VEGF Trap In Combination With Radiotherapy Improves Tumor Control In U87 Glioblastoma

Purpose To determine the effect of vascular endothelial growth factor VEGF Trap (Regeneron Pharmaceuticals, Tarrytown, NY), a humanized soluble vascular endothelial growth factor (VEGF) receptor protein, and radiation (RT) on tumor growth in U87 glioblastoma xenografts in nude mice. Methods and Materials U87 cell suspensions were implanted subcutaneously into hind limbs of nude mice. VEGF Trap (2.5–25 mg/kg) was administered every 3 days for 3 weeks alone or in combination with a single dose of 10 Gy or fractionated RT (3 x 5 Gy). In addition, three scheduling protocols for VEGF Trap plus fractionated RT were examined. Results Improved tumor control was seen when RT (either single dose or fractionated doses) was combined with the lowest dose of VEGF Trap (2.5 mg/kg). Scheduling did not significantly affect the efficacy of combined therapy. Although high-dose VEGF Trap (10 mg/kg or 25 mg/kg) significantly reduced tumor growth over that of RT alone, there was no additional benefit to combining high-dose VEGF Trap with RT. Conclusions Vascular endothelial growth factor Trap plus radiation is clearly better than radiation alone in a U87 subcutaneous xenograft model. Although high doses of VEGF Trap alone are highly efficacious, it is unclear whether such high doses can be used clinically without incurring normal tissue toxicities. Thus, information on lower doses of VEGF Trap and ionizing radiation is of clinical relevance. Int. J. Radiation Oncol. Biol. Physics, Volume 67, Issue 5, pages 1526-1537, 2007

A synthetic lethal screen reveals enhanced sensitivity to ATR inhibitor treatment in mantle cell lymphoma with ATM loss-of-function

Maintain to maintain genomic integrity are essential for cells to remain viable. Not surprisingly, disruption of key DNA damage response pathway factors, such as ataxia telangiectasia-mutated (ATM)/ataxia telangiectasia and RAD3-related (ATR) results in loss of genomic integrity. Here, a synthetic lethal siRNA-screening approach not only confirmed ATM but identified additional replication checkpoint proteins, when ablated, enhanced ATR inhibitor (ATRi) response in a high-content γ-H2AX assay. Cancers with inactivating ATM mutations exhibit impaired DNA double-stranded break (DSB) repair and rely on compensatory repair pathways for survival. Therefore, impairing ATR activity may selectively sensitize cancer cells to killing. ATR inhibition in an ATM-deficient context results in phosphorylation of DNA-dependent protein kinase catalytic subunits (DNA-PKcs) and leads to induction of γ-H2AX. Using both in vitro and in vivo models, ATR inhibition enhanced efficacy in ATM loss-of-function mantle cell lymphoma (MCL) compared with ATM wildtype cancer cells. In summary, single-agent ATR inhibitors have therapeutic utility in the treatment of cancers, like MCL, in which ATM function has been lost. Implications: These data suggest that single-agent ATR inhibitors have therapeutic utility and that ATR uses a complex and coordinated set of proteins to maintain genomic stability that could be further exploited

Neutralization of Prolactin Receptor Function by Monoclonal Antibody LFA102, A Novel Potential Therapeutic for the Treatment of Breast Cancer

Numerous lines of evidence suggest that the polypeptide hormone prolactin (PRL) may contribute to breast and prostate tumorigenesis through its interactions with the prolactin receptor (PRLR). Here we describe the biological properties of LFA102, a humanized neutralizing monoclonal antibody directed against the extracellular domain of PRLR. This antibody was found to effectively antagonize PRL-induced signaling in breast cancer cells in vitro and in vivo and to block PRL-induced proliferation in numerous cell line models, including examples of autocrine/paracrine PRL activity. A single administration of LFA102 resulted in regression of PRL-dependent Nb2-11 tumor xenografts and significantly prolonged time to progression. Finally, LFA102 treatment significantly inhibited PRLR signaling as well as tumor growth in a carcinogen-induced, estrogen receptor (ER)-positive rat mammary cancer model as a monotherapy and enhanced the efficacy of the aromatase inhibitor letrozole when administered in combination. The biological properties of LFA102, elucidated by the preclinical studies presented here, suggest that this antibody has the potential to be a first in class, effective therapeutic for the treatment of PRL-dependent cancers

Pim2 is required for maintaining multiple myeloma cell growth through modulating TSC2 phosphorylation

