Changing Body Weight-Based Dosing to a Flat Dose for Avelumab in Metastatic Merkel Cell and Advanced Urothelial Carcinoma

Avelumab, an anti–programmed death‐ligand 1 monoclonal antibody approved for the treatment of metastatic Merkel cell carcinoma and platinum‐treated urothelial carcinoma, was initially approved with a 10 mg/kg weight‐based dose. We report pharmacokinetic (PK)/pharmacodynamic analyses for avelumab comparing weight‐based dosing and a flat 800 mg dose, developed using data from 1,827 patients enrolled in 3 clinical trials (NCT01772004, NCT01943461, and NCT02155647). PK metrics were simulated for weight‐based and flat‐dosing regimens and summarized by quartiles of weight. Derived exposure metrics were used in simulations of exposure‐safety (various tumors) and exposure‐efficacy (objective responses; Merkel cell or urothelial carcinoma). Flat dosing was predicted to provide similar exposure to weight‐based dosing, with slightly lower variability. Exposure‐safety and exposure‐efficacy simulations suggested similar benefit:risk profiles for the two dosing regimens. These pharmacometric analyses provided the basis for the US Food and Drug Administration approval of a flat dose of avelumab 800 mg every 2 weeks in approved indications.

Time-Varying Clearance and Impact of Disease State on the Pharmacokinetics of Avelumab in Merkel Cell Carcinoma and Urothelial Carcinoma

Avelumab, a human anti-programmed death ligand 1 immunoglobulin G1 antibody, has shown efficacy and manageable safety in multiple tumors. A two-compartment population pharmacokinetic model for avelumab incorporating intrinsic and extrinsic covariates and time-varying clearance (CL) was identified based on data from 1,827 patients across three clinical studies. Of 14 tumor types, a decrease in CL over time was more notable in metastatic Merkel cell carcinoma and squamous cell carcinoma of the head and neck, which had maximum decreases of 32.1% and 24.7%, respectively. The magnitude of reduction in CL was higher in responders than in nonresponders. Significant covariate effects of baseline weight, baseline albumin, and sex were identified on both CL and central distribution volume. Significant covariate effects of black/African American race, C-reactive protein, and immunogenicity were found on CL. None of the covariate or time-dependent effects were clinically important or warranted dose adjustment.

Effect of food or proton pump inhibitor treatment on the bioavailability of dacomitinib in healthy volunteers

This phase 1, open-label crossover study evaluated the relative bioavailability of dacomitinib in healthy volunteers under fed and fasted conditions and following coadministration with rabeprazole, a potent acid-reducing proton pump inhibitor (PPI). Twenty-four male subjects received a single dacomitinib 45-mg dose under 3 different conditions separated by washout periods of ≥ 16 days: coadministered with rabeprazole 40 mg under fasting conditions; alone under fasting conditions; and alone after a high-fat, high-calorie meal. Increased peak exposure of 23.7% (90% confidence interval [CI], 5.3%-45.2%) was detected with dacomitinib taken after food versus fasting. The adjusted geometric mean ratio (fed/fasted) for area under the plasma concentration-time curve from time zero to infinity (AUCinf ) was 114.2% (90%CI, 104.7%-124.5%) and not considered clinically meaningful. In the fasted state, a decrease in dacomitinib AUCinf was observed following rabeprazole versus dacomitinib alone (PPI+fasted/fasted alone): 71.1% (90%CI, 61.7%-81.8%). Dacomitinib was generally well tolerated. Dacomitinib may be taken with or without food. Use of long-acting acid-reducing agents, such as PPIs with dacomitinib should be avoided if possible. Shorter-acting agents such as antacids and H2-receptor antagonists may have lesser impact on dacomitinib exposure and may be preferable to PPIs if acid reduction is clinically required.

