Prothena to Present Preclinical Data for PRX003 at 2016 AAAAI Annual Meeting

DUBLIN, Ireland, Feb. 29, 2016 -- Prothena Corporation plc (Nasdaq:PRTA), a late-stage clinical biotechnology company focused on the discovery, development and commercialization of novel protein immunotherapies, today announced that preclinical data from its PRX003 program will be presented at the American Academy of Allergy, Asthma & Immunology (AAAAI) 2016 Annual Meeting to be held March 4-7, 2016 in Los Angeles, CA.

Featured Poster Session

Preclinical data demonstrating the ability of PRX003 to inhibit migration of disease causing immune cells will be featured in the following poster presentation:

(Abstract #24545) Anti-MCAM Monoclonal Antibody PRX003 Inhibits the Unique Migratory Potential of Pathogenic IL-17–Producing T Cells

• Presenter:  Kenneth Flanagan, Prothena Biosciences Inc
• Session:  3802/ Research Advancement in Allergy and Inflammation
• Date and Time:  Sunday, March 6, 2016, 4:45 p.m. – 6:15 p.m. PST
• Location:  Los Angeles Convention Center, Level One, Concourse, Foyer

About PRX003

PRX003 is a humanized monoclonal antibody being developed for the potential treatment of inflammatory diseases. Within the immune system, a small population of T cells known as Th17 cells, initiate the body's response to infections, and are known to be a key participant in both normal inflammatory reactions as well as pathogenic autoimmune diseases. MCAM is an adhesion molecule expressed on the surface of Th17 cells, and confers upon these cells the ability to interact with vasculature and subsequently migrate from the circulation into tissues, in some cases to initiate or perpetuate a disease process. While only 2-6 percent of T cells in circulation express MCAM, these cells uniquely secrete the Th17 signature cytokines, IL-17A and IL-17F, but can also produce other cytokines such as such as IFNγ, GM-CSF, TNFα and IL-22 that play a role in disease pathogenesis. PRX003 is designed to occupy a specific epitope on MCAM, which serves to functionally neutralize MCAM and subsequently sequester pathogenic T cells in the bloodstream, preventing their migration into tissues. As MCAM expressing T cells appear to be disproportionately involved in propagation of inflammation, targeting the T cell, rather than any individual cytokine, may provide a highly specific way to impact multiple pathogenic processes, while leaving the vast majority of immune function intact. PRX003 may be useful for treating a variety of inflammatory diseases such as psoriasis, psoriatic arthritis, rheumatoid arthritis, multiple sclerosis, sarcoidosis, uveitis, giant cell arteritis, and Behcet's disease. For more information about Prothena’s ongoing Phase 1 clinical study of PRX003 in patients with psoriasis please visit www.clinicaltrials.gov and search identifier NCT02630901.

About Prothena

Prothena Corporation plc is a global biotechnology company seeking to fundamentally change the course of progressive diseases with its late-stage clinical pipeline of novel therapeutic antibodies. Fueled by its deep scientific understanding built over decades of research in protein misfolding and cell adhesion – the root causes of many serious or currently untreatable amyloid and inflammatory diseases – Prothena has advanced several drug candidates into clinical trials while pursuing discovery of additional novel therapies.  Our clinical pipeline of antibody-based product candidates targets a number of potential indications including AL amyloidosis (NEOD001), Parkinson’s disease and other related synucleinopathies (PRX002) and inflammatory diseases including psoriasis (PRX003).

Forward-looking Statements

This press release contains forward-looking statements. These statements relate to, among other things, PRX003’s method of action and whether it will be useful for treating a variety of inflammatory diseases. These statements are based on estimates, projections and assumptions that may prove not to be accurate, and actual results could differ materially from those anticipated due to known and unknown risks, uncertainties and other factors, including but not limited to the risks, uncertainties and other factors described in the "Risk Factors" sections of our Annual Report on Form 10-K filed with the Securities and Exchange Commission (SEC) on February 25, 2016 and our subsequent Quarterly Reports on Form 10-Q filed with the SEC. Prothena undertakes no obligation to update publicly any forward-looking statements contained in this press release as a result of new information, future events or changes in Prothena's expectations.

Contacts:

Investors: Tran Nguyen, CFO
650-837-8535, [email protected]

Media: Ellen Rose, Head of Communications 
650-922-2405, [email protected]