Phase 1 study of sorafenib and irinotecan in pediatric patients with relapsed or refractory solid tumors.

BACKGROUND: Sorafenib,an orally bioavailable, multitarget tyrosine kinase inhibitor, and irinotecan, a topoisomerase I inhibitor, have demonstrated activity in pediatric and adult malignancies. We evaluated the toxicity, pharmacokinetic (PK), and pharmacogenomic (PGX) profile of sorafenib with irinotecan in children with relapsed or refractory solid tumors and assessed the feasibility of incorporating patient-reported outcome (PRO) measures as an adjunct to traditional endpoints. METHODS: Sorafenib, continuous oral twice daily dosing, was administered with irinotecan, orally, once daily days 1-5, repeated every 21 days (NCT01518413). Based on tolerability, escalation of sorafenib followed by escalation of irinotecan was planned. Three patients were initially enrolled at each dose level. Sorafenib and irinotecan PK analyses were performed during cycle 1. PRO measurements were collected during cycles 1 and 2. RESULTS: Fifteen patients were evaluable. Two of three patients at dose level 2 experienced dose-limiting toxicity (DLT), grade 3 diarrhea, and grade 3 hyponatremia. Therefore, dose level 1 was expanded to 12 patients and two patients had DLT, grade 4 thrombocytopenia, grade 3 elevated lipase. Nine of 15 (60%) patients had a best response of stable disease with four patients receiving ≥6 cycles. CONCLUSIONS: The recommended dose for pediatric patients was sorafenib 150 mg/m2 /dose twice daily with irinotecan 70 mg/m2 /dose daily × 5 days every 21 days. This oral outpatient regimen was well tolerated and resulted in prolonged disease stabilization. There were no significant alterations in the PK profile of either agent when administered in combination. Patients were willing and able to report their subjective experiences with this regimen.

Vincristine Sulfate Liposomes Injection (VSLI, Marqibo®): Results From a Phase I Study in Children, Adolescents, and Young Adults With Refractory Solid Tumors or Leukemias.

BACKGROUND: Vincristine sulfate liposome injection (VSLI; Marqibo®) is an encapsulated preparation of standard vincristine in sphingomyelin/cholesterol liposomes. Clinical trials in adults have demonstrated safety, tolerability, and activity, leading to Food and Drug Administration (FDA) approval for adults with relapsed acute lymphoblastic leukemia (ALL). Pediatric experience with VSLI is limited. PROCEDURE: This single center, phase I dose escalation study examined the safety, toxicity, maximum tolerated dose, and pharmacokinetics of VSLI administered weekly to pediatric patients age <21 years with relapsed or chemotherapy-refractory solid tumors or leukemia. RESULTS: Twenty-one subjects were treated in total. Median age was 13.3 years (range 2-19). Fourteen subjects completed one 28-day cycle of therapy and five subjects completed more than one cycle. No subject experienced dose-limiting toxicity (DLT) at the first dose level (1.75 mg/m(2) /dose, dose range: 2-3.7 mg). At the second dose level (2.25 mg/m(2) /dose, dose range: 1.3-4.5 mg), one subject had transient dose-limiting grade 4 transaminase elevation, and this dose level was expanded with no additional DLT observed. The second dose level then opened to an expansion phase to evaluate activity in ALL. Clinical activity included minimal residual disease negative complete remission in one subject with ALL and stable disease in nine subjects. Clearance of total vincristine was found to be approximately 100-fold lower in comparison to published data using standard vincristine. CONCLUSIONS: Children tolerate 2.25 mg/m(2) /dose of weekly VSLI (the adult FDA-approved dose) with evidence for clinical activity without dose-limiting neurotoxicity. Future plans include studying VSLI as substitution for standard vincristine with combination chemotherapy in children with ALL.

Phase 2 trial of sorafenib in children and young adults with refractory solid tumors: A report from the Children's Oncology Group.

BACKGROUND: Sorafenib is an oral small molecule inhibitor of multiple kinases controlling tumor growth and angiogenesis. The purpose of the phase 2 study was to determine the response rate of sorafenib and gain further information on the associated toxicities, pharmacokinetics, and pharmacodynamics of sorafenib in children and young adults with relapsed or refractory tumors including rhabdomyosarcoma, Wilms tumor, hepatocellular carcinoma (HCC), and papillary thyroid carcinoma (PTC). PROCEDURE: Sorafenib, 200 mg/m(2) /dose, was administered every 12 hr continuously for 28 day cycles using a two-stage design in two primary strata (rhabdomyosarcoma and Wilms tumor) and two secondary strata (HCC and PTC). Correlative studies in consenting patients included determination of sorafenib steady state trough concentrations and assessments of VEGF and sVEGFR2. RESULTS: Twenty patients (median age of 11 years; range, 5-21) enrolled. No objective responses (RECIST) were observed in the 10 evaluable patients enrolled in each of the two primary disease strata of rhabdomyosarcoma and Wilms tumor. No patients with HCC or PTC were enrolled. Sorafenib was not associated with an excessive rate of dose-limiting toxicity (DLT). The mean ± SD steady state concentration during cycle 1 day 15 was 6.5 ± 3.9 µg/ml (n = 10). CONCLUSIONS: Sorafenib was well tolerated in children at 200 mg/m(2) /dose twice daily on a continuous regimen with toxicity profile and steady state drug concentrations similar to those previously reported. Single agent sorafenib was inactive in children with recurrent or refractory rhabdomyosarcoma or Wilms tumor.

Phase II/III trial of a pre-transplant farnesyl transferase inhibitor in juvenile myelomonocytic leukemia: a report from the Children's Oncology Group.

BACKGROUND: Juvenile myelomonocytic leukemia (JMML) is not durably responsive to chemotherapy, and approximately 50% of patients relapse after hematopoietic stem cell transplant (HSCT). Here we report the activity and acute toxicity of the farnesyl transferase inhibitor tipifarnib, the response rate to 13-cis retinoic acid (CRA) in combination with cytoreductive chemotherapy, and survival following HSCT in children with JMML. PROCEDURE: Eighty-five patients with newly diagnosed JMML were enrolled on AAML0122 between 2001 and 2006. Forty-seven consented to receive tipifarnib in a phase II window before proceeding to a phase III trial of CRA in combination with fludarabine and cytarabine followed by HSCT and maintenance CRA. Thirty-eight patients enrolled only in the phase III trial. RESULTS: Overall response rate was 51% after tipifarnib and 68% after fludarabine/cytarabine/CRA. Tipifarnib did not increase pre-transplant toxicities. Forty-six percent of the 44 patients who received protocol compliant HSCT relapsed. Five-year overall survival was 55 ± 11% and event-free survival was 41 ± 11%, with no significant difference between patients who did or did not receive tipifarnib. CONCLUSIONS: Administration of tipifarnib in the window setting followed by HSCT in patients with newly diagnosed JMML was safe and yielded a 51% initial response rate as a single agent, but failed to reduce relapse rates or improve long-term overall survival.

Phase I trial and pharmacokinetic study of sorafenib in children with neurofibromatosis type I and plexiform neurofibromas.

