Elizabeth Fox

Tariquidar (XR9576): a P-glycoprotein drug efflux pump inhibitor.

P-glycoprotein actively transports structurally unrelated compounds out of cells, conferring the multidrug resistance phenotype in cancer. Tariquidar is a potent, specific, noncompetitive inhibitor of P-glycoprotein. Tariquidar inhibits the ATPase activity of P-glycoprotein, suggesting that the modulating effect is derived from the inhibition of substrate binding, inhibition of ATP hydrolysis or both. In clinical trials, tariquidar is tolerable and does not have significant pharmacokinetic interaction with chemotherapy. In patients, inhibition of P-glycoprotein has been demonstrated for 48 h after a single dose of tariquidar. Studies to assess a possible increase in toxicity of chemotherapy and the impact of P-glycoprotein inhibition on tumor response and patient outcome are ongoing. Tariquidar can be considered an ideal agent for testing the role of P-glycoprotein inhibition in cancer.

Phase I Trial and Pharmacokinetic Study of the Farnesyltransferase Inhibitor Tipifarnib in Children With Refractory Solid Tumors or Neurofibromatosis Type I and Plexiform Neurofibromas

PURPOSE This pediatric phase I trial of tipifarnib determined the maximum-tolerated dose (MTD), pharmacokinetics, and pharmacodynamics of tipifarnib in children with refractory solid tumors and neurofibromatosis type 1 (NF1) -related plexiform neurofibromas. PATIENTS AND METHODS Tipifarnib was administered twice daily for 21 days, repeated every 28 days starting at 150 mg/m2/dose (n = 4), with escalations to 200 (n = 12), 275 (n = 12), and 375 (n = 6) mg/m2/dose. The MTD was also evaluated on a chronic continuous dosing schedule (n = 6). Pharmacokinetic sampling was performed for 36 hours after the first dose and peripheral-blood mononuclear cells (PBMCs) were collected at baseline and steady state for determination of farnesyl protein transferase (FTase) activity and HDJ-2 farnesylation. RESULTS Twenty-three solid tumor and 17 NF1 patients were assessable for toxicity. The MTD was 200 mg/m2/dose, and dose-limiting toxicities on cycle 1 were myelosuppression, rash, nausea, vomiting, and diarrhea. The 200 mg/m2/dose was also tolerable on the continuous dosing schedule. Cumulative toxicity was not observed in the 17 NF1 patients who received a median of 10 cycles (range, 1 to 32 cycles). The plasma pharmacokinetics of tipifarnib were highly variable but not age dependent. At steady state on 200 mg/m2/dose, FTase activity was 30% compared with baseline, and farnesylation of HDJ-2 was inhibited in PBMCs. CONCLUSION Oral tipifarnib is well tolerated in children receiving the drug twice daily for 21 days and a continuous dosing schedule at 200 mg/m2/dose, which is equivalent to the MTD in adults. The pharmacokinetic profile of tipifarnib in children is similar to that in adults, and at the MTD, FTase is inhibited in PBMC in vivo.

NF1 plexiform neurofibroma growth rate by volumetric MRI Relationship to age and body weight

Objective: To longitudinally analyze changes in plexiform neurofibroma (PN) volume in relation to age and body growth in children and young adults with neurofibromatosis type 1 and inoperable, symptomatic, or progressive PNs, using a sensitive, automated method of volumetric MRI analysis. Methods: We included patients 25 years of age and younger with PNs entered in a natural history study or in treatment trials who had volumetric MRI over ≥16 months. Results: We studied 49 patients (median age 8.3 years) with 61 PNs and a median evaluation period of 34 months (range 18 to 70). The PN growth rates varied among patients, but were constant within patients. Thirty-four patients (69%) experienced ≥20% increase in PN volume during the observation period. PN volume increased more rapidly than body weight over time (p = 0.026). Younger patients had the most rapid PN growth rate. Conclusions: Volume increase of plexiform neurofibromas is a realistic and meaningful trial endpoint. In most patients plexiform neurofibroma growth rate exceeded body growth rate. The youngest patients had the fastest plexiform neurofibroma growth rate, and clinical drug development should be directed toward this population. Age stratification for clinical trials for plexiform neurofibromas should be considered.

Vandetanib in Children and Adolescents with Multiple Endocrine Neoplasia Type 2B Associated Medullary Thyroid Carcinoma

Purpose: Medullary thyroid carcinoma (MTC) is a manifestation of multiple endocrine neoplasia type 2 (MEN2) syndromes caused by germline, activating mutations in the RET (REarranged during Transfection) proto-oncogene. Vandetanib, a VEGF and EGF receptor inhibitor, blocks RET tyrosine kinase activity and is active in adults with hereditary MTC. Experimental Design: We conducted a phase I/II trial of vandetanib for children (5–12 years) and adolescents (13–18 years) with MTC to define a recommended dose and assess antitumor activity. The starting dose was 100 mg/m2 administered orally, once daily, continuously for 28-day treatment cycles. The dose could be escalated to 150 mg/m2/d after two cycles. Radiographic response to vandetanib was quantified using RECIST (v1.0), biomarker response was measured by comparing posttreatment serum calcitonin and carcinoembryonic antigen (CEA) levels to baseline, and a patient-reported outcome was used to assess clinical benefit. Results: Sixteen patients with locally advanced or metastatic MTC received vandetanib for a median (range) 27 (2–52) cycles. Eleven patients remain on protocol therapy. Diarrhea was the primary dose-limiting toxicity. In subjects with M918T RET germline mutations (n = 15) the confirmed objective partial response rate was 47% (exact 95% confidence intervals, 21%–75%). Biomarker partial response was confirmed for calcitonin in 12 subjects and for CEA in 8 subjects. Conclusion: Using an innovative trial design and selecting patients based on target gene expression, we conclude that vandetanib 100 mg/m2/d is a well-tolerated and highly active new treatment for children and adolescents with MEN2B and locally advanced or metastatic MTC. Clin Cancer Res; 19(15); 4239–48. ©2013 AACR.

A Phase 1 Trial and Pharmacokinetic Study of Cediranib, an Orally Bioavailable Pan–Vascular Endothelial Growth Factor Receptor Inhibitor, in Children and Adolescents With Refractory Solid Tumors

PURPOSE To determine the toxicity profile, dose-limiting toxicities (DLTs), maximum-tolerated dose (MTD), pharmacokinetics, and pharmacodynamics of cediranib administered orally, once daily, continuously in children and adolescents with solid tumors. PATIENTS AND METHODS Children and adolescents with refractory solid tumors, excluding primary brain tumors, were eligible. DLT at the starting dose of 12 mg/m(2)/d resulted in de-escalation to 8 mg/m(2)/d and subsequent re-escalation to 12 and 17 mg/m(2)/d. Pharmacokinetic and pharmacodynamic studies were performed during cycle 1. Response was evaluated using WHO criteria. RESULTS Sixteen patients (median age, 15 years; range, 8 to 18 years) were evaluable for toxicity. DLTs (grade 3 nausea, vomiting, fatigue in one; hypertension and prolonged corrected QT interval in another) occurred in patients initially enrolled at 12 mg/m(2)/d. Subsequently, 8 mg/m(2)/d was well tolerated in three patients. An additional seven patients were enrolled at 12 mg/m(2)/d; one had DLT (grade 3 diarrhea). At 17 mg/m(2)/d, two of four patients had DLTs (grade 3 nausea; intolerable grade 2 fatigue). Non-dose-limiting toxicities included left ventricular dysfunction, elevated thyroid stimulating hormone, palmar-plantar erythrodysesthesia, weight loss, and headache. The MTD of cediranib was 12 mg/m(2)/d (adult fixed dose equivalent, 20 mg). At 12 mg/m(2)/d, the median area under the plasma concentration-time curve extrapolated to infinity (AUC(0-∞)) was 900 ng·h/mL, which is similar to adults receiving 20 mg. Objective responses were observed in patients with Ewing sarcoma, synovial sarcoma, and osteosarcoma. CONCLUSION The recommended monotherapy dose of cediranib for children with extracranial solid tumors is 12 mg/m(2)/d administered orally, once daily, continuously. A phase II study is in development.

