Current Report · Items 2.02, 9.01 · 8-K

PROTHENA CORP PUBLIC LTD CO

PRTANASDAQEQUITYCurrent

Results of Operations and Financial Condition

Filed Aug 6, 2026Accepted Aug 6, 2026, 4:16 PM EDTCIK 1559053Accession 0001559053-26-000021

Company context

Prothena Corporation plc is a late-stage clinical biotechnology company with expertise in protein dysregulation and a pipeline of investigational therapeutics with the potential to change the course of devastating neurodegenerative and rare peripheral amyloid diseases. Fueled by its deep scientific expertise built over decades of research, Prothena is advancing a pipeline of therapeutic candidates for a number of indications and novel targets for which its ability to integrate scientific insights around neurological dysfunction and the biology of misfolded proteins can be leveraged. Prothena’s pipeline includes both wholly-owned and partnered programs being developed for the potential treatment of diseases including ATTR amyloidosis with cardiomyopathy, Alzheimer’s disease, Parkinson’s disease and a number of other neurodegenerative diseases. For more information, please visit the Company’s website at www.prothena.com and follow the Company on X (formerly Twitter) @ProthenaCorp.

Current securities

PRTANASDAQ · EQUITY · Current

Recent company filings

Disclosure sections

Items 2.02, 9.01

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Item 2.02Item 2.02 - Results of Operations

Item 2.02. Results of Operations and Financial Condition. The information in Item 2.02 of this Current Report on Form 8-K and Exhibit 99.1 attached hereto shall not be deemed “filed” for purposes of Section 18 of the Securities Exchange Act of 1934, as amended (the “Exchange Act”), or otherwise subject to the liabilities of that section. It may only be incorporated by reference in another filing under the Exchange Act or the Securities Act of 1933, as amended, if such subsequent filing specifically incorporate by reference the information furnished pursuant to Item 2.02 (including Exhibit 99.1) of this Current Report. On August 6, 2026, Prothena Corporation plc issued a press release announcing its financial results for the second quarter ended June 30, 2026. A copy of that press release is furnished as Exhibit 99.1 to this Current Report on Form 8-K and is incorporated herein by reference.