Prothena to Present Clinical Results From Its Phase 1 Single Ascending Dose Study of PRX002 at 19th International Congress of Parkinson's Disease and Movement Disorders

• Investor Conference Call and Webcast to be Held Wednesday, June 17, 2015 at 5:30 p.m. EDT

DUBLIN, Ireland, June 8, 2015 (GLOBE NEWSWIRE) -- Prothena Corporation plc (Nasdaq:PRTA), a late-stage clinical biotechnology company focused on the discovery, development and commercialization of novel protein immunotherapy programs, today announced that Gene Kinney, PhD, Chief Scientific Officer and Head of Research and Development of Prothena, will highlight clinical results from a Phase 1 single ascending dose study of PRX002, as part of the late breaker abstract track, during a poster presentation at the 19^th International Congress of Parkinson's Disease and Movement Disorders to be held June 14 - 18, 2015 in San Diego, CA. PRX002 is a monoclonal antibody for the potential treatment of Parkinson's disease and other related synucleinopathies, and the focus of a worldwide collaboration between Prothena and Roche.

Clinical data on PRX002 will be presented in the following session:

(Abstract #LBA 19) Results from a Randomized, Double-Blind, Placebo-Controlled, Single Ascending-Dose Study in Healthy Subjects with PRX002, an Anti-Alpha-Synuclein Monoclonal Antibody

• Presenter: Gene Kinney, PhD, Prothena Corporation plc
• Session: Late Breaking Abstract Poster Presentation
• Date and Time: Wednesday, June 17, 2015, 3:00 p.m. - 4:30 p.m. EDT
• Location: Harbor Foyer

Conference Call and Webcast Details

Prothena management will discuss the clinical trial results from the Phase 1 single ascending dose study of PRX002 during a live audio webcast and conference call on Wednesday, June 17, 2015 at 5:30 p.m. EDT. The webcast and slide presentation will be made available on the company's website at www.prothena.com under the Investors tab in the Events and Presentations section. Following the live audio webcast, a replay of the webcast will be available on the Company's website for 90 days.

To access the conference call via dial-in, please dial (877) 887-5215 (U.S. toll free) or (315) 625-3069 (international) five minutes prior to the start time and refer to conference ID number 54868803. A replay of the call will be available until June 24, 2015 via dial-in at (855) 859-2056 (U.S. toll free) or (404) 537-3406 (international), Conference ID Number 54868803.

About PRX002

PRX002, a monoclonal antibody targeting alpha-synuclein, is the focus of a license agreement between Prothena and Roche. The companies are evaluating PRX002 in a multiple ascending dose study in patients with Parkinson's disease, with results expected in the first half of 2016. PRX002 is designed to slow or reduce the progressive neurodegeneration associated with synuclein misfolding and/or the cell-to-cell transmission of the pathogenic forms of synuclein in Parkinson's disease and other synucleinopathies. Prior to initiating clinical trials, Prothena demonstrated the efficacy of PRX002 in various cellular and animal models of synuclein-related disease. In transgenic mouse models of Parkinson's disease, passive immunization with 9E4, the murine version of PRX002, reduced the appearance of synuclein pathology, protected synapses and improved performance by the mice in behavioral testing. For more information on the ongoing multiple ascending dose study, please visit www.clinicaltrials.gov and search identifier NCT02157714.

About Parkinson's Disease

Parkinson's disease is a degenerative disorder of the central nervous system that affects one in 100 people over age 60, and after Alzheimer's disease is the second most common neurodegenerative disorder. There are an estimated seven to ten million patients living with Parkinson's disease worldwide. Current treatments for Parkinson's disease are only effective at managing the early motor symptoms of the disease, mainly through the use of levodopa and dopamine agonists. As the disease progresses and dopaminergic neurons continue to be lost, these drugs eventually become less effective at treating the symptoms. In contrast, PRX002 targets disease-causing alpha-synuclein, and may slow or reduce the neurodegeneration associated with aberrant forms of alpha-synuclein.

About Prothena

Prothena Corporation plc is a late-stage clinical biotechnology company focused on the discovery, development and commercialization of novel protein immunotherapy programs for the potential treatment of diseases that involve amyloid or cell adhesion. The company is developing antibody-based product candidates that target a number of potential indications including AL amyloidosis (NEOD001), Parkinson's disease and other related synucleinopathies (PRX002), and psoriasis and other inflammatory diseases (PRX003).

For more information, please visit the company's web site at www.prothena.com.

CONTACT: Investors: Tran Nguyen, CFO
         650-837-8535, IR@prothena.com
         Media: Angela Bitting
         925-202-6211, angela.bitting@prothena.com