Population pharmacokinetics and site of action exposures of veliparib with topotecan plus carboplatin in patients with haematological malignancies.

AIMS: Veliparib is a potent inhibitor of poly(ADP-ribose) polymerase (PARP) enzyme. The objectives of the analysis were to evaluate the effect of baseline covariates and co-administration of topotecan plus carboplatin (T + C) on pharmacokinetics of veliparib in patients with refractory acute leukaemia, and compare veliparib concentration in various biological matrices. METHODS: A population pharmacokinetic model was developed and effect of age, body size indices, sex, creatinine clearance (CrCL) and co-administration of T + C on the pharmacokinetics of veliparib were evaluated. The final model was qualified using bootstrap and quantitative predictive check. Linear regression was conducted to correlate concentrations of veliparib in various biological matrices. RESULTS: A two compartment model with first-order absorption with Tlag described veliparib pharmacokinetics. The apparent clearance (CL/F) and volume (Vc /F) were 16.5 l h-1 and 122.7 l, respectively. The concomitant administration of T + C was not found to affect veliparib CL/F. CrCL and lean body mass (LBM) were significant covariates on CL/F and Vc/F, respectively. While a strong positive relationship was observed between veliparib concentrations in plasma and bone marrow supernatant, no correlation was observed between plasma and peripheral blood or bone marrow blasts. CONCLUSIONS: Consistent with veliparib's physiochemical properties and its elimination mechanism, LBM and CrCL were found to affect pharmacokinetics of veliparib while concomitant administration of T + C did not affect veliparib's CL/F. Plasma concentrations were found to be a reasonable surrogate for veliparib concentrations in peripheral blood and bone marrow supernatant but not blasts. The current model will be utilized to conduct exposure-response analysis to support dosing recommendations.

Multi-institutional phase 2 clinical and pharmacogenomic trial of tipifarnib plus etoposide for elderly adults with newly diagnosed acute myelogenous leukemia.

Tipifarnib (T) exhibits modest activity in elderly adults with newly diagnosed acute myelogenous leukemia (AML). Based on preclinical synergy, a phase 1 trial of T plus etoposide (E) yielded 25% complete remission (CR). We selected 2 comparable dose levels for a randomized phase 2 trial in 84 adults (age range, 70-90 years; median, 76 years) who were not candidates for conventional chemotherapy. Arm A (T 600 mg twice a day × 14 days, E 100 mg days 1-3 and 8-10) and arm B (T 400 mg twice a day × 14 days, E 200 mg days 1-3 and 8-10) yielded similar CR, but arm B had greater toxicity. Total CR was 25%, day 30 death rate 7%. A 2-gene signature of high RASGRP1 and low aprataxin (APTX) expression previously predicted for T response. Assays using blasts from a subset of 40 patients treated with T plus E on this study showed that AMLs with a RASGRP1/APTX ratio of more than 5.2 had a 78% CR rate and negative predictive value 87%. This ratio did not correlate with outcome in 41 patients treated with conventional chemotherapies. The next T-based clinical trials will test the ability of the 2-gene signature to enrich for T responders prospectively. This study is registered at www.clinicaltrials.gov as #NCT00602771.

A phase II trial of sequential ribonucleotide reductase inhibition in aggressive myeloproliferative neoplasms.

Myeloproliferative neoplasms are a varied group of disorders that can have prolonged chronic phases, but eventually accelerate and can transform into a secondary acute myeloid leukemia that is ultimately fatal. Triapine is a novel inhibitor of the M2 subunit of ribonucleotide reductase. Sequential inhibition of ribonucleotide reductase with triapine and an M1 ribonucleotide reductase inhibitor (fludarabine) was noted to be safe, and led to a 29% complete plus partial response rate in myeloproliferative neoplasms. This article reports the findings of a phase II trial of triapine (105 mg/m(2)/day) followed by fludarabine (30 mg/m(2)/day) daily for 5 consecutive days in 37 patients with accelerated myeloproliferative neoplasms and secondary acute myeloid leukemia. The overall response rate was 49% (18/37), with a complete remission rate of 24% (9/37). Overall response rates and complete remissions were seen in all disease subsets, including secondary acute myeloid leukemia, in which the overall response rate and complete remission rate were 48% and 33%, respectively. All patients with known JAK2 V617F mutations (6/6) responded. The median overall survival of the entire cohort was 6.9 months, with a median overall survival of both overall responders and complete responders of 10.6 months. These data further demonstrate the promise of sequential inhibition of ribonucleotide reductase in patients with accelerated myeloproliferative neoplasms and secondary acute myeloid leukemia. This study was registered with clinicaltrials.gov (NCT00381550).

Phase 1 and pharmacokinetic study of bolus-infusion flavopiridol followed by cytosine arabinoside and mitoxantrone for acute leukemias.

Flavopiridol is a protein bound, cytotoxic, cyclin-dependent kinase inhibitor. Flavopiridol given by 1-hour bolus at 50 mg/m(2) daily 3 times followed by cytosine arabinoside and mitoxantrone (FLAM) is active in adults with poor-risk acute leukemias. A pharmacologically derived "hybrid" schedule (30-minute bolus followed by 4-hour infusion) of flavopiridol was more effective than bolus administration in refractory chronic lymphocytic leukemia. Our phase 1 trial "hybrid FLAM" in 55 adults with relapsed/refractory acute leukemias began at a total flavopiridol dose of 50 mg/m(2) per day 3 times (20-mg/m(2) bolus, 30-mg/m(2) infusion). Dose-limiting toxicity occurred at level 6 (30-mg/m(2) bolus, 70-mg/m(2) infusion) with tumor lysis, hyperbilirubinemia, and mucositis. Death occurred in 5 patients (9%). Complete remission occurred in 22 (40%) across all doses. Overall and disease-free survivals for complete remission patients are more than 60% at more than 2 years. Pharmacokinetics demonstrated a dose-response for total and unbound plasma flavopiridol unrelated to total protein, albumin, peripheral blast count, or toxicity. Pharmacodynamically, flavopiridol inhibited mRNAs of multiple cell cycle regulators, but with uniform increases in bcl-2. "Hybrid FLAM" is active in relapsed/refractory acute leukemias, with a recommended "hybrid" dose of bolus 30 mg/m(2) followed by infusion of 60 mg/m(2) daily for 3 days. This clinical trial is registered at www.clinicaltrials.gov as #NCT00470197.

Phase 1 dose-escalation trial of clofarabine followed by escalating dose of fractionated cyclophosphamide in adults with relapsed or refractory acute leukaemias.

The prognosis of patients with relapsed and refractory acute leukaemia (RRAL) is very poor. Forty patients with RRAL were enroled [28 acute myeloid leukaemia (AML), 12 acute lymphoblastic leukaemia (ALL)] in this Phase 1 dose-escalation trial of daily-infused clofarabine (CLO) followed by cyclophosphamide (CY) for four consecutive days (CLO-CYx4). The median age was 48·5 years. The median number of prior regimens was 2 (range 1-5), and 6/40 patients (15%) had prior allogeneic haematopoietic stem cell transplant. 28/40 patients (70%) had adverse genetic features. 6/40 patients (15%) died within 60 d of induction (two infections, four progressive disease). The average time to neutrophil recovery (absolute neutrophil count ≥0·5 × 10(9) /l was 34 d, (range, 17-78). The overall response rate (ORR) was 33% (13/40), with seven complete remissions (18%), four complete remissions with incomplete recovery of blood counts (10%), and two partial remissions (5%). ORR was 25% (7/28), and 50% (6/12), for AML and ALL respectively. Notably, the clinical responses were independent of dose level. 7/17 patients (41%) exhibited CLO-mediated enhancement of CY-induced DNA, which was associated with, but not necessary for, improved clinical outcomes. In summary, the CLO-CYx4 regimen was well tolerated and had activity in patients with RRAL, especially relapsed ALL. Therefore, CLO-CYx4 can be considered a salvage therapy for adults with RRALs, and warrants further investigations.

Randomized phase II study of two schedules of flavopiridol given as timed sequential therapy with cytosine arabinoside and mitoxantrone for adults with newly diagnosed, poor-risk acute myelogenous leukemia.

