Exhibit 10.191

EMPLOYMENT AGREEMENT

This EMPLOYMENT AGREEMENT, dated as of August 15, 2002, is by and between James F. Young (the "Executive") and MEDIMMUNE, INC., a Delaware
corporation (the "Company").

The
Company and the Executive hereby agree as follows:

1.Employment.The Company hereby employs the Executive, and the Executive hereby accepts employment by the
Company, upon the terms and conditions hereinafter set forth.

2.Term.Subject to the provisions for earlier termination as herein provided, the employment of the Executive
hereunder will be for the period commencing on the date hereof and ending on the third anniversary of such date. The term of this Agreement shall be automatically extended for an additional year on
each anniversary of the date hereof, unless written notice of non-extension is provided by either party to the other party at least 90 days prior to such anniversary. The period of
the Executive's employment under this Agreement, as it may be terminated or extended from time to time as provided herein, is referred to hereafter as the "Employment Period."

3.Duties and Responsibilities.The Executive will be employed by the Company in the position set forth on Annex
A, a copy of which is attached hereto and the terms of which are incorporated herein by reference. The Executive will faithfully perform the duties and responsibilities of such office, as they may be
assigned from time to time by the Board of Directors of the Company (the "Board") or the Board's designee.

4.Time to be Devoted to Employment.Except for vacation in accordance with the Company's policy in effect from
time to time and absences due to temporary illness, the Executive shall devote full time, attention and energy during the Employment Period to the business of the Company. During the Employment
Period, the Executive will not be engaged in any other business activity which, in the
reasonable judgment of the Board or its designee, conflicts with the duties of the Executive hereunder, whether or not such activity is pursued for gain, profit or other pecuniary advantage.

5.Compensation; Reimbursement.

(a)Base Salary.The Company (or, at the Company's option, any subsidiary or affiliate thereof) will pay to the
Executive an annual base salary of not less than the amount specified as the Initial Base Salary on Annex A, payable semi-monthly. The Executive's base salary shall be reviewed annually by
the Compensation and Stock Committee of the Board ("Compensation Committee") and shall be subject to increase at the option and sole discretion of the Compensation Committee.

(b)Bonus.The Executive shall be eligible to receive, at the sole discretion of the Compensation Committee, an
annual cash bonus based on pre-determined performance standards of the Company.

(c)Benefits; Stock Options.In addition to the salary and cash bonus referred to above, the Executive shall be
entitled during the Employment Period to participate in such employee benefit plans or programs of the Company, and shall be entitled to such other fringe benefits, as are from time to time made
available by the Company generally to employees of the Executive's position, tenure, salary, age, health and other qualifications. Without limiting the generality of the foregoing, the Executive shall
be eligible for such awards, if any, under the Company's stock option plan as shall be granted to the Executive by the Compensation Committee or other appropriate designee of the Board acting in its
sole discretion. The Executive acknowledges and agrees that the Company does not guarantee the adoption or continuance of any particular employee benefit plan or program or other fringe benefit during
the Employment Period, and participation by the Executive in any such plan or program shall be subject to the rules and regulations applicable thereto.

(d)Expenses.The Company will reimburse the Executive, in accordance with the practices in effect from time to
time for other officers or staff personnel of the Company, for all reasonable and necessary traveling expenses and other disbursements incurred by the Executive for or on behalf of the

---

Company in the performance of the Executive's duties hereunder, upon presentation by the Executive to the Company of appropriate vouchers.

