EXHIBIT A AGREEMENT OF REPORTING PERSONS Each of the undersigned hereby agrees that Amendment No. 1 to the Schedule 13G filed on the date hereof with respect to the shares of Common Stock of Esperion Therapeutics, Inc. has been filed on behalf of the...

Cusip No. 00000X000                   13G                    Page 16 of 21 pages
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                                    EXHIBIT A

AGREEMENT OF REPORTING PERSONS

      Each of the undersigned hereby agrees that Amendment No. 1 to the Schedule
13G filed on the date hereof with respect to the shares of Common Stock of
Esperion Therapeutics, Inc. has been filed on behalf of the undersigned.


SIGNATURE:

      Dated: February 14, 2002

      Entities:

Oak Investment Partners VII, Limited Partnership
Oak Associates VII, LLC
Oak VII Affiliates Fund, Limited Partnership
Oak VII Affiliates, LLC
Oak Management Corporation


                                        By: /s/ Xxxxxx X. Xxxxxxxxxx
                                            ------------------------------------
                                                Xxxxxx X. Xxxxxxxxxx, as
                                                General Partner or
                                                Managing Member or as
                                                Attorney-in-fact for the
                                                above-listed entities

Individuals:

Xxxxxx X. Xxxxxx
Xxxxxx X. Xxxxxxxxx
Xxxxxx X. Xxxxxxxxxx
Xxxxxxx X. Xxxxxx
Xxx X. Xxxxxx


                                        By: /s/ Xxxxxx X. Xxxxxxxxxx
                                            ------------------------------------
                                                Xxxxxx X. Xxxxxxxxxx, as
                                                Individually and as
                                                Attorney-in-fact for the
                                                above-listed entities