**Exhibit 10.5**

**SEPRACOR INC.**

Executive Retention Agreement

THIS EXECUTIVERETENTION AGREEMENT by and between Sepracor Inc., a Delaware corporation (the“Company”), and Andrew I. Koven (the “Executive”) is made as March 1, 2007 (the“Effective Date”).

WHEREAS, theCompany recognizes that, as is the case with many publicly-held corporations,the possibility of a change in control of the Company exists and that suchpossibility, and the uncertainty and questions which it may raise among keypersonnel, may result in the departure or distraction of key personnel to thedetriment of the Company and its stockholders, and

WHEREAS, the Boardof Directors of the Company (the “Board”) has determined that appropriate stepsshould be taken to reinforce and encourage the continued employment anddedication of the Company’s key personnel without distraction from thepossibility of a change in control of the Company and related events andcircumstances.

NOW, THEREFORE, asan inducement for and in consideration of the Executive remaining in itsemploy, the Company agrees that the Executive shall receive the severancebenefits set forth in this Agreement (including a certain “gross up” paymentoriginally authorized by the Board on February 25, 1999 and set forth inSection 4.3 of this Agreement) in the event the Executive’s employment with theCompany is terminated under the circumstances described below subsequent to aChange in Control (as defined in Section 1.1).

# 1.                                       KeyDefinitions.

As used herein,the following terms shall have the following respective meanings:

## 1.1                                 “Change in Control” means an event oroccurrence set forth in any one or more of subsections (a) through (d) below(including an event or occurrence that constitutes a Change in Control underone of such subsections but is specifically exempted from another suchsubsection):

#### (a)                                  the acquisition by an individual, entity orgroup (within the meaning of Section 13(d)(3) or 14(d)(2) of the SecuritiesExchange Act of 1934, as amended (the “Exchange Act”)) (a “Person”) of beneficialownership of any capital stock of the Company if, after such acquisition, suchPerson beneficially owns (within the meaning of Rule 13d-3 promulgated underthe Exchange Act) 30%****or more of either (x) thethen-outstanding shares of common stock of the Company (the “OutstandingCompany Common Stock”) or (y) the combined voting power of the then-outstandingsecurities of the Company entitled to vote generally in the election ofdirectors (the “Outstanding Company Voting Securities”); provided, however,that for purposes of this subsection (a), the following acquisitions shall notconstitute a Change in Control: (i) any acquisition directly from the Company(excluding an acquisition pursuant to the exercise, conversion or exchange ofany security exercisable for, convertible into or exchangeable for common stockor voting securities of the Company, unless the Person

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#### exercising, converting or exchanging such security acquired suchsecurity directly from the Company or an underwriter or agent of the Company),(ii) any acquisition by the Company, (iii) any acquisition by any employeebenefit plan (or related trust) sponsored or maintained by the Company or anycorporation controlled by the Company, or (iv) any acquisition by anycorporation pursuant to a transaction which complies with clauses (i) and (ii)of subsection (c) of this Section 1.1; or

#### (b)                                 such time as the Continuing Directors (asdefined below) do not constitute a majority of the Board (or, if applicable,the Board of Directors of a successor corporation to the Company), where theterm “Continuing Director” means at any date a member of the Board (i) who wasa member of the Board on the date of the execution of this Agreement or (ii)who was nominated or elected subsequent to such date by at least a majority ofthe directors who were Continuing Directors at the time of such nomination orelection or whose election to the Board was recommended or endorsed by at leasta majority of the directors who were Continuing Directors at the time of such nominationor election; provided, however, that there shall be excluded fromthis clause (ii) any individual whose initial assumption of office occurred asa result of an actual or threatened election contest with respect to theelection or removal of directors or other actual or threatened solicitation ofproxies or consents, by or on behalf of a person other than the Board; or

#### (c)                                  the consummation of a merger, consolidation,reorganization, recapitalization or statutory share exchange involving theCompany or a sale or other disposition of all or substantially all of theassets of the Company in one or a series of transactions (a “BusinessCombination”), unless, immediately following such Business Combination, each ofthe following two conditions is satisfied: (i) the beneficial owners of all orsubstantially all of the Outstanding Company Common Stock and OutstandingCompany Voting Securities immediately prior to such Business Combinationbeneficially own, directly or indirectly, more than 50% of the then-outstandingshares of common stock and the combined voting power of the then-outstandingsecurities entitled to vote generally in the election of directors,respectively, of the resulting or acquiring corporation in such BusinessCombination (which shall include, without limitation, a corporation which as aresult of such transaction owns the Company or substantially all of theCompany’s assets either directly or through one or more subsidiaries) (suchresulting or acquiring corporation is referred to herein as the “AcquiringCorporation”) in substantially the same proportions as their ownership,immediately prior to such Business Combination, of the Outstanding CompanyCommon Stock and Outstanding Company Voting Securities, respectively; and (ii)no Person (excluding the Acquiring Corporation or any employee benefit plan (orrelated trust) maintained or sponsored by the Company or by the AcquiringCorporation) beneficially owns, directly or indirectly, 30%****or more of the then outstanding shares ofcommon stock of the Acquiring Corporation, or of the combined voting power ofthe then-outstanding securities of such corporation entitled to vote generallyin the election of directors (except to the extent that such ownership existedprior to the Business Combination); or

#### (d)                                 approval by the stockholders of the Companyof a complete liquidation or dissolution of the Company.

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## 1.2                                 “Change in Control Date” means thefirst date during the Term (as defined in Section 2) on which a Change inControl occurs.  Anything in thisAgreement to the contrary notwithstanding, if (a) a Change in Controloccurs, (b)  the Executive’s employment with the Company is terminatedprior to the date on which the Change in Control occurs, and (c) either(i) such termination of employment (x) was at the request of a third party whohas taken steps reasonably calculated to effect a Change in Control or (y)otherwise arose in connection with or in anticipation of a Change in Control,or (ii) such termination of employment occurs following the execution of adefinitive agreement for such Change in Control, then for all purposes of thisAgreement the “Change in Control Date” shall mean the date immediately prior tothe date of such termination of employment.

## 1.3                                 “Cause” means:

#### (a)                                  the Executive’s willful and continued failureto substantially perform his reasonable assigned duties (other than any suchfailure resulting from incapacity due to physical or mental illness or anyfailure after the Executive gives notice of termination for Good Reason and GoodReason exists), which failure is not cured within 30 days after a writtendemand for substantial performance is received by the Executive from the Boardof Directors of the Company which specifically identifies the manner in whichthe Board of Directors believes the Executive has not substantially performedthe Executive’s duties;

#### (b)                                 the Executive’s willful engagement in illegalconduct or gross misconduct which is materially and demonstrably injurious tothe Company; or

#### (c)                                  a material breach by the Executive of Section6 or 7 of the Employment Agreement between the Company and the Executive ofeven date herewith (the “Employment Agreement”).

For purposes ofthis Section 1.3, no act or failure to act by the Executive shall be considered“willful” unless it is done, or omitted to be done, in bad faith and withoutreasonable belief that the Executive’s action or omission was in the bestinterests of the Company.

## 1.4                                 “Good Reason” means the occurrence,without the Executive’s written consent, of any of the events or circumstancesset forth in clauses (a) through (f) below. Notwithstanding the occurrence of any such event or circumstance, suchoccurrence shall not be deemed to constitute Good Reason if, prior to the Dateof Termination specified in the Notice of Termination (each as defined inSection 3.2(a)) given by the Executive in respect thereof, such event orcircumstance has been fully corrected and the Executive has been reasonablycompensated for any losses or damages resulting therefrom (provided that suchright of correction by the Company shall only apply to the first Notice ofTermination for Good Reason given by the Executive).

