Document:

<PAGE>

                                                                     EXHIBIT 4.4

                                            *** CERTAIN CONFIDENTIAL INFORMATION
                                            CONTAINED IN THIS DOCUMENT
                                            (INDICATED BY ASTERISKS) HAS BEEN
                                            OMITTED AND FILED SEPARATELY WITH
                                            THE SECURITIES AND EXCHANGE
                                            COMMISSION PURSUANT TO A REQUEST FOR
                                            CONFIDENTIAL TREATMENT UNDER 17
                                            C.F.R. SECTIONS 200.80(B)(4), 200.83
                                            AND 230.406.

               STOCK RESTRICTION AND REGISTRATION RIGHTS AGREEMENT

        THIS STOCK RESTRICTION AND REGISTRATION RIGHTS AGREEMENT is made as of
January 26, 2001 the ("Effective Date") by and between Santarus, Inc., a
California corporation (the "Corporation"), and The Curators of the University
of Missouri, a public corporation organized under the laws of Missouri (the
"University"). All capitalized terms used herein and not otherwise defined shall
have the same meaning given to such terms in the Stock Purchase Agreement of
even date between the Corporation and the University ("Stock Purchase
Agreement") and the Exclusive License Agreement dated of even date between the
Corporation and the University ("License Agreement").

        WHEREAS, under the terms of the Stock Purchase Agreement and in partial
consideration for the University's execution of the License Agreement, the
Corporation has issued the Stock to the University.

        WHEREAS, the Corporation and the University have agreed that the Stock
will be held subject to the terms of this Stock Restriction and Registration
Rights Agreement.

        NOW, THEREFORE, IT IS AGREED between the parties as follows:

        1. Unvested Share Repurchase Option. In the event of the termination of
the License Agreement by the Corporation pursuant to Section 8.2 thereof, the
Corporation shall have the right to reacquire the shares of the Stock which have
not vested pursuant to the provisions of this Section 1 ("Unvested Shares")
under the terms and subject to the conditions set forth in this Section 1 (the
"Unvested Share Repurchase Option").

                1.1. Vesting of Shares. The term "Initial Vesting Date" shall
mean the Effective Date. The shares of Stock will vest (the "Vested Shares") on
the dates and/or upon the occurrence of the events set forth below:

<TABLE>
<CAPTION>
--------------------------------------------------------------------------------
DATE                                            NUMBER OF SHARES VESTED
--------------------------------------------------------------------------------
<S>                                             <C>
On the Initial Vesting Date                       ***    shares of Stock
--------------------------------------------------------------------------------
Upon           ***                                ***    shares of Stock
               ***
        ***
--------------------------------------------------------------------------------
Upon           ***                                ***   shares of Stock
               ***
        ***
--------------------------------------------------------------------------------
</TABLE>

The foregoing notwithstanding, all shares of the Stock shall become fully vested
effective upon termination of the License Agreement by the University pursuant
to Section 8.3 thereof or by the Corporation pursuant to Section 8.4 thereof.

***     Portions of this page have been omitted pursuant to a request for
        Confidential Treatment and filed separately with the Commission.

<PAGE>

                1.2. Exercise of Unvested Share Repurchase Option. The
Corporation may exercise the Unvested Share Repurchase Option by written notice
to University within ninety (90) days after the Corporation's termination of the
License Agreement pursuant to Section 8.2 thereof.

                1.3. Payment for Shares and Return of Shares. Payment by the
Corporation to University shall be made in cash within sixty (60) days after the
date of the mailing of the written notice of exercise of the Unvested Share
Repurchase Option. The purchase price per share being purchased by the
Corporation shall be an amount equal to the Original Issue Price, as adjusted
for stock splits, stock dividends, recapitalizations and the like after the date
hereof. Within thirty (30) days after payment by the Corporation, University
shall deliver to the Corporation a certificate for the shares which the
Corporation has purchased.

                1.4. Legends. The Corporation may at any time place a legend or
legends referencing the Unvested Share Repurchase Option on any certificates for
shares subject to the Unvested Share Repurchase Option. Upon request of the
University at any time that any Unvested Shares have vested, the Corporation
will remove such legend from the applicable certificates.

        2. Stock Dividends. etc. If, from time to time, there is any stock
dividend, stock split or other change in the character or amount of any of the
outstanding stock of the Corporation, then in such event any and all new
substituted or additional securities to which University is entitled by reason
of University's ownership of Unvested Shares acquired pursuant to this Agreement
shall be considered Stock and shall be an adjustment to the number of shares set
forth in Section 1.1 above to which such shares relate, shall be subject to
vesting in accordance with Section 1.1 and shall be immediately subject to the
Unvested Share Repurchase Option with the same force and effect as the shares
subject to the Unvested Share Repurchase Option immediately before such event in
accordance with the provisions set forth in Section 1.1 above.

        3. Right of First Refusal. University cannot transfer, assign or
otherwise dispose of, voluntarily or involuntarily, any Unvested Shares or any
interest in those shares. Before any Vested Shares registered in the name of
University may be sold or transferred (including transfer by operation of law)
other than a transfer to an affiliate or employee of the University (a
"Permitted Transferee") which transfer shall be expressly subject to this
Agreement, such shares shall first be offered to the Corporation, which will
have the right to purchase all, but not less than all, of the Vested Shares
proposed to be transferred ("Right of First Refusal"), in the following manner:

                3.1. University shall first give written notice (the "Transfer
Notice") of any proposed transfer other than to a Permitted Transferee to the
Corporation. The Transfer Notice shall name the proposed transferee, state the
number of shares of Stock to be transferred, and if the transfer is voluntary,
the price per share and all other terms of the offer. The Transfer Notice shall
be signed by University and the prospective transferee and must constitute a
binding agreement for the transfer of the Stock subject only to the Right of
First Refusal.

                                       2
<PAGE>

                3.2. Within thirty (30) days of delivery of University's notice
of a proposed voluntary transfer, the Corporation shall determine the bona fide
nature of the proposed voluntary transfer and give University written notice of
its determination. If the proposed transfer is deemed to be bona fide, the
remaining subsections of this section shall apply to the sale. If the proposed
transfer is deemed not to be bona fide, University will be responsible for
providing additional information to the Corporation to show the bona fide nature
of the proposed transfer and no Stock will be transferred on the books of the
Corporation until the Corporation has approved the proposed transfer as bona
fide.

                3.3. If the Corporation fails to exercise in full the Right of
First Refusal within thirty (30) days from the later of the date the Transfer
Notice is delivered to the Corporation or thirty (30) days after the date the
transfer is determined to be bona fide (if University is required to provide
additional information as provided in Section 3.2 above), University may, not
later than one hundred twenty (120) days following delivery to the Corporation
of the Transfer Notice, conclude a transfer of the shares of Stock subject to
the Transfer Notice on the terms and conditions described in the Transfer
Notice. Any proposed transfer on terms and conditions different from those
described in the Transfer Notice, as well as any subsequent proposed transfer by
University, shall again be subject to the Right of First Refusal and shall
require compliance by University with the procedure described in this Section 3.
If the Corporation exercises the Right of First Refusal, the parties shall
consummate the sale of shares of Stock on the terms set forth in the Transfer
Notice by the later of sixty (60) days after the delivery of the Transfer Notice
to the Corporation or thirty (30) days after the date the transfer is determined
to be bona fide (if University is required to provide additional information as
provided in Section 3.2 above); provided, however, in the event the Transfer
Notice provides for the payment for the shares of Stock other than in cash, the
Corporation shall have the option of paying for the shares of Stock by the
discounted cash equivalent of the consideration described in the Transfer Notice
as reasonably determined by University and the Corporation.

                3.4. The foregoing notwithstanding, University may sell or
otherwise assign, with or without consideration, any shares of Stock to any
Permitted Transferee who shall thereafter be bound by the provisions of this
Agreement.

                3.5. All transferees of shares of Stock or any interest therein
including any Permitted Transferee other than the Corporation shall be required
as a condition of such transfer to agree in writing (in a form satisfactory to
the Corporation) that they will receive and hold such shares of Stock or
interests subject to the provisions of this Agreement, including the Right of
First Refusal and upon thereby becoming a party to this Agreement shall have all
of the rights of the University under this Agreement with respect to such
shares.

                3.6. The Right of First Refusal shall terminate at such time as
a public market exists for the Corporation's Common Stock (or any other stock
issued by the Corporation, or any successor, in exchange for the Stock). For the
purpose of this Agreement, a "public market" shall be deemed to exist if (a)
such stock is listed on a national securities exchange (as that term is used in
the Securities Exchange Act of 1934) or (b) such stock is traded on the
over-the-counter market and prices therefore are published daily on business
days in a recognized financial journal.

                                       3
<PAGE>

        4. Legends. All certificates representing any shares of Stock subject to
the provisions of this Agreement shall have endorsed thereon the following
legends:

                4.1. "THE SHARES REPRESENTED BY THIS CERTIFICATE ARE SUBJECT TO
A RIGHT OF FIRST REFUSAL AS SET FORTH IN AN AGREEMENT EXECUTED BY THE REGISTERED
HOLDER, OR HIS OR ITS PREDECESSOR IN INTEREST, A COPY OF WHICH IS ON FILE AT THE
PRINCIPAL OFFICE OF THIS CORPORATION."

                4.2. "THE SECURITIES EVIDENCED BY THIS CERTIFICATE HAVE. NOT
BEEN REGISTERED UNDER THE SECURITIES ACT OF 1933, AS AMENDED, AND MAY NOT BE
SOLD, TRANSFERRED, ASSIGNED OR HYPOTHECATED UNLESS THERE IS AN EFFECTIVE
REGISTRATION STATEMENT UNDER SUCH ACT COVERING SUCH SECURITIES, THE SALE IS MADE
IN ACCORDANCE WITH RULE 144 UNDER THE ACT, OR THE COMPANY RECEIVES AN OPINION OF
COUNSEL FOR THE HOLDER OF THESE SECURITIES REASONABLY SATISFACTORY TO THE
COMPANY, STATING THAT SUCH SALE, TRANSFER, ASSIGNMENT OR HYPOTHECATION IS EXEMPT
FROM THE REGISTRATION AND PROSPECTUS DELIVERY REQUIREMENTS OF SUCH ACT."

                4.3. For Unvested Shares only subject to Section 1.4 above, the
certificates shall have the following additional legend:

"THE SHARES REPRESENTED BY THIS CERTIFICATE ARE SUBJECT TO A REPURCHASE OPTION
AS SET FORTH IN AN AGREEMENT EXECUTED BY THE REGISTERED HOLDER, OR HIS OR ITS
PREDECESSOR IN INTEREST, A COPY OF WHICH IS ON FILE AT THE PRINCIPAL OFFICE OF
THIS CORPORATION."

        5. Registration.

                5.1. Definitions. As used in this Section 5:

                        (a) The terms "register", "registered" and
"registration" refer to a registration effected by preparing and filing a
registration statement in compliance with the Securities Act and the declaration
or ordering of the effectiveness of such registration statement;

                        (b) The term "Registrable Securities" means: (i) the
Stock, and (ii) any other shares of the Corporation's stock issued as a dividend
or other distribution with respect to, or in exchange for or in replacement of,
the Stock;

                        (c) The term "Holder" means any holder of outstanding
Registrable Securities who acquired such Registrable Securities in a transaction
or series of transactions not involving any registered public offering;

                                       4
<PAGE>

                5.2. Corporation Registration.

                        (a) Notice of Registration. If at any time or from time
to time, the Corporation shall determine to register any of its securities,
either for its own account or the account of a security holder or holders (other
than a registration relating solely to employee stock option or purchase plans
or relating solely to an SEC Rule 145 transaction or to debt securities), the
Corporation will:

                                (i) promptly give to each Holder written notice
thereof; and

                                (ii) include in such registration (and any
related qualification under state securities laws or other compliance), and in
any underwriting involved therein, all the Registrable Securities specified in a
written request or requests, received within twenty (20) days after such written
notice from the Corporation, by any Holder or Holders, except as set forth in
Section 5.2(b) below.

                        (b) Underwriting. If the registration of which the
Corporation gives notice is for a registered public offering involving an
underwriting, the Corporation shall so advise the Holders as a part of the
written notice given pursuant to Section 5.2(a)(i). In such event the right of
any Holder to registration pursuant to this Section 5.2 shall be conditioned
upon the inclusion of such Holder's Registrable Securities in the underwriting.
All Holders proposing to distribute their securities shall (together with the
Corporation and other holders distributing their securities through such
underwriting) enter into an underwriting agreement in customary form with the
underwriter or underwriters selected for such underwriting by the Corporation.
Notwithstanding any other provision of this Section 5.2, if the underwriter
determines that marketing factors require a limitation of the number of
securities to be included in the registration, the underwriter may cause to be
excluded some or all of the Registrable Securities on a pro rata basis based on
the total number of the Registrable Securities held by the Holders and shall
have no obligation to limit or reduce the inclusion of other securities (other
than Registrable Securities) entitled to registration held by other persons or
organizations selling securities pursuant to registration rights granted them by
the Corporation. The Corporation shall advise all Holders of Registrable
Securities which would otherwise be registered and underwritten pursuant hereto
of any such limitations, and the number of shares of Registrable Securities that
may be included in the registration. If any Holder disapproves of the terms of
any such underwriting, it may elect to withdraw therefrom by written notice to
the Corporation and the underwriter. Any securities excluded or withdrawn from
such underwriting shall not be transferred prior to 90 days after the effective
date of the registration statement for such underwriting, or such shorter period
as the underwriter may require.

                5.3. Expenses of Registration. All expenses incurred in
connection with any registration, qualification or compliance pursuant to this
Section 5, including all registration, filing and qualification fees, printing
expenses, fees and disbursements of counsel for the Corporation, and expenses of
any special audits incidental to such registration, shall be borne by the
Corporation; provided, however, the Corporation shall not be required to pay
underwriters' discounts, commissions, or stock transfer taxes relating to
Registrable Securities or the fees of any counsel retained by the Holders.

                                       5
<PAGE>

                5.4. Registration Procedures. In the case of each registration,
qualification or compliance effected by the Corporation pursuant to Section 5,
the Corporation will keep each Holder participating therein advised in writing
as to the initiation of each registration, qualification and compliance and as
to the completion thereof. At its expense the Corporation will:

                        (a) keep such registration, qualification or compliance
pursuant to Section 5.2, effective for a period of three months or until the
Holder or Holders have completed the distribution described in the registration
statement relating thereto, whichever first occurs; and

                        (b) furnish such number of prospectuses and other
documents incident thereto as a Holder from time to time may reasonably request.

                5.5. Indemnification.

                        (a) The Corporation will indemnify each Holder of
Registrable Securities, each of its officers, directors and partners, and each
person controlling such Holder, with respect to which registration,
qualification or compliance has been effected pursuant to this Section 5,
against all claims, losses, damages, costs, expenses and liabilities whatsoever
(or actions in respect thereof) arising out of or based on any untrue statement
(or alleged untrue statement) of a material fact contained in any registration
statement, prospectus, offering circular or other documents (including any
related registration, statement, notification or the like) incident to any such
registration, qualification or compliance, or based on any omission (or alleged
omission) to state therein a material fact required to be stated therein or
necessary to make the statements therein not misleading, or any violation by the
Corporation of the Securities Act or any state securities law or of any rule or
regulation promulgated under the Securities Act or any state securities law
applicable to the Corporation and relating to action or inaction required of the
Corporation in connection with any such registration, qualification or
compliance, and will reimburse each such Holder, each of its officers and
directors, and each person controlling such Holder, for any legal and any other
expenses reasonably incurred in connection with investigating or defending any
such claim, loss, damage, cost, expense, liability or action, provided that the
Corporation will not be liable in any such case to the extent that any such
claim, loss, damage, cost, expense, or liability arises out of or is based on
any untrue statement or omission based upon written information furnished to the
Corporation by an instrument duly executed by any such Holder and stated to be
specifically for use therein.

                        (b) Each Holder will, if Registrable Securities held by
or issuable to such Holder are included in the securities as to which such
registration, qualification or compliance is being effected, indemnify the
Corporation, each of its directors and officers who sign such registration
statement, each underwriter, if any, of the Corporation's securities covered by
such a registration statement, each person who controls the Corporation within
the meaning of the Securities Act, and each other Holder, each of such other
Holder's officers and directors and each person controlling such other Holder,
against all claims, losses, damages, costs, expenses and liabilities whatsoever
(or actions in respect thereof) arising out of or based on any untrue statement
(or alleged untrue statement) of a material fact contained in any such
registration statement, prospectus, offering circular or other documents
(including any related registration

                                       6
<PAGE>

statement, notification or the like) incident to any such registration,
qualification or compliance, or based on any omission (or alleged omission) to
state therein a material fact required to be stated therein or necessary to make
the statements therein not misleading, and will reimburse the Corporation, such
other Holders, such directors, officers, persons or underwriters for any legal
or any other expenses reasonably incurred in connection with investigating or
defending any such claim, loss, damage, cost, expense, liability or action, in
each case to the extent, but only to the extent, that such untrue statement (or
alleged untrue statement) or omission (or alleged omission) is made in such
registration statement, prospectus, offering circular or other document in
reliance upon and in conformity with written information furnished to the
Corporation by an instrument duly executed by such Holder and stated to be
specifically for use therein; provided, however, that the foregoing indemnity
agreement is subject to the condition that, insofar as it relates to any such
untrue statement (or alleged untrue statement) or omission (or alleged omission)
made in the preliminary prospectus but eliminated or remedied in the amended
prospectus on file with the SEC at the time the registration statement becomes
effective or the amended prospectus filed with the SEC pursuant to Rule 424(b)
(the "Final Prospectus"), such indemnity agreement shall not inure to the
benefit of any underwriter or any Holder, if there is no underwriter, if a copy
of the Final Prospectus was furnished to the person or entity asserting the
loss, liability, claim or damage at or prior to the time such action is required
by the Securities Act; and provided further, the total amount for which any
Holder shall be liable under this Section 5.5 shall not in any event exceed the
aggregate proceeds received by such Holder from the sale of Registrable
Securities held by such Holder in such registration.

                        (c) Each party entitled to indemnification under this
Section 5.5 (the "Indemnified Party") shall give notice to the party required to
provide indemnification (the "Indemnifying Party") promptly after such
Indemnified Party has actual knowledge of any claim as to which indemnity may be
sought, and shall permit the Indemnifying Party to assume the defense of any
such claim or any litigation resulting therefrom, provided that counsel for the
Indemnifying Party, who shall conduct the defense of such claim or litigation,
shall be approved by the Indemnified Party (whose approval shall not
unreasonably be withheld), and the Indemnified Party may participate in such
defense at such party's expense, and provided further that the failure of any
Indemnified Party to give notice as provided herein shall not relieve the
Indemnifying Party of its obligations under this Section 5. No Indemnifying
Party, in the defense of any such claim or litigation, shall, except with the
consent of each Indemnified Party, consent to entry of any judgment or enter
into any settlement which does not include as an unconditional term thereof the
giving by the claimant or plaintiff to such Indemnified Party of a release from
all liability in respect to such claim or litigation. If any such Indemnified
Party shall have been advised by counsel chosen by it that there may be one or
more legal defenses available to such Indemnified Party which are different from
or additional to those available to the Indemnifying Party, the Indemnifying
Party shall not have the right to assume the defense of such action on behalf of
such Indemnified Party and will reimburse such Indemnified Party and any person
controlling such Indemnified Party for the reasonable fees and expenses of any
counsel retained by the Indemnified Party, it being understood that the
Indemnifying Party shall not, in connection with any one action or separate but
similar or related actions in the same jurisdiction arising out of the same
general allegations or circumstances, be liable for the reasonable fees and
expenses of more than one separate firm of attorneys for such Indemnified Party
or controlling person, which firm shall be designated in writing by the
Indemnified Party to the Indemnifying Party.

                                       7
<PAGE>

                5.6. Information by Holder. The Holder or Holders of Registrable
Securities included in any registration shall furnish to the Corporation such
information regarding such Holder or Holders and the distribution proposed by
such Holder or Holders as the Corporation may request in writing and as shall be
required in connection with any registration, qualification or compliance
referred to in this Section 5.

                5.7. Sale Without Registration. If at the time of any transfer
(other than a transfer not involving a change in beneficial ownership or other
than to a Permitted Transferee) of any Registrable Securities, such Registrable
Securities shall not be registered under the Securities Act, the Corporation may
require, as a condition of allowing such transfer, that the Holder or transferee
furnish to the Corporation (a) such information as is necessary in order to
establish that such transfer may be made without registration under the
Securities Act; and (b) at the expense of the Holder or transferee, an opinion
by legal counsel designated by such Holder or transferee and satisfactory to the
Corporation, satisfactory in form and substance to the Corporation, to the
effect that such transfer may be made without registration under such Act;
provided that nothing contained in this Section 5 shall relieve the Corporation
from complying with any request for registration, qualification or compliance
made pursuant to the other provisions of this Section 5.

                5.8. Rule 144 Reporting. With a view to making available to the
Holders the benefits of certain rules and regulations of the U.S. Securities and
Exchange Commission ("SEC") which may permit the sale of the Registrable
Securities to the public without registration, the Corporation agrees to:

                        (a) make and keep public information available, as those
terms are understood and defined in SEC Rule 144, at all times after ninety days
after the effective date of the first registration filed by the Corporation
which involves a sale of securities of the Corporation to the general public;

                        (b) file with the SEC in a timely manner all reports and
other documents required of the Corporation under the Securities Act and the
Securities Exchange Act of 1934, as amended (the "Securities Exchange Act");

                        (c) furnish to Holders so long as Holders own any
Registrable Securities forthwith upon request a written statement by the
Corporation that it has complied with the reporting requirements of said Rule
144 (at any time after ninety days after the effective date of said first
registration statement filed by the Corporation) and of the Securities Act and
the Securities Exchange Act (at any time after it has become subject to such
reporting requirements), a copy of the most recent annual or quarterly report of
the Corporation, and such other reports and documents so filed by the
Corporation as may be reasonably requested in availing Holders of any rule or
regulation of the SEC permitting the selling of any such securities without
registration.

                5.9. Transfer of Registration Rights. The fights to cause the
Corporation to register securities granted by the Corporation under Section 5.2,
may be assigned by any Holder to a transferee or assignee, provided that such
transfer must otherwise be effected in accordance with applicable securities
laws and provided further that the Corporation is given written notice

                                       8
<PAGE>

by such Holder at the time of or within a reasonable time after said transfer,
stating the name and address of said transferee or assignee and identifying the
securities with respect to which such registration rights are being assigned.

               5.10. "Market Stand-Off' Agreement. Each Holder hereby agrees
that, during the period of duration specified by the Corporation and an
underwriter of common stock or other securities of the Corporation (such period
shall not exceed one hundred eighty days), following the effective date of a
registration statement of the Corporation filed under the Securities Act, it
shall not, to the extent requested by the Corporation and such underwriter,
directly or indirectly sell, offer to sell, contract to sell (including, without
limitation, any short sale), grant any option to purchase or otherwise transfer
or dispose of (other than to donees who agree to be similarly bound) any
securities of the Corporation held by it at any time during such period except
common stock included in such registration; provided, however, that such
agreement shall not be required unless all officers and directors of the
Corporation and all other persons with registration rights (whether or not
pursuant to this Agreement) or purchasing common stock of the Corporation enter
into similar agreements.

        In order to enforce the foregoing covenant, the Corporation may impose
stop-transfer instructions with respect to the Registrable Securities of each
Holder (and the shares of securities of every other person subject to the
foregoing restriction) until the end of such period.

                5.11. Expiration of Rights. All registration rights shall expire
and not apply to any Holder upon the earlier of seven years from the
Corporation's initial public offering or the date such Holder is eligible to
sell in a three-month period pursuant to SEC Rule 144 all Registrable Securities
held by such Holder.

        6. Miscellaneous.

                6.1. Waivers and Amendments. With the written consent of the
record holders of at least a majority of the Registrable Securities, the
obligations of the Corporation and the rights of the Holders under this
Agreement may be waived or amended (either generally or in a particular
instance); provided, however, that no such waiver or amendment shall reduce the
aforesaid proportion of Registrable Securities, the holders of which are
required to consent to any waiver or supplemental agreement, without the consent
of the record holders of all of the Registrable Securities. Upon the
effectuation of each such waiver or amendment, the Corporation shall promptly
give written notice thereof to the record holders of the Registrable Securities
who have not previously consented thereto in writing. Except to the extent
provided in this subsection 6.1, this Agreement or any provision hereof may be
amended, waived, discharged or terminated only by a statement in writing signed
by the party against which enforcement of the amendment, waiver, discharge or
termination is sought.

