<PAGE>

                                                                    EXHIBIT 10.5

                               SAFESCIENCE, INC.
                         REGISTRATION RIGHTS AGREEMENT
                         -----------------------------

          THIS REGISTRATION RIGHTS AGREEMENT (the "Agreement") is made as of
                                                   ---------
June 29, 2001 by and between SafeScience, Inc., a Nevada corporation (the
"Company"), and Elan International Services, Ltd., a Bermuda exempted limited
 -------
liability company ("EIS").
                    ---

                               R E C I T A L S:

          A.  Pursuant to a Securities Purchase Agreement dated as of the date
hereof by and between the Company and EIS (as amended at any time, the "Purchase
                                                                        --------
Agreement"), EIS has acquired, or may acquire in the future, (a) certain shares
---------
of Series A Preferred Stock, par value U.S.$.01 per share, of the Company (the
"Series A Preferred Stock") convertible into shares of common stock, par value
 ------------------------
U.S.$.01 per share, of the Company (the "Common Stock"), (b) certain shares of
                                         ------------
Series B Preferred Stock, par value U.S.$.01 per share, of the Company (the
"Series B Preferred Stock") convertible into shares of Common Stock, (c) certain
 ------------------------
shares of Series C Preferred Stock, par value U.S.$.01 per share, of the Company
(the "Series C Preferred Stock," together with the Series A Preferred Stock and
      ------------------------
the Series B Preferred Stock, the "Preferred Stock") convertible into shares of
Common Stock, (d) certain shares of Common Stock and (e) warrants (the
"Warrants") to purchase certain shares of Common Stock.  The Preferred Stock,
 --------
the Common Stock and the Warrants collectively are referred to herein as the
"Securities".
 ----------

          B.  The execution of the Purchase Agreement has occurred on the date
hereof and it is a condition to the closing of the transactions contemplated
thereby that the parties execute and deliver this Agreement.

          C.  The parties desire to set forth herein their agreement on the
terms and subject to the conditions set forth herein related to the granting of
certain registration rights to the Holders (as defined below) relating to the
Common Stock held and the Common Stock issuable upon conversion or exercise of
the Securities, as applicable, by such Holders.

                              A G R E E M E N T:

          The parties hereto agree as follows:

     1.   Certain Definitions.  As used in this Agreement, the following terms
          -------------------
shall have the following respective meanings:

          "Commission" shall mean the U.S. Securities and Exchange Commission.
           ----------

          "Exchange Act" shall mean the U.S. Securities Exchange Act of 1934, as
           ------------
amended, and the rules and regulations of the Commission promulgated thereunder,
all as the same shall be in effect from time to time.
<PAGE>

          "Holders" or "Holders of Registrable Securities" shall mean EIS and
           -------      ---------------------------------
any Person who shall have acquired Registrable Securities from EIS as permitted
herein, either individually or jointly, as the case may be, in a transaction
pursuant to which registration rights are transferred pursuant to Section 10
hereof.

          "Person" shall mean an individual, a partnership, a corporation, a
           ------
limited liability company, an association, a joint stock company, a trust, a
joint venture, an unincorporated organization or a governmental or quasi-
governmental entity, or any department, agency or political subdivision thereof
or any other entity of any kind.

          "Registrable Securities" means (i) any shares of Common Stock acquired
           ----------------------
pursuant to the Purchase Agreement; (ii) any shares of Common Stock issued or
issuable upon conversion or exercise of any of the Securities, as the case may
be; and (iii) any shares of Common Stock issued or issuable in respect of the
securities referred to in clauses (i) and (ii) above, upon any stock split,
stock dividend, recapitalization, anti-dilution adjustment, or otherwise, until,
in the case of any such security, it is (A) sold pursuant to an effective
registration statement under the Securities Act; (B) eligible to be sold into
the public market without regard to volume limitations under Rule 144(k)
promulgated under the Securities Act (or any successor rule); (C) sold pursuant
to Rule 144 under the Securities Act (or any successor rule); or (D) sold by a
Person in a transaction in which registration rights are not transferred
pursuant to Section 10 hereof.  Whenever a number or percentage of Registrable
Securities is to be determined pursuant to this Agreement, each then outstanding
Security that is convertible into or exercisable for shares of Common Stock will
be deemed to be equal to the number of shares of Common Stock for which such
Security is then so convertible or exercisable.

          The terms "register," "registered" and "registration" refer to a
                     --------    ----------       ------------
registration effected by preparing, filing and having declared effective a
registration statement in compliance with the Securities Act.

          "Registration Expenses" shall mean (i) all expenses, other than
           ---------------------
Selling Expenses (defined below), incurred by the Company in complying with
Sections 2 or 3 hereof, including without limitation, all registration,
qualification and filing fees, exchange or quotation medium listing fees,
printing and delivery expenses, escrow and custodian fees, fees and
disbursements of counsel for the Company, blue sky fees and expenses and the
expenses of accountants for the Company including the expenses of any special
audits incident to or required by any such registration and (ii) the reasonable
fees and disbursements of one counsel chosen by the holders of a majority of the
Registrable Securities included in such registration for the purpose of
rendering a legal opinion on behalf of such holders in connection with any
Demand Registration or Piggyback Registration.

          "Securities Act" shall mean the U.S. Securities Act of 1933, as
           --------------
amended, and the rules and regulations of the Commission promulgated thereunder,
all as the same shall be in effect from time to time.

          "Selling Expenses" shall mean all underwriting discounts, selling
           ----------------
commissions and stock transfer taxes and the costs, fees and expenses of any
accountants, attorneys (other than

                                       2
<PAGE>

the cost, fees and expenses of attorneys, which are Registration Expenses) or
other experts retained by the Holders.

     2.   Demand Registrations.
          --------------------

          (a)  Requests for Registration. As long as the Company is obligated to
               -------------------------
file reports with the Commission pursuant to Section 12 or Section 15(d) of the
Exchange Act, any Holder or Holders who collectively hold Registrable Securities
representing at least 20% of the Registrable Securities then outstanding shall
have the right (subject to the limitations set forth below), exercisable by
written notice to the Company (each a "Registration Request"), to have the
                                       --------------------
Company prepare and file with the Commission a registration statement under the
Securities Act covering the Registrable Securities that are the subject of such
request (each, a "Demand Registration").  The Holders shall have the right to
                  -------------------
one Demand Registration collectively.  Within 10 days after receipt of any such
request, the Company will give written notice of such requested registration to
all other Holders of Registrable Securities.  The Company shall include such
other Holders' Registrable Securities in such offering if they have responded
affirmatively within 10 days after the receipt of the Company's notice.

     A request for registration under this Section 2(a) will not count as a
Demand Registration until the registration statement has become effective and
remained effective until the earlier of 30 days and the sale of all securities
registered thereunder (unless such registration statement has not become
effective due solely to the actions or failure to act with respect to such
registration of the Holders requesting such registration, including a request by
such Holders that such registration be withdrawn).

          (b)  Priority on Demand Registrations.  If a Demand Registration is an
               --------------------------------
underwritten offering and the managing underwriters determine in good faith and
advise the Company in writing that in their opinion the number of Registrable
Securities and, if permitted hereunder, other securities requested to be
included in such offering, exceeds the number of Registrable Securities and
other securities, if any, which could be sold in such offering without adversely
affecting the marketability of the offering, the Company will include in such
registration:

          (i) first, the Registrable Securities requested to be included in such
     registration by the Holders (or, if necessary, such Registrable Securities
     pro rata among the Holders thereof based upon the number of Registrable
     --- ----
     Securities owned by each such Holder or such other arrangement agreed to
     among the Holders); and

          (ii) thereafter, other securities requested to be included in such
     registration, as determined by the Company.

If the managing underwriters have not limited the number of Registrable
Securities or other securities to be underwritten, the Company may include
securities for its own account in such registration if the managing underwriters
so agree and if the number of Registrable Securities and other securities which
would otherwise have been included in such registration and underwriting will
not thereby be limited. The Holders of any Registrable Securities to be included
in such an
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<PAGE>

underwritten offering shall enter into an underwriting agreement (which shall be
in customary form, may include agreements as to indemnification and contribution
and shall provide that the representations and warranties by the Company to and
for the benefit of such underwriters shall also be made to and for the benefit
of such Holders).

          (c) Restrictions on Demand Registration.  The Company may postpone or
              -----------------------------------
suspend, for up to 120 days in the aggregate in any 12-month period, the filing
or the effectiveness of a registration statement for a Demand Registration if
the Company's board of directors determines in good faith and notifies the
Holders in writing that such Demand Registration (i) would reasonably be
expected to have a material adverse effect on (x) any proposal or plan by the
Company to engage in any financing, acquisition or disposition of assets or
other plan outside the ordinary course of business or (y) any merger,
consolidation, tender offer or similar transaction, (ii) would require
disclosure of any information that the board of directors of the Company
determines in good faith the disclosure of which would be detrimental to the
Company or (iii) would require a special audit by the Company; provided, that in
                                                               --------
such event, the Holders initially requesting such Demand Registration shall be
entitled to withdraw such request and, if such request is withdrawn, such Demand
Registration will not count as a permitted Demand Registration hereunder and the
Company will pay any Registration Expenses in connection with such registration.