Abstract 763: A phase 1 open-label study to investigate the potential drug-drug interaction (DDI) between single-dose (SD) dacomitinib (PF-00299804; DC) and steady-state (SS) paroxetine (PX) in healthy volunteers (HVs)

Introduction: DC, a small molecule, pan-HER inhibitor, is partly metabolized by cytochrome P450 (CYP) 2D6. Concomitant administration with therapeutic agents that are inhibitors of CYP2D6 could potentially cause DDIs. This study evaluated the effect of PX, a potent CYP2D6 inhibitor, on the pharmacokinetics (PK) of DC in HVs who were extensive CYP2D6 metabolizers. The safety and tolerability of SD DC was also assessed when given alone and co-administered with PX. Methods: In this Phase 1, single fixed-sequence, 2-period study, 14 HVs received a 45 mg SD of DC alone (Period 1). After a 21-day washout, 30 mg of PX was given daily for 10 days (Period 2) and on Day 4, a 45 mg SD of DC was co-administered with PX. Blood samples were collected up to 240 h post DC dose in both periods and analyzed for DC, its CYP2D6 metabolite PF-05199265, and PX using validated high performance liquid chromatographic tandem mass spectrometric methods. PK parameters were calculated using noncompartmental methods. Analysis of variance was performed on natural log transformed AUC and Cmax to estimate adjusted mean treatment differences and 90% confidence intervals (CI) which were exponentiated to produce the adjusted geometric mean ratio (GMR) and 90% CI of the ratios. Results: 14 males (median age 41 [23-54] yrs; 9 black, 5 Caucasian) were evaluated for PK and safety. The GMR and 90% CI of AUCinf and Cmax for DC when given as DC + PX vs DC alone was 137.2% (109.1%, 172.6%) and 110% (82.9%, 145.1%), respectively. Median Tmax of DC was 8 and 10 h post dose, and its half-life was 96 and 90 h, in the presence and absence of PX, respectively. Total exposure (AUC240) to PF-05199265 was decreased in the presence of SS PX (33.5 vs 322 ng.hr/mL). There were no serious adverse events (AEs), severe AEs, or deaths during the study. The majority of AEs were mild (including all 14 events reported during DC treatment alone) and resolved. Conclusions: PX inhibited DC metabolism resulting in 90% reduction in exposure (AUC240) of the CYP2D6 metabolite, PF-05199265. No meaningful change in absorption was observed when DC was given with SS concentrations of PX. DC seems to present a low extraction profile and high variability during the absorption phase, the latter probably due to its physicochemical characteristics (BCS Class II). In the presence of PX, there was an approximate 37% increase in DC exposure (AUCinf) with a wide CI, reflecting large intra-subject variability. The DC change in exposure reported in this study is likely to be less in the clinical setting (45 mg QD). As the exposure of DC reported in the presence of PX is within the range shown to be tolerated and efficacious, no dose adjustment is recommended for DC when administered concomitantly with a CYP2D6 inhibitor, such as PX. SD DC administered alone and in combination with PX was well tolerated.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 763. doi:1538-7445.AM2012-763

Abstract 1291: A phase 1 open-label single-radiolabeled dose study of PF299804 in healthy male volunteers

Objectives: To characterize the primary routes of elimination of the second-generation, oral, irreversible, pan-HER tyrosine kinase inhibitor, PF299804; to evaluate the pharmacokinetics (PK) of total radioactivity and of PF299804; and to identify the metabolites of PF299804 in plasma, urine, and feces in healthy volunteers (HVs).

Methods: This Phase 1 study evaluated the mass balance and PK of PF299804 in HVs (18-55 yrs), following a single 45-mg oral dose containing ∼100 µCi [14C] PF299804. Serial samples were collected over an 18-day period. Radioactivity measurements of blood, plasma, urine, and feces were conducted by liquid scintillation spectroscopy. Plasma samples were analyzed for PF299804 and the metabolite PF5199265 using high-performance liquid chromatography with atmospheric pressure ionization tandem mass spectrometry. Plasma, urine, and fecal samples were analyzed for metabolic profiling of PF299804; major metabolites of PF299804 were identified where possible.

