<PAGE>
                                                                     EXHIBIT 4.2

                      FORM OF REGISTRATION RIGHTS AGREEMENT

         This REGISTRATION RIGHTS AGREEMENT (this "AGREEMENT") is made as of
January ____, 2002 by and among (i) La Jolla Pharmaceutical Company, a Delaware
corporation (the "COMPANY"), (ii) each person listed on Exhibit A attached
hereto (collectively, the "INITIAL INVESTORS" and each individually, an "INITIAL
INVESTOR"), and (iii) each person or entity that subsequently becomes a party to
this Agreement pursuant to, and in accordance with, the provisions of Section 12
hereof (each an "INVESTOR PERMITTED Transferee" and collectively, the "INVESTOR
PERMITTED TRANSFEREES").

         WHEREAS, the Company has agreed to issue and sell to the Initial
Investors, and the Initial Investors have agreed to purchase from the Company,
an aggregate of 7,000,000 shares (the "PURCHASED SHARES") of the Company's
common stock, $0.01 par value per share (the "COMMON STOCK"), all upon the terms
and conditions set forth in that certain Stock Purchase Agreement, dated of even
date herewith, between the Company and the Initial Investors (the "STOCK
PURCHASE AGREEMENT"); and

         WHEREAS, the terms of the Stock Purchase Agreement provide that it
shall be a condition precedent to the closing of the transactions thereunder,
for the Company and the Initial Investors to execute and deliver this Agreement.

         NOW, THEREFORE, in consideration of the premises and mutual covenants
contained herein, the parties hereto hereby agree as follows:

         1. Definitions. The following terms shall have the meanings provided
therefor below or elsewhere in this Agreement as described below:

                  "Board" shall mean the board of directors of the Company.

                  "Closing" shall have the meaning ascribed to such term in the
Stock Purchase Agreement.

                  "Closing Date" shall have the meaning ascribed to such term in
the Stock Purchase Agreement.

                  "Effectiveness Deadline" shall be one hundred five (105) days
after the Closing Date.

                  "Exchange Act" shall mean the Securities Exchange Act of 1934,
as amended, and all of the rules and regulations promulgated thereunder.

                  "Filing Date Deadline" shall be fifteen (15) business days
after the Closing Date.

                  "Investors" shall mean, collectively, the Initial Investors
and the Investor Permitted Transferees; provided, however, that the term
"Investors" shall not include any of the Initial Investors or any of the
Investor Permitted Transferees that ceases to own or hold any Purchased Shares.

                  "Majority Holders" shall mean, at the relevant time of
reference thereto, those Investors holding and/or having the right to acquire,
as the case may be, more than fifty percent (50%) of the Registrable Shares held
by all of the Investors.
<PAGE>
                  "NASD" shall mean the National Association of Securities
Dealers, Inc.

                  "Qualifying Holder" shall have the meaning ascribed thereto in
Section 12 hereof.

                  "Registrable Shares" shall mean (i) the Purchased Shares and
(ii) any Common Stock of the Company issued as (or issuable upon the conversion
or exercise of any warrant, right or other security that is issued as) a
dividend or other distribution (including a stock split or reverse stock split)
with respect to, or in exchange for, or in replacement of, the shares referenced
in (i) above after the Closing and prior to the date upon which the Registration
Statement is declared effective by the SEC; provided, however, such term shall
not, after the Mandatory Registration Termination Date, include any of the
Purchased Shares that become or have become eligible for resale pursuant to
subsection (k) of Rule 144.

                  "Rule 144" shall mean Rule 144 promulgated under the
Securities Act and any successor or substitute rule, law or provision.

                  "SEC" shall mean the Securities and Exchange Commission.

                  "Securities Act" shall mean the Securities Act of 1933, as
amended, and all of the rules and regulations promulgated thereunder.

         2. Effectiveness; Termination. This Agreement shall become effective
and legally binding only if the Closing occurs. This Agreement shall terminate
and be of no further force or effect, automatically and without any action being
required of any party hereto, upon the termination of the Stock Purchase
Agreement pursuant to Section 7 thereof. Nothing contained herein or in any
agreement or document relating to this transaction, and no action taken by any
Investor, shall be deemed to constitute the Investors as, or to create any
presumption that the Investors are in any way acting in concert or as, a group
with respect to the obligations or transaction hereunder. Each Investor shall be
entitled to independently protect and enforce its rights hereunder.

         3.       Mandatory Registration.

                  (a) Within fifteen (15) business days after the Closing Date,
the Company shall prepare and file with the SEC a registration statement on Form
S-3 for the purpose of registering under the Securities Act all of the
Registrable Shares for resale by, and for the account of, the Investors as
selling stockholders thereunder (the "REGISTRATION STATEMENT"). The Registration
Statement shall permit the Investors to offer and sell, on a delayed or
continuous basis pursuant to Rule 415 under the Securities Act, any or all of
the Registrable Shares. The Company shall be required to keep the Registration
Statement effective until such date that is the earlier of (i) the date when all
of the Registrable Shares registered thereunder shall have been sold or (ii) the
date on which all of the Registrable Shares may be immediately sold without
restriction (including without any limitation as to volume or manner of sale by
each Investor) and without registration under the Securities Act (the "MANDATORY
REGISTRATION TERMINATION DATE"). Thereafter, the Company shall be entitled to
withdraw the Registration Statement and the Investors shall have no further
right to offer or sell any of the Registrable Shares pursuant to the
Registration Statement (or any prospectus relating thereto).