          (d) Selection of Investment Bankers and Managers.  The Company will
              --------------------------------------------
have the right, but not the obligation, to select the investment banker(s) and
manager(s) to administer an offering pursuant to the Demand Registration,
subject to the prior written approval of a majority of the Holders participating
in the offering, which will not be unreasonably withheld, delayed or
conditioned.

          (e) The Company represents that it is not a party to, or otherwise
subject to, any agreement, other than this Agreement or as set forth on Schedule
2(e) hereto, granting registration rights to any other Person with respect to
any securities of the Company.

     3.   Piggyback Registrations.
          -----------------------

          (a) Right to Piggyback.  If at any time the Company shall propose to
              ------------------
register shares of Common Stock under the Securities Act (other than in a
registration statement relating to solely to sales of securities to participants
in a Company dividend reinvestment plan, or Form S-4 or S-8 or any successor
form or in connection with an acquisition or exchange offer or an offering of
securities solely to the existing shareholders or employees of the Company), the
Company will (i) give prompt written notice to all Holders of Registrable
Securities of its intention to effect such a registration and (ii) subject to
Section 3(b) and the other terms of this Agreement, include in such registration
all Registrable Securities which are permitted under applicable securities laws
to be included in the form of registration statement selected by the Company and
with respect to which the Company has received written requests for inclusion
therein within 15 days after the receipt of the Company's notice (each, a
"Piggyback Registration").  The Holders will be permitted to withdraw all or any
 ----------------------
part of the Registrable Securities from a Piggyback Registration at any time
prior to the effective date of such Piggyback Registration.

                                       4
<PAGE>

          (b)   Priority on Piggyback Registrations. If a Piggyback Registration
                -----------------------------------
is to be an underwritten offering, and the managing investment bank advises the
Company in writing that in their opinion the number of securities requested to
be included in such registration exceeds the number which can be sold in such
offering without adversely affecting the marketability of the offering, the
Company will include in such registration:

          (i)   first, the securities the Company proposes to sell for its own
     account;

          (ii)  second, the Registrable Securities requested to be included in
     such registration by the Holders and any securities requested to be
     included in such registration by any other Person pursuant to a demand
     registration request, other than Persons having a lower priority of
     registration than the Holders, pro rata among the Holders of such
                                    --- ----
     Registrable Securities and such other Persons, on the basis of the number
     of securities requested to be included in such registration by each of such
     Holders and such other Persons; and

          (iii) thereafter, other securities requested to be included in such
     registration, as determined by the Company.

The Holders of any Registrable Securities to be included in an underwritten
offering shall enter into an underwriting agreement (which shall be in customary
form, may include agreements as to indemnification and contribution, and shall
provide that the representations and warranties by the Company to and for the
benefit of such underwriters shall also be made to and for the benefit of such
Holders).

          (c)   Right to Terminate Registration.  If at any time after giving
                -------------------------------
written notice of its intention to register any of its securities as set forth
in Section 3(a) and prior to the effective date of the registration statement
filed in connection with such registration, the Company shall determine for any
reason not to register such securities, the Company may, at its election, give
written notice of such determination to each Holder of Registrable Securities
and thereupon be relieved of its obligation to register any Registrable
Securities in connection with such registration (but not from its obligation to
pay the Registration Expenses in connection therewith as provided herein).

          (d)   Selection of Underwriters/Placement Agents. The Company will
                ------------------------------------------
have the right to select the investment banker(s) and manager(s) to administer
an offering pursuant to a Piggyback Registration, subject to the approval of the
Holders of a majority of the Registrable Securities participating in such
offering, which approval will not be unreasonably withheld, delayed or
conditioned.

     4.   Expenses of Registration.
          ------------------------

          Except as otherwise provided herein or as may otherwise be prohibited
by applicable law, all Registration Expenses incurred in connection with all
registrations pursuant to Sections 2 and 3 hereof shall be borne by the Company.
All Selling Expenses relating to

                                       5
<PAGE>

securities registered on behalf of the Holders of Registrable Securities shall
be borne by such Holders.

     5.   Holdback Agreements.
          -------------------

          (a) The Company agrees (i) not to effect any public sale or
distribution of its equity securities, or any securities convertible into or
exchangeable or exercisable for such securities, during the 10-day period prior
to, and during the 90-day period following, the effective date of any
underwritten Demand Registration or any underwritten Piggyback Registration
(except as part of such underwritten registration or pursuant to registration
statements on Form S-4 or Form S-8 or any successor form), unless the
underwriters managing the offering otherwise agree, and (ii) to use its best
efforts to cause its executive officers and directors and each holder of at
least 2% (on a fully-diluted basis) of its outstanding shares of Common Stock,
or any securities convertible into or exchangeable or exercisable for shares of
Common Stock, purchased from the Company at any time after the date of this
Agreement (other than in a registered public offering) to agree not to effect
any public sale or distribution (including sales pursuant to Rule 144) of any
such securities during such periods (except as part of such underwritten
registration, if otherwise permitted), unless the underwriters managing the
registered public offering otherwise agree; provided, that no executive officer,
                                            --------
director or such 2% stockholder shall be required to enter into more than one
such agreement in any 12-month period.

          (b) If requested by the managing underwriter(s) in an underwritten
offering of Common Stock or securities convertible for Common Stock of the
Company (including without limitation the Company's initial public offering of
Common Stock), each Holder agrees, unless such Holder is a participant in such
offering, not to effect any offer, sale, distribution or transfer, including a
sale pursuant to Rule 144 (or any similar provision then effect) under the
Securities Act (except as part of such underwritten registration), during the
10-day period prior to, and during the 90-day period in the case of any other
public offering of Common Stock (or , in each case, such shorter period as may
be agreed to in writing by the Company and the Holders of at least 50% of the
Registrable Securities) following, the effective date of such Registration
Statement; provided, that (i) no Holder shall be required to enter into more
           --------
than one such agreement in any 12-month period and (ii) no Holder shall be
required to enter into such an agreement unless all Persons holding at least 2%
(on a fully diluted basis) of the Company's outstanding shares of Common Stock,
purchased from the Company any time after the date of this Agreement (other than
that purchased in a registered public offering) and all executive officers and
directors of the Company shall also have agreed not to offer, sell, distribute a
transfer under the circumstances and pursuant to the terms set forth in this
Section 5(b).

     6.   Registration Procedures.
          -----------------------

          Whenever the Holders of Registrable Securities have requested that any
Registrable Securities be registered pursuant to this Agreement, the Company
will use its best efforts to effect the registration and the sale of such
Registrable Securities in accordance with the intended method or methods of
distribution thereof, and pursuant thereto the Company will under the time
frames provided herein, or if not so provided, as expeditiously as possible:

                                       6
<PAGE>

          (a) prepare and file with the Commission a registration statement on
     any appropriate form for which the Company qualifies with respect to such
     Registrable Securities and use its best efforts to cause such registration
     statement to become effective (provided that before filing a registration
                                    --------
     statement or prospectus or any amendments or supplements thereto, the
     Company will (i) furnish to the counsel selected by the Holders copies of
     all such documents proposed to be filed, which documents will be subject to
     the review of such counsel, and (ii) notify each Holder of Registrable
     Securities covered by such registration of any stop order issued or
     threatened by the Commission);

          (b) prepare and file with the Commission such amendments and
     supplements to such registration statement and the prospectus used in
     connection therewith as may be reasonably necessary to keep such
     registration statement effective for a period equal to the shorter of (i)
     nine months and (ii) the time by which all securities covered by such
     registration statement have been sold, and comply with the provisions of
     the Securities Act with respect to the disposition of all securities
     covered by such registration statement during such period in accordance
     with the intended methods of disposition by the sellers thereof set forth
     in such registration statement;

          (c) furnish to each seller of Registrable Securities such number of
     copies of such registration statement, each amendment and supplement
     thereto, the prospectus included in such registration statement (including
     each preliminary prospectus) and such other documents as such seller may
     reasonably request in order to facilitate the disposition of the
     Registrable Securities owned by such seller;

          (d) use all reasonable efforts to register or qualify such Registrable
     Securities under the securities or blue sky laws of such jurisdictions as
     any seller reasonably requests and do any and all other acts and things
     which may be reasonably necessary or advisable to enable such seller to
     consummate the disposition in such jurisdictions of the Registrable
     Securities owned by such seller (provided that the Company will not be
                                      --------
     required to (i) qualify generally to do business in any jurisdiction where
     it would not otherwise be required to qualify but for this Section 6(d),
     (ii) subject itself to taxation in any jurisdiction or (iii) take any
     action that would subject it to general service of process in any such
     jurisdiction);

          (e) promptly notify each seller of such Registrable Securities, 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 contains an untrue
     statement of a material fact or omits any material fact necessary to make
     the statements therein not misleading, and,  the Company will prepare and
     deliver to each Holder a supplement or amendment to such prospectus so
     that, as thereafter delivered to the purchasers of such Registrable
     Securities, such prospectus will not contain an untrue statement of a
     material fact or omit to state any material fact necessary to make the
     statements therein not misleading; provided, that the Company shall be
                                        --------
     required to notify the Holders, but shall not be required to amend the
     registration statement or supplement the prospectus for a period of up to
     three months if the board of directors determines in good faith that to do
     so would reasonably be expected

                                       7
<PAGE>

     to have a material adverse effect on any proposal or plan by the Company to
     engage in any financing, acquisition or disposition of assets (other than
     in the ordinary course of business) or any merger, consolidation, tender
     offer or similar transaction or would require the disclosure of any
     information that the board of directors determines in good faith the
     disclosure of which would be materially detrimental to the Company, it
     being understood that the period for which the Company is obligated to keep
     the Registration Statement effective shall be extended for a number of days
     equal to the number of days the Company delays amendments or supplements
     pursuant to this provision. Upon receipt of any notice pursuant to this
     Section 6(e), the Holders shall suspend all offers and sales of securities
     of the Company and all use of any prospectus until advised by the Company
     that offers and sales may resume, and shall keep confidential the fact and
     content of any notice given by the Company pursuant to this Section 6(e);

          (f) cause all such Registrable Securities to be listed on each
     securities exchange or quoted on Nasdaq or other quotation medium, if any,
     on which similar securities issued by the Company are then listed or
     quoted;

          (g) provide a transfer agent and registrar for all such Registrable
     Securities not later than the effective date of such registration
     statement;

          (h) enter into such customary agreements (including underwriting
     agreements in customary form) and take all such other actions as the
     Holders of a majority of the Registrable Securities being sold or the
     underwriters, if any, reasonably request in order to expedite or facilitate
     the disposition of such Registrable Securities (including effecting a stock
     split or a combination of shares);

          (i) make available for inspection by the Holders of Registrable
     Securities included in the registration statement, any underwriter
     participating in any disposition pursuant to such registration statement
     and any attorney, accountant or other agent retained by any such seller or
     underwriter, all pertinent financial and other records, pertinent corporate
     documents and properties of the Company, and cause the Company's officers,
     directors, employees and independent accountants to supply all information
     reasonably requested by any such seller, underwriter, attorney, accountant
     or agent in connection with such registration statement and participate in
     presentations to prospective purchasers as reasonably requested by any
     underwriter or placement agent;

          (j) otherwise use its best efforts to comply with all applicable rules
     and regulations of the Commission, and make available to its security
     holders, as soon as reasonably practicable, an earnings statement covering
     a period of at least 12 months beginning after the effective date of the
     registration statement, which earnings statement shall satisfy the
     provisions of Section 11(a) of the Securities Act and Rule 158 thereunder;

          (k) in the event of the issuance of any stop order suspending the
     effectiveness of a registration statement, or of any order suspending or
     preventing the use of any related prospectus or suspending the
     qualification of any shares of Common Stock included in

                                       8
<PAGE>

     such registration statement for sale in any jurisdiction, use its best
     efforts promptly to obtain the withdrawal of such order;

          (l)  obtain a so-called "cold comfort" letter from the Company's
     independent public accountants in customary form and covering such matters
     of the type customarily covered by cold comfort letters;

          (m)  use its best efforts to cause such Registrable Securities covered
     by such registration statement to be registered with or approved by such
     other governmental agencies or authorities as may be necessary to enable
     the sellers thereof to consummate the disposition of such Registrable
     Securities; and

          (n)  if any such registration or comparable statement refers to any
     Holder by name or otherwise as the holder of any securities of the Company
     and if in its sole and exclusive judgment, such Holder is or might be
     deemed to be an underwriter or a controlling person of the Company, such
     Holder shall have the right to require (i) the insertion therein of
     language, in form and substance satisfactory to such Holder and presented
     to the Company in writing, to the effect that the holding by such Holder of
     such securities is not to be construed as a recommendation by such Holder
     of the investment quality of the Company's securities covered thereby and
     that such holding does not imply that such Holder shall assist in meeting
     any future financial requirements of the Company, or (ii) in the event that
     such reference to such Holder by name or otherwise is not required by the
     Securities Act or any similar Federal statute then in force, the deletion
     of the reference to such Holder; provided that with respect to this clause
                                      --------
     (ii) such Holder shall (a) furnish to the Company an opinion of counsel to
     such effect, which opinion and counsel shall be reasonably satisfactory to
     the Company and (b) indemnify the Company against any loss or liability
     imposed upon and any reasonable expenses incurred by the Company as a
     result of such deletion.

     7.   Obligations of Holders.
          ----------------------

          Whenever the Holders of Registrable Securities sell any Registrable
Securities pursuant to a Demand Registration or a Piggyback Registration, such
Holders shall be obligated to comply with the applicable provisions of the
Securities Act, including the prospectus delivery requirements thereunder, and
any applicable state securities or blue sky laws.  In addition, each Holder of
Registrable Securities will be deemed to have agreed by virtue of its
acquisition of such Registrable Securities that, upon receipt of any notice
described in Section 6(e), such Holder will forthwith discontinue disposition of
such Registrable Securities covered by such registration statement or prospectus
until such Holder's receipt of the copies of the supplemented or amended
prospectus contemplated by Section 6(e), or until it is advised in writing by
the Company that the use of the applicable prospectus may be resumed, and has
received copies of any additional or supplemental filings that are incorporated
or deemed to be incorporated by reference in such prospectus.

                                       9
<PAGE>

     8.   Indemnification.
          ---------------

          (a) The Company agrees to indemnify, to the fullest extent permitted
by applicable law, each Holder of Registrable Securities, its officers and
directors and each Person who controls such Holder (within the meaning of the
Securities Act) against all losses, claims, damages, liabilities, expenses or
any amounts paid in settlement of any litigation, investigation or proceeding
commenced or threatened (collectively, "Claims") to which each such indemnified
                                        ------
party may become subject under the Securities Act insofar as such Claim arose
out of (i) any untrue or alleged untrue statement of material fact contained, in
any registration statement, prospectus or preliminary prospectus or any
amendment thereof or supplement thereto or (ii) 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, except insofar as the same are
caused by or contained in any information furnished in writing to the Company by
such Holder expressly for use therein, or by such Holder's failure to deliver a
copy of the registration statement or prospectus or any amendments or
supplements thereto after the Company has furnished such Holder with a
sufficient number of copies of the same if such untrue or alleged untrue
material fact or omission or alleged omission is corrected in such prospectus,
amendment or supplement.  In connection with an underwritten offering, the
Company will indemnify the underwriters, their officers and directors and each
Person who controls the underwriters (within the meaning of the Securities Act)
to the same extent as provided above with respect to the indemnification of the
Holders of Registrable Securities.

          (b) In connection with any registration statements in which a Holder
of Registrable Securities is participating, each such Holder will, to the
fullest extent permitted by applicable law, indemnify the Company, its directors
and officers and each Person who controls the Company (within the meaning of the
Securities Act) against any and all Claims to which each such indemnified party
may become subject under the Securities Act insofar as such Claim arose out of
(i) any untrue or alleged untrue statement of material fact contained in any
registration statement, prospectus or preliminary prospectus or any amendment
thereof or supplement thereto or (ii) 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; provided, that with respect to a Claim
                                   --------
arising pursuant to clause (i) or (ii) above, the material misstatement or
omission is contained in the information such Holder provided to the Company in
writing expressly for use in such registration statement; provided further, that
                                                          -------- -------
the obligation to indemnify will be individual to each Holder and will be
limited to the amount of proceeds received by such Holder from the sale of
Registrable Securities pursuant to such registration statement.

          (c) Any Person entitled to indemnification hereunder will (i) give
prompt written notice to the indemnifying party of any Claim with respect to
which it seeks indemnification (but the failure to provide such notice shall not
release the indemnifying party of its obligation under paragraphs (a) and (b),
unless and then only to the extent that, the indemnifying party has been
prejudiced by such failure to provide such notice) and (ii) unless in such
indemnified party's reasonable judgment, based on written advice of counsel, a
conflict of interest between such indemnified and indemnifying parties may exist
with respect to such Claim, permit such indemnifying party to assume the defense
of such Claim with counsel reasonably satisfactory to the indemnified party.  An
indemnifying party who is not entitled to, or

                                       10
<PAGE>

elects not to, assume the defense of a Claim will not be obligated to pay the
fees and expenses of more than one counsel for all parties indemnified by such
indemnifying party with respect to such Claim, unless in the reasonable judgment
of any indemnified party, based on written advice of counsel, a conflict of
interest may exist between such indemnified party and any other of such
indemnified parties with respect to such Claim.

          (d) The indemnifying party shall not be liable to indemnify an
indemnified party for any settlement, or consent to judgment of any such action
effected without the indemnifying party's written consent (but such consent will
not be unreasonably withheld, delayed or conditioned).  Furthermore, the
indemnifying party shall not, except with the prior written approval 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 each indemnified party of a release from all liability
in respect of such claim or litigation without any payment or consideration
provided by each such indemnified party.

