Whitney P. Caron

Interpatient pharmacokinetic and pharmacodynamic variability of carrier-mediated anticancer agents

Major advances in the field of carrier‐mediated agents (CMAs) have revolutionized drug delivery capabilities over the past decade. While providing numerous advantages over their small‐molecule counterparts (solubility, duration of exposure, and delivery to the site of action are higher), these agents display substantial variability in systemic clearance (CL) and distribution, tumor delivery, and pharmacologic effects. This review provides an overview of factors that affect the pharmacokinetics (PK) and pharmacodynamics (PD) of CMAs in preclinical models and patients.

Translational Studies of Phenotypic Probes for the Mononuclear Phagocyte System and Liposomal Pharmacology

As nanoparticles (NPs) are cleared via phagocytes of the mononuclear phagocyte system (MPS), we hypothesized that the function of circulating monocytes and dendritic cells (MO/DC) in blood can predict NP clearance (CL). We measured MO/DC phagocytosis and reactive oxygen species (ROS) production in mice, rats, dogs, and patients with refractory solid tumors. Pharmacokinetic studies of polyethylene glycol (PEG)-encapsulated liposomal doxorubicin (PEGylated liposomal doxirubicin [PLD]), CKD-602 (S-CKD602), and cisplatin (SPI-077) were performed at the maximum tolerated dose. MO/DC function was also evaluated in patients with recurrent epithelial ovarian cancer (EOC) administered PLD. Across species, a positive association was observed between cell function and CL of PEGylated liposomes. In patients with EOC, associations were observed between PLD CL and phagocytosis (R2 = 0.43, P = 0.04) and ROS production (R2 = 0.61, P = 0.008) in blood MO/DC. These findings suggest that probes of MPS function may help predict PEGylated liposome CL across species and PLD CL in patients with EOC.

Meta-analysis of inter-patient pharmacokinetic variability of liposomal and non-liposomal anticancer agents.

UNLABELLED A meta-analysis was conducted to evaluate the inter-patient pharmacokinetic (PK) variability of liposomal and small molecule (SM) anticancer agents. Inter-patient PK variability of 9 liposomal and SM formulations of the same drug was evaluated. PK variability was measured as coefficient of variance (CV%) of area under the plasma concentration versus time curve (AUC) and the fold-difference between AUCmax and AUCmin (AUC range). CV% of AUC and AUC ranges were 2.7-fold (P<0.001) and 16.7-fold (P=0.13) greater, respectively, for liposomal compared with SM drugs. There was an inverse linear relationship between the clearance (CL) of liposomal agents and PK variability with a lower CL associated with greater PK variability (R(2)=0.39). PK variability of liposomal agents was greater when evaluated from 0-336 h compared with 0-24h. PK variability of liposomes is significantly greater than SM. The factors associated with the PK variability of liposomal agents need to be evaluated. FROM THE CLINICAL EDITOR In this meta-analysis, the inter-patient pharmacokinetic variability of 9 liposomal and small molecule anti-cancer agents was studied. The authors determined that several parameters are in favor of the liposomal formulation; however, the PK variability of the formulation was higher compared with small molecule agents, the reason for which remains to be determined in future studies.

A Review of Study Designs and Outcomes of Phase I Clinical Studies of Nanoparticle Agents Compared with Small-Molecule Anticancer Agents

Purpose: Nanoparticles or carrier-mediated agents have been designed to prolong drug circulation time, increase tumor delivery, and improve therapeutic index compared to their small-molecule counterparts. The starting dose for phase I studies of small molecules and nanoparticles anticancer agents is based on the toxicity profile of the most sensitive species (e.g., rat or canine), but the optimal animal model for these studies of nanoparticles is unclear. The objective of this study was to evaluate the design, progression, and outcomes of phase I studies of nanoparticles compared with small-molecule anticancer agents. Experimental design: In preclinical studies, the maximum tolerated dose (MTD) in rats and dogs was evaluated for nanoparticles and their respective small molecules. In phase I clinical trials in patients with advanced solid tumors, the basis for starting dose, the number of dose escalations, number of patients enrolled, and the ratio of MTD to starting dose was determined for nanoparticles and small molecules. Results: The mean ratio of MTD to starting dose in clinical phase I studies was significantly greater for nanoparticles (13.9 ± 10.8) compared with small molecules (2.1 ± 1.1; P = 0.005). The number of dose levels in a clinical phase I study was also significantly greater for nanoparticles (7.3 ± 2.9) compared with small molecules (4.1 ± 1.5; P = 0.008). Conclusions: The degree of dose escalation from starting dose to MTD was significantly greater for nanoparticles as compared with small-molecule anticancer drugs. These findings necessitate the need to identify the most appropriate preclinical animal model to use when evaluating nanoparticles toxicity. Clin Cancer Res; 19(12); 3309–15. ©2013 AACR.

