Document:

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                                                                  Exhibit 10.169

                                SIXTH AMENDMENT

     THIS SIXTH AMENDMENT (this "Amendment") dated as of June 30, 2001, to the
                                 ---------
Loan Agreement referenced below, is by and among Pharmaceutical Product
Development, Inc., a North Carolina corporation (the "Borrower"), the
                                                      --------
Subsidiaries of the Borrower identified on the signature pages hereto (the

"Guarantors") and First Union National Bank (the "Bank").  Terms used herein but
-----------                                       ----
not otherwise defined herein shall have the meanings provided to such terms in
the Loan Agreement.

                              W I T N E S S E T H

     WHEREAS, a $50 million credit facility has been established in favor of the
Borrower pursuant to the terms of that Loan Agreement dated as of June 24, 1998
(as amended and modified from time to time, the "Loan Agreement") among the
                                                 --------------
Borrower, the Guarantors and the Bank;

     WHEREAS, the Borrower has requested certain modifications to Loan
Agreement; and

     WHEREAS, the Bank has agreed to the modifications on the terms and
conditions set forth herein.

     NOW, THEREFORE, IN CONSIDERATION of the premises and other good and
valuable consideration, the receipt and sufficiency of which are hereby
acknowledged, the parties hereto agree as follows:

     1.   Amendments.
          ----------

     1.1  In Section 1.1 of the Loan Agreement, the following definitions are
added or amended to read as follows:

          "Committed Amount" means the aggregate amount of the commitments of
           ----------------
     the Bank hereunder, being initially $50,000,000.

          "Consolidated EBITDA" means, for any period for the Borrower and its
           -------------------
     subsidiaries on a consolidated basis, the sum of (i) Consolidated Net
     Income, plus (ii) to the extent deducted in determining net income, (A)
             ----
     Consolidated Interest Expense, (B) taxes and (C) depreciation and
     amortization, in each case on a consolidated basis determined in accordance
     with GAAP.

          "Consolidated EBITDAR" means, for any period for the Borrower and its
           --------------------
     subsidiaries on a consolidated basis, the sum of Consolidated EBITDA plus
                                                                          ----
     rental and lease expense, in each case on a consolidated basis determined
     in accordance with GAAP

          "Consolidated Fixed Charge Coverage Ratio" means, as of the last day
           ----------------------------------------
     of each fiscal quarter, the ratio of Consolidated EBITDAR for the period of
     four consecutive fiscal quarters ending as of such day to Consolidated
     Fixed Charges for the period of four consecutive fiscal quarters ending as
     of such day.

          "Consolidated Senior Funded Debt" means Consolidated Funded Debt that
           -------------------------------
     is not Subordinated Debt.

          "Consolidated Senior Leverage Ratio" means, as of the last day of each
           ----------------------------------
     fiscal quarter, the ratio of Consolidated Senior Funded Debt on such day to
     Consolidated EBITDA for the period of four consecutive fiscal quarters
     ending as of such day.
<PAGE>

          "Consolidated Total Leverage Ratio" means, as of the last day of each
           ---------------------------------
     fiscal quarter, the ratio of Consolidated Funded Debt on such day to
     Consolidated EBITDA for the period of four consecutive fiscal quarters
     ending as of such day.

          "Subordinated Debt" means any indebtedness of the Borrower or any of
           -----------------
     its subsidiaries which by its terms is expressly subordinated in right of
     payment to the prior payment of the obligations of the Borrower and the
     Guarantors under the Credit Documents on terms and conditions and evidenced
     by documentation satisfactory to the Bank.

          "Termination Date" means June 29, 2002, or such later date as to which
           ----------------
     the Bank may agree in its sole discretion.

     1.2  Clause (a) of Section 2.3 of the Loan Agreement is amended to read as
follows:

          (a)  Loans. Loans outstanding hereunder shall bear interest at a per
               -----
          annum rate equal to (i) for any day that the average amount of
          outstanding Obligations for such day exceeds an amount equal to fifty
          percent (50%) of the Committed Amount, the LIBOR Rate plus seven-
                                                                ----
          eighths of one percent (0.875%), (ii) for any day that the average
          amount of outstanding Obligations for such day is less than an amount
          equal to fifty percent (50%) of the Committed Amount, the LIBOR Rate
          plus five-eighths of one percent (0.625%) or (iii) the Prime Rate, as
          ----
          the Borrower may elect; provided that after the occurrence and during
                                  --------
          the continuance of an Event of Default, the principal and, to the
          extent permitted by law, interest on the Loan and any other amounts
          owing hereunder shall bear interest, payable on demand, at a rate
          equal to the Prime Rate plus two percent (2%).  Interest will be
                                  ----
          payable in arrears on each Interest Payment Date.