          (e) If the indemnification provided for in this Section 8 is
unavailable to an indemnified party under clauses (a) and (b) above in respect
of any Claims, then each indemnifying party, in lieu of indemnifying such
indemnified party, shall contribute to the amount paid or payable by such
indemnified party as a result of such losses, claims, damages or liabilities in
such proportion as is appropriate to reflect not only the relative benefits
received by the Company, the underwriters, the sellers of Registrable Securities
and any other sellers participating in the registration statement from the sale
of shares pursuant to the registered offering of securities for which indemnity
is sought but also the relative fault of the Company, the underwriters, the
sellers of Registrable Securities and any other sellers participating in the
registration statement in connection with the misstatement or omission which
resulted in such losses, claims, damages or liabilities, as well as any other
relevant equitable considerations.  The relative benefits received by the
Company, the underwriters, the sellers of Registrable Securities and any other
sellers participating in the registration statement shall be deemed to be based
on the relative relationship of the total net proceeds from the offering (before
deducting expenses) to the Company, the total underwriting commissions and fees
from the offering (before deducting expenses) to the underwriters and the total
net proceeds from the offering (before deducting expenses) to the sellers of
Registrable Securities and any other sellers participating in the registration
statement.  The relative fault of the Company, the underwriters, the sellers of
Registrable Securities and any other sellers participating in the registration
statement shall be determined by reference to, among other things, whether the
untrue or alleged untrue statement of a material fact or the omission or alleged
omission to state a material fact relates to information supplied by the Company
or by the sellers of Registrable Securities and the parties' relative intent,
knowledge, access to information and opportunity to correct or prevent such
statement or omission; provided, that in no event shall the liability of any
                       --------
selling Holder hereunder be greater in amount than the dollar amount of the
proceeds received by such Holder upon the sale of the Registrable Securities
giving rise to such indemnification obligation.

          (f) The indemnification provided for under this Agreement will remain
in full force and effect regardless of any investigation made by or on behalf of
the indemnified party or any officer, director or controlling person of such
indemnified party and will survive the transfer of the Registrable Securities.

                                       11
<PAGE>

     9.   Participation in Underwritten Registrations.
          -------------------------------------------

          No Person may participate in any registration hereunder which is
underwritten unless such Person (a) agrees to sell such Person's securities on
the basis provided in any underwriting arrangements approved by the Person or
Persons entitled hereunder to approve such arrangements and (b) completes and
executes all questionnaires, powers of attorney, indemnities, underwriting
agreements and other documents reasonably required under the terms of such
underwriting arrangements; provided, that no Holder of Registrable Securities
                           --------
included in any underwritten registration shall be required to make any
representations or warranties to the Company or the underwriters (other than
representations and warranties regarding such Holder and such Holder's intended
method of distribution) or to undertake any indemnification obligations to the
Company or the underwriters with respect thereto, except as otherwise provided
in paragraph 8 hereof.

     10.  Transfer of Registration Rights.
          -------------------------------

          The rights granted to any Holder under this Agreement may be assigned
to any Person in connection with any transfer or assignment of Registrable
Securities by a Holder; provided, that:  (a) such transfer is otherwise effected
                        --------
in accordance with applicable securities laws, (b) such transfer is not in
violation of the Purchase Agreement, (c) if not already a party hereto, the
assignee or transferee agrees in writing prior to such transfer to be bound by
the provisions of this Agreement and, (d) unless otherwise notified by the
Holder, EIS shall act as agent and representative for such Holder for the giving
and receiving of notices hereunder.

     11.  Information by Holder.
          ---------------------

          Each Holder shall furnish to the Company such written information
regarding such Holder and any distribution proposed by such Holder as the
Company may reasonably request in writing and as shall be reasonably required in
connection with any registration, qualification or compliance referred to in
this Agreement and shall promptly notify the Company of any changes in such
information.

     12.  Exchange Act Compliance.
          -----------------------

          The Company shall comply with all of the reporting requirements of the
Exchange Act then applicable to it, if any, and shall comply with all other
public information reporting requirements of the Commission which are conditions
to the availability of Rule 144 for the sale of the Registrable Securities.  The
Company shall cooperate with each Holder in supplying such information as may be
necessary for such Holder to complete and file any information reporting forms
presently or hereafter required by the Commission as a condition to the
availability of Rule 144.

     13.  Miscellaneous.
          -------------

          (a) No Inconsistent Agreements.   So long as any Holder owns any
              --------------------------
Registrable Securities, the Company will not enter into any agreement that is
inconsistent with or violates the rights granted hereunder to the Holders of
Registrable Securities, including, without limitation,

                                       12
<PAGE>

any agreement that would require the Company to register any of its securities
with priority with respect to registration over, the rights granted to the
Holders hereunder, without the prior written consent of the Holders of at least
50% of the Registrable Securities not to be unreasonably withheld.

          (b) Remedies.  Any Person having rights under any provision of this
              --------
Agreement will be entitled to enforce such rights specifically to recover
damages caused by reason of any breach of any provision of this Agreement and to
exercise all other rights granted by law.  The parties hereto agree and
acknowledge that money damages may not be an adequate remedy for any breach of
the provisions of this Agreement and that any party may in its sole discretion
apply to any court of law or equity of competent jurisdiction (without posting
any bond or other security) for specific performance and for other injunctive
relief in order to enforce or prevent violation of the provisions of this
Agreement; provided, that in no event shall any Holder have the right to enjoin,
           --------
delay or interfere with any offering of securities by the Company.

