<PAGE>   1
                                                                   EXHIBIT 10.07

THESE SECURITIES HAVE NOT BEEN REGISTERED UNDER THE SECURITIES ACT OF 1933, AS
AMENDED, OR ANY STATE SECURITIES LAWS. THEY MAY NOT BE SOLD, OFFERED FOR SALE,
PLEDGED, OR HYPOTHECATED IN THE ABSENCE OF AN EFFECTIVE REGISTRATION STATEMENT
RELATED THERETO OR AN OPINION OF COUNSEL (WHICH MAY BE COMPANY COUNSEL)
REASONABLY SATISFACTORY TO THE COMPANY THAT SUCH REGISTRATION IS NOT REQUIRED
UNDER THE SECURITIES ACT OF 1933, AS AMENDED, OR ANY APPLICABLE STATE SECURITIES
LAWS.

                                WARRANT AGREEMENT

             To Purchase Shares of the Series B Preferred Stock of

                            ALLOS THERAPEUTICS, INC.

                Dated as of April 15, 1996 (the "Effective Date")

     WHEREAS, Allos Therapeutics, Inc., a Virginia corporation (the "Company")
has entered into a Master Lease Agreement dated as of April 15, 1996, Equipment
Schedule No. VL-1 dated as of April 15, 1996, and related Summary Equipment
Schedules (collectively, the "Leases") with Comdisco, Inc., a Delaware
corporation (the "Warrantholder"); and

     WHEREAS, the Company desires to grant to Warrantholder, in consideration
for such Leases, the right to purchase shares of its Series B Preferred Stock;

     NOW, THEREFORE, in consideration of the Warrantholder executing and
delivering such Leases and in consideration of mutual covenants and agreements
contained herein, the Company and Warrantholder agree as follows:

1.   GRANT OF THE RIGHT TO PURCHASE PREFERRED STOCK.

     The Company hereby grants to the Warrantholder, and the Warrantholder is
entitled, upon the terms and subject to the conditions hereinafter set forth, to
subscribe to and purchase, from the Company, 17,500 fully paid and
non-assessable shares of the Company's Series B Preferred Stock ("Preferred
Stock") at a purchase price of $1.60 per share (the "Exercise Price"). The
number and purchase price of such shares are subject to adjustment as provided
in Section 8 hereof.

2.   TERM OF THE WARRANT AGREEMENT.

     (a) Except as otherwise provided for herein, the term of this Warrant
Agreement and the right to purchase Preferred Stock as granted herein shall
commence on the Effective Date and shall be exercisable for a period of (i) ten
(10) years or (ii) five (5) years from the effective date of the Company's
initial public offering, whichever is longer.

     (b) Notwithstanding the term of this Warrant Agreement fixed pursuant to
Section 2(a) hereof, the right to purchase Preferred Stock as granted herein
shall expire, if not previously exercised, immediately upon the closing of a
merger, reorganization, consolidation or sale of all or substantially all of the
Company's properties and assets in which the Company's shareholders immediately
prior to such transaction possess less than fifty percent (50%) of the voting
securities of the surviving, continuing or purchasing entity (or parent, if any,
immediately after the transaction) (an "Accelerating Merger").




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     The company shall notify the Warrantholder in writing at least fifteen (15)
days in advance of the closing of an Accelerating Merger, and if the company
fails to deliver such written notice, then notwithstanding anything to the
contrary in the Warrant Agreement, the rights to purchase the Company's
Preferred Stock shall not expire until the Company complies with such notice
provisions. Such notice shall also contain such details of the proposed
Accelerating Merger as are reasonable in the circumstances. If such closing does
not take place, the Company shall promptly notify the Warrantholder that such
proposed transaction has been terminated, and the Warrantholder may rescind any
exercise of its purchase rights promptly after such notice of termination of the
proposed transaction if the exercise of warrants occurred after the Company had
notified the Warrantholder that the Accelerating Merger was proposed or if the
exercise was otherwise precipitated by such proposed Accelerating Merger. In the
event of such rescission, the Warrants will continue to be exercisable on the
terms and conditions contained herein.

