Document:

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             Void after 5:00 P.M. New York Time on December 23, 2004

No. W-1                                                      Warrant to Purchase
                                                                  200,000 Shares
                                                                 of Common Stock

                   WARRANT TO PURCHASE SHARES OF COMMON STOCK
                                       OF
                                   ECOGEN INC.

         THIS IS TO CERTIFY THAT, FOR VALUE RECEIVED, MOMAR CORPORATION, a
Maryland corporation, or registered assigns (the "Holder"), is entitled to
purchase, subject to the provisions of this Warrant, from Ecogen Inc., a
Delaware corporation (the "Company"), at the Exercise Price hereinafter set
forth, up to 200,000 shares (as adjusted from time to time as provided
hereunder) of Common Stock at any time and from time to time on or after the
date hereof and not later than 5:00 P.M. New York time on December 23, 2004 (the
"Expiration Date").

         (a) DEFINITIONS. For the purposes of this Warrant, the following terms
shall have the following meanings:

                  (1) "Common Stock" shall mean the Common Stock, $0.01 par
         value per share, of the Company of the class authorized as of the date
         hereof and any other class of stock ranking on a parity with such
         Common Stock. However, subject to the provisions of Section (l) hereof,
         shares issuable upon exercise hereof shall include only shares of the
         class designated as Common Stock of the Company as of the date hereof.

                  (2) "Exercise Price" shall mean $1.25 per share, as adjusted
         from time to time as provided hereunder.

                  (3) "Registry Office" shall mean the principal executive
         office of the Company at 2000 Cabot Boulevard West, Langhorne,
         Pennsylvania 19047.

                  (4) "Warrant Stock" shall mean the shares of Common Stock
         deliverable upon exercise of the Warrants, as adjusted from time to
         time as provided hereunder.

         (b) EXERCISE OF WARRANT. Subject to the provisions of this Warrant, the
Holder shall have the right to purchase from the Company, and the Company shall
be obligated to issue and sell to the Holder, the number of fully paid and
nonassessable shares of Warrant Stock purchasable hereunder, free of all
preemptive rights of stockholders and all other liens, claims and encumbrances
of any nature whatsoever. This Warrant may be exercised in whole or in part at
any time or from time to time, but not
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later than the Expiration Date, or if the Exercise Time is a day on which
banking institutions in the Commonwealth of Pennsylvania are authorized by law
to close, then on the next succeeding day which shall not be such a day, by
presentation and surrender hereof to the Registry Office of the Company, with
the form of Election to Purchase annexed hereto duly executed and accompanied by
payment of the Exercise Price multiplied by the number of shares specified in
such form. Payment of the Exercise Price may be made in cash, or by check, bank
draft or postal or express money order payable in United States currency, to the
order of the Company. Upon such surrender of this Warrant and payment of the
Exercise Price, the Company shall issue and cause to be delivered with all
reasonable dispatch to or upon the written order of the Holder and in such name
or names as the Holder may designate a certificate or certificates for the
number of full shares of Common Stock so purchased upon the exercise of this
Warrant together with cash as provided in Section (d) in respect of any fraction
of a share of Common Stock otherwise issuable upon such surrender. If this
Warrant should be exercised in part only, the Company shall, upon surrender of
this Warrant for cancellation, promptly execute and deliver to the Holder a new
Warrant evidencing the right of the Holder to purchase the balance of the shares
purchasable hereunder. Upon receipt by the Company of this Warrant at the
Registry Office, in proper form for exercise, the Holder shall be deemed to be
the holder of record of the shares of Common Stock issuable upon such exercise,
notwithstanding that the stock transfer books of the Company shall then be
closed or that certificates representing such shares of Common Stock shall not
then be actually delivered to the Holder.

         (c) RESERVATION OF SHARES. The Company hereby agrees that at all times
there shall be reserved for issuance and/or delivery upon exercise of this
Warrant such number of shares of its Common stock as shall be required for
issuance or delivery upon exercise of this Warrant.

         (d) FRACTIONAL SHARES. No fractional shares or scrip representing
fractional shares shall be issued upon the exercise of this Warrant; provided,
however, that if more than one Warrant is exercised by the same holder at the
same time, fractional shares of all such Warrants shall be consolidated and the
holder shall be entitled to purchase the number of whole shares obtained by
consolidating such fractional shares. With respect to any remaining fraction of
a share called for upon any exercise hereof, the Company shall pay to the Holder
an amount in cash equal to such fraction multiplied by the excess over the
Exercise Price of the current market value of a share of Common Stock determined
for all purposes of this Warrant as follows:

                  (1) If the Common Stock is listed on a national securities
         exchange or admitted to unlisted trading privileges on such exchange,
         or is listed on NASDAQ, the current value shall be the last reported
         sale price of the Common Stock on such exchange or NASDAQ on the last
         day such exchange was open prior to the date of exercise of this
         Warrant or, if no such sale is made on such day, the average closing
         bid and asked prices for such day on such exchange; or

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                  (2) If the Common Stock is not so listed or admitted to
         unlisted trading privileges, the current value shall be the mean of the
         last reported bid and asked prices reported by any national stock price
         quotation service on the last day on which such bid and asked prices
         were reported prior to the date of the exercise of this Warrant; or

                  (3) If the Common Stock is not so listed or admitted to
         unlisted trading privileges and bid and asked prices are not so
         reported, the current value shall be an amount, not less than book
         value, determined in good faith and in such reasonable manner as may be
         prescribed by the Board of Directors of the Company, such determination
         to be final and binding on the Holder.

         (e) REGISTRATION. The Company shall maintain books for the transfer and
registration of the Warrants. Upon the initial issuance of the Warrants, the
Company shall issue and register the Warrants in the names of the respective
registered holders thereof, and upon subsequent re-issuances of Warrants, such
Warrants shall be registered in the names of their respective registered
holders.

         (f) PAYMENT OF TAXES. The Company shall pay all state and federal
taxes, if any, attributable to the exercise of this Warrant and to the initial
issuance of the Warrant Stock; provided that the Company shall not be required
to pay any tax or taxes which may be payable because of the transfer involved in
the issue or delivery of any certificates for Warrant Stock in a name other than
that of the registered holder of the Warrants being exercised or any income
taxes or capital gains tax of the Holder.

         (g) EXCHANGE, ASSIGNMENT OR LOSS OF WARRANT. This Warrant is
exchangeable, without expense, at the option or the Holder, upon presentation
and surrender hereof to the Company, alone or with other Warrants with the same
Exercise Price, for any other warrants of different denominations entitling the
holder thereof to purchase in the aggregate the same number of shares of Common
Stock purchasable hereunder at the same Exercise Price. This Warrant is
transferable in the same manner and with the same effect upon payment by the
Holder of all federal and state taxes applicable to such transfer, subject to
the provisions of Section (o) hereof. Upon surrender of this Warrant to the
Company with the form of Assignment annexed hereto duly executed, with funds
sufficient to pay any transfer tax, the Company shall, without charge, execute
and deliver a new Warrant in the name of the assignee named in such instrument
of assignment and this Warrant shall promptly be cancelled. If and when this
Warrant is assigned in blank, the Company shall, subject to the provisions of
Section (o) hereof, treat the bearer hereof as the absolute owner of this
Warrant for all purposes and the Company shall not be affected by any notice to
the contrary. This Warrant may be divided or combined with other Warrants which
carry the same rights upon presentation hereof at the office or agency of the
Company maintained for that purpose, together with a written notice specifying
the names and denominations in which new Warrants are to be issued and signed by
the Holder hereof. The term "Warrant" as used herein includes any Warrants into
which this Warrant may be divided or exchanged, and the term "Holder"

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as used herein includes any holder of any Warrant into which this Warrant may be
divided or exchanged. Upon receipt by the Company of evidence satisfactory to it
of the loss, theft, destruction or mutilation of this Warrant, and (in the case
of loss, theft or destruction) of reasonably satisfactory indemnification, and
upon surrender and cancellation of this Warrant, if mutilated, the Company will
execute and deliver a new Warrant of like tenor and date. Any such new Warrant
executed and delivered shall constitute an additional contractual obligation on
the part of the Company, whether or not this Warrant so lost or stolen,
destroyed or mutilated shall be at any time enforceable by anyone.

         (h) RIGHTS OF THE HOLDER. The Holder shall not, by virtue hereof, be
entitled to any rights of a shareholder in the Company, either at law or equity,
and the rights of the Holder are limited to those expressed in this Warrant and
are not enforceable against the Company except to the extent set forth herein.

         (i) ANTI-DILUTION PROVISIONS.

         (1) ADJUSTMENTS OF EXERCISE PRICE. If the Company should at any time or
from time to time hereafter issue or sell any share of Common Stock (other than
the shares which are to be issued upon exercise of the options or warrants
described in clause (A), or conversions of the Convertible Securities described
in clause (B), of this subsection (i)(1) or the Warrant Stock which may be
purchased under the Warrants) without consideration or for a consideration per
share less than the greater of (i) the Exercise Price of the Warrant in effect
immediately prior to the time of such issue or sale and (ii) the then current
market value of a share of Common Stock (such greater amount, the "Floor
Amount"), then forthwith upon such issue or sale, the Exercise Price of all
Warrants shall be adjusted to a price (computed to the nearest cent) determined
by dividing (i) the sum of (x) the number of shares of Common Stock outstanding
immediately prior to such issue or sale multiplied by the Floor Amount, and (y)
the consideration, if any, received by the Company upon such issue or sale, by
(ii) the total number of shares of Common Stock outstanding immediately after
such issue or sale. For the purposes of this subsection (i)(1), the following
provisions (A) through (G) shall also be applicable:

                  (A) OPTIONS AND RIGHTS. In case at any time hereafter the
         Company shall in any manner grant any right to subscribe for or to
         purchase, or any option for the purchase of, Common Stock or any stock
         or other securities convertible into or exchangeable for Common Stock
         (such convertible or exchangeable stock or securities being hereinafter
         referred to as "Convertible Securities") and the minimum price per
         share for which Common Stock is issuable, pursuant to such rights or
         options or upon conversion or exchange of such Convertible Securities
         (determined by dividing (i) the total amount, if any, received or
         receivable by the Company as consideration for the granting of such
         rights or options, plus the minimum aggregate amount of additional
         consideration payable to the Company upon the exercise of such rights
         and options, plus, in the case of such Convertible

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         Securities, the minimum aggregate amount of additional consideration,
         if any, payable upon the conversion or exchange thereof, by (ii) the
         total maximum number of shares of Common Stock issuable pursuant to
         such rights or options or upon the conversion or exchange of the total
         maximum amount of such Convertible Securities issuable upon the
         exercise of such rights or options) shall be less than the highest
         Exercise Price in effect immediately prior to the time of the granting
         of such rights or options, then the total maximum number of shares of
         Common Stock issuable pursuant to such rights or options or upon
         conversion or exchange of the total maximum amount of such Convertible
         Securities issuable upon the exercise of such rights or options shall
         (as of the date of granting of such rights or options) be deemed to be
         outstanding and to have been issued for said price per share as so
         determined; provided, however, that no further adjustment of the
         Exercise Price shall be made upon the actual issue of Common Stock so
         deemed to have been issued; and, further provided, that, upon the
         expiration of such rights (including rights to convert or exchange) or
         options, (a) a number of shares of Common Stock deemed to have been
         issued and outstanding by reason of the fact that they were issuable
         pursuant to such rights or options or upon conversion or exchange of
         Convertible Securities so issuable, which rights or options (including
         rights to convert or exchange) were not exercised, shall no longer be
         deemed to be issued and outstanding, and (b) the Exercise Price shall
         forthwith be adjusted to the price which would have prevailed had all
         adjustments been made on the basis of the issue only of the shares of
         Common Stock actually issued upon the exercise of such rights or
         options or upon conversion or exchange of such Convertible Securities.

                  (B) CONVERTIBLE SECURITIES. In case the Company shall
         hereafter in any manner issue or sell any Convertible Securities other
         than as described in clause (A) of this Section (i)(1) and the minimum
         price per share for which Common Stock is issuable upon conversion or
         exchange of such Convertible Securities (determined by dividing (i) the
         total amount received or receivable by the Company as consideration for
         the issue or sale of such Convertible Securities, plus the minimum
         aggregate amount of additional consideration, if any, payable to the
         Company upon the conversion or exchange thereof, by (ii) the total
         maximum number of shares of Common Stock issuable upon the conversion
         or exchange of all such Convertible Securities) shall be less than the
         highest Exercise Price of any of the Warrants in effect immediately
         prior to the time of such issue or sale, then the total maximum number
         of shares of Common Stock issuable upon conversion or exchange of all
         such Convertible Securities shall (as of the date of the issue or sale
         of such Convertible Securities) be deemed to be outstanding and to have
         been issued for said Price per share as so determined; provided that no
         further adjustment of the Exercise Price shall be made upon the actual
         issue of Common Stock so deemed to have been issued; and, further
         provided, that if any such issue or sale of such Convertible Securities
         is made upon exercise of any right to subscribe for or to purchase or
         any option to purchase any such Convertible Securities for which an
         adjustment of the Exercise

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         Price has been or is to be made pursuant to other provisions of this
         subsection (i)(1), no further adjustment of the Exercise Price shall be
         made by reason of such issue or sale; and, further provided, that, upon
         the termination of the right to convert or to exchange such Convertible
         Securities for Common Stock, (a) the number of shares of Common Stock
         deemed to have been issued and outstanding by reason of the fact that
         they were issuable upon conversion of exchange of any such Convertible
         Securities, which were not so converted or exchanged, shall no longer
         be deemed to be issued and outstanding, and (b) the Exercise Price
         shall forthwith be adjusted to the price which would have prevailed had
         all adjustments been made on the basis of the issue only of the number
         of shares of Common Stock actually issued upon conversion or exchange
         of such Convertible Securities.

                  (C) DISTRIBUTIONS. In case the Company shall, at any time
         prior to the expiration of this Warrant and prior to the exercise
         thereof, make any distribution of its assets to holders of its Common
         Stock as a liquidation or partial liquidation dividend or by way of
         return of capital, or other than as a dividend payable out of earnings
         or any surplus legally available for dividends under the laws of the
         State of Delaware, then the Holder of this Warrant who thereafter
         exercises the same as herein provided after the date of record for the
         determination of those holders of Common Stock entitled to such
         distribution of assets shall be entitled to receive for the purchase
         price of the shares of Common Stock stated in this Warrant, in addition
         to the shares of Common Stock, the amount of such assets (or at the
         option of the Company a sum equal to the value thereof at the time of
         such distribution to holders of Common Stock as such value is
         determined by the Board of Directors of the company in good faith),
         which would have been payable to such Holder had it been the holder of
         record of such shares of Common Stock, receivable upon the exercise of
         this Warrant on the record date for the determination of those entitled
         to such distribution.

                  (D) DISSOLUTION OR LIQUIDATION. In case the Company shall, at
         any time prior to the expiration of this Warrant and prior to the
         exercise thereof, dissolve, liquidate or wind up its affairs, the
         Holder of this Warrant shall be entitled, upon the exercise thereof, to
         receive, in lieu of the shares of Common Stock of the Company which it
         would have been entitled to receive, the same kind and amount of assets
         as would have been issued, distributed or paid to it upon any such
         dissolution, liquidation or winding up with respect to such shares of
         Common Stock of the Company, had it been the holder of record of such
         shares of Common Stock receivable upon the exercise of this Warrant on
         the record date for the determination of those entitled to receive any
         such liquidation distribution. After any such dissolution, liquidation
         or winding up which shall result in any cash distribution in excess of
         the Exercise Price provided for by this Warrant, the Holder of this
         Warrant may at its option exercise the same without making payment of
         the Exercise Price and in such case the Company shall upon the
         distribution to said Warrant Holder consider that said Exercise Price
         has been paid

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         in full to it and in making settlement to said Warrant Holder, shall
         deduct from the amount payable to such Holder an amount equal to such
         Exercise Price.

                  (E) DETERMINATION OF ISSUE PRICE. In case any shares of Common
         Stock or Convertible Securities or any rights or options to purchase
         any such stock or securities shall be issued for cash, the
         consideration received therefor, after deducting therefrom any
         commissions or other expenses paid or incurred by the Company for any
         underwriting of, or otherwise in connection with, the issuance thereof,
         shall be deemed to be the amount received by the Company therefor. In
         case any shares of Common Stock or Convertible Securities or any rights
         or options to purchase any such stock or securities shall be issued for
         a consideration, part or all of which shall be other than cash, then,
         for the purpose of this subsection (i)(1), such Common Stock,
         Convertible Securities, rights or options shall be deemed to have been
         issued for an amount of cash equal to the fair market value of such
         consideration. The reclassification of securities other than Common
         Stock into securities including Common Stock shall be deemed to involve
         the issuance for a consideration other than cash of such Common Stock
         immediately prior to the close of business on the date fixed for the
         determination of securityholders entitled to receive such Common Stock.
         In case any shares of Common Stock or Convertible Securities or any
         rights or options to purchase any such stock or other securities shall
         be issued together with other stock or securities or other assets of
         the Company for a consideration which includes both, the consideration
         for the issuance of the shares of Common Stock or Convertible
         Securities or rights or options shall be determined by subtracting the
         fair market value of the other stock or securities or assets from the
         total consideration received.

                  (F) DETERMINATION OF DATE OF ISSUE. In case the Company shall
         take a record of the holders of any Common Stock for the purpose of
         entitling them (i) to receive a dividend or other distribution payable
         in Common Stock or in Convertible Securities, or (ii) to subscribe for
         or purchase Common Stock or Convertible Securities, then such record
         date shall be deemed to be the date 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.

                  (G) TREASURY SHARES. For the purpose of this subsection
         (i)(1), shares of Common Stock at any relevant time owned or held by or
         for the account of the Company shall not be deemed outstanding.

         (2) ADJUSTMENT OF NUMBER OF SHARES. Anything in this Section (i) to the
contrary notwithstanding, in case the Company shall any time issue Common Stock
or Convertible Securities by way of dividend or other distribution on any stock
of the Company or subdivide or combine the outstanding shares of Common Stock,
the Exercise

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Price shall be proportionately decreased in the case of such issuance (on the
day following the date fixed for determining shareholders entitled to receive
such dividend or other distribution) or decreased in the case of such
subdivision or increased in the case of such combination (on the date that such
subdivision or combination shall become effective).

         (3) NO ADJUSTMENTS FOR SMALL AMOUNTS. Anything in this Section (i) to
the contrary notwithstanding, the Company shall not be required to give effect
to any adjustment in the Exercise Price unless and until the net effect of one
or more adjustments, determined as above provided, shall have required a change
of the Exercise Price by at least 1%, but when the cumulative net effect of more
than one adjustment so determined shall be to change the actual Exercise Price
by at least 1%, such change in the Exercise Price shall thereupon be given
effect.

         (4) NUMBER OF SHARES ADJUSTED. Upon any adjustment of the Exercise
Price, the holder of this Warrant shall thereafter (until another such
adjustment) be entitled to purchase, at the new Exercise Price, the number of
shares, calculated to the nearest full share, obtained by multiplying the number
of shares of Common Stock initially issuable upon exercise of this Warrant by
the Exercise Price in effect on the date hereof and dividing the product so
obtained by the new Exercise Price.

         (j) OFFICER'S CERTIFICATE. Whenever the Exercise Price shall be
adjusted as required by the provisions of Section (i) hereof, the Company shall
forthwith file, in the custody of its Secretary or an Assistant Secretary at its
Registry Office, an officer's certificate showing the adjusted Exercise Price
determined as herein provided and setting forth in reasonable detail the facts
requiring such adjustment. Each such officer's certificate shall be made
available at all reasonable times for inspection by the Holder and the Company
shall, forthwith after each such adjustment, deliver a copy of such certificate
to the Holder.

         (k) NOTICES TO WARRANT HOLDERS. So long as this Warrant shall be
outstanding and unexercised (i) if the Company shall pay any dividend or make
any distribution upon the Common Stock or (ii) if the Company shall offer to the
holders of Common Stock for subscription or purchase by them any share of stock
of any class or any other rights or (iii) if any capital reorganization of the
Company, reclassification of the capital stock of the Company, consolidation or
merger of the Company with or into another corporation, sale, lease or transfer
of all or substantially all of the property and assets of the Company to another
corporation, or voluntary or involuntary dissolution, liquidation or winding up
of the Company shall be effected, then, in any such case, the Company shall
cause to be delivered to the Holder, at least ten (10) days prior to the date
specified in (x) or (y) below, as the case may be, a notice containing a brief
description of the proposed action and stating the date on which (x) a record is
to be taken for the purpose of such dividend, distribution or rights, or (y)
such reclassification, reorganization, consolidation, merger, conveyance, lease,
dissolution, liquidation or winding up is to take place and the date, if any is
to be fixed, as of which the holders of Common Stock of record shall be entitled
to

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exchange their shares of Common Stock for securities or other property
deliverable upon such reclassification, reorganization, consolidation, merger,
conveyance, dissolution, liquidation or winding up.

         (l) RECLASSIFICATION, REORGANIZATION OR MERGER. In case of any
reclassification, capital reorganization or other change of outstanding shares
of Common Stock of the Company (other than a change in par value, or from par
value to no par value, or from no par value to par value, or as a result of an
issuance of Common Stock by way of dividend or other distribution or of a
subdivision or combination), or in case of any consolidation or merger of the
Company with or into another corporation (other than a merger with a subsidiary
in which merger the Company is the continuing corporation and which does not
result in any reclassification, capital reorganization or other change of
outstanding shares of Common Stock of the class issuable upon exercise of this
Warrant) or in case of any sale or conveyance to another corporation of the
property of the Company as an entirety or substantially as an entirety, the
Company shall cause effective provision to be made so that the Holder shall have
the right thereafter, by exercising this Warrant, to purchase the kind and
amount of shares of stock and other securities and property receivable upon such
reclassification, capital reorganization or other change, consolidation, merger,
sale or conveyance by a holder of the number of shares of Common Stock which
might have been purchased upon exercise of this Warrant immediately prior to
such reclassification, change, consolidation, merger, sale or conveyance. Any
such provision shall include provision for adjustments which shall be as nearly
equivalent as may be practicable to the adjustments provided for in this
Warrant. The foregoing provisions of this Section (l) shall similarly apply to
successive reclassifications, capital reorganizations and changes of shares of
Common Stock and to successive consolidations, mergers, sales or conveyances. In
the event that in any such capital reorganization or reclassification,
consolidation, mergers, sale or conveyance, additional shares of Common Stock
shall be issued in exchange, conversion, substitution or payment, in whole or in
part, for or of a security of the Company other than Common Stock, any such
issue shall be treated as an issue of Common Stock covered by the provisions of
subsection (i)(1) hereof.

         (m) SECURITIES ACT REGISTRATION.

         (1) In the event that the Company files a registration statement under
the Securities Act of 1933, as amended (the "Act"), which relates to a current
offering of securities of the Company for its own account or the account of any
of its shareholders, such registration statement and the prospectus included
therein shall also, at the written request to the Company by the Holder, relate
to, and meet the requirements of the Act with respect to, any public offering of
the Warrant Stock so as to permit the public sale thereof in compliance with the
Act. The Company shall give written notice to the Holder of its intention to
file a registration statement under the Act relating to a current offering of
the aforesaid securities of the Company, thirty (30) or more days prior to the
filing of such registration statement, and the written request provided for in
the first sentence of this subsection (m)(1), shall be made by the Holder
fifteen (15) or more days prior to the

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date specified in the notice as the date on which it is intended to file such
registration statement. Neither the delivery of such notice by the Company nor
of such request by the Holder shall in any way obligate the Company to file such
registration statement and notwithstanding the filing of such registration
statement, the Company may, at any time prior to the effective date thereof,
determine not to offer the securities to which such registration statement
relates, without liability to the Holder, except that the Company shall pay such
expenses as are contemplated to be paid by it under subsection (4) of this
Section (m).

         (2) In addition, upon written notice from the Holder that it
contemplates the transfer of all or any of its Warrant Stock under such
circumstances that a public offering, within the meaning of the Act, of the
Warrant Stock will be involved, the Company, as promptly as possible after the
receipt of such notice, shall file a new registration statement with respect to
the offering and sale or other disposition of the Warrant Stock with respect to
which it shall have received such notice; provided, however, that the Company
shall not be required to file more than two registration statements pursuant to
this Section (m)(2). Notwithstanding the foregoing, the Company shall not be
obligated to effect a registration pursuant to this Section (m)(2) if the
Company shall furnish to the Holder within ten (10) days of a registration
request a certificate signed by the president of the Company stating that in the
good faith judgment of the board of directors of the Company it would be
seriously detrimental to the Company and its stockholders for such registration
statement to be effected at such time, in which event the Company shall have the
right to defer the filing of the registration statement for a period of not more
than ninety (90) days after the receipt of the request of the Holder.

         (3) In each instance in which pursuant to subsections (1) and (2) of
this Section (m) , the Company shall take any action to permit a public offering
and sale or other distribution of Warrant Stock, the Company shall:

                  (A) Supply to the Holder a conformed copy of the new
         registration statement and of the preliminary, final and other
         prospectus in conformity with requirements of the Act and the Rules and
         Regulations and true copies of such other documents as the Holder shall
         reasonably request;

                  (B) Cooperate in taking such action as may be necessary to
         register or qualify the Warrant Stock under such other securities acts
         or blue sky laws of such jurisdictions as the Holder shall reasonably
         request and do any and all other acts and things which may be necessary
         or advisable to enable the Holder to consummate such proposed sale or
         other disposition of the Warrant Stock in any such jurisdiction;
         provided, however, that in no event shall the Company be obligated, in
         connection therewith, to qualify to do business or to file a general
         consent to service of process in any jurisdiction where it shall not
         then be qualified;

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                  (C) Keep effective for a period of 180 days after the initial
         effectiveness thereof or until all Warrant Stock covered thereby has
         been sold, whichever is later, all such registrations and
         qualifications under the Act and state securities and blue sky laws,
         and do any and all other acts and things for such period as may be
         necessary to permit the public sale or other disposition of such
         Warrant Stock by the Holder; and

                  (D) Indemnify and hold harmless the Holder and each
         underwriter, within the meaning of the Act, who may purchase from or
         sell for the Holder any Warrant Stock, and their respective officers,
         directors, partners, stockholders, agents, representatives and
         controlling persons from and against any and all losses, claims,
         damages, and liabilities (including, but not limited to, any and all
         expenses whatsoever reasonably incurred in investigating, preparing,
         defending or settling any claim) arising from (i) any untrue or alleged
         untrue statement of a material fact contained in any registration
         statement furnished pursuant to clause (A) of this subsection (m)(3),
         or any prospectus or offering circular included therein or (ii) any
         omission or alleged omission to state therein a material fact required
         to be stated therein or necessary to make the statements therein not
         misleading (unless such untrue statement or omission or such alleged
         untrue statement or omission was based upon information furnished or
         required to be furnished in writing to the Company by the Holder or
         underwriter expressly for use therein), which indemnification shall
         include each person, if any, who controls the Holder or underwriter
         within the meaning of the Act; provided, however, that the Company
         shall not be so obligated to indemnify the Holder or underwriter or
         controlling person unless the Holder and underwriter shall at the same
         time indemnify the Company, its directors, each officer signing any
         registration statement or any amendment to any registration statement
         and each person, if any, who controls the Company within the meaning of
         the Act, from and against any and all losses, claims, damages, and
         liabilities (including, but not limited to, any and all expenses
         whatsoever reasonably incurred in investigating, preparing, defending
         or settling any claim) arising from (a) any untrue or alleged untrue
         statement of a material fact contained in any registration statement or
         any amendment to any registration statement or prospectus furnished
         pursuant to clause (A) of this subsection (m)(3), or (b) any omission
         or alleged omission to state therein a material fact required to be
         stated therein or necessary to make the statements therein not
         misleading, based upon information furnished, or required to be
         furnished, in writing to the Company by the Holder or underwriter
         expressly for use therein. This indemnity agreement shall not inure to
         the benefit of any such underwriter (or to the benefit of any person
         who controls such underwriter) on account of any losses, claims,
         damages, liabilities or actions or proceedings in respect thereof)
         arising from the sale of any of such Warrant Stock by such underwriter
         to any person if such underwriter failed to send or give a copy of the
         prospectus furnished pursuant to clause (A) of this subsection (m)(3),
         as the same may then be supplemented or amended (if such supplement or
         amendment shall

                                      -11-
<PAGE>   12
         have been furnished to the Holder pursuant to said clause (A)), to such
         person with or prior to the written confirmation of the sale involved.

         (4) The Company shall bear all costs and expenses incurred in
connection with the Company's obligations under this Section (m) , including,
without limiting the generality of the foregoing, accounting fees, fees and
disbursements of counsel for the Company, all costs and expenses incurred in
connection with the compliance with state securities or blue sky laws of such
jurisdictions as the Holder shall reasonably request, and expenses incurred for
preparing, printing and distributing such quantity of prospectuses as the Holder
shall reasonably request; provided, however, that any discounts, commissions,
broker's fees and similar fees to securities industry professionals, and any
transfer taxes relating to the sale of the Warrant Stock shall be paid by the
Holder.

         (5) The Company's obligations under subsections (1) and (2) of this
Section (m) shall be conditioned, as to each such public offering, upon a timely
receipt by the Company in writing of:

                  (A) Information as to the terms of such public offering
         furnished by or on behalf of the Holder; and

                  (B) Such other information as the Company may reasonably
         require from the Holder or any underwriter for inclusion in such
         registration statement or post-effective amendment.

         (6) Any notices or certificates by the Company to the Holder and by the
Holder to the Company shall be deemed delivered if in writing and delivered
personally or sent by certified mail, if to the Holder, addressed to it at its
registered address or, if the Holder has designated by notice in writing to the
Company any other address, to such other address, and, if to the Company,
addressed to it at its Registry Office. The Company may change its Registry
Office by written notice to the holders of the Warrants and the Holder may
change its address by written notice to the Company.

         (7) The Company's agreements with respect to registration of the
Warrant Stock in this Section (m) shall apply to and continue in effect,
regardless of the exercise or surrender of this Warrant; provided, however, that
the Company shall have no obligation to register Warrant Stock pursuant hereto
if (i) in the written opinion of counsel for the Company, which opinion shall be
satisfactory in form and substance to the Holder, the Warrant Stock is freely
tradable without the need for such registration, (ii) the Holder is provided
with unlegended certificates representing the Warrants or Warrant Stock and
(iii) all stop transfer orders on the Warrants and Warrant Stock are removed by
the Company

         (n) GOVERNMENTAL APPROVALS AND STOCK EXCHANGE LISTINGS. The Company
shall from time to time take all action which may be necessary to obtain and
keep

                                      -12-
<PAGE>   13
effective any and all permits, consents and approvals of governmental agencies
and authorities which may be or become requisite in connection with the
issuances, sales, transfer, delivery and exercise of the Warrants by the
registered holders thereof, and the issuance, sale, transfer and delivery of the
Warrant Stock by such holders, and all action which may be necessary so that
such shares of Warrant Stock, immediately upon their issuance pursuant to the
exercise of the Warrants, will be listed or entitled to unlisted trading
privileges each securities exchange (or on NASDAQ, if applicable) on which
Common Stock is then listed or entitled to unlisted trading privileges, and on
the identical basis.

         (o) TRANSFER RESTRICTIONS.

         (1) This Warrant or the Warrant Stock may not be sold, transferred or
otherwise disposed of except as follows:

                  (A) to any person who, in the opinion of counsel provided by
         the Holder and satisfactory to the Company, is a person to whom this
         Warrant or such Warrant Stock may legally be transferred without
         registration and without the delivery of a current prospectus or
         offering circular under the Act with respect thereto and then only
         against receipt of an agreement of such person to comply with the
         provisions of this Section (o) with respect to any resale or other
         disposition of such securities; or

                  (B) with respect to the Warrant Stock, to any person upon
         delivery of a prospectus then meeting the registration requirements of
         the Act relating to the Warrant Stock and the offering thereof for such
         sale or disposition.

         (2) The Company may cause a legend substantially in the following form
to be set forth on each certificate representing Warrant Stock not theretofore
distributed to the public or sold to underwriters for distribution to the public
pursuant to Section (m) hereof, unless counsel for the Company is of the opinion
as to any such certificate that such legend is unnecessary:

         "THE SECURITIES REPRESENTED BY THIS CERTIFICATE HAVE NOT BEEN
         REGISTERED UNDER THE SECURITIES ACT OF 1933, AS AMENDED, OR THE
         SECURITIES LAWS OF ANY STATE AND MAY NOT BE SOLD OR OTHERWISE DISPOSED
         OF EXCEPT PURSUANT TO AN EFFECTIVE REGISTRATION STATEMENT UNDER SUCH
         ACT AND APPLICABLE STATE SECURITIES LAWS OR AN APPLICABLE EXEMPTION TO
         THE REGISTRATION REQUIREMENTS OF SUCH ACT OR SUCH LAWS."

         (p) APPLICABLE LAW. THIS WARRANT SHALL BE GOVERNED BY, AND CONSTRUED IN
ACCORDANCE WITH, THE LAWS OF THE STATE OF NEW YORK WITHOUT REGARD TO PRINCIPLES
OF CONFLICTS OF LAWS.

                                      -13-
<PAGE>   14
         (q) AMENDMENT. This Warrant may only be amended by a written instrument
executed by the Company and the Holder.

         (r) REPRESENTATIONS AND WARRANTIES. The Company hereby represents and
warrants to the Holder as follows: (i) execution and delivery of this Warrant by
the Company has been duly authorized by all necessary corporate action, and this
Warrant constitutes the valid and binding obligation of the Company in
accordance with its terms; (ii) the Warrant and the Warrant Stock have been duly
authorized for issuance, and upon delivery of the Warrant the Holder will have
good and valid title thereto, free and clear of any and all liens, claims and
encumbrances of any nature whatsoever; (iii) the Warrant Stock has been, and
will continue to be, duly reserved for issuance; and (iv) upon exercise of the
Warrant in accordance with the terms thereof, the Warrant Stock shall have been
duly and validly issued, fully paid and non-assessable.

                                      -14-
<PAGE>   15
         (s) BINDING EFFECT. Subject to the provisions of Sections (g) and (o),
this Warrant and the rights evidenced hereby shall inure to the benefit of, and
be binding upon, the Company and the Holder and their respective successors and
assigns, including any permitted transferee of the Warrant or Warrant Stock.

                                               ECOGEN INC.

                                               By ____________________________
                                                                 President
Date: ____________________

(SEAL)

Attest:

__________________________
Secretary

                                      -15-
<PAGE>   16
                                 ACKNOWLEDGEMENT

STATE OF NEW YORK               |
                                | SS:
COUNTY OF NEW YORK              |

         On December __, 1999, before me, the undersigned, a Notary Public in
and for said State, personally appeared _______________, personally known to me
or proved to me on the basis of satisfactory evidence to be the individual whose
name is subscribed to the within instrument and acknowledged to me that he
executed the same in his capacity, and that by his signature on the instrument,
the individual, or the person upon behalf of which the individual acted,
executed the instrument.

         IN WITNESS WHEREOF, I hereunto set my hand and official seal.

                                        ______________________________________
                                                    Notary Public

                                         My commission expires: ______________
<PAGE>   17
                                    [FORM OF]
                              ELECTION TO PURCHASE

Ecogen Inc.
2000 Cabot Boulevard West
Langhorne, Pennsylvania 19047
Attention: Treasurer

         The undersigned registered owner of the within Warrant hereby
irrevocably elects to exercise the right of purchase represented by the within
Warrant for, and to purchase thereunder ______________ shares of the stock
provided for therein, and requests that certificates for such shares shall be
issued in the name of

________________________________________________________________________________
                                 (Please Print)

and be delivered to ____________________________________________________________

at _____________________________________________________________________________

and, if said number of shares shall not be all the shares purchasable
thereunder, that a new Warrant for the balance remaining of the shares
purchasable under the within Warrant be registered in the name of, and delivered
to, the undersigned at the address stated below.

Dated: ____________________

Name of Registered Owner:

________________________________________________________________________________
                                 (Please Print)

Address: _______________________________________________________________________

Signature: _____________________________________________________________________

Note: The above signature must correspond with the name as written upon the face
of this Warrant in every particular, without alteration or enlargement or any
change whatever.

Signature Guaranteed: ___________________________
<PAGE>   18
                                    [FORM OF]
                                   ASSIGNMENT

For value received, the undersigned registered owner of the within Warrant

________________________________________________________________________________

does hereby sell, assign and transfer unto

________________________________________________________________________________

the within Warrant, together with all right, title and interest therein, with
respect to ___________________ shares of Common Stock, and does hereby
irrevocably constitute and appoint

________________________________________________________________________________

attorney, to transfer said Warrant on the books of the within-named Company,
with full power of substitution in the premises.

Social Security or
other identifying number
of assignee:                        ______________________________

Dated: _______________________

Signature: ________________________

Note: The above signature must correspond with the name as written upon the face
of this Warrant in every particular, without alteration or enlargement or any
change whatever.

Signature Guaranteed: ___________________________<PAGE>   1
                            SECOND AMENDMENT TO LEASE

         This AMENDMENT TO LEASE, dated as of this 17th day of December 1999, by
and between ECOGEN INC., a corporation organized and existing under the laws of
the State of Delaware ("Tenant"), and Brandywine Operating Partnership, L.P., a
Pennsylvania limited partnership, acting through its Agent, Brandywine Realty
Services Corporation ("Landlord").

                                   BACKGROUND

WHEREAS, Landlord's predecessor in interest, Advent Realty Limited Partnership,
and Tenant, by Lease Agreement dated January 13, 1988, (and an Amendment thereto
dated March 31, 1992) leased 14,900 rentable square feet of space, located in
that certain Building known as 2000 Cabot Boulevard West, Langhorne,
Pennsylvania (said Lease Agreement and Amendment being hereinafter referred to
as the "Lease").

         WHEREAS, by acquisition of the Land and Building of which the Premises
is a part, the Landlord herein has acquired all right, title and interest of
said predecessor therein and thereto, including all rights and obligations as
Landlord under said Lease and

         WHEREAS, Landlord and Tenant mutually desire to extend the Term of said
Lease, which is currently due to expire on March 31, 2000, and modify certain
other provisions thereof all on the terms and conditions as hereinafter
provided.

         NOW THEREFORE, in consideration of the mutual covenants herein set
forth, intending to be legally bound hereby, Landlord and Tenant agree as
follows:

         1. Incorporation; Definitions. The defined terms used in this Second
Amendment to Lease shall be deemed to have the meanings ascribed thereto in the
Lease or, if defined herein, in this Second Amendment to Lease. The headings of
paragraphs are for convenience only and shall not be deemed to enlarge or
diminish the provisions of this Second Amendment to Lease.

         2. Extension Term. The Term of said Lease is hereby extended for a
period of five (5) years from April 1, 2000 to March 31, 2005 (the "New Ending
Date of Term").

         3. Tenant Improvements. No improvements to the Premises are required of
the Landlord in connection with the extension of the Lease Term provided herein
- the Premises being accepted by Tenant in its current condition, "As-Is".
Landlord shall reimburse Tenant up to $20,000 for improvements tenant shall make
to the Premises. Landlord shall pay Tenant, within forty five (45) days of
Landlord's receipt of invoices, for such improvements, which expenses shall be
certified by Tenant as incurred. Tenant shall have one (1) year from, April 1,
2000 to use and request reimbursement for Tenant Improvements.
<PAGE>   2
         4. Renewal Option. The Option to renew provided for in paragraph (6) of
the above mentioned Amendment dated March 31, 1992 (i.e. Lease Extension
Agreement) is hereby deleted and shall be of no further force or effect - this
Amendment being deemed in lieu thereof.

         5. Annual Base Rent. During the extension Term the Annual Base Rent
shall be payable by Tenant to Landlord, at the times and in the manner set forth
in the Lease, according to the following schedule:

<TABLE>
<CAPTION>
                   Monthly
Period of          Installment of     Total Annual        Base Rent Per
Lease Term         Base Rent          Rent for Period     Rentable Square Foot
<S>                <C>                <C>                 <C>
4/1/00-3/31/01     $15,694.67         $188,336.00         $12.64
4/1/01-3/31/02     $16,005.08         $192,061.00         $12.89
4/1/02-3/31/03     $16,315.50         $195,786.00         $13.14
4/1/03-3/31/04     $16,625.92         $199,511.00         $13.39
4/1/04-3/31/05     $16,936.33         $203,236.00         $13.64
</TABLE>

         6. Operating Expenses. The parties agree that with respect the Tenants
obligations under Articles 4 and 7 of said Lease, same are hereby Amended as
follows:

         Article 4 - Commencing April 1, 2000 and continuing throughout the
Extension Term the Tenant shall only be responsible to pay its proportionate
share of Real Estate Taxes that are in excess of the Real Estate Taxes allocable
to the Base Year 2000 (i.e. calendar year 2000 for County Taxes and 7/1/99 -
6/30/00 - fiscal year for school Taxes). It is anticipated therefore that the
billing for Real Estate Taxes for the Extension Term would not occur until after
December 31, 2000, whether the billings would be estimated or actual as
contemplated in said Article 4.

         Article 7 - This provision shall during the extension Term be deemed
modified to the extent that Landlord shall undertake all services for and make
all repairs to the Building and the Premises except that Tenant will continue to
be responsible for (a) all interior non structural repairs to Premises and any
repairs or replacement necessitated by acts or immersions of Tenant, its agents
or employees, (b) the janitorial services to the Premises (c) HVAC maintenance
and repair and (d) cost of all services and utilities as contemplated in Lease
Article 14.

         After the commencement of the Extension Term, Landlord will deliver to
Tenant a Statement of Expenses covering any unpaid amounts due and owing from
Tenant under the Lease for the period ending March 31, 2000.
<PAGE>   3
         7. Broker. Each party warrants to the others that it has had no
dealings with any broker or agent, other than Gola Corporate Real Estate, in
connection with the negotiation or execution of this Extension of Term and/or
Amendment to Lease. Tenant agrees to indemnify Owner, and Owner agrees to
indemnify Tenant, against all costs, expenses, reasonable attorney's fees or
other liability for commissions or other compensation or charges claimed by an
broker or agent claiming the same by, through or under said indemnifying party.

         8. Affirmation and Applicability of Original Lease. Each term,
  condition and provision of the Lease is in full force and effect as of the
  date hereof and shall remain in full force and effect as is fully set forth in
  this Second Amendment to Lease, except as expressly modified and amended by
  this Second Amendment to Lease.

         IN WITNESS WHEREOF, the parties hereto have caused this Second
Amendment to Lease to be duly executed as of the day and year first written
above.

ATTEST:                                     TENANT:  Ecogen Inc.
                                                     A Delaware Corporation

By: _________________________               By: ________________________________
                                                Authorized Representative

                                            By: ________________________________
                                                Please print name and title

ATTEST:                                     LANDLORD: Brandywine Operating
                                            Partnership, L.P. by its Agent,
                                            Brandywine Realty Services
                                            Corporation, Landlord

By: _________________________               By: ________________________________
    Authorized Representative                   Jeff DeVuono
                                                Vice President-Operations

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