Abstract This study aims at evaluating the utility of the population pharmacokinetics approach in therapeutic protein drug‐drug‐interaction (DDI) assessment. Simulations were conducted for 2 representative victim drugs, methotrexate and trastuzumab, using a parallel‐group design with and without the interaction drug. The effect of a perpetrator on the exposure of the victim drug is described as the ratio of clearance/apparent clearance of the victim drug given with or without the perpetrator. The power of DDI assessment was calculated as the percentage of runs with 90% confidence interval of the estimated DDI effect within 80% to 125% for the scenarios of no DDI, benchmarked with the noncompartmental approach with intensive sampling. The impact of the number of subjects, the number of sampling points per subject, sampling time error, and model misspecification on the power of DDI determination were evaluated. Results showed that with equal numbers of subjects in each arm, the population pharmacokinetics approach with sparse sampling may need about the same or a higher number of subjects compared to a noncompartmental approach in order to achieve similar power. Increasing the number of subjects, even if only in the study drug alone arm, can increase the power. Sampling or dosing time error had notable impacts on the power for methotrexate but not for trastuzumab. Model misspecification had no notable impacts on the power for trastuzumab. Overall, the population pharmacokinetics approach with sparse sampling built in phase 2/3 studies allows appropriate DDI assessment with adequate study design and analysis and can be considered as an alternative to dedicated DDI studies.
Abstract The purpose of this study is to investigate Hsp90/Cdc37 interaction and identify residues critical for the interaction using real-time luciferase complementation imaging and computational modeling. Molecular imaging using a split Renilla luciferase fragment complementation (SRL-FC) was established to monitor real-time Hsp90/Cdc37interactions in living cells. Computational modeling and molecular dynamics simulations were used to evaluate the interaction interface of Hsp90/Cdc37 complex and critical residues in the interaction interface were identified for mutagenesis. Western Blotting and co-immunoprecipitation were used to determine protein expression and complex formation. The molecular imaging in living cells showed that Hsp90 and Cdc37 helped the complementation of N-terminus of Renilla luciferase (fused with Hsp90; N-RL-Hsp90) and C-terminus of Renilla luciferase (fused with Cdc37, Cdc37-C-RL) with 170-fold higher luciferase activity than controls without Hsp90/Cdc37. This suggests that the SRL-FC is sensitive and specific to monitor the interaction of full length human Hsp90 and Cdc37. Molecular dynamics simulations revealed that the interface was constituted by a series of residues interacting through hydrophobic or polar interactions. Mutagenesis confirmed that mutations in Hsp90 (A121N, Q133A, F134A) and mutations in Cdc37 (M164K, R167A) led to the loss of complementation of N-RL-Hsp90 and Cdc37-C-RL (5 to 10-fold lower luciferase activity compared to wild-type), indicating these residues are critical in Hsp90/Cdc37 interactions. In comparison, mutations in Hsp90 (E47A, S113A) and mutations in Cdc37 (A204E) only decreased 50% of the complementation of N-RL-Hsp90 and Cdc37-C-RL, which suggests that these residues contribute less to Hsp90/Cdc37 interaction. In contrast, mutations of Hsp90 (R46A, S50A) and mutation in Cdc37 (L165H) did not change the complementation of N-RL-Hsp90 and Cdc37-C-RL, indicating that these residues did not contribute to Hsp90/Cdc37 interaction. The data suggests that molecular imaging using split Renilla luciferase fragment complementation (SRL-FC) can be used to identify the critical residues in Hsp90/Cdc37 interaction. Although Hsp90/Cdc37 interactions are through both hydrophobic and polar interactions, mutation in a single amino acid residue, including Ala121, Gln133, Phe134 in human Hsp90 and Met164, Arg167 in human Cdc37, is sufficient to disrupt Hsp90/Cdc37 interaction. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 2672.
Transforming growth factor β (TGF-β) causes growth arrest at the G1 phase of the cell cycle in most cell types. Both the cyclin dependent kinase inhibitor p15INK4B and p21(Cip1/WAF1) genes have been found to be induced by TGF-β in human keratinocyte HaCaT cells. Analyses of the human p15 and p21 promoters have led to the identification of GC-rich sequences capable of binding to Sp1 transcription factors as necessary elements for the TGF-β induction of both promoters. We report here that canonical Sp1 binding sites derived from the SV40 21 bp repeat could also support promoter induction by TGF-β when placed upstream of a minimal luciferase reporter construct containing only the TATA and Inr elements. Gel retardation assays identified Sp1, Sp3 and ΔSp3 as major factors binding to the canonical Sp1 sites in HaCaT cells and that TGF-β treatment did not change their binding activities over a 24 h period. More importantly, GAL4-Sp1, but not GAL4-Sp3, chimeric protein supported TGF-β mediated gene induction from a luciferase reporter construct driven by five GAL4 DNA binding sites. Our results suggest that Sp1 binding site can function as a distinct TGF-β responsive element for TGF-β mediated promoter expression and Sp1 per se can mediate this response.
This phase I study investigated talazoparib pharmacokinetics (PK) and safety in patients with advanced solid tumours and varying degrees of hepatic function.Patients with advanced solid tumours and normal hepatic function or varying degrees of hepatic impairment (mild, moderate or severe, based on National Cancer Institute Organ Dysfunction Working Group classification) received talazoparib 0.5 mg once daily for 22 calendar days. Plasma and urine samples after single and multiple doses were collected and analysed for talazoparib using validated assays. Plasma PK data from all patients were analysed using the population PK method. Plasma and urine PK parameters in PK-evaluable patients were calculated using noncompartmental analysis (NCA). Safety was monitored in all enrolled patients.Thirty-eight patients were enrolled; 37 had ≥1 PK concentration, among which 17 were evaluable for NCA. Population PK analysis (n = 37) indicated no significant impact of hepatic function on apparent clearance (CL/F) of talazoparib. Baseline creatinine clearance was the only significant covariate on CL/F (α = 0.05). NCA of data (n = 17) showed no clear trend for increase in exposure on day 22 with worsening hepatic function. Talazoparib protein binding was comparable in patients with varying hepatic function. Talazoparib was generally well tolerated, and the safety profile observed in this study was consistent with the known safety profile of the drug.Hepatic impairment (mild, moderate or severe) has no impact on the PK of talazoparib. No dose modification is recommended for patients with advanced solid tumours and various degrees of hepatic impairment, and this labelling language has been approved by the US Food and Drug Administration and the European Medicines Agency.
<div>Purpose:<p>To assess the preclinical efficacy, clinical safety and efficacy, and MTD of palbociclib plus nab-paclitaxel in patients with advanced pancreatic ductal adenocarcinoma (PDAC).</p>Experimental Design:<p>Preclinical activity was tested in patient-derived xenograft (PDX) models of PDAC. In the open-label, phase I clinical study, the dose-escalation cohort received oral palbociclib initially at 75 mg/day (range, 50‒125 mg/day; modified 3+3 design; 3/1 schedule); intravenous nab-paclitaxel was administered weekly for 3 weeks/28-day cycle at 100‒125 mg/m<sup>2</sup>. The modified dose–regimen cohorts received palbociclib 75 mg/day (3/1 schedule or continuously) plus nab-paclitaxel (biweekly 125 or 100 mg/m<sup>2</sup>, respectively). The prespecified efficacy threshold was 12-month survival probability of ≥65% at the MTD.</p>Results:<p>Palbociclib plus nab-paclitaxel was more effective than gemcitabine plus nab-paclitaxel in three of four PDX models tested; the combination was not inferior to paclitaxel plus gemcitabine. In the clinical trial, 76 patients (80% received prior treatment for advanced disease) were enrolled. Four dose-limiting toxicities were observed [mucositis (<i>n</i> = 1), neutropenia (<i>n</i> = 2), febrile neutropenia (<i>n</i> = 1)]. The MTD was palbociclib 100 mg for 21 of every 28 days and nab-paclitaxel 125 mg/m<sup>2</sup> weekly for 3 weeks in a 28-day cycle. Among all patients, the most common all-causality any-grade adverse events were neutropenia (76.3%), asthenia/fatigue (52.6%), nausea (42.1%), and anemia (40.8%). At the MTD (<i>n</i> = 27), the 12-month survival probability was 50% (95% confidence interval, 29.9–67.2).</p>Conclusions:<p>This study showed the tolerability and antitumor activity of palbociclib plus nab-paclitaxel treatment in patients with PDAC; however, the prespecified efficacy threshold was not met.</p>Trial Registration:<p>Pfizer Inc (NCT02501902)</p>Significance:<p>In this article, the combination of palbociclib, a CDK4/6 inhibitor, and nab-paclitaxel in advanced pancreatic cancer evaluates an important drug combination using translational science. In addition, the work presented combines preclinical and clinical data along with pharmacokinetic and pharmacodynamic assessments to find alternative treatments for this patient population.</p></div>
Supplementary Table S3 from A Preclinical and Phase Ib Study of Palbociclib plus Nab-Paclitaxel in Patients with Metastatic Adenocarcinoma of the Pancreas