3.   EXERCISE OF THE PURCHASE RIGHTS.

     The purchase rights set forth in this Warrant Agreement are exercisable by
the Warrantholder, in whole or in part, at any time, or from time to time, prior
to the expiration of the term set forth in Section 2 above, by tendering to the
Company at its principal office a notice of exercise in the form attached hereto
as Exhibit I (the "Notice of Exercise"), duly completed and executed. Promptly
upon receipt of the Notice of Exercise and the payment of the purchase price in
accordance with the terms set forth below, and in no event later than twenty-one
(21) days thereafter, the Company shall issue to the Warrantholder a certificate
for the number of shares of Preferred Stock purchased and shall execute the
acknowledgment of exercise in the form attached hereto as Exhibit II (the
"Acknowledgment of Exercise") indicating the number of shares which remain
subject to future purchases, if any.

     The Exercise Price may be paid at the Warrantholder's election either (i)
by cash or check, or (ii) by surrender of Warrants ("Net Issuance") as
determined below. If the Warrantholder elects the Net Issuance method, the
Company will issue Preferred Stock in accordance with the following formula:

                  X = Y(A-B)
                      ------
                       A

Where:            X = the number of shares of Preferred Stock to be issued to
                  the Warrantholder.

                  Y = the number of shares of Preferred Stock requested to be
                  exercised under this Warrant Agreement.

                  A = the fair market value of one (1) share of Preferred Stock.

                  B = the Exercise Price.

     For purposes of the above calculation, current fair market value of
Preferred Stock shall mean with respect to each share of Preferred Stock:

         (i) if the exercise is in connection with an initial public offering of
         the Company's Common Stock, and if the Company's Registration Statement
         relating to such public offering has been declared effective by the
         SEC, then the fair market value per share shall be the product of (x)
         the initial "Price to Public" specified in the final prospectus with
         respect to the offering and (y) the number of shares of Common Stock
         into which each share of Preferred Stock is convertible at the time of
         such exercise;

         (ii) if this Warrant is exercised after, and not in connection with the
         Company's initial public offering, and:

                  (a) if traded on a securities exchange, the fair market value
                  shall be deemed to be the product of (x) the average of the
                  closing prices over a twenty-one (21) day period ending three
                  days before the day the current fair market value of the
                  securities is being determined and (y) the number of shares of
                  Common Stock into which each share of Preferred Stock is
                  convertible at the time of such exercise; or




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                   (b) if actively traded over-the-counter, the fair market
                   value shall be deemed to be the product of (x) the average
                   of the closing bid and asked prices quoted on the NASDAQ
                   system (or similar system) over the twenty-one (21) day
                   period ending three days before the day the current fair
                   market value of the securities is being determined and (y)
                   the number of shares of Common Stock into which each share of
                   Preferred Stock is convertible at the time of such exercise;

     (iii) if at any time the Common Stock is not listed on any securities
     exchange or quoted in the NASDAQ System or the over-the-counter market, the
     current fair market value of Preferred Stock shall be the product of (x)
     the highest price per share which the Company could obtain from a willing
     buyer (not a current employee or director) for shares of Common Stock sold
     by the Company, from authorized but unissued shares, as determined in good
     faith by its Board of Directors and (y) the number of shares of Common
     Stock into which each share of Preferred Stock is convertible at the time
     of such exercise, unless the Company shall become subject to a merger,
     acquisition or other consolidation pursuant to which the Company is not the
     surviving party, in which case the fair market value of Preferred Stock
     shall be deemed to be the value received by the holders of the Company's
     Preferred Stock on a common equivalent basis pursuant to such merger or
     acquisition.

     Upon partial exercise by either cash or Net Issuance, the Company shall
promptly issue an amended Warrant Agreement representing the remaining number of
shares purchasable hereunder. All other terms and conditions of such amended
Warrant Agreement shall be identical to those contained herein, including, but
not limited to the Effective Date hereof.

 4.  RESERVATION OF SHARES.


     (a) Authorization and Reservation of Shares. During the term of this
Warrant Agreement, the Company will at all times have authorized and reserved a
sufficient number of shares of its Preferred Stock to provide for the exercise
of the rights to purchase Preferred Stock as provided for herein.

     (b) Registration or Listing. If any shares of Preferred Stock required to
be reserved hereunder require registration with or approval of any governmental
authority under any Federal or State law (other than any registration under the
1933 Act, as then in effect, or any similar Federal statute then enforced, or
any state securities law, required by reason of any transfer involved in such
conversion), or listing on any domestic securities exchange, before such shares
may be issued upon conversion, the Company will, at its expense and as
expeditiously as possible, use its best efforts to cause such shares to be duly
registered, listed or approved for listing on such domestic securities exchange,
as the case may be.

5.   NO FRACTIONAL SHARES OR SCRIP.

     No fractional shares or scrip representing fractional shares shall be
issued upon the exercise of the Warrant, but in lieu of such fractional shares
the Company shall make a cash payment therefor upon the basis of the Exercise
Price then in effect.

6.   NO RIGHTS AS SHAREHOLDER.

     This Warrant Agreement does not entitle the Warrantholder to any voting
rights or other rights as a shareholder of the Company prior to the exercise of
the Warrant.

7.   WARRANTHOLDER REGISTRY.

     The Company shall maintain a registry showing the name and address of the
registered holder of this Warrant Agreement.



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8.   ADJUSTMENT RIGHTS.

     The purchase price per share and the number of shares of Preferred Stock
purchasable hereunder are subject to adjustment, as follows:

     (a) Merger and Sale of Assets. Except as otherwise set forth in Sections 2
and 3 hereof, at any time there shall be a capital reorganization of the shares
of the Company's stock (other than a combination, reclassification, exchange or
subdivision of shares otherwise provided for herein), or a merger or
consolidation of the Company with or into another corporation when the Company
is not the surviving corporation, or the sale of all or substantially all of the
Company's properties and assets to any other person (hereinafter referred to as
a "Merger Event"), then, as a part of such Merger Event, lawful provision shall
be made so that the Warrantholder shall thereafter be entitled to receive, upon
exercise of the Warrant, the number of shares of preferred stock or other
securities of the successor corporation resulting from such Merger Event,
equivalent in value to that which would have been issuable if Warrantholder had
exercised this Warrant immediately prior to the Merger Event. In any such case,
appropriate adjustment (as determined in good faith by the Company's Board of
Directors) shall be made in the application of the provisions of this Warrant
Agreement with respect to the rights and interest of the Warrantholder after the
Merger Event to the end that the provisions of this Warrant Agreement (including
adjustments of the Exercise Price and number of shares of Preferred Stock
purchasable) shall be applicable to the greatest extent possible.

     (b) Reclassification of Shares. If the Company at any time shall, by
combination, reclassification, exchange or subdivision of securities or
otherwise, change any of the securities as to which purchase rights under this
Warrant Agreement exist into the same or a different number of securities of any
other class or classes, this Warrant Agreement shall thereafter represent the
right to acquire such number and kind of securities as would have been issuable
as the result of such change with respect to the securities which were subject
to the purchase rights under this Warrant Agreement immediately prior to such
combination, reclassification, exchange, subdivision or other change.

     (c) Subdivision or Combination of Shares. If the Company at any time shall
combine or subdivide its Preferred Stock, the Exercise Price shall be
proportionately decreased in the case of a subdivision, or proportionately
increased in the case of a combination.

     (d) Stock Dividends. If the Company at any time shall pay a dividend
payable in, or make any other distribution (except any distribution specifically
provided for in the foregoing subsections (a) or (b)) of the Company's stock,
then the Exercise Price shall be adjusted, from and after the record date of
such dividend or distribution, to that price determined by multiplying the
Exercise Price in effect immediately prior to such record date by a fraction (i)
the numerator of which shall be the total number of all shares of the Company's
stock outstanding immediately prior to such dividend or distribution, and (ii)
the denominator of which shall be the total number of all shares of the
Company's stock outstanding immediately after such dividend or distribution. The
Warrantholder shall thereafter be entitled to purchase, at the Exercise Price
resulting from such adjustment, the number of shares of Preferred Stock
(calculated to the nearest whole share) obtained by multiplying the Exercise
Price in effect immediately prior to such adjustment by the number of shares of
Preferred Stock issuable upon the exercise hereof immediately prior to such
adjustment and dividing the product thereof by the Exercise Price resulting from
such adjustment.

     (e) Right to Purchase Additional Stock. If, the Warrantholder's total cost
of equipment leased pursuant to the Leases exceeds $350,000, Warrantholder shall
have the right to purchase from the Company, at the Exercise Price (adjusted as
set forth herein), an additional number of shares, which number shall be
determined by (i) multiplying the amount by which the Warrantholder's total
equipment cost exceeds $350,000 by 8%, and (ii) dividing the product thereof by
the Exercise Price per share referenced above.

     (f) Antidilution Rights. Additional antidilution rights applicable to the
Preferred Stock purchasable hereunder are as set forth in the Company's Amended
and Restated Articles of Incorporation, as amended through the Effective Date, a
true and complete copy of which is attached hereto as Exhibit IV (the "Charter")
and the




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Company shall provide Warrantholder with copies of all notices provided to
holders of Preferred Stock. The Company shall promptly provide the Warrantholder
with any restatement, amendment, modification or waiver of the Charter. The
Company shall provide Warrantholder with prior written notice of any issuance of
its stock or other equity security (other than such issuances as are set forth
in the Charter) to occur after the Effective Date of this Warrant, which notice
shall include (a) the price at which such stock or security is to be sold, (b)
the number of shares to be issued, and (c) such other information as necessary
for Warrantholder to determine if a dilutive event has occurred.

     (g) Notice of Adjustments. If: (i) the Company shall declare any dividend
or distribution upon its stock, whether in cash, property, stock or other
securities; (ii) the Company shall offer for subscription prorata to the holders
of any class of its Preferred or other convertible stock any additional shares
of stock of any class or other rights; (iii) there shall be any Merger Event;
(iv) there shall be an initial public offering; or (v) there shall be any
voluntary dissolution, liquidation or winding up of the Company; then, in
connection with each such event, the Company shall send to the Warrantholder:
(A) at least twenty (20) days' prior written notice of the date on which the
books of the Company shall close or a record shall be taken for such dividend,
distribution, subscription rights (specifying the date on which the holders of
Preferred Stock shall be entitled thereto) or for determining rights to vote in
respect of such Merger Event, dissolution, liquidation or winding up; (B) in the
case of any such Merger Event, dissolution, liquidation or winding up, at least
twenty (20) days' prior written notice of the date when the same shall take
place (and specifying the date on which the holders of Preferred Stock shall be
entitled to exchange their Preferred Stock for securities or other property
deliverable upon such Merger Event, dissolution, liquidation or winding up); and
(C) in the case of a public offering, the Company shall give the Warrantholder
at least twenty (20) days written notice prior to the closing date thereof.

     Each such written notice shall set forth, in reasonable detail, (i) the
event requiring the adjustment, (ii) the amount of the adjustment, (iii) the
method by which such adjustment was calculated, (iv) the Exercise Price, and (v)
the number of shares subject to purchase hereunder after giving effect to such
adjustment, and shall be given by first class mail, postage prepaid, addressed
to the Warrantholder, at the address as shown on the books of the Company.

     (g) Timely Notice. Failure to timely provide such notice required by
subsection (f) above shall entitle Warrantholder to retain the benefit of the
applicable notice period notwithstanding anything to the contrary contained in
any insufficient notice received by Warrantholder. The notice period shall begin
on the date Warrantholder actually receives a written notice containing all the
information specified above.

 9.  REPRESENTATIONS, WARRANTIES AND COVENANTS OF THE COMPANY.

     (a) Reservation of Preferred Stock. The Preferred Stock issuable upon
exercise of the Warrantholder's rights has been duly and validly reserved and,
when issued in accordance with the provisions of this Warrant Agreement, will be
validly issued, fully paid and non-assessable, and will be free of any taxes,
liens, charges or encumbrances of any nature whatsoever; provided, however, that
the Preferred Stock issuable pursuant to this Warrant Agreement may be subject
to restrictions on transfer under state and/or Federal securities laws. The
Company has made available to the Warrantholder true, correct and complete
copies of its Charter and Bylaws, as amended. The issuance of certificates for
shares of Preferred Stock upon exercise of the Warrant Agreement shall be made
without charge to the Warrantholder for any issuance tax in respect thereof, or
other cost incurred by the Company in connection with such exercise and the
related issuance of shares of Preferred Stock. The Company shall not be required
to pay any tax which may be payable in respect of any transfer involved and the
issuance and delivery of any certificate in a name other than that of the
Warrantholder.

     (b) Due Authority. The execution and delivery by the Company of this
Warrant Agreement and the performance of all obligations of the Company
hereunder, including the issuance to Warrantholder of the right to acquire the
shares of Preferred Stock, have been duly authorized by all necessary corporate
action on the part of the Company, and the Leases and this Warrant Agreement are
not inconsistent with the Company's Charter or Bylaws, do not contravene any law
or governmental rule, regulation or order applicable to it, do not and will not
contravene any provision of, or constitute a default under, any indenture,
mortgage, contract or other instrument to which it is



                                      -5-
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a party or by which it is bound, and the Leases and this Warrant Agreement
constitute legal, valid and binding agreements of the Company, enforceable in
accordance with their respective terms.

     (c) Consents and Approvals. No consent or approval of, giving of notice to,
registration with, or taking of any other action in respect of any state,
Federal or other governmental authority or agency is required with respect to
the execution, delivery and performance by the Company of its obligations under
this Warrant Agreement, except for the filing of notices pursuant to Regulation
D under the 1933 Act and any filing required by applicable state securities law,
which filings will be effective by the time required thereby.

     (d) Issued Securities. All issued and outstanding shares of Common Stock,
Preferred Stock or any other securities of the Company have been duly authorized
and validly issued and are fully paid and nonassessable. All outstanding shares
of Common Stock, Preferred Stock and any other securities were issued in full
compliance with all Federal and state securities laws. In addition:

     (i) The authorized capital of the Company consists of (A) 20,000,000 shares
of Common Stock, of which 2,940,242 shares are issued and outstanding, and (B)
10,050,000 shares of preferred stock, consisting of 5,000,000 of Series A of
which 5,000,000 are issued and outstanding and 5,050,000 of Series B of which
5,000,000 are issued and outstanding and are convertible into 10,050,000 shares
of Common Stock.

     (ii) The Company has reserved (A) 2,000,000 shares of Common Stock for
issuance under its 1995 Stock Option Plan, under which 326,000 options are
outstanding at an average price of $.10 per share. There are no other options,
warrants, conversion privileges or other rights presently outstanding to
purchase or otherwise acquire any authorized but unissued shares of the
Company's capital stock or other securities of the Company.

     (iii) In accordance with the Company's Amended and Restated Articles of
Incorporation, no shareholder of the Company has preemptive rights to purchase
new issuances of the Company's capital stock.

     (e) Insurance. The Company has in full force and effect insurance policies,
with extended coverage, insuring the Company and its property and business
against such losses and risks, and in such amounts, as are customary for
corporations engaged in a similar business and similarly situated and as
otherwise may be required pursuant to the terms of any other contract or
agreement.

     (f) Other Commitments to Register Securities. Except as set forth in this
Warrant Agreement and the Amended and Restated Shareholder Rights Agreement, the
Company is not, pursuant to the terms of any other agreement currently in
existence, under any obligation to register under the 1933 Act any of its
presently outstanding securities or any of its securities which may hereafter be
issued.

     (g) Exempt Transaction. Subject to the accuracy of the Warrantholder's
representations in Section 10 hereof, the issuance of the Preferred Stock upon
exercise of this Warrant will constitute a transaction exempt from (i) the
registration requirements of Section 5 of the 1933 Act, and (ii) the
qualification requirements of the applicable state securities laws.

     (h) Compliance with Rule 144. At the written request of the Warrantholder,
who proposes to sell Preferred Stock issuable upon the exercise of the Warrant
in compliance with Rule 144 promulgated by the Securities and Exchange
Commission, the Company shall furnish to the Warrantholder, within ten days
after receipt of such request, a written statement confirming the Company's
compliance with the filing requirements of the Securities and Exchange
Commission as set forth in such Rule, as such Rule may be amended from time to
time.

10.  REPRESENTATIONS AND COVENANTS OF THE WARRANTHOLDER.

         This Warrant Agreement has been entered into by the Company in reliance
upon the following representations and covenants of the Warrantholder:





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     (a) Investment Purpose. The right to acquire Preferred Stock or the
Preferred Stock issuable upon exercise of the Warrantholder's rights contained
herein will be acquired for investment and not with a view to the sale or
distribution of any part thereof, and the Warrantholder has no present intention
of selling or engaging in any public distribution of the same except pursuant to
a registration or exemption.

     (b) Private Issue. The Warrantholder understands (i) that the Preferred
Stock issuable upon exercise of this Warrant is not registered under the 1933
Act or qualified under applicable state securities laws on the ground that the
issuance contemplated by this Warrant Agreement will be exempt from the
registration and qualifications requirements thereof, and (ii) that the
Company's reliance on such exemption is predicated on the representations set
forth in this Section 10.

     (c) Disposition of Warrantholder's Rights. In no event will the
Warrantholder make a disposition of any of its rights to acquire Preferred Stock
or Preferred Stock issuable upon exercise of such rights unless and until (i) it
shall have notified the Company of the proposed disposition, and (ii) if
requested by the Company, it shall have furnished the Company with an opinion of
counsel (which counsel may either be inside or outside counsel to the
Warrantholder) satisfactory to the Company and its counsel to the effect that
(A) appropriate action necessary for compliance with the 1933 Act has been
taken, or (B) an exemption from the registration requirements of the 1933 Act is
available. Notwithstanding the foregoing, the restrictions imposed upon the
transferability of any of its rights to acquire Preferred Stock or Preferred
Stock issuable on the exercise of such rights do not apply to transfers from the
beneficial owner of any of the aforementioned securities to its nominee or from
such nominee to its beneficial owner, and shall terminate as to any particular
share of Preferred Stock when (1) such security shall have been effectively
registered under the 1933 Act and sold by the holder thereof in accordance with
such registration or (2) such security shall have been sold without registration
in compliance with Rule 144 under the 1933 Act, or (3) a letter shall have been
issued to the Warrantholder at its request by the staff of the Securities and
Exchange Commission or a ruling shall have been issued to the Warrantholder at
its request by such Commission stating that no action shall be recommended by
such staff or taken by such Commission, as the case may be, if such security is
transferred without registration under the 1933 Act in accordance with the
conditions set forth in such letter or ruling and such letter or ruling
specifies that no subsequent restrictions on transfer are required. Whenever the
restrictions imposed hereunder shall terminate, as hereinabove provided, the
Warrantholder or holder of a share of Preferred Stock then outstanding as to
which such restrictions have terminated shall be entitled to receive from the
Company, without expense to such holder, one or more new certificates for the
Warrant or for such shares of Preferred Stock not bearing any restrictive
legend.

     (d) Financial Risk. The Warrantholder has such knowledge and experience in
financial and business matters as to be capable of evaluating the merits and
risks of its investment, and has the ability to bear the economic risks of its
investment.

     (e) Risk of No Registration. The Warrantholder understands that if the
Company does not register with the Securities and Exchange Commission pursuant
to Section 12 of the 1933 Act, or file reports pursuant to Section 15(d), of the
Securities Exchange Act of 1934 (the "1934 Act"), or if a registration statement
covering the securities under the 1933 Act is not in effect when it desires to
sell (i) the rights to purchase Preferred Stock pursuant to this Warrant
Agreement, or (ii) the Preferred Stock issuable upon exercise of the right to
purchase, it may be required to hold such securities for an indefinite period.
The Warrantholder also understands that any sale of its rights of the
Warrantholder to purchase Preferred Stock or Preferred Stock which might be made
by it in reliance upon Rule 144 under the 1933 Act may be made only in
accordance with the terms and conditions of that Rule.

     (f) Accredited Investor. Warrantholder is an "accredited investor" within
the meaning of the Securities and Exchange Rule 501 of Regulation D, as
presently in effect.

11. TRANSFERS. Subject to the terms and conditions contained in Section 10
hereof, this Warrant Agreement and all rights hereunder are transferable in
whole or in part by the Warrantholder and any successor transferee, provided,
however, in no event shall the number of transfers of the rights and interests
in all of the Warrants exceed three (3) transfers. The transfer shall be
recorded on the books of the Company upon receipt by the





                                       -7-
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Company of a notice of transfer in the form attached hereto as Exhibit III (the
"Transfer Notice"), at its principal offices and the payment to the Company of
all transfer taxes and other governmental charges imposed on such transfer.

12.   MISCELLANEOUS.

     (a) Effective Date. The provisions of this Warrant Agreement shall be
construed and shall be given effect in all respects as if it had been executed
and delivered by the Company on the date hereof. This Warrant Agreement shall be
binding upon any successors or assigns of the Company.

     (b) Attorneys' Fees. In any litigation, arbitration or court proceeding
between the Company and the Warrantholder relating hereto, the prevailing party
shall be entitled to attorneys' fees and expenses and all costs of proceedings
incurred in enforcing this Warrant Agreement.

     (c) Governing Law. This Warrant Agreement shall be governed by and
construed for all purposes under and in accordance with the laws of the State of
Illinois.

     (d) Counterparts. This Warrant Agreement may be executed in two or more
counterparts, each of which shall be deemed an original, but all of which
together shall constitute one and the same instrument.

     (e) Notices. Any notice required or permitted hereunder shall be given in
writing and shall be deemed effectively given upon personal delivery, facsimile
transmission (provided that the original is sent by personal delivery or mail as
hereinafter set forth) or seven (7) days after deposit in the United States
mail, by registered or certified mail, addressed (i) to the Warrantholder at
6111 North River Road, Rosemont, Illinois 60018, attention: James Labe, Venture
Group, cc: Legal Department, attn: General Counsel, (and/or, if by facsimile,
(847) 518-5465 and (847) 518-5088) and (ii) to the Company at 7000 North
Broadway, Denver, Colorado, attention: John T. Greff, Chief Financial Officer,
(and/or if by facsimile, (303) 412-9160) or at such other address as any such
party may subsequently designate by written notice to the other party.

         (f) Remedies. In the event of any default hereunder, the non-defaulting
party may proceed to protect and enforce its rights either by suit in equity
and/or by action at law, including but not limited to an action for damages as a
result of any such default, and/or an action for specific performance for any
default where Warrantholder will not have an adequate remedy at law and where
damages will not be readily ascertainable. The Company expressly agrees that it
shall not oppose an application by the Warrantholder or any other person
entitled to the benefit of this Agreement requiring specific performance of any
or all provisions hereof or enjoining the Company from continuing to commit any
such breach of this Agreement.

         (g) No Impairment of Rights. The Company will not, by amendment of its
Charter or through any other means, avoid or seek to avoid the observance or
performance of any of the terms of this Warrant, but will at all times in good
faith assist in the carrying out of all such terms and in the taking of all such
actions as may be necessary or appropriate in order to protect the rights of the
Warrantholder against impairment.

         (h) Survival. The representations, warranties, covenants and conditions
of the respective parties contained herein or made pursuant to this Warrant
Agreement shall survive the execution and delivery of this Warrant Agreement.

         (i) Severability. In the event any one or more of the provisions of
this Warrant Agreement shall for any reason be held invalid, illegal or
unenforceable, the remaining provisions of this Warrant Agreement shall be
unimpaired, and the invalid, illegal or unenforceable provision shall be
replaced by a mutually acceptable valid, legal and enforceable provision, which
comes closest to the intention of the parties underlying the invalid, illegal or
unenforceable provision.

                                       -8-


<PAGE>   9




     (j) Amendments. Any provision of this Warrant Agreement may be amended by a
written instrument signed by the Company and by the Warrantholder.

     (k) Additional Documents. The Company, upon execution of this Warrant
Agreement, shall provide the Warrantholder with certified resolutions with
respect to the representations, warranties and covenants set forth in
subparagraphs (a) through (d), (f) and (g) of Section 9 above. If the purchase
price for the Leases referenced in the preamble of this Warrant Agreement
exceeds $1,000,000, the Company will also provide Warrantholder with an opinion
from the Company's counsel with respect to those same representations,
warranties and covenants. The Company shall also supply such other documents as
the Warrantholder may from time to time reasonably request.

     IN WITNESS WHEREOF, the parties hereto have caused this Warrant Agreement
to be executed by its officers thereunto duly authorized as of the Effective
Date.

Company: ALLOS THERAPEUTICS, INC.       Warrantholder: COMDISCO, INC.

By: /s/ JOHN GREFF                                    By: /s/ JAMES P. LABE
   -----------------------------                  -------------------------

Title: VP Finance & CFO                            JAMES P. LABE, PRESIDENT

                                               Title: VENTURE LEASE DIVISION


                                       -9-


<PAGE>   10




                                    EXHIBIT I

                               NOTICE OF EXERCISE

To:
   ---------------------

(1)  The undersigned Warrantholder hereby elects to purchase ____________ shares
     of the Series B Preferred Stock of _________________, pursuant to the terms
     of the Warrant Agreement dated the ______ day of April, 1996 (the "Warrant
     Agreement") between _______________________ and the Warrantholder, and
     tenders herewith payment of the purchase price for such shares in full,
     together with all applicable transfer taxes, if any.

(2)  In exercising its rights to purchase the Series B Preferred Stock of Allos
     Therapeutics, Inc., the undersigned hereby confirms and acknowledges the
     investment representations and warranties made in Section 10 of the Warrant
     Agreement.

(3)  Please issue a certificate or certificates representing said shares of
     Series B Preferred Stock in the name of the undersigned or in such other
     name as is specified below.

------------------------------
(Name)

------------------------------
(Address)

Warrantholder: COMDISCO, INC.

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

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

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


                                      -10-


<PAGE>   11





                                   EXHIBIT II

                           ACKNOWLEDGMENT OF EXERCISE


     The undersigned _______________________________________, hereby acknowledge
receipt of the "Notice of Exercise" from Comdisco, Inc., to purchase ___ shares
of the Series B Preferred Stock of Allos Therapeutics, Inc., pursuant to the
terms of the Warrant Agreement, and further acknowledges that ________ shares
remain subject to purchase under the terms of the Warrant Agreement.


                                        Company:


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

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

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



                                     - 11 -


<PAGE>   12




                                   EXHIBIT III

                                 TRANSFER NOTICE

     (To transfer or assign the foregoing Warrant Agreement execute this form
     and supply required information. Do not use this form to purchase shares.)

     FOR VALUE RECEIVED, the foregoing Warrant Agreement and all rights
evidenced thereby are hereby transferred and assigned to


-----------------------------------------------------
(Please Print)

whose address is
                -------------------------------------

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

               Dated
                    ----------------------------------------

               Holder's Signature
                                 ---------------------------

               Holder's Address
                               -----------------------------

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

Signature Guaranteed:
                     --------------------------------

         NOTE:    The signature to this Transfer Notice must correspond with the
                  name as it appears on the face of the Warrant Agreement,
                  without alteration or enlargement or any change whatever.
                  Officers of corporations and those acting in a fiduciary or
                  other representative capacity should file proper evidence of
                  authority to assign the foregoing Warrant Agreement.



                                      -12-