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                                                                    EXHIBIT 10.1

(FPFR-LIBOR30)(R032204)4160000001 *LOAN5404*

                                PROMISSORY NOTE

                               DECEMBER 22, 2004
                               -----------------
                                     (DATE)

FOR VALUE RECEIVED, ALKERMES, INC. a corporation located at the address stated
below ("MAKER") promises, jointly and severally if more than one, to pay to the
order of GENERAL ELECTRIC CAPITAL CORPORATION or any subsequent holder hereof
(each, a "PAYEE") at its office located at 83 WOOSTER HEIGHTS ROAD, DANBURY, CT
06810 or at such other place as Payee or the holder hereof may designate
(written notice of which will be provided by Payee to Maker), the principal sum
of THREE MILLION SIX HUNDRED SEVENTY-SIX THOUSAND ONE HUNDRED FORTY AND 94/100
DOLLARS ($3,676,140.94), with interest on the unpaid principal balance, from the
date hereof through and including dates of payment, at a floating per annum
simple interest rate ("Contract Rate") as hereinafter calculated.

The Contract Rate for any given period ("Effective Period") following the first
Effective Period shall be equal to the sum of (i) Five and Forty-Five Hundredths
percent (5.45%) per annum plus (ii) a variable per annum interest rate ("Current
LIBOR"), which shall be equal to the rate listed for one month London Interbank
Offered Rate ("LIBOR") which is published in the "Money Rates" column of the
Wall Street Journal, Eastern Edition (or, in the event such rate is not so
published, in such other nationally recognized publication as Payee may specify)
on the first Business Day of the calendar month in which the applicable
Effective Period ends (notwithstanding any statement in such publication as to
the effective date of any published rate). As used herein, the term "Business
Day" shall mean and include any calendar day other than a day on which all
commercial banks in the City of New York, New York are required or authorized to
be closed.

The first Effective Period shall begin on the date hereof, and shall continue
through the earlier of (w) the date the first Periodic Installment (or part
thereof) is received by Payee and (x) the date on which the first Periodic
Installment is due. Each subsequent Effective Period shall begin on the day
after the last day of the previous Effective Period and shall continue through
the earlier of (y) the date the earliest due and unpaid Periodic Installment (or
part thereof) is received by Payee and (z) the date on which the next Periodic
Installment is due. The Contract Rate for the first Effective Period shall be
equal to the sum of (i) Five and Forty-Five Hundredths percent (5.45%) per annum
plus (ii) a variable per annum interest rate, which shall be equal to the rate
listed for one month London Interbank Offered Rate ("LIBOR"), which is published
in the "Money Rates" column of the Wall Street Journal, Eastern Edition on the
first Business Day of the current month in which the first Effective Period
ends.

Subject to the other provisions hereof, the principal and interest on this Note
is payable in lawful money of the United States in Thirty-Six (36) consecutive
monthly installments as follows:

<TABLE>
<CAPTION>
 Periodic
Installment                 Amount
----------------          -----------
<S>                       <C>
Thirty-Five (35)          $105,834.93
</TABLE>

each ("Periodic Installment") and a final installment which shall be in the
amount of Four Hundred Seventy-Three Thousand Four Hundred Forty-Nine and 03/100
Dollars ($473,449.03) plus any outstanding principal and interest. The first
Periodic Installment shall be due and payable on 2/01/05 and the following
Periodic Installments shall be due and payable on the same day of each
succeeding period (each, a "Payment Date"). All payments shall be applied first
to interest and then to principal. The acceptance by Payee of any payment which
is less than payment in full of all amounts due and owing at such time shall not
constitute a waiver of Payee's right to receive payment in full at such time or
at any prior or subsequent time. Interest shall be calculated on the basis of a
365 day year (366 day leap year) and will be charged at the Contract Rate for
each calendar day on which any principal is outstanding.

