Exhibit 10.1

CONTINGENT VALUE RIGHTS AGREEMENT

THIS CONTINGENT VALUE RIGHTS AGREEMENT, dated as of [    ], 200[    ] (this
“Agreement”), is entered into by and among VIROPHARMA INCORPORATED, a Delaware
corporation (“Buyer”), LEV PHARMACEUTICALS, INC., a Delaware corporation
(“Target”), and STOCKTRANS, INC., a Pennsylvania corporation, as Rights Agent
(the “Rights Agent”) and as initial CVR Registrar (as defined herein).

Preamble

Buyer, HAE Acquisition Corp., a Delaware corporation (“Sub”), and Target have
entered into an Agreement and Plan of Merger dated as of July 15, 2008 (the
“Merger Agreement”), pursuant to which Sub will merge with and into Target, with
Target surviving the Merger as a subsidiary of Buyer.

Pursuant to the Merger Agreement, Buyer agreed to create and issue to Target’s
stockholders of record immediately prior to the Effective Time contingent value
rights as hereinafter described.

The parties have done all things necessary to make the contingent value rights,
when issued pursuant to the Merger Agreement and hereunder, the valid
obligations of Buyer and to make this Agreement a valid and binding agreement of
Buyer, in accordance with its terms.

NOW, THEREFORE, for and in consideration of the premises and the consummation of
the transactions referred to above, it is mutually covenanted and agreed, for
the equal and proportionate benefit of all Holders (as hereinafter defined), as
follows:

ARTICLE I

DEFINITIONS

Section 1.1 Definitions.

(a) For all purposes of this Agreement, except as otherwise expressly provided
or unless the context otherwise requires:

(i) the terms defined in this Article have the meanings assigned to them in this
Article, and include the plural as well as the singular;

(ii) all accounting terms used herein and not expressly defined herein shall
have the meanings assigned to such terms in accordance with U.S. generally
accepted accounting principles, as in effect on the date hereof;

(iii) the words “herein,” “hereof” and “hereunder” and other words of similar
import refer to this Agreement as a whole and not to any particular Article,
Section or other subdivision;

(iv) unless the context otherwise requires, words describing the singular number
shall include the plural and vice versa, words denoting any gender shall include
all genders and words denoting natural Persons shall include corporations,
partnerships and other Persons and vice versa; and

(v) all references to “including” shall be deemed to mean including without
limitation.

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(b) Capitalized terms used but not otherwise defined herein shall have the
meanings ascribed thereto in the Merger Agreement. The following terms shall
have the meanings ascribed to them as follows:

“Board of Directors” means the board of directors of Buyer.

“Board Resolution” means a copy of a resolution certified by the secretary or an
assistant secretary of Buyer to have been duly adopted by the Board of Directors
and to be in full force and effect on the date of such certification, and
delivered to the Rights Agent.

“Business Day” means any day other than a Saturday, Sunday or a day on which
banking institutions in New York, New York are authorized or obligated by law or
executive order to remain closed.

“Cinryze” means Target’s C1 inhibitor (human) product.

“CVRs” means the contingent value rights issued by Buyer pursuant to the Merger
Agreement and this Agreement.

“CVR Payment Amounts” means the First CVR Payment Amount and the Second CVR
Payment Amount.

“CVR Payment Date” means the date that a CVR Payment Amount is paid by Buyer to
the Holders, which date shall be established pursuant to Section 2.4.

“First CVR Payment Amount” means an amount equal to $0.50 per CVR, payable in
cash.

“HAE” means hereditary angioedema.

“Holder” means a Person in whose name a CVR is registered in the CVR Register.

“Net Sales” means those sales of Cinryze for the applicable fiscal period as
reported by Buyer or, in the event any sales of Cinryze are not reported by
Buyer, from the books and records of any Permitted Sellers, which shall be
maintained in accordance with GAAP or such other successor standard as is
mandated by the SEC, as net sales in its audited annual and unaudited quarterly
financial statements filed with the Securities and Exchange Commission, provided
that if Buyer or any Permitted Seller is not a publicly reporting company, Buyer
or Permitted Seller shall audit its calculation of “Net Sales.”

“Officer’s Certificate” means a certificate signed by the chief executive
officer, president, chief financial officer, any vice president, the controller,
the treasurer or the secretary, in each case of Buyer, in his or her capacity as
such an officer, and delivered to the Rights Agent.

“Orphan Exclusivity” means, as set forth in 21 U.S.C. § 360aa and 21 C.F.R. Part
316, Subpart D, the seven year exclusive marketing period applicable to the
holder of U.S. Marketing Approval for a product that has received orphan
designation under 21 U.S.C. § 360bb for a rare disease or condition.

