Bone cancer pain can be difficult to control, as it appears to be driven simultaneously by inflammatory, neuropathic and tumorigenic mechanisms. As nerve growth factor (NGF) has been shown to modulate inflammatory and neuropathic pain states, we focused on a novel NGF sequestering antibody and demonstrated that two administrations of this therapy in a mouse model of bone cancer pain produces a profound reduction in both ongoing and movement-evoked bone cancer pain-related behaviors that was greater than that achieved with acute administration of 10 or 30 mg/kg of morphine. This therapy also reduced several neurochemical changes associated with peripheral and central sensitization in the dorsal root ganglion and spinal cord, whereas the therapy did not influence disease progression or markers of sensory or sympathetic innervation in the skin or bone. Mechanistically, the great majority of sensory fibers that innervate the bone are CGRP/TrkA expressing fibers, and if the sensitization and activation of these fibers is blocked by anti-NGF therapy there would not be another population of nociceptors, such as the non-peptidergic IB4/RET-IR nerve fibers, to take their place in signaling nociceptive events.
Background: An antagonistic anti-PCSK9 antibody exhibits target-mediated clearance, resulting in a dose-dependent PK. Results: Engineering of an antibody with pH-sensitive binding to PCSK9 decreases target-mediated clearance, resulting in increased PK and efficacy in vivo. Conclusion: pH-sensitive anti-PCSK9 antibodies are excellent candidates for therapeutic development. Significance: pH-sensitive antibodies may enable less frequent or lower dosing of antibodies hampered by target-mediated clearance and high antigen load.
Prostate cancer is unique in that bone is often the only clinically detectable site of metastasis. Prostate tumors that have metastasized to bone frequently induce bone pain which can be difficult to fully control as it seems to be driven simultaneously by inflammatory, neuropathic, and tumorigenic mechanisms. As nerve growth factor (NGF) has been shown to modulate inflammatory and some neuropathic pain states in animal models, an NGF-sequestering antibody was administered in a prostate model of bone cancer where significant bone formation and bone destruction occur simultaneously in the mouse femur. Administration of a blocking antibody to NGF produced a significant reduction in both early and late stage bone cancer pain-related behaviors that was greater than or equivalent to that achieved with acute administration of 10 or 30 mg/kg of morphine sulfate. In contrast, this therapy did not influence tumor-induced bone remodeling, osteoblast proliferation, osteoclastogenesis, tumor growth, or markers of sensory or sympathetic innervation in the skin or bone. One rather unique aspect of the sensory innervation of bone, that may partially explain the analgesic efficacy of anti-NGF therapy in relieving prostate cancer-induced bone pain, is that nearly all nerve fibers that innervate the bone express trkA and p75, and these are the receptors through which NGF sensitizes and/or activates nociceptors. The present results suggest that anti-NGF therapy may be effective in reducing pain and enhancing the quality of life in patients with prostate tumor-induced bone cancer pain. (Cancer Res 2005; 65(20): 9426-35)
Calcineurin, a conserved Ca 2+/calmodulin-regulated protein phosphatase, plays a crucial role in Ca 2+ signaling in a wide variety of cell types. In Saccharomyces cerevisiae, calcineurin positively regulates transcription in response to stress by dephosphorylating the transcription factor Crz1p/Tcn1p. Dephosphorylation promotes Crz1p nuclear localization in part by increasing the efficiency of its nuclear import. In this work, we show that calcineurin-dependent dephosphorylation of Crz1p also down-regulates its nuclear export. Using a genetic approach, we identify Msn5p as the exportin for Crz1p. In addition, we define the Crz1p nuclear export signal (NES) and show that it interacts with Msn5p in a phosphorylation-dependent manner. This indicates that calcineurin regulates Crz1p nuclear export by dephosphorylating and inactivating its NES. Finally, we define a motif in Crz1p, PIISIQ, similar to the PxIxIT docking site for calcineurin on the mammalian transcription factor NFAT, that mediates the in vivo interaction between calcineurin and Crz1p and is required for calcineurin-dependent regulation of Crz1p nuclear export and activity. Therefore, in yeast as in mammals, a docking site is required to target calcineurin to its substrate such that it can dephosphorylate it efficiently.
The ability of monoclonal antibodies (mAbs) to target specific antigens with high precision has led to an increasing demand to generate them for therapeutic use in many disease areas. Historically, the discovery of therapeutic mAbs has relied upon the immunization of mammals and various in vitro display technologies. While the routine immunization of rodents yields clones that are stable in serum and have been selected against vast arrays of endogenous, non-target self-antigens, it is often difficult to obtain species cross-reactive mAbs owing to the generally high sequence similarity shared across human antigens and their mammalian orthologs. In vitro display technologies bypass this limitation, but lack an in vivo screening mechanism, and thus may potentially generate mAbs with undesirable binding specificity and stability issues. Chicken immunization is emerging as an attractive mAb discovery method because it combines the benefits of both in vivo and in vitro display methods. Since chickens are phylogenetically separated from mammals, their proteins share less sequence homology with those of humans, so human proteins are often immunogenic and can readily elicit rodent cross-reactive clones, which are necessary for in vivo proof of mechanism studies. Here, we compare the binding characteristics of mAbs isolated from chicken immunization, mouse immunization, and phage display of human antibody libraries. Our results show that chicken-derived mAbs not only recapitulate the kinetic diversity of mAbs sourced from other methods, but appear to offer an expanded repertoire of epitopes. Further, chicken-derived mAbs can bind their native serum antigen with very high affinity, highlighting their therapeutic potential.
NGF mRNA is increased and a large-molecular-weight form of NGF protein is expressed in the region adjacent to the incision. NGF immunoreactivity is present in nerve bundles; both Schwann cells and axons are labeled. Immunoreactive NGF in axons is likely taken up into cut axons. This study suggests some common mechanisms for neuropathic and incisional pain.
T cell-engaging bispecific antibodies (TCBs) are highly potent therapeutics that direct the activity of cytotoxic T cells to tumors. TCBs have shown clinical activity in hematologic malignancies, but development of TCBs for solid tumor indications is proving more challenging. Due to their high potency, TCBs can target normal tissues with low antigen expression, resulting in significant on-target, off-tumor toxicity that can limit dosing to low levels. As a result, it has been difficult to reach the level of drug exposure required for efficacy without excessive toxicity. Therefore, novel methods are needed to enable the potent antitumor activity of TCBs while minimizing toxicity due to cytokine release and damage to healthy tissues. CytomX has developed a new class of recombinant, proteolytically activated antibody prodrugs (ProbodyTM therapeutics) that are “masked” to prevent binding to antigen in healthy tissue, but can become “unmasked” by proteases that are preferentially activated in the tumor microenvironment. In this way, Probody therapeutics are designed to increase therapeutic index by maximizing efficacy and minimizing on-target toxicity in normal tissues. Here we describe a T cell-engaging Bispecific Probody therapeutic (Pb-TCB) targeting Epidermal Growth Factor Receptor (EGFR) and CD3 that has been optimized for affinity, effector function, masking, and cleavability. In vitro, under protease-deficient conditions, we demonstrate that the unmasked EGFR-CD3 TCB has potent, EGFR-dependent tumor cell killing, while the doubly-masked EGFR-CD3 Pb-TCB reduces target-dependent cytotoxicity by more than 100,000-fold. However, in established tumor models where tumor-resident proteases are expected to be active, we demonstrate that Pb-TCBs potently induce tumor regressions. In nonhuman primates, the maximum tolerated dose (MTD) of the EGFR-CD3 Pb-TCB is more than 60-fold higher than the MTD of the unmasked TCB, and the tolerated exposure (AUC) is more than 10,000-fold higher. Finally, despite the 60-fold dose differential at the MTDs, transient serum cytokine and AST/ALT increases observed in nonhuman primates treated with the Pb-TCB are still lower than those induced by the TCB. By localizing activity to the tumor microenvironment, Pb-TCBs have the potential to expand clinical opportunities for T cell-engaging bispecific therapies that are limited by on-target toxicities, especially in solid tumors. Moreover, an EGFR-CD3 Pb-TCB has the potential to address EGFR-expressing tumors that are poorly responsive to existing EGFR-directed therapies. PROBODY is a trademark of CytomX Therapeutics, Inc. Citation Format: Leila M. Boustany, Laurie Wong, Clayton W. White, Linnea Diep, Yuanhui Huang, Shouchun Liu, Jennifer H. Richardson, W. Michael Kavanaugh, Bryan A. Irving. EGFR-CD3 bispecific Probody™ therapeutic induces tumor regressions and increases maximum tolerated dose >60-fold in preclinical studies [abstract]. In: Proceedings of the AACR-NCI-EORTC International Conference: Molecular Targets and Cancer Therapeutics; 2017 Oct 26-30; Philadelphia, PA. Philadelphia (PA): AACR; Mol Cancer Ther 2018;17(1 Suppl):Abstract nr A164.
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