13G Filing: James E. Flynn and Biocryst Pharmaceuticals Inc (BCRX)

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Page 13 of 14 – SEC Filing

Exhibit A

Agreement

The undersigned agree that this Schedule
13G, and all amendments thereto, relating to the Common Stock of BioCryst Pharmaceuticals, Inc. 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

DEERFIELD SPECIAL SITUATIONS 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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