#### (a)                                  the assignment to the Executive of dutiesinconsistent in any material respect with the Executive’s position (includingstatus, offices, titles or reporting requirements), authority orresponsibilities in effect immediately prior to the earliest to occur of(i) the Change in Control Date, (ii) the date of the execution by theCompany of the initial written agreement or instrument providing for the Changein Control or (iii) the date of the

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#### adoption by the Board of Directors of a resolution providing for theChange in Control (with the earliest to occur of such dates referred to hereinas the “Measurement Date”), or any other action or omission by the Companywhich results in a material diminution in such position, authority orresponsibilities;

#### (b)                                 a reduction in the Executive’s annual basesalary or bonus eligibility as in effect on the Measurement Date or as the samewas or may be increased thereafter from time to time;

#### (c)                                  the failure by the Company to (i) continue ineffect any material compensation or benefit plan or program (including withoutlimitation any life insurance, medical, health and accident or disability planand any vacation or automobile program or policy) (a “Benefit Plan”) in whichthe Executive participates or which is applicable to the Executive immediatelyprior to the Measurement Date, unless an equitable arrangement (embodied in anongoing substitute or alternative plan) has been made with respect to such planor program, (ii) continue the Executive’s participation therein (or in suchsubstitute or alternative plan) on a basis not materially less favorable, interms of the amount of benefits provided, than the basis existing immediatelyprior to the Measurement Date or (iii) award cash bonuses to the Executive inamounts and in a manner substantially consistent with past practice in light ofthe Company’s financial performance;

#### (d)                                 a change by the Company in the location atwhich the Executive performs his principal duties for the Company to a newlocation that increases the Executive’s daily commute by more than 40 miles (asmeasured immediately prior to the Measurement Date); or a requirement by theCompany that the Executive travel on Company business to a substantiallygreater extent than required immediately prior to the Measurement Date;

#### (e)                                  the failure of the Company to obtain theagreement from any successor to the Company to assume and agree to perform thisAgreement, as required by Section 6.1; or

#### (f)                                    any failure of the Company to pay or provideto the Executive any portion of the Executive’s compensation or benefits dueunder any Benefit Plan within seven days of the date such compensation orbenefits are due, or any material breach by the Company of this Agreement orany employment agreement with the Executive.

The Executive’sright to terminate his employment for Good Reason shall not be affected by hisincapacity due to physical or mental illness.

## 1.5                                 “Disability” means the Executive’sabsence from the full-time performance of the Executive’s duties with theCompany for 180 consecutive calendar days as a result of incapacity due tomental or physical illness which is determined to be total and permanent by aphysician selected by the Company or its insurers and acceptable to theExecutive or the Executive’s legal representative.

# 2.               Termof Agreement.  This Agreement, andall rights and obligations of the parties hereunder, shall take effect upon theEffective Date and shall expire upon the first to occur of (a) the expirationof the Term (as defined below) if a Change in Control has not occurred duringthe

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# Term, (b) thetermination of the Executive’s employment with the Company prior to the Changein Control Date, (c) the date 24 months after the Change in Control Date,if the Executive is still employed by the Company as of such later date (unlessthe Company has provided notice of termination of Executive’s employment withinsuch 24 month period in which case the Agreement shall expire on thetermination of the Executive’s employment with the Company), or (d) thefulfillment by the Company of all of its obligations under Sections 4 and5.2 and 5.3****if the Executive’semployment with the Company terminates within 24 months (or after 24 months ifthe Company provides notice to the Executive of termination of his employmentwithin such 24 month period) following the Change in Control Date.  “Term” shall mean the period commencing as ofthe Effective Date and continuing in effect through March 1, 2010; provided,however, that commencing on March 1, 2010 and each March 1 thereafter, the Termshall be automatically extended for one additional year unless, not later than90 days prior to the scheduled expiration of the Term (or any extensionthereof), the Company shall have given the Executive written notice that theTerm will not be extended.

# 3.               EmploymentStatus; Termination Following Change in Control.

## 3.1                                 Not an Employment Contract.  TheExecutive acknowledges that this Agreement does not constitute a contract ofemployment or impose on the Company any obligation to retain the Executive asan employee and that this Agreement does not prevent the Executive fromterminating employment at any time.  Ifthe Executive’s employment with the Company terminates for any reason andsubsequently a Change in Control shall occur, the Executive shall not beentitled to any benefits hereunder except as otherwise provided pursuant toSection 1.2.