          (c) Amendments and Waivers.  Except as otherwise provided herein, the
              ----------------------
provisions of this Agreement may be amended or waived only with the prior
written consent of the Company and Holders of at least 50% of the Registrable
Securities; provided, that without the prior written consent of all the Holders,
            --------
no such amendment or waiver shall reduce the foregoing percentage required to
amend or waive any provision of this Agreement.

          (d) Successors and Assigns.  This Agreement and all of the provisions
              ----------------------
hereof shall be binding upon and inure to the benefit of the parties and their
respective successors and permitted assigns.  In addition, whether or not any
express assignment has been made, the provisions of this Agreement which are for
the benefit of Holders of Registrable Securities are also for the benefit of,
and enforceable by, any permitted transferee of Registrable Securities, in
accordance with Section 10 hereof.

          (e) Severability.  In case any provision of this Agreement shall be
              ------------
invalid, illegal or unenforceable, the validity, legality and enforceability of
the remaining provisions shall not be in any way affected or impaired thereby.

          (f) Counterparts and Facsimile.  This Agreement may be executed in any
              --------------------------
number of counterparts, and each such counterpart hereof shall be deemed to be
an original instrument, but all such counterparts together shall constitute one
agreement.  This Agreement may be signed and delivered to the other party by
facsimile transmission; such transmission shall be deemed a valid signature.

          (g) Descriptive Headings.  The section and paragraph headings
              --------------------
contained in this Agreement are for reference purposes only and shall not affect
in any way the meaning or interpretation of this Agreement.

          (h) Governing Law; Disputes.  This Agreement shall be governed by and
              -----------------------
construed in accordance with the internal laws of the State of New York, without
giving effect to conflicts of laws rules or principles.  Any dispute under this
Agreement that is not settled by mutual consent shall be finally adjudicated by
any federal or state court sitting in the County,

                                       13
<PAGE>

City and State of New York, and each party consents to the exclusive
jurisdiction of such courts (or any appellate court therefrom) over any such
dispute.

          (i)      Notices.  All notices, demands and requests of any kind to be
                   -------
delivered to any party in connection with this Agreement shall be in writing and
shall be deemed to have been duly given if personally or hand delivered or if
sent by internationally-recognized overnight courier or by registered or
certified mail, return receipt requested and postage prepaid, or by facsimile
transmission, addressed as follows:

          (i)      if to the Company, to:

                   SafeScience, Inc.
                   Park Square Building
                   31 St. James Avenue, 8/th/ Floor
                   Boston, Massachusetts 02116
                   Attention: Chief Executive Officer
                   Facsimile: (617) 422-0675

                   with a copy to:

                   McDermott, Will & Emery
                   50 Rockefeller Plaza
                   New York, New York 10020
                   Attention: Cheryl Reicin
                   Facsimile: (212) 547-5444

                   and

                   Reitler Brown LLC
                   800 Third Avenue
                   New York, New York 10022
                   Attention: David Robbins
                   Facsimile: (212) 371-5500

          (ii)(a)  if to EIS, to:

                   Elan International Services, Ltd.
                   102 St. James Court
                   Flatts, Smiths Parish
                   Bermuda FL 04
                   Attention: Chief Executive Officer
                   Facsimile: (441) 292-2224

          with a copy to:

                                       14
<PAGE>

                   Reitler Brown LLC
                   800 Third Avenue
                   New York, New York  10022
                   Attention:  David Robbins
                   Facsimile:  212-371-5500

or to such other address as the party to whom notice is to be given may have
furnished to the other party hereto in writing in accordance with provisions of
this Section 13(i). Any such notice or communication shall be deemed to have
been effectively given (i) in the case of personal or hand delivery, on the date
of such delivery, (ii) in the case of an internationally-recognized overnight
delivery courier, on the second business day after the date when sent or earlier
upon receipt of evidence of acceptance of delivery, (iii) in the case of U.S.
mailing, on the fifth business day following that day on which the piece of mail
containing such communication is posted and (iv) in the case of facsimile
transmission, on the date of telephone confirmation of receipt.

          (j)      Entire Agreement.  This Agreement constitutes the full and
                   ----------------
entire understanding and agreement of the parties with regard to the subject
matter hereof and supersedes all prior agreements and understandings among the
parties with respect thereto.

                            [Signature page follows]

                                       15
<PAGE>

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

                            SAFESCIENCE, INC.


                            By:   /s/ Bradley J. Carver
                                 -----------------------------------
                                 Name:
                                 Title:

                            ELAN INTERNATIONAL SERVICES, LTD.


                            By:   /s/ Kevin Insley
                                 -----------------------------------
                                 Name:
                                 Title: