A phase II trial of R115777, an oral farnesyl transferase inhibitor, in patients with advanced urothelial tract transitional cell carcinoma

Landscape of targeted therapies for advanced urothelial carcinoma

Bladder cancer (BC) is the tenth most common malignancy globally. Urothelial carcinoma (UC) is a major type of BC, and advanced UC (aUC) is associated with poor clinical outcomes and limited survival rates. Current options for aUC treatment mainly include chemotherapy and immunotherapy. These options have moderate efficacy and modest impact on overall survival and thus highlight the need for novel therapeutic approaches. aUC patients harbor a high tumor mutation burden and abundant molecular alterations, which are the basis for targeted therapies. Erdafitinib is currently the only Food and Drug Administration (FDA)-approved targeted therapy for aUC. Many potential targeted therapeutics aiming at other molecular alterations are under investigation. This review summarizes the current understanding of molecular alterations associated with aUC targeted therapy. It also comprehensively discusses the related interventions for treatment in clinical research and the potential of using novel targeted drugs in combination therapy.

Targeting HRAS in Head and Neck Cancer: Lessons From the Past and Future Promise

ABSTRACT

HRAS mutations define a unique biologic subset of head and neck squamous cell carcinoma. Oncogenic HRAS is uniquely dependent on posttranslational farnesylation for membrane localization and activation of downstream signaling. Tipifarnib, a farnesyltransferase inhibitor, demonstrated encouraging antitumor activity for HRAS mutant head and neck squamous cell carcinoma and modest activity for HRAS mutant salivary gland cancer. New combination strategies to circumvent intrinsic and acquired resistance to TFIs are being investigated.

Biology, pathology, and therapeutic targeting of RAS

RAS was identified as a human oncogene in the early 1980s and subsequently found to be mutated in nearly 30% of all human cancers. More importantly, RAS plays a central role in driving tumor development and maintenance. Despite decades of effort, there remain no FDA approved drugs that directly inhibit RAS. The prevalence of RAS mutations in cancer and the lack of effective anti-RAS therapies stem from RAS' core role in growth factor signaling, unique structural features, and biochemistry. However, recent advances have brought promising new drugs to clinical trials and shone a ray of hope in the field. Here, we will exposit the details of RAS biology that illustrate its key role in cell signaling and shed light on the difficulties in therapeutically targeting RAS. Furthermore, past and current efforts to develop RAS inhibitors will be discussed in depth.

A Phase II Trial of Tipifarnib for Patients with Previously Treated, Metastatic Urothelial Carcinoma Harboring HRAS Mutations

PURPOSE

To assess the antitumor activity and safety of tipifarnib, a highly potent and selective farnesyltransferase inhibitor, we performed a phase II clinical trial in patients with advanced and refractory urothelial carcinoma harboring missense HRAS mutations.

PATIENTS AND METHODS

A total of 245 adult patients with previously treated, advanced urothelial carcinoma entered the molecular screening program including HRAS. Those with missense HRAS mutations or STK11:rs2075606 received oral tipifarnib 900 mg twice daily on days 1-7 and 15-21 of 28-day treatment cycles. The primary endpoint was progression-free survival at 6 months (PFS6).

RESULTS

We identified 16 (7%) missense HRAS mutations (G13R, 7; Q61R, 4; G12S, 3; G12C, 2) and 104 (46%) STK11:rs2075606 carriers. In 21 patients enrolled in the study, 14 and 7 patients had missense HRAS mutations and STK11:rs2075606, respectively. The most frequently observed adverse events included fatigue (86%) and hematologic toxicities. With a median follow-up of 28 months, 4 patients (19%) reached PFS6: 3 had missense HRAS mutations and one patient, enrolled as an STK11 carrier, had HRAS frameshift insertions at H27fs and H28fs rendering a nonsense HRAS mutation. The overall response rate by intent-to-treat analysis was 24% (4 missense and one nonsense frameshift HRAS mutation); no response was observed in patients with urothelial carcinoma with wild-type HRAS tumors. Five responses were observed in 12 evaluable patients of 15 with tumors carrying HRAS mutations.

CONCLUSIONS

Oral tipifarnib resulted in a manageable safety profile and encouraging antitumor efficacy against treatment-refractory urothelial carcinoma containing HRAS mutations.

Effectiveness of durvalumab versus chemotherapy in metastatic urothelial cancer: an observational, indirect comparison

Aim: To compare the overall survival of patients with metastatic urothelial carcinoma (mUC) who failed platinum-based chemotherapy and received durvalumab or chemotherapy. Patients & methods: In an indirect comparison of patients with mUC who failed platinum-based chemotherapy, those who received durvalumab in a single-arm study were matched to patients from the Flatiron oncology electronic medical record database who received chemotherapy (n = 158 for each cohort). Matching was based on propensity scores. Kaplan-Meier methods and Cox regression models were utilized. Results: Median overall survival was 11.2 months (95% CI: 7.2-16.9) for durvalumab versus 8.2 months (95% CI: 6.7-9.8) for chemotherapy (hazard ratio: 0.63; 95% CI: 0.48-0.84). Conclusion: As a second-line therapy for mUC, durvalumab was associated with longer overall survival than chemotherapy.

Low-Dose Farnesyltransferase Inhibitor Suppresses HIF-1α and Snail Expression in Triple-Negative Breast Cancer MDA-MB-231 Cells In Vitro

The aggressiveness of triple-negative breast cancer (TNBC), which lacks estrogen receptor, progesterone receptor and epidermal growth factor receptor 2 (HER2), represents a major challenge in breast cancer. Migratory and self-renewal capabilities are integral components of invasion, metastasis and recurrence of TNBC. Elevated hypoxia-inducible factor-1α (HIF-1α) expression is associated with aggressiveness of cancer. Nonetheless, how HIF-1α expression is regulated and how HIF-1α induces aggressive phenotype are not completely understood in TNBC. The cytotoxic effects of farnesyltransferase (FTase) inhibitors (FTIs) have been studied in cancer and leukemia cells. In contrast, the effect of FTIs on HIF-1α expression has not yet been studied. Here, we show that clinically relevant low-dose FTI, tipifarnib (300 nM), decreased HIF-1α expression, migration and tumorsphere formation in human MDA-MB-231 TNBC cells under a normoxic condition. In contrast, the low-dose FTIs did not inhibit cell growth and activity of the Ras pathway in MDA-MB 231 cells. Tipifarnib-induced decrease in HIF-1α expression was associated with amelioration of the Warburg effect, hypermetabolic state, increases in Snail expression and ATP release, and suppressed E-cadherin expression, major contributors to invasion, metastasis and recurrence of TBNC. These data suggest that FTIs may be capable of ameliorating the aggressive phenotype of TNBC by suppressing the HIF-1α-Snail pathway. J. Cell. Physiol. 232: 192-201, 2017. © 2016 Wiley Periodicals, Inc.

Molecular biology and targeted therapies for urothelial carcinoma

Metastatic urothelial cancer (UC) is associated with poor prognosis. In the first-line setting, platinum-based chemotherapy is the standard of care but resistance rapidly occurs. With no validated treatment proven to increase survival after platinum failure, there is an urgent unmet medical need to develop new and efficacious cytotoxic agents. A better understanding of the molecular signaling pathways regulating UC has led to the development of new and innovative therapeutic strategies. Despite this, many recent drugs show only modest activity as single agents, and combining them with standard chemotherapy does not seem to enhance efficacy. Ongoing research is producing, however, a generation of new drugs that are showing promising results in clinical trials. This paper aims to review the most important mechanisms in bladder cancer tumorigenesis and describe the new therapeutic options currently undergoing evaluation in clinical trials.

Six-month progression-free survival as the primary endpoint to evaluate the activity of new agents as second-line therapy for advanced urothelial carcinoma

OBJECTIVE

Second-line systemic therapy for advanced urothelial carcinoma (UC) has substantial unmet needs, and current agents show dismal activity. Second-line trials of metastatic UC have used response rate (RR) and median progression-free survival (PFS) as primary endpoints, which may not reflect durable benefits. A more robust endpoint to identify signals of durable benefits when investigating new agents in second-line trials may expedite drug development. PFS at 6 months (PFS6) is a candidate endpoint, which may correlate with overall survival (OS) at 12 months (OS12) and may be applicable across cytostatic and cytotoxic agents.

METHODS

Ten second-line phase II trials with individual patient outcomes data evaluating chemotherapy or biologics were combined for discovery, followed by external validation in a phase III trial. The relationship between PFS6/RR and OS12 was assessed at the trial level using Pearson correlation and weighted linear regression, and at the individual level using Pearson chi-square test with Yates continuity correction.

RESULTS

In the discovery dataset, a significant correlation was observed between PFS6 and OS12 at the trial (R(2) = 0.55, Pearson correlation = 0.66) and individual levels (82%, Қ = 0.45). Response correlated with OS12 at the individual level less robustly (78%, Қ = 0.36), and the trial level association was not statistically significant (R(2) = 0.16, Pearson correlation = 0.37). The correlation of PFS6 (81%, Қ = 0.44) appeared stronger than the correlation of response (76%, Қ = 0.17) with OS12 in the external validation dataset.

CONCLUSIONS

PFS6 is strongly associated with OS12 and appears more optimal than RR to identify active second-line agents for advanced UC.

