SBIR-STTR Award

Radical prostatectomy (RP) is a commonly used treatment option for localized prostate cancer. Unfortunately, the procedure carries a risk of post-surgical complications including a high risk of erectile dysfunction (ED). According to The Prostate Cancer Outcomes Study, virtually all men experience ED after surgery, including a profound loss of nocturnal erections. The Prostate Cancer Outcomes Study further reveals that 60% of men experienced self-reported ED 18 months after RP, and only 28% of men reported erections firm enough for intercourse at a 5-year follow-up. The main pathophysiological mechanism behind this is damage to the cavernous nerves (CN). Consequently, the mechanisms that facilitate cavernosal oxygenation fail; fibrosis ensues and leads to cavernosal smooth muscle apoptosis. Whereas neuropraxia may be reversible, the penile fibrosis resulting from poor oxygenation permanently damages cavernosal function and produces chronic ED. Accelerated wound healing and nerve growth would preserve penile anatomy and corporal smooth muscle and potentially reduce the time patients experience ED following RP. However, there are at present no clinically approved strategies for this procedure. Several promising studies in animal models have used gene therapy approaches, usually involving overexpression of ?nerve growth factors.? Clinical translation of these gene therapy approaches will be hampered by safety issues over the use of viral vectors or transformed stem cells in a ?benign urological disease? as well as concerns over the ease of application. In addition, there are no orally or topically administered therapeutics that reliably elicit an erection in men with RP-induced ED. Our goal is to develop a novel therapeutic that enhances EF after RP via RNAi-mediated silencing of the microtubule severing enzyme, Fidgetin-like 2 (FL2). Preliminary results in an animal model of RP demonstrate that FL2 can be targeted by nanoparticle-delivered siRNA to dramatically and predictably recover EF. FL2 acts through mechanisms dramatically different from other genes/proteins/factors currently being investigated; the experiments presented in this application represent the first reported success of siRNA in treating ED associated with RP. In addition, our recent preliminary findings indicate that a polyplex-based carrier (?wafer?) of FL2-siRNA is at least as effective as FL2-siRNA-np in restoring EF in an animal RP model. In Specific Aim 1 we will compare a range of concentrations of FL2-siRNA incorporated in a wafer formulation for efficacy in restoring EF following CN injury (transection). Finally, in Specific Aim 2, we will perform toxicity studies to provide evidence of safety for the different siRNA concentrations. Thus, at the end of the project, we will have identified the siRNA-wafer formulation that restores EF and is safe for further IND-enabling studies.

Project Terms:
Anatomy; Animal Model; Animals; Apoptosis; Autopsy; base; Benign; cell motility; Cells; Chronic; Clinical; Clinical Chemistry; clinical translation; Code; Collagen; commercialization; comparative efficacy; Comparative Histology; Cytoskeleton; Electrocoagulation; Enzymes; Erectile dysfunction; erection; Evaluation; experience; experimental study; Fibrosis; flexibility; follow-up; Formulation; Gene Proteins; gene therapy; Goals; Grant; Growth; Hematology; Heparin; high risk; Histologic; improved; Inflammation; injured; Injury; Investigation; knock-down; Lead; Malignant neoplasm of prostate; Mediating; men; Messenger RNA; Meta-Analysis; Microtubules; Modeling; molecular marker; nanoparticle; nanoparticle delivery; Nerve; Nerve Growth Factors; nerve injury; Nerve Regeneration; nerve transection; Nervous System Trauma; novel; novel therapeutics; Operative Surgical Procedures; Oral; Outcome; overexpression; Patient Self-Report; Patients; Physiological; Plasmids; Procedures; Prostate Cancer Outcomes Study; Proteins; Publishing; Radical Prostatectomy; Reaction Time; Reagent; Recovery; relating to nervous system; repaired; Reporting; research clinical testing; Risk; RNA Interference; Robotics; Safety; Site; Small Interfering RNA; Smooth Muscle; Stem cells; success; Surgical complication; System; Techniques; Therapeutic; Time; Tissues; Toxic effect; Trauma; Urologic Diseases; Viral Vector; virtual; Work; Wound Healing;

