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                                                                   EXHIBIT 10.13

                                                               EXECUTION VERSION

                          REGISTRATION RIGHTS AGREEMENT

     THIS REGISTRATION RIGHTS AGREEMENT is entered into as of December 13,
2001. by and between Silicon Valley Bank (the "Bank") and GATX Ventures, Inc.
("GATX") (individually, each of the Bank and GATX are sometimes referred to
herein as a "Purchaser", and the Bank and GATX are collectively sometimes
referred to herein as the "Purchasers") and TolerRx, Inc., a Delaware
corporation (the "Company").

                                    RECITALS

     A.   Concurrently with the execution of this Agreement, each Purchaser is
acquiring from the Company a Warrant to Purchase Stock (the "Warrant") pursuant
to which Purchaser has rights to acquire from the Company the Shares (as defined
in each Warrant), which Shares when issued shall be either shares of the
Company's common stock, $.01 par value per share ("Common Stock") or shares that
are convertible into shares of Common Stock ("Conversion Shares").

     B.   By this Agreement, the Purchasers and the Company desire to set forth
the registration rights of the Conversion Shares or the Shares all as provided
herein.

          NOW, THEREFORE, in consideration of the premises and the mutual
promises, covenants and conditions hereinafter set forth, the parties hereto
mutually agree as follows:

     1.   REGISTRATION RIGHTS. The Company covenants and agrees as follows:

          1.1   DEFINITIONS. For purposes of this Section 1:

                (a)   The term "register," "registered," and "registration"
refer to a registration effected by preparing and filing a registration
statement or similar document in compliance with the Securities Act of 1933, as
amended, and the rules and regulations thereunder (the "Securities Act"), and
the declaration or ordering of effectiveness of such registration statement or
document;

                (b)   The term "Registrable Securities" means (i) (A) the
Conversion Shares, or (B) the Shares, at any time when the Shares are shares of
Common Stock, and (ii) any Common Stock or other securities of the Company
issued as (or issuable upon the conversion or exercise of any warrant, right or
other security which is issued as) a dividend or other distribution with respect
to, or in exchange for or in replacement of, the Shares or Conversion Shares.

                (c)   The terms "Holder" or "Holders" means the Purchasers and
each such entity's qualifying transferees under Section 1.9 hereof who hold
Registrable Securities.

                (d)   The term "SEC" means the Securities and Exchange
Commission.

                (e)   The terms "Form S-1," "Form S-3" etc. shall mean those
forms with such designations as are required by the SEC and any successor or
replacement forms adopted by the SEC.

          1.2   COMPANY REGISTRATION.

                (a)   REGISTRATION. If at any time or from time to time, the
Company shall determine to register any of its securities, for its own account
or the account of any of its shareholders, other than a registration on Form S-1
with respect to the Company's initial public offering. Form S-8 relating solely
to employee stock option or purchase plans, and/or on Form S-4 relating solely
to an SEC Rule 145 transaction, the Company will:

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                      (i)    promptly give to each Holder written notice thereof
(which shall ?? a list of the jurisdictions in which the Company intends to
attempt to qualify such securities under applicable blue sky or other state
securities laws); and

                      (ii)   include in such registration (and qualifications),
and in any ?? writing involved therein, all the Registrable Securities specified
in a written request or requests, made within 30 days after receipt of such
written notice from the Company, by any Holder or Holders, except as set forth
in subsection 1.2(c) below.

                (b)   UNDERWRITING. If the registration of which the Company
gives notice is for ? registered public offering involving a firm-commitment
underwriting, the Company shall so advise the Holders as a part of the written
notice given pursuant to subsection 1.2(a)(i). In such event the right of any
Holder to registration pursuant to this subsection 1.2 shall be conditioned upon
such Holder's participation in such underwriting and the inclusion of such
Holder's Registrable Securities in the underwriting to the extent provided
herein. All Holders proposing to distribute their securities through such
underwriting shall (together with the Company and the other shareholders
distributing their securities through such underwriting) enter into an
underwriting agreement in customary form (and not inconsistent with the terms
hereof) with the underwriter or underwriters selected for such underwriting by
the Company.

                (c)   In the case of any registration of Common Stock by the
Company in a firm-commitment underwriting, if the managing underwriters give
written advice to the Company that marketing factors require a limitation on the
number of shares of Common Stock (or other securities convertible into or
exercisable or exchangeable for Common Stock) to be offered and sold by
stockholders of Company in such offering, there shall be included in the
offering: (i) first, all securities proposed by Company to be sold for its
account; and (ii) second, that number of shares of Common Stock, if any,
requested to be included in such registration statement by Holders and by
stockholders of the Company having contractual rights to include shares in such
registration, on a pro rata basis based upon the number of shares of Common
Stock each Holder and each such stockholder beneficially owns.

          1.3   REGISTRATION ON FORM S-3. If at any time (i) a Holder of
Registrable Securities requests in writing that the Company file a registration
statement on Form S-3 or any successor thereto for a public offering of all or
any portion of the shares of Registrable Securities held by the requesting
Holder, (ii) the aggregate price to the public of such offering would reasonably
be expected to exceed $200,000, and (iii) the Company is a registrant entitled
to use Form S-3 or any successor thereto to register such shares, then the
Company shall use its best efforts to register under the Securities Act on Form
S-3 or any successor thereto, for public sale in accordance with the method of
disposition specified in such notice, the number of shares of Registrable
Securities specified in such notice. Whenever the Company is required by this
Section 1.3 to use its best efforts to effect the registration of Registrable
Securities, each of the procedures and requirements of Sections 1.5(d) and 1.8
(as applicable) shall apply to such registration; PROVIDED, HOWEVER, that the
Company shall not be obligated to register Registrable Securities under this
Section 1.3 on more than one occasion in any six-month period.

