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                                                                    EXHIBIT 10.1

                                 ALKERMES, INC.

               AMENDED AND RESTATED 1990 OMNIBUS STOCK OPTION PLAN

                   (ADOPTED ON SEPTEMBER 19, 1990, AS AMENDED
                             THROUGH JULY 29, 1998)



1.       OBJECTIVES

                  The objectives of this Plan are to assist Alkermes, Inc. (the
"Company") in attracting and retaining employees, officers and directors of and
consultants to the Company and in promoting the identification of such persons'
interests with those of the Company's shareholders.

2.       DEFINITIONS

                  "Board" shall mean the Board of Directors of the Company.

                  "Code" shall mean the Internal Revenue Code of 1986, as
amended, and any successor statute or codification of the income tax laws of the
United States.

                  "Committee" shall mean the Stock Option Committee of the Board
of Directors, which shall consist of at least two directors, each of whom is a
disinterested person within the meaning of Rule 16b-3(c)(2)(i) under the
Exchange Act.

                  "Common Stock" shall mean the Company's Common Stock, par
value $.01 per share.

                  "Date of Grant" in relation to any option granted under this
Plan shall mean the date on which, or the future date as of which, the Board or
the Committee grants that option.

                  "Eligible Person" shall mean any employee, consultant, officer
or director of the Company or any Parent or Subsidiary. For the purposes of
Incentive Stock Options, Eligible Persons must meet all the requirements under
Section 422 of the Code.

                  "Exchange Act" shall mean the Securities Exchange Act of 1934,
as amended from time to time.


                  "Exercise" in respect of an option shall mean the delivery by
the Optionee to the Company of (a) written notice of exercise of the option as
to a specified number of Shares; (b) payment of the option exercise price for
such Shares; and (c) any other statement or evidence required pursuant to
Section 9 hereof.

                  "Fair Market Value" of a Share with respect to any day shall
mean (i) the average of the high and low price on such day for a share of Common
Stock as reported on the principal securities 


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exchange on which shares of Common Stock are then listed or as quoted on the
NASDAQ National Market System, (ii) if not so listed or quoted, the average of
the closing bid and asked prices on such day as reported on NASDAQ, and (iii) if
not so listed, quoted or reported, the value as determined in good faith by the
Board or the Committee, as the case may be.

                  "Incentive Stock Option" shall mean any option that, at the
time of grant, meets the requirements of Section 422 of the Code and is
identified as an incentive stock option.

                  "ISO Plans" shall mean the Plan and all other incentive stock
option plans under Section 422 of the Code adopted or assumed by corporations
that are Qualified Employers.

                  "NASDAQ" shall mean the National Association of Securities
Dealers Automated Quotation System.

                  "Non-Qualified Stock Option" shall mean any option granted
under the Plan other than an Incentive Stock Option.

                  "Non-Section 16 Eligible Person" shall mean an Eligible Person
who is not an Officer or a director of the Company.

                  "Officer" shall mean a person who has been designated by the 
Board as an officer of the Company within the meaning of Rule 16a-1(f) of the
Exchange Act.

                  "Optionee" shall mean a person holding an option granted under
this Plan which has not been exercised or surrendered and has not expired.

                  "Parent" shall mean a corporation which, at the time in
question, owns at least 50% of the total combined voting power of all classes of
outstanding stock of the Company (or of a corporation that has issued or assumed
a stock option of the Company in a transaction to which Section 424(a) of the
Code applies) and a corporation which, at such time, owns at least 50% of the
total combined voting power of all classes of stock in another Parent.

                  "Plan" means this Amended and Restated 1990 Omnibus Stock
Option Plan, as amended from time to time.

                  "Qualified Employer" shall mean the Company, any Parent or any
Subsidiary.

                  "Section 16 Eligible Person" shall mean an Eligible Person who
is an Officer or a director of the Company.

                  "Shares" shall mean shares of Common Stock of the Company for
which options may be granted hereunder.

                  "Subsidiary" shall mean a corporation in which, at the time in
question, the Company (or a corporation that issued or assumed a stock option of
the Company in a transaction to which Section 424(a) of the Code applies) owns
at least 50% of the total combined voting power of all classes of stock


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outstanding and a corporation in which, at such time, another Subsidiary owns at
least 50% of the total combined voting power of all classes of stock
outstanding.