A molecular taxonomy for urothelial carcinoma

PURPOSE

Even though urothelial cancer is the fourth most common tumor type among males, progress in treatment has been scarce. A problem in day-to-day clinical practice is that precise assessment of individual tumors is still fairly uncertain; consequently efforts have been undertaken to complement tumor evaluation with molecular biomarkers. An extension of this approach would be to base tumor classification primarily on molecular features. Here, we present a molecular taxonomy for urothelial carcinoma based on integrated genomics.

EXPERIMENTAL DESIGN

We use gene expression profiles from 308 tumor cases to define five major urothelial carcinoma subtypes: urobasal A, genomically unstable, urobasal B, squamous cell carcinoma like, and an infiltrated class of tumors. Tumor subtypes were validated in three independent publically available data sets. The expression of 11 key genes was validated at the protein level by immunohistochemistry.

RESULTS

The subtypes show distinct clinical outcomes and differ with respect to expression of cell-cycle genes, receptor tyrosine kinases particularly FGFR3, ERBB2, and EGFR, cytokeratins, and cell adhesion genes, as well as with respect to FGFR3, PIK3CA, and TP53 mutation frequency. The molecular subtypes cut across pathologic classification, and class-defining gene signatures show coordinated expression irrespective of pathologic stage and grade, suggesting the molecular phenotypes as intrinsic properties of the tumors. Available data indicate that susceptibility to specific drugs is more likely to be associated with the molecular stratification than with pathologic classification.

CONCLUSIONS

We anticipate that the molecular taxonomy will be useful in future clinical investigations.

A phase I multicenter study of continuous oral administration of lonafarnib (SCH 66336) and intravenous gemcitabine in patients with advanced cancer

We conducted a phase I study to assess safety, pharmacokinetics, pharmacodynamics, and activity of lonafarnib plus gemcitabine. Subjects received oral lonafarnib twice daily and gemcitabine on days 1, 8, and 15 every 28 days; multiple dose levels were explored. Lonafarnib had no apparent effect on gemcitabine PK. Mean lonafarnib half-life ranged from 4 to 7 hr; median T(max) values ranged from 4 to 8 hr. Two patients had partial response; seven patients had stable disease at least 6 months. Oral lonafarnib at 150 mg a.m./100 mg p.m. plus gemcitabine at 1,000 mg/m(2) is the maximum tolerated dose with acceptable safety and tolerability.

Advanced bladder cancer: new agents and new approaches. A review

OBJECTIVE

The aim of the present paper is to review findings from the most relevant studies and evaluate the potential of new drugs in treatment of metastatic urothelial cancer.

METHODS

Studies were identified by searching MEDLINE and Pubmed databases up to 2009 using both medical subject heading (Mesh) and a free text strategy with the name of known individual chemotherapeutic drug and the following key words: 'muscle-invasive bladder cancer', 'urothelial/transitional carcinoma', 'chemotherapeutics drugs and agents'. At the end of our research in literature we selected 63 articles and we have considered only studies in which almost 30 patients were enrolled.

RESULTS

Radical cystectomy with pelvic lymph node dissection is the gold standard of treatment for clinically localized muscle-invasive bladder cancer. While more extensive lymph node dissection may have both prognostic and therapeutic significance, effective systemic therapies that eliminate micrometastases may improve outcome. Perioperative chemotherapy can be administered before (neoadjuvant) or after (adjuvant) cystectomy to eradicate subclinical disease and to improve survival.

CONCLUSION

The challenge remains as to how to integrate all of the relevant knowledge and data in a systematic manner so that researchers can gain the knowledge needed to devise the best therapeutic and diagnostic strategies. Future improvements in the treatment of advanced bladder cancer will rely not only on the optimization of currently available cytotoxic agents but also on the biologic profile of individual patient tumors and the appropriate therapies that target molecular aberrations unique to this malignancy.

Therapeutic modulation of k-ras signaling in colorectal cancer

KRAS has an important role in colorectal carcinogenesis and mutant KRAS leads to a permanently activated k-ras protein. To exert its biological activity, k-ras requires post-translational modification by prenylation. K-ras modulation has become a promising concept for new therapies, mostly by interference with the mevalonate pathway and subsequently by the prenylation of k-ras. Clinical data of agents interfering with the mevalonate pathway and the prenylation of ras are summarized and suggest that these agents might be effective when administered in combination with anticancer drugs that target k-ras. Here, we discuss the novel concept that modulation of k-ras might potentiate EGFR therapy by altering the KRAS phenotype.

