• Appointed Paula K. Cobb to Prothena's Board of Directors. Ms. Cobb is the Chief Operating Officer of Decibel Therapeutics, Inc., and has extensive global development, business strategy and commercial experience. Prior to joining Decibel in 2016, Ms. Cobb worked in a variety of global leadership roles at Biogen, including as Senior Vice President of the rare disease group, where she was responsible for the company's marketed hemophilia assets and Phase 3 programs in spinal muscular atrophy and neuropathic pain. She served on the board of directors of Nightstar Therapeutics plc, a clinical-stage gene therapy company, until its acquisition by Biogen.
  
  
• Appointed Michael J. Malecek as Chief Legal Officer and Company Secretary. Prior to joining Prothena, Mr. Malecek was Vice President and Deputy General Counsel of Intellectual Property & Litigation at Snowflake Computing. Previously, he was a Partner at the law firms of Arnold & Porter Kaye Scholer, Kaye Scholer and Dewey & LeBoeuf. In these positions he served as Managing Partner of the Silicon Valley offices and represented a range of life science companies, including Affymetrix and Complete Genomics, on intellectual property, compliance and securities law matters. Mr. Malecek's experience in the life science industry also includes six years as Vice President and Chief Advocacy Counsel at Affymetrix.

For the second quarter and first six months of 2019, Prothena reported a net loss of $15.8 million and $36.7 million, respectively, as compared to a net loss of $59.9 million and $108.6 million for the second quarter and first six months of 2018, which included restructuring charges of $20.9 million associated with the discontinuation of the NEOD001 program. Net loss per share for the second quarter and first six months of 2019 was $0.40 and $0.92, respectively, as compared to a net loss per share of $1.50 and $2.77 for the second quarter and first six months of 2018, respectively.

Research and development (R&D) expenses totaled $9.6 million and $22.9 million for the second quarter and first six months of 2019, respectively, as compared to $31.5 million and $66.2 million for the second quarter and first six months of 2018, respectively. The decrease in R&D expenses for the second quarter and the first six months compared to the same periods in the prior year was primarily due to lower clinical trial costs and to a lesser extent lower product manufacturing expenses, lower personnel costs and lower consulting costs. R&D expenses included non-cash share-based compensation expense of $2.1 million and $4.2 million for the second quarter and first six months of 2019, respectively, as compared to $2.6 million and $4.8 million for the second quarter and first six months of 2018, respectively.

General and administrative (G&A) expenses totaled $9.1 million and $19.0 million for the second quarter and first six months of 2019, respectively, as compared to $11.0 million and $25.2 million for second quarter and first six months of 2018, respectively. The decrease in G&A expenses for the second quarter and the first six months compared to the same periods in the prior year was primarily due to lower personnel costs, sublease rental income and lower legal expenses. G&A expenses included non-cash share-based compensation expense of $4.2 million and $8.3 million for the second quarter and first six months of 2019, respectively, as compared to $3.8 million and $8.4 million for the second quarter and first six months of 2018, respectively.

The Company continues to expect its full year 2019 net cash burn from operating and investing activities to be $57-65 million, and to end the year with approximately $371 million in cash, cash equivalents and restricted cash (midpoint). The estimated full year 2019 cash burn from operating and investing activities is primarily driven by an estimated net loss of $83-94 million, which includes an estimated $24 million of non-cash shared-based compensation expense.

Prothena Corporation plc is a clinical-stage neuroscience company focused on the discovery and development of novel therapies with the potential to fundamentally change the course of devastating neurological disorders. Fueled by its deep scientific understanding built over decades of neuroscience research, Prothena is advancing a pipeline of therapeutic candidates for a number of indications and novel targets including Parkinson's disease and other related synucleinopathies (prasinezumab - PRX002/RG7935, in collaboration with Roche) and ATTR amyloidosis (PRX004), as well as tau and TDP-43 (both programs in collaboration with Celgene) for which its scientific understanding of disease pathology can be leveraged. For more information, please visit the Company's website at www.prothena.com and follow us on Twitter @ProthenaCorp.

This press release contains forward-looking statements. These statements relate to, among other things: the sufficiency of our funding to advance our neuroscience pipeline; our expected timing of reporting interim data from the Phase 1 study of PRX004 and the expected scope of that data; our expected timing of reporting data from the Phase 2 PASADENA study of prasinezumab; the design of prasinezumab and its potential as a treatment for Parkinson's disease; the design of PRX004 and its potential as a treatment for ATTR amyloidosis; our goal of advancing a neuroscience pipeline of therapeutic candidates for a number of indications; our expected net cash burn from operating and investing activities in 2019 and cash balance at the end of 2019; and our estimated net loss and non-cash share-based compensation expense for 2019. 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) March 15, 2019 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.