6.Death; Disability.If the Executive dies or is incapacitated or disabled by accident, sickness or otherwise,
so as to render the Executive mentally or physically incapable of performing the services required to be performed by the Executive under this Agreement for a period that would entitle the Executive
to qualify for long-term disability benefits under the Company's then-current long-term disability insurance program or, in the absence of such a program, for a
period of 90 consecutive days or longer (such condition being herein referred to as a "Disability"), then (i) in the case of the Executive's death, the Executive's employment shall be deemed to
terminate on the date of the Executive's death or (ii) in the case of a Disability, the Company, at its option, may terminate the employment of the Executive under this Agreement immediately
upon giving the Executive notice to that effect. Disability shall be determined by the Board or the Board's designee. In the case of a Disability, until the Company shall have terminated the
Executive's employment hereunder in accordance with the foregoing, the Executive shall be entitled to receive compensation provided for herein notwithstanding any such physical or mental disability.

7.Termination For Cause.The Company may, with the approval of a majority of the Board, terminate the
employment of the Executive hereunder at any time during the Employment Period for "cause" (such termination being hereinafter called a "Termination for Cause") by giving the Executive notice of such
termination, upon the giving of which such termination will take effect immediately. For purposes of this Agreement, "cause" means (i) the Executive's willful and substantial misconduct,
(ii) the Executive's repeated, after written notice from the Company, neglect of duties or failure to act which can reasonably be expected to affect materially and adversely the business or
affairs of the Company or any subsidiary or affiliate thereof, (iii) the Executive's material breach of any of the agreements contained in Sections 13, 14 or 15 hereof, (iv) the
commission by the Executive of any material fraudulent act with respect to the business and affairs of the Company or any subsidiary or affiliate thereof or (v) the Executive's conviction of
(or plea ofnolo contendereto) a crime constituting a felony.

8.Termination Without Cause.The Company may terminate the employment of the Executive hereunder at any time
without "cause" (such termination being hereinafter called a "Termination Without Cause") by giving the Executive notice of such termination, upon the giving of which such termination will take effect
not later than 30 days from the date such notice is given.

9.Voluntary Termination.Any termination of the employment of the Executive hereunder, otherwise than as a
result of death or Disability, a Termination For Cause, a Termination Without Cause or a termination for Good Reason (as defined below) following a Change in Control (as defined below), will be deemed
to be a "Voluntary Termination." A Voluntary Termination will be deemed to be effective immediately upon such termination.

10.Effect of Termination of Employment.

(a)Voluntary Termination; Termination For Cause.Upon the termination of the Executive's employment hereunder
pursuant to a Voluntary Termination or a Termination For Cause, neither the Executive nor the Executive's beneficiaries or estate will have any further rights or claims against the Company under this
Agreement except the right to receive (i) the unpaid portion of the base salary provided for in Section 5(a) hereof, computed on apro
ratabasis to the date of termination, (ii) payment of his accrued
but unpaid rights in accordance with the terms of any incentive compensation, stock option, retirement, employee welfare or other employee benefit plans or programs of the Company in which the
Executive is then participating in accordance with Sections 5(b) and 5(c) hereof and (iii) reimbursement for any expenses for which the Executive shall not have theretofore been reimbursed as
provided in Section 5(d) hereof.

2

---

(b)Termination Without Cause.Upon the termination of the Executive's employment as a Termination Without
Cause, neither the Executive nor the Executive's beneficiaries or estate will have any further rights or claims against the Company under this Agreement except the right to receive (i) the
payments and other rights provided for in Section 10(a) hereof, (ii) severance payments in the form of semi-monthly payment of the Executive's base salary (as in effect
immediately prior to such termination) and of the Pro-Rata Bonus Amount (as defined below) for a period of 24 months following the effective date of such termination, and
(iii) continuation of the medical benefits coverage to which the Executive is entitled under Section 5(c) hereof over the 24 month period provided in clause (ii) above,
with such coverage to be provided at the same level and subject to the same terms and conditions (including, without limitation, any applicable co-pay obligations of the Executive, but
excluding any applicable tax consequences for the Executive) as in effect from time to time for officers of the Company generally. For the purposes of this Agreement, "Pro-Rata Bonus
Amount" shall mean one-twenty-fourth (1/24th) of the greater of (a) the most recent annual cash bonus paid to the Executive prior to the date of his termination, or (b) the
average of the three most recent annual cash bonuses paid to the Executive prior to the date of his termination. The rights of the Executive and the obligations of the Company under this
Section 10(b) shall remain in full force and effect notwithstanding the expiration of the Employment Period, whether by failure of the Compensation Committee to extend such period or otherwise.

