<PAGE>   1
                                                                  EXHIBIT 10.146


NEITHER THESE SECURITIES NOR THE SECURITIES INTO WHICH THESE SECURITIES ARE
EXERCISABLE HAVE BEEN REGISTERED WITH THE SECURITIES AND EXCHANGE COMMISSION OR
THE SECURITIES COMMISSION OF ANY STATE IN RELIANCE UPON AN EXEMPTION FROM
REGISTRATION UNDER SECURITIES ACT OF 1933, AS AMENDED (THE "SECURITIES ACT"),
AND, ACCORDINGLY, MAY NOT BE OFFERED OR SOLD EXCEPT PURSUANT TO AN EFFECTIVE
REGISTRATION STATEMENT UNDER THE SECURITIES ACT OR PURSUANT TO AN AVAILABLE
EXEMPTION FROM THE REGISTRATION REQUIREMENTS THEREUNDER AND IN COMPLIANCE WITH
APPLICABLE STATE SECURITIES OR BLUE SKY LAWS.



                                   ECOGEN INC.

                                     WARRANT

                               Dated: May 12, 1999


         Ecogen Inc., a Delaware corporation (the "Company"), hereby certifies
that, for value received, KA Investments LDC, or its registered assigns
("Holder"), is entitled, subject to the terms set forth below, to purchase from
the Company up to a total of 120,000 shares of Common Stock, $.01 par value per
share (the "Common Stock"), of the Company (each such share, a "Warrant Share"
and all such shares, the "Warrant Shares") at an exercise price equal to $3.98
per share (as adjusted from time to time as provided in Section 11, the
"Exercise Price"), at any time and from time to time from and after the date
hereof and through and including May 12, 2004 (the "Expiration Date"), and
subject to the following terms and conditions:

         1. Registration of Warrant. The Company shall register this Warrant,
upon records to be maintained by the Company for that purpose (the "Warrant
Register"), in the name of the record Holder hereof from time to time. The
Company may deem and treat the registered Holder of this Warrant as the absolute
owner hereof for the purpose of any exercise hereof or any distribution to the
Holder, and for all other purposes, and the Company shall not be affected by
notice to the contrary.

         2. Registration of Transfers and Exchanges.

                  (a) The Company shall register the transfer of any portion of
this Warrant in the Warrant Register, upon surrender of this Warrant, with the
Form of Assignment attached



<PAGE>   2

hereto duly completed and signed, to the Transfer Agent or to the Company at the
office specified in or pursuant to Section 3(b). Upon any such registration or
transfer, a new warrant to purchase Common Stock, in substantially the form of
this Warrant (any such new warrant, a "New Warrant"), evidencing the portion of
this Warrant so transferred shall be issued to the transferee and a New Warrant
evidencing the remaining portion of this Warrant not so transferred, if any,
shall be issued to the transferring Holder. The acceptance of the New Warrant by
the transferee thereof shall be deemed the acceptance of such transferee of all
of the rights and obligations of a holder of a Warrant.

                  (b) This Warrant is exchangeable, upon the surrender hereof by
the Holder to the office of the Company specified in or pursuant to Section 3(b)
for one or more New Warrants, evidencing in the aggregate the right to purchase
the number of Warrant Shares which may then be purchased hereunder. Any such New
Warrant will be dated the date of such exchange.

         3. Duration and Exercise of Warrants.

                  (a) This Warrant shall be exercisable by the registered Holder
on any business day before 5:30 P.M., Eastern time, at any time and from time to
time on or after the date hereof to and including the Expiration Date. At 5:30
P.M., Eastern time on the Expiration Date, the portion of this Warrant not
exercised prior thereto shall be and become void and of no value. Prior to the
Expiration Date, the Company may not call or otherwise redeem this Warrant
without the prior written consent of the Holder.

                  (b) Subject to Sections 2(b) and 6, upon surrender of this
Warrant, with the Form of Election to Purchase attached hereto duly completed
and signed, to the Company at its address for notice set forth in Section 11 and
upon payment of the Exercise Price multiplied by the number of Warrant Shares
that the Holder intends to purchase hereunder, in lawful money of the United
States of America, in cash, by certified or official bank check or checks or
wire transfer of immediately available funds, all as specified by the Holder in
the Form of Election to Purchase, the Company shall promptly (but in no event
later than five (5) business days after the Date of Exercise) issue or cause to
be issued and cause to be delivered to or upon the written order of the Holder
and in such name or names as the Holder may designate, a certificate for the
Warrant Shares issuable upon such exercise, free of restrictive legends other
than as required by applicable law. Any person so designated by the Holder to
receive Warrant Shares shall be deemed to have become holder of record of such
Warrant Shares as of the Date of Exercise of this Warrant.

                  A "Date of Exercise" means the date on which the Company shall
have received (i) this Warrant (or any New Warrant, as applicable), with the
Form of Election to Purchase attached hereto (or attached to such New Warrant)
appropriately completed and duly signed, and (ii) payment of the Exercise Price
for the number of Warrant Shares so indicated by the holder hereof to be
purchased.



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                  (c) This Warrant shall be exercisable, either in its entirety
or, from time to time, for a portion of the number of Warrant Shares. If less
than all of the Warrant Shares which may be purchased under this Warrant are
exercised at any time, the Company shall issue or cause to be issued, at its
expense, a New Warrant evidencing the right to purchase the remaining number of
Warrant Shares for which no exercise has been evidenced by this Warrant.

                  (d)(i) The Holder may not exercise this Warrant to the extent
such exercise would result in the Holder, together with any affiliate thereof,
beneficially owning (as determined in accordance with Section 13(d) of the
Securities Exchange Act of 1934, as amended (the "Exchange Act") and the rules
thereunder) in excess of 4.999% of the then issued and outstanding shares of
Common Stock. The Holder shall have the sole authority and obligation to
determine whether the restriction contained in this Section applies and to the
extent that the Holder determines that the limitation contained in this Section
applies, the determination of which portion of this Warrant is exercisable shall
be in the sole discretion of the Holder, and the Company shall have no
obligation to verify or confirm the accuracy of any such determination. The
provisions of this Section may be waived by the Holder upon not less than 75
days prior notice to the Company, and the provisions of this Section shall
continue to apply until such 75th day (or later, if stated in the notice of
waiver).

                  (ii) The Holder may not exercise this Warrant to the extent
such exercise would result in the Holder, together with any affiliate thereof,
beneficially owning (as determined in accordance with Section 13(d) of the
Exchange Act and the rules thereunder) in excess of 9.999% of the then issued
and outstanding shares of Common Stock. The Holder shall have the sole authority
and obligation to determine whether the restriction contained in this Section
applies and to the extent that the Holder determines that the limitation
contained in this Section applies, the determination of which portion of this
Warrant is exercisable shall be in the sole discretion of the Holder, and the
Company shall have no obligation to verify or confirm the accuracy of any such
determination. The provisions of this Section may be waived by the Holder upon
not less than 75 days prior notice to the Company, and the provisions of this
Section shall continue to apply until such 75th day (or later, if stated in the
notice of waiver).

                  (iii) Notwithstanding anything herein to the contrary, unless
the Company shall have previously (A) received the shareholder approval as may
be required under Rule 4310(H)(i)(b) of the NASDAQ Stock Market or (B) obtained
an exemption from the requirement from the NASDAQ Stock Market for such
shareholder approval, the Holder shall not exercise this Warrant to the extent
such exercise would result in the Holder holding in excess of 25% of the number
of shares of Common Stock outstanding on the date hereof.

         4. No Voting or Dividend Rights; Limitation of Liability. Nothing
contained in this Warrant shall construed as conferring upon the Holder the
right to vote or to consent or to receive notice as a stockholder in respect of
meetings of stockholders for the election of directors



                                      -3-
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of the Company or any other matters or any rights whatsoever as a stockholder of
the Company. No cash dividends shall be payable or accrued in respect of this
Warrant or the Warrant Shares until, and only to the extent that, this Warrant
shall have been exercised. No provisions hereof, in the absence of affirmative
action by the Holder to purchase shares of Common Stock, and no mere enumeration
herein of the rights or privileges of the Holder hereof, shall give rise to any
liability of the Holder for the Exercise Price or as a stockholder of the
company whether such liability is asserted by the Company or by its creditors.

         5. Registration Rights. This Warrant and the Warrant Shares are
entitled to certain registration rights pursuant to that certain Registration
Rights Agreement, dated as of May 12, 1999, between the Company and the
Purchaser named therein (as may be amended, modified or supplemented from time
to time, the "Registration Rights Agreement"). Pursuant to the terms of the
Registration Rights Agreement, the Company is obligated, among other things, to
file a registration statement registering for resale the Warrant Shares and
naming the Holder as a selling stockholder thereunder.

         6. Payment of Taxes. The Company will pay all documentary stamp taxes
attributable to the issuance of Warrant Shares upon the exercise of this
Warrant; provided, however, that the Company shall not be required to pay any
tax which may be payable in respect of any transfer involved in the registration
of any certificates for Warrant Shares or Warrants in a name other than that of
the Holder, and the Company shall not be required to issue or cause to be issued
or deliver or cause to be delivered the certificates for Warrant Shares unless
or until the person or persons requesting the issuance thereof shall have paid
to the Company the amount of such tax or shall have established to the
satisfaction of the Company that such tax has been paid. The Holder shall be
responsible for all other tax liability that may arise as a result of holding or
transferring this Warrant or receiving Warrant Shares upon exercise hereof.

         7. Replacement of Warrant. If this Warrant is mutilated, lost, stolen
or destroyed, the Company shall issue or cause to be issued in exchange and
substitution for and upon cancellation hereof, or in lieu of and substitution
for this Warrant, a New Warrant, but only upon receipt of evidence reasonably
satisfactory to the Company of such loss, theft or destruction and indemnity
and/or bond, if requested, satisfactory to it. Applicants for a New Warrant
under such circumstances shall also comply with such other reasonable
regulations and procedures and pay such other reasonable charges as the Company
may prescribe.

         8. Reservation of Warrant Shares. The Company covenants that it will at
all times reserve and keep available out of the aggregate of its authorized but
unissued Common Stock, solely for the purpose of enabling it to issue Warrant
Shares upon exercise of this Warrant as herein provided, the number of Warrant
Shares which are then issuable and deliverable upon the exercise of this entire
Warrant, free from preemptive rights or any other actual contingent purchase
rights of persons other than the Holder (taking into account the adjustments and
restrictions of Section 9) The



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Company covenants that all Warrant Shares that shall be so issuable and
deliverable shall, upon issuance and the payment of the applicable Exercise
Price in accordance with the terms hereof, be duly and validly authorized,
issued and fully paid and nonassessable.

         9. Certain Adjustments. The Exercise Price and number of Warrant Shares
issuable upon exercise of this Warrant are subject to adjustment from time to
time as set forth in this Section 9. Upon each such adjustment of the Exercise
Price pursuant to this Section 9, the Holder shall thereafter prior to the
Expiration Date be entitled to purchase, at the Exercise Price resulting from
such adjustment, the number of Warrant Shares obtained by multiplying the
Exercise Price in effect immediately prior to such adjustment by the number of
Warrant Shares issuable upon exercise of this Warrant immediately prior to such
adjustment and dividing the product thereof by the Exercise Price resulting from
such adjustment.

                  (a) If the Company, at any time while this Warrant is
outstanding, (i) shall pay a stock dividend (except scheduled dividends paid on
outstanding preferred stock as of the date hereof which contain a stated divided
rate) or otherwise make a distribution or distributions on shares of its Common
Stock (as defined below) or on any other class of capital stock and not the
Common Stock) payable in shares of Common Stock, (ii) subdivide outstanding
shares of Common Stock into a larger number of shares, or (iii) combine
outstanding shares of Common Stock into a smaller number of shares, the Exercise
Price shall be multiplied by a fraction of which the numerator shall be the
number of shares of Common Stock (excluding treasury shares, if any) outstanding
before such event and of which the denominator shall be the number of shares of
Common Stock (excluding treasury shares, if any) outstanding after such event.
Any adjustment made pursuant to this Section shall become effective immediately
after the record date for the determination of stockholders entitled to receive
such dividend or distribution and shall become effective immediately after the
effective date in the case of a subdivision or combination, and shall apply to
successive subdivisions and combinations.

                  (b) In case of any reclassification of the Common Stock, any
consolidation or merger of the Company with or into another person, the sale or
transfer of all or substantially all of the assets of the Company or any
compulsory share exchange pursuant to which the Common Stock is converted into
other securities, cash or property, then the Holder shall have the right
thereafter to exercise this Warrant only into the shares of stock and other
securities and property receivable upon or deemed to be held by holders of
Common Stock following such reclassification, consolidation, merger, sale,
transfer or share exchange, and the Holder shall be entitled upon such event to
receive such amount of securities or property equal to the amount of Warrant
Shares such Holder would have been entitled to had such Holder exercised this
Warrant immediately prior to such reclassification, consolidation, merger, sale,
transfer or share exchange. The terms of any such consolidation, merger, sale,
transfer or share exchange shall include such terms so as to continue to give to
the Holder the right to receive the securities or property set forth in this
Section 9(b) upon any exercise following any such reclassification,
consolidation, merger, sale, transfer or share exchange.



                                      -5-
<PAGE>   6

                  (c) If the Company, at any time while this Warrant is
outstanding, shall distribute to all holders of Common Stock (and not to holders
of this Warrant) evidences of its indebtedness or assets or rights or warrants
to subscribe for or purchase any security (excluding those referred to in
Sections 9(a), (b) and (d)), then in each such case the Exercise Price shall be
determined by multiplying the Exercise Price in effect immediately prior to the
record date fixed for determination of stockholders entitled to receive such
distribution by a fraction of which the denominator shall be the Exercise Price
determined as of the record date mentioned above, and of which the numerator
shall be such Exercise Price on such record date less the then fair market value
at such record date of the portion of such assets or evidence of indebtedness so
distributed applicable to one outstanding share of Common Stock as determined by
the Company's independent certified public accountants that regularly examines
the financial statements of the Company (an "Appraiser").

                  (d) If, at any time while this Warrant is outstanding, the
Company shall issue or cause to be issued rights or warrants to acquire, or
securities convertible into, or otherwise sell or distribute, shares of Common
Stock for a consideration per share less than the Market Value in effect on the
date of issuance of such rights, warrants or shares, then, forthwith upon such
issue or sale, the Exercise Price shall be reduced to the price (calculated to
the nearest cent) determined by multiplying the Exercise Price in effect
immediately prior thereto by a fraction, the numerator of which shall be the sum
of the number of shares of Common Stock which the aggregate consideration
received (or to be received, assuming exercise or conversion in full of such
rights, warrants and convertible securities) for the issuance of such additional
shares of Common Stock would purchase at such Market Value, and the denominator
of which shall be the sum of the number of shares of Common Stock outstanding
immediately after the issuance of such additional shares. Such adjustment shall
be made successively whenever such an issuance is made. For purposes hereof, the
"Market Value" of the Common Stock as at a date of determination shall mean the
arithmetic average of the Per Share Market Value (as defined in the Convertible
Preferred Stock Purchase Agreement, dated as of May 12, 1999, between the
Company and the original Holder of this Warrant) for the ten (10) business days
preceding the date of determination.

                  (e) For the purposes of this Section 9, the following clauses
shall also be applicable:

                  (i) Record Date. In case the Company shall take a record of
the holders of its Common Stock for the purpose of entitling them (A) to receive
a dividend or other distribution payable in Common Stock or in securities
convertible or exchangeable into shares of Common Stock, or (B) to subscribe for
or purchase Common Stock or securities convertible or exchangeable into shares
of Common Stock, then such record date shall be deemed to be the date



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<PAGE>   7

of the issue or sale of the shares of Common Stock deemed to have been issued or
sold upon the declaration of such dividend or the making of such other
distribution or the date of the granting of such right of subscription or
purchase, as the case may be.

                  (ii) Treasury Shares. The number of shares of Common Stock
outstanding at any given time shall not include shares owned or held by or for
the account of the Company, and the disposition of any such shares shall be
considered an issue or sale of Common Stock.

                  (f) All calculations under this Section 9 shall be made to the
nearest cent or the nearest 1/100th of a share, as the case may be.

                  (g) Whenever the Exercise Price is adjusted pursuant to
Section 9(c) above, the Holder, after receipt of the determination by the
Appraiser, shall have the right to select an additional appraiser (which shall
be a nationally recognized accounting firm), in which case the adjustment shall
be equal to the average of the adjustments recommended by each of the Appraiser
and such appraiser. The Holder shall promptly mail or cause to be mailed to the
Company, a notice setting forth the Exercise Price after such adjustment and
setting forth a brief statement of the facts requiring such adjustment. Such
adjustment shall become effective immediately after the record date mentioned
above.

                  (h) If:

                           (i)      the Company shall declare a dividend (or any
                                    other distribution) on its Common Stock; or

                           (ii)     the Company shall declare a special
                                    nonrecurring cash dividend on or a
                                    redemption of its Common Stock; or

                           (iii)    the Company shall authorize the granting to
                                    all holders of the Common Stock rights or
                                    warrants to subscribe for or purchase any
                                    shares of capital stock of any class or of
                                    any rights; or

                           (iv)     the approval of any stockholders of the
                                    Company shall be required in connection with
                                    any reclassification of the Common Stock of
                                    the Company, any consolidation or merger to
                                    which the Company is a party, any sale or
                                    transfer of all or substantially all of the
                                    assets of the Company, or any compulsory
                                    share exchange whereby the Common Stock is
                                    converted into other securities, cash or
                                    property; or


                                      -7-
<PAGE>   8

                           (v)      the Company shall authorize the voluntary
                                    dissolution, liquidation or winding up of
                                    the affairs of the Company,

then the Company shall cause to be mailed to each Holder at their last addresses
as they shall appear upon the Warrant Register, at least ten (10) business days
prior to the applicable record or effective date hereinafter specified, a notice
stating (x) the date on which a record is to be taken for the purpose of such
dividend, distribution, redemption, rights or warrants, or if a record is not to
be taken, the date as of which the holders of Common Stock of record to be
entitled to such dividend, distributions, redemption, rights or warrants are to
be determined or (y) the date on which such reclassification, consolidation,
merger, sale, transfer or share exchange is expected to become effective or
close, and the date as of which it is expected that holders of Common Stock of
record shall be entitled to exchange their shares of Common Stock for
securities, cash or other property deliverable upon such reclassification,
consolidation, merger, sale, transfer, share exchange, dissolution, liquidation
or winding up; provided, however, that the failure to mail such notice or any
defect therein or in the mailing thereof shall not affect the validity of the
corporate action required to be specified in such notice.

                  (i) No adjustment in the Exercise Price under Sections 9(c) or
(d) shall be required to be made if such adjustment would result in a change of
less than $.10 in the Exercise Price, but any adjustments not made by reason of
this clause (i) shall be carried forward and shall be made at the time of and
together with the next subsequent adjustment(s) which, together with any
adjustment(s) so carried forward, shall require an increase or decrease of at
least $.10 in the Exercise Price then in effect.

         10. Fractional Shares. The Company shall not be required to issue or
cause to be issued fractional Warrant Shares on the exercise of this Warrant.
The number of full Warrant Shares which shall be issuable upon the exercise of
this Warrant shall be computed on the basis of the aggregate number of Warrant
Shares purchasable on exercise of this Warrant so presented. If any fraction of
a Warrant Share would, except for the provisions of this Section 10, be issuable
on the exercise of this Warrant, the Company shall pay an amount in cash equal
to the Exercise Price multiplied by such fraction.

         11. Notices. Any and all notices or other communications or deliveries
hereunder shall be in writing and shall be deemed given and effective on the
earliest of (i) the date of transmission, if such notice or communication is
delivered via confirmed facsimile at the facsimile telephone number specified in
this Section prior to 8:00 p.m. (New York City time) on a business day, (ii) the
business day after the date of transmission, if such notice or communication is
delivered



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<PAGE>   9

via confirmed facsimile at the facsimile telephone number specified in this
Section later than 8:00 p.m. (New York City time) on any date and earlier than
11:59 p.m. (New York City time) on such date, (iii) the business day following
the date of mailing, if sent by nationally recognized overnight courier service,
or (iv) upon actual receipt by the party to whom such notice is required to be
given. The addresses for such communications shall be: (i) if to the Company, to
Ecogen Inc., 2000 Cabot Boulevard West, Suite 170, Langhorne, PA 19047,
Attention: Chief Financial Officer, or to facsimile no. (215) 757-3339, or (ii)
if to the Holder, to the Holder at the address or facsimile number appearing on
the Warrant Register or such other address or facsimile number as the Holder may
provide to the Company in accordance with this Section 11.

         12. Warrant Agent.

                  (a) The Company shall serve as warrant agent under this
Warrant. Upon not less than thirty (30) days' notice to the Holder, the Company
may appoint a new warrant agent.

                  (b) Any corporation into which the Company or any new warrant
agent may be merged or any corporation resulting from any consolidation to which
the Company or any new warrant agent shall be a party or any corporation to
which the Company or any new warrant agent transfers substantially all of its
corporate trust or shareholders services business shall be a successor warrant
agent under this Warrant without any further act. Any such successor warrant
agent shall promptly cause notice of its succession as warrant agent to be
mailed (by first class mail, postage prepaid) to the Holder at the Holder's last
address as shown on the Warrant Register.

         13. Miscellaneous.

                  (a) This Warrant shall be binding on and inure to the benefit
of the parties hereto and their respective successors and permitted assigns.
This Warrant may be amended only in writing signed by the Company and the
Holder.

                  (b) Subject to Section 13(a) above, nothing in this Warrant
shall be construed to give to any person or corporation other than the Company
and the Holder any legal or equitable right, remedy or cause under this Warrant.
This Warrant shall inure to the sole and exclusive benefit of the Company and
the Holder.

                  (c) This Warrant shall be governed by and construed and
enforced in accordance with the internal laws of the State of New York without
regard to the principles of conflicts of law thereof.

                  (d) The headings herein are for convenience only, do not
constitute a part of this Warrant and shall not be deemed to limit or affect any
of the provisions hereof.



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<PAGE>   10

                  (e) In case any one or more of the provisions of this Warrant
shall be invalid or unenforceable in any respect, the validity and
enforceability of the remaining terms and provisions of this Warrant shall not
in any way be affected or impaired thereby and the parties will attempt in good
faith to agree upon a valid and enforceable provision which shall be a
commercially reasonable substitute therefor, and upon so agreeing, shall
incorporate such substitute provision in this Warrant.


                  [REMAINDER OF PAGE INTENTIONALLY LEFT BLANK,
                             SIGNATURE PAGE FOLLOWS]


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<PAGE>   11






         IN WITNESS WHEREOF, the Company has caused this Warrant to be duly
executed by its authorized officer as of the date first indicated above.


                                        ECOGEN INC.

                                        By: /s/ James P. Reilly, Jr.
                                           ----------------------------------
                                        Name:  James P. Reilly, Jr.
                                        Title: Chairman and Chief Executive
                                               Officer

<PAGE>   12






                          FORM OF ELECTION TO PURCHASE

(To be executed by the Holder to exercise the right to purchase shares of Common
Stock under the foregoing Warrant)

To Ecogen Inc.

         In accordance with the Warrant enclosed with this Form of Election to
Purchase, the undersigned hereby irrevocably elects to purchase _____________
shares of Common Stock ("Common Stock"), $.01 par value per share, of Ecogen
Inc. and, if such Holder is not utilizing the cashless exercise provisions set
forth in this Warrant, encloses herewith $________ in cash, certified or
official bank check or checks or wire transfer of immediately available funds,
which sum represents the aggregate Exercise Price (as defined in the Warrant)
for the number of shares of Common Stock to which this Form of Election to
Purchase relates, together with any applicable taxes payable by the undersigned
pursuant to the Warrant.

         The undersigned requests that certificates for the shares of Common
Stock issuable upon this exercise be issued in the name of:

                                                PLEASE INSERT SOCIAL SECURITY OR
                                                TAX IDENTIFICATION NUMBER


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


--------------------------------------------------------------------------------
                         (Please print name and address)


         If the number of shares of Common Stock issuable upon this exercise
shall not be all of the shares of Common Stock which the undersigned is entitled
to purchase in accordance with the enclosed Warrant, the undersigned requests
that a New Warrant (as defined in the Warrant) evidencing the right to purchase
the shares of Common Stock not issuable pursuant to the exercise evidenced
hereby be issued in the name of and delivered to:


--------------------------------------------------------------------------------
                         (Please print name and address)


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


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

Dated:                                        Name of Holder:
      ------------------, ----
                                              (Print)
                                                     ---------------------------
                                              (By:)
                                                   -----------------------------
                                              (Name:)
                                              (Title:)
                                              (Signature must conform in all
                                              respects to name of holder as
                                              specified on the face of the
                                              Warrant)


<PAGE>   13



                               FORM OF ASSIGNMENT

           [To be completed and signed only upon transfer of Warrant]

         FOR VALUE RECEIVED, the undersigned hereby sells, assigns and transfers
unto ________________________________ the right represented by the within
Warrant to purchase ____________ shares of Common Stock of Ecogen Inc. to which
the within Warrant relates and appoints ________________ attorney to transfer
said right on the books of [ ] with full power of substitution in the premises.

Dated:

---------------, ----


                                         ---------------------------------------
                                         (Signature must conform in all respects
                                         to name of holder as specified on the
                                         face of the Warrant)


                                         ---------------------------------------
                                         Address of Transferee

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

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



In the presence of:


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