BACKGROUND: Flavopiridol is a protein-bound, cytotoxic, cyclin dependent kinase inhibitor. A phase II trial of flavopiridol followed by ara-C and mitoxantrone with flavopiridol given by 1-h bolus for adults with newly-diagnosed, poor-risk acute myelogenous leukemia yielded 67% complete remission with median disease-free survival of 13.6 months. DESIGN AND METHODS: We compared bolus flavopiridol (50 mg/m(2)/day, Arm A) versus 'hybrid' flavopiridol (30 mg/m(2) over 30 min followed by 40 mg/m(2) over 4 h, Arm B) followed by ara-C and mitoxantrone in 78 patients (39 per arm) with newly diagnosed, poor-risk acute myelogenous leukemia. To mitigate imbalance, patients were stratified by presence or absence of secondary leukemia and therapy for antecedent disorder. RESULTS: Death at or before Day 60 occurred in 8% of patients per arm. Complete remission plus complete remission with incomplete recovery was 68% (Arm A, 62%; Arm B, 74%) overall, and 65% or over in both arms for patients with secondary leukemia and leukemia with adverse genetics. In Arm A 91% and in Arm B 86% of patients received chemotherapy and/or allogeneic transplantation in complete remission. Median overall survival for all remission patients has not been reached for either arm, with median disease free survival of 13.6 months for Arm A and of 12.0 months for Arm B. CONCLUSIONS: Both flavopiridol schedules produce comparably encouraging results in adults with poor-risk acute myelogenous leukemia. Given the greater ease of bolus administration, we are conducting a randomized phase II study of bolus flavopiridol followed by ara-c and mitoxantrone versus conventional induction therapy for patients aged 70 years and under with intermediate or poor-risk acute myelogenous leukemia. This study is registered at www.clinicaltrials.gov as #NCT 00407966.

Active oral regimen for elderly adults with newly diagnosed acute myelogenous leukemia: a preclinical and phase 1 trial of the farnesyltransferase inhibitor tipifarnib (R115777, Zarnestra) combined with etoposide.

The farnesyltransferase inhibitor tipifarnib exhibits modest activity against acute myelogenous leukemia. To build on these results, we examined the effect of combining tipifarnib with other agents. Tipifarnib inhibited signaling downstream of the farnesylated small G protein Rheb and synergistically enhanced etoposide-induced antiproliferative effects in lymphohematopoietic cell lines and acute myelogenous leukemia isolates. We subsequently conducted a phase 1 trial of tipifarnib plus etoposide in adults over 70 years of age who were not candidates for conventional therapy. A total of 84 patients (median age, 77 years) received 224 cycles of oral tipifarnib (300-600 mg twice daily for 14 or 21 days) plus oral etoposide (100-200 mg daily on days 1-3 and 8-10). Dose-limiting toxicities occurred with 21-day tipifarnib. Complete remissions were achieved in 16 of 54 (30%) receiving 14-day tipifarnib versus 5 of 30 (17%) receiving 21-day tipifarnib. Complete remissions occurred in 50% of two 14-day tipifarnib cohorts: 3A (tipifarnib 600, etoposide 100) and 8A (tipifarnib 400, etoposide 200). In vivo, tipifarnib plus etoposide decreased ribosomal S6 protein phosphorylation and increased histone H2AX phosphorylation and apoptosis. Tipifarnib plus etoposide is a promising orally bioavailable regimen that warrants further evaluation in elderly adults who are not candidates for conventional induction chemotherapy. These clinical studies are registered at www.clinicaltrials.gov as #NCT00112853.

Population pharmacokinetics and exposure-response assessment of veliparib co-administered with temozolomide in patients with myeloid leukemias.

PURPOSE: Veliparib is an oral inhibitor of poly(ADP-ribose) polymerase enzyme. Combination of veliparib and temozolomide was well-tolerated and demonstrated clinical activity in older patients with relapsed or refractory acute myeloid leukemia (AML) or AML arising from pre-existing myeloid malignancies. We aimed to perform quantitative assessments of pharmacokinetics, efficacy, and safety of veliparib in this patient population to inform future trial design. METHODS: Population pharmacokinetic analysis was performed using Phoenix® NLME with pharmacokinetic data obtained from 37 subjects after oral administration of veliparib in a Phase I study with and without temozolomide. Effect of covariates (age, sex, BMI, creatinine clearance (CLCR), and co-administration of temozolomide) on the pharmacokinetics of veliparib were evaluated, as well as impact of veliparib exposure on mucositis (dose-limiting toxicity), objective response rate (ORR), and overall survival. RESULTS: A two-compartment model with first-order elimination and a first-order absorption with lag-time adequately described veliparib pharmacokinetics. CLCR and body weight were clinically significant covariates for veliparib disposition. The proportion of subjects with all grade mucositis increased with veliparib exposure (AUC). However, no trend in ORR and overall survival was observed with increasing exposure. CONCLUSIONS: Veliparib with temozolomide presents a promising combination for older patients with myeloid leukemias. An exposure-safety relationship was established for this combination. Further clinical investigations aimed at elucidating the veliparib exposure-efficacy/safety relationship and optimizing dosing recommendations for maximizing benefit-risk in patients with advanced myeloid malignancies should study veliparib doses ranging up to 120 mg in combination with temozolomide.

Sorafenib Dose Recommendation in Acute Myeloid Leukemia Based on Exposure-FLT3 Relationship.

Sorafenib administered at the approved dose continuously is not tolerated long-term in patients with acute myeloid leukemia (AML). The purpose of this study was to optimize the dosing regimen by characterizing the sorafenib exposure-response relationship in patients with AML. A one-compartment model with a transit absorption compartment and enterohepatic recirculation described the exposure. The relationship between sorafenib exposure and target modulation of kinase targets (FMS-like tyrosine kinase 3 (FLT3)-ITD and extracellular signal-regulated kinase (ERK)) were described by an inhibitory maximum effect (Emax ) model. Sorafenib could inhibit FLT3-ITD activity by 100% with an IC50 of 69.3 ng/mL and ERK activity by 84% with an IC50 of 85.7 ng/mL (both adjusted for metabolite potency). Different dosing regimens utilizing 200 or 400 mg at varying frequencies were simulated based on the exposure-response relationship. Simulations demonstrate that a 200 mg twice daily (b.i.d.) dosing regimen showed similar FLT3-ITD and ERK inhibitory activity compared with 400 mg b.i.d. and is recommended in further clinical trials in patients with AML.

Exposure-Response of Veliparib to Inform Phase II Trial Design in Refractory or Relapsed Patients with Hematological Malignancies.

Purpose: A phase I trial of veliparib in combination with topotecan plus carboplatin (T+C) demonstrated a 33% objective response rate in patients with hematological malignancies. The objective is to perform exposure-response analysis to inform the phase II trial design.Experimental Design: Pharmacokinetic, efficacy, and safety data from 95 patients, who were administered 10 to 100 mg b.i.d. doses of veliparib for either 8, 14, or 21 days with T+C, were utilized for exposure-efficacy (objective response and overall survival) and exposure-safety (≥grade 3 mucositis) analysis. Multivariate cox proportional hazards and logistic regression analyses were conducted. The covariates evaluated were disease status, duration of treatment, and number of prior therapies.Results: The odds of having objective response were 1.08-fold with 1,000 ng/hr/mL increase in AUC, 1.8-fold with >8 days treatment, 2.8-fold in patients with myeloproliferative neoplasms (MPN), and 0.5-fold with ≥2 prior therapies. Based on analysis of overall survival, hazard of death decreased by 1.5% for 1,000 ng/hr/mL increase in AUC, 39% with >8 days treatment, 44% in patients with MPN, while increased by 19% with ≥2 prior therapies. The odds of having ≥grade 3 mucositis increased by 29% with 1,000 ng.h/mL increase in AUC.Conclusions: Despite shallow exposure-efficacy relationship, doses lower than 80 mg do not exceed veliparib single agent preclinical IC50 Shallow exposure-mucositis relationship also supports the 80-mg dose. Based on benefit/risk assessment, veliparib at a dose of 80 mg b.i.d. for at least 14 days in combination with T+C is recommended to be studied in MPN patients. Clin Cancer Res; 23(21); 6421-9. ©2017 AACR.

Exposure-Response Analysis of Alvocidib (Flavopiridol) Treatment by Bolus or Hybrid Administration in Newly Diagnosed or Relapsed/Refractory Acute Leukemia Patients.

Purpose: To elucidate any differences in the exposure-response of alvocidib (flavopiridol) given by 1-hour bolus or a hybrid schedule (30-minute bolus followed by a 4-hour infusion) using a flavopiridol/cytosine arabinoside/mitoxantrone sequential protocol (FLAM) in patients with acute leukemia. The hybrid schedule was devised to be pharmacologically superior in chronic leukemia based on unbound exposure.Experimental Design: Data from 129 patients in three FLAM studies were used for pharmacokinetic/pharmacodynamic modeling. Newly diagnosed (62%) or relapsed/refractory (38%) patients were treated by bolus (43%) or hybrid schedule (57%). Total and unbound flavopiridol concentrations were fit using nonlinear mixed-effect population pharmacokinetic methodologies. Exposure-response relationships using unbound flavopiridol AUC were explored using recursive partitioning.Results: Flavopiridol pharmacokinetic parameters were estimated using a two-compartment model. No pharmacokinetic covariates were identified. Flavopiridol fraction unbound was 10.9% and not different between schedules. Partitioning found no association between dosing schedule and clinical response. Clinical response was associated with AUC ≥ 780 h*ng/mL for newly diagnosed patients and AUC ≥ 1,690 h*ng/mL for relapsed/refractory patients. Higher exposures were not associated with increases in severe adverse events (≥ grade 3).Conclusions: Pharmacokinetic modeling showed no difference in flavopiridol plasma protein binding for bolus versus hybrid dosing. Further trials in newly diagnosed patients with acute leukemia should utilize the bolus FLAM regimen at the MTD of 50 mg/m2/day. Trials in relapsed/refractory patients should use the hybrid dosing schedule at the MTD (30/60 mg/m2/day) to achieve the higher exposures required for maximal efficacy in this population. Clin Cancer Res; 23(14); 3592-600. ©2017 AACR.

Phase I and pharmacologic trial of cytosine arabinoside with the selective checkpoint 1 inhibitor Sch 900776 in refractory acute leukemias.

PURPOSE: Incorporation of cytarabine into DNA activates checkpoint kinase 1 (Chk1), which stabilizes stalled replication forks, induces S-phase slowing, and diminishes cytarabine cytotoxicity. The selective Chk1 inhibitor SCH 900776 abrogates cytarabine-induced S-phase arrest and enhances cytarabine cytotoxicity in acute leukemia cell lines and leukemic blasts in vitro. To extend these findings to the clinical setting, we have conducted a phase I study of cytarabine and SCH 900776. EXPERIMENTAL DESIGN: Twenty-four adults with relapsed and refractory acute leukemias received timed sequential, continuous infusion cytarabine 2 g/m(2) over 72 hours (667 mg/m(2)/24 hours) beginning on day 1 and again on day 10. SCH 900776 was administered as a 15- to 30-minute infusion on days 2, 3, 11, and 12. The starting dose of SCH 900776 was 10 mg/m(2)/dose. RESULTS: Dose-limiting toxicities consisting of corrected QT interval prolongation and grade 3 palmar-plantar erythrodysesthesia occurred at 140 mg flat dosing (dose level 5, equivalent to 80 mg/m(2)). Complete remissions occurred in 8 of 24 (33%) patients, with 7 of 8 at 40 mg/m(2) or higher. SCH 900776 did not accumulate at any dose level. Marrow blasts obtained pretreatment and during therapy showed increased phosphorylation of H2Ax after SCH 900776 beginning at 40 mg/m(2), consistent with unrepaired DNA damage. CONCLUSIONS: These data support a randomized phase II trial of cytarabine +/- SCH 900776 at a recommended flat dose of 100 mg (equivalent to 56 mg/m(2)) for adults with poor-risk leukemias. The trial (SP P05247) was registered at www.clinicaltrials.gov as NCT00907517.

Clinical activity of sequential flavopiridol, cytosine arabinoside, and mitoxantrone for adults with newly diagnosed, poor-risk acute myelogenous leukemia.

Flavopiridol, a cyclin-dependent kinase inhibitor, is cytotoxic to leukemic blasts. In a Phase II study, flavopiridol 50 mg/m(2) was given by 1-h infusion daily x 3 beginning day 1 followed by 2 g/m(2)/72 h ara-C beginning day 6 and 40 mg/m(2) mitoxantrone on day 9 (FLAM) to 45 adults with newly diagnosed acute myelogenous leukemia (AML) with multiple poor-risk features. Thirty patients (67%) achieved complete remission (CR) and 4 (9%) died. Twelve (40%) received myeloablative allogeneic bone marrow transplant (BMT) in first CR. Median OS and DFS are not reached (67% alive 12.5-31 months, 58% in CR 11.4-30 months), with median follow-up 22 months. Sixteen received FLAM in CR, with median OS and DFS 9 and 13.1 months, and 36% alive at 21-31 months. Short OS and DFS correlated with adverse cytogenetics, regardless of age or treatment in CR. The addition of allogeneic BMT in CR translates into long OS and DFS in the majority of eligible patients.