<PAGE>

                                                                     EXHIBIT 4.4


                                SIPEX CORPORATION

                       2002 NONSTATUTORY STOCK OPTION PLAN

                             STOCK OPTION AGREEMENT

      Unless otherwise defined herein, the terms defined in the Plan shall have
the same defined meanings in this Option Agreement.
I.    NOTICE OF STOCK OPTION GRANT

      [OPTIONEE'S NAME AND ADDRESS]

      You have been granted an option to purchase Common Stock of the Company,
subject to the terms and conditions of the Plan and this Option Agreement, as
follows:

      Grant Number
                                    ------------------------------

      Date of Grant
                                    ------------------------------

      Vesting Commencement Date
                                    ------------------------------

      Exercise Price per Share      $
                                     -----------------------------

      Total Number of Shares Granted
                                     -----------------------------

      Total Exercise Price          $
                                     -----------------------------

      Type of Option:               Nonstatutory Stock Option

      Term/Expiration Date:
                                    ------------------------------

      Vesting Schedule:

      Subject to the Optionee continuing to be a Service Provider on such dates,
this Option shall vest and become exercisable in accordance with the following
schedule:

      [VESTING SCHEDULE]

      Termination Period:

      This Option may be exercised for [THREE (3) MONTHS] after Optionee ceases
to be a Service Provider. Upon the death or Disability of the Optionee, this
Option may be exercised for [SIX (6) MONTHS] after Optionee ceases to be a
Service Provider. In no event shall this Option be exercised later than the
Term/Expiration Date as provided above.
<PAGE>
II.   AGREEMENT

         (1) Grant of Option. The Plan Administrator of the Company hereby
grants to the Optionee named in the Notice of Grant attached as Part I of this
Agreement (the "Optionee") an option (the "Option") to purchase the number of
Shares, as set forth in the Notice of Grant, at the exercise price per share set
forth in the Notice of Grant (the "Exercise Price"), subject to the terms and
conditions of the Plan, which is incorporated herein by reference. Subject to
Section 14(b) of the Plan, in the event of a conflict between the terms and
conditions of the Plan and the terms and conditions of this Option Agreement,
the terms and conditions of the Plan shall prevail.

         (2) Exercise of Option.

                  (a)      Right to Exercise. This Option is exercisable during
                           its term in accordance with the Vesting Schedule set
                           out in the Notice of Grant and the applicable
                           provisions of the Plan and this Option Agreement.

                  (b)      Method of Exercise. This Option is exercisable by
                           delivery of an exercise notice, in the form attached
                           as Exhibit A (the "Exercise Notice"), which shall
                           state the election to exercise the Option, the number
                           of Shares in respect of which the Option is being
                           exercised (the "Exercised Shares"), and such other
                           representations and agreements as may be required by
                           the Company pursuant to the provisions of the Plan.
                           The Exercise Notice shall be completed by the
                           Optionee and delivered to the Stock Option
                           Administrator. The Exercise Notice shall be
                           accompanied by payment of the aggregate Exercise
                           Price as to all Exercised Shares. This Option shall
                           be deemed to be exercised upon receipt by the Company
                           of such fully executed Exercise Notice accompanied by
                           such aggregate Exercise Price.

                           No Shares shall be issued pursuant to the exercise of
                           this Option unless such issuance and exercise
                           complies with Applicable Laws. Assuming such
                           compliance, for income tax purposes the Exercised
                           Shares shall be considered transferred to the
                           Optionee on the date the Option is exercised with
                           respect to such Exercised Shares.

         (3) Method of Payment. Payment of the aggregate Exercise Price shall be
by any of the following, or a combination thereof, at the election of the
Optionee:

                  (a)      cash;

                  (b)      check;

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

                  (d)      surrender of other Shares which (i) in the case of
                           Shares acquired upon exercise of an option, have been
                           owned by the Optionee for more than six (6) months on
                           the date of surrender, AND (ii) have a Fair Market
                           Value on the date of surrender equal to the aggregate
                           Exercise Price of the Exercised Shares.


                                      -2-
<PAGE>
         (4) Non-Transferability of Option. This Option may not be transferred
in any manner otherwise than by will or by the laws of descent or distribution
and may be exercised during the lifetime of Optionee only by the Optionee. The
terms of the Plan and this Option Agreement shall be binding upon the executors,
administrators, heirs, successors and assigns of the Optionee.

         (5) Term of Option. This Option may be exercised only within the term
set out in the Notice of Grant, and may be exercised during such term only in
accordance with the Plan and the terms of this Option Agreement.

         (6) Tax Consequences. Some of the federal tax consequences relating to
this Option, as of the date of this Option, are set forth below. THIS SUMMARY IS
NECESSARILY INCOMPLETE, AND THE TAX LAWS AND REGULATIONS ARE SUBJECT TO CHANGE.
THE OPTIONEE SHOULD CONSULT A TAX ADVISER BEFORE EXERCISING THIS OPTION OR
DISPOSING OF THE SHARES.

                  (a)      Exercising the Option. The Optionee may incur regular
                           federal income tax liability upon exercise of a
                           nonstatutory stock option. The Optionee will be
                           treated as having received compensation income
                           (taxable at ordinary income tax rates) equal to the
                           excess, if any, of the Fair Market Value of the
                           Exercised Shares on the date of exercise over their
                           aggregate Exercise Price. If the Optionee is an
                           Employee or a former Employee, the Company will be
                           required to withhold from his or her compensation or
                           collect from Optionee and pay to the applicable
                           taxing authorities an amount in cash equal to a
                           percentage of this compensation income at the time of
                           exercise, and may refuse to honor the exercise and
                           refuse to deliver Shares if such withholding amounts
                           are not delivered at the time of exercise.

                  (b)      Disposition of Shares. If the Optionee holds
                           nonstatutory stock option Shares for at least one
                           year, any gain realized on disposition of the Shares
                           will be treated as long-term capital gain for federal
                           income tax purposes.

         (7) Entire Agreement; Governing Law. The Plan is incorporated herein by
reference. The Plan and this Option Agreement constitute the entire agreement of
the parties with respect to the subject matter hereof and supersede in their
entirety all prior undertakings and agreements of the Company and Optionee with
respect to the subject matter hereof, and may not be modified adversely to the
Optionee's interest except by means of a writing signed by the Company and
Optionee. This agreement is governed by the internal substantive laws, but not
the choice of law rules, of Massachusetts.

         (8) NO GUARANTEE OF CONTINUED SERVICE. OPTIONEE ACKNOWLEDGES AND AGREES
THAT THE VESTING OF SHARES PURSUANT TO THE VESTING SCHEDULE HEREOF IS EARNED
ONLY BY CONTINUING AS A SERVICE PROVIDER AT THE WILL OF THE COMPANY (AND NOT
THROUGH THE ACT OF BEING HIRED, BEING GRANTED AN OPTION OR PURCHASING SHARES
HEREUNDER). OPTIONEE FURTHER ACKNOWLEDGES AND AGREES THAT THIS AGREEMENT, THE
TRANSACTIONS CONTEMPLATED HEREUNDER AND THE VESTING SCHEDULE SET FORTH HEREIN DO
NOT CONSTITUTE AN EXPRESS OR IMPLIED PROMISE OF CONTINUED ENGAGEMENT AS A
SERVICE PROVIDER FOR THE VESTING PERIOD, FOR ANY PERIOD, OR AT ALL, AND SHALL
NOT INTERFERE WITH OPTIONEE'S RIGHT OR THE COMPANY'S RIGHT TO TERMINATE
OPTIONEE'S RELATIONSHIP AS A SERVICE PROVIDER AT ANY TIME, WITH OR WITHOUT
CAUSE.


                                      -3-
<PAGE>
      By your signature and the signature of the Company's representative below,
you and the Company agree that this Option is granted under and governed by the
terms and conditions of the Plan and this Option Agreement. Optionee has
reviewed the Plan and this Option Agreement in their entirety, has had an
opportunity to obtain the advice of counsel prior to executing this Option
Agreement and fully understands all provisions of the Plan and Option Agreement.
Optionee hereby agrees to accept as binding, conclusive and final all decisions
or interpretations of the Administrator upon any questions relating to the Plan
and Option Agreement. Optionee further agrees to notify the Company upon any
change in the residence address indicated below.

OPTIONEE                                  SIPEX CORPORATION

------------------------------------         ----------------------------------
Signature                                 By

------------------------------------         ----------------------------------
Print Name                                Title

------------------------------------
Residence Address

------------------------------------


                                      -4-
<PAGE>
                                    EXHIBIT A



                                SIPEX CORPORATION

                       2002 NONSTATUTORY STOCK OPTION PLAN

                                 EXERCISE NOTICE



Sipex Corporation
22 Linnell Circle
Billerica, Massachusetts 01821

Attention: Stock Option Administrator

         1. Exercise of Option. Effective as of today, ________________, _____,
the undersigned ("Purchaser") hereby elects to purchase ______________ shares
(the "Shares") of the Common Stock of Sipex Corporation (the "Company") under
and pursuant to the 2002 Nonstatutory Stock Option Plan (the "Plan") and the
Stock Option Agreement dated, _________, ___ (the "Option Agreement"). The
purchase price for the Shares shall be $_____________, as required by the Option
Agreement.

         2. Delivery of Payment. Purchaser herewith delivers to the Company the
full purchase price for the Shares.

         3. Representations of Purchaser. Purchaser acknowledges that Purchaser
has received, read and understood the Plan and the Option Agreement and agrees
to abide by and be bound by their terms and conditions.

         4. Rights as Shareholder. Until the issuance (as evidenced by the
appropriate entry on the books of the Company or of a duly authorized transfer
agent of the Company) of the Shares, no right to vote or receive dividends or
any other rights as a shareholder shall exist with respect to the Optioned
Stock, notwithstanding the exercise of the Option. The Shares so acquired shall
be issued to the Optionee as soon as practicable after exercise of the Option.
No adjustment will be made for a dividend or other right for which the record
date is prior to the date of issuance, except as provided in Section 12 of the
Plan.

         5. Tax Consultation. Purchaser understands that Purchaser may suffer
adverse tax consequences as a result of Purchaser's purchase or disposition of
the Shares. Purchaser represents that Purchaser has consulted with any tax
consultants Purchaser deems advisable in connection with the purchase or
disposition of the Shares and that Purchaser is not relying on the Company for
any tax advice.

         6. Entire Agreement; Governing Law. The Plan and Option Agreement are
incorporated herein by reference. This Agreement, the Plan and the Option
Agreement constitute the entire agreement of the parties with respect to the
subject matter hereof and supersede in their entirety all prior undertakings and
agreements of the Company and Purchaser with respect to the subject matter
hereof, and may not be modified adversely to the Purchaser's interest except by
means of a writing signed by the Company and Purchaser. This agreement is
governed by the internal substantive laws, but not the choice of law rules, of
Massachusetts.
<PAGE>
Submitted by:                             Accepted by:

PURCHASER                                 SIPEX CORPORATION

------------------------------------      ----------------------------------
Signature                                 By

------------------------------------      ----------------------------------
Print Name                                Title


                                          -------------------------------------
                                          Date Received

Address:                                  Address:  22 Linnell Circle
-------  ---------------------------      -------

                                              Billerica, Massachusetts 01821
         ---------------------------

         ---------------------------


                                      -2-