William C. Zamboni

Challenges and Key Considerations of the Enhanced Permeability and Retention Effect for Nanomedicine Drug Delivery in Oncology

Enhanced permeability of the tumor vasculature allows macromolecules to enter the tumor interstitial space, whereas the suppressed lymphatic filtration allows them to stay there. This phenomenon, enhanced permeability and retention (EPR), has been the basis of nanotechnology platforms to deliver drugs to tumors. However, progress in developing effective drugs using this approach has been hampered by heterogeneity of EPR effect in different tumors and limited experimental data from patients on effectiveness of this mechanism as related to enhanced drug accumulation. This report summarizes the workshop discussions on key issues of the EPR effect and major gaps that need to be addressed to effectively advance nanoparticle-based drug delivery.

Using mechanobiological mimicry of red blood cells to extend circulation times of hydrogel microparticles

It has long been hypothesized that elastic modulus governs the biodistribution and circulation times of particles and cells in blood; however, this notion has never been rigorously tested. We synthesized hydrogel microparticles with tunable elasticity in the physiological range, which resemble red blood cells in size and shape, and tested their behavior in vivo. Decreasing the modulus of these particles altered their biodistribution properties, allowing them to bypass several organs, such as the lung, that entrapped their more rigid counterparts, resulting in increasingly longer circulation times well past those of conventional microparticles. An 8-fold decrease in hydrogel modulus correlated to a greater than 30-fold increase in the elimination phase half-life for these particles. These results demonstrate a critical design parameter for hydrogel microparticles.

Liposomal, Nanoparticle, and Conjugated Formulations of Anticancer Agents

Major advances in the use of liposomes, conjugates, nanoparticles, and microspheres as vehicles delivering pharmacologic agents and enzymes to sites of disease have occurred in the past 10 years ([1][1]–[3][2]). Pegylated-STEALTH liposomal doxorubicin (Doxil, Caelyx) was the first liposomal

Multiple Roles of Cyclin-Dependent Kinase 4/6 Inhibitors in Cancer Therapy

BACKGROUND Cyclin-dependent kinases (CDKs) regulate cell proliferation and coordinate the cell cycle checkpoint response to DNA damage. Although inhibitors with varying selectivity to specific CDK family members have been developed, selective CDK4/6 inhibitors have emerged as the most attractive antineoplastic agents because of the importance of CDK4/6 activity in regulating cell proliferation and the toxic effects associated with inhibition of other CDKs (eg, CDK1 and CDK2). METHODS FVB/N wild-type mice (n = 13) were used to evaluate carboplatin-induced myelosuppression in bone marrow by complete blood cell counts after treatment with the CDK4/6 inhibitor PD0332991. Genetically engineered murine models of retinoblastoma (Rb)-competent (MMTV-c-neu) and Rb-incompetent (C3-TAg) breast cancer (n = 16 MMTV-c-neu mice in the carboplatin plus vehicle control group, n = 17 MMTV-c-neu mice in the carboplatin plus PD0332991 group, n = 17 C3-TAg mice in the carboplatin plus vehicle control group, and n = 14 C3-TAg mice in the carboplatin plus PD0332991 group) were used to investigate the antitumor activity of PD0332991 alone or in combination with chemotherapy. All statistical tests were two-sided. RESULTS Coadministration of PD0332991 with carboplatin compared with carboplatin alone in FVB/N wild-type mice increased hematocrit (51.2% vs 33.5%, difference = 17.7%, 95% confidence interval [CI] = -26.7% to -8.6%, P < .001), platelet counts (1321 vs 758.5 thousand cells per μL, difference = 562.5 thousand cells per μL, 95% CI = -902.8 to -222.6, P = .002), myeloid cells (granulocytes and monocytes; 3.1 vs 1.6 thousand cells per μL, difference = 1.5 thousand cells per μL, 95% CI = -2.23 to -0.67, P < .001), and lymphocytes (7.9 vs 5.4 thousand cells per μL, difference = 2.5 thousand cells per μL, 95% CI = -4.75 to -0.18, P = .02). Daily administration of PD0332991 exhibited antitumor activity in MMTV-c-neu mice as a single agent. However, the combination of carboplatin plus PD0332991 decreased antitumor activity compared with carboplatin alone in Rb-competent mice (mean percent change in tumor volume at day 21 = -52.6% vs 3.7% for carboplatin and carboplatin plus PD0332991, respectively, difference = 56.3%, 95% CI = -109.0% to -3.6%, P = .04). In contrast, Rb-deficient tumors in C3-Tag mice were resistant to PD0332991, and coadministration of PD0332991 plus carboplatin had no effect on in vivo tumor growth (mean percent change in tumor volume at day 21 = 118.8% and 109.1% for carboplatin and carboplatin plus PD0332991, respectively, difference = 9.7%, 95% CI = -183.5% to 202.9%, P = .92). Finally, in tumor-bearing mice, coadministration of PD0332991 with carboplatin provided statistically significant protection of platelets (P = .04). CONCLUSION We believe that the present data support a possible role for CDK4/6 inhibitors in a majority of patients with advanced cancer: to either inhibit tumor growth in CDK4/6-dependent tumors or ameliorate the dose-limiting toxicities of chemotherapy in CDK4/6-indepdendent tumors. Our data also suggest CDK4/6 inhibitors should not be combined with DNA-damaging therapies, such as carboplatin, to treat tumors that require CDK4/6 activity for proliferation.

