity index and histological injury scores. AL0035 significantly decreased the mRNA and protein expression of different pro-inflammatory cytokines (TNFalpha, IL-1beta, IL-6, IL-12, IFN-gamma) and enhanced the expression of IL-10. In addition, the probiotic promoted the expression of tight junction proteins, such as ZO-1, keeping the intestinal mucosal barrier function to attenuate colitis symptoms in mice. Markers of inflammation cascade such as myeloperoxidase (MPO) and PPAR-gamma measured in the colon were also modified by AL0035 treatment. AL0035 was also able to reduce different lymphocyte markers' infiltration in the colon (GATA-3, T-Bet, NK1.1) and monocyte chemoattractant protein-1 (MCP-1/CCL2), a key chemokine involved in the migration and infiltration of monocytes/macrophages in the immunological surveillance of tissues and inflammation. In colonic microbiota profile analysis through 16S rRNA sequencing, AL0035 increased the microbial diversity depleted by TNBS administration and the relative abundance of the Lactobacillaceae and Lachnospiraceae families, whereas it decreased the abundance of Proteobacteria. Altogether, these data indicated that AL0035 could lower the severity of colitis induced by TNBS by regulating inflammatory cytokines, increasing the expression of tight junction proteins and modulating intestinal microbiota, thus preventing tissue damage induced by colitis.

Velusetrag rescues GI dysfunction, gut inflammation and dysbiosis in a mouse model of Parkinson's disease

In patients with Parkinson's disease (PD), constipation is common, and it appears in a prodromal stage before the hallmark motor symptoms. The present study aimed to investigate whether Velusetrag, a selective 5‑HT4 receptor agonist, may be a suitable candidate to improve intestinal motility in a mouse model of PD. Five months old PrP human A53T alpha-synuclein transgenic (Tg) mice, which display severe constipation along with decreased colonic cholinergic transmission already at 3 months, were treated daily with the drug for 4 weeks. Velusetrag treatment reduced constipation by significantly stimulating both the longitudinal and circular-driven contractions and improved inflammation by reducing the level of serum and colonic IL1β and TNF-α and by decreasing the number of GFAP-positive glia cells in the colon of treated mice. No significant downregulation of the 5-HT4 receptor was observed but instead Velusetrag seemed to improve axonal degeneration in Tgs as shown by an increase in NF-H and VAChT staining. Ultimately, Velusetrag restored a well-balanced intestinal microbial composition comparable to non-Tg mice. Based on these promising data, we are confident that Velusetrag is potentially eligible for clinical studies to treat constipation in PD patients.

Characterization of Early and Late Damage in a Mouse Model of Pelvic Radiation Disease

Pelvic radiation disease (PRD), a frequent side effect in patients with abdominal/pelvic cancers treated with radiotherapy, remains an unmet medical need. Currently available preclinical models have limited applications for the investigation of PRD pathogenesis and possible therapeutic strategies. In order to select the most effective irradiation protocol for PRD induction in mice, we evaluated the efficacy of three different locally and fractionated X-ray exposures. Using the selected protocol (10 Gy/day × 4 days), we assessed PRD through tissue (number and length of colon crypts) and molecular (expression of genes involved in oxidative stress, cell damage, inflammation, and stem cell markers) analyses at short (3 h or 3 days after X-ray) and long (38 days after X-rays) post-irradiation times. The results show that a primary damage response in term of apoptosis, inflammation, and surrogate markers of oxidative stress was found, thus determining a consequent impairment of cell crypts differentiation and proliferation as well as a local inflammation and a bacterial translocation to mesenteric lymph nodes after several weeks post-irradiation. Changes were also found in microbiota composition, particularly in the relative abundance of dominant phyla, related families, and in alpha diversity indices, as an indication of dysbiotic conditions induced by irradiation. Fecal markers of intestinal inflammation, measured during the experimental timeline, identified lactoferrin, along with elastase, as useful non-invasive tools to monitor disease progression. Thus, our preclinical model may be useful to develop new therapeutic strategies for PRD treatment.

ErbB2 Targeted Epigenetic Modulation: Anti-tumor Efficacy of the ADC Trastuzumab-HDACi ST8176AA1

Targeted therapy using monoclonal antibodies conjugated to toxins is gaining space in the treatment of cancer. Here, we report the anti-tumor effect of a new antibody drug conjugate (ADC) delivering a HDAC inhibitor to ErbB2+ solid tumors. Trastuzumab was partially reduced with tris [2-carboxyethyl] phosphine (TCEP) and conjugated to ST7464AA1, the active form of the prodrug HDAC inhibitor ST7612AA1, through a maleimide-thiol linker to obtain the Antibody Drug Conjugate (ADC) ST8176AA1. The average drug/antibody ratio (DAR) was 4.5 as measured by hydrophobic interaction chromatography (HIC). Binding of ST8176AA1 to ErbB2 receptor and internalization in tumor cells were investigated by enzyme-linked immunosorbent assay (ELISA), surface plasmon resonance (SPR), cytofluorimetry, and High Content Screening (HCS) Imaging. The biological activity of the ADC was evaluated in vitro and in vivo by measuring cell proliferation/cell cycle, apoptosis/DNA damage, tubulin, and histone acetylation and modulation of Epithelial/Mesenchymal Transition (EMT) markers. Receptor binding and internalization of ST8176AA1 were confirmed to be similar to trastuzumab. Higher anti-tumor activity of ST8176AA1 compared to trastuzumab was observed in vitro in tumor cell lines. Such higher activity correlated with increased acetylation of histones and alfa-tubulin as a consequence of HDAC inhibitor-mediated epigenetic modulation that also induced increased expression of ErbB2 and estrogen receptor in triple negative breast cancer cells. Consistently with in vitro data, ST8176AA1 exhibited higher tumor growth inhibition than trastuzumab in xenograft models of ovary and colon carcinoma and in two patient-derived xenograft (PDX) models of pancreatic carcinoma. Immunohistochemistry analysis of tumor masses showed lower expression of the proliferation marker Ki67 and higher expression of cleaved caspase-3 in mice treated with the ADC compared to those treated with trastuzumab and results correlated with increased acetylation of both histones and tubulin. Collectively, present data indicate that ADC ST8176AA1 can target epigenetic modulation to ErbB2+ tumors. Interestingly, the amount of HDACi estimated to be delivered at the ST8176AA1 effective dose would correspond to ~1/1,000 of ST7612AA1 effective dose. Therefore, ST8176AA1 is an attractive new therapeutic candidate because it exhibits increased anti-tumor potency compared to trastuzumab by exerting epigenetic modulation at a much safer dose compared to standard HDACi-based therapeutic protocols.

