**EXHIBIT 4.20****Execution Version**     THIS SECURITY AND THE SECURITIES INTO WHICH THIS SECURITY IS EXERCISABLE HAVE NOT BEENREGISTERED UNDER THE SECURITIES ACT OF 1933, AS AMENDED (THE “SECURITIES ACT”), OR THESECURITIES LAWS OF ANY STATE OR OTHER JURISDICTION AND MAY NOT BE OFFERED, SOLD OR OTHERWISETRANSFERRED EXCEPT (1) PURSUANT TO AN EXEMPTION FROM REGISTRATION UNDER THE SECURITIES ACT OR (2)PURSUANT TO AN EFFECTIVE REGISTRATION STATEMENT UNDER THE SECURITIES ACT, IN EACH CASE INACCORDANCE WITH ALL APPLICABLE SECURITIES LAWS OF THE STATES AND OTHER JURISDICTIONS, AND IN THECASE OF A TRANSACTION EXEMPT FROM REGISTRATION, UNLESS THE COMPANY HAS RECEIVED AN OPINION OFCOUNSEL REASONABLY SATISFACTORY TO IT THAT SUCH TRANSACTION DOES NOT REQUIRE REGISTRATION UNDER THESECURITIES ACT AND SUCH OTHER APPLICABLE LAWS.**ARTES MEDICAL, INC.****COMMON STOCK PURCHASE WARRANT**To Purchase 1,300,000 Shares of Common Stock     THIS COMMON STOCK PURCHASE WARRANT CERTIFIES that, for value received, Cowen HealthcareRoyalty Partners, L.P. (the “Holder”), is entitled, upon the terms and subject to thelimitations on exercise and the conditions hereinafter set forth, at any time on or after February11, 2009 (the “Initial Exercise Date”) and on or prior to the close of business on thefourth (4th) anniversary following the Initial Exercise Date (the “Termination Date”) butnot thereafter, to subscribe for and purchase from Artes Medical, Inc., a Delaware corporation (the“Company”), up to 1,300,000 shares, subject to adjustment as set forth herein (the“Warrant Shares”) of Common Stock, par value $0.001 per share, of the Company (the“Common Stock”). The purchase price of one share of Common Stock (the “ExercisePrice”) under this Warrant shall be $5.00 subject to adjustment hereunder. The Exercise Priceand the number of Warrant Shares for which the Warrant is exercisable shall be subject toadjustment as provided herein. Capitalized terms used and not otherwise defined herein shall havethe meanings set forth in that certain Note and Warrant Purchase Agreement (the “Note andWarrant Purchase Agreement”), dated January 28, 2008, between the Company and the Holder.     1. Title to Warrant. Prior to the Termination Date and subject to compliance withapplicable laws and Section 7 hereof, this Warrant and all rights hereunder are transferable, inwhole or in part, at the office or agency of the Company by the Holder in person or by dulyauthorized attorney, upon surrender of this Warrant together with the Assignment Form annexedhereto properly endorsed. The transferee shall sign an investment letter in form and substancereasonably satisfactory to the Company.     2. Authorization of Shares. The Company covenants that all Warrant Shares which maybe issued upon the exercise of the purchase rights represented by this Warrant will, upon exerciseof the purchase rights represented by this Warrant in accordance with the terms of this Warrant, beduly authorized, validly issued, fully paid and nonassessable and free from all
 

 
taxes, liens and charges in respect of the issue thereof (other than taxes in respect of any transfer occurringcontemporaneously with such issue). The Company shall at all times reserve and keep available forissue upon the exercise of this Warrant such number of its authorized but unissued Common Stock aswill be sufficient to permit the exercise in full of this Warrant.     3. Exercise of Warrant.          (a) Exercise of the purchase rights represented by this Warrant may be made at any time ortimes on or after the Initial Exercise Date and on or before the Termination Date by the surrenderof this Warrant and the Notice of Exercise annexed hereto duly executed, at the office of theCompany (or such other office or agency of the Company as it may designate by notice in writing tothe registered Holder at the address of such Holder appearing on the books of the Company) to theattention of the Chief Financial Officer and upon payment of the Exercise Price of the sharesthereby purchased the Holder shall be entitled to receive a certificate for the number of WarrantShares so purchased. Payment of the Exercise Price may be made at the option of the Holder by (i)by wire transfer or cashier’s check drawn on a United States bank of United States dollars or (ii)the surrender and cancellation of Warrant Shares issuable upon such exercise of this Warrant (i.e.on a “cashless exercise” basis), in which event the Company shall issue to the Holder a number ofshares of Common Stock computed using the following formula:     Y (A - B)   X =A     Where:          X = The net number of shares of Common Stock to be issued to the Holder pursuant to theelection to exercise;          Y = The gross number of shares of Common Stock in respect of which the election to exercise ismade;          A = The average of the Market Price of one share of the Common Stock for the ten (10) TradingDays immediately prior to the date of exercise; and          B = The Exercise Price.“Market Price” shall mean the closing sale price of the Company’s Common Stock as reportedon the Nasdaq Stock Market, or if not then traded on the Nasdaq Stock Market, such closing sale orbid price as reported on any exchange over which the Company’s Common Stock may then be traded, orif not then traded over any exchange, then the market price of the Company’s Common Stock shall bethe fair market value of the Company’s Common Stock as determined in good faith by the Board ofDirectors of the Company. Certificates for shares purchased hereunder shall be delivered to theHolder (at an address in the United States specified by the Holder) within five (5) Trading Daysafter the date on which this Warrant shall have been exercised as aforesaid or the Company shall instruct its transfer agent to register the sharespurchased hereunder in book entry form within five (5) Trading Days after the date on which thisWarrant shall have been exercised as aforesaid. This Warrant shall be deemed to have been exercisedand such certificate or certificates (or book entry shares) shall be deemed to have
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been issued, and the Holder or any other person so designated to be named therein shall be deemed to havebecome a holder of record of such shares for all purposes, as of the date the Warrant has been exercisedby payment to the Company of the Exercise Price, delivery of the required documentation and alltaxes required to be paid by the Holder, if any, pursuant to Section 5 hereof prior to the issuanceof such shares, have been paid. For purposes of this Warrant, a “Trading Day” shall meanany day on which the national securities exchange or the national market system of the NASD areopen for trading.          (b) If this Warrant shall have been exercised in part, the Company shall, at the time ofdelivery of the certificate or certificates representing Warrant Shares, deliver to the Holder anew Warrant evidencing the rights of the Holder to purchase the unpurchased Warrant Shares calledfor by this Warrant, which new Warrant shall in all other respects be identical with this Warrant.          (c) The Holder understands that, until such time as the Registration Statement has beendeclared effective or the Warrant Shares may be sold pursuant to Rule 144 under the Securities Actwithout any restriction as to the number of securities as of a particular date that can then beimmediately sold, the certificates representing any Warrants Shares issued upon exercise of thisWarrant will bear a restrictive legend in substantially the following form:“THE SECURITIES EVIDENCED BY THIS CERTIFICATE HAVE NOT BEEN REGISTERED UNDERTHE SECURITIES ACT OF 1933, AS AMENDED (THE “SECURITIES ACT”) OR THESECURITIES LAWS OF ANY STATE OR OTHER JURISDICTION. THE SECURITIES MAY NOTBE OFFERED, SOLD OR OTHERWISE TRANSFERRED EXCEPT (1) PURSUANT TO ANEXEMPTION FROM REGISTRATION UNDER THE SECURITIES ACT OR (2) PURSUANT TO ANEFFECTIVE REGISTRATION STATEMENT UNDER THE SECURITIES ACT, IN EACH CASE INACCORDANCE WITH ALL APPLICABLE SECURITIES LAWS OF THE STATES AND OTHERJURISDICTIONS, AND IN THE CASE OF A TRANSACTION EXEMPT FROM REGISTRATION,UNLESS THE COMPANY HAS RECEIVED AN OPINION OF COUNSEL REASONABLYSATISFACTORY TO IT THAT SUCH TRANSACTION DOES NOT REQUIRE REGISTRATION UNDERTHE SECURITIES ACT AND SUCH OTHER APPLICABLE LAWS.”     For purposes of clarity, Warrants Shares issued upon exercise of this Warrant shall bear therestrictive legend provided in this Section 3(c) until the Holder is ready to sell or otherwisetransfer such shares under Registration Statement.          (d) If the Company shall fail for any reason or for no reason to issue to the Holder (at anaddress in the United States specified by the Holder) within five (5) Trading Daysafter the date the Warrant is validly exercised by payment to the Company of the ExercisePrice, delivery of the required documentation and payment of all taxes required to be paid by theHolder, if any, pursuant to Section 5 hereof (a “Valid Exercise”), a certificate for thenumber of Warrant Shares to which the Holder is entitled and register such Warrant Shares on
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the Company’s share register or instruct its transfer agent to register in book entry form the numberof Warrant Shares to which the Holder is entitled or to credit the Holder’s balance account withthe Depository Trust Company (“DTC”) for such number of Warrant Shares to which the Holderis entitled upon the Holder’s exercise of this Warrant, then, in addition to all other remediesavailable to the Holder, the Company shall pay in cash to the Holder on each day after such third(3rd) Trading Day that the issuance of such shares of Common Stock is not timely effected an amountequal to 2.0% of the product of (A) the number of Warrant Shares not issued to the Holder on atimely basis and to which the Holder is entitled and (B) the closing sale price of the Common Stockon the Trading Day immediately preceding the last possible date which the Company could have issuedsuch Warrant Shares to the Holder without violating this Section 3(e) hereof (the “DeliveryDate Price”); provided, however, that in no event shall the Company beobligated to pay damages pursuant to this sentence in an aggregate amount that exceeds 100% of theDelivery Date Price per Warrant Share. In addition to the foregoing, if within five (5) TradingDays after the date of a Valid Exercise the Company shall fail to issue and deliver a certificateto the Holder (at an address in the United States specified by the Holder) and register suchWarrant Shares on the Company’s share register, or instruct its transfer agent to register in bookentry form the number of Warrant Shares to which the Holder is entitled or credit the Holder’sbalance account with DTC for the number of Warrant Shares to which the Holder is entitled upon theHolder’s exercise hereunder, and if on or after such Trading Day the Holder purchases (in an openmarket transaction or otherwise) shares of Common Stock to deliver in satisfaction of a sale by theHolder of Warrant Shares issuable upon such exercise that the Holder anticipated receiving from theCompany, then the Company shall, within five (5) Trading Days after the Holder’s request promptlyhonor its obligation to deliver to the Holder a certificate or certificates representing suchWarrant Shares and pay cash to the Holder in an amount equal to the excess (if any) of the Holder’stotal purchase price (including brokerage commissions, if any) for the shares of Common Stock sopurchased over the product of (A) such number of shares of Common Stock, times (B) the DeliveryDate Price.     4. No Fractional Shares or Scrip. No fractional shares or scrip representingfractional shares shall be issued upon the exercise of this Warrant. As to any fraction of a sharewhich the Holder would otherwise be entitled to purchase upon such exercise, the Company shall paya cash adjustment in respect of such final fraction in an amount equal to such fraction multipliedby the Market Price of one share of the Common Stock for the ten (10) Trading Days immediatelyprior to the date of exercise of this Warrant.     5. Charges, Taxes and Expenses. Issuance of certificates for Warrant Shares shall bemade without charge to the Holder for any issue or transfer tax or other incidental expense inrespect of the issuance of such certificate, all of which taxes and expenses shall be paid by theCompany, and such certificates shall be issued in the name of the Holder or in such name or names(provided the Holder has complied with the restrictions on transfer set forth herein) as may bedirected by the Holder; provided, however, that in the event certificates forWarrant Shares are to be issued in a name other than the name of the Holder, this Warrant whensurrendered for exercise shall be accompanied by the Assignment Form attached hereto dulyexecuted by the Holder; and the Company may require, as a condition thereto, the payment of asum sufficient to reimburse it for any transfer tax incidental thereto.
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     6. Closing of Books. The Company will not close its stockholder books or records inany manner which prevents the timely exercise of this Warrant, pursuant to the terms hereof.     7. Transfer, Division and Combination.          (a) Subject to compliance with any applicable securities laws and the conditions set forth inSections 1 and 7(e) hereof, this Warrant and all rights hereunder are transferable, in whole or inpart, upon surrender of this Warrant at the principal office of the Company, together with awritten assignment of this Warrant substantially in the form attached hereto duly executed by theHolder or its agent or attorney and funds sufficient to pay any transfer taxes payable upon themaking of such transfer. Upon such surrender and, if required, such payment, the Company shallexecute and deliver a new Warrant or Warrants in the name of the assignee or assignees and in thedenomination or denominations specified in such instrument of assignment, and shall issue to theassignor a new Warrant evidencing the portion of this Warrant not so assigned, and this Warrantshall promptly be cancelled. A Warrant, if properly assigned, may be exercised by a new holder forthe purchase of Warrant Shares without having a new Warrant issued.          (b) This Warrant may be divided or combined with other Warrants upon presentation hereof atthe aforesaid office of the Company, together with a written notice specifying the names anddenominations in which new Warrants are to be issued, signed by the Holder or its agent orattorney. Subject to compliance with Section 7(a) hereof, as to any transfer which may be involvedin such division or combination, the Company shall execute and deliver a new Warrant or Warrants inexchange for the Warrant or Warrants to be divided or combined in accordance with such notice.          (c) The Company shall prepare, issue and deliver at its own expense (other than transfertaxes) the new Warrant or Warrants under this Section 7.          (d) The Company agrees to maintain, at its aforesaid office, books for the registration andthe registration of transfer of the Warrants.          (e) Prior to, and as a condition of, any transfer of this Warrant, the Holder or transferee ofthis Warrant, as the case may be must (i) furnish to the Company a written opinion of counsel(which opinion shall be reasonably acceptable to the Company and in form, substance and scopecustomary for opinions of counsel in comparable transactions) to the effect that such transfer maybe made without registration under the Securities Act and under applicable state securities or bluesky laws, (ii) execute and deliver to the Company an investment letter in form and substancereasonably acceptable to the Company and (iii) qualify as an “accredited investor” as defined inRule 501(a) promulgated under the Securities Act.     8. No Rights as Stockholder until Exercise. This Warrant does not entitle the Holderto any voting rights or other rights as a stockholder of the Company prior to the exercise hereof.Upon the surrender of this Warrant and the payment of the aggregate Exercise Price, the WarrantShares so purchased shall be and be deemed to be issued to such Holder as therecord owner of such shares as of the close of business on the later of the date of suchsurrender or payment.
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     9. Loss, Theft, Destruction or Mutilation of Warrant. The Company covenants that uponreceipt by the Company of evidence reasonably satisfactory to it of the loss, theft, destruction ormutilation of this Warrant or any stock certificate relating to the Warrant Shares, and in case ofloss, theft or destruction, of indemnity or security reasonably satisfactory to it (which, in thecase of the Warrant, shall not include the posting of any bond), and upon surrender andcancellation of such Warrant or stock certificate, if mutilated, the Company will make and delivera new Warrant or stock certificate of like tenor and dated as of such cancellation, in lieu of suchWarrant or stock certificate.     10. Saturdays, Sundays, Holidays, etc. If the last or appointed day for the taking ofany action or the expiration of any right required or granted herein shall be a Saturday, Sunday ora legal holiday, then such action may be taken or such right may be exercised on the nextsucceeding day not a Saturday, Sunday or legal holiday.     11. Adjustments of Exercise Price and Number of Warrant Shares. The number and kindof securities purchasable upon the exercise of this Warrant and the Exercise Price shall be subjectto adjustment from time to time upon the happening of any of the following. In case the Companyshall (i) pay a dividend in shares of Common Stock or make a distribution in shares of Common Stockto holders of its outstanding Common Stock, (ii) subdivide its outstanding shares of Common Stockinto a greater number of shares, (iii) combine its outstanding shares of Common Stock into asmaller number of shares of Common Stock, or (iv) issue any shares of its capital stock in areclassification of the Common Stock, then the number of Warrant Shares purchasable upon exerciseof this Warrant immediately prior thereto shall be adjusted so that the Holder shall be entitled toreceive the kind and number of Warrant Shares or other securities of the Company which it wouldhave owned or have been entitled to receive had such Warrant been exercised in advance thereof.Upon each such adjustment of the kind and number of Warrant Shares or other securities of theCompany which are purchasable hereunder, the Holder shall thereafter be entitled to purchase thenumber of Warrant Shares or other securities resulting from such adjustment at an Exercise Priceper Warrant Share or other security obtained by multiplying the Exercise Price in effectimmediately prior to such adjustment by the number of Warrant Shares purchasable pursuant heretoimmediately prior to such adjustment and dividing by the number of Warrant Shares or othersecurities of the Company resulting from such adjustment. An adjustment made pursuant to thisparagraph shall become effective immediately after the effective date of such event retroactive tothe record date, if any, for such event.     12. Reorganization, Reclassification, Merger, Consolidation or Disposition of Assets.In case of (i) any capital reorganization or reclassification, (ii) any consolidation or merger towhich the Company is a party other than a merger or consolidation in which the Company is thecontinuing corporation, (iii) any sale or conveyance to another entity of the property of theCompany as an entirety or substantially as an entirety, or (iv) any statutory exchange ofsecurities with another corporation (including any exchange effected in connection with a merger ofa third corporation into the Company) (each, a “Fundamental Transaction”), the Holder ofthis Warrant shall have the right thereafter to receive on the exercise of thisWarrant the kind and amount of securities, cash or other property which the Holder would haveowned or have been entitled to receive immediately after such Fundamental Transaction had thisWarrant been exercised immediately prior to the effective date of such Fundamental
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Transaction and in any such case, if necessary, appropriate adjustment shall be made in the application of theprovisions set forth in Section 11 hereof with respect to the rights and interests thereafter ofthe Holder of this Warrant to the end that the provisions set forth in Section 11 hereof shallthereafter correspondingly be made applicable, as nearly as may reasonably be, in relation to anyshares of stock or other securities or property thereafter deliverable on the exercise of thisWarrant. The above provisions of this Section 12 shall similarly apply to successive FundamentalTransactions. The Company shall require the issuer of any shares of stock or other securities orproperty thereafter deliverable on the exercise of this Warrant to be responsible for all of theagreements and obligations of the Company hereunder. Notice of any such Fundamental Transactionand of said provisions so proposed to be made, shall be mailed to the Holder of this Warrant notless than twenty (20) days prior to such event. A sale of all or substantially all of the assetsof the Company for a consideration consisting primarily of securities shall be deemed aconsolidation or merger for the foregoing purposes.     13. Notice of Adjustment. Whenever the number of Warrant Shares or number or kind ofsecurities or other property purchasable upon the exercise of this Warrant or the Exercise Price isadjusted, as herein provided, the Company shall give notice thereof to the Holder, which noticeshall state the number of Warrant Shares (and other securities or property) purchasable upon theexercise of this Warrant and the Exercise Price of such Warrant Shares (and other securities orproperty) after such adjustment, setting forth a brief statement of the facts requiring suchadjustment and setting forth the computation by which such adjustment was made.     14. Notice of Distribution. If the Board of Directors of the Company shall declareany dividend or other distribution with respect to its Common Stock other than a cash distributionout of earned surplus, the Company shall mail notice thereof to the Holder of this Warrant not lessthan ten (10) days prior to the record date fixed for determining stockholders entitled toparticipate in such dividend or other distribution. Each such written notice shall be sufficientlygiven if addressed to the Holder at the last address of the Holder appearing on the books of theCompany and delivered in accordance with Section 17(d) hereof.     15. Investors Rights Agreement. The Common Stock issuable upon exercise of thisWarrant shall constitute Registrable Securities (as such term is defined in the Investors RightsAgreement of even date herewith between the Holder and the Company (the “Investors RightsAgreement”)). The original Holder of this Warrant, and any valid transferees thereof pursuantto the Investors Rights Agreement, shall be entitled to all of the benefits afforded to a holder ofany Registrable Securities under the Investors Rights Agreement and such holder, by its acceptanceof this Warrant, agrees to be bound by and to comply with the terms and conditions of the InvestorsRights Agreement applicable to the holder as a holder of Registrable Securities.     16. Miscellaneous.          (a) Jurisdiction. This Warrant shall constitute a contract under the laws of theState of Delaware.
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          (b) Restrictions. The Holder acknowledges that the Warrant Shares acquired upon theexercise of this Warrant, if not registered, will have restrictions upon resale imposed by stateand federal securities laws.          (c) Nonwaiver. No course of dealing or any delay or failure to exercise any righthereunder on the part of the Holder shall operate as a waiver of such right or otherwise prejudicethe Holder’s rights, powers or remedies, notwithstanding all rights hereunder terminate on theTermination Date.          (d) Notices. Any notice, request or other document required or permitted to be givenor delivered to the Holder by the Company shall be delivered in accordance with the noticeprovisions of the Note and Warrant Purchase Agreement; provided, that upon any permittedassignment of this Warrant, the assignee shall promptly provide the Company with its contactinformation.          (e) Limitation of Liability. No provision hereof, in the absence of any affirmativeaction by the Holder to exercise this Warrant or purchase Warrant Shares, and no enumeration hereinof the rights or privileges of the Holder, shall give rise to any liability of the Holder for thepurchase price of any Common Stock or as a stockholder of the Company, whether such liability isasserted by the Company or by creditors of the Company.          (f) Successors and Assigns. Subject to applicable securities laws, this Warrant andthe rights and obligations evidenced hereby shall inure to the benefit of and be binding upon thesuccessors of the Company and the successors and permitted assigns of the Holder.          (g) Amendment. This Warrant may be modified or amended or the provisions hereofwaived with the written consent of the Company and the Holder.          (h) Severability. Wherever possible, each provision of this Warrant shall beinterpreted in such manner as to be effective and valid under applicable law, but if any provisionof this Warrant shall be prohibited by or invalid under applicable law, such provision shall beineffective to the extent of such prohibition or invalidity, without invalidating the remainder ofsuch provisions or the remaining provisions of this Warrant.          (i) Headings. The headings used in this Warrant are for the convenience of referenceonly and shall not, for any purpose, be deemed a part of this Warrant.* * *
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     IN WITNESS WHEREOF, the Company has caused this Warrant to be executed by its officerthereunto duly authorized.Dated: February 12, 2008      ARTES MEDICAL, INC.