Best Practices in Cancer Nanotechnology: Perspective from NCI Nanotechnology Alliance

Historically, treatment of patients with cancer using chemotherapeutic agents has been associated with debilitating and systemic toxicities, poor bioavailability, and unfavorable pharmacokinetics. Nanotechnology-based drug delivery systems, on the other hand, can specifically target cancer cells while avoiding their healthy neighbors, avoid rapid clearance from the body, and be administered without toxic solvents. They hold immense potential in addressing all of these issues, which has hampered further development of chemotherapeutics. Furthermore, such drug delivery systems will lead to cancer therapeutic modalities that are not only less toxic to the patient but also significantly more efficacious. In addition to established therapeutic modes of action, nanomaterials are opening up entirely new modalities of cancer therapy, such as photodynamic and hyperthermia treatments. Furthermore, nanoparticle carriers are also capable of addressing several drug delivery problems that could not be effectively solved in the past and include overcoming formulation issues, multidrug-resistance phenomenon, and penetrating cellular barriers that may limit device accessibility to intended targets, such as the blood–brain barrier. The challenges in optimizing design of nanoparticles tailored to specific tumor indications still remain; however, it is clear that nanoscale devices carry a significant promise toward new ways of diagnosing and treating cancer. This review focuses on future prospects of using nanotechnology in cancer applications and discusses practices and methodologies used in the development and translation of nanotechnology-based therapeutics. Clin Cancer Res; 18(12); 3229–41. ©2012 AACR.

Concept and Clinical Evaluation of Carrier-Mediated Anticancer Agents

Major advances in the use of carrier vehicles delivering pharmacologic agents and enzymes to sites of disease have occurred over the past 10 years. This review focuses on the concepts and clinical evaluation of carrier-mediated anticancer agents that are administered i.v. or orally. The primary types of carrier-mediated anticancer agents are nanoparticles, nanosomes, which are nanoparticle-sized liposomes, and conjugated agents. Nanosomes are further subdivided into stabilized and nonstabilized or conventional nanosomes. Nanospheres and dendrimers are subclasses of nanoparticles. Conjugated agents consist of polymer-linked and pegylated agents. The theoretical advantages of carrier-mediated drugs are greater solubility, longer duration of exposure, selective delivery of entrapped drug to the site of action, superior therapeutic index, and the potential to overcome resistance associated with the regular anticancer agent. The pharmacokinetic disposition of carrier-mediated agents depends on the physiochemical characteristics of the carrier, such as size, surface charge, membrane lipid packing, steric stabilization, dose, and route of administration. The primary sites of accumulation of carrier-mediated agents are the tumor, liver, and spleen, compared with noncarrier formulations. The drug that remains encapsulated in or linked to the carrier (e.g., the nanosome or nanoparticle) is an inactive prodrug, and thus the drug must be released from the carrier to be active. The factors affecting the pharmacokinetic and pharmacodynamic variability of these agents remain unclear, but most likely include the reticuloendothelial system, which has also been called the mononuclear phagocyte system. Future studies need to evaluate the mechanism of clearance of carrier-mediated agents and identify the factors associated with the pharmacokinetic and pharmacodynamic variability of carrier agents in patients and specifically in tumors.

