<PAGE>   1

                                                                   EXHIBIT 10.21

                            ALLOS THERAPEUTICS, INC.
                            EMPLOYMENT AGREEMENT FOR
                               STEPHEN J. HOFFMAN

         THIS EMPLOYMENT AGREEMENT (the "AGREEMENT") is made as of this 17th day
of January, 2001, by and between ALLOS THERAPEUTICS, INC., (the "COMPANY"), and
STEPHEN J. HOFFMAN, PHD, MD, ("EXECUTIVE") (collectively, the "PARTIES").

         WHEREAS, Executive is critical to current product development
activities and NDA submissions, as well as the ongoing operation of the Company;
and

         WHEREAS, the Company wishes to continue to employ Executive and to
assure itself of the continued services of Executive during this critical
period, on the terms set forth herein; and

         WHEREAS, Executive wishes to be so employed under the terms set forth
herein.

         NOW, THEREFORE, in consideration of the promises, mutual covenants, the
above recitals, and the agreements herein set forth, and for other good and
valuable consideration, the sufficiency of which is hereby acknowledged, the
Parties agree to the following terms and conditions of the Executive's
employment:

         1. EMPLOYMENT. The Company hereby agrees to continue to employ
Executive as PRESIDENT AND CHIEF EXECUTIVE OFFICER and Executive hereby accepts
such employment upon the terms and conditions set forth herein as of the date
first written above.

         2. AT-WILL EMPLOYMENT. IT IS UNDERSTOOD AND AGREED BY THE COMPANY AND
EXECUTIVE THAT THIS AGREEMENT DOES NOT CONTAIN ANY PROMISE OR REPRESENTATION
CONCERNING THE DURATION OF EXECUTIVE'S EMPLOYMENT WITH THE COMPANY. EXECUTIVE
SPECIFICALLY ACKNOWLEDGES THAT HIS EMPLOYMENT WITH THE COMPANY IS AT-WILL AND
MAY BE ALTERED OR TERMINATED BY EITHER EXECUTIVE OR THE COMPANY AT ANY TIME,
WITH OR WITHOUT CAUSE AND/OR WITH OR WITHOUT NOTICE. THE NATURE, TERMS OR
CONDITIONS OF EXECUTIVE'S EMPLOYMENT WITH THE COMPANY CANNOT BE CHANGED BY ANY
ORAL REPRESENTATION, CUSTOM, HABIT OR PRACTICE, OR ANY OTHER WRITING. IN
ADDITION, THAT THE RATE OF SALARY, ANY BONUSES, PAID TIME OFF, OTHER
COMPENSATION, OR VESTING SCHEDULES ARE STATED IN UNITS OF YEARS OR MONTHS DOES
NOT ALTER THE AT-WILL NATURE OF THE EMPLOYMENT, AND DOES NOT MEAN AND SHOULD NOT
BE INTERPRETED TO MEAN THAT EXECUTIVE IS GUARANTEED EMPLOYMENT TO THE END OF ANY
PERIOD OF TIME OR FOR ANY PERIOD OF TIME. IN THE EVENT OF CONFLICT BETWEEN THIS
DISCLAIMER AND ANY OTHER STATEMENT, ORAL OR WRITTEN, PRESENT OR FUTURE,
CONCERNING TERMS AND CONDITIONS OF EMPLOYMENT, THE AT-WILL RELATIONSHIP
CONFIRMED BY THIS DISCLAIMER SHALL CONTROL. THIS AT-WILL STATUS CANNOT BE
ALTERED EXCEPT IN WRITING SIGNED BY EXECUTIVE AND THE CHAIRMAN OF THE BOARD OF
DIRECTORS.

         3. DUTIES. Executive shall render full-time services to the Company as
its President and Chief Executive Officer. Executive shall devote his best
efforts and his full business time, skill and attention to the performance of
his duties on behalf of the Company, however, the Executive shall be able to sit
on the Boards of Directors for up to two (2) outside companies that



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do not compete with the Company's main area of business, development and
commercialization of a radiosensitizer product.

         4. POLICIES AND PROCEDURES. Executive agrees that he is subject to and
will comply with the policies and procedures of the Company, as such policies
and procedures may be modified, added to or eliminated from time to time at the
sole discretion of the Company, except to the extent any such policy or
procedure specifically conflicts with the express terms of this Agreement.
Executive further agrees and acknowledges that any written or oral policies and
procedures of the Company do not constitute contracts between the Company and
Executive.

         5. COMPENSATION. For all services rendered and to be rendered
hereunder, the Company agrees to pay to the Executive, and the Executive agrees
to accept a salary of $225,000 per annum. Any such salary shall be payable in
equal biweekly installments and shall be subject to such deductions or
withholdings as the Company is required to make pursuant to law, or by further
agreement with the Executive. The Board of Directors may adjust the Executive's
compensation from time to time in its sole and complete discretion.

         6. BONUS. Executive will be eligible for a discretionary bonus in an
amount equal to 35% of base salary ("Bonus"). The decision to award the Bonus
and/or to modify the amount of any bonus given is within the sole and complete
discretion of the Board.

         7. OTHER BENEFITS. While employed by the Company as provided herein:

                  (a) EXECUTIVE AND EMPLOYEE BENEFITS. The Executive shall be
entitled to all benefits to which other executive officers of the Company are
entitled, on terms comparable thereto, including, without limitation,
participation in pension and profit sharing plans, 401(k) plan, group insurance
policies and plans, medical, health, vision, and disability insurance policies
and plans, and the like, which may be maintained by the Company for the benefit
of its executives. The Company reserves the right to alter and amend the
benefits received by Executive from time to time at the Company's discretion.

                  (b) EXPENSE REIMBURSEMENT. The Executive shall receive,
against presentation of proper receipts and vouchers, reimbursement for direct
and reasonable out-of-pocket expenses incurred by him in connection with the
performance of his duties hereunder, according to the policies of the Company.

                  (c) PERSONAL TIME OFF. The Executive shall be entitled to four
weeks personal time off per year of paid vacation, and sick leave according to
the Company's benefits package.

         8. PROPRIETARY AND OTHER OBLIGATIONS. Executive agrees to continue to
abide by Executive's previously executed Non-Competition, Proprietary
Information and Inventions Agreement attached hereto as Exhibit A.

         9. TERMINATION. Executive and the Company each acknowledge that either
party has the right to terminate Executive's employment with the Company at any
time for any reason whatsoever, with or with cause or advance notice pursuant to
the following:



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                  (a) TERMINATION BY DEATH OR DISABILITY. Subject to applicable
state or federal law, in the event Executive shall die during the period of his
employment hereunder or become permanently disabled, as evidenced by notice to
the Company and Executive's inability to carry out his job responsibilities for
a continuous period of more than three months, Executive's employment and the
Company's obligation to make payments hereunder shall terminate on the date of
his death, or the date upon which, in the sole determination of the Board of
Directors, Executive has failed to carry out his job responsibilities for three
months except the Company shall pay the Executive's estate any salary earned but
unpaid prior to termination, all accrued but unused personal time and any
business expenses that were incurred but not reimbursed as of the date of
termination. Vesting of any unvested Options shall cease on the date of
termination.

                  (b) VOLUNTARY RESIGNATION BY EXECUTIVE. In the event the
Executive voluntarily terminates his employment with the Company (other than for
Good Reason as defined below), the Company's obligation to make payments
hereunder shall cease upon such termination, except the Company shall pay
Executive any salary earned but unpaid prior to termination, all accrued but
unused personal time and any business expenses that were incurred but not
reimbursed as of the date of termination. Vesting of any unvested Options shall
cease on the date of termination.

                  (c) TERMINATION FOR JUST CAUSE. In the event the Executive is
terminated by the Company for Just Cause (as defined below), the Company's
obligation to make payments hereunder shall cease upon the date of receipt by
Executive of written notice of such termination (the "DATE OF TERMINATION" for
purposes of this paragraph 9(c)), except the Company shall pay Executive any
salary earned but unpaid prior to termination, all accrued but unused personal
time and any business expenses that were incurred but not reimbursed as of the
date of termination. Vesting of the Option shall cease on the date of
termination.

                  (d) TERMINATION BY THE COMPANY WITHOUT JUST CAUSE OR
RESIGNATION FOR GOOD REASON (OTHER THAN CHANGE IN CONTROL). Company will have
the right to terminate Executive's employment with Company at any time without
Just Cause. In the event Executive is terminated without Just Cause or resigns
for Good Reason (as defined below), and upon the execution of a full general
release by Executive ("RELEASE", attached as Exhibit B), releasing all claims
known or unknown that Executive may have against Company as of the date
Executive signs such release, and upon the written acknowledgment of his
continuing obligations under the Confidentiality Agreement, attached as Exhibit
A, Executive shall be entitled to receive the following Severance Benefits: (i)
continuation of Executive's base salary, then in effect, for a period of twelve
(12) months following the Termination Date, paid on the same basis and at the
same time as previously paid; (ii) payment of any accrued but unused vacation
and sick leave; (iii) the Company shall reimburse Executive, on a grossed-up
basis, for the after-tax payment of the premiums of Executive's supplemental
disability plan for a period of 24 months following a Termination without Just
Cause or for reasons other than Change in Control; and (iv) the Company shall
pay the premiums of Executive's group health insurance COBRA continuation
coverage, including coverage for Executive's eligible dependents, for a maximum
period of twelve (12) months following a Termination without Just Cause or for
reasons other than Change in Control; provided, however, that (a) the Company
shall pay premiums for Executive's eligible dependents only for coverage for
which those eligible dependents were enrolled immediately



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prior to the Change in Control Termination and (b) the Company's obligation to
pay such premiums shall cease immediately upon Executive's eligibility for
comparable group health insurance provided by a new employer of Executive.

                  (e) CHANGE IN CONTROL SEVERANCE BENEFITS. In the event that
the Company terminates Executive's employment without Just Cause or Executive
resigns for Good Reason within one (1) month prior to or thirteen (13) months
following the effective date of a Change in Control (as defined below), ("Change
in Control Termination"), and upon the execution of a Release (Exhibit B),
Executive shall be entitled to receive the following Change in Control Severance
Benefits: (i) continuation of Executive's base salary, then in effect, for a
period of two (2) years following the Termination Date, paid on the same basis
and at the same time as previously paid; (ii) payment of any accrued but unused
vacation and sick leave; (iii) the Company shall reimburse Executive, on a
grossed-up basis, for the after-tax payment of the premiums of Executive's
supplemental disability plan for a period of 24 months following a Termination
without Just Cause or for reasons other than Change in Control; (iv) a bonus in
the amount equal to the bonus amount paid in the year immediately preceding the
Change in Control; and (v) the Company shall pay the premiums of Executive's
group health insurance COBRA continuation coverage, including coverage for
Executive's eligible dependents, for a maximum period of eighteen (18) months
following a Change in Control Termination; provided, however, that (a) the
Company shall pay premiums for Executive's eligible dependents only for coverage
for which those eligible dependents were enrolled immediately prior to the
Change in Control Termination and (b) the Company's obligation to pay such
premiums shall cease immediately upon Executive's eligibility for comparable
group health insurance provided by a new employer of Executive. If Executive
obtains new employment pursuant to which he is employed on an average of 30
hours or more each week he may elect, upon written notification to the Company,
to receive any unpaid severance benefits (subject to required deductions and tax
withholdings) within 14 days after receipt by the company of such written
notice. Executive agrees that the Company's payment of health insurance premiums
will satisfy its obligations under COBRA for the period provided. No premium
payments will be made following the effective date of Executive's coverage by a
health insurance plan of a subsequent employer. For the balance of the period
that Executive is entitled to coverage under federal COBRA law, if any,
Executive shall be entitled to maintain such coverage at Executive's own
expense.

         In addition, in the event the Company terminates Executive's employment
without Just Cause or that Executive resigns for Good Reason within one (1)
month prior to or thirteen (13) months following the effective date of a Change
in Control, the vesting of Executive's then outstanding stock options shall be
accelerated in full, and the time during which such options may be exercised
shall be extended to 24 months following the date of such Change in Control.

         10. DEFINITIONS.

                  (a) JUST CAUSE. As used in this Agreement, "Just Cause" shall
mean the occurrence of one or more of the following: (i) Executive's conviction
of a felony or a crime involving moral turpitude or dishonesty; (ii) Executive's
participation in a fraud or act of dishonesty against the Company; (iii)
Executive's intentional and material damage to the Company's property; (iv)
material breach of Executive's employment agreement, the Company's written
policies, or the Proprietary Information and Inventions Agreement that is not
remedied by



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Executive within fourteen (14) days of written notice of such breach from the
Board or conduct by Executive which demonstrates Executive's gross unfitness to
serve the Company as President or Chief Executive Officer. Executive's physical
or mental disability or death shall not constitute cause hereunder.

                  (b) GOOD REASON. As used in this Agreement, "Good Reason"
shall mean any one of the following events which occurs on or after the
commencement of Executive's employment without Executive's consent: (i) any
reduction of Executive's then existing annual salary base or annual bonus target
by more than ten percent (10%), unless the Executive accepts such change in
compensation opportunity; or, (ii) any request that the Executive relocate to a
work site that would increase the Executive's one-way commute distance by more
than thirty-five (35) miles from his then principal residence, unless the
Executive accepts such relocation opportunity, or (iii) within 90 days of a
Change in Control (as defined below) should the Company fail to offer the
Executive a position that is equivalent in pay, benefits and responsibilities.

                  (c) CHANGE IN CONTROL. As used in this Agreement, a "Change in
Control" is defined as; (a) a sale, lease, exchange or other transfer in one
transaction or a series of related transactions of all or substantially all of
the assets of the Company (other than the transfer of the Company's assets to a
majority-owned subsidiary corporation); (b) a merger or consolidation in which
the Company is not the surviving corporation (other than a merger or
consolidation in which shareholders immediately before the merger or
consolidation have, immediately after the merger or consolidation, greater stock
voting power); (c) a reverse merger in which the Company is the surviving
corporation but the shares of the Company's common stock outstanding immediately
preceding the merger are converted by virtue of the merger into other property,
whether in the form of securities, cash or otherwise (other than a reverse
merger in which shareholders immediately before the merger have, immediately
after the merger, greater stock voting power); or (d) any transaction or series
of related transactions in which in excess of 50% of the Company's voting power
is transferred.

         11. TERMINATION OF COMPANY'S OBLIGATIONS. Notwithstanding any
provisions in this Agreement to the contrary, the Company's obligations, and
Executive's rights pursuant to Sections 9(d) and 9(e) herein, regarding salary
continuation and the payment of COBRA premiums, shall cease and be rendered a
nullity immediately should Executive fail to comply with the provisions of the
Proprietary Information & Inventions Agreement attached hereto as Exhibit A or
if Executive directly or indirectly competes with the Company.

         12. CONTINUATION OF EMPLOYMENT/RESTRICTIVE COVENANT. Executive
acknowledges that he will be a member of executive and management personnel at
the Company. Executive further acknowledges that during his employment at the
Company, he will be privy to extremely sensitive, confidential and valuable
commercial information, which constitutes trade secrets belonging to the
Company, the disclosure of which information and secrets would greatly harm the
Company. Accordingly, during the term of Executive's employment and for a period
of twelve (12) months immediately following Executive's termination, Executive
shall not without first obtaining the prior written approval of the Company,
directly or indirectly engage or prepare to engage, in any activities in
competition with the Company, or accept employment or establish



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a business relationship with a business that directly competes with the Company
with regard to radiation sensitizers.

         13. NONSOLICITATION. While employed by the Company, and for twelve (12)
months immediately following the Executive's termination of employment,
Executive agrees not to interfere with the business of the Company by
soliciting, attempting to solicit, inducing, or otherwise causing any employee
of the Company to terminate his or her employment in order to become an
employee, consultant or independent contractor to or for any competitor of the
Company.

         14. MISCELLANEOUS.

                  (a) TAXES. Executive agrees to be responsible for the payment
of any taxes due on any and all compensation, stock option, or benefits provided
by the Company pursuant to this Agreement.

                  (b) MODIFICATION/WAIVER. This Agreement may not be amended,
modified, superseded, canceled, renewed or expanded, or any terms or covenants
hereof waived, except by a writing executed by each of the parties hereto or, in
the case of a waiver, by the party waiving compliance. Failure of any party at
any time or times to require performance of any provision hereof shall in no
manner affect his or its right at a later time to enforce the same. No waiver by
a party of a breach of any term or covenant contained in this Agreement, whether
by conduct or otherwise, in any one or more instances shall be deemed to be or
construed as a further or continuing waiver of agreement contained in the
Agreement.

                  (c) SEVERABILITY. Whenever possible, each provision of this
Agreement will be interpreted in such manner as to be effective and valid under
applicable law, but if any provision of this Agreement is held to be invalid,
illegal or unenforceable in any respect under any applicable law or rule in any
jurisdiction, such invalidity, illegality or unenforceability will not affect
any other provision or any other jurisdiction, but this Agreement will be
reformed, construed and enforced in such jurisdiction as if such invalid,
illegal or unenforceable provisions had never been contained herein.

                  (d) SUCCESSORS AND ASSIGNS. This Agreement is intended to bind
and inure to the benefit of and be enforceable by Executive and the Company, and
their respective successors, assigns, heirs, executors and administrators,
except that Executive may not assign any of his duties hereunder and he may not
assign any of his rights hereunder without the written consent of the Company,
which shall not be withheld unreasonably.

                  (e) NOTICES. All notices given hereunder shall be given by
certified mail, addressed, or delivered by hand, to the other party at his or
its address as set forth herein, or at any other address hereafter furnished by
notice given in like manner. Executive promptly shall notify Company of any
change in Executive's address. Each notice shall be dated the date of its
mailing or delivery and shall be deemed given, delivered or completed on such
date.

                  (f) GOVERNING LAW; PERSONAL JURISDICTION AND VENUE. This
Agreement and all disputes relating to this Agreement shall be governed in all
respects by the laws of the State of Colorado as such laws are applied to
agreements between Colorado residents entered



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into and performed entirely in Colorado. The Parties acknowledge that this
Agreement constitutes the minimum contacts to establish personal jurisdiction in
Colorado and agree to Colorado court's exercise of personal jurisdiction. The
Parties further agree that any disputes relating to this Agreement shall be
brought in courts located in the State of Colorado.

                  (g) ENTIRE AGREEMENT. This Agreement together with the
Exhibits A and B attached hereto set forth the entire agreement and
understanding of the parties hereto with regard to the employment of the
Executive by the Company and supersede and any and all prior agreements,
arrangements and understandings, written or oral, pertaining to the subject
matter hereof. No representation, promise or inducement relating to the subject
matter hereof has been made to a party that is not embodied in these Agreements,
and no party shall be bound by or liable for any alleged representation, promise
or inducement not so set forth.

                  (h) SURVIVAL. The following provisions of this Agreement shall
survive the termination of Executive's employment and the assignment of this
Agreement by the Company to any successor in interest or other assignee: Section
8, Section 12 and Section 13.

                  (i) INJUNCTIVE RELIEF. Executive acknowledges that the
restrictions set forth in Sections 8, 12, and 13 above are necessary to protect
the Company's confidential proprietary information and other legitimate business
interests and are reasonable in all respects, including duration, territory and
scope of activity restricted. Executive further acknowledges that the provisions
of Sections 8, 12 and 13 hereof are essential to the Company, that the Company
would not enter into this Agreement if it did not include these provisions and
that damages sustained by the Company as a result of a breach of these
provisions cannot be adequately remedied by damages, and Executive agrees that
the Company, in addition to any other remedy it may have under this Agreement or
at law, shall be entitled to injunctive and other equitable relief to prevent or
curtail any breach of Sections 8, 12 and 13 of this Agreement. Executive agrees
that the existence of any claim or cause of action by Executive against the
Company or its affiliates, whether predicated on this Agreement or otherwise,
shall not constitute a defense to the enforcement by the Company of any of the
provisions of Sections 8, 12 and 13 hereof. Executive shall have no right to
enforce any of his rights under this Agreement by seeking or obtaining
injunctive or other equitable relief and acknowledges that damages are an
adequate remedy for any breach by the Company of this Agreement.

         IN WITNESS WHEREOF, the parties have each duly executed this Restated
Employment Agreement as of the day and year first above written.




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                                        ALLOS THERAPEUTICS, INC.


                                        /s/ John Freund
                                        ---------------------------------------

                                        By:     John Freund
                                        Its:    Member of the Board of Directors



                                        EXECUTIVE:


                                        /s/ Stephen J. Hoffman
                                        ---------------------------------------
                                        Stephen J. Hoffman, PhD, MD





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                                    EXHIBIT A

                   MANAGER, EXECUTIVE PERSONNEL OR ASSISTANTS'
                      PROPRIETARY INFORMATION, INVENTIONS,
                 NON-COMPETITION, AND NON-SOLICITATION AGREEMENT
                                    COLORADO


         This Manager, Executive Personnel or Assistants' Proprietary
Information, Inventions, Non-competition, and Non-solicitation Agreement
("Agreement") is made in consideration for my employment or continued employment
by ALLOS THERAPEUTICS, INC. or its subsidiaries or affiliates (the "Company"),
and the compensation now and hereafter paid to me. I hereby agree as follows:

1.       NONDISCLOSURE.

         1.1 RECOGNITION OF COMPANY'S RIGHTS; NONDISCLOSURE. At all times during
         my employment and thereafter, I will hold in strictest confidence and
         will not disclose, use, lecture upon or publish any of the Company's
         Proprietary Information (defined below), except as such disclosure, use
         or publication may be required in connection with my work for the
         Company, or unless an officer of the Company expressly authorizes such
         in writing. I will obtain Company's written approval before publishing
         or submitting for publication any material (written, verbal, or
         otherwise) that relates to my work at Company and/or incorporates any
         Proprietary Information. I hereby assign to the Company any rights I
         may have or acquire in such Proprietary Information and recognize that
         all Proprietary Information shall be the sole property of the Company
         and its assigns.