“Permitted Seller” means any licensee or sublicensee of Buyer (but not a
distributor of Buyer or of any such licensee or sublicensee) having the right to
sell Cinryze.

“Permitted Transfer” means: (i) the transfer of any or all of the CVRs on death
by will or intestacy; (ii) transfer by instrument to an inter vivos or
testamentary trust in which the CVRs are to be

 

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passed to beneficiaries upon the death of the trustee; (iii) transfers made
pursuant to a court order; or (iv) a transfer made by operation of law
(including a consolidation or merger) or as in connection with the dissolution,
liquidation or termination of any corporation, limited liability company,
partnership or other entity.

“Rights Agent” means the Rights Agent named in the first paragraph of this
Agreement, until a successor Rights Agent shall have become such pursuant to the
applicable provisions of this Agreement, and thereafter “Rights Agent” shall
mean such successor Rights Agent.

“Second CVR Payment Amount” means an amount equal to $0.50 per CVR, payable in
cash.

ARTICLE II

CONTINGENT VALUE RIGHTS

Section 2.1 Issuance of CVRs.

The CVRs shall be issued pursuant to the Merger at the time and in the manner
set forth in the Merger Agreement.

Section 2.2 Nontransferable.

The CVRs shall not be sold, assigned, transferred, pledged, encumbered or in any
other manner transferred or disposed of, in whole or in part, other than through
a Permitted Transfer.

Section 2.3 No Certificate; Registration; Registration of Transfer; Change of
Address.

(a) The CVRs shall not be evidenced by a certificate or other instrument.

(b) The Rights Agent shall keep a register (the “CVR Register”) for the
registration of CVRs. The Rights Agent is hereby initially appointed “CVR
Registrar” for the purpose of registering CVRs and transfers of CVRs as herein
provided.

(c) Subject to the restriction on transferability set forth in Section 2.2,
every request made to transfer a CVR must be in writing and accompanied by a
written instrument of transfer in form reasonably satisfactory to the CVR
Registrar, pursuant to Securities Transfer Association guidelines, duly executed
by the Holder thereof, his attorney duly authorized in writing, personal
representative or survivor and setting forth in reasonable detail the
circumstances relating to the transfer. Upon receipt of such written notice, the
CVR Registrar shall, subject to its reasonable determination that the transfer
instrument is in proper form and the transfer otherwise complies with the other
terms and conditions herein, register the transfer of the CVRs in the CVR
Register. All duly transferred CVRs registered in the CVR Register shall be the
valid obligations of Buyer, evidencing the same right, and shall entitle the
transferee to the same benefits and rights under this Agreement, as those held
by the transferor. No transfer of a CVR shall be valid until registered in the
CVR Register, and any transfer not duly registered in the CVR Register will be
void ab initio. Any transfer or assignment of the CVRs shall be without charge
(other than the cost of any transfer tax) to the Holder.

(d) A Holder may make a written request to the CVR Registrar to change such
Holder’s address of record in the CVR Register. The written request must be duly
executed by the Holder. Upon receipt of such written notice, the CVR Registrar
shall promptly record the change of address in the CVR Register.

 

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Section 2.4 Payment Procedures.

(a) Promptly following the occurrence of a First CVR Payment Event, but in no
event later than five Business Days of such event, Buyer shall deliver to the
Rights Agent a certificate (the “First CVR Payment Compliance Certificate”),
certifying that the Holders are entitled to receive the First CVR Payment
Amount. “First CVR Payment Event” shall mean the occurrence of either of the
following events:

(i) Both (A) Cinryze is approved by the FDA for the acute treatment of HAE and
(B) the FDA grants to Target, Buyer or any of their Affiliates Orphan
Exclusivity for Cinryze encompassing the acute treatment of HAE to the exclusion
of all other human C1 inhibitor products; or

(ii) Orphan Exclusivity for the acute treatment of HAE has not become effective
for any third party’s (i.e., a party other than Target, Buyer or any of their
Affiliates) human C1 inhibitor product for two years from the later of the date
hereof and the date on which Orphan Exclusivity for Cinryze for the prophylaxis
of HAE becomes effective.

(b) Following the second anniversary of this Agreement (or earlier if Orphan
Exclusivity becomes effective for a third party’s (i.e., a party other than
Target, Buyer or any of their Affiliates) human C1 inhibitor product for the
acute treatment of HAE), if events or circumstances occur prior to the delivery
of the First CVR Payment Compliance Certificate that cause Buyer to reasonably
believe to cause the conditions in clauses 2.4(a)(i) and 2.4(a)(ii) hereof not
to be satisfied and can never be satisfied, then within 30 days of the
occurrence of such events or circumstances, Buyer shall deliver to the Rights
Agent a certificate (the “First CVR Payment Non-Compliance Certificate”),
setting forth in reasonable detail the events or circumstances that have caused
or would cause the conditions set forth in clauses 2.4(a)(i) and 2.4(a)(ii)
hereof not to be satisfied and not capable of ever being satisfied.

(c) Buyer shall provide to the Rights Agent, as soon as is reasonably
practicable, but not later than 30 days, after the end of each fiscal quarter of
Buyer prior to the fiscal quarter ended [    ], 201[    ] [10 years from
closing] (the “Outside Date”), a certificate signed by the chief executive
officer or chief financial officer of Buyer setting forth the Net Sales for such
fiscal quarter and cumulative Net Sales through the end of such fiscal quarter
(the “Sales Notice”). If Buyer and any of its Subsidiaries achieve at least
$600,000,000 in cumulative Net Sales (the “Sales Target”) during the period
beginning on the date hereof and ending on the Outside Date, then upon delivery
of the Sales Notice reflecting that the Sales Target is met, Buyer shall deliver
to the Rights Agent a certificate (the “Second CVR Payment Compliance
Certificate” and, together with the First CVR Payment Compliance Certificate,
the “Compliance Certificates”), certifying that the Holders are entitled to
receive the Second CVR Payment Amount. If the Sales Target is not met by the
Outside Date, then within 30 days of the Outside Date, Buyer shall deliver to
the Rights Agent a certificate (the “Second CVR Payment Non-Compliance
Certificate” and, together with the First CVR Payment Non-Compliance
Certificate, the “Non-Compliance Certificates”), certifying that the Sales
Target was not met by the Outside Date, and as a result the Holders are not
entitled to receive the Second CVR Payment Amount.

(d) From and after the date hereof but prior to the Outside Date, in the event
of the sale of substantially all of the rights to Cinryze in North America by
Buyer, Target or any of their Affiliates, Buyer shall deliver to the Rights
Agent an amount, payable in cash, equal to the aggregate CVR Payment Amounts
with respect to all Holders to the extent not previously paid in full; provided,
that the First CVR Payment Amount shall not be required to be paid if there has
been a final determination in accordance

 

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with this Agreement, following delivery and approval of a First CVR Payment
Non-Compliance Certificate, that no First CVR Payment Amount is, or can ever be,
payable under this Agreement. Upon such payment, no further payment of the CVR
Payment Amounts shall be required. Notwithstanding the foregoing, (i) Buyer,
Target or any of their Affiliates shall have the right to license Cinryze to
third parties for the purposes of providing services, including and not limited
to, services related to research, development or commercialization of Cinryze
and (ii) no transaction in compliance with Section 6.1 shall trigger a
requirement to make the payment described in the first sentence of this
Section 2.4(d).

(e) Except as otherwise requested by any Holder, the Rights Agent shall promptly
(and in no event later than five Business Days) send each Holder a copy of each
Compliance Certificate and Non-Compliance Certificate at its registered address.
In addition, upon the request of any Holder, the Rights Agent shall promptly
(and in no event later than five Business Days after such request) send such
Holder a copy of any Sales Notice delivered by Buyer.

(f) Upon demand by any Holder or Holders of at least 20% in the aggregate of the
outstanding CVRs, within 45 days of receipt of a Non-Compliance Certificate,
that the Rights Agent deliver a written notice, prepared by said Holder or
Holders, specifying whether said Holder or Holders agree with (a “Notice of
Agreement”) or object to (a “Notice of Objection”) such Non-Compliance
Certificate, the Rights Agent shall deliver such Notice of Agreement or Notice
of Objection, as applicable, to Buyer. If the Rights Agent delivers a Notice of
Agreement from said Holder or Holders to Buyer in response to such
Non-Compliance Certificate, then, so long as any other Holder or Holders of at
least 20% in the aggregate of the outstanding CVRs has not caused the Rights
Agent to deliver a Notice of Objection to Buyer, the applicable CVR Payment
Amount shall not be due and payable to the Holders, and Buyer and the Rights
Agent shall have no further obligations with respect to such CVR Payment Amount.

(g) If the Rights Agent delivers a Notice of Objection to Buyer within the
45-day period set forth in Section 2.4(f), the Rights Agent shall deliver
together with the Notice of Objection, a certificate on behalf of the Holders
(the “Objection Certificate”) setting forth in reasonable detail, as prepared by
the objecting Holder or Holders of at least 20% in the aggregate of the
outstanding CVRs, each of the objections to the events or circumstances
described in the applicable Non-Compliance Certificate (collectively, the
“Determinations”). If Buyer does not agree with the objections to the applicable
Non-Compliance Certificate in the Objection Certificate, the Determinations that
are in dispute shall be resolved by the procedure set forth in Section 7.12,
which decision shall be binding on the parties hereto and the Holders.