Phase I trial and pharmacokinetic (PK) and pharmacodynamics (PD) study of topotecan using a five-day course in children with refractory solid tumors: A Pediatric Oncology Group study

Purpose A phase I trial was conducted in children with refractory solid tumors to determine the maximum tolerated dose (MTD), dose-limiting toxicity (DLT), pharmacokinetics, and pharmacodynamics for topotecan administered by a 30-min infusion for 5 consecutive days. Patients and Methods Forty children with a variety of recurrent solid tumors, including nine patients with neuroblastoma and 10 with brain tumors, were given topotecan as a 30-min infusion for 5 consecutive days, beginning with a dose of 1.4 mg/m2/day. The dose was escalated in 20% increments after establishing that DLT was not present at the prior dose. Drug toxicity was graded using standard criteria. Dose-limiting toxicity was defined as grade 3 or 4 nonhematopoietic toxicity or grade 4 hematopoietic toxicity lasting >7 days. Pharmacokinetic studies were performed during the first infusion course. Results The DLT was hematopoietic and involved both platelets and neutrophils. Grade 4 hematopoietic toxicity of brief duration was seen at all dose levels. Over half of the patients received red blood cell transfusion support, and 19/40 received platelet transfusions. Hospital admissions for fever and neutropenia or for documented infections occurred in 32 of 169 courses of therapy. Gastrointestinal symptoms with nausea and vomiting or diarrhea were mild to moderate in 12 of the 40 patients. Antitumor responses were seen in three patients with neuroblastoma. An additional four patients (one with neuroblastoma. two with anaplastic astrocytomas, one with Ewing) had stable disease with continued therapy for >6 months. Using a limited sampling model, pharmacokinetic studies were performed in 36 of the 40 patients. Topotecan lactone and total clearance were similar to those reported in other pediatric populations receiving topotecan by continuous infusion. A pharmacodynamic relation between systemic exposure to topotecan lactone and myelosuppression was observed. Conclusions In heavily pretreated children, the MTD for topotecan given by intermittent 30-min infusion for 5 days is 1.4 mg/m2 without GCSF and 2.0 mg/m2/day with GCSK. The dose-limiting toxicity is hematopoietic. Data from this study provide the basis for further studies of topotecan in children with cancer.

Sensitive liquid chromatography–mass spectrometry assay for quantitation of docetaxel and paclitaxel in human plasma

We have developed a high-performance liquid chromatography-electrospray ionization mass spectrometry (LC-MS) method for quantifying docetaxel and paclitaxel in human plasma. The assay fulfills the need for defining the lower plasma concentrations of these antineoplastic agents that result from a number of changes in how these agents are used clinically. The assay uses paclitaxel as the internal standard for docetaxel, and vice versa; solid-phase extraction; a Phenomenex Hypersil ODS (5 micrometer, 100x2 mm) reversed-phase analytical column; an isocratic mobile phase of 0.1% formic acid in methanol-water (70:30, v/v); and mass spectrometric detection using electrospray positive mode electron ionization. The assay has a lower limit of quantitation (LLOQ) of 0.3 nM and is linear between 0.3 nM and 1 microM for docetaxel. For paclitaxel, the LLOQ was 1 nM, and the assay is linear between 1 nM and 1 microM. We demonstrated the suitability of this assay for docetaxel by using it to quantify the docetaxel concentrations in plasma of a patient given 40 mg/m(2) of docetaxel and comparing those results to results produced when the same samples were assayed with an HPLC assay using absorbance detection. In a similar manner, the suitability of the assay for paclitaxel was demonstrated by using it to quantify the concentrations of paclitaxel in the plasma of a patient given 15 mg/m(2) of paclitaxel and comparing those results to results produced when the same samples were assayed with an HPLC assay using absorbance detection. The LC-MS assay, which proved superior because of its greater sensitivity and relatively short (7 min) run time, should be an important tool for future pharmacokinetic analyses of docetaxel and paclitaxel.