     1.3  Clause (a) of Section 2.6 of the Loan Agreement is amended to read as
follows:

          (a)  Facility Fee.  In consideration of the commitments hereunder, the
               ------------
          Borrower agrees to pay to the Bank a facility fee (the "Facility Fee")
                                                                  ------------
          equal to fifteen basis points (0.15%) per annum on the average daily
          unused portion of the Committed Amount for the applicable period.  The
          Facility Fee shall be payable quarterly in arrears on the 15th day
          following the last day of each calendar quarter for the immediately
          preceding quarter (or portion thereof) beginning with the first such
          date to occur after the date hereof.

     1.4  Section 6.5 of the Loan Agreement is amended to read as follows:

          6.5  Financial Covenants.
               -------------------

          (a)  Consolidated Total Leverage Ratio. As of the last day of each
               ---------------------------------
          fiscal quarter, the Consolidated Total Leverage Ratio shall be not
          less than 3.25:1.0.

          (b)  Consolidated Senior Leverage Ratio. As of the last day of each
               ----------------------------------
          fiscal quarter, the Consolidated Senior Leverage Ratio shall be not
          less than 2.0:1.0.

          (c)  Consolidated Fixed Charge Coverage Ratio. As of the last day of
               ----------------------------------------
          each fiscal quarter, the Consolidated Fixed Charge Coverage Ratio
          shall be not less than 3.0:1.0.

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<PAGE>

     1.5  Section 6.6 of the Loan Agreement is amended to read as follows:

          6.6  [Reserved]

     1.6  Section 6.9 of the Loan Agreement is amended to read as follows:

          6.9  Investments.  The Borrower will not, nor will it permit any of
               -----------
          its subsidiaries to, make loans or advances or otherwise make an
          investment in or capital contribution to (collectively, an
          "Investment"), any other Person, except:
           ----------

          (a)  cash and cash equivalents and other publicly traded equity and
          debt instruments reasonably acceptable to the Bank;

          (b)  loans and advances to officers, directors, employees and
          shareholders not to exceed $2,000,000;

          (c)  Investments in and to Digital Arts & Science in an aggregate
          principal amount (on a cost basis) not to exceed $1,500,000 at any
          time;

          (d)  seller financing promissory note from current management of
          APBI in favor of the Borrower in an aggregate principal amount not to
          exceed $18,000,000 in connection with the sale of APBI to current
          management of APBI;

          (e)  cash equity investments in and to ADoctorInYourHouse.com in an
          aggregate principal amount (on a cost basis) not to exceed $5,000,000
          at any time;

          (f)  loans and advances to NeoRx in an aggregate principal amount not
          to exceed $5,000,000 at any time;

          (g)  capital stock of DNA Sciences, Inc. in an amount (on a cost
          basis) not to exceed $15,000,000;

          (h)  Investments in and to a Credit Party; and

          (i)  Investments of a nature not contemplated in the foregoing
          subsections in an amount not to exceed (a) $20,000,000 for any single
          Investment (or any series of related Investments) and (b) $50,000,000
          in the aggregate in any fiscal year.

     2.   This Amendment shall be effective upon execution hereof by the
Borrower, the Guarantor and the Bank.

     3.   Except as expressly modified hereby, all of the terms and provisions
of the Loan Agreement (including schedules and exhibits thereto) shall remain in
full force and effect.

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<PAGE>

     4.   The Borrower agree to pay all reasonable costs and expenses of the
Bank in connection with the preparation, execution and delivery of this
Amendment, including without limitation the reasonable fees and expenses of
Moore & Van Allen, PLLC.

     5.   This Amendment may be executed in any number of counterparts, each of
which when so executed and delivered shall be deemed an original and it shall
not be necessary in making proof of this Amendment to produce or account for
more than one such counterpart.

     6.   This Amendment shall be deemed to be a contract made under, and for
all purposes shall be construed in accordance with, the laws of the State of
North Carolina.

                 [Remainder of Page Intentionally Left Blank]

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<PAGE>

     IN WITNESS WHEREOF, each of the parties hereto has caused a counterpart of
this Sixth Amendment to be duly executed and delivered as of the date first
above written.

BORROWER:                     PHARMACEUTICAL PRODUCT DEVELOPMENT, INC.,
                              a North Carolina corporation

                              By: /s/ Philippe M. Maitre
                                  -----------------------
                              Name:  Philippe M. Maitre
                              Title:  Chief Financial Officer

GUARANTORS:                   PPD DEVELOPMENT, LLC,
                              a Texas limited liability company

                              By: /s/ Philippe M. Maitre
                                  -----------------------
                              Name:  Philippe M. Maitre
                              Title:  Vice President

BANK:                         FIRST UNION NATIONAL BANK

                              By: /s/ Keith S. Law
                                  -----------------
                              Name:  Keith S. Law
                              Title:  Vice President<PAGE>

                                                                  EXHIBIT 10.170

                             EMPLOYMENT AGREEMENT

          THIS AGREEMENT (the "Agreement"), is effective as of this 9/th/ day of
July, 2001, by and among Pharmaceutical Product Development, Inc. (the
"Company"), a North Carolina corporation whose mailing address for notice
purposes is 3151 South Seventeenth Street, Wilmington, North Carolina 28412,
Attention: Chief Executive Officer, and Brainard Judd Hartman ("Employee"), an
individual whose mailing address for notice purposes is 3151 South Seventeenth
Street, Wilmington, North Carolina  28412.

                                   RECITALS

          A.  The Company is engaged in providing research, discovery and
development services to pharmaceutical companies by technology companies,
governmental entities and others (the "Business").

          B.  The Company desires to employ Employee and Employee desires to be
employed by the Company, all upon the terms and conditions set forth herein.

          NOW, THEREFORE, in consideration of the foregoing recitals, the mutual
covenants of the parties hereinafter set forth and other good and valuable
consideration, the receipt and sufficiency of which are hereby acknowledged, the
parties hereby agree as follows:

                                   ARTICLE 1
                             EMPLOYMENT AND DUTIES
                             ---------------------

          1.1  Engagement of Employee.  The Company agrees to employ Employee
               ----------------------
and Employee accepts such employment  pursuant and subject to the terms and
conditions of this Agreement.

          1.2. Duties and Powers.   During the Employment Period (as defined
               -----------------
herein), Employee shall serve as General Counsel and will have such
responsibilities, duties and authority, and will render such services for and in
connection with the Company and its affiliates as are customary in such position
and as the Board of Directors of the Company (the "Board"), the Chief Executive
Officer and the Executive Vice President shall from time to time reasonably
direct.  Employee shall devote Employee's  full business time and attention
exclusively to the Business of the Company and shall use best efforts to
faithfully carry out Employee's duties and responsibilities hereunder.  Employee
shall comply with all personnel policies and procedures of the Company as the
same now exist or may be hereafter implemented by the Company from time to time,
including those policies contained in the Pharmaceutical Product Development,
Inc. ("PPD") employee manual or handbook which sets forth policies and
procedures generally for employees of the Company and its subsidiaries and
affiliates (the "Handbook") to the extent not inconsistent with this Agreement.
<PAGE>

                                   ARTICLE 2
                              TERM OF EMPLOYMENT
                              ------------------

     Unless sooner terminated as provided elsewhere in this Agreement,
Employee's employment under this Agreement shall be for a period of one year
beginning on July 9, 2001 and ending at 11:59 p.m. on July 8, 2002 ("Initial
Employment Period").   This Agreement automatically shall renew for successive
one-year periods, unless either the Company or Employee provides written notice
to the other at least sixty (60) days prior to the termination of any such
period stating said party's desire to terminate this Agreement.  The Initial
Employment Period and any extension or renewal thereof shall be referred to
herein together as the "Employment Period".  Notwithstanding anything to the
contrary contained herein, the Employment Period is subject to termination
pursuant to Article 4 hereof.

                                   ARTICLE 3
                           COMPENSATION AND BENEFITS
                           -------------------------

          3.1  Compensation.   The Company will pay Employee a base salary at a
               ------------
rate of $175,000.00 per annum (the "Base Salary"), payable in accordance with
the Company's regular payroll policy for salaried employees.   The Base Salary
of Employee may be subject to increase annually during the Employment Period by
the Board of the Company or its designee.  If the Employment Period is
terminated pursuant to Article 4 hereof, then the Base Salary for any partial
year will be prorated based on the number of days elapsed in such year during
which services were actually performed by Employee.

          3.2  Benefits.  During the Employment Period, Employee shall be
               --------
eligible to participate in and/or receive benefits under such employee and
welfare benefit plans as may be established from time to time by the Company,
including any profit-sharing, stock purchase, stock option, bonus, pension,
disability, group-term life insurance, health insurance and flexible benefit
payroll deduction plans, subject in each instance to Employee meeting all
eligibility and qualification requirements of such plans.

