Document:

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                                                                   Exhibit 10.70

                               GENTA INCORPORATED
                           99 HAYDEN AVENUE, SUITE 200
                         LEXINGTON, MASSACHUSETTS 02421

                                                    Dated as of October 28, 1999

Raymond P. Warrell, Jr., MD.
6 Kimble Circle
Westfield, NJ 07090

Dear Dr. Warrell:

                  We are pleased that you are interested in becoming an employee
of Genta Incorporated, a Delaware corporation (the "Company"). Accordingly, I
would like to offer you the following terms of engagement (the "Agreement"):

                  1.       Employment; Duties.

                  (a) As of October 28, 1999, the Company hereby engages and
employs you, and you hereby accept engagement and employment, as an employee of
the Company. Commencing on December 1, 1999, the Company will engage and employ
you, and you hereby accept engagement and employment, as Chief Executive Officer
and President of the Company.

                  (b) You shall perform your duties as are customarily
associated with your title, consistent with the By-laws of the Company and as
required by the Board of Directors of the Company (the "Board of Directors").
You shall perform your duties hereunder at such places as shall be necessary
according to the needs, business or opportunities of the Company; provided, that
you acknowledge and agree that the performance of the duties hereunder may
require significant domestic and international travel by you.

                  (c) Upon commencement of your employment as President and
Chief Executive Officer, you shall devote your full business time and best
efforts as shall be necessary to the proper discharge of your duties and
responsibilities under this Agreement. You shall not, directly or indirectly, on
a full time, part time, temporary, consulting, or any other basis, work for or
provide your services to any other person, firm, corporation, partnership, joint
venture or any other entity, except that you may engage in up to eight hours a
week of other activities, provided that such other activities are consistent in
all respects with your obligations under sections 5, 6, 7 and 8 of this
Agreement. However, notwithstanding anything else contained in this Agreement,
you shall not engage in any other business activities, whether or not pursued
for gain or profit, which will interfere with your ability to perform any of the
functions, powers or duties required under this Agreement.
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                  2. Term. Your employment hereunder shall be for a term of
three years commencing on October 28, 1999 (the "Effective Date") and continuing
through November 30, 1999 (the "Term"), unless sooner terminated as hereinafter
provided.

                  3.       Compensation and Benefits.

                  (a) In consideration of the services you rendered as an
employee of the Company for the period beginning on the Effective Date and
ending upon commencement of your employment as Chief Executive Officer and
President on December 1 1999, you will be paid $15,000, less all applicable
federal state and local taxes, social security and worker's compensation
contributions and such other amounts as may be required by law.

                  (b) As compensation and benefits for the performance of your
duties on behalf of the Company as Chief Executive Officer and President, so
long as your employment has not been terminated in accordance with this
Agreement, you shall be compensated and shall receive benefits upon commencement
of your employment as President and Chief Executive Officer, as follows:

                  (i)      a base salary of $325,000 per annum (the "Base
                           Salary"), payable in accordance with the Company's
                           standard payroll practice;

                  (ii)     in consideration of your entry into this Agreement,
                           you will receive $100,000, which is payable within 30
                           days from the date this Agreement is executed or
                           later at your discretion;

                  (iii)    a guaranteed bonus of $100,000 at the end of your
                           first twelve months of employment;

                  (iv)     a provisional bonus of at least $100,000 at the end
                           of each subsequent twelve months of employment
                           provided that mutually agreed upon milestones have
                           been met.

                  The Company shall withhold all applicable federal, state and
local taxes, social security and workers' compensation contributions and such
other amounts as may be required by law or agreed upon by the parties with
respect to the compensation payable to you pursuant to this Section 3(a).

                  (c) Subject to subsection 3(n), you shall be entitled to
receive annual stock options for the purchase of 300,000 shares of Common Stock,
adjusted for stock splits, reverse stock splits, and stock reclassifications,
(at an exercise price equal to Fair Market Value, as defined in the Genta
Incorporated 1998 Stock Incentive Plan, on the date of grant, or, in the event
of a Trigger Event, calculated as provided below) provided that mutually agreed
upon milestones have been met. All stock options granted pursuant to this
subsection 3(c) (the "3(c) Options") shall be evidenced by a stock option
agreement, which shall contain customary terms and shall provide for immediate
vesting upon the occurrence of one of the events (each a "Trigger Event")
described in Section 4.1 of the Stock Option Agreement (as defined below). In
addition, if a Trigger Event occurs, whether or not your employment has been
terminated pursuant to clause 4.1(ii) of the Stock Option

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Agreement, you shall be entitled to receive all Section 3(c) Options which you
would have been entitled to receive within twelve months following such Trigger
Event, provided that the relevant milestones have been met during such twelve
month period. The Company shall grant such options to you as soon as practicable
after you become entitled to receive them. Such options shall have an exercise
price equal to the average closing price of the Company's Common Stock for the
60 consecutive calendar days prior to the occurrence of the Trigger Event and
shall vest and be fully exercisable upon grant.

                  (d) In addition, from time to time, in the discretion of the
Board of Directors, you may be entitled to additional stock options pursuant to
the Company's stock option plans.

                  (e) The Company agrees to reimburse you for all reasonable and
necessary travel, business entertainment and other business expenses incurred by
you in connection with the performance of your duties under this Agreement. Such
reimbursements shall be made by the Company on a timely basis upon submission by
you of vouchers in accordance with the Company's standard procedures.

                  (f) You shall be entitled during the Term to four weeks per
annum vacation time. You may "carry over" up to four weeks of unused vacation
time to the succeeding year.

                  (g) The Company shall pay the premiums on an ordinary life
insurance policy on your behalf in the principal amount of not less than
$3,250,000, provided such premiums do not exceed $20,000 annually.

                  (h) You shall be entitled to participate in any and all
medical insurance, dental insurance, group health, disability insurance and
other benefit plans which are made generally available by the Company to its
senior executives. The Company, in its sole discretion, may at any time amend or
terminate any such benefit plans or programs.

                  (i) You shall be covered by the Company's director's and
officer's insurance policy as is generally provided to the Company's directors
and officers.

                  (j) The Company shall provide you with a car or car allowance
in an amount not to exceed $500 per month which shall be paid in appropriate pro
rata amounts at the same time Base Salary is paid unless the Company pays all
related expenses directly.

                  (k) The Company shall pay all of your reasonable relocation
expenses, provided that such expenses are incurred within 18 months from the
Effective Date of this Agreement.

                  (l) The Company shall pay attorney's fees incurred by you in
connection with this Agreement in an amount not to exceed $10,000.

                  (m) Subject to subsection 10(f) and Section 11, you must be an
employee of the Company at the time that any compensation is due in order to
receive such compensation.

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                  (n) No option provided for under this Section 3 shall be
exercisable unless the Company's Amended and Restated Certificate of
Incorporation has been amended (the "Amendment") to increase the Company's
authorized capital stock by an amount sufficient to permit the issuance of
Common Stock issuable upon exercise or conversion of all options, warrants, and
convertible securities issued by the Company, including the shares and warrants
issuable in the Company's contemplated private placement and the options
provided for under this agreement. The Company shall use its best efforts,
subject to applicable law, to obtain shareholder approval of the Amendment;
provided, however, that nothing in this subsection 3(n) shall be interpreted so
as to require the Company pay a consent fee or hire third party proxy
solicitors.

                  (o) The Company shall pay the premiums on a medical
malpractice insurance policy on your behalf in the principal amount of not less
than $1,000,000, provided such premiums do not exceed $20,000 annually.

                  4. Representations and Warranties. You hereby represent and
warrant to the Company as follows:

                  (a) Neither the execution and delivery of this Agreement nor
the performance by you of your duties and other obligations hereunder violate or
will violate any statute, law, determination or award, or conflict with or
constitute a default under (whether immediately, upon the giving of notice or
lapse of time or both) any prior employment agreement, contract, or other
instrument to which you are a party or by which you are bound.

                  (b) You have the full right, power and legal capacity to
execute and deliver this Agreement and to perform your duties and other
obligations hereunder. This Agreement constitutes your legal, valid and binding
obligation, enforceable against you in accordance with its terms. No approvals
or consents of any persons or entities are required for you to execute and
deliver this Agreement or perform your duties and other obligations hereunder.

                  5.       Non-competition and Non-solicitation.

                  (a) You understand and recognize that your services to the
Company are special and unique and agree that, upon commencement of your
employment as President and Chief Executive Officer on December 1, 1999, and,
except as provided below, for a period of two years following any termination of
your employment, you shall not in any manner directly or indirectly on behalf of
yourself or any person, firm, partnership, joint venture, corporation or other
business entity (collectively, "Person"), solicit, enter into, engage in any
business which is or proposes to be competitive with a technology or service of,
or product manufactured or distributed by, the Company or its subsidiaries or in
which the Company or any of its subsidiaries has intellectual property rights
(except as provided below, "Conflicting Field"), either as an individual for
your own account, or as a partner, joint venturer, executive, agent, consultant,
salesperson, officer, director or shareholder of such Person ("Competitor");
provided, however, that (x) following any termination of your employment,
Conflicting Field shall refer only to the field of using antisense technology as
therapy for cancer as its primary business and, subject to Section 1, nothing in
this agreement shall be interpreted so as to prevent you from accepting
employment with any Person which is or proposes to be competitive with a
Conflicting Field so long as you work solely in a division of such Person

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which division carries on a bona fide business that is not or does not propose
to be competitive with a Conflicting Field ; and (y) nothing herein will
preclude you from holding five percent (5%) or less of the stock of any publicly
traded company, calculated on a fully diluted basis.

                  (b) In further consideration of the payment by the Company to
you of amounts that may hereafter be paid to you pursuant to this Agreement
(including, without limitation, pursuant to Sections 3 and 11 hereof, and the
Stock Option Agreement between you and the Company dated October 28, 1999 (the
"Stock Option Agreement")), you agree that upon commencement of your employment
as President and Chief Executive Officer, and for a period of two years
thereafter or a period of two years subsequent to any termination hereunder, but
subject to section 5(f), you shall not, without the prior written consent of the
Company:

                  (i)      directly or indirectly take any action, or attempt to
                           take any action, which is intended to, or could
                           reasonably be foreseen by you to, induce a material
                           breach of a contract or agreement known to you
                           between the Company and any of its licensors,
                           licensees, clients, customers, vendors, suppliers,
                           agents, consultants, employees (whether or not such
                           employees are "at will" employees) or other person or
                           entity with which the Company has an agreement (each,
                           a "Covered Party", collectively, "Covered Parties");
                           provided, however, that such action or attempted
                           action could reasonably be expected to cause a
                           material detriment to the Company; or

                  (ii)     directly or indirectly solicit or attempt to solicit
                           any of the Covered Parties to terminate his, her or
                           its relationship with the Company in material breach
                           of a contract or agreement with the Company known to
                           you; provided, however, that such action or attempted
                           action is likely to cause a material detriment to the
                           Company; or

                  (iii)    subject to subsection 5(f), directly or indirectly
                           solicit or attempt to solicit any of the employees or
                           consultants of the Company to become employees,
                           agents, consultants, representatives or advisors of
                           any other Person; or

                  (iv)     directly or indirectly persuade or seek to persuade
                           any customer of or supplier to the Company to cease
                           to do business or to reduce the amount of business
                           which any customer or supplier has done or
                           contemplates doing with the Company, whether or not
                           the relationship between the Company and such Person
                           was originally established in whole or in part
                           through your efforts, in material breach of a
                           contract or agreement known to you between the
                           Company and such customer or supplier; provided,
                           however, that such action or attempted action could
                           reasonably be expected to cause a material detriment
                           to the Company.

                  (c) Upon commencement of your employment as President and
Chief Executive Officer, and for a period of two years following any termination
of your employment, you agree that upon the earlier of you (a) negotiating with
any Competitor concerning the possible employment of you by the Competitor, (b)
receiving an offer of employment from a Competitor, or (c) becoming

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employed by a Competitor, you will (x) immediately provide notice to the Company
of such circumstances and (y) provide copies of Sections 5, 6, 7, 8 and 9 of
this Agreement to the Competitor. You further agree that the Company may provide
notice to a Competitor of your obligations under this Agreement, including
without limitation your obligations pursuant to Sections 5, 6, 7 and 8 hereof.

                  (d) You understand that the provisions of this Section 5 may
limit your ability to earn a livelihood in a business similar to the business of
the Company but nevertheless agree and hereby acknowledge that the consideration
provided under this Agreement, including any compensation or benefits provided
under Sections 3 and 11 hereof and the Stock Option Agreement, is sufficient to
justify the restrictions contained in such provisions. In consideration thereof
and in light of your education, skills and abilities, you agree that you will
not assert in any forum that such provisions prevent you from earning a living
or otherwise are void or unenforceable or should be held void or unenforceable.

                  (e) Section 5(a) hereof shall not apply to any Conflicting
Field that is identified on Annex I to this Agreement. Annex I to this Agreement
may hereafter be amended through a writing signed by you and the Company and
approved by the Company's Board of Directors.

                  (f) Nothing in subsection 5(b)(iii) shall be interpreted so as
to prohibit you from accepting offers from persons employed by the Company to be
employed by you or an entity with which you become associated, provided that
such offers were not solicited, directly or indirectly, or otherwise encouraged
by you.

                  6.       Ownership of Proprietary Information.

                  (a) You confirm and agree that all information relating to the
Company's, or an Affiliate's (as defined below) business that has been created
by, discovered by, developed by, learned by, or made known to, the Company, or
any of its subsidiaries, affiliates, licensors, licensees, successors or assigns
(each, an "Affiliate" and, collectively, the "Affiliates") from the commencement
of your employment and at all times thereafter (including, without limitation,
information relating to the Company's business created by, discovered by,
developed by, learned by, reduced to practice by or made known to the Company,
an Affiliate, or you, either alone or jointly with others, during your
employment and information relating to the Company's customers, clients,
suppliers, vendors, consultants, licensors and licensees) or assigned, licensed
or otherwise conveyed to the Company or any Affiliate, has been, is and shall be
the sole property of the Company or such Affiliate, as applicable, and the
Company or the Affiliate, as the case may be, has been, is and shall be the sole
owner of all designs, ideas, patents, patent applications, copyrights, copyright
applications and other rights in connection therewith, including but not limited
to the right to make application for statutory protection of any kind in any
country. All of the aforementioned information is hereinafter called
"Proprietary Information" (and shall be deemed Proprietary Information
regardless of whether or not the Proprietary Information is patentable or
copyrightable). By way of illustration, but not limitation, Proprietary
Information includes trade secrets, processes, discoveries, structures, works of
authorship, copyrightable works, trademarks, copyrights, formulas, data, data
structures, know-how, show-how, improvements, information relating to products
(both

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current and under development), services and technologies, product concepts,
specifications, techniques, information or statistics contained in, or relating
to, promotion or marketing plans and programs, strategies, forecasts,
blueprints, sketches, records, notes, devices, drawings, customer lists,
continuation applications of any kind, trademark applications and information
about the Company's or the Affiliate's employees and/or consultants and
confidential business information of the Company or any Affiliate or any of its
or their clients, consultants, suppliers, customers, vendors, licensors,
licensees and other third parties (including, without limitation, the
compensation, job responsibility and job performance of such employees and/or
consultants).

                  (b) You agree that all Proprietary Information shall be, the
extent permitted by law, "works made for hire" as that term is defined in the
United States Copyright Act (17 USA, Section 101). You hereby assign to the
Company all right, title and interest you may have or acquire in all Proprietary
Information; provided, that, subject to subsection 6(d) hereof, the provisions
of this Section 6 only applies to information, and Proprietary Information shall
only include such information which:

                  (i)      relate at the time of conception or reduction to
                           practice of the invention to the Company's business,
                           or actual or demonstrably anticipated research or
                           development of the Company except when the
                           information more closely relates to the business, or
                           actual or demonstrably anticipated research or
                           development of a person or entity listed in Annex I
                           hereto, as amended; or

                  (ii)     result from any work performed by you for the
                           Company; or

                  (iii)    was developed on the Company's time or using the
                           Company's equipment, supplies, facilities, or trade
                           secret information.

                  (c) Notwithstanding the foregoing, Proprietary Information
shall not include; (i) information (x) in the public domain not as a result of
the breach of this Agreement or the breach of any other duty owed to the Company
or any other person (y) information lawfully in your possession prior to the
date hereof and not disclosed to you by the Company or an Affiliate and (z)
information disclosed to you without restriction by a third party who had the
right to disclose such information to you; and (ii) information that more
closely relates to the business, or actual or demonstrably anticipated research
or development, of a person or entity set forth on Annex I.

                  (d) It is understood that no patent, copyright, trademark, or
other proprietary right of license is granted to you under this Agreement. Any
disclosure of Proprietary Information and any materials which may accompany any
such disclosure pursuant to your employment under this Agreement shall not
result in the grant to you of any rights, express or implied, of any kind.

                  7.       Confidential Information.

                  (a) You agree at all times, including after the Term, to keep
in strictest trust and confidence and will not disclose or make accessible to
any other person without the prior written consent of the Company, the Company's
or any Affiliate's Proprietary Information. You further

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agree that upon commencement of your employment and at all times thereafter (i)
not to use any such Proprietary Information for yourself or others; and (ii) not
to take any such material or reproductions embodying Proprietary Information
from the Company's facilities (or any of the Affiliates' facilities) at any
time, except as required during the Term in connection with your duties to the
Company.

                  (b) Except with prior written authorization of the Board of
Directors, you agree not to disclose or publish any of the Proprietary
Information, except as required in the performance of your obligations under
this Agreement. You further agree not to disclose or publish information
relating to your former employers, to whom you, the Company or any of its
Affiliates owes an obligation of confidence, at the time of disclosure to you,
at any time during or after your employment with the Company.

                  (c) Upon written notice by the Company, you shall promptly
deliver to the Company, or, if requested by the Company, promptly destroy all
written Proprietary Information and any other written material containing any
Proprietary Information (whether prepared by the Company, you or a third party),
and will not retain any copies, extracts, summaries or other reproductions in
whole or in part of such written Proprietary Information or other material.

                  (d) You recognize that the Company has received and in the
future will receive confidential or proprietary information from third parties
subject to a duty on the Company's part to maintain the confidentiality of such
information and, in some cases, to use it only for certain limited purposes. You
agree that you owe the Company and such third parties, both during your
employment and thereafter, a duty to hold all such confidential or proprietary
information in the strictest confidence and not to disclose it to any Person
(except in a manner that is consistent with the Company's agreement with the
third party) or use it for the benefit of anyone other than the Company or such
third party (consistent with the Company's agreement with the third party),
unless expressly authorized to act otherwise by the Board of Directors.

                  (e) If during the term and thereafter you are requested or
required (by oral questions, deposition, interrogatories, requests for
information or documents, subpoena, civil investigative demand or any other
process) to disclose all or any part of any Confidential Information, you will
provide the Company with prompt notice of such request or requirement, as well
as notice of the terms and circumstances surrounding such request or
requirement, so that the Company, or, as applicable, one or more of its
Affiliates, may seek an appropriate protective order or waive compliance with
the provisions of this Agreement. In such case, the parties will consult with
each other on the advisability of pursuing any such order or other legal action
or available steps to resist or narrow such request or requirement. If, failing
the entry of a protective order or the receipt of a waiver hereunder, you are,
in the opinion of your counsel, legally compelled to disclose Proprietary
Information, you may disclose that portion of such information which counsel
advises you that you are legally compelled to disclose. In any event, you will
use reasonable efforts to cooperate with the Company in obtaining and will not
oppose action by the Company (or, as applicable, one or more of its Affiliates)
to obtain, an appropriate protective order or other reliable assurance that
confidential treatment will be accorded the disclosure of any Proprietary
Information.

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All reasonable expenses incurred by you in compliance with this subsection 7(e)
will be reimbursed by the Company.

                  8.       Disclosure of Proprietary Information.

                  (a) During the Term, and thereafter, you agree that you will
promptly disclose to the Company, or any persons designated by the Company, all
Proprietary Information developed, created, made, conceived, reduced to practice
or learned by the Company, any Affiliate or you, either alone or jointly with
others, during the Term and not otherwise known to the Company's officers and
directors.

                  (b) You further agree to assist the Company in every proper
way (but at the Company's expense) to obtain and confirm and from time to time
enforce patents, copyrights or other rights on said Proprietary Information in
any and all countries, and to that end you will execute all documents necessary:

                  (i)      to apply for, obtain and vest in the name of the
                           Company alone (unless the Company otherwise directs)
                           letters patent, copyrights or other analogous
                           protection in any country throughout the world and
                           when so obtained or vested to renew and restore the
                           same on behalf of the Company; and

                  (ii)     to defend any opposition proceedings in respect of
                           such applications and any opposition proceedings or
                           petitions or applications for revocation of such
                           letters patent, copyright or other analogous
                           protection.

                  (c) Your obligation to assist the Company in obtaining and
enforcing patents and copyrights for the Proprietary Information in any and all
countries shall continue beyond the Term, but the Company agrees to compensate
you at a reasonable rate after the expiration of the Term for time actually
spent by you at the Company's request on such assistance.

                  9. Enforcement. You agree that the remedy at law for any
breach or threatened breach of any covenant contained in Sections 5, 6, 7 or 8
of this Agreement would be inadequate and cause irreparable damage to the
Company. In the event that you breach or threaten to breach any provisions of
Sections 5, 6, 7 or 8, in addition to any other rights which the Company may
have at law or in equity, the Company shall be entitled, without the posting of
a bond or other security, to injunctive relief to enforce the restrictions
contained in this Agreement. In the event that an actual proceeding is brought
in equity to enforce any of the provisions of Sections 5, 6, 7 or 8, you shall
not assert as a defense that there is an adequate remedy at law nor shall the
Company be prevented from seeking any other remedies, including without
limitation monetary damages, which may be available to it.

                  10. Termination. Your employment hereunder as President and
Chief Executive Officer shall commence as provided for under subsection 1(a) and
shall continue for the period set forth in Section 2 hereof unless sooner
terminated upon the first to occur of the following events:

                  (a)      Death. Your death;

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                  (b) Disability. You have been unable, for a period of one
hundred eighty (180) consecutive business days, to perform your duties under
this Agreement, as a result of physical or mental illness or injury ("Becoming
Totally Disabled") and the Company shall have communicated to you the fact of
your termination by written notice, which termination shall be effective on the
30th day after receipt of such notice by you (the "Total Disability Effective
Date"), unless you return to full-time performance of your duties before the
Total Disability Effective Date;

                  (c) Termination by the Company for Cause. For purposes of this
Agreement, the term "Cause" shall mean any of the following; provided, however,
that the Company has terminated you pursuant to this subsection 10(c) within 60
days of the Board of Directors having first obtained knowledge of a basis for
termination under this subsection 10(c):

                  (i)      A breach by you of any of the provisions of Sections
                           4, 5, 6, 7 or 8 of this Agreement which results in a
                           material detriment to the Company or any Affiliate
                           thereof;

                  (ii)     Any breach by you of subsection 1(b) or (c) which is
                           not cured by you within 30 days of written notice
                           thereof from the Company; provided, however, your
                           right to such 30 day cure period shall be conditioned
                           upon your good faith attempt to cure such breach;

                  (iii)    Any action or omission by you to intentionally harm
                           the Company which is in bad faith and likely to cause
                           a material harm to the Company or any other act or
                           bad faith omission having the effect of materially
                           harming the Company, its business or reputation;

                  (iv)     The perpetration of an intentional and knowing fraud
                           against or adversely affecting the Company or any
                           Covered Party which causes or is likely to cause a
                           material detriment to the Company; or

                  (v)      The conviction of you of any crime classified as a
                           felony.

                  (d) Termination by the Company Without Cause. The Company may
terminate your employment hereunder at any time for any reason or no reason by
giving you thirty (30) days prior written notice of the termination.

                  (e) Termination By You For Good Reason. You may terminate your
employment hereunder for "Good Reason" for (i) having been assigned duties by
the Board of Directors which are inconsistent in any material respect with
Section 1 of this Agreement or any other action by the Company that results in a
material diminution in your title, position, authority, duties or
responsibilities, either of which is not cured by the Company within 30 days of
written notice thereof from you; or (ii) any failure by the Company to comply
with Section 3 other than an isolated, insubstantial and inadvertent failure
that is not taken in bad faith and is remedied by the Company promptly after
receipt of notice thereof from you; (iii) your failure to be re-elected to the
Company's Board of Directors, unless , at the time you are not re-elected, the
Company has the right to terminate you for Cause under subsection 10(c) of this
Agreement and does so within 45 days of

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your failure to be re-elected; or (iv) relocation of the Company's principal
place of operations, provided that such relocation results in a principal place
of operations more than 75 miles from New York, New York.

                  (f) Termination by You Without Good Reason. You may terminate
your employment hereunder at any time for any reason or no reason by giving
thirty (30) days prior written notice of termination. If you do, you shall be
entitled only to the following compensation:

                  (i)      Any accrued but unpaid Base Salary as of the date of
                           termination for services rendered to the date of
                           termination;

                  (ii)     Any accrued but unpaid expenses required to be
                           reimbursed pursuant to Section 3;

                  (iii)    Any vacation accrued to the date of termination.

                  (iv)     Any accrued but unpaid bonus payments;  and

                  (v)      The amounts set forth in subsection 3(b)(ii), if not
                           already paid.

                  11. Compensation Following Termination Prior to the End of the
Term.

                  In the event that your employment hereunder is terminated
prior to the end of the Term, you shall be entitled only to the following
compensation and benefits upon such termination:

                  (a) Termination by Reason of Death or Becoming Totally
Disabled; Termination by the Company for Cause.

                  In the event that your employment is terminated by reason of
your death or your becoming Totally Disabled, or by the Company for Cause,
pursuant to Sections 10(a), 10(b) or 10(c), the Company shall pay the following
amounts to you (or your estate, as the case may be):

                  (i)      Any accrued but unpaid Base Salary as of the date of
                           termination for services rendered to the date of
                           termination;

                  (ii)     Any accrued but unpaid expenses required to be
                           reimbursed pursuant to Section 3;

                  (iii)    Any vacation accrued to the date of termination;

                  (iv)     Any accrued but unpaid bonus payments; and

                  (v)      The amounts set forth in subsection 3(b)(ii), if not
                           already paid.

                  The benefits to which you may be entitled upon termination
pursuant to the plans, programs and arrangements referred to in Section 3 hereof
shall be determined and paid in accordance with the terms of such plans,
policies and arrangements.

                                     - 11 -
<PAGE>   12
                  (b) Termination by the Company Without Cause; Termination by
You for Good Reason. In the event that your employment is terminated by the
Company without Cause pursuant to Section 10(d) or by you for Good Reason
pursuant to Section 10(e), the Company shall pay the following amounts to you:

                  (i)      Any accrued but unpaid Base Salary as of the date of
                           termination for services rendered to the date of
                           termination, payable within 30 days;

                  (ii)     Any accrued but unpaid expenses required to be
                           reimbursed pursuant to Section 3, payable within 30
                           days;

                  (iii)    Any vacation accrued to the date of termination,
                           payable within 30 days; and

                  (iv)     As your sole damages; (i) the Base Salary which you
                           would have received during the twelve month period
                           following the date on which your employment is
                           terminated and any bonus which would have been
                           payable to you within 12 months of the date of
                           termination pursuant to section 3(iii) or 3(iv) had
                           you still been employed by the Company; provided
                           that, in the event that you have terminated your
                           employment pursuant to subsection 10(e), and the
                           Company has provided you notice of a basis of a
                           breach, within 45 days of the Board of Director's of
                           the Company having obtained first knowledge of such
                           basis, of any covenant contained in Sections 5, 6, 7
                           or 8 hereof, you shall not be entitled to any payment
                           under this clause (iv) of this Section 11(b); and
                           (ii) all stock options received pursuant to
                           subsection 3(c) hereof shall become fully vested. Any
                           payments to be made pursuant to this subsection 11(b)
                           shall be made in accordance with the Company's
                           standard payroll practices then in effect; and

                  (v)      The amounts set forth in subsection 3(b)(ii), if not
                           already paid.

                  The benefits to which you may be entitled upon termination
pursuant to the plans, policies and arrangements referred to in Section 3 hereof
shall be determined and paid in accordance with the terms of such plans,
policies and arrangements.

                  (c) It is the intention of the parties that all cash payouts
that may be due subject to this Section 11 shall be guaranteed by either
Paramount Capital, the Aries Funds, or some other party that the Company and you
mutually agree upon.

                  (d) No Other Benefits or Compensation. Except as may be
provided under this Agreement, under the terms of any incentive compensation,
employee benefit or fringe benefit plan applicable to you at the time of the
termination of your employment prior to the end of the Term, you shall have no
right to receive any other compensation, or to participate in any other plan,
arrangement or benefit, with respect to any future period after such
termination.

                  12. Notices. Any notice or other communication under this
Agreement shall be in writing and shall be deemed to have been given: when
delivered personally after receipt therefor;

                                     - 12 -
<PAGE>   13
one (1) day after being sent by Federal Express or similar overnight delivery;
or three (3) days after being mailed registered or certified mail, postage
prepaid, return receipt requested, to either party at the address set forth
below, or to such other address as such party shall give by notice hereunder to
the other party.

                  If to the Company:

                                    Genta Incorporated
                                    c/o Paramount Capital, Inc.
                                    787 Seventh Avenue
                                    New York, NY  10019
                                    (212) 554-4514
                                    Attention: Mark C. Rogers, M.D.

                  With a copy to:

                                    Kramer Levin Naftalis & Frankel LLP
                                    919 Third Avenue
                                    New York, NY 10022
                                    (212) 715-9100
                                    Attention: Monica C. Lord, Esq.

                  If to you:

                                    Raymond Warrell, Jr., M.D.
                                    6 Kimball Circle
                                    Westfield, NJ 07090
                                    (908) 301-1022

                  With a copy to:

                                    Morrison & Foerster LLP
                                    755 Page Mill Road
                                    Palo Alto, CA 94304
                                    (650) 813-5746
                                    Attention:  Joseph Lin,  Esq.

                  13. Severability of Provisions. If any provision of this
Agreement shall be declared by a court of competent jurisdiction to be invalid,
illegal or incapable of being enforced in whole or in part, the remaining
conditions and provisions or portions thereof shall nevertheless remain in full
force and effect and enforceable to the extent they are valid, legal and
enforceable, and no provision shall be deemed dependent upon any other covenant
or provision unless so expressed herein. If any provision of this Agreement, or
any part thereof, is held to be invalid or unenforceable because of the scope or
duration of or the area covered by such provision, the parties hereto agree that
the court making such determination shall reduce the scope, duration and/or
area of such
                                     - 13 -
<PAGE>   14
provision (and shall substitute appropriate provisions for any such invalid or
unenforceable provisions) in order to make such provision enforceable to the
fullest extent permitted by law and/or shall delete specific words and phrases,
and such modified provision shall then be enforceable and shall be enforced. The
parties hereto recognize that if, in any judicial proceeding, a court shall
refuse to enforce any of the separate covenants contained in this Agreement,
then that invalid or unenforceable covenant contained in this Agreement shall be
deemed eliminated from these provisions to the extent necessary to permit the
remaining separate covenants to be enforced. In the event that any court
determines that the time period or the area, or both, are unreasonable and that
any of the covenants is to that extent invalid or unenforceable, the parties
hereto agree that such covenants will remain in full force and effect, first,
for the greatest time period, and second, in the greatest geographical area that
would not render them unenforceable.

                  14. Entire Agreement; Modification. This Agreement contains
the entire agreement of the parties relating to the subject matter hereof, and
the parties hereto have made no agreements, representations or warranties
relating to the subject matter of this Agreement which are not set forth herein.
No modification of this Agreement shall be valid unless made in writing and
signed by the parties hereto.

                  15. Binding Effect. The rights, benefits, duties and
obligations under this Agreement shall inure to, and be binding upon, the
Company, its successors and assigns, and upon you and your legal
representatives. This Agreement constitutes a personal service agreement, and
the performance of your obligations hereunder may not be transferred or assigned
by you.

                  16. Non-waiver. The failure of either party to insist upon the
strict performance of any of the terms, conditions and provisions of this
Agreement shall not be construed as a waiver or relinquishment of future
compliance therewith, and said terms, conditions and provisions shall remain in
full force and effect. No waiver of any term or condition of this Agreement on
the part of either party shall be effective for any purpose whatsoever unless
such waiver is in writing and signed by such party.

                  17. Governing Law. This Agreement shall be governed by, and
construed and interpreted in accordance with, the laws of the State of New York
without regard to principles of conflict of laws.

                  18. Survivability. The provisions of this Agreement which by
their terms call for performance subsequent to termination of your employment
hereunder, or of this Agreement, shall so survive such termination.

                  19. Headings. The headings of paragraphs are inserted for
convenience and shall not affect any interpretation of this Agreement.

                  If this letter agreement meets with your approval and you
desire to accept this offer of employment on the terms and conditions set forth
herein, please execute the enclosed copy of this letter and return it to me as
soon as possible.

                                     - 14 -
<PAGE>   15
                                                 Sincerely,

                                                 GENTA INCORPORATED

                                                 By:___________________________

                                                       Mark C. Rogers, M.D.

AGREED AND ACCEPTED
AS OF THE DATE FIRST SET FORTH ABOVE:

____________________________________
Dr. Raymond P. Warrell, Jr.

                                     - 15 -<PAGE>   1
                                                                   Exhibit 10.71

                               GENTA INCORPORATED
                            1998 STOCK INCENTIVE PLAN

                             STOCK OPTION AGREEMENT

         STOCK OPTION AGREEMENT (the "Agreement"), dated as of October 28, 1999,
between GENTA INCORPORATED, a Delaware corporation (the "Company"), and the
other party signatory hereto (the "Optionee"). Capitalized terms used here
without definition shall have the meanings ascribed thereto in the Company's
1998 Stock Incentive Plan (the "Plan").

         All options granted herein (the "Options") shall be appropriately
adjusted pursuant to Section 1.5.3 of the Plan.

         The Company hereby represents and warrants to Optionee that, as of the
date of this Agreement, the sum of the number of outstanding shares of Common
Stock and the number of shares of Common Stock underlying all outstanding
convertible or exercisable derivative securities is 63,510,163 shares. In the
event that the foregoing representation is inaccurate, the number of shares
underlying the Options granted under Section 1 of this Agreement shall be
proportionately adjusted.

         The Optionee hereby represents and warrants to the Company that, upon
commencing his employment with the Company on October 28, 1999, the Optionee was
not violating the terms of his employment with any third person, nor did the
commencement of his employment with the Company on October 28, 1999 provide the
basis for a claim of such a violation.
<PAGE>   2
         In consideration of the foregoing and of the mutual undertakings set
forth in this Agreement, the Company and the Optionee agree as follows:

         SECTION 1. Grant of Options.

         (a) In consideration of the commencement of his employment by the
Company on October 28, 1999, the Company hereby grants to the Optionee Options
(the "Initial Options") to purchase 3,175,508 shares of the Company common
stock, par value $.001 (the "Common Stock"), at an initial exercise price per
share of $2.67 (the "Exercise Price"). These Initial Options are exercisable
immediately subject to the satisfaction of the Option Conditions (defined
below); provided, however, the unvested portion of the Common Stock issuable
upon exercise of the Initial Option shall be subject to the nontransferability,
forfeiture and repayment provisions of Section 2, 5 and 7 hereof, respectively,
until such shares vest in accordance with the following vesting schedule: 25% of
the Initial Options shall vest immediately: the remaining 75% of the Initial
Options and Common Stock issuable upon exercise thereof shall vest in 36
substantially equal installments on the last day of each month commencing
November 30, 1999; and provided, further, that the Initial Options granted
hereunder shall not be exercisable until all of the following conditions (the
"Option Conditions") have been satisfied: (x) the Company's Amended and Restated
Certificate of Incorporation has been amended to increase the Company's
authorized capital stock by an amount sufficient to permit the issuance of
Common Stock upon the exercise or conversion of all options, warrants and
convertible securities issued by the Company, including all of the Options
granted pursuant to this Agreement (the "Reservation Requirements"); and (y) the
Company's shareholders shall have approved an amendment to the Plan authorizing
an increase in the shares of Common Stock available under the Plan sufficient to
satisfy the Options referred to herein. The Company shall use its best efforts,
subject to

                                      -2-
<PAGE>   3
applicable law, to obtain shareholder approval of such amendments; provided,
however, that nothing in this Section 1(a) shall be interpreted so as to require
the Company pay a consent fee or hire third party proxy solicitors.

         (b) The Company hereby grants to the Optionee Options (the "FDA
Option") to purchase 793,877 shares of Common Stock at the Exercise Price;
provided, however, that this FDA Option and the Common Stock issuable upon
exercise thereof shall only vest when the Optionee has been employed by the
Company for six years (the "Term Condition") and provided, further, that in no
event shall this FDA Option be exercisable unless all Option Conditions have
been satisfied. The FDA Option is immediately exercisable; provided, however,
that the Common Stock issuable upon exercise of the FDA Option shall be subject
to the nontransferability, forfeiture and repayment provisions of Section 2, 5
and 7 hereof, respectively. Notwithstanding the foregoing, the Term Condition
shall be waived in respect of this FDA Option and the FDA Option and Common
Stock issuable upon exercise thereof shall vest in their entirety when the
Company has received from the Food and Drug Administration a letter providing
that Company's product G3139, or its substantial equivalent, is approved for
marketing in any indication.

         (c) The Company hereby grants to the Optionee Options (the "Market
Capitalization Option") (and, together with the FDA Option, the "Performance
Options") to purchase 793,877 shares of Common Stock at the Exercise Price;
provided, however, that this Market Capitalization Option and the Common Stock
issuable upon exercise thereof shall only vest upon the satisfaction of the Term
Condition; and provided, further, that in no event shall this Market
Capitalization Option be exercisable unless all Option Conditions have been
satisfied. The Market Capitalization Option is immediately exercisable;
provided, however, the unvested

                                      -3-
<PAGE>   4
portion of the Common Stock issuable upon exercise of the Market Capitalization
Option shall be subject to the nontransferability, forfeiture and repayment
provisions of Section 2, 5 and 7 hereof, respectively. Notwithstanding the
foregoing, the Term Condition shall be waived in respect of this Market
Capitalization Option and the Market Capitalization Option and Common Stock
issuable upon exercise thereof shall vest in its entirety when the average of
the product of the Fair Market Value of the Company Common Stock (or any
successor security issued as a replacement for Company Common Stock) multiplied
by the number of shares of Company Common Stock outstanding and issuable upon
exercise of all warrants, options and convertible securities, during any 60
consecutive calendar day period, exceeds $541,106,489.

         (d) All the options described above may from time to time hereinafter
be referred to singularly as an "Option" and collectively as the "Options."

         SECTION 2. Nontransferability.

         (a) No Option shall be assignable or transferable, voluntarily or
involuntarily, by operation of law, or otherwise, and any such assignment or
transfer which may be attempted shall be null and void and of no effect;
provided, however, that this Section 2 shall not prevent transfers by will or by
the laws of descent and distribution. During the lifetime of the Optionee, the
Options shall be exercisable only by the Optionee.

         (b) Until a share of Common Stock vests in accordance with the
provisions of Section 1(a), (b) or (c), as the case may be, the Optionee
acknowledges that the Optionee may not, and the Optionee agrees that the
Optionee shall not, transfer or assign the Optionee's rights to such share of
Common Stock or to any cash payment related thereto. Until a share of Common
Stock so vests, no attempt to transfer or assign such shares or the right to any
cash

                                      -4-
<PAGE>   5
payment related thereto, whether by transfer, pledge, hypothecation or otherwise
and whether voluntary or involuntary, by operation of law or otherwise, shall
vest the transferee or assignee with any interest or right in or with respect to
such share of Common Stock or such cash payment, and the attempted transfer or
assignment shall be of no force and effect.

         SECTION 3. Certificates; Custodianship.

         (a) Reasonably promptly after Optionee has exercised his right to
acquire any such shares of Common Stock already vested pursuant to the
provisions of Section 1 or Section 6 of this Agreement, but in no event more
than ten (10) business days after such date, the Company (i) shall cause to be
issued certificates evidencing such shares of Common Stock, including such
legends as the Company deems necessary or appropriate to comply with federal and
applicable state securities laws, and (ii) shall cause such certificates to be
delivered to the Optionee (or such Optionee's legal representative, beneficiary
or heir), together with any other property directly related to such vested
shares of Common Stock of the Optionee.

         (b) Reasonably promptly after the date that the Optionee exercises his
right to purchase any shares of Common Stock that have not theretofore vested or
been forfeited, but in no event more than ten (10) business days after such
date, provided that the Company has first received a stock power endorsed by the
Optionee in blank with respect to such shares of Common Stock, the Company shall
issue stock certificates, registered in the name of the Optionee, evidencing
such shares of Common Stock. Each such certificate shall bear the following
legend:

          "The transferability of this certificate and the shares of stock
     represented hereby are subject to the restrictions, terms and conditions
     (including forfeiture and restrictions against transfer) contained in the
     Genta Incorporated 1998 Stock Incentive Plan and an

                                      -5-
<PAGE>   6
     Agreement entered into between the registered owner of such shares and
     Genta Incorporated. A copy of the Plan and Agreement is on file in the
     office of the Secretary of Genta Incorporated."

         Such legend shall not be removed from the certificates evidencing such
exercised shares of Common Stock until such shares vest pursuant to the
provisions of Section 1 and Section 6 of this Agreement.

         (c) Each certificate issued pursuant to Section 3(b) hereof, together
with the stock powers relating to such shares of Common Stock, shall be
deposited by the Company with a custodian designated by the Company (the
"Certificate Custodian"). The Company may designate itself as Certificate
Custodian hereunder. The Company shall cause such Certificate Custodian to issue
to the Optionee a receipt evidencing the certificates held by it which are
registered in the name of the Optionee.

         (d) Reasonably promptly after any previously unvested shares of Common
Stock vest pursuant to the provisions of Section 1 or Section 6 of this
Agreement, but in no event more than ten (10) business days after such date, the
Company (i) shall cause to be issued certificates evidencing such shares of
Common Stock, free of the legend provided in Section 3(b) hereof, but including
such legends as the Company deems necessary or appropriate to comply with
federal and applicable state securities laws, and (ii) shall cause such
certificates to be delivered to the Optionee (or such Optionee's legal
representative, beneficiary or heir), together with any other property directly
related to such vested shares of Common Stock of the Optionee held by the
Certificate Custodian pursuant to Section 3(e) hereof.

         (e) Any securities or other property (excluding cash dividends)
received by the Optionee with respect to a share of Common Stock as a result of
any stock dividend, stock split,

                                      -6-
<PAGE>   7
recapitalization, merger, consolidation, combination or exchange of shares and
for which the issue date of such Common Stock occurs prior to such event but
which has not vested as of the date of such event will not vest until such share
of Common Stock vests and shall be promptly deposited with the Certificate
Custodian as though such securities and other property were part of such share.

         SECTION 4. Method of Exercise.

         (a) The Options or any part thereof may be exercised only by the giving
of written notice to the Company on such form and in such manner as the
Committee shall prescribe. Such written notice must be accompanied by payment of
the full purchase price for the number of shares being purchased. Such payment
may be made by one or a combination of the following methods:

             (i) by a certified or official bank check (or the equivalent
thereof acceptable to the Company);

             (ii) by delivery of shares of Common Stock having a Fair Market
Value on such date of exercise equal to part or all of the purchase price,
provided such shares of Common Stock would not upon delivery of such shares for
such purpose result in an accounting compensation charge with respect to the
shares of Common Stock used to pay the Exercise Price;

             (iii) by delivery of a promissory note issued by Optionee for up to
the full amount of the purchase price of the optioned shares (except that an
amount equal to the par value of Common Stock shall be paid in cash), on terms
acceptable to the Company, which promissory note shall be full recourse to the
Optionee personally for all amounts due thereunder

                                      -7-
<PAGE>   8
and shall be fully secured by the Common Stock purchased pursuant to the
exercise of the Option;

             (iv) by payment through a broker-dealer sale and remittance
procedure pursuant to which the Optionee (i) shall provide written instructions
to a Company designated brokerage firm to effect the immediate sale of some or
all of the purchased Common Stock and remit to the Company, out of the sale
proceeds available on the settlement date, sufficient funds to cover the
aggregate exercise price payable for the purchased shares of Common Stock and
(ii) shall provide written directives to the Company to deliver the certificates
for the purchased shares of Common Stock directly to such brokerage firm in
order to complete the sale transactions; or

             (v) at the discretion of the Committee and to the extent permitted
by law, by such other method as the Committee may authorize, including, without
limitation, at the discretion of the Committee, by the withholding of shares
(valued at their Fair Market Value on the exercise date of the Common Stock)
underlying the Options.

         Pursuant to Section 3.2 of the Plan, it shall be a condition precedent
to the issuance of shares upon exercise of the Options that the Optionee shall
remit to the Company any amount sufficient to satisfy all applicable withholding
tax requirements, which may be satisfied through the withholding of Common Stock
as provided in Section 3.2.2 of the Plan. The date of the exercise of the
Options shall be the date on which written notice of exercise is delivered to
the Company, during normal business hours, at its address as provided in Section
10 of this Agreement, or if mailed, the date on which it is postmarked, provided
such notice is actually received.

                                      -8-
<PAGE>   9
         (b) The Optionee agrees not to exercise any Options granted hereunder
until the later of (i) the day the Option Conditions are satisfied or (ii) one
day after the Optionee has been employed by the Company for six (6) months.
Furthermore, the Optionee agrees that any disposition of any Options (and any
shares of Common Stock issuable upon exercise of any options) will be carried
out in a manner consistent with Section 16(b) of the Securities and Exchange Act
of 1934, as amended, and any and all other applicable requirements of law.

         SECTION 5. Termination of Option.

         (a) Except as otherwise provided for under this Section 5, the
unexercised portion of the Initial Option shall expire and cease to be
exercisable at 12:01 a.m. on October 27, 2009; the unexercised portion of the
Market Capitalization Option shall expire and cease to be exercisable on the
tenth anniversary of the date such option vests in accordance with the
provisions of Section 1(b) hereof; and the unexercised portion of the FDA Option
shall expire and cease to be exercisable on the tenth anniversary of the date
such option vests in accordance with the provisions of Section 1(c) hereof.

         (b) Except as provided in Section 6 of this Agreement, upon termination
of the Optionee's employment with the Company or any of its subsidiaries for any
reason (including death), all unvested Options immediately shall terminate and
expire and all unvested shares of Common Stock exercised pursuant to any Option
hereunder shall be immediately and irrevocably forfeited except as provided in
Section 5(c) and (d) hereof.

         (c) Except as provided in Section 6 of this Agreement, if the
Optionee's employment with the Company or any of its subsidiaries terminates for
any reason other than death, the Options shall be exercisable but only to the
extent they were exercisable and vested at

                                      -9-
<PAGE>   10
the time of such termination and only until the earlier of the expiration date
of such Options, or the expiration of one year following the date of
termination.

         (d) If the Optionee dies while still an employee of the Company or any
of its subsidiaries or following the termination of Optionee's employment with
the Company and its subsidiaries, but during the period in which any Option is
exercisable pursuant to Section 5(c) of this Agreement, such vested Option shall
be exercisable but only to the extent they were exercisable at the time of death
and only until the earlier of the expiration date of such Option or the first
anniversary of the date of the Optionee's death.

         SECTION 6. Acceleration of Vesting.

         If:

             (i) prior to the termination of Optionee's employment with the
Company, there is (A) a sale or other disposition of all or substantially all of
the assets of the Company or the product G3139 or its substantial equivalent,
(B) an acquisition of the Company by another entity by means of any transaction
or series of related transactions (including, without limitation, any
reorganization, merger or consolidation but, excluding any merger effected
exclusively for the purpose of changing the domicile of the Company) unless the
Company's stockholders as constituted immediately prior to such acquisition
will, immediately after such acquisition (by virtue of securities issued as
consideration for the Company's acquisition or otherwise) hold at least fifty
percent (50%) of the voting power of the surviving or acquiring entity and
unless the Company's directors as constituted immediately prior to such
acquisition, constitute a majority of directors of the surviving or acquiring
entity, or (C) an acquisition by any person or related group of persons (other
than the Company, a Company-sponsored employee benefit plan

                                      -10-
<PAGE>   11
or such person or entity who as of September 14, 1999, beneficially owned
(within the meaning of Rule 13d-3 of the Securities Exchange Act of 1934, as
amended) more than fifty percent (50%) of the Company's Common Stock) of
securities possessing more than fifty percent (50%) of the total combined voting
power of the Company's outstanding securities; or

             (ii) Optionee's employment is terminated by the Company pursuant to
Section 10(d) of the employment agreement between you and the Company dated as
of October 28, 1999 (the "Employment Agreement")) or the Optionee terminates his
employment for Good Reason under subsection 10(e) of the Employment Agreement;
or

             (iii) prior to the termination of Optionee's employment with the
Company, at any time Lindsay Rosenwald, or after his death or incapacity, his
successor or legal representative (collectively "LR") directly or indirectly
(through Paramount Capital Management Inc., Paramount Capital Inc., or any fund,
trust or other entity for whom any of them, or any entity controlled by LR or
any of them, serves as investment advisor and/or general partner or otherwise
acts as an advisor or manager) ceases to control and direct at least 35% (thirty
five percent) of the total combined voting power of the Company's outstanding
securities; or

             (iv) prior to termination of Optionee's employment with the Company
the Company, within the meaning of any Bankruptcy Law:

                  (A)      commences a voluntary case,

                  (B)      consents to the entry of an order for relief against
                           it in an involuntary case,

                                      -11-
<PAGE>   12
                  (C)      consents to the appointment of a Custodian of it or
                           for all or substantially all of its property, and
                           such Custodian is not discharged within 60 days; or

             (v) prior to termination of Optionee's employment with the Company,
a court of competent jurisdiction enters an order or decree under any Bankruptcy
Law that:

                  (A)      is for relief in any involuntary case against the
                           Company,

                  (B)      appoints a Custodian of the Company or for all or
                           substantially all of the property of the Company, or

                  (C)      orders the liquidation of the Company, and, in each
                           case, the order or decree remains unstayed and in
                           effect for 60 consecutive days;

then any Initial Options previously granted and the Common Stock issuable
thereof under this Agreement but not yet vested shall immediately vest. In
addition, all Performance Options that would have vested during the 12-month
period following the events set forth in this Section 6 (the "Section 6 Events")
shall vest, if a Section 6 Event occurs within such 12-month period, immediately
upon the occurrence of such Section 6 Events; provided, however, that no Options
granted hereunder shall be exercisable unless the Option Conditions have been
met. At the time the Section 6 Event occurs, the Options referred to in this
Section 6 shall be fully exercisable.

         The term "Bankruptcy Law" means Title 11 of the U.S. Code or any
similar federal, foreign or state law for the relief of debtors. The term
"Custodian" means any receiver, trustee, assignee, liquidator, examiner or
similar official under any Bankruptcy Law.

         SECTION 7. Right to Repayment.

         If in accordance with the terms of Section 5 of this Agreement,
Optionee forfeits any unvested shares of Common Stock received upon exercise of
an Option, Optionee acknowledges and agrees that the Certificate Custodian shall
surrender to the Company as soon

                                      -12-
<PAGE>   13
as practicable after the effective date of such forfeiture all certificates for
such shares issued to Optionee by the Company pursuant to Section 3(b) of this
Agreement. As soon as practicable after such surrender, but in no event later
than 30 days after such surrender, Optionee shall be entitled to a payment by
the Company in an amount, in cash equal to the aggregate of the Exercise Prices
paid for each exercised but unvested share of Common Stock so forfeited.

         SECTION 8. Plan Provisions to Prevail.

         This Agreement is subject to all of the terms and provisions of the
Plan. Without limiting the generality of the foregoing, by entering into this
Agreement the Optionee agrees that no member of the Board of Directors or the
Committee shall be liable for any action or determination made in good faith
with respect to the Plan or any award thereunder or this Agreement. In the event
that there is any inconsistency between the provisions of this Agreement and of
the Plan, the provisions of the Plan shall govern. Notwithstanding the
foregoing, Section 2.10 of the Plan shall not apply to this Agreement.

         SECTION 9. Right of Discharge Preserved.

         Nothing in this Agreement shall confer upon the Optionee the right to
continue in the employ of the Company and its subsidiaries, or to continue in
the service of the Company and its subsidiaries as a consultant or director, or
affect any right which the Company and its subsidiaries may have to terminate
such employment or service.

         SECTION 10. Notices.

         All notices required or permitted hereunder shall be given in writing
by personal delivery; by confirmed facsimile transmission (with a copy
dispatched by express delivery or registered or certified mail); or by express
delivery via express mail or any reputable express

                                      -13-
<PAGE>   14
courier service. Notice shall be addressed (a) to Genta Incorporated, c/o Dr.
Mark C. Rogers, Paramount Capital Inc., 787 Seventh Avenue, 48th Floor, New
York, New York 10019; and (b) to the Optionee at the address set forth on the
signature page hereto; or (c) as to either party, at such other address as may
be designated by notice in the manner set forth herein. Notices which are
delivered personally, by confirmed facsimile transmission, or by courier as
aforesaid, shall be effective on the date of delivery.

         SECTION 11. Successors and Assigns.

         This Agreement shall be binding upon and inure to the benefit of the
parties hereto and the successors and assigns of the Company and, to the extent
consistent with Section 5 of this Agreement and with the Plan, the heirs and
personal representatives of the Optionee.

         SECTION 12. Entire Contract; Waiver; Amendment.

         This Agreement constitutes the entire contract between the parties
hereto and supersedes all prior oral and written agreements between the parties
with regard to the subject matter hereof. No waiver of any breach or condition
of this Agreement shall be deemed to be a waiver of any other or subsequent
breach or condition, whether of like or different nature. This Agreement may be
amended as provided in Section 3.1.3 of the Plan. Headings are for convenience
only, and are not themselves part of the Agreement.

         SECTION 14. Severability.

         If any provision of this Agreement (including any provision of the Plan
that is incorporated herein by reference) shall hereafter be held to be invalid,
unenforceable or illegal in whole or in part, in any jurisdiction under any
circumstances for any reason, (a) such provision

                                      -14-
<PAGE>   15
shall be reformed to the minimum extent necessary to cause such provision to be
valid, enforceable and legal while preserving the intent of the parties as
expressed in, and the benefits to the parties provided by, this Agreement and
the Plan or (b) if such provision cannot be so reformed, such provision shall be
severed from this Agreement and an equitable adjustment shall be made to this
Agreement (including, without limitation, addition of necessary further
provisions to this Agreement) so as to give effect to the intent as so expressed
and the benefits so provided. Such holding shall not affect or impair the
validity, enforceability or legality of such provision in any other jurisdiction
or under any other circumstances. Neither such holding nor such reformation or
severance shall affect or impair the legality, validity or enforceability of any
other provision of this Agreement or the Plan.

         SECTION 15. Governing Law.

         This Agreement shall be interpreted, construed and administered in
accordance with the laws of the State of New York, without giving effect to
principles of conflicts of laws, as they apply to contracts made, delivered and
performed in the State of New York.

         IN WITNESS WHEREOF, the parties hereto have executed this agreement as
of the date and year first written above.

                                             GENTA INCORPORATED

                                             By:
                                                -------------------------
                                                 Name:  Mark C. Rogers
                                                 Title: Chairman of the Board of
                                                        Directors

                                      -15-
<PAGE>   16
                                             OPTIONEE

                                             Dr. Raymond P. Warrell, Jr.

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

                                             Address:

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

                                             Social Security Number:

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

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