The amount and number of the Periodic Installments will not change with
fluctuations in the Contract Rate. Any increase in the Contract Rate shall be
reflected by a corresponding decrease in the portion of the Periodic Installment
credited to the remaining unpaid principal balance. Any decrease in the Contract
Rate shall be reflected as a corresponding increase in the portion of the
Periodic Installment credited to the remaining unpaid principal balance.
Notwithstanding the foregoing, at the end of each three (3) month period
commencing with the first Payment Date hereof, Maker agrees to pay to Payee
forthwith an additional sum ("Quarterly Payment") sufficient to amortize the
unpaid principal over the balance of the original term hereof at the Contract
Rate applicable for the first Periodic Installment.

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If, and for so long as, the amount of interest due exceeds the amount of the
Periodic Installment, Maker agrees to pay forthwith, in addition to (i) any
Periodic Installment then due and (ii) any Quarterly Payment, the amount by
which said interest exceeds the Periodic Installment. In the event interest only
is required to be paid during any period, the interest for such period shall be
due and payable monthly as it accrues and shall be calculated on the unpaid
principal balance existing at the commencement of such period.

The Maker hereby expressly authorizes the Payee to insert the date value is
actually given in the blank space on the face hereof and on all related
documents pertaining hereto.

This Note may be secured by a security agreement, chattel mortgage, pledge
agreement or like instrument (each of which is hereinafter called a "SECURITY
AGREEMENT").

Time is of the essence hereof. If any installment or any other sum due under
this Note or any Security Agreement is not received within ten (10) days after
its due date, the Maker agrees to pay, in addition to the amount of each such
installment or other sum, a late payment charge of five percent (5%) of the
amount of said installment or other sum, but not exceeding any lawful maximum.
If (i) Maker fails to make payment of any amount due hereunder within ten (10)
days after the same becomes due and payable; or (ii) Maker is in default under,
or fails to perform under any term or condition contained in any Security
Agreement, then the entire principal sum remaining unpaid, together with all
accrued interest thereon and any other sum payable under this Note or any
Security Agreement, at the election of Payee (written notice of which will be
provided by Payee to Maker), shall immediately become due and payable, with
interest thereon at the lesser of eighteen percent (18%) per annum or the
highest rate not prohibited by applicable law from the date of such accelerated
maturity until paid (both before and after any judgment).

Maker may not prepay in full or in part at any time any indebtedness hereunder
without the express written consent of Payee in its sole discretion, provided
however that if Maker prepays all indebtedness under this Note in connection
with the closing of additional financing under the Master Lease Agreement dated
as of October 16, 2002 in an amount equal to or greater than the original
principal balance under this Note, then no premium or penalty shall be due.

It is the intention of the parties hereto to comply with the applicable usury
laws; accordingly, it is agreed that, notwithstanding any provision to the
contrary in this Note or any Security Agreement, in no event shall this Note or
any Security Agreement require the payment or permit the collection of interest
in excess of the maximum amount permitted by applicable law. If any such excess
interest is contracted for, charged or received under this Note or any Security
Agreement, or if all of the principal balance shall be prepaid, so that under
any of such circumstances the amount of interest contracted for, charged or
received under this Note or any Security Agreement on the principal balance
shall exceed the maximum amount of interest permitted by applicable law, then in
such event (a) the provisions of this paragraph shall govern and control, (b)
neither Maker nor any other person or entity now or hereafter liable for the
payment hereof shall be obligated to pay the amount of such interest to the
extent that it is in excess of the maximum amount of interest permitted by
applicable law, (c) any such excess which may have been collected shall be
either applied as a credit against the then unpaid principal balance or refunded
to Maker, at the option of the Payee, and (d) the effective rate of interest
shall be automatically reduced to the maximum lawful contract rate allowed under
applicable law as now or hereafter construed by the courts having jurisdiction
thereof. It is further agreed that without limitation of the foregoing, all
calculations of the rate of interest contracted for, charged or received under
this Note or any Security Agreement which are made for the purpose of
determining whether such rate exceeds the maximum lawful contract rate, shall be
made, to the extent permitted by applicable law, by amortizing, prorating,
allocating and spreading in equal parts during the period of the full stated
term of the indebtedness evidenced hereby, all interest at any time contracted
for, charged or received from Maker or otherwise by Payee in connection with
such indebtedness; provided, however, that if any applicable state law is
amended or the law of the United States of America preempts any applicable state
law, so that it becomes lawful for the Payee to receive a greater interest per
annum rate than is presently allowed, the Maker agrees that, on the effective
date of such amendment or preemption, as the case may be, the lawful maximum
hereunder shall be increased to the maximum interest per annum rate allowed by
the amended state law or the law of the United States of America.

The Maker consents hereby to any and all extensions of time, renewals, waivers
or modifications of, and all substitutions or releases of, security or of any
party primarily or secondarily liable on this Note or any Security Agreement or
any term and provision of either, which may be made, granted or consented to by
Payee, and agrees that suit may be brought and maintained against Maker, at the
election of Payee without joinder of any other as a party thereto, and that
Payee shall not be required first to foreclose, proceed against, or exhaust any
security hereof in order to enforce payment of this Note. The Maker hereby
waives presentment, demand for payment, notice of nonpayment, protest, notice of
protest, notice of dishonor, and all other notices in connection herewith, as
well as filing of suit (if permitted by law) and diligence in collecting this
Note or enforcing any of the security hereof, and agrees to pay (if permitted by
law) all expenses reasonably incurred in collection, including Payee's actual
attorneys' fees.

THE MAKER HEREBY UNCONDITIONALLY WAIVES ITS RIGHTS TO A JURY TRIAL OF ANY CLAIM
OR CAUSE OF ACTION BASED UPON OR ARISING OUT OF, DIRECTLY OR INDIRECTLY, THIS
NOTE, ANY OF THE RELATED DOCUMENTS, ANY DEALINGS BETWEEN MAKER AND PAYEE
RELATING TO THE SUBJECT MATTER OF THIS TRANSACTION OR ANY RELATED TRANSACTIONS,

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AND/OR THE RELATIONSHIP THAT IS BEING ESTABLISHED BETWEEN MAKER AND PAYEE. THE
SCOPE OF THIS WAIVER IS INTENDED TO BE ALL ENCOMPASSING OF ANY AND ALL DISPUTES
THAT MAY BE FILED IN ANY COURT (INCLUDING, WITHOUT LIMITATION, CONTRACT CLAIMS,
TORT CLAIMS, BREACH OF DUTY CLAIMS, AND ALL OTHER COMMON LAW AND STATUTORY
CLAIMS.) THIS WAIVER IS IRREVOCABLE MEANING THAT IT WAY NOT BE MODIFIED EITHER
ORALLY OR IN WRITING, AND THE WAIVER SHALL APPLY TO ANY SUBSEQUENT AMENDMENTS,
RENEWALS, SUPPLEMENTS OR MODIFICATIONS TO THIS NOTE, ANY RELATED DOCUMENTS, OR
TO ANY OTHER DOCUMENTS OR AGREEMENTS RELATING TO THIS TRANSACTION OR ANY RELATED
TRANSACTION. IN THE EVENT OF LITIGATION, THIS NOTE MAY BE FILED AS A WRITTEN
CONSENT TO A TRIAL BY THE COURT.

This Note and other Debt Documents (as defined in any Security Agreement)
constitute the entire agreement of the Maker and Payee with respect to the
subject matter hereof and supercedes all prior understandings, agreements and
representations, express or implied.

No variation or modification of this Note, or any waiver of any of its
provisions or conditions, shall be valid unless in writing and signed by an
authorized representative of Maker and Payee. Any such waiver, consent,
modification or change shall be effective only in the specific instance and for
the specific purpose given.

Any provision in this Note or any of the other Debt Documents which is in
conflict with any statute, law or applicable rule shall be deemed omitted,
modified or altered to conform thereto.

                                 ALKERMES, INC.

______________________________   By: /s/ James Frates
(Witness)                            ----------------
______________________________   Name: James Frates
(Print name)
______________________________   Title: VP
(Address)
                                 Federal Tax ID #: 232472830

                                 Address: 88 Sidney Street, Cambridge,
                                          Middlesex County, MA 02139