Activity of SCH 66336, a tricyclic farnesyltransferase inhibitor, against human tumor colony-forming units

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.

Farnesyl transferase expression determines clinical response to the docetaxel-lonafarnib combination in patients with advanced malignancies

BACKGROUND

Lonafarnib (LNF) is a protein farnesyl transferase (FTase) inhibitor that has shown synergistic activity with taxanes in preclinical models and early stage clinical trials. Preclinical findings suggested tubulin acetylation and FTase expression levels may be important determinants of drug sensitivity that would help identify patient populations more likely to benefit from this regimen. This pilot study evaluated the biological effects of LNF and docetaxel (DTX) combination therapy in refractory solid tumors by comparing pretreatment and post-treatment tumor biopsies.

METHODS

Patients with histologically confirmed locally advanced or metastatic solid malignancies refractory to standard therapies or with no effective therapies available were eligible. Patients were randomized to 1 of 4 dosing cohorts: 1) 30 mg/m², 100 mg; 2) 36 mg/m², 100 mg; 3) 30 mg/m², 150 mg; or 4) 36 mg/m², 150 mg of DTX intravenously weekly, LNF orally twice daily, respectively.

RESULTS

Of the 38 patients enrolled, 36 were treated, and 29 were evaluable for toxicity and response assessment. The combination of LNF and DTX was tolerated in all cohorts with the exception of a 28% incidence of grade 3/4 diarrhea, which was manageable with aggressive antidiarrheal regimens. Seven patients derived clinically meaningful benefit from this combination treatment; these patients had significantly lower basal FTase-beta mRNA expression levels than the mean study population level (P < .05). Correlation of clinical benefit with tubulin acetylation content as well as basal acetyl-tubulin content were evaluated. However, no significant correlation was found.

CONCLUSIONS

Despite the small number of patients, these findings support our preclinical mechanistic studies and warrant further clinical investigations using FTase-beta mRNA expression as a potential predictive biomarker to select for an enriched patient population to study the effects of taxane and FTase inhibitor combination therapies.

A phase I safety, pharmacological, and biological study of the farnesyl protein transferase inhibitor, lonafarnib (SCH 663366), in combination with cisplatin and gemcitabine in patients with advanced solid tumors

PURPOSE

This phase I study was conducted to evaluate the safety, tolerability, pharmacological properties and biological activity of the combination of the lonafarnib, a farnesylproteintransferase (FTPase) inhibitor, with gemcitabine and cisplatin in patients with advanced solid malignancies.

EXPERIMENTAL DESIGN

This was a single institution study to determine the maximal tolerated dose (MTD) of escalating lonafarnib (75-125 mg po BID) with gemcitabine (750-1,000 mg/m(2) on days 1, 8, 15) and fixed cisplatin (75 mg/m(2) day 1) every 28 days. Due to dose-limiting toxicities (DLTs) of neutropenia and thrombocytopenia in initial patients, these patients were considered "heavily pre-treated" and the protocol was amended to limit prior therapy and re-escalate lonafarnib in "less heavily pre-treated patients" on 28-day and 21-day schedules. Cycle 1 and 2 pharmacokinetics (PK), and farnesylation of the HDJ2 chaperone protein and FPTase activity were analyzed.

RESULTS

Twenty-two patients received 53 courses of therapy. Nausea, vomiting, and fatigue were frequent in all patients. Severe toxicities were observed in 91% of patients: neutropenia (41%), nausea (36%), thrombocytopenia (32%), anemia (23%) and vomiting (23%). Nine patients withdrew from the study due to toxicity. DLTs of neutropenia, febrile neutropenia, thrombocytopenia, and fatigue limited dose-escalation on the 28-day schedule. The MTD was established as lonafarnib 75 mg BID, gemcitabine 750 mg/m(2) days 1, 8, 15, and cisplatin 75 mg/m(2) in heavily pre-treated patients. The MTD in the less heavily pre-treated patients could not be established on the 28-day schedule as DLTs were observed at the lowest dose level, and dose escalation was not completed on the 21-day schedule due to early study termination by the Sponsor. No PK interactions were observed. FTPase inhibition was not observed at the MTD, however HDJ-2 gel shift was observed in one patient at the 100 mg BID lonafarnib dose. Anti-cancer activity was observed: four patients had stable disease lasting >2 cycles, one subject had a complete response, and another had a partial response, both with metastatic breast cancer.