BACKGROUND: Sorafenib targets multiple pathways thought to be crucial in growth of plexiform neurofibroma (PN) in children with neurofibromatosis type 1 (NF1). Sorafenib has been tolerated with manageable toxicities in adults and children with refractory cancer. We conducted a separate study in this population. Monitoring long-term toxicities such as effects on growth and obtaining additional pharmacokinetic data were of importance due to the young age and long duration of therapy seen in previous phase I trials in children with NF1. PROCEDURE: Children ≥3 and ≤18-year-old with NF1 and inoperable PN were eligible. Sorafenib was administered orally twice daily for consecutive 28-day cycles. Maximum tolerated dose (MTD) was determined from toxicities observed during the first three cycles. RESULTS: Nine children enrolled, median age 8 (6-12) years. At the starting 115 mg/m(2) /dose (n = 5), two experienced dose-limiting grade 3 pain in their PN. At the de-escalated 80 mg/m(2) /dose (n = 4), approximately 40% of the pediatric solid tumor MTD, two had dose-limiting toxicity (grade 3 rash and grade 4 mood alteration), exceeding the MTD. At 80 mg/m(2) /dose, the median AUC(0-12 hours) at steady-state was 39.5 µg hours/ml. Toxicities appeared to correspond with decreases in quality of life (QOL). No tumor shrinkage was observed. CONCLUSIONS: Children with NF1 and PN did not tolerate sorafenib at doses substantially lower than the MTD in children and adults with malignant solid tumors. Future trials with targeted agents for children with NF1 may require a more conservative starting dose and separate definitions of dose limiting toxicities (DLT) than children with cancer.

Sustained response and prevention of damage progression in patients with neonatal-onset multisystem inflammatory disease treated with anakinra: a cohort study to determine three- and five-year outcomes.

OBJECTIVE: Blocking interleukin-1 with anakinra in patients with the autoinflammatory syndrome neonatal-onset multisystem inflammatory disease (NOMID) reduces systemic and organ-specific inflammation. However, the impact of long-term treatment has not been established. This study was undertaken to evaluate the long-term effect of anakinra on clinical and laboratory outcomes and safety in patients with NOMID. METHODS: We conducted a cohort study of 26 NOMID patients ages 0.80-42.17 years who were followed up at the NIH and treated with anakinra 1-5 mg/kg/day for at least 36 months. Disease activity was assessed using daily diaries, questionnaires, and C-reactive protein level. Central nervous system (CNS) inflammation, hearing, vision, and safety were evaluated. RESULTS: Sustained improvements in diary scores, parent's/patient's and physician's global scores of disease activity, parent's/patient's pain scores, and inflammatory markers were observed (all P<0.001 at 36 and 60 months). At 36 and 60 months, CNS inflammation was suppressed, with decreased cerebrospinal fluid white blood cell counts (P=0.0026 and P=0.0076, respectively), albumin levels, and opening pressures (P=0.0012 and P<0.001, respectively). Most patients showed stable or improved hearing. Cochlear enhancement on magnetic resonance imaging correlated with continued hearing loss. Visual acuity and peripheral vision were stable. Low optic nerve size correlated with poor visual field. Bony lesions progressed. Adverse events other than viral infections were rare, and all patients continued to receive the medication. CONCLUSION: These findings indicate that anakinra provides sustained efficacy in the treatment of NOMID for up to 5 years, with the requirement of dose escalation. Damage progression in the CNS, ear, and eye, but not bone, is preventable. Anakinra is well tolerated overall.

Phase 1 trial and pharmacokinetic study of the farnesyl transferase inhibitor tipifarnib in children and adolescents with refractory leukemias: a report from the Children's Oncology Group.

BACKGROUND: The objectives of this trial were to define the toxicity profile, dose, pharmacokinetics, and pharmacodynamics of the farnesyl transferase (FTase) inhibitor, tipifarnib, in children and adolescents with hematological malignancies. PROCEDURE: Tipifarnib was administered twice daily for 21 days, repeated every 28 days starting at a dose of 300 mg/m(2) /dose. Pharmacokinetic sampling was performed for 36 hr after the first dose and leukemic blasts were collected pre-treatment and at steady state for determination of FTase activity. RESULTS: Of 29 patients enrolled, 18 were fully evaluable for toxicity, and 23 for response; 26 had pharmacokinetic and pharmacodynamic sampling. The recommended dose is 300 mg/m(2) /dose and toxicities included skin rash, mucositis, nausea, vomiting, and diarrhea. Neurotoxicity, which was dose-limiting in adults at doses exceeding 600 mg/dose, was infrequent and mild. The plasma pharmacokinetics of tipifarnib were highly variable but comparable to adults with acute leukemia and children with solid tumors. The median apparent clearance of tipifarnib was 630 ml/min/m(2) and the median half-life was 4.7 hr. At steady state on 300 mg/m(2) /dose, FTase activity was inhibited by 82% in leukemic blasts. No objective responses were observed. CONCLUSIONS: Oral tipifarnib is well tolerated in children with leukemia on a twice daily for 2 days schedule at 300 mg/m(2) /dose.

Targeting Sporadic and Neurofibromatosis Type 1 (NF1) Related Refractory Malignant Peripheral Nerve Sheath Tumors (MPNST) in a Phase II Study of Everolimus in Combination with Bevacizumab (SARC016).

PURPOSE: There are no known effective medical treatments for refractory MPNST. Inactivation of the NF1 tumor suppressor in MPNST results in upregulation of mTOR (mammalian target of rapamycin) signaling and angiogenesis, which contributes to disease progression. We conducted a phase II study for patients (pts) with refractory MPNST combining everolimus (10 mg PO once daily) with bevacizumab (10 mg/kg IV every 2 weeks) to determine the clinical benefit rate (CBR) (complete response, partial response (PR), or stable disease (SD) ≥ 4 months). PATIENTS AND METHODS: Patients ≥18 years old with chemotherapy refractory sporadic or NF1 MPNST were eligible. Tumor response was assessed after every 2 cycles (the WHO criteria). A two-stage design targeting a 25% CBR was used: if ≥ 1/15 pts in stage 1 responded, enrollment would be expanded by 10 pts, and if ≥ 4/25 patients had clinical benefit, the combination would be considered active. RESULTS: Twenty-five pts, 17 with NF1 and 8 with sporadic MPNST, enrolled. One of 15 pts in stage 1 had clinical benefit. Of 10 additional pts enrolled, 2 had clinical benefit. The median number of completed cycles was 3 (range 1-16). Adverse events were similar to those known for this combination. CONCLUSION: With a CBR of 12% (3/25), the combination of everolimus and bevacizumab did not reach the study's target response rate and is not considered active in refractory MPNST.

A phase I trial and pharmacokinetic study of tipifarnib, a farnesyltransferase inhibitor, and tamoxifen in metastatic breast cancer.

PURPOSE: Farnesyltransferase (FTase) inhibitors, which were designed to inhibit oncogenic Ras, act synergistically with tamoxifen in preclinical breast cancer models. We studied the safety and toxicity of tipifarnib in combination with tamoxifen in metastatic breast cancer. The pharmacokinetics and pharmacodynamics of tipifarnib were also assessed. PATIENTS AND METHODS: Patients with metastatic, hormone receptor-positive breast cancer were enrolled. Two cohorts of patients were treated with tipifarnib at either 200 or 300 mg p.o. twice daily for 21 of 28 days. Tamoxifen (20 mg once daily) was started after 1 week of tipifarnib monotherapy to perform pharmacokinetics and FTase inhibition levels in peripheral blood mononuclear cells with tipifarnib alone and with tipifarnib and tamoxifen. RESULTS: A total of 12 heavily pretreated patients with prior progression on hormonal therapy were enrolled. Minimal toxicity was observed at the 200-mg dose level of tipifarnib. At the 300-mg dose, all six patients required dose reduction of tipifarnib due to toxicities that included grade 2 nausea, rash, and fatigue and grade 3 diarrhea and neutropenia. Tipifarnib pharmacokinetic and pharmacodynamic variables were similar in the presence and absence of tamoxifen. Average FTase inhibition was 42% at 200 mg and 54% at 300 mg in peripheral blood mononuclear cells. Of the 12 patients treated, there were two partial responses and one stable disease for >6 months. CONCLUSIONS: Tipifarnib (200 mg twice daily for 21 of 28 days) and tamoxifen (20 mg once daily) can be given safely with minimal toxicity. Tamoxifen does not have a significant effect on tipifarnib pharmacokinetics.

Efficacy of glucarpidase (carboxypeptidase g2) in patients with acute kidney injury after high-dose methotrexate therapy.

STUDY OBJECTIVE: Because the incidence rate of renal impairment is 2-10% for patients treated with high-dose methotrexate and renal impairment develops in 0-12.4% of patients treated for osteosarcoma, we sought to evaluate the efficacy of glucarpidase, a recently approved drug that rapidly hydrolyzes methotrexate to inactive metabolites, which allows for nonrenal clearance in patients with delayed renal methotrexate elimination. DESIGN: Pooled analysis of efficacy data from four multicenter single-arm compassionate-use clinical trials using protocols from 1993 to 2007. PATIENTS: Of 476 patients with renal toxicity and delayed methotrexate elimination who were treated with intravenous glucarpidase for rescue after high-dose methotrexate, 169 patients had at least one preglucarpidase (baseline) plasma methotrexate concentration greater than 1 µmol/L and one postglucarpidase methotrexate concentration measurement by high-performance liquid chromatography and were included in the efficacy analysis; renal recovery was assessed in 436 patients who had at least one recorded preglucarpidase and postglucarpidase serum creatinine concentration measurement. MEASUREMENTS AND MAIN RESULTS: Efficacy was defined as rapid and sustained clinically important reduction (RSCIR) in plasma methotrexate concentration, with a concentration of 1 µmol/L or lower at all postglucarpidase determinations. Median age of efficacy-evaluable patients was 20 years (range 5 weeks-84 years). Osteosarcoma (36%), non-Hodgkin lymphoma (27%), and acute lymphoblastic leukemia (20%) were the most frequent underlying diagnoses. Median preglucarpidase serum methotrexate was 11.7 µmol/L. At the first (median 15 minutes) through the last (median 40 hours) postglucarpidase measurement, plasma methotrexate concentrations demonstrated consistent 99% median reduction. RSCIR was achieved by 83 (59%) of 140 patients. A total of 64% of patients with renal impairment greater than or equal to Common Terminology Criteria for Adverse Events grade 2 recovered to grade 0 or 1 at a median of 12.5 days after glucarpidase administration. CONCLUSION: Glucarpidase caused a clinically important 99% or greater sustained reduction of serum methotrexate levels and provided noninvasive rescue from methotrexate toxicity in renally impaired patients.

The serum and cerebrospinal fluid pharmacokinetics of anakinra after intravenous administration to non-human primates.

Anakinra improves the central nervous system manifestations of neonatal-onset multisystem inflammatory disease, which is mediated by IL-1beta oversecretion. The cerebrospinal fluid (CSF) penetration of the IL-1 receptor antagonist anakinra was studied in rhesus monkeys after intravenous doses of 3 and 10 mg/kg. Drug exposure (area under concentration-time curve) in CSF was 0.28% of that in serum. The average CSF concentration at 3 mg/kg was 1.8 ng/mL, which is 30-fold higher than endogenous CSF levels of IL-1Ra. The CSF penetration was not dose-dependent, indicating that the CSF penetration was not saturated in the 3 to 10 mg/kg dose range.

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.

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.

Randomized trial and pharmacokinetic study of pegfilgrastim versus filgrastim after dose-intensive chemotherapy in young adults and children with sarcomas.

