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NASDAQ · PRTAHealthcarePharmaceuticals

Prothena Corporation plc Ordinary Shares (PRTA)

$8.39+2.19%
Close Nov 4, 2026 · split-adjusted
Nov 3, 2026$8.21▼ 22.11% in range
Nov 3, 2025Low $7.91 · High $11.51Nov 3, 2026
What changed · written from our data
As of Nov 4, 2026

Prothena Corporation plc closed at $8.39 on Nov 4, up 2.19%, 27.1% below its 52-week closing high. Volume of 289.7K shares was 0.54× its 20-day average (below normal).

Split-adjusted performance: +4.6% over one month, -25.0% over six months, -20.4% over one year.

In the quarter ended Jun 30, 2026, revenue was $1.01M, down 77.1% from a year earlier, with a net margin of -1839.9%.

Short interest was 7.9M shares at the Oct 15 settlement (18.9% of float, 13.3 days to cover).

Market cap$430.7M51.3M shares
Revenue · quarter$1.0M−77.1% YoY
Diluted EPS$-0.36—
P/E · TTM—P/S 7.9×
Net margin-1,839.9%Gross 100.0%
Dividend yieldNone
52-week range7.91 – 11.51−27.1% from high
Volume289.7K0.54× 20-day avg
Volatility · 60d45.9%Annualised
Short % of float18.9%13.3 days to cover
Net cash$288.2MCash $288.2M
Next earnings—Not scheduled
Split-adjusted performance
1W −7.8%1M +4.6%3M −2.2%6M −25.0%YTD −12.1%1Y −20.4%3Y −76.3%5Y −84.7%

Earnings reactions

History →

No reported quarters with price history yet.

Rank within Pharmaceuticals

Percentile among 420 companies (100 = best)

6-month momentum51
Revenue growth16
Net margin14
Value (low P/E)—
Size58

Industry medians: 6-month return −25.5%, revenue growth +6.2%, net margin −33.8%, P/E 16.1×.

Short interest

Details →
Shares short7.9M−0.9% vs prior
Days to cover13.3Settled Oct 15
% of float18.9%
Short vol. 10d65.3%of daily volume

Closest peers by size in Pharmaceuticals

CompanyPriceToday6MRev. growthNet marginP/EMkt cap
PRTAProthena$8.39+2.19%−25.0%−77.1%−1839.9%—$430.7M
TLRYTilray Brands$2.96+11.70%−48.6%+22.7%−16.8%—$437.5MCompare
INDPIndaptus Therapeutics$3.30+1.85%+61.0%———$439.7MCompare
CRMDCorMedix$5.66+1.80%−29.7%+156.5%25.5%2.4$441.2MCompare
RLMDRelmada Therapeutics$4.17−2.34%−46.9%———$444.8MCompare
ALTAltimmune$2.12+3.92%−35.0%−100.0%——$412.4MCompare
ASMBAssembly Biosciences$19.87−0.25%−36.6%+38.9%−28.8%—$404.6MCompare
PHATPhathom Pharmaceuticals$5.68−1.05%−55.2%+71.1%−16.4%—$461.7MCompare
GYREGyre Therapeutics$4.440.00%−44.8%−2.1%−40.1%—$470.8MCompare

News about Prothena

All news →
Prothena's Partnership Strategy: Growth Driver or Limitation?Zacks Investment Research · Oct 20, 2026▲ PositiveCRMD vs. PRTA: Which Stock Should Value Investors Buy Now?Zacks Investment Research · Oct 8, 2026▼ Negative

Quick answers

What does Prothena Corporation plc do?
Prothena Corp PLC is a late-stage clinical biotechnology company that focuses on protein dysregulation and a pipeline of investigational therapeutics with the potential to change the course of devastating neurodegenerative and rare and peripheral amyloid diseases. Prothena is developing and applying its proprietary CYTOPE technology to target a broad spectrum of intracellular disease pathways in the brain and periphery.
What is PRTA's market cap?
$430.72M, based on the Nov 4 close of $8.39.
Does Prothena Corporation plc pay a dividend?
No regular cash dividend has been paid in the last year.
How much of PRTA is sold short?
7.9M shares, 18.9% of float, as of Oct 15, 2026.
What sector is PRTA in?
Healthcare, in the Pharmaceuticals industry.

About Prothena

Prothena Corp PLC is a late-stage clinical biotechnology company that focuses on protein dysregulation and a pipeline of investigational therapeutics with the potential to change the course of devastating neurodegenerative and rare and peripheral amyloid diseases. Prothena is developing and applying its proprietary CYTOPE technology to target a broad spectrum of intracellular disease pathways in the brain and periphery. The company's pipeline includes both wholly-owned and partnered programs like Prasinezumab, Coramitug (PRX004), BMS-986446 (PRX005), PRX019, TDP-43 CYTOPE, and PRX012-TfR, being developed for the potential treatment of Parkinson's disease, ATTR amyloidosis with cardiomyopathy, Alzheimer's disease, Amyotrophic lateral sclerosis (ALS), and other neurodegenerative diseases.

HQ: Dublin 2, L267 employeesListed Dec 18, 2012prothena.com

Sources: Massive / Polygon daily aggregates (split-adjusted) · SEC filings via Massive · FINRA settlements via Massive · Financial Modeling Prep. Figures are dated where shown; research is informational, not investment advice. Methodology