Document:

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EXHIBIT 10.1
                                                                    NEWS RELEASE

GENTA AND MOLECULAR BIOSYSTEMS ANNOUNCE LICENSING DEAL FOR KEY ANTISENSE
TECHNOLOGY

LEXINGTON, Mass., June 5 /PRNewswire/ -- Genta Incorporated (Nasdaq:
GNTA - NEWS) and Molecular Biosystems Inc., (MBI) San Diego, CA (OTC Bulletin
Board: MBIO - NEWS) announced the licensing of a broad portfolio of patents and
technology that relate to antisense for therapeutic and diagnostic applications.
The agreement includes grants of both exclusive and non-exclusive rights to
Genta from MBI on a royalty-free basis in return for cash and shares of Genta
common stock.

The patent and technology portfolio relates to work conducted by MBI scientists,
which spans almost two decades of research. Fundamental claims in the key
foreign and domestic patents are very broad and relate to methods, compositions,
and processes for in vitro and in vivo inhibition of protein synthesis by
antisense oligonucleotides, some of which are covered in U.S. patent number
5,919,619 (issued 7/6/99) and 5,023,243 (issued 7/11/91), respectively. Patent
5,919,619 covers the use of oligonucleotides in the down-regulation of any gene
in cells in vitro. Both patents have very early priority in the field of
antisense technology and derive from a parent application filed in 1981.

"As a world leader in applications of antisense in oncology, Genta already has
an extremely strong intellectual property position," commented Dr. Raymond P.
Warrell, Jr., Genta's President and CEO. "The issued claims in this patent
portfolio are exceptionally broad and enabling for most clinical uses, as well
as many diagnostic applications. Having obtained an exclusive right to grant
unrestricted sublicenses to these patents, we are interested in rapidly
expanding antisense technology to other companies that are working in this
area." Mr. Bobba Venkatadri, President and Chief Executive Officer of Molecular
Biosystems, Inc., stated: "MBI has formally committed to a different research
and development path. Accordingly, we sought to monetize the assets covered by
this agreement on behalf of our shareholders. We are greatly pleased that this
technology can be developed by our partner in this agreement."

Genta Incorporated is a biopharmaceutical company with a product portfolio
focused on anticancer therapy, including its Anticode-TM- (antisense) platform
technology, as well as other important anticancer drugs. The Company's lead
compound, Genasense-TM-, is designed to reduce levels of Bcl-2, a protein that
contributes to resistance of cancer cells to current forms of cancer treatment.
Treatment with Genasense may markedly improve the effectiveness of standard
anticancer therapies. Genasense, which has received "Fast Track" designation
from the Food and Drug Administration for treatment of advanced melanoma in
combination with dacarbazine, has recently entered Phase 3 trials in patients
with advanced melanoma. Genta aims to become a direct marketer of its
pharmaceutical products in the United States. For more detailed information
about Genta, please visit their website at http://www.genta.com.

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MBI is a world leader in developing contrast agents for diagnostic imaging. Its
innovative product, OPTISON, enables improved diagnosis of heart disease through
clearer ultrasound images.

The statements contained in this press release that are not
historical are forward-looking statements within the meaning of Section 27A of
the Securities Act of 1933, as amended, and Section 21E of the Securities
Exchange Act of 1934, as amended, including statements regarding the
expectations, beliefs, intentions or strategies regarding the future. Without
limiting the foregoing, the words "anticipates," "believes," "expects,"
"intends," "may" and "plans" and similar expressions are intended to identify
forward-looking statements. The companies intend that all forward-looking
statements be subject to the safe harbor provisions of the Private Securities
Litigation Reform Act of 1995. These forward-looking statements reflect the
companies' views as of the date they are made with respect to future events, but
are subject to many risks and uncertainties, which could cause the actual
results to differ materially from any future results expressed or implied by
such forward-looking statements. Examples of such risks and uncertainties also
include, but are not limited to, the inability to grant or enforce patent rights
or to obtain rights, patents, and technologies under the agreement. The
companies do not undertake to update forward-looking statements. Although both
companies believe that the forward-looking statements contained herein are
reasonable, neither company provides assurance that these expectations are
correct. All forward-looking statements are expressly qualified in their
entirety by this cautionary statement and other factors detailed in the
companies' reports filed with the Securities and Exchange Commission.

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EXHIBIT 10.2

                                LICENSE AGREEMENT

                                 by and between

                                   Genta, Inc.

                                       and

                           Molecular Biosystems, Inc.

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                                LICENSE AGREEMENT

         This License Agreement (the "Agreement") is made effective this _______
day of May, 2000 (the "Effective Date") by and between Genta, Inc. a corporation
having a place of business at 66 Hayden Avenue, Lexington, MA 02421 ("Genta"),
and Molecular Biosystems, Inc., a corporation having a place of business at
10030 Barnes Canyon Road, San Diego, CA 92121-2789 ("MBI").

                                    RECITALS

         WHEREAS MBI has developed, owns, and/or controls certain technology
relating to the production or use for therapeutic purposes of stabilized
synthetic oligonucleotides ("Antisense") and certain intellectual property
relating thereto;

         WHEREAS, pursuant to that certain license agreement between MBI and
Isis Pharmaceuticals, Inc. ("Isis") dated September 14, 1992 ("Isis Agreement")
(attached hereto as Exhibit A), MBI has granted Isis a non-exclusive license,
under certain United States and foreign patents and patent applications that are
owned by MBI relating to Antisense ("Non-Exclusive Licensed Patents," as further
defined herein);

         WHEREAS Genta desires (a) a worldwide license, co-exclusive with Isis,
under the Non-Exclusive Licensed Patents, (b) an exclusive, worldwide license
under certain other patents and patent applications owned or controlled by MBI
relating to Antisense ("Exclusive Licensed Patents," as further defined herein),
and (c) a non-exclusive, worldwide license under any know-how relating to
Antisense ("MBI Technology," as further defined herein); and

         WHEREAS MBI is willing and able to grant Genta the rights and licenses
it desires under the terms and conditions specified herein.

         THEREFORE, the parties agree as follows:

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1.       DEFINITIONS

         1.1 "Affiliate" means any corporation or other business entity which
controls, is controlled by or is under common control with a party. For purposes
of this Section 1.1, "control" shall mean direct or indirect ownership of (i) at
least fifty percent (50%) of the outstanding stock or other voting rights
entitled to elect directors, or (ii) in any country where the local law shall
not permit foreign equity participation of at least 50%, then the maximum
percentage of such outstanding stock or voting rights permitted by local law.

         1.2 "Antisense" means the production and/or use for therapeutic
purposes of stabilized synthetic oligonucleotides.

         1.3 "Improvement(s)" means and includes any modification of a Licensed
Product or Licensed Method that is invented, conceived and/or reduced to
practice by MBI during the Term of this Agreement, provided such modification if
unlicensed would infringe one or more claims of the Licensed Patents.

         1.4 "Licensed Methods" means and collectively includes any and all
methods the practice of which would constitute, but for the license granted to
Genta in this Agreement, an infringement of the Licensed Patents.

         1.5 "Licensed Patents" means and collectively includes the
Non-Exclusive Licensed Patents and the Exclusive Licensed Patents.

                  1.5.1 "Non-Exclusive Licensed Patents" means and includes, to
         the extent the following are subject to the terms and conditions of the
         Isis Agreement:

                           (a) those patents and patent applications set forth
                  on Schedule A hereto, together with any patents that may issue
                  thereon, and any divisional, continuation or
                  continuation-in-part applications based thereon and any
                  patents that may issue thereon, any reissues or extensions
                  based upon such patents, and any equivalent patents and patent
                  applications of such patents; and

                           (b) any other patents or patent applications owned,
                  controlled, licensed by, being developed or subsequently
                  developed or acquired (by license or otherwise) by MBI which
                  relate to Antisense, all of which shall be set forth on the
                  attached Schedule A, which may be updated from time to time as
                  needed.

                  1.5.2 "Exclusive Licensed Patents" means and includes any and
         all United States and foreign patents and patent applications relating
         to oligonucleotide antisense technology that are owned or

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         controlled by MBI, jointly or solely, on the Effective Date that are
         not subject to or for any reason cease to be part of the Isis
         Agreement, as set forth on Schedule B, which may be updated from time
         to time as needed.

         1.6 "Licensed Products" means and collectively includes any and all
products the manufacture, use, sale, offer for sale or importation of which
would constitute, but for license granted to Genta in this Agreement, an
infringement of the Licensed Patents.

         1.7 "MBI Technology" means non-patented proprietary technology and
information relating to oligonucleotide antisense technology (including, without
limitation, research data, designs, formulas, process information, clinical data
and other information pertaining or relating to any technology or invention
claimed in the Licensed Patents) that is necessary or useful for the practice of
Licensed Patents.

                                    2. GRANT

         2.1 UNDER THE NON-EXCLUSIVE LICENSED PATENTS. MBI hereby grants Genta
an irrevocable, fully paid up, royalty-free, worldwide license, with the right
to sublicense, under the Non-Exclusive Licensed Patents to (a) make, have made,
use, offer for sale, sell, import and otherwise dispose of Licensed Products,
(b) offer for sale, sell, and practice Licensed Methods, and (c) make, have
made, use, offer for sale, sell, import, practice and otherwise dispose of
products and methods. Genta's license under the Non-Exclusive Licensed Patents
shall be co-exclusive with Isis. MBI agrees, and shall require any successor in
interest to or assignee of the Non-Exclusive Licensed Patents to agree, not to
grant any further license(s) or transfer(s) of rights in or to any of the
Non-Exclusive Licensed Patents or the subject matter thereof during the Term of
this Agreement. If, during the Term of this Agreement, Isis's license under the
Isis Agreement with respect to the Non-Exclusive Licensed Patents, or any
portion(s) thereof, is terminated or expires or otherwise ceases, MBI shall
promptly notify Genta and MBI agrees that, upon such termination, expiration or
cessation, Genta's rights under this Agreement to the Non-Exclusive Licensed
Patents, or relevant portion(s) thereof, shall automatically become exclusive,
without further cost to Genta, and the Non-Exclusive Licensed Patents shall
thereafter be deemed Exclusive Licensed Patents for purposes of this Agreement.

         2.2 UNDER THE EXCLUSIVE LICENSED PATENTS. MBI hereby grants Genta an
irrevocable, exclusive, fully paid up, royalty-free, worldwide license, with the
right to sublicense, under the Non-Exclusive Licensed Patents to

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(a) make, have made, use, offer for sale, sell, import and otherwise dispose of
Licensed Products, (b) offer for sale, sell, and practice Licensed Methods, and
(c) make, have made, use, offer for sale, sell, import, practice and otherwise
dispose of products and methods.

