<PAGE>
                                       
                                                                  EXHIBIT 10.23

                                EMPLOYMENT AGREEMENT

       THIS EMPLOYMENT AGREEMENT (the "Agreement") is made and entered into 
effective as of December 28, 1998, by and between Maxim Pharmaceuticals, 
Inc., (the "Company"), and Geoffrey B. Altman ("Executive").  The Company and 
Executive are hereinafter collectively referred to as the "Parties," and 
individually referred to as a "Party."
                                          
                                      RECITALS

       A.     The Company desires assurance of the association and services 
of Executive in order to retain Executive's experience, skills, abilities, 
background and knowledge, and is willing to engage Executive's services on 
the terms and conditions set forth in this Agreement.

       B.     Executive desires to be in the employ of the Company, and is 
willing to accept such employment on the terms and conditions set forth in 
this Agreement.
                                          
                                     AGREEMENT

       In consideration of the foregoing recitals and the mutual promises and 
covenants herein contained, and for other good and valuable consideration, 
the Parties, intending to be legally bound, agree as follows:

1.     EMPLOYMENT.

       1.1    The Company hereby employs Executive, and Executive hereby 
accepts employment by the Company, upon the terms and conditions set forth in 
this Agreement, effective as of the date first set forth above ("Commencement 
Date"). This Agreement shall continue in effect for a period beginning with 
the Commencement Date and ending December 31, 2000, unless terminated earlier 
pursuant to Section 5 below.

       1.2    Executive shall be the Vice-President, Marketing & Sales of the 
Company and shall serve in such other capacity or capacities as the Chief 
Executive Officer and/or the Company's Board of Directors ("Board") may from 
time to time prescribe.

       1.3    Executive shall do and perform all services, acts or things 
necessary or advisable to manage and conduct the business of the Company and 
which are normally associated with the position Vice-President, Marketing & 
Sales of the Company, consistent with the Bylaws of the Company, as well as 
its general employment policies and practices.  However, at all times during 
his employment Executive shall be subject to the direction and policies from 
time to time established by the Board.

       1.4    Unless the Parties otherwise agree in writing, during the term 
of this Agreement, Executive shall perform the services he is required to 
perform pursuant to this Agreement at the Company's offices, located at 8899 
University Center Lane, Suite 400 or at any other place at which the Company 
maintains an office; provided, however, that the Company may from time to 
time require Executive to travel temporarily to other locations in connection 
with the Company's business.

                                       

<PAGE>

2.     LOYAL AND CONSCIENTIOUS PERFORMANCE; NONCOMPETITION.

       2.1    During his employment by the Company, Executive shall devote 
his full business energies, interest, abilities and productive time to the 
proper and efficient performance of his duties under this Agreement.

       2.2    During the term of this Agreement, Executive shall not engage 
in competition with the Company, either directly or indirectly, in any manner 
or capacity, as adviser, principal, agent, partner, officer, director, 
employee, member of any association or otherwise, in any phase of the 
business of developing, manufacturing and marketing of products which are in 
the same field of use or which otherwise compete with the products or 
proposed products of the Company.

       2.3    Ownership by Executive, as a passive investment, of less than 
one percent (1%) of the outstanding shares of capital stock of any 
corporation with one or more classes of its capital stock listed on a 
national securities exchange or publicly traded in the over-the-counter 
market shall not constitute a breach of this paragraph.

3.     COMPENSATION OF EXECUTIVE.

       3.1    While employed by the Company, as compensation for proper and 
satisfactory performance of all duties to be performed hereunder, the Company 
shall pay Executive an annual base salary of One Hundred Forty-Five Thousand 
Dollars, $145,000 per year (the "Base Salary"), payable in regular periodic 
payments in accordance with Company policy.  Such salary shall be prorated 
for any partial year of employment on the basis of a 365-day fiscal year. In 
addition, Executive will be eligible for an incentive bonus of up to 20% of 
the Executive's annualized base salary hereunder, based upon defined 
milestones during the agreement period.

       3.2    Executive's compensation may be changed from time to time by 
mutual agreement of Executive and the Board.

       3.3    All of Executive's compensation shall be subject to customary 
withholding taxes and any other employment taxes as are commonly required to 
be collected or withheld by the Company.

       3.4    Executive shall be entitled to vacation and illness days 
consistent with the Company's standard practice for its employees generally.

       3.5    Executive shall, at the discretion of the Board, be entitled to 
participate in the benefits for which he is eligible under the terms and 
conditions of the standard Company benefits which may be in effect from time 
to time and provided by the Company.

4.     EXPENSE REIMBURSEMENT.

       4.1    Executive shall be entitled to receive prompt reimbursement of 
all reasonable business and travel expenses incurred by Executive in 
connection with the business of the Company.  Such expenses must be properly 
accounted for under the policies and procedures established by the Company.