                6.2. Governing Law. This Agreement shall be governed in all
respects by the laws of the State of California as such laws are applied to
agreements between California residents entered into and to be performed
entirely within California.

                                       9
<PAGE>

                6.3. Successors and Assigns. Except as otherwise expressly
provided herein, the provisions hereof shall inure to the benefit of, and be
binding upon, the successors, assigns, heirs, executors and administrators of
the parties hereto.

                6.4. Entire Agreement. This Agreement and the Stock Purchase
Agreement constitute the full and entire understanding and agreement between the
parties with regard to the subjects hereof and thereof and they supersede, merge
and render void every other prior written and/or oral understanding or agreement
among or between the parties hereto.

                6.5. Notices. etc. All notices and other communications required
or permitted hereunder shall be in writing and shall be delivered personally,
mailed by first class mail, postage prepaid, or delivered by courier or
overnight delivery, addressed (a) if to the University, at its address set forth
in the Stock Purchase Agreement, or at such other address as the University
shall have furnished to the Corporation in writing or (b) if to the Corporation,
at its address set forth in the Stock Purchase Agreement, or at such other
address as the Corporation shall have furnished to the University in writing.
Notices that are mailed shall be deemed received five (5) days after deposit in
the United States mail. Notices sent by courier or overnight delivery shall be
deemed received two (days) after they have been so sent.

                6.6. Severability. In case any provision of this Agreement shall
be found by a court of law to be invalid, illegal or unenforceable, the
validity, legality and enforceability of the remaining provisions of this
Agreement shall not in any way be affected or impaired thereby.

                6.7. Titles and Subtitles. The titles of the sections and
subsections of this Agreement are for convenience of reference only and are not
to be considered in construing this Agreement.

                6.8. Counterparts. This Agreement may be executed in any number
of counterparts, each of which shall be an original, but all of which together
shall constitute one instrument.

                6.9. Delays or Omissions. No delay or omission to exercise any
right, power or remedy accruing to the Corporation or to any holder of any
securities issued or to be issued hereunder shall impair any such right, power
or remedy of the Corporation or such holder, nor shall it be construed to be a
waiver of any breach or default under this Agreement, or an acquiescence
therein, or of or in any similar breach or default thereafter occurring; nor
shall any delay or omission to exercise any right, power or remedy or any waiver
of any single breach or default be deemed a waiver of any other right, power or
remedy or breach or default theretofore or thereafter occurring. All remedies,
either under this Agreement, or by law otherwise afforded to the Corporation or
any holder, shall be cumulative and not alternative.

                                       10
<PAGE>

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

SANTARUS, INC.                          THE CURATORS OF THE UNIVERSITY
                                        OF MISSOURI

By: /s/ Gerald T. Proehl                By: /s/ Thomas R. Sharpe
   --------------------------------        -------------------------------------
   Gerald T. Proehl, President & COO      Thomas R. Sharpe, Executive Director
                                          Office of Technology
                                          & Special Projects

                                                        APPROVED
                                                         AS TO
                                                       LEGAL FORM
                                                        /s/ PJH
                                                     -------------
                                                        1-26-01

                                       11<PAGE>

                                                                     EXHIBIT 4.5

THE SECURITIES REPRESENTED HEREBY HAVE NOT BEEN REGISTERED UNDER THE SECURITIES
ACT OF 1933, AS AMENDED, AND MAY NOT BE SOLD, TRANSFERRED, ASSIGNED OR
HYPOTHECATED UNLESS THERE IS AN EFFECTIVE REGISTRATION STATEMENT UNDER SUCH ACT
COVERING SUCH SECURITIES, THE SALE IS MADE IN ACCORDANCE WITH RULE 144 UNDER THE
ACT, OR THE COMPANY RECEIVES AN OPINION OF COUNSEL FOR THE HOLDER OF THESE
SECURITIES REASONABLY SATISFACTORY TO THE COMPANY, STATING THAT SUCH SALE,
TRANSFER, ASSIGNMENT OR HYPOTHECATION IS EXEMPT FROM THE REGISTRATION AND
PROSPECTUS DELIVERY REQUIREMENTS OF SUCH ACT.

WC-___

                                 SANTARUS, INC.
                    SERIES C PREFERRED STOCK PURCHASE WARRANT

         THIS CERTIFIES THAT, for value received, _________________ ("Holder")
is entitled to purchase _________________ (_________________) shares of Series C
Preferred Stock of SANTARUS, INC., a California corporation (the "Company"), at
the Warrant Price (as defined in subsection 1(j) below), subject to adjustments
and all other terms and conditions set forth in this Warrant.

1. Definitions: As used herein, the following terms, unless the context
otherwise requires, shall have the following meanings:

         (a) "Act" shall mean the Securities Act of 1933, as amended, or any
successor federal statute, and the rules and regulations of the Commission
thereunder, all as the same shall be in effect at the time.

         (b) "Articles of Incorporation" shall mean the Company's Amended and
Restated Articles of Incorporation in the form filed with the California
Secretary of State in connection with the Company's Series C Preferred Stock
Financing.

         (c) "Commission" shall mean the Securities and Exchange Commission, or
any other federal agency at the time administering the Act.

         (d) "Company" shall mean SANTARUS, INC., a California corporation, and
any corporation which shall succeed to or assume the obligations of SANTARUS,
INC., under this Warrant.

         (e) "Date of Grant" shall mean _________________, 20__.

         (f) "Exercise Date" shall mean the effective date of the delivery of
the Notice of Exercise pursuant to Sections 3 and 10 below.

                                       1
<PAGE>
         (g) "Holder" shall mean Holder or any other person or entity who shall
at the time be the registered holder of this Warrant.

         (h) "Series, C Preferred Stock" shall mean shares of the, Company's
Series C Preferred Stock to be authorized after the Date of Grant upon the
filing by the Company of the Articles of Incorporation.

         (i) "Series C Preferred Stock Financing" shall mean the Company's
issuance of shares of Series C Preferred Stock to the Holder and the other
persons participating therein in a transaction, or series of related
transactions, in which the Company receives gross proceeds of at least
$13,000,000.