         1.2 PROPRIETARY INFORMATION. The term "PROPRIETARY INFORMATION" shall
         mean any and all confidential and/or proprietary knowledge, data or
         information of the Company. By way of illustration but not limitation,
         "Proprietary Information" includes (a) trade secrets, inventions, mask
         works, ideas, processes, formulas, source and object codes, data,
         programs, other works of authorship, know-how, improvements,
         discoveries, developments, designs and techniques (hereinafter
         collectively referred to as "Inventions"); and (b) information
         regarding plans for research, development, new products, marketing and
         selling, business plans, budgets and unpublished financial statements,
         licenses, prices and costs, suppliers and customers; and (c)
         information regarding the skills and compensation of other employees of
         the Company. Notwithstanding the foregoing, it is understood that, at
         all such times, I am free to use information which is generally known
         in the trade or industry, which is not gained as result of a breach of
         this Agreement, and my own, skill, knowledge, know-how and experience
         to whatever extent and in whichever way I wish.

         1.3 THIRD PARTY INFORMATION. I understand, in addition, that the
         Company has received and in the future will receive from third parties
         confidential or proprietary information ("Third Party Information")
         subject to a duty on the Company's part to maintain the confidentiality
         of such information and to use it only for certain limited purposes.
         During the term of my employment and thereafter, I will hold Third
         Party Information in the strictest confidence and will not disclose to
         anyone (other than Company personnel who need to know such information
         in connection with their work for the Company) or use, except in
         connection with my work for the Company, Third Party Information unless
         expressly authorized by an officer of the Company in writing.

         1.4 NO IMPROPER USE OF INFORMATION OF PRIOR EMPLOYERS AND OTHERS.
         During my employment by the Company I will not improperly use or
         disclose any confidential information or trade secrets, if any, of any
         former employer or any other person to whom I have an obligation of
         confidentiality, and I will not bring onto the premises of the Company
         any unpublished


<PAGE>   10

         documents or any property belonging to any former employer or any other
         person to whom I have an obligation of confidentiality unless consented
         to in writing by that former employer or person. I will use in the
         performance of my duties only information which is generally known and
         used by persons with training and experience comparable to my own,
         which is common knowledge in the industry or otherwise legally in the
         public domain, or which is otherwise provided or developed by the
         Company.

2.       ASSIGNMENT OF INVENTIONS.

         2.1 PROPRIETARY RIGHTS. The term "PROPRIETARY RIGHTS" shall mean all
         trade secret, patent, copyright, mask work and other intellectual
         property rights throughout the world.

         2.2 PRIOR INVENTIONS. Inventions, if any, patented or unpatented, which
         I made prior to the commencement of my employment with the Company are
         excluded from the scope of this Agreement. To preclude any possible
         uncertainty, I have set forth on Exhibit A (Previous Inventions)
         attached hereto a complete list of all Inventions that I have, alone or
         jointly with others, conceived, developed or reduced to practice or
         caused to be conceived, developed or reduced to practice prior to the
         commencement of my employment with the Company, that I consider to be
         my property or the property of third parties and that I wish to have
         excluded from the scope of this Agreement (collectively referred to as
         "Prior Inventions"). If disclosure of any such Prior Invention would
         cause me to violate any prior confidentiality agreement, I understand
         that I am not to list such Prior Inventions in Exhibit A but am only to
         disclose a cursory name for each such invention, a listing of the
         party(ies) to whom it belongs and the fact that full disclosure as to
         such inventions has not been made for that reason. A space is provided
         on Exhibit A for such purpose. If no such disclosure is attached, I
         represent that there are no Prior Inventions. If, in the course of my
         employment with the Company, I incorporate a Prior Invention into a
         Company product, process or machine, the Company is hereby granted and
         shall have a nonexclusive, royalty-free, irrevocable, perpetual,
         worldwide license (with rights to sublicense through multiple tiers of
         sublicensees) to make, have made, modify, use and sell such Prior
         Invention. Notwithstanding the foregoing, I agree that I will not
         incorporate, or permit to be incorporated, Prior Inventions in any
         Company Inventions without the Company's prior written consent.

         2.3 ASSIGNMENT OF INVENTIONS. Subject to Sections 2.4, and 2.6, I
         hereby assign and agree to assign in the future (when any such
         Inventions or Proprietary Rights are first reduced to practice or first
         fixed in a tangible medium, as applicable) to the Company all my right,
         title and interest in and to any and all Inventions (and all
         Proprietary Rights with respect thereto) whether or not patentable or
         registrable under copyright or similar statutes, made or conceived or
         reduced to practice or learned by me, either alone or jointly with
         others, during the period of my employment with the Company. Inventions
         assigned to the Company, or to a third party as directed by the Company
         pursuant to this Section 2, are hereinafter referred to as "Company
         Inventions."

         2.4 NONASSIGNABLE INVENTIONS. I recognize that, in the event of a
         specifically applicable state law, regulation, rule, or public policy
         ("Specific Inventions Law"), this Agreement will not be deemed to
         require assignment of any invention which qualifies fully for
         protection under a Specific Inventions Law by virtue of the fact that
         any such invention was, for example, developed entirely on my own time
         without using the Company's equipment, supplies, facilities, or trade
         secrets and neither related to the Company's actual or anticipated
         business, research or development, nor resulted from work performed by
         me for the Company. In the absence of a Specific Inventions Law, the
         preceding sentence will not apply.

         2.5 OBLIGATION TO KEEP COMPANY INFORMED. During the period of my
         employment and for six months after the last day of my employment with
         the Company, I will promptly disclose to the Company fully and in
         writing all Inventions authored,


<PAGE>   11

         conceived or reduced to practice by me, either alone or jointly with
         others. In addition, I will promptly disclose to the Company all patent
         applications filed by me or on my behalf within a year after
         termination of employment. At the time of each such disclosure, I will
         advise the Company in writing of any Inventions that I believe fully
         qualify for protection under the provisions of a Specific Inventions
         Law; and I will at that time provide to the Company in writing all
         evidence necessary to substantiate that belief. The Company will keep
         in confidence and will not use for any purpose or disclose to third
         parties without my consent any confidential information disclosed in
         writing to the Company pursuant to this Agreement relating to
         Inventions that qualify fully for protection under a Specific
         Inventions Law. I will preserve the confidentiality of any Invention
         that does not fully qualify for protection under a Specific Inventions
         Law.

         2.6 GOVERNMENT OR THIRD PARTY. I also agree to assign all my right,
         title and interest in and to any particular Invention to a third party,
         including without limitation the United States, as directed by the
         Company.

         2.7 WORKS FOR HIRE. I acknowledge that all original works of authorship
         which are made by me (solely or jointly with others) within the scope
         of my employment and which are protectable by copyright are "works made
         for hire," pursuant to United States Copyright Act (17 U.S.C., Section
         101).

         2.8 ENFORCEMENT OF PROPRIETARY RIGHTS. I will assist the Company in
         every proper way to obtain, and from time to time enforce, United
         States and foreign Proprietary Rights relating to Company Inventions in
         any and all countries. To that end I will execute, verify and deliver
         such documents and perform such other acts (including appearances as a
         witness) as the Company may reasonably request for use in applying for,
         obtaining, perfecting, evidencing, sustaining and enforcing such
         Proprietary Rights and the assignment thereof. In addition, I will
         execute, verify and deliver assignments of such Proprietary Rights to
         the Company or its designee. My obligation to assist the Company with
         respect to Proprietary Rights relating to such Company Inventions in
         any and all countries shall continue beyond the termination of my
         employment, but the Company shall compensate me at a reasonable rate
         after my termination for the time actually spent by me at the Company's
         request on such assistance.

         In the event the Company is unable for any reason, after reasonable
         effort, to secure my signature on any document needed in connection
         with the actions specified in the preceding paragraph, I hereby
         irrevocably designate and appoint the Company and its duly authorized
         officers and agents as my agent and attorney in fact, which appointment
         is coupled with an interest, to act for and in my behalf to execute,
         verify and file any such documents and to do all other lawfully
         permitted acts to further the purposes of the preceding paragraph with
         the same legal force and effect as if executed by me. I hereby waive
         and quitclaim to the Company any and all claims, of any nature
         whatsoever, which I now or may hereafter have for infringement of any
         Proprietary Rights assigned hereunder to the Company.

3. NO CONFLICTS OR SOLICITATION. I acknowledge that during my employment I will
have access to and knowledge of Proprietary Information. I also acknowledge that
during my employment with the Company, I have held and/or will hold a management
or executive position or am, or will be, an assistant to a manager or executive.
To protect the Company's Proprietary Information, I agree that during the period
of my employment by the Company I will not, without the Company's express
written consent, engage in any other employment or business activity directly
related to the business in which the Company is now involved or becomes
involved, nor will I engage in any other activities which conflict with my
obligations to the Company. To protect the Company's Proprietary Information,
and because of the position in the Company that I hold, I agree that during my
employment with the Company whether full-time or part-time and for a period of
one year after my last day of employment with the Company, I will not (a)
directly or indirectly solicit or induce any employee of the Company to
terminate or negatively alter his or her relationship with the Company or (b)
directly or indirectly solicit the business of any client or customer of the
Company (other than on behalf of the Company) or (c) directly or indirectly
induce any


<PAGE>   12

client, customer, supplier, vendor, consultant or independent contractor of the
Company to terminate or negatively alter his, her or its relationship with the
Company. I agree that the geographic scope of the non-solicitation should
include the "Restricted Territory" (as defined below).

4. If any restriction set forth in this Section is found by any court of
competent jurisdiction to be unenforceable because it extends for too long a
period of time or over too great a range of activities or in too broad a
geographic area, it shall be interpreted to extend only over the maximum period
of time, range of activities or geographic area as to which it may be
enforceable.

5. COVENANT NOT TO COMPETE. I acknowledge that during my employment I will have
access to and knowledge of Proprietary Information. I also acknowledge that
during my employment with the Company, I have held and/or will hold a management
or executive position or am, or will be, an assistant to a manager or executive.
To protect the Company's Proprietary Information, and because of the position in
the Company that I may hold, I agree that during my employment with the Company
whether full-time or part-time and for a period of one year after my last day of
employment with the Company, I will not directly or indirectly engage in
(whether as an employee, consultant, proprietor, partner, director or
otherwise), or have any ownership interest in, or participate in the financing,
operation, management or control of, any person, firm, corporation or business
that engages in a "Restricted Business" in a "Restricted Territory" (as defined
below). It is agreed that ownership of (i) no more than one percent (1%) of the
outstanding voting stock of a publicly traded corporation, or (ii) any stock I
presently own shall not constitute a violation of this provision.

         5.1 REASONABLE. I agree and acknowledge that the time limitation on the
         restrictions in this paragraph, combined with the geographic scope, is
         reasonable. I also acknowledge and agree that this paragraph is
         reasonably necessary for the protection of Company's Proprietary
         Information as defined in paragraph 1.2 herein, that through my
         employment I shall receive adequate consideration for any loss of
         opportunity associated with the provisions herein, and that these
         provisions provide a reasonable way of protecting Company's business
         value which will be imparted to me. If any restriction set forth in
         this paragraph 4 is found by any court of competent jurisdiction to be
         unenforceable because it extends for too long a period of time or over
         too great a range of activities or in too broad a geographic area, it
         shall be interpreted to extend only over the maximum period of time,
         range of activities or geographic area as to which it may be
         enforceable.

         5.2 As used herein, the terms:

                  (i) "Restricted Business" shall mean the design, development,
         marketing or sales of hardware, software, or service marketed, sold or
         under development by the Company at any time during my employment with
         the Company.

                  (ii) "Restricted Territory" shall mean any state, county, or
         locality in the United States in which the Company conducts business
         and any other country, city, state, jurisdiction, or territory in which
         the Company does business.

6. RECORDS. I agree to keep and maintain adequate and current records (in the
form of notes, sketches, drawings and in any other form that may be required by
the Company) of all Proprietary Information developed by me and all Inventions
made by me during the period of my employment at the Company, which records
shall be available to and remain the sole property of the Company at all times.

7. NO CONFLICTING OBLIGATION. I represent that my performance of all the terms
of this Agreement and as an employee of the Company does not and will not breach
any agreement to keep in confidence information acquired by me in confidence or
in trust prior to my employment by the Company. I have not entered into, and I
agree I will not enter into, any agreement either written or oral in conflict
herewith.

8. RETURN OF COMPANY MATERIALS. When I leave the employ of the Company, I will
deliver to the Company any and all drawings, notes, memoranda, specifications,
devices, formulas, and documents, together with all copies thereof, and any
other material containing or disclosing any Company Inventions, Third Party
Information or Proprietary Information of the Company, unless agreed to by the
Company. I further agree that any property situated


<PAGE>   13

on the Company's premises and owned by the Company, including disks and other
storage media, filing cabinets or other work areas, is subject to inspection by
Company personnel at any time with or without notice.

9. LEGAL AND EQUITABLE REMEDIES. Because my services are personal and unique and
because I may have access to and become acquainted with the Proprietary
Information of the Company, the Company shall have the right to enforce this
Agreement and any of its provisions by injunction, specific performance or other
equitable relief, without bond and without prejudice to any other rights and
remedies that the Company may have for a breach of this Agreement.

10. NOTICES. Any notices required or permitted hereunder shall be given to the
appropriate party at the address specified below or at such other address as the
party shall specify in writing. Such notice shall be deemed given upon personal
delivery to the appropriate address or if sent by certified or registered mail,
three days after the date of mailing.

11. NOTIFICATION OF NEW EMPLOYER. In the event that I leave the employ of the
Company, I hereby consent to the notification of my new employer of my rights
and obligations under this Agreement.

12.      GENERAL PROVISIONS.

         12.1 GOVERNING LAW; CONSENT TO PERSONAL JURISDICTION AND EXCLUSIVE
         FORUM. This Agreement will be governed by and construed according to
         the laws of the State of Colorado as such laws are applied to
         agreements entered into and to be performed entirely within Colorado
         between Colorado residents. I hereby expressly understand and consent
         that my employment is a transaction of business in the State of
         Colorado and constitutes the minimum contacts necessary to make me
         subject to the personal jurisdiction of the federal courts located in
         the State of Colorado, and the state courts located in the County of
         Denver, Colorado, for any lawsuit filed against me by Company arising
         from or related to this Agreement. I agree and acknowledge that any
         controversy arising out of or relating to this Agreement or the breach
         thereof, or any claim or action to enforce this Agreement or portion
         thereof, or any controversy or claim requiring interpretation of this
         Agreement must be brought in a forum located within the State of
         Colorado. No such action may be brought in any forum outside the State
         of Colorado. Any action brought in contravention of this paragraph by
         one party is subject to dismissal at any time and at any stage of the
         proceedings by the other, and no action taken by the other in
         defending, counter claiming or appealing shall be construed as a waiver
         of this right to immediate dismissal. A party bringing an action in
         contravention of this paragraph shall be liable to the other party for
         the costs, expenses and attorney's fees incurred in successfully
         dismissing the action or successfully transferring the action to the
         federal courts located in the State of Colorado, or the state courts
         located in the County of Denver, Colorado.

         12.2 SEVERABILITY. In case any one or more of the provisions contained
         in this Agreement shall, for any reason, be held to be invalid, illegal
         or unenforceable in any respect, such invalidity, illegality or
         unenforceability shall not affect the other provisions of this
         Agreement, and this Agreement shall be construed as if such invalid,
         illegal or unenforceable provision had never been contained herein. If
         moreover, any one or more of the provisions contained in this Agreement
         shall for any reason be held to be excessively broad as to duration,
         geographical scope, activity or subject, it shall be construed by
         limiting and reducing it, so as to be enforceable to the extent
         compatible with the applicable law as it shall then appear.

         12.3 SUCCESSORS AND ASSIGNS. This Agreement will be binding upon my
         heirs, executors, administrators and other legal representatives and
         will be for the benefit of the Company, its successors, and its
         assigns.

         12.4 SURVIVAL. The provisions of this Agreement shall survive the
         termination of my employment and the assignment of this Agreement by
         the Company to any successor in interest or other assignee.


<PAGE>   14

         12.5 EMPLOYMENT. I agree and understand that my employment is at-will
         which means I or the company each have the right to terminate my
         employment at will, with or without advanced notice and with or without
         cause. I further agree and understand that nothing in this Agreement
         shall confer any right with respect to continuation of employment by
         the Company, nor shall it interfere in any way with my right or the
         Company's right to terminate my employment at any time, with or without
         cause.

         12.6 WAIVER. No waiver by the Company of any breach of this Agreement
         shall be a waiver of any preceding or succeeding breach. No waiver by
         the Company of any right under this Agreement shall be construed as a
         waiver of any other right. The Company shall not be required to give
         notice to enforce strict adherence to all terms of this Agreement.

         12.7 ENTIRE AGREEMENT. The obligations pursuant to Sections 1 through 4
         and Sections 6 and 7 (including all subparts) of this Agreement shall
         apply to any time during which I was previously employed, or am in the
         future employed, by the Company as a consultant if no other agreement
         governs nondisclosure and assignment of inventions during such period.
         This Agreement is the final, complete and exclusive agreement of the
         parties with respect to the subject matter hereof and supersedes and
         merges all prior discussions between us. No modification of or
         amendment to this Agreement, nor any waiver of any rights under this
         Agreement, will be effective unless in writing and signed by the party
         to be charged. Any subsequent change or changes in my duties, salary or
         compensation will not affect the validity or scope of this Agreement

         This Agreement shall be effective as of the _______________, 2001.

         I HAVE READ THIS AGREEMENT CAREFULLY AND UNDERSTAND ITS TERMS. I HAVE
COMPLETELY FILLED OUT EXHIBIT A TO THIS AGREEMENT.


Dated:
      -----------------


-------------------------------------------
Stephen J. Hoffman


ACCEPTED AND AGREED TO:


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




<PAGE>   15

                                    EXHIBIT B


TO:       ALLOS THERAPEUTICS, INC.

FROM:     STEPHEN J. HOFFMAN

DATE:
          ------------------------

SUBJECT:  PREVIOUS INVENTIONS

         1. Except as listed in Section 2 below, the following is a complete
list of all inventions or improvements relevant to the subject matter of my
employment by ALLOS THERAPEUTICS, INC. that have been made or conceived or first
reduced to practice by me alone or jointly with others prior to my engagement by
the Company:

         [ ]      No inventions or improvements.

         [ ]      See below:
                  ______________________________________________________________

                  ______________________________________________________________

                  ______________________________________________________________

         [ ]      Additional sheets attached.


         2. Due to a prior confidentiality agreement, I cannot complete the
disclosure under Section 1 above with respect to inventions or improvements
generally listed below, the proprietary rights and duty of confidentiality with
respect to which I owe to the following party(ies):

<TABLE>
<CAPTION>
      INVENTION OR IMPROVEMENT                PARTY(IES)                         RELATIONSHIP
<S>                                     <C>                      <C>

1.    ________________________          ____________________     _________________________________________

2.    ________________________          ____________________     _________________________________________

3.    ________________________          ____________________     _________________________________________

</TABLE>

         [ ]      Additional sheets attached.


<PAGE>   16

                                    EXHIBIT B

                                RELEASE AGREEMENT

I understand that my position with Allos Therapeutics, Inc. (the "Company")
terminated effective ___________, _____ (the "Separation Date"). The Company has
agreed that if I choose to sign this Release, the Company will pay me certain
severance or consulting benefits pursuant to the terms of the Executive
Employment (the "Agreement") between myself and the Company, and any agreements
incorporated therein by reference. I understand that I am not entitled to such
benefits unless I sign this Release and it becomes fully effective. I understand
that, regardless of whether I sign this Release, the Company will pay me all of
my accrued salary and vacation through the Separation Date, to which I am
entitled by law.

In consideration for the severance benefits I am receiving under the Agreement,
I hereby release the Company and its officers, directors, agents, attorneys,
employees, shareholders, parents, subsidiaries, and affiliates from any and all
claims, liabilities, demands, causes of action, attorneys' fees, damages, or
obligations of every kind and nature, whether they are now known or unknown,
arising at any time prior to the date I sign this Release. This general release
includes, but is not limited to: all federal and state statutory and common law
claims, claims related to my employment or the termination of my employment or
related to breach of contract, tort, wrongful termination, discrimination, wages
or benefits, or claims for any form of equity or compensation. Notwithstanding
the release in the preceding sentence, I am not releasing any right of
indemnification I may have for any liabilities arising from my actions within
the course and scope of my employment with the Company.

If I am forty (40) years of age or older as of the Separation Date, I
acknowledge that I am knowingly and voluntarily waiving and releasing any rights
I may have under the federal Age Discrimination in Employment Act of 1967, as
amended ("ADEA"). I also acknowledge that the consideration given for the waiver
in the above paragraph is in addition to anything of value to which I was
already entitled. I have been advised by this writing, as required by the ADEA
that: (a) my waiver and release do not apply to any claims that may arise after
my signing of this Release; (b) I should consult with an attorney prior to
executing this Release; (c) I have twenty-one (21) days within which to consider
this Release (although I may choose to voluntarily execute this Release
earlier); (d) I have seven (7) days following the execution of this release to
revoke the Release; and (e) this Release will not be effective until the eighth
day after this Release has been signed both by me and by the Company ("Effective
Date").

Agreed:

ALLOS THERAPEUTICS. INC.                     STEPHEN J. HOFFMAN

By:
   ---------------------------------         ----------------------------------

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

Title:
      ------------------------------

Date:                                        Date:
     ----------------------                       ----------------------