Brian F. Kiesel

A Phase I Study of Veliparib in Combination with Metronomic Cyclophosphamide in Adults with Refractory Solid Tumors and Lymphomas

Purpose: Oral administration of the alkylating agent cyclophosphamide at low doses, metronomic dosing, is well tolerated, with efficacy in multiple tumor types. PARP inhibition potentiates effects of cyclophosphamide in preclinical models. We conducted a phase I trial of the PARP inhibitor veliparib and metronomic cyclophosphamide in patients with refractory solid tumors and lymphoid malignancies. Experimental Design: Objectives were to establish the safety and maximum tolerated dose (MTD) of the combination; characterize veliparib pharmacokinetics (PK); measure poly(ADP-ribose) (PAR), a product of PARP, in tumor biopsies and peripheral blood mononuclear cells (PBMC); and measure the DNA-damage marker γH2AX in PBMCs and circulating tumor cells (CTC). Cyclophosphamide was administered once daily in 21-day cycles in combination with veliparib administered once daily for 7, 14, or 21 days. Results: Thirty-five patients were enrolled. The study treatment was well tolerated, and the MTD was established as veliparib 60 mg with cyclophosphamide 50 mg given once daily. Seven patients had partial responses; an additional six patients had disease stabilization for at least six cycles. PAR was significantly decreased in PBMCs (by at least 50%) and tumor biopsies (by at least 80%) across dose levels (DL); γH2AX levels were increased in CTCs from seven of nine patients evaluated after drug administration. Conclusions: The combination of veliparib with metronomic cyclophosphamide is well tolerated and shows promising activity in a subset of patients with BRCA mutations. A phase II trial of the combination compared with single-agent cyclophosphamide is ongoing in BRCA-positive ovarian cancer, triple-negative breast cancer, and low-grade lymphoma. Clin Cancer Res; 18(6); 1726–34. ©2012 AACR.

Phase I Study of Veliparib (ABT-888) Combined with Cisplatin and Vinorelbine in Advanced Triple-Negative Breast Cancer and/or BRCA Mutation–Associated Breast Cancer

Purpose: Cisplatin is synergistic with vinorelbine and the PARP inhibitor veliparib, and has antineoplastic activity in triple-negative breast cancer (TNBC) and BRCA mutation–associated breast cancer. This phase I study assessed veliparib with cisplatin and vinorelbine. Experimental Design: A 3+3 dose-escalation design evaluated veliparib administered twice daily for 14 days with cisplatin (75 mg/m2 day 1) and vinorelbine (25 mg/m2 days 1, 8) every 21 days, for 6 to 10 cycles, followed by veliparib monotherapy. Pharmacokinetics, measurement of poly(ADP-ribose) in peripheral blood mononuclear cells, and preliminary efficacy were assessed. IHC and gene-expression profiling were evaluated as potential predictors of response. Results: Forty-five patients enrolled in nine dose cohorts plus five in an expansion cohort at the highest dose level and recommended phase II dose, 300 mg twice daily. The MTD of veliparib was not reached. Neutropenia (36%), anemia (30%), and thrombocytopenia (12%) were the most common grade 3/4 adverse events. Best overall response for 48 patients was radiologic response with 9-week confirmation for 17 (35%; 2 complete, 15 partial), and stable disease for 21 (44%). Germline BRCA mutation presence versus absence was associated with 6-month progression-free survival [PFS; 10 of 14 (71%) vs. 8 of 27 (30%), mid-P = 0.01]. Median PFS for all 50 patients was 5.5 months (95% confidence interval, 4.1–6.7). Conclusions: Veliparib at 300 mg twice daily combined with cisplatin and vinorelbine is well tolerated with encouraging response rates. A phase II randomized trial is planned to assess veliparibs contribution to cisplatin chemotherapy in metastatic TNBC and BRCA mutation–associated breast cancer. Clin Cancer Res; 22(12); 2855–64. ©2016 AACR.

LC–MS/MS assay for the quantitation of the HDAC inhibitor belinostat and five major metabolites in human plasma

The histone deacetylase inhibitor belinostat is being evaluated clinically as a single agent in the treatment of peripheral T-cell lymphomas and in combination with other anticancer agents to treat a wide range of human cancers including acute leukemias and solid tumors. To determine the pharmacokinetics of belinostat in the NCI ODWG liver dysfunction study, we developed and validated an LC-MS/MS assay for the quantitation of belinostat and five major metabolites in 0.05 mL human plasma. After protein precipitation, chromatographic separation was achieved with a Waters Acquity BEH C18 column and a linear gradient of 0.1% formic acid in acetonitrile and water. Detection with an ABI 4000Q mass spectrometer utilized both electrospray positive and negative mode ionization. The assay was linear from 30 to 5000 ng/mL for all six analytes and proved to be accurate (92.0-104.4%) and precise (CV <13.7%), and fulfilled FDA criteria for bioanalytical method validation. We demonstrated the suitability of this assay for measuring parent drug and five major metabolites in plasma from a patient who was administered belinostat IV at a dose of 400 mg/m(2). The LC-MS/MS assay that has been developed will be an essential tool to further define the metabolism and pharmacology of belinostat in the ongoing liver organ dysfunction as well as other studies that investigate belinostat with other anticancer agents.

Outcome of BRCA 1/2-mutated (BRCA+) and triple-negative, BRCA wild type (BRCA-wt) breast cancer patients in a phase I study of single-agent veliparib (V).

135 Background: Veliparib (V) (ABT-888) is an oral, potent inhibitor of PARP 1/2. PARP inhibitors have preclinical and clinical efficacy in BRCA+ malignancies. There are genotypic and phenotypic similarities between BRCA+ cancers, serous ovarian cancer and basal-like breast cancer and we postulated that these tumors types may be similarly sensitive to single-agent PARP inhibition. This study sought to establish the maximum tolerated dose (MTD), dose -limiting toxicities (DLT), pharmacokinetic and pharmocodynamic properties, and preliminary efficacy of chronically-dosed V in 2 cohorts of patients, BRCA+ and BRCA-wt (consisting of serous ovarian cancer and triple-negative breast cancer (TNBC). METHODS A 3+3 dose escalation phase I trial was performed. Nine dose levels (DL) were planned, and dose escalation started at 50 mg BID to a maximum of 500 mg BID to determine a maximum tolerated dose (MTD) and recommended phase II dose (RP2D). V was administered orally continuously on a 28 day cycle. BRCA+ and BRCA-wt patients were enrolled in 2 separate cohorts with 2 separate escalations. RESULTS 98 (70 BRCA+ and 28 BRCA-wt) pts have been enrolled. The maximum administered dose (MAD) was 500mg BID and the MTD/RP2D is 400mg BID for both cohorts. 59 BRCA+ pts and 24 BRCA-wt pts (21 TNBC and 3 ovary) were evaluable for response. ORR was defined as CR+PR and clinical benefit rate (CBR) as CR+PR+SD > 6 months. Results are summarized in the table. CONCLUSIONS There is evidence of anti-tumor activity with V comparable to that of other PARP inhibitors in the BRCA+ population. There was indication of dose responsiveness with greater activity in this population at higher doses. There is less activity in the mostly TNBC, BRCA-wt population, although there was evidence of benefit in a small number of patients. Ongoing tissue correlative studies will help to identify potential mechanisms of sensitivity and resistance. CLINICAL TRIAL INFORMATION NCT00892736. [Table: see text].

LC–MS/MS assay for the quantitation of the tyrosine kinase inhibitor neratinib in human plasma

HIGHLIGHTSNeratinib is an orally available TKI targeting EGRR and HER2 in clinical development.An LC–MS/MS assay from 2 to 1000 ng/mL in 0.1 mL plasma was developed and validated.Signal degradation was observed but corrected with isotopic internal standard.Assay is being utilized to support neratinib combination clinical studies. ABSTRACT Neratinib is an orally available tyrosine kinase inhibitor targeting HER2 (ERBB2) and EGFR (ERBB). It is being clinically evaluated for the treatment of breast and other solid tumors types as a single agent or in combination with other chemotherapies. In support of several phase I/II clinical trials investigating neratinib combinations, we developed and validated a novel LC–MS/MS assay for the quantification of neratinib in 100 &mgr;L of human plasma with a stable isotopic internal standard. Analytes were extracted from plasma using protein precipitation and evaporation of the resulting supernatant followed by resuspension. Chromatographic separation was achieved using an Acquity UPLC BEH Shield RP18 column and a gradient methanol‐water mobile phase containing 10% ammonium acetate. An ABI 4000 mass spectrometer and electrospray positive mode ionization were used for detection. The assay was linear from 2 to 1,000 ng/mL and proved to be accurate (98.9–106.5%) and precise (<6.2%CV), and met the FDA guidance for bioanalytical method validation. This LC–MS/MS assay will be an essential tool to further define the pharmacokinetics of neratinib.

Pharmacologic ATM but not ATR kinase inhibition abrogates p21-dependent G1 arrest and promotes gastrointestinal syndrome after total body irradiation

We show that ATM kinase inhibition using AZ31 prior to 9 or 9.25 Gy total body irradiation (TBI) reduced median time to moribund in mice to 8 days. ATR kinase inhibition using AZD6738 prior to TBI did not reduce median time to moribund. The striking finding associated with ATM inhibition prior to TBI was increased crypt loss within the intestine epithelium. ATM inhibition reduced upregulation of p21, an inhibitor of cyclin-dependent kinases, and blocked G1 arrest after TBI thereby increasing the number of S phase cells in crypts in wild-type but not Cdkn1a(p21CIP/WAF1)−/− mice. In contrast, ATR inhibition increased upregulation of p21 after TBI. Thus, ATM activity is essential for p21-dependent arrest while ATR inhibition may potentiate arrest in crypt cells after TBI. Nevertheless, ATM inhibition reduced median time to moribund in Cdkn1a(p21CIP/WAF1)−/− mice after TBI. ATM inhibition also increased cell death in crypts at 4 h in Cdkn1a(p21CIP/WAF1)−/−, earlier than at 24 h in wild-type mice after TBI. In contrast, ATR inhibition decreased cell death in crypts in Cdkn1a(p21CIP/WAF1)−/− mice at 4 h after TBI. We conclude that ATM activity is essential for p21-dependent and p21-independent mechanisms that radioprotect intestinal crypts and that ATM inhibition promotes GI syndrome after TBI.

Parent‐Metabolite Pharmacokinetic Modeling and Pharmacodynamics of Veliparib (ABT‐888), a PARP Inhibitor, in Patients With BRCA 1/2–Mutated Cancer or PARP‐Sensitive Tumor Types

Veliparib (ABT‐888) is a novel oral poly‐ADP‐ribose polymerase (PARP) inhibitor that is being developed for the treatment of hematologic malignancies and solid tumors. Although the pharmacokinetics of veliparib have been studied in combination with cytotoxic agents, limited information exists regarding the pharmacokinetics (PK) of chronically dosed single‐agent veliparib in patients with either BRCA 1/2–mutated cancer or PARP‐sensitive tumors. The objectives of the current analysis were to characterize the population pharmacokinetics of veliparib and its primary, active metabolite, M8, and to evaluate the relationship between veliparib and M8 concentrations and poly‐ADP‐ribose (PAR) level observed in peripheral blood mononuclear cells (PBMCs). Seventy‐one subjects contributed with veliparib plasma concentrations, M8 plasma concentrations, and PAR levels in PBMCs. Veliparib and M8 concentrations were modeled simultaneously using a population PK approach. A 2‐compartment model with delayed first‐order absorption and the elimination parameterized as renal (CLR/F) and nonrenal clearance (CLNR/F) adequately described veliparib pharmacokinetics. The pharmacokinetics of the M8 metabolite was described with a 2‐compartment model. Creatinine clearance(CLCR) and lean body mass (LBM) were identified as significant predictors of veliparib CLR/F and central volume of distribution, respectively. For a typical subject (LBM, 48 kg; CLCR, 95 mL/min), total clearance (CLR/F + CLNR/F), and central and peripheral volume of distribution for veliparib were estimated as 17.3 L/h, 98.7 L, and 48.3 L, respectively. At least 50% inhibition of PAR levels in PBMCs was observed at dose levels ranging from 50 to 500 mg.

The PARP Inhibitor Veliparib Can Be Safely Added to Bendamustine and Rituximab and Has Preliminary Evidence of Activity in B-Cell Lymphoma

Purpose: The PARP inhibitor veliparib enhances the cytotoxicity of alkylating agents. This phase I study evaluated veliparib with the bifunctional alkylator bendamustine (VB) in patients with relapsed/refractory lymphoma, multiple myeloma, and solid malignancies, with a cohort expansion of VB with rituximab (VBR) in patients with B-cell lymphomas. Experimental Design: This dose-escalation study evaluated safety, pharmacokinetics, and preliminary efficacy of veliparib (20–400 mg twice a day, days 1–7 of 28-day cycle) and bendamustine (70 and 90 mg/m2 intravenously, days 1 and 2). A cohort expansion was conducted, which combined veliparib and bendamustine at the maximum tolerated dose (MTD) with rituximab (375 mg/m2, day 1) in patients with B-cell lymphomas. Thirty-four patients were treated in seven dose-escalation cohorts and seven patients in the dose-expansion cohort. Results: The MTD was veliparib 300 mg twice daily plus bendamustine 90 mg/m2. Dose-limiting toxicities (DLT) were anemia, nausea, hypertension, and hyperhidrosis. Grade ≥3 toxicities included lymphopenia (87.8%), anemia (19.5%), neutropenia (12.2%), thrombocytopenia (9.8%), leukopenia (9.8%), nausea (7.3%), and hypophosphatemia (7.3%). Apparent veliparib clearance was slightly lower than previously reported. Of 14 patients with lymphoma evaluable for response, five of seven (71%) on VB and six of seven (86%) on VBR achieved objective response. One patient with multiple myeloma achieved partial response. Conclusions: VB and VBR were generally well-tolerated. VBR had preliminary clinical activity in patients with B-cell lymphoma, which warrants further investigation in a phase II trial. This trial was registered at www.clinicaltrials.gov as NCT01326702. Clin Cancer Res; 23(15); 4119–26. ©2017 AACR.

Human hepatocyte assessment of imatinib drug-drug interactions - Complexities in clinical translation

AIM Inducers and inhibitors of CYP3A, such as ritonavir and efavirenz, may be used as part of the highly active antiretroviral therapy (HAART) to treat HIV patients. HIV patients with chronic myeloid leukemia or gastrointestinal stromal tumour may need imatinib, a CYP3A4 substrate with known exposure response-relationships. Administration of imatinib to patients on ritonavir or efavirenz may result in altered imatinib exposure leading to increased toxicity or failure of therapy, respectively. We used primary human hepatocyte cultures to evaluate the magnitude of interaction between imatinib and ritonavir/efavirenz. METHODS Hepatocytes were pre-treated with vehicle, ritonavir, ketoconazole, efavirenz or rifampicin, and the metabolism of imatinib was characterized over time. Concentrations of imatinib and metabolite were quantitated in combined lysate and medium, using LC-MS. RESULTS The predicted changes in imatinib CLoral (95% CI) with ketoconazole, ritonavir, rifampicin and efavirenz were 4.0-fold (0, 9.2) lower, 2.8-fold (0.04, 5.5) lower, 2.9-fold (2.2, 3.5) higher and 2.0-fold (0.42, 3.5) higher, respectively. These predictions were in good agreement with clinical single dose drug-drug interaction studies, but not with reports of imatinib interactions at steady-state. Alterations in metabolism were similar after acute or chronic imatinib exposure. CONCLUSIONS In vitro human hepatocytes predicted increased clearance of imatinib with inducers and decreased clearance with inhibitors of CYP enzymes. The impact of HAART on imatinib may depend on whether it is being initiated or has already been dosed chronically in patients. Therapeutic drug monitoring may have a role in optimizing imatinib therapy in this patient population.

Abstract 759: Quantitation of the HDAC inhibitor belinostat (PXD-101) and metabolites in human plasma by a novel LC-MS/MS assay.

Proceedings: AACR 103rd Annual Meeting 2012‐‐ Mar 31‐Apr 4, 2012; Chicago, IL Introduction: Histone deacetylases (HDAC) are frequently deregulated in human cancers and their inhibition allows re-expression of silenced genes. Belinostat is an HDAC inhibitor with in vitro and in vivo activity in multiple malignancies, currently in phase II trials. To date, the pharmacokinetics and metabolism of belinostat have not been adequately characterized. To support an organ dysfunction study and clinical development of belinostat, we developed and validated an LC-MS/MS assay for the sensitive, accurate, and precise quantitation of belinostat and its metabolites belinostat-glucuronide, methylated-belinostat, belinostat amide, 3-ASBA, and belinostat acid in human plasma. Methods: The assay used 50 µL of plasma, [13C6]-belinostat and [D5]-3-ASBA as internal standards and acetonitrile (0.1% TFA) for protein precipitation. A UPLC C18 column was used with a gradient elution from 90:10 to 10:90 water-acetonitrile (0.1% formic acid) over the course of 4 min followed by re-equilibration for 3 min (7 min total run time). Flow rate was 0.5 mL/min. An ABI 4000 tandem MS/MS with ESI positive and negative ionization in MRM mode was used to detect the analytes. Bioanalytical method validation was performed based on FDA guidelines. The applicability of the assay was demonstrated by quantitating belinostat and its metabolites in plasma of a human patient sampled over the course of 24 h. Results: Belinostat eluted at 2.9 min, while all metabolites eluted between 2.7 and 3.6 min. The assay was linear and accurate between 30 and 5000 ng/mL for all analytes; 3 triplicate standard curves assayed on 3 separate days displayed a CV 69% for belinostat and >64% for metabolites. Belinostat and all metabolites could be quantitated in human plasma after IV administration of belinostat over 30 min. Belinostat glucuronide appeared to be the major metabolite with up to 10-fold exposure relative to belinostat. Conclusion: We have developed a sensitive, accurate and precise LC-MS/MS assay that allows quantitation of belinostat and its 5 metabolites in human plasma. UGT1A1 is responsible for glucuronidation, which appears to be a major metabolic route. This assay will be a valuable tool to assess the pharmacokinetics and metabolism of belinostat in humans, and it is being used to support clinical studies employing belinostat in multiple clinical trials. Supported by Grants U01-CA099168 and N01-CM62209, P30-CA47904 from the NCI, and Spectrum Pharmaceuticals Inc and Topotarget A/S 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 759. doi:1538-7445.AM2012-759