Radical prostatectomy (RP) is a commonly used treatment option for localized prostate cancer, which carries ahigh risk for development of erectile dysfunction (ED) because of cavernous nerve (CN) injury. Even newer,nerve-sparing, robotic procedures do not convincingly improve erectile function (EF) outcomes after RP. Inaddition, ED resulting from RP is often refractory to treatment by orally administered phosphodiesterase type 5inhibitors (PDE5i) leaving patients with poor treatment options that are invasive, associated with side-effects,have limited efficacy, and treat symptoms rather than being curative. There is a real and urgent need toidentify new therapeutic strategies to treat ED associated with RP.As a consequence of CN injury there is decreased neuronal nitric oxide (NO) release in corporal tissue, theprimary activator of the molecular pathways leading to an erection. Lower levels of NO release lead to a failurein mechanisms that facilitate cavernosal oxygenation, resulting in fibrosis and cavernosal smooth muscleapoptosis, which then act as potentially irreversible barriers to recovery of EF, even after CN regeneration. SinceEF is impacted within 48 hours of CN injury, a strategy called "penile rehabilitation" such as oral PDE5iadministration, is initiated as early as possible after RP with the goal of raising basal corporal blood flow andpreserving penile architecture until there is functional CN regeneration.Based on the central role that CN injury plays in the development of ED following RP, our novel treatmentstrategy uses siRNA technology to target expression of a newly discovered microtubule regulator, Fidgetin-like2 (FL2) to enhance CN regeneration. Preliminary and published studies suggest FL2 is a negative regulator ofaxon growth and wound repair; in Phase I studies a novel lead therapeutic formulation (a "wafer" releasing FL2-siRNA; SiFi2) was identified that when administered to rats undergoing bilateral CN transection resulted in visibleCN regeneration and improved erectile function. Compared to other pre-clinical strategies under investigationfor CN regeneration, SiFi2 is exceptionally fast and effective in promoting CN regeneration, inducing reformationof nerve tissue across a gap of several millimeters, and resulting in significant improvement in erectile functionas early as two weeks following transection. However, this and other preclinical strategies being explored forCN regeneration may fail to recover optimal EF because irreversible changes may occur in penile architectureduring the time it takes for nerve regeneration. Therefore, we will explore a two-pronged approach enhancingnerve regeneration and mitigating corporal tissue damage while the nerve is healing.The goal for this Phase II proposal is to initiate steps towards an Investigational New Drug application (IND)filing, over three specific aims: (1) evaluate the ability of orally administered PDE5i to enhance SiFi2 treatment;(2) initiate a GMP start-up program at a contract manufacturing organization (CMO); and (3) evaluate toxicity ofSiFi2 produced at the CMO.

Public Health Relevance Statement:
Radical prostatectomy (RP), a commonly used treatment option for localized prostate cancer, often results in erectile dysfunction (ED) and, unfortunately, no orally or topically administered therapeutics exist which reliably restore erectile function in these afflicted men. Phase I studies have shown that when siRNA targeting the newly discovered microtubule regulator, Fidgetin-like 2 (FL2-siRNA-wafer; SiFi2), is administered to rats that underwent CN transection, visible CN regeneration and improved erectile function outcomes as early as two weeks post-transection were observed; these effects were both faster and more effective than other pre-clinical strategies. The goal for this Phase II proposal is to initiate steps towards an Investigational New Drug application (IND) filing, over three specific aims: (1) evaluate the ability of the commonly prescribed, orally administered phosphodiesterase type 5 inhibitors (PDE5i) to enhance SiFi2 treatment; (2) initiate a good manufacturing process (GMP) start-up program at drug substance and drug product contract manufacturing organizations (CMO); and (3) evaluate toxicity of the CMO generated SiFi2.

Project Terms: