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                                                                     EXHIBIT 4.3

                                SIPEX CORPORATION

            AMENDED AND RESTATED 2002 NONSTATUTORY STOCK OPTION PLAN

      1.    Purposes of the Plan. The purposes of this Nonstatutory Stock Option
Plan are:

            -     to attract and retain the best available personnel for
                  positions of substantial responsibility,

            -     to provide additional incentive to Employees, Directors and
                  Consultants, and

            -     to promote the success of the Company's business.

            Options granted under the Plan will be Nonstatutory Stock Options.

      2.    Definitions. As used herein, the following definitions shall apply:

            (a)   "Administrator" means the Board or any of its Committees as
shall be administering the Plan, in accordance with Section 4 of the Plan.

            (b)   "Applicable Laws" means the requirements relating to the
administration of stock option plans under U.S. state corporate laws, U.S.
federal and state securities laws, the Code, any stock exchange or quotation
system on which the Common Stock is listed or quoted and the applicable laws of
any foreign country or jurisdiction where Options are, or will be, granted under
the Plan.

            (c)   "Board" means the Board of Directors of the Company.

            (d)   "Code" means the Internal Revenue Code of 1986, as amended.

            (e)   "Committee" means a committee of Directors appointed by the
Board in accordance with Section 4 of the Plan.

            (f)   "Common Stock" means the Common Stock of the Company.

            (g)   "Company" means Sipex Corporation, a Massachusetts
corporation.

            (h)   "Consultant" means any person, including an advisor, engaged
by the Company or a Parent or Subsidiary to render services to such entity.

            (i)   "Director" means a member of the Board.

            (j)   "Disability" means total and permanent disability as defined
in Section 22(e)(3) of the Code.

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            (k)   "Employee" means any person, including Officers, employed by
the Company or any Parent or Subsidiary of the Company. A Service Provider shall
not cease to be an Employee in the case of (i) any leave of absence approved by
the Company or (ii) transfers between locations of the Company or between the
Company, its Parent, any Subsidiary, or any successor. Neither service as a
Director nor payment of a director's fee by the Company shall be sufficient to
constitute "employment" by the Company.

            (l)   "Exchange Act" means the Securities Exchange Act of 1934, as
amended.

            (m)   "Fair Market Value" means, as of any date, the value of Common
Stock determined as follows:

                  (ii)  If the Common Stock is listed on any established stock
exchange or a national market system, including without limitation the Nasdaq
National Market or The Nasdaq SmallCap Market of The Nasdaq Stock Market, its
Fair Market Value shall be the closing sales price for such stock (or the
closing bid, if no sales were reported) as quoted on such exchange or system on
the date of grant, or if unavailable, for the last market trading day prior to
date of grant, as reported in The Wall Street Journal or such other source as
the Administrator deems reliable;

                  (iii) If the Common Stock is regularly quoted by a recognized
securities dealer but selling prices are not reported, the Fair Market Value of
a Share of Common Stock shall be the mean between the high bid and low asked
prices for the Common Stock on the date of grant, or if unavailable, on the last
market trading day prior to the date of grant, as reported in The Wall Street
Journal or such other source as the Administrator deems reliable;

                  (iv)  In the absence of an established market for the Common
Stock, the Fair Market Value shall be determined in good faith by the
Administrator.

            (n)   "Notice of Grant" means a written or electronic notice
evidencing certain terms and conditions of an individual Option grant. The
Notice of Grant is part of the Option Agreement.

            (o)   "Officer" means any Employee who holds office at the level of
Vice President or above.

            (p)   "Option" means a nonstatutory stock option granted pursuant to
the Plan, that is not intended to qualify as an incentive stock option within
the meaning of Section 422 of the Code and the regulations promulgated
thereunder.

            (q)   "Option Agreement" means an agreement between the Company and
an Optionee evidencing the terms and conditions of an individual Option grant.
The Option Agreement is subject to the terms and conditions of the Plan.

            (r)   "Option Exchange Program" means a program whereby outstanding
options are surrendered in exchange for options with a lower exercise price.

            (s)   "Optioned Stock" means the Common Stock subject to an Option.

            (t)   "Optionee" means the holder of an outstanding Option granted
under the Plan.

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            (u)   "Parent" means a "parent corporation," whether now or
hereafter existing, as defined in Section 424(e) of the Code.

            (v)   "Plan" means this 2002 Nonstatutory Stock Option Plan.

            (w)   "Service Provider" means an Employee including an Officer,
Consultant or Director.

            (x)   "Share" means a share of the Common Stock, as adjusted in
accordance with Section 12 of the Plan.

            (y)   "Subsidiary" means a "subsidiary corporation," whether now or
hereafter existing, as defined in Section 424(f) of the Code.

      3.    Stock Subject to the Plan. Subject to the provisions of Section 12
of the Plan, the maximum aggregate number of Shares which may be optioned and
sold under the Plan is One Million (1,000,000) Shares. The Shares may be
authorized, but unissued, or reacquired Common Stock.

            If an Option expires or becomes unexercisable without having been
exercised in full, or is surrendered pursuant to an Option Exchange Program, the
unpurchased Shares which were subject thereto shall become available for future
grant or sale under the Plan (unless the Plan has terminated).

      4.    Administration of the Plan.

            (a)   Administration. The Plan shall be administered by (i) the
Board or (ii) a Committee, which committee shall be constituted to satisfy
Applicable Laws.

            (b)   Powers of the Administrator. Subject to the provisions of the
Plan, and in the case of a Committee, subject to the specific duties delegated
by the Board to such Committee, the Administrator shall have the authority, in
its discretion:

                  (i)   to determine the Fair Market Value of the Common Stock;

                  (ii)  to select the Service Providers to whom Options may be
granted hereunder;

                  (iii) to determine whether and to what extent Options are
granted hereunder;

                  (iv)  to determine the number of shares of Common Stock to be
covered by each Option granted hereunder;

                  (v)   to approve forms of agreement for use under the Plan;

                  (vi)  to determine the terms and conditions, not inconsistent
with the terms of the Plan, of any award granted hereunder. Such terms and
conditions include, but are not limited to, the exercise price, the time or
times when Options may be exercised (which may be based on performance
criteria), any vesting acceleration or waiver of forfeiture restrictions, and
any restriction or limitation regarding any Option or the shares of Common Stock
relating thereto, based in each case on such factors as the Administrator, in
its sole discretion, shall determine;

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                  (vii)  to reduce the exercise price of any Option to the then
current Fair Market Value if the Fair Market Value of the Common Stock covered
by such Option shall have declined since the date the Option was granted;

                  (viii) to institute an Option Exchange Program;

                  (ix)   to construe and interpret the terms of the Plan and
awards granted pursuant to the Plan;

                  (x)    to prescribe, amend and rescind rules and regulations
relating to the Plan, including rules and regulations relating to sub-plans
established for the purpose of qualifying for preferred tax treatment under
foreign tax laws;

                  (xi)   to modify or amend each Option (subject to Section
14(b) of the Plan), including the discretionary authority to extend the
post-termination exercisability period of Options longer than is otherwise
provided for in the Plan;

                  (xii)  to authorize any person to execute on behalf of the
Company any instrument required to effect the grant of an Option previously
granted by the Administrator;

                  (xiii)  to determine the terms and restrictions applicable to
Options;

                  (xiv)  to allow Optionees to satisfy withholding tax
obligations by electing to have the Company withhold from the Shares to be
issued upon exercise of an Option that number of Shares having a Fair Market
Value equal to the amount required to be withheld. The Fair Market Value of the
Shares to be withheld shall be determined on the date that the amount of tax to
be withheld is to be determined. All elections by an Optionee to have Shares
withheld for this purpose shall be made in such form and under such conditions
as the Administrator may deem necessary or advisable; and

                  (xv)  to make all other determinations deemed necessary or
advisable for administering the Plan.

            (c)   Effect of Administrator's Decision. The Administrator's
decisions, determinations and interpretations shall be final and binding on all
Optionees and any other holders of Options.

      5.    Eligibility. Options may be granted to Service Providers.

      6.    Limitation. Neither the Plan nor any Option shall confer upon an
Optionee any right with respect to continuing the Optionee's relationship as a
Service Provider with the Company, nor shall they interfere in any way with the
Optionee's right or the Company's right to terminate such relationship at any
time, with or without cause.

      7.    Term of Plan. The Plan shall become effective upon its adoption by
the Board. It shall continue in effect for ten (10) years, unless sooner
terminated under Section 14 of the Plan.

      8.    Term of Option. The term of each Option shall be stated in the
Option Agreement.

      9.    Option Exercise Price and Consideration.

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            (a)   Exercise Price. The per share exercise price for the Shares to
be issued pursuant to exercise of an Option shall be determined by the
Administrator.

            (b)   Waiting Period and Exercise Dates. At the time an Option is
granted, the Administrator shall fix the period within which the Option may be
exercised and shall determine any conditions which must be satisfied before the
Option may be exercised.

            (c)   Form of Consideration. The Administrator shall determine the
acceptable form of consideration for exercising an Option, including the method
of payment. Such consideration may consist entirely of:

                  (i)   cash;

                  (ii)  check;

                  (iii) promissory note;

                  (iv)  other Shares which (A) in the case of Shares acquired
upon exercise of an option, have been owned by the Optionee for more than six
months on the date of surrender, and (B) have a Fair Market Value on the date of
surrender equal to the aggregate exercise price of the Shares as to which said
Option shall be exercised;

                  (v)   consideration received by the Company under a cashless
exercise program implemented by the Company in connection with the Plan;

                  (vi)  a reduction in the amount of any Company liability to
the Optionee, including any liability attributable to the Optionee's
participation in any Company-sponsored deferred compensation program or
arrangement;

                  (vii) such other consideration and method of payment for the
issuance of Shares to the extent permitted by Applicable Laws; or

                  (viii) any combination of the foregoing methods of payment.

      10.   Exercise of Option.

            (a)   Procedure for Exercise; Rights as a Shareholder. Any Option
granted hereunder shall be exercisable according to the terms of the Plan and at
such times and under such conditions as determined by the Administrator and set
forth in the Option Agreement. An Option may not be exercised for a fraction of
a Share.

                  An Option shall be deemed exercised when the Company receives:
(i) written or electronic notice of exercise (in accordance with the Option
Agreement) from the person entitled to exercise the Option, and (ii) full
payment for the Shares with respect to which the Option is exercised. Full
payment may consist of any consideration and method of payment authorized by the
Administrator and permitted by the Option Agreement and the Plan. Shares issued
upon exercise of an Option shall be issued in the name of the Optionee or, if
requested by the Optionee, in the name of the Optionee and his or her spouse.
Until the Shares are issued (as evidenced by the appropriate entry on the books
of the Company or of a duly authorized transfer agent of the Company), no right
to vote or receive dividends or any other rights as a shareholder shall

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exist with respect to the Optioned Stock, notwithstanding the exercise of the
Option. The Company shall issue (or cause to be issued) such Shares promptly
after the Option is exercised. No adjustment will be made for a dividend or
other right for which the record date is prior to the date the Shares are
issued, except as provided in Section 12 of the Plan.

                  Exercising an Option in any manner shall decrease the number
of Shares thereafter available, both for purposes of the Plan and for sale under
the Option, by the number of Shares as to which the Option is exercised.

            (b)   Termination of Relationship as a Service Provider. If an
Optionee ceases to be a Service Provider, other than upon the Optionee's death
or Disability, the Optionee may exercise his or her Option, but only within such
period of time as is specified in the Option Agreement, and only to the extent
that the Option is vested on the date of termination (but in no event later than
the expiration of the term of such Option as set forth in the Option Agreement).
In the absence of a specified time in the Option Agreement, the Option shall
remain exercisable for three (3) months following the Optionee's termination.
If, on the date of termination, the Optionee is not vested as to his or her
entire Option, the Shares covered by the unvested portion of the Option shall
revert to the Plan. If, after termination, the Optionee does not exercise his or
her Option within the time specified by the Administrator, the Option shall
terminate, and the Shares covered by such Option shall revert to the Plan.

            (c)   Disability of Optionee. If an Optionee ceases to be a Service
Provider as a result of the Optionee's Disability, the Optionee may exercise his
or her Option within such period of time as is specified in the Option
Agreement, to the extent the Option is vested on the date of termination (but in
no event later than the expiration of the term of such Option as set forth in
the Option Agreement). In the absence of a specified time in the Option
Agreement, the Option shall remain exercisable for six (6) months following the
Optionee's termination. If, on the date of termination, the Optionee is not
vested as to his or her entire Option, the Shares covered by the unvested
portion of the Option shall revert to the Plan. If, after termination, the
Optionee does not exercise his or her Option within the time specified herein,
the Option shall terminate, and the Shares covered by such Option shall revert
to the Plan.

            (d)   Death of Optionee. If an optionee dies while a Service
Provider, the Option may be exercised to the extent that the Option is vested on
the date of death within such period of time as is specified in the Option
Agreement (but in no event later than he expiration of the term of such Option
as set forth in the Notice of Grant), by the Optionee's designated beneficiary,
provided such beneficiary has been designated prior to Optionee's death in a
form acceptable to the Administrator. If no such beneficiary has been designated
by the Optionee, then such Option may be exercised within such period of time as
is specified in the Option Agreement (but in no event later than he expiration
of the term of such Option as set forth in the Notice of Grant) by the personal
representative of the Optionee's estate or by the person(s) to whom the Option
is transferred pursuant to the Optionee's will or in accordance with the laws of
descent and distribution. In the absence of a specified time in the Option
Agreement the Option shall remain exercisable for six (6) months following the
optionees termination. If, at the time of death, the Optionee is not vested as
to his or her entire Option, the Shares covered by the unvested portion of the
Option shall immediately revert to the Plan. If the Option is not so exercised
within the time specified herein, the option shall terminate, and the Shares
covered by such Option shall revert to the Plan.

            (e)   Buyout Provisions. The Administrator may at any time offer to
buy out for a payment in cash or Shares, an Option previously granted based on
such terms and conditions as the Administrator shall establish and communicate
to the Optionee at the time that such offer is made.

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      11.   Non-Transferability of Options. Unless determined otherwise by the
Administrator, an Option may not be sold, pledged, assigned, hypothecated,
transferred, or disposed of in any manner other than by the Optionee's
designated beneficiary in accordance with Section 10(d) of the Plan, by will or
by the laws of descent or distribution and may be exercised, during the lifetime
of the Optionee, or by the Optionee. If the Administrator makes an Option
transferable, such Option shall contain such additional terms and conditions as
the Administrator deems appropriate.

      12.   Adjustments Upon Changes in Capitalization, Dissolution, Merger or
Asset Sale.

            (a)   Changes in Capitalization. Subject to any required action by
the shareholders of the Company, the number of shares of Common Stock covered by
each outstanding Option, and the number of shares of Common Stock which have
been authorized for issuance under the Plan but as to which no Options have yet
been granted or which have been returned to the Plan upon cancellation or
expiration of an Option, as well as the price per share of Common Stock covered
by each such outstanding Option, shall be proportionately adjusted for any
increase or decrease in the number of issued shares of Common Stock resulting
from a stock split, reverse stock split, stock dividend, combination or
reclassification of the Common Stock, or any other increase or decrease in the
number of issued shares of Common Stock effected without receipt of
consideration by the Company; provided, however, that conversion of any
convertible securities of the Company shall not be deemed to have been "effected
without receipt of consideration." Such adjustment shall be made by the Board,
whose determination in that respect shall be final, binding and conclusive.
Except as expressly provided herein, no issuance by the Company of shares of
stock of any class, or securities convertible into shares of stock of any class,
shall affect, and no adjustment by reason thereof shall be made with respect to,
the number or price of shares of Common Stock subject to an Option.

            (b)   Dissolution or Liquidation. In the event of the proposed
dissolution or liquidation of the Company, the Administrator shall notify each
Optionee as soon as practicable prior to the effective date of such proposed
transaction. The Administrator in its discretion may provide for an Optionee to
have the right to exercise his or her Option within a specified number of days
of the date of such notice as to all of the Optioned Stock covered thereby,
including, in the discretion of the Administrator, Shares as to which the Option
would not otherwise be exercisable. To the extent it has not been previously
exercised, an Option will terminate immediately prior to the consummation of
such proposed action.

            (c)   Merger or Asset Sale. In the event of a merger of the Company
with or into another corporation or other reorganization in which the holders of
the outstanding voting stock of the Company immediately preceding the
consummation of such event, shall, immediately following such event, hold, as a
group, less than a majority of the voting securities of the surviving or
successor entity, or the sale of substantially all of the assets of the Company
(each, an "Acquisition"), the committee or the board of directors of any entity
assuming the obligations of the Company hereunder (the "Successor Board"),
shall, with respect to each outstanding Option, either (i) make appropriate
provision for the continuation of such Options by substituting on an equitable
basis for the Shares then subject to such Options either (a) the consideration
payable with respect to the outstanding Shares in connection with the
Acquisition; (b) shares of stock of the surviving or successor corporation or
(c) such other securities as the Successor Board deems appropriate, the fair
market value of which shall not materially exceed the fair market value of the
Shares subject to such Options immediately preceding the Acquisition; or (ii)
upon written notice to the Optionees, provide that all Options must be
exercised, to the extent then exercisable or to be exercisable as a result of
the Acquisition, within a specified number of days of the date of such notice,
and the Option shall terminate upon the expiration of such period; or (iii)
terminate all Options in exchange for a cash payment equal to the excess

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of the fair market value of the Shares subject to such Options (to the extent
then exercisable or to be exercisable as a result of the Acquisition) over the
exercise price thereof.

            (d)   Recapitalization or Reorganization. In the event of a
recapitalization or reorganization of the Company (other than a transaction
described in Section 12(c), above) pursuant to which securities of the Company
or of another corporation are issued with respect to the outstanding Shares, an
Optionee upon exercising an Option shall be entitled to receive, in exchange for
the exercise price paid, the securities Optionee would have received if Optionee
had exercised such Option prior to such recapitalization or reorganization.

      13.   Date of Grant. The date of grant of an Option shall be, for all
purposes, the date on which the Administrator makes the determination granting
such Option, or such other later date as is determined by the Administrator.
Notice of the determination shall be provided to each Optionee within a
reasonable time after the date of such grant.

      14.   Amendment and Termination of the Plan.

            (a)   Amendment and Termination. The Board may at any time amend,
alter, suspend or terminate the Plan.

            (b)   Effect of Amendment or Termination. No amendment, alteration,
suspension or termination of the Plan shall impair the rights of any Optionee,
unless mutually agreed otherwise between the Optionee and the Administrator,
which agreement must be in writing and signed by the Optionee and the Company.
Termination of the Plan shall not affect the Administrator's ability to exercise
the powers granted to it hereunder with respect to options granted under the
Plan prior to the date of such termination.

      15.   Conditions Upon Issuance of Shares.

            (a)   Legal Compliance. Shares shall not be issued pursuant to the
exercise of an Option unless the exercise of such Option and the issuance and
delivery of such Shares shall comply with Applicable Laws and shall be further
subject to the approval of counsel for the Company with respect to such
compliance.

            (b)   Investment Representations. As a condition to the exercise of
an Option the Company may require the person exercising such Option to represent
and warrant at the time of any such exercise that the Shares are being purchased
only for investment and without any present intention to sell or distribute such
Shares if, in the opinion of counsel for the Company, such a representation is
required.

      16.   Inability to Obtain Authority. The inability of the Company to
obtain authority from any regulatory body having jurisdiction, which authority
is deemed by the Company's counsel to be necessary to the lawful issuance and
sale of any Shares hereunder, shall relieve the Company of any liability in
respect of the failure to issue or sell such Shares as to which such requisite
authority shall not have been obtained.

      17.   Reservation of Shares. The Company, during the term of this Plan,
will at all times reserve and keep available such number of Shares as shall be
sufficient to satisfy the requirements of the Plan.