Mallinckrodt Announces Extracorporeal Photopheresis (ECP) Research Collaboration Agreement With Transimmune AG

-- Collaboration with experts in photopheresis field expected to further enhance understanding of photopheresis' effect on immune modulation across a range of severe and critical conditions --

-- Agreement includes joint development activities for potential next-generation photopheresis system that may benefit patients in multiple disease states --

STAINES-UPON-THAMES,United Kingdom,Feb. 25,2019 --Mallinckrodt plc (NYSE:MNK),a leading global specialty pharmaceutical company,today announced it has entered into a research collaboration agreement with Transimmune AG,a company developing novel immunotherapies based on its unique understanding of the physiologic processes underlying the activation of antigen-presenting cells. The companies will collaborate on translational research to further expand understanding of the underlying mechanism of action (MOA) for extracorporeal photopheresis,and its application toward the development of potential next-generation photopheresis technology,with plans to expand on Mallinckrodt's current THERAKOS™ Photopheresis platform through new clinical trials.

Beyond enhancing MOA understanding and advancing the technology platform,it is also anticipated that the insights gained through the joint research endeavor with the Transimmune experts can expand potential clinical applicability across diverse immune-mediated disease states. If clinical evidence is shown,these conditions may include Cutaneous T-Cell Lymphoma (CTCL),Graft-versus-Host Disease (GvHD),organ transplant rejection and all autoimmune diseases – all exclusively licensed to Mallinckrodt under the agreement.

Transimmune was founded by Richard Edelson,M.D.,Lerner Professor of Dermatology,Chair and Professor,Department of Dermatology,Yale University School of Medicine,and a photopheresis pioneer. Dr. Edelson has spent decades studying the photopheresis mechanism of action and founded Transimmune to translate those insights into improving photopheresis therapy.

"Mallinckrodt invests in assets and technologies to further their application in conditions with few or limited therapeutic options,and for the treatment of underserved patients with severe and critical conditions," said Steven Romano,Executive Vice President and Chief Scientific Officer,Mallinckrodt. "This agreement is an example of our model of collaboration and partnership with experts in both basic and clinical research – similar to the recent collaborative research partnership announced with Washington University School of Medicine in St. Louis – to expand our access to innovative science and technology in areas of mutual interest."

Mallinckrodt and Transimmune will establish a joint governance committee consisting of representatives from both companies to oversee,review and coordinate the activities under the agreement.

The companies intend to explore a joint commercial collaboration arrangement related to a next-generation Mallinckrodt photopheresis system. Mallinckrodt is the only provider of an integrated closed loop photopheresis therapy,which is delivered through its latest generation THERAKOS™ CELLEX™ Photopheresis System.

About Therakos ECP Immunomodulation™

The THERAKOS™ Photopheresis platform is the worlds only approved,fully-integratedsystem for administering ECP Immunomodulation. Our system is used by academic medical centres,hospitals and treatment centres in more than 30 countries and has delivered over one million treatments globally.

THERAKOS™ Photopheresis Systems are the only CE marked devices for the administration of ECP.

CAUTION: READ THE THERAKOS™UVAR XTS™or THERAKOS™CELLEX™PHOTOPHERESIS SYSTEMS' OPERATOR'S MANUAL PRIOR TO PRESCRIBING OR DISPENSING THIS MEDICATION.

For the THERAKOS™UVAR XTS™/CELLEX™Photopheresis Procedure:

INDICATIONS

The THERAKOS™ UVAR XTS™ and THERAKOS™ CELLEX™ Photopheresis Systems are indicated for the administration of photopheresis.

IMPORTANT SAFETY INFORMATION

Contraindications

THERAKOS™ Photopheresis is contraindicated in patients possessing a specific history of a light sensitive disease. THERAKOS™ Photopheresis is contraindicated in patients who cannot tolerate extracorporeal volume loss or who have white blood cell counts greater than 25,000 mm3. THERAKOS™ Photopheresis is contraindicated in patients who have coagulation disorders or who have previously had a splenectomy.

Warnings and Precautions

THERAKOS™ Photopheresis treatments should always be performed in locations where standard medical emergency equipment is available. Volume replacement fluids and/or volume expanders should be readily available throughout the procedure. Both men and women should take adequate contraceptive precautions both during and after completion of photopheresis therapy. Safety in children has not been established.

Adverse Events

Hypotension may occur during any treatment involving extracorporeal circulation. Closely monitor the patient during the entire treatment for hypotension.

Transient pyretic reactions,37.7–38.9°C (100–102°F),have been observed in some patients within six to eight hours of reinfusion of the photoactivated leukocyte-enriched blood. A temporary increase in erythroderma may accompany the pyretic reaction.

Treatment frequency exceeding labelling recommendations may result in anaemia.

Venous access carries a small risk of infection and pain.

Please see the appropriate THERAKOS™Photopheresis System Operator's Manual for full product information.

ABOUT MALLINCKRODT

Mallinckrodt is a global business that develops,manufactures,markets and distributes specialty pharmaceutical products and therapies. Areas of focus include autoimmune and rare diseases in specialty areas like neurology,rheumatology,nephrology,pulmonology and ophthalmology; immunotherapy and neonatal respiratory critical care therapies; analgesics and gastrointestinal products. To learn more about Mallinckrodt,visit www.mallinckrodt.com.

Mallinckrodt uses its website as a channel of distribution of important company information,such as press releases,investor presentations and other financial information. It also uses its website to expedite public access to time-critical information regarding the company in advance of or in lieu of distributing a press release or a filing with the U.S. Securities and Exchange Commission (SEC) disclosing the same information. Therefore,investors should look to the Investor Relations page of the website for important and time-critical information. Visitors to the website can also register to receive automatic e-mail and other notifications alerting them when new information is made available on the Investor Relations page of the website.

Cautionary Statements Related to Forward-Looking Statements

This release includes forward-looking statements concerning the collaboration with Transimmune AG,including expectations regarding future research and clinical trial plans,potential commercial arrangements and the potential impact on patients. The statements are based on assumptions about many important factors,including the following,which could cause actual results to differ materially from those in the forward-looking statements: clinical trial results,uncertainties inherent in research and development; satisfaction of regulatory and other requirements; actions of regulatory bodies and other governmental authorities; changes in laws and regulations; issues with product quality,manufacturing or supply,or patient safety issues; and other risks identified and described in more detail in the "Risk Factors" section of Mallinckrodt's most recent Annual Report on Form 10-K and other filings with the SEC,all of which are available on its website. The forward-looking statements made herein speak only as of the date hereof and Mallinckrodt does not assume any obligation to update or revise any forward-looking statement,whether as a result of new information,future events and developments or otherwise,except as required by law.

CONTACTS

Investor Relations

Daniel J. Speciale,CPA

Vice President,Investor Relations and IRO

314-654-3638

daniel.speciale@mnk.com

Media

Daniel Yunger

Kekst CNC

212-521-4879

mallinckrodt@kekstcnc.com

Mallinckrodt,the "M" brand mark and the Mallinckrodt Pharmaceuticals logo are trademarks of a Mallinckrodt company. Other brands are trademarks of a Mallinckrodt company or their respective owners. © 2019 Mallinckrodt. AU-190001 02/19

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