# Targeted Secretion Inhibition

Targeted Secretion Inhibition: Applications in Oncology, Endocrinology, and Neurology/Pain

Offered by Harvard Catalyst's Reactor Program, this pilot funding opportunity provided up to $50,000 in funding plus access to Ipsen's Targeted Secretion Inhibitor (TSI) technology platform to expand the clinical potential for this novel class of biopharmaceuticals. This pilot grant opportunity promoted the design, development, and evaluation of novel TSIs for their potential clinical application in cancer, endocrine, neurological disorders, or pain. A critical feature of this research program is Ipsen's commitment to provide any awardees, who may require it, with scientific and technical support to design and develop project-related TSIs. Successful applicants did not necessarily need to be able to generate the TSI molecular constructs for their proposed work. TSIs are based on the structure and function of botulinum neurotoxins which are comprised of two peptide chains linked via a disulfide bond. The light chain (LC) possesses a proteolytic activity that can disrupt vesicle function and the associated secretion process. The heavy chain (HC) contains two domains, a transmembrane domain responsible for membrane insertion and translocation of the LC and a targeting domain responsible for binding to the motor neuron by the parent molecule. Botulinum neurotoxin stops secretion of vesicle components by its targeted proteolytic activity. Replacement of the neurotoxin targeting domain with another protein sequence (receptor, mAb, hormone, etc.) directs the recombinant secretion inhibitor to any desired cell type where it can disrupt normal secretion processes. TSIs can inhibit cellular secretion for prolonged periods and may be suitable for use in a wide range of diseases where inhibition of cellular secretion could provide new therapeutic potential. Pilot grant proposals described innovative and translational research projects that, if successful, could provide new insights into the application of TSI technologies to inform: (1) clinical decisions; (2) disease detection, causation, progression, or treatment; or (3) the development of new therapeutics, diagnostics, or clinically informative biomarkers. Proposals should focus on applications in the fields of oncology, endocrinology, or neurology/pain. Five pilot grants were awarded in amounts of up to$50,000 for each one-year project - starting February 1, 2018

## Targeting Growth Factors and Cytokine Secretion in Tumor Associated Fibroblasts to Counter Therapeutic Resistance in Non-small Cell Lung Cancer

#### Principal Investigator: Cyril Benes, PhD. Massachusetts General Hospital

Tyrosine kinase inhibitors (TKIs) have become the standard of care for many cancer types harboring specific genetic alternations. This includes non-small cell lung cancer (NSCLC) patients with EGFR mutations and initial response to EGFR TKI is generally good. However, drug resistance universally emerges and limits clinical benefit. Resistance can be mediated by growth factors (GFs) in the tumor microenvironment. Tumor associated fibroblasts constitute a major component of the tumor microenvironment and source of growth factors. We have built a large collection of patient-derived fibroblast (PDFs) to decipher their function in development of therapeutic resistance and to profile their cytokine secretion profiles. Half of these PDFs confer resistance to EGFR TKI through secretion of growth factors. Importantly, in some instances multiple GFs act simultaneously to confer resistance and targeting a single receptor or ligand is insufficient to counter resistance. Systemic delivery of high order combinations of GF receptors is likely to be too toxic in the clinic. Therefore, we believe that targeting tumor fibroblast’s secretion of growth factors using Ipsen’s innovative targeted secretion inhibition (TSI) approach could represent a new modality to counter acquired and de novo drug resistance in NSCLC.

## Targeted Secretion Inhibition (TSI) as a Novel Therapeutic Strategy in Plasma Cell Disorders

#### Principal Investigator: Giada Bianchi, MD. Dana Farber Cancer Institute

Multiple myeloma (MM) and AL amyloidosis (AL) are diseases of clonal plasma cell (PC) proliferation and hyper-secretion of monoclonal immunoglobulin (paraprotein) and/or free light chain (FLC). MM is the second most frequent blood cancer in the western world, with a peak incidence in the 7th decade of life. AL is a rare, rapidly fatal disorder characterized by deposition of amyloidogenic FLC in target organs, leading to failure and eventually death. Despite novel therapies such as proteasome inhibitors (PI), MM/AL are incurable. My prior work showed that MM cells have baseline excess protein synthesis/misfolding in the face of limited proteasome-mediated degradation. PI exacerbate this imbalance, leading to proteotoxicity and apoptosis. Proteotoxicity similarly underlies PI sensitivity in AL. While PI are effective in treating MM/AL, resistance is inevitable, underscoring an important, unmet therapeutic need. Botulinum toxin (BoNT) proved effective in reducing paraprotein secretion in PC, suggesting its utility in MM/AL treatment. I hypothesize that: targeted inhibition of paraprotein/FLC secretion via chimeric BoNT is a feasible and effective therapeutic strategy in MM/AL, leading to decreased paraprotein/FLC secretion and direct cytotoxicity against MM/AL cells via exacerbation of baseline proteotoxicity. In this proposal, I present an experimental plan to test these hypotheses in well-established MM/AL in vitro and in vivo models. The support of Harvard Catalyst and IPSEN is crucial for the successful design and proof of concept of chimeric BoNT targeting paraprotin/FLC in MM/AL, with the ultimate goal of bench to bedside translation of chimeric BoNT for patients with MM/AL and/or other paraprotein/FLC-related disorders.