         (j) "Warrant Price" shall mean $____ per share.

         (k) "Warrant Shares" shall mean shares of the Company's Series C
Preferred Stock; provided, however, in the event of the automatic conversion of
the Company's outstanding Series C Preferred Stock into Common Stock pursuant to
the provisions of the Company's current charter documents or the Articles of
Incorporation, then, effective upon such conversion, "Warrant Shares" shall
thereafter mean shares of the Company's Common Stock.

2. Term. The purchase right represented by this Warrant is exercisable during
the period commencing upon the earlier of (a) the Company's filing of the
Articles of Incorporation with the California Secretary of State and (b)
_________________, 20__, and ending on _________________, 20__. The foregoing
notwithstanding, in the event of the Acquisition of the Company prior to the
occurrence of (a) and (b) in the preceding sentence, then the purchase right
represented by this Warrant shall be exercisable immediately prior to, and shall
terminate immediately after, the consummation of such Acquisition.

3. Exercise of Warrant.

         (a) Exercise. This Warrant may be exercised, in whole or in part, by
the Holder hereof by surrender of this Warrant, with the form of subscription at
the end hereof duly executed by the Holder, to the Company at its principal
office, accompanied by payment of the Warrant Price in cash or by certified or
official bank check payable to the order of the Company.

         (b) Right to Convert Warrant. Notwithstanding the payment provisions of
subsection 3(a) hereof:

            (i) The Holder shall have the right (the "Conversion Right") to
require the Company to convert this Warrant, in whole or in part, at any time
into Warrant Shares as provided for in this subsection (b). At the sole option
of the Holder, upon exercise of the Conversion Right, the Company shall deliver
to the Holder (without payment by the Holder of any Warrant Price) that number
of Warrant Shares equal to the quotient obtained by dividing (x) the value of
the Warrant at the time the Conversion Right is exercised (determined by
subtracting the aggregate Warrant Price for the number of Warrant Shares then
issuable upon exercise of this Warrant in effect immediately prior to the
exercise of the Conversion Right from the aggregate Fair Market Value (as
defined below) of such number of Warrant Shares immediately prior to

                                       2
<PAGE>
the exercise of the Conversion Right) by (y) the Fair Market Value of one
Warrant Share immediately prior to the exercise of the Conversion Right.

            (ii) The Conversion Right may be exercised by the Holder, at any
time, or from time to time, on any business day by delivering a written notice
(the "Conversion Notice") to the Company exercising the Conversion Right and
specifying (i) the total number of Warrant Shares the Holder will purchase
pursuant to such conversion and (ii) a place and date not less than one nor more
than 20 business days from the date of the Conversion Notice for the closing of
such purchase.

            (iii) Fair Market Value of a Warrant Share as of a particular date
(the "Determination Date") shall mean:

                  (1) If the Company's Warrant Shares are traded on an exchange
or are quoted on the Nasdaq National Market, then the closing or last sale
price, respectively, reported for the last business day immediately preceding
the Determination Date.

                  (2) If the Company's Warrant Shares are not traded on an
exchange or on the Nasdaq National Market but are traded in the over-the-counter
market, then the mean of the closing bid and asked prices reported for the last
business day immediately preceding the Determination Date.

                  (3) If the Company's Warrant Shares are not publicly traded,
then as determined in good faith by the Company's Board of Directors upon review
of relevant factors.

         (c) Delivery of Certificate. In the event of any exercise of the
purchase right represented by this Warrant, certificates for the Warrant Shares
so purchased shall be delivered to the Holder within thirty (30) days of
delivery of the notice of exercise (the "Notice of Exercise") in the form of
Exhibit A attached hereto and, unless this Warrant has been fully exercised or
has expired, a new warrant representing the portion of the Warrant Shares with
respect to which this Warrant shall not then have been exercised shall also be
issued to the Holder within such thirty (30) day period.

         (d) No Fractional Shares. No fractional shares shall be issued in
connection with any exercise hereunder, but in lieu of such fractional shares
the Company shall make a cash payment therefor upon the basis of the Fair Market
Value of a Warrant Share as of the Exercise Date.

         (e) Company's Representations.

            (i) All Warrant Shares which may be issued upon the exercise of the
purchase right represented by this Warrant shall, upon issuance, be duly
authorized, validly issued, fully paid and nonassessable, and free of any liens
and encumbrances except for restrictions on transfer provided for herein or
under applicable federal and state securities laws. During the period within
which the purchase right represented by this Warrant may be exercised, the
Company shall at all times have authorized, and reserved for the purpose of
issuance upon exercise of the purchase right represented by this Warrant, a
sufficient number of Warrant Shares to provide for the exercise of the purchase
right represented by this Warrant;

                                       3
<PAGE>
            (ii) This Warrant has been duly authorized and executed by the
Company and is a valid and binding obligation of the Company enforceable in
accordance with its terms, subject to applicable bankruptcy, insolvency,
reorganization, moratorium or other laws of general application affecting the
enforcement of creditors' rights;

            (iii) The execution and delivery of this Warrant are not, and the
issuance of the Warrant Shares upon exercise of this Warrant in accordance with
the terms hereof will not be inconsistent with the Company's Articles of
Incorporation or Bylaws, do not and will not contravene any law, governmental
rule or regulation, judgment or order applicable to the Company, and do not and
will not conflict with or contravene any provision of, or constitute a material
default under, any material indenture, mortgage, contract or other instrument of
which the Company is a party or by which it is bound or require the consent or
approval of, the giving of notice to, the registration or filing with or the
taking of any action in respect of or by, any federal, state or local government
authority or agency (other than such consents, approvals, notices, actions,
filings, etc., as have already been obtained or made, as the case may be).

