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Exhibit 10.1

Baxter International Inc.
One Baxter Parkway
Deerfield, Illinois 60015

January 11, 2016

Shire plc
5 Riverwalk, Citywest Business Campus
Dublin 24
Republic of Ireland
Attention: Bill Mordan, General Counsel

Baxalta Incorporated
1200 Lakeside Drive
Bannockburn, Illinois 60015
Attention: Peter G. Edwards

Ladies and Gentlemen:

        This letter agreement is entered into on the date first set forth above
by and among Shire plc, a company incorporated in Jersey ("Parent"), Baxalta
Incorporated, a Delaware corporation ("Baxalta"), and Baxter International Inc.,
a Delaware corporation ("Baxter") (this "Letter Agreement"). Reference is made
to that certain Tax Matters Agreement, dated as of June 30, 2015, by and among
Baxter, by and on behalf of itself and each Affiliate of Baxter, and Baxalta, by
and on behalf of itself and each Affiliate of Baxalta (the "Tax Matters
Agreement") and that certain Shareholder's and Registration Rights Agreement,
dated as of June 30, 2015, by and between Baxter and Baxalta (the "Registration
Rights Agreement"). Pursuant to a merger agreement to be entered into among
Parent, BearTracks, Inc., a Delaware corporation, and Baxalta (the "Merger
Agreement"), Parent will, directly or indirectly, acquire all of the outstanding
shares of Baxalta Common Stock (the "Merger"), subject to the satisfaction of
certain closing conditions as described in the Merger Agreement. Capitalized
terms used but not defined herein have the meanings given to them in the Tax
Matters Agreement.

        Parent, Baxalta and Baxter hereby agree as follows:

        1.    Support of Baxter; Waiver of Appraisal Rights.     

        (a)   Baxter hereby consents to the inclusion of a statement, attributed
to its chief executive officer, expressing its support for the Merger in the
form attached hereto as Annex I (the "Baxter Support Statement") in any Baxalta
or Parent press release announcing the entry into the Merger Agreement. Each of
Parent and Baxalta agrees that, except as required by applicable law or in the
discharge of its obligations hereunder, it will not make any public statement
(other than the Baxter Support Statement) of non-public information regarding
Baxter's support for the Merger or any statement regarding Baxter's plans with
respect to, or the anticipated timing or sizing of, any Retained Shares
Transaction (as defined below), in each case, without Baxter's prior consent;
provided that, Parent and Baxalta may publish, make, repeat or otherwise use the
Baxter Support Statement unless and until Baxter objects in writing to the use
thereof.

        (b)   Baxter hereby waives, and agrees not to exercise or assert, any
appraisal rights under applicable law, including Section 262 of the General
Corporation Law of the State of Delaware, in connection with the Merger.

        2.    Opinion Matters.     

        (a)   Immediately prior to the closing of the Merger (the "Merger
Closing"), Baxter shall execute and deliver representation letters (the "Baxter
Closing Representation Letters") to Cravath, Swaine & Moore LLP and KPMG LLP
substantially in the form of the representation letters (the "Baxter Signing
Representation Letters") executed and delivered by Baxter on the date
immediately prior to the date that the Merger Agreement is entered into by
Parent and Baxalta

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(the "Merger Signing Date") with such changes as are necessary to reflect any
changes in facts prior to the Merger Closing.

        (b)   Immediately prior to the Merger Closing, Parent shall execute and
deliver representation letters (the "Parent Closing Representation Letters") to
Cravath, Swaine & Moore LLP and KPMG LLP substantially in the form of the
representation letters (the "Parent Signing Representation Letters") executed
and delivered by Parent on the date immediately prior to the Merger Signing Date
with such changes as are necessary to reflect any changes in facts prior to the
Merger Closing.

        (c)   Immediately prior to the Merger Closing, Baxalta shall execute and
deliver representation letters (the "Baxalta Closing Representation Letters"
and, together with the Baxter Closing Representation Letters and the Parent
Closing Representation Letters, the "Closing Representation Letters") to
Cravath, Swaine & Moore LLP and KPMG LLP substantially in the form of the
representation letters (together with the Baxter Signing Representation Letters
and Parent Signing Representation Letters, the "Signing Representation Letters"
and together with the Closing Representation Letters, the "Representation
Letters") executed and delivered by Baxalta on the date immediately prior to the
Merger Signing Date with such changes as are necessary to reflect any changes in
facts prior to the Merger Closing.

        (d)   Baxter hereby represents and warrants that the Baxter Signing
Opinion (as defined below) has been furnished to Baxter, such that the condition
set forth in Section 2(g)(ii)(A) is satisfied. Baxter shall (i) use its
reasonable best efforts to cause KPMG LLP to deliver the Baxter Closing Opinion
(as defined below) immediately prior to the Merger Closing, such that the
condition set forth below in Section 2(g)(ii)(B) is satisfied and (ii) certify
in writing to Parent and Baxalta immediately upon receipt of such opinion that
such opinion has been furnished. As of the date immediately prior to the Merger
Signing Date, Baxter knows of no reason (x) why it would not be able to deliver
the Baxter Closing Representation Letters, or (y) why it would not be able to
obtain the Baxter Closing Opinion.

        (e)   Parent shall use its reasonable best efforts to cause Cravath,
Swaine & Moore LLP to deliver the Parent Closing Opinion (as defined below)
immediately prior to the Merger Closing, such that the condition set forth below
in Section 2(g)(i)(B) is satisfied. As of the date immediately prior to the
Merger Signing Date, Parent knows of no reason (i) why it would not be able to
deliver the Parent Closing Representation Letters or (ii) why it would not be
able to obtain the Parent Closing Opinion.

        (f)    As of the date immediately prior to the Merger Signing Date,
Baxalta knows of no reason why it would not be able to deliver the Baxalta
Closing Representation Letters.

        (g)   Section 4.02(c) of the Tax Matters Agreement shall be waived with
respect to the Merger Closing if:

          (i)  (A) A tax opinion of Cravath, Swaine & Moore LLP is furnished to
Parent, and a true, correct and complete copy of such opinion is provided to
Baxter and Baxalta, on the date immediately prior to the Merger Signing Date,
and (B) Cravath, Swaine & Moore LLP furnishes a tax opinion to Parent
immediately prior to the Merger Closing that is a tax opinion substantially the
same in form and substance as the opinion referenced in clause (i)(A) (the
"Parent Closing Opinion"), a true, correct and complete copy of which shall be
provided by Parent to Baxter and Baxalta. In each case, such opinion may rely on
the applicable Representation Letters.