Combined PI3K/mTOR and MEK Inhibition Provides Broad Antitumor Activity in Faithful Murine Cancer Models

Purpose: Anticancer drug development is inefficient, but genetically engineered murine models (GEMM) and orthotopic, syngeneic transplants (OST) of cancer may offer advantages to in vitro and xenograft systems. Experimental Design: We assessed the activity of 16 treatment regimens in a RAS-driven, Ink4a/Arf-deficient melanoma GEMM. In addition, we tested a subset of treatment regimens in three breast cancer models representing distinct breast cancer subtypes: claudin-low (T11 OST), basal-like (C3-TAg GEMM), and luminal B (MMTV-Neu GEMM). Results: Like human RAS-mutant melanoma, the melanoma GEMM was refractory to chemotherapy and single-agent small molecule therapies. Combined treatment with AZD6244 [mitogen-activated protein–extracellular signal-regulated kinase kinase (MEK) inhibitor] and BEZ235 [dual phosphoinositide-3 kinase (PI3K)/mammalian target of rapamycin (mTOR) inhibitor] was the only treatment regimen to exhibit significant antitumor activity, showed by marked tumor regression and improved survival. Given the surprising activity of the “AZD/BEZ” combination in the melanoma GEMM, we next tested this regimen in the “claudin-low” breast cancer model that shares gene expression features with melanoma. The AZD/BEZ regimen also exhibited significant activity in this model, leading us to testing in even more diverse GEMMs of basal-like and luminal breast cancer. The AZD/BEZ combination was highly active in these distinct breast cancer models, showing equal or greater efficacy compared with any other regimen tested in studies of over 700 tumor-bearing mice. This regimen even exhibited activity in lapatinib-resistant HER2+ tumors. Conclusion: These results show the use of credentialed murine models for large-scale efficacy testing of diverse anticancer regimens and predict that combinations of PI3K/mTOR and MEK inhibitors will show antitumor activity in a wide range of human malignancies. Clin Cancer Res; 18(19); 5290–303. ©2012 AACR.

Low overexpression of HER-2/PPPNeu in advanced colorectal cancer limits the usefulness of trastuzumab (herceptin®) and irinotecan as therapy. A phase II trial

Background: To determine the response rate of trastuzumab and irinotecan in HER-2/neu overexpressing advanced colorectal cancer (CRC), determine the frequency of HER-2/neu expression in CRC, and evaluate the pharmacokinetics of trastuzumab in a phase II study. Patients and Methods: Patients were screened for HER-2/neu by immunohistochemistry (DAKO HercepTest™). Prior chemotherapy was limited to one regimen. Trastuzumab was administered weekly (loading dose of 4 mg/kg IV and 2 mg/kg thereafter). Irinotecan 125 mg/m2, IV was administered weekly for 4 weeks with a 2-week rest period. Results: HER-2/neu overexpression was detected in 11 of 138 (8.0%) of screened tumors (2 + in 5 and 3 + in 6 patients). Nine patients were entered in the study; 6 had received prior chemotherapy. Partial responses were seen in 5 of 7 evaluable patients. Grade 3–4 toxicities in 31 cycles of therapy included diarrhea (19%), nausea (10%), and vomiting (6%). Leukopenia occurred in 6%, and congestive heart failure and acute renal failure (secondary to diarrhea and dehydration) were seen in 3% of cycles. The study was prematurely closed due to low accrual. Conclusions: The low overexpression rate of HER-2/neu (8.0%) in advanced CRC limits the potential for further investigation of regimens involving trastuzumab, despite evidence suggestive of activity. Irinotecan did not alter the pharmacokinetic disposition of trastuzumab.