Results: 6 HVs (male; median age 31.5 yrs) received treatment and were evaluated for PK and safety. 78.8% of the radiolabeled material was excreted in feces, and a further 3.2% was recovered in urine. Peak concentrations of PF299804 in plasma generally occurred 12 hrs after oral dosing, and 6 hrs post-dose for PF5199265. Plasma exposure for the metabolite was approximately one-third of that for the parent compound. Terminal plasma half-life (t1/2) averaged about 55 hrs for PF299804 and 73 hrs for PF5199265. Peak concentrations of total radioactivity in plasma occurred at 12 hrs. Geometric mean Cmax was approximately 2-fold higher and total exposure (AUCinf) was almost 6-fold higher for total radioactivity than for PF299804 in plasma. t1/2 for plasma radioactivity was 182 hrs. PF299804 and its O-desmethyl metabolite, PF5199265, were the major drug-related components in plasma. Other trace components were observed in the profile. The most abundant drug-related components identified in excreta were proposed to be PF299804, PF5199265, a cysteine conjugate (M2), and a mono-oxygenated metabolite (M7). There were no serious adverse events (AEs), severe AEs, or deaths during the study. Mild AEs were reported in 2 HVs: dermatitis acneiform, dizziness, insomnia, and photophobia (all considered related to study drug).

Conclusions: Following single-dose administration of [14C] PF299804 the radiolabeled material was primarily eliminated in feces (78.8%) and, to a lesser degree, in urine (3.2%). Estimates of exposure for total radioactivity in plasma (Cmax and AUCinf) were 2- and 6-fold higher, respectively, than exposure for plasma PF299804, indicating the presence of circulating metabolic product(s). The metabolic profiles indicated that [14C] PF299804 underwent oxidative and conjugative metabolism in HVs.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 1291. doi:10.1158/1538-7445.AM2011-1291

Pharmacokinetics and safety of sunitinib malate in subjects with impaired renal function

This phase I, open-label, single-dose study evaluates the effects of severe renal impairment and end-stage renal disease (ESRD) requiring hemodialysis on the pharmacokinetics, safety, and tolerability of sunitinib and its primary active metabolite, SU12662. Subjects with normal renal function (creatinine clearance > 80 mL/min), severe renal impairment (creatinine clearance < 30 mL/min), and ESRD requiring hemodialysis receive a single dose of sunitinib 50 mg. Serial blood samples are collected for quantification of plasma concentrations using a validated liquid chromatography with tandem mass spectrometry assay. Safety is monitored. Twenty-four subjects complete the study. Pharmacokinetics in subjects with severe renal impairment appear similar to those with normal renal function. Plasma exposure to sunitinib and SU12662 appears lower in subjects with ESRD compared with subjects with normal renal function or severe renal impairment. Single-dose sunitinib 50 mg is well tolerated regardless of renal function. The currently approved starting dose of sunitinib 50 mg on Schedule 4/2 is expected to be appropriate for patients with renal impairment; any subsequent dose modifications should be based on patients' ability to tolerate treatment.

Molecular target modulation, imaging, and clinical evaluation of gastrointestinal stromal tumor patients treated with sunitinib malate after imatinib failure

PURPOSE

To evaluate sunitinib activity and potential cellular and molecular correlates in gastrointestinal stromal tumor (GIST) patients after imatinib failure, in addition to assessing the safety and pharmacokinetics (PK) of different dose schedules.

EXPERIMENTAL DESIGN

In this open-label, dose-ranging, phase I/II study, 97 patients with metastatic imatinib-resistant/intolerant GIST received sunitinib at doses of 25, 50, or 75 mg/d on one of three schedules. Serial tumor imaging was done using computed tomography and [18F]fluoro-2-deoxy-d-glucose positron emission tomography scanning. PK and cell proliferation and KIT phosphorylation status in tumor biopsies were also analyzed.

RESULTS

Clinical benefit was observed in 52 patients (54%: 7 objective partial responses, 45 stable disease > or =6 months). Decreased tumor glycolytic activity was shown in most patients within 7 days of starting sunitinib using [18F]fluoro-2-deoxy-d-glucose positron emission tomography. Sunitinib treatment was associated with reduced tumor cell proliferation by >25% in 52% of cases analyzed and reduced levels of phospho-KIT in tumor biopsies (indicating target modulation). The recommended dose schedule was 50 mg/d for 4 weeks followed by 2 weeks off treatment. On the 50-mg dose across all schedules, 79% of PK-evaluable patients achieved total drug trough concentrations above the target concentration (50 ng/mL) within 14 days of dosing. In addition, adverse events were generally mild to moderate in severity.

CONCLUSION

Cellular and molecular analyses showed that sunitinib clinical activity is associated with inhibition of KIT in GIST following imatinib failure, illustrating the rational approach used to develop a therapy aimed at the underlying oncogenic signaling pathway aberrancy.