         (ii)  (A) A tax opinion of KPMG LLP is furnished to Baxter on the date
immediately prior to the Merger Signing Date (the "Baxter Signing Opinion"), and
(B) KPMG LLP furnishes a tax opinion to Baxter immediately prior to the Merger
Closing that is a tax

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opinion substantially the same in form and substance as the opinion referenced
in clause (ii)(A) above (the "Baxter Closing Opinion"). In each case, such
opinion may rely on the applicable Representation Letters. Neither Baxalta nor
Parent shall (in writing or otherwise) publicly refer to or describe non-public
information regarding the Baxter Signing Opinion or the Baxter Closing Opinion
without the prior written consent of KPMG LLP or Baxter, except that the parties
may disclose this Letter Agreement and describe its terms in any Form 8-K,
registration statement, proxy statement or circular relating to the Merger
Agreement or the Merger.

        (h)   Prior to the earlier of (i) the Merger Closing and (ii) the
termination of the Merger Agreement, each of Parent, Baxalta, and Baxter shall
cooperate in good faith with the reasonable requests of the other parties in
connection with matters related to the opinions referred to in this Section 2
(including the preparation of materials by Parent, Baxalta, Baxter and their
respective agents documenting diligence and other matters related to the
Retained Shares Transactions). From and after the execution of this Letter
Agreement, at such time or times as may be reasonably requested by Baxter, each
of Baxalta and Parent shall use its reasonable best efforts to execute
certificates reasonably requested by Baxter containing appropriate
representations that Baxalta or Parent, as applicable, is, in good faith, able
to make at such time, in connection with KPMG LLP's delivery to Baxter of a tax
opinion or opinions rendered in connection with the initial distribution of
Baxalta Common Stock on July 1, 2015, one or more Debt-for-Equity Exchanges, one
or more Exchange Offers (as defined in the Registration Rights Agreement), one
or more contributions of Retained Shares to Baxter's U.S. pension fund or any
dividend of Retained Shares to Baxter's shareholders. Upon Baxter's reasonable
request, Baxalta (or, after the Merger Closing, Parent) shall use reasonable
best efforts to cause any person who is at the time of such request an executive
officer of such party and who was an executive officer of Baxter prior to the
initial distribution of Baxalta Common Stock on July 1, 2015 to assist Baxter in
confirming such facts as are within the knowledge of such executive officer.
Each party shall make any such requests for cooperation with reasonable advance
notice and under reasonable circumstances so as to minimize any disruption to or
impairment of the applicable party's business.

        (i)    Baxter acknowledges and agrees that Section 4.02(c) of the Tax
Matters Agreement has been waived with respect to the execution of the Merger
Agreement.

        3.    Indemnification and Guarantee.     

        (a)   Notwithstanding anything in the Tax Matters Agreement, the Merger
Agreement or the Distribution Agreement to the contrary,

          (i)  Baxalta agrees that from and after the Merger Closing, subject to
Section 3(b) hereof and clause (ii) below, Baxalta shall indemnify and hold
harmless Baxter and each of its Affiliates and each of their respective
officers, directors and employees from and against, one hundred percent (100%)
of any Tax-Related Losses attributable to or resulting from (in whole or in
part) the Merger; and

         (ii)  Baxalta shall not be obligated to indemnify Baxter for any
Tax-Related Losses attributable to or resulting from (in whole or in part) any
disposition of Baxalta Common Stock by Baxter (including through Debt-for Equity
Exchanges and Subsequent Distributions) other than:

        (A)  the initial distribution of Baxalta Common Stock on July 1, 2015;

        (B)  the transactions described in Section 4 (which for the avoidance of
doubt include one or more Debt-for-Equity Exchanges, one or more Exchange
Offers, one or more contributions of Retained Shares to Baxter's U.S. pension
fund and any dividend of

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Retained Shares to Baxter's shareholders) that in each case conclude prior to
any Parent or Baxalta shareholder vote with respect to the Merger; or

        (C)  the conversion at the Merger Closing of any Retained Shares held by
Baxter into the right to receive Parent American Depositary Shares and cash (it
being understood that any Taxes imposed on Baxter with respect to the receipt of
Parent American Depositary Shares and cash upon the Merger Closing do not
constitute Tax Related Losses subject to indemnification under Section 3(a)(i)).

        Parent also agrees that, from and after the Merger Closing, Parent will
guarantee the payment and performance by Baxalta of its obligations and
agreements under this Letter Agreement, the Tax Matters Agreement, the
Distribution Agreement and the Ancillary Agreements (as defined in the
Distribution Agreement).

        (b)   Notwithstanding anything in the Tax Matters Agreement, the Merger
Agreement, the Distribution Agreement, or this Letter Agreement to the contrary,
if Baxter intentionally misrepresents any fact in either the Baxter Signing
Representation Letters or the Baxter Closing Representation Letters, the
indemnification obligation of Baxalta under Section 3(a) hereof and the
indemnification obligation of Baxalta under Section 4.05 of the Tax Matters
Agreement shall not apply to the extent any Tax-Related Losses are attributable
to or resulting from any such intentional misrepresentations.

        (c)   From and after the Merger Closing, Parent shall be afforded the
same rights and have the same obligations as Baxalta under Section 3.04 of the
Tax Matters Agreement.

        4.    Retained Shares Transactions.     Each of Parent and Baxalta
understands and acknowledges that Baxter (a) intends to effectuate (or cause to
be effectuated) two Debt-for-Equity Exchanges (and related Underwritten
Offerings (as defined in the Registration Rights Agreement)), one Exchange Offer
and a contribution of Retained Shares (as defined in the Registration Rights
Agreement) to Baxter's U.S. pension fund, and (b) may potentially effectuate a
dividend of Retained Shares to Baxter's shareholders, in each case, in
connection with the offer, sale, exchange, placement, transfer, distribution or
other disposition of Baxter's 131,902,719 Retained Shares by Baxter or the then
holders of such shares (each such Debt-for-Equity Exchange and Exchange Offer
(but not, for the avoidance of doubt, any U.S. pension fund contribution or any
dividend of Retained Shares to Baxter's shareholders), a "Retained Shares
Transaction"), in each case, prior to any Parent or Baxalta shareholder vote
with respect to the Merger. Baxter shall use its reasonable best efforts to
complete all Retained Shares Transactions prior to any Parent or Baxalta
shareholder vote with respect to the Merger.

        5.    Cooperation and Support of Parent and Baxalta.     

        (a)   Parent shall cooperate with and support Baxter and Baxalta to
enable Baxalta to comply with the terms of, and fulfill Baxalta's obligations
under, the Registration Rights Agreement, including, without limitation,
Baxalta's obligation to use its reasonable best efforts to prepare and file
Registration Statements (as defined in the Registration Rights Agreement) on an
appropriate form with the Securities Exchange Commission ("SEC") as
expeditiously as possible upon receipt of a Demand Registration (as defined in
the Registration Rights Agreement), it being acknowledged and agreed that Baxter
delivered notice of a Demand Registration on August 10, 2015 and, as of the date
hereof, no Retained Shares have been registered or sold in connection therewith.
Notwithstanding the foregoing or anything to the contrary in the Registration
Rights Agreement (including, without limitation, Section 2.01(b) thereof),
Baxter shall be entitled to make at least three additional Demand Registrations
in connection with the Retained Shares Transactions contemplated hereby.

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        (b)   (i) Baxalta shall use its reasonable best efforts to provide or
update all information on an appropriate registration form under the Securities
Act of 1933, as amended (the "Securities Act"), including, without limitation,
all financial data (including selected financial data or "flash" numbers with
respect to recently completed periods), that (A) the SEC would require in a
registered offering of the Baxalta Common Stock or (B) is reasonably requested
by the underwriter(s) or dealer manager(s) in any Underwritten Offering or
Exchange Offer to ensure compliance with applicable laws (including, without
limitation, disclosure obligations under applicable federal securities laws),
respectively, in connection with each Retained Shares Transaction (collectively,
the "Offering Information"), in each case, as soon as practicable after (x) the
date hereof and (y) each such request by the underwriter(s) or dealer manager(s)
in such Underwritten Offering or Exchange Offer.

        In furtherance of the foregoing, Baxalta shall use its reasonable best
efforts to cause to be prepared:

        (1)   if and to the extent required or requested by the SEC or
reasonably requested by such underwriter(s) or dealer manager(s) to ensure
compliance with applicable laws (including, without limitation, disclosure
obligations under applicable federal securities laws), pro forma financial
statements regarding the Merger prepared in accordance with, or reconciled to,
generally accepted accounting principles in the United States and prepared in
accordance with Regulation S-X under the Securities Act in a Registration
Statement in a form ready for filing with the SEC (collectively, "Pro Forma
Financial Information"):

         (I)  would be required in (x) a Registration Statement that includes
interim financial information of Parent and Baxalta as of and for the nine-month
period ended September 30, 2015, (y) a Registration Statement that includes
annual financial information of Parent and Baxalta as of and for the year ended
December 31, 2015 or (z) a Registration Statement that includes interim
financial information of Parent and Baxalta as of and for the three-month period
ending March 31, 2016, in each case, to be delivered to Baxter and the
underwriter(s) or dealer manager(s), as applicable, by no later than January 25,
2016 (the "First PFFI Deadline") in the case of clause (x), by no later than
March 18, 2016 (the "Second PFFI Deadline") in the case of clause (y), and by no
later than May 12, 2016 (the "Third PFFI Deadline") in the case of clause (z);
or

        (II)  is otherwise required or requested by the SEC or reasonably
requested by such underwriter(s) or dealer manager(s) to ensure compliance with
applicable laws (including, without limitation, disclosure obligations under
applicable federal securities laws), in each case, to be delivered to Baxter and
such underwriter(s) or dealer manager(s) as soon as practicable after such
requirement or request (including, without limitation, requirements or requests
for updated Pro Forma Financial Information).

        (2)   all Baxalta executive compensation disclosure for fiscal year 2015
required to be included in a Registration Statement filed or amended between
January 1, 2016 and December 31, 2016 (x) prepared in accordance with all
applicable rules and regulations of the SEC and (y) delivered to Baxter and such
underwriter(s) or dealer manager(s) (the "Baxalta 2015 ECD") by no later than
January 25, 2016; and

        (3)   Baxalta's Annual Report on Form 10-K for the year ended
December 31, 2015 (the "Baxalta 2015 10-K") to be filed with the SEC by no later
than March 11, 2016 (the "Baxalta 10-K Deadline") and, if less than three
Marketing Periods have been completed as of May 11, 2016, Baxalta's Quarterly
Report on Form 10-Q for the fiscal quarter ending March 31, 2016 (the "Baxalta
2016 Q1 10-Q") to be filed with the SEC by no later than May 12, 2016 (the
"Baxalta Q1 10-Q Deadline").

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         (ii)  Parent shall use its reasonable best efforts to cause to be
prepared:

        (A)  if and to the extent required or requested by the SEC or reasonably
requested by such underwriter(s) or dealer manager(s) to ensure compliance with
applicable laws (including, without limitation, disclosure obligations under
applicable federal securities laws), Pro Forma Financial Information that:

        (1)   would be required in (x) a Registration Statement that includes
interim financial information of Parent and Baxalta as of and for the nine-month
period ended September 30, 2015, (y) a Registration Statement that includes
annual financial information of Parent and Baxalta as of and for the year ended
December 31, 2015 or (z) a Registration Statement that includes interim
financial information of Parent and Baxalta as of and for the three-month period
ending March 31, 2016, in each case, to be delivered to Baxter and the
underwriter(s) or dealer manager(s), as applicable, in any Underwritten Offering
or Exchange Offer by no later than the First PFFI Deadline in the case of
clause (x), by no later than the Second PFFI Deadline in the case of clause (y)
and by no later than the Third PFFI Deadline in the case of clause (z); or

        (2)   is otherwise required or requested by the SEC or reasonably
requested by such underwriter(s) or dealer manager(s) to ensure compliance with
applicable laws (including, without limitation, disclosure obligations under
applicable federal securities laws) to be delivered to Baxter and such
underwriter(s) or dealer manager(s) as soon as practicable after such
requirement or request (including, without limitation, requirements or requests
for updated Pro Forma Financial Information); and

        (B)  Parent's Annual Report on Form 10-K for fiscal year 2015 to be
filed with the SEC by no later than March 11, 2016 and, if less than three
Marketing Periods have been completed as of May 11, 2016, Parent's Quarterly
Report on Form 10-Q for the fiscal quarter ending March 31, 2016 to be filed
with the SEC no later than May 12, 2016.

        Notwithstanding the foregoing, without Parent's prior consent, the
financial information (other than Pro Forma Financial Information) or other
business information (other than information related to the Merger) of Parent
shall not be included in a Registration Statement for an Underwritten Offering
or Exchange Offer in connection with a Retained Shares Transaction unless
required or requested by the SEC.

        (c)   (i) Baxalta shall (A) use its reasonable best efforts to cause its
independent accounting firm to deliver customary "comfort" and bring-down
"comfort" letters (including, without limitation, customary "negative assurance"
comfort) to Baxter and such underwriter(s) or dealer manager(s) in connection
with Baxalta's financial information required to be included in the applicable
Registration Statement, and (B) if reasonably requested by such underwriter(s)
or dealer manager(s), cause its principal financial or accounting officer to
deliver certificate(s) certifying as to the accuracy of Baxalta's financial
information in the applicable Registration Statement as such underwriter(s) or
dealer manager(s) may reasonably request (together with such comfort letters,
the "Baxalta Comfort Documents"), including customary Baxalta Comfort Documents
with respect to any Pro Forma Financial Information required or requested as
provided above to be included in any Registration Statement pursuant to
Section 5(b) hereof and as may be necessary to enable the provision of the
Baxalta Comfort Documents described in subclause (A) above.

         (ii)  Parent shall (A) use its reasonable best efforts to cause its
independent accounting firm to deliver customary "comfort" and bring-down
"comfort" letters (including, without limitation, customary "negative assurance"
comfort) to Baxter and such underwriter(s) or

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dealer manager(s) in connection with Parent's financial information required by
the SEC to be included in the applicable Registration Statement, and (B) if
reasonably requested by such underwriter(s) or dealer manager(s), cause its
principal financial or accounting officer to deliver certificate(s) certifying
as to the accuracy of Parent's financial information required by the SEC to be
included in the applicable Registration Statement as such underwriter(s) or
dealer manager(s) may reasonably request (together with such comfort letters,
the "Parent Comfort Documents"), including customary Parent Comfort Documents
with respect to any Pro Forma Financial Information required or requested as
provided above to be included in any Registration Statement pursuant to
Section 5(b) and as may be necessary to enable the provision of the Parent
Comfort Documents described in subclause (A) above.

        (d)   (i) Baxalta shall use its reasonable best efforts to cause its
senior executive officers (including, without limitation, its chief executive
officer and chief financial officer) and other members of management to
participate at reasonable times and for reasonable periods in any customary due
diligence sessions and "road show" presentations that may be reasonably
requested by the managing underwriter(s) or dealer manager(s), as applicable, in
any Underwritten Offering or Exchange Offer, including, if reasonably requested
by the applicable underwriter(s) or dealer manager(s), in-person participation
of the chief executive officer and chief financial officer of Baxalta in
customary "road show" presentations for not more than two consecutive Business
Days (as defined in the Registration Rights Agreement) during each Marketing
Period (as defined below), at such times and locations as may be reasonably
requested by such underwriter(s) or dealer manager(s), and otherwise to use its
reasonable best efforts to facilitate, cooperate with, and participate in each
Underwritten Offering or Exchange Offer in connection with a Retained Shares
Transaction and customary due diligence and selling efforts related thereto,
except to the extent that such participation materially interferes with the
management of Baxalta's business (collectively, "Required Baxalta Management
Participation").

         (ii)  Parent shall use its reasonable best efforts to cause at least
one senior executive officer familiar with the financial and business affairs of
Parent and the Merger to participate at reasonable times and for reasonable
periods in any customary due diligence sessions and "road show" presentations
that may be reasonably requested by the managing underwriter(s) or dealer
manager(s), as applicable, in any Underwritten Offering or Exchange Offer,
including, if reasonably requested by the applicable underwriter(s) or dealer
manager(s), in-person participation of members of management of Parent in
customary "road show" presentations for not more than two consecutive Business
Days during each Marketing Period (as defined below), at such times and
locations as may be reasonably requested by such underwriter(s) or dealer
manager(s), and otherwise use its reasonable best efforts to facilitate,
cooperate with, and participate in each Underwritten Offering or Exchange Offer
in connection with a Retained Shares Transaction and customary due diligence and
selling efforts related thereto, except to the extent that such participation
materially interferes with the management of Parent's business (collectively,
together with Required Baxalta Management Participation, "Required Management
Participation"). Baxter acknowledges and agrees that any request for
participation by Parent or any Parent executive will take into account due
consideration of efforts Parent has taken and intends to take during the
applicable Marketing Period to promote the Merger.

        (e)   In connection with each Retained Shares Transaction:

          (i)  Baxalta shall use its reasonable best efforts to prepare, assist
in the preparation of, deliver and/or complete all of the following, as
applicable (collectively, the "Baxalta Marketing Period Deliverables") at least
two Business Days prior to the commencement of each Marketing Period: (A) a
preliminary prospectus (including all Offering Information and Pro Forma
Financial Information required or requested to be included therein pursuant to

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Section 5(b) hereof) for the applicable Registration Statement, (B) investor
presentation(s) or other marketing materials, (C) (x) substantially final draft
underwriting agreement(s) or exchange agreement(s), in the case of a
Debt-for-Equity Exchange and the related Underwritten Offering, or
(y) substantially final draft dealer manager agreement(s), and related
documents, in the case of an Exchange Offer, in each case, including
substantially final forms of all applicable legal opinions, (D) substantially
final draft Baxalta Comfort Documents, (E) all legal, business and accounting
due diligence of Baxalta in a manner reasonably satisfactory to Baxter and the
applicable underwriter(s) or dealer manager(s), as the case may be, (F) executed
lock-up agreements from Baxalta and its directors and executive officers in the
form contemplated in Section 8 hereof and (G) such other customary documents,
certificates, agreements and instruments reasonably requested by such
underwriter(s) or dealer manager(s), Baxter or third parties (including, without
limitation, any trustee, administrative agent, transfer agent, exchange agent or
information agent) involved in any Retained Shares Transaction and, in the case
of subclauses (A), (B), (C), (D) and (G), in a form reasonably satisfactory to
Baxalta, Baxter and such underwriter(s) or dealer manager(s), as applicable; and

         (ii)  Parent shall use its reasonable best efforts to prepare, assist
in the preparation of, deliver and/or complete all of the following, as
applicable (collectively, the "Parent Marketing Period Deliverables") at least
two Business Days prior to the commencement of each Marketing Period: (A) Pro
Forma Financial Information required or requested to be included in the
Registration Statement pursuant to Section 5(b) hereof for the applicable
Registration Statement, (B) substantially final draft Parent Comfort Documents,
if applicable, (C) all legal business and accounting due diligence of Parent in
a manner reasonably satisfactory to Baxter and the applicable underwriter(s) or
dealer manager(s), as the case may be, (D) executed lock-up agreements from
Parent in the form contemplated in Section 8 hereof and (E) such other customary
documents, certificates, agreements and instruments reasonably requested by such
underwriter(s) or dealer manager(s), Baxter or third parties (including, without
limitation, any trustee, administrative agent, transfer agent, exchange agent or
information agent) involved in any Retained Shares Transaction and, in the case
of subclauses (A), (B) and (E), in a form reasonably satisfactory to Parent,
Baxter and such underwriter(s) or dealer manager(s), as applicable.

        6.    Marketing Periods.     For each Underwritten Offering or Exchange
Offer in connection with a Retained Shares Transaction, Baxter, the
underwriter(s) or dealer manager(s), as applicable, and the applicable selling
shareholders shall be afforded a period of time (each, a "Marketing Period") to
publicly offer, sell, exchange, place, transfer or otherwise dispose of Retained
Shares in connection with which the following conditions (the "Marketing Period
Conditions") shall have been satisfied:

        (a)   all of the Baxalta Marketing Period Deliverables and, to the
extent required, the Parent Marketing Period Deliverables, in each case, that
have been requested with reasonable advance notice have been completed and/or
delivered, as applicable, prior to the commencement of the Marketing Period as
set forth in Section 5(e) hereof and to the extent applicable, executed prior to
or during (as applicable) the Marketing Period;

        (b)   the applicable Registration Statement has been, or could be
(without an amendment thereto, as applicable), declared effective under the
Securities Act ("SEC Clearance") prior to the commencement of the Marketing
Period (with the exception of a Marketing Period with respect to an Exchange
Offer, with respect to which the Registration Statement must have been declared
effective prior to the expiration of the Exchange Offer), and if declared
effective, such Registration Statement continues to be effective for the
remainder of the Marketing Period;

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        (c)   the Required Management Participation has been provided or made
available as set forth in Section 5(d) above;

        (d)   each of Parent and Baxalta has complied with Section 8 hereof,
with respect to any Underwritten Offering in connection with a Debt-for-Equity
Exchange, and no Restricted Period (as defined below) relating to a prior
Debt-for-Equity Exchange, if any, shall be in effect;

        (e)   in the case of an Underwritten Offering in connection with a
Debt-for-Equity Exchange in connection with which a tender offer is not being
made for outstanding notes of Baxter, such period continues for at least four
consecutive Business Days;

        (f)    in the case of an Underwritten Offering in connection with a
Debt-for-Equity Exchange in connection with which a tender offer is made for
outstanding notes of Baxter, such period continues until the later of four
consecutive Business Days following (i) SEC Clearance and (ii) 14 calendar days
after the early settlement date for such tender offer; and

        (g)   in the case of an Exchange Offer, such period continues until such
Exchange Offer has been held open for the greater of (i) at least 20 consecutive
Business Days and (ii) up to 40 consecutive calendar days, as directed by Baxter
in consultation with Parent, Baxalta and the dealer manager(s) for such Exchange
Offer.

        If a lead managing underwriter(s) or dealer manager(s), as applicable,
in consultation with Baxter, Parent and Baxalta, reasonably determines that the
occurrence of any calamity or crisis or change in financial, political or
economic conditions in the United States or elsewhere has caused a market
disruption such that the public offer, sale, exchange or placement, as
applicable, of Retained Shares at such time is impracticable or inadvisable, the
respective periods described in clauses (e), (f) and (g) above shall be tolled
during such period.

        In addition, each of Parent and Baxalta shall use its reasonable best
efforts to cause one Marketing Period with respect to a Debt-for-Equity Exchange
not involving a tender offer to be completed in full by no later than
February 8, 2016; provided, that, if such Marketing Period is not completed in
full by February 8, 2016, then each of Parent and Baxalta shall use its
reasonable best efforts to cause such Marketing Period to be completed in full
by no later than March 23, 2016, provided that no Pro Forma Financial
Information is required or requested in connection therewith. In addition,
Parent and Baxalta shall use their respective reasonable best efforts to cause
one Marketing Period with respect to all of the Marketing Period Conditions to
be separately satisfied with respect to two Debt-for-Equity Exchanges (whether
only one Registration Statement is filed in connection therewith or otherwise)
and one Exchange Offer prior to the Early Outside Date (as defined below) or the
Outside Date (as defined below), as applicable.

        The parties hereto shall use their respective reasonable best efforts to
cause one Marketing Period for a Debt-for-Equity Exchange not involving a tender
offer to be completed prior to February 8, 2016. If one Debt-for-Equity Exchange
Marketing Period is completed prior to February 8, 2016, (a) Baxter shall demand
that a Registration Statement for an Underwritten Offering in connection with a
Debt-for-Equity Exchange be filed by no later than as promptly as practicable
after the Second PFFI Deadline, (b) the parties purchasing notes in the related
tender offer shall use their reasonable best efforts to commence such tender
offer for outstanding notes of Baxter by no later than the Second PFFI Deadline
and (c) each party shall use reasonable best efforts to cause SEC Clearance for
such Registration Statement to occur prior to or as promptly as practicable
after the date that is 14 calendar days after the early settlement date for such
tender offer, which early settlement date shall occur no later than 13 Business
Days after the commencement of such tender offer.

        If one Debt-for-Equity Exchange Marketing Period is not completed prior
to February 8, 2016, (a) Baxter shall demand that an amended Registration
Statement for an Underwritten Offering in connection with a Debt-for-Equity
Exchange not involving a tender offer be filed as promptly as

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practicable after the Second PFFI Deadline and (b) the parties hereto shall use
their respective reasonable best efforts to cause the associated Marketing
Period to begin by no later than the date of SEC Clearance of the associated
Registration Statement. Thereafter, (i) Baxter shall demand that another
Registration Statement for an Underwritten Offering in connection with a second
Debt-for-Equity Exchange be filed by no later than as promptly as practicable
after the expiration of the Restricted Period with respect to the preceding
Debt-for-Equity Exchange (or, if the offering is not completed, as soon as
practicable after the expiration of the Marketing Period), (ii) the parties
purchasing notes in the related tender offer for outstanding notes of Baxter
shall use their reasonable best efforts to commence such tender offer by no
later than as promptly as practicable after the expiration of the Restricted
Period with respect to the preceding Debt-for-Equity Exchange and (iii) each
party shall use reasonable best efforts to cause SEC Clearance for such
Registration Statement to occur prior to or as promptly as practicable after the
date that is 14 calendar days after the early settlement date for such tender
offer, which early settlement date shall occur no later than 13 Business Days
after the commencement of such tender offer.

        Thereafter, (a) Baxter shall demand that a Registration Statement for an
Exchange Offer be filed by no later than as promptly as practicable following
fifteen calendar days after the public offering date set forth on the final
prospectus with respect to the second Debt-for-Equity Exchange transaction (or,
if the offering is not completed, as soon as practicable after the expiration of
the Marketing Period) and (b) the parties hereto shall use their respective
reasonable best efforts to commence such Exchange Offer as promptly as
practicable after the expiration of the Restricted Period with respect to the
preceding Debt-for-Equity Exchange.

        7.    Standstill.     Neither Baxalta nor Parent will conduct any
shareholder vote with respect to, or consummate, the Merger (the "Standstill")
until the earliest to occur of the following: (a) the date that all of the
Marketing Period Conditions have been separately satisfied with respect to two
Debt-for-Equity Exchanges (whether only one Registration Statement is filed in
connection therewith or otherwise) and one Exchange Offer, (b) the date that
Baxter has disposed of all its Retained Shares and (c) May 26, 2016, as such
date may be extended as set forth below (the "Early Outside Date"), or, if one
Marketing Period with respect to a Debt-for-Equity Exchange not involving a
tender offer has not been completed in full by February 8, 2016 and Baxter has
complied with its obligation to use its reasonable best efforts to cause such
completion, June 17, 2016, as such date may be extended as set forth below (the
"Outside Date").

        Each of the Early Outside Date and the Outside Date, as applicable,
shall be extended (in the case of each clause below but without duplication) by
the time periods indicated below:

          (i)  the number of days that the Baxalta 2015 10-K is filed with the
SEC after the Baxalta 10-K Deadline;

         (ii)  the number of days that the Baxalta 2016 Q1 10-Q is filed with
the SEC after the Baxalta Q1 10-Q Deadline;

        (iii)  the number of days that any requested or required (in accordance
with Section 5(b)) Pro Forma Financial Information is delivered after the Second
PFFI Deadline or the Third PFFI Deadline, as applicable, if Pro Forma Financial
Information is required or requested to be included in any Registration
Statement pursuant to Section 5(b) hereof;

        (iv)  (A) if Pro Forma Financial Information is not required or
requested to be included in any Registration Statement pursuant to Section 5(b)
hereof, the number of days that the Baxalta 2015 ECD is delivered after the
Baxalta 10-K Deadline or (B) if Pro Forma Financial Information is required or
requested to be included in any Registration Statement pursuant to Section 5(b)
hereof, the number of days that the Baxalta 2015 ECD is delivered after
March 18, 2016;

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         (v)  the number of days for which Parent or Baxalta determines that
maintaining the effectiveness of any Registration Statement in connection with
an Underwritten Offering or Exchange Offer or filing an amendment or supplement
to any Registration Statement (or, if a Registration Statement has not yet been
filed, filing such a Registration Statement) would require the public disclosure
of material nonpublic information and refuses to maintain such effectiveness or
make any filing of such amendment, supplement or Registration Statement, if each
of the Marketing Period Conditions could otherwise have been satisfied during
such period and any failure to satisfy such conditions is not due to Parent's or
Baxalta's failure to comply with its respective obligations hereunder; and

        (vi)  solely in the case of the Early Outside Date, if less than two
Marketing Periods have been completed as of the Early Outside Date (as it may be
extended pursuant to clauses (i)-(v) above), and Baxter has complied with its
obligations hereunder with respect to such Marketing Periods, the number of days
until the completion of two Marketing Periods; provided that the Early Outside
Date (as it may be extended pursuant to clauses (i)-(v) above) shall not be
extended by more than 30 days pursuant to this clause (vi).

        8.    Clear Market; Lock-Up.     

        (a)   During each Marketing Period described in Section 6(e) above and
each additional period of time for which Baxter agrees (with the lead
underwriter in connection with any Underwritten Offering) to similar
restrictions with respect to the Retained Shares in connection with any
Underwritten Offering contemplated hereby not to exceed (x) 30 days or (y) such
shorter period as is appropriate for such offering as determined in the good
faith judgment of the lead underwriter after consultation with Baxalta's and
Parent's advisors (each such period, a "Restricted Period"), Baxalta agrees that
it will not, and it will cause its executive officers and directors not to,
directly or indirectly, (i) pledge, issue, sell, contract to sell, sell any
option or contract to purchase, purchase any option or contract to sell, grant
any option, right or warrant to purchase, or otherwise transfer or dispose of,
directly or indirectly, Baxalta Common Stock or any other equity or
equity-linked securities of, or any securities convertible into or exercisable
or exchangeable for any equity or equity-linked securities of, Baxalta
(collectively, the "Baxalta Subject Securities"), (ii) subject to Section 1(a)
hereof, publicly disclose or engage in discussions concerning the intention to
make any issuance, sale, pledge, disposition or registration with respect to the
Baxalta Subject Securities, (iii) enter into any swap or other agreement that
transfers, in whole or in part, any of the economic consequences of ownership of
the Baxalta Subject Securities or (iv) file with the SEC or cause to become
effective any registration statement under the Securities Act relating to, or
make any demand for or exercise any right with respect to the registration with
the SEC of, any Baxalta Subject Securities, whether any such transaction
described in clause (i), (ii), (iii) or (iv) above is to be settled by delivery
of any Baxalta Subject Securities, in cash or otherwise, without Baxter's prior
written consent, which may be given, conditioned or withheld in Baxter's sole
discretion. Baxalta shall enter into an agreement evidencing the restrictions in
this Section 8 in customary form, which form is reasonably satisfactory to
Baxalta and Baxter and a single lead underwriter in any Underwritten Offering;
provided that such restrictions may be included in the applicable underwriting
agreement; provided, further, that any of the foregoing restrictions may be
waived by a single lead underwriter.

        The restrictions contained in the preceding paragraph shall not apply
to:

          (i)  the filing of any Registration Statement contemplated by this
Letter Agreement in connection with a Retained Shares Transaction (including,
without limitation, pursuant to a demand made by Baxter in accordance with
Section 6 hereof) and any sale, transfer or other disposition of any Baxalta
Subject Securities in connection with any Retained Shares Transaction;

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         (ii)  subject to the terms hereof (including, without limitation,
Sections 2 and 7 hereof), the consummation of the Merger;

        (iii)  the issuance by Baxalta of any Baxalta Subject Securities upon
the exercise of any option or warrant or the conversion of any Baxalta Subject
Security, in each case, outstanding on the date hereof, or the vesting of any
previously issued Baxalta Subject Security, including, without limitation, any
restricted stock, restricted stock units or performance stock units;

        (iv)  the grant of stock options, stock, restricted stock units or
performance stock units pursuant to employee benefit plans in effect on the date
hereof;

         (v)  the filing of one or more registration statements on Form S-8 with
the SEC with respect to any Baxalta Subject Securities issued or issuable under
any equity compensation plan in effect on the date hereof;

        (vi)  the sale or forfeiture of any Baxalta Subject Security to satisfy
any income, employment or social tax withholding and remittance obligations of
an officer, a director or Baxalta in connection with any options of such officer
or director that are expiring within 90 days or any restricted stock units or
performance share units that vest during any Restricted Period; or

       (vii)  the filing of the registration statement required to be filed by
Baxalta pursuant to the Registration Rights Agreement, dated as of June 23,
2015, by and among Baxalta, Baxter and Citigroup Global Markets Inc., Goldman,
Sachs & Co., J.P. Morgan Securities LLC and UBS Securities LLC as
representatives of the initial purchasers.

