<PAGE>   1
                                                                   EXHIBIT 10.15

                                  June 1, 1997



Edward O. Lanphier II
16 Oak Way
Ross, CA 94957

        Re: Employment Agreement

Dear Edward:

        Sangamo BioSciences, Inc. proposes to enter into the following
employment agreement ("Agreement") with you.

        I have incorporated the terms we have discussed regarding your
employment into this agreement and the proposed terms and conditions are set
forth below. If the terms of the Agreement are satisfactory, please indicate
your acceptance of the Agreement by executing this letter and returning it to
me.

        1.     Definitions. The terms defined in this section shall have the
               meanings set forth below for purposes of this Agreement.

               a.     "Board of Directors" shall mean the Board of Sangamo
                      BioSciences, Inc.

               b.     "Sangamo" or "Company" shall mean Sangamo BioSciences,
                      Inc.

               c.     "Employee" shall refer to you, Edward O. Lanphier II.

               d.     "Without Cause" shall mean that Sangamo has without
                      "Cause," as defined below, and without the Employee's
                      written consent:

                        (1)     terminated the Employee's services with the
                                Company;

                        (2)     materially reduced the Employee's duties,
                                responsibilities and status with Sangamo;

<PAGE>   2

                        (3)     reduced the Employee's base salary by more than
                                five percent (except pursuant to Company
                                mandated pay cuts or pay reductions which are
                                uniformly applied to the Company's management);
                                or

                        (4)     required that the Employee be based at a
                                location more than 40 miles from the Employee's
                                home location.

               e.     "Cause" shall mean misconduct, including but not limited
                      to the following:

                        (1)     embezzlement, theft, misuse of confidential
                                information or any other illegal or improper act
                                by the Employee against Sangamo;

                        (2)     conduct that constitutes a material breach of
                                Sangamo policy, after thirty (30) days' notice
                                and failure to cure;

                        (3)     unauthorized conduct that causes, or could
                                potentially cause, harm to the health or safety
                                of other Employees; and/or

                        (4)     any other unauthorized conduct that causes, or
                                could potentially cause, material harm to the
                                business or reputation of Sangamo, after thirty
                                (30) days' notice and failure to cure.

               f.     "Change of Control" solely for purposes of this Agreement
                      shall mean any transaction or series of related
                      transactions in which (i) substantially all of the assets
                      of the Company are sold; or (ii) any merger,
                      reorganization or acquisition in which the stockholders of
                      the Company immediately prior to such transaction or
                      series of related transactions hold less than 51% of the
                      equity securities of the surviving entity (or any parent
                      thereof) immediately after such transaction, unless, such
                      surviving entity elects in writing to assume this
                      Agreement and the obligations of the Company hereunder in
                      its entirety.

        2.     Duties and Obligations.

               a.     The Employee shall serve as the Company's President and
                      Chief Executive Officer which title was approved at the
                      Company's Board of Directors (the "Board") meeting on
                      April 5, 1997. Employee's duties shall include overseeing
                      all corporate functions and directing the organization to
                      ensure the attainment of the goals and objectives set
                      forth from time to time by the Board of Directors.


                                       2.
<PAGE>   3

               b.     Employee agrees to abide by the terms and conditions of
                      the Company's standard Proprietary Information and
                      Inventions Agreement between Employee and the Company.
                      Employee further agrees that at all times both during his
                      employment by the Company and after his Termination
                      (hereinafter as defined in Section 6(a)), he will keep in
                      confidence and trust, and will not use or disclose, except
                      as directed by the Company, any confidential or
                      proprietary information of the Company.

               c.     Employee agrees to indemnify and hold the Company harmless
                      against any liability, damage, claims, or suits and
                      related costs and expenses that may arise directly or
                      indirectly out of Employee's Termination of any prior
                      employment relationship or agreement. Further, Employee
                      represents that he has not entered into, and agrees not to
                      enter into, any agreement in conflict with the terms of
                      this Agreement or his employment with the Company.

        3.     Devotion of Time to the Company's Business.

               a.     Employee shall devote substantially all of his business
                      time, attention, knowledge, skills and interests to the
                      business of the Company and the Company shall be entitled
                      to all of the benefits and profits arising from or
                      incident to such work, services and advice of Employee.

               b.     During the term of this Agreement, Employee shall not,
                      whether directly or indirectly, render any services of a
                      commercial or professional nature to any other person or
                      organization, whether for compensation or otherwise,
                      without the prior consent of the Board of Directors.

               c.     During the term of this Agreement, Employee shall not,
                      directly or indirectly, engage or participate in any
                      business that is in competition with the business of the
                      Company.

        4.     Compensation and Benefits.

               a.     Base Compensation. Beginning June 1, 1997, the Company
                      shall pay to Employee an annual salary of one hundred
                      seventy-five thousand dollars ($175,000), less all
                      applicable withholdings, prorated for any partial
                      employment period and payable in equal monthly
                      installments in accordance with the Company's payroll
                      schedule. The Compensation Committee of the Board shall
                      annually review the then-current level of Employee's
                      salary to determine the amount, if any, of salary change,
                      provided that the foregoing shall not serve to exempt
                      Employee from any Company mandated pay cuts or pay
                      reductions which are uniformly applied to the Company's
                      management, any pay increase or pay cut will be effective
                      as of December 31 of the year such adjustment is made and
                      the Board shall advise Employee of such adjustment, if
                      any.

                                       3.
<PAGE>   4

               b.     Bonus. The Employee will be eligible to receive a cash
                      bonus in addition to the Employee's current base salary.
                      The Compensation Committee of the Board shall annually
                      review the contributions of the Employee to the Company
                      and determine the appropriate bonus, with the initial
                      bonus target being 50% of the Employee's base salary. The
                      actual bonus may be more or less than the target amount
                      based upon the Employee's achievements over the year,
                      provided that in no event shall the actual bonus be less
                      than $43,750 during the first year of this Agreement.

               c.     Long Term Loan. In lieu of any relocation or recruiting
                      expenses, the Employee will receive a loan of two hundred
                      fifty thousand dollars ($250,000). This loan shall be
                      forgiven annually on a pro-rated basis over a four-year
                      period beginning January 1, 1999 and shall bear interest
                      at the minimum rate otherwise imputed thereto by the
                      Internal Revenue Service. Upon any Termination of Employee
                      other than for Cause, the Company agrees to forgive any
                      remaining amount of the loan payoff made as part of this
                      Agreement. Should the Employee resign without cause, the
                      remaining balance will be due and payable within ninety
                      (90) days.

               d.     Benefits. At the time of this Agreement or for such time
                      as otherwise provided in this Agreement, Employee shall be
                      entitled to participate in such fringe benefits that are
                      available to employees of the Company at that time,
                      including: family health insurance, dental insurance,
                      group term life insurance, short-term disability
                      insurance, long-term disability insurance, vacation pay,
                      sick pay, 401(k) and other benefits that may be added to
                      the Company's benefit program from time to time.

                        (1)     Life Insurance. In addition to the group term
                                life insurance coverage provided to all
                                employees of the Company, the Company will
                                assist you in providing additional life
                                insurance protection through the establishment
                                of a split-dollar life insurance program, as
                                detailed in the Split-Dollar Life Insurance
                                Agreement included as Attachment A.

                        (2)     Disability Insurance. In addition to the
                                short-term and long-term disability insurance
                                coverage provided to all employees of the
                                Company, the Company will assist you in
                                providing additional long-term disability
                                insurance protection through the purchase of an
                                individual policy that will, without offsets for
                                social security, workers' compensation or other
                                disability benefits, provide insurance coverage
                                in the amount of $3,500 per year. Upon your
                                resignation or Termination from employment, this
                                disability insurance policy and any dividends
                                accrued thereon shall be released to you or your
                                successor employer upon written request.

               e.     Stock Options. Upon entering this Agreement, the Employee
                      shall receive stock options totalling Two Hundred Thousand
                      (200,000) shares of the Company's Common Stock (the
                      "Option Shares") under the Company's 1996 Stock Option
                      Plan (the "Plan"), which options shall have an exercise
                      price of $0.10 per share,

                                       4.
<PAGE>   5

                      and from time to time may be granted additional stock
                      options. If there is a Change of Control all unvested
                      stock options will vest and Employee will have up to three
                      years to exercise the stock options.

               f.     Stock Bonus. Upon completion of a financing or financings
                      totalling at least $7,000,000 on terms and conditions
                      acceptable to the Board of Directors, the Employee shall
                      receive a one-time stock bonus of One Hundred Fifty
                      Thousand (150,000) shares of the Company's Common Stock.

        5.     Eligibility for Severance Benefits.

               a.     General Rule. Except as otherwise provided in this
                      Agreement, should the employment of the Employee be
                      terminated Without Cause, the Employee shall be entitled
                      to Severance Benefits as set forth in Section 6. A Change
                      of Control shall be deemed to be a Termination Without
                      Cause.

               b.     Death or Disability. If the Employee dies after he has
                      ceased to be an Employee but prior to receiving full
                      payment of his Severance Benefits (as defined in Section
                      6(a)(i), if any, any portion of the Severance Benefits
                      that remains to be paid shall be paid to the surviving
                      spouse of the Employee, or, if there is no surviving
                      spouse, to the Employee's estate.

        6.     Termination of Employment.

               a.     The Company may terminate Employee's employment under this
                      Agreement at any time, for any reason, with or Without
                      Cause by giving written notice of its intent to terminate
                      the employment (a "Termination").

                      (1)    Should the Employee be terminated Without Cause,
                             the Company will thereafter pay twelve (12) months
                             base salary and a pro-rated bonus to the Employee
                             (the "Severance Benefits").

               b.     Continue Insurance Coverage. Sangamo shall continue to
                      provide the Employee and his family with medical and
                      dental insurance coverage by paying the COBRA payments for
                      a period equal to twelve (12) months. Notwithstanding the
                      foregoing, to the maximum extent permitted by law, the
                      number of months of continued insurance coverage provided
                      to the Employee under this section shall reduce the number
                      of months of continued coverage that must be made
                      available to the Employee (and his dependents, if
                      applicable) under COBRA.

               c.     Time and Form of Payment. The Employee shall not be
                      entitled to receive Severance Benefits during any period
                      in which he remains an Employee. The Employee must elect
                      to have his Severance Benefits paid in one of the
                      following ways:

                                       5.
<PAGE>   6

                      (1)    A single lump sum distribution paid upon, or as
                             soon as reasonably practicable after the
                             Termination of his employment; or

                      (2)    A deferred lump sum distribution paid in January of
                             the year following the year his employment
                             terminates; or

                      (3)    Two installments, which do not have to be of equal
                             amounts, with the first paid upon, or as soon as
                             reasonably practicable after, the Termination of
                             his employment and the second paid in January of
                             the year following the year his employment
                             terminates.

                             Election of one of the above methods is
                      accomplished by providing written notice to the Company of
                      such election within fifteen calendar days of the
                      Employee's Termination. If no election is made within that
                      period, the Severance Benefits will automatically be paid
                      pursuant to Section 6(e)(1). Without regard to the payment
                      method elected, no interest shall accrue or be paid with
                      respect to the amount of the Employee's Severance
                      Benefits.

                      d.     Reductions. The Severance Benefits paid to the
                             Employee shall be reduced to the extent legally
                             permissible by any amount that the Employee owes to
                             the he Company on the date he ceases to be an
                             Employee.

                             Except for any payments for earned salary, accrued
                      but unused vacation, 401(k) Plan distributions, and the
                      above mentioned Severance Benefits, if applicable, neither
                      party will be obligated to pay the other any payment as a
                      result of, or in connection with, the Termination of
                      Employee's employment with Sangamo (including but not
                      limited to any salary or benefits following the date of
                      Termination).

        7.     Miscellaneous.

               a.     Governing Law. This Agreement shall be interpreted,
                      construed, governed and enforced according to the laws of
                      the State of California.

               b.     Attorneys' Fees. In the event of any controversy, claim or
                      dispute between the parties, arising out of or relating to
                      this Agreement or the breach hereof, or the interpretation
                      hereof, each party shall bear its own legal fees and
                      expenses. Notwithstanding the foregoing, in the event of a
                      finding by any court having jurisdiction over such matter
                      that any party initiating an action under this Agreement
                      failed to have a reasonable prospect of prevailing on its
                      claim, the court shall have discretion to award the
                      prevailing party attorneys' fees and costs incurred by it
                      with respect to such claim or action. The "prevailing
                      party" means the party determined by the court to have
                      most nearly prevailed, even if such party did not prevail
                      in all matters, not necessarily the one in whose favor a
                      judgment is rendered.

                                       6.
<PAGE>   7

               c.     Amendments. No amendment or modification of the terms or
                      conditions of this Agreement shall be valid unless in
                      writing and signed by the parties hereto.

               d.     Severability. All agreements and covenants contained
                      herein are severable, and in the event any of the above
                      shall be held to be invalid or unenforceable, this
                      Agreement shall be interpreted as if such invalid
                      agreements or covenants were not contained herein.

               e.     Successors and Assigns. The rights and obligations of the
                      Company under this Agreement shall inure to the benefit of
                      and shall be binding upon the successors and assigns of
                      the Company. The Employee shall not be entitled to assign
                      any of his rights or obligations under this Agreement.

               f.     Entire Agreement. This Agreement, along with any other
                      Agreements set forth herein, including without limitation,
                      the Proprietary Information and Inventions Agreement,
                      constitutes the entire agreement between the parties with
                      respect to the employment of Employee.

        If you have any questions, please do not hesitate to call me at (415)
442-1123.

                                            Very truly yours,

                                            SANGAMO BIOSCIENCES, INC.



                                            By: /s/ JOHN W. LARSON
                                                --------------------------------
                                                John W. Larson
                                                Board of Directors

AGREED TO AND ACCEPTED BY:


/s/ EDWARD O. LANPHIER II
--------------------------------------
Edward O. Lanphier II
Employee
Date:
      --------------------------------



                                       7.
<PAGE>   8

                                  ATTACHMENT A

                      SPLIT-DOLLAR LIFE INSURANCE AGREEMENT


            This agreement, made and entered into this 1st day of June, 1997 by
and between Sangamo BioSciences, Inc., a Delaware corporation, hereinafter
referred to as the "Company," and Edward O. Lanphier II, hereinafter referred to
as the "Executive" and "Insured."

            Whereas the Executive has been a trusted and valued employee of the
Company for a number of years and the Company highly values the efforts,
abilities and accomplishments of the Executive; and

            Whereas the Company is concerned with the welfare of its employees
and their families and believes it is meritorious to assist them in providing
for their financial security; and

            Whereas the Board of Directors of the Company has determined that it
would be in the Company's best interest to participate in a Split-Dollar
Insurance Plan with the Executive; and

            Whereas the Executive has acquired a life insurance policy with a
face amount of $2,000,000; and

            Whereas, the Company and the Executive desire to make said insurance
policy subject to a Split-Dollar arrangement;

            Now therefore, the parties hereto mutually agree as follows:

I. Title to Policy and Incidents of Ownership

            The Executive shall be the owner of the policy and shall have all
incidents of ownership except those assigned pursuant to the provisions of
Article III for security purposes only, including but not limited to:

        A. The right to designate and to change the beneficiary.

        B. The right to receive and to have his successor or assigns receive any
amount in excess of the amount payable to the Company as hereinafter provided in
Article IV at the time of the death of the insured; and

        C. The right, at any time, to repay the amounts hereinafter described in
Article II, thereby releasing any claim which the Company might have against
such contract.

<PAGE>   9

            The intention of the parties is that the Company possess no policy
rights or incidents of ownership, other than those assigned as security for the
indebtedness, which will permit the Company to unilaterally impair the right or
interests of the Executive, or his designee or assignee in any way.

            The Executive hereby agrees, however, that while this agreement is
in effect, he shall notify the Company of any intent to exercise any right of
ownership in the policy other than the right to change the beneficiary at least
thirty (30) days prior to the exercise of such right of ownership.

II. Premium Payments

        A. The Company will pay the premium of the policy. The Company's portion
for this premium will be a minimum of $12,000 annually for split-dollar life.
Such premium may be paid annually or more frequently as the Company may elect.
The Company's premium payments shall be remitted to the insurer before the
expiration of the grace period for premium payments. The Executive may repay any
amount of such premiums advanced for his benefit at any time.

        B. The total amount of such payments by the Company, less the total
amount of any repayments by the Executive shall constitute an indebtedness to
the Company.

III. Security

        A. In order to secure the repayment of the indebtedness, the Executive
agrees to execute a Collateral Assignment of the insurance policy in a form
approved by the insurance company and shall deliver physical custody of the
policy to the Company.

        B. In the event of the termination of this agreement, pursuant to the
provisions of Article V hereof, the Company shall, upon receipt of an amount
equal to the total amount of the indebtedness then due to the Company, cancel
and release the Collateral Assignment of the insurance policy and redeliver
physical custody thereof to the Executive.

            In the event the Executive does not satisfy the indebtedness to the
Company within thirty (30) of the termination of this agreement, the Company
shall have the right, without further notice to the Executive, to exercise its
right as Collateral Assignee to obtain a cash loan from the Insurer in
accordance with the loan provisions of the policy, provided, however, that the
total amount of any cash loan or loans so obtained shall not exceed the total
amount of the indebtedness of the Executive then due under the terms of this
agreement.

IV. Death Benefits

        A. The portion of the death benefit to be paid to the Company shall be
the amount equal to the net cash surrender value of the policy up to, but not
exceeding, the then remaining balance of any indebtedness incurred for the
purposes of paying premiums under the policy. Such value shall be determined as
of the end of the period for which premiums have been paid.

        B. The portion of the death benefit payable to the beneficiary or
beneficiaries designated by the Executive shall be the balance of the proceeds,
if any as provided in the policy.

                                       2.
<PAGE>   10

V. Term

            This agreement shall be effective as of the date of this agreement
and shall continue until terminated by the death of the insured or mutual
agreement of the parties hereto.

VI. Amendment

            This agreement may be amended at any time by the mutual consent of
the parties hereto.

VII. Applicable Law

            This agreement shall be governed by the laws of the State of
California.

VIII. Benefit

            This agreement shall be binding upon the parties hereto, the
Executive's heirs, executors and administrators, and either party's successors
or assigns. The parties hereto hereby agree for themselves, their heirs,
executors, administrators, successors or assigns to execute any and all
instruments and to perform all acts which may be necessary and proper to carry
out the purposes of this agreement.

IX. Administrator

            Cameron M. Lanphier shall serve as the administrator of this plan.


                                       3.
<PAGE>   11

            IN WITNESS WHEREOF, the parties have executed this agreement on the
date indicated.

                                     Company

                                     SANGAMO BIOSCIENCES, INC.



                                     By:
                                         ---------------------------------------
                              Witness
                                         ---------------------------------------


                                     Executive



                                     -------------------------------------------
                                     Edward O. Lanphier II

                              Witness
                                         ---------------------------------------


                                       4.
<PAGE>   12

                                  ATTACHMENT B

             PREMIUM SCHEDULE FOR SPLIT-DOLLAR LIFE INSURANCE POLICY

                     Royal Maccabees Life Insurance Company

                                  Diplomat MFC
                                    FPAL-892
                AN ILLUSTRATION OF PROJECTED VALUES AND BENEFITS


Insured:              Edward O. Lanphier II          Agent:      Brian L. Dunn
                      Male, Age 40

Rating Class:         Preferred Non-Smoker

Mode of Premium Payment:  Annual

<TABLE>
<CAPTION>
           End Year                Age                 Premium            Death Benefit
<S>                                <C>                 <C>               <C>
               1                   41                   12,000              2,000,000
               2                   42                   12,000              2,000,000
               3                   43                   12,000              2,000,000
               4                   44                   12,000              2,000,000
               5                   45                   12,000              2,000,000
               6                   46                   12,000              2,000,000
               7                   47                   12,000              2,000,000
               8                   48                   12,000              2,000,000
               9                   49                   12,000              2,000,000
              10                   50                   12,000              2,000,000
</TABLE>