Phase I population pharmacokinetics of irofulven

Application of population pharmacokinetic modeling in early clinical development of the anticancer agent E7820

The aim of this study was to assess the population pharmacokinetics (PopPK) of the novel oral anti-cancer agent E7820. Both a non-linear mixed effects modeling analysis and a non-compartmental analysis (NCA) were performed and results were compared. Data were obtained from a phase I dose escalation study in patients with malignant solid tumors or lymphomas. E7820 was administered daily for 28 days, followed by a washout period of 7 days prior to the start of subsequent cycles. A one compartment model with linear elimination from the central compartment was shown to give adequate fit, while absorption was described using a turnover model. Final population parameter estimates of basic PK parameters obtained with the PopPK method were (RSE): clearance, 6.24 L/h (7.1%), volume of distribution, 66.0 L (8.5%), mean transit time to the absorption compartment, 0.638 h (6.5%). The intake of food prior to dose administration slowed absorption (2.8-fold, RSE 13%) and increased relative bioavailability of E7820 by 36% (RSE 14%), although the effect on C (max) and AUC was not significant. Comparison with the NCA approach showed approximately equal PK parameter estimates and food effect measures, although specific advantages of PopPK included efficiency in use of data and more appropriate assessment of variability.

A phase I and pharmacokinetic study of irofulven and capecitabine administered every 2 weeks in patients with advanced solid tumors

PURPOSE

To determine the maximum tolerated dose (MTD), recommended dose, dose limiting toxicities (DLT), safety and pharmacokinetics of irofulven combined with capecitabine in advanced solid tumor patients.

EXPERIMENTAL DESIGN

Irofulven was given i.v. over 30 min on days 1 and 15 every 4 weeks; capecitabine was given orally twice daily, day 1 to 15. Dose levels (DL) were: irofulven (mg/kg)/capecitabine (mg/m2/day): DL1: 0.3/1,700; DL2: 0.4/1,700; DL3: 0.4/2,000; DL4: 0.5/2,000.

RESULTS

Between May 2002 and March 2004, 37 patients were treated and 36 evaluable for MTD. DLT occurred in 1/6 evaluable patients in DL1 (grade 3 thrombocytopenia); 1/6 in DL3 (grade 3 thrombocytopenia); 2/7 in DL4 (grade 3 febrile neutropenia, grade 3 thrombocytopenia). DL4 was defined as the MTD and DL3 was established as the recommended dose (RD). DLTs occurred in 1 of 14 additional patients treated at DL3. No treatment-related deaths or grade 4 non-hematological toxicity occurred, and grade 3 toxicities were infrequent. Antitumor activity was observed; two partial responses were noted in thyroid carcinoma (DL1, DL4); one unconfirmed partial response was observed in a patient with nasopharyngeal carcinoma, (DL3); 12 patients had disease stabilization >3 months; of eight patients with hormone refractory prostate cancer (HRPC), one patient had PSA normalization and four short-term stabilizations of PSA occurred. Capecitabine and irofulven pharmacokinetics results did not suggest drug-drug interactions.

CONCLUSIONS

Irofulven with capecitabine was adequately tolerated and evidence of antitumor activity was observed. The recommended dose is irofulven 0.4 mg/kg and capecitabine 2,000 mg/m2/day.

Pharmacokinetics, metabolism, and routes of excretion of intravenous irofulven in patients with advanced solid tumors

Irofulven is currently in Phase 2 clinical trials against a wide variety of solid tumors and has demonstrated activity in ovarian, prostate, gastrointestinal, and non-small cell lung cancer. The objectives of this study were to determine its pharmacokinetics and route of excretion and to characterize its metabolites in human plasma and urine samples after a 30-min i.v. infusion at a dose of 0.55 mg/kg in patients with advanced solid tumors. Three patients were administered i.v. 100 microCi of [14C]irofulven over a 30-min infusion on day 1 of cycle 1. Serial blood and plasma samples were drawn at 0 (before irofulven infusion) and up to 144 h after the start of infusion. Urine and fecal samples were collected for up to 144 h after the start of infusion. The mean urinary and fecal excretion of radioactivity up to 144 h were 71.2 and 2.9%, respectively, indicating renal excretion was the major route of elimination of [14C]irofulven. The C(max), AUC(0-infinity), and terminal half-life values for total radioactivity were 1130 ng-Eq/ml, 24,400 ng-Eq . h/ml, and 116.5 h, respectively, and the corresponding values for irofulven were 82.7 ng/ml, 65.5 ng . h/ml, and 0.3 h, respectively, suggesting that the total radioactivity in human plasma was a result of the metabolites. Twelve metabolites of irofulven were detected in human urine and plasma by electrospray ionization/tandem mass spectrometry. Among these metabolites, the cyclopropane ring-opened metabolite (M2) of irofulven was found, and seven others were proposed as glucuronide and glutathione conjugates.