                  "Ten Percent Shareholder" shall mean an Eligible Person who
owns at the Date of Grant more than 10% of the total combined voting power of
all classes of stock of a Qualified Employer.

3.       MAXIMUM NUMBER OF SHARES TO BE OPTIONED AND ADJUSTMENTS IN OPTIONED 
         SHARES

         The maximum number of Shares for which options may be granted
hereunder is 3,250,000. This number shall be adjusted if the number of
outstanding shares of Common Stock of the Company is increased or
reduced by split-up, reclassification, stock dividend, or the like. The
number of Shares previously optioned and not theretofore delivered and
the option exercise price per Share shall likewise be adjusted whenever
the number of outstanding shares of Common Stock is increased or
reduced by any such procedure. Shares for which options have expired or
have been surrendered may again be optioned pursuant to the Plan.

4.       ADMINISTRATION AND INTERPRETATION

         Except to the extent provided below, this Plan shall be
administered by the Board. The Board may delegate responsibility for
administration to the Committee. The Board, or such Committee, may make
such rules and establish such procedures as it deems appropriate for
the administration of the Plan. In the event of any disagreement as to
the interpretation of the Plan or any rule or procedure thereunder, the
decision of the Board, or such Committee, shall be final and binding
upon all persons in interest. Members of the Board who are eligible to
participate in or have been granted options under the Plan may vote on
matters affecting administration of the Plan; provided, however, that
the Committee shall have the authority and sole responsibility for
granting options to Section 16 Eligible Persons and authorizing the
issuance of Shares upon the exercise thereof, and for the
administration of the Plan with respect thereto.

5.       GRANTING OF OPTIONS

         The Board is authorized to grant options to Non-Section 16
Eligible Persons pursuant to this Plan. The number of Shares, if any,
optioned in each year, the Non-Section 16 Eligible Persons to whom and
the time or times at which options are granted, the number of Shares
optioned to each Non-Section 16 Eligible Person and the other terms and
provisions of such options shall be wholly within the discretion of the
Board, subject to the limitation that no option shall be granted
(notwithstanding any other provisions of this Plan to the contrary)
later than September 19, 2000.

         The Committee is authorized to grant options to Section 16
Eligible Persons pursuant to this Plan. The number of Shares, if any,
optioned in each year, the Section 16 Eligible Persons to whom and the
time or times at which options are granted, the number of Shares
optioned to each Section 16 Eligible Person and the other terms and
provisions of such options shall be wholly within the discretion of the
Committee, subject to the limitation that no option shall be granted
(notwithstanding any other provisions of this Plan to the contrary)
later than September 19, 2000. 

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6.       TYPE OF OPTIONS

                  This Plan permits the grant of Non-Qualified Stock Options, as
well as Incentive Stock Options. Options granted under the Plan will be
designated as Non-Qualified Stock Options or Incentive Stock Options at the time
of their grant.

7.       OPTION TERMS

                  Subject to the limitation prescribed in Section 5 above, the
options granted under this Plan shall be on the terms stated in clauses (a)
through (h) below. The Board or the Committee, as the case may be, may specify
additional terms not inconsistent with this Plan by rules of general application
or by specific direction in connection with a particular option or group of
options.

                  (a) The option exercise price shall be fixed by the Board or
the Committee, as the case may be, but shall not be less than 100% (110% in the
case of an Incentive Stock Option granted to a Ten Percent Shareholder) of the
Fair Market Value of the underlying Shares on the Date of Grant.

                  (b) The option exercise price shall be payable in cash,
property, services rendered or, under certain circumstances, in shares of Common
Stock of the Company having a Fair Market Value equal to the option exercise
price on the date of exercise, or any combination thereof, or any other means
which the Board or the Committee, as the case may be, determines are consistent
with the Plan's purpose and applicable laws.

                  (c) The option shall not be transferable otherwise than by
will or the laws of descent and distribution and shall be exercisable during the
Optionee's lifetime only by the Optionee or after his death by the person or
persons entitled thereto by will or the laws of descent and distribution.

                  (d) The term of the option shall be fixed by the Board or the
Committee, as the case may be, but no option shall be granted for a term to
exceed ten years or, in the case of an Incentive Stock Option being granted to a
Ten Percent Shareholder, for a term to exceed five years.

                  (e) The option shall terminate and may not be exercised if the
Optionee ceases for any reason (including death, retirement or disability) to be
an employee of the Qualified Employer, except to the extent provided in Section
9 hereof.

                  (f) In the event that the Company is succeeded by another
company in a reorganization, merger, consolidation, acquisition of property or
stock, separation or liquidation, the successor company shall assume the
outstanding options granted under this Plan or shall substitute new options for
them, which shall provide that the Optionee, at the same cost, shall be entitled
upon the exercise of such option to receive such securities of the surviving or
resulting corporation as the Board of Directors of such corporation shall
determine to be equivalent, as nearly as practicable, to the nearest whole
number and class of shares of stock or other securities to which the Optionee
would have been entitled under the terms of the agreement governing the
reorganization, merger, consolidation, acquisition of property or stock,
separation or liquidation as if, immediately prior to such event, the Optionee
had been the holder of record of the number of Shares which were then subject to
such option.

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                  (g) The aggregate Fair Market Value (determined as of the Date
of Grant) of the Shares for which Incentive Stock Options are granted under the
ISO Plans to any one Eligible Person that are exercisable for the first time
during any calendar year shall not exceed $100,000.

                  (h) The terms and conditions of the grant of each option
granted hereunder shall be embodied in a written award certificate in a form
prescribed by the Board or by the Committee, as the case may be, which (i) has
been completed with the date, name of Optionee, number of Shares to which it
relates, type of option, term of option, option price per Share, name of
Optionee's employing company and (with respect to Incentive Stock Options) the
conditions required to qualify as an incentive stock option under Section 422 of
the Code, (ii) has been signed by a member of the Board or the Committee or an
officer of the Company designated by the Board or by the Committee, as the case
may be, and (iii) has been delivered to the Optionee.

8.       LIMITED STOCK APPRECIATION RIGHTS

                  (a) The Committee is authorized, in its discretion, to grant
limited stock appreciation rights ("LSARs") with respect to all or any portion
of the Shares covered by stock options granted hereunder to Officers and
directors of the Company, simultaneously with the grant of, or at any time
during the term of, non-qualified options or simultaneously with the grant of
incentive stock options. The grant of the LSAR will not be effective until six
months after the date of its grant. Those options with respect to which an LSAR
has been granted and become effective shall become immediately exercisable upon
the occurrence of any of the following events (each, a "Triggering Event"): (i)
the consummation by the Company of a reorganization, merger, or consolidation
after approval of any such transaction by shareholders, other than Section 16
Eligible Persons, holding at least the minimum number of shares necessary to
approve such transaction under the Company's Articles of Incorporation and
applicable law, (ii) the consummation by the Company of a sale of substantially
all its assets after approval of any such transaction by shareholders, other
than Section 16 Eligible Persons, holding at least the minimum number of shares
necessary to approve such transaction under the Company's Articles of
Incorporation and applicable law, or (iii) the acquisition by a single purchaser
or group of related purchasers of in excess of 51% of the issued and outstanding
shares of Common Stock from shareholders of the Company other than Section 16
Eligible Persons, in any case other than in a transaction in which the surviving
corporation or the purchaser is the Company or a Subsidiary of the Company
(other than a transaction in which the surviving corporation or the purchaser is
the Company or a Subsidiary of the Company but the capital stock of the Company
or a Subsidiary of the Company is converted into capital stock of any entity
other than the Company or any such Subsidiary) or an entity controlled by
Section 16 Eligible Persons.

                  (b) The LSARs shall provide that upon the occurrence of any
Triggering Event, the Optionee shall receive from the Company, for each LSAR, an
amount in cash equal to the amount by which the option exercise price per Share
of the option to which the LSAR relates is exceeded by the Fair Market Value of
the Shares issuable upon exercise of such option on the date such Triggering
Event occurs. When a Triggering Event occurs, the option to which the LSAR
relates will cease to be exercisable, but will be deemed to have been exercised
for purposes of determining the number of Shares for which options may be
granted hereunder.

                  (c) An LSAR shall be expressly subject to the following
additional requirements: (i) the LSAR shall expire no later than the expiration
of the underlying option; (ii) the LSAR shall be transferable only when the
underlying option is transferable, and under the same conditions; and (iii) a


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Triggering Event shall be deemed to have occurred only when the Fair Market
Value of the Shares subject to the underlying option exceeds the exercise price
of such option.

9.       EXERCISE RIGHTS UPON CEASING TO BE AN EMPLOYEE, OFFICER, CONSULTANT
         OR DIRECTOR

                  (a) If an Optionee becomes permanently and totally disabled,
he may exercise his option for up to one year after the date he ceases to be an
employee, officer or director of or a consultant to a Qualified Employer on
account of such disability, but in no event later than the date on which the
option would have expired if the Optionee had not become disabled. During such
period, the option may be exercised only to the extent that the Optionee was
entitled to do so at the date of disability and, to the extent the option is not
so exercised, it shall expire at the end of such period. For purposes of this
Section 9(a), an Optionee shall be deemed to be disabled if, in the
determination of the Board or the Committee, as the case may be, he is unable to
engage in any substantial gainful activity by reason of any medically
determinable physical or mental impairment which can be expected to result in
death or which has lasted or can be expected to last for a continuous period of
not less than 12 months.

                  (b) If an Optionee dies during a period in which he is
entitled to exercise an option (including the period referred to in subsection
(a) above), the option shall terminate one year after the date of death, but in
no event later than the date on which the option would have expired if the
Optionee had lived. During such period, the option may be exercised by the
Optionee's executor or administrator or by any person or persons who shall have
acquired the option directly from the Optionee by bequest or inheritance or by
reason of the death of the Optionee, but only to the extent that the Optionee
was entitled to do so at the date of death and, to the extent the option is not
so exercised, it shall expire at the end of such period.

                  (c) If an Optionee ceases to be an employee, officer or
director of or consultant to any and all Qualified Employers in circumstances
other than those described in subsections (a) or (b) above, he may exercise
options granted hereunder for a period not to exceed three months after the date
of such cessation, but in no event later than the date on which the option would
have expired if the Optionee had remained an employee, officer or director of or
consultant to a Qualified Employer. During such period, the option may be
exercised only to the extent that the Optionee was entitled to do so on the date
of cessation and, to the extent the option is not so exercised, it shall expire
at the end of such three-month period. This provision shall not apply if the
Optionee's employment or consultant relationship was terminated for "cause," or
if the officer or director was removed for "cause," which shall include theft,
falsification of records, fraud, embezzlement, gross negligence or willful
misconduct, causing a Qualified Employer to violate any federal, state, or local
law, or administrative regulation or ruling having the force and effect of law,
insubordination, conflict of interest, diversion of corporate opportunity, or
conduct that results in publicity that reflects unfavorably on a Qualified
Employer.

                  (d) For purposes of this section an Optionee who is an
employee shall not be treated as having ceased employment if (1) the Optionee is
on military, sick leave or other bona fide leave of absence (such as temporary
employment by the United States Government); and (2) the period of such leave
does not exceed 90 days, or, if longer, so long as the Optionee's right to
reemployment with a Qualified Employer is guaranteed by statute or by contract.
Where the period of leave exceeds 90 days and the Optionee's right to
reemployment is not guaranteed by statute or by contract, such Optionee shall be
deemed to have ceased being an employee on the 91st day of such leave.


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10.      ADDITIONAL REQUIREMENTS

                  Upon the exercise of an option granted hereunder the Board or
the Committee, as the case may be, may require the Optionee to deliver the
following:

                  (a) A written statement satisfactory to the Company or its
counsel that the Optionee is purchasing the Shares for investment and not with a
view toward their distribution or sale and will not sell or transfer any Shares
received upon the exercise of the option except in accordance with the
Securities Act of 1933 and applicable state securities laws; and

                  (b) Evidence reasonably satisfactory to the Company that at
the time of exercise the Optionee meets such other requirements as the Board or
the Committee, as the case may be, may determine.

11.      SHARES SUBJECT TO OPTION

                  The Shares issuable upon exercise of options granted hereunder
may be unissued shares or treasury shares, including shares bought on the open
market. The Company at all times during the term of this Plan shall reserve for
issuance the number of Shares issuable upon exercise of options granted
hereunder.

12.      COMPLIANCE WITH GOVERNMENTAL AND OTHER REGULATIONS

                  The Company will not be obligated to issue and sell the Shares
issued pursuant to options granted hereunder if, in the opinion of its counsel,
such issuance and sale would violate any applicable federal or state securities
laws. The Company will seek to obtain from each regulatory commission or agency
having jurisdiction such authority as may be required to issue and sell Shares
issuable upon exercise of any option granted hereunder. Inability of the Company
to obtain from any such regulatory commission or agency authority which counsel
for the Company deems necessary for the lawful issuance and sale of Shares upon
exercise of an option granted hereunder shall relieve the Company from any
liability for failure to issue and sell such Shares until the time when such
authority is obtained or is obtainable.

13.      NONASSIGNMENT OF OPTIONS

                  Except as otherwise provided in Paragraph 7(c) hereof, any
option granted hereunder and the rights and privileges conferred hereby shall
not be transferred, assigned, pledged or hypothecated in any way (whether by
operation of law otherwise) and shall not be subject to execution, attachment,
or similar process. Upon any attempt to transfer, assign, pledge, hypothecate,
or otherwise dispose of such option, right or privilege contrary to the
provisions hereof, or upon the levy or any attachment or similar process upon
the rights and privileges conferred hereby, such option and the rights and
privileges conferred hereby shall immediately terminate.

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14.      RIGHTS OF OPTIONEE IN SHARES

                  Neither any Optionee nor the legal representatives, heirs,
legatees, or distributees of any Optionee, shall be deemed to be the holder of,
or to have any rights of a holder with respect to, any Shares issuable upon
exercise of an option granted hereunder unless and until such Shares are issued
to him or them.

15.      DELIVERY OF SHARES ISSUED PURSUANT TO OPTION

                  Subject to the other terms and conditions of this Plan, upon
the exercise of an option granted hereunder, the Company shall sell to the
Optionee the Shares with respect to which the option has been exercised.

16.      WITHHOLDING OF APPLICABLE TAXES

                  A Qualified Employer shall have the right to reduce the number
of Shares otherwise required to be issued upon exercise of an option granted
hereunder by an amount which would have a Fair Market Value on the date of such
exercise equal to all Federal, state, city, or other taxes as shall be required
to be withheld by the Qualified Employer pursuant to any statute or other
governmental regulation or ruling. In connection with all such withholding
obligations (whether arising in connection with an exercise of an option granted
hereunder or in connection with a disqualifying disposition (as defined in
Section 421(b) of the Code) of stock obtained upon exercise of an Incentive
Stock Option granted hereunder), a Qualified Employer may make any other
arrangements consistent with this Plan as it may deem appropriate, including but
not limited to withholding such taxes from cash compensation payable to the
Optionee and requiring the Optionee to remit cash in an amount equal to the
taxes required to be withheld.

17.      PLAN AND OPTIONS NOT TO AFFECT EMPLOYMENT OR OTHER AFFILIATION

                  Neither this Plan nor any options granted hereunder shall
confer upon any Eligible Person any right to continue employment or affiliation
with any Qualified Employer.

18.      AMENDMENT OF PLAN

                  The Board may make such amendments to this Plan as it deems
necessary or advisable, provided that, without further action by the
shareholders of the Company, no such amendment shall (a) materially increase the
maximum number of Shares for which options may be granted, except as provided in
Section 3, (b) materially increase the benefits under the Plan, or (c)
materially modify the requirements as to eligibility for participation in the
Plan, and in no event shall any such amendment impair the rights of any
participant under any option theretofore granted.

19.      NOTICES

                  Any notice required or permitted hereunder shall be
sufficiently given only if sent by registered or certified mail, postage
prepaid, addressed to the Company, 26 Landsdowne Street, Cambridge, MA 02139 and
to the Optionee at the address on file with the Company at the time of grant


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hereunder, or to such other address as either party may hereafter designate in
writing by notice similarly given by one party to the other.

20.      SUCCESSORS

                  The Plan shall be binding upon and inure to the benefit of any
successor, successors or assigns of the Company.

21.      SEVERABILITY

                  If any part of this Plan shall be determined to be invalid or
void in any respect, such determination shall not affect, impair, invalidate, or
nullify the remaining provisions of this Plan which shall continue in full force
and effect.

22.      TERMINATION OF THE PLAN

                  The Board may terminate this Plan at any time; otherwise this
Plan shall terminate September 19, 2000. Termination of the Plan shall not
deprive Optionees of their rights under previously granted options.

23.      GRANTS OF OPTIONS AFTER AMENDMENTS TO PLAN

                  The grant of any option hereunder on or after the date the
Board has adopted any amendments to the Plan that require shareholder approval
pursuant to Section 18 hereof, is subject to the express condition that within
12 months after such date, the holders of a majority of the outstanding shares
of Common Stock present, or represented, and entitled to vote thereon shall have
approved the Plan at a duly held meeting of the shareholders of the Company.

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