Andrew Brenner

Safety, Pharmacokinetics, and Activity of GRN1005, a Novel Conjugate of Angiopep-2, a Peptide Facilitating Brain Penetration, and Paclitaxel, in Patients with Advanced Solid Tumors

GRN1005 is a novel peptide–drug conjugate composed of paclitaxel covalently linked to a peptide, angiopep-2, that targets the low-density lipoprotein receptor-related protein 1. This first-in-human study evaluated the safety, tolerability, pharmacokinetics, and efficacy of GRN1005 in patients with advanced solid tumors. Patients in sequential cohorts (one patient per cohort until grade 2 toxicity, then 3 + 3 design) received intravenous GRN1005 at escalating doses between 30 and 700 mg/m2 once in every 21 days. In the maximum tolerated dose (MTD) expansion group, patients were required to have brain metastases. Fifty-six patients received GRN1005, including 41 with brain metastases (median number of prior therapies = 4). MTD was 650 mg/m2; the main dose-limiting toxicity was myelosuppression. Sixteen of 20 patients dosed at the MTD had brain metastases. Pharmacokinetics was dose linear and the mean terminal-phase elimination half-life was 3.6 hours. No evidence of accumulation was observed after repeat dosing. No anti-GRN1005 antibodies were detected. Five of the 20 patients (25%) dosed at 650 mg/m2 (MTD), three of whom had previous taxane therapy, achieved an overall partial response (breast, n = 2; non–small cell lung cancer, n = 2; and ovarian cancer, n = 1); responses in all five patients were also accompanied by shrinkage of brain lesions (−17% to −50%). In addition, six patients (11%; doses 30–700 mg/m2) experienced stable disease that lasted 4 months or more. GRN1005 was well tolerated and showed activity in heavily pretreated patients with advanced solid tumors, including those who had brain metastases and/or failed prior taxane therapy. Mol Cancer Ther; 11(2); 308–16. ©2011 AACR.

Common toxicities of mammalian target of rapamycin inhibitors.

The toxicities of newer targeted therapies are different from those seen with the traditional chemotherapy. Mammalian target of rapamycin (mTOR) inhibitors are evolving into an important class of drugs in oncology, and this class of drugs presents with a variety of different toxicities. Although similar to the toxicities seen in transplantation, these rapamycin analogs have unique side effects when compared to traditional chemotherapy agents. While most of the toxicities are mild, few can be severe and require routine monitoring. Mucositis and rash are the most common side effects. The metabolic toxicities, hyperglycemia, hyperlipidemia, and hypophosphatemia are different from the side effects traditionally seen with chemotherapy. This review will focus on the common toxicities seen with the mTOR inhibitors.

Phase I Study of GRN1005 in Recurrent Malignant Glioma

Purpose: GRN1005 is a peptide–drug conjugate with the ability to penetrate the blood–brain barrier (BBB) and tumor cells by targeting the low-density lipoprotein receptor–related protein-1. We conducted a first-in-human phase I trial of GRN1005 in patients with recurrent glioma. Methods: Patients received GRN1005 by intravenous infusion every 3 weeks. Doses were escalated using a modified Fibonacci scheme. Study objectives included safety, tolerability, identification of the maximum tolerated dose (MTD), pharmacokinetics, and preliminary evidence of efficacy. Tumor extracted from patients undergoing surgery following administration of GRN1005 was analyzed to determine whether therapeutic concentrations of GRN1005 were achieved. Results: Sixty-three patients received GRN1005 at doses of 30 to 700 mg/m2 every 3 weeks. Therapy was well tolerated with neutropenia, leucopenia, and fatigue as the most frequent drug-associated grade 3/4 or higher toxicities. The MTD was 650 mg/m2 every 3 weeks. Dose-limiting toxicities were grade 3 mucositis and grade 4 neutropenia. There was no evidence of central nervous system toxicity or antibody production. Pharmacokinetic analysis showed that exposure to GRN1005 was dose proportional. We observed one complete and two partial responses. Eight of 27 patients dosed ≥420 mg/m2 had stable disease, which lasted a median of 51 days. Therapeutic concentrations of GRN1005 and free paclitaxel were shown in tumor tissue of surgical patients dosed with ≥200 mg/m2. Conclusion: GRN1005 delivers paclitaxel across the BBB and achieves therapeutic concentrations in tumor tissue. It has similar toxicity to paclitaxel and appears to have activity in recurrent glioma. The recommended phase II dose is 650 mg/m2 every 3 weeks. Clin Cancer Res; 19(6); 1567–76. ©2013 AACR.

