Exhibit 4.1

                          REGISTRATION RIGHTS AGREEMENT

         This REGISTRATION RIGHTS AGREEMENT (this "Agreement") is made as of
April 9, 2007, by and among (i) Advancis Pharmaceutical Corporation, a Delaware
corporation (the "Company"), (ii) each person listed on Exhibit A attached
hereto (collectively, the "Initial Investors" and each individually, an "Initial
Investor"), and (iii) each person or entity that subsequently becomes a party to
this Agreement pursuant to, and in accordance with, the provisions of Section 12
hereof (collectively, the "Investor Permitted Transferees" and each individually
an "Investor Permitted Transferee").

         WHEREAS, the Company has agreed to issue and sell to the Initial
Investors, and the Initial Investors have agreed to purchase from the Company,
an aggregate of approximately 10,155,000 shares (the "Purchased Shares") of the
Company's common stock, $0.01 par value per share (the "Common Stock"), and
warrants to purchase an aggregate of approximately 7,616,250 shares of Common
Stock (each a "Warrant" and together the "Warrants"), all upon the terms and
conditions set forth in that certain Securities Purchase Agreement, dated of
even date herewith, between the Company and the Initial Investors (the
"Securities Purchase Agreement"); and

         WHEREAS, the terms of the Securities Purchase Agreement provide that it
shall be a condition precedent to the closing of the transactions thereunder,
for the Company and the Initial Investors to execute and deliver this Agreement.

         NOW, THEREFORE, in consideration of the premises and mutual covenants
contained herein, the parties hereto hereby agree as follows:

         1.     DEFINITIONS. The following terms shall have the meanings
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provided therefor below or elsewhere in this Agreement as described below:

         "Board" shall mean the board of directors of the Company.

         "Closing" and "Closing Dates" shall have the meanings ascribed to such
terms in the Securities Purchase Agreement.

         "Exchange Act" shall mean the Securities Exchange Act of 1934, as
amended, and all of the rules and regulations promulgated thereunder.

         "Effectiveness Date" means, with respect to the Initial Registration
Statement, as soon as practicable, but in no event later than one hundred twenty
(120) calendar days after the First Closing (or one hundred fifty (150) calendar
days if the Initial Registration Statement is reviewed by the SEC) and, with
respect to any additional Registration Statements which may be required to be
filed hereunder pursuant to Section 3(d) or otherwise, sixty (60) calendar days
following the date on which the additional Registration Statement is required to
be filed hereunder (or ninety (90) calendar days if such additional Registration
Statement is reviewed by the SEC); provided, however, that in the event the
Company is notified by the SEC that one of the above Registration Statements
will not be reviewed or is no longer subject to further review and comments, the
Effectiveness Date as to such Registration Statement shall be the fifth (5th)
Trading Day following the date on which the Company is so notified if such date
precedes the dates required above.

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         "Filing Date" means, with respect to the Initial Registration
Statement, within thirty (30) business days after the First Closing and, with
respect to any additional Registration Statements required to be filed hereunder
pursuant to Section 3(d) or otherwise, one hundred ninety (190) days after any
preceding Registration Statement is declared effective by the SEC or the
earliest practicable date thereafter on which the Company is permitted by SEC
Guidance to file such additional Registration Statement related to the
Registrable Securities.

         "Initial Registration Statement" means the initial Registration
Statement filed pursuant to this Agreement.

         "Investors" shall mean, collectively, the Initial Investors and the
Investor Permitted Transferees; provided, however, that the term "Investors"
shall not include any of the Initial Investors or any of the Investor Permitted
Transferees that does not own or hold any Registrable Securities.

         "Majority Holders" shall mean, at the relevant time of reference
thereto, those Investors holding more than fifty percent (50%) of the
Registrable Securities held by all of the Investors.

         "Registrable Securities" shall mean the Purchased Shares and the
Underlying Shares, provided, however, such term shall not, after the Mandatory
Registration Termination Date, include any of the Purchased Shares or Underlying
Shares that become or have become eligible for resale without restrictions or
volume limitations pursuant to Rule 144 or pursuant to Regulation S.

         "Registration Statement" means any one or more registration statements
filed with the SEC by the Company on Form S-3, or in the event the Company is
not eligible to use Form S-3, on Form S-1, for the purpose of registering under
the Securities Act all of the Registrable Securities for resale by, and for the
account of, the Investors, including the Initial Registration Statement and any
additional registration statements required to be filed hereunder pursuant to
Section 3(d) or otherwise, including (in each case) the Prospectus, amendments
and supplements to such registration statement or Prospectus, including pre- and
post-effective amendments, all exhibits thereto, and all material incorporated
by reference or deemed to be incorporated by reference in such registration
statement.

         "Rule 144" shall mean Rule 144 promulgated by the SEC pursuant to the
Securities Act and any successor or substitute rule, law or provision.

         "Rule 415" means Rule 415 promulgated by the SEC pursuant to the
Securities Act, as such Rule may be amended from time to time, or any similar
rule or regulation hereafter adopted by the SEC having substantially the same
purpose and effect as such Rule.

         "Rule 424" means Rule 424 promulgated by the SEC pursuant to the
Securities Act, as such Rule may be amended from time to time, or any similar
rule or regulation hereafter adopted by the SEC having substantially the same
purpose and effect as such Rule.

