Until recently, the therapeutic treatment of breast cancer has been dominated by endocrine-based drugs (oestrogen receptor antagonists, aromatase inhibitors etc.) and conventional cytotoxics (doxorubicin, cyclophosphamide, 5-fluorouracil etc.). However, the advent of new generation signal transduction inhibitor drugs targeted against the molecular abnormalities of breast cancer (e.g., the antibody trastuzumab, directed against the cERBB2 receptor) has the promise of providing a new era of more tumour selective therapy. Inhibitors of the enzyme farnesyl transferase (FTIs) are now undergoing early-stage clinical trials, including in patients with advanced breast cancer. Although originally developed as inhibitors of RAS signal transduction pathways, it is now apparent that these drugs are better described as prenylation inhibitors; the addition of a 15-carbon prenyl or farnesyl moiety by farnesyl transferase being critical to the function of a number of proteins, including RAS. At least three FTIs are currently undergoing clinical evaluation; R115777 (tipifarnib, Zarnestra), SCH66336 (lonafarnib, Sarasar) and BMS-214662. In terms of their potential use in the chemotherapeutic treatment of advanced breast cancer, a Phase II trial of R115777 (using either continuous or intermittent twice-daily oral dosing) has demonstrated promising activity (approximately 10% partial response rate). Overall, however, the single agent activity of FTIs in various Phase II trials has been rather modest (as well as the above mentioned breast cancer trial, some responses have been seen in patients with acute and chronic myeloid leukaemias). The main dose-limiting toxicities that have been reported are myelosuppression and fatigue and neurotoxicity (with R115777). Two Phase III trials of R115777 in colorectal (versus placebo) and pancreatic (with gemcitabine versus placebo) cancer have failed to show a survival benefit. It is likely that the future clinical direction of FTIs will be as combination therapy, especially with the taxanes, where synergy has been seen in a variety of preclinical studies.

The farnesyltransferase inhibitors (FTIs) are in active clinical development in a variety of human malignancies. The most promising activity to date has been demonstrated in patients with hematological malignancies, in particular acute myeloid leukemia (AML) and myelodysplastic syndrome (MDS). In patients with MDS, two non-peptidomimetic agents, tipifarnib (Zarnestra, Johnson & Johnson, New Brunswick, NJ) and lonafarnib (Sarasar, Schering-Plough, Kenilworth, NJ) have been the most extensively studied. In both phase I and phase II trials, tipifarnib has demonstrated significant efficacy with overall response rates of 30%, with complete remissions in about 15%. Dose-limiting side effects have been primarily myelosuppression, although fatigue, neurotoxicity, and occasional renal dysfunction have required dose reductions. Lonafarnib in patients with MDS has also resulted in clinical responses in approximately 30%, including significant improvements in platelet counts. Lonafarnib has been associated with primarily diarrhea and other gastrointestinal toxicity, anorexia, and nausea, which has limited its efficacy. Clinical response correlation with documentation of inhibition of farnesyltransferase and/or evidence of decreased farnesylation of downstream protein targets has not been demonstrated with either agent. In addition, the presence of an activating Ras mutation has not predicted response to therapy with FTIs in MDS and AML. Despite this, significant clinical efficacy of the FTIs in MDS, on par with that of currently available chemotherapeutic agents, has been observed, leading to further development of this new class of drugs in MDS and AML.

The treatment of hematologic malignancies has progressed in the last few years. Identification of new pathways and target molecules in leukemia has ushered in a promising new era of therapy. Ras mutations have recently been implicated in the pathogenesis of acute leukemia, and inhibition of Ras signaling through the use of farnesyltransferase inhibitors (FTIs) has shown promise in early trials in acute myeloid leukemia (AML). Responses have not correlated with the presence of Ras mutations, suggesting that novel pathways are involved. In several early trials, FTIs have shown activity as single agents in poor-risk AML, suggesting a potential role in combination with standard chemotherapy. FTIs are now being tested in other clinical settings, such as myelodysplasia, chronic myelogenous leukemia and multiple myeloma, with encouraging preliminary activity.

BACKGROUND

Resistance to imatinib monotherapy frequently emerges in advanced stages of chronic myelogenous leukemia (CML), supporting the rationale for combination drug therapy. In the present study, the activities of the farnesyltransferase inhibitors (FTIs) L744,832 and LB42918, as single agents and in combination with imatinib, were investigated in different imatinib-sensitive and -resistant BCR-ABL-positive CML cells.

METHODS

Growth inhibition of the cell lines and primary patient cells was assessed by MTT assays and colony-forming cell assays, respectively. Drug interactions were analyzed according to the median-effect method of Chou and Talalay. The determination of apoptotic cell death was performed by annexin V/propidium iodide staining.

RESULTS

Combinations of both FTIs with imatinib displayed synergism or sensitization (potentiation) in all the cell lines tested. In primary chronic phase CML cells, additive and synergistic effects were discernible for the combination of imatinib plus L744,832 and imatinib plus LB42918, respectively. Annexin V/propidium iodide staining showed enhancement of imatinib-induced apoptosis with either drug combination, both in imatinib-sensitive and -resistant cells.

CONCLUSIONS

The results indicated the potential of L744,832 and LB42918 as combination agents for CML patients on imatinib treatment.

Farnesyltransferase inhibitors (FTIs) are small-molecule inhibitors that selectively inhibit farnesylation of a number of intracellular substrate proteins such as Ras. Preclinical work has revealed their ability to effectively inhibit tumor growth in vitro and in vivo in animal models across a wide range of malignant phenotypes. Myeloid malignancies are appropriate disease targets, in that they express relevant biologic targets, such as Ras, Mitogen-Activated Protein Kinase (MAPK), AKT, and others that may depend upon farnesyl protein transferase (FTase) activity to promote proliferation and survival. Phase I trials in acute leukemias and myelodysplasia have demonstrated biologic and clinical activities as determined by target enzyme inhibition, low toxicity, and both complete and partial responses. As a result, phase II trials have been initiated in a variety of hematologic malignancies and disease settings, in order to further validate clinical activity and to identify downstream signal transduction targets that may be modified by these agents. It is anticipated that these studies will serve to define the optimal roles of FTIs in patients with hematologic malignancies and provide insight into effective methods by which to combine FTIs with other agents.

Farnesyltransferase inhibitors (FTI) are a class of therapeutic agents designed to target tumors with mutations of the ras oncogene. However, the biological effect of FTIs is often independent of ras mutation status, which suggests the existence of additional mechanisms. In this study, we investigated the molecular effects of SCH66336, an FTI, in head and neck squamous cell carcinoma cells using proteomic approaches. We showed that SCH66336 induced phosphorylation (inactivation) of eukaryotic translation elongation factor 2 (eEF2), an important molecule for protein synthesis, as early as 3 hours after SCH66336 administration. Protein synthesis was subsequently reduced in the cells. Paradoxically, activation of eEF2 kinase (eEF2K), the only known kinase that regulates eEF2, was observed only at 12 hours after SCH66336 treatment. Consistent with this observation, the inhibition of phosphorylated-MEK and phosphorylated-p70S6K, the two key signaling molecules responsible for activation of eEF2K, also occurred at least 12 hours after SCH66336 administration. Our data suggest that inhibition of protein synthesis through inactivation of eEF2 is a novel mechanism of SCH66336-mediated growth inhibition and that this effect is independent of ras-MEK/p70S6K-eEF2K signaling cascades.

1. Our goal in this study was to evaluate the effect of haemodynamic overload on cross-bridge (XBr) kinetics in the rabbit heart independently of myosin heavy chain (MHC) isoforms, which are known to modulate kinetics in small mammals. We applied a myothermal-mechanical protocol to isometrically contracting papillary muscles from two rabbit heart populations: (1) surgically induced right ventricular pressure overload (PO), and (2) sustained treatment with propylthiouracil (PTU). Both treatments resulted in a 100 % V3 MHC profile. 2. XBr force-time integral (FTI), evaluated during the peak of the twitch from muscle FTI and tension-dependent heat, was greater in the PO hearts (0.80 +/- 0.10 versus 0.45 +/- 0.05 pN s, means +/- S.E.M., P = 0.01). 3. Within the framework of a two-state XBr model, the PO XBr developed more force while attached (5.8 +/- 0.9 versus 2.7 +/- 0.3 pN), with a lower cycling rate (0.89 +/- 0.10 versus 1.50 +/- 0.14 s(-1)) and duty cycle (0.14 +/- 0.03 versus 0.24 +/- 0.02). 4. Only the ventricular isoforms of myosin light chain 1 and 2 and cardiac troponin I (cTnI) were expressed, with no difference in cTnI phosphorylation between the PO and PTU samples. The troponin T (TnT) isoform compositions in the PO and PTU samples were significantly different (P = 0.001), with TnT2 comprising 2.29 +/- 0.03 % in PO hearts versus 0.98 +/- 0.01 % in PTU hearts of total TnT. 5. This study demonstrates that MHC does not mediate dramatic alterations in XBr function induced by haemodynamic overload. Our findings support the likelihood that differences among other thick and thin filament proteins underlie these XBr alterations.

A series of analogs of tipifarnib (1) has been synthesized as inhibitors of FTase by substituting the benzimidazolones and indoles for the 2-quinolone of tipifarnib. The novel benzimidazolones are potent and selective FTase inhibitors (FTIs) with IC(50) values of the best compounds close to that of tipifarnib. The current series demonstrate good cellular activity as measured in their inhibiting the Ras processing in NIH-3T3 cells, with compounds 2c and 2f displaying EC(50) values of 18 and 22nM, respectively.

BACKGROUND

Ras activation by mutation, overexpression, or receptor signaling can increase tumor cell survival after irradiation.

METHODS

We examined whether inhibiting Ras activity with farnesyltransferase inhibitors (FTI) altered the radiosensitivity and tumor micro-environment in prostate tumors.

RESULTS

Treatment with FTIs L-744,832 or FTI-277 reduced clonogenic survival of prostate tumor cells expressing oncogenic H-ras after irradiation. PI3-kinase/Akt and MAPK signaling pathways were downregulated by FTIs in these cells. FTI treatment reduced tumor hypoxia and also reduced MMP-9 expression in tumors with activated mutant H-ras. FTI treatment did not, however, increase apoptosis in irradiated intestine, demonstrating that acute radiation injury of this normal tissue was not enhanced by FTIs.

CONCLUSIONS

FTIs can enhance the killing of prostate tumors with activated H-Ras. Together with the absence of increased acute toxicity to normal bowel, these results imply that FTI treatment should be further studied as a possible adjuvant to radiotherapy in the treatment of abdominal cancers with activated Ras signaling.

The xylitol productivity increased by about 15% with the use of cells of Candida guilliermondii FTI 20037 previously recycled through four consecutive batch cultures and adapted to the sugar cane bagasse hemicellulosic hydrolysate. Furthermore, the more concentrated the hydrolysate, the more necessary was the adaptation of the cells, owing to the presence of toxic substances at high concentration which inhibited the xylose-xylitol conversion by the yeast.

The M1 serotype of Streptococcus pyogenes plays an important role in streptococcal toxic shock syndrome. Simvastatin, a 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase inhibitor, has been shown to inhibit streptococcal M1 protein-induced acute lung damage, although downstream mechanisms remain elusive. Protein isoprenylation, such as farnesylation and geranylgeranylation, has been suggested to regulate anti-inflammatory effects exerted by statins. Here, we examined the effect of a farnesyltransferase inhibitor (FTI-277) on M1 protein-triggered lung inflammation. Male C57BL/6 mice were treated with FTI-277 prior to M1 protein challenge. Bronchoalveolar fluid and lung tissue were harvested for quantification of neutrophil recruitment, edema, and CXC chemokine formation. Flow cytometry was used to determine Mac-1 expression on neutrophils. The gene expression of CXC chemokines was determined in alveolar macrophages by using quantitative reverse transcription (RT)-PCR. We found that the administration of FTI-277 markedly decreased M1 protein-induced accumulation of neutrophils, edema formation, and tissue damage in the lung. Notably, inhibition of farnesyltransferase abolished M1 protein-evoked production of CXC chemokines in the lung and gene expression of CXC chemokines in alveolar macrophages. Moreover, FTI-277 completely inhibited chemokine-induced neutrophil migration in vitro. However, farnesyltransferase inhibition had no effect on M1 protein-induced expression of Mac-1 on neutrophils. Our findings suggest that farnesyltransferase is a potent regulator of CXC chemokine formation in alveolar macrophages and that inhibition of farnesyltransferase not only reduces neutrophil recruitment but also attenuates acute lung injury provoked by streptococcal M1 protein. We conclude that farnesyltransferase activity is a potential target in order to attenuate acute lung damage in streptococcal infections.

A characteristic thyroid test profile is observed in pregnancy; it consists of an elevated serum thyroxine (T4I), thyroxine binding globulin (TBG) and electrophoretic index (EI) with lowered triiodothyronine resin uptake (T3U), the free thyroxine index (FTI) remaining in the normal range. An investigation was made of progressive changes in these parameters in 70 normal pregnant women, 34 pregnant women with a past history of habitual abortion who carried to term, seven habitual aborters who miscarried again, and 49 women at the time of spontaneous miscarriage. The results indicated that normal women reached a typical pregnancy thyroid test profile at seven to eight weeks' gestation while habitual aborters carrying a pregnancy to term reached it at 14 to 15 weeks and almost all patients who miscarried never reached it at all. In addition, four women who had aborted previously and were treated with thyroxine throughout six pregnancies, developed a normal "thyroid profile" and carried their pregnancy to term. The significance of the "predictive value" of the test profile is discussed.

Basal TSH levels and the TSH response to TRH have been evaluated in 26 males aged 20-48 years with primary testicular failure, and 6 males aged 58-69 years who had been orchidectomised for prostatic carcinoma. The patients with testicular failure were sequentially challenged at 30 min intervals with iv LRH (100 microgram), TRH (200 microgram) and the dopaminergic antagonist, metoclopramide (10 mg). The castrates received a bolus of LRH and TRH given together. The responses in the 2 patient groups were compared to a group of 28 healthy male controls aged 20-40 years, who received the sequential protocol and 8 elderly controls aged 65-79 years, who were given the LRH, TRH bolus. Mean +/- SD basal TSH levels were 3.0 +/- 1.2 muU/ml in primary testicular failure and significantly greater than both control and castrate groups. The peak TSH response to TRH was 18.4 +/- 7.4 muU/ml in testicular failure and significantly greater than in the young controls, where it was 11.5 +/- 5.0 muU/ml. The peak levels in the castrates and in the elderly controls were similar to the young male controls. Total T4 and T3, as well as FTI, primary testicular failure had a reduction in their T3 resin uptake. The normal TSH profile in the castrates indicates that a testicular factor produces the exaggerated responses in primary testicular failure.

Tipifarnib, a farnesyltransferase inhibitor (FTI), was initially designed to disrupt RAS farnesylation and membrane localization necessary for RAS function. However, alternative geranylgeranylation has been postulated as an escape mechanism by which RAS bypasses the effect of FTI treatment. In this study, we demonstrate that simvastatin, an HMG-CoA reductase inhibitor, augments the cytotoxic effect of tipifarnib by blocking the alternative geranylgeranylation of RAS. Notably, this effect was accompanied by disruption of RAS membrane localization and ERK downregulation. In addition, the apoptotic effect of this combination was associated with downregulation of the antiapoptotic Mcl-1 protein and activation of the caspase cascade. These findings demonstrate that combining tipifarnib and simvastatin was successful in targeting RAS/ERK signaling and inducing apoptosis in leukemia cells. Both simvastatin and tipifarnib were used at clinically achievable doses, which make the combination promising for future clinical studies.

Thyroid function was assessed at the time of initial diagnosis in 204 patients with lung cancer and compared with that of age and sex-matched patients with non-malignant lung disease. Abnormalities in thyroid function were found in 67 patients (33%). The most prevalent abnormality was a low T3 concentration; this was not associated with other clinical or biochemical evidence of hypothyroidism, but the short-term prognosis of these patients was worse than that of matched patients with lung cancer having normal T3 concentrations. Primary hypothyroidism occurred in three patients, low T4 concentrations and free thyroxine index (FTI) with normal thyrotrophin (TSH) concentrations in four patients, and moderately raised TSH with normal thyroid hormone concentrations in six patients; nine patients had a raised FTI with or without raised T4 concentration as the sole abnormality.Overall, the pattern of thyroid hormone metabolism in lung cancer was a tendency towards reduced T3 concentrations with significantly increased T4/T3 ratios and modestly increased 3,3',5'-triiodothyronine (rT3) concentrations. The altered T4/T3 ratio was particularly noticeable in patients with anaplastic tumours of small ("oat cell") and large cell types, but was not apparently related to detectable extrathoracic metastases.These data suggest that thyroid hormone metabolism is altered in patients with lung cancer by decreased 5'-monodeiodination of T4. The resulting low T3 concentrations and altered T4/T3 ratio may be partly responsible for the reduced ratio of androsterone to aetiocholanolone observed in lung cancer, which is known to be a poor prognostic sign.

Farnesyltransferase inhibitors (FTIs) block the growth of tumor cells in vitro and in vivo with minimal toxicity toward normal cells. In general, inhibition of protein farnesylation results in G0/G1 cell cycle block, G2/M cell cycle arrest, or has no effect on cell cycle progression. One aspect of FTI biology that is poorly understood is the ability of these drugs to induce cancer cell growth arrest at the G2/M phase of cell cycle. In the present study, we investigated the effects of the farnesyltransferase inhibitor FTI-277 on two human liver cancer cell lines, HepG2 and Huh7. Treatment of these cells with FTI-277 inhibited Ras farnesylation in a dose-dependent manner. Both HepG2 and Huh7 cell growth was inhibited by FTI-277 and cells accumulated at the G2/M phase of the cell cycle. In HepG2 and Huh7 cells, FTI-277 induced an up-regulation of the cyclin-dependent kinase inhibitor p27(Kip1) without affecting the cellular levels of p53 and p21(Waf1). This event correlated with reduced activity of the cyclin-dependent kinase 2 and cyclin-dependent kinase 1. Moreover, increased expression of Bcl-2 protein was observed in HepG2 and Huh7 cells treated with FTI-277, and this was coincidental with reduced association between Raf-1 and Bcl-2. Finally, transient transfection of a dominant-negative Ras allele induced Bcl-2 expression and reduced Bcl-2/Raf-1 association demonstrating a requirement for Ras. Taken together, these findings show that increased expression of p27(Kip1) and Bcl-2 is concomitant with altered association between Ras, Raf-1 and Bcl-2 and suggest that this is responsible for the growth-inhibitory properties of FTI-277.

Objectives: To compare one-year freedom from atrial arrhythmia, complication rates, procedural times, and pulmonary vein (PV) reconnection patterns with high-power, short-duration (HPSD) atrial fibrillation (AF) ablation versus an FTI-guided low-power, long-duration (LPLD) strategy.

Background: The effectiveness, safety, and PV reconnection patterns of point-by-point HPSD ablation relative to conventional force-time integral (FTI)-guided strategies for AF are unknown.

Methods: We compared consecutive patients undergoing a first ablation procedure for paroxysmal or persistent AF. The HPSD protocol utilized a power of 50W and durations of 6-8 seconds posteriorly and 8-10 seconds anteriorly. The LPLD protocol was FTI-guided with a power of ≤25W posteriorly (FTI≥300g.s) and ≤35W anteriorly (FTI≥400g.s).

Results: 214 patients were prospectively included (107 HPSD, 107 LPLD). Freedom from AA at one-year was achieved in 79% in the HPSD group versus 73% in the LPLD group (p=0.339; adjusted hazard ratio with HPSD, 0.67; 95% confidence interval, 0.36-1.23; p<0.004 for non-inferiority). Procedure duration was shorter in the HPSD group (229±60 vs 309±77 minutes, p<0.005). Patients undergoing repeat ablation had a higher propensity for reconnection at the right PV carina in the HPSD group compared to the LPLD group (14/30=46.7% vs. 7/34=20.6%, p=0.035). There were no differences in complication rates.

Conclusion: HPSD AF ablation resulted in similar freedom from AAs at one-year, shorter procedure times, and a similar safety profile when compared to a LPLD ablation strategy. Patients undergoing HPSD ablation required more applications at the right carina to achieve isolation, and had a significantly higher rate of right carinal reconnections at redo procedures. This article is protected by copyright. All rights reserved.

Keywords: Atrial fibrillation ablation; high-power short-duration ablation; pulmonary vein reconnection patterns.

The mean values of serum thyroxine (T4), in vitro radioactive triiodothyronine uptake and free-thyroxine index (FTI) in 41 drug-free schizophrenic patients did not differ significantly from those of euthyroid controls. Following 6 weeks' treatment of 24 schizophrenics with chlorpromazine, trifluoperazine or clozapine, a significant decrease in serum T4 and FTI was noted after chlorpromazine and clozapine, whereas after trifluoperazine only serum T4 decreased, but not FTI. The questions arising from these findings are discussed and the need for a future investigation of serum triiodothyronine and serum TSH in schizophrenic patients before and after neuroleptic treatment is stressed.

The rate of introduction of new pharmaceuticals is growing as a result of advances in molecular pharmacology and targeted drug development. The Fatal Toxicity Index (FTI) has been proposed as a means for monitoring drug toxicity through post-marketing surveillance. The FTI requires data regarding the general availability of a particular agent in the community which, in the US, is proprietary. The authors propose a Mortality Index as an alternative method for calculating relative lethality that does not rely on proprietary information for postmarketing surveillance. Using data from the Toxic Exposure Surveillance System (TESS) a Mortality Index was calculated from the proportion of deaths occurring among all patients who present to a health care facility with an overdose on the same agent or class of agents. The average Mortality Index for various drugs or drug classes for the years 1989 to 1997 is reported. Because the Mortality Index for desipramine appeared much greater than that for the other tricyclics, a chi-squared analysis was performed. The authors conclude, based on this analysis, that desipramine is significantly more likely to lead to death after overdosage than any other tricyclic antidepressant in the study. Also, the Mortality Index appeared to identify the impact of pediatric formulations on overdose lethality. We conclude that the Mortality Index may be a useful tool for determining the safety of agents during the postmarketing surveillance phase.

Farnesyl protein transferase inhibitors (FTIs) represent a new class of anticancer agents specifically targeting aberrant biologic processes involved with cellular transformation and malignancy. Originally developed to inhibit tumors by preventing activation of oncogenic ras genes via suppression of their posttranslational farnesylation, their anticancer activity appears to stem from their ability to inhibit farnesylation of various proteins that mediate signal transduction, growth, apoptosis, and angiogenesis. The safety, biologic activity, clinical response, and pharmacokinetics of R115777, a potent, orally active FTI, were recently investigated in a phase I dose-ranging study in patients with acute leukemias. Patients with acute myelogenous leukemia (AML), acute lymphocytic leukemia (ALL), or chronic myelogenous leukemia (CML) in blast crisis received R115777 100 mg, 300 mg, 600 mg, 900 mg, or 1,200 mg twice daily for 21 days. Cycles were repeated every 28 to 31 days for up to four cycles. An overall response rate of 29% (10/34 evaluable patients) was observed across all R115777 doses. R115777 was well tolerated; common adverse events included fatigue, increased creatinine, nausea, and neutropenia. Dose-limiting toxicity occurred at 1,200 mg twice daily. Farnesylation of lamin A and HDJ-2, examined as biologic end points, was inhibited by R115777 doses>> or = 600 mg twice daily. Pharmacokinetic evaluation suggests that R115777 is concentrated in bone marrow at steady state. The biologic and antitumor activity and favorable tolerability of R115777 support further clinical evaluation alone and in combination therapy in hematologic malignancies.

Ras oncogenes can contribute to tumour development by stimulating vascular endothelial growth factor (VEGF)-dependent angiogenesis. The effect of Ras on angiogenesis may be affected by farnesyltransferase inhibitors (FTI) since farnesylation of Ras is required for its biological activity. In this paper we evaluated the effect of A-170634, a novel and potent CAAX FTI on angiogenesis. Human umbilical vein endothelial cell (HUVEC) tube formation and VEGF secretion were used to assess the effect of A-170634 on angiogenesis in vitro. In vivo, nude mice were injected with the K-ras mutant colon carcinoma cell line HCT116 and treated subcutaneously with A-170634 using osmotic minipump infusion for 10 days. The effect of A-170634 on corneal angiogenesis in vivo was assessed using pellets containing hydron, VEGF, A-170634 or vehicle. In vitro, A-170634 selectively inhibited farnesyltransferase activity over the closely related geranylgeranyltransferase I, inhibited Ras processing, blocked anchorage-dependent and -independent growth of HCT116 K-ras mutated cells, decreased HUVEC capillary structure formation, decreased VEGF secretion from tumour cells and HUVEC growth stimulating activity in a dose-dependent manner. In vivo, tumour growth was decreased by 30% and vascularisation in and around the tumours was reduced by 41% following drug-treatment with no apparent toxicity to the animals. VEGF-induced corneal neovascularisation was reduced by 80% following A-170634 treatment for 7 days. The data presented here demonstrated that A-170634 was a potent and selective peptidomimetic CAAX FTI with anti-angiogenic properties. These results implied that A-170634 may affect tumour growth in vivo by one or more antitumour pathways.

Farnesyltransferase inhibitors (FTIs) belong to a group of agents originally designed to prevent membrane attachment of Ras protein by inhibiting a key step in its post-translational processing. It was thus hypothesized that FTIs would curtail the oncogenic ras-mediated proliferative and antiapoptotic signals that are activated in human tumors. Although the Ras protein is mutated in only < 5% of breast cancers, there are multiple aberrant pathways that lead to activation of wild-type ras signaling. Moreover, FTIs have consistently demonstrated efficacy in tumors regardless of their ras mutational status. Thus, the role of other protein targets in mediating the antitumor effect of FTIs is being elucidated. This article reviews current data on the use of FTIs in breast cancer.

Lonafarnib is a potent, selective farnesyltransferase inhibitor (FTI) undergoing clinical studies for the treatment of solid tumors and hematological malignancies. Preclinically, a number of FTIs, including lonafarnib, interact with taxanes to inhibit cancer cell growth in an additive/synergistic manner. These observations provided rationale for investigating the effects of combining lonafarnib and docetaxel on preclinical prostate cancer models. To date, docetaxel is the only chemotherapeutic agent in clinical use for hormone-refractory prostate cancer. In vitro experiments with 22Rv1, LNCaP, DU-145, PC3 and PC3-M prostate cancer cell lines showed significantly enhanced inhibition of cell proliferation and apoptosis when lonafarnib was added to docetaxel. In human tumor xenograft models, continuous coadministration of lonafarnib with docetaxel caused marked tumor regressions (24-47%) in tumors from all of the cell types as well as parental CWR22 xenografts. Intermittent dosing of lonafarnib (5 days on then 5 days off) coadministered with docetaxel produced similar regressions in hormone-refractory 22Rv1 tumors. 22Rv1 tumors progressing on docetaxel treatment also responded to treatment with intermittent lonafarnib (5 days on then 5 days off). Moreover, animals did not exhibit any signs of toxicity during coadministration of lonafarnib and docetaxel. In conclusion, coadministration of continuous and intermittent lonafarnib enhanced the antitumor activity of docetaxel in a panel of prostate cancer models. An intermittent dosing schedule of lonafarnib coadministered with docetaxel may allow enhanced efficacy to that of continuous dosing by improving the tolerability of higher doses of lonafarnib.

Ras mutation has been detected in approximately 20-30% of all human carcinomas, primarily in pancreatic, colorectal, lung and bladder carcinomas. The indirect inhibition of Ras activity by inhibiting farnesyltransferase (FTase) function is one therapeutic intervention to control tumor growth. Here we report the preclinical anti-tumor activity of our most advanced FTase inhibitor (FTI), ABT-100, and a direct comparison with the current clinical candidates. ABT-100 is a highly selective, potent and orally bioavailable FTI. It broadly inhibits the growth of solid tumors in preclinical animal models. Thus, ABT-100 is an attractive candidate for further clinical evaluation. In addition, our results provide plausible insights to explain the impressive potency and selectivity of ABT-100. Finally, we have demonstrated that ABT-100 significantly suppresses the expression of vascular endothelial growth factor (VEGF) mRNA and secretion of VEGF protein, as well as inhibiting angiogenesis in the animal model.