<PAGE>

                                                               Exhibit 10.26.1

                 LEASE MODIFICATION AGREEMENT

         LEASE MODIFICATION AGREEMENT dated as of the 5th day of April 2000
between 224 West 30 LLC, having an office in care of C & K Properties, Pier
40; West Houston & West Streets, New York, New York 10014 (hereinafter
referred to as "Owner") and Medscape, Inc., a Delaware corporation, having an
office at 224 West 30th Street, New York, New York 10001 (hereinafter
referred to as "Tenant")

                         WITNESSETH:

         WHEREAS, Owner and Tenant entered into that certain Loft Lease
agreement dated as of February 8, 2000, covering certain commercial loft
space more particularly described in said Loft Lease agreement (the "Demised
Premises") in the building known as 224 West 30th Street, New York, New York
("the Building"), under the terms and conditions contained therein
(hereinafter referred to as the "Loft Lease"); and

         WHEREAS, Tenant desires to add to the Demised Premises the entire
third (3rd) floor of the Building, approximately as indicated on the location
plan annexed hereto and made a part hereof, the rentable square foot area of
which Owner and Tenant acknowledge and agree shall be deemed to be 11,286
rentable square feet (the "3rd Floor Additional Space); and

         WHEREAS, Tenant and Owner wish to modify the Loft Lease as set forth
below;

         NOW, THEREFORE, in consideration of the premises and the mutual
covenants contained herein, the parties agree as follows:

    1.   ADDITION OF SPACE. A. The 3rd Floor Additional Space is hereby added
to the Demised Premises effective as of June 1, 2000 (the A3rd Floor
Additional Space

<PAGE>

Commencement Date) under the same terms, covenants and conditions of the
Loft Lease, except as specifically modified by this agreement and except for
Articles 48, 61, 64 and 65 of the Lease which shall not apply to this
agreement or the 3rd Floor Additional Space. Tenant acknowledges and agrees
that the 3rd Floor Additional Space is presently occupied by another tenant
of the Building (the "Existing Tenant"), who has agreed to surrender and
vacate the 3rd Floor Additional Space on or before May 31, 2000, in
accordance with a surrender agreement with Owner. Owner and Tenant agree that
if the Existing Tenant does not surrender and vacate the 3rd Floor Additional
Space on or before May 31, 2000, and as a result Owner is unable to deliver
possession of the 3rd Floor Additional Space to Tenant as required by this
agreement, then Owner shall not be subject to any liability for such failure,
and this agreement shall remain in full force and effect without extension of
the term of the Lease, however, Tenant's obligation to pay rent and
additional rent hereunder for such portion of the 3rd Floor Additional Space
which has not been delivered by Owner shall not commence and that part of any
rent credits to which Tenant is entitled hereunder and which is allocable to
such portion of the 3rd Floor Additional Space shall be similarly delayed
until possession thereof is delivered to Tenant, subject to the provisions of
Article 24 of the Lease. In the event of such a failure by the Existing
Tenant to surrender and vacate all or a portion of the 3rd Floor Additional
Space, Owner shall promptly commence and diligently prosecute to completion
appropriate summary proceedings in order to evict the Existing Tenant
therefrom and recover lawful possession thereof. In such event, upon Owner's
recovery of actual and lawful possession thereof, Owner shall furnish Tenant
with notice to that effect and deliver possession to Tenant promptly
thereafter, at which point Tenant's obligation to pay rent and additional
rent, to the extent

                                       2

<PAGE>

delayed pursuant to the provisions of this Article, shall commence and any
rent credits to which Tenant is entitled hereunder shall commence as well.

     B.    Effective as of the 3rd Floor Additional Space Commencement Date
in order to reflect the addition of the 3rd Floor Additional Space to the
Demised Premises: (1) the fixed annual rent payable under the Loft Lease
(exclusive of electricity) shall be increased by the sum of:

(a) $327,294.00 per annum for the period from the 3rd Floor Additional Space
Commencement Date through January 31, 2001 and (b) by the sum of $342,022.23
per annum for the period from February 1, 2001 through January 31, 2002 and
(c) by the sum of $357,413.23 per annum for the period from February 1, 2002
through January 31, 2003 and (d) by the sum of $373,496.83 per annum for the
period from February 1, 2003 through January 31, 2004 and (e) by the sum of
$390,304.18 per annum for the period from February 1, 2004 through January
31, 2005; and (2) Tenant's Share, as defined in Article 53 of the Loft Lease,
shall be amended and increased by seven and eight tenths (7.8%) percent to
forty-one and eight tenths (41.8%) percent; and (3) the deemed rentable
square foot area of the Demised Premises shall be amended and increased by
11.286 deemed rentable square feet to 60,462 deemed rentable square feet for
purposes of the Loft Lease including, without limitation, Articles 53 and 62
thereof; and (4) it shall be a material obligation of Tenant under this
agreement and the Lease that it shall increase the security deposited with
Landlord pursuant to Article 32 of the Lease by means of cash payment in the
sum of $109,098.00 to be delivered to Owner upon execution and delivery of
this agreement by Tenant, to be held by Owner in accordance with the
provisions of said Article 32 of the Lease, in

                                       3
<PAGE>

order that the aggregate amount of security deposited with Landlord shall
thereafter be the sum of $446,842.00.

           2.    CONDITION OF 3RD FLOOR ADDITIONAL SPACE. Tenant expressly
acknowledges that it has inspected the 3rd Floor Additional Space and is
fully familiar with the physical condition thereof. Tenant agrees to accept
the 3rd Floor Additional Space as of the 3rd Floor Additional Space
Commencement Date in its then "as is" condition. Owner shall have no
obligation to do any work in or to the 3rd Floor Additional Space in order to
make them suitable and ready for occupancy and use by Tenant other than the
work expressly set forth below which Owner shall perform with reasonable
dispatch, subject to delay by causes beyond its control or by the action or
inaction of Tenant:

           (i)   demolish and remove the existing interior installation and
                 build-out throughout the 3rd Floor Additional Space within
                 thirty (30) days after Owner's recovery of lawful possession
                 thereof; and

           (ii)  obtain and deliver to Tenant a form ACP-5 with respect to
                 the 3rd Floor Additional Space; and

           (iii) furnish and install, at Owner's sole cost and expense within
                 ninety (90) days after Owner's delivery of possession of the
                 3rd Floor Additional Space to Tenant, new windows in the 3rd
                 Floor Additional Space in a building standard manner using
                 building standard materials in accordance with Owner's ongoing
                 Building window replacement program.

     The performance by Owner of the above work ("Owner's 3rd Floor
Additional Space Work") is expressly conditioned upon compliance by Tenant
with all the terms and conditions of the Lease, as amended hereby, including
payment of rent.

     B.    Any changes in or additions to the work and installations
mentioned in Section A above which shall be consented to by Owner as provided
in Article 7 of the Lease, and further changes in or additions to the 3rd
Floor Additional Space after said Owner's 3rd Floor


                                       4
<PAGE>

Additional Space Work has been completed, if so consented to by Owner and if
made at Tenant's request by Owner or its agents, shall be paid for by Tenant
promptly when billed at cost plus 10% for insurance and overhead and plus 10%
for profit, and in the event of the failure of Tenant so to pay for said
changes or additions, Owner at its option may consider the cost thereof, plus
the above percentages, as additional rent payable by Tenant and collectible
as such hereunder, as part of the rent for the next ensuing months.

     C.    Owner agrees to use reasonable efforts to complete Owner's 3rd
Floor Additional Space Work on or before June 15, 2000, subject to acts or
omissions of Tenant and causes beyond Owner's reasonable control. Owner's
failure to complete Owner's 3rd Floor Additional Space Work on or before June
15, 2000 shall not entitle Tenant to any abatement or set-off of any monies
due under the Loft Lease or to cancel the Loft Lease or this agreement. In
the event that Owner shall not have delivered to Tenant possession of the 3rd
Floor Additional Space on or before September 1, 2000, Tenant may within
thirty (30) days thereafter unequivocally and unconditionally notify Owner
that Tenant elects to terminate and cancel this agreement effective as of the
date which is thirty (30) days after the delivery of Tenant's notice (the "3rd
Floor Additional Space Cancellation Date") provided, however, that the 3rd
Floor Additional Cancellation Date shall be extended by one (1) day for each
day of delay in Owner's delivery of the 3rd Floor Additional Space which is
due to any acts or omissions by Tenant. If Tenant duly exercises this option,
this agreement shall be cancelled on the 3rd Floor Additional Cancellation
Date and neither Owner nor Tenant shall have any further liability hereunder
except that the representations and indemnifications contained in Article 9
hereof shall survive and any security deposited with Owner hereunder shall be
returned to Tenant. Notwithstanding the


                                       5
<PAGE>

foregoing, however, in the event that Owner shall give Tenant notice that the
3rd Floor Additional Space shall be delivered to Tenant prior to the 3rd
Floor Additional Space Cancellation Date, and provided same occurs prior to
the 3rd Floor Additional Space Cancellation Date then, in such event, Owner's
notice shall negate and nullify Tenant's notice.

     D.    If the substantial completion of Owner's 3rd Floor Additional
Space Work is delayed by acts, omissions or changes made or requested by
Tenant, its agents, designers, architects or any other party acting or
apparently acting on Tenant's behalf, then Tenant shall pay as hereinbefore
provided rent and additional rent on a per diem basis for each day of delay
of Owner's substantial completion caused by Tenant or any of the
aforementioned parties.

     E.    Owner's 3rd Floor Additional Space Work shall be deemed to be
substantially completed notwithstanding that (i) minor or non-material
details of construction, mechanical adjustment or decoration ("Punch List
Items") remain to be performed, provided that said Punch List Items shall be
completed by Owner within a reasonable time thereafter or (ii) a portion of
Owner's 3rd Floor Additional Space Work is incomplete because construction
scheduling requires that such work be done after incomplete finishing or
after other work to be done by or on behalf of Tenant is completed.

     F.    Any failure by Owner to complete Owner's 3rd Floor Additional
Space Work within any time period provided for in this Article shall not
entitle Tenant to any abatement or set-off of rent or additional rent or to
cancel the Lease or this agreement, or to make any claim for damages as a
result thereof unless caused by the willful misconduct of Owner.


                                       6

<PAGE>

    3. RENT COMMENCEMENT. A. Tenant's obligation to pay fixed annual rent
under this agreement for the 3rd Floor Additional Space shall commence on a
date (the "3rd Floor Additional Space Rent Commencement Date") which shall be
the earlier of:

             (1) the date that Owner delivers to Tenant possession of the 3rd
Floor Additional Space with Owner's 3rd Floor Additional Space Work as set
forth in Article 2, Section A hereof substantially complete; or

             (2) the date that Tenant first occupies the 3rd Floor Additional
Space for either (a) the conduct of its business in accordance with the terms
hereof or (b) the commencement of any initial alteration work to be performed
by Tenant, at its sole cost and expense, in order to prepare the 3rd Floor
Additional Space for the conduct of Tenant's business.

        B. When the 3rd Floor Additional Space Rent Commencement Date has
occurred, Tenant, upon the request of Owner, shall execute a statement
prepared by Owner, fixing the 3rd Floor Additional Space Rent Commencement
Date unless Tenant disputes the correctness thereof. Any failure of Tenant to
execute such statement shall not affect the 3rd Floor Additional Space Rent
Commencement Date as determined by Owner.

        C. Tenant expressly waives any right to rescind this agreement under
Section 223-a of the New York Real Property Law or under any present or
future statute of similar import then in force and further expressly waives
the right to recover any damages, direct or indirect, which may result from
Owner's failure to deliver possession of the 3rd Floor Additional Space on a
date certain. Tenant agrees that the provisions of this Article, Article 2 of
this agreement and Article 24 of the Lease are intended to constitute "an
express provision to the contrary" within the meaning of said New York Real
Property Law Section 223-a.

                                       7

<PAGE>

    4. RENT CREDIT. A. If and so long as Tenant is not in default under the
Loft Lease after notice and beyond any grace period, in addition to the rent
credit currently provided for therein, Tenant shall be entitled to a further
rent credit in the sum of $81,823.50, to be applied in equal monthly
increments, each in the sum of $13,637.25, against the first six (6) full
monthly installments of fixed annual rent (without electricity) accruing
under the Loft Lease from and after the 3rd Floor Additional Space
Commencement Date.

         B. Anything contained hereinabove to the contrary notwithstanding,
if Tenant at any time during the term of this Loft Lease, breaches any
covenant, condition or provision of this Loft Lease and fails to cure such
breach within any applicable grace period, and provided that this Loft Lease
is terminated by Owner because of such default, then, in addition to all
other damages and remedies herein provided and to which Owner may be
otherwise entitled, Owner shall also be entitled to the repayment in full of
any rent credit theretofore enjoyed by Tenant, which repayment Tenant shall
make upon demand therefor.

    5. SUCCESSORS/ASSIGNS. This agreement shall be binding upon and inure to
the benefit of the parties and their respective successors and permitted
assigns.

    6. ENTIRE AGREEMENT.

         A. This agreement represents the entire understanding between the
parties with regard to the matters addressed herein and may only be modified
by written agreement executed by all parties hereto. All prior understandings
or representations between the parties hereto, oral or written, to the extent
that they pertain to the matters addressed herein, are hereby merged herein.

                                      8

<PAGE>

         B. Tenant acknowledges that neither Owner nor any representative or
agent of Owner has made any representation or warranty, express or implied,
as to the physical condition, state of repair, layout, footage or use of the
Demised Premises or any matter or thing affecting or relating to the Demised
Premises except as specifically set forth in this Agreement. Tenant has not
been induced by and has not relied upon any statement, representation or
agreement, whether express or implied, not specifically set forth in this
agreement. Tenant shall not be liable or bound in any manner by any oral or
written statement, broker's "set-up", representation, agreement or
information pertaining to the Demised Premises or this agreement furnished by
any real estate broker, agent, servant, employee or other person, unless
specifically set forth herein, and no rights are or shall be acquired by
Tenant by implication or otherwise unless expressly set forth herein.

    7. EFFECTIVENESS. This agreement shall not be binding upon Owner until
executed and delivered by both Owner and Tenant.

    8. RATIFICATION. Except as specifically modified herein, all other terms,
covenants and conditions of the Loft Lease are and shall remain in full force
and effect and are hereby ratified and confirmed.

    9. NO BROKERS/INDEMNIFICATION: Tenant warrants that it has not dealt with
any broker, agent or finder in connection with the 3rd Floor Additional Space
and that no broker, finder or consultant participated in procuring this
agreement other than Harry Krausman of Colliers/ABR, Inc. and Sam Gavish of
SAG, Inc., each of whom acted solely as consultants to Tenant ("Tenant's
Consultants"). Tenant warrants to Owner that it shall pay any fee due to
Tenant's Consultants, in accordance with the terms of separate agreements
with each of them.


                                       9

<PAGE>

Tenant hereby indemnifies and agrees to defend and hold Owner, its agents,
servants and employees harmless from any suit, action, proceeding,
controversy, claim or demand whatsoever at law or in equity that may be
instituted against Owner by anyone who claimed to have dealt with Tenant for
recovery of compensation or damages for procuring this Agreement or by reason
of a breach or purported breach of the representations and warranties
contained herein.

    10.  MISCELLANEOUS.

         A. The captions in this agreement are for convenience only are not
to be considered in construing this agreement.

         B. This agreement shall be construed without regard to any
presumption or other rule requiring construction against the party causing
this agreement to be drafted.

         C. Terms used in this agreement and not otherwise defined herein
shall have the respective meanings ascribed thereto in the Loft Lease.

         D. If any provision of this agreement or its application to any
person or circumstances is invalid or unenforceable to any extent, the
remainder of this agreement, or the applicability of such provision to other
persons or circumstances, shall be valid and enforceable to the fullest
extent permitted by law and shall be deemed to be separate from such invalid
or unenforceable provisions and shall continue in full force and effect.

IN WITNESS WHEREOF, the parties hereto have executed this agreement as of the
date first set forth above.

224 WEST 30 LLC                            MEDSCAPE, INC.

By:  /s/ Ben Korman                        By: /s/ Peter Frishauf
   ----------------                          --------------------
   Ben Korman    Managing Partner          Peter Frishauf - Chairman and Founder
    (Name)         (Title)


                                        10