        (b)   During each Marketing Period described in Section 6(e) above and
each Restricted Period, Parent agrees that it will not, directly or indirectly,
(i) pledge, issue, sell, contract to sell, sell any option or contract to
purchase, purchase any option or contract to sell, grant any option, right or
warrant to purchase, or otherwise transfer or dispose of, directly or
indirectly, Parent American Depositary Shares or any other equity or
equity-linked securities of, or any securities convertible into or exercisable
or exchangeable for any equity or equity-linked securities of, Parent
(collectively, the "Parent Subject Securities"), (ii) subject to Section 1(a)
hereof, publicly disclose or engage in discussions concerning the intention to
make any issuance, sale, pledge, disposition or registration with respect to the
Parent Subject Securities, (iii) enter into any swap or other agreement that
transfers, in whole or in part, any of the economic consequences of ownership of
the Parent Subject Securities or (iv) file with the SEC or cause to become
effective any registration statement under the Securities Act relating to, or
make any demand for or exercise any right with respect to the registration with
the SEC of, any Parent Subject Securities, whether any such transaction
described in clause (i), (ii), (iii) or (iv) above is to be settled by delivery
of any Parent Subject Securities, in cash or otherwise, without Baxter's prior
written consent, which may be given, conditioned or withheld in Baxter's sole
discretion. Parent shall enter into an agreement evidencing the restrictions in
this Section 8 in customary form, which form is reasonably satisfactory to
Parent and Baxter and a single lead underwriter in any Underwritten Offering;
provided that such restrictions may be included in the applicable underwriting
agreement; provided, further, that any of the foregoing restrictions may be
waived by a single lead underwriter.

        The restrictions contained in the preceding paragraph shall not apply
to:

          (i)  subject to the terms hereof (including, without limitation,
Sections 2 and 7 hereof), the filing of the Registration Statement on Form S-4
with respect to the Merger and the consummation of the Merger;

         (ii)  the issuance by Parent of any equity awards or of any Parent
Subject Securities upon the exercise or settlement of equity awards of Parent;
or

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        (iii)  the filing of one or more registration statements on Form S-8
with the SEC with respect to any Parent Subject Securities issued or issuable
under any equity compensation plan in effect on the date hereof.

        9.    Certain Acknowledgments and Agreements of Parent, Baxter and
Baxalta.     

        (a)   Baxter and Baxalta hereby acknowledge and agree that, (i) except
as contemplated by this Letter Agreement, their obligations under the Tax
Matters Agreement, the Distribution Agreement and the Ancillary Agreements are
and will be unaffected by the transactions contemplated by the Merger Agreement
in the form reviewed on the date hereof); and (ii) if the Merger is not
completed, nothing in this Letter Agreement shall operate to modify Baxter's and
Baxalta's obligations under the Tax Matters Agreement.

        (b)   Baxter hereby acknowledges and agrees that, notwithstanding
anything to the contrary in the Registration Rights Agreement, the Registration
Rights Agreement shall terminate upon the Merger Closing; provided that the
provisions of Section 2.06, Section 2.07 and Article IV of the Registration
Rights Agreement shall survive any such termination; provided, further, that, if
in the reasonable judgment of Baxter's external counsel, Baxter will be, or will
be deemed to be, an "affiliate" of Parent for purposes of Rule 405 under the
Securities Act upon Merger Closing, then (i) any Retained Shares held by Baxter
will constitute "Registrable Securities" under the Registration Rights Agreement
upon any conversion or exchange of such shares into equity securities of Parent
and (ii) the obligations for registration of the Registrable Securities (and
Baxter's rights relating thereto) will be obligations of Parent.

        (c)   Each party hereto agrees that, if legally permissible and
reasonably practicable, (i) each of Parent and Baxalta shall notify Baxter at
least five Business Days prior to the mailing of the Merger proxy statement to
its shareholders (with respect to its shareholder vote with respect to the
Merger) and (ii) prior to any public disclosure, description or filing of any
provision of this Letter Agreement, it will consult with each other party hereto
and provide each other party hereto with reasonable advance notice of such
disclosure, description or filing and the proposed form and substance thereof.
Each party hereto acknowledges that (A) this Letter Agreement will be filed
with, and a description of its terms included in, a Form 8-K of each of Baxter,
Baxalta and Parent to be filed in connection with the entering into of this
Letter Agreement, the announcement of the entering into of the Merger Agreement
and with each Registration Statement, (B) this Letter Agreement will be
incorporated by reference into, and a description of its terms included in, the
registration statement on Form S-4 of Parent related to the Merger and (C) a
description of the terms of this Letter Agreement will be included in the
prospectus to be made available by Parent in connection with the listing of new
ordinary shares to be offered to Baxalta shareholders, the circular to be
provided to Parent shareholders in connection with Parent's shareholder vote
with respect to the Merger and other documents filed or made publicly available
pursuant to the listing, prospectus and disclosure and transparency rules
maintained by the UK Financial Conduct Authority.

        10.    Termination.     This Letter Agreement may be terminated (a) by
mutual written consent of Baxalta, Baxter and Parent, provided that the
provisions of Section 9(a) and Sections 11-15 hereof shall survive such
termination, (b) by Parent or Baxalta upon termination of the Merger Agreement,
provided that, the provisions of Section 8 (solely with respect to any
Restricted Period then in effect for Baxalta or its directors and executive
officers), Section 9(a) and Sections 11-15 hereof shall survive such termination
or (c) subject to compliance with Section 7 hereof, upon Merger Closing,
provided that the provisions of Section 2(g), Section 2(h), Section 3, Section 8
(solely with respect to any Restricted Period then in effect), Section 9 and
Sections 11-16 hereof shall survive such termination. If this Letter Agreement
is terminated under clause (a), (b) or (c) above, Baxter acknowledges and agrees
that

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Section 4.02(c) of the Tax Matters Agreement has been waived with respect to the
execution of the Merger Agreement (and this sentence shall survive the
termination of this Letter Agreement).

        11.    Notices.     All notices, requests, claims, demands or other
communications under this Letter Agreement shall be in writing and shall be
given, and shall be deemed to have been duly given, upon delivery by hand,
sending by registered or certified mail (postage prepaid, return receipt
requested) or sending by email to the respective parties at the following
addresses (or at such other address for a party as shall be specified by like
notice):

(a)if to Parent:

Shire plc
5 Riverwalk, Citywest Business Campus
Dublin 24
Republic of Ireland
Attention:  Bill Mordan, General Counsel
Email:  wrmordan@shire.com

with a copy to (which shall not constitute notice):

Ropes & Gray LLP
Prudential Tower
800 Boylston Street
Boston, Massachusetts 02199
Attention:  Christopher D. Comeau
                    Paul M. Kinsella
Email:  christopher.comeau@ropesgray.com
             paul.kinsella@ropesgray.com

(b)if to Baxalta:

Baxalta Incorporated
1200 Lakeside Drive
Bannockburn, Illinois 60015
Attention:  General Counsel
Email:  peter.edwards@baxalta.com

with copies to (which shall not constitute notice):

Mayer Brown LLP
71 South Wacker Drive
Chicago, Illinois 60606
Attention:  David A. Schuette
Email:  dschuette@mayerbrown.com

Kirkland & Ellis LLP
300 North LaSalle Street
Chicago, Illinois 60654
Attention:  R. Scott Falk, P.C.
Email:  scott.falk@kirkland.com

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(c)if to Baxter:

Baxter International Inc.
One Baxter Parkway
Deerfield, Illinois 60015
Attention:  General Counsel
Email:  general_counsel@baxter.com

with a copy to (which shall not constitute notice):

Skadden, Arps, Slate, Meagher & Flom LLP
4 Times Square
New York, New York 10036
Attention:  David J. Goldschmidt
Email:  David.Goldschmidt@skadden.com

Skadden, Arps, Slate, Meagher & Flom LLP
155 North Wacker Drive
Chicago, Illinois 60606
Attention:  Charles W. Mulaney, Jr.
                    Joseph Miron
Email: Charles.Mulaney@skadden.com
             Joseph.Miron@skadden.com

        12.    Headings.     Section headings used herein are for convenience of
reference only, are not part of this Letter Agreement and are not to affect the
construction of, or to be taken into consideration in interpreting, this Letter
Agreement.

        13.    Counterparts.     This Letter Agreement may be executed in one or
more counterparts, all of which counterparts shall be considered one and the
same agreement, and shall become effective when one or more counterparts have
been signed by each party and delivered to the other party. This Letter
Agreement may be executed by facsimile or PDF signature and a facsimile or PDF
signature shall constitute an original signature for all purposes.

        14.    Governing Law.     This Letter Agreement shall be governed by and
construed and interpreted in accordance with the laws of the State of Delaware,
irrespective of the choice of laws and principles of the State of Delaware, as
to all matters, including, without limitation, matters of validity,
construction, effect, enforceability, performance and remedies.

        15.    Jurisdiction; Waiver of Jury Trial.     Each of the parties
hereto irrevocably submits to the exclusive jurisdiction of the Court of
Chancery of the State of Delaware, or, in the event (but only in the event) that
such court does not have subject matter jurisdiction over any action, suit or
proceeding (each, a "Proceeding"), the federal courts of the United States of
America located in the State of Delaware, in respect of all matters arising out
of or relating to this Letter Agreement, the interpretation and enforcement of
the provisions of this Letter Agreement, and of the documents referred to in
this Letter Agreement, and hereby waives, and agrees not to assert, as a defense
in any Proceeding for the interpretation or enforcement hereof or of any such
document, that (i) it is not subject thereto, (ii) such Proceeding may not be
brought or is not maintainable in said courts, (iii) the venue thereof may not
be appropriate or (iv) this Letter Agreement or any such document may not be
enforced in or by such courts, and each of the parties hereto irrevocably agrees
that all claims with respect to such Proceeding shall be heard and determined
exclusively in such courts. The parties hereto irrevocably consent and submit to
the personal jurisdiction of such courts in respect of the interpretation and
enforcement of the provisions of this Letter Agreement. Each party hereto
acknowledges and agrees that any controversy that may arise under this Letter
Agreement is likely to involve complicated and difficult issues, and therefore
each party hereto irrevocably and unconditionally

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waives any right such party may have to a trial by jury in respect of any
Proceeding directly or indirectly arising out of or relating to this Letter
Agreement.

        16.    Specific Enforcement.     The parties hereto acknowledge and
agree that irreparable damage would occur in the event that any of the
provisions of this Letter Agreement were not performed in accordance with its
specific terms or were otherwise breached, and that monetary damages, even if
available, would not be an adequate remedy therefor. It is accordingly agreed
that the parties hereto shall be entitled to an injunction or injunctions, or
any other appropriate form of equitable relief, to prevent breaches of this
Letter Agreement and to enforce specifically the performance of the terms and
provisions of this Letter Agreement in any court referred to in the preceding
paragraph, without proof of damages or otherwise (and each party hereto hereby
waives any requirement for the securing or posting of any bond in connection
with such remedy), this being in addition to any other remedy to which any party
hereto may be entitled at law or in equity. Each of the parties hereto
acknowledges and agrees that the right to specific enforcement is an integral
part of this Letter Agreement and without such right, none of the parties hereto
would have entered into this Letter Agreement. The parties hereto further agree
not to assert that a remedy of specific enforcement is unenforceable, invalid,
contrary to law or inequitable for any reason, nor to assert that a remedy of
monetary damages would provide an adequate remedy.

* * *

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    Very truly yours,
 
 
BAXTER INTERNATIONAL INC.
 
 
By:
 
/s/ JAMES K. SACCARO

--------------------------------------------------------------------------------

James K. Saccaro
Corporate Vice President and
Chief Financial Officer

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        If the above correctly reflects our understanding and agreement with
respect to the foregoing matters, please confirm by endorsing this Letter
Agreement below.

Acknowledged and agreed to
as of the date first written above:

SHIRE PLC    
By:
 
/s/ FLEMMING ORNSKOV

--------------------------------------------------------------------------------

 
      Name:   Flemming Ornskov         Title:   Chief Executive Officer    

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        If the above correctly reflects our understanding and agreement with
respect to the foregoing matters, please confirm by endorsing this Letter
Agreement below.

Acknowledged and agreed to
as of the date first written above:

BAXALTA INCORPORATED    
By:
 
/s/ ROBERT J. HOMBACH

--------------------------------------------------------------------------------

 
      Name:   Robert J. Hombach         Title:   Executive Vice President,
Chief Financial Officer,
Chief Operations Officer    

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Annex I:

Baxter Support Statement

        "Baxter fully supports the proposed combination of Shire and Baxalta,
which will create a major biotechnology company and global leader in rare
diseases. Baxter is pleased to support this value enhancing transaction."

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QuickLinks

Exhibit 10.1

Baxter International Inc. One Baxter Parkway Deerfield, Illinois 60015

1. Support of Baxter; Waiver of Appraisal Rights.

2. Opinion Matters.

3. Indemnification and Guarantee.

4. Retained Shares Transactions.

5. Cooperation and Support of Parent and Baxalta.

6. Marketing Periods.

7. Standstill.

8. Clear Market; Lock-Up.

9. Certain Acknowledgments and Agreements of Parent, Baxter and Baxalta.

10. Termination.

11. Notices.

12. Headings.

13. Counterparts.

14. Governing Law.

15. Jurisdiction; Waiver of Jury Trial.

16. Specific Enforcement.

Annex I: Baxter Support Statement