CHEMOCENTRYX, INC.

                     INVESTORS RIGHTS AGREEMENT

                          February 2, 2001

                          TABLE OF CONTENTS

                                                          Page
1.      REGISTRATION RIGHTS                                 1
1.1     DEFINITIONS                                         1
1.2     REQUEST FOR REGISTRATION                            2
1.3     COMPANY REGISTRATION                                4
1.4     FORM S-3 REGISTRATION                               4
1.5     OBLIGATIONS OF THE COMPANY                          5
1.6     FURNISH INFORMATION                                 6
1.7     EXPENSES OF REGISTRATION                            6
1.8     UNDERWRITING REQUIREMENTS                           7
1.9     DELAY OF REGISTRATION                               7
1.10    INDEMNIFICATION                                     8
1.11    REPORTS UNDER SECURITIES EXCHANGE ACT OF 1934      10
1.12    ASSIGNMENT OF REGISTRATION RIGHTS                  10
1.13    LIMITATIONS ON SUBSEQUENT REGISTRATION RIGHTS      11
1.14    MARKET-STANDOFF AGREEMENT                          11
1.15    TERMINATION OF REGISTRATION RIGHTS                 12
2.      COVENANTS OF THE COMPANY                           12
2.1     DELIVERY OF FINANCIAL STATEMENTS                   12
2.2     INSPECTION                                         12
2.3     RIGHT OF FIRST OFFER                               12
2.4     BOARD OF DIRECTORS                                 14
2.5     OBSERVATION RIGHTS                                 14
2.6     TERMINATION OF COVENANTS                           15
3.      MISCELLANEOUS                                      15
3.1     SUCCESSORS AND ASSIGNS                             15
3.2     AMENDMENTS AND WAIVERS                             15
3.3     NOTICES                                            15
3.4     SEVERABILITY                                       16
3.5     GOVERNING LAW                                      16
3.6     COUNTERPARTS                                       16
3.7     TITLES AND SUBTITLES                               16
3.8     AGGREGATION OF STOCK                               16
3.9     ADDITIONAL INVESTORS                               16
3.10    CONSENT                                            16



                       CHEMOCENTRYX, INC.
                    INVESTORS RIGHTS AGREEMENT

     This Investors Rights Agreement (the "Agreement") is made as of the
2nd day of February, 2001, by and among ChemoCentryx, Inc., a Delaware
corporation (the "Company"), Techne Corporation, a Minnesota corporation
("Techne"), the individuals or entities who are signatories hereto, each
of which is herein referred to as an "Investor," and Thomas J. Schall (the
"Founder").

                           RECITALS

     The Investors have entered into agreements (the "Purchase Agreements"),
pursuant to which the Investors purchased shares (the "Shares") of Preferred
Stock of the Company.  In connection with the Purchase Agreements, the Company
has and is granting certain registration rights to the Investors.  All terms
not otherwise defined in this Agreement shall have the meaning defined in the
Purchase Agreements.

                          AGREEMENT

     The parties hereby agree as follows:

     1. Registration Rights.  The Company, Techne, the Investors and
the Founder covenant and agree as follows:

        1.1  Definitions.  For purposes of this Section 1:

             (a) The terms "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
(the "Securities Act"), and the declaration or ordering of effectiveness of
such registration statement or document;

             (b) The term "Registrable Securities" means (i) the shares of
Common Stock issuable or issued upon conversion of the Series A
Preferred Stock, (ii) the shares of Common Stock issuable or issued upon
conversion of the Series B Preferred Stock, (iii) the shares of Common
Stock issued to the Founder (the "Founder's Stock"); provided, however,
that for the purposes of Section 1.2, 1.4 or 1.13 the Founder's Stock
shall not be deemed Registrable Securities and the Founder shall not be
deemed a Holder, and (iv) any other shares of Common Stock 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 listed in (i), (ii) and (iii); provided, however, that the
foregoing definition shall exclude in all cases any Registrable Securities
sold by a person in a transaction in which his or her rights under this
Agreement are not assigned.  Notwithstanding the foregoing, Common Stock
or other securities shall only be treated as Registrable Securities if and
so long as they have not been (A) sold to or through a broker or dealer or
underwriter in a public distribution or a public securities transaction,
or (B) sold in a transaction exempt from the registration and prospectus
delivery requirements of the Securities Act under Section 4(1) thereof so
that all transfer restrictions, and restrictive legends with respect
thereto, if any, are removed upon the consummation of such sale;

             (c) The number of shares of "Registrable Securities then
outstanding" shall be determined by the number of shares of Common Stock
outstanding which are, and the number of shares of Common Stock issuable
pursuant to then exercisable or convertible securities which are,
Registrable Securities;

             (d) The term "Holder" means any person owning or having
the right to acquire Registrable Securities or any assignee thereof in
accordance with Section 1.12 of this Agreement;

             (e) The term "Form S-3" means such form under the
Securities Act as in effect on the date hereof or any successor form under
the Securities Act;

             (f) The term "SEC" means the Securities and Exchange
Commission; and

             (g) The term "Qualified IPO" means a firm commitment
underwritten public offering by the Company of shares of its Common Stock
pursuant to a registration statement on Form S-1 under the Securities Act,
the public offering price of which is not less than $8.00 per share
(appropriately adjusted for any stock split, dividend, combination or
other recapitalization) and which results in aggregate cash proceeds to
the Company of $20,000,000 (net of underwriting discounts and
commissions).

