13G Filing: James E. Flynn and Mallinckrodt PLC (MNK)

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Page 12 of 13 – SEC Filing

Exhibit A

Agreement

The undersigned agree that this Schedule
13G, and all amendments thereto, relating to the Common Stock of Mallinckrodt PLC shall be filed on behalf of the undersigned.

DEERFIELD MGMT, L.P.

By: J.E. Flynn Capital, LLC, General Partner

By: /s/ Jonathan Isler

       Jonathan Isler, Attorney-In-Fact

DEERFIELD MANAGEMENT COMPANY, L.P.

By: Flynn Management LLC, General Partner

By: /s/ Jonathan Isler

       Jonathan Isler, Attorney-In-Fact

DEERFIELD PARTNERS, L.P.

By: Deerfield Mgmt, L.P., General Partner

By: J.E. Flynn Capital, LLC, General Partner

By: /s/ Jonathan Isler

       Jonathan Isler, Attorney-In-Fact

DEERFIELD INTERNATIONAL MASTER FUND, L.P.

By: Deerfield Mgmt, L.P., General Partner

By: J.E. Flynn Capital, LLC, General Partner

By: /s/ Jonathan Isler

       Jonathan Isler, Attorney-In-Fact

JAMES E. FLYNN

/s/ Jonathan Isler

Jonathan Isler, Attorney-In-Fact

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