         2.3 UNDER THE MBI TECHNOLOGY. MBI hereby grants Genta a non-exclusive,
fully paid up, royalty-free, worldwide license, with the right to sublicense, to
use the MBI Technology to make, have made, use, offer for sale, sell, import,
practice and otherwise dispose of Licensed Products, products, Licensed Methods,
and methods.

                                 3. IMPROVEMENTS

         3.1 MBI agrees to provide written notice to Genta of each Improvement
within thirty (30) days of the date of conception of such Improvement. Such
notice shall contain a description of the Improvement(s) in detail sufficient to
allow evaluation by Genta.

         3.2 Genta shall have an exclusive option to obtain a license under
Improvements in accordance with the terms and conditions of this Agreement.
Genta may exercise its option at any time within sixty (60) days of receipt by
Genta of notice of any such Improvement by providing written notice to MBI that
Genta is exercising its option. Upon Genta's exercise of such option, such
Improvements shall automatically be added to this Agreement, and all patents and
patent applications covering such Improvements, worldwide, shall be added to
Licensed Patents hereunder, and this Agreement and/or Schedule A or Schedule B
shall be modified accordingly.

         3.3 If Genta fails to exercise its option as provided in this Section 3
with respect to any Improvement, MBI shall have no further obligation to Genta
with respect to that Improvement, and shall be free to dispose thereof by
license or otherwise, but the rights and obligations of the parties with respect
to any subsequent Improvements shall not be affected.

                                4. CONSIDERATION

         4.1 In consideration of the rights and licenses set forth herein, Genta
agrees to pay MBI, upon the execution of this Agreement by both parties, a
one-time, lump sum payment of: (a) two-hundred and fifty-thousand United States
dollars ($250,000.00) and (b) a number of shares of Genta's Common Stock equal
in value to two-million four-hundred thousand United States dollars
($2,400,000.00), in accordance with the terms and conditions of Exhibit B,
attached hereto. The parties acknowledge and agree that, for the rights granted
herein, Genta shall not be

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required to pay to MBI any further consideration, including without limitation
any royalties, milestone payments, or sublicensing payments.

         4.2 If the Registration Statement (as defined in Exhibit B) for the
shares paid to MBI pursuant to Section 4.1(b) hereof has not been declared
effective by the Securities and Exchange Commission ("SEC") by August 24, 2000,
then MBI and Genta shall make the following exchanges:

                  4.2.1 On August 25, 2000, (a) MBI shall transfer to Genta
either (i) a number of shares of Genta's Common Stock (as defined in Exhibit B)
equal to one-million two-hundred thousand United States dollars ($1,200,000.00)
in value, calculated using the Closing Genta Stock Price (as defined in Exhibit
B) on August 24, 2000 (rounded to the nearest whole share) or (ii) all of the
shares of Genta's Common Stock transferred to MBI pursuant to Section 4.1(b)
hereof if the value of all such shares is less than one-million two-hundred
thousand United States dollars ($1,200,000.00), calculated using the Closing
Genta Stock Price (as defined in Exhibit B) on August 24, 2000; and (b) Genta
shall pay to MBI one-million two-hundred thousand United States dollars
($1,200,000.00); and

                  4.2.2 On September 25, 2000, (a) MBI shall transfer to Genta
all of the shares of Genta's Common Stock paid to MBI pursuant to Section 4.1(b)
hereof, to the extent same have not already been transferred to Genta pursuant
to Section 4.2.1 hereof, and (b) Genta shall pay to MBI one-million two-hundred
thousand United States dollars ($1,200,000.00); PROVIDED, HOWEVER, that, if the
Registration Statement (as defined in Exhibit B) for the shares paid to MBI
pursuant to Section 4.1(b) hereof is declared effective by the SEC after August
24, 2000 but on or before September 24, 2000 then, within one business day of
the date on which such Registration Statement is declared effective
("Declaration Date"),

                  (i) if the value of the Retained Shares (as defined below) is
         more than one-million two-hundred thousand United States dollars
         ($1,200,000.00) calculated using the Closing Genta Stock Price on the
         business day immediately preceding the Declaration Date ("Retained
         Share Closing Price"), MBI shall transfer to Genta the number of shares
         of Genta's Common Stock (rounded to the nearest whole share) equal in
         value to the difference between the value of the Retained Shares and
         one-million two-hundred thousand United States dollars ($1,200,000.00)
         calculated using the Retained Share Closing Price; or

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                  (ii) if the value of the Retained Shares (as defined below),
         if any, is less than one-million two-hundred thousand United States
         dollars ($1,200,000.00) calculated using the Retained Share Closing
         Price (including if the number of Retained Shares is zero), Genta shall
         issue to MBI a number of shares of Genta's Common Stock (rounded to the
         nearest whole share) equal in value to the difference between the value
         of the Retained Shares and one-million two-hundred thousand United
         States dollars ($1,200,000.00) calculated using the Retained Share
         Closing Price; or

                  (iii) if the value of the Retained Shares (as defined below)
         is equal to one-million two-hundred thousand United States dollars
         ($1,200,000.00) calculated using the Retained Share Closing Price, then
         MBI shall keep the Retained Shares and Genta shall have no further
         payment obligations to MBI hereunder.

For purposes of this Section 4.2.2, the "Retained Shares" means the number of
shares of Genta's Common Stock paid to MBI pursuant to Section 4.1(b) hereof
minus the number of shares transferred by MBI to Genta pursuant to Section
4.2.1(a) hereof.

                                  5. DILIGENCE

         5.1 Genta shall, directly and/or through one or more Affiliate(s) or
sublicensee(s), use reasonable efforts to develop, file for regulatory approval
or registration of, market and sell Licensed Products and/or Licensed Methods to
the extent same are covered by the Exclusive Licensed Patents, in the United
States and abroad for those uses and in those countries that Genta, in its sole
good faith judgment, determines to be commercially and scientifically
reasonable.

                                6. PATENT MATTERS

         6.1      PATENT PROSECUTION AND MAINTENANCE.

                  6.1.1 WITH RESPECT TO NON-EXCLUSIVE LICENSED PATENTS. MBI
         shall be solely responsible for the prosecution and maintenance of the
         Non-Exclusive Licensed Patents and expenses relating thereto. MBI shall
         keep Genta advised of the status of such Non-Exclusive Licensed Patents
         and promptly provide Genta with copies of all papers, documents and
         things received from, or filed with, the United States Patent

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         and Trademark Office and/or any analogous foreign authority or any
         attorney or agent handling such matters on behalf of MBI in connection
         with such Non-Exclusive Licensed Patent(s), including without
         limitation providing prompt notice of any notice(s) of allowance or
         equivalent received in connection with any patent application and the
         filing of any patent application. If MBI does not desire to prosecute
         and/or maintain any Non-Exclusive Licensed Patent(s), then, subject to
         the rights and obligations of Isis pursuant to the Isis Agreement,
         Genta shall have the right, but not the obligation, to prosecute and/or
         maintain such Non-Exclusive Licensed Patent(s). If Isis assumes
         responsibility for the prosecution, maintenance, and/or defense of any
         Non-Exclusive Licensed Patent, pursuant to Section 6.2 of the Isis
         Agreement, then MBI shall, and/or shall require Isis to, keep Genta
         advised of the status of such Non-Exclusive Licensed Patents and
         promptly provide Genta with copies of all papers, documents and things
         received from, or filed with, the United States Patent and Trademark
         Office and/or any analogous foreign authority or any attorney or agent
         handling such matters on behalf of Isis in connection with such
         Non-Exclusive Licensed Patent(s), including without limitation
         providing prompt notice of any notice(s) of allowance or equivalent
         received in connection with any patent application, and the filing of
         any patent application. If Isis does not desire to prosecute and/or
         maintain any Non-Exclusive Licensed Patent(s), then MBI shall, or shall
         require Isis to, provide Genta with prompt written notice and in any
         event sufficient advance notice to allow Genta to prosecute and/or
         maintain such Non-Exclusive Licensed Patent(s).

                  6.1.2 WITH RESPECT TO EXCLUSIVE LICENSED PATENTS. Genta shall
         have the right, but not the obligation, to apply for, prosecute,
         maintain and defend, during the Term of this Agreement, any and all
         Exclusive Licensed Patents in any country(ies) and/or region(s) in the
         world. All reasonable costs and expenses of the prosecution and
         maintenance of the Exclusive Licensed Patents in such countries
         (including all governmental filing fees) shall be borne by Genta. MBI
         shall render reasonable assistance to Genta in filing, prosecuting, and
         maintaining the Exclusive Licensed Patens in such countries whenever
         requested to do so, at Genta's expense. If Genta elects not to
         prosecute, obtain issuance of, and/or maintain any patents or patent
         applications within the Exclusive Licensed Patents in any country(ies)
         or region(s) in the world, Genta shall promptly notify MBI in writing
         in sufficient time for MBI to take such

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         action, and MBI shall thereafter have the right, but not any
         obligation, to prosecute, obtain issuance of, and/or maintain such
         Exclusive Licensed Patents in such country(ies) or region(ies) at its
         own cost.

         6.2 PATENT LITIGATION.

                  6.2.1 WITH RESPECT TO NON-EXCLUSIVE LICENSED PATENTS. In the
         event that either Genta or MBI becomes aware of any potential
         infringement of the Non-Exclusive Licensed Patents, such party shall
         notify the other party of the potential infringement in writing and
         provide a summary of the relevant facts and circumstances known to such
         party relating to such infringement and reasonable evidence of such
         infringement. MBI agrees that Genta, and only Genta, shall have the
         right, but not the obligation, to sublicense such alleged infringer of
         the Licensed Patents hereunder. If Genta is unable or unwilling, based
         on the exercise of reasonable business judgment, to execute a mutually
         agreeable sublicense hereunder with such alleged infringer then,
         prosecution of such infringer by MBI shall proceed as follows. In
         accordance with Section 6.4 of the Isis Agreement, MBI, Isis and Genta
         shall consult with each other using best efforts to come to agreement
         regarding (i) the allocation of responsibility and expense of
         prosecution, and (ii) the disposition of any recovery. If no agreement
         is reached among Genta, MBI, and Isis on the subject matter of (i) and
         (ii) hereof within thirty (30) days of the date on which MBI or Genta,
         as applicable, first notified the other of infringement under this
         Section 6.2.1, then MBI, at Genta's request, shall have the obligation
         to prosecute such alleged infringer at Genta's sole expense, and Genta
         shall retain any damages recovered in connection therewith. MBI shall
         not notify a third person of the potential infringement of any of the
         Non-Exclusive Licensed Patents without first obtaining consent of
         Genta.

                  6.2.2 WITH RESPECT TO EXCLUSIVE LICENSED PATENTS. During the
         Term of this Agreement, Genta shall have the sole right, but not the
         obligation, to prosecute, at its own expense, any infringements of the
         Exclusive Licensed Patents, to defend the Exclusive Licensed Patents
         and to recover, for its own account, any damages, awards or settlements
         resulting therefrom. MBI hereby agrees that Genta may join MBI as a
         party plaintiff in any such suit, without expense to MBI. Genta shall
         hold harmless and indemnify MBI from and against any order for costs
         arising without fault or negligence of MBI that may be made against MBI
         by reason of being named a party plaintiff in such proceedings. Genta
         shall have sole control of any such suit and all negotiations for its
         settlement or compromise, and shall have the sole right in accordance

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         with the terms and conditions herein to sublicense any alleged
         infringer for future use of the Exclusive Licensed Patents. The total
         cost of any infringement action commenced or defended solely by Genta
         shall be borne by Genta.

         6.3 In the event that any action, suit or proceeding is brought
against, or written notice or threat thereof is provided to, Genta alleging
infringement of any patent or unauthorized use or misappropriation of technology
arising out of or in connection with Genta's practice of Licensed Patents, Genta
shall have the right to defend at its own expense such action, suit or
proceeding and, in furtherance of such rights, MBI hereby agree that Genta may
join MBI as a party in such suit, without expense to MBI. Genta shall hold
harmless and indemnify MBI from and against any order for costs arising without
fault of MBI that may be made against MBI in such proceedings, unless such order
arises out of or relates to facts and circumstances involving a breach of any
representation or warranty by MBI in this Agreement. MBI agrees to cooperate
with Genta, at Genta's expense, in connection with Genta's response to or
defense of such action, suit or proceeding, or notice or threat thereof.

         6.4 In the event that a party shall undertake the enforcement and/or
defense of the Licensed Patents by legal or patent office proceedings pursuant
to this Agreement, the other party shall, at the request and expense of the
party undertaking such enforcement and/or defense, cooperate in all reasonable
respects and, to the extent possible, have its employees testify when requested
and make available relevant records, papers, information, samples and the like.

                                7. PATENT MARKING

         7.1 Genta shall mark all Licensed Products or Licensed Methods made,
used or sold under the terms of this Agreement, or their containers, in
accordance with the applicable patent marking laws.

                               8. CONFIDENTIALITY

         8.1 Except to the extent permitted by this Agreement or as otherwise
agreed by the parties in writing, at all times during the term of this Agreement
and for the five (5) year period following the termination or expiration hereof,
each party agrees (a) to keep all information received by it (the "Receiving
Party") from the other party (the "Disclosing Party") that is stamped or
otherwise designated in writing as confidential ("Confidential Information")
confidential using the same degree of care as it exercises with its own
confidential information of a similar nature,

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but in no event less than a reasonable degree of care; (b) not to publish or
otherwise disclose Confidential Information; and (c) not to use Confidential
Information directly or indirectly for any purpose. The parties acknowledge
having received Confidential Information prior to the Effective Date hereof,
including without limitation the terms and conditions of that certain Letter
of Intent entered into between Genta and MBI an May 11, 2000 ("Letter of
Intent"), which Confidential Information shall be treated in accordance with
this Section 8.

         8.2 The obligations of Section 8.1 shall not apply to any Confidential
         Information that the Receiving Party can establish by competent proof :

                           (a) was already known to the Receiving Party at the
                           time of disclosure by the Disclosing Party;

                           (b) was part of the public domain at the time of its
                           disclosure by the Disclosing Party;

                           (c) becomes part of the public domain after its
                           disclosure by the Disclosing Party, other than
                           through any act or omission of the Receiving Party in
                           breach of this Agreement; or

                           (d) was lawfully disclosed to the Receiving Party by
                           a third party.

         8.3 PERMITTED DISCLOSURES BY EITHER PARTY. Notwithstanding anything to
the contrary in this Section 8, each party may disclose Confidential Information
to the extent that such disclosure is reasonably necessary, in accordance with
the term and conditions of this Agreement, (a) to file or prosecute patent
applications within the Licensed Patents, and/or to pursue or defend litigation
relating to the Licensed Patents, (b) to comply with applicable governmental
regulations, including without limitation obligations under the securities laws,
and (c) to comply with due diligence requests from third parties in connection
with each such party's corporate development activities, provided that such
third parties agree to be bound in writing by the terms and conditions of this
Section 8 and to use such information solely for purposes of conducting such due
diligence. If the Receiving Party intends to make any disclosure under this
Section 8.3, it shall give reasonable advance written notice to the Disclosing
Party of such intention. In the event that either party is requested or required
by subpoena, civil investigative demand, interrogatories or other similar legal
process to disclose any information that is considered Confidential Information
hereunder, such party will provide the other party with prompt notice of such
request(s) so that such other party may seek an appropriate protective order (at
its sole expense) or waive compliance with this Section 8.

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         8.4 PERMITTED DISCLOSURES BY GENTA. Notwithstanding anything to the
contrary in this Section 8, Genta may disclose Confidential Information (a) to
third parties in connection with the development, and/or commercialization of
Licensed Products, products, Licensed Methods and/or methods, including, without
limitation, sublicensing, co-development, co-marketing and co-promotion in
connection therewith, as long as such third party(ies) agrees in writing to be
bound by the provisions of this Section 8, and (b) in the process of seeking
and/or maintaining regulatory approval for Licensed Products, Licensed Methods,
products, and methods.

                                   9. NOTICES

         9.1 Any notice or payment required to be given to any party will the
deemed to have been properly given and to be effective (a) on the date of
delivery if delivered in person, by telefax, or overnight courier, or (b) five
(5) days after mailing if mailed by first-class certified mail, postage paid, to
the respective addresses given below, or to another address as it shall
designate by written notice given to the other party.

In the case of Genta:                       ATTN: Raymond P. Warrell, Jr., M.D.
                                            99 Hayden Avenue, Suite 200
                                            Lexington, MA 02421
                                            Fax: (781) 860-5137

In the case of MBI:                         ATTN:_______________________________
                                            Molecular Biosystems, Inc
                                            10030 Barnes Canyon Road
                                            San Diego, CA 92121-2789
                                            Fax:________________________________

                            10. TERM AND TERMINATION

         10.1 Unless otherwise terminated by operation of law or by acts of the
parties in accordance with the terms of this Agreement, this Agreement and the
licenses granted hereunder shall begin on the Effective Date and terminate upon
expiration of the last to expire of the Licensed Patents ("Term").

         10.2 This Agreement and all of Genta's rights and obligations hereunder
shall be terminable by Genta at any time, and for any or no reason, upon thirty
(30) days written notice to MBI.

         10.3 MBI shall not have any right to terminate the licenses granted to
Genta pursuant to Section 2 hereof for any reason whatsoever and,
notwithstanding Section 10.4, such licenses shall continue in full force and
effect beginning on the Effective Date and continuing until the expiration of
the last to expire of the Licensed

                                       12
<PAGE>

Patents, except that MBI may terminate such licenses in the following two
instances only, by providing thirty (30) days written notice to Genta:

                  (a) if Genta has materially breached its obligations under
                  Section 4 hereof; or

                  (b) if Genta has materially breached it obligations under
                  Section 13 hereof.

Such written notice shall state whether the material breach by Genta is alleged
under subsection (a) or (b) of this Section 10.3 and shall state the factual
basis of such allegation. If Genta disputes its alleged material breach, Genta
shall notify MBI in writing within ten (10) days of MBI's notice, and the
dispute regarding MBI's right to terminate and Genta's alleged breach will be
adjudicated by binding arbitration under the American Arbitration Association by
a panel of three arbitrators, one selected by each party and the third selected
by the other two arbitrators. Any arbitration proceeding commenced by any party
shall be held in New York City, New York. The decision of the arbitrators shall
be final and binding upon the parties and judgment upon the decision by the
arbitrators may be entered in any court of competent jurisdiction, and execution
may be had thereon. The expense of such arbitration, including attorneys' fees,
shall be allocated between the parties as the arbitrators may decide and as the
claims and interests of each party may prevail. Pending final determination of
such arbitration, the licenses granted to Genta pursuant to Section 2 hereof
shall continue in full force and effect.

         10.4 This Agreement shall be terminable upon the material breach or
default of any party. In the event of a material breach or default by a party
("Defaulting Party"), the other party ("non-Defaulting Party") shall give the
Defaulting Party written notice of the default and its election to terminate
this Agreement at the expiration of a probation period of sixty (60) days from
the date of the notice. If the Defaulting Party fails to resolve the default in
the probation period by (i) curing the default, (ii) providing a written
explanation satisfactory to the Non-Defaulting Party that a default has not
occurred, or (iii) entering into a written agreement with the Non-Defaulting
Party for the cure or other resolution of the default, then the Non-Defaulting
Party may terminate this Agreement by giving written notice to the Defaulting
Party, and the termination will be effective upon the date specified in such
notice. All termination rights shall be in addition to and not in substitution
for any other remedies that may be available to the Non-Defaulting Party.
Termination pursuant to this Section 10.4 shall not relieve the Defaulting Party
from liability and damages to the Non-Defaulting Party for default. Waiver by
any party of a single default or a

                                       13
<PAGE>

succession of defaults shall not deprive such party of any right to terminate
this Agreement arising by reason of any subsequent default.

         10.5 Any termination of this Agreement for any reason does not relieve
any party of any obligation or liability accrued prior to the termination or
rescind anything done by any party and the termination does not affect in any
manner any rights of any party arising under this Agreement prior to the
termination.

                      11. DISPOSITION OF LICENSED PRODUCTS
                            ON HAND UPON TERMINATION

         11.1 Upon termination of this Agreement under Sections 10.2, 10.3, or
10.4, Genta is entitled to complete the manufacture of and dispose of all
previously made or partially made Licensed Products, but no more, within a
period of one hundred and twenty (120) days, provided, however, that the sale of
the Licensed Products is subject to the terms of this Agreement.

