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                                                               EXHIBIT 10.11

                                                              EXECUTION COPY

                               PHOTOGEN NEWCO LTD.
                          REGISTRATION RIGHTS AGREEMENT

                  THIS REGISTRATION RIGHTS AGREEMENT (the "AGREEMENT") is
made as of October 20, 1999 by and among PHOTOGEN NEWCO LTD., a Bermuda
exempted limited liability company (the "COMPANY"), PHOTOGEN TECHNOLOGIES,
INC., a Nevada corporation ("PHOTOGEN"), and ELAN INTERNATIONAL SERVICES,
LTD., a Bermuda exempted limited liability company ("EIS").

                                R E C I T A L S:

                  A. Pursuant to a Subscription, Joint Development and
Operating Agreement dated as of the date hereof by and among the Company,
Photogen, ELAN PHARMA INTERNATIONAL LIMITED, an Irish public limited company
and EIS (the "JDOA"), Photogen has acquired certain common shares, par value
$1.00 per share (the "COMMON SHARES"), and EIS has acquired certain
convertible preferred shares, par value $1.00 per share (the "PREFERRED
SHARES") of the Company.

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

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

                               A G R E E M E N T:

                  The parties hereto agree as follows:

                  1.       CERTAIN DEFINITIONS.  As used in this Agreement,
the following terms shall have the following respective meanings:

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

                  "EXCHANGE ACT" shall mean the Securities Exchange Act of
1934, as amended, and the rules and regulations of the Commission thereunder,
all as the same shall be in effect from time to time.

                  "HOLDERS" or "HOLDERS OF REGISTRABLE SECURITIES" shall mean
Photogen, EIS and any Person who shall have acquired Registrable Securities
from either Photogen or EIS as

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permitted herein, either individually or jointly, as the case may be, in a
transaction pursuant to which registration rights are transferred pursuant to
Section 10 hereof.

                  "PERSON" shall mean an individual, a partnership, a
company, an association, a joint stock company, a trust, a joint venture, an
unincorporated organization and a governmental or quasi-governmental entity,
or any department, agency or political subdivision thereof.

                  "REGISTRABLE SECURITIES" means (i) any Common Shares
subscribed for pursuant to the JDOA; (ii) any Common Shares issuable upon
conversion the Preferred Shares; and (iii) any Common Shares issued or
issuable in respect of the securities referred to in clause (i) and (ii)
above upon any stock split, stock dividend, recapitalization or similar
event; excluding in all cases, however, any Registrable Securities that may
be sold under Rule 144 promulgated under the Securities Act, without being
subject to the volume limitations under Rule 144, and Registrable Securities
sold by a Person in a transaction (including a transaction pursuant to a
registration statement under this Agreement and a transaction pursuant to
Rule 144 promulgated under the Securities Act) in which registration rights
are not transferred pursuant to Section 10 hereof.

                  The terms "REGISTER," "REGISTERED" and "REGISTRATION" refer
to a registration effected by preparing and filing a registration statement
in compliance with the Securities Act.

                  "REGISTRATION EXPENSES" shall mean all expenses, other than
Selling Expenses, incurred by the Company in complying with Sections 2 or 3
hereof, including without limitation, all registration, qualification and
filing fees, exchange listing fees, printing expenses, escrow fees, fees and
disbursements of counsel for the Company, blue sky fees and expenses, the
expense of any special audits incident to or required by any such
registration.

                  "SECURITIES ACT" shall mean the Securities Act of 1933, as
amended.

                  "SELLING EXPENSES" shall mean all underwriting discounts,
selling commissions and stock transfer taxes applicable to the securities
registered by the Holders and the costs and fees of any accountants,
attorneys or other experts retained by the Holders or Holder.

                  2.       DEMAND REGISTRATIONS.

                  (a) REQUESTS FOR REGISTRATION From and after the occurrence
of the initial public offering of the Company's Common Shares under the
Securities Act, any Holder or Holders who collectively hold Registrable
Securities representing at least 5% of the Registrable Securities then
outstanding shall have the right at any time from time to time (subject to
the limitations below), to request registration under the Securities Act of
all or part of their Registrable Securities on Form S-3 (or any successor
form to Form S-3 or any similar short-form registration statement (each, a
"Demand Registration"); provided, that the Company qualifies under the
Securities Act for registration on Form S-3. The request for the Demand
Registration shall specify the

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approximate number of Registrable Securities requested to be registered,
which must have a minimum expected aggregate offering price to the public of
at least $2,000,000. Within 10 days after receipt of any such request, the
Company will give written notice of such requested registration to all other
Holders of Registrable Securities. The Company shall include such other
Holders' Registrable Securities in such offering if they have responded
affirmatively within 10 days after the receipt of the Company's notice. EIS
shall be permitted to at least one Demand Registration; provided, however,
that the Holders in aggregate will be entitled to request only one Demand
Registration hereunder within any 12-month period. A registration will not
count as a permitted Demand Registration until it has become effective
(unless such Demand Registration has not become effective due solely to the
fault of the Holders requesting such registration, including a request by
such Holders that such registration be withdrawn).

                  (b) PRIORITY ON DEMAND REGISTRATIONS. If a Demand
Registration is an underwritten offering and the managing underwriters advise
the Company in writing that in their opinion the number of Registrable
Securities and, if permitted hereunder, other securities requested to be
included in such offering, exceeds the number of Registrable Securities and
other securities, if any, which can be sold in such offering without
adversely affecting the marketability of the offering, the Company will
include in such registration:

                           (i) first, the Registrable Securities requested to be
         included in such registration by the Holders (or, if necessary, such
         Registrable Securities PRO RATA among the Holders thereof based upon
         the number of Registrable Securities owned by each such Holder)
         together with any securities held by third parties holding a similar,
         previously granted right to be included in such registration; and

                           (ii) thereafter, other securities requested to be
         included in such registration.

                  (c) RESTRICTIONS ON DEMAND REGISTRATION. The Company may
postpone for up to six months in any 12-month period, the filing or the
effectiveness of a registration statement for a Demand Registration if the
Company determines in good faith that such Demand Registration would
reasonably be expected to have a material adverse effect on any proposal or
plan by the Company to engage in any financing, acquisition or disposition of
assets (other than in the ordinary course of business) or any merger,
consolidation, tender offer or similar transaction or would require
disclosure of any information that the board of directors of the Company
determines in good faith the disclosure of which would be detrimental to the
Company; provided, however, that in such event, the Holders initially
requesting such Demand Registration will be entitled to withdraw such request
and, if such request is withdrawn, such Demand Registration will not count as
a permitted Demand Registration hereunder and the Company will pay any
Registration Expenses in connection with such registration.

                  (d) SELECTION OF UNDERWRITERS. The Holders will have the
right to select the investment banker(s) and manager(s) to administer an
offering pursuant to the Demand Registration, subject to the Company's prior
written approval, which will not be unreasonably withheld or delayed.

                  (e) OTHER REGISTRATION RIGHTS. Except as provided in this
Agreement, so long as

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any Holder owns any Registrable Securities, the Company will not grant to any
Persons the right to request the Company to register any equity securities of
the Company, or any securities convertible or exchangeable into or
exercisable for such securities, which conflicts with the rights granted to
the Holders hereunder, without the prior written consent of the Holders of at
least 50% of the Registrable Securities; provided, however, that the Company
may grant rights to other Persons demand and piggyback registrations so long
as the Holders of Registrable Securities are entitled to participate in any
such registrations with such Persons PRO RATA on the basis of the number of
shares owned by each such Holder.

                  3.       PIGGYBACK REGISTRATIONS.

                  (a) RIGHT TO PIGGYBACK. At any time the Company shall
propose to register Common Shares under the Securities Act (other than in a
registration statement on Form S-3 relating to sales of securities to
participants in a Company dividend reinvestment plan, or Form S-4 or S-8 or
any successor form or in connection with an acquisition or exchange offer or
an offering of securities solely to the existing shareholders or employees of
the Company) (each, a "Piggyback Registration"), the Company will give prompt
written notice to all Holders of Registrable Securities of its intention to
effect such a registration and, subject to Section 3(b) and the other terms
of this Agreement, will include in such registration all Registrable
Securities which are permitted under applicable securities laws to be
included in the form of registration statement selected by the Company and
with respect to which the Company has received written requests for inclusion
therein within 10 days after the receipt of the Company's notice.

                  (b) PRIORITY ON PIGGYBACK REGISTRATIONS. If a Piggyback
Registration is to be an underwritten offering, and the managing underwriters
advise the Company in writing that in their opinion the number of securities
requested to be included in such registration exceeds the number which can be
sold in such offering without adversely affecting the marketability of the
offering, the Company will include in such registration:

                           (i) first, the securities the Company proposes
         to sell;

                           (ii) any securities having the right to be
         included in such registration prior to the securities of the
         Holders;

                           (iii) the Registrable Securities requested to be
         included in such registration by the Holders and any securities
         requested to be included in such registration by any other Person
         having equal priority to registration with the Holders, PRO RATA among
         the Holders of such Registrable Securities and such other Persons, on
         the basis of the number of shares owned by each of such Holders; and

                           (iv) thereafter, other securities requested to be
         included in such registration.