CONCLUSION

Lonafarnib 75 mg BID, gemcitabine 750 mg/m(2) days 1, 8, 15, and cisplatin 75 mg/m(2) day 1 on a 28-day schedule was established as the MTD. Lonafarnib did not demonstrate FTPase inhibition at these doses. Despite the observed efficacy, substantial toxicity and questionable contribution of anti-tumor activity of lonafarnib to gemcitabine and cisplatin limits further exploration of this combination.

Pilot study of lonafarnib, a farnesyl transferase inhibitor, in patients with chronic myeloid leukemia in the chronic or accelerated phase that is resistant or refractory to imatinib therapy

BACKGROUND

Lonafarnib (SCH66336) is a nonpeptidomimetic farnesyl transferase inhibitor that has demonstrated significant preclinical activity against chronic myelogenous leukemia (CML) cells and in CML animal models.

METHODS

In the current study, the efficacy of lonafarnib was investigated in patients with CML in the chronic or accelerated phase that was resistant or intolerant to imatinib. Thirteen patients with CML in the chronic (n = 6 patients) or accelerated (n = 7 patients) phase were treated with lonafarnib at a dose of 200 mg orally twice daily. Ten patients had failed therapy with imatinib and 3 patients were intolerant to imatinib. The median age of the patients was 62 years (range, 38-80 yrs) and the median time from the diagnosis of CML to therapy with lonafarnib was 5 years (range, 0.3-13 yrs). In addition to imatinib mesylate, all patients had received prior therapy with interferon-alpha and seven patients had received other treatments. The median duration of therapy with lonafarnib was 8 weeks (range, 2-41 wks).

RESULTS

Two patients responded. One patient in the accelerated phase of CML returned to the chronic phase, a response that lasted for 3 months. Another patient with chronic phase disease had lowering of the leukocyte count without the need for hydroxyurea and normalization of the differential count that lasted for 5 months. The most common adverse event was diarrhea, which was noted in 11 patients (84%) (Grade > or = 3 in 4 patients; 31%; toxicity was graded according to the National Cancer Institute Common Toxicity Criteria [version 2.0]). Therapy was discontinued in one patient because of diarrhea not responding to dose adjustments.

CONCLUSIONS

Single-agent lonafarnib appears to have clinical activity in a small proportion of patients with CML refractory to imatinib.

A multinomial Phase II study of lonafarnib (SCH 66336) in patients with refractory urothelial cancer☆

PURPOSE

Protein farnesylation by farnesyltransferase (FTase) is required for membrane localization and effective signal transduction by G-proteins, including Ras. Lonafarnib inhibits FTase and has shown antitumor activity in both preclinical and clinical settings. As disturbances in Ras signaling pathways have been implicated in the pathogenesis of transitional cell carcinoma (TCC), the antitumor activity of lonafarnib was studied in a National Cancer Institute of Canada Clinical Trials Group Phase II trial in patients with previously treated TCC.

PATIENTS AND METHODS

Patients had at least 1 prior chemotherapy regimen for advanced unresectable or metastatic TCC, or recurrence less than 1 year after adjuvant or neoadjuvant chemotherapy. Lonafarnib was given at a dose of 200 mg PO twice daily continuously, with cycles repeated every 4 weeks.

RESULTS

Between December 1999 and December 2000, 19 eligible patients were enrolled at 8 National Cancer Institute of Canada Clinical Trials Group centers. Median time on treatment was 7.1 weeks (range, 0.6-23.9). Drug-related Grade 3 toxicities included fatigue, anorexia, nausea, confusion, dehydration, muscle weakness, depression, headache, and dyspnea. Five patients discontinued the study protocol due to toxicity. No responses were observed in 10 patients who were evaluable. Of 9 patients not evaluable for response, 5 had symptomatic progression, fulfilling multinomial criteria to stop the study after the first stage.

CONCLUSION

No single-agent activity of lonafarnib was observed in this study of patients with aggressive TCC failing prior chemotherapy.

A Phase I Trial of the Novel Farnesyl Protein Transferase Inhibitor, BMS-214662, in Combination with Paclitaxel and Carboplatin in Patients with Advanced Cancer

PURPOSE

This phase I study was conducted to determine the toxicities, pharmacokinetics, and pharmacodynamics of BMS-214662, a farnesyl transferase inhibitor, in combination with paclitaxel and carboplatin, in patients with advanced solid tumors.