Clinical risk factors of PEGylated liposomal doxorubicin induced palmar plantar erythrodysesthesia in recurrent ovarian cancer patients

INTRODUCTION Studies have shown that body composition, age, gender, changes in monocyte count and repeated dosing alter pharmacokinetic properties of PEGylated liposomal doxorubicin (PLD). However, limited information exists regarding the clinical risk factors of ovarian cancer patients who develop palmar plantar erythrodysesthesia (PPE) while receiving PLD for cancer recurrence. METHODS We conducted a retrospective cohort analysis of consecutive patients with recurrent ovarian and primary peritoneal cancer who were treated with PLD from 2005 to 2009. Clinical and pathologic data were abstracted from electronic medical records. Statistical analyses were performed using univariate and bivariate analyses, logistic regression, and log rank-tests. RESULTS Twenty-three percent (31/133) of patients developed PPE. Age, body mass index (BMI), race, stage, and histology did not significantly differ between PPE and non-PPE patients. There was a possible trend for decreasing PPE with increasing body mass index (BMI) (24.5% of normal weight, 27.5% of overweight; 23.8% of obese class I; 13.3% of obese class II; and 0% of obese class III), though not statistically significant. The number of chemotherapy regimens prior to PLD, and the mean cycles of PLD received did not differ between patients with and without PPE. 77.4% of PPE cases occurred within the first 3 infusion cycles. PPE was not associated with time to progression. CONCLUSION Nearly one-quarter of ovarian cancer patients receiving PLD will develop PPE. Further investigation of factors such as BMI associated with PPE may aid in patient selection for PLD, and future development of other nanoparticle and liposomal agents.

Abstract 2673: Relationship between serum hormone levels and pharmacokinetics (PK) of PEGylated liposomal doxorubicin (PLD) in patients with refractory ovarian cancer

Proceedings: AACR 103rd Annual Meeting 2012‐‐ Mar 31‐Apr 4, 2012; Chicago, IL Background: Pharmacokinetics (PK) of nanoparticle agents, such as PEGylated liposomes, are dependent upon the carrier and not the encapsulated drug. Previous studies have demonstrated a high degree of interpatient variability in the PK of PEGylated liposomal doxorubicin (PLD). We have previously demonstrated that circulating monocytes play a major role in clearance (CL) of PEGylated liposomes in patients. Estrogen and testosterone, which are largely secreted via the gonads, have been shown to modulate monocyte function and chemotaxis. In addition, estrone is converted from other steroid hormones in adipose tissue. Thus, we evaluated the relationship between serum hormone concentrations in blood samples and PK of PLD in patients with refractory ovarian cancer. Methods: PLD was administered at 30 or 40mg/m2 IV every 28 days with or without concurrent carboplatin at an AUC = 5 in patients (n = 10) with recurrent ovarian cancer. All patients had undergone bilateral salpingo-oophorectomy (BSO). Serial PK samples were obtained from time 0 h to 168 h and day 28 post PLD dose. Plasma was processed to measure encapsulated and released doxorubicin using solid phase separation and HPLC with fluorescence detection. CL of encapsulated doxorubicin in plasma was calculated by non-compartmental methods. Prior to administration of PLD, serum samples were collected and concentrations of estrone, estrogen, testosterone, and dihydrotestosterone were measured. Results: There was a direct linear relationship between encapsulated doxorubicin CL and both testosterone (R2 = 0.72) and estrone concentrations (R2 = 0.54) in all patients. When patients were subdivided based on PLD monotherapy (n = 6) or PLD + carboplatin (n = 4), there was a stronger relationship between encapsulated doxorubicin CL and both testosterone (R2 = 0.88) and estrone concentrations (R2 = 0.86) in patients receiving PLD monotherapy. Estrogen and dihydrotestosterone concentrations were below quantification limits for the majority of patients and thus were not evaluated. There was no relationship between patient body weight and BMI and estrone concentrations (R2 = 0.25 and R2 = 0.13 respectively). Conclusions: These findings indicate that serum hormone concentrations are associated with encapsulated doxorubicin CL and thus may be useful for individualizing PLD therapy in patients with ovarian cancer and other malignancies. Patient body weight and BMI were not associated with estrone concentrations in patients with ovarian cancer, suggesting phenotypic and/or genotypic differences in estrone production in adipose tissue. Low estrogen concentrations are consistent with the patients undergoing BSO surgery as standard treatment of ovarian cancer. The relationship between hormone levels and PK of nanoparticles needs to be further evaluated as a method to individualize nanoparticle therapy. 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 2673. doi:1538-7445.AM2012-2673

Abstract 371: Comparison of toxicity and study design issues of nanoparticle and small molecule anticancer agents in preclinical models and phase I clinical trials

Proceedings: AACR 102nd Annual Meeting 2011‐‐ Apr 2‐6, 2011; Orlando, FL Background: Carrier-mediated agents (CMA) are classified as nanoparticles, nanosomes (nanoparticle sized liposomes) and conjugates. Anticancer CMA offer many unique advantages over their traditional small molecule (SM) counterparts, including improved solubility, longer duration of exposure, tumor-selective delivery, increased antitumor response and reduced toxicity. The interpatient variability in pharmacokinetics (PK) and pharmacodynamics (PD) associated with nanoparticles are greater than that observed with SM. The starting dose for phase I studies of SM and CMA anticancer agents is based on the toxicity profile of the most sensitive species (e.g. rat or canine). However, the optimal animal model for toxicologic and pharmacologic studies of CMA is unclear. Our preliminary data suggests that dogs are highly sensitive to nanoparticles and thus may not be an appropriate animal model in determining the starting dose of CMA for phase I clinical trials. We evaluated preclinical toxicology data and how this affected the design and progression of phase I studies of CMA compared to SM anticancer agents. Methods: In preclinical studies, the maximum tolerated dose (MTD) in rats and dogs was evaluated for CMA and their respective SM. In phase I clinical trials of CMA and their respective SM in patients with advanced solid tumors, the basis for starting dose, the number of dose escalations, number of patients and the ratio of MTD to starting dose was determined. Results: Starting dose in phase I studies of CMA was based on dogs. ![Figure][1] Conclusions: The degree of dose escalation from starting dose to MTD was significantly greater for CMA compared to SM drugs. This was also associated with a significantly greater number of dose levels, patients, and time required to complete phase I studies of CMA compared to SM. These findings necessitate the need to identify the most appropriate preclinical animal model to use to evaluate CMA toxicity in phase I studies. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 371. doi:10.1158/1538-7445.AM2011-371 [1]: pending:yes

Abstract 3697: Evaluation of monocyte and granulocyte function with and without ex vivo pegylated liposomal doxorubicin (PLD) exposure in blood of healthy volunteers

Proceedings: AACR 101st Annual Meeting 2010‐‐ Apr 17‐21, 2010; Washington, DC Background: PLD is a nanoparticle approved for treatment of refractory ovarian cancer. The reticuloendothelial system (RES), which includes monocytes (MO), may have a key role in clearance (CL) of nanoparticle sized pegylated liposomes such as PLD, though factors affecting the CL of liposomes are unclear. Previously we reported that the CL of liposomes is associated with age and monocyte counts. This studys objective was to characterize the function of MO and granulocytes with and without ex vivo PLD exposure in the blood of healthy volunteers. Methods: Blood samples were obtained from six (4 males, 2 females) healthy human volunteers, immediately placed on ice and processed. Blood samples were incubated with PLD 10 mcg/mL or 5% dextrose solution (control) for 1 hour (h) at 37°C with 5% CO2. After incubation, PHAGOTEST® and PHAGOBURST® (Orpegen Pharma) tests were performed to evaluate phagocytic activity and respiratory burst activity. PHAGOBURST® tests were performed after fMLP and PMA stimulation. Samples were analyzed using Dako CyAn Flow Cytometer with Summit software. Comparisons were made between samples with and without PLD exposure, gender, and age >60 and <60 years old (yo) based on previously reported trends. Results: The mean + SD age of healthy volunteers was 45.9 + 14.9 yo. The mean fluorescence per cell, grouped by functional test and age, gender, and with or without PLD exposure are summarized in Table [1][1]. View this table: Table 1. Mean Fluorescence Conclusions: Differences in phagocytic and respiratory burst activity in granulocytes and MO of healthy volunteers were observed. There is variability in activity based on the type of assay used. There appears to be both age and gender differences in activity. A 1 h ex vivo exposure to PLD does not seem to significantly alter cell function. Future studies will characterize MO and granulocyte function, PLD uptake, and viability with and without PLD exposure in additional healthy subjects and ovarian and breast cancer patients. 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 3697. [1]: #T1

Abstract 1295: Relationship between pharmacokinetic (PK) sampling schema and reported PK variability of liposomes in patients