Therapeutic efficacy of intra-tumor AvidinOX and low systemic dose biotinylated cetuximab, with and without cisplatin, in an orthotopic model of head and neck cancer

In a previous study, the efficacy of low intraperitoneal doses of biotinylated cetuximab (bCet) in mice with subcutaneous tumor xenografts of human head and neck cancer (HNC) treated intra-tumors with AvidinOX was reported. Taking into account that the current standard treatment for HNC is the combination of cetuximab and cisplatin, the present study investigated the activity of AvidinOX-targeted bCet with and without cisplatin in an orthotopic model. The results confirmed that administration of intra-tumor AvidinOX makes an otherwise inactive dose of bCet effective in reducing tumor growth, and the addition of a low dose of cisplatin further improved tumor growth inhibition. Supporting the in vivo data, immunohistochemical staining of tumor masses from mice treated with AvidinOX, bCet and cisplatin exhibited the highest tumor cell damage and the lowest angiogenic activity among all treatment groups, measured as the number of γ-H2A.X and cleaved caspase-3-positive cells, and vascular endothelial growth factor-C and platelet and endothelial cell adhesion molecule 1-positive cells, respectively. AvidinOX is currently under clinical investigation to assess its use in delivering radioactive biotin to inoperable tumor lesions (ClinicalTrials.gov: NCT02053324 and NCT03188328). The present study further supported the potential clinical use of AvidinOX to target low bCet doses to inoperable tumor lesions, with or without an additional low dose of cisplatin. Since low doses of highly expensive monoclonal antibodies become effective with AvidinOX and low dose cisplatin, such therapies promise to be cheaper and less toxic than current treatments.

Growth inhibition of human ovarian carcinoma by a novel AvidinOX-anchored biotinylated camptothecin derivative

Oxidized form of avidin, named AvidinOX, provides stable fixation of biotinylated molecules in tissues thus representing a breakthrough in topical treatment of cancer. AvidinOX proved to be a stable receptor for radiolabeled biotin, biotinylated antibodies and cells. In order to expand applicability of the AvidinOX-based delivery platform, in the present study we investigated the possibility to hold biotinylated chemotherapeutics in AvidinOX-treated sites. A novel biotinylated gimatecan-derived camptothecin, coded ST8161AA1, was injected at suboptimal doses into human tumors xenografted in mice alone or pre-complexed to AvidinOX. Significantly higher growth inhibition was observed when the drug was anchored to AvidinOX suggesting the potential utility of this delivery modality for the local treatment of inoperable tumors.

Antibody drug conjugates (ADCs) charged with HDAC inhibitor for targeted epigenetic modulation

We describe here two novel antibody-drug conjugates loaded with the HDAC inhibitor ST7612AA1 (IC50 equal to 0.07 μM on NCI-H460 cells), a thiol-based molecule with a moderate toxicity in vivo. Two payloads were prepared using cleavable and non-cleavable linkers. After anchoring to cetuximab through amide bond with lysines, the resulting HDAC inhibitor-antibody conjugates showed ability to recognize EGFR and efficient internalization in tumor cells. Both ADCs induced sensible increment of histones 3 and 4 and alpha-tubulin acetylation. Animal models of human solid tumors showed high anti-tumor efficacy of the conjugates without the toxicity generally observed with traditional ADCs delivering highly potent cytotoxic drugs. These compounds, the first ADCs charged with not highly cytotoxic warheads, are potentially suitable for epigenetic modulation, extending the ADC strategy to the targeted delivery of HDAC inhibitors with many possible therapeutic applications beyond cancer.

Hedgehog pathway inhibitors of the acylthiourea and acylguanidine class show antitumor activity on colon cancer in vitro and in vivo

Small series of acylguanidine and acylthiourea derivatives were synthesized in gram-scale and assayed for their ability to modulate the Hh signalling pathway. In vitro studies showed a low micromolar inhibitory activity toward tumor cell lines, while the oral administration revealed an excellent ADME profile in vivo. Compound 5 emerged as the most active and safe inhibitor of colon cancer cells both in vitro and in a xenograft mouse model. Based on these data, 5 could be prioritized to further development with the perspective of clinical studies.

AvidinOX-anchored biotinylated trastuzumab and pertuzumab induce down-modulation of ErbB2 and tumor cell death at concentrations order of magnitude lower than not-anchored antibodies

The oxidized version of Avidin, known as AvidinOX, was previously shown to link to tissue proteins upon injection or nebulization, thus becoming a stable receptor for biotinylated therapeutics. AvidinOX is currently under clinical investigation to target radioactive biotin to inoperable tumor lesions (ClinicalTrials.gov NCT02053324). Presently, we show that the anti-ErbB2 monoclonal antibodies Trastuzumab and Pertuzumab can be chemically biotinylated while maintaining their biochemical and biological properties. By using several and diverse experimental conditions, we show that when AvidinOX is conjugated to tumor cells, low antibody concentrations of biotinylated Trastuzumab (bTrast) or Pertuzumab (bPert) prevent internalization of ErbB2, induce endoplasmic reticulum stress, cell cycle arrest and apoptosis leading to inhibition of proliferation and ErbB2 signaling. Moreover, we found that the treatment is able to induce down-modulation of ErbB2 thus bypassing the known resistance of this receptor to degradation. Interestingly, we show that AvidinOX anchorage is a way to counteract agonistic activities of Trastuzumab and Pertuzumab. Present data are in agreement with previous observations from our group indicating that the engagement of the Epidermal Growth Factor Receptor (EGFR) by AvidinOX-bound biotinylated Cetuximab or Panitumumab, leads to potent tumor inhibition both in vitro and in animal models. All results taken together encourage further investigation of AvidinOX-based treatments with biotinylated antibodies directed to the members of the EGFR family.

Intra-tumor AvidinOX allows efficacy of low dose systemic biotinylated Cetuximab in a model of head and neck cancer

For locally advanced and metastatic head and neck squamous cell carcinoma (HNSCC), the current clinical use of Cetuximab in chemo/radiotherapy protocols is often associated to severe systemic toxicity. Here we report in vitro data in human FaDu pharynx SCC cells, showing that inactive concentrations of biotinylated Cetuximab (bCet) become active upon anchorage to AvidinOX on the surface of tumor cells. AvidinOX-anchored bCet induces apoptosis and DNA damage as well as specific inhibition of signaling, degradation and abrogation of nuclear translocation of EGFR. In the mouse model of FaDu cancer, we show that intra-tumor injection of AvidinOX allows anti-tumor activity of an otherwise inactive, intraperitoneally delivered, low dose bCet. Consistently with in vitro data, in vivo tumor inhibition is associated to induction of apoptosis, DNA damage and reduced angiogenesis. AvidinOX is under clinical investigation for delivering radioactive biotin to inoperable tumors (ClinicalTrials.gov NCT02053324) and present data support its use for the local treatment of HNSCC in combination with systemic administration of low dose bCet.