Emerging targeted therapies for bladder cancer: a disease waiting for a drug

Urothelial cell carcinoma is the fifth most common cancer and the costliest to treat. This is largely because of all new cases, about 70% present as superficial disease and this while rarely fatal, tends to recur, requiring long-term follow-up and repeat interventions. The standard of care, intravesical chemo- and immunotherapy, while effective, is associated with a considerable side-effect profile and approximately 30% of patients either fail to respond to treatment or suffer recurrent disease within 5 years. Muscle-invasive bladder cancer is life threatening, showing modest chemosensitivity, and usually requires radical cystectomy. Although bladder cancer is fairly well-genetically characterized, clinical trials with molecularly targeted agents have, in comparison to other solid tumors such as lung, breast and prostate, been few in number and largely unsuccessful, with no new agents being registered in the last 20 years. Hence, bladder cancer represents a considerable opportunity and challenge for molecularly targeted therapy.

Preclinical in vivo evaluation of rapamycin in human malignant peripheral nerve sheath explant xenograft

Neurofibromatosis type 1 (NF1) patients are prone to the development of malignant tumors, the most common being Malignant Peripheral Nerve Sheath Tumor (MPNST). NF1-MPNST patients have an overall poor survival due to systemic metastasis. Currently, the management of MPNSTs includes surgery and radiation; however, conventional chemotherapy is not very effective, underscoring the need for effective biologically-targeted therapies. Recently, the NF1 gene product, neurofibromin, was shown to negatively regulate the phosphoinositide-3-kinase (PI3K)/Protein Kinase-B (Akt)/mammalian Target Of Rapamycin (mTOR) pathway, with loss of neurofibromin expression in established human MPNST cell lines associated with high levels of mTOR activity. We developed and characterized a human NF1-MPNST explant grown subcutaneously in NOD-SCID mice, to evaluate the effect of the mTOR inhibitor rapamycin. We demonstrate that rapamycin significantly inhibited human NF1-MPNST mTOR pathway activation and explant growth in vivo at doses as low as 1.0 mg/kg/day, without systemic toxicities. While rapamycin was effective at reducing NF1-MPNST proliferation and angiogenesis, with decreased CyclinD1 and VEGF respectively, there was no increase in tumor apoptosis. Rapamycin effectively decreased activation of S6 downstream of mTOR, but there was accompanied increased Akt activation. This study demonstrates the therapeutic potential and limitations of rapamycin in NF1-associated, and likely sporadic, MPNSTs.

Management of bladder cancer: current and emerging strategies

Cancer of the urinary bladder is the fifth most prevalent solid tumour in the US. Urothelial carcinoma is the most common form of bladder cancer, accounting for about 90% of cases. About 25% of patients with bladder cancer have advanced disease (muscle-invasive or metastatic disease) at presentation and are candidates for systemic chemotherapy. Urothelial carcinoma is a chemo-sensitive disease, with a high overall and complete response rate to combination chemotherapy. In the setting of muscle-invasive urothelial carcinoma, use of neoadjuvant chemotherapy is associated with overall survival benefit. The role of adjuvant chemotherapy in this setting is yet to be validated. In the setting of metastatic disease, use of cisplatin-based regimens improves survival. However, despite initial high response rates, the responses are typically not durable leading to recurrence and death in the vast majority of these patients. Currently, there is no standard second-line therapy for patients in whom first-line chemotherapy for metastatic disease has failed. Many newer chemotherapeutic agents have shown modest activity in urothelial carcinoma. Improved understanding of molecular biology and pathogenesis of urothelial carcinoma has opened avenues for the use of molecularly targeted therapies, several of which are being tested in clinical trials. Currently, several novel drugs seem particularly promising including inhibitors of the epidermal growth factor receptor pathway, such as cetuximab, and inhibitors of tumour angiogenesis, such as bevacizumab and sunitinib. Development of reliable molecular predictive markers is expected to improve treatment decisions, therapy development and outcomes in urothelial carcinoma. Funding of and participation in clinical trials are key to advancing the care of urothelial cancer patients. Current and emerging strategies in the medical management of urothelial carcinoma are reviewed.

Novel therapeutics in metastatic bladder cancer

BACKGROUND

Albeit transitional cell carcinoma of the urinary bladder is a chemosensitive neoplasm, metastatic disease is related with poor prognosis and short-term survival data.

OBJECTIVE

Cisplatin-based combination chemotherapy is recognised as the golden standard therapy for patients with inoperable locally advanced or metastatic bladder cancer. However, owing to treatment-related toxicities and short-response durations, novel treatment options or agents, with both enhanced efficacy and tolerability, have been sought.

METHODS

Reviewing the current status and addressing the future of novel anticancer therapeutics in metastatic urinary bladder cancer.

RESULTS/CONCLUSION

Non-platinum, single agents, such as gemcitabine and taxanes, as well as multidrug regimens in doublet or triplet chemotherapeutic combinations are regarded as promising alternatives. Dose intensification of conventional regimens, dose-dense sequential administration of new agents, the use of molecular markers for predicting chemosensitivity and the integration of biologically targeted agents to enhance chemotherapeutic efficacy are promising approaches.

Phase I and pharmacokinetic study of the oral farnesyltransferase inhibitor lonafarnib administered twice daily to pediatric patients with advanced central nervous system tumors using a modified continuous reassessment method: a Pediatric Brain Tumor Consortium Study

PURPOSE

A dose-escalation phase I and pharmacokinetic study of the farnesyltransferase inhibitor lonafarnib (SCH66336) was conducted in children with recurrent or progressive CNS tumors. Primary objectives were to estimate the maximum-tolerated dose (MTD) and to describe the dose-limiting toxicities (DLTs) and pharmacokinetics of lonafarnib. Farnesylation inhibition of HDJ-2 in peripheral blood was also measured.

PATIENTS AND METHODS

Lonafarnib was administered orally twice daily at dose levels of 70, 90, 115, 150, and 200 mg/m2/dose bid. A modified continual reassessment method (CRM) was used to estimate the MTD based on actual dosages of lonafarnib administered and toxicities observed during the initial 4 weeks of treatment.

RESULTS

Fifty-three children with progressive or recurrent brain tumors were enrolled, with a median age of 12.2 years (range, 3.9 to 19.5 years). Dose-limiting pneumonitis or myelosuppression was observed in three of three patients at the 200 mg/m2/dose level. A relatively constant DLT rate at the 70, 90, and 115 mg/m2/dose levels resulted in a recommended phase II dose of 115 mg/m2/dose. Significant diarrhea did not occur with prophylactic loperamide. Both radiographic response (one anaplastic astrocytoma) and stable disease (one medulloblastoma, two high-grade and four low-grade gliomas, one ependymoma, and one sarcoma) were noted, and seven patients remained on treatment for 1 year or longer.

CONCLUSION

Although the estimated MTD by the CRM model was 98.5 mg/m2/dose, because of the relatively constant observed DLT rate at the lower four dose levels, the recommended phase II dose of lonafarnib is 115 mg/m2/dose administered twice daily by mouth with concurrent loperamide.

Experimental therapeutic approaches to peripheral nerve tumors

✓Discovery that the Schwann cell is the primary cell type responsible for both the neurofibroma as well as the schwannoma has proven to represent a crucial milestone in understanding the pathogenesis of peripheral nerve tumor development. This information and related findings have served as a nidus for research aimed at more fully characterizing this family of conditions. Recent discoveries in the laboratory have clarified an understanding of the molecular mechanisms underlying the pathogenesis of benign peripheral nerve tumors. Similarly, the mechanisms whereby idiopathic and syndromic (NF1- andNF2-associated) nerve sheath tumors progress to malignancy are being elucidated. This detailed understanding of the molecular pathogenesis of peripheral nerve tumors provides the information necessary to create a new generation of therapies tailored specifically to the prevention, cessation, or reversal of pathological conditions at the fundamental level of dysfunction. The authors review the data that have helped to elucidate the molecular pathogenesis of this category of conditions, explore the current progress toward exploitation of these findings, and discuss potential therapeutic avenues for future research.

Therapy of metastatic bladder carcinoma

The methotrexate, vinblastine, doxorubicin, cisplatin (M-VAC) regimen has been considered as standard treatment of metastatic bladder carcinoma till recent years. The superiority of M-VAC both to cisplatin alone and to another cisplatin combination regimen has been demonstrated in randomized studies. During the last years, the use of gemcitabine in metastatic bladder carcinoma has considerably increased, mainly in combination with cisplatin (CG). A phase III trial comparing M-VAC and CG demonstrated similar activity and less toxicity for CG, which has now become the new standard of care for patients with metastatic bladder carcinoma. The substitution of cisplatin with carboplatin, the combination of platinum and taxanes, and the addition of a third drug to basal CG combination represent possible ways to improve outcome. Among the novel cytotoxic compounds, pemetrexed has raised interest, since a phase II second-line study showed a 28% response rate with a manageable toxicity profile. Vinflunine is a novel antitubulin agent with a relevant clinical activity in pretreated metastatic bladder carcinoma (18% response rate, 6.6 months median survival). Novel biologic compounds (in particular drugs targeting epidermal growth factor receptor) are being tested in metastatic bladder carcinoma also and much effort is being pursued in understanding the determinants of tumor response. Crucial mutations to which the tumor becomes addicted have to be discovered so that more effective and specific drugs or combinations can be delivered.

Targeting the PI3K and MAPK pathways to treat Kaposi's-sarcoma-associated herpes virus infection and pathogenesis

Cells require the ability to appropriately respond to signals in their extracellular environment. To initiate, inhibit and control these processes, the cell has developed a complex network of signaling cascades. The phosphatidylinositol 3-kinase (PI3K) and mitogen-activated protein kinase (MAPK) signaling pathways regulate several responses including mitosis, apoptosis, motility, proliferation, differentiation and many others. It is not surprising, therefore, that many viruses target the PI3K and MAPK pathways as a means to manipulate cellular function. Recently, Kaposi's sarcoma-associated herpes virus (KSHV) has been added to the list. KSHV manipulates the PI3K and MAPK pathways to control such divergent processes as cell survival, cellular migration, immune responses, and to control its own reactivation and lytic replication. Manipulation of the PI3K and MAPK pathways also plays a role in malignant transformation. Here, the authors review the potential to target the PI3K and MAPK signaling pathways to inhibit KSHV infection and pathogenesis.

New agents for treatment of advanced transitional cell carcinoma

The prognosis for any patient with progressive or recurrent invasive transitional cell carcinoma remains poor. In this context, the focus of clinical research in these invasive cancers concentrates on identifying systemic treatment options and new agents in order to improve survival of patients. Cisplatin-based chemotherapy is standard treatment of patients with metastatic urothelial cancer; however, despite regimens as the cisplatin-gemcitabine combination, the overall response rates vary between 40% and 65%, with complete response in 15%-25% with survivals up to 16 months. This survival is frequently achieved with severe and life-threatening side effects. None the less, almost all responding patients relapse within the first year; therefore, the need for development of new and tolerable agents is urgent. This review highlights some new active chemotherapeutic as new platinum compounds (oxaliplatin, lobaplatin), gallium nitrate, ifosfamide, the antifolates piritrexim and pemetrexed (Alimta, LY231514), vinflunine and molecular targeting agents such as farnesyltransferase inhibitors (lonafarnib, R115777, SCH66336), ribozyme (RPI.4610), histone deacetylase inhibitor (CI-994) and monoclonal antibodies (epidermal growth factor receptor, Her 2/neu).

Population pharmacokinetics of tipifarnib in healthy subjects and adult cancer patients

AIMS

To characterize the population pharmacokinetics of tipifarnib.

METHODS

A total of 1083 subjects treated orally with a solution, capsule or tablet formulations of tipifarnib, given as a single dose or as multiple twice-daily doses (range 25-1300 mg) were combined with data from 1, 2 and 24 h intravenous infusions. A total of 3445 concentrations in the index data set were fitted by an open three-compartment linear disposition model with sequential zero-order input into the depot compartment, followed by a first-order absorption process, and lag time, using NONMEM V. The effect of patient covariates on tipifarnib pharmacokinetics was explored. The model was evaluated using goodness of fit plots and relative error measurements for 3894 concentrations in the test data set. Computer simulations were undertaken to evaluate the effect of covariates on tipifarnib pharmacokinetics.

RESULTS

Tipifarnib oral bioavailability (26.7%) did not differ between the formulations. The absorption rate from the solution was faster than from the solid forms. Whereas the absorption rate and systemic clearance were more rapid in healthy subjects, the extent of absorption and the steady-state volume of distribution were comparable in cancer patients and healthy subjects. Systemic clearance in cancer patients (21.9 l h-1) exhibited a statistically significant relationship with total bilirubin. The typical volume of the central compartment in cancer patients (54.6 l 70 kg-1) was directly proportional to body weight. The clinical relevance of these covariates in cancer patients is questionable as there was a substantial overlap in simulated concentration-time profiles across a wide range of covariate values.

CONCLUSIONS

A population PK approach has been used to integrate data gathered during clinical development and to characterize the pharmacokinetics of tipifarnib. Individualization of dose based on body weight or total bilirubin concentration in adult cancer patients is not warranted.

Exposure-toxicity relationships for tipifarnib in cancer patients

AIMS

To explore the potential relationship between systemic exposure to tipifarnib and the incidence of toxicity in cancer patients.

METHODS

Data from 673 subjects (540 receiving tipifarnib and 133 receiving placebo) were included in the analysis. Tipifarnib was administered in doses ranging from 100 mg to 850 mg twice daily under fed conditions for 21 days in a 28 day cycle. Univariate and multivariate logistic regression models were used to evaluate the relationships between tipifarnib exposure and haematological (neutropenia and thrombocytopenia) and nonhaematological toxicities. Tipifarnib exposure was quantified as the area under the curve during the first cycle of chemotherapy (AUC), the maximum plasma concentration (C(max)), the time above plasma tipifarnib concentrations of 400 (T400) and 600 ng ml(-1) (T600), the cumulative area under the curve (AUC(T)), and the area under the curve density (AUC(D)), defined as the ratio AUC(T) to the duration of treatment. The nonhaematological toxicities measured were elevation of AST, ALT, bilirubin and serum creatinine, the occurrence of a skin rash, CNS or peripheral neuropathy, nausea and vomiting, diarrhoea and inflammation of the gastrointestinal tract. Odds ratios (OR) associated with drug exposure were used to measure the effect of the drug.

RESULTS

Tipifarnib AUC exhibited a positive and significant association with neutropenia grade > or =3 (OR 1.69, 95% CI 1.47, 1.95) and thrombocytopenia grade > or =3 (OR 1.41, 95% CI 1.21, 1.63) in patients with solid tumours, but not in refractory or relapsed AML patients. The incidence of exposure-related nonhaematological toxicity is small regardless of tumour type. No association was found between tipifarnib AUC and the elevation of AST, ALT and total bilirubin, and nausea and vomiting. There was a weak relationship between tipifarnib AUC and serum creatinine elevation (OR 1.18, 95% CI 1.11, 1.26), CNS (OR 1.05, 95% CI 1.01, 1.10) and peripheral neurotoxicity (OR 1.10, 95% CI 1.03, 1.18), diarrhoea (OR 1.14, 95% CI 1.08, 1.21), gastrointestinal tract inflammation (OR 1.13, 95% CI 1.07, 1.19), and skin rash (OR 1.10, 95% CI 1.04, 1.17).

CONCLUSIONS

In those patients who develop severe toxicity, dose reduction may improve the tolerability of tipifarnib. However, an exposure-guided approach to dosage adjustment to limit haematological and nonhaematological toxicity is not warranted.

Chemotherapy practices and perspectives in invasive bladder cancer

Bladder cancer is the fifth most common cancer in adult patients. Two-thirds of patients have superficial tumors and their treatment is conservative. Nevertheless, 30% of superficial tumors become infiltrative and represent a third of tumors at initial diagnosis. Overall mortality from bladder cancer is 30%. Important molecular events may explain the carcinogenesis and evolution of these tumors. Infiltrating bladder cancers are currently treated by radical cystectomy. Neoadjuvant chemotherapy has demonstrated a positive impact on patients' outcomes before cystectomy. Adjuvant chemotherapy after cystectomy is currently being studied in an international randomized trial. Patients with advanced disease are treated by chemotherapy with palliative intentions. Two regimens are standard: the combination of methotrexate, vinblastine, adriamycin and cisplatin, and the combination of gemcitabine and cisplatin. The addition of paclitaxel to the latter regimen is the subject of ongoing study. Only a few patients have long-term nonevolutive disease. Research must be focused on the combination of chemotherapy and targeted drugs directed through gene methylation, cytokine-receptor activation and signaling pathways.

Percutaneous Bladder Cryoablation in Porcine Model

PURPOSE

To demonstrate the morphologic changes of full-thickness bladder cryoablation utilizing contemporary percutaneous technology.

MATERIALS AND METHODS

Cryoablation of the bladder wall was conducted in 24 pigs. The bladders were exposed laparoscopically and inspected cystoscopically. The animals underwent either extravesical (serosal) or transvesical (mucosal) approaches for the creation of the cryoablation lesion. Single or double freeze/thaw cycles were applied, and no bladder drainage was used. The bladder was evaluated for perforation, and histologic examination was undertaken to assess the extent of acute, subacute (2 weeks), or chronic (1 month) lesions.

RESULTS

Cryoablation reliably produced a controlled transmural area of necrosis (both serosa and mucosa) by both techniques. The size and extent of the lesion were directly proportional to the duration of freezing and the type of cryoprobe used. The pathology report confirmed the full-thickness coagulative necrosis of muscle. Bladder perforation was not detected clinically or at autopsy.

CONCLUSION

Cryoablation produces reliable zones of tissue destruction without bladder perforation. These preliminary data show the safety and feasibility for trials in the treatment of bladder tumors by laparoscopic, cystoscopic, or image-guided techniques.

Systemic chemotherapy for urothelial cancer

Although metastatic transitional cell carcinoma of the bladder and urothelium commonly responds to first-line chemotherapy, eventual progression is nearly universal. Current salvage therapy for progressive disease after first-line chemotherapy is ineffective, and such patients are candidates for clinical trials. Neoadjuvant chemotherapy improves long-term outcome and provides an exciting paradigm for the rapid development of systemic therapy. Neoadjuvant chemotherapy with or without radiation also facilitates bladder conservation in patients who attain pathologic complete remission. Definitive data supporting adjuvant chemotherapy are lacking. With the unraveling of bladder cancer biology and the discovery of novel agents targeting several carcinogenic pathways, the future of therapy for transitional cell carcinoma appears promising.

A phase I safety, pharmacological and biological study of the farnesyl protein transferase inhibitor, tipifarnib and capecitabine in advanced solid tumors

BACKGROUND

To evaluate the toxicity and pharmacological and biological properties of the farnesyl protein transferase (FPTase) inhibitor, tipifarnib (R115777, ZARNESTRAtrade mark) and capecitabine administered for 14 days every 3 weeks.

PATIENTS AND METHODS

Patients with advanced cancers received twice daily tipifarnib (100-500 mg) and capecitabine (1000-1125 mg/m(2)) for 14 days every 3 weeks. Pharmacokinetics of tipifarnib, capecitabine and 5-fluorouracil (5-FU) were determined. Peripheral blood mononuclear cells were analyzed for farnesylation of the HDJ2 chaperone protein and FPTase activity.

RESULTS

Forty-one patients received 185 courses of treatment. Diarrhea and palmar-plantar erythrodysesthesia were dose limiting at 300 mg tipifarnib/1125 mg/m(2) capecitabine b.i.d. When the capecitabine dose was fixed at 1000 mg/m(2) b.i.d., neutropenia was dose limiting at 400 and 500 mg b.i.d. of tipifarnib. Capecitabine did not affect the pharmacology of tipifarnib at 100-300 mg b.i.d., although tipifarnib significantly increased the C(max) of 5-FU at 400 mg b.i.d. HDJ2 farnesylation and FPTase activity decreased between 200 and 400 mg b.i.d. doses of tipifarnib, without a dose-response relationship. Five patients demonstrated partial remissions and 11 patients maintained prolonged stable disease.

CONCLUSIONS

Tipifarnib and capecitabine are well tolerated at 300 mg/1000 mg/m(2) b.i.d., respectively, resulting in biologically relevant plasma concentrations and antitumor activity. The recommended dose for further disease-focused studies is 300 mg b.i.d. tipifarnib and 1000 mg/m(2) b.i.d. capecitabine, given for 14 days every 3 weeks.

Tipifarnib: farnesyl transferase inhibition at a crossroads

Tipifarnib is an oral nonpeptidomimetic farnesyl transferase inhibitor developed to inhibit a variety of farnesylated targets potentially relevant to the therapy of various malignancies. The agent has, thus far, been tested in a wide array of both solid tumors and myeloid malignancies. Phase I trials have demonstrated that tipifarnib is best given in a twice-daily fashion in doses of 600-1200 mg/day to avoid significant neuropathy, fatigue and myelosuppression. Subsequent trials demonstrated that pauses in therapy (with staccato dosing schedules) seem to increase tolerability without a clear decrease in efficacy. Phase II and III trials of tipifarnib as monotherapy for breast, colorectal, lung (both non-small cell and small cell), brain, pancreatic and urothelial cancers have all been disappointing. Combination trials of tipifarnib with cytotoxic, hormonal or biological therapies are ongoing. Tipifarnib has displayed the most interesting activity in the myeloid malignancies of myelodysplastic syndrome, myelofibrosis with myeloid metaplasia and elderly/high-risk acute myeloid leukemia. Overall clinical response rates of approximately 20-30% have been reported in myelodysplastic syndrome and acute myeloid leukemia patients who have few alternative therapeutic options. US FDA approval for tipifarnib awaits results of subsequent Phase III trials of the agent in elderly acute leukemia.

Thematic review series: Lipid Posttranslational Modifications. Farnesyl transferase inhibitors

Some proteins undergo posttranslational modification by the addition of an isoprenyl lipid (farnesyl- or geranylgeranyl-isoprenoid) to a cysteine residue proximal to the C terminus. Protein isoprenylation promotes membrane association and contributes to protein-protein interactions. Farnesylated proteins include small GTPases, tyrosine phosphatases, nuclear lamina, cochaperones, and centromere-associated proteins. Prenylation is required for the transforming activity of Ras. Because of the high frequency of Ras mutations in cancer, farnesyl transferase inhibitors (FTIs) were investigated as a means to antagonize Ras function. Evaluation of FTIs led to the finding that both K- and N-Ras are alternatively modified by geranylgeranyl prenyltransferase-1 in FTI-treated cells. Geranylgeranylated forms of Ras retain the ability to associate with the plasma membrane and activate substrates. Despite this, FTIs are effective at inhibiting the growth of human tumor cells in vitro, suggesting that activity is dependent on blocking the farnesylation of other proteins. FTIs also inhibit the in vivo growth of human tumor xenografts and sensitize these models to chemotherapeutics, most notably taxanes. Several FTIs have entered clinical trials for various cancer indications. In some clinical settings, primarily hematologic malignancies, FTIs have displayed evidence of single-agent activity. Clinical studies in progress are exploring the antitumor activity of FTIs as single agents and in combination. This review will summarize the basic biology of FTIs, their antitumor activity in preclinical models, and the current status of clinical studies with these agents.

Developing innovative strategies for advanced transitional cell carcinoma of the bladder

Several improvements in the treatment of advanced transitional cell malignancies have been provided by clinical trials in the past 10 years. Nonetheless, there are conflicting results regarding the effect of perioperative chemotherapy of muscle-invasive disease and new cytotoxic agents in the metastatic setting. The authors will discuss the results of major clinical trials and examine developing targeted-oriented treatment strategies.