                  The Holders of any Registrable Securities included in such
an underwritten offering must execute an underwriting agreement, in customary
form and in form and substance satisfactory to the managing underwriters.

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

                  (d) SELECTION OF UNDERWRITERS. The Company will have the
right to select the investment banker(s) and manager(s) to administer an
offering pursuant to a Piggyback Registration.

                  4.       EXPENSES OF REGISTRATION. Except as otherwise
provided herein or as may otherwise be prohibited by applicable law, all
Registration Expenses incurred in connection with all registrations pursuant
to Section 3 shall be borne by the Company; provided that, and
notwithstanding anything herein contained to the contrary, the Company shall
not have any obligation pursuant to the provisions hereof unless and until
the Company is able to satisfy (after taking into account such obligations)
the requirements of Section 39A (2A) of the Bermuda Companies Act of 1981 (or
any successor legislation). All Registration Expenses incurred in connection
with all registrations pursuant to Section 3 and all Selling Expenses
relating to securities registered on behalf of the Holders of Registrable
Securities shall be borne by such Holders.

                  5.       HOLDBACK AGREEMENTS.

                  (a) The Company agrees (i) not to effect any public sale or
distribution of its equity securities, or any securities convertible into or
exchangeable or exercisable for such securities, during the seven days prior
to and during the 180-day period beginning on the effective date of any
underwritten Demand Registration or any underwritten Piggyback Registration
(except as part of such underwritten registration or pursuant to registration
statements on Form S-4 or Form S-8 or any successor form), unless the
underwriters managing the registered public offering otherwise agree, and
(ii) to use reasonable efforts to cause each holder of at least 5% (on a
fully-diluted basis) of its outstanding Common Shares, or any securities
convertible into or exchangeable or exercisable for Common Shares, purchased
from the Company at any time after the date of this Agreement (other than in
a registered public offering) to agree not to effect any public sale or
distribution (including sales pursuant to Rule 144) of any such securities
during such periods (except as part of such underwritten registration, if
otherwise permitted), unless the underwriters managing the registered public
offering otherwise agree.

                  (b) Each Holder agrees, if requested by the managing
underwriter or underwriters in an underwritten offering of securities of the
Company, not to effect any offer, sale, distribution

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or transfer, including a sale pursuant to Rule 144 (or any similar provision
then effect) under the Securities Act (except as part of such underwritten
registration), during the seven-day period prior to, and during the 180-day
period (or such shorter period as may be agreed to in writing by the Company
and the Holders of at least 50% of the Registrable Securities) following the
effective date of such Registration Statement to the extent timely notified
in writing by the managing underwriter or underwriters.

                  6.       REGISTRATION PROCEDURES. Whenever the Holders of
Registrable Securities have requested that any Registrable Securities be
registered pursuant to this Agreement, the Company will use all reasonable
efforts to effect the registration and the sale of such Registrable
Securities in accordance with the intended method of distribution thereof,
and pursuant thereto the Company will as expeditiously as possible:

                  (a) subject to Section 2(c) hereof, prepare and file with
the Commission a registration statement on any form for which the Company
qualifies with respect to such Registrable Securities and use all reasonable
efforts to cause such registration statement to become effective (provided
that before filing a registration statement or prospectus or any amendments
or supplements thereto, the Company will (i) furnish to the counsel selected
by the Holders copies of all such documents proposed to be filed, which
documents will be subject to the review of such counsel, and (ii) notify each
Holder of Registrable Securities covered by such registration of any stop
order issued or threatened by the Commission);

                  (b) subject to Section 2(c) hereof, prepare and file with
the Commission such amendments and supplements to such registration statement
and the prospectus used in connection therewith as may be necessary to keep
such registration statement effective for a period equal to the shorter of
(i) six months and (ii) the time by which all securities covered by such
registration statement have been sold, and comply with the provisions of the
Securities Act with respect to the disposition of all securities covered by
such registration statement during such period in accordance with the
intended methods of disposition by the sellers thereof set forth in such
registration statement;

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

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

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                  (e) notify each seller of such Registrable Securities, at
any time when a prospectus relating thereto is required to be delivered under
the Securities Act, of the happening of any event as a result of which the
prospectus included in such registration statement contains an untrue
statement of a material fact or omits any fact necessary to make the
statements therein not misleading, and, at the request of any such seller,
the Company will prepare a supplement or amendment to such prospectus so
that, as thereafter delivered to the purchasers of such Registrable
Securities, such prospectus will not contain an untrue statement of a
material fact or omit to state any fact necessary to make the statements
therein not misleading; provided, however, that the Company shall not be
required to amend the registration statement or supplement the Prospectus for
a period of up to six months if the board of directors determines in good
faith that to do so would reasonably be expected to have a material adverse
effect on any proposal or plan by the Company to engage in any financing,
acquisition or disposition of assets (other than in the ordinary course of
business) or any merger, consolidation, tender offer or similar transaction
or would require the disclosure of any information that the board of
directors determines in good faith the disclosure of which would be
detrimental to the Company, it being understood that the period for which the
Company is obligated to keep the Registration Statement effective shall be
extended for a number of days equal to the number of days the Company delays
amendments or supplements pursuant to this provision. Upon receipt of any
notice pursuant to this Section 6(e), the Holders shall suspend all offers
and sales of securities of the Company and all use of any prospectus until
advised by the Company that offers and sales may resume, and shall keep
confidential the fact and content of any notice given by the Company pursuant
to this Section 6(e);

                  (f) cause all such Registrable Securities to be listed on
each securities exchange on which similar securities issued by the Company
are then listed;

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

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

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

                  (j) otherwise use its reasonable efforts to comply with all
applicable rules and regulations of the Commission, and make available to its
security holders, as soon as reasonably practicable, an earnings statement
covering the period of at least 12 months beginning with the

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first day of the Company's first full calendar quarter after the effective
date of the registration statement, which earnings statement shall satisfy
the provisions of Section 11(a) of the Securities Act and Rule 158 thereunder;

                  (k) in the event of the issuance of any stop order
suspending the effectiveness of a registration statement, or of any order
suspending or preventing the use of any related prospectus or suspending the
qualification of any Common Shares included in such registration statement
for sale in any jurisdiction, use all reasonable efforts promptly to obtain
the withdrawal of such order; and

                  (l) if the registration is an underwritten offering, use
all reasonable efforts to obtain a so-called "cold comfort" letter from the
Company's independent public accountants in customary form and covering such
matters of the type customarily covered by cold comfort letters.

                  7.       OBLIGATIONS OF HOLDERS. Whenever the Holders of
Registrable Securities sell any Registrable Securities pursuant to a Demand
Registration or a Piggyback Registration, such Holders shall be obligated to
comply with the applicable provisions of the Securities Act, including the
prospectus delivery requirements thereunder, and any applicable state
securities or blue sky laws.

                  8.       INDEMNIFICATION. (a) The Company agrees to
indemnify, to the fullest extent permitted by applicable law, each Holder of
Registrable Securities, its officers and directors and each Person who
controls such Holder (within the meaning of the Securities Act) against all
losses, claims, damages, liabilities, expenses or any amounts paid in
settlement of any litigation, investigation or proceeding commenced or
threatened (collectively, "CLAIMS") to which each such indemnified party may
become subject under the Securities Act insofar as such Claim arose out of
(i) any untrue or alleged untrue statement of material fact contained, on the
effective date thereof, in any registration statement, prospectus or
preliminary prospectus or any amendment thereof or supplement thereto or (ii)
any omission or alleged omission to state therein a material fact required to
be stated therein or necessary to make the statements therein not misleading,
except insofar as the same are caused by or contained in any information
furnished in writing to the Company by such Holder expressly for use therein,
by such Holder's failure to deliver a copy of the registration statement or
prospectus or any amendments or supplements thereto after the Company has
furnished such Holder with a sufficient number of copies of the same or by
such Holder's failure to comply with applicable securities laws. In
connection with an underwritten offering, the Company will indemnify the
underwriters, their officers and directors and each Person who controls the
underwriters (within the meaning of the Securities Act) to the same extent as
provided above with respect to the indemnification of the Holders of
Registrable Securities.

                  (b) In connection with any registration statements in which a
Holder of Registrable Securities is participating, each such Holder will furnish
to the Company in writing

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such customary information as the Company reasonably requests for use in
connection with any such registration statement or prospectus (the "SELLER'S
INFORMATION") and, to the fullest extent permitted by applicable law, will
indemnify the Company, its directors and officers and each Person who
controls the Company (within the meaning of the Securities Act) against any
and all Claims to which each such indemnified party may become subject under
the Securities Act insofar as such Claim arose out of (i) any untrue or
alleged untrue statement of material fact contained, on the effective date
thereof, in any registration statement, prospectus or preliminary prospectus
or any amendment thereof or supplement thereto regarding Seller's
Information, (ii) any omission or alleged omission to state therein a
material fact required to be stated therein or necessary to make the
statements therein regarding Seller's Information not misleading or (iii) any
failure to comply with applicable securities laws; provided that with respect
to a Claim arising pursuant to clause (i) or (ii) above, the material
misstatement or omission is contained in such Seller's Information; provided,
further, that the obligation to indemnify will be individual to each Holder
and will be limited to the amount of proceeds received by such Holder from
the sale of Registrable Securities pursuant to such registration statement.

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

                  (d) The indemnifying party shall not be liable to indemnify
an indemnified party for any settlement, or consent to judgment of any such
action effected without the indemnifying party's written consent (but such
consent will not be unreasonably withheld). Furthermore, the indemnifying
party shall not, except with the prior written approval of each indemnified
party, consent to entry of any judgment or enter into any settlement which
does not include as an unconditional term thereof the giving by the claimant
or plaintiff to each indemnified party of a release from all liability in
respect of such claim or litigation without any payment or consideration
provided by each such indemnified party.

                  (e) If the indemnification provided for in this Section 8
is unavailable to an indemnified party under clauses (a) and (b) above in
respect of any losses, claims, damages or liabilities referred to therein,
then each indemnifying party, in lieu of indemnifying such indemnified party,
shall contribute to the amount paid or payable by such indemnified party as a
result of such losses, claims, damages or liabilities in such proportion as
is appropriate to reflect not only the relative benefits received by the
Company, the underwriters, the sellers of

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Registrable Securities and any other sellers participating in the
registration statement from the sale of shares pursuant to the registered
offering of securities for which indemnity is sought but also the relative
fault of the Company, the underwriters, the sellers of Registrable Securities
and any other sellers participating in the registration statement in
connection with the statement or omission which resulted in such losses,
claims, damages or liabilities, as well as any other relevant equitable
considerations. The relative benefits received by the Company, the
underwriters, the sellers of Registrable Securities and any other sellers
participating in the registration statement shall be deemed to be based on
the relative relationship of the total net proceeds from the offering (before
deducting expenses) to the Company, the total underwriting commissions and
fees from the offering (before deducting expenses) to the underwriters and
the total net proceeds from the offering (before deducting expenses) to the
sellers of Registrable Securities and any other sellers participating in the
registration statement. The relative fault of the Company, the underwriters,
the sellers of Registrable Securities and any other sellers participating in
the registration statement shall be determined by reference to, among other
things, whether the untrue or alleged untrue statement of a material fact or
the omission or alleged omission to state a material fact relates to
information supplied by the Company or by the sellers of Registrable
Securities and the parties' relative intent, knowledge, access to information
and opportunity to correct or prevent such statement or omission.

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

                  9.       PARTICIPATION IN UNDERWRITTEN REGISTRATIONS. No
Holder may participate in any registration hereunder which is underwritten
unless such Holder (a) agrees to sell such Holder's securities on the basis
provided in any underwriting arrangements approved by the Holder or Holders
entitled hereunder to approve such arrangements, (b) as expeditiously as
possible notifies the Company of the occurrence of any event as a result of
which any prospectus contains an untrue statement of material fact or omits
to state a material fact required to be stated therein or necessary to make
the statements therein not misleading and (c) completes and executes all
questionnaires, powers of attorney, indemnities, underwriting agreements and
other documents reasonably required under the terms of such underwriting
arrangements.

                  10.      TRANSFER OF REGISTRATION RIGHTS. The rights
granted to any Holder under this Agreement may be assigned to any permitted
transferee of Registrable Securities, in connection with any transfer or
assignment of Registrable Securities by a Holder; provided, however, that:
(a) such transfer is otherwise effected in accordance with applicable
securities laws, (b) if not already a party hereto, the assignee or
transferee agrees in writing prior to such transfer to be bound by the
provisions of this Agreement applicable to the transferor, (c) such
transferee shall own Registrable Securities representing at least 5% of the
Common Shares (as adjusted for any combinations, consolidations, stock
distributions, stock dividends or other recapitalizations with respect to
such shares), and (d) Photogen or EIS, as applicable, shall act as agent and
representative for such Holder for the giving and receiving of notices
hereunder.

                  11.      INFORMATION BY HOLDER. Each Holder shall furnish
to the Company such

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

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

                  13.      TERMINATION OF REGISTRATION RIGHTS. All
registration rights granted under this Agreement shall terminate and be of no
further force and effect, as to any particular Holder, at such time as all
Registrable Securities held by such Holder are eligible to be sold under the
volume limitations of Rule 144 within a three-month period without compliance
with the registration requirements of the Securities Act pursuant to Rule 144
(including Rule 144(k)) promulgated thereunder or have been resold pursuant
to a registration statement hereunder.

                  14.      MISCELLANEOUS.

                  (a) NO INCONSISTENT AGREEMENTS. The Company will not
hereafter enter into any agreement with respect to its securities which is
inconsistent with or violates the rights granted to the Holders of
Registrable Securities in this Agreement without the prior written consent of
a majority in interest of such Registrable Securities.

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

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

                  (d) SUCCESSORS AND ASSIGNS. All covenants and agreements in
this Agreement by or on behalf of any of the parties hereto will bind and
inure to the benefit of the respective

                                       11
<PAGE>

successors and assigns of the parties hereto, and shall inure to the benefit
and be enforceable by each Holder of Registrable Securities from time to
time. In addition, whether or not any express assignment has been made, the
provisions of this Agreement which are for the benefit of Holders of
Registrable Securities are also for the benefit of, and enforceable by, any
permitted transferee of Registrable Securities, in accordance with Section 10
hereof.

                  (e) SEVERABILITY. Whenever possible, each provision of this
Agreement will be interpreted in such manner as to be effective and valid
under applicable law, but if any provision of this Agreement is held to be
prohibited by or invalid under applicable law, such provision will be
ineffective only to the extent of such prohibition or invalidity, without
invalidating the remainder of this Agreement.

                  (f) COUNTERPARTS. This Agreement may be executed
simultaneously in two or more counterparts, any one of which need not contain
the signatures of more than one party, but all such counterparts taken
together will constitute one and the same Agreement.

                  (g) DESCRIPTIVE HEADINGS. The descriptive headings of this
Agreement are inserted for convenience only and do not constitute a part of
this Agreement.

                  (h) GOVERNING LAW. All questions concerning the
construction, validity and interpretation of this Agreement will be governed
by the laws of the State of New York without regard to principles of
conflicts of laws.

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

                           (i) if to the Company, to:

                           Photogen Newco Ltd.
                           c/o Conyers Dill & Pearman
                           Clarendon House
                           Church Street, P.O. Box HM 666
                           Hamilton HM CX, Bermuda
                           Attention:  David J. Doyle
                           Facsimile:  (441) 292-4720

                           with a copy to each of Photogen, EIS and their
                           respective counsel at the addresses indicated below

                           (ii) if to Photogen, to:

                           Photogen Technologies, Inc.

                                       12
<PAGE>

                           7327 Oak Ridge Highway, Suite B
                           Knoxville, Tennessee  37931
                           Attention:  Chief Executive Officer
                           Facsimile:  423-769-4013

                           with a copy to:

                           Grippo  & Elden
                           Suite 3600
                           227 West Monroe Street
                           Chicago, Illinois 60606
                           Attn: Theodore Grippo, Esq.
                           Facsimile: 312-558-1195

                           (iii) if to EIS, to:

                           Elan International Services, Ltd.
                           Flatts, Smiths Parish
                           Bermuda, FL 04
                           Facsimile:  (441) 292-2224
                           Attention:  President

                           with a copy to:

                           Brock Silverstein LLC
                           800 Third Avenue
                           New York, New York 10022
                           Facsimile:  (212) 371-5500
                           Attention:  David Robbins, Esq.

                  (j) ENTIRE AGREEMENT. This Agreement constitutes the full
and entire understanding and agreement between the parties with regard to the
subject matter hereof.

                            [Signature page follows]

                                       13

<PAGE>


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

                                       PHOTOGEN NEWCO LTD.

                                       By:         /s/ John Smolik
                                           -------------------------------
                                           Name: John Smolik
                                           Title: President


                                       PHOTOGEN TECHNOLOGIES, INC.

                                       By:        /s/ John Smolik
                                           -------------------------------
                                           Name:   John Smolik
                                           Title:  President


                                       ELAN INTERNATIONAL SERVICES, LTD.



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