Case: Prothena Corporation plc
Class Period: 10/15/2015 - 4/20/2018
Lead Plaintiff Deadline: 9/17/2018
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July 24, 2018 – Kaplan Fox & Kilsheimer LLP (www.kaplanfox.com) is investigating claims on behalf of investors of Prothena Corporation plc (“Prothena” or the “Company”) (NASDAQ: PRTA).  Investors who purchased Prothena common stock between October 15, 2015 and April 20, 2018 (the “Class Period”) may be affected.  A Class Action has been filed against Prothena and certain current and former Company executives on behalf of investors who purchased Prothena’s publicly traded common stock during the Class Period.

Prothena is a development-stage biotechnology company.  During the Class Period, Prothena’s principal asset was NEOD001, a monoclonal antibody designed to treat amyloid light chain amyloidosis (“AL amyloidosis”), a debilitating disease that can lead to organ failure and death.

The Class Action alleges that throughout the Class Period, defendants cited the “best response” results of Prothena’s ongoing Phase 1/2 clinical study of NEOD001 as evidence that the drug was effective, while withholding relevant trial data showing NEOD001 was not an effective treatment for AL amyloidosis.  

On April 23, 2018, before the market opened, Prothena announced that it was ending all development of NEOD001 after data from its Phase 2b PRONTO trial showed that NEOD001 failed to reach either its primary or secondary endpoints.  The Company also disclosed that the independent data monitoring committee had determined that it would be futile to continue the Phase 3 VITAL study.  

Following the April 23, 2018 news, Prothena shares fell $25.34 per share, nearly 69%, to close at $11.50 per share.

The complaint alleges that throughout the Class Period defendants misleadingly cited the results of Prothena’s ongoing Phase 1/2 clinical study of NEOD001 as evidence that the drug was effective and provided a strong basis for late-stage Phase 2b and Phase 3 studies of NEOD001.  According to the complaint, in truth, the full Phase 1/2 study data did not provide an adequate basis for the late-stage Phase 2b and Phase 3 studies.

If you are a member of the proposed Class, you may move the court no later than September 17, 2018 to serve as a lead plaintiff for the purported class.  You need not seek to become a lead plaintiff in order to share in any possible recovery.  If you would like to discuss the complaint or our investigation, please contact us by emailing This e-mail address is being protected from spambots. You need JavaScript enabled to view it or by calling 800-290-1952.

This press release may be considered Attorney Advertising in some jurisdictions under the applicable law and ethical rules.

Kaplan Fox & Kilsheimer LLP, with offices in New York, San Francisco, Los Angeles, Chicago and New Jersey, has many years of experience in prosecuting investor class actions. For more information about Kaplan Fox & Kilsheimer LLP, you may visit our website at www.kaplanfox.com.  If you have any questions about this Notice, the action, your rights, or your interests, please contact: 

Donald R. Hall
KAPLAN FOX & KILSHEIMER LLP
850 Third Avenue, 14th Floor
New York, New York 10022
(800) 290-1952
(212) 687-1980
Fax: (212) 687-7714
E-mail: This e-mail address is being protected from spambots. You need JavaScript enabled to view it

Laurence D. King
KAPLAN FOX & KILSHEIMER LLP
350 Sansome Street, Suite 400 
San Francisco, California  94104
(415) 772-4700
Fax:  (415) 772-4707
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