(h) If the Rights Agent has not received from a Holder or Holders of at least
20% in the aggregate of the outstanding CVRs, within 45 days of receipt of a
Non-Compliance Certificate and, therefore, does not deliver a Notice of
Objection and Objection Certificate to the applicable Non-Compliance Certificate
within the periods described above, the Rights Agent shall be deemed to have
delivered a Notice of Agreement with respect to such Non-Compliance Certificate
and the applicable CVR Payment Amount shall not be due and payable to the
Holders, and Buyer and the Rights Agent shall have no further obligations with
respect to such CVR Payment Amount.

(i) If Buyer delivers a Compliance Certificate to the Rights Agent or if a CVR
Payment Amount is determined to be payable pursuant to Section 2.4(g) above,
Buyer shall establish a CVR Payment Date with respect to such CVR Payment Amount
that is within 15 days of the date of the applicable Compliance Certificate or
decision, as applicable. At least 5 business days prior to such CVR Payment
Date, Buyer shall cause the applicable aggregate CVR Payment Amount with respect
to all Holders to be delivered to the Rights Agent, who will in turn, on the CVR
Payment Date, pay the applicable CVR Payment Amount to each of the Holders (the
amount to which each Holder is entitled to

 

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receive will be based on the number of CVRs held by such Holder as reflected on
the CVR Register) (i) by check mailed to the address of each Holder as reflected
in the CVR Register as of the close of business on the last Business Day prior
to such CVR Payment Date, or, (ii) with respect to Holders that are due CVR
Payment Amounts in excess of $1,000,000 who have provided the Rights Agent with
wire transfer instructions in writing, by wire transfer of immediately available
funds to such account.

(j) Buyer shall be entitled to deduct and withhold, or cause to be deducted or
withheld, from each CVR Payment Amount otherwise payable pursuant to this
Agreement, such amounts as it is required to deduct and withhold with respect to
the making of such payment under the Internal Revenue Code, or any provision of
state, local or foreign tax Law. To the extent that amounts are so withheld or
paid over to or deposited with the relevant governmental entity, such withheld
amounts shall be treated for all purposes of this Agreement as having been paid
to the Holder in respect of which such deduction and withholding was made.

(k) Buyer shall promptly furnish to the Rights Agent all information and
documentation in connection with this Agreement and the CVRs that the Rights
Agent or any Holder or Holders of at least 5% in the aggregate of the
outstanding CVRs may reasonably request in connection with the determination of
whether a First CVR Payment Event has occurred or whether the Sales Target has
been met. The Rights Agent shall forward any information and documentation it
receives to the Holders who request such information.

Section 2.5 No Voting, Dividends Or Interest; No Equity Or Ownership Interest In
Buyer.

(a) The CVRs shall not have any voting or dividend rights, and interest shall
not accrue on any amounts payable on the CVRs to any Holder.

(b) The CVRs shall not represent any equity or ownership interest in Buyer or in
any constituent company to the Merger.

ARTICLE III

THE RIGHTS AGENT

Section 3.1 Certain Duties And Responsibilities.

(a) The Rights Agent shall not have any liability for any actions taken or not
taken in connection with this Agreement, except to the extent of its willful
misconduct, bad faith or gross negligence. No provision of this Agreement shall
require the Rights Agent to expend or risk its own funds or otherwise incur any
financial liability in the performance of any of its duties hereunder or in the
exercise of any of its rights or powers.

(b) Any Holder or Holders of at least 20% in the aggregate of the outstanding
CVRs may direct the Rights Agent to act on behalf of the Holders in enforcing
any of their rights hereunder, including, without limitation, the delivery of
Notices of Objection, Objection Certificates and negotiation or arbitration
pursuant to Section 7.12. The Rights Agent shall be under no obligation to
institute any action, suit or legal proceeding or to take any other action
likely to involve material expense unless the Holders shall furnish the Rights
Agent with reasonable security and indemnity for any costs and expenses which
may be incurred. All rights of action under this Agreement may be enforced by
the Rights Agent, and any action, suit or proceeding instituted by the Rights
Agent shall be brought in its name as Rights Agent, and any recovery of judgment
shall be for the ratable benefit of all the Holders, as their respective rights
or interests may appear.

 

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Section 3.2 Certain Rights of Rights Agent.

The Rights Agent undertakes to perform such duties and only such duties as are
specifically set forth in this Agreement, and no implied covenants or
obligations shall be read into this Agreement against the Rights Agent. In
addition:

(a) the Rights Agent may rely and shall be protected in acting or refraining
from acting upon any resolution, certificate, statement, instrument, opinion,
report, notice, request, direction, consent, order or other paper or document
believed by it to be genuine and to have been signed or presented by the proper
party or parties;

(b) whenever the Rights Agent shall deem it desirable that a matter be proved or
established prior to taking, suffering or omitting any action hereunder, the
Rights Agent may, in the absence of bad faith, gross negligence or willful
misconduct on its part, rely upon an Officer’s Certificate;

(c) the Rights Agent may engage and consult with counsel of its selection and
the written advice of such counsel or any opinion of counsel shall be full and
complete authorization and protection in respect of any action taken, suffered
or omitted by it hereunder in good faith and in reliance thereon;

(d) in the event of arbitration, the Rights Agent may engage and consult with
tax experts, valuation firms and other experts and third parties that it, in its
sole and absolute discretion, deems appropriate or necessary to enable it to
discharge its duties hereunder;

(e) the permissive rights of the Rights Agent to do things enumerated in this
Agreement shall not be construed as a duty;

(f) the Rights Agent shall not be required to give any note or surety in respect
of the execution of such powers or otherwise in respect of the premises; and

(g) Buyer agrees to indemnify Rights Agent for, and hold Rights Agent harmless
against, any loss, liability, claim, demands, suits or expense arising out of or
in connection with Rights Agent’s duties under this Agreement, including the
costs and expenses of defending Rights Agent against any claims, charges,
demands, suits or loss, unless such loss shall have been determined by a court
of competent jurisdiction to be a result of Rights Agent’s gross negligence, bad
faith or willful or intentional misconduct, provided, however, that Agent’s
aggregate liability during any term of this Agreement with respect to, arising
from, or arising in connection with this Agreement, or from all services
provided or omitted to be provided under this Agreement, whether in contract, or
in tort, or otherwise, is limited to, and shall not exceed, the amounts paid
hereunder by Buyer to Rights Agent as fees and charges, but not including
reimbursable expenses.

(h) Buyer agrees (i) to pay the fees and expenses of the Rights Agent in
connection with this Agreement, as set forth on Schedule 1 hereto, and (ii) to
reimburse the Rights Agent for all taxes and governmental charges, reasonable
expenses and other charges of any kind and nature incurred by the Rights Agent
in the execution of this Agreement (other than taxes measured by the Rights
Agent’s net income). The Rights Agent shall also be entitled to reimbursement
from Buyer for all reasonable and necessary out-of-pocket expenses paid or
incurred by it in connection with the administration by the Rights Agent of its
duties hereunder. An invoice for the Project Management Fee will be rendered a
reasonable time prior to, and paid on, the effective date of the transaction. An
invoice for any out-of-pocket

 

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expenses and per item fees realized will be rendered and payable within thirty
(30) days after receipt by Buyer, except for postage and mailing expenses, which
funds must be received one (1) business day prior to the scheduled mailing date.
Buyer agrees to pay to the Rights Agent any amounts, including fees and
expenses, payable in favor of the Rights Agent in connection with any dispute,
resolution or arbitration arising under or in connection with this Agreement;
provided, however, that in the event of a resolution in favor of Buyer any
amounts, including fees and expenses, payable in favor of the Rights Agent
related to such dispute, resolution or arbitration shall be offset against the
CVR Payment Amounts, if any.

Section 3.3 Resignation And Removal; Appointment of Successor.

(a) The Rights Agent may resign at any time by giving written notice thereof to
Buyer specifying a date when such resignation shall take effect, which notice
shall be sent at least 30 days prior to the date so specified.

(b) If at any time the Rights Agent shall become incapable of acting, any Holder
of a CVR may, on behalf of himself and all others similarly situated, petition
any court of competent jurisdiction for the removal of the Rights Agent and the
appointment of a successor Rights Agent.

(c) If the Rights Agent shall resign, be removed or become incapable of acting,
Buyer, by a Board Resolution, shall promptly appoint a qualified successor
Rights Agent who may be a Holder and is not an officer of Buyer. The successor
Rights Agent so appointed shall, forthwith upon its acceptance of such
appointment in accordance with this Section 3.3(c), become the successor Rights
Agent.

(d) Buyer shall give notice of each resignation and each removal of a Rights
Agent and each appointment of a successor Rights Agent by mailing written notice
of such event by first-class mail, postage prepaid, to the Holders as their
names and addresses appear in the CVR Register. Each notice shall include the
name and address of the successor Rights Agent. If Buyer fails to send such
notice within ten days after acceptance of appointment by a successor Rights
Agent, the successor Rights Agent shall cause the notice to be mailed at the
expense of Buyer.

Section 3.4 Acceptance of Appointment By Successor.

Every successor Rights Agent appointed hereunder shall execute, acknowledge and
deliver to Buyer and to the retiring Rights Agent an instrument accepting such
appointment and a counterpart of this Agreement, and thereupon such successor
Rights Agent, without any further act, deed or conveyance, shall become vested
with all the rights, powers, trusts and duties of the retiring Rights Agent;
but, on request of Buyer or the successor Rights Agent, such retiring Rights
Agent shall execute and deliver an instrument transferring to such successor
Rights Agent all the rights, powers and trusts of the retiring Rights Agent.

ARTICLE IV

COVENANTS

Section 4.1 List of Holders.

Buyer shall furnish or cause to be furnished to the Rights Agent (a) in such
form as Buyer receives from its transfer agent (or other agent performing
similar services for Buyer), the names and addresses of the Holders within five
Business Days of the Effective Time, and (b) at such times as the

 

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Rights Agent may request in writing, within five days after receipt by Buyer of
any such request, a list, in such form as Buyer receives from its transfer agent
(or other agent performing similar services for Buyer), of the names and the
addresses of the Holders as of a date not more than 15 days prior to the time
such list is furnished.

Section 4.2 Payment of CVR Payment Amount.

Buyer shall duly and promptly pay each Holder the applicable CVR Payment Amount,
if any, in the manner provided for in Section 2.4 and in accordance with the
terms of this Agreement.

Section 4.3 Commercially Reasonable Efforts.

Unless this Agreement and the CVRs shall have earlier terminated as provided
herein, from and after the date hereof, Buyer shall use commercially reasonable
efforts consistent with pharmaceutical industry practice relating to products in
a similar stage of marketing, development and approval and with similar economic
potential, and considering the regulatory, legal, business, commercial and other
facts and circumstances presented to Buyer from and after the date hereof, to
achieve, as soon as practicable, a First CVR Payment Event and the Sales Target.

Section 4.4 Ability To Make Prompt Payment.

Neither Buyer nor any of its Subsidiaries shall enter into any agreement that
would restrict Buyer’s right to be able to promptly make payments to the Holders
under this Agreement or otherwise restrict Buyer’s ability to fund such
payments.

ARTICLE V

AMENDMENTS

Section 5.1 Amendments Without Consent of Holders.

(a) Without the consent of any Holders or the Rights Agent, Buyer, when
authorized by a Board Resolution, at any time and from time to time, may enter
into one or more amendments hereto, for any of the following purposes:

(i) subject to Section 6.1, to evidence the succession of another Person to
Buyer and the assumption by any such successor of the covenants of Buyer herein;
or

(ii) to evidence the termination of the CVR Registrar and the succession of
another Person as a successor CVR Registrar and the assumption by any successor
of the obligations of the CVR Registrar herein.

(b) Without the consent of any Holders, Buyer, when authorized by a Board
Resolution, and the Rights Agent, in the Rights Agent’s sole and absolute
discretion, at any time and from time to time, may enter into one or more
amendments hereto, for any of the following purposes:

(i) to evidence the succession of another Person as a successor Rights Agent and
the assumption by any successor of the covenants and obligations of the Rights
Agent herein;

 

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(ii) to add to the covenants of Buyer such further covenants, restrictions,
conditions or provisions as the Board of Directors and the Rights Agent shall
consider to be for the protection of the Holders; provided, that in each case,
such provisions shall not adversely affect the interests of the Holders;

(iii) to cure any ambiguity, to correct or supplement any provision herein that
may be defective or inconsistent with any other provision herein, or to make any
other provisions with respect to matters or questions arising under this
Agreement; provided, that in each case, such provisions shall not adversely
affect the interests of the Holders;

(iv) as may be necessary or appropriate to ensure that the CVRs are not subject
to registration under the Securities Act or the Exchange Act; provided that such
provisions shall not adversely affect the interests of the Holders; or

(v) any other amendments hereto for the purpose of adding, eliminating or
changing any provisions of this Agreement unless such addition, elimination or
change is adverse to the interests of the Holders.

(c) Promptly after the execution by Buyer and the Rights Agent of any amendment
pursuant to the provisions of this Section 5.1, Buyer shall mail a notice
thereof by first class mail to the Holders at their addresses as they shall
appear on the CVR Register, setting forth in general terms the substance of such
amendment.

Section 5.2 Amendments With Consent of Holders.

(a) Subject to Section 5.1 (which amendments pursuant to Section 5.1 may be made
without the consent of the Holders), with the consent of the Holders of not less
than a majority of the outstanding CVRs, whether evidenced in writing or taken
at a meeting of the Holders, Buyer, when authorized by a Board Resolution, and
the Rights Agent may enter into one or more amendments hereto for the purpose of
adding, eliminating or changing any provisions of this Agreement, even if such
addition, elimination or change is in any way adverse to the interest of the
Holders.