Proceedings: AACR 102nd Annual Meeting 2011‐‐ Apr 2‐6, 2011; Orlando, FL Introduction: Liposomal formulations offer advantages over small molecules including increased solubility, selective targeting potential and prolonged drug exposure. Compared with conventional formulations, these agents often have greater PK and pharmacodynamic variability, which is attributed to the role of the mononuclear phagocyte system in the clearance of liposomes. Inter-patient variability in drug exposure, represented by area under the curve (AUC), of encapsulated drug can be 20- to 100-fold. However, some nanoparticle and liposomal agents report lower inter-patient PK variability. Study design and sampling schema may affect the documentation of PK variability, due to the prolonged systemic exposure of encapsulated drug. Thus, we evaluated the reported PK variability of PEGylated CKD-602 (S-CKD602) and non-liposomal CKD-602 (NL-CKD-602) using a short (0-24 h) and long (0-336 h) sampling schema. Methods: S-CKD602 and NL-CKD-602 were administered at doses ranging from 0.5 to 2.1 mg/m2 in phase I studies of patients with advanced solid tumors. Blood samples were obtained from baseline to 336 h for S-CKD602 and from baseline to 24 h for NL-CKD-602. Plasma concentration of total (lactone + hydroxy acid) encapsulated CKD-602 from S-CKD602 and total CKD-602 from NL-CKD-602 were measured by LC-MS/MS. AUC from 0 to 24 h (AUC0-24) and 0 to 336 h (AUC0-336) were calculated. The coefficient of variance % (CV%) in AUC0-24 and AUC0-336 at each dose level were calculated for S-CKD602 and NL-CKD-602. Results: ![Figure][1] Conclusion: The inter-patient variability of exposure of S-CKD602 is 2.5- to 3.4-fold greater than that of NL- CKD-602. Current PK study designs limited to 24 h underestimate the inter-patient variability of exposure of S-CKD602. PK study design of liposomal agents requires an extended PK sampling schema to accurately describe its PK disposition. A limited sampling strategy that may be applied for all nanoparticles is under development to address this issue. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 1295. doi:10.1158/1538-7445.AM2011-1295 [1]: pending:yes

Abstract 373: Allometric scaling of the pharmacokinetics of pegylated liposomal anticancer drugs

Background: Pegylated liposomal formulations contain lipid conjugated to polyethylene glycol. These formulations of anticancer agents have been designed to prolong the drug circulation time, increase tumor delivery, and improve the therapeutic index. The disposition of encapsulated drug is dictated by the liposomal carriers, thus altering the pharmacokinetic (PK) profile of the drug. Allometric scaling is based on a power-log relationship between body weight (W) and drug clearance (CL) among mammals and has been used to compare the PK of small molecule drugs across species. However, it has not been used to compare PK of liposomes or nanoparticle agents. The objectives of this study were to use allometric scaling to: 1) compare the disposition of pegylated liposomal drugs across species and determine the best scaling model, and 2) predict PK parameters of pegylated liposomal drugs in patients. Methods: PK studies of pegylated liposomal CKD-602 (S-CKD602), pegylated liposomal doxorubicin (PLD), and pegylated liposomal cisplatin (SPI-077) were performed at the maximum tolerated dose (MTD) in male and female rats and dogs and in patients with advanced solid tumors as part of phase I studies. Plasma samples were analyzed for sum total (encapsulated + released) drug. The standard allometric equation, CL = a(W)m (a = empirical coefficient; m = allometric exponent) was used to evaluate the relationship between W and CL in each species. The relationship between measures of the mononuclear phagocyte system (MPS) and CL were also evaluated, by substituting the MPS-associated factors for W (liver weight, spleen weight, spleen blood flow, liver blood flow, and monocyte count). Dedrick Plots were used to determine scaling feasibility. Results: Standard allometric scaling using W showed that CL scaled across all agents: [S-CKD602 (R2 = 0.92), PLD (R2 = 0.90), and SPI-077 (R2 = 0.98).] However, the percent (%) difference from scaled predicted and observed PK parameters in humans were still > 30%. All MPS associated factors showed correlation with the CL of all three agents (R2 > 0.90). Based on R2 values, total monocyte count displayed the strongest correlation (R2 = 0.99) with drug clearance across the three species for all three agents. Conclusions: The model that scaled CL the best across all species was the standard allometric method when using potential measures of the MPS, including liver weight, spleen weight, and total monocyte count compared to W. The selection of PK parameters, physiological variables, and pegylated liposomal agent used in this study all contribute to the determination of the optimal scaling method. However, a consistent and predictive allometric model with new methods of allometric scaling and measures of MPS function need to be developed for pegylated liposomal agents. This potential new method could then be used to facilitate the development of future liposomal and nanoparticle agents. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 373. doi:10.1158/1538-7445.AM2011-373