13G Filing: Foresite Capital Fund III, L.P. and Verona Pharma PLC (VRNA)

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CUSIP # 925050106 Page 9 of 9

exhibit A

Agreement of Joint Filing

The undersigned hereby agree
that a single Schedule 13G (or any amendment thereto) relating to the ordinary shares of the Issuer shall be filed on behalf of
each of the undersigned and that this Agreement shall be filed as an exhibit to such Schedule 13G.

Date: May 5, 2017

FORESITE CAPITAL FUND III, L.P.
By: FORESITE CAPITAL MANAGEMENT III, LLC
Its: General Partner
By: /s/ James Tananbaum
Name: James Tananbaum
Title: Managing Member
FORESITE CAPITAL MANAGEMENT III, LLC
By: /s/ James Tananbaum
Name: James Tananbaum
Title: Managing Member
JAMES TANANBAUM
By: /s/ James Tananbaum
Name: James Tananbaum

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