Document:

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                                                                   Exhibit 10.38

                            FIRST AMENDMENT TO LEASE

         WHEREAS, NEW BOSTON WILMAR LIMITED PARTNERSHIP (hereinafter referred to
as "Landlord") and ASCENT PEDIATRICS, INC. (hereinafter referred to as "Tenant")
entered into a certain lease of premises located at the building known and
numbered as 187 Ballardvale Street, Wilmington, Massachusetts, and dated
November 21, 1996 (hereinafter referred to as "Lease"); and

         WHEREAS, Landlord and Tenant now desire to amend the Lease.

         NOW THEREFORE, in consideration of the mutual covenants herein
contained, and other good and valuable consideration the receipt and sufficiency
of which are hereby acknowledged by both parties, it is agreed as follows:

         1. Section I of the Lease is amended by inserting the following
language at the end of the second paragraph thereof:

                  "Effective September 15, 1997, the premises shall also include
         approximately 4,542 square feet of net rentable area on the Second
         Floor of the Building, as more particularly shown as the cross-hatched
         area on Exhibit A-1 attached hereto and incorporated herein by
         reference (hereinafter referred to as the "Additional Space")."

         2. Section IV of the Lease is amended by inserting the following
language at the end of the first paragraph thereof:

                  "Effective September 15, 1997, Tenant shall pay rent with
         respect to the Additional Space at the annual rental rates set forth
         below:

<PAGE>   2

<TABLE>
<CAPTION>

                                                     PER SQUARE FOOT RENTAL RATE
                                                     ---------------------------
<S>                                                            <C>
      September 15, 1997 - September 30, 1998                  $16.50
      October 1, 1998 - September 30, 2000                     $17.00
      October 1, 2000 - February 28, 2002                      $17.50"
</TABLE>

         3. Section V(a) of the Lease is amended by inserting the following
language at the end thereof:

                  "Landlord shall do no work in or to the Additional Space to
         prepare the same for occupancy by Tenant, it being understood and
         agreed that Tenant accepts the same in their "as-is" condition. The
         taking of possession of the Additional Space by Tenant shall be
         conclusive evidence of the acceptance of the Additional Space by Tenant
         and the Additional Space is in good and satisfactory condition, in
         accordance with Landlord's obligations hereunder."

         4. Section XI(c) of the Lease is amended by inserting the following
language at the end thereof:

                  "Effective September 15, 1997, "Tenant's Proportionate Share"
         for taxes shall be eighteen and 20/100 percent (18.2%)."

         5. Section XI(i) of the Lease is amended by inserting the following
language after the first sentence thereof:

                  "Effective September 15, 1997, "Tenant's Proportionate Share
         for Operating Cost Escalation" shall be eighteen and 20/100 percent
         (18.2%)."

         6. Section XLIII of the Lease is amended by inserting the following
language at the end thereof:

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                  "Neither Landlord nor Tenant has dealt with any broker in
         connection with the transaction reflected in this Second Amendment to
         Lease, and each agrees to indemnify and hold the other harmless on
         account of any claims or demands for a brokerage commission as a result
         hereof."

         7. Section XLV of the Lease is amended by inserting the following
language at the end thereof:

                  "On or before September 15, 1997, Tenant shall increase the
         security deposit hereunder by Six Thousand Two Hundred Forty-Five
         Dollars ($6,245)."

         8. The Lease shall be amended by inserting the following language after
Section XLVIII thereof:

                  "SECTION XLIX. RIGHT OF FIRST OFFER. Provided Tenant is not in
         default of its obligations hereunder, Landlord shall provide Tenant
         with written notice (the "Right of First Offer Notice") if during the
         term of this lease that portion of the first floor of the Building and
         containing approximately 4,629 square feet of rentable area, as more
         particularly shown as the cross-hatched area on Exhibit O attached
         hereto and incorporated herein by reference, is or will become
         available for lease (the "First Offer Premises"). The Landlord's Right
         of First Offer Notice to Tenant shall set forth the premises' square
         footage, availability date, term, tenant improvement allowance, if any,
         and rental rate, which rental rate shall reflect the fair market rental
         value for such premises which Landlord would accept from a new tenant
         to lease the Premises as of the stated availability date. Tenant shall
         have five (5) business days following receipt of the Right of First
         Offer Notice to exercise its Right of First Offer, which Right of First
         Offer shall apply only with respect to the entire premises offered, and
         if Tenant shall fail to

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         exercise said Right of First Officer within said five (5) business
         day period, Tenant shall have waived its right to space offered and
         shall have no further right pursuant to this Section XLIX to said
         space for the remainder of the term of this lease, as it may be
         extended. In the event Tenant accepts the offer of any space pursuant
         to this Section XLIX, Landlord and Tenant shall execute an amendment to
         this lease, setting forth the terms and conditions for the lease by
         Tenant of the space so acquired.

                  "Notwithstanding the provisions of this Section XLIX, Landlord
         expressly reserves the right the right to renew, extend, amend or
         modify the lease of the existing tenant with respect to the First Offer
         Premises as it sees fit."

         9. This First Amendment to Lease is contingent upon Landlord entering
into a Lease Termination Agreement with Netcore Systems, Inc., with respect to
the Additional Space, effective September 14, 1997.

         10. Except as modified hereby the Lease is hereby ratified and
affirmed.

         IN WITNESS WHEREOF, the parties have set their hands and seals this
18th day of September 1997.

                                             LANDLORD:

                                             NEW BOSTON WILMAR
                                             LIMITED PARTNERSHIP

                                             By:   New Boston Fund, Inc.
                                                   Its General Partner

                                             By: /s/ Jerome L. Rappaport, Jr.
                                                --------------------------------
                                                   Jerome L. Rappaport, Jr.
                                                   Its President

                                      -4-
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                                             TENANT:

                                             ASCENT PEDIATRICS, INC.

                                             By: /s/ Alan R. Fox
                                                --------------------------------
                                                 Its President
                                      -5-

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                                   Exhibit A-1

                     [Diagram of floor plan of Second Floor
              of 187 Ballardvale Drive, Wilmington, Massachusetts]

                                      -6-<PAGE>   1
                                                                   Exhibit 10.13

                            BTU INTERNATIONAL, INC.

                       1988 EMPLOYEE STOCK PURCHASE PLAN

1. PURPOSE OF PLAN.

         This 1988 Employee Stock Purchase Plan (the "Plan") is intended to
provide a method by which eligible employees of BTU International, Inc. ("BTU")
and its participating subsidiaries (BTU and such subsidiaries being hereinafter
referred to as the "Company") may use voluntary, systematic payroll deductions
to purchase shares of BTU Common Stock ("Stock") and thereby acquire an interest
in the future of the Company. For purposes of the Plan, a subsidiary is any
corporation in which BTU owns, directly or indirectly, stock possessing 50% or
more of the total combined voting power of all classes of stock and which has
been designated by the Board (as defined in Section 16) as a participating
subsidiary.

2. OPTIONS TO PURCHASE STOCK

         Under the Plan, there is available an aggregate of not more than
100,000 shares of Stock (subject to adjustment as provided in Section 15) for
sale pursuant to the exercise of options ("options") granted under the Plan to
employees (within the meaning of Section 3401(c) of the Internal Revenue Code of
1986 (the "Code")) of the Company ("employees") who meet the eligibility
requirements set forth in Section 3 hereof ("eligible employees"). The Stock to
be delivered upon exercise of options under the Plan may be either shares of
BTU authorized but unissued Stock of shares of reacquired Stock, as the Board
shall determine.

3. ELIGIBLE EMPLOYEES

         Except as otherwise provided below, each employee who has completed six
months or more of continuous service in the employ of the Company shall be
eligible to participate in the Plan.