## Assessing the Potential of TSI for Treating Hyperparathyroidism

#### Principal Investigator: Michael Mannstadt, MD. Massachusetts General Hospital

The purpose of the proposal is to explore the suitability of the Targeted Secretion Inhibitor (TSI) platform as a novel treatment of hyperparathyroidism. Primary hyperparathyroidism is a common endocrine disorder caused by overproduction of parathyroid hormone (PTH) from the parathyroid glands. Recent trends in the US suggest that the incidence of the disease is >100,000 new cases annually, predominantly affecting post-menopausal women. In the majority of patients, the culprit lesion is an adenoma that developed in one of the four parathyroid glands and overproduces PTH. This leads to high blood calcium and high urine calcium, which can result in kidney stones, kidney failure, and osteoporosis. The only curative approach is surgical removal of the adenoma, but some patients either do not wish to undergo neck surgery or are poor surgical candidates. Medical therapy using the oral calcium-sensing agonist cinacalcet fails to improve skeletal health and is rarely used in practice because of significant gastrointestinal side effects including nausea. Therefore, new therapies are needed. Here, we are exploring the potential of the TSI platform to inhibit PTH secretion, and we propose a multi-step project. The pilot grant would permit completion of the first steps: determining which SNARE proteins are expressed in human parathyroid adenomas using RNA-seq and Western blot; searching for proteins expressed in human parathyroid adenoma that are suitable as TSI targets; developing a primary cell culture system using fresh human parathyroid adenoma.

## Overcoming Microenvironment-Mediated Drug Resistance in Pancreatic Cancer

#### Principal Investigator: Taru Muranen, PhD. Beth Israel Deaconess Medical Center

The overarching goal of these studies is to uncover mechanisms by which secreted stromal proteins promote drug resistance in pancreatic cancer and to develop strategies to inhibit these mechanisms. Pancreatic ductal adenocarcinoma is one of the most lethal and drug resistant of all cancers. The average survival time is only six months, and in most cases curative surgery is not feasible. Our previous data show that stromal cells and the tumor microenvironment promote drug and stress resistance, and our preliminary data show that pancreatic stellate cells, which are the main secretory cell type in pancreatic cancer, induce drug resistance through protein secretion. Pancreatic stellate cells become activated in pancreatic cancer and obtain a secretory phenotype, which could be used to target these cells. Our current efforts are aimed at identifying the molecules responsible for inducing drug resistance, and this proposal aims at identifying ways to selectively inhibit secretion by the activated stellate cells in order to improve therapy outcomes in pancreatic cancer. With the help of this grant and Ipsen’s platform we will develop treatment strategies to block secretion by the pancreatic stellate cells and test their efficacy in our co-culture model systems.

## Restoring Vision by Inhibition of Zinc Release

#### Principal Investigator: Paul Rosenberg, MD PhD. Boston Children's Hospital

Retinal ganglion cells (RGCs), the projection neurons of the eye, cannot regenerate their axons once the optic nerve has been injured, and soon begin to die. Within an hour after the optic nerve is injured, mobile Zn2+ increases several-fold in the terminals of retinal amacrine cells (AC) in the inner plexiform layer and continues to rise over the first day, while accumulating more slowly within RGCs themselves. Zn2+ accumulation in AC terminals involves the Zn2+ transporter protein ZnT3 that is responsible for Zn2+ import into synaptic vesicles, and knockout of ZnT3 blocks Zn2+ accumulation while promoting RGC survival and axon regeneration. Intravitreal injection of Zn2+ chelators enables many RGCs to survive for months after nerve injury and regenerate axons. Importantly, the therapeutic window for Zn2+ chelation extends for several days. Of great interest, intraocular injection of tetanus toxin prevents the translocation of Zn2+ from the AC processes to the RGCs while increasing the Zn2+ in AC processes, and mimics the protective effect of Zn2+ chelation. These results suggest that exocytotic release of mobile Zn2+ from the AC processes is critical for the deleterious effects of Zn2+ accumulation. These results point to the viability of targeted secretion inhibition as a therapeutic strategy for promoting neuronal survival and axon regeneration after optic nerve injury. The specific question to be addressed in this project is whether a botulinum toxin based strategy can be used to block Zn2+ secretion from AC processes following optic nerve injury and effectively promote axonal regeneration and neuronal survival.