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                                  Exhibit 4.3

                       1997 INCENTIVE AND NON-INCENTIVE

                               STOCK OPTION PLAN

                                      OF
                            NEXELL THEAPEUTICS INC.
                  (FORMERLY NAMED VIMRx PHARMACEUTICALS INC.)


     1.   Purpose of Plan.

          The purpose of this Incentive and Non-Incentive Stock Option Plan
("Plan") is to further the growth and development of VIMRx Pharmaceuticals Inc.
("Company") and any subsidiaries thereof by encouraging selected employees,
directors and other persons who contribute and are expected to contribute
materially to the Company's success to obtain a proprietary interest in the
Company through the ownership of stock, thereby providing such persons with an
added incentive to promote the best interests of the Company and affording the
Company a means of attracting to its service persons of outstanding ability.

     2.   Stock Subject to the Plan.

          An aggregate of 1,312,500 shares of the Company's Common Stock, $.001
par value ("Common Stock") subject, however, to adjustment or change pursuant to
paragraph 12 hereof, shall be reserved for issuance upon the exercise of options
which may be granted from time to time in accordance with the Plan ("Options").
Such shares may be, in whole or in part, as the committee appointed by the Board
of Directors to administer the Plan (hereinafter, the "Committee") shall from
time to time determine, authorized but unissued shares or issued shares which
have been reacquired by the Company. If, for any reason, an Option shall lapse,
expire or terminate without having been exercised in full, the unpurchased
shares covered thereby shall again be available for purposes of the Plan.

     3.   Administration.

          (a) Except as provided in paragraph (c) below, the Plan shall be
administered by the Committee. The Board of Directors shall appoint the
Committee from among its members. Such Committee shall be composed of two or
more Directors who, to the extent practicable, shall be "outside directors" as
defined in regulations under Section 162(m) of the Internal Revenue Code of
1986, as amended (the "Code"), and "non-employee directors" as defined by
Regulation 240.16b-3 under the Securities Exchange Act of 1934, as amended. Such
Committee shall have and may exercise any and all of the powers relating to the
administration of the Plan and the grant of Options thereunder as are set forth
in subparagraph 3(b) hereof as the Board of Directors shall confer and delegate.
The Board of Directors shall have power at any time to fill vacancies in, to
change the membership of, or to discharge such Committee. The Committee shall
select one of its members as its chairman and shall hold its meetings at such
time and at such places as it shall deem advisable. A majority of such Committee
shall constitute a quorum and such majority shall determine its action. Any
action may be taken without a meeting by written consent of all the members of
the Committee. The Committee shall keep minutes of its proceedings and shall
report the same to the Board of Directors at the meeting next succeeding.

          (b) The Committee shall administer the Plan and, subject to the
provisions of the Plan, shall have sole authority in its discretion to determine
the persons to whom, and the time or times at which, Options shall be granted;
the number of shares to be subject to each such Option; the provisions regarding
exercisability of each Option; the expiration date of each Option; whether the
Option shall contain a "cashless exercise" provision; whether all or any portion
of the Options shall be incentive stock options ("Incentive Options") qualifying
under Section 422A of the Code or stock options which do not so qualify ("Non-
Incentive Options"); whether a Non-Incentive Option shall have limited
transferability as permitted under the Plan; and whether a Non-Incentive Option
granted to a non-employee shall terminate following
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the non-employee's termination of engagement in performing services for the
Company or its subsidiaries pursuant to Section 9 of the Plan. Both Incentive
Options and Non-Incentive Options may be granted to the same person at the same
time provided each type of Option is clearly designated. In making such
determinations, the Committee may take into account the nature of the services
rendered by such persons, their present and potential contribution to the
Company's success and such other factors as the Committee in its sole discretion
may deem relevant. Subject to the express provisions of the Plan, the Committee
shall also have authority to interpret the Plan; to prescribe, amend and rescind
rules and regulations relating thereto; to determine the terms and provisions of
the respective Option Agreements, which shall be substantially in the forms
attached hereto as Exhibit A and Exhibit B; to amend the provisions of
outstanding Options to provide for accelerated exercisability or the extension
of the expiration date of such Options; and to make all other determinations
necessary or advisable for the administration of the Plan, all of which
determinations shall be conclusive and not subject to review.

          (c) The Board of Directors may administer the Plan, in lieu of and
with the same powers as the Committee, with respect to any Options granted or to
be granted under the Plan, provided that such administration is consistent with
the provisions of Section 162(m) of the Code.


     4.   Eligibility for Receipt of Options.

          (a) Incentive Options. Incentive Options may be granted only to
employees (including officers) of the Company and/or any of its subsidiaries. A
director of the Company or any subsidiary who is not an employee of the Company
or of one of its subsidiaries is not eligible to receive Incentive Options under
the Plan. Further, Incentive Options may not be granted to any person who, at
the time the Incentive Option is granted, owns (or is considered as owning
within the meaning of Section 425(d) of the Code) stock possessing more than 10%
of the total combined voting power of all classes of stock of the Company or any
subsidiary (10% Owner), unless at the time the Incentive Option is granted to
the 10% Owner, the option price is at least 110% of the fair market value of the
Common Stock subject thereto and such Incentive Option by its terms is not
exercisable subsequent to five years from the date of grant. The aggregate fair
market value (determined as of the time an Incentive Option is granted) of the
shares of the Company's Common Stock initially purchasable upon exercise of an
Incentive Option during any calendar year may not exceed $100,000.

          (b) Non-Incentive Options. Non-Incentive Options may be granted to any
employees (including employees who have been granted Incentive Options),
directors, consultants, agents, independent contractors and other persons whom
the Board of Directors (or Committee) determines will contribute to the
Company's success.

          (c) The maximum number of shares that may be subject to options under
this Plan granted during any calendar year to any executive officer of the
Company is 200,000 shares.

          (d) In the event an outstanding Incentive Option or a portion thereof
no longer qualifies as an incentive stock option under Section 422A of the Code,
such Option or portion thereof, as applicable, thereafter shall be deemed a Non-
Incentive Option under the Plan.

     5.   Option Price.

          The purchase price of the shares of Common Stock under each Option
shall be determined by the Committee, which determination shall be conclusive
and not subject to review, but in no event shall the purchase price be less than
100% of the fair market value of the Common Stock on the date of grant in the
case of Incentive Options (110% of fair market value in the case of Incentive
Options granted to a 10% Owner) and 50% of the fair market value of the Common
Stock on the date of the grant in the case of Non-Incentive Options.

          For purposes of the Plan, unless the Committee determines otherwise,
the fair market value" of a share of Common Stock as of a certain date shall be
the closing sale price of the Common Stock on The Nasdaq Stock Market or, if the
Common
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Stock is not then traded on The Nasdaq Stock Market, such national securities
exchange on which the Common Stock is then traded, on the trading date
immediately preceding the date the fair market value is being determined. The
Committee may make such other determination of fair market value, based on other
factors, as it shall deem appropriate.

          For purposes of the Plan, the date of grant of an Option shall be the
date on which the Committee shall by resolution duly authorize such Option.

     6.   Term of Options.

          The term of each Option shall be such number of years as the Committee
shall determine, subject to earlier termination as herein provided, but in no
event more than ten years from the date the Option is granted.

     7.   Exercise of Options.

          (l) Each Option shall be exercisable to the extent determined by the
Committee, but in no event shall an Option be exercisable until at least six
months from the date of grant, except as otherwise provided in Paragraph 13
herein.

          (m) An Option may not be exercised for fractional shares of the
Company's Common Stock.

          (n) Except as provided in paragraphs 9, 10 and 11 hereof, and unless
determined otherwise by the Committee with respect to Non-Incentive Options
granted to non-employees, no Option shall be exercisable unless the holder
thereof shall have been an employee, director, consultant, agent, independent
contractor or other person employed by or engaged in performing services for the
Company and/or a subsidiary continuously from the date of grant to the date of
exercise.

          (o) The exercise of an Option shall be contingent upon receipt from
the holder thereof of a written representation that at the time of such exercise
it is the optionee's then present intention to acquire the Option shares for
investment and not with a view to the distribution or resale thereof (unless a
Registration Statement covering the shares purchasable upon exercise of the
Options shall have been declared effective by the Securities and Exchange
Commission) and upon receipt by the Company of cash, or a check to its order,
for the full purchase price of such shares. The Committee may, in its
discretion, include a "cashless exercise" provision in the applicable Option
Agreement, in which event the optionee will be permitted (i) to deliver
previously owned shares of Common Stock with a fair market value equal to the
exercise price in payment of the full purchase price of such shares, or (ii) to
request that the Company withhold shares of Common Stock issuable upon exercise
of such Option with a fair market value equal to the exercise price of the
shares being purchased under the Option (thereby reducing the number of shares
issuable upon exercise of the Option).

          (p) The holder of an Option shall have none of the rights of a
stockholder with respect to the shares purchasable upon exercise of the Option
until a certificate for such shares shall have been issued to the holder upon
due exercise of the Option.

          (q) The proceeds received by the Company upon exercise of an Option
shall be added to the Company's working capital and be available for general
corporate purposes.

     8.   Transferability of Options.

          No Option granted pursuant to the Plan shall be transferable otherwise
than by will or the laws of descent or distribution and an Option may be
exercised during the lifetime of the holder only by such holder, provided,
however, that the Committee may provide for transferability of a Non-Incentive
Option to an optionee's family members or family trusts.

     9.   Termination of Employment or Engagement.

          (a) Except as provided in paragraph (b) below, in the event the
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employment of the holder of an Option shall be terminated by the Company or a
subsidiary for any reason other than by reason of death or disability, or the
engagement of a non-employee holder of a Non-Incentive Option shall be
terminated by the Company or a subsidiary for any reason, such holder may,
within three months from the date of such termination, exercise such Option to
the extent such Option was exercisable by such holder at the date of such
termination. Notwithstanding the foregoing, no Option may be exercised
subsequent to the date of its expiration. Absence on leave approved by the
employer corporation shall not be considered an interruption of employment for
any purpose under the Plan. In addition, at the discretion of the Committee, the
exercisability of an outstanding Non-Incentive Option may be extended to a date
determined by the Committee but not beyond ten years from the date of grant.

          (b) The Committee may, in its discretion, at the time of grant or by
amending the applicable outstanding Non-Incentive Option, delete the foregoing
termination provision with respect to a Non-Incentive Option granted to a non-
employee of the Company or its subsidiaries.

          (c) Nothing in the Plan or in any Option Agreement granted hereunder
shall confer upon any Optionholder any right to continue in the employ of the
Company or any subsidiary or obligate the Company or any subsidiary to continue
the engagement of any Optionholder or interfere in any way with the right of the
Company or any such subsidiary to terminate such Optionholder's employment or
engagement at any time.

     10.  Disability of Holder of Option.

          If the employment of the holder of an Option shall be terminated by
reason of such holder's disability, such holder may, within twelve months from
the date of such termination, exercise such option to the extent such Option was
exercisable by such holder at the date of such termination. Notwithstanding the
foregoing, no Option may be exercised subsequent to the date of its expiration.

     11.  Death of Holder of Option.

          If the holder of any Option shall die while in the employ of, or while
performing services for, the Company or one or more of its subsidiaries (or
within six months following termination of employment due to disability), the
Option theretofore granted to such person may be exercised, but only to the
extent such Option was exercisable by the holder at the date of death (or, with
respect to employees, the date of termination of employment due to disability)
by the legatee or legatees of such person under such person's Last Will, or by
such person's personal representative or distributees, within twelve months from
the date of death but in no event subsequent to the expiration date of the
Option.

     12.  Adjustments Upon Changes in Capitalization.

          If at any time after the date of grant of an Option, the Company shall
by stock dividend, split-up, combination, reclassification or exchange, or
through merger or consolidation or otherwise, change its shares of Common Stock
into a different number or kind or class of shares or other securities or
property, then the number of shares covered by such Option and the price per
share thereof shall be proportionately adjusted for any such change by the
Committee whose determination thereon shall be conclusive.

     13.  Acceleration of Exercisability Upon Change in Control.

          Upon the occurrence of a "change in control" of the Company (as
defined below), all outstanding Options shall become immediately fully
exercisable. For purposes of the Plan, a "change in control" of the Company
shall mean (i) the acquisition at any time by a "person" or "group" (as such
terms are used Sections 13(d) and 14(d)(2) of the Exchange Act of beneficial
ownership (as defined in Rule 13d-3 under the Exchange Act), directly or
indirectly, of securities representing 50% or more of the combined voting power
in the election of directors of the then outstanding securities of the Company
or any successor or the Company; (ii) the termination of service of directors,
for any reason other than death, disability or retirement from the Board of
Directors, during any period of two consecutive years or less, of individuals
who at the beginning of such period constituted a majority of the
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Board of Directors, unless the election of or nomination for election of each
new director during such period was approved by a vote of at least two-thirds of
the directors still in office who were directors at the beginning of the period;
(iii) approval by the stockholders of the Company of any merger, consolidation,
or statutory share exchange as a result of which the Common Stock shall be
changed, converted or exchanged (other than a merger, consolidation or share
exchange with a wholly-owned Subsidiary) or liquidation of the Company or any
sale or disposition of 80% or more of the assets or earning power or the
Company; or (iv) approval by the stockholders of the Company of any merger,
consolidation, or statutory share exchange to which the Company is a party as a
result of which the persons who were stockholders immediately prior to the
effective date of the merger, consolidation or share exchange shall have
beneficial ownership of less than 50% of the combined voting power in the
election of directors of the surviving corporation; provided, however, that no
change in control shall be deemed to have occurred if, prior to such time as a
change in control would otherwise be deemed to have occurred, the Company's
Board of Directors deems otherwise.

     14.  Vesting of Rights Under Options.

          Neither anything contained in the Plan nor in any resolution adopted
or to be adopted by the Committee, the Board of Directors or the stockholders of
the Company shall constitute the vesting of any rights under any Option. The
vesting of such rights shall take place only when a written Option Agreement,
substantially in the form of the Incentive Stock Option Agreement attached
hereto as Exhibit A or the Non-Incentive Stock Option Agreement attached hereto
as Exhibit B, shall be duly executed and delivered by and on behalf of the
Company and the person to whom the Option shall be granted.

     15.  Withholding Taxes.

          Whenever under the Plan shares are to be issued in satisfaction of the
exercise of Options granted thereunder, the Company shall have the right to
require the recipient to remit to the Company an amount sufficient to satisfy
federal, state and local withholding tax requirements prior to the delivery of
any certificate or certificates for such shares.

     16.  Termination and Amendment.

          The Plan, which was adopted by the Board of Directors on February 6,
1997 and is subject to stockholder approval, shall terminate on February 6, 2007
and no Option shall be granted under the Plan after such date. The Board of
Directors may at any time prior to such date terminate the Plan or make such
modifications or amendments thereto as it shall deem advisable, provided,
however, that shareholder approval shall be required:

     (i)    to increase the number of shares reserved for issuance under the
            Plan;

     (ii)   materially increase the benefits accruing to participants under the
            Plan;

     (iii)  materially modify the requirements of eligibility for participation
            in the Plan; or

     (iv)   if otherwise required to comply with the incentive stock option
            provisions of Section 162(m) of the Code or the listed company
            requirements of The Nasdaq Stock Market or of a national securities
            exchange on which the Common Stock is then traded,

and, provided, further, that no modification or amendment shall adversely affect
the rights of a holder of an Option previously granted under the Plan without
such holder's written consent.