         (a)      Any employee who immediately after the grant of an option to
                  him would (in accordance with the provisions of Sections 423
                  and 425 (d) of the Code) own Stock possessing 5% or more of
                  the total combined voting power or value of all classes of
                  Stock of the employer corporation or of its parent or
                  subsidiary corporations, as defined in Section
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                  425 of the Code, shall not be eligible to receive an option to
                  purchase stock pursuant to the Plan.

         (b)      No employee shall be granted an option under the Plan which
                  would permit his rights to purchase shares of stock under all
                  employee stock purchase plans of the Company and any parent
                  and subsidiary corporations to accrue at a rate which exceeds
                  $25,000 in fair market value of such stock (determined at the
                  time the option is granted) for each calendar year during
                  which any such option granted to such employee is outstanding
                  at any time, as provided in Sections 423 and 425 of the Code.

         (c)      No employee shall be eligible to participate in the Plan
                  unless such employee's customary employment with the Company
                  is in excess of twenty hours in each week and in excess of
                  five months in each calendar year.

4. METHOD OF PARTICIPATION

         The period July 1, 1989 to December 31, 1989, and thereafter the
periods January 1 to June 30, and July 1 to December 31 of each year shall be
option periods. Each person who will be an eligible employee on the first day of
any option period may elect to participate in the Plan by executing and
delivering to BTU, at least 15 days prior to such day, a payroll deduction
authorization in accordance with Section 5. Such employee shall thereby become a
participant ("participant") on the first day of such option period and shall
remain a participant until his participation is terminated as provided in the
Plan.

5. PAYROLL DEDUCTION

         The payroll deduction authorization shall request withholding at a rate
of not less than 0.5% nor more than 10% (increasing in increments of 0.5%) from
the participant's Compensation by means of substantially equal payroll
deductions over the option period. For purposes of the Plan, "Compensation"
shall mean all regular base compensation paid to the participant by the Company
and currently includible in his gross income, including any withholding or
deductions, but excluding bonuses, commissions, incentive compensation and other
similar amounts. A participant may change the withholding rate of his payroll
deduction authorization by written notice delivered to BTU at least 15 days
prior to the first day of the option period as to which the change is to be
effective. All amounts withheld in accordance with a

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participant's payroll deduction authorization shall be credited to a withholding
account for such participant.

6. GRANT OF OPTIONS

         Each person who is a participant on the first day of an option period
shall as of such day be granted an option for such period. Such option shall be
for the number of whole shares of Stock to be determined by dividing (a) the
balance in the participant's withholding account on the last day of the option
period, by (b) the purchase price per share of the Stock determined under
Section 7. The Board shall reduce, on a substantially proportionate basis, the
number of shares of Stock receivable by each participant upon exercise of his
option for an option period in the event that the number of shares then
available under the Plan is otherwise insufficient.

7. PURCHASE PRICE

         The purchase price of Stock issued pursuant to the exercise of an
option shall be 85% of the fair market value of the Stock at (a) the time of
grant of the option or (b) the time at which the option is deemed exercised,
whichever is less. Fair market value shall mean the Closing Price of the Stock.
The "Closing Price" of Stock on any business day shall be the last sale price as
reported on the principal market on which the Stock is traded or, if no last
sale is reported, then the mean between the highest bid and lowest asked prices
on that day. A good faith determination by the Board as to fair market value
shall be final and binding.

8. EXERCISE OF OPTIONS

         If any employee is a participant in the Plan on the last business day
of an option period, he shall be deemed to have exercised the option granted to
him for that period. Upon such exercise, the Company shall apply the balance of
the participant's withholding account to the purchase of the number of whole
shares of Stock determined under Section 6 and as soon as practicable
thereafter, BTU shall issue and deliver certificates for said shares to the
participant. No fractional shares shall be issued hereunder. Any balance of a
participant's withholding account shall be returned to the participant, except
that any such balance representing a fractional share shall be retained in the
withholding account and applied to the next option period.

9. INTEREST.

         No interest will be payable on withholding accounts.

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10. CANCELLATION AND WITHDRAWAL

         A participant who holds an option under the Plan may at any time prior
to exercise thereof under Section 8 cancel all (but not less than all) of his
options by written notice delivered to BTU. Upon such cancellation, the balance
in his withholding account shall be returned to him in the month following
withdrawal.

         A participant may terminate his payroll deduction authorization as of
any date by written notice delivered to BTU and shall thereby cease to be a
participant as of such date. Any participant who voluntarily terminates his
payroll deduction authorization prior to the last business day of an option
period shall be deemed to have cancelled his option.

11. TERMINATION OF EMPLOYMENT

         Except as provided in the immediately following sentence, upon the
termination of a participant's service with the Company for any reason,
including without limitation death, retirement, resignation, layoff or
discharge, he shall cease to be a participant, and any option held by him under
the Plan shall be deemed cancelled, the balance of his withholding account shall
be returned to him, and he shall have no further rights under the Plan.
Notwithstanding the immediately preceding sentence, in the event that a
participant commences a leave of absence during an option period and such leave
of absence has been approved by the Board, such participant shall be eligible to
participate in the Plan with respect to such option period to the extent of
payroll deductions withheld during such option period.

12. LIMITATIONS ON RESALE

         The Plan is intended to provide to employees of BTU a favorable
opportunity to acquire shares of Stock at prices below the prevailing current
market price so that they will be able to participate as stockholders in BTU,
and this purpose would not be furthered if participants disposed of Stock
acquired pursuant to the Plan immediately after its acquisition. Therefore, no
participant shall sell or otherwise dispose of any Stock acquired pursuant to
the Plan if such disposition would occur within the period beginning at the end
of the option period with respect to which such Stock was acquired and ending on
the date six months later unless such participant notifies BTU in writing of
such intended disposition and the number of shares of Stock of which such
participant intends to dispose and unless such notice is received by BTU not
less than 15 days prior to such intended disposition. Upon receipt of such
notice, BTU shall automatically have the option, exercisable at any time prior

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to the fifteenth day after such notice has been received by BTU, to repurchase
from such participant the number of shares of Stock specified in such notice at
a price per share equal to the price at which such participant acquired such
shares from BTU pursuant to the Plan. No interest will be payable on any amounts
so paid by BTU to any participant. Each certificate representing shares of Stock
delivered pursuant to the Plan shall bear an appropriate legend to give notice
of the restrictions on transfer contained in this Section 12.

13. PARTICIPANT'S RIGHTS NOT TRANSFERABLE

         All participants granted options under the Plan shall have the same
rights and privileges, and each participant's rights and privileges under any
option granted under the Plan shall be exercisable during his lifetime only by
him, and shall not be sold, pledged, assigned, or transferred in any manner. In
the event any participant violates the terms of this Section, any options held
by him may be terminated by the Company and upon return to the participant of
the balance of his withholding account, all his rights under the Plan shall
terminate.

14. EMPLOYMENT RIGHTS

         Nothing contained in the provisions of the Plan shall be construed to
give to any employee the right to be retained in the employ of the Company or to
interfere with the right of the Company to discharge any employee at any time;
nor shall it be construed to give the Company the right to require any employee
to remain in its employ or to interfere with any employee's right to terminate
his employment at any time.

15. CHANGE IN CAPITALIZATION

         In the event of any change in the outstanding Stock of BTU by reason of
a stock dividend, split-up, recapitalization, merger, consolidation,
reorganization, or other capital change, the aggregate number and class of
shares available under the Plan and the number and class of shares under option
but not exercised, the option price, and the share limit provided for in Section
6 shall be appropriately adjusted.

16. ADMINISTRATION OF PLAN

         The Plan shall be administered by the Board of Directors of BTU (the
"Board"), which shall have the right to determine any questions which may arise
regarding the interpretation and application of the provisions of the Plan and
to make, administer, and interpret such rules and regulations as it shall deem
necessary or advisable.

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