Exhibit
      10.1

    
 

    SECURITIES
      PURCHASE AGREEMENT

     

    This
      Securities Purchase Agreement (this
      “Agreement”)
      is
      made and entered into as of July 15, 2008 by and between Lev
      Pharmaceuticals, Inc.,
      a
      Delaware corporation (the “Company”),
      and
ViroPharma
      Incorporated,
      a
      Delaware corporation (the “Purchaser”).
      

     

    WHEREAS,
      the Company, the Purchaser and HAE Acquisition Corp. have entered into that
      certain Agreement and Plan of Merger, dated as of the date hereof (the
“Merger
      Agreement”),
      whereby on the terms and subject to the conditions set forth therein, HAE
      Acquisition Corp. will merge with and into the Company and the Company will
      become a wholly-owned subsidiary of the Purchaser (the “Merger”);
      

     

    WHEREAS,
      on the terms and subject to the conditions set forth in this Agreement, the
      Company desires to issue and sell to the Purchaser, and the Purchaser desires
      to
      purchase from the Company, securities of the Company as more fully described
      in
      this Agreement; and 

     

    WHEREAS,
      the Shares (as defined below) will be sold to the Purchaser pursuant to the
      Company’s effective Registration Statement on Form S-3 (Reg. No. 333-143196)
      (the “Registration
      Statement”).
      

     

    NOW,
      THEREFORE, IN CONSIDERATION of the mutual covenants contained in this Agreement,
      and for other good and valuable consideration the receipt and adequacy of which
      are hereby acknowledged, the Company and the Purchaser agree as
      follows:

     

    ARTICLE
      I.

    DEFINITIONS

     

    1.1 Definitions.
      Capitalized terms used but not otherwise defined herein shall have the meanings
      ascribed thereto in the Merger Agreement. In addition to the terms defined
      elsewhere in this Agreement, for all purposes of this Agreement, the following
      terms have the meanings indicated in this Section 1.1:

     

    “Commission”
means
      the Securities and Exchange Commission.

     

    “Common
      Stock”
means
      the common stock of the Company, par value $0.01 per share. 

     

    “Exchange
      Act”
means
      the Securities and Exchange Act of 1934, as amended.

     

    “Person”
means
      an individual or corporation, partnership, trust, incorporated or unincorporated
      association, joint venture, limited liability company, joint stock company,
      government (or an agency or subdivision thereof) or other entity of any
      kind.

     

    “Securities
      Act”
shall
      mean the Securities Act of 1933, as amended.

     

    “Shares”
means
      the 9,661,836 shares of Common Stock issued to the Purchaser pursuant to this
      Agreement.

     

    “Termination
      Date”
means
      the date the Merger Agreement is terminated in accordance with its
      terms.

     

    
      
        
        

      

      
        
        

        
          

        

      

      
        
        

      

    

    ARTICLE
      II.

    PURCHASE
      AND SALE

     

    2.1 Closing.
      Concurrent with the execution and delivery of this Agreement, on the basis
      of
      the representations, warranties and agreements herein and subject to the
      satisfaction of the conditions set forth in Section 2.2, the Company shall
      sell,
      and the Purchaser shall purchase, the Shares for an aggregate cash purchase
      price of $20,000,000 (the “Purchase Price”). The closing of such issuance and
      purchase (the “Closing”) shall take place at 9:00 A.M., New York City time, on
      the date hereof (the
      “Closing Date”), at
      the
      offices of Becker & Poliakoff, 45 Broadway 11th Floor New York, NY, or at
      such other time and place as the Purchaser and the Company shall mutually
      select.

     

    2.2 Deliveries.
      At the
      Closing, 

     

    (a) the
      Company shall deliver or cause to be delivered to the Purchaser a copy of
      irrevocable instructions to the Company’s transfer agent instructing the
      transfer agent to deliver, on an expedited basis, a certificate evidencing
      the
      Shares, registered in the name of the Purchaser; and

     

    (b) the
      Purchaser shall deliver or cause to be delivered to the Company the Purchase
      Price by wire transfer in immediately available funds to the account as
      specified in writing by the Company; and

     

    (c) the
      Company shall deliver to Purchaser (i) a certificate of good standing, dated
      a
      recent date, with respect to the Company, and (ii) a copy, certified by the
      Secretary or an Assistant Secretary of the Company, of resolutions duly adopted
      by the Company’s Board of Directors evidencing the taking of all corporate
      action necessary to authorize the execution, delivery and performance of this
      Agreement and the
      consummation of the transactions
      contemplated hereby.

     

    ARTICLE
      III.

    REPRESENTATIONS
      AND WARRANTIES

     

    3.1 Representations
      and Warranties of the Company.
      

     

    (a) The
      representations and warranties of the Company set forth in Article 5 of the
      Merger Agreement, including the definitions of all capitalized terms used
      therein, are hereby incorporated by reference herein as if set forth in full
      in
      this Agreement. Any references in such Article 5 or any such definitions (other
      than in Section 5.2 thereof) to “this Agreement” or “this Agreement and the
      transactions contemplated hereby,” or words of similar import, shall mean this
      Agreement and the purchase and sale of the Shares contemplated by this
      Agreement.

     

    (b) In
      addition to the foregoing, the Company hereby makes the following
      representations and warranties to the Purchaser:

     

    (i) Authorization;
      Enforcement.
      The
      Company has the requisite corporate power and authority to enter into and to
      consummate the transactions contemplated by this Agreement and otherwise to
      carry out its obligations hereunder. The execution and delivery of this
      Agreement by the Company and the consummation by it of the transactions
      contemplated hereby have been duly authorized by all necessary action on the
      part of the Company. This Agreement has been duly executed by the Company and
      constitutes the valid and binding obligation of the Company enforceable against
      the Company in accordance with its terms except (A) as limited by general
      equitable principles and applicable bankruptcy, insolvency, reorganization,
      moratorium and other laws of general application affecting enforcement of
      creditors’ rights generally, and (B) as limited by laws relating to the
      availability of specific performance, injunctive relief or other equitable
      remedies. 

     

    
      
        
        

      

      
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    (ii) Filings,
      Consents and Approvals.
      The
      Company is not required to obtain any consent, waiver, authorization or order
      of, give any notice to, or make any filing or registration with, any court
      or
      other federal, state, local or other governmental authority or other Person
      in
      connection with the execution, delivery and performance by the Company of this
      Agreement, including the sale and issuance of the Shares, other than (A) filings
      required pursuant to this Agreement, (B) filings with the Commission (such
      as
      any prospectus, prospectus supplement and any Current Report on Form 8-K) and
      such filings as are required to be made under applicable state securities laws,
      and (C) those made or obtained prior to the date hereof. 

     

    (iii) Issuance
      of the Shares.
      The
      Shares are duly authorized and, when issued and paid for in accordance with
      this
      Agreement, will be duly and validly issued, fully paid and nonassessable, free
      and clear of all liens imposed by the Company other than restrictions on
      transfer provided for in this Agreement. 

     

    (iv) Anti-Takeover
      Laws.
      The
      Company has taken all necessary action to exempt the transactions contemplated
      by this Agreement from, or if necessary to challenge the validity or
      applicability of, any applicable “moratorium,” “fair price,” “business
      combination,” “control share,” or other anti-takeover Laws, including Section
      203 of the DGCL.

     

    (v) Registration
      Statement and Prospectus Supplement.
      The
      Registration Statement has been declared effective and includes sufficient
      shares of Common Stock for the Company to issue and sell the Shares thereunder.
      No stop order suspending the effectiveness of the Registration Statement has
      been issued and no proceeding for that purpose has been initiated or, to the
      Company’s knowledge, threatened by the SEC. The Company will file a prospectus
      supplement covering the sale of the Shares to the Purchaser with the SEC within
      two (2) business days after the date hereof (the “Prospectus
      Supplement”).
      At
      the time of the filing of the Prospectus Supplement, the Registration Statement
      (including the base prospectus, the Prospectus Supplement and the
      documents
      incorporated by reference therein), and any amendments and supplements thereto,
      will comply in all material respects with the applicable provisions of the
      Securities Act, will not contain an untrue statement of a material fact and
      will
      not omit to state any material fact required to be stated therein or necessary
      in order to make the statements therein not misleading.

     

    (vi) Over-the-Counter
      (“OTC”) Bulletin Board Requirements.
      The
      Company’s Common Stock is registered pursuant to Section 12 of the Exchange Act,
      and the Company has taken no action designed to, or which, to its knowledge,
      is
      likely to have the effect of, terminating the registration under the Exchange
      Act nor has the Company received any notification that the SEC is contemplating
      terminating such registration. The Company has not, in the two (2) years
      preceding the date hereof, received notice from the OTC Bulletin Board to the
      effect that the Company is not in compliance with the requirements to maintain
      eligibility for quotation of the Common Stock thereon. The Company is, and
      has
      no reason to believe that it will not in the foreseeable future continue to
      be,
      in compliance with the requirements to maintain eligibility for quotation of
      the
      Company’s Common Stock thereon. 

     

    3.2 Representations
      and Warranties of the Purchaser.
      The
      Purchaser hereby represents and warrants to the Company as follows:

     

    (a) Organization;
      Authority.
      The
      Purchaser is an entity duly organized, validly existing and in good standing
      under the laws of the jurisdiction of its organization with full right,
      corporate or partnership power and authority to enter into and to consummate
      the
      transactions contemplated by this Agreement and otherwise to carry out its
      obligations hereunder. The execution, delivery and performance by the Purchaser
      of the transactions contemplated by this Agreement have been duly authorized
      by
      all necessary corporate or similar action on the part of the Purchaser. This
      Agreement has been duly executed by the Purchaser and constitutes the valid
      and
      binding obligation of the Purchaser enforceable against the Purchaser in
      accordance with its terms except (i) as limited by general equitable principles
      and applicable bankruptcy, insolvency, reorganization, moratorium and other
      laws
      of general application affecting enforcement of creditors’ rights generally, and
      (ii) as limited by laws relating to the availability of specific performance,
      injunctive relief or other equitable remedies.

     

    
      
        
        

      

      
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    (b) Filings,
      Consents and Approvals.
      The
      Purchaser is not required to obtain any consent, waiver, authorization or order
      of, give any notice to, or make any filing or registration with, any court
      or
      other federal, state, local or other governmental authority or other Person
      in
      connection with the execution, delivery and performance by the Purchaser of
      this
      Agreement, other than (A) filings required pursuant to this Agreement, and
      (B)
      the filing of a Form 8-K with the Commission and such filings as are required
      to
      be made under applicable state securities laws. 

     

    (c) Access
      to Information.
      The
      Purchaser acknowledges that it has been afforded (i) the opportunity to ask
      such
      questions as it has deemed necessary of, and to receive answers from,
      representatives of the Company concerning the terms and conditions of the
      offering of the Shares and the merits and risks of investing in the Shares;
      (ii)
      access to information about the Company and its financial condition, results
      of
      operations, business, properties, management and prospects sufficient to enable
      it to evaluate its investment; and (iii) the opportunity to obtain such
      additional information that the Company possesses or can acquire without
      unreasonable effort or expense that is necessary to make an informed investment
      decision with respect to the investment. 

     

    (d) Independent
      Investment Decision.
      The
      Purchaser has independently evaluated the merits of its decision to purchase
      the
      Shares pursuant to this Agreement, such decision has been independently made
      by
      the Purchaser and the Purchaser confirms that it has only relied on the advice
      of its own business and/or legal counsel in making such decision. Purchaser
      has
      not relied on the truth, accuracy or completeness of the statements contained
      in
      any research report concerning the Company that was prepared by an investment
      banking firm. 

     

    ARTICLE
      IV.

    OTHER
      AGREEMENTS OF THE PARTIES

     

    4.1 Use
      of
      Proceeds.
      The
      Company shall use the net proceeds from the sale of the Shares solely for the
      research, development and commercialization of Cinryze, including but not
      limited to (i) building inventory for the potential launch of Cinryze for the
      treatment of HAE in the United States; (ii) obtaining approval for Cinryze;
      (iii) independently commercializing Cinryze for the treatment of HAE in the
      United States; (iv) conducting research and development activities of Cinryze
      for HAE, including clinical trials, (v) opening and operating plasma centers,
      (vi) developing and implementing related marketing plans; and (vii) related
      payroll, travel, entertainment, education and other related expenses and
      corporate overhead. Notwithstanding anything in this Agreement to the contrary,
      this Section 4.1 shall terminate upon the earlier of the termination of the
      Merger Agreement or the consummation of the Merger.

     

    4.2 Agreement
      to Vote Shares. 

     

    (a) The
      Purchaser understands and agrees that if it attempts to vote or provide any
      other person with the authority to vote any of the Shares other than in
      compliance with this Agreement, the Company shall not, and the Purchaser hereby
      unconditionally and irrevocably instructs the Company not to, record such vote
      unless and until the Purchaser shall have complied with the terms of this
      Agreement.

     

    
      
        
        

      

      
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    (b) 
      From and
      after the date hereof, except as otherwise permitted by this Agreement or by
      order of a court of competent jurisdiction, the Purchaser will not commit any
      act that would restrict its legal power, authority and right to vote all of
      the
      Shares purchased hereunder or otherwise prevent or disable the Purchaser from
      performing any of its obligations under this Agreement. Without limiting the
      generality of the foregoing, except for this Agreement, the Purchaser will
      not
      enter into any voting agreement with any person or entity with respect to any
      of
      the Shares purchased hereunder, grant any person or entity any proxy (revocable
      or irrevocable) or power of attorney with respect to any of such Shares, deposit
      any of such Shares in a voting trust or otherwise enter into any agreement
      or
      arrangement with any person or entity limiting or affecting the Purchaser’s
      legal power, authority or right to vote such Shares in favor of the approval
      of
      the Proposed Transaction (as defined below).

     

    (c) Prior
      to
      the Termination Date, at every meeting of the stockholders of Company called,
      and at every adjournment or postponement thereof, and on every action or
      approval by written consent of the stockholders of the Company, the Purchaser
      shall appear at the meeting or otherwise cause the Shares to be present thereat
      for purposes of establishing a quorum and, to the extent not voted by the
      persons appointed as proxies pursuant to this Agreement, vote the Shares, in
      proportion to the vote by the other stockholders of the Company, (i) in favor
      of
      approval of the Merger, the Merger Agreement and the other transactions
      contemplated thereby (collectively, the “Proposed Transaction”), (ii) against
      the approval or adoption of any proposal made in opposition to, or in
      competition with, the Proposed Transaction, and (iii) against any of the
      following (to the extent unrelated to the Proposed Transaction): (A) any merger,
      consolidation or business combination involving the Company or any of its
      subsidiaries other than the Proposed Transaction; (B) any sale, lease or
      transfer of all or substantially all of the assets of the Company or any of
      its
      subsidiaries; (C) any reorganization, recapitalization, dissolution, liquidation
      or winding up of the Company or any of its subsidiaries; or (D) any other action
      that is intended, or would reasonably be expected to materially impede,
      interfere with, delay, postpone, discourage or adversely affect the consummation
      of the Proposed Transaction. The Purchaser shall ensure that any of its
      Affiliates to whom it transfers Shares shall vote such Shares in accordance
      with
      this Section 4.2. Notwithstanding the foregoing, the parties acknowledge and
      agree that the provisions of this Section 4.2 shall not be deemed to prohibit
      the Purchaser from selling or transferring any interest in any of the Shares
      at
      any time and shall apply to Shares only if and for so long as such Shares shall
      continue to be beneficially owned by the Purchaser or an Affiliate of the
      Purchaser (determined in accordance with Rule 13d-3 under the Exchange Act).
      

     

    4.3 Transfers
      of Shares; Compliance with Applicable Securities Laws. The Purchaser
      acknowledges that during the period commencing with the execution and delivery
      of this Agreement and expiring on the Termination Date, the Purchaser may have
      access to material non-public information concerning the Company, and agrees
      that during such period any sale or transfer of any of the Shares shall be
      in
      compliance with all applicable securities laws. 

     

    ARTICLE
      V.

    MISCELLANEOUS

     

    5.1 Survival
      of Representations, Warranties, Agreements, Etc. Each of the representations
      and
      warranties set forth in this Agreement shall survive the Closing but only for
      a
      period of 12 months following the Closing Date and thereafter shall expire
      and
      have no further force and effect.

     

    5.2 Fees
      and
      Expenses. Each party shall pay the fees and expenses of its advisers, counsel,
      accountants and other experts, if any, and all other expenses incurred by such
      party incident to the negotiation, preparation, execution, delivery and
      performance of this Agreement. The Company shall pay all transfer agent fees,
      stamp taxes and other taxes and duties levied in connection with the delivery
      of
      the Shares to the Purchaser.

     

    
      
        
        

      

      
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    5.3 Amendments,
      Modifications and Waivers. No amendment, modification or waiver in respect
      of
      this Agreement shall be effective against any party unless it shall be in
      writing and signed by the Company and the Purchaser.

     

    5.4 Entire
      Agreement. This Agreement constitutes the entire agreement among the parties
      hereto with respect to the subject matter hereof and supersedes all other prior
      agreements and understandings, both written and oral, among or between any
      of
      the parties with respect to the subject matter hereof and thereof.

     

    5.5 Governing
      Law. This Agreement shall be governed by and construed in accordance with the
      laws of the State of Delaware, regardless of the laws that might otherwise
      govern under applicable principles of conflicts of law thereof.

     

    5.6 Consent
      to Jurisdiction; Venue. Regardless of any conflict of law or choice of law
      principles that might otherwise apply, the parties agree that this Agreement
      shall be governed by an construed in all respects in accordance with the laws
      of
      the State of Delaware. The parties all expressly agree and acknowledge that
      the
      State of Delaware has a reasonable relationship to the parties and/or this
      Agreement. As to any dispute, claim or litigation arising out of or relating
      in
      any way to this Agreement or the transaction contemplated hereby, the parties
      hereto hereby agree and consent to be subject to the exclusive jurisdiction
      of
      any Delaware state court, or federal court of the United States of America
      sitting in Delaware, and any appellate court from any thereof. Each party hereto
      hereby irrevocably waives, to the fullest extent permitted by law, (a) any
      objection that it may now or hereafter have to laying venue of any suit, action
      or proceeding brought in such court, (b) any claim that any suit, action or
      proceeding brought in such court has been brought in an inconvenient forum,
      and
      (c) any defense that it may now or hereafter have based on lack of personal
      jurisdiction in such forum. 

     

    5.7 WAIVER
      OF
      JURY TRIAL. EACH OF THE PARTIES IRREVOCABLY WAIVES ANY AND ALL RIGHTS TO TRIAL
      BY JURY IN ANY ACTION OR PROCEEDING BETWEEN THE PARTIES ARISING OUT OF OR
      RELATING TO THIS AGREEMENT AND THE TRANSACTIONS CONTEMPLATED BY THIS
      AGREEMENT.

     

    5.8 Assignment
      and Successors. This Agreement and all of the provisions hereof shall be binding
      upon and inure to the benefit of the parties hereto and their respective
      successors and permitted assigns, provided
      that
      except as otherwise specifically provided herein, neither this Agreement nor
      any
      of the rights, interests or obligations of the parties hereto may be assigned
      by
      any of the parties hereto without the prior written consent of the other parties
      hereto. Any assignment in violation of the foregoing shall be void and of no
      effect.

     

    5.9 No
      Third
      Party Rights. Nothing in this Agreement, express or implied, is intended to
      or
      shall confer upon any Person (other than the parties hereto) any right, benefit
      or remedy of any nature whatsoever under or by reason of this
      Agreement.

     

    5.10 Cooperation.
      Each of the Purchaser and the Company agrees to reasonably cooperate with the
      other party and to execute and deliver such further documents, certificates,
      agreements and instruments and to take such other actions as may be reasonably
      requested by such party to evidence or reflect the transactions contemplated
      by
      this Agreement and to carry out the intent and purpose of this Agreement.


     

    5.11 Severability.
      If any term or other provision of this Agreement is held invalid or
      unenforceable by any court of competent jurisdiction, the other provisions
      of
      this Agreement will remain in full force and effect so long as the economic
      or
      legal substance of this Agreement is not affected in any manner materially
      adverse to any party. Upon such determination that any term or other provision
      is invalid, illegal or incapable of being enforced, the parties hereto shall
      negotiate in good faith to modify this Agreement so as to effect the original
      intent of the parties as closely as possible in a mutually acceptable manner
      in
      order that the terms of this Agreement remain as originally contemplated to
      the
      fullest extent possible.

     

    
      
        
        

      

      
        6

        
          

        

      

      
        
        

      

    

    5.12 Specific
      Performance; Injunctive Relief. The parties hereto acknowledge that the parties
      shall be irreparably harmed and that there shall be no adequate remedy at law
      for a violation of any of the covenants or agreements of the other parties
      set
      forth in this Agreement. Therefore, each party hereby agrees that, in addition
      to any other remedies that may be available to the Purchaser or the Company,
      as
      applicable upon any such violation, such party shall have the right to enforce
      such covenants and agreements by specific performance, injunctive relief or
      by
      any other means to which they are entitled at law or in equity.

     

    5.13 Notices.
      All notices, consents, requests, claims, demands and other communications under
      this Agreement shall be in writing and shall be deemed given if (a) delivered
      to
      the appropriate address by hand or overnight courier (providing proof of
      delivery), or (b) sent by facsimile with confirmation of transmission by the
      transmitting equipment confirmed with a copy delivered as provided in clause
      (a), in each case to the parties at the address or facsimile address (or at
      such
      other address or facsimile address for a party as shall be specified by like
      notice) provided in the Merger Agreement, including to the persons designated
      therein to receive copies.

     

    5.14 Counterparts.
      This Agreement may be executed in several counterparts, including by facsimile,
      each of which shall be deemed an original and all of which shall constitute
      one
      and the same instrument, and shall become effective when counterparts have
      been
      signed by each of the parties and delivered to the other parties; it being
      understood that all parties need not sign the same counterpart.

     

    5.15 Headings.
      The headings contained in this Agreement are for the convenience of reference
      only, shall not be deemed to be a part of this Agreement and shall not be
      referred to in connection with the construction or interpretation of this
      Agreement.

     

    5.16 Legal
      Representation. This Agreement was negotiated by the parties with the benefit
      of
      legal representation and any rule of construction or interpretation otherwise
      requiring this Agreement to be construed or interpreted against any party shall
      not apply to any construction or interpretation thereof.

     

    (Signature
      Pages Follow)

     

    
      
        
        

      

      
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    IN
      WITNESS WHEREOF, the parties hereto have caused this Securities Purchase
      Agreement to be duly executed by their respective authorized signatories as
      of
      the date first indicated above.

     

    
      	 	 	 
	 	
              LEV
                PHARMACEUTICALS, INC.

            
	 
 	 
 	 
 
	 	By:  	/s/ Judson
              Cooper
	 	
              
Name:
              Judson Cooper
	 	Title:  
              Chairman


    

     

    
      	 	 	 
	 	VIROPHARMA
              INCORPORATED
	 
 	 
 	 
 
	 	By:  	/s/ Vincent
              J. Milano
	 	
              
Name:
              Vincent J. Milano
	 	Title:  
              President and Chief Executive Officer
	 	 


    

     

    
      
        
        

      

      
        8