(b) Promptly after the execution by Buyer and the Rights Agent of any amendment
pursuant to the provisions of this Section 5.2, Buyer shall mail a notice
thereof by first class mail to the Holders at their addresses as they shall
appear on the CVR Register, setting forth in general terms the substance of such
amendment.

Section 5.3 Execution of Amendments.

In executing any amendment permitted by this Article V, the Rights Agent shall
be entitled to receive, and shall be fully protected in relying upon, an opinion
of counsel selected by Buyer stating that the execution of such amendment is
authorized or permitted by this Agreement. The Rights Agent may, but is not
obligated to, enter into any such amendment that affects the Rights Agent’s own
rights, privileges, covenants or duties under this Agreement or otherwise.

Section 5.4 Effect of Amendments.

Upon the execution of any amendment under this Article V, this Agreement shall
be modified in accordance therewith, such amendment shall form a part of this
Agreement for all purposes and every Holder shall be bound thereby.

 

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ARTICLE VI

CONSOLIDATION, MERGER, SALE OR CONVEYANCE

Section 6.1 Company May Consolidate, Etc.

(a) Buyer shall not consolidate with or merge into any other Person or convey,
transfer or lease its properties and assets substantially as an entirety to any
Person, unless:

(i) in case Buyer shall consolidate with or merge into any other Person or
convey, transfer or lease its properties and assets substantially as an entirety
to any Person, the Person formed by such consolidation or into which Buyer is
merged or the Person that acquires by conveyance or transfer, or that leases,
the properties and assets of Buyer substantially as an entirety (the “Surviving
Person”) shall expressly assume payment of amounts on all the CVRs and the
performance of every duty and covenant of this Agreement on the part of Buyer to
be performed or observed; and

(ii) Buyer has delivered to the Rights Agent an Officer’s Certificate, stating
that such consolidation, merger, conveyance, transfer or lease complies with
this Article VI and that all conditions precedent herein provided for relating
to such transaction have been complied with.

(b) For purposes of this Section 6.1, “convey, transfer or lease its properties
and assets substantially as an entirety” shall mean properties and assets
contributing in the aggregate at least 80% of Buyer’s total consolidated
revenues as reported in Buyer’s last available periodic financial report
(quarterly or annual, as the case may be).

Section 6.2 Successor Substituted.

Upon any consolidation of or merger by Buyer with or into any other Person, or
any conveyance, transfer or lease of the properties and assets substantially as
an entirety to any Person in accordance with Section 6.1, the Surviving Person
shall succeed to, and be substituted for, and may exercise every right and power
of, Buyer under this Agreement with the same effect as if the Surviving Person
had been named as Buyer herein, and thereafter, except in the case of a lease,
the predecessor Person shall be relieved of all obligations and covenants under
this Agreement and the CVRs.

ARTICLE VII

OTHER PROVISIONS OF GENERAL APPLICATION

Section 7.1 Notices To Rights Agent And Buyer.

Any request, demand, authorization, direction, notice, consent, waiver or other
document provided or permitted by this Agreement shall be sufficient for every
purpose hereunder if in writing and sent by facsimile transmission, delivered
personally, or by certified or registered mail (return receipt requested and
first-class postage prepaid) or sent by a nationally recognized overnight
courier (with proof of service), addressed as follows:

(a) if to the Rights Agent, addressed to it at 44 West Lancaster Avenue,
Ardmore, PA 19003, facsimile at 610-649-7302, or at any other address previously
furnished in writing to the Holders and Buyer by the Rights Agent; or

 

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(b) if to Buyer, addressed to it at 397 Eagleview Boulevard, Exton, Pennsylvania
19341, facsimile at 610-458-7380, or at any other address previously furnished
in writing to the Rights Agent and the Holders by Buyer.

Section 7.2 Notice To Holders.

Where this Agreement provides for notice to Holders, such notice shall be
sufficiently given (unless otherwise herein expressly provided) if in writing
and mailed, first-class postage prepaid, to each Holder affected by such event,
at his, her or its address as it appears in the CVR Register, not later than the
latest date, and not earlier than the earliest date, prescribed for the giving
of such notice. In any case where notice to Holders is given by mail, neither
the failure to mail such notice, nor any defect in any notice so mailed, to any
particular Holder shall affect the sufficiency of such notice with respect to
other Holders.

Section 7.3 Effect of Headings.

The Article and Section headings herein are for convenience only and shall not
affect the construction hereof.

Section 7.4 Successors and Assigns.

All covenants and agreements in this Agreement by Buyer shall bind its
successors and assigns, whether so expressed or not.

Section 7.5 Benefits of Agreement.

Nothing in this Agreement, express or implied, shall give to any Person (other
than the parties hereto, the Holders and their permitted successors and assigns
hereunder) any benefit or any legal or equitable right, remedy or claim under
this Agreement or under any covenant or provision herein contained, all such
covenants and provisions being for the sole benefit of the parties hereto, the
Holders and their permitted successors and assigns.

Section 7.6 Governing Law.

This Agreement and the CVRs shall be governed by and construed in accordance
with the laws of the State of Delaware without regards to its rules of conflicts
of laws.

Section 7.7 Legal Holidays.

In the event that a CVR Payment Date shall not be a Business Day, then,
notwithstanding any provision of this Agreement to the contrary, any payment
required to be made in respect of the CVRs on such date need not be made on such
date, but may be made on the next succeeding Business Day with the same force
and effect as if made on the applicable CVR Payment Date.

Section 7.8 Severability Clause.

In case any one or more of the provisions contained in this Agreement shall for
any reason be held to be invalid, illegal or unenforceable in any respect, such
invalidity, illegality or unenforceability

 

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shall not affect any other provisions of this Agreement, but this Agreement
shall be construed as if such invalid or illegal or unenforceable provision had
never been contained herein. Upon such determination that any term or other
provision is invalid, illegal or unenforceable, the court or other tribunal
making such determination is authorized and instructed to modify this Agreement
so as to effect the original intent of the parties as closely as possible so
that the transactions and agreements contemplated herein are consummated as
originally contemplated to the fullest extent possible.

Section 7.9 Counterparts.

This Agreement may be signed in any number of counterparts (which may be
effectively delivered by facsimile or other electronic means), each of which
shall be deemed to constitute but one and the same instrument.

Section 7.10 Termination.

This Agreement shall be terminated and of no force or effect, and the parties
hereto shall have no liability hereunder, upon the earlier to occur of (a) the
payment of all potential CVR Payment Amounts required to be paid under the terms
of this Agreement and (b) the final determination in accordance with this
Agreement, following delivery and approval of Non-Compliance Certificates
relating to both CVR Payment Amounts, that no CVR Payment Amount is, or can ever
be, payable under of this Agreement.

Section 7.11 Entire Agreement.

This Agreement and the Merger Agreement represent the entire understanding of
the parties hereto with reference to the transactions and matters contemplated
hereby and thereby and this Agreement supersedes any and all other oral or
written agreements hereto made except for the Merger Agreement. If and to the
extent that any provision of this Agreement is inconsistent or conflicts with
the Merger Agreement, this Agreement shall govern and be controlling.

Section 7.12 Negotiation; Arbitration.

(a) Prior to any arbitration pursuant to Section 7.12(b), Buyer, the Rights
Agent and any Holder or Holders of at least 5% in the aggregate of the
outstanding CVRs shall negotiate in good faith for a period of 30 days to
resolve any controversy or claim arising out of or relating to this Agreement,
or the breach thereof.

(b) After expiration of the 30-day period contemplated by Section 7.12(a), such
controversy or claim, including any claims for breach of this Agreement, shall
be settled by arbitration administered by the American Arbitration Association
under its Commercial Arbitration Rules, and judgment on the award rendered by
the arbitrators may be entered in any court having jurisdiction thereof. Buyer,
the Rights Agent and any Holder or Holders of at least 20% in the aggregate of
the outstanding CVRs may initiate an arbitration for any matter relating to this
Agreement. The number of arbitrators shall be three. Within 15 days after the
commencement of arbitration, each party shall select one person to act as
arbitrator, and the two selected shall select a third arbitrator within 15 days
of their appointment. If the arbitrators selected by the parties are unable or
fail to agree upon the third arbitrator, the third arbitrators shall be selected
by the American Arbitration Association. The place of the arbitration shall be
New York, New York. The arbitrators shall be lawyers or retired judges with
experience in the life sciences industry and with mergers and acquisitions.
Except as may be required by law, neither a party nor an arbitrator may disclose
the existence, content or results of any arbitration hereunder without the prior

 

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written consent of both parties. Any award payable in favor of the Holder or
Rights Agent as a result of arbitration shall be distributed to the Holders on a
pro rata basis, based on the number of CVRs held by each Holder. Buyer shall pay
all fees and expenses incurred in connection with any arbitration, including the
costs and expenses billed by the Arbitrator in connection with the performance
of its duties described herein; provided, however, that if the arbitrator rules
in favor of Buyer, the Arbitrator’s fees and expenses shall be offset against
the CVR Payment Amounts, if any.

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IN WITNESS WHEREOF, each of the parties has caused this Agreement to be executed
on its behalf by its duly authorized officers as of the day and year first above
written.

 

VIROPHARMA INCORPORATED By:  

 

Name:   Title:   LEV PHARMACEUTICALS, INC. By:  

 

Name:   Title:   STOCKTRANS, INC. By:  

 

Name:   Title: