EXHIBIT 4.2

                          REGISTRATION RIGHTS AGREEMENT

     THIS REGISTRATION RIGHTS AGREEMENT (the "AGREEMENT") is made and entered
into as of November 26, 2002, by and between Ligand Pharmaceuticals
Incorporated, a Delaware corporation (the "COMPANY"), and UBS Warburg LLC (the
"INITIAL PURCHASER") pursuant to that certain Purchase Agreement, dated as of
November 21, 2002 (the "PURCHASE AGREEMENT") between the Company and the Initial
Purchaser.

     In order to induce the Initial Purchaser to enter into the Purchase
Agreement, the Company has agreed to provide the registration rights set forth
in this Agreement. The execution of this Agreement is a condition to the closing
under the Purchase Agreement.

     The Company agrees with the Initial Purchaser (i) for its benefit as
Initial Purchaser and (ii) for the benefit of the beneficial owners (including
the Initial Purchaser) from time to time of the Notes (as defined herein) and
the beneficial owners from time to time of the Underlying Common Stock (as
defined herein) issued upon conversion of the Notes (each of the foregoing a
"HOLDER" and together the "HOLDERS"), as follows:

     Section 1. DEFINITIONS. Capitalized terms used herein without definition
shall have their respective meanings set forth in the Purchase Agreement. As
used in this Agreement, the following terms shall have the following meanings:

     "AFFILIATE" means with respect to any specified person, an "affiliate," as
defined in Rule 144, of such person.

     "AMENDMENT EFFECTIVENESS DEADLINE DATE" has the meaning set forth in
Section 2(d) hereof.

     "APPLICABLE CONVERSION PRICE" means, as of any date of determination,
$1,000 divided by the Conversion Rate then in effect as of the date of
determination or, if no Notes are then outstanding, the Conversion Rate that
would be in effect were Notes then outstanding.

     "BUSINESS DAY" means each day on which the Nasdaq National Market is open
for trading.

     "COMMON STOCK" means the shares of common stock, par value $.001 per share,
of the Company and any other shares of capital stock as may constitute "COMMON
STOCK" for purposes of the Indenture, including the Underlying Common Stock.

     "CONVERSION RATE" has the meaning assigned to such term in the Indenture.




     "DAMAGES ACCRUAL PERIOD" has the meaning set forth in Section 2(e) hereof.

     "DAMAGES PAYMENT DATE" means each interest payment date under the Indenture
in the  case of  Notes,  and  each  May 16 and  November  16 in the  case of the
Underlying Common Stock.

     "EFFECTIVENESS  DEADLINE  DATE" has the meaning  set forth in Section  2(a)
hereof.

     "EFFECTIVENESS PERIOD" means a period (subject to extension pursuant to
Section 3(i) hereof ) of two years after the later of (1) the original issuance
of the Notes and (2) the last date that the Company or any of its Affiliates was
the owner of such Notes (or any predecessor thereto), or such shorter period of
time (x) as permitted by Rule 144(k) under the Securities Act or any successor
provisions thereunder or (y) that will terminate when each of the Registrable
Securities covered by the Shelf Registration Statement ceases to be a
Registrable Security.

     "EVENT" has the meaning set forth in Section 2(e) hereof.

     "EVENT DATE" has the meaning set forth in Section 2(e) hereof.

     "EXCHANGE ACT" means the Securities Exchange Act of 1934, as amended, and
the rules and regulations of the SEC promulgated thereunder.

     "FILING DEADLINE DATE" has the meaning set forth in Section 2(a) hereof.

     "HOLDER" has the meaning set forth in the third paragraph of this
Agreement.

     "INDENTURE" means the Indenture, dated as of November 26, 2002, between the
Company and J.P. Morgan Trust Company, National Association, as trustee,
pursuant to which the Notes are being issued.

     "INITIAL PURCHASER" has the meaning set forth in the preamble hereto.

     "INITIAL SHELF REGISTRATION STATEMENT" has the meaning set forth in Section
2(a) hereof.

     "ISSUE DATE" means the first date of original issuance of the Notes.

     "LIQUIDATED DAMAGES AMOUNT" has the meaning set forth in Section 2(e)
hereof.

     "MATERIAL EVENT" has the meaning set forth in Section 3(i) hereof.

     "NOTES" means the 6% Convertible Subordinated Notes due 2007 of the Company
to be purchased pursuant to the Purchase Agreement.


                                       2



     "NOTICE AND QUESTIONNAIRE" means a written notice and questionnaire
delivered to the Company containing substantially the information called for by
the Selling Securityholder Notice and Questionnaire attached as Annex A to the
Offering Memorandum dated November 21, 2002 relating to the Notes.

     "NOTICE HOLDER" means, on any date, any Holder that has delivered a Notice
and Questionnaire to the Company on or prior to such date, so long as all of
their Registrable Securities that have been registered for resale pursuant to a
Notice and Questionnaire have not been sold in accordance with a Shelf
Registration Statement.

     "PURCHASE AGREEMENT" has the meaning set forth in the preamble hereof.

     "PROSPECTUS" means the prospectus included in any Shelf Registration
Statement (including, without limitation, a prospectus that discloses
information previously omitted from a prospectus filed as part of an effective
registration statement in reliance upon Rule 415 promulgated under the
Securities Act), as amended or supplemented by any amendment or prospectus
supplement, including post-effective amendments, and all materials incorporated
by reference or explicitly deemed to be incorporated by reference in such
Prospectus.

     "RECORD HOLDER" means (i) with respect to any Damages Payment Date relating
to any Notes as to which any such Liquidated Damages Amount has accrued, the
holder of record of such Note on the record date with respect to the interest
payment date under the Indenture on which such Damages Payment Date shall occur
and (ii) with respect to any Damages Payment Date relating to the Underlying
Common Stock as to which any such Liquidated Damages Amount has accrued, the
registered holder of such Underlying Common Stock fifteen (15) days prior to
such Damages Payment Date.

     "REGISTRABLE SECURITIES" means the Notes until such Notes have been
converted into the Underlying Common Stock and, at all times the Underlying
Common Stock and any securities into or for which such Underlying Common Stock
has been converted, and any security issued with respect thereto upon any stock
dividend, split or similar event until, in the case of any such security, the
earliest of (x) the date on which such security has been effectively registered
under the Securities Act and disposed of, whether or not in accordance with the
Shelf Registration Statement and (y) the date that is two years after the later
of (1) the original issuance of the Notes and (2) the last date that the Company
or any of its Affiliates was the owner of such Notes (or any predecessor
thereto), or such shorter period of time as permitted by Rule 144(k) under the
Securities Act or any successor provisions thereunder.

     "REGISTRATION EXPENSES" has the meaning set forth in Section 5 hereof.

     "REGISTRATION STATEMENT" means any registration statement of the Company
that covers any of the Registrable Securities pursuant to the provisions


                                       3



of this Agreement including the Prospectus, amendments and supplements to such
registration statement, including post-effective amendments, all exhibits, and
all materials incorporated by reference or explicitly deemed to be incorporated
by reference in such registration statement.

     "RULE 144" means Rule 144 under the Securities Act, as such Rule may be
amended from time to time, or any similar rule or regulation hereafter adopted
by the SEC.

     "RULE 144A" means Rule 144A under the Securities Act, as such Rule may be
amended from time to time, or any similar rule or regulation hereafter adopted
by the SEC.

     "SEC" means the Securities and Exchange Commission.

     "SECURITIES ACT" means the Securities Act of 1933, as amended, and the
rules and regulations promulgated by the SEC thereunder.

     "SHELF REGISTRATION STATEMENT" has the meaning set forth in Section 2(a)
hereof.

     "SUBSEQUENT SHELF REGISTRATION STATEMENT" has the meaning set forth in
Section 2(b) hereof.

     "SUSPENSION NOTICE" has the meaning set forth in Section 3(i) hereof.

     "SUSPENSION PERIOD" has the meaning set forth in Section 3(i) hereof.

     "TIA" means the Trust Indenture Act of 1939, as amended.

     "TRUSTEE" means J.P. Morgan Trust Company, National Association, the
Trustee under the Indenture.

     "UNDERLYING COMMON STOCK" means the Common Stock into which the Notes are
convertible or issued upon any such conversion.

     Section 2. SHELF REGISTRATION. The Company shall prepare and file or cause
to be prepared and filed with the SEC, as soon as practicable but in any event
by the date (the "FILING DEADLINE DATE") that is ninety (90) days after the
Issue Date, a Registration Statement for an offering to be made on a delayed or
continuous basis pursuant to Rule 415 of the Securities Act (a "SHELF
REGISTRATION STATEMENT") registering the resale from time to time by Holders
thereof of all of the Registrable Securities (the "INITIAL SHELF REGISTRATION
Statement"). The Initial Shelf Registration Statement shall be on Form S-1 or
S-3 or another appropriate form permitting registration of such Registrable
Securities for resale by such Holders in accordance with the reasonable methods
of distribution elected by the Holders, approved by the Company, and set forth
in the Initial Shelf Registration Statement. The Company shall use its
reasonable best efforts to cause the Initial


                                       4



Shelf Registration Statement to be declared effective under the Securities Act
as promptly as is practicable but in any event by the date (the "EFFECTIVENESS
DEADLINE DATE") that is one hundred eighty (180) days after the Issue Date, and
to keep the Initial Shelf Registration Statement (or any Subsequent Shelf
Registration Statement) continuously effective under the Securities Act until
the expiration of the Effectiveness Period. At the time the Initial Shelf
Registration Statement is declared effective, each Holder that became a Notice
Holder on or prior to the date that is ten (10) Business Days prior to such time
of effectiveness shall be named as a selling securityholder in the Initial Shelf
Registration Statement and the related Prospectus in such a manner as to permit
such Holder to deliver such Prospectus to purchasers of Registrable Securities
in accordance with applicable law.

     (b) If the Initial Shelf Registration Statement or any Subsequent Shelf
Registration Statement ceases to be effective for any reason at any time during
the Effectiveness Period, the Company shall use its reasonable best efforts to
obtain the prompt withdrawal of any order suspending the effectiveness thereof,
and in any event shall within thirty (30) days of such cessation of
effectiveness amend the Shelf Registration Statement in a manner reasonably
expected to obtain the withdrawal of the order suspending the effectiveness
thereof, or file an additional Shelf Registration Statement covering all of the
securities that as of the date of such filing are Registrable Securities (a
"SUBSEQUENT SHELF REGISTRATION STATEMENT"). If a Subsequent Shelf Registration
Statement is filed, the Company shall use its reasonable best efforts to cause
the Subsequent Shelf Registration Statement to become effective as promptly as
is practicable after such filing and to keep such Shelf Registration Statement
(or subsequent Shelf Registration Statement) continuously effective until the
end of the Effectiveness Period.

     (c) The Company shall supplement and amend the Shelf Registration Statement
if required by the rules, regulations or instructions applicable to the
registration form used by the Company for such Shelf Registration Statement, if
required by the Securities Act or as reasonably requested by the Initial
Purchaser or by the Trustee on behalf of the Holders of the Registrable
Securities covered by such Shelf Registration Statement.

     (d) Each Holder of Registrable Securities agrees that if such Holder wishes
to sell Registrable Securities pursuant to a Shelf Registration Statement and
related Prospectus, it will do so only in accordance with this Section 2(d) and
Section 3(i). Each Holder of Registrable Securities wishing to sell Registrable
Securities pursuant to a Shelf Registration Statement and related Prospectus
agrees to deliver a completed and executed Notice and Questionnaire to the
Company prior to any attempted or actual distribution of Registrable Securities
under the Shelf Registration Statement; PROVIDED that Holders of Registrable
Securities shall have at least twenty (20) Business Days from the date on which
the Notice and Questionnaire is first sent to such Holders by the Company to
complete and return the Notice and Questionnaire to the Company. From and after
the date the Initial Shelf Registration Statement is declared effective, the


                                       5



Company shall, as promptly as practicable after the date a Notice and
Questionnaire is delivered, and in any event within the later of (x) five (5)
Business Days after such date or (y) five (5) Business Days after the expiration
of any Suspension Period (1) in effect when the Notice and Questionnaire is
delivered or (2) put into effect within five (5) Business Days of such delivery
date, (i) if required by applicable law, file with the SEC a post-effective
amendment to the Shelf Registration Statement or, if required by applicable law,
prepare and file a supplement to the related Prospectus or a supplement or
amendment to any document incorporated therein by reference or file any other
required document so that the Holder delivering such Notice and Questionnaire is
named as a selling securityholder in the Shelf Registration Statement and the
related Prospectus in such a manner as to permit such Holder to deliver such
Prospectus to purchasers of the Registrable Securities in accordance with
applicable law and, if the Company shall file a post-effective amendment to the
Shelf Registration Statement, use its reasonable best efforts to cause such
post-effective amendment to be declared effective under the Securities Act as
promptly as is practicable, but in any event by the date (the "AMENDMENT
EFFECTIVENESS DEADLINE DATE") that is thirty (30) days after the date such
post-effective amendment is required by this clause to be filed; (ii) provide
such Holder a reasonable number of copies of any documents filed pursuant to
Section 2(d)(i); and (iii) notify such Holder as promptly as practicable after
the effectiveness under the Securities Act of any post-effective amendment filed
pursuant to Section 2(d) (i); PROVIDED that if such Notice and Questionnaire is
delivered during a Suspension Period, or a Suspension Period is put into effect
within five (5) Business Days after such delivery date, the Company shall so
inform the Holder delivering such Notice and Questionnaire and shall take the
actions set forth in clauses (i), (ii) and (iii) above within five (5) Business
Days after expiration of the Suspension Period in accordance with Section 3(i);
PROVIDED FURTHER that if under applicable law, the Company has more than one
option as to the type or manner of making any such filing, the Company shall
make the required filing or filings in the manner or of a type that is
reasonably expected to result in the earliest availability of the Prospectus for
effecting resales of Registrable Securities. Notwithstanding anything contained
herein to the contrary, the Company shall be under no obligation to name any
Holder that is not a Notice Holder as a selling securityholder in any Shelf
Registration Statement or related Prospectus; PROVIDED, HOWEVER, that any Holder
that becomes a Notice Holder pursuant to the provisions of this Section 2(d)
(whether or not such Holder was a Notice Holder at the time the Shelf
Registration Statement was declared effective) shall be named as a selling
securityholder in the Shelf Registration Statement or related Prospectus in
accordance with the requirements of this Section 2(d).

     (e) The parties hereto agree that the Holders of Registrable Securities
will suffer damages, and that it would not be feasible to ascertain the extent
of such damages with precision, if (i) the Initial Shelf Registration Statement
has not been filed on or prior to the Filing Deadline Date, (ii) the Initial
Shelf Registration Statement has not been declared effective under the
Securities Act on or prior to the Effectiveness Deadline Date or (iii) the
Initial Shelf Registration


                                       6



Statement is filed and declared effective but shall thereafter cease to be
effective (without being succeeded immediately by an additional registration
statement filed and declared effective) or usable for the offer and sale of
Registrable Securities for a period of time (including any Suspension Period)
which shall exceed thirty (30) days in the aggregate in any three (3) month
period or sixty (60) days in the aggregate in any twelve (12) month period (each
of the events of a type described in any of the foregoing clauses (i) through
(iii) are individually referred to herein as an "EVENT," and the Filing Deadline
Date in the case of clause (i), the Effectiveness Deadline Date in the case of
clause (ii), the date on which the duration of the ineffectiveness or
unusability of the Initial Shelf Registration Statement in any period exceeds
the number of days permitted by clause (iii) hereof in the case of clause (iii),
being referred to herein as an "EVENT DATE"). Events shall be deemed to continue
until the following dates with respect to the respective types of Events: the
date the Initial Shelf Registration Statement is filed in the case of an Event
of the type described in clause (i), the date the Initial Shelf Registration
Statement is declared effective under the Securities Act in the case of an Event
of the type described in clause (ii), and the date the Initial Shelf
Registration Statement becomes effective or usable again in the case of an Event
of the type described in clause (iii).

     Accordingly, commencing on (and including) any Event Date and ending on
(but excluding) the next date on which there are no Events that have occurred
and are continuing (a "DAMAGES ACCRUAL PERIOD"), the Company agrees to pay, as
liquidated damages and not as a penalty, an amount (the "LIQUIDATED DAMAGES
AMOUNT") at the rate described below, payable periodically on each Damages
Payment Date to Record Holders of Notes that are Registrable Securities and of
shares of Underlying Common Stock issued upon conversion of Notes that are
Registrable Securities, as the case may be, to the extent of, for each such
Damages Payment Date, accrued and unpaid Liquidated Damages Amount to (but
excluding) such Damages Payment Date (or, if the Damages Accrual Period shall
have ended prior to such Damages Payment Date, the date of the end of the
Damages Accrual Period); PROVIDED that any Liquidated Damages Amount accrued
with respect to any Note or portion thereof called for redemption on a
redemption date or converted into Underlying Common Stock on a conversion date
prior to the Damages Payment Date, shall, in any such event, be paid instead to
the Holder who submitted such Note or portion thereof for redemption or
conversion on the applicable redemption date or conversion date, as the case may
be, on such date (or promptly following the conversion date, in the case of
conversion). The Liquidated Damages Amount shall accrue at a rate per annum
equal to one-quarter of one percent (0.25%) for the first 90-day period from the
Event Date, at a rate per annum equal to one-half of one percent (0.50%) for the
next 90-day period and thereafter at a rate per annum equal to three-quarters of
one percent (0.75%) of (i) the principal amount of such Notes or, without
duplication, (ii) in the case of Notes that have been converted into Underlying


                                       7



Common Stock, the Applicable Conversion Price of such shares of Underlying
Common Stock, as the case may be, in each case determined as of the Business Day
immediately preceding the next Damages Payment Date. Notwithstanding the
foregoing, no Liquidated Damages Amounts shall accrue as to any Registrable
Security from and after the earlier of (x) the date such security is no longer a
Registrable Security and (y) expiration of the Effectiveness Period. The rate of
accrual of the Liquidated Damages Amount with respect to any period shall not
exceed the rate provided for in this paragraph notwithstanding the occurrence of
multiple concurrent Events. Following the cure of all Events requiring the
payment by the Company of Liquidated Damages Amounts to the Holders of
Registrable Securities pursuant to this Section, the accrual of Liquidated
Damages Amounts shall cease (without in any way limiting the effect of any
subsequent Event requiring the payment of Liquidated Damages Amount by the
Company).

     The Trustee shall be entitled, on behalf of Holders of Notes, to seek any
available remedy for the enforcement of this Agreement, including for the
payment of any Liquidated Damages Amount. Notwithstanding the foregoing, the
parties agree that the sole damages payable for a violation of the terms of this
Agreement with respect to which liquidated damages are expressly provided shall
be such liquidated damages.

     All of the Company's obligations set forth in this Section 2(e) that are
outstanding with respect to any Registrable Security at the time such security
ceases to be a Registrable Security shall survive until such time as all such
obligations with respect to such security have been satisfied in full
(notwithstanding termination of this Agreement pursuant to Section 8(k)).

     The parties hereto agree that the liquidated damages provided for in this
Section 2(e) constitute a reasonable estimate of the damages that may be
incurred by Holders of Registrable Securities by reason of the failure of the
Shelf Registration Statement to be filed or declared effective or available for
effecting resales of Registrable Securities in accordance with the provisions
hereof.

     Section 3. REGISTRATION PROCEDURES. In connection with the registration
obligations of the Company under Section 2 hereof, the Company shall:

     (a) Prepare and file with the SEC a Shelf Registration Statement or Shelf
Registration Statements on Form S-1 or S-3 or any other appropriate form under
the Securities Act available for the sale of the Registrable Securities by the
Holders thereof in accordance with the intended method or methods of
distribution thereof, and use its reasonable best efforts to cause each such
Shelf Registration Statement to become effective and remain effective as
provided herein; PROVIDED that before filing any Shelf Registration Statement or
Prospectus or any amendments or supplements thereto with the SEC, the Company
shall furnish to the Initial Purchaser and counsel for the Holders and for the
Initial Purchaser (or, if applicable, separate counsel for the Holders) copies
of all such documents proposed to be filed and use its reasonable best efforts
to reflect in


                                       8



each such document when so filed with the SEC such comments as the such counsel
reasonably shall propose within three (3) Business Days of the delivery of such
copies to the Initial Purchaser and such counsel.

     (b) Prepare and file with the SEC such amendments and post-effective
amendments to each Shelf Registration Statement as may be necessary to keep such
Shelf Registration Statement continuously effective until the expiration of the
Effectiveness Period; cause the related Prospectus to be supplemented by any
required Prospectus supplement, and as so supplemented to be filed pursuant to
Rule 424 (or any similar provisions then in force) under the Securities Act; and
use its reasonable best efforts to comply with the provisions of the Securities
Act applicable to it with respect to the disposition of all securities covered
by such Shelf Registration Statement during the Effectiveness Period in
accordance with the intended methods of disposition by the sellers thereof set
forth in such Shelf Registration Statement as so amended or such Prospectus as
so supplemented.

     (c) As promptly as practicable give notice to the Notice Holders and the
Initial Purchaser (i) when any Prospectus, Prospectus supplement, Shelf
Registration Statement or post-effective amendment to a Shelf Registration
Statement has been filed with the SEC and, with respect to a Shelf Registration
Statement or any post-effective amendment, when the same has been declared
effective, (ii) of any request, following the effectiveness of the Initial Shelf
Registration Statement under the Securities Act, by the SEC or any other federal
or state governmental authority for amendments or supplements to any Shelf
Registration Statement or related Prospectus or for additional information,
(iii) of the issuance by the SEC or any other federal or state governmental
authority of any stop order suspending the effectiveness of any Shelf
Registration Statement or the initiation or threatening of any proceedings for
that purpose, (iv) of the receipt by the Company of any notification with
respect to the suspension of the qualification or exemption from qualification
of any of the Registrable Securities for sale in any jurisdiction or the
initiation or threatening of any proceeding for such purpose and (v) of the
determination by the Company that a post-effective amendment to a Shelf
Registration Statement will be filed with the SEC, which notice may, at the
discretion of the Company (or as required pursuant to Section 3(i)), state that
it constitutes a Suspension Notice, in which event the provisions of Section
3(i) shall apply.

     (d) Use its reasonable best efforts to prevent the issuance of, and, if
issued, to obtain the withdrawal of any order suspending the effectiveness of a
Shelf Registration Statement or the lifting of any suspension of the
qualification (or exemption from qualification) of any of the Registrable
Securities for sale in any jurisdiction in which they have been qualified for
sale, in either case at the earliest possible moment, and provide prompt notice
to each Notice Holder and the Initial Purchaser of the withdrawal of any such
order.

     (e) If reasonably requested by the Initial Purchaser or any Notice Holder,
as promptly as practicable incorporate in a Prospectus supplement or


                                       9


post-effective amendment to a Shelf Registration Statement such information as
the Initial Purchaser or such Notice Holder shall determine to be required to be
included therein by applicable law and make any required filings of such
Prospectus supplement or such post-effective amendment; PROVIDED that the
Company shall not be required to take any actions under this Section 3(e) that,
in the written opinion of counsel for the Company, are not in compliance with
applicable law.

     (f) As promptly as practicable furnish to each Notice Holder and the
Initial Purchaser, without charge, at least one (1) conformed copy of the Shelf
Registration Statement and any amendment thereto, including financial statements
but excluding schedules, all documents incorporated or deemed to be incorporated
therein by reference and all exhibits (unless requested in writing to the
Company by such Notice Holder or the Initial Purchaser).

     (g) During the Effectiveness Period, deliver to each Notice Holder and the
Initial Purchaser, in connection with any sale of Registrable Securities
pursuant to a Shelf Registration Statement, without charge, as many copies of
the Prospectus or Prospectuses relating to such Registrable Securities
(including each preliminary prospectus) and any amendment or supplement thereto
as such Notice Holder and the Initial Purchaser may reasonably request; and the
Company hereby consents (except during such periods that a Suspension Notice is
outstanding and has not been revoked) to the use of such Prospectus or each
amendment or supplement thereto by each Notice Holder, in connection with any
offering and sale of the Registrable Securities covered by such Prospectus or
any amendment or supplement thereto in the manner set forth therein.

     (h) Prior to any public offering of the Registrable Securities pursuant to
the Shelf Registration Statement, use its reasonable best efforts to register or
qualify or cooperate with the Notice Holders in connection with the registration
or qualification (or exemption from such registration or qualification) of such
Registrable Securities for offer and sale under the securities or Blue Sky laws
of such jurisdictions within the United States as any Notice Holder reasonably
requests in writing (which request may be included in the Notice and
Questionnaire); prior to any public offering of the Registrable Securities
pursuant to the Shelf Registration Statement, use its reasonable best efforts to
keep each such registration or qualification (or exemption therefrom) effective
during the Effectiveness Period in connection with such Notice Holder's offer
and sale of Registrable Securities pursuant to such registration or
qualification (or exemption therefrom) and do any and all other acts or things
reasonably necessary or advisable to enable the disposition in such
jurisdictions of such Registrable Securities in the manner set forth in the
relevant Shelf Registration Statement and the related Prospectus; PROVIDED that
the Company will not be required to (i) qualify as a foreign corporation or as a
dealer in securities in any jurisdiction where it would not otherwise be
required to qualify but for this Agreement or (ii) take any action that would
subject it to general service of process in suits or to taxation in any such
jurisdiction where it is not then so subject.


                                       10



     (i) Upon (A) the issuance by the SEC of a stop order suspending the
effectiveness of the Shelf Registration Statement or the initiation of
proceedings with respect to the Shelf Registration Statement under Section 8(d)
or 8(e) of the Securities Act, (B) the occurrence of any event or the existence
of any fact as a result of which any Shelf Registration Statement shall contain
any untrue statement of a material fact or omit to state any material fact
required to be stated therein or necessary to make the statements therein not
misleading, or any Prospectus shall contain any untrue statement of a material
fact or omit to state any material fact necessary in order to make the
statements therein, in the light of the circumstances under which they were
made, not misleading, or (C) the occurrence or existence of any pending
corporate development (a "MATERIAL EVENT") that, in the reasonable discretion of
the Company, makes it appropriate to suspend the availability of the Shelf
Registration Statement and the related Prospectus, (i) in the case of clause (B)
or (C) above, subject to the next sentence, as promptly as practicable, prepare
and file, if necessary pursuant to applicable law, a post-effective amendment to
such Shelf Registration Statement or a supplement to the related Prospectus or
any document incorporated therein by reference or file any other required
document that would be incorporated by reference into such Shelf Registration
Statement and Prospectus so that such Shelf Registration Statement does not
contain any untrue statement of a material fact or omit to state any material
fact required to be stated therein or necessary to make the statements therein
not misleading, and such Prospectus does not contain any untrue statement of a
material fact or omit to state any material fact necessary in order to make the
statements therein, in the light of the circumstances under which they were
made, not misleading (it being understood that the Company may rely on
information provided by each Notice Holder with respect to such Notice Holder),
as thereafter delivered to the purchasers of the Registrable Securities being
sold thereunder, and, in the case of a post-effective amendment to a Shelf
Registration Statement, subject to the next sentence, use its reasonable best
efforts to cause it to be declared effective as promptly as is practicable, and
(ii) give prompt notice to the Notice Holders and the Initial Purchaser that the
availability of the Shelf Registration Statement is suspended (a "SUSPENSION
NOTICE") and, upon receipt of any Suspension Notice, each Notice Holder agrees
not to sell any Registrable Securities pursuant to such Shelf Registration
Statement until such Notice Holder's receipt of copies of the supplemented or
amended Prospectus provided for in clause (i) above, or until it is advised in
writing by the Company that the Prospectus may be used, and has received copies
of any additional or supplemental filings that are incorporated or deemed
incorporated by reference in such Prospectus. The Company will use its
reasonable best efforts to ensure that the use of the Prospectus may be resumed
(x) in the case of clause (A) above, as promptly as is practicable, (y) in the
case of clause (B) above, as soon as, in the reasonable judgment of the Company,
the Shelf Registration Statement does not contain any untrue statement of a
material fact or omits to state any material fact required to be stated therein
or necessary to make the statements therein not misleading and the Prospectus
does not contain any untrue statement of a material fact or omits to state any
material fact


                                       11



necessary in order to make the statements therein, in the light of the
circumstances under which they were made, not misleading, and (z) in the case of
clause (C) above, as soon as, in the reasonable discretion of the Company, such
suspension is no longer appropriate. The period during which the availability of
the Shelf Registration Statement and any Prospectus may be suspended (the
"SUSPENSION PERIOD") without the Company incurring any obligation to pay
liquidated damages pursuant to Section 2(e) shall not exceed thirty (30) days in
any three (3) month period and sixty (60) days in any twelve (12) month period.
The Effectiveness Period shall be extended by the number of days from and
including the date of the giving of the Suspension Notice to and including the
date on which the Notice Holder received copies of the supplemented or amended
Prospectus provided in clause (i) above, or the date on which it is advised in
writing by the Company that the Prospectus may be used, and has received copies
of any additional or supplemental filings that are incorporated or deemed
incorporated by reference in such Prospectus.

     (j) Make available for inspection during normal business hours by
representatives for the Notice Holders of such Registrable Securities, and any
broker-dealers, attorneys and accountants retained by such Notice Holders, all
relevant financial and other records and pertinent corporate documents and
properties of the Company and its subsidiaries, and cause the appropriate
officers, directors and employees of the Company and its subsidiaries to make
available for inspection during normal business hours all relevant information
reasonably requested by such representatives for the Notice Holders, or any such
broker-dealers, attorneys or accountants in connection with such disposition, in
each case as is customary for similar "due diligence" examinations; PROVIDED,
HOWEVER, that such persons shall, at the Company's request, first agree in
writing with the Company that any information that is reasonably and in good
faith designated by the Company in writing as confidential at the time of
delivery of such information shall be kept confidential by such persons and
shall be used solely for the purposes of exercising rights under this Agreement,
unless (i) disclosure of such information is required by court or administrative
order or is necessary to respond to inquiries of regulatory authorities, (ii)
disclosure of such information is required by law (including any disclosure
requirements pursuant to federal securities laws in connection with the filing
of any Shelf Registration Statement or the use of any Prospectus referred to in
this Agreement), (iii) such information becomes generally available to the
public other than as a result of a disclosure or failure to safeguard by any
such person or (iv) such information becomes available to any such person from a
source other than the Company and such source is not bound by a confidentiality
agreement or is not otherwise under a duty of trust to the Company, and PROVIDED
that the foregoing inspection and information gathering shall, to the greatest
extent possible, be coordinated on behalf of all the Notice Holders and the
other parties entitled thereto by the counsel referred to in Section 5.


                                       12


     (k) Comply with all applicable rules and regulations of the SEC and make
generally available to its securityholders earning statements (which need not be
audited) satisfying the provisions of Section 11(a) of the Securities Act and
Rule 158 thereunder (or any similar rule promulgated under the Securities Act)
no later than 45 days after the end of any 12-month period (or 90 days after the
end of any 12-month period if such period is a fiscal year) commencing on the
first day of the first fiscal quarter of the Company commencing after the
effective date of a Shelf Registration Statement, which statements shall cover
said 12-month periods.

     (l) Cooperate with each Notice Holder to facilitate the timely preparation
and delivery of certificates representing Registrable Securities sold pursuant
to a Shelf Registration Statement, which certificates shall not bear any
restrictive legends, and cause such Registrable Securities to be in such
denominations as are permitted by the Indenture and registered in such names as
such Notice Holder may request in writing at least (2) Business Days prior to
any sale of such Registrable Securities.

     (m) Provide a CUSIP number for all Registrable Securities covered by each
Shelf Registration Statement not later than the effective date of such Shelf
Registration Statement and provide the Trustee and the transfer agent for the
Common Stock with certificates for the Registrable Securities that are in a form
eligible for deposit with The Depository Trust Company.

     (n) Cooperate and assist in any filings required to be made with the
National Association of Securities Dealers, Inc.

     (o) Upon (i) the filing of the Initial Registration Statement and (ii) the
effectiveness of the Initial Registration Statement, announce the same, in each
case by release to Reuters Economic Services and Bloomberg Business News or
other equivalent means of dissemination reasonably expected to make such
information publicly known.

     (p) Enter into such customary agreements and take all such other necessary
actions in connection therewith (including those requested by the holders of a
majority of the Registrable Securities being sold) in order to expedite or
facilitate disposition of such Registrable Securities; provided that the Company
shall not be required to take any action in connection with an underwritten
offering without its consent, which consent shall not be unreasonably withheld.

     (q) Cause the Indenture to be qualified under the TIA not later than the
effective date of any Shelf Registration Statement; and in connection therewith,
cooperate with the Trustee to effect such changes to the Indenture as may be
required for the Indenture to be so qualified in accordance with the terms of
the TIA and execute, and use its reasonable best efforts to cause the Trustee to
execute, all documents as may be required to effect such changes, and all other


                                       13



forms and documents required to be filed with the SEC to enable the Indenture to
be so qualified in a timely manner.

     Section 4. HOLDER'S OBLIGATIONS. Each Holder agrees, by acquisition of the
Registrable Securities, that no Holder of Registrable Securities shall be
entitled to sell any of such Registrable Securities pursuant to a Shelf
Registration Statement or to receive a Prospectus relating thereto, unless such
Holder has furnished the Company with a Notice and Questionnaire as required
pursuant to Section 2(d) hereof (including the information required to be
included in such Notice and Questionnaire) and the information set forth in the
next sentence. Each Notice Holder agrees promptly to furnish to the Company all
information required to be disclosed in order to make the information previously
furnished to the Company by such Notice Holder not misleading and any other
information regarding such Notice Holder and the distribution of such
Registrable Securities as the Company may from time to time reasonably request.
Any sale of any Registrable Securities by any Holder shall constitute a
representation and warranty by such Holder that the information relating to such
Holder and its plan of distribution is as set forth in the Prospectus delivered
by such Holder in connection with such disposition, that such Prospectus does
not as of the time of such sale contain any untrue statement of a material fact
relating to or provided by such Holder or its plan of distribution and that such
Prospectus does not as of the time of such sale omit to state any material fact
relating to or provided by such Holder or its plan of distribution necessary in
order to make the statements in such Prospectus, in the light of the
circumstances under which they were made, not misleading.

     SECTION 5. REGISTRATION EXPENSES. The Company shall bear all fees and
expenses incurred in connection with the performance by the Company of its
obligations under Section 2 and 3 of this Agreement whether or not any of the
Shelf Registration Statements are declared effective. Such fees and expenses
("REGISTRATION EXPENSES") shall include, without limitation, (i) all
registration and filing fees (including, without limitation, fees and expenses
(x) with respect to filings required to be made with the National Association of
Securities Dealers, Inc. and (y) of compliance with federal and state securities
or Blue Sky laws (including, without limitation, reasonable fees and
disbursements of counsel for the Holders in connection with Blue Sky
qualifications of the Registrable Securities under the laws of such
jurisdictions as the Notice Holders of a majority of the Registrable Securities
being sold pursuant to a Shelf Registration Statement may designate), (ii)
printing expenses (including, without limitation, expenses of printing
certificates for Registrable Securities in a form eligible for deposit with The
Depository Trust Company), (iii) duplication and mailing expenses relating to
copies of any Shelf Registration Statement or Prospectus delivered to any
Holders hereunder, (iv) fees and disbursements of counsel for the Company and
the reasonable fees and disbursements of one counsel for the Holders in
connection with the Shelf Registration Statement (which counsel shall be
nationally recognized counsel experienced in securities law matters), (v) fees
and


                                       14



disbursements of the Trustee and its counsel and of the registrar and transfer
agent for the Common Stock and (vi) Securities Act liability insurance obtained
by the Company in its sole discretion. In addition, the Company shall pay the
internal expenses of the Company (including, without limitation, all salaries
and expenses of officers and employees performing legal or accounting duties),
the expense of any annual audit, the fees and expenses incurred in connection
with the listing by the Company of the Registrable Securities on any securities
exchange on which similar securities of the Company are then listed and the fees
and expenses of any person, including special experts, retained by the Company.
Except as provided for in this Agreement, the Company shall not be obligated to
pay for the fees and expenses incurred by the Holders.

     SECTION 6. INDEMNIFICATION; CONTRIBUTION.

     (a) The Company agrees to indemnify, defend and hold harmless each Holder
and each person who controls any Holder within the meaning of Section 15 of the
Securities Act or Section 20 of the Exchange Act (each, a "HOLDER INDEMNIFIED
PARTY"), from and against any loss, damage, expense, liability or claim
(including the reasonable cost of investigation) which such Holder Indemnified
Party may incur under the Securities Act, the Exchange Act or otherwise, insofar
as such loss, damage, expense, liability or claim arises out of or is based upon
any untrue statement or alleged untrue statement of a material fact contained in
any Shelf Registration Statement or Prospectus or in any amendment or supplement
thereto or in any preliminary prospectus, or arises out of or is based upon any
omission or alleged omission to state a material fact required to be stated in
any Shelf Registration Statement or in any amendment or supplement thereto or
necessary to make the statements therein not misleading, or arises out of or is
based upon any omission or alleged omission to state a material fact necessary
in order to make the statements made in any Prospectus or in any amendment or
supplement thereto or in any preliminary prospectus, in the light of the
circumstances under which they were made, not misleading, except insofar as any
such loss, damage, expense, liability or claim arises out of or is based upon
any untrue statement or omission or alleged untrue statement or omission of a
material fact contained in, or omitted from, and in conformity with information
furnished in writing by or on behalf of any Holder to the Company expressly for
use therein, including, without limitation, all information, to the extent
provided by such Holder, regarding such Holder and its affiliates included in a
Notice and Questionnaire provided by such Holder to the Company.

     (b) Each Holder, severally and not jointly, agrees to indemnify, defend and
hold harmless the Company, its directors and officers and any person who
controls the Company within the meaning of Section 15 of the Securities Act or
Section 20 of the Exchange Act (each, a "COMPANY INDEMNIFIED PARTY") from and
against any loss, damage, expense, liability or claim (including the reasonable
cost of investigation) which such Company Indemnified Party may incur under the
Securities Act, the Exchange Act or otherwise, insofar as such loss, damage,
expense, liability or claim arises out of or is based upon any untrue statement
or


                                       15



alleged untrue statement of a material fact contained in information furnished
in writing by or on behalf of such Holder to the Company expressly for use in
any Shelf Registration Statement or Prospectus or in any amendment or supplement
thereto or in any preliminary prospectus, including, without limitation, all
information, to the extent provided by such Holder, regarding such Holder and
its affiliates included in a Notice and Questionnaire provided by such Holder to
the Company, or arises out of or is based upon any omission or alleged omission
to state a material fact required to be stated in any Shelf Registration
Statement or in any amendment or supplement thereto or necessary to make the
statements therein not misleading, or arises out of or is based upon any
omission or alleged omission to state a material fact necessary in order to make
the statements in any Prospectus or in any amendment or supplement thereto or in
any preliminary prospectus, in the light of the circumstances under which they
were made, not misleading, in connection with such information. In no event
shall the liability of any selling Holder of Registrable Securities hereunder be
greater in amount than the dollar amount of the proceeds received by such Holder
upon the sale of the Registrable Securities pursuant to the Shelf Registration
Statement giving rise to such indemnification obligation.

     (c) If any action, suit or proceeding (each, a "PROCEEDING") is brought
against any person in respect of which indemnity may be sought pursuant to
either subsection (a) or (b) of this Section 6, such person (the "INDEMNIFIED
PARTY") shall promptly notify the person against whom such indemnity may be
sought (the "INDEMNIFYING PARTY") in writing of the institution of such
Proceeding and the Indemnifying Party shall assume the defense of such
Proceeding; PROVIDED, HOWEVER, that the omission to notify such Indemnifying
Party shall not relieve such Indemnifying Party from any liability which it may
have to such Indemnified Party or otherwise. Such Indemnified Party shall have
the right to employ its own counsel in any such case, but the fees and expenses
of such counsel shall be at the expense of such Indemnified Party unless the
employment of such counsel shall have been authorized in writing by such
Indemnifying Party in connection with the defense of such Proceeding or such
Indemnifying Party shall not have employed counsel to have charge of the defense
of such Proceeding within 30 days of the receipt of notice thereof or such
Indemnified Party shall have reasonably concluded upon the written advice of
counsel that there may be one or more defenses available to it that are
different from, additional to or in conflict with those available to such
Indemnifying Party (in which case such Indemnifying Party shall not have the
right to direct that portion of the defense of such Proceeding on behalf of the
Indemnified Party, but such Indemnifying Party may employ counsel and
participate in the defense thereof but the fees and expenses of such counsel
shall be at the expense of such Indemnifying Party), in any of which events such
reasonable fees and expenses shall be borne by such Indemnifying Party and paid
as incurred (it being understood, however, that such Indemnifying Party shall
not be liable for the expenses of more than one separate counsel in any one
Proceeding or series of related Proceedings together with reasonably necessary
local counsel representing the Indemnified Parties who are parties to


                                       16



such action). An Indemnifying Party shall not be liable for any settlement of
such Proceeding effected without the written consent of such Indemnifying Party,
but if settled with the written consent of such Indemnifying Party, such
Indemnifying Party agrees to indemnify and hold harmless an Indemnified Party
from and against any loss or liability by reason of such settlement.
Notwithstanding the foregoing sentence, if at any time an Indemnified Party
shall have requested an Indemnifying Party to reimburse such Indemnified Party
for fees and expenses of counsel as contemplated by the second sentence of this
paragraph, then such Indemnifying Party agrees that it shall be liable for any
settlement of any Proceeding effected without its written consent if (i) such
settlement is entered into more than 60 Business Days after receipt by such
Indemnifying Party of the aforesaid request, (ii) such Indemnifying Party shall
not have reimbursed such Indemnified Party in accordance with such request prior
to the date of such settlement and (iii) such Indemnified Party shall have given
such Indemnifying Party at least 30 days' prior notice of its intention to
settle. No Indemnifying Party shall, without the prior written consent of any
Indemnified Party, effect any settlement of any pending or threatened Proceeding
in respect of which such Indemnified Party is or could have been a party and
indemnity could have been sought hereunder by such Indemnified Party, unless
such settlement includes an unconditional release of such Indemnified Party from
all liability on claims that are the subject matter of such Proceeding and does
not include an admission of fault, culpability or a failure to act, by or on
behalf of such Indemnified Party.

     (d) If the indemnification provided for in this Section 6 is unavailable to
an Indemnified Party under subsections (a) and (b) of this Section 6 in respect
of any losses, damages, expenses, liabilities or claims referred to therein,
then each applicable 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, damages, expenses, liabilities or
claims (i) in such proportion as is appropriate to reflect the relative benefits
received by the Company on the one hand and the Holders on the other hand from
the offering of the Registrable Securities or (ii) if the allocation provided by
clause (i) above is not permitted by applicable law, in such proportion as is
appropriate to reflect not only the relative benefits referred to in clause (i)
above but also the relative fault of the Company on the one hand and of the
Holders on the other in connection with the statements or omissions which
resulted in such losses, damages, expenses, liabilities or claims, as well as
any other relevant equitable considerations. The relative fault of the Company
on the one hand and of the Holders on the other shall be determined by reference
to, among other things, whether the untrue statement or alleged untrue statement
of a material fact or omission or alleged omission relates to information
supplied by the Company or by the Holders and the parties' relative intent,
knowledge, access to information and opportunity to correct or prevent such
statement or omission. The amount paid or payable by a party as a result of the
losses, damages, expenses, liabilities and claims referred to above shall be
deemed to include any reasonable legal or


                                       17



other fees or expenses reasonably incurred by such party in connection with
investigating or defending any Proceeding.

     (e) The Company and the Holders agree that it would not be just and
equitable if contribution pursuant to this Section 6 were determined by pro rata
allocation or by any other method of allocation which does not take account of
the equitable considerations referred to in subsection (d) above.
Notwithstanding the provisions of this Section 6, no Holder shall be required to
contribute any amount in excess of the amount by which the total price at which
the Registrable Securities sold by it were offered to the public exceeds the
amount of any damages which it has otherwise been required to pay by reason of
such untrue or alleged untrue statement or omission or alleged omission. No
person guilty of fraudulent misrepresentation (within the meaning of Section
11(f) of the Securities Act) shall be entitled to contribution from any person
who was not guilty of such fraudulent misrepresentation. The Holders' respective
obligations to contribute pursuant to this Section 6 are several in proportion
to the respective amount of Registrable Securities they have sold pursuant to a
Shelf Registration Statement, and not joint. The remedies provided for in this
Section 6 are not exclusive and shall not limit any rights or remedies which may
otherwise be available to any indemnified party at law or in equity.

     (f) The indemnity and contribution provisions contained in this Section 6
shall remain operative and in full force and effect regardless of (i) any
termination of this Agreement, (ii) any investigation made by or on behalf of
any Holder or any person controlling any Holder, or the Company, or the
Company's officers or directors or any person controlling the Company and (iii)
the sale of any Registrable Security by any Holder.

     SECTION 7. INFORMATION REQUIREMENTS. (a) The Company covenants that, if at
any time before the end of the Effectiveness Period it is not subject to the
reporting requirements of the Exchange Act, it will cooperate with any Holder of
Registrable Securities and take such further action as any Holder of Registrable
Securities may reasonably request in writing (including, without limitation,
making such representations as any such Holder may reasonably request in order
to facilitate sales by such Holder pursuant to an available exemption from
registration under the Securities Act), all to the extent required from time to
time to enable such Holder to sell Registrable Securities without registration
under the Securities Act within the limitation of the exemptions provided by
Rule 144, Rule 144A and Regulation D under the Securities Act and customarily
taken in connection with sales pursuant to such exemptions. Upon the written
request of any Holder of Registrable Securities, the Company shall deliver to
such Holder a written statement as to whether it has complied with such filing
requirements, unless such a statement has been included in the Company's most
recent report filed with the SEC pursuant to Section 13 or Section 15(d) of
Exchange Act. Notwithstanding the foregoing, nothing in this Section 7 shall be
deemed to require the Company to register any of its securities (other than the
Common Stock) under any section of the Exchange Act.


                                       18



     (b) The Company shall file the reports required to be filed by it under the
Exchange Act and shall comply with all other requirements set forth in the
instructions to Form S-1 or Form S-3, as the case may be, in order to allow the
Company to be eligible to file registration statements on Form S-1 or Form S-3.

     SECTION 8. MISCELLANEOUS.

     (a) NO CONFLICTING AGREEMENTS. The Company is not, as of the date hereof, a
party to, nor shall it, on or after the date of this Agreement, enter into, any
agreement with respect to its securities that conflicts with the rights granted
to the Holders of Registrable Securities in this Agreement. The Company
represents and warrants that the rights granted to the Holders of Registrable
Securities hereunder do not in any way conflict with the rights granted to the
holders of the Company's securities under any other agreements.

     (b) AMENDMENTS AND WAIVERS. The provisions of this Agreement, including the
provisions of this sentence, may not be amended, modified or supplemented, and
waivers or consents to departures from the provisions hereof may not be given,
unless the Company has obtained the written consent of Holders of a majority of
the then outstanding Underlying Common Stock constituting Registrable Securities
(with Holders of Notes deemed to be the Holders, for purposes of this Section,
of the number of outstanding shares of Underlying Common Stock into which such
Notes are or would be convertible as of the date on which such consent is
requested). Notwithstanding the foregoing, a waiver or consent to depart from
the provisions hereof with respect to a matter that relates exclusively to the
rights of Holders of Registrable Securities whose securities are being sold
pursuant to a Shelf Registration Statement and that does not directly or
indirectly affect the rights of other Holders of Registrable Securities may be
given by Holders of at least a majority of the Registrable Securities being sold
by such Holders pursuant to such Shelf Registration Statement; PROVIDED that the
provisions of this sentence may not be amended, modified, or supplemented except
in accordance with the provisions of the immediately preceding sentence. Each
Holder of Registrable Securities outstanding at the time of any such amendment,
modification, supplement, waiver or consent or thereafter shall be bound by any
such amendment, modification, supplement, waiver or consent effected pursuant to
this Section 8(b), whether or not any notice, writing or marking indicating such
amendment, modification, supplement, waiver or consent appears on the
Registrable Securities or is delivered to such Holder.

     (c) NOTICES. All notices and other communications provided for or permitted
hereunder shall be made in writing by hand delivery, by telecopier, by courier
guaranteeing overnight delivery or by first-class mail, return receipt
requested, and shall be deemed given (i) when made, if made by hand delivery,
(ii) upon confirmation, if made by telecopier, (iii) one (1) Business Day after
being deposited with such courier, if made by overnight courier or (iv) on the
date


                                       19



indicated on the notice of receipt, if made by first-class mail, to the parties
as follows:

     (x) if to a Holder of Registrable Securities, at the most current address
given by such Holder to the Company in a Notice and Questionnaire or any
amendment thereto;

     (y) if to the Company, to:

                Ligand Pharmaceuticals Incorporated
                10275 Science Center Drive
                San Diego, California   92121-1117
                Attention: David E. Robinson, President and Chief Executive
                Officer
                Telecopy No.: (858) 550-1825

                with a copy to (for informational purposes only):

                Clifford Chance US LLP
                3811 Valley Centre Drive, Second Floor
                San Diego, California   92130-3318
                Attention:  Faye H. Russell
                Telecopy No.: (858) 720-3501

     (z) if to the Initial Purchaser, to:

                UBS Warburg LLC
                299 Park Avenue
                New York, New York 10171
                Attention: Syndicate Department
                Telecopy No.: (212) 713-1205

                with a copy to (for informational purposes only):

                UBS Warburg LLC
                677 Washington Boulevard
                Stamford, Connecticut 06901
                Attention: Legal Affairs--Convertibles
                Telecopy No.: (203) 719-7317

or to such other address as such person may have furnished to the other persons
identified in this Section 8(c) in writing in accordance herewith.

     (d) APPROVAL OF HOLDERS. Whenever the consent or approval of Holders of a
specified percentage of Registrable Securities is required hereunder,
Registrable Securities held by the Company or its affiliates (as such term is
defined in Rule 405 under the Securities Act) (other than the Initial Purchaser
or


                                       20



subsequent Holders of Registrable Securities if such subsequent Holders are
deemed to be such affiliates solely by reason of their holdings of such
Registrable Securities) shall not be counted in determining whether such consent
or approval was given by the Holders of such required percentage.

     (e) SUCCESSORS AND ASSIGNS. Any person who purchases any Registrable
Securities from the Initial Purchaser or any Holder shall be deemed, for
purposes of this Agreement, to be an assignee of the Initial Purchaser or such
Holder, as the case may be. This Agreement shall inure to the benefit of and be
binding upon the successors and assigns of each of the parties and shall inure
to the benefit of and be binding upon each Holder of any Registrable Securities.

     (f) COUNTERPARTS. This Agreement may be executed in any number of
counterparts and by the parties hereto in separate counterparts, each of which
when so executed shall be deemed to be original and all of which taken together
shall constitute one and the same agreement.

     (g) HEADINGS. The headings in this Agreement are for convenience of
reference only and shall not limit or otherwise affect the meaning hereof.

     (h) GOVERNING LAW. THIS AGREEMENT SHALL BE GOVERNED BY, AND CONSTRUED IN
ACCORDANCE WITH, THE LAWS OF THE STATE OF NEW YORK, WITHOUT REGARD TO CONFLICTS
OF LAWS PRINCIPLES THEREOF.

     (i) SEVERABILITY. If any term, provision, covenant or restriction of this
Agreement is held to be invalid, illegal, void or unenforceable, the remainder
of the terms, provisions, covenants and restrictions set forth herein shall
remain in full force and effect and shall in no way be affected, impaired or
invalidated thereby, and the parties hereto shall use its reasonable best
efforts to find and employ an alternative means to achieve the same or
substantially the same result as that contemplated by such term, provision,
covenant or restriction, it being intended that all of the rights and privileges
of the parties shall be enforceable to the fullest extent permitted by law.

     (j) ENTIRE AGREEMENT. This Agreement is intended by the parties as a final
expression of their agreement and is intended to be a complete and exclusive
statement of the agreement and understanding of the parties hereto in respect of
the subject matter contained herein and the registration rights granted by the
Company with respect to the Registrable Securities. Except as provided in the
Purchase Agreement, there are no restrictions, promises, warranties or
undertakings, other than those set forth or referred to herein, with respect to
the registration rights granted by the Company with respect to the Registrable
Securities. This Agreement supersedes all prior agreements and undertakings
among the parties with respect to such registration rights. No party hereto
shall have any rights, duties or obligations other than those specifically set
forth in this Agreement.


                                       21



     (k) TERMINATION. This Agreement and the obligations of the parties
hereunder shall terminate upon the end of the Effectiveness Period, except for
any liabilities or obligations under Section 4, 5 or 6 hereof and the
obligations to make payments of and provide for liquidated damages under Section
2(e) hereof to the extent such damages accrue prior to the end of the
Effectiveness Period, each of which shall remain in effect in accordance with
its terms.

     (l) SUBMISSION TO JURISDICTION. Except as set forth below, no Proceeding
may be commenced, prosecuted or continued in any court other than the courts of
the State of New York located in the City and County of New York or in the
United States District Court for the Southern District of New York, which courts
shall have jurisdiction over the adjudication of such matters, and the Company
hereby consents to the jurisdiction of such courts and personal service with
respect thereto. The Company hereby consents to personal jurisdiction, service
and venue in any court in which any Proceeding arising out of or in any way
relating to this Agreement is brought by any third party against the Initial
Purchaser. The Company hereby waives all right to trial by jury in any
Proceeding (whether based upon contract, tort or otherwise) in any way arising
out of or relating to this Agreement. The Company agrees that a final judgment
in any such Proceeding brought in any such court shall be conclusive and binding
upon the Company and may be enforced in any other courts in the jurisdiction of
which the Company is or may be subject, by suit upon such judgment.




                                       22




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

                           LIGAND PHARMACEUTICALS INCORPORATED
                           By:       /s/ David E. Robinson
                                     ---------------------------
                                     Name:
                                     Title:



Confirmed and accepted as of the date first above written:

UBS WARBURG LLC


By:  /s/ Mark Saad
     Name:
     Title:

By:  /s/ Sage Kelly
     Name:
     Title:







                                       23