                         12. WARRANTIES AND DISCLAIMERS

         12.1 MBI warrants and represents to Genta that (a) it has the lawful
right to enter into this Agreement and to grant the licenses set forth herein
without the consent or approval of another person or entity; (b) subject only to
the Isis Agreement, MBI owns all right, title, and interest in and to the
Licensed Patents; (c) MBI has not, and shall not during the Term of this
Agreement, license or otherwise transfer rights in the Non-Exclusive Licensed
Patents to any party other than Isis; and (d) MBI has not granted any rights,
options or licenses to, or otherwise encumbered in any way the Exclusive
Licensed Patents and shall not, during the Term of this Agreement, do or cause
to be done anything inconsistent with the exclusive license granted to Genta
pursuant to Section 2.2 hereof. MBI further represents and warrants to Genta
that the Non-Exclusive Licensed Patents set forth on Appendix A, the Exclusive
Licensed Patents set forth on Appendix B, and the MBI Technology licensed to
Genta hereunder constitute the entirety of MBI's present right, title, and
interest in and to Antisense and oligonucleotide antisense technology and that,
with respect to such subject matter, MBI has no rights in any patents, patent
applications, or technology, nor any option in or expectation of any rights in
same, apart from those identified in this Agreement and/or set forth in the
attached Appendices. If any patent(s), patent application(s), or technology
relating to Antisense and/or oligonucleotide antisense technology has been
omitted from this Agreement or the relevant

                                       14
<PAGE>

Appendix, intentionally or unintentionally, it shall nonetheless be deemed a
part of this Agreement and licensed to Genta in accordance with the terms and
conditions hereof.

         12.2 Genta represents and warrants to MBI that it has the lawful right
and authority to enter into this Agreement without the consent or approval of
another person or entity.

         12.3 IN NO EVENT WILL EITHER PARTY BE LIABLE FOR ANY INCIDENTAL,
SPECIAL OR CONSEQUENTIAL DAMAGES RESULTING FROM THE EXERCISE OF THIS LICENSE OR
THE USE OF LICENSED PRODUCTS OR LICENSED METHODS.

                               13. INDEMNIFICATION

         13.1 Genta shall indemnify, hold harmless and defend MBI, and their
respective directors, officers, employees and agents (the "Indemnitees") against
any and all claims, suits, losses, damage, costs, fees, and expenses resulting
from or arising out of Genta's exercise of this license. This indemnification
includes, but is not limited to, any product liability. MBI shall have no
responsibility for development, production, sale, safety and efficacy of
Licensed Products and Licensed Methods. However, Genta shall not indemnify
Indemnitees to the extent that a claim, suit, loss, damage, cost, fee or expense
arises out of the gross negligence or intentional misconduct of an Indemnitee.

         13.2 Genta shall have the exclusive right to control the defense of any
action, including the right to select counsel to defend an Indemnitee and Genta,
and to settle any claim. The provisions of this Section 13 shall survive and
remain in full force and effect after any termination, expiration or
cancellation of this Agreement and obligations hereunder shall apply whether or
not claims are rightfully brought.

         13.3 The obligations of Genta stated in Section 13 shall apply only if
an Indemnitee notifies Genta in writing within fifteen (15) days following
receipt of written notice of any claim or suit brought against Indemnitee in
respect of which Indemnitee intends to invoke the provisions of this Section 13.
Genta shall keep the Indemnitee informed on a current basis of its defense of
any claims pursuant to this Section 13.

                                14. ASSIGNABILITY

         14.1 This Agreement is not assignable by any party without the written
consent of the other parties, which consent shall not be unreasonably withheld,
provided that each party may make an assignment without the

                                       15
<PAGE>

consent of the other in connection with any merger, acquisition, consolidation,
reorganization, or sale of all or substantially all of its assets to which this
Agreement relates if such assignee expressly assumes all right, duties and
obligations of the assignor hereunder.

                                   15. WAIVER

         15.1 No waiver by any party of any breach or default of any of the
covenants or agreements set forth will be deemed a waiver of any subsequent or
similar breach or default.

                                16. MISCELLANEOUS

         16.1 The headings of the several sections are inserted for convenience
of reference only and are not intended to be a part of or to affect the meaning
or interpretation of this Agreement.

         16.2 No amendment or modification of this Agreement is valid or binding
upon the parties unless made in writing and signed on behalf of each party.

         16.3 This Agreement embodies the entire understanding of the parties
and supersedes all previous communications, representations, or understandings,
either oral or written, between the parties relating to the Licensed Patents,
including without limitation that certain Confidentiality Agreement entered into
between Genta and MBI on May 6, 2000 and the Letter of Intent.

         16.4 In case any of the provisions contained in this Agreement are held
to be invalid, illegal or unenforceable in any respect, such invalidity,
illegality or unenforceability must not affect any other provisions, but this
Agreement must be construed as if such invalid or illegal or unenforceable
provisions had never been contained in this Agreement.

         16.5 Unless otherwise provided herein, all costs and expenses incurred
in connection with this Agreement and the transactions contemplated thereby
shall be paid by the party which shall have incurred the same and the other
party shall have no liability relating thereto.

         16.6 This agreement shall be interpreted and construed in accordance
with the laws of the state of New York without reference to choice of law
doctrine, but the scope and validity of any patent or patent application shall
be governed by the applicable laws of the country of such patent or patent
application. Each party hereby submits

                                       16
<PAGE>

itself for the sole purpose of this Agreement and any controversy arising
hereunder to the jurisdiction of the courts located in the Southern District of
New York, any courts of appeal therefrom, and waives any objection on the
grounds of lack of jurisdiction (FORUM NON CONVENIENS or otherwise) to the
exercise of such jurisdiction over it by any such courts.

         16.7 This Agreement may be signed in two (2) counterparts, each of
which shall be deemed an original.

                            [SIGNATURE PAGE FOLLOWS]

                                       17
<PAGE>

         IN WITNESS WHEREOF, Genta and MBI, by their respective officers duly
authorized have executed this Agreement, in duplicate originals, on the day and
year written below.

Genta, Inc.                                Molecular Biosystems, Inc.

By:                                        By:
   ------------------------------------       ----------------------------------
(Signature)                                (Signature)

Name:   Raymond P. Warrell, Jr., M.D.      Name:   Bobba Venkatadri
      ---------------------------------         --------------------------------
(Please Print)                             (Please Print)

Title:  President and CEO                  Title:  President and CEO
      ---------------------------------          -------------------------------

Date:   May 30, 2000                       Date:   May 30, 2000
      ---------------------------------          -------------------------------

                                       18
<PAGE>

                                   SCHEDULE A
                         NON-EXCLUSIVE LICENSED PATENTS

<TABLE>
<CAPTION>

-------------------------------------------------------------------------------------------------------------
       TTC REF.        CLIENT'S REF.          TITLE             INVENTOR(S)       APPL. NO.     PATENT NO.
       COUNTRY                                                                   FILING DATE    ISSUE DATE
   ATTY(S) HANDLING
-------------------------------------------------------------------------------------------------------------
<S>                    <C>            <C>                   <C>                 <C>           <C>
016243-000100AT                       Oligonucleotide       Tullis, Richard H.  82903424.8    0092574
(KAW)                                 therapeutic agent &                       10/08/82      04/29/92
                                      method of making
                                      same

-------------------------------------------------------------------------------------------------------------
016243-000100AU                       Oligonucleotide       Tullis, Richard H.  91243/82      568067
(KAW)                                 therapeutic agent &                       10/08/82      05/17/88
                                      method of making
                                      same
-------------------------------------------------------------------------------------------------------------
016243-000100BE                       Oligonucleotide       Tullis, Richard H.  82903424.8    BE0092574
(KAW)                                 therapeutic agent &                       10/08/82      04/29/92
                                      method of making
                                      same

-------------------------------------------------------------------------------------------------------------
016243-000100CA                       Oligonucleotide       Tullis, Richard H.  413643        1208147
(KAW)                                 therapeutic agent &                       10/08/82      07/22/86
                                      method of making
                                      same
-------------------------------------------------------------------------------------------------------------
016243-000100CH                       Oligonucleotide       Tullis, Richard H.  82903424.8    CH0092574
(KAW)                                 therapeutic agent &                       10/08/82      04/29/92
                                      method of making
                                      same

-------------------------------------------------------------------------------------------------------------
016243-000100DE                       Oligonucleotide       Tullis, Richard H.  82903424.8    P3280400.8
(KAW)                                 therapeutic agent &                       10/08/82      04/29/92
                                      method of making
                                      same
-------------------------------------------------------------------------------------------------------------
016243-000100DK                       Oligonucleotide       Tullis, Richard H.  2881/83
(KAW)                                 therapeutic agent &                       10/08/82
                                      method of making
                                      same

-------------------------------------------------------------------------------------------------------------
016243-000100EP                       Oligonucleotide       Tullis, Richard H.  82903424.8    0092574
(KAW)                                 therapeutic agent &                       10/08/82      04/29/92
                                      method of making
                                      same
-------------------------------------------------------------------------------------------------------------
016243-000100FR                       Oligonucleotide       Tullis, Richard H.  82903424.8    FR0092574
(KAW)                                 therapeutic agent &                       10/08/82      04/29/92
                                      method of making
                                      same

-------------------------------------------------------------------------------------------------------------
016243-000100GB                       Oligonucleotide       Tullis, Richard H.  82903424.8    GB0092574
(KAW)                                 therapeutic agent &                       10/08/82      04/29/92
                                      method of making
                                      same

-------------------------------------------------------------------------------------------------------------
016243-000100IE                       Oligonucleotide       Tullis, Richard H.  2547/82       58009
(KAW)                                 therapeutic agent &                       10/22/82      06/16/93
                                      method of making
                                      same
=============================================================================================================
</TABLE>

<TABLE>
<CAPTION>

---------------------------------------------------------------------------------------
                                                    STATUS AND
                                                     REMARKS

---------------------------------------------------------------------------------------
<S>                         <C>
016243-000100AT             Revoked
(KAW)                       Priority (Cntry, Appl No, Date): US 314124 10/23/81
                            Publication no. 0092574
                            Designating AT BE CH/LI DE FR GB NL SE Client handles
                            annuities.
                            due 10/29/94; completed
---------------------------------------------------------------------------------------
016243-000100AU             Issued
(KAW)                       Priority (Cntry, Appl No, Date): US 314124 10/23/81
                            due 05/17/91; completed , annuities current

---------------------------------------------------------------------------------------
016243-000100BE             Revoked
(KAW)                       Priority (Cntry, Appl No, Date): US 314124 10/23/81
                            Publication no. 0092574
                            Client handles annuities.
                            due 10/29/94; completed
---------------------------------------------------------------------------------------
016243-000100CA             Issued
(KAW)                       Priority (Cntry, Appl No, Date): US 314124 10/23/81
                            No annuities due (old law).
                            due 10/08/88; completed
---------------------------------------------------------------------------------------
016243-000100CH             Revoked
(KAW)                       Priority (Cntry, Appl No, Date): US 314124 10/23/81
                            Publication no. 0092574
                            Client handles annuities.
                            due 10/29/94; completed
---------------------------------------------------------------------------------------
016243-000100DE             Revoked
(KAW)                       Priority (Cntry, Appl No, Date): US 314124 10/23/81
                            Publication no. 0092574
                            Client handles annuities.
---------------------------------------------------------------------------------------
016243-000100DK             Abandoned
(KAW)                       Priority (Cntry, Appl No, Date): US 314124 10/23/81
                            Confirm annuity due date. File shows last tax paid in
                            '92! Client handles annuities.
                            Annuity due 10/08/96 completed 06/18/96
                            Annuity due 10/08/97 completed 08/06/97
---------------------------------------------------------------------------------------
016243-000100EP             Nat'l Phase REVOKED
(KAW)                       Priority (Cntry, Appl No, Date): US 314124 10/23/81
                            Publication no. 0092574
                            Designating AT BE CH/LI DE FR GB NL SE
---------------------------------------------------------------------------------------
016243-000100FR             Revoked
(KAW)                       Priority (Cntry, Appl No, Date): US 314124 10/23/81
                            Publication no. 0092574
                            Client handles annuities.
                            due 10/29/94; completed
---------------------------------------------------------------------------------------
016243-000100GB             Revoked
(KAW)                       Priority (Cntry, Appl No, Date): US 314124 10/23/81
                            Publication no. 0092574
                            Associate confirms 1995 annuity paid. Client handles
                            annuities.
                            due 10/29/94; completed
---------------------------------------------------------------------------------------
016243-000100IE             Abandoned
(KAW)                       Priority (Cntry, Appl No, Date): US 314124 10/23/81
                            Published 06/16/93

=======================================================================================
</TABLE>

                                       i
<PAGE>

<TABLE>
<CAPTION>

-------------------------------------------------------------------------------------------------------------
       TTC REF.        CLIENT'S REF.          TITLE             INVENTOR(S)       APPL. NO.     PATENT NO.
       COUNTRY                                                                   FILING DATE    ISSUE DATE
   ATTY(S) HANDLING
-------------------------------------------------------------------------------------------------------------
<S>                    <C>            <C>                   <C>                 <C>           <C>
016243-000100IL                       Oligonucleotide       Tullis, Richard H.  67053         67053
(KAW)                                 therapeutic agent &                       10/24/82      10/14/97
                                      method of making
                                      same

-------------------------------------------------------------------------------------------------------------
016243-000100IT                       Oligonucleotide       Tullis, Richard H.  23872A/82     1206311
(KAW)                                 therapeutic agent &                       10/22/82      04/14/89
                                      method of making
                                      same
-------------------------------------------------------------------------------------------------------------
016243-000100JP                       Oligonucleotide       Tullis, Richard H.  57-503427     2547714
(KAW)                                 therapeutic agent &                       10/08/82      08/08/96
                                      method of making
                                      same
-------------------------------------------------------------------------------------------------------------
016243-000100NL                       Oligonucleotide       Tullis, Richard H.  82903424.8    NL0092574
(KAW)                                 therapeutic agent &                       10/08/82      04/29/92
                                      method of making
                                      same

-------------------------------------------------------------------------------------------------------------
016243-000100PC                       Oligonucleotide       Tullis, Richard H.  82/01447
(KAW)                                 therapeutic agent &                       10/08/82
                                      method of making
                                      same
-------------------------------------------------------------------------------------------------------------
016243-000100SE                       Oligonucleotide       Tullis, Richard H.  82903424.8    SE0092574
(KAW)                                 therapeutic agent &                       10/08/82      04/29/92
                                      method of making
                                      same

-------------------------------------------------------------------------------------------------------------
016243-000101JP                       Oligonucleotide       Tullis, Richard H.  8-70762
(KAW)                                 therapeutic agent &                       03/06/96
                                      method of making
                                      same
-------------------------------------------------------------------------------------------------------------
016243-000110US                       Oligonucleotide       Tullis, Richard     07/002014
(KAW)                                 therapeutic agent &                       01/09/87
                                      method of making
                                      same
-------------------------------------------------------------------------------------------------------------
016243-000120US                       Oligonucleotide       Tullis, Richard     140916
(KAW)                                 therapeutic agent &                       12/29/87
                                      methods of making
                                      same
-------------------------------------------------------------------------------------------------------------
016243-000130US                       Oligonucleotide                           355140        5023243
(KAW)                                 therapeutic agent &                       05/15/89      06/11/91
                                      method of making
                                      same
-------------------------------------------------------------------------------------------------------------
016243-000140US                       Oligonucleotide       Tullis, Richard H   633452
(KAW)                                 therapeutic agent &   .                   12/20/90
                                      methods of making
                                      same
-------------------------------------------------------------------------------------------------------------
016243-000150US                       Oligonucleotide       Tullis, Richard     08/078768
(KAW)                                 therapeutic agent &                       06/16/93
                                      methods of making
                                      same

-------------------------------------------------------------------------------------------------------------
016243-000160US                       Oligonucleotide       Tullis, Richard H.  08/455760     5919619
(KAW)                                 therapeutic agent &                       05/31/95      07/06/99
                                      methods of making
                                      same
-------------------------------------------------------------------------------------------------------------
016243-000170US                       Oligonucleotide
(KAW)                                 therapeutic agent
                                      and methods of
                                      making
-------------------------------------------------------------------------------------------------------------

</TABLE>

<TABLE>
<CAPTION>

--------------------------------------------------------------------------------------
                                                   STATUS AND
                                                    REMARKS

--------------------------------------------------------------------------------------
<S>                         <C>
016243-000100IL             Issued
(KAW)                       Priority (Cntry, Appl No, Date): US 314124 10/23/81
                            Published 07/13/97
                            Annuities for  the entire 20-yr.term have already been
                            paid by Reinhold Cohn (rd) , annuities current
--------------------------------------------------------------------------------------
016243-000100IT             Abandoned
(KAW)                       Priority (Cntry, Appl No, Date): US 314124 10/23/81

--------------------------------------------------------------------------------------
016243-000100JP             Issued
(KAW)                       Priority (Cntry, Appl No, Date): US 314124 10/23/81
                            CLIENT HANDLES ANNUITITES am.(8/9/99),
                            annuities current
--------------------------------------------------------------------------------------
016243-000100NL             Abandoned
(KAW)                       Priority (Cntry, Appl No, Date): US 314124 10/23/81
                            Publication no. 0092574
                            Per. assoc. abandoned in '93 prior to our takeover.
                            Abandon form sent to KAW for signature.
--------------------------------------------------------------------------------------
016243-000100PC             Nat'l Phase
(KAW)                       Priority (Cntry, Appl No, Date): US 314124 10/23/81
                            EP (AT BE CH/LI DE FR GB NL SE) AU DK JP

--------------------------------------------------------------------------------------
016243-000100SE             Revoked
(KAW)                       Priority (Cntry, Appl No, Date): US 314124 10/23/81
                            Publication no. 0092574
                            Client handles annuities.
                            due 10/29/94; completed
--------------------------------------------------------------------------------------
016243-000101JP             Abandoned
(KAW)                       Published 11/12/96; no. 8-294393
                            Exam requested upon filing (rd) Abandoned per KAW/jms

--------------------------------------------------------------------------------------
016243-000110US             Abandoned
(KAW)

--------------------------------------------------------------------------------------
016243-000120US             Abandoned
(KAW)

--------------------------------------------------------------------------------------
016243-000130US             Issued and Removed
(KAW)                       client pays m.fees;  maintenance fees current

--------------------------------------------------------------------------------------
016243-000140US             Abandoned
(KAW)

--------------------------------------------------------------------------------------
016243-000150US             Pending on appeal
(KAW)                       Response due 05/22/94 (ext. to 08/22/94) ; completed
                            08/19/94
                            Notice of appeal due 02/28/95 (ext. to 05/28/95) ;
                            completed 04/28/95
                            Appeal brief due 06/28/95 (ext. to 10/28/95) ; completed
                            02/02/96
                            Response to communication due 02/19/96 (ext. to 05/19/96)
                            ; completed 02/02/96
--------------------------------------------------------------------------------------
016243-000160US             Issued
(KAW)                       Maint. Fee (3-1/2 yrs.) due 01/06/03 Maint. Fee (7-1/2
                            yrs.) due 01/06/07 Maint. Fee (11-1/2 yrs.) due 01/06/11

--------------------------------------------------------------------------------------
016243-000170US             Extra copies of file history
(KAW)

======================================================================================

</TABLE>

                                      -ii-
<PAGE>

                                   SCHEDULE B

                           EXCLUSIVE LICENSED PATENTS

<TABLE>
<CAPTION>

================================================================================================================================

FIRST             COUNTRY          SERIAL        APPLICATION        PATENT        ISSUE       TITLE
INVENTOR          OR REGION        NUMBER        DATE               NUMBER        DATE
================================================================================================================================
<S>               <C>              <C>           <C>                <C>           <C>         <C>

</TABLE>

Including, without limitation, the United States and foreign patents and patent
applications identified in Schedule A, to the extent same are not subject to the
Isis Agreement.

                                     -iii-
<PAGE>

                                   EXHIBIT A

                    NON-EXCLUSIVE PATENT LICENSE AGREEMENT

     LICENSE AND DISTRIBUTION AGREEMENT ("this Agreement"), dated as of
September 14, 1992, between MOLECULAR BIOSYSTEMS, INC. ("MBI"), a Delaware
corporation with its principal place of business at 10030 Barnes Canyon Road,
San Diego, California 92121, and Isis Pharmaceuticals, Inc. ("Isis"), a
Delaware corporation with its principal place of business 2280 Faraday
Avenue, Carlsbad, California 92008.

                                   RECITALS

     A. MBI is the exclusive owner of certain patents relating to the
production and use of certain oligonucleotide therapeutic agents in the field
known generically as "antisense."

     B. Isis is conducting research and developing medical products which use
antisense technology which may be covered by MBI's antisense patents.

     C. MBI and Isis desire to enter into an agreement by which MBI shall
issue Isis a nonexclusive worldwide license to use the antisense patents for
all purposes, and Isis shall pay MBI a royalty on the sales of all products
employing MBI's antisense patents.

     THEREFORE, in consideration of the mutual promises contained in this
Agreement, the parties agree as follows:

                                   ARTICLE 1

                                  DEFINITIONS

     1.1. AFFILIATE. "Affiliate" means any entity which controls, is
controlled by, or is under common control with, any identified entity.

     1.2. ANTISENSE. "Antisense" means the production or use for therapeutic
purposes of stabilized synthetic oligonucleotides.

     1.3. CONFIDENTIAL INFORMATION. "Confidential Information" means
information in the possession of a party that is not generally known and that
gives such party a competitive advantage over third parties, including but
not limited to techniques, designs, drawings, data, processes, inventions,
concepts, substances, specifications, developments, equipment, protocols,
sales and customer information, trade secrets, and business and financial
information, relating to the research, products, practices and businesses of
such party.

<PAGE>

     1.4. EFFECTIVE DATE. "Effective Date" means September 14, 1992.

     1.5. FDA. "FDA" means the United States Food and Drug Administration and,
where the context requires, corresponding foreign agencies.

     1.6. LICENSED PRODUCT. "Licensed Product" means any product whose use,
manufacture, or sale by Isis in any jurisdiction in which a Patent has been
allowed, but for the provisions of this Agreement, would constitute an
infringement of such Patent.

     1.7. LICENSES. "Licenses" means the licenses granted in Article 2.

     1.8. LOSSES. "Losses" or "Loss" means any loss, damages, injury or
expense, including but not limited to lost profits, attorney's fees, damage
awards, costs of investigation and litigation, sunk expenditures in plant,
equipment and overhead, and diminution in value.

     1.9. NET SALES. "Net Sales" means the gross sales revenues received by a
seller of Licensed Products, minus (a) all sales, use, and excise taxes, and
customs duties or other charges; (b) transportation and handling charges
(including transport insurance) actually incurred and paid by the buyer as
part of the purchase price; and (c) amounts repaid or credited by reason of
timely rejections or returns.

     1.10. PATENTS. "Patents" means any issued patents of any type or
description within the Technology Rights which have not been held to be
invalid.

     1.11. TECHNOLOGY RIGHTS. "Technology Rights" means:

          (a) Those patents and applications set forth in Appendix A hereto,
     together with any patents that may issues thereon, and any divisional,
     continuation or continuation-in-part applications based thereon and any
     patents that may issue thereon, any reissues or extensions based upon
     such patents, and any equivalent patents or patent applications of such
     patents; and

          (b) Any other patents or patent applications presently owned,
     controlled, licensed by, being developed or subsequently developed or
     acquired (by license or otherwise) by MBI which relate to Antisense.

     1.12. THIRD PARTY. "Third Party" means, with respect to either party
hereto, any non-party entity that is not an Affiliate of that party.

     1.13. OTHER DEFINITIONS. Definitions of the following words and phrases
are found in the indicated paragraphs:

          AGREEMENT                                                   Preamble

          BREACHING PARTY                                     Paragraph 8.2(c)

          CLAIMING PARTY                                      Paragraph 8.2(c)

                                      -2-
<PAGE>

          DISCLOSING PARTY                                       Paragraph 9.1

          ISIS                                                        Preamble

          ISIS TECHNOLOGY                                        Paragraph 2.2

          MBI                                                         Preamble

          ROYALTY(IES); ROYALTY RATE                             Paragraph 3.2

                                   ARTICLE 2

                                   LICENSES

     2.1. BASIC LICENSE. MBI grants Isis a nonexclusive worldwide license to
use the Technology Rights to use, make, have made, test, research, develop,
promote, commercialize, market, distribute, and sell Licensed Products on the
terms and conditions set forth in this Agreement.

     2.2. SUBLICENSES. MBI grants Isis the right to issue sublicenses of the
same or lesser scope as the license described in Paragraph 2.1, provided that
such sublicense may only be issued in connection with the grant by Isis to
the sublicensee of a license of patented, secret, or otherwise proprietary
Isis-developed technology ("Isis Technology") necessary to the development,
manufacture, sale, and/or use of a product using the Technology Rights, such
sublicense to be limited in scope or field of use to the use of the
Technology Rights for a Licensed Product employing Isis Technology as a
material element thereof. It is the intention of the parties that this
limitation is intended to prevent the "brokering" or other transfer of the
Technology rights to parties whose use thereof does not substantially employ
Isis Technology. Isis shall provide MBI with a copy each sublicense. No
sublicense shall contain terms contrary to or inconsistent with the terms of
this Agreement.

     2.3. END-USER SUBLICENSES. MBI grants Isis a license to issue
irrevocable sublicenses to end users of Licensed Products to use them for
their respective intended purposes.

                                   ARTICLE 3

                  LICENSE FEES; ROYALTIES; SUBLICENSE REVENUES

     3.1. LICENSE FEE. Isis shall pay MBI a license fee of $250,000, as
follows:

          (a) $125,000 on the date of execution of this Agreement;

          (b) $125,000 on January 1, 1993.

These payments shall be non-refundable, non-cancelable, and shall not be
credited against any other payments due to MBI from Isis.

                                      -3-
<PAGE>

     3.2. ANNUAL MAINTENANCE FEE. Isis shall pay MBI an annual maintenance fee
of $15,000 on every anniversary of the Effective Date through the term of
this Agreement as described in Paragraph 8.1. It shall not be credited toward
or be deemed a prepayment of any other amounts owing to MBI from Isis under
this Agreement.

     3.3. ROYALTIES. Isis shall pay MBI a royalty of 1.5% of the Net Sales of
Licensed Products manufactured and sold by Isis ("Royalty(ies)" or "Royalty
Rate," as the context requires).

     3.4. SUBLICENSE REVENUES. With respect to each sublicensee, Isis shall
pay MBI the greater of the following, measured on a quarter-by-quarter, basis:

          (a) 15% of Isis's sublicense revenues relating to the sublicensee's
     sales of Licensed Products (excluding revenues from any transaction
     counted towards Net Sales under Paragraph 3.3), or

          (b) 0.75% of the sublicensee's Net Sales.

("Sublicense Payments.") All sublicenses shall require the sublicensee to
report Net Sales (as defined in this Agreement) to Isis on a quarterly basis.
If MBI enters into any license agreement for the Technology Rights similar in
scope to this Agreement after the Effective Date containing a Royalty Rate,
annual maintenance fee, or Sublicense Payment formula(s) more favorable to
that licensee than provided in Paragraph 3.3 or this Paragraph of this
Agreement, then this Agreement shall be deemed amended as of the effective
date of such other license to provide that Isis shall be subject to the
identical Royalty Rate or Sublicense Payment formula(s).

     3.5. PAYMENT OF ROYALTIES AND SUBLICENSE PAYMENTS. Royalties and
Sublicense Payments shall be calculated on a quarterly basis and payable to
MBI no later than forty-five (45) days after the close of each calendar
quarter in which Isis makes the sales included in Net Sales or receives
revenues or Net Sales reports from sublicensees. Isis shall be deemed to have
made a sale of a Licensed Product when it recognizes the revenue for its
internal accounting purposes, using Generally Accepted Accounting Principles;
provided that an unpaid receivable for a sale of Licensed Products shall be
counted as a sale resulting in recognized Net Sales (for the purposes of this
Agreement) 180 days after the date of the invoice from Isis to the delinquent
account. Each Royalty payment and Sublicense Payment shall be accompanied by
a statement showing the calculation of the Royalty (including all adjustments
to gross sales of Licensed Products by Isis or any sublicensee used to
calculate Net Sales) and of the Sublicense Payment.

     3.6. EXCHANGE RATES. In the case of revenues collected in currencies
other than U.S. dollars, the amount due to MBI shall be determined using the
exchange rate quoted at the U.S. Federal Reserve Bank clearing house in New
York, New York, at the close of business on the last business day of the
quarter.

     3.7. RECORDS AND ACCOUNTING REVIEW. Isis shall keep complete and
accurate books of account containing all particulars which may be necessary
for the purpose of showing the transfer prices, Royalties and Sublicense
Payments payable to MBI. Such books and the supporting data shall be open and
accessible on reasonable prior written notice at all reasonable times during
the term of this Agreement to the inspection of an independent certified
public accountant retained by MBI and reasonably acceptable to Isis for the
purpose of verifying Isis's Royalty and Sublicense Payments and

                                     -4-
<PAGE>

statements. Isis may take reasonable steps to provide MBI's accountant with
only such information as is necessary for such verification, and MBI's
accountant shall report to MBI only such information as is required by MBI to
confirm whether Isis has provided accurate statements under Paragraph 3.5, and,
if not, the respects in which the reports were inaccurate. All such
information provided to MBI and its accountant shall be subject to Article 9
("Confidentially"). Such inspection may take place no more frequently than
once in any calendar year, and the accountant's inspection shall be limit to
books and records no older than those for the three calendar years prior to
the date of the inspection.

                                   ARTICLE 4

                                  ISIS DUTIES

     In addition to other duties and obligations imposed by this Agreement,
Isis shall have the following duties:

     4.1. REGULATORY REQUIREMENTS. Isis's development and commercialization of
Licensed Products shall comply with applicable FDA regulations. Isis shall
secure all necessary FDA and other regulatory approvals as required to
develop and commercialize Licensed Products.

     4.2. NO CONTEST. During the term of this Agreement and for a period of
five years thereafter, Isis shall not contest, oppose, interfere with, or
challenge the validity of the Patents, or support any such action by any
Third Party.

                                   ARTICLE 5

                        REPRESENTATIONS AND WARRANTIES

     Each party represents, warrants, and promises to the other that, as of
the Effective Date:

     5.1. ORGANIZATION. It is a corporation duly organized, validly existing
and in good standing under the laws of the state of Delaware and has full
power and authority to conduct its business as it is now being conducted. It
is qualified to do business in each other jurisdiction where qualification is
required by applicable law, except where any failure to so qualify would not
have a material adverse impact on the party.

     5.2 AUTHORITY. This Agreement constitutes its legal, valid and binding
obligation, enforceable in accordance with its terms, except as
enforceability may be limited by applicable bankruptcy, insolvency, or other
similar laws affecting the enforcement of creditors' rights generally, and by
legal and equitable limitations on the availability of specific remedies. No
consent or approval of any other party is required for it to enter into this
Agreement. The execution, delivery, and performance of this Agreement does
not and will not violate its articles of incorporation or bylaws.

     5.3 DEFAULTS. Its execution, delivery, and performance of this Agreement
does not and shall not result in a breach of or constitute a default (or an
event which, with or without notice or lapse of time, would constitute a
default) under any contract or agreement to which it is party.

                                      -5-
<PAGE>

     5.4. TITLE. MBI owns the Patents free and clear of all liens and
encumbrances.

                                   ARTICLE 6

                                 PATENT MATTERS

     6.1 PATENT RESPONSIBILITIES AND EXPENSES. MBI shall be solely
responsible for the prosecution and maintenance of the Patents and all
expenses relating thereto.

     6.2 ISIS'S RIGHT TO MAINTAIN AND DEFEND. If MBI does not desire to
prosecute, maintain and defend any Patent which Isis believes essential for
it to protect its rights to manufacture and sell Licensed Products, Isis may
elect to assume responsibility for the prosecution, maintenance, and defense
of such Patent.

     6.3 COOPERATION REGARDING PROSECUTION AND MAINTENANCE. At Isis's
request, MBI shall keep Isis reasonably advised of the status of the Patents.
Upon request, MBI shall provide Isis with copies of applications, office
action responses, and other filings, and drafts thereof, filed or proposed to
be filed with the U.S. Patent and Trademark Office and its foreign
equivalents, which documents shall be subject to Article 9
("Confidentiality").

     6.4 INFRINGEMENT BY A THIRD PARTY. MBI shall be responsible for
prosecuting or licensing infringers of the Patents. MBI shall consult with
Isis and any other non-exclusive licensee of the Technology Rights regarding
(i) the allocation of responsibility and expense of prosecution, and (ii) the
disposition of any recovery, in the event that the infringer's activities
directly and materially injure one or more such non-exclusive licensees. If
no agreement on these subjects is reached, then MBI shall have the right to
prosecute infringers of the Patents at its expense. It shall retain sole
control of any proceedings, including the defense of any counterclaim or
allegation that any of the patents included in the Patents is invalid. If any
portion of a recovery or settlement is for lost Net Sales of Isis or any
sublicensee, MBI shall pay Isis an amount representing Isis's lost profits
after deduction of MBI's costs of prosecution not separately awarded as an
element of damage and the applicable Royalties on such lost Net Sales. If MBI
declines to prosecute any given infringer, Isis may undertake such
prosecution, PROVIDED THAT if any of the recovery is for the Net Sales on
lost sales of Licensed Products (or other lost revenues), Isis shall pay MBI
an amount representing the appropriate Royalties or other amounts after
deduction of Isis's costs of prosecution or defense not separately awarded as
an element of damage. In the event Isis undertakes the prosecution of such a
claim, MBI shall have the right to join as a party aligned with Isis at MBI's
expense, and shall, at its option, have control over the defense of any claim
that any patent in the Patents is invalid.

     6.5 INVALIDITY. Unless otherwise agreed in a particular case, MBI shall
be responsible for the defense of any claim that any patent included in the
Patents is invalid.

     6.6 COOPERATION REGARDING LITIGATION. The parties shall cooperate with
one other in any action undertaken in connection with the proceedings
described in this Article at the request of the party bringing the action.
The cooperation shall be at the expense of the requesting party, except that
if the cooperating party desires to be represented by separate counsel,
it shall be at its own expense.

                                      -6-
<PAGE>

                                   ARTICLE 7

                                INDEMNIFICATION

     7.1 INDEMNIFICATION BY ISIS. Isis shall indemnify MBI for all Losses
incurred by MBI as a result of: (a) Isis's breach of this Agreement,
including representations and warranties, or (b) any claim for death or
personal injury which shall have been caused or alleged to have been caused
by any negligence on the part of Isis arising out of the manufacture, sale or
use of the Licensed Products, including claims based on strict liability or
other tort cause of action.

     7.2 PROCEDURE RESPECTING THIRD PARTY CLAIMS. In the event a Third Party
assets any claim with respect to any matter as to which the indemnities
in this Article relate, MBI shall give prompt notice to Isis, and the Isis
shall have the right to take over the defense or settlement of the Third
Party's claim at its own expense by giving prompt notice to MBI. If Isis does
not give such notice and does not proceed diligently to defend the claim
within 30 days after receipt of the notice of the Third Party's claim, then
Isis shall be estopped to object to any defense or settlement that MBI may
make as to those claims, and shall reimburse the MBI for its Losses related
to the defense or settlement of the Third Party's claim. Regardless of any
dispute over whether indemnification shall be had, the parties shall cooperate
to defend the Third Party's claim. Indemnification under this Article shall
include indemnification of MBI's employees, agents, Affiliates, and Third
Parties performing services for MBI.

                                  ARTICLE 8

                             TERM AND TERMINATION

     8.1 TERM. Except as provided in Paragraph 8.2, this Agreement shall be
in effect until the expiration date of the last of the Patents to expire, on
a jurisdiction-by-jurisdiction basis.

     8.2 TERMINATION. This Agreement may be terminated prior to its
expiration under Paragraph 8.1:

          (a) MUTUAL CONSENT. By the written consent of Isis and MBI;

          (b) INSOLVENCY. By either party by notice to the other in the event
     such other party shall dissolve, cease active business operations or
     liquidate, or in the event such other party shall have been determined
     to be insolvent by a court of competent jurisdiction, or insolvency or
     reorganization proceedings shall have been commenced by such other party,
     or such proceedings shall have been brought against such other party and
     remained undismissed for a period of 60 days, or such other party shall
     have made a general assignment for the benefit of creditors, or a
     receiver of all or substantially all of such other party's assets shall
     have been appointed and not discharged within 60 days;

          (c) MATERIAL BREACH. Subject to Subparagraph (d), by either party
     ("the Claiming Party") if the other ("the Breaching Party") shall breach
     any material provision, condition, representation, or warranty in this
     Agreement, PROVIDED THAT this Agreement shall not be deemed breached by
     the Breaching Party until (a) the Claiming Party has given the Breaching

                                      -7-
<PAGE>

     Party written notice specifying the respects in which the Claiming Party
     claims the Agreement has been breached; (b) the Breaching Party fails to
     remedy such breach, or fails to provide information to the Claiming Party
     sufficient to show that it has not breached this Agreement, for a period
     of 60 days or such longer period of time as is necessary to effect a
     cure if such breach is not reasonably curable within 60 days, and the
     Breaching Party is pursuing a cure in good faith; and (c) following the
     expiration of the 60-day period, the Claiming Party has served final
     written notice of termination on the Breaching Party.

          (d) ISIS FAILURE TO PAY. By MBI if Isis shall fail to timely make
     any payment required by this Agreement and such payment shall not have
     been made within 30 days after receipt of MBI's written demand therefor
     unless Isis is, in good faith and in writing, contesting or disputing
     its obligation to make any such payment or disputing the amount thereof,
     provided that Isis shall deposit disputed amounts into an escrow account
     established at a commercial bank in San Diego, California, where such
     sum shall remain until the dispute is resolved either by agreement of the
     parties or order of a court of competent jurisdiction. Isis shall
     instruct any such escrowee to provide account balance information
     directly to MBI.

          (e) ISIS TERMINATION. Isis shall have the right to terminate this
     Agreement for any reason upon 30 days' written notice.

     8.3 CONSEQUENCES OF TERMINATION. Isis shall pay MBI all sums due as of
the termination date within 30 days. If this Agreement terminates (a) pursuant
to Paragraph 8.2(a), the Licenses shall survive (or not) on such terms as the
parties may agree. If this Agreement terminates pursuant to any other
provision, the Licenses shall terminate. All warranty, confidentiality,
indemnification, choice-of-law-and-forum, and recordkeeping/audit rights and
obligations of the parties shall survive termination. All accrued Royalties
on Licensed Products manufactured by Isis in Isis's inventory at termination
(which may be subsequently sold despite termination), shall be paid as
provided herein.

                                  ARTICLE 9

                               CONFIDENTIALITY

     9.1 CONFIDENTIAL INFORMATION. Each party acknowledges that this
Agreement may from time to time the disclosure to it by the other party of
Confidential Information. Each party ("the Receiving Party") shall regard and
preserve Confidential Information that it obtains from the other party ("the
Disclosing Party") as secret and confidential. During the term of this
Agreement and for a period of five (5) years thereafter, no Receiving Party
shall publish or disclose any Confidential Information in any manner without
the Disclosing Party's prior written consent. The Receiving Party shall use
the same level of care to prevent the disclosure of Confidential Information
that it exercises in protecting its own Confidential Information, and shall
in any event take all reasonable precautions to prevent the disclosure of
Confidential Information to third parties. Notwithstanding these
restrictions, a Receiving Party may disclose Confidential Information to the
FDA, to persons conducting preclinical or clinical trials of any Licensed
Product, and to vendors and suppliers of goods, materials and services
(including consulting services) as necessary to the performance of this
Agreement, upon securing from such persons (except the FDA) executed
confidentiality agreements in the form customarily employed by the Receiving
Party when required to disclose its own confidential information. A

                                      -8-
<PAGE>

party required to disclose Confidential Information under legal compulsion
shall use its best efforts to secure a protective order limiting the use and
disclosure thereof.

     9.2 EXCEPTIONS. The following shall not be considered Confidential
Information:

          (a) Information which is public knowledge or which becomes public
     knowledge through no fault of the Receiving Party.

          (b) Information which is lawfully obtained by the Receiving Party
     from a third party (which itself lawfully obtained the Confidential
     Information and has no obligation of confidentiality).

          (c) Information which is in the Receiving Party's lawful
     possession, as documented by its records, prior to its initial
     disclosure by the Disclosing Party. This exception shall not apply to
     release either party from the terms of any confidentiality agreement it
     entered into prior to the Effective Date.

          (d) Information which is independently developed by the Receiving
     Party without reference to any Confidential Information of the
     Disclosing Party.

     9.3 EQUITABLE RELIEF. Each party acknowledges that the unlawful
disclosure of Confidential Information would cause the Disclosing Party
immediate and irreparable damage, that the damage is not readily capable of
monetary recompense, and that a temporary restraining order or preliminary or
permanent injunction is an appropriate remedy for the threatened or continued
unlawful disclosure of the Confidential Information provided that notice of
any claimed wrongful disclosure shall first be given to the Receiving Party by
the Disclosing Party.

     9.4 AGREEMENT. Either party may disclose the terms of this Agreement to
their respective attorneys, accountants, lenders, insurance brokers and
underwriters, and investment bankers, or as required by law.

                                  ARTICLE 10

                                  ASSIGNMENT

     10.1 GENERAL PROHIBITION. Except as provided in Paragraph 10.2, this
Agreement may not be assigned by either party without the prior written
consent of the other party.

     10.2 EXCEPTIONS. Either party may assign this Agreement to a
wholly-owned subsidiary or to a purchaser of substantially all of its assets.

                                      -9-
<PAGE>

                                  ARTICLE 11

                              GENERAL PROVISIONS

     11.1 NOTICES. Any notices permitted or required to be given hereunder
shall be effective if they are delivered personally, by certified mail
(return receipt requested), by overnight air courier (with return receipt),
or by facsimile machine (with proof of transmission) and delivered:

          (a) in the case of MBI, to:

          Mr. Vincent A. Frank
            President
          MOLECULAR BIOSYSTEMS, INC.
          10030 Barnes Canyon Road
          San Diego, California 92121

          FAX: (619) 452-6187

     with required copies to:

          Steven Lawson, Esq.
          Vice President, Legal Affairs
            and General Counsel
          MOLECULAR BIOSYSTEMS, INC.
          10030 Barnes Canyon Road
          San Diego, California 92121

          FAX: (619) 452-6187

     and

          Craig P. Colmar, Esq.
          Michael Bonn, Esq.
          JOHNSON AND COLMAR
          Suite 1000
          75 East Wacker Drive
          Chicago, Illinois 60601

          FAX: (312) 444-9283

     and

                                     -10-
<PAGE>

          (b) in the case of Isis, to:

          President
          ISIS PHARMACEUTICALS, INC.
          Carlsbad Research Center
          2292 Faraday Avenue
          Carlsbad, California 92008

          FAX: (619) 931-9639

     with a required copy to:

          B. Lynne Parshall
          General Counsel
          Carlsbad Research Center
          2292 Faraday Avenue
          Carlsbad, California 92008

Notices may be sent to any changed address of any of the above of which the
sender has actual knowledge.

     11.2 INTEGRATION. This Agreement represents the entire agreement of the
parties with respect to its subject matter, and supersedes any and all prior
agreements, understandings, promises and representations by any party to any
other respecting its subject matter.

     11.3 NO BROKERS. No party to this Agreement employed any broker or agent
in connection with this transaction or its subject matter.

     11.4 CAPTIONS; APPENDICES. All captions contained in this Agreement are
inserted for convenience of reference only and shall not be deemed a part of
this Agreement. The Appendices are incorporated into and deemed a part of this
Agreement.

     11.5 SEVERABILITY. If any provision of this Agreement is held
unenforceable, the provision shall be regarded as severable from this
Agreement and the remaining provisions shall remain in full force and effect.

     11.6 STATUS OF THE PARTIES. MBI and Isis shall not be deemed to be
partners, joint venturers or one another's agents, and neither shall have the
right to act on behalf the other except as expressly provided herein or
otherwise expressly agreed in writing.

     11.7 WAIVER. The failure or neglect of MBI or Isis to enforce the terms
and conditions of this Agreement shall not be deemed a waiver thereof nor
shall it be deemed a condonation of any breach. Such failure or neglect shall
not be deemed a waiver or condonation of any later breach. All remedies under
this Agreement are cumulative and are not exclusive of other remedies.

     11.8 AMENDMENT. Except as provided in the last sentence of Paragraph
3.4, this Agreement may only be amended by a writing signed by the parties
hereto and expressly designated as an amendment to this Agreement.

                                      -11-
<PAGE>

     11.9 BINDING EFFECT; SUCCESSORS AND ASSIGNS. This Agreement shall be
binding upon and inure to the benefit of the parties hereto and their
successors and permitted assigns.

     11.10 FORCE MAJEURE. A party shall not be liable to the other for
inability to perform any of its obligations under this Agreement when its
inability is the result of an act of God, earthquake, epidemic, order of
civil or military authorities, flood, fire, war, civil disturbance, strike
or other labor dispute, vandalism, or other natural, civil or commercial
disturbance over which the party has no control, except that lack of finances
shall not be deemed a circumstance not within a party's control.

     11.11 COUNTERPARTS. This agreement may be executed in counterparts, to
be evidenced by the simultaneous (within physical limits) exchange of
signature pages (telefaxed, if necessary) and confirmatory cover letters, and
the counterparts together shall be regarded as a single instrument binding on
the parties.

     11.12 CHOICE OF LAW; CHOICE OF FORUM. This Agreement shall be construed
and enforced in accordance with the laws of California, without regard to
conflict-of-laws rules. Any lawsuit relating to this Agreement shall be
brought in a court of competent jurisdiction in San Diego, California, which
court the parties acknowledge has IN PERSONAM jurisdiction over each of them.

     11.13 PUBLICITY. No party shall issue a press release relating to this
transaction without the prior review and approval of the other. Approval
shall not be unreasonably withheld. Such press release shall not disclose the
economic terms of the transaction. When filing necessary disclosures with the
Securities and Exchange Commission ("SEC"), each party shall request
confidential treatment with respect to the economic terms of this Agreement
pursuant to SEC Rule 24(b)-2. Nothing in this paragraph shall be construed to
prevent MBI form (a) publically disclosing revenue information from all
licensees of MBI's Antisense technology in the aggregate (as opposed to
Isis's economic terms alone) or (b) disclosing economic information on this
transaction to analysts or parties under an obligation of confidentiality.

     WHEREFORE, the parties have executed this Agreement as of September 14,
1992

                                       MOLECULAR BIOSYSTEMS, INC.

                                       By: /s/ Vincent A. Frank
                                           -----------------------------------
                                           Vincent A. Frank
                                           President & Chief Operating Officer

                                       ISIS PHARMACEUTICALS, INC.

                                       By: /s/ Daniel L. Kisner, M.D.
                                           -----------------------------------
                                           Daniel L. Kisner, M.D.
                                           Executive Vice President

                                      -12-
<PAGE>

                                   APPENDIX A

                PATENTS AND PATENT APPLICATIONS BY JURISDICTION

<TABLE>
<CAPTION>

--------------------------------------------------------------------------------------------------------
FIRST       COUNTRY       SERIAL       APPLICATION       PATENT       ISSUE         TITLE
INVENTOR    OR REGION     NUMBER       DATE              NUMBER       DATE
========================================================================================================
<S>         <C>           <C>          <C>               <C>          <C>           <C>
TULLIS      AUSTRALIA     91243/82     10/08/82          1,208,147    07/22/86
TULLIS      CANADA        413,643      10/18/82          1,208,147    07/22/86
TULLIS      DENMARK       2881/83      06/23/83
TULLIS      EUROPE*       82903424.8   10/08/82          0,092,574    04/29/92
TULLIS      IRELAND       2547/82      10/22/82
TULLIS      ITALY         23872A/82    10/23/82          12063311     04/14/89
TULLIS      ISRAEL        6705316      10/23/82
TULLIS      JAPAN         57-503427    06/23/83
TULLIS      US            355,140      05/15/89          5,023,243    06/11/91      OLIGONUCLEOTIDE
                                                                                    THERAPEUTIC AGENT
                                                                                    AND METHOD OF
                                                                                    MAKING SAME
TULLIS      US            633,452      12/20/90                                     OLIGONUCLEOTIDE
                                                                                    THERAPEUTIC AGENT
                                                                                    AND METHOD OF
                                                                                    MAKING SAME
========================================================================================================

</TABLE>

* Designated Contracting States:    Austria, Belgium, Switzerland, Germany,
                                    United Kingdom, Liechtenstein, Netherlands
                                    and Sweden.

<PAGE>

                                    EXHIBIT B

I.       CONSIDERATION

         (a) Upon the execution of this Agreement by both parties ("the Closing
Date") as consideration for the rights and licenses granted pursuant to the
Agreement, Genta shall issue to MBI the Subject Shares. The "Subject Shares"
shall mean the number of shares of Genta's common stock, par value $0.001 per
share ("Common Stock"), equal to $2,400,000 in value, calculated using the
closing sale price of the Common Stock on the Nasdaq National Market (the
"Closing Genta Stock Price") on the business day immediately prior to the
Closing Date (rounded to the nearest whole share).

         (b) In the event the Subject Shares have a Value (as defined below) of
less than $2,400,000 on the business day immediately prior to the date that the
Registration Statement (as defined below) is declared effective (such date, the
"Readjustment Date") by the Securities and Exchange Commission ("SEC"), Genta
shall issue shares of Common Stock to MBI in an amount equal to the Additional
Shares (as defined below). In the event the Subject Shares have a Value (as
defined below) of greater than $2,400,000 on the Readjustment Date, MBI shall
refund shares of Common Stock to Genta in an amount equal to the Additional
Shares (as defined below). The "Additional Shares" shall mean the number of
shares of Common Stock (rounded to the nearest whole share) equal to the
quotient of (i) the difference between $2,400,000 and the Value of the Subject
Shares on the Readjustment Date divided by (ii) the Closing Genta Stock Price on
the Readjustment Date. The "Value" of the Subject Shares on the Readjustment
Date shall be calculated using the Closing Genta Stock Price on the Readjustment
Date. Notwithstanding anything herein to the contrary, Genta may, at its option,
pay in cash the Value of the Additional Shares.

II.      ACCREDITED INVESTOR

         MBI represents and warrants to Genta as follows:

         (a) MBI is acquiring the Subject Shares (and, in the event that it
should acquire any Additional Shares, MBI will be acquiring such Additional
Shares) for its own account, for investment purposes and not with a view to the
distribution of any part thereof within the meaning of the Securities Act of
1933, as amended (the "Securities Act"), in any transaction that would violate
the registration requirements of the securities laws of the United States of
America or any state thereof; without prejudice, however, to the rights of MBI
at all times to sell or otherwise dispose of the Subject Shares and the
Additional Shares, as the case may be, under an effective registration statement
or applicable exemption from registration under the Securities Act and any
applicable state securities law.

         (b) MBI is an "accredited investor" within the meaning of Rule 501(a)
of Regulation D, promulgated under the Securities Act, and was not organized for
the specific purpose of acquiring the Subject Shares or the Additional Shares.

<PAGE>

         (c) MBI, by reason of its financial and business experience, has such
knowledge, sophistication and experience in financial and business matters as to
be capable of evaluating the merits and risks of an investment in the Subject
Shares and the Additional Shares and is able to bear the economic risk of such
investment.

         (d) MBI hereby acknowledges that Genta has made available to it the
opportunity to ask questions and receive answers from Genta concerning the terms
and conditions under which the Subject Shares and the Additional Shares, if any,
will be issued to it.

         (e) MBI understands that (i) the issuance to MBI of the Subject Shares
has not been, and the issuance to MBI of the Additional Shares will not be,
registered under the Securities Act, by reason of their issuance by Genta in
transactions exempt from the registration requirements of the Securities Act and
(ii) Genta is relying upon the accuracy of the representations and warranties of
MBI set forth in this License Agreement for purposes of compliance with the
exemptions from registration under the Securities Act.

         (f) No placement agent, banker, broker or finder has acted directly or
indirectly for MBI in connection with this License Agreement or the transactions
contemplated hereby, and no placement agent, banker, broker or finder is
entitled to any commission, brokerage or finder's fee in respect thereof based
in any way on agreements, arrangements or understandings made by or on behalf of
MBI.

III.     COMPLIANCE

         MBI covenants and agrees that it will comply with all applicable laws
relating to Genta's common stock, including, without limitation, the securities
laws of the United States of America and the applicable state securities laws.

IV.      REGISTRATION STATEMENT

         (a) Genta shall use its reasonable efforts to cause the Subject Shares
and the Additional Shares, if any, to be registered for resale by MBI on a
registration statement on Form S-3 (the "Registration Statement") under the
Securities Act with the SEC, and to have the Registration Statement declared
effective by the SEC as soon as practicable after the Closing Date and in any
event within three (3) months of such date. MBI shall provide all necessary
information to Genta to enable Genta to comply with the foregoing obligation.

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