EXPERIMENTAL DESIGN

Patients with solid tumors received one of six escalating dose levels of BMS-214662 infused over 1 hour given following paclitaxel and carboplatin on the first day of a 21-day cycle. Toxicities were graded by the National Cancer Institute common toxicity criteria and recorded as maximum grade per patient for each treatment cycle. Inhibition of farnesyl transferase activity in peripheral blood mononuclear cells (PBMCs) was evaluated. Accumulation of unfarnesylated HDJ-2 in PBMCs of patients was evaluated as a marker of farnesyl transferase inhibition by BMS-214662.

RESULTS

Thirty patients received 141 cycles of treatment through six dose levels. Dose-limiting toxicities were neutropenia, thrombocytopenia, nausea, and vomiting. There was no pharmacokinetic interaction between BMS-214662 and paclitaxel. The maximum tolerated dose was established as BMS-214662 (160 mg/m(2)), paclitaxel (225 mg/m(2)) and carboplatin (area under the curve = 6 on day 1), every 21 days. Inhibition of HDJ-2 farnesylation in PBMCs of patients was shown. One measurable partial response was observed in a patient with taxane-resistant esophageal cancer. There was partial regression of evaluable disease in two other patients (endometrial and ovarian cancer). Stable disease (> 4 cycles) occurred in eight other patients.

CONCLUSIONS

The combination of BMS-214662 with paclitaxel and carboplatin was well tolerated, with broad activity in solid tumors. There was no correlation between dose level and accumulation of unfarnesylated HDJ-2 in PBMCs nor tumor response.

Therapeutic efficacy of prenylation inhibitors in the treatment of myeloid leukemia

Farnesyltransferase inhibitors (FTIs) represent a new class of anticancer agents that specifically target post-translational farnesylation of various proteins that mediate several cellular processes such as signal transduction, growth, differentiation, angiogenesis and apoptosis. These compounds were originally designed to block oncogenic RAS-induced tumor growth by impeding RAS localization to the membrane, but it is now evident that FTIs also affect processing of several other proteins. The need for novel therapies in myeloid leukemia is underscored by the high rate of treatment failure due to high incidences of relapse- and treatment-related toxicities. As RAS deregulation is important in the pathogenesis of myeloid leukemias, targeting of RAS signaling may provide a new therapeutic strategy. Several FTIs (eg BMS-214662, L-778,123, R-115777 and SCH66336) have entered phase I and phase II clinical trials in myeloid leukemias. This review discusses recent clinical results, potential combination therapies, mechanisms of resistance and the clinical challenges of toxicities associated with prenylation inhibitors.

AMD473 (ZD0473) exhibits marked in vitro anticancer activity in human tumor specimens taken directly from patients

AMD473 (ZD0473; cis-amminedichloro[2-methylpyridine]platinum [II]) is a new generation anticancer agent that, in preclinical studies, shows evidence of an extended spectrum of antitumor activity and overcomes platinum resistance mechanisms. Here we evaluate the activity of AMD473 (ZD0473) in a panel of 120 human tumor specimens using a soft agar cloning assay (human tumor colony-forming assay). When tumor cells were treated with 1.0, 4.0 or 16.0 microg/ml AMD473 (ZD0473) for 2 h, in vitro responses were observed in 18% (9/51), 33% (17/51) and 44% (19/43) of assessable specimens. Treatment of tumor cells with the same concentrations of AMD473 (ZD0473) for 24 h resulted in responses of 33% (16/48), 63% (30/48) and 85% (35/41). AMD473 (ZD0473) (16 microg/ml; 24 h) demonstrated activity towards 100% of the non-small cell lung (5/5) and ovarian (8/8) cancer specimens and 73% (8/11) of the breast cancer specimens treated. Low levels of cross-resistance to cisplatin cyclophosphamide, 5-flurouracil, etoposide and gemcitabine were observed. There was a positive relationship between AMD473 (ZD0473) concentration and effect, and a significant difference between response to 2- versus 24-h exposure to 4 or 16 microg/ml (p=0.003 and p=0.001, respectively). These responses demonstrate efficacy at pharmacologically relevant concentrations, suggesting AMD473 (ZD0473) deserves further evaluation.

Preclinical and clinical evaluation of farnesyltransferase inhibitors

Farnesylation of Ras, a protooncogene that is frequently mutated in a number of malignancies, is critical for its biologic function. This observation has led to the development of several agents that inhibit farnesyltransferase, known as farnesyltransferase inhibitors (FTIs). The antiproliferative and antitumor effects of these agents have been demonstrated in preclinical and clinical studies. Interestingly, FTI activity does not necessarily rely on ras mutational status, indicating that Ras is not the only FTI target. Clinical data suggest that FTIs, alone and in combination with other agents, have antitumor activity. Further study is needed to determine the precise mechanism of FTI antitumor activity as well as how and where FTIs will be best used clinically.

Novel agents for the prevention of breast cancer: targeting transcription factors and signal transduction pathways

Transformation of breast cells occurs through loss or mutation of tumor suppressor genes, or activation or amplification of oncogenes, leading to deregulation of signal transduction pathways, abnormal amplification of growth signals, and aberrant expression of genes that ultimately transform the cells into invasive cancer. The goal of cancer preventive therapy, or "chemoprevention," is to eliminate premalignant cells or to block the progression of normal cells into cancer. Multiple alterations in signal pathways and transcription factors are observed in mammary gland tumorigenesis. In particular, estrogen receptor (ER) deregulation plays a critical role in breast cancer development and progress, and targeting ER with selective ER modulators (SERMs) has achieved significant reduction of breast cancer incidence in women at high risk for breast cancer. However, not all breast cancer is prevented by SERMs, because 30-40% of the tumors are ER-negative. Other receptors for retinoids, vitamin D analogs and peroxisome proliferator-activiator, along with transcription factors such as AP-1, NF-kappaB, and STATs (signal transducers and activators of transcription) affect breast tumorigenesis. This is also true for the signal transduction pathways, for example cyclooxygenase 2 (Cox-2), HER2/neu, mitogen-activated protein kinase (MAPK), and PI3K/Akt. Therefore, proteins in pathways that are altered during the process of mammary tumorigenesis may be promising targets of future chemopreventive drugs. Many newly-developed synthetic or natural compounds/agents are now under testing in preclinical studies and clinical trials. Receptor selective retinoids, receptor tyrosine kinase inhibitors (TKIs), SERMs, Cox-2 inhibitors, and others are some of the promising novel agents for the prevention of breast cancer. The chemopreventive activity of these agents and other novel signal transduction inhibitors are discussed in this chapter.

Phase I and pharmacological study of the oral farnesyltransferase inhibitor SCH 66336 given once daily to patients with advanced solid tumours

A single-agent dose-escalating phase I study on the farnesyl transferase inhibitor SCH 66336 was performed to determine the safety profile and recommended dose for phase II studies. Plasma pharmacokinetics were determined as well as the SCH 66336-induced inhibition of farnesyl protein transferase in vivo. SCH 66336 was given orally once daily (OD) without interruption to patients with histologically-confirmed solid tumours. Routine antiemetics were not prescribed. 12 patients were enrolled into the study. Dose levels studied were 300 mg (6 patients) and 400 mg (6 patients) OD. Pharmacokinetic sampling was performed on days 1 and 15. Although at 400 mg OD only 1 patient had a grade 3 diarrhoea, 3 out of 6 patients interrupted treatment early due to a combination of various grade 1-3 toxicities (diarrhoea, uremiacreatinine, asthenia, vomiting, weight loss) indicating that this dose was not tolerable for a prolonged period of time. At 300 mg OD, the same pattern of toxicities was observed, but all were grade 1-2. Therefore, this dose can be recommended for phase II studies. Pharmacokinetic analysis showed that peak plasma concentrations as well as the AUCs were dose-related, with increased parameters at day 15 compared with day 1, indicating some accumulation upon multiple dosing. Plasma half-life ranged from 5 to 9 h and appeared to increase with increasing dose. Steady state plasma concentrations were attained by day 14. A large volume of distribution at steady state suggested extensive distribution outside the plasma compartment. There is evidence of inhibition of protein prenylation in some patients after OD oral administration of SCH 66336. SCH 66336 can be safely administered using a continuous oral OD dosing regimen. The recommended dose for phase II studies using this regimen is 300 mg OD.

The use of molecular markers in farnesyltransferase inhibitor (FTI) therapy of breast cancer

The hypothesis that pharmacologic inhibitors of Ras can be effective anti-cancer agents has led to the development of Farnesyltransferase inhibitors (FTIs). These agents inhibit the requisite processing of a number of cellular proteins including Ras. FTIs have shown good anti-tumor efficacy and little toxicity in preclinical models and based on these results, numerous clinical trials are currently underway to evaluate the clinical potential of these agents in patients with cancer. However, contrary to the ideas that led to their design, mechanistic studies have not confirmed that they inhibit tumors through the inhibition of Ras. FTIs inhibit the growth of a broad variety of human tumor cells in vitro and studies to date have not identified cellular characteristics that predict the antitumor efficacy of this class of agents. We have studied a panel of breast cancer cell lines that differ widely in their sensitivity to FTI in order to determine which molecular characteristics may determine sensitivity to this class of agents. In these cells we find that FTI sensitivity does not correlate with the relative expression of Ras isoforms or the inhibition of Ras processing, growth factor signaling, expression of estrogen receptor or the overexpression of growth factor receptors. Looking for other molecular correlates of FTI sensitivity we have compared the activity of farnesylprotein transferase (FPTase) among these cells and although we find no overall correlation with FTI sensitivity, we find that two cell lines with unusually low FPTase activity are sensitive. Comparing p53 genotype with FTI-sensitivity we find that although most cell lines in our panel have mutant p53, all three cell lines with wild-type p53 are quite sensitive to FTI. In fact, MCF-7 cells which have both wild-type p53 and the lowest FPTase activity are the most FTI-sensitive cell type we have ever seen. Although these studies do not identify any single molecular marker that can accurately predict FTI sensitivity in breast tumors, they highlight the potential roles of FPTase activity and p53 function for further analysis.

Evolving therapies: farnesyltransferase inhibitors

Farnesyltransferase inhibitors (FTIs) are compounds designed to interfere with the signal transduction of cancer cells containing ras gene mutations. Specifically, FTIs were designed to prevent the farnesylation of Ras and other intracellular proteins, and they have been shown to have an effect on malignant cell proliferation and survival. However, the actual intracellular target of FTIs and the cellular determinants of drug action that correlate with antitumor effects currently are unknown. The following are key questions relating to FTI cell biology and clinical development: 1) Are ras gene mutations required for FTIs to be effective? 2) Does the effect of FTI therapy depend on which ras isoform is active (ie, H-ras, K-ras4A/B, or N-ras) in cancer cells? 3) What level of farnesyltransferase inhibition is required for clinical effect? 4) What surrogate biomarkers can be used to evaluate the biologic effect of FTIs in ongoing clinical trials? 5) What is the mechanism of FTI antitumor activity? Although the preliminary results are encouraging, more understanding of the intracellular mechanism of the FTIs is needed to determine how best to administer them in patients with cancer and to test their antitumor effects.

Phase I and pharmacokinetic study of the oral farnesyl transferase inhibitor SCH 66336 given twice daily to patients with advanced solid tumors

PURPOSE

A single-agent dose-escalating phase I and pharmacokinetic study on the farnesyl transferase inhibitor SCH 66336 was performed to determine the safety profile, maximum-tolerated dose, and recommended dose for phase II studies. Plasma and urine pharmacokinetics were determined.

PATIENTS AND METHODS

SCH 66336 was given orally bid without interruption to patients with histologically or cytologically confirmed solid tumors. Routine antiemetics were not prescribed.

RESULTS

Twenty-four patients were enrolled onto the study. Dose levels studied were 25, 50, 100, 200, 400, and 300 mg bid. Pharmacokinetic sampling was performed on days 1 and 15. At 400 mg bid, the dose-limiting toxicity (DLT) consisted of grade 4 vomiting, grade 4 neutropenia and thrombocytopenia, and the combination of grade 3 anorexia and diarrhea with reversible grade 3 plasma creatinine elevation. After dose reduction, at 300 mg bid, the DLTs consisted of grade 4 neutropenia, grade 3 neurocortical toxicity, and the combination of grade 3 fatigue with grade 2 nausea and diarrhea. The recommended dose for phase II studies is 200 mg bid, which was found feasible for prolonged periods of time. Pharmacokinetic analysis showed a greater than dose-proportional increase in drug exposure and peak plasma concentrations, with increased parameters at day 15 compared with day 1, indicating some accumulation on multiple dosing. Plasma half-life ranged from 4 to 11 hours and seemed to increase with increasing doses. Steady-state plasma concentrations were attained at days 7 through 14. A large volume of distribution at steady-state indicated extensive distribution outside the plasma compartment.

CONCLUSION

SCH 66336 can be administered safely using a continuous oral bid dosing regimen. The recommended dose for phase II studies using this regimen is 200 mg bid.