Document:

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                                                                    EXHIBIT 10.4

                              [AspenBio Letterhead]

                                 March __, 2002

Gregory Pusey
President
Cambridge Holdings, Ltd.
106 S. University Blvd. Unit 14
Denver, CO  80209

Re:   Consulting Agreement by and between AspenBio, Inc. (the "Company") and
      Cambridge Holdings, Ltd. dated December 28, 2001 (the "Consulting
      Agreement")

Dear Greg:

      Section 1 of the Consulting Agreement provides that the Consulting
Agreement may be terminated by the mutual agreement of the parties. Because the
Company considers all of the terms of the Consulting Agreement to have been
fulfilled to its satisfaction, the Company proposes that the Consulting
Agreement hereby terminate effective as of the date indicated below. In
addition, the Company proposes that the risk of forfeiture provided for in
Section 3 of the Consulting Agreement shall be lifted as of the same date.

      Please indicate your acceptance of the proposals in this letter by signing
in space provided below.

                                               Very truly yours,

                                               ASPENBIO, INC.

                                               Roger Hurst
                                               President

AGREED AND ACCEPTED EFFECTIVE THIS __ DAY OF MARCH, 2002:

____________________________
Gregory Pusey
President
Cambridge Holdings, Ltd.<PAGE>

                                                                    EXHIBIT 10.5

                             SHAREHOLDERS AGREEMENT

      THIS SHAREHOLDERS AGREEMENT (the "Agreement") is entered into this 28th
day of December, 2001 by and among AspenBio, Inc., a Colorado corporation (the
"Company"), Roger Hurst, an individual ("Hurst") and Cambridge Holdings, Ltd., a
Colorado corporation (the "Purchaser").

                                    RECITALS

      WHEREAS, the Purchaser has agreed to purchase securities of the Company
pursuant to that certain "Securities Purchase Agreement" of even date herewith
(the "Purchase Agreement"); and

      WHEREAS, the obligations in the Purchase Agreement are conditioned upon
the execution and delivery of this Agreement; and

      WHEREAS, Hurst is president, director and controlling shareholder of the
Company; and

      WHEREAS, the Company, the Purchaser and Hurst agree that their mutual
interests can best be served by providing for certain rights and obligations
with respect to the Company and the Company's securities as hereinafter
provided.

                                    AGREEMENT

      NOW, THEREFORE, in consideration of the foregoing recitals and the mutual
promises and covenants hereinafter set forth and for other good and valuable
consideration, the receipt and sufficiency of which are hereby acknowledged, the
parties hereto agree as follows:

      1. Board of Directors of the Company. During the period from the date
hereof to June 30, 2003, so long as the Purchaser owns a minimum of 250,000
shares of the Company's Common Stock, Hurst shall vote all shares of the
Company's voting stock owned or held of record by him at any meeting of
shareholders or in any written consent in lieu of any meeting to elect to the
Board of Directors of the Company one person designated by the Purchaser. The
designee of the Purchaser is Gregory Pusey.

      The Company and Hurst agree to use their respective best efforts to call,
or cause the appropriate officers and directors of the Company to call, a
special meeting of shareholders of the Company and to vote all of the shares of
Common Stock owned or held of record by Hurst for, or take all actions by
written consent in lieu of any such meeting necessary to cause, the removal
(with or without cause) of any designee of the Purchaser if the Purchaser
requests such director's removal in writing for any reason, and to cause the
election of the person newly designated by the Purchaser. Similarly, should a
designee of the Purchaser resign or a vacancy otherwise occur, Hurst shall vote
his shares of Common Stock in favor of the candidate
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designated by the Purchaser to serve on the Company's Board. Hurst shall take
all action otherwise reasonably necessary for the election to the Board of the
designee of the Purchaser. Provided, however, that Hurst shall have the right to
approve such designee, which approval shall not be unreasonably withheld.

      2. Tag-Along Rights.

            (a) During the period from the date hereof to January 20, 2005, if
Hurst proposes to sell any shares of the Common Stock of the Company owned by
Hurst as of the date of this Agreement representing (i) 35% or more of the
outstanding shares of the Company (on a cumulative basis) or (ii) more than 50%
of the Common Stock of the Company owned by Hurst if Hurst owns less than 35%
but more than 15% of the outstanding shares of the Common Stock of the Company
((i) and (ii) each to be considered a "Qualifying Sale"), to any person (the
"Proposed Purchaser") in a sale (other than a sale pursuant to a public offering
registered under the Securities Act of 1933 as amended), then Hurst shall afford
the Purchaser the opportunity to participate in such sale in accordance with
this Section 2.

            (b) The Purchaser shall have the right to sell at the same price and
upon identical terms and conditions as the proposed sale by Hurst, any part or
all of the shares of Common Stock owned by the Purchaser, but no more than the
number of shares of Common Stock proposed to be sold by Hurst. At the time any
sale to a Proposed Purchaser is proposed, Hurst shall give written notice (the
"Tag-Along Notice") to the Purchaser of its right to sell shares pursuant to
this Section 2, which Tag-Along Notice shall set forth the name and address of
the Proposed Purchaser, the number of shares of Common Stock proposed to be
sold, the proposed offering price, the proposed date of sale and any other terms
and conditions of the proposed sale. The Tag-Along Notice shall also contain a
copy of any written offer to Hurst by the Proposed Purchaser to purchase Hurst's
shares. The Tag-Along Notice shall also be given to the Company at the same time
as it is given to the Purchaser.

            (c) In the event that Hurst sells and proposes to sell shares of the
Common Stock of the Company to one person or entity through more than one sale
and the total number of shares to be sold would be considered a Qualifying Sale,
then Purchaser's rights as set forth in Section 2(b) shall become effective at
the time of the proposed sale that will cause the total shares sold by Hurst to
represent (i) 35% or more of the outstanding shares of the Company or (ii) more
than 50% of the Common Stock owned by the Hurst if Hurst owns less than 35% but
more than 15% of the outstanding shares of the Company. Purchaser shall be
entitled to sell any part or all of the shares of Common Stock owned by the
Purchaser up to the cumulative total number of shares sold and proposed to be
sold by Hurst.

            (d) In the event that the Purchaser wishes to participate, it shall
provide written notice (the "Tag-Along Acceptance Notice") to Hurst no more than
five (5) days after the Tag-Along Notice. The Tag-Along Acceptance Notice shall
set forth the number of shares of Common Stock the Purchaser elects to sell
(subject to the limitations set forth in Section 2(b)). The Notice given by the
Purchaser shall constitute its binding agreement to sell such shares on the
terms and conditions and for the same consideration per share applicable to the
sale by Hurst. If the Tag-Along Acceptance Notice is not received by Hurst prior
to the expiration of the 5-day period, then Hurst shall have the right to sell
the number of shares specified in the Tag-Along

                                      -2-
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Notice to the Proposed Purchaser without any participation by the Purchaser, but
only on terms and conditions with respect to the consideration (and other
material terms and conditions which a reasonable investor would consider
significant to the decision to include shares in the sale) paid by the Proposed
Purchaser to Hurst which are no more favorable in any material respect than as
stated in the Tag-Along Notice to the Purchaser and only if such sale occurs
within 60 days of the date specified for sale in the Tag-Along Notice.

      3. Termination. Except as otherwise provided herein, this Agreement shall
terminate upon the earlier to occur of (i) the mutual agreement of the Purchaser
and Hurst; (ii) the Purchaser ceasing to own more than 250,000 shares of the
Company's Common Stock; or (iii) June 30, 2003.

      4. General Provisions.

            (a) Recapitalization, Exchanges, etc. In the event that any Common
Stock or other securities are issued in respect of, in exchange for, or in
substitution of, any shares of Common Stock, by reason of any reorganization,
recapitalization, reclassification, merger, stock dividend, distribution to
shareholders or any other change in the capital structure of the Company, the
term Common Stock as used herein shall be deemed to include all shares of such
Common Stock or other securities, as appropriate, so as to fairly and equitably
preserve, as far as practicable, the original rights and obligations of the
Purchaser.

            (b) Successors and Assigns. This Agreement shall be binding upon and
shall inure to the benefit of the parties hereto, and their respective
successors and permitted assigns; provided that neither this Agreement nor any
rights or obligations hereunder may be transferred or assigned by the Company
(except by operation of law in any merger), by Hurst or by the Purchaser, except
by operation of law in any merger and except that the Purchaser may transfer and
assign its rights and obligations hereunder to a permitted transferee (as set
forth on Schedule 4(b) or otherwise agreed to in writing by Hurst) who executes
and delivers to each other party hereto an instrument or instruments reasonably
satisfactory to such parties confirming that the permitted transferee agrees to
be bound by and subject to the terms of this Agreement in the same manner as
such permitted transferee's transferor.

            (d) Notices. All notices, demands, consents or approvals required or
permitted to be given in this Agreement or given with respect to this Agreement
shall be in writing and shall be personally served or mailed, registered or
certified, return receipt requested, postage prepaid (or by a substantially
similar method), or delivered by a reputable courier service with charges
prepaid, or transmitted by hand-delivery or facsimile, addressed to the Company
or the Shareholders at their addresses set forth on the signature page of this
Agreement or such other address as such parties shall have specified most
recently by written notice. Notice shall be deemed given or delivered on the
date of service or transmission if personally served or transmitted by
facsimile. Notice otherwise sent as provided herein shall be deemed given or
delivered on the third business day following the date mailed or on the next
business day following delivery of such notice to a reputable courier service.

                                      -3-
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            (e) Inspection. So long as this Agreement shall be in effect, this
Agreement and any amendments hereto shall be made available for inspection at
the principal office of the Company by the Purchaser.

            (f) Governing Law. This Agreement shall be governed by and construed
in accordance with the laws of the State of Colorado.

            (g) Specific Performance. The Purchaser, in addition to being
entitled to exercise all rights provided herein, including recovery of damages,
will be entitled to specific performance of its rights under this Agreement.

            (h) Entire Agreement. This Agreement and the Purchase Agreement
constitute the entire agreement and understanding among the parties hereto with
respect to the subject matter hereof and thereof and supersede any and all prior
agreements and understandings, written or oral, relating to the subject matter
hereof and thereof.

            (i) Waivers; Amendments.

            (i) No failure or delay by any party in exercise of any right, power
      or privilege hereunder shall operate as a waiver thereof, nor shall any
      single or partial exercise thereof preclude any other or further exercise
      thereof or the exercise of any other right, power or privilege. The rights
      and remedies herein provided shall be cumulative and nonexclusive of any
      rights or remedies provided by law.

            (ii) Any provision of this Agreement may be waived if, but only if,
      such waiver is in writing and is signed by the party against whom the
      enforcement of such waiver is sought.

            (iii) This Agreement may not be amended, modified, or supplemented
      other than by a written instrument executed by both parties.

            (j) Time. Time is of the essence in performance of this Agreement.

            (k) Severability. Whenever possible, each provision of this
Agreement shall be interpreted in such a manner as to be effective and valid
under applicable law, and if any provision of this Agreement shall be or become
prohibited or invalid in whole or in part for any reason whatsoever, that
provision shall be ineffective only to the extent of such prohibition or
invalidity without invalidating the remaining portion of that provision or the
remaining provisions of this Agreement.

            (l) Counterparts. This Agreement may be executed in counterparts,
each of which shall constitute an original and which together shall constitute
one and the same agreement.

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

                                       4
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CAMBRIDGE HOLDINGS, LTD.                           ASPENBIO, INC.

By:                                          By:
   -------------------------------                 -----------------------------
      Gregory Pusey, President                         Roger Hurst, President

106 S. University Blvd., Unit 14                   8100 Southpark Way, Bldg. B-1
Denver, Colorado 80209                             Littleton, Colorado  80120
Facsimile:  (303) 722 4011                         Facsimile:  (303) 798-8332

                                                   -----------------------------
                                                   Roger Hurst, Individually

                                                   -----------------------------
                                                   -----------------------------
                                                   Facsimile:  (303) 798-8332

                                       5
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                                  SCHEDULE 4(B)

                              PERMITTED TRANSFEREES

Greg Pusey
Vermut-Weinberger Living Trust UDT 3/22/93
Jeff McGonegal
John Altshuler
Scott Menefee
Robert Bearman
Cambridge Holdings, Ltd.

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