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         "SEC" shall mean the Securities and Exchange Commission.

         "SEC Guidance" means (i) any publicly-available written guidance, or
rule of general applicability of the SEC staff, or (ii) written comments,
requirements or requests of the SEC staff to the Company in connection with the
review of a Registration Statement.

         "Securities" shall mean the Purchased Shares, the Warrants and the
Underlying Shares.

         "Securities Act" shall mean the Securities Act of 1933, as amended, and
all of the rules and regulations promulgated thereunder.

          "Trading Day" means (a) if the Common Stock is listed or quoted on the
NASDAQ Global Market, then any day during which securities are generally
eligible for trading on the NASDAQ Global Market, or (b) if the Common Stock is
not then listed or quoted and traded on the NASDAQ Global Market, then any
business day.

         "Underlying Shares" shall mean the shares of Common Stock issuable upon
exercise of the Warrants.

         2.     EFFECTIVENESS; TERMINATION. This Agreement shall become
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effective and legally binding only if the Closings occur. This Agreement shall
terminate and be of no further force or effect, automatically and without any
action being required of any party hereto, upon the termination of the
Securities Purchase Agreement pursuant to Section 7 thereof.

         3.     MANDATORY REGISTRATION.
                ----------------------

                (a)    The Company shall be required to file a Registration
Statement on or prior to each Filing Date until all of the Registrable
Securities are registered for resale by the Investors as selling stockholders
thereunder. On or prior to each Filing Date, the Company shall prepare and file
with the SEC a Registration Statement for the purpose of registering under the
Securities Act the resale of all, or such portion as permitted by SEC Guidance
(provided that, the Company shall use commercially reasonable efforts to
advocate with the SEC for the registration of all or the maximum number of the
Registrable Securities as permitted by SEC Guidance), of the Registrable
Securities by, and for the account of, the Investors as selling stockholders
thereunder, that are not then registered on an effective Registration Statement
for an offering to be made on a continuous basis pursuant to Rule 415. Each
Registration Statement shall contain (unless otherwise directed by the Majority
Holders) substantially the "Plan of Distribution" in the Investor Questionnaire
the form of which is attached to the Securities Purchase Agreement as Appendix
I. Subject to the terms of this Agreement, the Company shall cause a
Registration Statement to be declared effective under the Securities Act as
promptly as possible after the filing thereof, but in any event on or prior to
the applicable Effectiveness Date.

                (b)    The Company shall be required to keep a Registration
Statement effective until such date that is the earlier of (i) the date as of
which all of the Investors as selling stockholders thereunder may sell all of
the Registrable Securities registered for resale thereon without restriction
pursuant to Rule 144(k) (or any successor rule thereto) promulgated under the
Securities Act or (ii) the date when all of the Registrable Securities
registered thereunder shall

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have been sold (such date is referred to herein as the "Mandatory Registration
Termination Date"). Thereafter, the Company shall be entitled to withdraw such
Registration Statement and the Investors shall have no further right to offer or
sell any of the Registrable Securities registered for resale thereon pursuant to
the respective Registration Statement (or any prospectus relating thereto).

                (c)    Notwithstanding any other provision of this Agreement and
subject to the payment of liquidated damages in Section 4(a), if any SEC
Guidance sets forth a limitation of the number of Registrable Securities to be
registered on a particular Registration Statement (and notwithstanding that the
Company used commercially reasonable efforts to advocate with the SEC for the
registration of all or a greater number of Registrable Securities), unless
otherwise directed in writing by an Investor as to its Registrable Securities,
the number of Registrable Securities to be registered on such Registration
Statement will first be reduced by Registrable Securities represented by
Underlying Shares (applied, in the case that some Underlying Shares may be
registered, to the Investors on a pro rata basis based on the total number of
unregistered Underlying Shares held by such Investors on a fully diluted basis),
and second by Registrable Securities represented by Purchased Shares (applied,
in the case that some Purchased Shares may be registered, to the Investors on a
pro rata basis based on the total number of unregistered Purchased Shares held
by such Investors).

                (d)    If during the Effectiveness Period, subject to Section
3(a), the number of Registrable Securities at any time exceeds 100% of the
number of Purchased Shares then registered for resale in a Registration
Statement, then the Company shall file as soon as reasonably practicable an
additional Registration Statement covering the resale by the Investors of not
less than the number of such Registrable Securities.

                (e)    The offer and sale of the Registrable Securities pursuant
to any Registration Statement shall not be underwritten.

         4.     PENALTIES/SUSPENSION OF A REGISTRATION STATEMENT
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                (a)    If: (i) the Initial Registration Statement and any other
Registration Statement is not filed on or prior to its Filing Date or if the
Company files the Initial Registration Statement or any other Registration
Statement without affording the Investors the opportunity to review and comment
on the same, or (ii) the Company fails to file with the SEC a request for
acceleration in accordance with Rule 461 promulgated under the Securities Act,
within five (5) Trading Days of the date that the Company is notified (orally or
in writing, whichever is earlier) by the SEC that the Initial Registration
Statement or any other Registration Statement will not be "reviewed" or not be
subject to further review, or (iii) prior to the Effectiveness Date of the
Initial Registration Statement or any other Registration Statement, the Company
fails to file a pre-effective amendment and otherwise respond in writing to
comments made by the SEC in respect of such Initial Registration Statement or
any other Registration Statement within ten (10) calendar days after the receipt
of comments by or notice from the SEC that such amendment is required in order
for such Initial Registration Statement or any other Registration Statement to
be declared effective, or (iv) subject to the tolling provisions contained
herein, as to, in the aggregate among all Investors on a pro-rata basis based on
their purchase of the Securities pursuant to the Securities Purchase Agreement,
the lesser of (A) all of the Registrable Securities

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constituting the Securities and (B) the maximum number of Securities permitted
by SEC Guidance (collectively, the "Initial Shares"), a Registration Statement
registering for resale all of the Initial Shares is not declared effective by
the SEC by the Effectiveness Date of the Initial Registration Statement, or (v)
subject to the tolling provisions contained herein, all of the Registrable
Securities constituting the Securities other than the Initial Shares are not
registered for resale pursuant to one or more effective Registration Statements
on or before October 31, 2008, or (vi) after the Effectiveness Date of the
Initial Registration Statement or any other Registration Statement, such Initial
Registration Statement or other Registration Statement ceases for any reason to
remain continuously effective as to all Registrable Securities included in such
Initial Registration Statement or other Registration Statement, as applicable,
or the Investors are otherwise not permitted to utilize the Prospectus therein
to resell such Registrable Securities, for more than ten (10) consecutive
calendar days or more than an aggregate of fifteen (15) calendar days during any
twelve (12) month period (which need not be consecutive calendar days), provided
however that no such payments shall be required in connection with a Suspension
Period (as hereinafter defined) (any such failure or breach being referred to as
an "Event", and for purposes of clause (i), (iv) or (v) the date on which such
Event occurs, or for purposes of clause (ii) the date on which such five (5)
Trading Day period is exceeded, or for purposes of clause (iii) the date which
such ten (10) calendar day period is exceeded, or for purposes of clause (vi)
the date on which such ten (10) or fifteen (15) calendar day period, as
applicable, is exceeded being referred to as "Event Date"), then, in addition to
any other rights the Investors may have hereunder or under applicable law, on
each such Event Date and on each monthly anniversary of each such Event Date (if
the applicable Event shall not have been cured by such date) until the
applicable Event is cured, the Company shall pay to each Investor on a monthly
basis within three (3) business days of the end of the month an amount in cash,
as partial liquidated damages and not as a penalty, equal to 1% of the aggregate
purchase price paid by such Investor pursuant to the Securities Purchase
Agreement for any Registrable Securities then held by such Investor (as
applicable under clauses (iv) and (v)). The parties agree that the maximum
aggregate liquidated damages payable to a Investor under this Agreement shall be
20% of the aggregate amount paid by such Investor for its respective Securities
pursuant to the Securities Purchase Agreement. If the Company fails to pay any
partial liquidated damages pursuant to this Section in full within seven (7)
calendar days after the date payable, the Company will pay interest thereon at a
rate of 18% per annum (or such lesser maximum amount that is required to be paid
by applicable law) to the Investor, accruing daily from the date such partial
liquidated damages are due until such amounts, plus all such interest thereon,
are paid in full. The partial liquidated damages pursuant to the terms hereof
shall apply on a daily pro-rata basis for any portion of a month prior to the
cure of an Event.

                (b)    The Company shall notify the Investors by facsimile or
e-mail as promptly as practicable, and in any event, within two (2) Trading
Days, after a Registration Statement is declared effective and shall
simultaneously provide the Investors with copies of any related prospectus to be
used in connection with the sale or other disposition of the Securities covered
thereby. Failure to notify the Investors in accordance with this Section 4(b)
shall be deemed an Event under Section 4(a).

                (c)    No Investor shall be entitled to a payment pursuant to
this Section 4 if effectiveness of a registration statement has been delayed or
a prospectus has been unavailable as a result of (i) a failure by such Investor
to promptly provide on request by the Company the

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information required under the Securities Purchase Agreement or this Agreement
or requested by the SEC as a condition to effectiveness of a Registration
Statement; (ii) the provision of inaccurate or incomplete information by such
Investor; or (iii) a statement or determination of the SEC that any provision of
the rights of the Investor under this Agreement are contrary to the provisions
of the Securities Act.

         5.     OBLIGATIONS OF THE COMPANY. In connection with the Company's
                --------------------------
obligation under Section 3 hereof to file a Registration Statement with the SEC
and to use its commercially reasonable efforts to cause a Registration Statement
to become effective, the Company shall, as expeditiously as reasonably possible:

                (a)    Prepare and file with the SEC such amendments and
supplements to a Registration Statement and the prospectus used in connection
therewith as may be necessary to comply with the provisions of the Securities
Act with respect to the disposition of all Registrable Securities covered by a
Registration Statement;

                (b)    Furnish to the selling Investors such number of copies of
a prospectus, including a preliminary prospectus, in conformity with the
requirements of the Securities Act, and such other documents (including, without
limitation, prospectus amendments and supplements as are prepared by the Company
in accordance with Section 5(a) above) as the selling Investors may reasonably
request in order to facilitate the disposition of such selling Investors'
Registrable Securities;

                (c)    Use commercially reasonable efforts to comply with all
applicable rules and regulations of the SEC under the Securities Act and the
Exchange Act, including, without limitation, Rule 172 under the Securities Act,
file any final prospectus, including any supplement or amendment thereof, with
the SEC pursuant to Rule 424 under the Securities Act, promptly inform the
Investors in writing if, at any time during the Effectiveness Period, the
Company does not satisfy the conditions specified in Rule 172 and, as a result
thereof, the Investors are required to deliver a prospectus in connection with
any disposition of Registrable Securities; notify the selling Investors of the
happening of any event as a result of which the prospectus included in or
relating to a Registration Statement contains an untrue statement of a material
fact or omits any fact necessary to make the statements therein not misleading;
and, thereafter, subject to Section 11 hereof, the Company will promptly prepare
(and, when completed, give notice and provide a copy thereof to each selling
Investor) a supplement or amendment to such prospectus so that such prospectus
will not contain an untrue statement of a material fact or omit to state any
fact necessary to make the statements therein not misleading; provided that upon
such notification by the Company (which shall be a Suspension pursuant to
Section 11), the selling Investors will not offer or sell Registrable Securities
until the Company has notified the selling Investors that it has prepared a
supplement or amendment to such prospectus and filed it with the SEC or, if the
Company does not then meet the conditions for the use of Rule 172, delivered
copies of such supplement or amendment to the selling Investors (it being
understood and agreed by the Company that the foregoing proviso shall in no way
diminish or otherwise impair the Company's obligation to promptly prepare a
prospectus amendment or supplement as above provided in this Section 5(c) and
deliver copies of same as above provided in Section 5(b) hereof); and

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                (d)    Use commercially reasonable efforts to register and
qualify the Registrable Securities covered by a Registration Statement under
such other securities or Blue Sky laws of such states as shall be reasonably
appropriate in the opinion of the Company, provided that the Company shall not
be required in connection therewith or as a condition thereto to qualify to do
business or to file a general consent to service of process in any such states
or jurisdictions, and provided further that (notwithstanding anything in this
Agreement to the contrary with respect to the bearing of expenses) if any
jurisdiction in which any of such Registrable Securities shall be qualified
shall require that expenses incurred in connection with the qualification
therein of any such Registrable Securities be borne by the selling Investors,
then the selling Investors shall, to the extent required by such jurisdiction,
pay their pro rata share of such qualification expenses.

                (e)    Subject to the terms and conditions of this Agreement,
including Section 3 hereof, the Company shall use its commercially reasonable
efforts to (i) prevent the issuance of any stop order or other suspension of
effectiveness of a Registration Statement, or the suspension of the
qualification of any of the Registrable Securities for sale in any jurisdiction
in the United States, and (ii) if such an order or suspension is issued, obtain
the withdrawal of such order or suspension at the earliest practicable moment
and notify each holder of Registrable Securities of the issuance of such order
and the resolution thereof or its receipt of notice of the initiation or threat
of any proceeding such purpose.

                (f)    The Company shall (i) comply with all requirements of the
National Association of Securities Dealers, Inc. with regard to the issuance of
the Purchased Shares and the listing thereof on the NASDAQ Global Market and
such other securities exchange or automated quotation system, as applicable, and
(ii) engage a transfer agent and registrar to maintain the Company's stock
ledger for all Registrable Securities covered by a Registration Statement not
later than the effective date of a Registration Statement.

                (g)    The Company will notify the Investors of any pending
proceeding against the Company under Section 8A of the Securities Act in
connection with the offering of the Registrable Securities.

                (h)    The Company will file a Registration Statement and all
amendments and supplements thereto electronically on EDGAR.

         6.     FURNISH INFORMATION. It shall be a condition precedent to the
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obligations of the Company to take any action pursuant to this Agreement that
the selling Investors shall furnish to the Company such information regarding
them and the securities held by them as the Company shall reasonably request and
as shall be required in order to effect any registration by the Company pursuant
to this Agreement. Each Investor shall promptly notify the Company of any
changes in the information furnished to the Company.

         7.     EXPENSES OF REGISTRATION. Except as set forth in Section 5(d),
                ------------------------
all expenses incurred in connection with the registration of the Registrable
Securities pursuant to this Agreement (excluding underwriting, brokerage and
other selling commissions and discounts), including without limitation all
registration and qualification and filing fees, printing, and fees and
disbursements of counsel for the Company, shall be borne by the Company;

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provided however that the Investors shall be required to pay the expenses of
counsel and any other advisors for the Investors and any brokerage or other
selling discounts or commissions and any other expenses incurred by the
Investors for their own account.

         8.     DELAY OF REGISTRATION. The Investors shall not take any action
                ---------------------
to restrain, enjoin or otherwise delay any registration as the result of any
controversy which might arise with respect to the interpretation or
implementation of this Agreement.

         9.     INDEMNIFICATION.
                ---------------

                (a)    To the extent permitted by law, the Company will
indemnify and hold harmless each selling Investor, and each officer and director
of such selling Investor and each person, if any, who controls such selling
Investor, within the meaning of the Securities Act, against any losses, claims,
damages or liabilities, joint or several, to which they may become subject under
the Securities Act or otherwise, insofar as such losses, claims, damages or
liabilities (or actions in respect thereof) arise out of or are based upon (i)
any untrue or alleged untrue statement of any material fact contained in a
Registration Statement, in any preliminary prospectus or final prospectus
relating thereto or in any amendments or supplements to a Registration Statement
or any such preliminary prospectus or final prospectus, or arise out of or are
based upon the 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 (ii) (ii) any blue sky application or other document executed by
the Company specifically for that purpose or based upon written information
furnished by the Company filed in any state or other jurisdiction in order to
qualify any or all of the Registrable Securities under the securities laws
thereof (any such application, document or information herein called a "Blue Sky
Application"); (iii) the omission or alleged omission to state in a Blue Sky
Application a material fact required to be stated therein or necessary to make
the statements therein not misleading; (iv) any violation by the Company or its
agents of any rule or regulation promulgated under the Securities Act applicable
to the Company or its agents and relating to action or inaction required of the
Company in connection with such registration; or (v) any failure to register or
qualify the Registrable Securities included in any such Registration Statement
in any state where the Company or its agents has affirmatively undertaken or
agreed in writing that the Company will undertake such registration or
qualification on an Investor's behalf; and will reimburse such selling Investor,
or such officer, director or controlling person for any legal or other expenses
reasonably incurred by them in connection with investigating or defending any
such loss, claim, damage, liability or action; provided, however, that the
indemnity agreement contained in this Section 9(a) shall not apply to amounts
paid in settlement of any such loss, claim, damage, liability or action if such
settlement is effected without the consent of the Company (which consent shall
not be unreasonably withheld), nor shall the Company be liable in any such case
for any such loss, damage, liability or action to the extent that it arises out
of or is based upon (i) an untrue statement or alleged untrue statement or
omission made in connection with a Registration Statement, any preliminary
prospectus or final prospectus relating thereto or any amendments or supplements
to a Registration Statement or any such preliminary prospectus or final
prospectus, in reliance upon and in conformity with written information
furnished expressly for use in connection with a Registration Statement or any
such preliminary prospectus or final prospectus by the selling Investors or (ii)
at any time when the Company has advised the Investor in writing that the
Company does not meet the conditions for use of Rule 172 and as a result that

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the Investor is required to deliver a current prospectus in connection with any
disposition of Registrable Securities, an untrue statement or alleged untrue
statement or omission in a prospectus that is (whether preliminary or final)
corrected in any subsequent amendment or supplement to such prospectus that was
delivered to the selling Investor before the pertinent sale or sales by the
selling Investor.

                (b)    To the extent permitted by law, each selling Investor
will severally and not jointly indemnify and hold harmless the Company, each of
its directors, each of its officers who have signed a Registration Statement,
each person, if any, who controls the Company within the meaning of the
Securities Act, and all other selling Investors against any losses, claims,
damages or liabilities to which the Company or any such director, officer,
controlling person, or such other selling Investor may become subject to, under
the Securities Act or otherwise, insofar as such losses, claims, damages or
liabilities (or actions in respect thereto) arise out of or are based upon any
untrue or alleged untrue statement of any material fact contained in a
Registration Statement or any preliminary prospectus or final prospectus,
relating thereto or in any amendments or supplements to a Registration Statement
or any such preliminary prospectus or final prospectus, or arise out of or are
based upon the omission or alleged omission to state therein a material fact
required to be stated therein or necessary to make the statements therein not
misleading, in each case to the extent and only to the extent that such untrue
statement or alleged untrue statement or omission or alleged omission (i) was
made in a Registration Statement, in any preliminary prospectus or final
prospectus relating thereto or in any amendments or supplements to a
Registration Statement or any such preliminary prospectus or final prospectus,
in reliance upon and in conformity with written information furnished by the
selling Investor expressly for use in connection with a Registration Statement,
or any preliminary prospectus or final prospectus or (ii) at any time when the
Company has advised the Investor in writing that the Company does not meet the
conditions for use of Rule 172 and as a result that the Investor is required to
deliver a current prospectus in connection with any disposition of Registrable
Securities, was corrected in any subsequent amendment or supplement to such
prospectus that was delivered to the selling Investor before the pertinent sale
or sales by the selling Investor; and such selling Investor will reimburse any
legal or other expenses reasonably incurred by the Company or any such director,
officer, controlling person, or other selling Investor in connection with
investigating or defending any such loss, claim, damage, liability or action,
provided, however, that the liability of each selling Investor hereunder shall
be limited to the proceeds (net of underwriting discounts and commissions, if
any) received by such selling Investor from the sale of Registrable Securities
giving rise to such liability, and provided, further, however, that the
indemnity agreement contained in this Section 9(b) shall not apply to amounts
paid in settlement of any such loss, claim, damage, liability or action if such
settlement is effected without the consent of those selling Investor(s) against
which the request for indemnity is being made (which consent shall not be
unreasonably withheld).

                (c)    Promptly after receipt by an indemnified party under this
Section 9 of notice of the commencement of any action, such indemnified party
will, if a claim in respect thereof is to be made against any indemnifying party
under this Section 9, notify the indemnifying party in writing of the
commencement thereof and the indemnifying party shall have the right to
participate in and, to the extent the indemnifying party desires, jointly with
any other indemnifying party similarly noticed, to assume at its expense the
defense thereof with counsel satisfactory to the indemnifying party or
indemnifying parties, but the omission so to

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notify the indemnifying party will not relieve it from any liability which it
may have to any indemnified party for contribution or otherwise under the
indemnity agreement contained in this Section 9 (except to the extent that such
omission materially and adversely affects the indemnifying person's ability to
defend such action). In the event that the indemnifying party assumes any such
defense, the indemnified party may participate in such defense with its own
counsel and at its own expense, provided, however, if the defendants in any such
action include both the indemnified party and the indemnifying party and the
indemnified party shall have reasonably concluded, based on an opinion of
counsel reasonably satisfactory to the indemnifying party, that there may be a
conflict of interest between the positions of the indemnifying party and the
indemnified party in conducting the defense of any such action or that there may
be legal defenses available to it and/or other indemnified parties which are
different from or additional to those available to the indemnifying party, the
indemnified party or parties shall have the right to select separate counsel to
assume such legal defenses and to otherwise participate in the defense of such
action on behalf of such indemnified party or parties. Upon receipt of notice
from the indemnifying party to such indemnified party of its election to assume
the defense of such action and approval by the indemnified party of counsel, the
indemnifying party will not be liable to such indemnified party under this
Section 9 for any legal or other expenses subsequently incurred by such
indemnified party in connection with the defense thereof unless the indemnified
party shall have employed such counsel in connection with the assumption of
legal defenses in accordance with the proviso to the preceding sentence (it
being understood, however, that the indemnifying party shall not be liable for
the expenses of more than one separate counsel and one local counsel, reasonably
satisfactory to such indemnifying party, representing all of the indemnified
parties who are parties to such action in which case the reasonable fees and
expenses of counsel shall be at the expense of the indemnifying party.

                (d)    Notwithstanding anything to the contrary herein, the
indemnifying party shall not be entitled to settle any claim, suit or proceeding
unless in connection with such settlement the indemnified party receives an
unconditional release with respect to the subject matter of such claim, suit or
proceeding and such settlement does not contain any admission of fault by the
indemnified party.

                (e)    If the indemnification provided for in this Section 9 is
unavailable to or insufficient to hold harmless an indemnified party under
subsection (a) or (b) above in respect of any losses, claims, damages or
liabilities (or actions or proceedings in respect thereof) referred to therein,
then each indemnifying party shall contribute to the amount paid or payable by
such indemnified party as a result of such losses, claims, damages or
liabilities (or actions in respect thereof) in such proportion as is appropriate
to reflect the relative fault of the Company on the one hand and the Investors
on the other in connection with the statements or omissions or other matters
which resulted in such losses, claims, damages or liabilities (or actions in
respect thereof), as well as any other relevant equitable considerations. The
relative fault shall be determined by reference to, among other things, in the
case of an untrue statement, whether the untrue statement relates to information
supplied by the Company on the one hand or an Investor on the other and the
parties' relative intent, knowledge, access to information and opportunity to
correct or prevent such untrue statement. The Company and the Investors agree
that it would not be just and equitable if contribution pursuant to this
subsection (e) were determined by pro rata allocation (even if the Investors
were treated as one entity for such purpose) or by any other

                                      -10-
<PAGE>

method of allocation which does not take into account the equitable
considerations referred to above in this subsection (e). The amount paid or
payable by an indemnified party as a result of the losses, claims, damages or
liabilities (or actions in respect thereof) referred to above in this subsection
(e) shall be deemed to include any legal or other expenses reasonably incurred
by such indemnified party in connection with investigating or defending any such
action or claim. No person guilty of fraudulent misrepresentation (within the
meaning of Section 11(f) of the Securities Act) shall be entitled to
contribution from any person who was not guilty of such fraudulent
misrepresentation. The Investors' obligations in this subsection to contribute
are several in proportion to their sales of Registrable Securities to which such
loss relates and not joint. In no event shall the contribution obligation of an
Investor be greater in amount than the dollar amount of the proceeds (net of all
expenses paid by such Investor in connection with any claim relating to this
Section 9 and the amount of any damages such Investor has otherwise been
required to pay by reason of such untrue or alleged untrue statement or omission
or alleged omission) received by it upon the sale of the Registrable Securities
giving rise to such contribution obligation.

                (f)    The parties to this Agreement hereby acknowledge that
they are sophisticated business persons who were represented by counsel during
the negotiations regarding the provisions hereof including, without limitation,
the provisions of this Section 9, and are fully informed regarding said
provisions. They further acknowledge that the provisions of this Section 9
fairly allocate the risks in light of the ability of the parties to investigate
the Company and its business in order to assure that adequate disclosure is made
in a Registration Statement as required by the Securities Act and the Exchange
Act.

         10.    REPORTS UNDER THE EXCHANGE ACT. With a view to making available
                ------------------------------
to the Investors the benefits of Rule 144 and any other rule or regulation of
the SEC that may at any time permit the Investors to sell the Purchased Shares
to the public without registration, the Company agrees to use commercially
reasonable efforts: (i) to make and keep public information available as those
terms are understood in Rule 144, (ii) to file with the SEC in a timely manner
all reports and other documents required to be filed by an issuer of securities
registered under the Securities Act or the Exchange Act pursuant to Rule 144,
(iii) as long as any Investor owns any Purchased Shares, to furnish in writing
upon such Investor's request a written statement by the Company that it has
complied with the reporting requirements of Rule 144 and of the Securities Act
and the Exchange Act, and to furnish to such Investor a copy of the most recent
annual or quarterly report of the Company, and such other reports and documents
so filed by the Company as may be reasonably requested in availing such Investor
of any rule or regulation of the SEC permitting the selling of any such
Purchased Shares without registration and (iv) undertake any additional actions
reasonably necessary to maintain the availability of a Registration Statement or
the use of Rule 144.

