Prothena to lose up to $618M in PRX019 milestones

When the PRX019 agreement terminates, Prothena’s milestone and royalty eligibility ends; Bristol Myers Squibb continues moponetug development.

Rhea-AI Filing Summary

Prothena Corporation plc said Bristol Myers Squibb decided not to advance PRX019 further in the clinic; the PRX019 Global License Agreement will terminate on January 28, 2027. Prothena was eligible for up to $617.5 million in development, regulatory, and sales milestones, plus tiered royalties on annual, worldwide net sales. In connection with termination, Bristol Myers Squibb will not owe those milestones or royalties. The agreement included an upfront payment of $80 million in May 2024.

Bristol Myers Squibb continues developing moponetug and conducting the Phase 2 TargetTau-1 trial in patients with early Alzheimer’s disease. It has paid Prothena $135 million in licensing payments for moponetug, and Prothena is eligible for up to $562.5 million in regulatory and sales milestones plus tiered royalties on annual, worldwide net sales.

0 points · 0 major

NegativeiHow this balance works

How this balance works

Rhea-AI gives every point it takes from this document a weight. Minor counts 1, Moderate 3 and Major 9, so one Major point outweighs several Minor ones. The bar adds up the weights on each side, and when neither side holds more than 65% of the total the balance reads Mixed.

It reads the document as published, with the same rules for every company, and it does not look at what the market expected or at how the stock traded, so a point can be objectively good on a day the stock falls.

Rhea-AI Sentiment measures something else, the tone of the wording.

How the balance worksHow Sentiment works

1 major · 1 point

Hollow bars mark forward-looking points. How the balance works

Positive

• None.

Negative

• Major point. Forward-looking: it has not happened yet and may not happen.PRX019 termination will end eligibility for up to $617.5 million in milestones. 1.3× market cap

8-K Event Classification

2 items: 1.02, 9.01

2 items

Item 1.02 Termination of a Material Definitive Agreement Business

A significant contract was terminated, which may affect business operations or revenue.

Item 9.01 Financial Statements and Exhibits Exhibits

Financial statements, pro forma financial information, or exhibit attachments filed with this report.

Key Figures

PRX019 milestone eligibility: Up to $617.5 million PRX019 upfront payment: $80 million PRX019 agreement termination: January 28, 2027 +2 more

5 metrics

PRX019 milestone eligibility Up to $617.5 million Development, regulatory, and sales milestones; Bristol Myers Squibb will not owe these in connection with termination

PRX019 upfront payment $80 million Payment received under the license agreement in May 2024

PRX019 agreement termination January 28, 2027 Stated termination date

Moponetug licensing payments $135 million Paid to Prothena to date

Moponetug milestone eligibility Up to $562.5 million Regulatory and sales milestones

Key Terms

tiered royalties, pharmacokinetics, pharmacodynamic targets, immunogenicity

4 terms

tiered royalties financial

"tiered royalties on annual, worldwide net sales"

Tiered royalties are a payment structure where the percentage of earnings paid as royalties changes based on different levels of sales or production. For example, a company might pay a smaller percentage on initial sales and a higher percentage as sales increase beyond certain points. This system encourages higher sales by adjusting payments, making it important for investors to understand how revenue sharing may vary as a product or project grows.

pharmacokinetics medical

"dose-dependent pharmacokinetics and pharmacodynamic effects"

Pharmacokinetics is the study of how a substance, such as a drug or chemical, moves through and is processed by the body over time. It tracks how it is absorbed, distributed, broken down, and eventually eliminated. For investors, understanding pharmacokinetics helps gauge the effectiveness, safety, and potential risks of new medications or treatments, which can influence a company’s success and valuation in the healthcare industry.

pharmacodynamic targets medical

"meeting the Company’s prespecified pharmacodynamic targets"

immunogenicity medical

"no immunogenicity"

Immunogenicity is the ability of a substance, such as a vaccine or medication, to provoke an immune response in the body. It matters to investors because high immunogenicity can affect the effectiveness and safety of a product, potentially leading to increased costs or regulatory challenges. Understanding immunogenicity helps assess the long-term viability and market potential of pharmaceutical and biotech investments.

FAQ

AI-generated questions and answers. How Rhea-AI works. Not financial advice.

Why is Prothena (PRTA) ending its PRX019 license?

Bristol Myers Squibb informed Prothena on October 28, 2026, after an internal strategic review, that it had decided not to advance PRX019 further in the clinic. The PRX019 Global License Agreement will terminate on January 28, 2027.

How much could Prothena (PRTA) have received from PRX019 milestones?

Prothena was eligible for up to $617.5 million in development, regulatory, and sales milestones, plus tiered royalties on annual, worldwide net sales of Licensed Products. In connection with termination, Bristol Myers Squibb will not owe those milestones or royalties to Prothena.

What is the status of moponetug in Prothena’s (PRTA) collaboration?

Bristol Myers Squibb continues to develop moponetug and conduct the ongoing Phase 2 TargetTau-1 trial in patients with early Alzheimer’s disease. It has paid Prothena $135 million in licensing payments to date; Prothena is eligible for up to $562.5 million in regulatory and sales milestones, as well as tiered royalties.

AI-generated analysis. How Rhea-AI works. Not financial advice.

Understanding 8-K Material Events →

See more from StockTitan in Google Search and AI answers. Adds StockTitan as a preferred source · opens Google

Add on Google Not now

Available on EDGAR 10/29/2026 - 04:04 PM EDT Accepted by SEC EDGAR 10/29/2026 - 04:03 PM EDT Learn about SEC filing dates

0001559053FALSE00015590532026-10-282026-10-28

UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

WASHINGTON, D.C. 20549

_______________________________________________________

FORM 8-K 

_______________________________________________________

CURRENT REPORT

Pursuant to Section 13 or 15(d) of the

Securities Exchange Act of 1934

Date of Report (Date of earliest event reported): October 28, 2026

_______________________________________________________

PROTHENA CORPORATION PUBLIC LIMITED COMPANY

(Exact name of registrant as specified in its charter)

_______________________________________________________

Ireland

001-35676

98-1111119

(State or Other Jurisdiction of Incorporation)

(Commission File Number)

(IRS Employer Identification No.)

77 Sir John Rogerson's Quay, Block C

Grand Canal Docklands

Dublin 2,

D02 VK60,

Ireland

(Address of principal executive offices, including Zip Code)

Registrant’s telephone number, including area code: 011-353-1-236-2500

___________________________________________________

(Former Name or Former Address, if Changed Since Last Report.) 

___________________________________________________

Check the appropriate box below if the Form 8-K filing is intended to simultaneously satisfy the filing obligation of the registrant under any of the following provisions (see General Instruction A.2. below):

☐ Written communications pursuant to Rule 425 under the Securities Act (17 CFR 230.425)

☐ Soliciting material pursuant to Rule 14a-12 under the Exchange Act (17 CFR 240.14a-12)

☐ Pre-commencement communications pursuant to Rule 14d-2(b) under the Exchange Act (17 CFR 240.14d-2(b))

☐ Pre-commencement communications pursuant to Rule 13e-4(c) under the Exchange Act (17 CFR 240.13e-4(c))

Securities registered pursuant to Section 12(b) of the Act:

Title of Each Class			Trading Symbol			Name of Each Exchange on Which Registered
Ordinary Shares, par value $0.01 per share			PRTA			The Nasdaq Global Select Market

Indicate by check mark whether the registrant is an emerging growth company as defined in as defined in Rule 405 of the Securities Act of 1933 (§230.405 of this chapter) or Rule 12b-2 of the Securities Exchange Act of 1934 (§240.12b-2 of this chapter).

                                        Emerging growth company ☐

If an emerging growth company, indicate by check mark if the registrant has elected not to use the extended transition period for complying with any new or revised financial accounting standards provided pursuant to Section 13(a) of the Exchange Act. ☐

Item 1.02 Termination of a Material Definitive Agreement.

Following an internal strategic review, Bristol Myers Squibb informed Prothena Corporation plc (the “Company”) on October 28, 2026 that it has decided not to advance PRX019 further in the clinic. In May 2024, a subsidiary of the Company entered into an exclusive global license agreement for PRX019 with Bristol Myers Squibb (the “PRX019 Global License Agreement”) to develop, manufacture and commercialize antibody products globally targeting a specified target (including PRX019, and collectively, “Licensed Products”) for any and all uses or purposes with respect to any human or animal disease, disorder or condition, and received an upfront payment of $80 million. The PRX019 License Agreement will terminate on January 28, 2027.

In the first half of 2026, the Company completed the Phase 1 trial for PRX019, which successfully demonstrated a benign safety and tolerability profile, no immunogenicity, and dose-dependent pharmacokinetics and pharmacodynamic effects, meeting the Company’s prespecified pharmacodynamic targets.

Pursuant to the PRX019 Global License Agreement, in addition to the upfront payment, the Company was eligible to receive further development, regulatory, and sales milestones of up to $617.5 million. The Company was also eligible to receive tiered royalties on annual, worldwide net sales of Licensed Products. In connection with termination of the PRX019 Global License Agreement, Bristol Myers Squibb will not owe any of the foregoing to the Company.

Moponetug and PRX019 are both clinical-stage programs which were part of a research and development collaboration with Bristol Myers Squibb executed in 2018.

Bristol Myers Squibb continues to develop moponetug (formerly PRX005), a potential best-in-class antibody for the treatment of Alzheimer’s disease that specifically targets a key epitope within the microtubule binding region (MTBR) of tau, a protein implicated in the causal pathophysiology of Alzheimer’s disease. Bristol Myers Squibb is conducting the ongoing Phase 2 TargetTau-1 clinical trial in patients with early Alzheimer’s disease (NCT06268886). To date, Bristol Myers Squibb has paid the Company $135 million in licensing payments for moponetug and the Company is eligible to receive up to $562.5 million in regulatory and sales milestones, as well as tiered royalties on annual, worldwide net sales.

Item 9.01 Financial Statements and Exhibits.

(d) Exhibits.

Exhibit No.						Description
104						Cover Page Interactive Data File (embedded within the Inline XBRL document)

SIGNATURES

    Pursuant to the requirements of the Securities Exchange Act of 1934, the registrant has duly caused this report to be signed on its behalf by the undersigned hereunto duly authorized.

Date:

October 29, 2026

PROTHENA CORPORATION PLC

By:

/s/ Tran B. Nguyen

Name:

Tran B. Nguyen

Title:

Chief Financial Officer

Filing Exhibits & Attachments

3 documents

Other Documents

• EX-101 XBRL TAXONOMY EXTENSION SCHEMA DOCUMENT 1.8 KB
• EX-101 XBRL TAXONOMY EXTENSION LABEL LINKBASE DOCUMENT 22.7 KB
• EX-101 XBRL TAXONOMY EXTENSION PRESENTATION LINKBASE DOCUMENT 13.2 KB