        1.2  Request for Registration.

             (a) If the Company shall receive at any time after the
earlier of (i) November 15, 2004, or (ii) six (6) months after the
effective date of the first registration statement for a public offering
of securities of the Company (other than a registration statement relating
either to the sale of securities to employees of the Company pursuant to a
stock option, stock purchase or similar plan or an SEC Rule 145
transaction), a written request from either (x) the Holders of a majority
of the Series A Preferred Stock (or the Common Stock issuable or issued
upon conversion thereof) then outstanding or (y) the Holders of a majority
of the Series B Preferred Stock (or the Common Stock issuable or issued
upon conversion thereof) then outstanding that the Company file a
registration statement under the Securities Act covering the registration
of at least thirty percent (30%) of the Registrable Securities then
outstanding (or a lesser percent if the anticipated aggregate offering
price, net of underwriting discounts and commissions, would exceed
$10,000,000), then the Company shall, within ten (10) days of the receipt
thereof, give written notice of such request to all Holders and shall,
subject to the limitations of subsection 1.2(b), use its best efforts to
effect as soon as practicable, and in any event within 60 days of the
receipt of such request, the registration under the Securities Act of all
Registrable Securities which the Holders request to be registered within
twenty (20) days of the mailing of such notice by the Company in
accordance with Section 3.3.

             (b) If the Holders initiating the registration request
hereunder ("Initiating Holders") intend to distribute the Registrable
Securities covered by their request by means of an underwriting, they
shall so advise the Company as a part of their request made pursuant to
this Section 1.2 and the Company shall include such information in the
written notice referred to in subsection 1.2(a).  The underwriter will be
selected by a majority in interest of the Initiating Holders and shall be
reasonably acceptable to the Company.  In such event, the right of any
Holder to include his Registrable Securities in such registration shall be
conditioned upon such Holder's participation in such underwriting and the
inclusion of such Holder's Registrable Securities in the underwriting
(unless otherwise mutually agreed by a majority in interest of the
Initiating Holders and such Holder) to the extent provided herein.  All
Holders proposing to distribute their securities through such underwriting
shall (together with the Company as provided in subsection 1.5(e)) enter
into an underwriting agreement in customary form with the underwriter or
underwriters selected for such underwriting.  Notwithstanding any other
provision of this Section 1.2, if the underwriter advises the Initiating
Holders in writing that marketing factors require a limitation of the
number of shares to be underwritten, then the Initiating Holders shall so
advise all Holders of Registrable Securities which would otherwise be
underwritten pursuant hereto, and the number of shares of Registrable
Securities that may be included in the underwriting shall be allocated
among all Holders thereof, in proportion (as nearly as practicable) to the
amount of Registrable Securities of the Company owned by each Holder;
provided, however, that in no event shall (i) any securities held by a
Holder (other than an Initiating Holder) be included in such underwriting
if any Initiating Holder's securities are excluded from the underwriting,
or (ii) the number of shares of Registrable Securities to be included in
such underwriting be reduced unless all other securities are first
entirely excluded from the underwriting.

             (c) Notwithstanding the foregoing, if the Company shall
furnish to Holders requesting a registration statement pursuant to this
Section 1.2, a certificate signed by the President of the Company stating
that in the good faith judgment of the Board of Directors of the Company,
it would be seriously detrimental to the Company and its stockholders for
such registration statement to be filed and it is therefore essential to
defer the filing of such registration statement, the Company shall have
the right to defer such filing for a period of not more than 120 days
after receipt of the request of the Initiating Holders; provided, however,
that the Company may not utilize this right more than once in any twelve-
month period.

             (d) In addition, the Company shall not be obligated to
effect, or to take any action to effect, any registration pursuant to this
Section 1.2:

                 (i)   With respect to Holders of the Series A
Preferred Stock (or the Common Stock issuable or issued upon conversion
thereof), after the Company has effected one (1) registration pursuant to
this Section 1.2 at the request of such Holders of Series A Preferred
Stock and such registration has been declared or ordered effective;

                 (ii)  With respect to Holders of the Series B
Preferred Stock (or the Common Stock issuable or issued upon conversion
thereof), after the Company has effected one (1) registration pursuant to
this Section 1.2 at the request of such Holders of Series B Preferred
Stock and such registration has been declared or ordered effective;

                 (iii) During the period starting with the date sixty
(60) days prior to the Company's good faith estimate of the date of filing
of, and ending on a date one hundred eighty (180) days after the effective
date of, a registration subject to Section 1.3 hereof; provided that the
Company is actively employing in good faith all reasonable efforts to
cause such registration statement to become effective; or

                 (iv)  If the Initiating Holders propose to dispose
of shares of Registrable Securities that may be immediately registered on
Form S-3 pursuant to a request made pursuant to Section 1.4 below.

        1.3  Company Registration.  If (but without any obligation to
do so) the Company proposes to register (including for this purpose a
registration effected by the Company for stockholders other than the
Holders) any of its stock under the Securities Act in connection with the
public offering of such securities solely for cash (other than a
registration relating solely to the sale of securities to participants in
a Company stock plan or a transaction covered by Rule 145 under the
Securities Act, a registration in which the only stock being registered is
Common Stock issuable upon conversion of debt securities which are also
being registered, or any registration on any form which does not include
substantially the same information as would be required to be included in
a registration statement covering the sale of the Registrable Securities),
the Company shall, at such time, promptly give each Holder written notice
of such registration.  Upon the written request of each Holder given
within twenty (20) days after mailing of such notice by the Company in
accordance with Section 3.3, the Company shall, subject to the provisions
of Section 1.8, cause to be registered under the Securities Act all of the
Registrable Securities that each such Holder has requested to be
registered.

        1.4  Form S-3 Registration.  In case the Company shall receive
from any Holder or Holders of the Registrable Securities, a written
request or requests that the Company file a registration on Form S-3 and
the reasonably anticipated aggregate offering price, net of underwriting
discounts and commissions, would exceed $2,000,000, the Company will:

             (a) promptly give written notice of the proposed
registration, and any related qualification or compliance, to all other
Holders; and

             (b) as soon as practicable, effect such registration and
all such qualifications and compliances as may be so requested and as
would permit or facilitate the sale and distribution of all or such
portion of such Holder's or Holders' Registrable Securities as are
specified in such request, together with all or such portion of the
Registrable Securities of any other Holder or Holders joining in such
request as are specified in a written request given within 15 days after
receipt of such written notice from the Company; provided, however, that
the Company shall not be obligated to effect any such registration,
qualification or compliance, pursuant to this Section 1.4:  (i) if
Form S-3 is not available for such offering by the Holders; (ii) if the
Company shall furnish to the Holders a certificate signed by the President
of the Company stating that in the good faith judgment of the Board of
Directors of the Company, it would be seriously detrimental to the Company
and its stockholders for such Form S-3 Registration to be effected at such
time, in which event the Company shall have the right to defer the filing
of the Form S-3 registration statement for a period of not more than 120
days after receipt of the request of the Holder or Holders under this
Section 1.4; provided, however, that the Company shall not utilize this
right more than once in any twelve month period; (iii) if the Company has,
within the twelve (12) month period preceding the date of such request,
already effected a registration on Form S-3 for the Holders pursuant to
this Section 1.4; (iv) in any particular jurisdiction in which the Company
would be required to qualify to do business or to execute a general
consent to service of process in effecting such registration,
qualification or compliance; or (v) during the period ending one hundred
eighty (180) days after the effective date of a registration statement
subject to Section 1.3.

             (c) Subject to the foregoing, the Company shall file a
registration statement covering the Registrable Securities and other
securities so requested to be registered as soon as practicable after
receipt of the request or requests of the Holders.  Registrations effected
pursuant to this Section 1.4 shall not be counted as demands for
registration or registrations effected pursuant to Sections 1.2 or 1.3,
respectively.

        1.5  Obligations of the Company.  Whenever required under this
Section 1 to effect the registration of any Registrable Securities, the
Company shall, as expeditiously as reasonably possible:

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

             (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 for up to one
hundred twenty (120) days.

             (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.

             (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 of 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, such
obligation to continue for one hundred twenty (120) days.

             (g) Cause all such Registrable Securities registered
pursuant hereunder to be listed on each securities exchange on which
similar securities issued by the Company are then listed.

             (h) Provide a transfer agent and registrar for all
Registrable Securities registered pursuant hereunder and a CUSIP number
for all such Registrable Securities, in each case not later than the
effective date of such registration.

             (i) Use its best efforts to furnish, at the request of
any Holder requesting registration of Registrable Securities pursuant to
this Section 1, on the date that such Registrable Securities are delivered
to the underwriters for sale in connection with a registration pursuant to
this Section 1, if such securities are being sold through underwriters,
or, if such securities are not being sold through underwriters, on the
date that the registration statement with respect to such securities
becomes effective, (i) an opinion, dated such date, of the counsel
representing the Company for the purposes of such registration, in form
and substance as is customarily given to underwriters in an underwritten
public offering, addressed to the underwriters, if any, and to the Holders
requesting registration of Registrable Securities and (ii) a letter dated
such date, from the independent certified public accountants of the
Company, in form and substance as is customarily given by independent
certified public accountants to underwriters in an underwritten public
offering, addressed to the underwriters, if any, and to the Holders
requesting registration of Registrable Securities.

        1.6  Furnish Information.  It shall be a condition precedent
to the obligations of the Company to take any action pursuant to this
Section 1 with respect to the Registrable Securities of any selling Holder
that such Holder shall furnish to the Company such information regarding
itself, the Registrable Securities held by it, and the intended method of
disposition of such securities as shall be required to effect the
registration of such Holder's Registrable Securities.  The Company shall
have no obligation with respect to any registration requested pursuant to
Section 1.2 or Section 1.4 of this Agreement if, as a result of the
application of the preceding sentence, the number of shares or the
anticipated aggregate offering price of the Registrable Securities to be
included in the registration does not equal or exceed the number of shares
or the anticipated aggregate offering price required to originally trigger
the Company's obligation to initiate such registration as specified in
subsection 1.2(a) or subsection 1.4(b)(2), whichever is applicable.

        1.7  Expenses of Registration.  All expenses (other than
underwriting discounts and commissions incurred in connection with
registrations), filings or qualifications pursuant to Sections 1.2, 1.3
and 1.4, including (without limitation) all registration, filing and
qualification fees, printers' and accounting fees, fees and disbursements
of counsel for the Company, and the reasonable fees and disbursements of
one counsel for the selling Holders selected by them with the approval of
the Company, which approval shall not be unreasonably withheld, shall be
borne by the Company; provided, however, that the Company shall not be
required to pay for any expenses of any registration proceeding begun
pursuant to Section 1.2 if the registration request is subsequently
withdrawn at the request of the Holders of a majority of the Registrable
Securities to be registered (in which case all participating Holders shall
bear such expenses), unless the Initiating Holders of a majority of the
Registrable Securities agree to forfeit their right to one demand
registration pursuant to Section 1.2.

        1.8  Underwriting Requirements.  In connection with any
offering involving an underwriting of shares of the Company's capital
stock, the Company shall not be required under Section 1.3 to include any
of the Holders' securities in such underwriting unless they accept the
terms of the underwriting as agreed upon between the Company and the
underwriters selected by it (or by other persons entitled to select the
underwriters), and then only in such quantity as the underwriters
determine in their sole discretion will not jeopardize the success of the
offering by the Company.  If the total amount of securities, including
Registrable Securities, requested by stockholders to be included in such
offering exceeds the amount of securities sold other than by the Company
that the underwriters determine in their sole discretion is compatible
with the success of the offering, then the Company shall be required to
include in the offering only that number of such securities, including
Registrable Securities, which the underwriters determine in their sole
discretion will not jeopardize the success of the offering (the securities
so included to be apportioned pro rata among the selling stockholders
according to the total amount of securities entitled to be included
therein owned by each selling stockholder or in such other proportions as
shall mutually be agreed to by such selling stockholders) but in no event
shall (i) the amount of securities of the selling Holders included in the
offering be reduced below twenty percent (20%) of the total amount of
securities included in such offering unless such offering is the initial
public offering of the Company's securities, in which case the selling
Holders may be excluded if the underwriters make the determination
described above and no other stockholder's securities are included or (ii)
any securities held by a Founder be included if any securities held by any
selling Holder are excluded.  For purposes of the preceding parenthetical
concerning apportionment, for any selling stockholder which is a holder of
Registrable Securities and which is a partnership or corporation, the
partners, retired partners and stockholders of such holder, or the estates
and family members of any such partners and retired partners and any
trusts for the benefit of any of the foregoing persons shall be deemed to
be a single "selling stockholder," and any pro-rata reduction with respect
to such "selling stockholder" shall be based upon the aggregate amount of
shares carrying registration rights owned by all entities and individuals
included in such "selling stockholder," as defined in this sentence.

        1.9  Delay of Registration.  No Holder shall have any right to
obtain or seek an injunction restraining or otherwise delaying any such
registration as the result of any controversy that might arise with
respect to the interpretation or implementation of this Section 1.

        1.10 Indemnification.  In the event any Registrable Securities
are included in a registration statement under this Section 1:

             (a) To the extent permitted by law, the Company will
indemnify and hold harmless each Holder, its officers, directors,
employees, partners, members and agents, any underwriter (as defined in
the Securities Act) for such Holder and each person, if any, who controls
such Holder or underwriter within the meaning of the Securities Act or the
Securities Exchange Act of 1934, as amended (the "Exchange Act"), against
any losses, claims, damages, or liabilities (joint or several) and
reasonable expenses to which they may become subject under the Securities
Act, the Exchange Act or other federal or state law, insofar as such
losses, claims, damages, or liabilities (or actions in respect thereof)
arise out of or are based upon any of the following statements, omissions
or violations (collectively a "Violation"):  (i) any untrue statement or
alleged untrue statement of a material fact contained in such registration
statement, including any preliminary prospectus or final prospectus
contained therein or any amendments or supplements thereto, (ii) the
omission or alleged omission to state therein a material fact required to
be stated therein, or necessary to make the statements therein not
misleading, or (iii) any violation or alleged violation by the Company of
the Securities Act, the Exchange Act, any state securities law or any rule
or regulation promulgated under the Securities Act, the Exchange Act or
any state securities law; and the Company will pay to each such Holder,
underwriter or controlling person, as incurred, any legal or other
expenses reasonably incurred by them in connection with investigating or
defending any such loss, claim, damage, liability, or action; provided,
however, that the indemnity agreement contained in this subsection 1.10(a)
shall not apply to amounts paid in settlement of any such loss, claim,
damage, liability, or action if such settlement is effected without the
consent of the Company (which consent shall not be unreasonably withheld),
nor shall the Company be liable to any Holder, underwriter or controlling
person for any such loss, claim, damage, liability, or action to the
extent that it arises out of or is based upon a Violation which occurs in
reliance upon and in conformity with written information furnished
expressly for use in connection with such registration by any such Holder,
underwriter or controlling person.

             (b) To the extent permitted by law, each selling Holder
will indemnify and hold harmless the Company, each of its directors, each
of its officers who has signed the registration statement, each person, if
any, who controls the Company within the meaning of the Securities Act,
any underwriter, any other Holder selling securities in such registration
statement and any controlling person of any such underwriter or other
Holder, against any losses, claims, damages, or liabilities (joint or
several) and reasonable expenses to which any of the foregoing persons may
become subject, under the Securities Act, the Exchange Act or other
federal or state law, insofar as such losses, claims, damages, or
liabilities (or actions in respect thereto) arise out of or are based upon
any Violation, in each case to the extent (and only to the extent) that
such Violation occurs in reliance upon and in conformity with written
information furnished by such Holder expressly for use in connection with
such registration; and each such Holder will pay, as incurred, any legal
or other expenses reasonably incurred by any person intended to be
indemnified pursuant to this subsection 1.10(b), in connection with
investigating or defending any such loss, claim, damage, liability, or
action; provided, however, that the indemnity agreement contained in this
subsection 1.10(b) shall not apply to amounts paid in settlement of any
such loss, claim, damage, liability or action if such settlement is
effected without the consent of the Holder, which consent shall not be
unreasonably withheld; provided, that in no event shall any indemnity
under this subsection 1.10(b) exceed the net proceeds from the offering
received by such Holder, except in the case of willful fraud by such
Holder.

             (c) Promptly after receipt by an indemnified party under
this Section 1.10 of notice of the commencement of any action (including
any governmental action), such indemnified party will, if a claim in
respect thereof is to be made against any indemnifying party under this
Section 1.10, deliver to the indemnifying party a written notice of the
commencement thereof and the indemnifying party shall have the right to
participate in, and, to the extent the indemnifying party so desires,
jointly with any other indemnifying party similarly noticed, to assume the
defense thereof with counsel mutually satisfactory to the parties;
provided, however, 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
reasonable 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.  The failure to deliver
written notice to the indemnifying party within a reasonable time of the
commencement of any such action, if prejudicial to its ability to defend
such action, shall relieve such indemnifying party of any liability to the
indemnified party under this Section 1.10, but the omission so to deliver
written notice to the indemnifying party will not relieve it of any
liability that it may have to any indemnified party otherwise than under
this Section 1.10.

             (d) If the indemnification provided for in this
Section 1.10 is held by a court of competent jurisdiction to be
unavailable to an indemnified party with respect to any loss, liability,
claim, damage or expense referred to therein, then the indemnifying party,
in lieu of indemnifying such indemnified party hereunder, shall contribute
to the amount paid or payable by such indemnified party as a result of
such loss, liability, claim, damage, or expense in such proportion as is
appropriate to reflect the relative fault of the indemnifying party on the
one hand and of the indemnified party on the other in connection with the
statements or omissions that resulted in such loss, liability, claim,
damage or expense as well as any other relevant equitable considerations;
provided, that in no event shall any contribution by a Holder under this
Subsection 1.10(d) exceed the net proceeds from the offering received by
such Holder, except in the case of willful fraud by such Holder.  The
relative fault of the indemnifying party and of the indemnified party
shall be determined by reference to, among other things, whether the
untrue or alleged untrue statement of a material fact or the omission to
state a material fact relates to information supplied by the indemnifying
party or by the indemnified party and the parties' relative intent,
knowledge, access to information, and opportunity to correct or prevent
such statement or omission.

             (e) Notwithstanding the foregoing, to the extent that
the provisions on indemnification and contribution contained in the
underwriting agreement entered into in connection with the underwritten
public offering are in conflict with the foregoing provisions, the
provisions in the underwriting agreement shall control.

             (f) The obligations of the Company and Holders under
this Section 1.10 shall survive the completion of any offering of
Registrable Securities in a registration statement under this Section 1,
and otherwise.

        1.11 Reports Under Securities Exchange Act of 1934.  With a
view to making available to the Holders the benefits of Rule 144
promulgated under the Securities Act and any other rule or regulation of
the SEC that may at any time permit a Holder to sell securities of the
Company to the public without registration or pursuant to a registration
on Form S-3, the Company agrees to:

             (a) make and keep public information available, as those
terms are understood and defined in SEC Rule 144, at all times after
ninety (90) days after the effective date of the first registration
statement filed by the Company for the offering of its securities to the
general public so long as the Company remains subject to the periodic
reporting requirements under Sections 13 or 15(d) of the Exchange Act;

             (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; and

             (d) furnish to any Holder, so long as the Holder owns
any Registrable Securities, forthwith upon request (i) a written statement
by the Company that it has complied with the reporting requirements of SEC
Rule 144 (at any time after ninety (90) days after the effective date of
the first registration statement filed by the Company), the Securities Act
and the Exchange Act (at any time after it has become subject to such
reporting requirements), or that it qualifies as a registrant whose
securities may be resold pursuant to Form S-3 (at any time after it so
qualifies), (ii) a copy of the most recent annual or quarterly report of
the Company and such other reports and documents so filed by the Company,
and (iii) such other information as may be reasonably requested in
availing any Holder of any rule or regulation of the SEC which permits the
selling of any such securities without registration or pursuant to such
form.

        1.12 Assignment of Registration Rights.  The rights to cause
the Company to register Registrable Securities pursuant to this Section 1
may be assigned (but only with all related obligations) by a Holder to a
transferee or assignee of (a) at least 1,000,000 shares of such
securities, or (b) all securities owned by a Holder, provided the Company
is, within a reasonable time after such transfer, furnished with written
notice of the name and address of such transferee or assignee and the
securities with respect to which such registration rights are being
assigned.  For the purposes of determining the number of shares of
Registrable Securities held by a transferee or assignee, the holdings of
transferees and assignees of a partnership who are partners or retired
partners of such partnership (including spouses and ancestors, lineal
descendants and siblings of such partners or spouses who acquire
Registrable Securities by gift, will or intestate succession) shall be
aggregated together and with the partnership; provided that all assignees
and transferees who would not qualify individually for assignment of
registration rights shall have a single attorney-in-fact for the purpose
of exercising any rights, receiving notices or taking any action under
Section 1.

        1.13 Limitations on Subsequent Registration Rights.  From and
after the date of this Agreement, the Company shall not, without the prior
written consent of the Holders of a majority of the Series A Preferred
Stock (or the Common Stock issuable or issued upon conversion thereof) and
the Series B Preferred Stock (or the Common Stock issuable or issued upon
conversion thereof), voting together as a single class, enter into any
agreement with any holder or prospective holder of any securities of the
Company which would allow such holder or prospective holder (a) to include
such securities in any registration filed under Section 1.2 hereof, unless
under the terms of such agreement, such holder or prospective holder may
include such securities in any such registration only to the extent that
the inclusion of his securities will not reduce the amount of the
Registrable Securities of the Holders which is included or (b) to make a
demand registration which could result in such registration statement
being declared effective prior to the earlier of either of the dates set
forth in subsection 1.2(a) or within one hundred twenty (120) days of the
effective date of any registration effected pursuant to Section 1.2.

        1.14 Market-Standoff Agreement.

             (a) Market-Standoff Period; Agreement.  In connection
with the initial public offering of the Company's securities and upon
request of the Company or the underwriters managing such offering of the
Company's securities, each Holder agrees not to sell, make any short sale
of, loan, grant any option for the purchase of, or otherwise dispose of
any securities of the Company (other than those included in the
registration) without the prior written consent of the Company or such
underwriters, as the case may be, for such period of time (not to exceed
180 days) from the effective date of such registration as may be requested
by the Company or such managing underwriters and to execute an agreement
reflecting the foregoing as may be requested by the underwriters at the
time of the Company's initial public offering.

             (b) Limitations.  The obligations described in Section
1.14(a) shall apply only if all officers, directors and five percent (5%)
stockholders of the Company enter into similar agreements, and shall not
apply to a registration relating solely to employee benefit plans, or to a
registration relating solely to a transaction pursuant to Rule 145 under
the Securities Act.

             (c) Stop-Transfer Instructions.  In order to enforce the
foregoing covenants, the Company may impose stop-transfer instructions
with respect to the securities of each Holder (and the securities of every
other person subject to the restrictions in Section 1.14(a)).

             (d) Transferees Bound.  Each Holder agrees that prior to
the Company's initial public offering it will not transfer securities of
the Company unless each transferee agrees in writing to be bound by all of
the provisions of this Section 1.14.

        1.15 Termination of Registration Rights.  No Holder shall be
entitled to exercise any right provided for in this Section 1 after the
earlier of (i) five (5) years following the consummation of a Qualified
IPO, or (ii) such time as Rule 144 or another similar exemption under the
Securities Act is available for the sale of all of such Holder's shares
during a three (3)-month period without registration and without
limitation.

     2. Covenants of the Company.

        2.1  Delivery of Financial Statements.  The Company shall
deliver to each Holder of at least 400,000 shares of Registrable
Securities:

             (a) as soon as practicable, but in any event within
ninety (90) days after the end of each fiscal year of the Company, an
income statement for such fiscal year, a balance sheet of the Company and
statement of stockholder's equity as of the end of such year, and a
statement of cash flows for such year, such year-end financial reports to
be in reasonable detail, prepared in accordance with generally accepted
accounting principles ("GAAP"), and audited and certified by an
independent public accounting firm of nationally recognized standing
selected by the Company;

             (b) as soon as practicable, but in any event within
thirty (30) days after the end of each of the first three (3) quarters of
each fiscal year of the Company, an unaudited profit or loss statement, a
statement of cash flows for such fiscal quarter and an unaudited balance
sheet as of the end of such fiscal quarter prepared in accordance with
GAAP;

             (c) upon written request, within thirty (30) days of the
end of each month, an unaudited income statement and a statement of cash
flows and balance sheet for and as of the end of such month, in reasonable
detail;  provided, however, that only Holders of at least 2,000,000 shares
of Registrable Securities shall be entitled to request such statement; and

             (d) as soon as practicable, but in any event thirty (30)
days prior to the end of each fiscal year, a budget and business plan for
the next fiscal year, prepared on a monthly basis, and, as soon as
prepared, any other budgets or revised budgets prepared by the Company.

        2.2  Inspection.  The Company shall permit each Holder of at
least 400,000 shares of Registrable Securities, at such Holder's expense,
to visit and inspect the Company's properties, to examine its books of
account and records and to discuss the Company's affairs, finances and
accounts with its officers, all at such reasonable times as may be
requested by the Investor or Techne, as applicable; provided, however,
that the Company shall not be obligated pursuant to this Section 2.2 to
provide access to any information which it reasonably considers to be a
trade secret or similar confidential information, the disclosure of which
would have a material adverse effect on the Company or which would
jeopardize the trade secret's status as such.

        2.3  Right of First Offer.  Subject to the terms and
conditions specified in this Section 2.3, the Company hereby grants to
each Major Investor (as hereinafter defined) a right of first offer with
respect to future sales by the Company of its Shares (as hereinafter
defined).  For purposes of this Section 2.3, a "Major Investor" shall mean
any person who holds at least 1,000,000 shares of Registrable Securities.
For purposes of this Section 2.3, Major Investor includes any general
partners and affiliates of a Major Investor.  A Major Investor who chooses
to exercise the right of first offer may designate as purchasers under
such right itself or its partners or affiliates in such proportions as it
deems appropriate.

        Each time the Company proposes to offer any shares of, or
securities convertible into or exercisable for any shares of, any class of
its capital stock ("Shares"), the Company shall first make an offering of
such Shares to each Major Investor in accordance with the following
provisions:

             (a) The Company shall deliver a notice by certified mail
("Notice") to the Major Investors stating (i) its bona fide intention to
offer such Shares, (ii) the number of such Shares to be offered, and
(iii) the price and terms, if any, upon which it proposes to offer such
Shares.

             (b) Within 15 calendar days after delivery of the
Notice, the Major Investor may elect to purchase or obtain, at the price
and on the terms specified in the Notice, up to that portion of such
Shares which equals the proportion that the number of shares of Common
Stock issued and held, or issuable upon conversion and exercise of all
convertible or exercisable securities then held, by such Major Investor
bears to the total number of shares of Common Stock then outstanding
(assuming full conversion and exercise of all convertible or exercisable
securities).  The Company shall promptly, in writing, inform each Major
Investor that purchases all the shares available to it (each, a
"Fully-Exercising Investor") of any other Major Investor's failure to do
likewise.  During the ten (10)-day period commencing after receipt of such
information, each Fully-Exercising Investor shall be entitled to obtain
that portion of the Shares for which Major Investors were entitled to
subscribe but which were not subscribed for by the Major Investors that is
equal to the proportion that the number of shares of Common Stock issued
and held, or issuable upon conversion and exercise of all convertible or
exercisable securities then held, by such Fully-Exercising Investor bears
to the total number of shares of Common Stock then outstanding (assuming
full conversion and exercise of all convertible or exercisable
securities).

             (c) The Company may, during the 45-day period following
the expiration of the period provided in subsection 2.3(b) hereof, offer
the remaining unsubscribed portion of the Shares to any person or persons
at a price not less than, and upon terms no more favorable to the offeree
than those specified in the Notice.  If the Company does not enter into an
agreement for the sale of the Shares within such period, or if such
agreement is not consummated within 60 days of the execution thereof, the
right provided hereunder shall be deemed to be revived and such Shares
shall not be offered unless first reoffered to the Major Investors in
accordance herewith.

             (d) The right of first offer in this paragraph 2.3 shall
not be applicable (i) to the issuance or sale of up to 2,500,000 shares of
Common Stock (or options therefor) since the inception of the Company to
employees, consultants and directors, pursuant to plans or agreements
approved by the Board of Directors for the primary purpose of soliciting
or retaining their services, (ii) to or after consummation of a Qualified
IPO, (iii) to the issuance of securities pursuant to the conversion or
exercise of convertible or exercisable securities outstanding as of the
date hereof, (iv) to the issuance of securities in connection with a bona
fide business acquisition of or by the Company that is approved by the
Board of Directors, whether by merger, consolidation, sale of assets, sale
or exchange of stock or otherwise, (v) to the issuance of securities to
financial institutions or lessors in connection with commercial credit
arrangements, equipment financings, or similar transactions, (vi) to the
issuance or sale of up to 8,153,846 shares of Series B Preferred Stock, or
(vii) to the issuance of securities that, with unanimous approval of the
Board of Directors of the Company, are not offered to any existing
stockholder of the Company.

        2.4  Board of Directors.  As of the date of this Agreement,
and notwithstanding anything to the contrary in the Bylaws of the Company,
the Board of Directors of the Company shall consist of five (5) members,
not more than two (2) of which shall be employees of the Company. OrbiMed
Advisors LLC or its affiliates (collectively "OrbiMed") shall have the
right to designate one member of the Board of Directors and the OrbiMed
designee shall also be a member of each committee of the Board of
Directors, including, without limitation, the Compensation Committee and
the Audit Committee. The Board of Directors shall hold a regularly
scheduled meeting at least once every ninety (90) days. Each member of the
Board of Directors and the members of each committee of the Board of
Directors shall receive notice of each meeting at least fifteen (15) days
before the meeting and such notice shall be provided to each member in the
same manner. The Company will reimburse the OrbiMed director for his
reasonable out-of-pocket and travel expenses incurred in connection with
attending such meetings.

        2.5  Observation Rights.

             (a) The Company agrees that for so long as Healthcap III
or its affiliates (collectively "Healthcap") owns 269,231 shares of
Registrable Securities, Healthcap shall be entitled to designate one
individual to act as a non-voting observer of the Board of Directors of
the Company (the "Observer").  The Observer shall not have any right to
vote as a director of the Company but shall otherwise be entitled to
notice of and to attend all meetings of the Board of Directors of the
Company, and to receive any material distributed to the directors in their
capacity as directors of the Company.  The Company shall not have any
obligation to pay any expenses incurred in connection with the Observer's
attendance at such meetings.

             (b) The Observer shall be subject to the obligations of
confidentiality set forth in the Purchase Agreements.  Notwithstanding
Section 2.5(a), the Company reserves the right not to provide information
and to exclude the Observer from any meeting or portion thereof if
delivery of such information or attendance at such meeting would result in
a loss of trade secret protection for trade secrets of the Company, or
would adversely affect the attorney-client privilege between the Company
and its counsel.

        2.6  Termination of Covenants.

             (a) The covenants set forth in Sections 2.1 through
Section 2.5 shall terminate as to each Investor and Techne and be of no
further force or effect (i) immediately prior to the consummation of a
Qualified IPO, or (ii) at such time the Company becomes subject to the
reporting provisions of the Securities and Exchange Act of 1934, as
amended.

             (b) The covenants set forth in Sections 2.1 and 2.2
shall terminate as to each Holder and be of no further force or effect
when the Company first becomes subject to the periodic reporting
requirements of Sections 13 or 15(d) of the Exchange Act, if this occurs
earlier than the events described in Section 2.6(a) above.

     3. Miscellaneous.

        3.1  Successors and Assigns.  Except as otherwise provided in
this Agreement, the terms and conditions of this Agreement shall inure to
the benefit of and be binding upon the respective permitted successors and
assigns of the parties (including transferees of any of the Registrable
Securities).  Nothing in this Agreement, express or implied, is intended
to confer upon any party other than the parties hereto or their respective
successors and assigns any rights, remedies, obligations, or liabilities
under or by reason of this Agreement, except as expressly provided in this
Agreement.

        3.2  Amendments and Waivers.  Any term of this Agreement may
be amended or waived only with the written consent of the Company and the
holders of a majority of the Registrable Securities then outstanding, not
including the Founder's Stock; provided that if (i) such amendment has the
effect of affecting the Founder's Stock (a) in a manner different than
securities issued to the Investors or Techne and (b) in a manner adverse
to the interests of the holders of the Founder's Stock, then such
amendment shall require the consent of the holder or holders of a majority
of the Founder's Stock, (ii) such amendment has the effect of affecting
the Series A Preferred Stock (m) in a manner different than securities
issued to the Investors or (n) in a manner adverse to the interests of the
holders of the Series A Preferred Stock, then such amendment shall require
the consent of the holder or holders of a majority of the Series A
Preferred Stock, (iii) such amendment has the effect of affecting the
Series B Preferred Stock (x) in a manner different than securities issued
to Techne or (y) in a manner adverse to the interests of the holders of
the Series B Preferred Stock, then such amendment shall require the
consent of the holder or holders of a majority of the Series B Preferred
Stock, or (iv) such amendment alters Section 2.4, then such amendment
shall require the consent of OrbiMed.  Any amendment or waiver effected in
accordance with this paragraph shall be binding upon each holder of any
Registrable Securities then outstanding, each future holder of all such
Registrable Securities, and the Company.

        3.3  Notices.  Unless otherwise provided, any notice required
or permitted by this Agreement shall be in writing and shall be deemed
sufficient upon delivery, when delivered personally or by overnight
courier or sent by telegram or fax, or forty-eight (48) hours after being
deposited in the U.S. mail, as certified or registered mail, with postage
prepaid, and addressed to the party to be notified at such party's address
or fax number as set forth below hereto or as subsequently modified by
written notice.

        3.4  Severability.  If one or more provisions of this
Agreement are held to be unenforceable under applicable law, the parties
agree to renegotiate such provision in good faith.  In the event that the
parties cannot reach a mutually agreeable and enforceable replacement for
such provision, then (a) such provision shall be excluded from this
Agreement, (b) the balance of the Agreement shall be interpreted as if
such provision were so excluded and (c) the balance of the Agreement shall
be enforceable in accordance with its terms.

        3.5  Governing Law.  This Agreement and all acts and
transactions pursuant hereto shall be governed, construed and interpreted
in accordance with the laws of the State of New York, without giving
effect to principles of conflicts of laws.

        3.6  Counterparts.  This Agreement may be executed in two or
more counterparts, each of which shall be deemed an original, but all of
which together shall constitute one and the same instrument.

        3.7  Titles and Subtitles.  The titles and subtitles used in
this Agreement are used for convenience only and are not to be considered
in construing or interpreting this Agreement.

        3.8  Aggregation of Stock.  All shares of the Preferred Stock
held or acquired by affiliated entities or persons, successor entities,
investment funds managed or advised by an Investor, a manager or advisor
of an Investor, or an affiliate of such manager or advisor shall be
aggregated together for the purpose of determining the availability of any
rights under this Agreement.

        3.9  Additional Investors.  Notwithstanding anything to the
contrary contained herein, if the Company shall issue additional shares of
its Series B Preferred Stock, any purchaser of such shares of Series B
Preferred Stock may become a party to this Agreement by executing and
delivering an additional counterpart signature page to this Agreement and
shall be deemed an "Investor" hereunder.

        3.10 Consent.  The execution and delivery of this Agreement by
Techne shall constitute:  (i) a complete waiver of Techne's rights under
Sections 6.3, 6.4, 6.5, 6.13, 7.1, 7.2(a) and 8 of that certain Investment
Agreement, dated November 18, 1997, by and between the Company and Techne;
and (ii) consent to the Company's proposed Amended and Restated
Certificate of Incorporation, in the form attached as Exhibit A to the
Purchase Agreement.


     The parties have executed this Investors Rights Agreement as of the
date first above written.

COMPANY:                                           INVESTORS:


CHEMOCENTRYX, INC.                                 ________________________
                                                        (Investor)

By:_____________________                           By:_____________________
Name:  Thomas J. Schall
Title:  President and Chief Executive Officer      Name:___________________
                                                           (print)
Address:                                           Title:__________________

Fax:                                               Address:

                                                   Fax:

FOUNDER:                                           TECHNE:

___________________________                        TECHNE CORPORATION
Thomas J. Schall
                                                   By:______________________
                                                   Name:____________________
                                                   Title:___________________

                                                   Address:

                                                   Fax: