<PAGE>   1
                                                                     EXHIBIT 4.6

THIS WARRANT AND ANY SHARES ACQUIRED UPON THE EXERCISE OF THIS WARRANT HAVE NOT
BEEN REGISTERED UNDER THE SECURITIES ACT OF 1933, AS AMENDED, AND MAY NOT BE
SOLD OR OTHERWISE TRANSFERRED EXCEPT PURSUANT TO AN EFFECTIVE REGISTRATION
STATEMENT FILED UNDER SUCH ACT OR PURSUANT TO AN EXEMPTION FROM REGISTRATION
UNDER SUCH ACT.

                                                                  April 26, 2000

                                    WARRANT

                 TO SUBSCRIBE FOR AND PURCHASE COMMON STOCK OF
                              ANTEX BIOLOGICS INC.

          VOID AFTER 5:00 P.M., SAN FRANCISCO TIME, ON APRIL 26, 2005,
           OR IF NOT A BUSINESS DAY, AS DEFINED HEREIN, AT 5:00 P.M.,
         SAN FRANCISCO TIME, ON THE IMMEDIATELY PRECEDING BUSINESS DAY

No.___

        THIS CERTIFIES that, for good and valuable consideration, FIRST SECURITY
VAN KASPER ("FSVK"), or registered assigns (the "Warrantholder"), is entitled to
subscribe for and purchase from ANTEX BIOLOGICS INC., a Delaware corporation
(the "Company"), at a price of $1.5625 per share (such price, as from time to
time to be adjusted as hereinafter provided, being hereinafter called the
"Warrant Price"), at any time and from time to time prior to the Expiration
Date (as defined below), up to 50,000 fully paid, nonassessable shares of
Common Stock, par value $0.01 per share, of the Company ("Common Stock"),
subject, however, to the provisions and upon the terms and conditions,
hereinafter set forth, including without limitation the provisions of Section 2
hereof. "Expiration Date" shall mean 5:00 P.M., San Francisco time, on April
26, 2005, which is five years from the date hereof, or if not a Bussiness Day,
as defined herein, at 5:00 P.M., San Francisco time, on the immediately
preceding business day. "Business Day" shall mean a day other than a Saturday,
Sunday or other day on which banks in the State of California are authorized by
law to remain closed.


SECTION 1.      EXERCISE OF WARRANT


        (a)     CASH EXERCISE

        This Warrant may be exercised, at any time and from time to time prior
to the Expiration Date, by the Warrantholder, in whole or in part (but not as to
a fractional share of Common Stock and in no event for less than 25,000 shares
(unless less than the aggregate of 25,000 shares are then purchasable under all
outstanding Warrants held by a Warrantholder)), by the completion of the
subscription form attached hereto and by the surrender of this Warrant (properly
endorsed) at the Company's offices at 300 Professional Drive, Gaithersburg, MD
20879 (or at such other location in the United States as the Company may
designate by notice in writing to the Warrantholder at the address of the
Warrantholder appearing on the books of the Company), and by payment to the
Company of the Warrant Price, in cash or by certified or official bank check,
for each share being purchased.


        (b)     NET EXERCISE

        Notwithstanding anything to the contrary contained in Section 1(a), the
Warrantholder may elect to exercise this Warrant and receive shares on a "net
exercise" basis in an amount equal to the value of this Warrant by delivery of
the subscription form attached hereto and surrender of this Warrant at the
principal office of the Company, in which event the Company shall issue to
Holder a number of shares computed using the following formula:

                X-  (P)(Y)(A-B)
                    -----------
                          A
<PAGE>   2
      Where:      X-    the number of shares of Common Stock to be issued to
                        Holder.

                  P-    the portion of the Warrant being exercised.

                  Y-    the number of shares of Common Stock issuable upon
                        exercise of this Warrant.

                  A-    the Current Market Price (as determined pursuant to
                        Section 1(d)) of one share of Common Stock.

                  B=    Warrant Price.

      (c)   PROCEDURE FOR EXERCISE

      In the event of an exercise of the rights represented by this Warrant, a
certificate or certificates for the total number of whole shares of Common
Stock so purchased, registered in the name of the Warrantholder, shall be
delivered to the Warrantholder within a reasonable time, not exceeding ten
Business Days, after the rights represented by this Warrant shall have been so
exercised; and, unless this Warrant has expired, a new Warrant representing the
number of shares (except a remaining fractional share), if any, with respect to
which this Warrant shall not then have been exercised shall also be issued to
the Warrantholder within such time.  With respect to any such exercise, the
Warrantholder shall for all purposes be deemed to have become the holder of
record of the number of shares of Common Stock evidenced by such certificate or
certificates from the date on which this Warrant was surrendered and if
exercise is pursuant to Section 1(a), payment of the Warrant Price was made,
irrespective of the date of delivery of such certificate, except that, if the
date of such surrender and payment is a date on which the stock transfer books
of the Company are closed, such person shall be deemed to have become the
holder of such shares at the close of business on the next succeeding date on
which the stock transfer books are open.  No fractional shares shall be issued
upon exercise of this Warrant and no payment or adjustment shall be made upon
any exercise on account of any cash dividends on the Common Stock issued upon
such exercise.  If any fractional interest in a share of Common Stock would,
except for the provisions of this Section 1, be delivered upon any such
exercise, the Company, in lieu of delivering the fractional share thereof, shall
pay to the Warrantholder an amount in cash equal to the Current Market Price of
such fractional interest, as determined below.

      (d)   CURRENT MARKET PRICE

      For any computation hereunder, the "Current Market Price"  per share of
Common Stock on any date shall be deemed to be the average of the daily Market
Price per share for the 10 consecutive Trading Days preceding the date in
question.  "Market Price" is defined as the closing bid price of such security
on the principal United States securities exchange or trading market on which
such security is listed or traded as reported by the Research Service of Nasdaq
Trading and Market Services (or a comparable reporting service of national
reputation), or if the foregoing does not apply, the last reported sale price
of such security in the over-the-counter market on the electronic bulletin
board for such security as reported by Nasdaq, or, if no sale price is
reported for such security by Nasdaq, the average of the bid prices of any
market makers for such security as reported in the "pink sheets" by the
National Quotation Bureau, Inc.  If Market Price cannot be established as
described above, Market Price shall be the fair market value of the Common
Stock as determined in good faith by the Board of Directors.  The term
"Trading Day" shall mean a day on which Nasdaq or the principal national
securities exchange on which the Common Stock is listed or admitted to trading
is open for the transaction of business.

SECTION 2.  ADJUSTMENTS

            The Warrant Price and the number and kind of shares issuable
hereunder shall be subject to adjustment from time to time upon the happening
of certain events as provided in this Section 2.

      (a)   ADJUSTMENTS

            (1)   If at any time prior to the exercise of this Warrant in full,
the Company shall (A) declare a dividend or make a distribution on the Common
Stock payable in shares of its capital stock (whether shares of
<PAGE>   3
Common Stock or of capital stock of any other class); (B) subdivide, reclassify
or recapitalize its outstanding Common Stock into a greater number of shares;
(C) combine, reclassify or recapitalize its outstanding Common Stock into a
smaller number of shares; or (D) issue any shares of its capital stock by
reclassification of its Common Stock (excluding any such reclassification in
connection with a consolidation or a merger), the Warrant Price in effect at
the time of the record date of such dividend, distribution, subdivision,
combination, reclassification or recapitalization shall be adjusted so that the
Warrant Price shall be equal to the price determined by multiplying the Warrant
Price in effect immediately prior to such event by a fraction, the numerator of
which shall be (x) the total number of outstanding shares of Common Stock of
the Company immediately prior to such event; and the denominator of which
shall be (y) the total number of outstanding shares of Common Stock of the
Company immediately after such event and, as so adjusted or readjusted, the
Warrant Price shall remain in effect until a further adjustment or readjustment
is required by this Section 2.  Whenever the Warrant Price is adjusted pursuant
to this Section 2(a)(1), the shares issuable hereunder shall simultaneously be
adjusted by multiplying the number of shares issuable upon exercise of the
Warrant immediately prior to such event by the Warrant Price in effect on the
date thereof and dividing the product so obtained by the Warrant Price
resulting from such adjustment.  Any adjustment required by this Section
2(a)(1) shall be made successively immediately after the record date, in the
case of a dividend or distribution, or the effective date, in the case of a
subdivision, combination, reclassification or recapitalization, to allow the
purchase of such aggregate number and kind of shares.