A population pharmacokinetic meta-analysis of sunitinib malate (SU11248) and its primary metabolite (SU12662) in healthy volunteers and oncology patients

PURPOSE

Sunitinib malate is an oral multitargeted tyrosine kinase inhibitor approved for advanced renal cell carcinoma and imatinib-resistant or imatinib-intolerant gastrointestinal stromal tumor. Following administration, sunitinib is metabolized by cytochrome P450 3A4 to an active metabolite (SU12662). The objective of this analysis was to assess sunitinib and SU12662 pharmacokinetics and to identify covariates that might explain variability in exposure following oral administration.

EXPERIMENTAL DESIGN

Data from 590 subjects (73 volunteers and 517 patients) in 14 studies were analyzed. Plasma concentration-time data were analyzed using nonlinear mixed-effects modeling to estimate population pharmacokinetic parameters, as well as relationships between these parameters and gender, race, age, weight, creatinine clearance, Eastern Cooperative Oncology Group score, and tumor type. Simulations were done to determine the predicted effect of these covariates on exposure.

RESULTS

Separate models were developed for sunitinib and SU12662 (each a two-compartment model with first-order absorption and elimination). Sunitinib parameters were estimated as CL/F, 51.8 L/h and Vd/F(central), 2,030 liters. SU12662 parameters were estimated as CL/F, 29.6 L/h and Vd/F(central), 3,080 liters. Tumor type (except acute myeloid leukemia), Asian race, gender, body weight, and elevated Eastern Cooperative Oncology Group score described a portion of the variability in CL/F for sunitinib and metabolite; gender and body weight explained some of the variability in Vd/F(central) for sunitinib and metabolite. Among patients, the predicted changes in sunitinib and metabolite AUC and C(max) as a result of the individual covariates ranged up to 17%.

CONCLUSION

The magnitude of the predicted changes in exposure with the covariates studied minimizes the necessity for dose adjustment in any of these subpopulations.

Phase II Study of Sunitinib Malate, an Oral Multitargeted Tyrosine Kinase Inhibitor, in Patients With Metastatic Breast Cancer Previously Treated With an Anthracycline and a Taxane

Purpose

Sunitinib is an oral, multitargeted tyrosine kinase inhibitor that inhibits vascular endothelial growth factor receptor (VEGFR), platelet-derived growth factor receptor, stem cell factor receptor (KIT), and colony-stimulating factor-1 receptor. This phase II, open-label, multicenter study evaluated sunitinib monotherapy in patients with metastatic breast cancer (MBC).

Patients and Methods

Sixty-four patients previously treated with an anthracycline and a taxane received sunitinib 50 mg/d in 6-week cycles (4 weeks on, then 2 weeks off treatment). The primary end point was objective response rate. Plasma samples were obtained for pharmacokinetic and biomarker analysis.

Results

Seven patients achieved a partial response (median duration, 19 weeks), giving an overall response rate of 11%. Three additional patients (5%) maintained stable disease for ≥ 6 months. Median time to progression and overall survival were 10 and 38 weeks, respectively. Notably, responses occurred in triple negative tumors and HER2-positive, trastuzumab-treated patients. Thirty-three patients (52%) required dose interruption during ≥ 1 cycle, and 25 patients required dose reduction (39%). Thirty-six patients (56%) had dose modifications due to adverse events (AEs). Treatment was associated with increases in plasma VEGF and decreases in soluble VEGFRs and KIT. The most common AEs were fatigue, nausea, diarrhea, mucosal inflammation, and anorexia. Most AEs were mild to moderate (grade 1 to 2) in severity and were effectively managed with dose delays or reductions.

Conclusion

Sunitinib is active in patients with heavily pretreated MBC. Most AEs were of mild-to-moderate severity and manageable with supportive treatment and/or dose modification. Further studies in breast cancer are warranted.

Circulating protein biomarkers of pharmacodynamic activity of sunitinib in patients with metastatic renal cell carcinoma: modulation of VEGF and VEGF-related proteins

BACKGROUND

Sunitinib malate (SUTENT) is an oral, multitargeted tyrosine kinase inhibitor, approved multinationally for the treatment of advanced RCC and of imatinib-resistant or - intolerant GIST. The purpose of this study was to explore potential biomarkers of sunitinib pharmacological activity via serial assessment of plasma levels of four soluble proteins from patients in a phase II study of advanced RCC: VEGF, soluble VEGFR-2 (sVEGFR-2), placenta growth factor (PlGF), and a novel soluble variant of VEGFR-3 (sVEGFR-3).

METHODS

Sunitinib was administered at 50 mg/day on a 4/2 schedule (4 weeks on treatment, 2 weeks off treatment) to 63 patients with metastatic RCC after failure of first-line cytokine therapy. Predose plasma samples were collected on days 1 and 28 of each cycle and analyzed via ELISA.

RESULTS

At the end of cycle 1, VEGF and PlGF levels increased >3-fold (relative to baseline) in 24/54 (44%) and 22/55 (40%) cases, respectively (P < 0.001). sVEGFR-2 levels decreased >or= 30% in 50/55 (91%) cases and >or= 20% in all cases (P < 0.001) during cycle 1, while sVEGFR-3 levels were decreased >or= 30% in 48 of 55 cases (87%), and >or= 20% in all but 2 cases. These levels tended to return to near-baseline after 2 weeks off treatment, indicating that these effects were dependent on drug exposure. Overall, significantly larger changes in VEGF, sVEGFR-2, and sVEGFR-3 levels were observed in patients exhibiting objective tumor response compared with those exhibiting stable disease or disease progression (P < 0.05 for each analyte; analysis not done for PlGF).

CONCLUSION

Sunitinib treatment in advanced RCC patients leads to modulation of plasma levels of circulating proteins involved in VEGF signaling, including soluble forms of two VEGF receptors. This panel of proteins may be of value as biomarkers of the pharmacological and clinical activity of sunitinib in RCC, and of angiogenic processes in cancer and other diseases.

A phase I and pharmacokinetic study of sunitinib administered daily for 2 weeks, followed by a 1-week off period

PURPOSE

Sunitinib, an oral multitargeted tyrosine kinase inhibitor that inhibits VEGFR, PDGFR, FLT3, KIT, and RET, is currently approved for the treatment of imatinib-refractory GIST and advanced renal cell carcinoma at a dose of 50 mg daily for 4 weeks followed by a 2-week off period (4/2 schedule). This trial was performed to investigate the safety, tolerability, and pharmacokinetics of sunitinib 50 mg daily for 2 weeks followed by a 1-week off period (2/1 schedule).

EXPERIMENTAL DESIGN

Twelve patients with advanced refractory malignancies were treated with sunitinib on the 2/1 schedule. Intensive safety monitoring included serial measurements of left ventricular ejection fraction (LVEF). Extensive pharmacokinetic sampling was performed on days 1 and 14 of course 1, and on day 14 of courses 2 and 3 to evaluate sunitinib and the SU12662 metabolite.

RESULTS

Twelve patients received a total of 50 courses with an average (+/-SD) off-drug period of 11.5 +/- 5.7 days. Two patients experienced DLT: one patient had asymptomatic grade 4 elevations in lipase and amylase, and another patient had an asymptomatic grade 2 decline in LVEF in course 1. In total, five patients demonstrated asymptomatic grade 2 declines in LVEF. Other principal effects were similar to previous experience with sunitinib, including fatigue, myelosuppression, skin discoloration, and gastrointestinal effects. Pharmacokinetic studies revealed no significant accumulation of sunitinib or SU12662. One patient with papillary thyroid cancer developed a partial response, and was on study for 16 courses, followed by an additional 18 courses on a continuation protocol.

CONCLUSIONS

The 2/1 schedule of sunitinib 50 mg was tolerable, and no significant drug accumulation was demonstrated. The safety profile on this schedule was consistent with the safety profile of sunitinib when administered on a 4-week on, 2-week off schedule.

Efficacy and safety of sunitinib in patients with advanced gastrointestinal stromal tumour after failure of imatinib: a randomised controlled trial

BACKGROUND

No effective therapeutic options for patients with unresectable imatinib-resistant gastrointestinal stromal tumour are available. We did a randomised, double-blind, placebo-controlled, multicentre, international trial to assess tolerability and anticancer efficacy of sunitinib, a multitargeted tyrosine kinase inhibitor, in patients with advanced gastrointestinal stromal tumour who were resistant to or intolerant of previous treatment with imatinib.

METHODS

Blinded sunitinib or placebo was given orally once daily at a 50-mg starting dose in 6-week cycles with 4 weeks on and 2 weeks off treatment. The primary endpoint was time to tumour progression. Intention-to-treat, modified intention-to-treat, and per-protocol analyses were done. This study is registered at ClinicalTrials.gov, number NCT00075218.

FINDINGS

312 patients were randomised in a 2:1 ratio to receive sunitinib (n=207) or placebo (n=105); the trial was unblinded early when a planned interim analysis showed significantly longer time to tumour progression with sunitinib. Median time to tumour progression was 27.3 weeks (95% CI 16.0-32.1) in patients receiving sunitinib and 6.4 weeks (4.4-10.0) in those on placebo (hazard ratio 0.33; p<0.0001). Therapy was reasonably well tolerated; the most common treatment-related adverse events were fatigue, diarrhoea, skin discolouration, and nausea.

INTERPRETATION

We noted significant clinical benefit, including disease control and superior survival, with sunitinib compared with placebo in patients with advanced gastrointestinal stromal tumour after failure and discontinuation of imatinab. Tolerability was acceptable.

Sunitinib malate for the treatment of solid tumours: a review of current clinical data

Receptor tyrosine kinases (RTKs) play important roles in the regulation of cellular growth, and mutated or overexpressed RTKs have been implicated in various human cancers. Sunitinib malate is an oral multitargeted tyrosine kinase inhibitor with antitumour and antiangiogenic activity that recently received approval from the FDA for the treatment of advanced renal cell carcinoma and of gastrointestinal stromal tumours after disease progression on or intolerance to imatinib mesilate therapy. Sunitinib has also demonstrated promising clinical activity in the treatment of other advanced solid tumours. The present review provides an updated summary of emerging clinical experience with this promising new anticancer agent.

Effect of food on the pharmacokinetics of sunitinib malate (SU11248), a multi-targeted receptor tyrosine kinase inhibitor: results from a phase I study in healthy subjects

The effect of food on the oral bioavailability of sunitinib malate (SU11248, an oral, multi-targeted tyrosine kinase inhibitor with anti-angiogenic and anti-tumor activities) was assessed in a randomized open-label, two-way crossover study. A 50-mg dose of SU11248 was administered to 16 healthy subjects after a 10-h fast in one period and after a high-fat, high-calorie meal in the other period. The 90% confidence intervals (CIs) for maximum plasma concentration (Cmax) and area under the concentration-time curve (AUC) were within the 80-125% bioequivalence range, indicating the absence of a food effect. SU11248 exposure increased slightly in the fed compared with the fasted state (ratios of fed/fasted geometric least square means: Cmax 104%, AUC0-last and AUC0-infinity both 112%). There was a delay in the formation/absorption of the active metabolite SU12662 in the fed state (mean Cmax decreased 23%), but exposure remained unaffected (90% CIs for AUC0-last and AUC0-infinity were within 80-125%). These results indicate that SU11248 can be administered with or without food.

Activity of SU11248, a multitargeted inhibitor of vascular endothelial growth factor receptor and platelet-derived growth factor receptor, in patients with metastatic renal cell carcinoma

PURPOSE

Renal cell carcinoma (RCC) is characterized by loss of von Hippel Lindau tumor suppressor gene activity, resulting in high expression of pro-angiogenic growth factors: vascular endothelial growth factor (VEGF) and platelet-derived growth factor (PDGF). SU11248 (sunitinib malate), a small molecule inhibitor with high binding affinity for VEGF and PDGF receptors, was tested for clinical activity in patients with metastatic RCC.

PATIENTS AND METHODS

Patients with metastatic RCC and progression on first-line cytokine therapy were enrolled onto a multicenter phase II trial. SU11248 monotherapy was administered in repeated 6-week cycles of daily oral therapy for 4 weeks, followed by 2 weeks off. Overall response rate was the primary end point, and time to progression and safety were secondary end points. Results Twenty-five (40%) of 63 patients treated with SU11248 achieved partial responses; 17 additional patients (27%) demonstrated stable disease lasting > or = 3 months. Median time to progression in the 63 patients was 8.7 months. Dosing was generally tolerated with manageable toxicities.