PURPOSE: To compare the effectiveness, tolerance, and pharmacokinetics of a single dose of pegfilgrastim to daily filgrastim in children and young adults with sarcomas treated with dose-intensive combination chemotherapy. EXPERIMENTAL DESIGN: Patients were randomized to receive a single dose of 100 mcg/kg of pegfilgrastim s.c. or 5 mcg/kg/day of filgrastim s.c., daily until neutrophil recovery after two treatment cycles with vincristine, doxorubicin, and cyclophosphamide (VDC) and two cycles of etoposide and ifosfamide (IE). The duration of severe neutropenia (absolute neutrophil count, < or =500/mcL) during cycles 1 to 4 and cycle duration for all cycles were compared. Pharmacokinetics of pegfilgrastim and filgrastim and CD34+ stem cell mobilization were studied on cycle 1. Growth factor-related toxicity, transfusions, and episodes of fever and neutropenia and infections were collected for cycles 1 to 4. RESULTS: Thirty-four patients (median age, 20 years; range 3.8-25.8) were enrolled, and 32 completed cycles 1 to 4. The median (range) duration of absolute neutrophil count of <500/mcL was 5.5 (3-8) days for pegfilgrastim and 6 (0-9) days for filgrastim (P = 0.76) after VDC, and 1.5 (0-4) days for pegfilgrastim and 3.75 (0-6.5) days for filgrastim (P = 0.11) after IE. More episodes of febrile neutropenia and documented infections occurred on the filgrastim arm. Serum pegfilgrastim concentrations were highly variable. Pegfilgrastim apparent clearance (11 mL/h/kg) was similar to that reported in adults. CONCLUSION: A single dose per cycle of pegfilgrastim was well tolerated and may be as effective as daily filgrastim based on the duration of severe neutropenia and number of episodes of febrile neutropenia and documented infections after dose-intensive treatment with VDC and IE.

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.

The bioavailability of oral methotrexate in children with inflammatory bowel disease.

OBJECTIVES: Methotrexate is used to treat patients with inflammatory bowel disease. Although no available pharmacologic data support the assumption that the bioavailability of methotrexate is diminished in patients with inflammatory bowel disease, most such patients receive methotrexate parenterally. METHODS: The oral bioavailability of methotrexate was determined in 11 pediatric patients being treated with methotrexate for inflammatory bowel disease. Serial plasma methotrexate concentrations were determined after equal subcutaneous and oral doses of methotrexate. RESULTS: The mean bioavailability of methotrexate in patients with inflammatory bowel disease was 84% +/- 38%. Interpatient variability in drug exposure was similar after oral and subcutaneous administration. CONCLUSIONS: The bioavailability of methotrexate in patients with inflammatory bowel disease is no different from that observed in other disease states. Subcutaneous administration of methotrexate does not appear to decrease the interpatient variability in drug exposure. There is no sound pharmacologic basis for favoring administration of methotrexate via the subcutaneous route for patients with inflammatory bowel disease.

Treatment of accidental intrathecal methotrexate overdose with intrathecal carboxypeptidase G2.

The bacterial enzyme carboxypeptidase G2 (CPDG2) rapidly hydrolyzes methotrexate to inactive metabolites. We administered recombinant CPDG2 (2000 U) intrathecally to seven cancer patients 3 to 9 hours after they had received an accidental overdose of intrathecal methotrexate (median dose = 364 mg; range = 155-600 mg). Four of the seven patients had cerebrospinal fluid (CSF) exchange to remove methotrexate before CPDG2 administration. Immediate symptoms of the methotrexate overdoses included seizures (n = 5), coma (n = 2), and cardiopulmonary compromise (n = 2). Before CPDG2 administration, the median concentrations of methotrexate in CSF were 264 microM (range = 97-510 microM) among patients who had CSF exchange and 8050 microM (range = 2439-16 500 microM) among patients who did not. After intrathecal CPDG2 administration, methotrexate concentrations in CSF declined by more than 98%. All patients recovered completely from the intrathecal methotrexate overdose except for two patients who had memory impairments. Antibodies to CPDG2 were not detected in plasma after treatment with intrathecal CPDG2. Intrathecal CPDG2 is well tolerated, rapidly decreases CSF methotrexate concentrations, and appears to be efficacious for treating accidental intrathecal methotrexate overdoses.