A Phase I Trial and Pharmacokinetic Study of Sorafenib in Children with Refractory Solid Tumors or Leukemias: A Children's Oncology Group Phase I Consortium Report

Purpose To determine the dose-limiting toxicities (DLT), maximum tolerated dose (MTD), pharmacokinetics and pharmacodynamics of sorafenib in children with refractory extracranial solid tumors and evaluate the tolerability of the solid tumor MTD in children with refractory leukemias. Experimental Design Sorafenib was administered orally q12h for consecutive 28 day cycles. Pharmacokinetics (day 1 and steady state) and pharmacodynamics were performed during cycle 1. Results Of sixty-five patients enrolled, 60 were eligible. In the solid tumor cohort (n=49), 4/6 patients experienced a DLT (hypertension, pain, rash/urticaria, thrombocytopenia, ALT/AST) at the starting dose (150 mg/m2/dose) which resulted in de-escalation to 105 mg/m2/dose. After eligibility criteria modification and dose re-escalation, the MTD was 200 mg/m2/dose for solid tumors and 150 mg/m2/dose for leukemias. Sorafenib exposure was highly variable between patients, but was within the ranges reported in adults. The apparent sorafenib clearance increased with patient age. Diarrhea, rash, fatigue, and increased ALT/AST were the most common sorafenib-related toxicities. Stable disease for ≥ 4 cycles was observed in 14 solid tumor patients, and two patients with acute myeloid leukemia and FLT3 internal tandem duplication experienced a decrease in bone marrow blasts toPurpose: To determine the dose-limiting toxicities (DLT), maximum tolerated dose (MTD), pharmacokinetics, and pharmacodynamics of sorafenib in children with refractory extracranial solid tumors and evaluate the tolerability of the solid tumor MTD in children with refractory leukemias. Experimental Design: Sorafenib was administered orally every 12 hours for consecutive 28-day cycles. Pharmacokinetics (day 1 and steady-state) and pharmacodynamics were conducted during cycle 1. Results: Of 65 patients enrolled, 60 were eligible. In the solid tumor cohort (n = 49), 4 of 6 patients experienced a DLT [hypertension, pain, rash/urticaria, thrombocytopenia, alanine aminotransferase (ALT)/aspartate aminotransferase (AST)] at the starting dose (150 mg/m2/dose) which resulted in de-escalation to 105 mg/m2/dose. After eligibility criteria modification and dose re-escalation, the MTD was 200 mg/m2/dose for solid tumors and 150 mg/m2/dose for leukemias. Sorafenib exposure was highly variable between patients but was within the ranges reported in adults. The apparent sorafenib clearance increased with patient age. Diarrhea, rash, fatigue, and increased ALT/AST were the most common sorafenib-related toxicities. Stable disease for 4 or more cycles was observed in 14 solid tumor patients, and 2 patients with acute myeloid leukemia (AML) and FLT3 internal tandem duplication (FLT3ITD) experienced a decrease in bone marrow blasts to less than 5%. Conclusions: The recommended phase II dose of sorafenib administered every 12 hours continuously for children with solid tumors is 200 mg/m2/dose and 150 mg/m2/dose for children with leukemias. Sorafenib toxicities and distribution in children are similar to adults. The activity of sorafenib in children with AML and FLT3ITD is currently being evaluated, and a phase II study for select solid tumors is ongoing. Clin Cancer Res; 18(21); 6011–22. ©2012 AACR.

Glucarpidase, Leucovorin, and Thymidine for High-Dose Methotrexate-Induced Renal Dysfunction: Clinical and Pharmacologic Factors Affecting Outcome

PURPOSE To assess the role of the recombinant bacterial enzyme, glucarpidase (carboxypeptidase-G(2)), leucovorin, and thymidine in the management and outcome of patients with high-dose methotrexate (HDMTX) -induced nephrotoxicity. METHODS Patients with HDMTX-induced nephrotoxicity received one to three doses of intravenous (IV) glucarpidase and leucovorin rescue. The initial cohort (n = 35) also received thymidine by continuous IV infusion. Subsequently, thymidine was restricted to patients with prolonged exposure (> 96 hours) to methotrexate (MTX) or with substantial MTX toxicity at study entry. Plasma MTX, leucovorin, and 5-methyltetrahydrofolate (5-mTHF) concentrations were measured pre- and postglucarpidase. Toxicities were monitored, and logistic regression analysis was used to assess the relationship of baseline characteristics to the development of severe toxicity and death. RESULTS Glucarpidase was administered at a median of 96 hours (receiving thymidine, n = 44) and 66 hours (not receiving thymidine, n = 56) after the start of the MTX infusion. Plasma MTX concentrations decreased within 15 minutes of glucarpidase by 98.7%. Plasma 5-mTHF concentrations also decreased more than 98% after administration of glucarpidase. Of 12 deaths, six were directly attributed to irreversible MTX toxicity. Presence of grade 4 toxicity before administration of glucarpidase, inadequate initial increase in leucovorin dosing, and administration of glucarpidase more than 96 hours after the start of the MTX infusion were associated with development of grade 4 and 5 toxicity. CONCLUSION Early intervention with the combination of leucovorin and glucarpidase is highly effective in patients who develop HDMTX-induced renal dysfunction. Severe toxicity and mortality occurred in patients in whom glucarpidase rescue was delayed and occurred despite thymidine administration.

Pediatric Phase I Trial and Pharmacokinetic Study of MLN8237, an Investigational Oral Selective Small-Molecule Inhibitor of Aurora Kinase A: A Children's Oncology Group Phase I Consortium Study

Purpose: MLN8237, a selective small-molecule inhibitor of Aurora kinase A, has activity in a broad range of preclinical pediatric cancer models. We conducted a phase I trial in children with refractory/recurrent solid tumors to define the maximum-tolerated dose, toxicities, and pharmacokinetic properties of MLN8237. Experimental Design: MLN8237 was administered orally either once daily or divided twice daily for seven days, every 21 days. Using a rolling-six design, four dose levels (45, 60, 80, and 100 mg/m2/day) were evaluated on the once-daily schedule, and two dose levels (60 and 80 mg/m2/d) on the twice-daily schedule. Pharmacokinetic studies were conducted with the initial dose and trough drug concentrations also measured at the steady state. Results: Thirty-seven patients were enrolled. On the once-daily dosing schedule, myelosuppression was dose limiting in three of four patients at 100 mg/m2, and one of six patients had dose-limiting mood alteration at 80 mg/m2. At 45 mg/m2, one of six patients experienced dose-limiting mucositis. Mucositis and myelosuppression were dose limiting at 80 mg/m2 on the twice-daily schedule, and one of five patients at 60 mg/m2 on the twice-daily schedule experienced a dose-limiting alkaline phosphatase. Five of 11 patients experienced hand–foot–skin syndrome with twice-daily dosing versus one of 21 after once-daily dosing. There was one partial response and six with prolonged stable disease among 33 evaluable subjects. Conclusion: The twice-daily dose regimen is well tolerated in adults; however, children experienced a greater frequency of myelosuppression and hand–foot–skin syndrome on this schedule. Children tolerated a higher dose and the recommended pediatric phase II dose is 80 mg/m2/d once daily for seven days. Clin Cancer Res; 18(21); 6058–64. ©2012 AACR.

A Phase I Trial and Pharmacokinetic Study of the Raf Kinase and Receptor Tyrosine Kinase Inhibitor Sorafenib in Children with Refractory Solid Tumors or Refractory Leukemias