A phase I and pharmacokinetic study of irofulven and cisplatin administered in a 30-min infusion every two weeks to patients with advanced solid tumors

BACKGROUND

To determine maximum tolerated dose (MTD), recommended dose, safety and pharmacokinetics of irofulven combined with cisplatin in advanced solid tumor patients.

PATIENTS AND METHODS

Cisplatin and irofulven were given sequentially i.v. over 30 min on day 1 and 15 every 4 weeks. Four dose levels (DL) were explored: irofulven (mg/kg)/cisplatin (mg/m2): DL1: 0.3/30; DL2: 0.4/30; DL3: 0.4/40; DL4: 0.5/40. Dose-limiting toxicity (DLT) included dosing omission and delay > 1 week. MTD was the DL with DLT in 2/2 or > or = 2/6 patients during cycle 1-2.

RESULTS

Between March 2002 and April 2003, 33 patients were treated. DLT occurred in 1/6 patients in DL1 (hypomagnesemia, hypocalcemia); 1/6 in DL2 (thrombocytopenia); 2 heavily pretreated patients out of 6 patients in DL3 (neutropenic infection, thrombocytopenia, stomatitis); 2/3 in DL4 (asthenia, blurred vision). Three DLT occurred in 12 additional patients treated at DL2. No toxic deaths occurred; grade 4 toxicity and grade 3 non-hematological toxicity were infrequent. Six patients reported grade 1-2 visual events. Antitumor activity was observed over a broad spectrum of tumor types in all DLs: 1 partial response in bulky sarcoma (DL1); 1 clinical response in endometrial carcinoma (DL1); 2 partial responses not confirmed due to discontinuation (ovarian DL2, renal DL4); 8 stabilizations > 3 months; PSA response: 3/9 prostate cancer patients. Irofulven showed rapid elimination and high interpatient variability. Platinum and irofulven pharmacokinetics did not suggest drug-drug interactions.

CONCLUSION

Irofulven with cisplatin was adequately tolerated and substantial evidence of antitumor activity was observed. The recommended dose is irofulven 0.4 mg/kg and cisplatin 30 mg/m2.

Characterizations of irofulven cytotoxicity in combination with cisplatin and oxaliplatin in human colon, breast, and ovarian cancer cells

PURPOSE

This study assessed the cytotoxic effects of irofulven in combination with oxaliplatin and cisplatin in a panel of human cancer cell lines.

METHODS

Growth inhibition studies were performed using the human HT29 colon cancer cell line, irofulven-resistant derivative HT29/IF2, breast cancer cell line MCF7, and ovarian cancer line CAOV3. Irofulven-oxaliplatin combinations were compared with irofulven-cisplatin combinations in the same cell lines using similar experimental settings. Cells were exposed for 1 h to irofulven and then for 24 h to oxaliplatin or cisplatin and vice versa.

RESULTS

Single agent irofulven displayed cytotoxic effects against human colon HT29 cells, human breast cancer cell lines including MCF7, SKBR3, and ZR-75-1, and human ovarian cancer cell lines CAOV3, OVCAR3, and IGROV1, with OVCAR3 being the most sensitive cancer cell line (IC50: 2.4 microM). In all tested cell lines the oxaliplatin-irofulven combination led to clear evidence of synergistic activity. In HT29 and HT29/IF2, the sequence oxaliplatin followed by irofulven appears to be the most effective whereas in MCF7 cells, irofulven given prior to or simultaneously with oxaliplatin is more effective than the other schedule. The combination displays additive activity toward CAOV3 ovarian cells when irofulven was administered prior to or simultaneously with oxaliplatin and partially synergistic when oxaliplatin was followed by irofulven. In most of the cell lines, the sequence oxaliplatin followed by irofulven appears to be the most effective as compared to other schedules. A combination of irofulven with cisplatin has the same efficacy as with oxaliplatin for the same cell lines. Cell cycle studies show that irofulven increases the proportion of cells in the S phase. Cisplatin-irofulven and oxaliplatin-irofulven combinations block cells in G1/S and potently induce apoptosis.