         11.    SUSPENSION. Notwithstanding anything in this Agreement to the
                ----------
contrary, in the event (i) of any request by the SEC or any other federal or
state governmental authority during the period of effectiveness of a
Registration Statement for amendments or supplements to a Registration Statement
or related prospectus or for additional information; (ii) of the issuance by the
SEC or any other federal or state governmental authority of any stop order
suspending the effectiveness of a Registration Statement or the initiation of
any proceedings for that purpose; (iii) of the receipt by the Company of any
notification with respect to the suspension of the

                                      -11-
<PAGE>

qualification or exemption from qualification of any of the Registrable
Securities for sale in any jurisdiction or the initiation of any proceeding for
such purpose; (iv) of any event or circumstance which necessitates the making of
any changes in a Registration Statement or related prospectus, or any document
incorporated or deemed to be incorporated therein by reference, so that, in the
case of a Registration Statement, it will not contain any untrue statement of a
material fact or any omission to state a material fact required to be stated
therein or necessary to make the statements therein not misleading, and that in
the case of the prospectus, it will not contain any untrue statement of a
material fact or any omission to state a material fact required to be stated
therein or necessary to make the statements therein, in the light of the
circumstances under which they were made, not misleading; or (v) that the Board
has made the good faith determination (A) that continued use by the selling
Investors of a Registration Statement for purposes of effecting offers or sales
of Registrable Securities pursuant thereto would require, under the Securities
Act, premature disclosure in a Registration Statement (or the prospectus
relating thereto) of material, nonpublic information concerning the Company, its
business or prospects or any proposed material transaction involving the
Company, (B) that such premature disclosure would be materially adverse to the
Company, its business or prospects or any such proposed material transaction or
would make the successful consummation by the Company of any such material
transaction significantly less likely and (C) that it is therefore essential to
suspend the use by the Investors of such Registration Statement (and the
prospectus relating thereto) for purposes of effecting offers or sales of
Registrable Securities pursuant thereto, then the Company shall furnish to the
selling Investors a certificate signed by the President or Chief Executive
Officer of the Company setting forth one or more of the above described
circumstances, and the right of the selling Investors to use a Registration
Statement (and the prospectus relating thereto) shall be suspended for a period
(the "Suspension Period") of not more than forty-five (45) days after delivery
by the Company of the certificate referred to above in this Section 11; provided
that the Company shall be entitled to no more than two such Suspension Periods
during the twelve (12) month period commencing on the First Closing and during
each subsequent twelve (12) month period until the Mandatory Registration
Termination Date (including any extension thereto). During the Suspension
Period, none of the Investors shall offer or sell any Registrable Securities
pursuant to or in reliance upon a Registration Statement (or the prospectus
relating thereto) and each of the Investors shall keep the fact of the above
described certificate and its contents confidential. The Company shall use
commercially reasonable efforts to terminate any Suspension Period as promptly
as practicable.

         12.    TRANSFER OF REGISTRATION RIGHTS. [An Investor may transfer or
                -------------------------------
assign, in whole or from time to time in part, to one or more persons its rights
hereunder in connection with the transfer of Registrable Securities by such
Investor to such person, provided that such Investor complies with all laws
applicable thereto and provides written notice of assignment to the Company
promptly after such assignment is effected and, provided, further that such
person agrees to become a party to, and bound by, all of the terms and
conditions of, this Agreement by duly executing and delivering to the Company an
Instrument of Adherence in the form attached as Exhibit B hereto.]

         13.    ENTIRE AGREEMENT. This Agreement, the Warrant and the Securities
                ----------------
Purchase Agreement constitute and contain the entire agreement and understanding
of the parties with respect to the subject matter hereof, and supersede any and
all prior negotiations, correspondence, agreements or understandings with
respect to the subject matter hereof.

                                      -12-
<PAGE>

         14.    MISCELLANEOUS.
                -------------

                (a)    This Agreement may not be amended, modified or
terminated, and no rights or provisions may be waived, except with the written
consent of the Majority Holders and the Company.

                (b)    This Agreement shall be governed by and construed and
enforced in accordance with the laws of the State of New York and without regard
to any conflicts of laws concepts which would apply the substantive law of some
other jurisdiction, and shall be binding upon and inure to the benefit of the
parties hereto and their respective heirs, personal representatives, successors
or assigns, provided that, to the extent applicable, the terms and conditions of
Section 12 hereof are satisfied. This Agreement shall also be binding upon and
inure to the benefit of any transferee of any of the Purchased Shares provided
that the terms and conditions of Section 12 hereof are satisfied.
Notwithstanding anything in this Agreement to the contrary, if at any time any
Investor shall cease to own any Registrable Securities, all of such Investor's
rights under this Agreement shall immediately terminate.

                (c)    Each of the parties hereto irrevocably submits to the
exclusive jurisdiction of the courts of the State of New York located in New
York County and the United States District Court for the Southern District of
New York for the purpose of any suit, action, proceeding or judgment relating to
or arising out of this Agreement and the transactions contemplated hereby.
Service of process in connection with any such suit, action or proceeding may be
served on each party hereto anywhere in the world by the same methods as are
specified for the giving of notices under this Agreement. Each of the parties
hereto irrevocably consents to the jurisdiction of any such court in any such
suit, action or proceeding and to the laying of venue in such court. Each party
hereto irrevocably waives any objection to the laying of venue of any such suit,
action or proceeding brought in such courts and irrevocably waives any claim
that any such suit, action or proceeding brought in any such court has been
brought in an inconvenient forum. EACH OF THE PARTIES HERETO WAIVES ANY RIGHT TO
REQUEST A TRIAL BY JURY IN ANY LITIGATION WITH RESPECT TO THIS AGREEMENT AND
REPRESENTS THAT COUNSEL HAS BEEN CONSULTED SPECIFICALLY AS TO THIS WAIVER.

                (d)    Any notices, reports or other correspondence (hereinafter
collectively referred to as "correspondence") required or permitted to be given
hereunder shall be in writing and shall be sent by postage prepaid first class
mail, courier or telecopy or delivered by hand to the party to whom such
correspondence is required or permitted to be given hereunder, and shall be
deemed sufficient upon receipt when delivered personally or by courier,
overnight delivery service or confirmed facsimile, or three (3) business days
after being deposited in the regular mail as certified or registered mail
(airmail if sent internationally) with postage prepaid, if such notice is
addressed to the party to be notified at such party's address or facsimile
number as set forth below:

                (i)    All correspondence to the Company shall be addressed as
follows:

                                      -13-
<PAGE>

                           20425 Seneca Meadows Parkway
                           Germantown, Maryland 20878
                           Attention:  Edward M. Rudnic, Ph.D.
                                       President and Chief Executive Officer
                           Facsimile:  (301) 944-6700

                with a copy to:

                           Dewey Ballantine LLP
                           1301 Avenue of the Americas
                           New York, New York 10019
                           Attention:  Frederick W. Kanner, Esq.
                           Facsimile:  (212) 259-6333

                (ii)   All correspondence to any Investor shall be sent to such
Investor at the address set forth in Exhibit A.

                (iii)  Any entity may change the address to which correspondence
to it is to be addressed by written notification as provided for herein.

                (e)    The parties acknowledge and agree that in the event of
any breach of this Agreement, remedies at law may be inadequate, and each of the
parties hereto shall be entitled to seek specific performance of the obligations
of the other parties hereto and such appropriate injunctive relief as may be
granted by a court of competent jurisdiction.

                (f)    Should any part or provision of this Agreement be held
unenforceable or in conflict with the applicable laws or regulations of any
jurisdiction, the invalid or unenforceable part or provisions shall be replaced
with a provision which accomplishes, to the extent possible, the original
business purpose of such part or provision in a valid and enforceable manner,
and the remainder of this Agreement shall remain binding upon the parties
hereto.

                (g)    This Agreement may be executed in a number of
counterparts, any of which together shall for all purposes constitute one
Agreement, binding on all the parties hereto notwithstanding that all such
parties have not signed the same counterpart.

                           [Signature Page to Follow]

                                      -14-
<PAGE>

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


                                             ADVANCIS PHARMACEUTICAL CORPORATION


                                             By:    /s/: Edward M. Rudnic
                                                    ----------------------------
                                             Name:  Edward M. Rudnic, Ph.D.
                                             Title: President and
                                                    Chief Executive Officer

THE INITIAL INVESTOR'S SIGNATURE TO THE INVESTOR QUESTIONNAIRE DATED OF EVEN
DATE HEREWITH SHALL CONSTITUTE THE INITIAL INVESTOR'S SIGNATURE TO THIS
REGISTRATION RIGHTS AGREEMENT.


                 Signature Page to Registration Rights Agreement

<PAGE>

                                    EXHIBIT A
                                    ---------

                            INVESTOR NAME AND ADDRESS
                            -------------------------

                                       A-1
<PAGE>

                                    EXHIBIT B
                                    ---------

                             INSTRUMENT OF ADHERENCE
                             -----------------------

         Reference is hereby made to that certain Registration Rights Agreement,
dated as of April __, 2007, among Advancis Pharmaceutical Corporation, a
Delaware corporation (the "Company"), the Initial Investors and the Investor
Permitted Transferees, as amended and in effect from time to time (the
"Registration Rights Agreement"). Capitalized terms used herein without
definition shall have the respective meanings ascribed thereto in the
Registration Rights Agreement.

         The undersigned, in order to become the owner or holder of
[___________] shares of common stock, par value $0.01 per share (the "Common
Stock"), of the Company, or a Warrant or Warrants to purchase [_______]
Underlying Shares, hereby agrees that, from and after the date hereof, the
undersigned has become a party to the Registration Rights Agreement in the
capacity of an Investor Permitted Transferee, and is entitled to all of the
benefits under, and is subject to all of the obligations, restrictions and
limitations set forth in, the Registration Rights Agreement that are applicable
to Investor Permitted Transferees. This Instrument of Adherence shall take
effect and shall become a part of the Registration Rights Agreement immediately
upon execution.

         Executed as of the date set forth below under the laws of the State of
New York.

                                             Signature:
                                                        ------------------------
                                             Name:
                                             Title:

Accepted:

[                        ]


By:
       ------------------------
Name:
Title:

Date: _________, 200__

                                       B-1