Prothena to Present Updated Clinical Data From Ongoing Phase 1/2 Study of NEOD001 at 2015 ASCO Annual Meeting

• Investor Conference Call and Webcast to be Held Tuesday, June 2, 2015 at 3:00 p.m. EDT

DUBLIN, Ireland, May 13, 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 updated clinical data, from the multiple ascending dose portion of its ongoing Phase 1/2 trial of NEOD001 in patients with AL amyloidosis and persistent organ dysfunction, will be highlighted in an oral presentation at the 2015 American Society of Clinical Oncology (ASCO) Annual Meeting to be held May 29 - June 2, 2015 in Chicago, IL. In addition, there will be a poster presentation on the study design of Prothena's VITAL Amyloidosis Study, a randomized, double-blind, placebo-controlled, global Phase 3 study of NEOD001 in patients with AL amyloidosis and cardiac dysfunction.

NEOD001 will be featured in the following sessions:

(Abstract #8514) Phase 1/2 study of NEOD001 in patients with AL amyloidosis and persistent organ dysfunction

• Presenter: Morie A. Gertz, MD, Mayo Clinic
• Session: Myeloma
• Date and Time: Tuesday, June 2, 10:45 a.m. - 1:45 p.m. EDT (NEOD001 presentation: 12:45 - 12:57 p.m. EDT)
• Location: E354b

Data contained in the published abstract was current as of September 30, 2014. Updated clinical data from the ongoing Phase 1/2 trial of NEOD001 will be presented at ASCO.

(Abstract #TPS8614) The VITAL study: A randomized, double-blind, placebo-controlled, global phase III study of NEOD001 in patients with AL amyloidosis and cardiac dysfunction

• Presenter: Michaela Liedtke, MD, Stanford Comprehensive Cancer Center
• Session: Lymphoma and Plasma Cell Disorders
• Date and Time: Sunday, May 31, 9:00 a.m. - 12:30 p.m. EDT
• Location: S Hall A

Conference Call and Webcast Details

Dr. Gertz will join Prothena management to discuss the updated clinical data from its ongoing Phase 1/2 trial of NEOD001 in patients with AL amyloidosis and persistent organ dysfunction during a live audio webcast and conference call on Tuesday, June 2, 2015 at 3:00 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 44777703. A replay of the call will be available until June 9, 2015 via dial-in at (855) 859-2056 (U.S. toll free) or (404) 537-3406 (international), Conference ID Number 44777703.

About NEOD001

NEOD001 is a humanized monoclonal antibody that specifically targets the circulating soluble amyloid and deposited insoluble amyloid that accumulates in both the AL and AA forms of amyloidosis. The ongoing multi-center Phase 1/2 clinical trial is evaluating the safety, tolerability, pharmacokinetics and immunogenicity of NEOD001 in patients with AL amyloidosis and persistent organ dysfunction. The study is also evaluating exploratory biomarkers for cardiac and renal function. Separately, The VITAL Amyloidosis Study, a double-blind, placebo-controlled, global Phase 3 registrational trial, will evaluate NEOD001 in newly-diagnosed, treatment-naïve patients with AL amyloidosis, and will assess all-cause mortality and cardiac hospitalizations in addition to biomarker, functional and quality of life endpoints. For more information on both the Phase 1/2 and VITAL Phase 3 trials, please visit www.clinicaltrials.gov, and search identifiers NCT01707264 (Phase 1/2) and NCT02312206 (VITAL Phase 3).

About AL Amyloidosis

Systemic amyloidoses are a complex group of progressive diseases caused by tissue deposition of misfolded proteins that result in progressive organ damage. The most common type, AL amyloidosis or primary amyloidosis, involves a hematological disorder caused by plasma cells that produce misfolded AL protein resulting in deposits of abnormal AL protein (amyloid) in the tissues and organs of individuals with this disease. There are no approved treatments for AL amyloidosis that directly target potentially toxic forms of the AL protein. AL amyloidosis is a rare disorder and it is estimated that about 30,000 to 45,000 patients in the U.S. and Europe suffer from this disease. Both the causes and origins of AL amyloidosis remain poorly understood. For more information on AL amyloidosis, please visit the websites of the Amyloidosis Support Group and the Amyloidosis Foundation.

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