            (2)   If at any time prior to the exercise of this Warrant in full,
the Company shall make a distribution to all holders of the Common Stock of
stock of a subsidiary or other corporation or securities convertible into or
exercisable for such stock, then in lieu of an adjustment in the Warrant Price
or the number of shares of Common Stock purchasable upon the exercise of this
Warrant, the Warrantholder, upon the exercise hereof at any time after such
distribution, shall be entitled to receive from the Company the stock or other
securities to which the Warrantholder would have been entitled if the
Warrantholder had exercised this Warrant immediately prior thereto, all subject
to further adjustment as provided in this Section 2, and the Company shall
reserve, for the life of the Warrant, such securities of such subsidiary or
other corporation; provided, however, that no adjustment in respect of
dividends or interest on such stock or other securities shall be made during
the term of this Warrant or upon its exercise.

            (3)   If at any time prior to the expiration of this Warrant in
full, the Company shall issue rights or warrants to all holders of Common Stock
as such entitling them to subscribe for or purchase Common Stock at a price per
share less than the Current Market Price per share on such record date, then,
in each such case the number of shares subject to this Warrant thereafter
purchasable upon the exercise of this Warrant shall be determined by
multiplying the number of shares of Common Stock theretofore purchasable upon
exercise of this Warrant by a fraction, the numerator of which shall be (x) the
number of shares of Common Stock outstanding on the date of issuance of such
rights or warrants, plus the number of additional shares of Common Stock
offered for subscription or purchase, and the denominator of which shall be (y)
the number of shares of Common Stock outstanding on the date of issuance of
such rights or warrants plus the number of shares that the aggregate offering
price of the total number of shares of Common Stock so offered would purchase
at the Current Market Price on such record date.  For purposes of this Section
2(a)(3), the issuance of rights or warrants to subscribe for or purchase
securities convertible into Common Stock shall be deemed to be the issuance of
rights or warrants to purchase the Common Stock into which such securities are
convertible at an aggregate offering price equal to the aggregate offering
price of such securities plus the minimum aggregate amount (if any) payable
upon conversion of such securities into Common Stock.  In addition to the
adjustment in the number of shares in this Section 2(a)(3), the Warrant Price
per share shall be appropriately adjusted so that the aggregate Warrant Price
shall remain constant.

            (4)   If at any time prior to the exercise of this Warrant in full,
the Company shall distribute to all holders of its Common Stock evidence of
indebtedness of the Company or assets of the Company (excluding cash dividends
or distributions out of earned surplus) or rights or warrants to subscribe for
securities of the Company (excluding those referred to in Section 2(a)(3)
above), then in each case the Warrant Price shall be adjusted to a price
determined by multiplying the Warrant Price in effect immediately prior to such
distribution by a fraction, the numerator of which shall be (x) the then Current
Market Price per share of Common Stock on the record date for determination of
stockholders entitled to receive such distribution, less the then fair value (as
reasonably determined by the Board of Directors of the Company, whose
determination shall be conclusive) of the portion of the assets or evidences of
indebtedness so distributed or of such subscription rights or warrants which are
applicable to one share of Common stock, and the denominator of which shall be
(y) the Current Market Price per share of Common Stock; provided, however, that
if the then Current Market Price per share of Common Stock on
<PAGE>   4
the record date for determination of stockholders entitled to receive such
distribution is less than the then fair value of the portion of the assets or
evidence of indebtedness so distributed or of such subscription rights or
warrants which are applicable to one share of Common Stock, the foregoing
adjustment of the Warrant Price shall not be made and in lieu thereof the
number of shares purchasable upon exercise of each Warrant immediately prior to
such distribution shall be adjusted so that the holder of such Warrant shall be
entitled to receive upon exercise of such Warrant the kind and number of
assets, evidence of indebtedness, subscription rights and warrants (or, in the
event of the redemption of such evidence of indebtedness, subscription rights or
warrants, any cash paid in respect of such redemption) that such Warrantholder
would have owned or have been entitled to receive in such distribution had such
Warrant been exercised immediately prior to the record date of such
distribution.

                (5)     For purposes of any computation under this Section
2(a), the Current Market Price per share of Common Stock on any date shall be
deemed calculated as provided in Section 1(d).

                (6)     No adjustment in the Warrant Price shall be required
unless such adjustment would require an increase or decrease of at least five
cents ($.05) in such price; provided, however, that any adjustments which by
reason of this Section 2(a)(6) are not required to be made shall be carried
forward and taken into account in any subsequent adjustment. All calculations
under this Section 2(a) shall be made to the nearest cent or to the nearest one
hundredth of a share, as the case may be. Notwithstanding anything in this
Section 2(a) to the contrary, the Warrant Price shall not be reduced to less
than the then existing par value of the Common Stock as a result of any
adjustment made hereunder.

                (7)     In the event that at any time, as the result of any
adjustment made pursuant to this Section 2(a), the Warrantholder thereafter
shall become entitled to receive any securities other than Common Stock,
thereafter the number of such other securities so receivable upon exercise of
this Warrant shall be subject to adjustment from time to time in a manner and
on terms as nearly equivalent as practicable to the provisions with respect to
the Common Stock contained in Section 2(a).

        (b)     NO ADJUSTMENT FOR DIVIDENDS

        Except as provided in Section 2(a) of this Agreement, no adjustment in
respect of any cash dividends shall be made during the term of this Warrant or
upon the exercise of this Warrant.

        (c)     PRESERVATION OF PURCHASE RIGHTS IN CERTAIN TRANSACTIONS

        In case of any consolidation of the Company with or merger of the
Company into another corporation 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 or such successor or purchasing
corporation, as the case may be, shall execute an agreement with the
Warrantholder whereby the Warrantholder shall have the right thereafter upon
payment of the Warrant Price in effect immediately prior to such action to
purchase upon exercise of the Warrant the kind and amount of shares and other
securities and property which the Warrantholder would have owned or have been
entitled to receive after the happening of such consolidation, merger, sale or
conveyance had the Warrant been exercised immediately prior to such action. The
Company shall mail by first class mail, postage prepaid, to the Warrantholder,
notice of the execution of any such agreement. Such agreement shall provide for
adjustments, which shall be as nearly equivalent as may be practicable to the
adjustments provided for in this Section 2. The provisions of this Section 2
shall similarly apply to successive consolidations, mergers, sales or
conveyances. The Warrantholder shall be under no duty or responsibility to
determine the correctness of any provisions contained in any such agreement
relating either to the kind or amount of shares of stock or other securities or
property receivable upon exercise of warrants or with respect to the method
employed and provided therein for any adjustments.

        (d)     FORM OF WARRANT AFTER ADJUSTMENTS

        The form of this Warrant need not be changed because of any adjustments
in the Warrant Price or the number or kind of the shares purchasable pursuant
to this Warrant, and Warrants theretofore or thereafter issued may continue to
express the same price and number and kind of shares as are stated in this
Warrant, as initially issued; provided, however, that the Company may, at any
time in its sole discretion (which shall be conclusive), make any change in the
form of Warrant certificate that it may deem appropriate and that does not
affect the substance thereof. Any Warrant certificate thereafter issued,
whether upon registration of transfer of, or in exchange
<PAGE>   5
or substitution for, an outstanding Warrant certificate may be in the form so
changed.

        (e)     TREATMENT OF WARRANTHOLDER

        Prior to due presentment for registration of transfer of this Warrant,
the Company may deem and treat the Warrantholder as the absolute owner of this
Warrant (notwithstanding any notation of ownership or other writing hereon) for
all purposes and shall not be affected by any notice to the contrary.

        (f)     NOTICE OF ADJUSTMENT

        Upon any adjustment under this Section 2, then and in each such case
the Company shall give written notice thereof, by first-class mail, postage
prepaid, addressed to the Warrantholder at the address of such holder as shown
on the books of the Company, which notice shall state the Warrant Price and the
number or kind of the shares purchasable pursuant to this Warrant resulting
from such adjustment, setting forth in reasonable detail the method of
calculation and the facts upon which such calculation is based.

        (g)     STOCK TO BE RESERVED

        The Company will at all times reserve and keep available out of its
authorized Common Stock, solely for the purpose of issuance upon the exercise
of this Warrant as herein provided, such number of shares of Common Stock as
shall then be issuable upon the exercise of this Warrant. The Company covenants
that all shares of Common Stock which shall be so issued, upon full payment of
the Warrant Price therefore or as otherwise set forth herein, shall be duly and
validly issued and fully paid and nonassessable and free from all taxes, liens
and charges with respect to the issue thereof, and, without limiting the
generality of the foregoing, the Company covenants that it will from time to
time take all such action as may be required to ensure that the par value per
share, if any, of the Common Stock is at all times equal to or less than the
effective Warrant Price. The Company will take all such action as may be
necessary to ensure that all such shares of Common Stock may be so issued
without violation of any applicable law or regulation, or of any requirement of
any national securities exchange or automated quotation system upon which the
Common Stock of the Company may be listed. The Company will not take any action
that results in any adjustment under this Section 2, if the total number of
shares of Common Stock issued and issuable after such action upon exercise of
this Warrant would exceed the total number of shares of Common Stock then
authorized by the Company's Certificate of Incorporation. The Company has not
granted and will not grant any right of first refusal with respect to shares
issuable upon exercise of this Warrant, and there are no preemptive rights
associated with such shares.

        (h)     ISSUE TAX

        The issuance of certificates for shares of Common Stock upon exercise
of any Warrant shall be made without a charge to the Warrantholder for any
issuance tax in respect thereof, provided that the Company shall not be
required to pay any tax which may be payable in respect of any transfer
involved in the issuance and delivery of any certificate in a name other than
that of the Warrantholder.

        (i)     CLOSING OF BOOKS

        The Company will at no time close its transfer books against the
transfer of the shares of Common Stock issued or issuable upon the exercise of
this Warrant in any manner that interferes with the timely exercise of this
Warrant.

        (j)     DEFINITION OF COMMON STOCK

        As used herein the term "Common Stock" shall mean and include the
Common Stock, par value $0.01, of the Company as authorized on the date hereof,
or shares of any class or classes resulting from any recapitalization or
reclassification thereof which are not limited to any fixed sum or percentage
and are not subject to redemption by the Company and in case at any time there
shall be more than one such resulting class, the shares of each class then so
issuable shall be substantially in the proportion which the total number of
shares of such class resulting from all such reclassification bears to the
total number of shares of all such classes resulting from all such
reclassification.
<PAGE>   6
SECTION 3.      REGISTRATION RIGHTS

                (a)     PIGGYBACK REGISTRATION

        If the Company proposes to register with the SEC any of the Common Stock
under the Regulations of the SEC (other than pursuant to a request under Section
3(a) and other than securities to be issued pursuant to a stock option or other
employee benefit or similar plan, or in connection with a merger, acquisition,
or a Rule 145 transaction), the Company shall, as promptly as practicable, but
at least 30 days prior to the filing of the applicable registration statement
give written notice to the Warrantholder of its intention to effect such
registration. If, within 20 days after receipt of such notice, the
Warrantholder submits a written request to the Company specifying the amount of
Registrable Stock that the Warrantholder proposes to sell, the Company shall
include the shares specified in such request in such registration statement
(and any related qualification under blue sky laws or other compliance) and the
Company shall keep each such registration statement in effect and maintain
compliance with each federal and state law and regulation as set forth in
Section 3(d).

                (b)     COVENANTS OF THE COMPANY

        In connection with any offering of Subject Stock registered pursuant to
this Section 3, the Company shall (a) furnish to the Warrantholder such number
of copies of any registration statement (including any preliminary prospectus)
as it may reasonably request in order to effect the offering and sale of the
Subject Stock, but only while the Company shall be required under the
provisions hereof to cause the registration statement to remain current, (b)
take such action as shall be desirable or necessary to qualify the Subject
Stock covered by such registration statement under such blue sky or other state
securities laws for offer and sale as the Warrantholder shall request, and (c)
keep the Warrantholder advised in writing as to the initiation of each
registration and as to the completion thereof. Upon any registration becoming
effective pursuant to this Section 3, the Company shall use its best efforts
to: (i) keep such registration statement current for a period of 180 days; (ii)
prepare and file with the SEC such amendments and supplements to such
registration statement as may be necessary to comply with the provisions of the
Regulations of the SEC with respect to the disposition of all securities covered
by such registration statement; (iii) cause all such Subject Stock registered
pursuant to such registration statement to be listed on each securities exchange
or automated quotation system on which the Common Stock is then listed; (iv)
provide a transfer agent and registrar for all Subject Stock registered pursuant
to such registration statement and CUSIP number for all such Subject Stock, in
each case not later than the effective date of such registration; and (v)
otherwise use its best efforts to comply with all applicable rules and
regulations of the SEC.

                (c)   EXPENSES

        With respect to the piggyback registration of Subject Stock pursuant to
Section 3(a), the Company will pay all expenses incident to its performance of
or compliance with this Section 3 including, without limitation, all
registration and filing fees, fees and expenses of compliance with securities
or blue sky laws, printing expenses, messenger, telephone and delivery
expenses, and fees and disbursements of its counsel and independent certified
public accountants. The Warrantholder will be responsible for any stock
transfer taxes, broker's fees or other direct marketing expenses, all internal
management, personnel and administrative costs of the Warrantholder and the
fees and expenses of its attorneys, if any, incurred by it in connection with
effecting any such transaction.

                (d)     INDEMNIFICATION

        The Company will indemnify, to the maximum extent permitted by law, the
Warrantholder, its officers and directors and each person who controls the
Warrantholder (within the meaning of the Regulations of the SEC) against all
losses, claims, damages, liabilities and expenses (or actions, proceedings or
settlements in respect thereof) caused by, arising out of or based on any
untrue or alleged untrue statement of a material fact contained in any
registration statement (or any amendment or supplement thereto) of the Company
relating to the sale of Subject Stock registered pursuant to this Section 3, or
any exhibits or materials incorporated by reference therein, filed with the
SEC, or 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, except insofar as the same are caused by or contained in any
information furnished in writing to the Company by the Warrantholder expressly
for use therein.

        The Warrantholder will indemnify, to the maximum extent permitted by
law, the Company, its officers and
<PAGE>   7
directors and each person who controls the Company (within the meaning of the
Regulations of the SEC) against all losses, claims, damages, liabilities and
expenses (or actions, proceedings or settlements in respect thereof) caused by,
arising out of or based on any untrue or alleged untrue statement of a material
fact contained in any registration statement (or any amendment or supplement
thereto) of the Company relating to the sale of Subject Stock registered
pursuant to this Section 3, or any exhibits or materials incorporated by
reference therein, filed with the SEC, or 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, but only insofar as the same are
caused by or contained in any information furnished in writing to the Company by
the Warrantholder expressly for use therein.

        Any person entitled to indemnification under this Section 3(d) will (i)
give prompt written notice to the indemnifying party of any claim with respect
to which it seeks indemnification and (ii) unless in such indemnified party's
reasonable judgment a conflict of interest between such indemnified and
indemnifying parties may exist with respect to such claim, permit such
indemnifying party to assume the defense of such claim with counsel reasonably
satisfactory to the indemnified party. If such defense is assumed, the
indemnifying party will not be subject to any liability for any settlement made
by the indemnified party without its consent (but such consent will not be
unreasonably withheld). An indemnifying party who is not entitled to, or elects
not to, assume the defense of a claim will not be obligated to pay the fees and
expenses of more than one counsel for all parties indemnified by such
indemnifying party with respect to such claim, unless in the reasonable judgment
of any idemnified party a conflict of interest may exist between such
indemnified party and any other of such indemnified parties with respect to such
claim in which case, the indemnifying party shall be obligated to pay the fees
and expenses of up to two counsel for all parties indemnified by such
indemnifying party with respect to such claim.

        The indemnifications set forth in this Section 3(d) shall survive the
termination or expiration of this Warrant.

Section 4.      Notices of Record Dates

        In the event of:

                (a)   any taking by the Company of the record of the holders of
                      any class of securities for the purpose of determining the
                      holders thereof who are entitled to receive any dividend
                      or other distribution (other than cash dividends out of
                      earned surplus), or any right to subscribe for, purchase
                      or otherwise acquire any shares of stock of any class or
                      any other securities or property, or to receive any right
                      to sell shares of stock of any class or any other right,
                      or

                (b)   any capital reorganization of the Company, any
                      reclassification or recapitalization of the capital stock
                      of the Company or any transfer of all or substantially all
                      the assets of the Company to or consolidation or merger of
                      the Company with or into any other corporation or entity,
                      or

                (c)   any voluntary or involuntary dissolution, liquidation or
                      winding-up of the Company, then and in each such event the
                      Company will give notice to the Warrentholder specifying
                      (1) the date on which any such record is to be taken for
                      the purpose of such dividend, distribution or right and
                      stating the amount and character of such dividend,
                      distribution or right, and (2) the date on which any such
                      reorganization, reclassification, recapitalization,
                      transfer, consolidation, merger, dissolution, liquidation
                      or winding-up is to take place, and the time, if any is to
                      be fixed, as of which the holders of record of Common
                      Stock will be entitled to exchange their shares of Common
                      Stock for securities or other property deliverable upon
                      such reorganization, reclassification, recapitalization,
                      transfer, consolidation, merger, dissolution, liquidation
                      or winding-up. Such notice shall be given at least 20 days
                      and not more than 90 days prior to the date therein
                      specified, and such notice shall state that the action in
                      question or the record date is subject to the
                      effectiveness of a registration statement under the
                      Securities Act or to a favorable vote of stockholders, if
                      either is required. Failure to mail or receive such notice
                      or any defect therein shall not affect the validity of any
                      action with respect thereto.



<PAGE>   8




Section 5.       No Stockholders Rights or Liabilities

        This Warrant shall not entitle the Warrantholder to any voting rights or
other rights as a stockholder of the Company. No provision hereof, in the
absence of affirmative action by the Warrantholder to purchase shares of Common
Stock, and no more enumeration herein of the rights or privileges of the
Warrantholder shall give rise to any liability of such Warrantholder for the
Warrant Price or as a stockhoder of the Company, whether such liability is
asserted by the Company or by creditors of the Company.

Section 6.      Lost, Stolen, Mutilated or Destroyed Warrant

        In case the certificate or certificates evidencing the Warrants shall be
mutilated, lost, stolen or destroyed, the Company shall, at the request of the
Warrantholder, issue and deliver in exchange and substitution for and upon
cancellation of the mutilated certificate or certificates, or in lieu of and
substitution for the certificate or certificates lost, stolen or destroyed, a
new Warrant certificate or certificates of like tenor and representing an
equivalent right or interest, but only upon receipt of evidence satisfactory to
the Company of such loss, theft or destruction of such Warrant and an agreement
of indemnity, if requested.

Section 7.      Notices

        All notices, requests and other communications required or permitted to
be given or delivered hereunder shall be in writing, and shall be delivered, or
shall be sent by certified or registered mail or overnight courier, postage
prepaid, or by facsimile, and if to the Warrantholder to such address or
facsimile number as shall have been furnished to the Company by notice from such
Warrantholder and if to the Company, at 300 Professional Drive, Gaithersburg, MD
20879; Attention: Chief Financial Officer, facsimile number (301) 590-1252, or
at such other address or facsimile number as shall have been furnished to the
Warrantholder by notice from the Company.

Section 8.      Restrictions on Transfer

        This Warrant and the securities issued hereunder may not be sold,
transferred, hypothecated or assigned to any other person or entity except in
accordance with all applicable laws. This Warrant and such securities shall bear
a legend setting forth the foregoing restriction, if appropriate.

Section 9.      Amendments and Waivers

        This Warrant and any term hereof may be changed, waived, discharged or
terminated only by an instrument in writing signed by the party against which
enforcement of such change, waiver, discharge or termination is sought.

Section 10.     Severability

        If one or more provisions of this Warrant are held to be unenforceable
under applicable law, such provisions shall be excluded from this Warrant, and
the balance of this Warrant shall be interpreted as if such provision were so
excluded and shall be enforceable in accordance with its terms.

Section 11.     Governing Law

        THIS WARRANT SHALL BE GOVERNED BY AND CONSTRUED UNDER THE LAWS OF THE
STATE OF CALIFORNIA WITHOUT REGARD TO CONFLICT OF LAW PRINCIPLES.

Section 12.     Headings

        The headings in this Warrant are for purposes of reference only and
shall not limit or otherwise affect any of the terms hereof.

Section 13.     Counterparts

        This Warrant may be executed in any number of counterparts, each of
which shall be deemed an original





<PAGE>   9

but all of which together shall constitute one and the same instrument.

     IN WITNESS WHEREOF, the Company and FSVK have executed this Warrant on and
as of the day and year first above written.


                                        ANTEX BIOLOGICS INC.,
                                        a Delaware corporation

                                        /s/ V.M. ESPOSITO
                                        --------------------------
                                        V.M. Esposito
                                        President, CEO and Chairman of the Board




Attest:
[SIG]
------------------



                                        FIRST SECURITY VAN KASPER

                                        /s/ HAROLD GERBER
                                        --------------------------
                                        Harold Gerber
                                        Managing Director
<PAGE>   10
                               SUBSCRIPTION FORM


          (To be executed upon exercise of this Warrant)

Antex Biologics Inc.
300 Professional Drive
Gaithersburg, MD 20879
Telephone No.:(301)590-0129
Facsimile No.:(301)590-1252
Attention: V.M. Esposito, Ph.D.



        The undersigned hereby irrevocably elects to exercise the right of
purchaser represented by the within Warrant for, and to purchase
thereunder, ______________ shares of Common Stock, as provided for therein, and
either tenders herewith payment of the purchase price in full in the form of
cash or a certified or official bank check in the amount of $______________ or,
if the undersigned elects pursuant to Section 1(b) of the within Warrant to
convert such Warrant into Common Stock a net issuance basis, the undersigned
exercises the within Warrant by exchange under the terms of Section 1(b).

        Please issue a certificate or certificates for such Common Stock in the
name of, and pay any cash for any fractional share to:

                                   Name:
                                        -------------------------

                                   Address:
                                           ----------------------

                                   Social
                                   Security No:
                                               ------------------


        If said number of shares shall not be all the shares purchasable under
the within Warrant, a new Warrant is to be issued in the name of said
undersigned for the balance remaining of the shares purchasable thereunder
rounded up to the next higher number of shares.


                                   Name
                                        -------------------------

                                   Signature
                                             --------------------

                                   Note:     The above signature must
                                             correspond exactly with the
                                             name on the first page of this
                                             Warrant or with the name of the
                                             assignee appearing in the
                                             assignment form below.
<PAGE>   11
                                   ASSIGNMENT

          (To be executed only upon assignment of Warrant)


        For value received, __________________________________ hereby sells,
assigns and transfers unto _____________________ the within Warrant Certificate,
together with all right, title and interest therein, and does hereby irrevocably
constitute and appoint __________________ attorney, to transfer said Warrant on
the books of the within-named Company with respect to the number of Warrants set
forth below, with full power of substitution in the premises:


                    Name(s) of
                    Assignee(s)/Address                No. of Warrants
                    -------------------                ---------------



And if said number of Warrants shall not be all the Warrants represented by the
Warrant, a new Warrant is to be issued in the name of said undersigned for the
balance remaining of the Warrants registered by said Warrant.


                                   Name
                                       -------------------------

Dated:                             Signature
      -----------------                     --------------------

                                   Note:    The above signature must correspond
                                            exactly with the name on the face of
                                            this Warrant