## 3.2                                 Termination of Employment.

#### (a)                                  If the Change in Control Date occurs duringthe Term, any termination of the Executive’s employment by the Company or bythe Executive within 24 months following the Change in Control Date (other thandue to the death of the Executive) shall be communicated by a written notice tothe other party hereto (the “Notice of Termination”), given in accordance withSection 7.  Any Notice ofTermination shall: (i) indicate the specific termination provision (if any) ofthis Agreement relied upon by the party giving such notice, (ii) to the extentapplicable, set forth in reasonable detail the facts and circumstances claimedto provide a basis for termination of the Executive’s employment under theprovision so indicated and (iii) specify the Date of Termination (as definedbelow).  The effective date of anemployment termination (the “Date of Termination”) shall be the close ofbusiness on the date specified in the Notice of Termination (which date may notbe less than 15 days or more than 45 days after the date of delivery of suchNotice of Termination), in the case of a termination other than one due to theExecutive’s death, or the date of the Executive’s death, as the case maybe.  In the event the Company fails tosatisfy the requirements of Section 3.2(a) regarding a Notice of Termination,the purported termination of the Executive’s employment pursuant to such Noticeof Termination shall not be effective for purposes of this Agreement.

#### (b)                                 The failure by the Executive or the Companyto set forth in the Notice of Termination any fact or circumstance whichcontributes to a showing of Good Reason or Cause shall not waive any right ofthe Executive or the Company, respectively, hereunder or

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#### preclude the Executive or the Company, respectively, from asserting anysuch fact or circumstance in enforcing the Executive’s or the Company’s rightshereunder.

#### (c)                                  Any Notice of Termination for Cause given bythe Company must be given within 90 days of the occurrence of the event(s) orcircumstance(s) which constitute(s) Cause. Prior to any Notice of Termination for Cause being given (and prior toany termination for Cause being effective), the Executive shall be entitled toa hearing before the Board of Directors of the Company at which he may, at hiselection, be represented by counsel and at which he shall have a reasonableopportunity to be heard.  Such hearingshall be held on not less than 15 days prior written notice to the Executivestating the Board of Directors’ intention to terminate the Executive for Causeand stating in detail the particular event(s) or circumstance(s) which theBoard of Directors believes constitutes Cause for termination.

#### (d)                                 Any Notice of Termination for Good Reasongiven by the Executive must be given within 90 days of the occurrence of theevent(s) or circumstance(s) which constitute(s) Good Reason.

# 4.               Benefitsto Executive.

## 4.1                                 Stock Acceleration.  Ifthe Change in Control Date occurs during the Term, then, effective upon theChange in Control Date, (a) each outstanding option to purchase shares ofCommon Stock of the Company held by the Executive shall vest and becomeimmediately exercisable in full and shares of Common Stock of the Companyreceived upon exercise of any options will no longer be subject to a right ofrepurchase by the Company, (b) each outstanding restricted stock awardshall be deemed to be fully vested and will no longer be subject to a right ofrepurchase by the Company and (c) if the Executive’s employment isthereafter terminated for any reason (other than by the Company for Cause),then each such option (or any option into which such option is converted,exchanged or substituted in connection with the Change in Control) shallcontinue to be exercisable by the Executive (to the extent such option wasexercisable on the Date of Termination) for a period of six months followingthe Date of Termination, notwithstanding any provision in any applicable optionagreement to the contrary; provided however that if stock options heldgenerally by employees of the Company under the stock option or stock incentiveplan under which Executive’s stock option was granted terminate or expire ifnot exercised upon, immediately prior to or otherwise in connection with theChange in Control, such stock option held by Executive shall likewise terminateor expire.

## 4.2                                 Compensation.  Ifthe Change in Control Date occurs during the Term and the Executive’semployment with the Company terminates within 24 months following the Change inControl Date, the Executive shall be entitled to the following benefits:

#### (a)                                  Termination Without Cause or for Good Reason.  Ifthe Executive’s employment with the Company is terminated by the Company (otherthan for Cause, Disability or Death) or by the Executive for Good Reason within24 months following the Change in Control Date, then the Executive shall beentitled to the following benefits:

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##### (i)                                     the Company shall pay to the Executive in alump sum in cash within 30 days after the Date of Termination the aggregate ofthe following amounts:

###### (1)                                  the sum of (A) the Executive’s basesalary through the Date of Termination, (B) the product of (x) theannual bonus paid or payable (including any bonus or portion thereof which hasbeen earned but deferred) for the most recently completed fiscal year and(y) a fraction, the numerator of which is the number of days in thecurrent fiscal year through the Date of Termination, and the denominator ofwhich is 365 and (C) the amount of any compensation previously deferred bythe Executive (together with any accrued interest or earnings thereon) and anyaccrued vacation pay, in each case to the extent not previously paid (the sumof the amounts described in clauses (A), (B), and (C) shall be hereinafterreferred to as the “Accrued Obligations”); and

###### (2)                                  the amount equal to (A) two multipliedby (B) the sum of (x) the Executive’s highest annual base salaryduring the five-year period prior to the Change in Control Date and(y) the Executive’s highest annual bonus during the five-year period priorto the Change in Control Date.

##### (ii)                                  for 24 months after the Date of Termination,or such longer period as may be provided by the terms of the appropriate plan,program, practice or policy, the Company shall continue to provide benefits tothe Executive and the Executive’s family at least equal to those which wouldhave been provided to them if the Executive’s employment had not beenterminated, in accordance with the applicable Benefit Plans in effect on theMeasurement Date or, if more favorable to the Executive and his family, in effectgenerally at any time thereafter with respect to other peer executives of theCompany and its affiliated companies; provided, however, that if theExecutive becomes reemployed with another employer and is eligible to receive aparticular type of benefits (e.g., health insurance benefits) from suchemployer on terms at least as favorable to the Executive and his family asthose being provided by the Company, then the Company shall no longer berequired to provide those particular benefits to the Executive and his family;and

##### (iii)                               to the extent not previously paid or provided, the Company shall timelypay or provide to the Executive any other amounts or benefits required to bepaid or provided or which the Executive is eligible to receive following theExecutive’s termination of employment under any plan, program, policy,practice, contract or agreement of the Company and its affiliated companies(such other amounts and benefits shall be hereinafter referred to as the “OtherBenefits”).

#### (b)                                 Resignation without Good Reason; Terminationfor Death or Disability.  If the Executive voluntarily terminates hisemployment with the Company within 24 months following the Change in ControlDate, excluding a termination for Good Reason, or if the Executive’s employmentwith the Company is terminated by reason of the Executive’s death or Disabilitywithin 24 months following the Change in Control Date, then the Company shall(i) pay the Executive (or his estate, if applicable), in a lump sum incash within 30 days after the Date of Termination, the Accrued Obligations and(ii) timely pay or provide to the Executive the Other Benefits.

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#### (c)                                  Termination for Cause.  Ifthe Company terminates the Executive’s employment with the Company for Causewithin 24 months following the Change in Control Date, then the Company shall(i) pay the Executive, in a lump sum in cash within 30 days after the Dateof Termination, the sum of (A) the Executive’s annual base salary throughthe Date of Termination and (B) the amount of any compensation previouslydeferred by the Executive, in each case to the extent not previously paid, and(ii) timely pay or provide to the Executive the Other Benefits.

## 4.3                                 Taxes.

#### (a)                                  In the event that the Company undergoes a“Change in Ownership or Control” (as defined below), the Company shall, within30 days after each date on which the Executive becomes entitled to receive(whether or not then due) a Contingent Compensation Payment (as defined below)relating to such Change in Ownership or Control, determine and notify theExecutive (with reasonable detail regarding the basis for its determinations)(i) which of the payments or benefits due to the Executive (under thisAgreement or otherwise) following such Change in Ownership or Controlconstitute Contingent Compensation Payments, (ii) the amount, if any, of theexcise tax (the “Excise Tax”) payable pursuant to Section 4999 of the InternalRevenue Code of 1986, as amended (the “Code”), by the Executive with respect tosuch Contingent Compensation Payment and (iii) the amount of the Gross-UpPayment (as defined below) due to the Executive with respect to such ContingentCompensation Payment.  Within 30 daysafter delivery of such notice to the Executive, the Executive shall deliver aresponse to the Company (the “Executive Response”) stating either (A) that heagrees with the Company’s determination pursuant to the preceding sentence or(B) that he disagrees with such determination, in which case he shall indicatewhich payment and/or benefits should be characterized as a ContingentCompensation Payment, the amount of the Excise Tax with respect to suchContingent Compensation Payment and the amount of the Gross-Up Payment due tothe Executive with respect to such Contingent Compensation Payment.  The amount and characterization of any itemin the Executive Response shall be final; provided, however, that in the eventthat the Executive fails to deliver an Executive Response on or before therequired date, the Company’s initial determination shall be final.  Within 90 days after the due date of eachContingent Compensation Payment to the Executive, the Company shall pay to theExecutive, in cash, the Gross-Up Payment with respect to such ContingentCompensation Payment, in the amount determined pursuant to this Section 4.3.

#### (b)                                 For purposes of this Section 4.3, thefollowing terms shall have the following respective meanings:

##### (i)                                     “Change in Ownership or Control” shall mean achange in the ownership or effective control of the Company or in the ownershipof a substantial portion of the assets of the Company determined in accordancewith Section 280G(b)(2) of the Code.

##### (ii)                                  “Contingent Compensation Payment” shall meanany payment (or benefit) in the nature of compensation that is made or madeavailable (under this Agreement or otherwise) to a “disqualified individual”(as defined in Section 280G(c) of the Code) and that is contingent (within themeaning of Section 280G(b)(2)(A)(i) of the Code) on a Change in Ownership orControl of the Company.

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##### (iii)                               “Gross-Up Payment” shall mean an amount equal to the sum of (i) theamount of the Excise Tax payable with respect to a Contingent CompensationPayment and (ii) the amount necessary to pay all additional taxes imposed on(or economically borne by) the Executive (including the Excise Taxes, state andfederal income taxes and all applicable employment taxes) attributable to thereceipt of such Gross-Up Payment.  Forpurposes of the preceding sentence, all taxes attributable to the receipt ofthe Gross-Up Payment shall be computed assuming the application of the maximumtax rates provided by law.

## 4.4                                 Mitigation.  The Executive shall not berequired to mitigate the amount of any payment or benefits provided for in thisSection 4 by seeking other employment or otherwise. Further, except as providedin Section 4.2(a)(ii), the amount of any payment or benefits provided for inthis Section 4 shall not be reduced by any compensation earned by the Executiveas a result of employment by another employer, by retirement benefits, byoffset against any amount claimed to be owed by the Executive to the Company orotherwise.

## 4.5                                 Outplacement Services.  Inthe event the Executive is terminated by the Company (other than for Cause,Disability or Death), or the Executive terminates employment for Good Reason,within 24 months following the Change in Control Date, the Company shallprovide outplacement services through one or more outside firms of theExecutive’s choosing up to an aggregate amount equal to 15 percent of theExecutive’s annual base salary, with such services to extend until the earlierof (i) 12 months following the termination of Executive’s employment or (ii)the date the Executive secures full time employment.

## 4.6                                 Six Month Delay.  Ifany payment, compensation or other benefit provided to the Executive inconnection with his employment termination is determined, in whole or in part,to constitute “nonqualified deferred compensation” within the meaning ofSection 409A and the Executive is a specified employee as defined in Section409A(2)(B)(i), no part of such payments shall be paid before the day that issix (6) months plus one (1) day after the date of his termination (the “NewPayment Date”).  In the case of welfarebenefit continuation, the Company shall use its best efforts to enable Executiveto obtain such benefits at Executive’s expense prior to the New PaymentDate.  The aggregate of any payments thatotherwise would have been paid to the Executive (or on Executive’s behalf)during the period between the date of his termination and the New Payment Dateshall be paid to the Executive in a lump sum on such New Payment Date.  Thereafter, any payments that remainoutstanding as of the day immediately following the New Payment Date shall bepaid without delay over the time period originally scheduled, in accordancewith the terms of this Agreement.

# 5.               Disputes.

## 5.1                                 Settlement of Disputes; Arbitration.  Allclaims by the Executive for benefits under this Agreement shall be directed toand determined by the Board of Directors of the Company and shall be inwriting.  Any denial by the Board ofDirectors of a claim for benefits under this Agreement shall be delivered tothe Executive in writing and shall set forth the specific reasons for thedenial and the specific provisions of this Agreement relied upon.  The Board of Directors shall afford areasonable opportunity to the Executive for a review of the decision denying aclaim.  Any further dispute orcontroversy arising under or in connection with this Agreement shall be settledexclusively by arbitration in Boston, Massachusetts, in

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## accordance with the rules of the American Arbitration Association thenin effect.  Judgment may be entered onthe arbitrator’s award in any court having jurisdiction.

## 5.2                                 Expenses.  The Company agrees to pay as incurred,to the full extent permitted by law, all legal, accounting and other fees andexpenses which the Executive may reasonably incur as a result of any claim orcontest by the Company or others, or any bona fide claim or contest by theExecutive, regarding the validity or enforceability of, or liability under, anyprovision of this Agreement or any guarantee of performance thereof (includingas a result of any contest by the Executive regarding the amount of any paymentor benefits pursuant to this Agreement), plus in each case interest on anydelayed payment at the applicable Federal rate provided for in Section7872(f)(2)(A) of the Code, provided that the Executive shall reimburse any feesand expenses to the extent any such claim or contest is not resolved in favorof the Executive, provided further that notwithstanding the forgoing, theExecutive shall not be required to reimburse any fees and expenses if suchclaim or contest relates to termination by the Executive for Good Reason

## 5.3                                 Compensation During a Dispute.  Ifthe Change in Control Date occurs during the Term and the Executive’semployment with the Company terminates within 24 months following the Change inControl Date, and the right of the Executive to receive benefits underSection 4 (or the amount or nature of the benefits to which he is entitledto receive) are the subject of a dispute between the Company and the Executive,the Company shall continue (a) to pay to the Executive his base salary ineffect as of the Measurement Date and (b) to provide benefits to theExecutive and the Executive’s family at least equal to those which would havebeen provided to them, if the Executive’s employment had not been terminated,in accordance with the applicable Benefit Plans in effect on the MeasurementDate, until such dispute is resolved either by mutual written agreement of theparties or by an arbitrator’s award pursuant to Section 5.1.  Following the resolution of such dispute, thesum of the payments made to the Executive under clause (a) of this Section5.3 shall be deducted from any cash payment which the Executive is entitled toreceive pursuant to Section 4; and if such sum exceeds the amount of thecash payment which the Executive is entitled to receive pursuant toSection 4, the excess of such sum over the amount of such payment shall berepaid (with interest at the applicable Federal rate provided for in Section7872(f)(2)(A) of the Code) by the Executive to the Company within 60 days ofthe resolution of such dispute.

# 6.               Successors.

## 6.1                                 Successor to Company.  TheCompany shall require any successor (whether direct or indirect, by purchase,merger, consolidation or otherwise) to all or substantially all of the businessor assets of the Company expressly to assume and agree to perform this Agreementto the same extent that the Company would be required to perform it if no suchsuccession had taken place.  Failure ofthe Company to obtain an assumption of this Agreement at or prior to theeffectiveness of any succession shall be a breach of this Agreement and shallconstitute Good Reason if the Executive elects to terminate employment, exceptthat for purposes of implementing the foregoing, the date on which any suchsuccession becomes effective shall be deemed the Date of Termination.  As used in this Agreement, “Company” shallmean the Company as defined above and any successor to its business or assetsas aforesaid which assumes and agrees to perform this Agreement, by operationof law or otherwise.

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## 6.2                                 Successor to Executive.  ThisAgreement shall inure to the benefit of and be enforceable by the Executive’spersonal or legal representatives, executors, administrators, successors,heirs, distributees, devisees and legatees. If the Executive should die while any amount would still be payable tothe Executive or his family hereunder if the Executive had continued to live,all such amounts, unless otherwise provided herein, shall be paid in accordancewith the terms of this Agreement to the executors, personal representatives oradministrators of the Executive’s estate.

# 7.               Notice.  All notices, instructions and othercommunications given hereunder or in connection herewith shall be inwriting.  Any such notice, instruction orcommunication shall be sent either (i) by registered or certified mail, returnreceipt requested, postage prepaid, or (ii) prepaid via a reputable nationwideovernight courier service, in each case addressed to the Company, at 111 LockeDrive, Marlborough, MA 01752, and to the Executive at the Executive’s addressindicated on the signature page of this Agreement (or to such other address aseither the Company or the Executive may have furnished to the other in writingin accordance herewith).  Any suchnotice, instruction or communication shall be deemed to have been deliveredfive business days after it is sent by registered or certified mail, returnreceipt requested, postage prepaid, or one business day after it is sent via areputable nationwide overnight courier service. Either party may give anynotice, instruction or other communication hereunder using any other means, butno such notice, instruction or other communication shall be deemed to have beenduly delivered unless and until it actually is received by the party for whomit is intended.

# 8.               Miscellaneous.

## 8.1                                 Employment by Subsidiary.  Forpurposes of this Agreement, the Executive’s employment with the Company shallnot be deemed to have terminated solely as a result of the Executive continuingto be employed by a wholly-owned subsidiary of the Company.

## 8.2                                 Severability.  Theinvalidity or unenforceability of any provision of this Agreement shall notaffect the validity or enforceability of any other provision of this Agreement,which shall remain in full force and effect.

## 8.3                                 Injunctive Relief.  TheCompany and the Executive agree that any breach of this Agreement by theCompany is likely to cause the Executive substantial and irrevocable damage andtherefore, in the event of any such breach, in addition to such other remedieswhich may be available, the Executive shall have the right to specificperformance and injunctive relief.

## 8.4                                 Governing Law.  Thevalidity, interpretation, construction and performance of this Agreement shallbe governed by the internal laws of the Commonwealth of Massachusetts, withoutregard to conflicts of law principles.

## 8.5                                 Waivers.  No waiver by the Executive atany time of any breach of, or compliance with, any provision of this Agreementto be performed by the Company shall be deemed a waiver of that or any otherprovision at any subsequent time.

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## 8.6                                 Counterparts.  ThisAgreement may be executed in counterparts, each of which shall be deemed to bean original but both of which together shall constitute one and the sameinstrument.

## 8.7                                 Tax Withholding.  Anypayments provided for hereunder shall be paid net of any applicable taxwithholding required under federal, state or local law.

## 8.8                                 Entire Agreement.  ThisAgreement, together with the Employment Agreement between the Company and theExecutive of even date herewith, sets forth the entire agreement of the partieshereto in respect of the subject matter contained herein and supersedes allprior agreements, promises, covenants, arrangements, communications,representations or warranties, whether oral or written, by any officer,employee or representative of any party hereto in respect of the subject mattercontained herein.  For the avoidance ofdoubt, except as specifically described herein in Section 4.1, the stockoptions and restricted stock awards held by Executive shall continue to be governedby the applicable stock option or stock incentive plan under which they weregranted or issued (or any successor plan thereto) and any related stock optionor restricted stock agreement, as the same may be amended or modified.

## 8.9                                 Amendments.  This Agreement may be amendedor modified only by a written instrument executed by both the Company and theExecutive.

## 8.10                           Executive’s Acknowledgements.  The Executive acknowledgesthat he: (a) has read this Agreement; (b) has been represented in the preparation,negotiation, and execution of this Agreement by legal counsel of theExecutive’s own choice or has voluntarily declined to seek such counsel; (c)understands the terms and consequences of this Agreement; and (d) understandsthat the law firm of Wilmer Cutler Pickering Hale and Dorr LLP is acting ascounsel to the Company in connection with the transactions contemplated by thisAgreement, and is not acting as counsel for the Executive.

## [Remainder of Page Intentionally Left Blank]

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IN WITNESSWHEREOF, the parties hereto have executed this Agreement as of the day and yearfirst set forth above.
|        | SEPRACOR INC.       |
|--------|---------------------|
|   |                |
|   | By:                 |  /s/ Timothy  J. Barberich |   |
|   |                |
|   | Title:              | Chairman and CEO |   |
|   |                |
|   |                |
|   | /s/ Andrew I. Koven |   |
|   | Andrew I. Koven     |
|   |                |
|   | Address:            |
|   |                |
|   |                |   |
|   |                |
|   |                |   |
|   |                |
|   |                |   |
|        |                     |  |  |  |

 

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