4. Adjustment of Warrant Price and Number of Warrant Shares. The number of
Warrant Shares issuable upon the exercise of this Warrant and the Warrant Price
shall be subject to adjustment from time to time upon the occurrence of certain
events, as follows:

         (a) Adjustment for Dividends in Stock. In case at any time or from time
to time the holders of Warrant Shares of the Company (or any shares of stock or
other securities at the time receivable upon the exercise of this Warrant) shall
have received or, on or after the record date fixed for the determination of
eligible stockholders, shall have become entitled to receive, without payment
therefor, other or additional stock of the Company by way of dividend then, and
in each case, the Holder of this Warrant shall, upon the exercise hereof, be
entitled to receive, in addition to the number of Warrant Shares receivable
thereupon, and without payment of any additional consideration therefor, the
amount of such other or additional stock of the Company which such Holder would
hold on the date of such exercise had it been the holder of record of Warrant
Shares on the date hereof and had thereafter, during the period from the date
hereof to and including the date of such exercise, retained such shares and/or
all other additional stock receivable by it as aforesaid during such period,
giving effect to all adjustments called for during such period by subparagraphs
(b) and (c) of this Paragraph 4.

         (b) Adjustment for Reclassification or Reorganization. In case of any
reclassification or change of the outstanding Warrant Shares of the Company or
of any reorganization of the Company, then and in each such case the Holder of
this Warrant, upon the exercise hereof at any time after the consummation of
such reclassification, change, or reorganization, shall be entitled to receive,
in lieu of or in addition to the stock or other securities and property
receivable upon the exercise hereof prior to such consummation, the stock or
other securities to which such Holder would have been entitled upon such
consummation if such Holder had exercised this Warrant immediately prior
thereto, all subject to further adjustment as provided in subparagraphs (a) and
(c); in each such case, the terms of this Paragraph 4 shall be applicable to the
shares. of stock or other securities and property receivable upon the exercise
of this Warrant after such consummation.

                                       4
<PAGE>
         (c) Stock Splits and Reverse Stock Splits. If the Company shall
subdivide its outstanding Warrant Shares into a greater number of shares, the
Warrant Price in effect immediately prior to such subdivision shall thereby be
proportionately reduced and the number of Warrant Shares receivable upon
exercise of this Warrant shall thereby be proportionately increased; and,
conversely, if the outstanding number of Warrant Shares shall be combined into a
smaller number of shares, the Warrant Price in effect immediately prior to such
combination shall thereby be proportionately increased and the number of Warrant
Shares receivable upon exercise of the Warrant shall be proportionately
decreased.

5. Notices of Record Date, Etc. In the event of (a) any taking by the Company of
a record of the holders of any class of securities for the purpose of
determining the holders thereof who are entitled to receive any dividend or
other distribution (the "Distribution"), (b) any capital reorganization or
reclassification of the stated capital of the Company or any consolidation or
merger of the Company with any other corporation or corporations (other than a
wholly-owned subsidiary), or the sale or distribution of all or substantially
all of the Company's property and assets (the "Reorganization Event"), or (c)
any proposed filing of a registration statement under the Act in connection with
a primary public offering of the Company's Common Stock (the "Registration
Event"), the Company will mail or cause to be mailed to the Holder a notice
specifying (i) the date of any such Distribution stating the amount and
character of such Distribution, (ii) the date on which any such Reorganization
Event or Registration Event is expected to become effective, and (iii) the time,
if any, that is to be fixed as to when the holders of record of the Company's
securities shall be entitled to exchange their shares of the Company's
securities for securities or other property deliverable upon such Reorganization
Event. Such notice shall be mailed at least thirty (30) days prior to the date
therein specified.

6. Compliance with Act; Transferability and Negotiability of Warrant;
Disposition of Shares.

         (a) Compliance with Act. The Holder, by acceptance hereof, agrees that
this Warrant and the Warrant Shares to be issued upon the exercise hereof are
being acquired solely for its own account and not as a nominee for any other
party and not with a view toward the resale or distribution thereof and that it
will not offer, sell or otherwise dispose of this Warrant or any Warrant Shares
to be issued upon the exercise hereof except under circumstances which will not
result in a violation of the Act. Upon the exercise of this Warrant, the Holder
shall confirm in writing, in a form satisfactory to the Company, that the
Warrant Shares so issued are being acquired solely for its own account and not
as a nominee for any other party and not with a view toward resale or
distribution thereof in violation of the Act. This Warrant and the Warrant.
Shares to be issued upon the exercise hereof (unless registered under the Act
and unless, in the case of the Warrant Shares, such Shares may thereupon be sold
pursuant to Commission Rule 144(k)) shall be imprinted with a legend in
substantially the following form:

         THE SECURITIES REPRESENTED HEREBY HAVE NOT BEEN REGISTERED UNDER THE
         SECURITIES ACT OF 1933, AS AMENDED AND MAY NOT BE SOLD, TRANSFERRED,
         ASSIGNED OR HYPOTHECATED UNLESS THERE IS AN EFFECTIVE REGISTRATION
         STATEMENT UNDER SUCH ACT COVERING SUCH SECURITIES, THE SALE IS MADE IN
         ACCORDANCE WITH RULE 144 UNDER THE ACT, OR

                                       5
<PAGE>
         THE COMPANY RECEIVES AN OPINION OF COUNSEL FOR THE HOLDER OF THESE
         SECURITIES REASONABLY SATISFACTORY TO THE COMPANY. STATING THAT SUCH
         SALE, TRANSFER, ASSIGNMENT OR HYPOTHECATION IS EXEMPT FROM THE
         REGISTRATION AND PROSPECTUS DELIVERY REQUIREMENTS OF SUCH ACT.

         In addition, this Warrant and the Warrant Shares to be issued upon the
exercise hereof shall bear any legends required by the securities laws of any
applicable states.

         (b) Transferability and Negotiability of Warrant. This Warrant may not
be transferred or assigned in whole or in part without compliance with all
applicable federal and state securities laws by the transferor and the
transferee (including the delivery of investment representation letters and
legal opinions reasonably satisfactory to the Company, if requested by the
Company and the transfer is to a person other than a general partner of the
initial Holder). Subject to the provisions of this Warrant with respect to
compliance with the Act, title to this Warrant may be transferred by endorsement
and delivery in the same manner as a negotiable instrument transferable by
endorsement and delivery. The Company shall act promptly to record transfers of
this Warrant on its books, but the Company may treat the registered holder of
this Warrant as the absolute owner of this Warrant for all purposes,
notwithstanding any notice to the contrary.

         (c) Disposition of Warrant Shares. With respect to any offer sale,
transfer or other disposition of any Warrant Shares acquired pursuant to the
exercise of this Warrant prior to registration of such Warrant Shares, except
for any such offer, sale, transfer or other disposition of Warrant Shares to a
partner of the initial Holder, the Holder and each subsequent holder of this
Warrant agrees to give written notice to the Company prior thereto, describing
briefly the manner thereof, together with a written opinion of legal counsel for
such holder, reasonably satisfactory to the Company and its legal counsel, if
requested by the Company, to the effect that such offer, sale or other
disposition may be effected without registration or qualification (under the Act
or any other federal or state securities laws) of such Warrant Shares and
indicating whether or not under the Act, certificates for such Warrant Shares to
be sold or otherwise disposed of require any restrictive legend as to the
applicable restrictions on transferability in order to ensure compliance with
the Act. Promptly upon receiving such written notice and reasonably satisfactory
opinion, if so requested, the Company, as promptly as practicable, shall notify
such holder that such holder may sell or otherwise dispose of such Warrant
Shares, all in accordance with the terms of the notice delivered to the Company.
If a determination has been made pursuant to this subsection (c) that the
opinion of legal counsel for the holder is not reasonably satisfactory to the
Company and its legal counsel, the Company shall so notify the holder promptly
after such determination has been made. Notwithstanding the foregoing, such
Warrant Shares may be offered, sold or otherwise disposed of in accordance with
Rule 144, provided that the Company shall have been furnished with such
information as the Company may reasonably request to provide a reasonable
assurance that the provisions of Rule 144 have been satisfied. Each certificate
representing the Warrant Shares thus transferred (except a transfer pursuant to
Rule l44(k) or an effective registration statement) shall bear a restrictive
legend as to the applicable restrictions on transferability in order to ensure
compliance with the Act, unless in the aforesaid opinion of legal counsel for
the holder, such legend is not required in

                                       6
<PAGE>
order to ensure compliance with the Act. The Company may issue stop transfer
instructions to its transfer agent in connection with such restrictions

7. Rights of Stockholders. No Holder shall be entitled to vote or receive
dividends or be deemed the holder of Warrant Shares or any other securities of
the Company which may at any time be issuable on the exercise of this Warrant
for any purpose, nor shall anything contained herein be construed to confer upon
the Holder, as such, any of the rights of a stockholder of the Company or any
right to vote for the election of directors or upon any matter submitted to
stockholders at any meeting thereof, or to give or withhold consent to any
corporate action (whether upon any recapitalization, issuance of stock,
reclassification of stock, consolidation, merger, transfer of assets or
otherwise) or to receive notice of meetings, or to receive dividends or
subscription rights or otherwise until this Warrant shall have been exercised
and the Warrant Shares issuable upon exercise hereof shall have become
deliverable, as provided herein.

8. Replacement of Warrants. On receipt of evidence reasonably satisfactory to
the Company of the loss, theft, destruction or mutilation of this Warrant and,
in the case of loss, theft or destruction, on delivery of an indemnity agreement
reasonably satisfactory in form and amount to the Company or, in the case of
mutilation, on surrender and cancellation of this Warrant, the Company at its
expense shall execute and deliver, in lieu of this Warrant, a new warrant of
like tenor.

9. Exchange of Warrant. Subject to the other provisions of this Warrant, on
surrender of this Warrant for exchange, properly endorsed and subject to the
provisions of this Warrant with respect to compliance with the Act, the Company
at its expense shall issue to or on the order of the Holder a new warrant or
warrants of like tenor, in the name of the Holder or as the Holder (on payment
by the Holder of any applicable transfer taxes) may direct, for the number of
Warrant Shares issuable upon exercise thereof.

10. Notices. All notices and other communications from the Company to the
Holder, or vice versa, shall be deemed delivered and effective when given
personally or three days after being mailed by first-class registered or
certified mail, postage prepaid, at such address as may have been furnished to
the Company or the Holder, as the case may be, in writing by the Company or such
Holder from time to time.

11. Waiver. This Warrant and any term hereof may be changed, waived, discharged
or terminated only by an instrument in writing signed by the party against which
enforcement of such change, waiver, discharge or termination is sought.

12. Governing Law. This Warrant shall be governed by and construed in accordance
with the Laws of the State of California, as such laws are applied to agreements
entered into in California and to be performed solely by California residents.

13. Titles and Subtitles; Forms of Pronouns. The titles of the Sections and
Subsections of this Warrant are for convenience only and are not to be
considered in construing this Warrant. All pronouns used in this Warrant shall
be deemed to include masculine, feminine and neuter forms.

                                       7
<PAGE>
14. Expiration. Subject to the provisions of Section 2 above, the right to
exercise this Warrant shall expire at 5:00 P.M. California time, on
_________________, 20__.

Dated: _________________

                                                     SANTARUS, INC.

                                                     By:____________________

                                       8
<PAGE>
                                    EXHIBIT A

                               NOTICE OF EXERCISE
                   (To be signed only on exercise of Warrant)

TO:      SANTARUS, INC.

         The undersigned, the holder of the within Warrant, hereby irrevocably
elects to exercise this Warrant for, and to purchase thereunder, ________ shares
of Series C Preferred Stock of Santarus, Inc. and herewith makes payment of
$__________ therefor (either in cash or in accordance with the cashless exercise
provisions of Section 3(b))and requests that the certificates for such shares be
issued in the name of, and delivered to __________________________ whose address
is
______________________________________________________________________________

Dated:_____________________                ________________________________
                                           (Signature must conform to name of
                                           holder as specified on the face of
                                           the Warrant)

                                           ________________________________
                                           (Name)

                                           ________________________________
                                           (Address)

Schedule to Exhibit 4.5

The preceding form of Series C Preferred Stock Purchase Warrant of the Company
was issued to the following entities on the dates and in the amounts listed
below:

(i) the Hale Family Trust, issued on December 21, 2000, and
January 17, 2001, and exercisable in the aggregate for 32,920 shares of
our Series C Preferred Stock, (ii) St. Paul Venture Capital V, LLC,
issued on October 23, 2000, November 3, 2000, November 28, 2000 and
February 1, 2001, and exercisable in the aggregate for 70,368 shares of
our Series C Preferred Stock and (iii) Fog City Fund, LLC, issued on
January 30, 2001, and exercisable for 41,152 shares of our Series C
Preferred Stock.  Each of the warrants set forth above is exercisable at
a price per share of $2.43.

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