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PRTA · Prothena Corp Public Ltd Co

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$8.16 -0.07 (-0.85%) At close · Nov 13
Russell 2000 member Rebalance outlook locked
Market Cap
$419.01M
Shares
51.35M
Volume · Nov 13 340.75K Avg daily vol (3M) 464.03K

Price & Indicators

Drag to pan · scroll to zoom
Indicators
Price
Panels
Event markers
20d MA 50d MA 200d MA Earnings Filing Insider Congress Investor day
Close$8.16 Open$8.21 Day$8.01–8.31 52W close$7.89–11.51 Avg vol 30d508K Short int7.9M · 15.4% of shares · 15.7d Short vol65% Last earningsFeb 19, 2026 DataJan 2020–Nov 2026 Filing10-Q · Nov 5

Up next

Q4 2025 earnings call transcript
call held Feb 19, 2026
Play latest call

Latest documents

2026
Nov 5
Quarterly report 10-Q FY2026 Q3, ended Sep 30
PRX019 license terminated; Phase 3 trials underway

Prothena’s PRX019 license was terminated by Bristol Myers Squibb in October 2026; Phase 3 trials of prasinezumab for early Parkinson’s disease and coramitug for ATTR-CM were initiated in the fourth quarter of 2025.

Revenue $620K ▼ 74.3% Net loss $16.51M Diluted EPS -$0.32
Read from the MD&A section
3 source passages
In October 2026, following a strategic review, Bristol Myers Squibb informed Prothena that it decided not to advance PRX019 further in the clinic and was exercising its right to terminate the associated license agreement. In the fourth quarter of 2025, Roche initiated the Phase 3 PARAISO clinical trial (NCT07174310) evaluating prasinezumab as a potential treatment for early Parkinson’s disease. PARAISO is a Phase 3, randomized, double-blind, placebo-controlled, multicenter clinical trial to evaluate the efficacy and safety of prasinezumab in approximately 900 participants with early-stage Parkinson's disease on stable symptomatic monotherapy with levodopa. In the fourth quarter of 2025, Novo Nordisk initiated the Phase 3 CLEOPATTRA clinical trial (NCT07207811) evaluating coramitug as a potential treatment for ATTR-CM. CLEOPATTRA is a randomized, double-blind, placebo-controlled, multicenter clinical trial in approximately 1,280 participants with ATTR-CM. Open the document at this passage
Nov 5
Current report 8-K
Third-quarter net loss narrows to $16.5 million

Prothena reported a third-quarter 2026 net loss of $16.5 million versus $36.5 million, while ending September 30, 2026 with $272.2 million in cash, cash equivalents and restricted cash and no debt.

Financial results
2 source passages
For the third quarter and first nine months of 2026, Prothena reported net loss of $16.5 million and $2.4 million, respectively, as compared to a net loss of $36.5 million and $222.5 million for the third quarter and first nine months of 2025, respectively. As of September 30, 2026, Prothena had $272.2 million in cash, cash equivalents and restricted cash, and no debt. Open the document at this passage
Oct 29
Current report 8-K Events of Oct 28
Ended a material agreement

Bristol Myers Squibb decided not to advance Prothena Corporation plc’s PRX019, and the license will terminate January 28, 2027; further development, regulatory and sales milestones of up to $617.5 million and tiered royalties will not be owed.

Oct 2
Current report 8-K
Director or officer change, or executive pay

Prothena Corporation Public Limited Company announced that Chief Development Officer Chad J. Swanson, Ph.D., resigned effective October 9, 2026, to join a strategic partner and lead a program partnered with Prothena.

All documents

Metrics snapshot

Useful current figures from the complete screener profile.

Revenue (TTM)
$52.73M
Trailing 12 months
Net income (TTM)
−$23.96M
Trailing 12 months
Revenue growth YoY
-74.3%
Year over year
Operating margin
-64.6%
Trailing 12 months
P / E (TTM)
—
Trailing earnings
FCF yield
—
TTM · current market cap
Return on invested capital
—
Trailing 12 months
Net cash
$271.37M
Latest balance sheet
Dividend yield
—
Trailing 12 months
Shares change YoY
-4.4%
Year over year · fewer shares
Price change (1Y)
-19.8%
Trailing year
Short interest
15.4%
Latest settlement · 15.7 days to cover
View all 125 metrics

Quarterly results

Revenue Net income Net loss
▲571.8% $2.12M −$57.96M '24 Q4* ▲5556% $2.83M −$60.20M '25 Q1 ▼96.7% $4.42M −$125.77M '25 Q2 ▲149% $2.42M −$36.54M '25 Q3 ▼99% $21,000 −$21.59M '25 Q4* ▲1706.4% $51.08M $32.72M '26 Q1 ▼77.1% $1.01M −$18.58M '26 Q2 LATEST ▼74.3% $620,000 −$16.51M '26 Q3

* Q4 derived as the full year minus Q1 to Q3.

Equibles Rating

blended score · not investment advice
Overall
Sell
SellHoldBuy
Technical Sell Momentum Very Weak Sentiment Neutral Fundamentals Weak Quant / Vol Very High
Market backdrop VIX 19.3 · elevated Equity put/call 0.63
Technical
price trend
Sell
50 / 200-day cross No cross
Price vs 200-day avg −11%
below
Price vs 50-day avg −4%
below
RSI (14) 46
neutral
MACD trend Negative
52-week position 7%
near low
Volume (OBV) Bullish div.
accumulating
Momentum
relative strength
Very Weak
1-month return −2%
trailing
6-month return −19%
trailing
YTD return −15%
this year
Relative strength −19%
vs S&P · 6-mo
Sentiment
smart money
Neutral
Trend (MA cross) No cross
50d $9 › 200d $9 — 200d above 50d
Institutional flow Distributing
144 of 192 funds reported for Sep 30 · net -1.3M sh shares · +13 new
Insider flow Flat
No net insider activity over 90 days
Short interest Falling
15.41% of shares out · ▼ -0.4% MoM · 15.7 days cover
Volume signal Normal
Volume near normal
Institution breadth Steady
192 holders — mid 3-yr range
Squeeze score 75
high risk · 0–100
Fundamentals
Weak
Revenue growth −15%
Y/Y
EPS growth −100%
Y/Y
Buyback $73.4M
remaining
Quant / Vol
risk profile
Very High
Volatility 49%
annualized · 1-yr
Max drawdown −31%
past year
ATR 5.4%
of price · 14-day

Blended from price, momentum, positioning, fundamentals & volatility · daily-close · not investment advice. Market backdrop is context, not part of the score.

Guidance & track record

Latest guidance · from the 8-K filed Aug 6, 2026
full year 2026
Net cash used in operating and investing activities Lowered $18M – $23M
Feb 19, 2026 $50M – $55M changed to Aug 6, 2026 $18M – $23M
year end 2026
Year end cash balance in cash, cash equivalents and restricted c $259M
Previous outlook earlier release · from the 8-K filed May 7, 2026

Still-open targets the latest release did not restate under the same label.

Non-cash share-based compensation expense · full year 2026 $26M

Guidance from company 8-Ks · delivered figures from as-reported statements · no analyst estimates involved.

Technicals

trend & momentum for long-term holders Sell
3 · 3 · 1
50 / 200-day cross
No cross Neutral
Price vs 200-day avg
−11% Bearish
Price vs 50-day avg
−4% Neutral
RSI (14)
46 Neutral
MACD trend
Negative Bearish
52-week position
7% Bearish
Volume (OBV)
Bullish div. Bullish
Market signals — smart money & positioning
Mixed
Trend (MA cross) No cross
50d $9 › 200d $9 — 200d above 50d
Institutional flow Distributing
144 of 192 funds reported for Sep 30 · net -1.3M sh shares · +13 new
Insider flow Flat
No net insider activity over 90 days
Short interest Falling
15.41% of shares out · ▼ -0.4% MoM · 15.7 days cover
Volume signal Normal
Volume near normal
Institution breadth Steady
192 holders — mid 3-yr range
Price context
position in its 52-week range
Range low $8 Now $8 · 7% Range high $12
vs 200-day avg -11% vs 50-day avg -4%

Illustrative technical + ownership context — a signal mix, not investment advice.

Key metrics

the company's own KPIs, from written earnings releases and filings
Metric Latest Period YoY
shares repurchased 1,454,898 the three months ended June 30, 2026 filing —

Figures exactly as the company stated them in writing · click a metric with a to chart its history · period links open the stating document · "filing" marks figures stated in the 10-K/10-Q · YoY needs an exactly comparable prior-year period

Versus peers

Biotechnology — same industry group
Open screener →
Company Mkt cap YTD Rev growth Y/Y P/E Short % shares
PRTA
Prothena Corp Public Ltd Co
this stock
$419.01M -14.6% -14.8% — 15.4%
VRTX
Vertex Pharmaceuticals Inc
 $136.56B +18.8% +46.2% 34.7 1.9%
REGN
Regeneron Pharmaceuticals, Inc.
 $98.84B +23.8% +20.8% 21.1 2.1%
MRNA
Moderna, Inc.
 $90.38B +657.4% +4.3% — 8.2%
CSLLY
Csl Ltd
 $66.05B — — — 0.0%

Peers by industry group · P/E from as-reported trailing EPS · short % is of shares outstanding

At a glance

key data from every section
Ownership
Institutional Holders Reducing
Holders
192
% held
91.5%
Reported
144 of 192
Top holder
FMR LLC
Held Float
View
Held by Funds
Fund positions
58
View
Short & Settlement
Short Interest Falling
Shares short
7.9M
Days to cover
15.7d
Change
-28.5K sh
View
Short Volume
Short vol %
65%
As of
Nov 13, 2026
Short Total
View
Fails to Deliver
FTD shares
318
Value
$2.8K
As of
Sep 29, 2026
View
Off-Exchange
Off-exchange %
39.6%
Week of
Oct 5, 2026
Off-exch Lit
View
Financials
Financials
Revenue (FY)
$9.7M
Net income (FY)
$-244.1M
EPS diluted
$-4.53
View
Buybacks
Authorized
$100.0M
Remaining
$73.4M
Spent Remaining
View
Filings
SEC Filings
Latest
10-Q
Filed
Nov 5, 2026
This year
17

Prothena’s PRX019 license was terminated by Bristol Myers Squibb in October 2026; Phase 3 trials of prasinezumab for early Parkinson’s disease and coramitug for ATTR-CM were initiated in the fourth quarter of 2025.

View
Proposed Sales
Value
$64.9K
Shares
7.7K
Filed
Jul 29, 2026
View
Earnings & Events
Webcasts
Last webcast
Sep 16, 2026
View
Investor Relations
Latest news
Prothena Reports Third Quarter 20…
Published
Nov 5, 2026
View

Performance

5D 20D 120D MTD YTD
PRTA +2.4% -2.3% -18.9% -3.7% -14.6%
SPY +2.6% -1.2% +0.5% -0.2% +10.6%
vs SPY -0.2% -1.1% -19.4% -3.5% -25.2%

Capital returns

Buyback program · as of Sep 30, 2026
Authorized
$100.00M
Spent (derived)
$26.60M
Remaining
$73.40M
Spent Remaining

Dividends per share over the trailing 365 days by ex-date · buyback figures as last reported in SEC filings ("spent" derived as authorized − remaining; when several programs run concurrently, authorized is their combined total per the newest filing) · components shown separately — trailing-year buyback spend isn't tracked, so no combined shareholder yield is derived.

Key facts CIK 1559053 CUSIP G72800108 13F (30d) 149 filings 122 filers Visit website Investor relations