Trans-farnesylthiosalicylic Acid Research Articles

Neuroprotective Effect of S-trans, Trans-farnesylthiosalicylic Acid via Inhibition of RAS/ERK Pathway for the Treatment of Alzheimer's Disease.

BackgroundAlzheimer’s disease (AD), a leading cause of dementia, becomes a serious health issue for individuals and society around the world. AD is a neurodegenerative disease characterized by the deposition of amyloid-β (Aβ) peptides and neurofibrillary tangles (NFT) and the loss of large numbers of neurons. To date, there is no effective treatment for AD, and thus, to enhance neurogenesis in the AD brain may be a therapeutic strategy. RAS signaling pathway involves in synaptic plasticity and memory formation, which is overexpressed in brains with AD. This study used Aβ1-42-injected mice (Aβ1-42-mice) as the AD model to investigate the effects of S-trans, trans-farnesylthiosalicylic acid (FTS), a synthetic Ras inhibitor, on the impairment of neurogenesis and the spatial cognitive deficits.Materials and methodsAD model mice were manufactured through intracerebroventricular injection of Aβ1-42. Morris water maze (MWM) was performed to evaluate the capacity of spatial memory, and Nissl staining was applied to assess neuronal damage in the hippocampus CA1. Immunohistochemistry of 5-bromo-2-deoxyuridine (BrdU), BrdU/neuronal nuclei (NeuN), and doublecortin (DCX) were used to detect progenitor cell proliferation, maturation, and neurite growth, respectively. And the expression levels of RAS, ERK/ERK phosphorylation (p-ERK) and CREB/CREB phosphorylation (p-CREB) were detected by Western blot.ResultsThe results demonstrated that FTS could prevent Aβ1-42 to impair survival and neurite growth of newborn neurons in the hippocampal dentate gyrus (DG) in Aβ1-42-mice. Furthermore, behavioral indexes and morphological findings showed that FTS improved the learning and spatial memory abilities of Aβ1-42-mice. In addition, FTS could inhibit the levels of hippocampal p-ERK and p-CREB activated by Aβ, which is the underlying molecular mechanism.ConclusionIn conclusion, these findings suggest that FTS as a RAS inhibitor could be a potential therapeutic agent for the treatment of AD.

Ras inhibitor S-trans, trans-farnesylthiosalicylic acid enhances spatial memory and hippocampal long-term potentiation via up-regulation of NMDA receptor

Statins by reducing farnesyl-pyrophosphate or farnesyl transferase inhibitors have been demonstrated to enhance spatial memory and long-term potentiation (LTP). The objective of this study was to investigate effects of the synthetic Ras inhibitor S-trans, trans-farnesylthiosalicylic acid (FTS) on spatial cognitive function in adult mice, synaptic plasticity in hippocampal CA1 regions, and NMDA receptor (NMDAr) activity of pyramidal cells. Here, we show that administering FTS (5 mg/kg, i.p.) enhanced spatial cognitive performance, as assessed via Morris water maze and Y-maze tests. Treating hippocampal slices with FTS (5 μM) for 2 h enhanced selectively NMDAr-dependent LTP without changing the synaptic properties. In comparison with the controls, the FTS-treated slices showed increases in the amplitude of NMDA-evoked currents (INMDA) and the phosphorylation of NMDAr GluN2A/GluN2B subunits and Src. The Src inhibitor PP2 blocked the enhancing effects of FTS on the activity and phosphorylation of NMDAr. In FTS-treated slices, basal levels of CaMKII, ERK2 and CREB phosphorylation did not differ significantly from those of controls; however, high-frequency stimulation-induced increases in CaMKII, ERK2 and CREB phosphorylation were more significant than in the controls, which were sensitive to PP2 and NMDAr antagonist MK801. Furthermore, the phosphorylation of AMPA receptor GluR1 during LTP was higher in FTS-treated slices compared with the control, which depended on Src and ERK1/2 signaling. The results indicate that the Ras inhibition by FTS can enhance NMDAr-dependent LTP by increasing Src activity to promote NMDAr GluN2A/GluN2B phosphorylation, which then leads to spatial memory potentiation.

128O Phase I study of S-trans, trans-farnesylthiosalicylic acid (salirasib), a novel oral RAS inhibitor in Japanese patients with advanced solid tumors

128O Phase I study of S-trans, trans-farnesylthiosalicylic acid (salirasib), a novel oral RAS inhibitor in Japanese patients with advanced solid tumors

Inhibition of malignant thyroid carcinoma cell proliferation by Ras and galectin-3 inhibitors.

Anaplastic Thyroid carcinoma is an extremely aggressive solid tumor that resists most treatments and is almost always fatal. Galectin-3 (Gal-3) is an important marker for thyroid carcinomas and a scaffold of the K-Ras protein. S-trans, transfarnesylthiosalicylic acid (FTS; Salirasib) is a Ras inhibitor that inhibits the active forms of Ras proteins. Modified citrus pectin (MCP) is a water-soluble citrus-fruit-derived polysaccharide fiber that specifically inhibits Gal-3. The aim of this study was to develop a novel drug combination designed to treat aggressive anaplastic thyroid carcinoma. Combined treatment with FTS and MCP inhibited anaplastic thyroid cells proliferation in vitro by inducing cell cycle arrest and increasing apoptosis rate. Immunoblot analysis revealed a significant decrease in Pan-Ras, K-Ras, Ras-GTP, p-ERK, p53, and Gal-3 expression levels and significant increase in p21 expression levels. In nude mice, treatment with FTS and MCP inhibited tumor growth. Levels of Gal-3, K-Ras-GTP, and p-ERK were significantly decreased. To conclude, our results suggest K-Ras and Gal-3 as potential targets in anaplastic thyroid tumors and herald a novel treatment for highly aggressive anaplastic thyroid carcinoma.

Enhancing FTS (Salirasib) efficiency via combinatorial treatment.

The Ras oncogene transmits signals, which regulate various cellular processes including cell motility, differentiation, growth and death. Since Ras signalling is abnormally activated in more than 30% of human cancers, Ras and its downstream signalling pathways are considered good targets for therapeutic interference. Ras is post-translationally modified by the addition of a farnesyl group, which permits its attachment to the plasma membrane. Exploiting this knowledge, a synthetic Ras inhibitor, S-trans, trans-farnesylthiosalicylic acid (FTS; Salirasib), was developed. FTS resembles the farnesylcysteine group of Ras, and acts as an effective Ras antagonist. In the present review, the effect of FTS in combination with various other drugs, as tested in vitro and in vivo, and its therapeutic potential are discussed. As reviewed, FTS cooperates with diverse therapeutic agents, which significantly improves treatment outcome. Therefore, combinations of FTS with other agents have a potential to serve as anti-cancer or anti-inflammatory therapies.

Analysis of gene expression array in TSC2-deficient AML cells reveals IRF7 as a pivotal factor in the Rheb/mTOR pathway.

Mutations in tuberous sclerosis (TSC) genes cause the genetic disorder TSC, as well as other neoplasms, including lymphangioleiomyomatosis (LAM) and angiomyolipomas (AMLs). AMLs are benign renal tumors occur both in sporadic LAM and in TSC. As they carry the same mutations, AML cell lines serve as a model for TSC and LAM. Rheb/mammalian target of rapamycin complex 1 (mTORC1) pathway is chronically activated in TSC-deficient cells, and this activation can be diminished using the appropriate inhibitors. Rapamycin (sirolimus) is a known specific inhibitor of mTORC1, whereas S-trans,trans-farnesylthiosalicylic acid (FTS; salirasib) has been shown to inhibit Rheb. To examine the effect of the Rheb/mTOR inhibition pathway, we used human TSC2-deficient AML cells, derived from a LAM patient. FTS indeed inhibited Rheb in these cells and attenuated their proliferation. After comparative treatments with FTS or rapamycin or by re-expression of TSC2, we carried out a gene array analysis. This yielded a substantial number of commonly altered genes, many of which we identified as downstream targets of the interferon (IFN) regulatory factor 7 (IRF7) transcription factor, a central activator of the IFN type 1 immune response. Furthermore, nuclear localization of IRF7 was impaired by each of the three treatments. Interestingly, the phenomena seen on FTS or rapamycin treatment were selective for TSC2-deficient cells. Moreover, knockdown of IRF7 by siRNA mimicked the decrease in number of the abovementioned genes and also inhibited AML cell proliferation. Altogether, these findings support FTS as a potential treatment for TSC and its related pathologies and IRF7 as a novel target for treatment.

Targeted Delivery of Curcumin to Tumors via PEG-Derivatized FTS-Based Micellar System

Curcumin and S-trans, trans-farnesylthiosalicylic acid (FTS) are two promising anticancer agents. In this study, we demonstrated that the two agents exerted significant synergy in antitumor activity in various types of cancer cells with combination indices ranging from 0.46 to 0.98 (a value of less than unity indicates synergism). We have further shown that synergistic-targeted co-delivery of the two agents can be achieved via formulating curcumin in polyethylene glycol (PEG)-derivatized FTS-based nanomicellar system. Curcumin formulated in PEG-FTS micelles had small size of around 20 nm. The nanomicellar curcumin demonstrated enhanced cytotoxicity towards several cancer cell lines in vitro. Intravenous application of curcumin-loaded micelle (20 mg kg(-1) curcumin) led to a significantly more effective inhibition of tumor growth in a syngeneic mouse breast cancer model (4T1.2) than curcumin formulated in Cremophor/EL (P < 0.05).

Interplay Between HGF/SF-Met-Ras Signaling, Tumor Metabolism and Blood Flow as a Potential Target for Breast Cancer Therapy.

High glucose uptake and increase blood flow is a characteristic of most metastatic tumors. Activation of Ras signaling increases glycolytic flux into lactate, de novo nucleic acid synthesis and uncoupling of ATP synthase from the proton gradient. Met tyrosine kinase receptor signaling upon activation by its ligand, hepatocyte growth factor/scatter factor (HGF/SF), increases glycolysis, oxidative phosporylation, oxygen consumption, and tumor blood volume. Ras is a key factor in Met signaling. Using the Ras inhibitor S-trans,trans-farnesylthiosalicylic acid (FTS), we investigated interplay between HGF/SF-Met-Ras signaling, metabolism, and tumor blood-flow regulation. In vitro, HGF/SF-activated Met increased Ras activity, Erk phosphorylation, cell motility and glucose uptake, but did not affect ATP. FTS inhibited basal and HGF/SF-induced signaling and cell motility, while further increasing glucose uptake and inhibiting ATP production. In vivo, HGF/SF rapidly increased tumor blood volume. FTS did not affect basal blood-flow but abolished the HGF/SF effect. Our results further demonstrate the complex interplay between growth-factor-receptor signaling and cellular and tumor metabolism, as reflected in blood flow. Inhibition of Ras signaling does not affect glucose consumption or basal tumor blood flow but dramatically decreases ATP synthesis and the HGF/SF induced increase in tumor blood volume. These findings demonstrate that the HGF/SF-Met-Ras pathway critically influences tumor-cell metabolism and tumor blood-flow regulation. This pathway could potentially be used to individualize tumor therapy based on functional molecular imaging, and for combined signaling/anti-metabolic targeted therapy.

PEG-Farnesylthiosalicylate Conjugate as a Nanomicellar Carrier for Delivery of Paclitaxel

S-trans, trans-farnesylthiosalicylic acid (FTS) is a synthetic small molecule that acts as a potent and especially nontoxic Ras antagonist. It inhibits both oncogenically activated Ras and growth factor receptor-mediated Ras activation, resulting in the inhibition of Ras-dependent tumor growth. In this work, an FTS conjugate with poly(ethylene glycol) (PEG) through a labile ester linkage, PEG5K-FTS2(L), was developed. PEG5K-FTS2 conjugate readily forms micelles in aqueous solutions with a critical micelle concentration of 0.68 μM, and hydrophobic drugs such as paclitaxel (PTX) could be effectively loaded into these particles. Both drug-free and PTX-loaded micelles were spherical in shape with a uniform size of 20-30 nm. The release of PTX from PTX-loaded PEG5K-FTS2 micelles was significantly slower than that from Taxol formulation. In vitro cytotoxicity studies with several tumor cell lines showed that PEG5K-FTS2(L) was comparable to FTS in antitumor activity. Western immunoblotting showed that total Ras levels were downregulated in several cancer cell lines treated with FTS or PEG5K-FTS2(L). The micellar formulation of PTX exhibited more in vitro cytotoxic activity against several tumor cell lines compared with free PTX, suggesting a possible synergistic effect between the carrier and the codelivered drug. The antitumor activity of the PTX loaded PEG5K-FTS2(L) micelles in a syngeneic murine breast cancer model was found to be significantly higher than that of Taxol, which may be attributed to their preferential tumor accumulation and a possible synergistic effect between PEG5K-FTS2 carrier and loaded PTX.

Ras inhibition enhances autophagy, which partially protects cells from death

Autophagy, a process of regulated turnover of cellular constituents, is essential for normal growth control but may be defective under pathological conditions. The Ras/PI3K/mTOR signaling pathway negatively regulates autophagy. Ras signaling has been documented in a large number of human cancers. In this in-vitro study we examined the effect of the Ras inhibitor Salirasib (S-trans, trans-farnesylthiosalicylic acid; FTS) on autophagy induction and cell viability. We show that Ras inhibition by FTS induced autophagy in several cell lines, including mouse embryonic fibroblasts and the human cancer cell lines HeLa, HCT-116 and DLD-1. The autophagy induced by FTS seems to inhibit the cell death induced by FTS, since in the absence of autophagy the death of FTS-treated cells was enhanced. Therefore, inhibition of autophagy may promote the inhibition of tumor cell growth and the cell death mediated by FTS.

Synergistic Effects of Combined Wnt/KRAS Inhibition in Colorectal Cancer Cells

Activation of Wnt signalling due to inability to degrade β-catenin is found in >85% of colorectal cancers. Approximately half of colon cancers express a constitutively active KRAS protein. A significant fraction of patients show both abnormalities. We previously reported that simultaneous down-regulation of both β-catenin and KRAS was necessary to induce significant cell death and tumor growth inhibition of colorectal cancer cells. Although attractive, an RNAi-based therapeutic approach is still far from being employed in the clinical setting. Therefore, we sought to recapitulate our previous findings by the use of small-molecule inhibitors of β-catenin and KRAS. We show here that the β-catenin inhibitors PKF115-584 and pyrvinium pamoate block β-catenin-dependent transcriptional activity and synergize with the KRAS inhibitor S-trans, trans-farnesylthiosalicylic acid (FTS, salirasib) in colon cancer cells driven by Wnt and KRAS oncogenic signals, but not in cells carrying BRAF mutations. The combined use of these compounds was superior to the use of any drug alone in inducing cell growth arrest, cell death, MYC and survivin down-modulation, and inhibition of anchorage-independent growth. Expression analysis of selected cancer-relevant genes revealed down-regulation of CD44 as a common response to the combined treatments. These data provide a proof of principle for a combination therapeutic strategy in colorectal cancer.

Integrated preclinical and clinical development of S-trans, trans-farnesylthiosalicylic acid (FTS, Salirasib) in pancreatic cancer

S-trans,trans-Farnesylthiosalicylic Acid (FTS, salirasib) inhibits Ras-dependent cell growth by dislodging all isoforms of Ras, including mutant Ras, from the plasma membrane. This study evaluated the activity, safety, and toxicity of salirasib in preclinical models and patients with metastatic pancreatic adenocarcinoma (PDA). In the preclinical study, salirasib was tested, alone and in combination with gemcitabine, in patient derived xenografts (PDX) of PDA. In the clinical study, treatment-naïve patients with advanced, metastatic PDA were treated with a standard dose schedule of gemcitabine and salirasib 200-800 mg orally (PO) twice daily (bid) for 21 days every 28 days. Tissue from preclinical models and patients' biopsies were collected pre-treatment and on Cycle (C) 1, Day (D) 9 to characterize the effect of gemcitabine and salirasib on activated Ras protein levels. Plasma samples for pharmacokinetics were collected for salirasib administered alone and in combination. Salirasib inhibited the growth of 2/14 PDX models of PDA and modulated Ras signaling in these tumors. Nineteen patients were enrolled. No DLTs occurred. Common adverse events included hematologic and gastrointestinal toxicities and fatigue. The median overall survival was 6.2 months and the 1 year survival 37 %. In 2 patients in whom paired tissue biopsies were available, Ras and KRas protein levels were decreased on C1D9. Salirasib exposure was not altered by gemcitabine and did not correlate with PD outcomes. The combination of gemcitabine and salirasib appears well-tolerated, with no alteration of salirasib exposure, and exerted clinical and PD activity in PDA.

Farnesylthiosalicylic acid (salirasib) inhibits Rheb in TSC2‐null ELT3 cells: A potential treatment for lymphangioleiomyomatosis

The small GTPase proteins, Ras and Rheb, serve as molecular switches regulating cell proliferation, differentiation and apoptosis. Ras also regulates Rheb by inactivating the tuberous sclerosis complex (TSC), which includes products of the TSC1 and TSC2 genes encoding hamartin (TSC1) and tuberin (TSC2), respectively, and acts as a Rheb-specific GTPase-activating protein. Loss of function of TSC1 or TSC2 results in an increase in active Rheb.GTP with the consequent translational abnormalities and excessive cell proliferation characteristic of the genetic disorders, tuberous sclerosis and lymphangioleiomyomatosis (LAM). To determine whether inactivation of Rheb, Ras or both might be a potential treatment for LAM, we used TSC2-null ELT3 cells as a LAM model. The cells were treated with the Ras inhibitor S-trans,trans-farnesylthiosalicylic acid (FTS; salirasib), which mimics the C-terminal S-farnesyl cysteine common to Ras and Rheb. This C-terminus is critical for their attachment to cellular membranes and for their biological activities. Untreated, the ELT3 cells expressed significant amounts of Rheb but little Ras.GTP, and this phenotype was reversed by TSC2 reexpression. Treatment with FTS decreased Ras.GTP only slightly in the TSC2-null cells, but reduced their overactive Rheb as well as their proliferation, migration and tumor growth. Notably, TSC2 reexpression in these ELT3 cells rescued them from the inhibitory effect of FTS. Evidently, therefore, FTS blocks active Rheb in TSC2-null ELT3 cells and may have therapeutic potential for LAM.

Galectin-3 Promotes Chronic Activation of K-Ras and Differentiation Block in Malignant Thyroid Carcinomas

Anaplastic thyroid carcinomas are deadly tumors that are highly invasive, particularly into the bones. Although oncogenic Ras can transform thyroid cells into a severely malignant phenotype, thyroid carcinomas do not usually harbor ras gene mutations. Therefore, it is not known whether chronically active Ras contributes to thyroid carcinoma cell proliferation, although galectin-3 (Gal-3), which is strongly expressed in thyroid carcinomas but not in benign tumors or normal glands, is known to act as a K-Ras chaperone that stabilizes and drives K-Ras.GTP nanoclustering and signal robustness. Here, we examined the possibility that thyroid carcinomas expressing high levels of Gal-3 exhibit chronically active K-Ras. Using cell lines representing three types of malignant thyroid tumors--papillary, follicular, and anaplastic--we investigated the possible correlation between Gal-3 expression and active Ras content, and then examined the therapeutic potential of the Ras inhibitor S-trans, trans-farnesylthiosalicylic acid (FTS; Salirasib) for thyroid carcinoma. Thyroid carcinoma cells strongly expressing Gal-3 showed high levels of K-Ras.GTP expression, and K-Ras.GTP transmitted strong signals to extracellular signal-regulated kinase. FTS disrupted interactions between Gal-3 and K.Ras, strongly reduced K-Ras.GTP and phospho-extracellular signal-regulated kinase expression, and enhanced the expression of the cell cycle inhibitor p21 as well as of the thyroid transcription factor 1, which is involved in thyroid cell differentiation. FTS also inhibited anaplastic thyroid carcinoma cell proliferation in vitro and tumor growth in nude mice. We conclude that wild-type K-Ras.GTP in association with Gal-3 contributes to thyroid carcinoma malignancy and that Ras inhibition might be a useful treatment strategy against these deadly tumors.

Prevention of Human Immunodeficiency Virus Type 1 Transmission by Pharmaceuticals Targeted to Host Proteins Required for Virus Infection? Consideration of Farnesyl Thiosalicylic Acid, a Ras Inhibitor

Recent success in defining the human immunodeficiency virus type 1 (HIV-1) – host cell protein interaction network has provided an opportunity for development of novel antiviral therapeutics targeted to host proteins required for virus infection. This expanded earlier successful development of antagonists for the cellular receptors (CD4) and co-receptors (CCR5 or CXCR4) involved in virus attachment. Induction of the G-alphaq signaling cascade by the HIV-1 envelope is required for virus entry, and it’s blocking prevented HIV-1-mediated membrane fusion and initiation of infection. One of the blockers, the Ras inhibitor S-trans, trans-farnesylthiosalicylic acid (FTS), was reported to interfere with HIV-1 infection. Since FTS appears to have an established safety record and is being evaluated (as Salirasib, oral) in phase II human clinical trials for treatment of lung cancer, it was of interest to evaluate the potential of FTS as a topical microbicide for prevention of sexual transmission of HIV-1. Data shown here indicated that this compound did not meet the criteria of an established screening algorithm for evaluation of topical microbicides. Nevertheless, the possibility remains to be explored that FTS (especially when used in combination with other anti-HIV drugs) might be useful in sustained pre-exposure prophylaxis to prevent HIV-1 transmission.

Phase 1 first-in-human clinical study of S-trans, trans-farnesylthiosalicylic acid (salirasib) in patients with solid tumors

This phase I first-in-human trial evaluated salirasib, an S-prenyl derivative of thiosalicylic acid that competitively blocks RAS signaling. Patients with advanced cancers received salirasib twice daily for 21 days every 4 weeks. Doses were escalated from 100 to 200, 400, 600, and 800 mg. The most common toxicity was dose-related diarrhea (Grade 1-2, 79% of 24 patients). Other toxicities included abdominal pain, nausea, and vomiting. No Grade 3-4 toxicity was noted. Nineteen (79%) patients had no drug-related toxicity >Grade 1. Dose-limiting toxicity (DLT) was not reached, but all three patients treated with 800 mg experienced Grade 1-2 diarrhea, brogating dose escalation. Six patients were treated at a dose of 600 mg with no DLTs. Seven (29%) patients had stable disease on salirasib for ≥4 months (range 4-23+). The salirasib pharmacokinetic profile was characterized by slow absorption and a rapid elimination phase following oral administration. Salirasib exposure (C(max); day 1 AUC(inf) vs. day 15 AUC(0-12 h)) was similar between days 1 and 15 (P > 0.05). The T(1/2) (mean ± SD) was 3.6 ± 2.2 h on day 1. Salirasib therapy was well tolerated. The recommended dose for phase II studies is 600 mg twice daily.

New Derivatives of Farnesylthiosalicylic Acid (Salirasib) for Cancer Treatment: Farnesylthiosalicylamide Inhibits Tumor Growth in Nude Mice Models

The Ras inhibitor S-trans,trans-farnesylthiosalicylic acid (FTS, Salirasib) interferes with Ras membrane interactions that are crucial for Ras-dependent transformation. It remains unknown whether modifications of the carboxyl group of FTS can affect its activity. Here we show that specific modifications of the FTS carboxyl group by esterification or amidation yield compounds with improved growth inhibitory activity, compared to FTS, as shown in Panc-1 and U87 cells. The most potent compounds were FTS-methoxymethyl ester and FTS-amide. However, selectivity toward active Ras-GTP, as known for FTS, was apparent with the amide derivatives of FTS. FTS-amide exhibited the overall highest efficacy in inhibition of Ras-GTP and cell growth. This new compound significantly inhibited growth of both Panc-1 tumors and U87 brain tumors. Thus amide derivatives of the FTS carboxyl group provide potent cell-growth inhibitors without loss of selectivity toward the active Ras protein and may serve as new candidates in cancer therapy.

Induction of the Galpha(q) signaling cascade by the human immunodeficiency virus envelope is required for virus entry.

Binding of human immunodeficiency virus type 1 (HIV-1) envelope glycoprotein (Env) with the primary receptor CD4 and one of two coreceptors, CXCR4 or CCR5, activates a signaling cascade resulting in Rac-1 GTPase activation and stimulation of actin cytoskeletal reorganizations critical for HIV-1-mediated membrane fusion. The mechanism by which HIV-1 Env induces Rac-1 activation and subsequent actin cytoskeleton rearrangement is unknown. In this study, we show that Env-mediated Rac-1 activation is dependent on the activation of Galpha(q) and its downstream targets. Fusion and Rac-1 activation are mediated by Galpha(q) and phospholipase C (PLC), as shown by attenuation of fusion and Rac-1 activation in cells either expressing small interfering RNA (siRNA) targeting Galpha(q) or treated with the PLC inhibitor U73122. Rac-1 activation and fusion were also blocked by multiple protein kinase C inhibitors, by inhibitors of intracellular Ca2+ release, by Pyk2-targeted siRNA, and by the Ras inhibitor S-trans,trans-farnesylthiosalicylic acid (FTS). Fusion was blocked without altering cell viability or cell surface localization of CD4 and CCR5. Similar results were obtained when cell fusion was induced by Env expressed on viral and cellular membranes and when cell lines or primary cells were the target. Treatment with inhibitors and siRNA specific for Galpha(i) or Galpha(s) signaling mediators had no effect on Env-mediated Rac-1 activation or cell fusion, indicating that the Galpha(q) pathway alone is responsible. These results could provide a new focus for therapeutic intervention with drugs targeting host signaling mediators rather than viral molecules, a strategy which is less likely to result in resistance.

Determination of salirasib ( S- trans, trans-farnesylthiosalicylic acid) in human plasma using liquid chromatography–tandem mass spectrometry

A liquid chromatography/tandem mass spectrometric (LC/MS/MS) assay was developed for the quantitative determination of salirasib ( S- trans, trans-farnesylthiosalicylic acid, FTS) in human plasma. Sample pretreatment involved liquid–liquid extraction with methyl t-butyl ether of 0.5-mL aliquots of lithium heparin plasma spiked with the internal standard, S- trans, trans-5-fluoro-farnesylthiosalicylic acid (5-F-FTS). Separation was achieved on Waters X-Terra™ C 18 (50 mm × 2.1 mm i.d., 3.5 μm) at room temperature using isocratic elution with acetonitrile/10 mM ammonium acetate buffer mobile phase (80:20, v/v) containing 0.1% formic acid at a flow rate of 0.20 mL/min. Detection was performed using electrospray MS/MS by monitoring the ion transitions from m/z 357.2 → 153.0 (salirasib) and m/z 375.1 → 138.8 (5-F-FTS). Calibration curves were linear in the concentration range of 1–1000 ng/mL. A 5000 ng/mL sample that was diluted 1:10 (v/v) with plasma was accurately quantitated. The values for both within day and between day precision and accuracy were well within the generally accepted criteria for analytical method (<8.0%). This assay was subsequently used for the determination of salirasib concentrations in plasma of cancer patients after oral administration of salirasib at a dose of 400 mg.

Phase I first-in-human study of s-trans, trans-farnesylthiosalicylic acid (salirasib) in patients with solid tumors

3536 Introduction: S-trans, trans-farnesylthiosalicylic acid (FTS, salirasib) is an oral synthetic small molecule with potent inhibitory properties against oncogenic Ras, which is involved in cell growth, differentiation, and survival in many human tumors. We conducted a phase 1 trial of salirasib in solid tumors. Methods: Salirasib was administered orally for 21D q. 28D. Doses were escalated from 100 to 200, 400, 600, and 800 mg BID. Pharmacokinetic (PK) studies were performed during the first cycle. Results: Twenty-four patients (pts.) were treated. The median age was 56 yrs. (range, 26–76); and 54% were women. Diagnoses were metastatic colon cancer (n=5); appendiceal carcinoma (n=3); pancreatic cancer (n=2); type 2 neurofibromatosis (NF2)-associated tumors (n=2); carcinoid tumors (n=2); osteosarcoma (n=1); ocular melanoma (n=1); and other cancers (n=8). ECOG performance status was 1 in 92% and 0 in 8% of pts. The median number of prior therapies was 3. Eighty-eight cycles were administered (median, 2; range, 1–13+). The most common toxicity was dose-related diarrhea (G1, 54% of pts.; G2, 25%), which was controlled with antidiarrheal agents. Other toxicities included abdominal pain (21% of pts.), nausea, vomiting, and fatigue (17%, respectively). No G3–4 toxicity was noted; and 19 (79%) pts. had no drug-related toxicity >G1. Classic dose-limiting toxicity was not reached, but all 3 pts. treated with 800 mg BID experienced prolonged G1–2 diarrhea, and it was felt that further dose escalation would not be tolerable. Seven (29%) pts. had stable disease (SD) on salirasib therapy for ≥4 months (range, 4–13+) (metastatic carcinoid tumor, n=2; NF2-associated tumors, n=2; myoepithelial cancer of lacrimal gland, n=1; thyroid medullary carcinoma, n=1; and breast cancer, n=1). The median half-life of salirasib was 3.6±2.2 and 2.1±0.9 hours (mean ± SD) on D1 and D15, respectively. PK results were linear with respect to Cmax and AUC across the dose levels studied. There was no difference in PK parameters between single- and multiple-dose salirasib. Conclusion: Salirasib therapy was well tolerated at doses up to 800 mg BID with the major adverse event being dose-related diarrhea. Seven (29%) pts. had SD for ≥4 months. The recommended dose for phase II studies is 800 mg BID. Author Disclosure Employment or Leadership Consultant or Advisory Role Stock Ownership Honoraria Research Expert Testimony Other Remuneration Averion International Corp Averion International Corp. Concordia Pharmaceuticals, Inc Concordia Pharmaceuticals, Inc