                1.3A  SUSPENSION/LIMITS. The Company shall not be obligated to
file and cause to become effective more than two (2) registration statements in
which Registrable Securities are registered under the Securities Act pursuant to
Section 1.3. Notwithstanding anything in this Section 1 to the contrary, if the
Company shall furnish to the holders of Registrable Securities who request
registration hereunder a certificate signed by the President or Chief Executive
Officer of the Company stating that the Board of Directors of the Company has
made a good faith determination (i) that use or continued use by the holders of
the registration statement filed by the Company pursuant to this Section 1 for
purposes of effecting offers or sales of Registrable Securities pursuant hereto
would require, under the Securities Act and the rules and regulations
promulgated thereunder, premature disclosure in the registration statement (or
the prospectus

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relating thereto) of material, nonpublic information concerning the Company;
(ii) that such premature disclosure would be materially adverse to the Company,
its business or prospects or any such proposed material transaction would make
the successful consummation by the Company of any such material transaction
significantly less likely and (iii) that it is therefore essential to delay or
suspend the use by the holders of such registration statement (and the
prospectus relating thereto) for purposes of effecting offers or sales of
Registrable Securities pursuant thereto, then the right of the holders to use
such registration statement (and the prospectus relating thereto) for purposes
of effecting offers or sales of Registrable Securities pursuant thereto shall be
delayed and/or suspended for a period (the "Suspension Period") of not more than
90 days after the delivery by the Company of the certificate referred to above
in this Section 1.3A. During the Suspension Period, the Company shall not be
obligated to file any registration statement and/or the holders shall not offer
or sell any Registrable Securities pursuant to or in reliance upon such
registration statement (or the prospectus relating thereto). The Company agrees
that, as promptly as practicable after the consummation, abandonment or public
disclosure of the event or transaction that caused the Company to delay or
suspend the use of the registration statement (and the prospectus relating
thereto), the Company will provide the holders with revised prospectuses, if
required, and will notify the investors of their ability to effect offers or
sales of Registrable Shares pursuant to or in reliance upon such registration
statement.

                1.3B  LOCK-UP. Each holder of Registrable Securities hereby
agrees that, at the written request of any managing underwriter of an
underwritten initial public offering of securities of the Company in connection
with the Company' initial public offering of securities, such holder shall not,
without the prior written consent of such managing underwriter, sell, assign,
transfer, make a short sale of, loan, grant any option for the purchase of,
pledge, hypothecate, encumber or otherwise convey or dispose of, or exercise
registration rights with respect to any Registrable Securities for such period
of time, not to exceed 180 days after the closing of such underwritten initial
public offering, as the Company or such managing underwriter shall request,
provided that all officers and directors, and all stockholders of the Company
holding more than 3% of the Company's capital stock on a fully-diluted basis are
similarly bound. The Company shall use commercially reasonable best efforts to
place similar contractual lockup restrictions on all capital stock issued now or
hereafter to officers, directors, employees and consultants of the Company and
holders of registration rights with respect to capital stock of the Company. If
a waiver or partial or total release from such a lock-up agreement, with respect
to any securities of the Company, is given to any officer, director or any
holder of more than 3% of the Company's capital stock on a fully diluted basis,
that is party to such an agreement, then (i) the Company shall immediately
notify the Holder, and (ii) the Holder shall be deemed immediately and
automatically released from this lock-up provision and any other lock-up
agreement with the Company.

          1.4   EXPENSES OF REGISTRATION. All expenses incurred in connection
with any registration, qualification or compliance pursuant to this Section 1
including without limitation, all registration, filing and qualification fees,
printing expenses, underwriting fees, discounts and commissions, fees and
disbursements of counsel for the Company and expenses of any special audits
incidental to or required by such registration, shall be borne by the Company.
All expenses of any registered offering not otherwise borne by the Company will
be borne pro rata among the Holders, any other shareholders of the Company
participating in such offering and the Company.

          1.5   REGISTRATION PROCEDURES. In the case of each registration,
qualification or compliance effected by the Company pursuant to this
Registration Rights Agreement, the Company will keep each Holder participating
therein advised in writing as to the initiation of each registration,
qualification and compliance and as to the completion thereof. At its expense
the Company will:

                (a)   Prepare and file with the SEC a registration statement
with respect to such Registrable Securities and use its best efforts to cause
such registration statement to become effective, and,

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upon the request of the Holders of a majority of the Registrable Securities
registered thereunder, keep such registration statement effective for up to 120
days (the "Effective Period").

                (b)   Prepare and file with the SEC such amendments and
supplements to such registration statement and the prospectus used in connection
with such registration statement as may be necessary to comply with the
provisions of the Securities Act with respect to the disposition of all
securities covered by such registration statement.

                (c)   Furnish to the Holders such numbers of copies of a
prospectus, including a preliminary prospectus, in conformity with the
requirements of the Securities Act, and such other documents as they may
reasonably request in order to facilitate the disposition of Registrable
Securities owned by them.

                (d)   Use its best efforts to register and qualify the
securities covered by such registration statement under such other securities or
Blue Sky laws of such jurisdictions as shall be reasonably requested by the
Holders, provided that the Company shall not be required in connection therewith
or as a condition thereto to qualify to do business or to file a general consent
to service of process in any such states or jurisdictions.

                (e)   In the event of any underwritten public offering, enter
into and perform its obligations under an underwriting agreement, in usual and
customary form, with the managing underwriter of such offering. Each Holder
participating in such underwriting shall also enter into and perform its
obligations under such an agreement provided that all other shareholders of the
Company participating in such offering do the same.

                (f)   Notify each Holder of Registrable Securities covered by
such registration statement at any time when a prospectus relating thereto is
required to be delivered under the Securities Act or the happening of any event
as a result of which the prospectus included in such registration statement, as
then in effect, includes an untrue statement of a material fact or omits to
state a material fact required to be stated therein or necessary to make the
statements therein not misleading in the light of the circumstances then
existing.