5.     TERMINATION.

       5.1    The Company may terminate Executive's employment under this 
Agreement "for cause" by delivery of written notice to Executive specifying 
the cause or causes relied upon for such termination.  If Executive's 
employment under this Agreement is terminated by the Company for cause under 
this section, Executive shall be entitled to receive only accrued Base Salary 
and other accrued benefits required by law, prorated to the date of 
termination. Executive will not be entitled to severance pay, pay in lieu of 
notice or any other such compensation.  Grounds for the Company to terminate 
this Agreement "for cause" shall be limited to the occurrence of any of the 
following events:

                                       2

<PAGE>

              5.1.1  If Executive is in material breach of any provision of 
this Agreement;

              5.1.2  Executive's engaging or in any manner participating in 
any activity which is competitive with or intentionally injurious to the 
Company or which violates any provision of Section 7 of this Agreement;

              5.1.3  Executive's commission of any fraud against the Company 
or use or appropriation for his personal use or benefit of any funds or 
properties of the Company not authorized by the Board to be so used or 
appropriated;

              5.1.4  Executive's conviction of any crime involving dishonesty 
or moral turpitude;

              5.1.5  Conduct by Executive which in good faith and reasonable 
determination of the Board demonstrates gross unfitness to serve.

       Any notice of termination given pursuant to this Section 5.1 shall 
effect termination as of the date specified in such notice or, in the event 
no such date is specified, on the last day of the month in which such notice 
is delivered or deemed delivered as provided in Section 9 below.

       5.2    The Company may terminate the Executive's employment at any 
time without cause upon delivery of written notice to the Executive.  Any 
notice of termination given pursuant to this Section 5.2 shall effect 
termination as of the date specified in such notice or, in the event no such 
date is specified, on the last day of the month in which such notice is 
delivered or deemed deliverable as provided in Section 9 below.  If such 
termination shall occur under this Section 5.2, then Executive shall be 
entitled to continuation of Base Salary and health benefits for a period of 
six (6) months from said date of termination with such Base Salary 
continuation to be at the rate set forth in Section 3.1 or, as the case may 
be, at the rate of Executive's then current Base Salary in effect as of the 
date of termination.

       5.3    The parties may mutually agree at any time to terminate this
Agreement upon such terms and conditions as may be agreed upon in writing.

       5.4    This Agreement shall terminate without notice upon the date of 
Executive's death or the date when Executive becomes "completely disabled" as 
that term is defined in Section 6.2

       5.5    Notwithstanding any provision to the contrary herein, unless 
otherwise provided herein or unless otherwise provided by law, Executive may 
at any time terminate his employment with the Company hereunder.  In such 
event, the Company shall not be liable to Executive for the payment of any 
amount other than accrued Base Salary and other accrued benefits required by 
law, prorated to the date of termination.  Executive will not be entitled to 
severance pay, pay in lieu of notice or any other such compensation.

6.     DEATH OR DISABILITY DURING TERM OF EMPLOYMENT.

       6.1    Upon termination of Executive's employment pursuant to Section 
5.4, Executive or his estate or personal representative, as the case may be, 
shall be entitled to receive Executive's Base Salary and benefits for a 
period of one month following the date of death or the date when Executive 
becomes completely disabled.

       6.2    The term "completely disabled" as used in this Agreement shall 
mean the inability of Executive to perform the essential functions of his 
position under this Agreement by reason of any incapacity, physical or 
mental, which the Board of the Company, based upon medical advice or an 
opinion provided by a licensed physician acceptable to the Board of the 
Company and approved by the Executive, which approval shall not be 
unreasonably withheld, determines to have incapacitated Executive from 
satisfactorily performing any or all essential functions of his position for 
the Company during the foreseeable future.  Based upon such medical advice or 
opinion, the determination of the Board of the Company shall be final and 
binding and the date such determination is made shall be the date of such 
complete disability for purposes of this Agreement.

                                       3

<PAGE>

7.     CONFIDENTIAL INFORMATION; NONSOLICITATION.

       7.1    Executive recognizes that his employment with the Company will 
involve contact with information of substantial value to the Company, which 
is not generally known in the trade, and which gives the Company an advantage 
over its competitors who do not know or use it, including but not limited to, 
techniques, designs, drawings, processes, inventions, developments, 
equipment, prototypes, sales and customer information, and business and 
financial information relating to the business, products, practices and 
techniques of the Company, (hereinafter referred to as "Confidential 
Information").  Executive will at all times regard and preserve as 
confidential such Confidential Information obtained by Executive from 
whatever source and will not, either during his employment with the Company 
or thereafter, publish or disclose any part of such Confidential Information 
in any manner at any time, or use the same except on behalf of the Company, 
without the prior written consent of the Company.  As a condition of this 
Agreement, Executive will sign and return a copy of the Company's 
"Proprietary Information and Inventions Agreement," attached as Exhibit A.

       7.2    While employed by the Company and for one (1) year thereafter, 
the Executive agrees that in order to protect the Company's confidential and 
proprietary information from unauthorized use, that Executive will not, 
either directly or through others, solicit or attempt to solicit any 
employee, consultant or independent contractor of the Company to terminate 
his or her relationship with the Company in order to become an employee, 
consultant or independent contractor to or for any other person or business 
entity; or the business of any customer, vendor or distributor of the Company 
which, at the time of termination or one (1) year immediately prior thereto, 
was listed on Company's customer, vendor or distributor list.

8.     ASSIGNMENT AND BINDING EFFECT.

       8.1    This Agreement shall be binding upon and inure to the benefit 
of Executive and Executive's heirs, executors, personal representatives, 
assigns, administrators and legal representatives.  Because of the unique and 
personal nature of Executive's duties under this Agreement, neither this 
Agreement nor any rights or obligations under this Agreement shall be 
assignable by Executive. This Agreement shall be binding upon and inure to 
the benefit of the Company and its successors, assigns and legal 
representatives.

9.     NOTICES.

       9.1    All notices or demands of any kind required or permitted to be 
given by the Company or Executive under this Agreement shall be given in 
writing and shall be personally delivered (and receipted for) or mailed by 
certified mail, return receipt requested, postage prepaid, addressed as 
follows:

              9.1.1         If to the Company:

                            LARRY STAMBAUGH
                            MAXIM PHARMACEUTICALS, INC.
                            8899 UNIVERSITY CENTER LANE
                            SUITE 400
                            SAN DIEGO, CA  92122

                                       4

<PAGE>

              9.1.2         If to Executive:

                            GEOFFREY B. ALTMAN
                            MAXIM PHARMACEUTICALS, INC.
                            8899 UNIVERSITY CENTER LANE
                            SUITE 400
                            SAN DIEGO, CA  92122

Any such written notice shall be deemed received when personally delivered or 
three (3) days after its deposit in the United States mail as specified 
above. Either Party may change its address for notices by giving notice to 
the other Party in the manner specified in this section.

10.    CHOICE OF LAW.

       10.1   This Agreement is made in San Diego, California.  This 
Agreement shall be construed and interpreted in accordance with the laws of 
the State of California.

11.    INTEGRATION.

       11.1   This Agreement contains the complete, final and exclusive 
agreement of the Parties relating to the subject matter of this Agreement, 
and supersedes all prior oral and written employment agreements or 
arrangements between the Parties.

12.    AMENDMENT.

       12.1   This Agreement cannot be amended or modified except by a 
written agreement signed by Executive and the Company.

13.    WAIVER.

       13.1   No term, covenant or condition of this Agreement or any breach 
thereof shall be deemed waived, except with the written consent of the Party 
against whom the wavier in claimed, and any waiver or any such term, 
covenant, condition or breach shall not be deemed to be a waiver of any 
preceding or succeeding breach of the same or any other term, covenant, 
condition or breach.

14.    SEVERABILITY.

       14.1   The finding by a court of competent jurisdiction of the 
unenforceability, invalidity or illegality of any provision of this Agreement 
shall not render any other provision of this Agreement unenforceable, invalid 
or illegal.  Such court shall have the authority to modify or replace the 
invalid or unenforceable term or provision with a valid and enforceable term 
or provision which most accurately represents the parties' intention with 
respect to the invalid or unenforceable term or provision.

15.    INTERPRETATION; CONSTRUCTION.

       15.1   The headings set forth in this Agreement are for convenience of 
reference only and shall not be used in interpreting this Agreement.  This 
Agreement has been drafted by legal counsel representing the Company, but 
Executive has been encouraged, and has consulted with, his own independent 
counsel and tax advisors with respect to the terms of this Agreement.  The 
Parties acknowledge that each Party and its counsel has reviewed and revised, 
or had an opportunity to review and revise, this Agreement, and the normal 
rule of construction to the effect that any ambiguities are to be resolved 
against the drafting party shall not be employed in the interpretation of 
this Agreement.

                                       5

<PAGE>

16.    REPRESENTATIONS AND WARRANTIES.

       16.1   Executive represents and warrants that he is not restricted or 
prohibited, contractually or otherwise, from entering into and performing 
each of the terms and covenants contained in this Agreement, and that his 
execution and performance of this Agreement will not violate or breach any 
other agreements between Executive and any other person or entity.

17.    COUNTERPARTS.

       17.1   This Agreement may be executed in two counterparts, each of 
which shall be deemed an original, all of which together shall contribute one 
and the same instrument.

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

                                          The Company:

                                          MAXIM PHARMACEUTICALS, INC.

                                          By: /s/ LARRY G. STAMBAUGH
                                              --------------------------------
                                          Larry G. Stambaugh
                                          Chairman of the Board, President and
                                          Chief Executive Officer
                                                 

                                          EXECUTIVE:
              
                                          /s/ GEOFFREY B. ALTMAN
                                          -------------------------------------
                                          Geoffrey B. Altman

                                       6