Multiple myeloma (MM) is the second most common hematologic malignancy. Despite recent treatment advances, it remains incurable. Here, we report that Pim2 kinase expression is highly elevated in MM cells and demonstrate that it is required for MM cell proliferation. Functional interference of Pim2 activity either by short hairpin RNAs or by a potent and selective small-molecule inhibitor leads to significant inhibition of MM cell proliferation. Pim inhibition results in a significant decrease of mammalian target of rapamycin C1 (mTOR-C1) activity, which is critical for cell proliferation.Weidentify TSC2, a negative regulator of mTOR-C1, as a novel Pim2 substrate and show that Pim2 directly phosphorylates TSC2 on Ser-1798 and relieves the suppression of TSC2 on mTOR-C1. These findings support Pim2 as a promising therapeutic target for MM and define a novel Pim2-TSC2-mTOR-C1 pathway that drives MM proliferation

VEGF Trap induces antiglioma effect at different stages of disease

Pathological angiogenesis is a hallmark of cancer, specifically of glioblastomas, the most malignant and common primary brain tumor. Vascular endothelial growth factor (VEGF) is the key protein in the regulation of the hypervascular phenotype of primary malignant brain tumors. In this study, we tested VEGF Trap, a soluble decoy receptor for VEGF, in an intracranial glioma model. VEGF Trap was administered in short or prolonged schedules to animals bearing human gliomas at different stages of disease. Of importance, VEGF Trap treatment was efficacious in both initial and advanced phases of tumor development by significantly increasing overall survival. Furthermore, this effect was enhanced in animals treated with more prolonged regimens. In addition, we observed the emergence of a VEGF Trap-resistant phenotype characterized by tumor growth and increased invasiveness. Our results suggest that VEGF Trap will be effective in treating both patients with recurrent or progressive resectable glioblastoma and patients that have undergone extensive initial surgery. Finally, our results indicate that the clinical success of VEGF Trap may depend on a prolonged treatment in combined therapy aiming to simultaneously inhibit angiogenesis and tumor invasion

Structure Guided Optimization, In Vitro Activity and In Vivo Activity of Pan-PIM Kinase Inhibitors

Proviral Insertion of Moloney virus (PIM) 1, 2 and 3 kinases are serine/threonine kinases that normally function in survival and proliferation of hematopoietic cells. High expression of PIM1, 2 & 3 is frequently observed in many human malignancies, including multiple myeloma, non-Hodgkins lymphoma, and myeloid leukemias. As such, there is interest in determining whether selective PIM inhibition can improve outcomes of these human cancers. Herein, we describe our efforts towards this goal. The structure guided optimization of a singleton high throughput screening hit in which the potency against all three PIM isoforms was increased >10,000 fold to yield compounds with pan PIM Ki’s < 10 picoM is described. During the optimization, a focus was initially placed on increasing potency while simultaneously reducing the liphophilicity and then, from a low logP space, a hydrophobic interaction was optimized. From these efforts, compound 5d was identified with suitable PK properties and kinase selectivity to establish a PK/PD-efficacy relationship in multiple myeloma and acute myeloid leukemia Pim dependent tumor models

Preclinical Antitumor Activity of a Novel Anti–c-KIT Antibody–Drug Conjugate against Mutant and Wild-type c-KIT–Positive Solid Tumors

Purpose: c-KIT overexpression is well recognized in cancers such as gastrointestinal stromal tumors (GIST), small cell lung cancer (SCLC), melanoma, non–small cell lung cancer (NSCLC), and acute myelogenous leukemia (AML). Treatment with the small-molecule inhibitors imatinib, sunitinib, and regorafenib resulted in resistance (c-KIT mutant tumors) or limited activity (c-KIT wild-type tumors). We selected an anti–c-KIT ADC approach to evaluate the anticancer activity in multiple disease models. Experimental Design: A humanized anti–c-KIT antibody LMJ729 was conjugated to the microtubule destabilizing maytansinoid, DM1, via a noncleavable linker (SMCC). The activity of the resulting ADC, LOP628, was evaluated in vitro against GIST, SCLC, and AML models and in vivo against GIST and SCLC models. Results: LOP628 exhibited potent antiproliferative activity on c-KIT–positive cell lines, whereas LMJ729 displayed little to no effect. At exposures predicted to be clinically achievable, LOP628 demonstrated single administration regressions or stasis in GIST and SCLC xenograft models in mice. LOP628 also displayed superior efficacy in an imatinib-resistant GIST model. Further, LOP628 was well tolerated in monkeys with an adequate therapeutic index several fold above efficacious exposures. Safety findings were consistent with the pharmacodynamic effect of neutropenia due to c-KIT–directed targeting. Additional toxicities were considered off-target and were consistent with DM1, such as effects in the liver and hematopoietic/ lymphatic system. Conclusions: The preclinical findings suggest that the c-KIT–directed ADC may be a promising therapeutic for the treatment of mutant and wild-type c-KIT–positive cancers and supported the clinical evaluation of LOP628 in GIST, AML, and SCLC patients