CONCLUSION

Irofulven displays synergistic antiproliferative and pro-apoptotic effects when combined with oxaliplatin over a broad range of concentrations in human colon and breast cancer cells. Acquired resistance to irofulven has limited impact on the effects of cisplatin-irofulven and oxaliplatin-irofulven combinations. Based on these data, irofulven-oxaliplatin and cisplatin-irofulven combinations will be further explored in clinical trials, favoring the use schedules of oxaliplatin given prior to irofulven in patients with cancer.

Phase I and pharmacokinetic study of irofulven administered weekly or biweekly in advanced solid tumor patients

PURPOSE

We performed a Phase I and pharmacokinetic study to determine the maximum tolerated dose of irofulven (6-hydroxymethylacylfulvene; MGI-114, MGI PHARMA, Inc.), administered in intermittent weekly schedules in patients with advanced solid tumors.

EXPERIMENTAL DESIGN

Three schedules were tested: A, days 1, 8, and 15 every 4 weeks; B, days 1 and 8 every 3 weeks; C, days 1 and 15 every 4 weeks. Drugs were administered as 5- and 30-min (schedules B and C) infusions. Dose levels of 10, 12, and 14 mg/m(2)/week were explored.

RESULTS

Ninety-nine patients received 256 cycles. Fifteen of 74 patients evaluable for maximum tolerated dose experienced 16 dose-limiting toxicities (5 of 17 patients on schedule A, 2 of 25 on schedule B, and 8 of 32 on schedule C), principally treatment delay for thrombocytopenia. Schedule A was considered unsuitable because of frequent thrombocytopenia and treatment discontinuations. Twenty-three percent of the overall population (22 patients with grade 1-2, and 1 patient with grade 3), including 37% of patients on dose level 3, experienced unexpected dose-limiting visual toxicity, which included color perception and visual field alterations linked to retinal cone cell toxicity; the visual toxicity had an early onset, was mostly reversible, and was related to higher dose per infusion. Safety profiles were similar for 5- and 30-min infusions. The relationships between dose and area under the plasma concentration-time curve and maximum plasma concentration were linear for both 5- and 30-min infusions in the 78 patients evaluated for pharmacokinetics. The area under the plasma concentration-time curve and clearance were comparable between infusion durations. Responses included one complete (ovarian), one partial (renal), and seven disease stabilizations lasting >4 months.

CONCLUSIONS

We recommend doses of 18 mg/m(2)/infusion for schedule B and 24 mg/m(2)/infusion for schedule C, limited to 0.55 mg/kg and a total dose of 50 mg/infusion, administered over 30-min.

Characterization and Multiparameter Analysis of Visual Adverse Events in Irofulven Single-Agent Phase I and II Trials

PURPOSE

Irofulven (6-hydroxymethylacylfulvene) is a novel agent, derived from illudin S, with potent apoptotic effects in preclinical models. In the Phase I trial evaluating intermittent weekly schedules, visual symptoms were dose limiting. The aim of this analysis was to better characterize the visual adverse events of irofulven and provide treatment guidelines.

EXPERIMENTAL DESIGN

Clinical data from 277 patients entered in single-agent Phase I to II clinical trials who received irofulven on days 1 and 15 every 4 weeks; days 1, 8, and 15 every 4 weeks; or days 1 and 8 every 3 weeks were included in this multiparameter analysis.