          3.3  Stock Options.  The Company shall grant to Employee as of the
               -------------
commencement date of the Initial Employment Period (the "Grant Date") options to
purchase 10,000 shares of the Company's common stock at a purchase price equal
to the NASDAQ market close price on the Grant Date. Said share options shall be
granted under the terms of the Company's 1995 Equity Compensation Plan (the
"Plan") and are subject to all of the terms and conditions of the Plan as more
specifically evidenced by that certain Stock Option Award Agreement entered into
by the Company as of the Grant Date, which Stock Option Award Agreement is in a
form substantially similar to that generally provided to Plan participants,
including a linear three-year vesting schedule with respect to the share options
granted under the Stock Award Agreement.

          3.4  Expenses.  The Company will reimburse Employee, in accordance
               --------
with and subject to Employee's compliance with the Company's policy, for
Employee's

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<PAGE>

necessary and reasonable out-of-pocket expenses incurred in the course of
performance of Employee's duties hereunder. All reimbursement of expenses to
Employee hereunder shall be conditioned upon presentation of sufficient
documentation evidencing such expenses.

          3.5  Vacation and Leave.  Employee shall be entitled to the number of
               ------------------
days of "Paid Time Off" ("PTO") allotted for the position of General Counsel in
each year of the Employment Period and other leave as may be established from
time to time by the Company for the benefit of its employees, subject to
Employee's compliance with the guidelines set forth in the Handbook.  During the
initial Employment Period, Employee shall be entitled to twenty-seven (27) days
of PTO.

          3.6  Working Facilities.  The Company shall furnish Employee with such
               ------------------
office space, equipment, technical, secretarial and clerical assistance and such
other facilities, services and supplies as shall be reasonably necessary to
enable Employee to perform the duties required of Employee hereunder in an
efficient and professional manner.

          3.7  Relocation Expenses.  Employee shall be entitled to certain
               -------------------
relocation assistance, as provided for in and subject to the terms and
conditions of that certain Relocation Agreement (the "Relo Agreement") of even
date herewith.

          3.8  Change of Control.  In the event of a Change of Control of the
               -----------------
Company, Employee shall be entitled to the benefits provided for in that certain
Severance Agreement (the "Severance Agreement") of even date herewith.  "Change
of Control" shall have the same meaning set forth in the Severance Agreement.

                                   ARTICLE 4
                           TERMINATION OF EMPLOYMENT
                           -------------------------

          4.1  Basis for Termination.  Notwithstanding any other provision in
               ---------------------
this Agreement to the contrary, the Employment Period and Employee's employment
hereunder shall terminate effective on the date indicated upon the happening of
any of the following events:

               a.   Upon the death of Employee, effective immediately on the
date of death without any notice.

               b.   A determination by the Executive Vice President of the
Company, acting in good faith but made in the sole discretion of the Executive
Vice President, that Employee has failed to substantially perform his duties
under or otherwise breached any of the material terms of this Agreement,
effective upon the date said determination is communicated to Employee or such
later date, if any, as specified by the Executive Vice President of the Company.

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<PAGE>

               c.   A determination by the Executive Vice President of the
Company, acting in good faith but made in the sole discretion of the Executive
Vice President, that Employee (i) has become physically or mentally
incapacitated and is unable to perform his duties under this Agreement as a
result of such disability, which inability continues for a period of sixty (60)
days during any twelve-month period hereunder, (ii) has demonstrated gross
negligence or willful misconduct in the execution of his duties, or (iii) has
been convicted of a felony, effective upon the date said determination is
communicated to Employee or such later date, if any, as specified by the
Executive Vice President of the Company.

          4.2  Compensation After Termination During Employment Period.  If the
               -------------------------------------------------------
Company shall terminate Employee's employment during the Employment Period
pursuant to Section 4.1 hereof, the Company shall have no further obligations
hereunder or otherwise with respect to Employee's employment from and after the
termination or expiration date, except that the Company shall pay Employee's
Base Salary accrued through the date of termination or expiration and shall
provide such benefits as are required by applicable law.  From and after such
termination or expiration date, the Company shall continue to have all other
rights available hereunder, including without limitation all rights at law or in
equity.

                                   ARTICLE 5
                            PROPRIETARY INFORMATION
                            -----------------------

     Prior to or coincident with the commencement date hereof, Employee shall
execute in favor of the Company its standard Proprietary Information and
Inventions Agreement (the "Proprietary Agreement"), a copy of which is attached
hereto.

                                   ARTICLE 6
                                 MISCELLANEOUS
                                 -------------

          6.1  Withholding Taxes.  All amounts payable under this Agreement,
               -----------------
whether such payment is to be made in cash or other property, shall be subject
to withholding for Federal, state and local income taxes, employment and payroll
taxes, and other legally required withholding taxes and contributions to the
extent appropriate in the determination of the Company, and Employee shall
report all such amounts as ordinary income on Employee's personal income returns
and for all other purposes.

          6.2  Assignment.  No party hereto may assign or delegate any of its
               ----------
rights or obligations hereunder without the prior written consent of the other
party hereto; provided, however, that the Company shall have the right to assign
all or any part of its rights and obligations under this Agreement (i) to any
subsidiary or affiliate of the Company or any surviving entity following any
merger or consolidation of any of those entities with any entity other than the
Company, or (ii) in connection with the sale of the Business by the Company.

                                       4
<PAGE>

          6.3  Binding Effect.  Except as otherwise expressly provided herein,
               --------------
all covenants and agreements contained in this Agreement by or on behalf of any
of the parties hereto shall be binding upon and inure to the benefit of the
respective legal representatives, heirs, successors and permitted assigns of the
parties hereto.

          6.4  Entire Agreement.  Except as otherwise expressly set forth
               ----------------
herein, this Agreement and all other agreements entered into by the parties
hereto on the date hereof, including the Proprietary Agreement, the Stock Option
Award Agreement, the Bonus Agreement, the Relo Agreement and the Severance
Agreement, set forth the entire understanding of the parties and supersede and
preempt all prior oral or written understandings and agreements with respect to
the subject matter hereof.

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

          6.6  Amendment; Modification.   No amendment or modification of this
               -----------------------
Agreement and no waiver by any party of the breach of any covenant contained
herein shall be binding unless executed in writing by the party against whom
enforcement of such amendment, modification or waiver is sought.  No waiver
shall be deemed a continuing waiver or a waiver in respect of any subsequent
breach or default, either of a similar or different nature, unless expressly so
stated in writing.

          6.7  Governing Law.  This Agreement shall be governed by and construed
               -------------
and enforced in accordance with the laws of the State of North Carolina, without
giving effect to provisions thereof regarding conflict of laws.

          6.8  Arbitration.  Any dispute, controversy or claim arising out of or
               -----------
relating to this Agreement, including but not limited to its existence,
validity, interpretation, performance or non-performance or breach, shall be
decided by a single neutral arbitrator agreed upon by the parties hereto in
Wilmington, North Carolina in binding arbitration pursuant to the commercial
arbitration rules of the American Arbitration Association then in effect.  The
parties to any such arbitration shall be limited to the parties to this
Agreement or any successor thereof.  The written decision of the arbitrator
shall be final and binding and may be entered and enforced in any court of
competent jurisdiction. Each party waives any right to a jury trial in any such
forum.  Each party to the arbitration shall pay its fees and expenses, unless
otherwise determined by the arbitrator.

          6.9  Notices.  All notices, demands or other communications to be
               -------
given or delivered hereunder or by reason of the provisions of this Agreement
shall be in writing and shall be deemed to have been properly served if (a)
delivered personally, (b) delivered by a recognized overnight courier service,
(c) sent by certified mail, return

                                       5
<PAGE>

receipt requested and first class postage prepaid, or (d) sent by facsimile
transmission followed by a confirmation copy delivered by a recognized overnight
courier service the next day. Such notices, demands and other communications
shall be sent to the address first set forth above, or to such other address or
to the attention of such other person as the recipient party has specified by
prior written notice to the sending party. Date of service of such notice shall
be (i) the date such notice is personally delivered or sent by facsimile
transmission (with issuance by the transmitting machine of a confirmation of
successful transmission), or (ii) the date of receipt if sent by certified mail
or by overnight courier.

          6.10 Counterparts.  This Agreement may be executed in multiple
               ------------
counterparts, each of which shall be deemed an original and all of which taken
together shall constitute one and the same Agreement.

          6.11 Descriptive Heading; Interpretation.  The descriptive headings
               -----------------------------------
in this Agreement are inserted for convenience of reference only and are not
intended to be part of or to affect the meaning or interpretation of this
Agreement.

          IN WITNESS WHEREOF, the parties hereto have executed this Agreement as
of the day and year first above written.

          COMPANY:                 Pharmaceutical Product
                                   Development, Inc.

                                   By: /s/Fred B. Davenport, Jr.
                                      --------------------------
                                      Fred B. Davenport, Jr.
                                      Executive Vice President

          EMPLOYEE:                By: /s/Brainard Judd Hartman
                                      -------------------------
                                      Brainard Judd Hartman

                                       6

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