(c)Death and Disability.Upon the termination of the Executive's employment hereunder as a result of death or
Disability, neither the Executive nor the Executive's beneficiaries or estate will have any further rights or claims against the Company under this Agreement except the right to receive (i) the
payments and other rights provided for in Section 10(a) hereof, (ii) a lump-sum payment, within 15 days after the effective date of such termination, equal to the
aggregate amount of the Executive's base salary as in effect immediately prior to such termination that would be payable over a period of 12 months following the effective date of such
termination and (iii) in the case of Disability only, continuation of the medical benefits coverage to which the Executive is entitled under Section 5(c) hereof over the same period with
respect to which the lump-sum payment is calculated under clause (ii) above, with such coverage to be provided at the same level and subject to the same terms and conditions
(including, without limitation, any applicable co-pay obligations of the Executive, but excluding any applicable tax consequences for the Executive) as in effect from time to time for
officers of the Company generally.

(d)Forfeiture of Rights.In the event that, subsequent to termination of employment hereunder, the Executive
(i) breaches any of the provisions of Section 13, 14 or 15 hereof or (ii) directly or indirectly makes or facilitates the making of any adverse public statements or disclosures
with respect to the business or securities of the Company, all payments and benefits to which the Executive may otherwise have been entitled pursuant to Section 10(a), 10(b) or 11 hereof shall
immediately terminate and be
forfeited, and any portion of such amounts as may have been paid to the Executive shall forthwith be returned to the Company.

11.Change in Control Provisions.

(a)Effect of Change in Control.In the event of a Change in Control during the Employment Period, all options
held by the Executive to purchase shares of the Company's stock that are not then vested and exercisable shall become immediately and fully vested and exercisable as of the effective date of the
Change in Control.

(b)Effect of Termination Following Change in Control.In the event of a Change in Control during the Employment
Period and a subsequent termination of the Executive's employment, either by the Company as a Termination Without Cause or by the Executive for Good Reason, whether or not such termination is during
the Employment Period, the Executive shall be entitled to receive (i) the payments and other rights provided in Section 10(a) hereof, (ii) a severance payment in the form a

3

---

cash lump sum, which shall be paid within 15 days of the date of termination, equal to the sum of the Executive's semi-monthly base salary (as in effect immediately prior to such
termination) and the Pro-Rata Bonus Amount (as determined under Section 10(b) above) multiplied by 72 (i.e., that would have been
payable on a semi-monthly basis during the 36 months following such termination), but discounted to present value from the dates such payments would be made if paid on a
semi-monthly basis for such 36 month period, based on the 100% short-term Applicable Federal Rate (compounded annually) under Section 1274(d) of the Internal
Revenue Code of 1986, as amended (the "Code") as in effect at the time of payment, and (iii) continuation of the medical benefits coverage to which the Executive is entitled under
Section 5(c) hereof for a period of 36 months from the date of the Executive's termination of employment, with such coverage to be provided at the same level and subject to the same
terms and conditions (including, without limitation, any applicable co-pay obligations of the Executive, but excluding any applicable tax consequences for the Executive) as in effect from
time to time for officers of the Company generally. In addition, upon any such Termination Without Cause or for Good Reason that occurs within six months following the effective date of a Change in
Control, the Executive shall retain the right to exercise any options to purchase shares of the Company's stock until the earlier of (a) 36 months following the date of such termination
or (b) the expiration of the original full term of each such option.