RESULTS

Overall, 74 patients (27%) experienced visual symptoms. The most frequently reported symptoms were flashing lights (12% of patients), blurred vision (9%), and photosensitivity (8%). Grade 3 toxicity was observed in 12 patients (4%). The incidence and severity of visual events were dose dependent, with no grade 3 visual events occurring at doses < or =0.50 mg/kg and grade 1 to 2 events in only 12% and 8% of patients, at doses of < or =0.50 mg/kg and < or =20 mg/m2, respectively. Grade 1 to 2 toxicity was reversible in most patients. Abnormal electroretinogram and abnormal visual fields were noted after irofulven treatment in 24 of 39 patients (62%) and 15 of 26 patients (58%), respectively. All but 1 patient who had electroretinogram assessment received doses >0.50 mg/kg. Clinical examination and visual field assessment were found to be better correlated with symptoms and appear to be more appropriate for surveillance of irofulven retinal symptoms than electroretinograms.

CONCLUSIONS

On the basis of retained antitumor activity and reversibility of grade 1 and 2 visual symptoms at lower doses, it appears that an irofulven dose of < or =0.50 mg/kg or < or =20 mg/m2, not to exceed 50 mg in a single dose, given as a 30-minute infusion on days 1 and 8 every 3 weeks or days 1 and 15 every 4 weeks minimizes the frequency and severity of visual symptoms.

Evaluation of irofulven (MGI-114) in the treatment of recurrent or persistent endometrial carcinoma: A phase II study of the Gynecologic Oncology Group

OBJECTIVE

This multi-center phase II trial was conducted by the Gynecologic Oncology Group to evaluate the activity and toxicity of irofulven in patients with previously treated adenocarcinoma of the endometrium.

METHODS

Eligible patients had documented recurrent or persistent endometrial carcinoma after receiving definitive locoregional therapy, and were required to have measurable disease, performance status of 0-2, and adequate bone marrow, hepatic and renal functions prior to study entry. Patients were allowed one prior chemotherapy regimen. The initial dose of irofulven was 11 mg/m(2)/day for four days administered intravenously. Cycles were repeated every 28 days. Doses were escalated or reduced based on previous cycle toxicity.

RESULTS

Twenty-five patients were enrolled onto the trial. There was one (4%) confirmed complete response. Seven (28%) patients had stable disease, with a median duration of 10.4 (range: 4.4-21.6) months. Patients received a median of one (range: 1-5) cycle of protocol treatment. There were three early treatment-related deaths due to renal failure and severe electrolyte disturbances. Two patients experienced grade 4 hematologic adverse effects.

CONCLUSION

Irofulven administered at the dose and schedule used in this trial was minimally active and resulted in significant toxicity.

Caspase-mediated apoptosis and caspase-independent cell death induced by irofulven in prostate cancer cells

Irofulven (hydroxymethylacylfulvene) is a novel antitumor drug, which acts by alkylating cellular macromolecular targets. The drug is a potent inducer of apoptosis in various types of tumor cells, whereas it is nonapoptotic in normal cells. This study defined molecular responses to irofulven involving mitochondrial dysfunction and leading to death of prostate tumor LNCaP-Pro5 cells. Irofulven caused early (2–5 hours) translocation of the proapoptotic Bax from cytosol to mitochondria followed by the dissipation of mitochondrial membrane potential and cytochrome c release at 4 to 12 hours. These effects preceded caspase activation and during the first 6 hours were not affected by caspase inhibitors. Processing of caspase-9 initiated the caspase cascade at ∼6 hours and progressed over time. The activation of the caspase cascade provided a positive feedback loop that enhanced Bcl-2-independent translocation and cytochrome c release. General and specific caspase inhibitors abrogated irofulven-induced apoptotic DNA fragmentation with the following order of potency: pan-caspase ≥ caspase-9 &gt; caspase-8/6 &gt; caspase-2 &gt; caspase-3/7 &gt; caspase-1/4. Abrogation of caspase-mediated DNA fragmentation failed to salvage irofulven-treated cells from growth inhibition and loss of viability, demonstrating a substantial contribution of a caspase-independent cell death. Monobromobimane, an inhibitor of alternative caspase-independent apoptotic pathway that is mediated by mitochondrial permeability transition, antagonized both apoptosis, measured as phosphatidylserine externalization, and cytotoxicity of irofulven. Collectively, the results indicate that irofulven-induced signaling is integrated at the level of mitochondrial dysfunction. The induction of both caspase-dependent and caspase-independent death pathways is consistent with pleiotropic effects of irofulven, which include targeting of cellular DNA and proteins.