This included samples from six patients who received biweekly dosing

This included samples from six patients who received biweekly dosing. G3, 4%), hypertension (44%; G3, 16%), and nausea (40%, all G1/2). No antiPRS-050 antibodies following multiple administration of the drug were detected. PRS-050 showed dose-proportional pharmacokinetics (PK), with a terminal half-life of approximately 6 days. Free VEGF-A was detectable at baseline in 9/25 patients, becoming rapidly undetectable after PRS-050 infusion for up to 3 weeks. VEGF-A/PRS-050 complex was detectable for up to 3 weeks at all dose levels, including in patients without detectable baseline-free VEGF-A. We also detected a significant reduction in circulating matrix metalloproteinase 2, suggesting this end point could be a pharmacodynamic (PD) marker of the drugs activity. == Conclusions == PRS-050, a novel Anticalin with high affinity for VEGF-A, was well-tolerated when administered at the highest dose tested, 10 mg/kg. Based on target engagement and PK/PD data, the recommended phase II dose is 5 mg/kg every 2 weeks administered as a 120-minute infusion. == Trial Registration == ClinicalTrials.govNCT01141257http://clinicaltrials.gov/ct2/show/NCT01141257 == Introduction == Angiogenesis is a key process required for the growth and metastasis of many solid tumors and is mediated by a range of angiogenic factors, including vascular endothelial growth factor A (VEGF-A) [1]. Activation of the VEGF-A signaling pathway leads to endothelial cell proliferation, migration, and survival, as well as increased vessel permeability and mobilization of endothelial progenitor cells [2,3]. In humans, the VEGF family includes five key members, VEGF-A to VEGF-D and the placental growth factor (PlGF) [4]. The biological functions of VEGFs are mediated by binding to one or more of the related family of protein tyrosine kinase receptors (VEGFR-1, -2, and -3) [5]. Overexpression of VEGF and/or its receptors has been documented in a broad range of solid tumors [2], suggesting a potential therapeutic role for VEGF inhibitors. First proof-of-principle came when anti-VEGF antibodies were shown to inhibit the growth of several tumor cell lines in nude mice, with an associated decrease in the density of tumor blood vessels [6]. Similarly, expression of a dominant-negative version of VEGFR-2 by endothelial cells prevented glioblastoma growth in nude mice KRas G12C inhibitor 2 [7]. Since then, approval of bevacizumab, a humanized monoclonal antibody that neutralizes VEGF-A, as well as several small molecule tyrosine kinase inhibitors, such as sunitinib and sorafenib, which include VEGFR among their targets, have validated the use of VEGF/VEGFR-directed therapy in several oncological indications [8-11]. Other selective VEGFR-targeted agents are currently undergoing clinical evaluation in patients with advanced solid tumors, such as telatinib, vatalanib, and cediranib [12,13]. The use of monoclonal antibodies (such as bevacizumab) as targeted biological agents has been validated during the past decade through their therapeutic and commercial success. Nevertheless, they possess several practical limitations including, but not limited to, manufacturability due, in part, to their large size, posttranslational modifications of multiple polypeptide chains, and often undesired immunological effector functions. Next-generation protein scaffolds, including Anticalins, have accordingly been proposed and engineered for specific target recognition and their potential for superior development properties and therapeutic index [14]. Lipocalins are a family of structurally conserved proteins involved in diverse physiological functions. At least ten different human lipocalins have been identified to date [15], including tear lipocalin (Tlc, Lcn1), for which a range of functions has been suggested, including inactivation of viral DNA and binding of microbial siderophores [16]. Lipocalins with different KRas G12C inhibitor 2 biochemical functions share limited sequence identity, which can be less than 10% [17]. Despite the low amino acid sequence conservation and diverse binding functions of the natural lipocalins, they share a highly conserved single -barrel backbone scaffold which supports four loops of variable lengths, sequences, and conformations at its open end. This lipocalin loop region is somewhat analogous to the hypervariable complementarity-determining regions of antibodies [18,19]. Lipocalins have several biotechnological advantages over antibodies, including smaller size, being composed of a single polypeptide chain, produced in bacteria KRas G12C inhibitor 2 (but also eukaryotic systems Rabbit Polyclonal to UBF1 if required), and possessing a simpler set of four hypervariable loops that can be more easily manipulated at the genetic level [14]. Lipocalins have been rationally engineered into Anticalins using targeted random mutagenesis and phage display selection to form novel binding proteins for specific and limited binding of low molecular excess weight compounds, peptides, as well as protein antigens with potential restorative applications [14,20]. KRas G12C inhibitor 2 Tlc shows broad ligand promiscuity, indicating flexibility of its binding site to accommodate a wide range of clinically relevant focuses on [21]. More recently, we developed an Anticalin against the cell surface tyrosine kinase receptor and transmission transducer MET, further assisting the broad range of applications of the technology [22]. Starting from a naive combinatorial library where residues forming the natural ligand-binding site of Tlc were randomized, followed by affinity maturation, the final Anticalin PRS-050 was selected to bind.