(c)Definition of Change in Control.For purposes of this Agreement, a "Change in Control" shall be deemed to
have occurred upon:



4

---



(c)Good Reason Following Change in Control.For purposes of this Agreement, termination for "Good Reason" shall
mean termination by the Executive of his employment with the Company, within six months immediately following a Change in Control, based on:



12.Parachute Tax Indemnity

(a)  If
it shall be determined that any amount paid, distributed or treated as paid or distributed by the Company to or for the Executive's benefit (whether paid or payable
or distributed or distributable pursuant to the terms of this Agreement or otherwise, but determined without regard to any additional payments required under this Section 12) (a "Payment")
would be subject to the excise tax imposed by Section 4999 of the Code, or any interest or penalties are incurred by the Executive with respect to such excise tax (such excise tax, together
with any such interest and penalties, being hereinafter collectively referred to as the "Excise Tax"), then the Executive shall be entitled to receive an additional payment (a "Gross-Up
Payment") in an amount such that after payment by the Executive of all federal, state and local taxes (including any interest or penalties imposed with respect to such taxes), including, without
limitation, any income taxes (and any interest and penalties imposed with respect thereto) and Excise Tax imposed upon the Gross-Up Payment, the Executive retains an amount of the
Gross-Up Payment equal to the Excise Tax imposed upon all the Payments.

(b)  All
determinations required to be made under this Section 12, including whether and when a Gross-Up Payment is required and the amount of such
Gross-Up Payment and the assumptions to be utilized in arriving at such determination, shall be made by a nationally recognized accounting firm as may be designated by the Executive (the
"Accounting Firm") which shall provide detailed supporting calculations both to the Company and the Executive within 15 business days of the receipt of notice from the Executive that there has been a
Payment, or such earlier time as is requested by the Company. In the event that the Accounting Firm is serving as accountant or auditor for the individual, entity or group effecting the change in
control, the Executive shall appoint another nationally recognized accounting firm to make the determinations required hereunder (which accounting firm shall then be referred to as the Accounting Firm
hereunder). All fees and expenses of the Accounting Firm shall be borne by the Company. Any Gross-Up Payment, as determined pursuant to this Section 12, shall be paid by the Company
to the Executive within five days of the receipt of the Accounting Firm's determination. Any determination by the Accounting Firm shall be binding upon the Company and the Executive. As a result of
the uncertainty in the application of Section 4999 of the Code at the time of the initial determination by the Accounting Firm hereunder, it is possible that Gross-Up Payments which
will not have been made by the Company should have been made ("Underpayment"), consistent with the calculations required to be made hereunder. In the event that the Company exhausts its remedies
pursuant to this Section 12 and the Executive thereafter is required to make a payment of any Excise Tax, the Accounting Firm shall determine the amount of the Underpayment that has occurred
and any such Underpayment shall be promptly paid by the Company to or for the Executive's benefit.

5

---

(c)  The
Executive shall notify the Company in writing of any claim by the Internal Revenue Service that, if successful, would require the payment by the Company of the
Gross-Up Payment. Such notification shall be given as soon as practicable but no later then ten business days after the Executive is informed in writing of such claim and shall apprise the
Company of the nature of such claim and the date on which such claim is requested to be paid. The Executive shall not pay such claim prior to the expiration of the 30-day period following
the date on which it gives such notice to the Company (or such shorter period ending on the date that any payment of taxes with respect to such claim is due). If the Company notifies the Executive in
writing prior to the expiration of such period that it desires to contest such claim, the Executive shall:



(d)  If,
after the Executive's receipt of an amount advanced by the Company pursuant to this Section 12, the Executive becomes entitled to receive any refund with
respect to such claim, the Executive shall (subject to the Company's complying with the requirements of this Section 12) promptly pay to the Company the amount of such refund (together with any
interest paid or credited thereon after taxes applicable thereto). If, after the Executive's receipt of an amount advanced by the Company pursuant to this Section 12, a determination is made
that the Executive shall not be entitled to any refund with respect to such claim and the Company does not notify the Executive in writing of its intent to contest such denial of refund prior to the
expiration of 30 days after such determination, then such advance shall be forgiven and shall not be required to be repaid and the amount of such advance shall offset, to the extent thereof,
the amount of Gross-Up Payment required to be paid.

6

---

(e)  The
foregoing provisions of this Section 12 are intended to supersede the provisions of Section 7(d) of the Company's 1991 Stock Option Plan as applied to
the Executive.

13.Disclosure of Information.The Executive will not, at any time during or after the Employment Period,
disclose to any person, firm, corporation or other business entity, except as required by law, any non-public information concerning the business, products, clients or affairs of the
Company or any subsidiary or affiliate thereof for any reason or purpose whatsoever, nor will the Executive make use of any of such non-public information for personal purposes or for the
benefit of any person, firm, corporation or other business entity except the Company or any subsidiary or affiliate thereof.

14.Restrictive Covenant.(a) The Executive hereby acknowledges and recognizes that, during the
Employment Period, the Executive will be privy to trade secrets and confidential proprietary information critical to the Company's business and the Executive further acknowledges and recognizes that
the Company would find it extremely difficult or impossible to replace the Executive and, accordingly, the Executive agrees that, in consideration of the benefits to be received by the Executive
hereunder, the Executive will not, from and after the date hereof until the first anniversary of the termination of the Employment Period (or six months after the termination of the Employment Period
if such termination is as a result of a termination for Good Reason following a Change in Control), (i) directly or indirectly engage in the development, production, marketing or sale of
products that compete (or, upon commercialization, would compete) with products of the Company or any subsidiary being developed (so long as such development has not been abandoned), marketed or sold
at the time of the Executive's termination (such business or activity being hereinafter called a "Competing Business") whether such engagement shall be as an officer, director, owner, employee,
partner, affiliate or other participant in any Competing Business, (ii) assist others in engaging in any Competing Business in the manner described in the foregoing clause (i), or
(iii) induce other employees of the Company or any subsidiary thereof to terminate their employment with the Company or any subsidiary thereof or engage in any Competing Business.
Notwithstanding the foregoing, the term "Competing Business"
shall not include any business or activity that was not conducted by the Company or an subsidiary prior to the effective date of a Change in Control.

(b)  The
Executive understands that the foregoing restrictions may limit the ability of the Executive to earn a livelihood in a business similar to the business of the
Company, but nevertheless believes that the Executive has received and will receive sufficient consideration and other benefits, as an employee of the Company and as otherwise provided hereunder, to
justify such restrictions which, in any event (given the education, skills and ability of the Executive), the Executive believes would not prevent the Executive from earning a living.

15.Company Right to Inventions.The Executive will promptly disclose, grant and assign to the Company, for its
sole use and benefit, any and all inventions, improvements, technical information and suggestions relating in any way to the business of the Company or an subsidiary which the Executive may develop or
acquire during the Employment Period (whether or not during usual working hours), together with all patent applications, letters patent, copyrights and reissues thereof that may at any time be granted
for or upon any such invention, improvement or technical information. In connection therewith:



7

---



16.Enforcement.It is the desire and intent of the parties hereto that the provisions of this Agreement be
enforceable to the fullest extent permissible under the laws and public policies applied in each jurisdiction in which enforcement is sought. Accordingly, to the extent that a restriction contained in
this Agreement is more restrictive than permitted by the laws of any jurisdiction where this Agreement may be subject to review and interpretation, the terms of such restriction, for the purpose only
of the operation of such restriction in such jurisdiction, will be the maximum restriction allowed by the laws of such jurisdiction and such restriction will be deemed to have been revised accordingly
herein.

17.Remedies; Survival.(a) The Executive acknowledges and understands that the provisions of the
covenants contained in Sections 13, 14 and 15 hereof, the violation of which cannot be accurately compensated for in damages by an action at law, are of crucial importance to the Company, and that the
breach or threatened breach of the provisions of this Agreement would cause the Company irreparable harm. In the event of a breach or threatened breach by the Executive of the provisions of
Section 13, 14 or 15 hereof, the Company will be entitled to an injunction restraining the Executive from such breach. Nothing herein contained will be construed as prohibiting the Company from
pursuing any other remedies available for any breach or threatened breach of this Agreement.

(b)  Notwithstanding
anything contained in this Agreement to the contrary, the provisions of Sections 10(b), 13, 14, 15, 16 and 17 hereof will survive the expiration or other
termination of this Agreement until, by their terms, such provisions are no longer operative.

18.Notices.Notices and other communications hereunder will be in writing and will be delivered personally or
sent by air courier or first class certified or registered mail, return receipt requested and postage prepaid, addressed as follows:

|if to the Executive:   |  | as specified in Annex A                                                                                  
|---------------------- |  | ---------------------------------------------------------------------------------------------------------
|and if to the Company: |  | MedImmune, Inc.
35 West Watkins Mill Road
Gaithersburg, Maryland 20878
Attention: Chief Executive Officer
|with a copy to:        |  | Frederick W. Kanner, Esq.
Dewey Ballantine LLP
1301 Avenue of the Americas
New York, NY 10019            

All
notices and other communications given to any party hereto in accordance with the provisions of this Agreement will be deemed to have been given on the date of delivery, if personally delivered;
on the business day after the date when sent, if sent by air courier; and on the third business day after the date when sent, if sent by mail, in each case addressed to such party as provided in this
Section 18 or in accordance with the latest unrevoked direction from such party.

19.Binding Agreement; Benefit.The provisions of this Agreement will be binding upon, and will inure to the
benefit of, the respective heirs, legal representatives and successors of the parties hereto.

8

---

20.Governing Law.This Agreement will be governed by and enforceable in accordance with the laws of the State
of Maryland applicable to contracts executed and performed within such state, without giving effect to the principles of conflict of laws thereof. The Company and the Executive agree that any claims
concerning the rights and obligations of the parties or any other issue arising under this Agreement shall be brought in the Circuit Court for Montgomery County or the United States District Court for
the District of Maryland, and that such courts shall have exclusive jurisdiction over litigation involving any such claims. The Company and the Executive agree to submit to the jurisdiction of such
courts and that they will not raise lack of personal jurisdiction or inconvenient forum as defenses in any such litigation.

21.Waiver of Breach.The waiver by either party of a breach of any provision of this Agreement by the other
party must be in writing and will not operate or be construed as a waiver of any subsequent breach by such other party.

22.Entire Agreement; Amendments.This Agreement (including Annex A) contains the entire agreement
between the parties with respect to the subject matter hereof and supersedes all prior agreements or understandings among the parties with respect thereto. This Agreement may be amended only by an
agreement in writing signed by the parties hereto.

23.Headings.The section headings contained in this Agreement are for reference purposes only and will not
affect in any way the meaning or interpretation of this Agreement.

24.Severability.Any provision of this Agreement that is prohibited or unenforceable in any jurisdiction will,
as to such jurisdiction, be ineffective to the extent of such prohibition or unenforceability without invalidating the remaining provisions hereof, and any such prohibition or unenforceability in any
jurisdiction will not invalidate or render unenforceable such provision in any other jurisdiction.

25.Assignment.This Agreement is personal in its nature and the parties hereto shall not, without the consent
of the other, assign or transfer this Agreement or any rights or obligations hereunder;provided,that the provisions hereof (including, without
limitation, Sections 13, 14 and 15) will inure to the benefit of, and be binding upon, each successor of the Company, whether by merger, consolidation, transfer of all or substantially all of
its assets or otherwise.

IN
WITNESS WHEREOF, the parties have duly executed this Agreement as of the date first above written.

|EXECUTIVE          |  | MEDIMMUNE, INC.      
|------------------ |  | ---------------------
|/s/ James F. Young |  | By: /s/ David M. Mott

9

---

QuickLinks