          1.6   INDEMNIFICATION.

                (a)   The Company will indemnify each Holder of Registrable
Securities and each of its officers, directors and partners, and each person
controlling such Holder within the meaning of Section 15 of the Securities Act
("controlling person"), and each underwriter, if any, and each controlling
person of such underwriter, with respect to which registration, qualification or
compliance of Registrable Securities has been effected pursuant to this
Registration Rights Agreement, against all claims, losses, expenses, damages and
liabilities (or actions in respect thereto) arising out of or based on any
untrue statement (or alleged untrue statement) of a material fact contained in
any prospectus, offering circular or other document (including any related
registration statement, notification or the like) incident to any such
registration, qualification or compliance, or based on any omission (or alleged
omission) to state therein a material fact required to be stated therein or
necessary to make the statement therein not misleading, or any violation or
alleged violation by the Company of the Securities Act, the Securities Exchange
Act of 1934, as amended, and the rules and regulations thereunder ("Exchange
Act") or any state securities law applicable to the Company or any rule or
regulation promulgated any such state law and relating to action or inaction
required of the Company in connection with any such registration, qualification
or compliance, and will reimburse each such Holder, each of its officers,
directors and partners, and each person controlling such Holder, each such
underwriter and each person who controls any such underwriter, within a
reasonable amount of time after incurred for any reasonable legal and any other
expenses incurred in connection with investigating, defending or settling any
such claim, loss, damage, liability or action; PROVIDED, HOWEVER, that the
indemnity

                                       -4-
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agreement contained in this subsection 1.6(a) shall not apply to amounts paid in
settlement of any such claim, loss, damage, liability, or action if such
settlement is effected without the consent of the Company (which consent shall
not be unreasonably withheld or delayed); AND PROVIDED FURTHER, that the Company
will not be liable in any such case to the extent that any such claim, loss,
damage or liability arises out of or is based on any untrue statement or
omission made in reliance upon and conformity with written information furnished
to the Company by an instrument duly executed by such Holder specifically for
use therein.

                (b)   Each Holder will, if Registrable Securities held by or
issuable to such Holder are included in the securities as to which such
registration, qualification or compliance is being effected, indemnify the
Company, each of its directors, officers and controlling persons, each
underwriter, if any, of the Company's securities covered by such a registration
statement, and each controlling person of such underwriter, and each other
Holder, each of its officers, directors, partners and controlling persons,
against all claims, losses, expenses, damages and liabilities (or actions in
respect thereof) arising out of or based on any untrue statement (or alleged
untrue statement) of a material fact contained in any such registration
statement, prospectus, offering circular or other document, or any omission (or
alleged omission) to state therein a material fact required to be stated therein
or necessary to make the statements therein not misleading, and will reimburse
the Company, such Holders, such directors, officers, partners, persons or
underwriters for any reasonable legal or any other expenses incurred in
connection with investigating, defending or settling any such claim, loss,
damage, liability or action, in each case to the extent, but only to the extent,
that such untrue statement (or alleged untrue statement) or omission (or alleged
omission) is made in such registration statement, prospectus, offering circular
or other document in reliance upon and in conformity with written information
furnished to the Company by an instrument duly executed by such Holder
specifically for use therein; PROVIDED, HOWEVER, that the indemnity agreement
contained in this subsection 1.6(b) shall not apply to amounts paid in
settlement of any such claim, loss, damage, liability or action if such
settlement is effected without the consent of the Holder, (which consent shall
not be unreasonably withheld or delayed); AND PROVIDED FURTHER, that the total
amount for which any Holder shall be liable under this subsection 1.6(b) shall
not in any event exceed the aggregate proceeds received by such Holder from the
sale of Registrable Securities held by such Holder in such registration.

                (c)   Each party entitled to indemnification under this
subsection 1.6 (the "Indemnified Party") shall give notice to the party required
to provide indemnification (the "Indemnifying Party") promptly after such
Indemnified Party has actual knowledge of any claim as to which indemnity may be
sought, and shall permit the Indemnifying Party to assume the defense of any
such claim or any litigation resulting therefrom; provided that counsel for the
Indemnifying Party, who shall conduct the defense of such claim or litigation,
shall be approved by the Indemnified Party (whose approval shall not be
unreasonably withheld), and the Indemnified Party may participate in such
defense at such party's expense; and provided further, that the failure of any
Indemnified Party to give notice as provided herein shall not relieve the
Indemnifying Party of its obligations hereunder, unless such failure resulted
in prejudice to the Indemnifying Party; and provided further, that an
Indemnified Party (together with all other Indemnified Parties which may be
represented without conflict by one counsel) shall have the right to retain one
separate counsel, with the fees and expenses to be paid by the Indemnifying
Party, if representation of such Indemnified Party by the counsel retained by
the Indemnifying Party would be inappropriate due to actual or potential
differing interests between such Indemnified Party and any other party
represented by such counsel in such proceeding. No Indemnifying Party, in the
defense of any such claim or litigation, shall, except with the consent of each
Indemnified Party, consent to entry of any judgment or enter into any settlement
which does not include as an unconditional term thereof the giving by the
claimant or plaintiff to such Indemnified Party of a release from all liability
in respect to such claim or litigation.

          1.7   INFORMATION BY HOLDER. Any Holder or Holders of Registrable
Securities included in any registration shall promptly furnish to the Company
such information regarding such Holder or Holders and the distribution proposed
by such Holder or Holders as the Company may request in writing and as shall be
required in connection with any registration, qualification or compliance
referred to herein.

                                       -5-
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          1.8   RULE 144 REPORTING AND FORM S-3. With a view to making available
to Holders the benefits of certain rules and regulations of the SEC which may
permit the sale of the Registrable Securities to the public without registration
or pursuant to a registration on Form S-3, the Company agrees at all times to:

                (a)   make and keep public information available, as those terms
are understood and defined in SEC Rule 144, after 90 days after the effective
date of the first registration filed by the Company for an offering of its
securities to the general public;

                (b)   take such action, including the voluntary registration of
its Common Stock under Section 12 of the Exchange Act, as is necessary to enable
the Holders to utilize Form S-3 for the sale of their Registrable Securities,
such action to be taken as soon as practicable after the end of the fiscal year
in which the first registration statement filed by the Company for the offering
of its securities to the general public is declared effective;

                (c)   file with the SEC in a timely manner all reports and other
documents required of the Company under the Securities Act and the Exchange Act
(at any time after it has become subject to such reporting requirements); and

                (d)   so long as a Holder owns any Registrable Securities, to
furnish to such Holder forthwith upon request a written statement by the Company
as to its compliance with the reporting requirements of said Rule 144 (at any
time after 90 days after the effective date of the first registration statement
filed by the Company for an offering of its securities to the general public),
and of the Securities Act and the Exchange Act (at any time after it has become
subject to such reporting requirements), or that it qualify as a registrant
whose securities may be resold pursuant to S-3 (at any time after it so
qualifies), a copy of the most recent annual or quarterly report of the Company,
and such other reports and documents so filed by the Company as the Holder may
reasonably request in complying with any rule or regulation of the SEC allowing
the Holder to sell any such securities without registration or pursuant to such
form.

          1.9   TRANSFER OF REGISTRATION RIGHTS. Each Holder's rights to cause
the Company to register their securities and keep information available, granted
to them by the Company under subsections 1.2, 1.3 and 1.8 may be assigned to a
transferee or assignee of a Holder's Registrable Securities not sold to the
public, provided, that the Company is given written notice by such Holder at the
time of or within a reasonable time after said transfer, stating the name and
address of said transferee or assignee and identifying the securities with
respect to which such registration rights are being assigned.

     2.   GENERAL.

          2.1   WAIVERS AND AMENDMENTS. With the written consent of the record
or beneficial holders of at least a majority of the Registrable Securities, the
obligations of the Company and the rights of the Holders of the Registrable
Securities under this agreement may be waived (either generally or in a
particular instance, either retroactively or prospectively, and either for a
specified period of time or indefinitely), and with the same consent the
Company, when authorized by resolution of its Board of Directors, may enter into
a supplementary agreement for the purpose of adding any provisions to or
changing in any manner or eliminating any of the provisions of this Agreement;
provided, however, that no such modification, amendment or waiver shall reduce
the aforesaid percentage of Registrable Securities without the consent of all of
the Holders of the Registrable Securities. Upon the effectuation of each such
waiver, consent, agreement of amendment or modification, the Company shall
promptly give written notice thereof to the record holders of the Registrable
Securities who have not previously consented thereto in writing. This Agreement
or any provision hereof may be changed, waived, discharged or terminated only by
a statement

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in writing signed by the party against which enforcement of the change, waiver,
discharge or termination is sought, except to the extent provided in this
subsection 2.1.

          2.2   GOVERNING LAW. This Agreement shall be governed in all respects
by the laws of the Commonwealth of Massachusetts as such laws are applied to
agreements between Massachusetts residents entered into and to be performed
entirely within Massachusetts.

          2.3   SUCCESSORS AND ASSIGNS. Except as otherwise expressly provided
herein, the provisions hereof shall inure to the benefit of, and be binding
upon, the successors, assigns, heirs, executors and administrators of the
parties hereto.

          2.4   ENTIRE AGREEMENT. Except as set forth below, this Agreement and
the other documents delivered pursuant hereto constitute the full and entire
understanding and agreement between the parties with regard to the subjects
hereof and thereof.

          2.5   NOTICES, ETC. All notices and other communications required or
permitted hereunder shall be in writing and shall be mailed by first class mail,
postage prepaid certified or registered mail, return receipt requested,
addressed (a) if to Holder, at such Holder's address(es) as set forth below, or
at such other address(es) as such Holder shall have furnished to the Company in
writing, or (b) if to the Company, at the Company's address set forth below, or
at such other address as the Company shall have furnished to the Holder in
writing.

          2.6   SEVERABILITY. In case any provision of this Agreement shall be
invalid, illegal, or unenforceable, the validity, legality and enforceability of
the remaining provisions of this Agreement or any provision of the other
Agreement's shall not in any way be affected or impaired thereby.

          2.7   TITLES AND SUBTITLES. The titles of the sections and subsections
of this Agreement are for convenience of reference only and are not to be
considered in construing this Agreement.

          2.8   COUNTERPARTS. This Agreement may be executed in any number of
counterparts, each of which shall be an original, but all of which together
shall constitute one instrument.

PURCHASERS                                   COMPANY

SILICON VALLEY BANK                          TOLERRX, INC.

By:  /s/ Michelle Giannini                    By:  /s/ Douglas J. Ringler
    ------------------------------------         ------------------------------
Name:    Michelle Giannini                   Name:    Douglas J. Ringler
      ----------------------------------           ----------------------------
Title:   Vice President                      Title:   Chief Executive Officer
         -------------------------------            ---------------------------
Address: 3003 Tasman Drive                   Address:  675 Massachusetts Avenue
         Santa Clara, California 95054                 Cambridge,
                                                       Massachusetts 02139

GATX VENTURES, INC.

By:  /s/ Robert D. Pomeroy, Jr.
    ------------------------------------
Name:    Robert D. Pomeroy, Jr.
      ----------------------------------
Title:   Senior Vice President
      ----------------------------------
Address: 3687 Mt. Diablo Blvd, Suite 200
         Lafayette, CA 94549

6771504

                                       -7-<Page>

                                                                   EXHIBIT 10.14

                            INDEMNIFICATION AGREEMENT

     This Indemnification Agreement ("AGREEMENT") is entered into as of the ___
day of ____________ by and between TolerRx, Inc., a Delaware corporation (the
"COMPANY") and ___________ ("INDEMNITEE").

                                    RECITALS

     A.   The Company and Indemnitee recognize the continued difficulty in
obtaining liability insurance for its directors, officers, employees, agents and
fiduciaries, the significant increases in the cost of such insurance and the
general reductions in the coverage of such insurance.

     B.   The Company and Indemnitee further recognize the substantial increase
in corporate litigation in general, subjecting directors, officers, employees,
agents and fiduciaries to expensive litigation risks at the same time as the
availability and coverage of liability insurance has been severely limited.

     C.   The Company desires to attract and retain the services of highly
qualified individuals, such as Indemnitee, to serve the Company and, in part, in
order to induce Indemnitee to continue to provide services to the Company,
wishes to provide for the indemnification and advancing of expenses to
Indemnitee to the maximum extent permitted by law.

     D.   In view of the considerations set forth above, the Company desires
that Indemnitee be indemnified by the Company as set forth herein.

     NOW, THEREFORE, the Company and Indemnitee hereby agree as follows:

     1.  INDEMNIFICATION.

         (a) INDEMNIFICATION OF EXPENSES. The Company shall indemnify Indemnitee
to the fullest extent permitted by law if Indemnitee was or is or becomes a
party to or witness or other participant in, or is threatened to be made a party
to or witness or other participant in, any threatened, pending or completed
action, suit, proceeding or alternative dispute resolution mechanism, or any
hearing, inquiry or investigation that Indemnitee in good faith believes might
lead to the institution of any such action, suit, proceeding or alternative
dispute resolution mechanism, whether civil, criminal, administrative,
investigative or other (hereinafter a "CLAIM") by reason of (or arising in part
out of) any event or occurrence related to the fact that Indemnitee is or was a
director, officer, employee, agent or fiduciary of the Company, or any
subsidiary of the Company, or is or was serving at the request of the Company as
a director, officer, employee, agent or fiduciary of another corporation,
partnership, joint venture, trust or other enterprise, or by reason of any
action or inaction on the part of Indemnitee while serving in such capacity
(hereinafter an "INDEMNIFIABLE EVENT") against any and all expenses (including
attorneys' fees and all other costs, expenses and obligations incurred in
connection with investigating, defending, being a witness in or participating in
(including on appeal),

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or preparing to defend, be a witness in or participate in, any such action,
suit, proceeding, alternative dispute resolution mechanism, hearing, inquiry or
investigation), judgments, fines, penalties and amounts paid in settlement (if
such settlement is approved in advance by the Company, which approval shall not
be unreasonably withheld) of such Claim and any federal, state, local or foreign
taxes imposed on Indemnitee as a result of the actual or deemed receipt of any
payments under this Agreement (collectively, hereinafter "EXPENSES"), including
all interest, assessments and other charges paid or payable in connection with
or in respect of such Expenses. Such payment of Expenses shall be made by the
Company as soon as practicable but in any event no later than five days after
written demand by Indemnitee therefor is presented to the Company.

         (b) REVIEWING PARTY. Notwithstanding the foregoing, (i) the obligations
of the Company under Section 1(a) shall be subject to the condition that the
Reviewing Party (as described in Section 10(e) hereof) shall not have determined
(in a written opinion, in any case in which the Independent Legal Counsel
referred to in Section 1(c) hereof is involved) that Indemnitee would not be
permitted to be indemnified under applicable law, and (ii) the obligation of the
Company to make an advance payment of Expenses to Indemnitee pursuant to
Section 2(a) (an "EXPENSE ADVANCE") shall be subject to the condition that,
if, when and to the extent that the Reviewing Party determines that
Indemnitee would not be permitted to be so indemnified under applicable
law, the Company shall be entitled to be reimbursed by Indemnitee (who
hereby agrees to reimburse the Company) for all such amounts theretofore
paid; provided, however, that if Indemnitee has commenced or thereafter
commences legal proceedings in a court of competent jurisdiction to secure
a determination that Indemnitee should be indemnified under applicable law,
any determination made by the Reviewing Party that Indemnitee would not be
permitted to be indemnified under applicable law shall not be binding and
Indemnitee shall not be required to reimburse the Company for any Expense
Advance until a final judicial determination is made with respect thereto
(as to which all rights of appeal therefrom have been exhausted or lapsed).
Indemnitees' obligation to reimburse the Company for any Expense Advance
shall be unsecured and no interest shall be charged thereon. If there has
not been a Change in Control (as defined in Section 10(c) hereof), the
Reviewing Party shall be selected by the Board of Directors, and if there
has been such a Change in Control (other than a Change in Control which has
been approved by a majority of the Company's Board of Directors who were
directors immediately prior to such Change in Control), the Reviewing Party
shall be the Independent Legal Counsel referred to in Section 1(c) hereof.
If there has been no determination by the Reviewing Party or if the
Reviewing Party determines that Indemnitee substantively would not be
permitted to be indemnified in whole or in part under applicable law,
Indemnitee shall have the right to commence litigation seeking an initial
determination by the court or challenging any such determination by the
Reviewing Party or any aspect thereof, including the legal or factual bases
therefor, and the Company hereby consents to service of process and to
appear in any such proceeding. Any determination by the Reviewing Party
otherwise shall be conclusive and binding on the Company and Indemnitee.

         (c) CHANGE IN CONTROL. The Company agrees that if there is a Change in
Control of the Company (other than a Change in Control which has been approved
by a majority of the Company's Board of Directors who were directors immediately
prior to such Change in Control) then, with

<Page>

respect to all matters thereafter arising concerning the rights of Indemnitees
to payments of Expenses and Expense Advances under this Agreement or any other
agreement or under the Company's Certificate of Incorporation or Bylaws as now
or hereafter in effect, Independent Legal Counsel (as defined in Section 10(d)
hereof) shall be selected by Indemnitee and approved by the Company (which
approval shall not be unreasonably withheld). Such counsel, among other things,
shall render its written opinion to the Company and Indemnitee as to whether and
to what extent Indemnitee would be permitted to be indemnified under applicable
law and the Company agrees to abide by such opinion. The Company agrees to pay
the reasonable fees of the Independent Legal Counsel referred to above and to
fully indemnify such counsel against any and all expenses (including attorneys'
fees), claims, liabilities and damages arising out of or relating to this
Agreement or its engagement pursuant hereto.

         (d) MANDATORY PAYMENT OF EXPENSES. Notwithstanding any other provision
of this Agreement other than Section 9 hereof, to the extent that Indemnitee has
been successful on the merits or otherwise, including, without limitation, the
dismissal of an action without prejudice, in defense of any action, suit,
proceeding, inquiry or investigation referred to in Section (1)(a) hereof or in
the defense of any claim, issue or matter therein, Indemnitee shall be
indemnified against all Expenses incurred by Indemnitee in connection therewith.

     2.  EXPENSES; INDEMNIFICATION PROCEDURE.

         (a) ADVANCEMENT OF EXPENSES. The Company shall advance all Expenses
incurred by Indemnitee. The advances to be made hereunder shall be paid by the
Company to Indemnitee as soon as practicable but in any event no later than five
days after written demand by Indemnitee therefor to the Company.

         (b) NOTICE/COOPERATION BY INDEMNITEE. Indemnitee shall, as a condition
precedent to Indemnitees' right to be indemnified under this Agreement, give the
Company notice in writing as soon as practicable of any Claim made against
Indemnitee for which indemnification will or could be sought under this
Agreement. Notice to the Company shall be directed to the Chief Executive
Officer of the Company at the address shown on the signature page of this
Agreement (or such other address as the Company shall designate in writing to
Indemnitee). In addition, Indemnitee shall give the Company such information and
cooperation as it may reasonably require and as shall be within Indemnitees'
power.

         (c) NO PRESUMPTIONS; BURDEN OF PROOF. For purposes of this Agreement,
the termination of any Claim by judgment, order, settlement (whether with or
without court approval) or conviction, or upon a plea of NOLO CONTENDERE, or its
equivalent, shall not create a presumption that Indemnitee did not meet any
particular standard of conduct or have any particular belief or that a court has
determined that indemnification is not permitted by applicable law. In addition,
neither the failure of the Reviewing Party to have made a determination as to
whether Indemnitee has met any particular standard of conduct or had any
particular belief, nor an actual determination by the Reviewing Party that
Indemnitee has not met such standard of conduct or did not have such belief,
prior to the commencement of legal proceedings by Indemnitee to secure a
judicial determination that

<Page>

Indemnitee should be indemnified under applicable law, shall be a defense to
Indemnitee's claim or create a presumption that Indemnitee has not met any
particular standard of conduct or did not have any particular belief. In
connection with any determination by the Reviewing Party or otherwise as to
whether Indemnitee is entitled to be indemnified hereunder, the burden of proof
shall be on the Company to establish that Indemnitee is not so entitled.

         (d) NOTICE TO INSURERS. If, at the time of the receipt by the Company
of a notice of a Claim pursuant to Section 2(b) hereof, the Company has
liability insurance in effect which may cover such Claim, the Company shall give
prompt notice of the commencement of such Claim to the insurers in accordance
with the procedures set forth in the respective policies. The Company shall
thereafter take all necessary or desirable action to cause such insurers to pay,
on behalf of Indemnitee, all amounts payable as a result of such action, suit,
proceeding, inquiry or investigation in accordance with the terms of such
policies.

         (e) SELECTION OF COUNSEL. In the event the Company shall be obligated
hereunder to pay the Expenses of any Claim, the Company shall be entitled to
assume the defense of such Claim with counsel approved by Indemnitee, which
approval shall not be unreasonably withheld, upon the delivery to Indemnitee of
written notice of its election so to do. After delivery of such notice, approval
of such counsel by Indemnitee and the retention of such counsel by the Company,
the Company will not be liable to Indemnitee under this Agreement for any fees
of counsel subsequently incurred by Indemnitee with respect to the same Claim;
provided that, (i) Indemnitee shall have the right to employ Indemnitees'
counsel in any such Claim at Indemnitee expense and (ii) if (A) the employment
of counsel by Indemnitee has been previously authorized by the Company, (B)
Indemnitee shall have reasonably concluded that there is a conflict of interest
between the Company and Indemnitee in the conduct of any such defense, or (C)
the Company shall not continue to retain such counsel to defend such Claim, then
the fees and expenses of Indemnitee counsel shall be at the expense of the
Company. The Company shall have the right to conduct such defense as it sees fit
in its sole discretion, including the right to settle any claim against
Indemnitee without the consent of the Indemnitee.

     3.  ADDITIONAL INDEMNIFICATION RIGHTS; NONEXCLUSIVITY.

         (a) SCOPE. The Company hereby agrees to indemnify Indemnitee to the
fullest extent permitted by law, notwithstanding that such indemnification is
not specifically authorized by the other provisions of this Agreement, the
Company's Certificate of Incorporation, the Company's Bylaws or by statute. In
the event of any change after the date of this Agreement in any applicable law,
statute or rule which expands the right of a Delaware corporation to indemnify a
member of its Board of Directors or an officer, employee, agent or fiduciary, it
is the intent of the parties hereto that Indemnitee shall enjoy by this
Agreement the greater benefits afforded by such change. In the event of any
change in any applicable law, statute or rule which narrows the right of a
Delaware corporation to indemnify a member of its Board of Directors or an
officer, employee, agent or fiduciary, such change, to the extent not otherwise
required by such law, statute or rule to be applied

<Page>

to this Agreement, shall have no effect on this Agreement or the parties' rights
and obligations hereunder except as set forth in Section 8(a) hereof.

         (b) NONEXCLUSIVITY. The indemnification provided by this Agreement
shall be in addition to any rights to which Indemnitee may be entitled under the
Company's Certificate of Incorporation, its Bylaws, any agreement, any vote of
stockholders or disinterested directors, the General Corporation Law of the
State of Delaware, or otherwise. The indemnification provided under this
Agreement shall continue as to Indemnitee for any action Indemnitee took or did
not take while serving in an indemnified capacity even though Indemnitee may
have ceased to serve in such capacity.

     4.  NO DUPLICATION OF PAYMENTS. The Company shall not be liable under this
Agreement to make any payment in connection with any Claim made against
Indemnitee to the extent Indemnitee has otherwise actually received payment
(under any insurance policy, Certificate of Incorporation, Bylaw or otherwise)
of the amounts otherwise indemnifiable hereunder.

     5.  PARTIAL INDEMNIFICATION. If Indemnitee is entitled under any provision
of this Agreement to indemnification by the Company for some or a portion of
Expenses incurred in connection with any Claim, but not, however, for all of the
total amount thereof, the Company shall nevertheless indemnify Indemnitee for
the portion of such Expenses to which Indemnitee are entitled.

     6.  MUTUAL ACKNOWLEDGEMENT. Both the Company and Indemnitee acknowledge
that in certain instances, Federal law or applicable public policy may prohibit
the Company from indemnifying its directors, officers, employees, agents or
fiduciaries under this Agreement or otherwise. Indemnitee understands and
acknowledges that the Company has undertaken or may be required in the future to
undertake with the Securities and Exchange Commission to submit the question of
indemnification to a court in certain circumstances for a determination of the
Company's right under public policy to indemnify Indemnitee.

     7.  LIABILITY INSURANCE. To the extent the Company maintains liability
insurance applicable to directors, officers, employees, agents or fiduciaries,
Indemnitee shall be covered by such policies in such a manner as to provide
Indemnitee the same rights and benefits as are accorded to the most favorably
insured of the Company's directors, if Indemnitee is a director; or of the
Company's officers, if Indemnitee is not a director of the Company but is an
officer; or of the Company's key employees, agents or fiduciaries, if Indemnitee
is not an officer or director but is a key employee, agent or fiduciary.

     8.  EXCEPTIONS. Any other provision herein to the contrary notwithstanding,
the Company shall not be obligated pursuant to the terms of this Agreement:

         (a) EXCLUDED ACTION OR OMISSIONS. To indemnify Indemnitee for
Indemnitee's acts, omissions or transactions from which Indemnitee or the
Indemnitee may not be relieved of liability under applicable law;

<Page>

         (b) CLAIMS INITIATED BY INDEMNITEE. To indemnify or advance expenses to
Indemnitee with respect to Claims initiated or brought voluntarily by Indemnitee
and not by way of defense, except (i) with respect to actions or proceedings
brought to establish or enforce a right to indemnification under this Agreement
or any other agreement or insurance policy or under the Company's Certificate of
Incorporation or Bylaws now or hereafter in effect relating to Claims for
Indemnifiable Events, (ii) in specific cases if the Board of Directors has
approved the initiation or bringing of such Claim, or (iii) as otherwise
required under Section 145 of the Delaware General Corporation Law, regardless
of whether Indemnitee ultimately is determined to be entitled to such
indemnification, advance expense payment or insurance recovery, as the case may
be;

         (c) LACK OF GOOD FAITH. To indemnify Indemnitee for any expenses
incurred by Indemnitee with respect to any proceeding instituted by Indemnitee
to enforce or interpret this Agreement, if a court of competent jurisdiction
determines that each of the material assertions made by Indemnitee in such
proceeding was not made in good faith or was frivolous; or

         (d) CLAIMS UNDER SECTION 16(b). To indemnify Indemnitee for expenses
and the payment of profits arising from the purchase and sale by Indemnitee of
securities in violation of Section 16(b) of the Securities Exchange Act of 1934,
as amended, or any similar successor statute.

     9.  PERIOD OF LIMITATIONS. No legal action shall be brought and no cause of
action shall be asserted by or in the right of the Company against Indemnitee,
Indemnitee's estate, spouse, heirs, executors or personal or legal
representatives after the expiration of two years from the date of accrual of
such cause of action, and any claim or cause of action of the Company shall be
extinguished and deemed released unless asserted by the timely filing of a legal
action within such two-year period; PROVIDED, HOWEVER, that if any shorter
period of limitations is otherwise applicable to any such cause of action, such
shorter period shall govern.

     10. CONSTRUCTION OF CERTAIN PHRASES.

         (a) For purposes of this Agreement, references to the "Company" shall
include, in addition to the resulting corporation, any constituent corporation
(including any constituent of a constituent) absorbed in a consolidation or
merger which, if its separate existence had continued, would have had power and
authority to indemnify its directors, officers, employees, agents or
fiduciaries, so that if Indemnitee is or was a director, officer, employee,
agent or fiduciary of such constituent corporation, or is or was serving at the
request of such constituent corporation as a director, officer, employee, agent
or fiduciary of another corporation, partnership, joint venture, employee
benefit plan, trust or other enterprise, Indemnitee shall stand in the same
position under the provisions of this Agreement with respect to the resulting or
surviving corporation as Indemnitee would have with respect to such constituent
corporation if its separate existence had continued.

         (b) For purposes of this Agreement, references to "other enterprises"
shall include employee benefit plans; references to "fines" shall include any
excise taxes assessed on Indemnitee with respect to an employee benefit plan;
and references to "serving at the request of the Company" shall include any
service as a director, officer, employee, agent or fiduciary of the Company
which

<Page>

imposes duties on, or involves services by, such director, officer, employee,
agent or fiduciary with respect to an employee benefit plan, its participants or
its beneficiaries; and if Indemnitee acted in good faith and in a manner
Indemnitee reasonably believed to be in the interest of the participants and
beneficiaries of an employee benefit plan, Indemnitee shall be deemed to have
acted in a manner "not opposed to the best interests of the Company" as referred
to in this Agreement.

         (c) For purposes of this Agreement a "Change in Control" shall be
deemed to have occurred if (i) any "person" (as such term is used in Sections
13(d) and 14(d) of the Securities Exchange Act of 1934, as amended), other than
a trustee or other fiduciary holding securities under an employee benefit plan
of the Company or a corporation owned directly or indirectly by the stockholders
of the Company in substantially the same proportions as their ownership of stock
of the Company, (A) who is or becomes the beneficial owner, directly or
indirectly, of securities of the Company representing 10% or more of the
combined voting power of the Company's then outstanding Voting Securities,
increases his beneficial ownership of such securities by 5% or more over the
percentage so owned by such person, or (B) becomes the "beneficial owner" (as
defined in Rule 13d-3 under said Act), directly or indirectly, of securities of
the Company representing more than 20% of the total voting power represented by
the Company's then outstanding Voting Securities, (ii) during any period of two
consecutive years, individuals who at the beginning of such period constitute
the Board of Directors of the Company and any new director whose election by the
Board of Directors or nomination for election by the Company's stockholders was
approved by a vote of at least two-thirds of the directors then still in office
who either were directors at the beginning of the period or whose election or
nomination for election was previously so approved, cease for any reason to
constitute a majority thereof, or (iii) the stockholders of the Company approve
a merger or consolidation of the Company with any other corporation other than a
merger or consolidation which would result in the Voting Securities of the
Company outstanding immediately prior thereto continuing to represent (either by
remaining outstanding or by being converted into Voting Securities of the
surviving entity) at least 80% of the total voting power represented by the
Voting Securities of the Company or such surviving entity outstanding
immediately after such merger or consolidation, or the stockholders of the
Company approve a plan of complete liquidation of the Company or an agreement
for the sale or disposition by the Company of (in one transaction or a series of
transactions) all or substantially all of the Company's assets.

         (d) For purposes of this Agreement, "Independent Legal Counsel" shall
mean an attorney or firm of attorneys, selected in accordance with the
provisions of Section 1(c) hereof, who shall not have otherwise performed
services for the Company or Indemnitee within the last three years (other than
with respect to matters concerning the rights of Indemnitee under this
Agreement, or of other indemnitees under similar indemnity agreements).

         (e) For purposes of this Agreement, a "Reviewing Party" shall mean any
appropriate person or body consisting of a member or members of the Company's
Board of Directors or any other person or body appointed by the Board of
Directors who is not a party to the particular Claim for which Indemnitee are
seeking indemnification, or Independent Legal Counsel.

<Page>

         (f) For purposes of this Agreement, "Voting Securities" shall mean any
securities of the Company that vote generally in the election of directors.

     11. COUNTERPARTS. This Agreement may be executed in one or more
counterparts, each of which shall constitute an original.

     12. BINDING EFFECT; SUCCESSORS AND ASSIGNS. This Agreement shall be binding
upon and inure to the benefit of and be enforceable by the parties hereto and
their respective successors, assigns, including any direct or indirect successor
by purchase, merger, consolidation or otherwise to all or substantially all of
the business and/or assets of the Company, spouses, heirs, and personal and
legal representatives. The Company shall require and cause any successor
(whether direct or indirect by purchase, merger, consolidation or otherwise) to
all, substantially all, or a substantial part, of the business and/or assets of
the Company, by written agreement in form and substance satisfactory to
Indemnitee, expressly to assume and agree to perform this Agreement in the same
manner and to the same extent that the Company would be required to perform if
no such succession had taken place. This Agreement shall continue in effect with
respect to Claims relating to Indemnifiable Events regardless of whether
Indemnitee continues to serve as a director, officer, employee, agent or
fiduciary of the Company or of any other enterprise at the Company's request.

     13. ATTORNEYS' FEES. In the event that any action is instituted by
Indemnitee under this Agreement or under any liability insurance policies
maintained by the Company to enforce or interpret any of the terms hereof or
thereof, Indemnitee shall be entitled to be paid all Expenses incurred by
Indemnitee with respect to such action, regardless of whether Indemnitee is
ultimately successful in such action, and shall be entitled to the advancement
of Expenses with respect to such action, unless, as a part of such action, a
court of competent jurisdiction over such action determines that each of the
material assertions made by Indemnitee as a basis for such action was not made
in good faith or was frivolous. In the event of an action instituted by or in
the name of the Company under this Agreement to enforce or interpret any of the
terms of this Agreement, Indemnitee shall be entitled to be paid all Expenses
incurred by Indemnitee in defense of such action (including costs and expenses
incurred with respect to Indemnitee counterclaims and cross-claims made in such
action), and shall be entitled to the advancement of Expenses with respect to
such action, unless, as a part of such action, a court having jurisdiction over
such action determines that each of Indemnitee material defenses to such action
was made in bad faith or was frivolous.

     14. NOTICE. All notices and other communications required or permitted
hereunder shall be in writing, shall be effective when given, and shall in any
event be deemed to be given (a) five (5) days after deposit with the U.S. Postal
Service or other applicable postal service, if delivered by first class mail,
postage prepaid, (b) upon delivery, if delivered by hand, (c) one business day
after the business day of deposit with Federal Express or similar overnight
courier, freight prepaid, or (d) one day after the business day of delivery by
facsimile transmission, if delivered by facsimile transmission, with copy by
first class mail, postage prepaid, and shall be addressed if to Indemnitee, at
the Indemnitee address as set forth beneath Indemnitee signatures to this
Agreement and if to the Company at the

<Page>

address of its principal corporate offices (attention: Secretary) or at such
other address as such party may designate by ten days' advance written notice to
the other party hereto.

     15. CONSENT TO JURISDICTION. The Company and Indemnitee each hereby
irrevocably consent to the jurisdiction of the courts of the State of Delaware
for all purposes in connection with any action or proceeding which arises out of
or relates to this Agreement and agree that any action instituted under this
Agreement shall be commenced, prosecuted and continued only in the Court of
Chancery of the State of Delaware in and for New Castle County, which shall be
the exclusive and only proper forum for adjudicating such a claim.

     16. SEVERABILITY. The provisions of this Agreement shall be severable in
the event that any of the provisions hereof (including any provision within a
single section, paragraph or sentence) are held by a court of competent
jurisdiction to be invalid, void or otherwise unenforceable, and the remaining
provisions shall remain enforceable to the fullest extent permitted by law.
Furthermore, to the fullest extent possible, the provisions of this Agreement
(including, without limitations, each portion of this Agreement containing any
provision held to be invalid, void or otherwise unenforceable, that is not
itself invalid, void or unenforceable) shall be construed so as to give effect
to the intent manifested by the provision held invalid, illegal or
unenforceable.

     17. CHOICE OF LAW. This Agreement shall be governed by and its provisions
construed and enforced in accordance with the laws of the State of Delaware, as
applied to contracts between Delaware residents, entered into and to be
performed entirely within the State of Delaware, without regard to the conflict
of laws principles thereof.

     18. SUBROGATION. In the event of payment under this Agreement, the Company
shall be subrogated to the extent of such payment to all of the rights of
recovery of Indemnitee who shall execute all documents required and shall do all
acts that may be necessary to secure such rights and to enable the Company
effectively to bring suit to enforce such rights.

     19. AMENDMENT AND TERMINATION. No amendment, modification, termination or
cancellation of this Agreement shall be effective unless it is in writing signed
by both the parties hereto. No waiver of any of the provisions of this Agreement
shall be deemed or shall constitute a waiver of any other provisions hereof
(whether or not similar) nor shall such waiver constitute a continuing waiver.

     20. INTEGRATION AND ENTIRE AGREEMENT. Subject to Section 3(b), this
Agreement sets forth the entire understanding between the parties hereto and
supersedes and merges all previous written and oral negotiations, commitments,
understandings and agreements relating to the subject matter hereof between the
parties hereto.

     21. NO CONSTRUCTION AS EMPLOYMENT AGREEMENT. Nothing contained in this
Agreement shall be construed as giving Indemnitee any right to be retained in
the employ of the Company or any of its subsidiaries.

                            [SIGNATURE PAGES FOLLOW]

<Page>

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

                                        TOLERRX, INC.

                                        By:
                                            ------------------------------------
                                            Name:
                                            Title
                                            Address:

     AGREED TO AND ACCEPTED BY:

     Signature:
                -------------------------

     Address:
                -------------------------

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

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

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