<DOCUMENT>
<TYPE>424B3
<SEQUENCE>1
<FILENAME>e424b3.txt
<DESCRIPTION>ALKERMES, INC.
<TEXT>

<PAGE>   1


Prospectus Supplement No. 12                    Filed pursuant to Rule 424(b)(3)
to Prospectus dated March 6, 2000                     Registration No. 333-31354


                                 ALKERMES, INC.

           $250,000,000 3 3/4% CONVERTIBLE SUBORDINATED NOTES DUE 2007
                        3,690,036 SHARES OF COMMON STOCK


     This prospectus supplement supplements the information contained in the
prospectus of Alkermes, Inc. dated March 6, 2000, as supplemented by Prospectus
Supplement No. 1 dated March 10, 2000, Prospectus Supplement No. 2 dated March
17, 2000, Prospectus Supplement No. 3 dated March 24, 2000, Prospectus
Supplement No. 4 dated April 5, 2000, Prospectus Supplement No. 5 dated April
13, 2000, Prospectus Supplement No. 6 dated April 21, 2000, Prospectus
Supplement No. 7 dated May 4, 2000, Prospectus Supplement No. 8 dated May 30,
2000, Prospectus Supplement No. 9 dated June 21, 2000, Prospectus Supplement No.
10 dated July 13, 2000 and Prospectus Supplement No. 11 dated July 25, 2000,
relating to the potential resale from time to time of the 3 3/4% Convertible
Subordinated Notes due 2007 of Alkermes and the resale of shares of common stock
of Alkermes issuable upon conversion of the notes. This prospectus supplement is
not complete without, and may not be delivered or utilized except in connection
with, the prospectus, including any amendments or supplements thereto.

     The following table supplements the information set forth in the prospectus
under the caption "Selling Securityholders" with respect to the selling
securityholders and the respective principal amount of notes which are
beneficially owned and may be sold by each selling securityholder, and the
number of shares of common stock that may be sold by the selling securityholders
pursuant to this prospectus, as amended or supplemented:

<TABLE>
<CAPTION>

                                                                                    Number of Shares of Common
                                                     Principal Amount of Notes      Stock Issued Upon Conversion
                                                     Beneficially Owned and         of the Notes that May be
Name of Selling Securityholder (1)                   Offered                        Offered (2)
<S>                                                        <C>                              <C>
Alta Partners Holdings, LDC                                $ 2,500,000                         36,900
Credit Suisse First Boston Corporation (8)                   2,500,000                         36,900
Forest Alternative Strategies Fund LP A5M (9)                   95,000                          1,402
Forest Fulcrum Fund LP (10)                                    795,000                         11,734
LLT Limited (11)                                               210,000                          3,099
Robertson Stephens (12)                                     82,203,000                      1,213,328
</TABLE>

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(1)  The information set forth herein is as of August 14, 2000 and will be
     updated as required.

(2)  Assumes conversion of the full principal amount of the notes held by such
     holder at the initial conversion price of $67.75 per share of common stock.
     This prospectus supplement reflects the impact of the two-for-one split of
     Alkermes' common stock effective April 28, 2000 on the shares of common
     stock issuable upon conversion of the notes.

(8)  The amount listed represents an additional $2,500,000 principal amount of
     the notes purchased by the holder in August 2000.

(9)  The amount listed includes an additional $55,000 principal amount of the
     notes beneficially owned by the holder as of August 14, 2000.

<PAGE>   2

(10)  The amount listed includes an additional $125,000 principal amount of the
     notes beneficially owned by the holder as of August 14, 2000.

(11) The amount listed includes an additional $85,000 principal amount of the
     notes beneficially owned by the holder as of August 14, 2000.

(12) The amount listed includes an additional $16,000,000 principal amount of
     the notes beneficially owned by the holder as of August 14, 2000.


            THE DATE OF THIS PROSPECTUS SUPPLEMENT IS AUGUST 14, 2000


                                       2
</TEXT>
</DOCUMENT>