                  (b) Unless otherwise agreed to by the Company, the offer and
sale of the Registrable Shares pursuant to the Registration Statement shall not
be underwritten.
<PAGE>
                  (c) The Company represents and warrants that, as of the date
of this Agreement, it meets the requirements for the use of Form S-3 for
registration of the resale by the Investors of the Registrable Shares, and it
will use its commercially reasonable efforts to continue to meet such
requirements during the period in which it takes to have the Registration
Statement declared effective.

                  (d) The Company shall cause all of the Registrable Shares to
be listed on The Nasdaq National Market.

                  (e) This Section 3(e) shall apply to the Company's obligation
under Section 3(a) hereof to file the Registration Statement with the SEC and to
cause such Registration Statement to become effective. The Company and Initial
Investors agree that the Investors will suffer damages if the Registration
Statement is not filed on or prior to the Filing Date Deadline and not declared
effective by the SEC on or prior to the Effectiveness Deadline. The Company and
the Initial Investors further agree that it would not be feasible to ascertain
the extent of such damages with precision. Accordingly, if (i) the Registration
Statement is not filed on or prior to the Filing Date Deadline; (ii) the
Registration Statement is not declared effective prior to the Effectiveness
Deadline; or (iii) the Company fails to file with the SEC a request for
acceleration in accordance with Rule 12d1-2 promulgated under the Exchange Act
as promptly as practicable after the date that the Company is notified (orally
or in writing, whichever is earlier) by the Commission that a Registration
Statement will not be reviewed, or not subject to further review (each of the
events listed in (i)-(iii) above being referred to as an "EVENT"), then the
Company shall pay as liquidated damages for any such failure and not as a
penalty (the "LIQUIDATED DAMAGES") $250,000 (the "LIQUIDATED DAMAGES AMOUNT") to
the Investors for each thirty (30) day period (pro rated for any period less
than thirty (30) days) following the Event until the applicable Event has been
cured; provided, however, that if the Registration Statement is not declared
effective by the SEC within one hundred eighty (180) days after the Closing
Date, then the Liquidated Damages Amount shall increase to $500,000 for each
such subsequent thirty (30) day period (pro rated for any period less than
thirty (30) days). Each Liquidated Damages payment, if any, shall by payable to
the Investors on a pro rata basis among them based on the number of shares each
Initial Investor purchased pursuant to the Stock Purchase Agreement. In any
event, no Liquidated Damages shall accrue after the twelve (12) month
anniversary of the Closing Date. Payments to be made pursuant to this Section
3(e) shall be due and payable in immediately available funds within three days
of such payment becoming payable hereunder. The parties agree that the
Liquidated Damages represent a reasonable estimate on the part of the parties,
as of the date of this Agreement, of the amount of damages that may be incurred
by the Investors if the Registration Statement is not filed on or prior to the
Filing Date Deadline or has not been declared effective by the SEC on or prior
to the Effectiveness Deadline.

         4.       "Piggyback" Registration Rights.

                  (a) If, at any time after the Mandatory Registration
Termination Date, the Company proposes to register any of its Common Stock under
the Securities Act, whether as a result of a primary or secondary offering of
Common Stock or pursuant to registration rights granted to holders of other
securities of the Company (but excluding in all cases any registrations to be
effected on Forms S-4 or S-8 or other applicable successor forms), the Company
shall, each such time, give to the Investors holding Registrable Shares written
notice of its intent to do so. Upon the written request of any such Investor
given within 20 days after the giving of any such notice by the Company, the
Company shall use reasonable efforts to cause to be included in such
registration the Registrable Shares of such selling Investor, to the extent
requested to be registered; provided that (i) the number of Registrable Shares
proposed to be sold by such selling Investor is equal to at least twenty-five
percent (25%) of the total number of Registrable Shares then held by such
participating selling Investor, (ii) such selling Investor agrees to sell those
of its Registrable Shares to be
<PAGE>
included in such registration in the same manner and on the same terms and
conditions as the other shares of Common Stock which the Company proposes to
register and (iii) if the registration is to include shares of Common Stock to
be sold for the account of the Company or any party exercising demand
registration rights pursuant to any other agreement with the Company, the
proposed managing underwriter does not advise the Company that in its opinion
the inclusion of such selling Investor's Registrable Shares (without any
reduction in the number of shares to be sold for the account of the Company or
such party exercising demand registration rights) is likely to affect materially
and adversely the success of the offering or the price that would be received
for any shares of Common Stock offered, in which case the rights of such selling
Investor shall be as provided in Section 4(b) hereof.

                  (b) If a registration pursuant to Section 4(a) hereof involves
an underwritten offering and the managing underwriter shall advise the Company
in writing that, in its opinion, the number of shares of Common Stock requested
by the Investors to be included in such registration is likely to affect
materially and adversely the success of the offering or the price that would be
received for any shares of Common Stock offered in such offering, then,
notwithstanding anything in Section 4(a) to the contrary, the Company shall only
be required to include in such registration, to the extent of the number of
shares of Common Stock which the Company is so advised can be sold in such
offering, (i) first, the number of shares of Common Stock proposed to be
included in such registration for the account of the Company and/or any
stockholders of the Company (other than the Investors) that have exercised
demand registration rights, in accordance with the priorities, if any, then
existing among the Company and/or such stockholders of the Company with
registration rights (other than the Investors), and (ii) second, the shares of
Common Stock requested to be included in such registration by all other
stockholders of the Company who have piggyback registration rights (including,
without limitation, the Investors), pro rata among such other stockholders
(including, without limitation, the Investors) on the basis of the number of
shares of Common Stock that each of them requested to be included in such
registration.

                  (c) In connection with any offering involving an underwriting
of shares under this Section 4, the Company shall not be required under Section
4 hereof or otherwise to include the Registrable Shares of any Investor therein
unless such Investor accepts and agrees to the terms of the underwriting, which
shall be reasonable and customary, as agreed upon between the Company and the
underwriters selected by the Company.

         5. Obligations of the Company. In connection with the Company's
obligation under Section 3 and 4 hereof to file the Registration Statement with
the SEC and to use its best efforts to cause the Registration Statement to
become effective, the Company shall, as expeditiously as reasonably possible:

                  (a) Prepare and file with the SEC such amendments and
supplements to the Registration Statement and the prospectus used in connection
therewith as may be necessary to comply with the provisions of the Securities
Act with respect to the disposition of all Registrable Shares covered by the
Registration Statement; provided, however, that before filing a registration
statement or prospectus or any amendments or supplements thereto, or comparable
statements under securities or blue sky laws of any jurisdiction, the Company
will furnish to Kelley, Drye & Warren LLP, Attn: Salvatore J. Vitiello, as
designated counsel for the Investors participating in the planned offering (the
"DESIGNATED COUNSEL"), copies of all such documents proposed to be filed
(including all exhibits thereto), which documents will be subject to the
reasonable review and reasonable comment of such counsel.

                  (b) Furnish to the selling Investors such number of copies of
a prospectus, including a preliminary prospectus, in conformity with the
requirements of the Securities Act, and such other documents (including, without
limitation, prospectus amendments and supplements as
<PAGE>
are prepared by the Company in accordance with Section 5(a) above) as the
selling Investors may reasonably request in order to facilitate the disposition
of such selling Investors' Registrable Shares.

                  (c) Promptly notify the selling Investors, at any time when a
prospectus relating to the Registration Statement is required to be delivered
under the Securities Act, of the happening of any event as a result of which the
prospectus included in or relating to the Registration Statement contains an
untrue statement of a material fact or omits any fact necessary to make the
statements therein not misleading; and, thereafter, the Company will promptly
prepare (and, when completed, give notice to each selling Investor) a supplement
or amendment to such prospectus so that, as thereafter delivered to the
purchasers of such Registrable Shares pursuant to the Registration Statement,
such prospectus will not contain an untrue statement of a material fact or omit
to state any fact necessary to make the statements therein not misleading;
provided that upon such notification by the Company of the foregoing and
instructing each selling Investor to cease to offer and sell Registrable
Securities, each selling Investor will use its commercially reasonable efforts
to cease its offer and sale of Registrable Shares until the Company has notified
the selling Investors that it has prepared a supplement or amendment to such
prospectus and delivered copies of such supplement or amendment to the selling
Investors (it being understood and agreed by the Company that the foregoing
proviso shall in no way diminish or otherwise impair the Company's obligation to
promptly prepare a prospectus amendment or supplement as above provided in this
Section 5(c) and deliver copies of same as above provided in Section 5(b)
hereof).

                  (d) Use commercially reasonable efforts to register and
qualify the Registrable Shares covered by the Registration Statement under such
other securities or Blue Sky laws of such jurisdictions as shall be reasonably
appropriate in the opinion of the Company and the managing underwriters, if any,
or if reasonably requested by the Investors; provided that the Company shall not
be required in connection therewith or as a condition thereto to qualify to do
business or to file a general consent to service of process in any such states
or jurisdictions; and provided further that (notwithstanding anything in this
Agreement to the contrary with respect to the bearing of expenses) if any
jurisdiction in which any of such Registrable Shares shall be qualified shall
require that expenses incurred in connection with the qualification therein of
any such Registrable Shares be borne by the selling Investors, then the selling
Investors shall, to the extent required by such jurisdiction, pay their pro rata
share of such qualification expenses.

                  (e) Promptly notify (i) each selling Investor (A) any time
when a registration statement, the prospectus relating thereto or any prospectus
supplement related thereto or post-effective amendment has been filed, and with
respect to the registration statement or any post-effective amendment, when the
same has become effective, (B) of the issuance of any stop order by the SEC
suspending the effectiveness of such registration statement or the initiation of
any proceedings by any person to such effect, and promptly use all commercially
reasonable efforts to obtain the release of such suspension, (C) of the receipt
by the Company of any notification with respect to the suspension of the
qualification of any Registrable Shares for sale under the securities or blue
sky laws of any jurisdiction or the initiation of any proceeding for such
purpose, (D) when a prospectus relating to the registration is required to be
delivered under the Securities Act, or (E) of the happening of any event as a
result of which the prospectus included in such registration statement, as then
in effect, includes and untrue statement of a material fact or omits to state a
material fact required to be stated therein or necessary to make the statements
therein not misleading in the light of the circumstances then existing; and (ii)
Designated Counsel of any request by the SEC for amendments or supplements to
such registration statement or prospectus related thereto or for additional
information. If the notification relates to an event described in Section 5(c),
the Company shall in accordance with Section 5(a), promptly prepare and furnish
to each Investor, if any, selling Registrable Shares covered by such
registration statement, a reasonable
<PAGE>
number of copies of a prospectus supplemented or amended so that, as thereafter
delivered to the purchasers of such Registrable Shares, such prospectus shall
not include an untrue statement of a material fact or omit to state a material
fact required to be stated therein or necessary to make the statements therein
in the light of the circumstances under which they were made not misleading.

                  (f) Cause all such Registrable Shares registered pursuant to
this Agreement to be listed on each securities exchange on which similar
securities issued by the Company are then listed, if the listing of such
Registrable Shares is then permitted under the rules of such exchange, or if no
similar securities are then so listed, to either cause all such Registrable
Shares to be listed on a national securities exchange or to secure designation
of all such Registrable Shares as a NASDAQ "national market system security"
within the meaning of Rule 11Aa2-1 of the Exchange Act, or failing that, secure
NASDAQ Authorization for such Registrable Shares.

                  (g) Provide a transfer agent and registrar for all Registrable
Shares registered pursuant to this Agreement and a CUSIP number for all such
Registrable Shares, in each case not later than the effective date of such
registration and, at the time of the sale of the Registrable Shares pursuant to
an effective registration statement or in accordance with Section 6.3 of the
Stock Purchase Agreement, use commercially reasonable efforts to cause the
transfer agent to remove restrictive legends on the securities covered by such
registration statement.

                  (h) Promptly deliver to Designated Counsel copies of all
correspondence between the SEC and the Company, its counsel or auditors and all
memoranda relating to discussions with the SEC or its staff with respect to the
registration statement, other than those portions of any such memoranda that
contain information subject to attorney client privilege with respect to the
Company, and, upon receipt of such confidentiality agreements as the Company may
reasonably request, make reasonably available for inspection by Designated
Counsel participating in any disposition to be effected pursuant to such
registration statement, all pertinent financial and other records, pertinent
corporate documents and properties of the Company, and cause all of the
Company's officers, directors and employees to supply all information reasonably
requested by Designated Counsel in connection with such registration statement.

                  (i) Use commercially reasonable best efforts to obtain the
withdrawal of any order suspending the effectiveness of the registration
statement.

                  (j) Upon written request, furnish to each selling Investor
participating in the offering, without charge, at least one (1) conformed copy
of the registration statement and any post-effective amendments thereto,
including financial statements and schedules, all documents incorporated therein
by reference and all exhibits (including those incorporated by reference).

                  (k) Comply with all applicable rules and regulations of the
SEC, and make generally available to its security holders, as soon as reasonably
practicable after the effective date of the registration statement (and in any
event within sixteen (16) months thereafter), an earnings statement (which need
not be audited) covering the period of at least twelve (12) consecutive months
beginning with the first day of the Company's first calendar quarter after the
effective date of the registration statement, which earnings shall satisfy the
provisions of Section 11(a) of the Securities Act and Rule 158 thereunder.

         6. Furnish Information. It shall be a condition precedent to the
obligations of the Company to take any action pursuant to this Agreement
(including, without limitation, to maintain the accuracy of any information
previously furnished by Investors for use in the Registration Statement) that
the selling Investors shall furnish to the Company such information regarding
them and the securities held by
<PAGE>
them as the Company shall reasonably request and as shall be required by
applicable securities laws in order to effect any registration by the Company
pursuant to this Agreement.

         7. Expenses of Registration. All of the expenses incurred by the
Company in connection with the registration of the Registrable Shares pursuant
to this Agreement (excluding underwriting, brokerage and other selling
commissions and discounts), including without limitation all registration and
qualification and filing fees, printing, and fees and disbursements of its
counsel and, to the extent provided in Section 8.13 of the Stock Purchase
Agreement, one counsel to the Investors, shall be borne by the Company, whether
or not such Registration Statement becomes effective or remains effective for
the period contemplated hereby.

         8. Delay of Registration. No Investor shall take any action to
restrain, enjoin or otherwise delay any registration as the result of any
controversy which might arise with respect to the interpretation or
implementation of this Agreement.

         9.       Indemnification.

                  (a) To the extent permitted by law, the Company will indemnify
and hold harmless each selling Investor, its directors, officers, employees,
fiduciaries, members, managers, or general or limited partners (and the
directors, officers, employees and stockholders thereof), any broker/dealer
acting on behalf of any selling Investor and each officer and director of such
selling Investor, such broker/dealer and each person, if any, who controls such
selling Investor, or broker/dealer and each person who controls such
broker/dealer within the meaning of the Securities Act, against any losses,
claims, damages or liabilities, joint or several, and expenses (including
reasonable fees of counsel and any amounts paid in any settlement effected with
the Company's prior written consent) to which they may become subject (including
the settlement of litigation) under the Securities Act, the Exchange Act, state
securities laws or otherwise, insofar as such losses, claims, damages or
liabilities (or actions or proceedings in respect thereof) arise out of or are
based upon (i) any untrue or alleged untrue statement of any material fact
contained in the Registration Statement, or any registration statement pursuant
to which Registrable Shares are registered pursuant to Section 4 hereof, in any
preliminary prospectus or final prospectus relating thereto or in any amendments
or supplements to the Registration Statement, or any registration statement
pursuant to which Registrable Shares are registered pursuant to Section 4
hereof, or any such preliminary prospectus or final prospectus, or arise out of
or are based upon the omission or alleged omission to state therein a material
fact required to be stated therein, or necessary to make the statements therein
not misleading or any violation or alleged violation by the Company of the
Securities Act, the Exchange Act, state securities laws, or otherwise or any
rule or regulation promulgated under the Securities Act, the Exchange Act, state
securities laws or NASDAQ or (ii) any failure of the Company to fulfill any
undertaking included in the Registration Statement, or any registration
statement pursuant to which Registrable Shares are registered pursuant to
Section 4 hereof; and will reimburse such selling Investor, broker/dealer or
such officer, director or controlling person for any expenses reasonably
incurred by them in connection with investigating or defending any such loss,
claim, damage, liability or action (including reasonable expenses of legal
counsel); provided, however, that the indemnity agreement contained in this
Section 9(a) shall not apply to amounts paid in settlement of any such loss,
claim, damage, liability or action if such settlement is effected without the
consent of the Company (which consent shall not be unreasonably withheld), nor
shall the Company be liable in any such case for any such loss, damage,
liability or action to the extent that it arises out of or is based upon an
untrue statement or alleged untrue statement or omission made in connection with
the Registration Statement or any registration statement pursuant to which
Registrable Shares are registered pursuant to Section 4 hereof, or any
preliminary prospectus or final prospectus relating thereto or any amendments or
supplements thereto or any such preliminary prospectus or final prospectus, in
reliance upon and in conformity with written information furnished expressly for
use in connection with the Registration
<PAGE>
Statement or any such preliminary prospectus or final prospectus by the selling
Investors or for them or controlling person with respect to them. Such indemnity
and reimbursement of expenses shall remain in full force and effect regardless
of any investigation made by or on behalf of such indemnified party and shall
survive the sale of such Registrable Shares by such selling Investor.

                  (b) To the extent permitted by law, each selling Investor will
severally, and not jointly, indemnify and hold harmless the Company, each of its
directors, each of its officers who have signed the Registration Statement, or
any registration statement pursuant to which Registrable Shares are registered
pursuant to Section 4 hereof, each person, if any, who controls the Company
within the meaning of the Securities Act, any investment banking firm acting as
underwriter for the Company or the selling Investors, or any broker/dealer
acting on behalf of the Company or any selling Investor, and all other selling
Investors against any losses, claims, damages or liabilities to which the
Company or any such director, officer, controlling person, underwriter, or
broker/dealer or such other selling Investor may become subject to, under the
Securities Act or otherwise, insofar as such losses, claims, damages or
liabilities (or actions in respect thereto) arise out of or are based upon any
untrue or alleged untrue statement of any material fact contained in the
Registration Statement, or any registration statement pursuant to which
Registrable Shares are registered pursuant to Section 4 hereof, or any
preliminary prospectus or final prospectus, relating thereto or in any
amendments or supplements to the Registration Statement, or any registration
statement pursuant to which Registrable Shares are registered pursuant to
Section 4 hereof, or any such preliminary prospectus or final prospectus, or
arise out of or are based upon the omission or alleged omission to state therein
a material fact required to be stated therein or necessary to make the
statements therein not misleading, in each case to the extent and only to the
extent that such untrue statement or alleged untrue statement or omission or
alleged omission was made in the Registration Statement, or any registration
statement pursuant to which Registrable Shares are registered pursuant to
Section 4 hereof, in any preliminary prospectus or final prospectus relating
thereto or in any amendments or supplements to the Registration Statement, or
any registration statement pursuant to which Registrable Shares are registered
pursuant to Section 4 hereof, or any such preliminary prospectus or final
prospectus, in reliance upon and in conformity with written information
furnished by the selling Investor expressly for use in connection with the
Registration Statement, or any preliminary prospectus or final prospectus; and
such selling Investor will reimburse any expenses reasonably incurred by the
Company or any such director, officer, controlling person, underwriter,
broker/dealer or other selling Investor in connection with investigating or
defending any such loss, claim, damage, liability or action (including
reasonable expenses of legal counsel); provided, however, that the liability of
each selling Investor hereunder shall be limited to the proceeds (net of
underwriting discounts and commissions, if any) received by such selling
Investor from the sale of Registrable Shares covered by the Registration
Statement, or any registration statement pursuant to which Registrable Shares
are registered pursuant to Section 4 hereof; and provided, further, however,
that the indemnity agreement contained in this Section 9(b) shall not apply to
amounts paid in settlement of any such loss, claim, damage, liability or action
if such settlement is effected without the consent of those selling Investor(s)
against which the request for indemnity is being made (which consent shall not
be unreasonably withheld). Such indemnity and reimbursement of expenses shall
remain in full force and effect regardless of any investigation made by or on
behalf of such indemnified party and, as relevant, shall survive the sale of
such Registrable Shares by any selling Investor.

                  (c) Promptly after receipt by an indemnified party under this
Section 9 of notice of the commencement of any action, such indemnified party
will, if a claim in respect thereof is to be made against any indemnifying party
under this Section 9, notify the indemnifying party in writing of the
commencement thereof and the indemnifying party shall have the right to
participate in and, to the extent the indemnifying party desires, jointly with
any other indemnifying party
<PAGE>
similarly noticed, to assume at its expense the defense thereof with counsel
mutually satisfactory to the indemnifying parties with the consent of the
indemnified party which consent will not be unreasonably withheld, conditioned
or delayed. In the event that the indemnifying party assumes any such defense,
the indemnified party may participate in such defense with its own counsel and
at its own expense; provided, however, that the counsel for the indemnifying
party shall act as lead counsel in all matters pertaining to such defense or
settlement of such claim and the indemnifying party shall only pay for such
indemnified party's expenses for the period prior to the date of its
participation on such defense. The failure to notify an indemnifying party
promptly of the commencement of any such action, if prejudicial to his ability
to defend such action, shall relieve such indemnifying party of any liability to
the indemnified party under this Section 9, but the omission so to notify the
indemnifying party will not relieve him of any liability which he may have to
any indemnified party otherwise other than under this Section 9.

                  (d) If the indemnification provided for in this Section 9 is
held by a court of competent jurisdiction to be unavailable to an indemnified
party with respect to any loss, claim, damage, liability or expense referred to
therein, then the indemnifying party, in lieu of indemnifying such indemnified
party hereunder, shall contribute to the amount paid or payable by such
indemnified party as a result of such loss, claim, or expense in such proportion
as is appropriate to reflect the relative fault of the indemnifying party on the
one hand and of the indemnified party on the other in connection with the
statements or omissions that resulted in such loss, claim or expense as well as
any other relevant equitable considerations. The relative fault of the
indemnifying party and of the indemnified party shall be determined by reference
to, among other things, whether the untrue or alleged untrue statement of a
material fact or the omission to state a material fact relates to information
supplied by the indemnifying party or by the indemnified party and the parties'
relative intent, knowledge, access to information, and opportunity to correct or
prevent such statement or omission. If, however, the allocation provided in the
first sentence of this paragraph is not permitted by applicable law, then each
indemnifying party shall contribute to the amount paid or payable by such
indemnified party in such proportion as is appropriate to reflect not only such
relative faults but also the relative benefits of the indemnifying party and the
indemnified party as well as any other relevant equitable considerations. The
parties hereto agree that it would not be just and equitable if contributions
pursuant to this Section 9(d) were to be determined by pro rata allocation or by
any other method of allocation which does not take account of the equitable
considerations referred to in the preceding sentences of this Section 9(d). The
amount paid or payable in respect of any claim shall be deemed to include any
legal or other expenses reasonably incurred by such indemnified party in
connection with investigating or defending such loss, claim, damage or liability
(including legal expenses reasonably incurred). 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. Notwithstanding anything in this Section 9(d) to
the contrary, no indemnifying party shall be required pursuant to this Section
9(d) to contribute any amount in excess of the net proceeds received by such
indemnifying party from the sale of Registrable Shares in the offering to which
the loss, claims, damage or liability of the indemnified parties relate, less
the amount of any indemnification payment made by such indemnifying party
pursuant to Section 9(b).

                  (e) The obligations of the Company and the selling Investors
under this Section 9 shall survive the completion of any offering of Registrable
Shares in a Registration Statement, or any registration statement pursuant to
which Registrable Shares are registered pursuant to Section 4 hereof, and
otherwise.

                  (f) Notwithstanding anything to the contrary herein, the
indemnifying party shall not be entitled to settle any claim, suit or proceeding
unless in connection with such settlement
<PAGE>
the indemnified party receives an unconditional release with respect to the
subject matter of such claim, suit or proceeding and such settlement does not
contain any admission of fault by the indemnified party.

         10. Reports under the Exchange Act. With a view to making available to
the Investors the benefits of Rule 144 and any other rule or regulation of the
SEC that may at any time permit the Investors to sell the Purchased Shares to
the public without registration, the Company agrees to use commercially
reasonable efforts: (i) to make and keep public information available, as those
terms are understood and defined in the General Instructions to Form S-3, or any
successor or substitute form, and in Rule 144; (ii) to file with the SEC in a
timely manner all reports and other documents required to be filed by an issuer
of securities registered under the Securities Act or the Exchange Act; (iii) as
long as any Investor owns any Purchased Shares, to furnish in writing upon such
Investor's request a written statement by the Company that it has complied with
the reporting requirements of Rule 144 and of the Securities Act and the
Exchange Act, and to furnish to such Investor a copy of the most recent annual
or quarterly report of the Company, and such other reports and documents so
filed by the Company as may be reasonably requested in availing such Investor of
any rule or regulation of the SEC permitting the selling of any such Purchased
Shares without registration; and (iv) undertake any additional actions
reasonably necessary to maintain the availability of the Registration Statement
or the use of Rule 144.

         11. Deferral and Lock-up. Notwithstanding anything in this Agreement to
the contrary, if the Company shall furnish to the selling Investors a
certificate signed by the President or Chief Executive Officer of the Company
stating that the Board of Directors of the Company has made the good faith
determination (i) that continued use by the selling Investors of the
Registration Statement, or any registration statement pursuant to which
Registrable Shares are registered pursuant to Section 4 hereof, for purposes of
effecting offers or sales of Registrable Shares pursuant thereto would require,
under the Securities Act, premature disclosure in the Registration Statement, or
any registration statement pursuant to which Registrable Shares are registered
pursuant to Section 4 hereof (or the prospectus relating thereto) of material,
nonpublic information concerning the Company, its business or prospects or any
proposed material transaction involving the Company, (ii) that such premature
disclosure would be materially adverse to the Company, its business or prospects
or any such proposed material transaction or would make the successful
consummation by the Company of any such material transaction significantly less
likely and (iii) that it is therefore essential to suspend the use by the
Investors of such Registration Statement, or any registration statement pursuant
to which Registrable Shares are registered pursuant to Section 4 hereof (and the
prospectus relating thereto) for purposes of effecting offers or sales of
Registrable Shares pursuant thereto, then the right of the selling Investors to
use the Registration Statement, or any registration statement pursuant to which
Registrable Shares are registered pursuant to Section 4 hereof (and the
prospectus relating thereto) for purposes of effecting offers or sales of
Registrable Shares pursuant thereto shall be suspended for not more than two
30-day periods in a twelve month period (the "SUSPENSION PERIOD(S)") after
delivery by the Company of the certificate referred to above in this Section 11.
In no event, however, will any suspension be any longer than is reasonably
necessary to avoid the adverse effect. During the Suspension Period, none of the
Investors shall offer or sell any Registrable Shares publicly pursuant to or in
reliance upon the Registration Statement, or any registration statement pursuant
to which Registrable Shares are registered pursuant to Section 4 hereof (or the
prospectus relating thereto).

         12. Transfer of Registration Rights. None of the rights of any Investor
under this Agreement shall be transferred or assigned to any person unless (i)
such person is a Qualifying Holder (as defined below), and (ii) such person
agrees to become a party to, and bound by, all of the terms and conditions of,
this Agreement by duly executing and delivering to the Company an Instrument of
Adherence in the form
<PAGE>
attached as Exhibit B hereto. For purposes of this Section 12, the term
"QUALIFYING HOLDER" shall mean, with respect to any Investor, (i) any partner
thereof, (ii) any corporation, partnership controlling, controlled by, or under
common control with, such Investor or any partner thereof, or (iii) any other
direct transferee from such Investor of at least 75,000 shares included as
Registrable Shares on the date hereof that are held or that may be acquired by
such Investor. None of the rights of any Investor under this Agreement shall be
transferred or assigned to any person (including, without limitation, a
Qualifying Holder) that acquires Registrable Shares in the event that and to the
extent that such person is eligible to resell such Registrable Shares pursuant
to Rule 144(k) of the Securities Act or may otherwise resell such Registrable
Shares pursuant to an exemption from the registration provisions of the
Securities Act.

         13. Limitations on Subsequent Registration Rights. From and after the
date of this Agreement, the Company shall not, without the prior written consent
of the Investors holding a majority of the Registrable Shares then outstanding,
enter into any agreement with any holder or prospective holder of any securities
of the Company that would allow such holder or prospective holder to include
such securities in any registration statement filed pursuant to Section 3
hereof, unless under the terms of such agreement, such holder or prospective
holder may include such securities in any such registration only to the extent
that the inclusion of his securities will not reduce the amount of the
Registrable Shares of the Investors that is included.

         14. No Required Sale. Nothing in this Agreement shall be deemed to
create an independent obligation on the part of any Investor to sell any
Registrable Shares pursuant to any effective registration statement.

         15. Nominees for Beneficial Owners. If Registrable Shares are held by a
nominee for the beneficial owner thereof, the beneficial owner thereof may, at
its option, be treated as the holder of such Registrable Shares for purposes of
any request or other action by any Investor pursuant to this Agreement (or any
determination of any number or percentage of shares constituting Registrable
Shares held by any Investor contemplated by this Agreement); provided that the
Company shall have received assurances reasonably satisfactory to it of such
beneficial ownership.

         16. Entire Agreement. This Agreement along with the schedules and
exhibits attached hereto and incorporated herewith constitute and contain the
entire agreement and understanding of the parties with respect to the subject
matter hereof, and supersedes any and all prior negotiations, correspondence,
agreements or understandings with respect to the subject matter hereof and
supercedes all prior agreements, negotiations, understandings, representations
and statements respecting the subject matter hereof, whether oral or written.

         17.      Miscellaneous.

                  (a) Amendment. No amendment, modification, alteration, waiver
or change in any of the terms of this Agreement shall be valid or binding upon
the parties hereto unless made in writing and duly executed by the Company and
(a) prior to Closing, not less than five (5) Initial Investors who represent at
least fifty percent (50%) of the Purchased Shares or (b) following Closing, a
majority of the Investors; provided, however, that in each case, no such
amendment shall increase the obligations of any Investor without such Investor's
written consent.

                  (b) Governing Law. This Agreement shall be governed by and
construed and enforced in accordance with the internal laws of the State of
California and without regard to any conflicts of laws concepts that would apply
the laws of another jurisdiction.
<PAGE>
                  (c) Assignment. The rights and obligations of the parties
hereto shall inure to the benefit of, and shall be binding upon the authorized
successors and permitted assigns of each party; provided that the terms and
conditions of Section 12 hereof are satisfied. This Agreement shall also be
binding upon and inure to the benefit of any transferee of any of the Purchased
Shares; provided the terms and conditions of Section 12 hereof are satisfied.
Notwithstanding anything in this Agreement to the contrary, if at any time any
Investor shall cease to own any Registrable Shares, all of such Investor's
rights under this Agreement shall immediately terminate; provided, however, that
if such Investor ceases to own Registrable Shares because such shares were sold
pursuant to an effective registration statement filed pursuant to Section 3 or 4
hereof, then such Investor shall continue to be subject to Section 9 hereof, as
provided in Section 9(e) hereof. In the event of any assignment by an Investor
in accordance with the terms of this Agreement, the assignee shall specifically
assume and be bound by the provisions of the Agreement by executing the
Instrument of Adherence attached hereto as Exhibit B.

                  (d) Specific Performance. Each of the parties hereto
acknowledges and agrees that damages will not be an adequate remedy for any
material breach or violation of this Agreement if such material breach or
violation would cause immediate and irreparable harm (an "IRREPARABLE BREACH").
Accordingly, in the event of a threatened or ongoing Irreparable Breach, each
party hereto shall be entitled to seek, in any state or federal court in the
State of California, equitable relief of a kind appropriate in light of the
nature of the ongoing or threatened Irreparable Breach, which relief may
include, without limitation, specific performance or injunctive relief;
provided, however, that if the party bringing such action is unsuccessful in
obtaining the relief sought, the moving party shall pay the non-moving party's
costs, including actual attorney's fees, incurred in connection with defending
such action. Such remedies shall not be the parties' exclusive remedies, but
shall be in addition to all other remedies provided in this Agreement.

                  (e) Notice. Any notices, reports or other correspondence
(hereinafter collectively referred to as "CORRESPONDENCE") required or permitted
to be given hereunder shall be sent by courier (overnight or same day) or
facsimile or delivered by hand to the party to whom such correspondence is
required or permitted to be given hereunder. The date of giving any notice shall
be the date of its actual receipt.

                           (i) All correspondence to the Company shall be
addressed as follows:

                                    La Jolla Pharmaceutical Company
                                    6455 Nancy Ridge Drive
                                    San Diego, CA 92121
                                    Attention:  Chief Executive Officer
                                    Facsimile:  (858) 626-2851

                                    with a copy to:

                                    Gibson, Dunn & Crutcher LLP
                                    4 Park Plaza, Suite 1700
                                    Irvine, California 92614
                                    Attention:  Leonard J. McGill
                                    Facsimile:  (949) 451-4220

                        (ii) All correspondence to any Investor shall be sent to
such Investor at the address set forth in Exhibit A, with a copy to Designated
Counsel at:
<PAGE>
                                    Kelley Drye & Warren LLP
                                    101 Park Avenue
                                    New York, New York 10178
                                    Attention:  Salvatore J. Vitiello, Esq.
                                    Facsimile:  (212) 808-7897

                        (iii)       Any entity may change the address to which
correspondence to it is to be addressed by notification as provided for herein.

                  (f) Waiver. No waiver of any term, provision or condition of
this Agreement, whether by conduct or otherwise, in any one or more instances,
shall be deemed to be, or be construed as, a further or continuing waiver of any
such term, provision or condition or as a waiver of any other term, provision or
condition of this Agreement.

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

         (The remainder of this page has been intentionally left blank;
                            signature page follows)
<PAGE>
         IN WITNESS WHEREOF, the parties hereto have executed this Registration
Rights Agreement as of the date and year first above written.

                                             LA JOLLA PHARMACEUTICAL COMPANY

                                             By:
                                                      Steven B. Engle
                                                      Chief Executive Officer

         THE INITIAL INVESTOR'S SIGNATURE TO THE INVESTOR QUESTIONNAIRE DATED
EVEN DATE HEREWITH SHALL CONSTITUTE THE INITIAL INVESTOR'S SIGNATURE TO THIS
REGISTRATION RIGHTS AGREEMENT.