Therapeutic significance of estrogen receptor β agonists in gliomas.

Gliomas are the most common and devastating central nervous system neoplasms. A gender bias exists in their development: females are at lower risk than males, implicating estrogen-mediated protective effects. Estrogen functions are mediated by two estrogen receptor (ER) subtypes: ERα, which functions as tumor promoter, and ERβ, which functions as tumor suppressor. We examined the potential use of ERβ agonists as a novel therapeutic to curb the growth of gliomas. Western analysis of six glioma model cells showed detectable expression of ERβ with little or no ERα. Treatment of glioma cells with ERβ agonists resulted in significant decrease in proliferation. Immunohistochemical analysis of tumor tissues revealed that ERβ expression is downregulated in high-grade gliomas. We found that ERβ agonists promote both expression and tumor-suppressive functions of ERβ in glioma cells. Liquiritigenin, a plant-derived ERβ agonist significantly reduced in vivo tumor growth in a xenograft model. Compared with control mice, animals treated with liquiritigenin had greater than 50% reduction in tumor volume and size. Immunohistochemical analysis of tumors revealed a significant increase in the nuclear ERβ expression with a concomitant decrease in cell proliferation in the liquiritigenin-treated group. Our results suggest that ERβ signaling has a tumor-suppressive function in gliomas. Because ERβ agonists are currently in clinical trials and are well tolerated with fewer side effects, identification of an ERβ agonist as a therapeutic agent can be readily extended to clinical use with current chemotherapies, providing an additional tool for enhancing survival in glioma patients. Mol Cancer Ther; 11(5); 1174–82. ©2012 AACR.

NSAID Use Reduces Breast Cancer Recurrence in Overweight and Obese Women: Role of Prostaglandin–Aromatase Interactions

Obesity is associated with a worse breast cancer prognosis and elevated levels of inflammation, including greater cyclooxygenase-2 (COX-2) expression and activity in adipose-infiltrating macrophages. The product of this enzyme, the proinflammatory eicosanoid prostaglandin E2 (PGE2), stimulates adipose tissue aromatase expression and subsequent estrogen production, which could promote breast cancer progression. This study demonstrates that daily use of a nonsteroidal anti-inflammatory drug (NSAID), which inhibits COX-2 activity, is associated with reduced estrogen receptor α (ERα)-positive breast cancer recurrence in obese and overweight women. Retrospective review of data from ERα-positive patients with an average body mass index of >30 revealed that NSAID users had a 52% lower recurrence rate and a 28-month delay in time to recurrence. To examine the mechanisms that may be mediating this effect, we conducted in vitro studies that utilized sera from obese and normal-weight patients with breast cancer. Exposure to sera from obese patients stimulated greater macrophage COX-2 expression and PGE2 production. This was correlated with enhanced preadipocyte aromatase expression following incubation in conditioned media (CM) collected from the obese-patient, sera-exposed macrophages, an effect neutralized by COX-2 inhibition with celecoxib. In addition, CM from macrophage/preadipocyte cocultures exposed to sera from obese patients stimulated greater breast cancer cell ERα activity, proliferation, and migration compared with sera from normal-weight patients, and these differences were eliminated or reduced by the addition of an aromatase inhibitor during CM generation. Prospective studies designed to examine the clinical benefit of NSAID use in obese patients with breast cancer are warranted.

The enhancing effects of obesity on mammary tumor growth and Akt/mTOR pathway activation persist after weight loss and are reversed by RAD001

The prevalence of obesity, an established risk and progression factor for postmenopausal breast cancer, remains high in US women. Activation of Akt/mammalian target of rapamycin (mTOR) signaling plays a key role in the obesity–breast cancer link. However, the impact of weight normalization in obese postmenopausal women on breast tumorigenesis and/or Akt/mTOR activation is poorly characterized. To model this, ovariectomized female C57BL/6 mice were fed a control diet (n = 20), a calorie restriction (CR) regimen (n = 20), or a diet‐induced obesity (DIO) diet (n = 30). At week 17, DIO mice were switched to control diet, resulting in formerly obese (FOb) mice with weights identical to the controls by week 20. MMTV‐Wnt‐1 mammary tumor cells were injected at 20 wk into each mouse. Two weeks post‐injection, vehicle or the mTOR inhibitor RAD001 at 10 or 15 mg/kg body weight (n = 10/diet group) was administered by gavage twice/week until termination. Relative to controls, CR mice had decreased (and DIO mice had increased) serum insulin‐like growth factor‐1 (IGF‐1) and phosphorylation of Akt/mTOR pathway components. RAD001 decreased tumor growth in the CR, control, and FOb mice. Wnt‐1 tumor cells treated in vitro with serum from mice from each group established that diet‐dependent circulating factors contribute to tumor growth and invasiveness. These findings suggest weight normalization in obese mice does not immediately reverse tumor progression or Akt/mTOR activation. Treatment with RAD001 blocked mammary tumor development and mTOR activation observed in the FOb mice, suggesting combination of lifestyle and pharmacologic strategies may be effective for breaking the obesity–breast cancer link.

The oncogenic RNA-binding protein Musashi1 is regulated by tumor suppressor miRNAs

Musashi1 (Msi1) is an evolutionarily conserved RNA-binding protein that has been implicated in processes like stem cell fate, nervous system development, and tumorigenesis via its activities as a specific regulator of translation. While Msi1 is barely detected in normal adult tissue, it has been observed to be highly expressed in numerous tumor types (e.g. breast, colon, medulloblastoma, glioblastoma, and et cetera). Unfortunately, the molecular cues that are responsible for Msi1 upregulation in cancer cells are largely unknown. Tumor suppressor microRNAs (miRNAs) are known for targeting genes with oncogenic properties like Msi1 and for being either downregulated or deleted in tumor tissue. We observed that Msi1 long 3’UTR region is potentially targeted by several tumor suppressor miRNAs (miR-34a, -101, -128, -137, and -138). Western blotting of endogenous Msi1 protein as well as luciferase assays confirmed Msi1 regulation by these tumor suppressor miRNAs. Furthermore, we observed when examining different cellular states that these miRNAs and Msi1 have opposite expression profiles. Cell proliferation inhibition induced by the tumor suppressor miRNAs was partially rescued by Msi1 transgenic expression. We conclude that tumor suppressor miRNAs are direct and influential regulators of Msi1, affecting its expression pattern during tumorigenesis of malignant nervous system tumors.

Rhenium-186 liposomes as convection-enhanced nanoparticle brachytherapy for treatment of glioblastoma

Although external beam radiation is an essential component to the current standard treatment of primary brain tumors, its application is limited by toxicity at doses more than 80 Gy. Recent studies have suggested that brachytherapy with liposomally encapsulated radionuclides may be of benefit, and we have reported methods to markedly increase the specific activity of rhenium-186 ((186)Re)-liposomes. To better characterize the potential delivery, toxicity, and efficacy of the highly specific activity of (186)Re-liposomes, we evaluated their intracranial application by convection-enhanced delivery in an orthotopic U87 glioma rat model. After establishing an optimal volume of 25 µL, we observed focal activity confined to the site of injection over a 96-hour period. Doses of up to 1850 Gy were administered without overt clinical or microscopic evidence of toxicity. Animals treated with (186)Re-liposomes had a median survival of 126 days (95% confidence interval [CI], 78.4-173 days), compared with 49 days (95% CI, 44-53 days) for controls. Log-rank analysis between these 2 groups was highly significant (P = .0013) and was even higher when 100 Gy was used as a cutoff (P < .0001). Noninvasive luciferase imaging as a surrogate for tumor volume showed a statistically significant separation in bioluminescence by 11 days after 100 Gy or less treatment between the experimental group and the control animals (χ(2)[1, N= 19] = 4.8; P = .029). MRI also supported this difference in tumor size. Duplication of tumor volume differences and survival benefit was possible in a more invasive U251 orthotopic model, with clear separation in bioluminescence at 6 days after treatment (χ(2)[1, N= 9] = 4.7; P = .029); median survival in treated animals was not reached at 120 days because lack of mortality, and log-rank analysis of survival was highly significant (P = .0057). Analysis of tumors by histology revealed minimal areas of necrosis and gliosis. These results support the potential efficacy of the highly specific activity of brachytherapy by (186)Re-liposomes convection-enhanced delivery in glioma.

Image-guided interventional therapy for cancer with radiotherapeutic nanoparticles

One of the major limitations of current cancer therapy is the inability to deliver tumoricidal agents throughout the entire tumor mass using traditional intravenous administration. Nanoparticles carrying beta-emitting therapeutic radionuclides that are delivered using advanced image-guidance have significant potential to improve solid tumor therapy. The use of image-guidance in combination with nanoparticle carriers can improve the delivery of localized radiation to tumors. Nanoparticles labeled with certain beta-emitting radionuclides are intrinsically theranostic agents that can provide information regarding distribution and regional dosimetry within the tumor and the body. Image-guided thermal therapy results in increased uptake of intravenous nanoparticles within tumors, improving therapy. In addition, nanoparticles are ideal carriers for direct intratumoral infusion of beta-emitting radionuclides by convection enhanced delivery, permitting the delivery of localized therapeutic radiation without the requirement of the radionuclide exiting from the nanoparticle. With this approach, very high doses of radiation can be delivered to solid tumors while sparing normal organs. Recent technological developments in image-guidance, convection enhanced delivery and newly developed nanoparticles carrying beta-emitting radionuclides will be reviewed. Examples will be shown describing how this new approach has promise for the treatment of brain, head and neck, and other types of solid tumors.

A prospective randomised study of a rotary powered device (OnControl) for bone marrow aspiration and biopsy

Introduction Bone marrow aspiration and biopsy is an invasive procedure associated with morbidity and mortality risk. We compared a powered bone marrow aspiration and biopsy device to the traditional method by relatively assessing pain scores, procedure times, biopsy capture rates, quality of material retrieved, and safety and operator satisfaction. Methods Two large academic medical centres participated in this trial. Patients were randomised to have procedures carried out using the powered system or the manual technique. A visual analogue scale pain score was recorded immediately following skin puncture and once again at the end of the procedure for each patient. Procedure time was measured from skin puncture to core specimen acquisition. Pathologic assessment of 30 randomised samples was carried out. Operator satisfaction with devices was measured on a scale of 0–10, with 10 as the highest rating. Results Five operators from two sites enrolled 50 patients (powered, n=25; manual, n=25). Groups were evenly matched, with no significant differences in the means for age, weight and height. The powered system was superior to the manual system with respect to patient perceived pain from needle insertion (2.6±2.0 vs 4.1±2.5, p=0.022) and procedural time (100.0±72.8 s vs 224.1±79.0 s, p<0.001). Overall pain scores at the end of both procedures were comparable (3.2±2.2 vs 3.8±3.0, p=0.438). No complications were observed in either arm of the study. Blinded pathologic analysis of the specimens retrieved revealed that cores obtained using the powered system were longer and wider than those obtained using the manual technique (25.4±12.3 mm2 vs 11.9±5.6 mm2, p=0.001). For marrow aspiration, no difference was seen between groups for clot/particle spicules or smear spicules. Operator assessment favoured the use of the powered device. Conclusions Results of this trial suggest that the use of a powered bone marrow biopsy device significantly reduces needle insertion pain and procedural time when compared to a manual technique. The superior size and overall quality of core specimens retrieved by the powered device provides more material for pathologic evaluation, thereby increasing diagnostic yield and reducing the need for repeat procedures.