Abstract 4727: ST7612AA1: focus on a drug candidate, front-runner of a new generation of HDAC inhibitors

After more than 20 years of research in the field of HDAC inhibitors, the oncological armamentarium has significantly enriched with new approved drugs. Currently, four drugs, Vorinostat (Zolinza; 2006), Romidepsin (Istodax; 2009) Belinostat (Beleodaq; 2014) and Panobinostat (Farydak; 2015) have been approved by the U.S. Food and Drug Administration (FDA) for the treatment of cutaneous T-cell lymphoma (CTCL), peripheral T-cell lymphoma (PTCL), and multiple myeloma, respectively. A fifth, Chidamide (Epidaza; 2015), has been recently approved by the China Food and Drug Administration for the treatment of PTCL.

Beyond them, more than twenty are currently under pre-clinical and clinical investigation as single agent and in combination therapies against different cancers and in other several novel therapeutic indications. However, it is to emphasize a feature: among all these, no one, with the exception of the natural product Romidepsin, is a thiol derivative.

After efforts lasted years, now we have selected ST7612AA1 - a new thiol-ω(γ-lactam amide) SAHA analogues, potential front-runner of a new generation of HDAC inhibitors, [1] highly competitive respect to other HDAC inhibitors drugs, orally administered with a negligible toxicity.

ST7612AA1 displays low-nanomolar inhibitor activity on HDACs, being especially powerful on HDAC6 isoform, associated to a wide spectrum of antitumor activity, both in vitro and in vivo [2]; it can be industrially developed with a quick and easy synthetic process [3]. Moreover, it has also been investigated as an enhancer in antiretroviral therapy against HIV, aimed to eradicate the viral reservoirs [4].

All these results encouraged further enrichment experiments with ST7612AA1 as a drug candidate, which is currently in a phase of pre-clinical evaluation.

The overall profile of ST7612AA1, including synthesis and a comprehensive pharmacological characterization, will be presented.

[1] G. Giannini et al. J Med Chem. 2014, 57, 8358-8377

[2] L. Vesci et al. Oncotarget 2015, 6, 5735-48

[3] G. Battistuzzi, G. Giannini. Bioorg. Med. Chem .Lett. 2015, submitted

[4] R. Badia Antiviral Research 2015, 123, 62-69

Citation Format: Giuseppe Giannini, Ferdinando Maria Milazzo, Gianfranco Battistuzzi, Loredana Vesci. ST7612AA1: focus on a drug candidate, front-runner of a new generation of HDAC inhibitors. [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 4727.

[Corrigendum] Trastuzumab and docetaxel in a preclinical organotypic breast cancer model using tissue slices from mammary fat pad: Translational relevance

Oncol Rep 34: [Related article:] 1146–1152, 2015; DOI: 10.3892/or.2015.4074 After the publication of the article, the authors decided to add an Acknowledgements section: Acknowledgments Research activity leading to the results shown in the paper is the continuation of the IMI Predect program that received support from the Innovative Medicines initiative Joint Undertaking under grant agreement no. 115188, resources of which are composed of financial contribution from the European Union's Seventh Framework Programme (FP7/2007–2013) and EFPIA companies in kind contribution. Present results and conclusions are not endorsed by the Predect Consortium.

Trastuzumab and docetaxel in a preclinical organotypic breast cancer model using tissue slices from mammary fat pad: Translational relevance

With the ever-increasing number of drugs approved to treat cancers, selection of the optimal treatment regimen for an individual patient is challenging. Breast cancer complexity requires novel predictive methods and tools. In the present study, we set up experimental conditions to obtain an 'ex vivo' organotypic culture from xenotransplanted mice aiming at recapitulating the human clinical condition. The effect of trastuzumab (large biological molecule) and docetaxel (small chemical entity) was subsequently investigated on this organotypic model and compared with in vivo and in vitro activity on tumor cells. Tissue slices of 200 µm were obtained from mammary fat pad of SCID mice xenotransplanted with human MCF-7 breast cancer cells. Viability and proliferation were evaluated by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) colorimetric assay and Ki-67 immunohistochemistry,and apoptosis by cleaved caspase-3 immunohistochemistry. In vivo antitumor activity of trastuzumab and docetaxel was determined by caliper measurement of tumor volume and Ki-67 expression on explanted masses by immunohistochemistry. A Teflon support and normoxia were necessary experimental conditions to obtain high viability of excised breast cancer infiltrated mammary fat pad slices upon 48 h cultivation, as shown by MTT proliferation assay, and Ki-67 expression. Breast cancer tissue slices treated for 48 h with trastuzumab or docetaxel showed a significant dose-dependent reduction of viability by MTT assay. Consistently, both drugs down-modulated Ki-67 and increased cleaved caspase-3. Tumor masses collected from docetaxel-or trastuzumab-treated mice showed a similar reduction of proliferation markers. By contrast, MCF-7 cell cultures were significantly inhibited by docetaxel but not by trastuzumab. Tumor tissue slices represent a more predictive experimental cancer model compared to cell cultures for both small and large molecule antitumor efficacy. This observation supports the relevance of microenvironment in the overall tumor biology and response to therapeutics.

Resistance to the atypical retinoid ST1926 in SK-N-AS cells selected the subline rAS-ST with enhanced sensitivity to ATRA mediated by not conventional mechanisms: DNA damage, G2 accumulation and late telomerase inhibition

BACKGROUND AND PURPOSE

13-cis-Retinoic acid represents a well-established clinical strategy for the management of minimal residual disease of high risk neuroblastoma (NB) patients. However, the clinical efficacy on the overall survival of these patients remains limited, addressing the issue of better understanding the molecular mechanisms and intracellular pathways mediating Retinoic Acid (RA) clinical effects.

EXPERIMENTAL APPROACH

This work investigates the mechanism underlying the sensitivity/resistance to RA in NB by taking advantage of the paired SK-N-AS/rAS-ST cells showing different responsivity to ATRA. The subline rAS-ST was selected by inducing resistance to the novel retinoid ST1926 in the NB SK-N-AS cell line.

KEY RESULTS

Resistance to ST1926 was neither dependent on cellular uptake nor on multi-drug resistance phenotype. Rather, both delayed/lower DNA damage and apoptosis appeared involved in reduced sensitivity of rAS-ST cells to ST1926. This subline showed enhanced responsivity to ATRA compared to the wt counterpart, that was associated with enhanced RARα/β expression, DNA damage, G2 accumulation, PI3K/AKT pathway inhibition, cellular differentiation and delayed telomerase inhibition, without involvement of either p27/p53 or caspase-mediated apoptosis.

CONCLUSIONS AND IMPLICATIONS

The present data add important information to the understanding of RA sensitivity in NB, providing further insights towards a more efficacious clinical use of this drug.

Abstract 2604: Characterization of the activity and the mechanism of action of the new retinoid derivative ST5589 in pre-clinical models of lymphomas: involvement of MYC and cell cycle genes

Innovative and effective treatments are necessary for lymphomas that are common and still deadly cancers for many patients. Atypical retinoids show cytotoxic activity in different pre-clinical tumor models even though their mechanism of action is still largely unclear. Here, we report activity and mechanistic data with ST5589 (adarotene derivative), an active representative of this new class of agents (1), in pre-clinical lymphoma models.

Methods. Cell lines from diffuse large B-cell lymphoma (DLBCL, n=17), mantle cell lymphoma (MCL, n=4), splenic marginal zone lymphoma (SMZL, n=3) underwent 72 hr exposure to increasing doses of ST5589 (Sigma Tau, Pomezia, IT) to assess anti-proliferative activity by MTT assay. Apoptosis was assessed by Annexin-V/7-AAD staining. Gene expression profiling (GEP) was done with Illumina HumanHT-12 Expression BeadChips at baseline on all cell lines and, in triplicate, on 1 ABC- (TMD8) and 1 GCB-DLBCL (DOHH2) cell line treated with 300 nM ST5589 or DMSO for 8 hrs. Cell lines with IC50 &lt; than the median were defined as sensitive. GEP/IC50 correlation was assessed by Pearson correlation. Differential expression analysis was performed with LIMMA, GSEA, Metacore.

Results. Median IC50 was 235 nM (91-2652) for all the cell lines without significant differences among histological subtypes or between GCB- and ABC-DLBCL: DLBCL, 269 (97-2652); GCB-DLBCL 250, (97-1684); ABC-DLBCL, 531 (181-2625); MCL, 237 (91-401); SMZL, 144 (135-203). ST5589 induced apoptosis in 4/5 DLBCL cell lines (DOHH2, TMD8, SU-DHL-2, VAL). GEP in two DLBCL treated with ST5589 or DMSO was performed, and ST5589 significantly affected transcripts involved in multiple cell cycle-related gene-sets. Aurora kinase A coding gene was one of the most down-regulated.

MYC translocation was associated with lower IC50 (P 0.045) and higher number of responders (P 0.021). Transcripts associated with resistance to ST5589 were significantly enriched of genes involved in MYD88/TLR/STAT3 signaling and MAPK pathway, while transcripts associated with sensitivity were enriched of MYC target genes, genes high in Burkitt lymphoma, and involved in cellular respiration, and proteoglycan biosynthesis.

Conclusions. ST5589 showed anti-proliferative and cytotoxic preclinical activity in lymphoma, affecting cell-cycle regulation. While MYD88, TLR, STAT3 and MAPK pathways activation correlated with reduced drug activity, MYC deregulation was associated with sensitivity to ST5589. Our data, together with direct cytotoxicity and immune-system mediated activity reported for the parent compound adarotene ST1926 (2), make ST5589 worth of further studies in MYC-driven lymphomas as a representative of the innovative therapeutic class of atypical retinoids.

References

1 Giannini et al. Bioorganic and Med Chemistry 2012, 20: 2405-15

2 Pisano et al. Proceedings AACR 2004 Abstract #2075

Citation Format: Elena Bernasconi, Ivo Kwee, Andrea Rinaldi, Luciano Cascione, Maurilio Ponzoni, Loredana Vesci, Giuseppe Giannini, Anastasios Stathis, Emanuele Zucca, Eugenio Gaudio, Francesco Bertoni. Characterization of the activity and the mechanism of action of the new retinoid derivative ST5589 in pre-clinical models of lymphomas: involvement of MYC and cell cycle genes. [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 2604. doi:10.1158/1538-7445.AM2014-2604

Abstract 3693: Preclinical antitumor activity of SST0116CL1, a novel heat shock protein 90 (HSP90) inhibitor

Hsp90 is a component of a molecular chaperone complex, involved in the folding, maturation and stabilisation of key signaling molecules which control cell proliferation, survival and transformation. It works by a modulation of a set of cancer-associated proteins, collectively referred to as ‘‘clients’'. Inhibition of Hsp90 causes simultaneous destabilization and eventual degradation of client proteins that result in suppression of tumor growth, and a number of novel synthetic HSP90 inhibitors are currently under oncology clinical investigations for the treatment of a wide variety of tumor types. SST0116CL1 (property of sigma-tau Research Switzerland S.A.) is a potent, second generation, small-molecule HSP90 inhibitor, with a chemical structure (4-amino substituted resorcino-isoxazole) unrelated to the first generation ansamycin family of HSP90 inhibitors. SST0116CL1 binds to the ATP binding pocket of HSP90, and interferes with HSP90 chaperone function thus resulting in client protein degradation and tumor growth inhibition. In in vitro studies, SST0116CL1 was shown to inhibit recombinant HSP90α and to induce the degradation of the oncogenic Her2 tyrosine kinase in BT-474 human breast cancer cells. Moreover, it was able to induce the destabilization and depletion of different client proteins, often overexpressed and constitutively activated in numerous types of hematological or solid human tumors. These results correlated well with those obtained from the cell proliferation assay as well as with the HSP90 competitive binding assay, and clearly suggested that target modulation of HSP90 was achieved. In preclinical in vivo studies, in different solid and hematological tumor xenograft models, such as A431 epidermoid carcinoma with EGFR overexpression, GTL-16 gastric carcinoma with c-Met overexpression, MV4;11 B-myelomonocytic leukemia with flt3 mutation, A2780/Dx multidrug resistant ovarian carcinoma with P-glycoprotein overexpression, SST0116CL1 delivered intravenously or intraperitoneally revealed a potency at least comparable or higher than that found with the HSP90 inhibitor NVP-AUY922, under Phase II clinical trials investigation, or chemotherapeutic drugs currently used in cancer therapy. SST0116CL1 showed to be a manageable compound when given according to different schedules (qd5x/w; q4d/w; q2dx3/w), since it was well-tolerated and active to inhibit the tumor growth. A modulation of PD biomarkers in terms of down-regulation of EGFR, AKT and CDK4 was reached in tumor lesions of A431 tumor bearing mice treated with SST0116CL1 and a down-regulation of c-Met, AKT and CDK4 was observed in tumors collected from GTL-16 tumor bearing mice. PK parameters demonstrated a rapid clearance of SST0116CL1 from normal tissues and a blood compartment with prolonged retention in tumors. On the complex, these results strongly encourage the selection of SST0116CL1 as a promising candidate for clinical trial.

Citation Format: Loredana Vesci, Ferdinando Milazzo, Valeria Carollo, Silvia Pace, Giuseppe Giannini. Preclinical antitumor activity of SST0116CL1, a novel heat shock protein 90 (HSP90) inhibitor. [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 3693. doi:10.1158/1538-7445.AM2014-3693

Preclinical antitumor activity of SST0116CL1: a novel heat shock protein 90 inhibitor

4-Amino substituted resorcino-isoxazole (SST0116CL1) (property of Sigma-Tau Research Switzerland S.A.) is a potent, second generation, small-molecule heat shock protein 90 inhibitor (Hsp90i). SST0116CL1 binds to the ATP binding pocket of Hsp90, and interferes with Hsp90 chaperone function thus resulting in client protein degradation and tumor growth inhibition. The aim of the study was to assess SST0116CL1 in various solid and haematological tumors. The antitumor properties of SST0116CL1 were assessed using in vitro cell proliferation and client protein degradation assays and in vivo different tumor xenograft models. Pharmacokinetic (PK) data were also generated in tumor-bearing mice to gain an understanding of optimal dosing schedules and regimens. SST0116CL1 was shown to inhibit recombinant Hsp90α and to induce the destabilization of different client proteins, often overexpressed and constitutively activated in different types of hematological or solid human tumors. In preclinical in vivo studies, it was revealed to induce antitumor effects in murine models of leukemia and of gastric and ovarian carcinoma. A modulation of PD biomarkers in terms of downregulation of Hsp90 client proteins in tumor-bearing mice was found. SST0116CL1 is a new clinical candidate for cancer therapy. The antitumor property of SST0116CL1, likely due to direct inhibition of the Hsp90 enzymatic activity, may prove to be a critical attribute as the compound enters phase I clinical trials.

Abstract 1010: New thiol-ω(γ-lactam amide) SAHA analogues as potent histone deacetylase (HDAC) inhibitors

Histone deacetylase inhibitors (HDACi) are one of the last frontiers in pharmaceutical research. Two HDACi are already part of armamentarium of the anticancer drugs of the oncologists: Vorinostat, Zolinza® (SAHA) and Romidepsin, Istodax® (depsipeptide; FK-228), both licensed by the FDA for the treatment of cutaneous T-cell lymphoma (CTCL). Beyond them, more than twenty new drugs are currently under pre-clinical and clinical investigation as single agent and in combination therapies against different cancers and in other several novel therapeutic indications. Mainly they are hydroxamic acids and benzamide derivatives; however none has emerged superior to SAHA in terms of potency.

In our search, we have selected a new generation of HDACi: thiol-based SAHA bearing a lactam amide in ω-position. This new generation was highly competitive compared to competing drugs, displaying sub-micromolar to low nanomolar inhibitor activity on HDACs, being especially powerful on HDAC6 isoform. They exhibited higher anti-proliferative activity than SAHA on different human cell lines. In vivo they were orally administered and showed a higher potency than SAHA, with a negligible toxicity.

The overall profile of this new class of HDAC inhibitors, including synthesis and a comprehensive pharmacological characterization, will be presented.

These encouraging results prompted us to select a drug candidate which is currently in a phase of pre-clinical evaluation.

Citation Format: Giuseppe Giannini, Gianfranco Battistuzzi, Davide Vignola, Loredana Vesci, Ferdinando Maria Milazzo, Mario Berardino Guglielmi, Marcella Barbarino, Claudio Pisano, Walter Cabri. New thiol-ω(γ-lactam amide) SAHA analogues as potent histone deacetylase (HDAC) inhibitors. [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 1010. doi:10.1158/1538-7445.AM2013-1010

Displacement of [(3)H]GABA binding to bovine brain receptors by sulfur-containing analogues

The displacement of [(3)H]GABA binding to GABA receptors of bovine brain cortical membranes by some sulfur-containing compounds (homothiotaurine, thiotaurine and carboxymethylcysteamine) was investigated and their potency was compared to that of other known sulfur-containing analogues of GABA, such as homotaurine, homohypotaurine and taurine. Displacement studies showed homotaurine to be more effective as a GABA displacer than homohypotaurine and homothiotaurine (IC(50): 3.9 x 10(?8), 6.7 x 10(?7) and 6.8 x 10(?7) M, respectively). Saturation experiments showed that the effect of taurine, homothiotaurine, homotaurine and homohypotaurine was due to a loss of high-affinity GABA sites (K(d) = 10.7 nM). Homotaurine seems also to interact with low-affinity sites, decreasing the affinity constant, whereas the number of binding sites remains unchanged.

Camptothecins in tumor homing via an RGD sequence mimetic

A RGD peptide mimetic was conjugated to four camptothecins, with the purpose to improve their therapeutic index. The conjugate derivatives were evaluated against two tumor cell lines, one overexpressing integrins (human ovarian carcinoma, A2780) and a second one with a low integrin expression (human prostate cancer, PC3). The in vitro screening was completed with the adhesion behavior to vitronectin. Compound 8 (ST7456CL1) was selected for the in vivo investigation after stability tests over 24h, in PBS solution and in rat plasma, and compared to irinotecan. The former showed a prolonged half-life.

Abstract 3896: New heat shock protein 90 inhibitors based on the 1,2,3-triazole structure

Hsp90 (heat shock protein 90) is a component of a molecular chaperone complex, involved in the folding, maturation and stabilisation of key signalling proteins which control cell proliferation, survival and transformation. It works by modulating a set of cancer-associated proteins, that are often over-expressed and/or mutated in tumor cells, collectively referred as ‘‘clients’’. Inhibition of Hsp90 causes destabilization and eventual degradation of client proteins involved in cell cycle, tumor growth, angiogenesis and apoptosis. Therefore, their modulation results in suppression of tumor growth by multiple parallel mechanisms. Consequently, inhibition of Hsp90 is believed to be a potential target for cancer therapy, also supported by a number of molecules currently under investigation in different phase of clinical trials. We recently synthesized 1,4,5-trisubstituted-1,2,3-triazole derivatives and surprisingly found that these new molecules demonstrated to be extremely active both on the biological target and on human tumor cell lines, even at nanomolar concentration. 3D QSAR analysis was also performed in order to rationalize HSP90 binding data. The overall profile of this new class of 1,2,3-triazoles, including stereoselective synthesis and a comprehensive pharmacological in vitro characterization, will be presented.

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 3896. doi:1538-7445.AM2012-3896

Abstract 1774: Dihydroartemisinin (DHA): A potent enhancer of PARP inhibitors and DNA-damaging agents activity in human tumor models

Synthetic lethality (SL) is a cellular condition in which two or more non-allelic and non-essential mutations, which are not lethal on their own, become deadly when present within the same cell. PARP inhibitors (PARPi) represent a paradigmatic example of therapeutic application of the SL approaches. In cancer cells with BRCA1 or BRCA2 loss of function, inhibition of PARP1 activity leads to an accumulation of single strand breaks converted to double strand breaks but cannot be repaired by homologous recombination. However, preclinical and preliminary clinical evidences suggest a potentially broader scope for PARPi. Currently, several PARPi are under different phases of clinical investigation as monotherapy or in combination with DNA damaging agents. Although PARPi in monotherapy are quite safe, their combination with cytotoxic agents leads to exacerbation of the typical cytotoxic-related side effects, thus reducing the potentiality to improve the therapeutic index (T.I.) of these combinations. The study aim was to assess if the combination of PARPi and DNA-damaging agents with the widely used antimalarial agent DHA could improve both their antitumor activity and T.I. We have preliminary observed, in different cancer cells, that DHA was an inducer of endoplasmic reticulum (ER) stress (increased expression of typical ER stress-related genes), activation of checkpoint kinases and transcriptional up-regulation of different p53-target genes and of mitochondrial membrane depolarization. A consequence is PARP activation that, in absence of other factors, leads the cells to recover from damage and to their rescue. On the contrary, we observed that the simultaneous use of DHA with a PARPi or cytotoxic agents causes a massive cell death. More specifically a strong synergism was observed on tumor cells, when DHA was combined with different drugs: doxorubicin and platinum compounds on NCI-H460, temozolomide (TMZ) on MDA-MB436 and CAPAN-1. In addition, a synergistic interaction was identified between DHA and the PARPi (ABT-888 or AZD-2281) on various tumor cells (e.g., A431, HCT116, SW620, MDA-MB436, NCI-H460, A2780/DDP, CAPAN-1). In vivo, the combination of DHA (delivered at 200 mg/kg p.o. according to the schedule qdx5/w) with ABT-888 or AZD-2281, resulted in a significantly higher tumor growth inhibition than with monotherapy in NCI-H460 NSCLC, HCT116 colon ca. and MDA-MB436 triple-negative breast cancer BRCA1 negative xenografted in nude mice. DHA was also able to synergize in vivo with the alkylating agent TMZ against MDA-MB436 tumor model. No toxic effects of administrations of DHA in combination with chemotherapeutics in terms of body weight recordings were found throughout the experiments.Taken together, these results clearly pinpoint the clinical potential offered by DHA in the SL approaches in developing less toxic and more efficacious therapies to treat cancer patients.

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 1774. doi:1538-7445.AM2012-1774

Novel 3,4-isoxazolediamides as potent inhibitors of chaperone heat shock protein 90

A structural investigation on the isoxazole scaffold led to the discovery of 3,4-isoxazolediamide compounds endowed with potent Hsp90 inhibitory properties. We have found that compounds possessing a nitrogen atom directly attached to the C-4 heterocycle ring possess in vitro Hsp90 inhibitory properties at least comparable to those of the structurally related 4,5-diarylisoxazole derivatives. A group of compounds from this series of diamides combine potent binding affinity and cell growth inhibitory activity in both series of alkyl- and aryl- or heteroarylamides, with IC50 in the low nanomolar range. The 3,4-isoxazolediamides were also very effective in causing dramatic depletion of the examined client proteins and, as expected for the Hsp90 inhibitors, always induced a very strong increase in the expression levels of the chaperone Hsp70. In vivo studies against human epidermoid carcinoma A431 showed an antitumor effect of morpholine derivative 73 comparable to that induced by the reference compound 10.

Abstract 3256: New retinoid derivatives as backups of adarotene

Adarotene (ST1926) (WO03/011808) belongs to a so-called class of atypical retinoids. It represents a new first-in-class potent proapoptotic and cytodifferentiating agent, and was selected by Sigma-Tau for clinical development as a “chemotherapy enhancer” in solid tumors (ovarian ca.).

In pre-clinical models of haematological as well as solid tumors, Adarotene induced a DNA damage response and affected the modulation of cancer cell survival pathways. When used in combination with other anticancer agents, Adarotene showed a significant synergistic effect in most of the combinations and models tested.(1-4) A possible mechanism has also been described.(5-6)

The presence of the phenolic hydroxyl group on Adarotene structure, allowed a rapid O-glucuronidation as a major mechanism of elimination of the drug, favoring a fast excretion of its glucuronide metabolite in the urines.

In order to protect the phenolic hydroxyl and improve the “drug-like” properties of the drug, a series of new derivatives have been synthesized. According to chemical structure, these can be grouped into three classes: ether-, carbamate- and ester-derivatives. All of them have been studied and evaluated for their stability at different pH (1.2 – 6.8 – 7.4). The cytotoxic activity in vitro on NCI-H460 non-small cell lung carcinoma and A2780 ovarian tumor cells was also tested.(7)

A potential back-up of Adarotene has been selected to be evaluated in vivo tumor models.

(1) J. Med. Chem. 2003, 46, 909-912

(2) Blood, 2004, 103, 194-207

(3) J. Med. Chem. 2005, 48, 4931-4946

(4) Bioorganic & Medicinal Chemistry, 2007, 15, 4863-4875

(5) J. Med. Chem. 2008, 51, 5650-5662

(6) J. Comput. Aided Mol. Des. 2010, 24, 943-956

(7) WIPO Patent Application WO2010/072727

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 3256. doi:10.1158/1538-7445.AM2011-3256

Abstract 2623: ST3595, a new histone deacetylase (HDAC) inhibitor endowed with a peculiar mechanism of action

The novel hydroxamic acid-based compound ST3595, was identified within an in vitro screening for its inhibitory activity on histone deacetylase's (HDAC's) (Pisano C. et al., Clin Cancer Res 2010, 16 (15): 3944-53; Dalla Valle S et al., Eur J Med Chem 2009, 44 (5): 1900-12). With aim to define its antitumor potential, we investigated the in vivo activity of ST3595 in a variety of tumor models. In addition, we performed a comparative study of ST3595 and vorinostat (SAHA) to better understand the cellular/molecular basis of the antiproliferative activity. In in vivo experiments, ST3595, delivered orally or i.p. at well-tolerated doses (100 mg/kg) induced a significant tumor growth inhibition (ranging from 57 to 87%) in a variety of human tumor xenografts (H460 non-small cell lung, HCT116 colon and A2780 ovarian carcinoma). In in vitro studies, ST3595 exhibited arrest of H460 cells (wt p53) in S phase associated with a large extent of apoptosis. Under conditions producing comparable antiproliferative effects, treatment with vorinostat resulted in a G2/M arrest with a marginal induction of apoptosis. In HT29 cells (mutant p53) ST3595 caused arrest in S and G2/M phases with apoptosis induction, whereas vorinostat induced G1 accumulation without evidence of apoptosis, thus suggesting only antiproliferative effects. To explore the basis of the different cellular effects, we investigated the modulation of various factors implicated in DNA damage response and repair, cell cycle control and regulation of apoptosis. In H460 cells, we found that, in contrast to vorinostat, ST3595 was an effective inducer of p53 acetylation, supporting a role of this p53 modification in the proapoptotic activity of ST3595. In addition, in contrast to vorinostat, ST3595 strongly affected the expression of critical proteins involved in cell cycle control and DNA damage response. In particular, ST3595 induced activation and phosphorylation of H2AX, and of the checkpoint kinases chk1 and chk2, thus supporting an interference of the HDAC inhibitor in the processes controlling DNA integrity. In the light of the use of broad-specificity HDAC inhibitors in cancer therapy and in combination with other antitumor agents, the ability of ST3595 to modulate DNA damage response and it proapoptotic efficacy may have relevant implications in enhancing antitumor activity of well-established cytotoxic agents. Preclinical studies of ST3595 with genotoxic agents support this interpretation.

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 2623. doi:10.1158/1538-7445.AM2011-2623

Conjugates of a novel 7-substituted camptothecin with RGD-peptides as α(v)β₃ integrin ligands: An approach to tumor-targeted therapy

Eight conjugates of a novel camptothecin derivative (Namitecan, NMT) with RGD peptides have been synthesized and biologically evaluated. This study focused on factors that optimize the drug linkage to the transport vector. The different linkages investigated consist of heterofunctional glycol fragments and a lysosomally cleavable peptide. The linkage length and conformation were systematically modified with the purpose to understand their effect on receptor affinity, systemic stability, cytotoxicity, and solubility of the corresponding conjugates. Among the new conjugates prepared, C6 and C7 showed high receptor affinity and tumor cell adhesion, acceptable stability in murine blood, and high cytotoxic activity (IC₅₀ = 8 nM). The rationale, synthetic strategy, and preliminary biological results will be presented.

The identification of a novel natural activator of p300 histone acetyltranferase provides new insights into the modulation mechanism of this enzyme

Many severe human pathologies are related to alterations of the fine balance between histone acetylation and deacetylation; because not all such diseases involve hypoacetylation, but also hyperacetylation, compounds able to enhance or repress the activities of histone acetyltransferases (HATs) could be promising therapeutic agents. We evaluated in vitro and in cell the ability of eleven natural polyisoprenylated benzophenone derivatives to modulate the HAT activity of p300/CBP, an enzyme that plays a pivotal role in a variety of cellular processes. Some of the tested compounds bound efficiently to the p300/CBP protein: in particular, guttiferone A, guttiferone E and clusianone inhibit its HAT activity, whereas nemorosone showed a surprising ability to activate the enzyme. The ability of nemorosone to penetrate cell membranes and modulate histone acetylation into the cell together with its high affinity for the p300/CBP enzyme made this compound a suitable lead for the design of optimized anticancer drugs. Besides, the studies performed at a cellular and molecular level on both the inhibitors and the activator provided new insights into the modulation mechanism of p300/CBP by small molecules.

Abstract 566: Interaction of acetyl-L-carnitine with platinum compounds: A possible role of protein acetylation in modulation of antitumor activity

Several lines of evidence support that acetyl-L-carnitine (ALC) plays a relevant role as modulator of cellular stress response and may have a protective action in chemotherapy-induced neurotoxicity. ALC is implicated in the regulation of acetyl-CoA levels, a function mediated by carnitine acetyltransferase, thus providing a source of acetyl groups for histone acetylation. Since HDAC inhibitors may influence cellular response to cytotoxic drugs, including DNA damaging agents, it is conceivable that ALC may have a cooperative effect in combination with agents able to modulate protein acetylation. In particular, since the acetylation of wild-type p53, a substrate of HDAC, may influence its activity and stability and, therefore, the response to platinum compounds, this study was designed to investigate the effect of ALC in combination with cisplatin and carboplatin. ALC (100 mg/kg;qdx14, p.o.), in combination with cisplatin (5 mg/kg, i.p., q4dx5), was able to enhance the life-span of mice bearing the EL-4 lymphoma tumor (ILS: ALC plus cisplatin &gt;500%; cisplatin 105% vs control), resulting in 5/7 mice without evidence of disease. In addition, the combination of ALC plus cisplatin significantly increased the antitumor activity of cisplatin in three xenograft models of human non-small cell lung carcinoma (NCI-H460, A549 and NCI-H1650). Noteworthy, in a metastatic NCI-H460 model, an impressive reduction of lung metastasis in ALC and ALC+cisplatin groups was observed as compared with untreated mice. An increased antitumor activity was also observed in the combination of ALC with carboplatin. In addition, ALC produced an enhancement of antitumor activity of a novel HDAC inhibitor. To assess the relevance of acetyl moiety of ALC in the antitumor response, we investigated the activity of the combination of cisplatin with the related compound L-carnitine in NCI-H460 tumor model. In this experiment, L-carnitine did not showed any significative increases of antitumor effect when combined with cisplatin (TVI: 80% cisplatin vs 70% cisplatin plus carnitine), thus confirming a specific effect of ALC. In order to investigate the molecular mechanisms of the ALC-cisplatin interaction, several signal transduction pathways were analysed in H460 tumors by protein analysis and/or gene expression. The results revealed a significant increase of the p53 protein levels (p&lt;0.05 ALC plus cisplatin vs cisplatin), associated Lys373 acetylation, and the up-regulation of genes under control of p53. These observations may have implications for the therapeutic use of ALC in platinum-based chemotherapy.

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 566.

Abstract 731: 4-Amino-substituted 5-resorcinol-isoxazole derivatives, a novel class of Hsp90 inhibitor: Synthesis and evaluation of in vitro activity

Hsp90 (heat shock protein 90) is a component of a molecular chaperone complex, involved in the folding, maturation and stabilisation of key signalling molecules which control cell proliferation, survival and transformation. It works by a modulation of a set of cancer-associated proteins, collectively referred to as “clients”. Inhibition of Hsp90 causes simultaneous destabilization and eventual degradation of client proteins that result in suppression of tumor growth. This observation led to the idea, among pharmaceutical chemists, to consider Hsp90 as a potential target for a new strategy in human cancer therapy. After pioneering studies with natural products (geldamycin and radicicol), many selective Hsp90 inhibitors from various institutions have entered in clinical trials. One of these classes of inhibitors is the 4,5-diaryl-isoxazole with a resorcinol in position 5 and a second substituted aryl in position 4. This scaffold was considered a prerequisite for the activity on Hsp90.

VER-52296/NVP-AUY922, currently in Phase II clinical trials, belongs to diaryl-isoxazole class.

In our project, we systematically investigated - with in silico pre-screening, in concert with structural information from X-ray protein crystallography - all possible modifications to make on the isoxazole scaffold. We have mainly focused our attention on the importance of an amide portion at the 4 position. Now we have identified a new class of synthetic small molecule Hsp90 inhibitors, characterized by a 4-amino-substituted 5-monoaryl-isoxazole (5-resorcinol-isoxazole) scaffold. We turned our attention to the 4 position of isoxazole where unexpectedly, we have found that compounds possessing a nitrogen atom directly attached to the isoxazole ring are endowed of activity against Hsp90 similar or even better than the diaryl analogues.

Here we describe design, synthesis and preliminary in vitro biological profile of a small library of these derivatives.

Examples from this series of compounds have activities ranging from low to high nM against Hsp90 as measured in a fluorescence polarization (FP) competitive binding assay, and are active in human cancer cell lines where they inhibit cell proliferation and exhibit a characteristic profile of depletion of oncogenic proteins and concomitant elevation of Hsp72.

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 731.

A placental growth factor variant unable to recognize vascular endothelial growth factor (VEGF) receptor-1 inhibits VEGF-dependent tumor angiogenesis via heterodimerization

Angiogenesis is one of the crucial events for cancer development and growth. Two members of the vascular endothelial growth factor (VEGF) family, VEGF-A and placental growth factor (PlGF), which are able to heterodimerize if coexpressed in the same cell, are both required for pathologic angiogenesis. We have generated a PlGF1 variant, named PlGF1-DE in which the residues Asp72 and Glu73 were substituted with Ala, which is unable to bind and activate VEGF receptor-1 but is still able to heterodimerize with VEGF. Here, we show that overexpression in tumor cells by adenoviral delivery or stable transfection of PlGF1-DE variant significantly reduces the production of VEGF homodimer via heterodimerization, determining a strong inhibition of xenograft tumor growth and neoangiogenesis, as well as significant reduction of vessel lumen and stabilization, and monocyte-macrophage infiltration. Conversely, the overexpression of PlGF1wt, also reducing the VEGF homodimer production comparably with PlGF1-DE variant through the generation of VEGF/PlGF heterodimer, does not inhibit tumor growth and vessel density compared with controls but induces increase of vessel lumen, vessel stabilization, and monocyte-macrophage infiltration. The property of PlGF and VEGF-A to generate heterodimer represents a successful strategy to inhibit VEGF-dependent angiogenesis. The PlGF1-DE variant, and not PlGF1wt as previously reported, acts as a "dominant negative" of VEGF and is a new candidate for antiangiogenic gene therapy in cancer treatment.

ω-Alkoxy analogues of SAHA (vorinostat) as inhibitors of HDAC: A study of chain-length and stereochemical dependence

A series of omega-alkoxy ethers were prepared with variation of the length of the aliphatic chain of suberoylanilide hydroxamic acid (SAHA, vorinostat). Eight carbon long chain analogues showed the best activity, among which several substituted benzyl ether derivatives exhibited inhibitory activity on HDAC comparable to SAHA, and antiproliferative activity on three human cell lines (NB4, H460, and HCT-116) better than SAHA. However, no significant difference in antiproliferative activity was observed between two enantiomers bearing the benzyl ether moiety.

Antitumor activity of the combination of synthetic retinoid ST1926 and cisplatin in ovarian carcinoma models

BACKGROUND

The novel adamantyl retinoid ST1926 is a potent inducer of apoptosis in ovarian carcinoma cells. Since the pro-apoptotic effect is associated with activation of p53, in this study we have investigated the efficacy of combination of ST1926 with cisplatin, a DNA-damaging agent that is known to induce p53-dependent apoptosis.

MATERIALS AND METHODS

The efficacy of ST1926 and its combination with cisplatin was evaluated in human ovarian carcinoma models, including resistant tumors.

RESULTS

Oral treatment with ST1926 alone caused a marginal tumor growth inhibition (<50%), but the combination with cisplatin resulted in an improved efficacy, most evident in terms of tumor growth delay without a substantial increase of toxicity. The combination therapy achieved the best effects against the HOC18 ovarian carcinoma tumor, resulting in an appreciable number of animals without evidence of disease at the end of the experiment. In contrast to the marginal effect of ST1926 alone against the subcutaneous-growing tumors, loco-regional (intraperitoneal) treatment achieved a marked increase of survival of animals with ascitic IGROV-1 tumor.

CONCLUSIONS

The present results document the efficacy of the combination of cisplatin with ST1926 and provide a rational basis for the design of novel, well-tolerated platinum-based treatment approaches in human ovarian carcinoma.

Synergistic apoptosis and antitumor activity induced by ST1926, an atypical retinoic acid derivative

14029

Background: ST1926 is a novel adamantyl retinoid active against a wide panel of human tumor cell lines, including p53-defective cells. Moreover, its cytotoxic activity is not affected by Pgp overexpression or resistance to cisplatin. The drug induces an early G1/S cell cycle arrest associated with a modulation of genes involved in apoptosis and DNA damage. Although the ST1926 molecular targets are still not fully elucidated, some in vitro studies suggest that this drug induces activation of both intrinsic and extrinsic apoptotic pathways. Methods: ST1926 antiproliferative activity was evaluated in vivo by oral route using fractionated daily schedules in CD1 nude mice against different human tumor xenografts, including NSCLC, ovarian carcinoma, H&N, neuroblastoma and melanoma, as well as hematological malignancies. Pharmacokinetic and toxicological studies were conducted in rodents and dogs after single and repeated (5 days and 4 weeks) oral administration. Results: As monotherapy, ST1926, showing a favorable tolerability profile, was effective in inhibiting tumor growth in several tumor models. In particular, ST1926 showed significant tumor inhibition on doxorubicin- and platinum-resistant ovarian carcinomas at 30 mg/kg po given according to different schedules. The most prominent tumor growth inhibitory effects were noted in combination regimens with cisplatin and carboplatin in both sensitive and resistant ovarian carcinoma. The plasma t1/2 was about two hours in all animal species tested. The hemolymphopoietic system and GI tract were identified as the main target organs of toxicity. Toxicology findings indicated the starting dose in humans at 30 mg daily for five consecutive days. Conclusions: ST1926 is a new antitumor proapototic agent acting through particular molecular mechanisms. ST1926 is active by oral administration on both solid tumors, especially ovarian carcinoma, and acute myeloid leukemia. A Phase I clinical program to evaluate safety and tolerability of ST1926 as monotherapy and in combination with platinum compounds is ongoing in women with advanced ovarian cancer.

[Table: see text]

Synthesis and structure-activity relationships of new antiproliferative and proapoptotic retinoid-related biphenyl-4-yl-acrylic acids

Atypical retinoids, or retinoid-related molecules (RRMs), represent a class of proapoptotic agents with a promising potential in the treatment of neoplastic diseases. In the present work, the synthesis and structure-activity relationship of a series of 3'-adamantan-1-yl-biphenyl-4-yl-acrylic acids substituted in ring A were studied. The synthesized compounds were evaluated for their antiproliferative activity in a human promyelocitic leukemia cell line (NB4), and in an ovarian carcinoma cell system including IGROV-1, carrying a functional wild-type p53, and a cisplatin-resistant subline, IGROV-1/Pt-1. The presence of at least one oxygenated substituent in positions 4' or 5' appears determinant for the antiproliferative activity. With two substituents of this kind the activity increases, particularly in the case of alkylenedioxy compounds. The activation of DNA damage response as indicated by phosphorylation of H2AX histone, RPA-2 protein, and p53 at serine 15 by the most apoptotic compounds provides additional support to the hypothesis that the genotoxic stress is a critical event mediating apoptosis induction by compounds of this group.