Purpose To determine the dose-limiting toxicities (DLT), maximum tolerated dose (MTD), pharmacokinetics and pharmacodynamics of sorafenib in children with refractory extracranial solid tumors and evaluate the tolerability of the solid tumor MTD in children with refractory leukemias. Experimental Design Sorafenib was administered orally q12h for consecutive 28 day cycles. Pharmacokinetics (day 1 and steady state) and pharmacodynamics were performed during cycle 1. Results Of sixty-five patients enrolled, 60 were eligible. In the solid tumor cohort (n=49), 4/6 patients experienced a DLT (hypertension, pain, rash/urticaria, thrombocytopenia, ALT/AST) at the starting dose (150 mg/m2/dose) which resulted in de-escalation to 105 mg/m2/dose. After eligibility criteria modification and dose re-escalation, the MTD was 200 mg/m2/dose for solid tumors and 150 mg/m2/dose for leukemias. Sorafenib exposure was highly variable between patients, but was within the ranges reported in adults. The apparent sorafenib clearance increased with patient age. Diarrhea, rash, fatigue, and increased ALT/AST were the most common sorafenib-related toxicities. Stable disease for ≥ 4 cycles was observed in 14 solid tumor patients, and two patients with acute myeloid leukemia and FLT3 internal tandem duplication experienced a decrease in bone marrow blasts toPurpose: To determine the dose-limiting toxicities (DLT), maximum tolerated dose (MTD), pharmacokinetics, and pharmacodynamics of sorafenib in children with refractory extracranial solid tumors and evaluate the tolerability of the solid tumor MTD in children with refractory leukemias. Experimental Design: Sorafenib was administered orally every 12 hours for consecutive 28-day cycles. Pharmacokinetics (day 1 and steady-state) and pharmacodynamics were conducted during cycle 1. Results: Of 65 patients enrolled, 60 were eligible. In the solid tumor cohort (n = 49), 4 of 6 patients experienced a DLT [hypertension, pain, rash/urticaria, thrombocytopenia, alanine aminotransferase (ALT)/aspartate aminotransferase (AST)] at the starting dose (150 mg/m2/dose) which resulted in de-escalation to 105 mg/m2/dose. After eligibility criteria modification and dose re-escalation, the MTD was 200 mg/m2/dose for solid tumors and 150 mg/m2/dose for leukemias. Sorafenib exposure was highly variable between patients but was within the ranges reported in adults. The apparent sorafenib clearance increased with patient age. Diarrhea, rash, fatigue, and increased ALT/AST were the most common sorafenib-related toxicities. Stable disease for 4 or more cycles was observed in 14 solid tumor patients, and 2 patients with acute myeloid leukemia (AML) and FLT3 internal tandem duplication (FLT3ITD) experienced a decrease in bone marrow blasts to less than 5%. Conclusions: The recommended phase II dose of sorafenib administered every 12 hours continuously for children with solid tumors is 200 mg/m2/dose and 150 mg/m2/dose for children with leukemias. Sorafenib toxicities and distribution in children are similar to adults. The activity of sorafenib in children with AML and FLT3ITD is currently being evaluated, and a phase II study for select solid tumors is ongoing. Clin Cancer Res; 18(21); 6011–22. ©2012 AACR.

Plasma and cerebrospinal fluid pharmacokinetics of intravenous oxaliplatin, cisplatin, and carboplatin in nonhuman primates

Purpose: Describe and compare the central nervous system pharmacology of the platinum analogues, cisplatin, carboplatin, and oxaliplatin and develop a pharmacokinetic model to distinguish the disposition of active drug from inert platinum species. Experimental Design: Oxaliplatin (7 or 5 mg/kg), cisplatin (2 mg/kg), or carboplatin (10 mg/kg) was given i.v. Serial plasma and cerebrospinal fluid (CSF) samples were collected over 24 hours. Plasma ultrafiltrates were prepared immediately. Platinum concentrations were measured using atomic absorption spectrometry. Areas under the concentration × time curve were derived using the linear trapezoidal method. CSF penetration was defined as the CSF AUC0-24/plasma ultrafiltrate AUC0-24 ratio. A four-compartment model with first-order rate constants was fit to the data to distinguish active drug from inactive metabolites. Results: The mean ± SD AUCs in plasma ultrafiltrate for oxaliplatin, cisplatin, and carboplatin were 61 ± 22, 18 ± 6, and 211 ± 64 μmol/L hour, respectively. The AUCs in CSF were 1.2 ± 0.4 μmol/L hour for oxaliplatin, 0.56 ± 0.08 μmol/L hour for cisplatin, and 8 ± 2.2 μmol/L hour for carboplatin, and CSF penetration was 2.0%, 3.6%, and 3.8%, respectively. For oxaliplatin, cisplatin, and carboplatin, the pharmacokinetic model estimated that active drug accounted for 29%, 79%, and 81% of platinum in plasma ultrafiltrate, respectively, and 25%, 89%, and 56% of platinum in CSF, respectively. The CSF penetration of active drug was 1.6% for oxaliplatin, 3.7% for cisplatin, and 2.6% for carboplatin. Conclusions: The CSF penetration of the platinum analogues is limited. The pharmacokinetic model distinguished between active drug and their inactive (inert) metabolites in plasma and CSF.