CONCLUSION

SU11248, a multitargeted receptor tyrosine kinase inhibitor of VEGF and PDGF receptors, demonstrates antitumor activity in metastatic RCC as second-line therapy, a setting where no effective systemic therapy is presently recognized. The genetics of RCC and these promising clinical results support the hypothesis that VEGF and PDGF receptor-mediated signaling is an effective therapeutic target in RCC.

A phase 1 study of SU11248 in the treatment of patients with refractory or resistant acute myeloid leukemia (AML) or not amenable to conventional therapy for the disease

Fifteen patients with refractory AML were treated in a phase 1 study with SU11248, an oral kinase inhibitor of fms-like tyrosine kinase 3 (Flt3), Kit, vascular endothelial growth factor (VEGF), and platelet-derived growth factor (PDGF) receptors. Separate cohorts of patients received SU11248 for 4-week cycles followed by either a 2- or a 1-week rest period. At the starting dose level of 50 mg (n = 13), no dose-limiting toxicities were observed. The most frequent grade 2 toxicities were edema, fatigue, and oral ulcerations. Two fatal bleedings possibly related to the disease, one from a concomitant lung cancer and one cerebral bleeding, were observed. At the 75 mg dose level (n = 2), one case each of grade 4 fatigue, hypertension, and cardiac failure was observed, and this dose level was abandoned. All patients with FLT3 mutations (n = 4) had morphologic or partial responses compared with 2 of 10 evaluable patients with wild-type FLT3. Responses, although longer in patients with mutated FLT3, were of short duration. Reductions of cellularity and numbers of Ki-67(+), phospho-Kit(+), phospho-kinase domain-containing receptor-positive (phospho-KDR(+)), phospho-signal transducer and activator of transcription 5-positive (phospho-STAT5(+)), and phospho-Akt(+) cells were detected in bone marrow histology analysis. In summary, monotherapy with SU11248 induced partial remissions of short duration in acute myeloid leukemia (AML) patients. Further evaluation of this compound, for example in combination with chemotherapy, is warranted.

Functional characteristics and steroid hormone-mediated regulation of an organic cation transporter in Madin-Darby canine kidney cells

Organic cation transporters (OCT1-3) play an important role in renal elimination of many drugs. The goals of this study were to 1) identify a cell culture model which constitutively expressed OCT2 that could be used to study the characteristics and regulation of this transporter, and 2) to study the mechanisms by which xenobiotics and hormones regulate the activity of OCT2. We characterized the endogenous organic cation transporter (OCT) activity in Madin-Darby canine kidney (MDCK) cells. The activity was localized to the basolateral membrane and was pH and membrane potential-dependent. The uptake of the model organic cation, tetraethylammonium, was saturable (Km, 19.5 +/- 4.6 microM; Vmax, 350 +/- 19.4 pmol/mg of protein/10 min) and was inhibited by known OCT inhibitors (e.g., cimetidine and quinidine). A cDNA fragment (711 base pairs) isolated by reverse transcriptase-polymerase chain reaction (RT-PCR) was greater than 83% identical to OCT2 cDNAs from mammalian species; no OCT1 or OCT3 was detected by RT-PCR, suggesting that OCT2 may be the primary basolateral OCT in MDCK. OCT2 mRNA levels were increased significantly following exposure of MDCK to the steroid hormones, dexamethasone (2.0-fold), hydrocortisone (2.4-fold), and testosterone (1.8-fold) with comparable increases in activity. Other compounds tested, including the cytochrome P450 inducers, rifampicin, phenobarbital, and phenytoin, and the OCT substrates, verapamil and metformin, had no inducing effects. Collectively, these data indicate that MDCK can serve as a useful and convenient tool in screening candidate drugs for interaction with OCT2 and for studying the regulation of this transporter. Furthermore, our data demonstrate that steroid hormones induce the transcription of OCT2 in the kidney.

[Nymphal feeding of Leptophlebiidae (Insecta: Ephemeroptera) in the Caño Paso del Diablo, Venezuela]

The food habits of aquatic nymphs of 12 species of the family Leptophlebiidae were determined in a tropical intermittent stream in Venezuela. Three monthly samples of aquatic insects were taken from January to June in 1989. Two hundred and twenty-five stomach contents were analyzed. The results obtained were compared by the functional feeding groups classification. Species of the Thraulodes and Farrodes genera show significant differences in their diets.