Document:

<PAGE>

                                                                 EXHIBIT 10.13.1

                   AMENDMENT NO. 1 TO STOCK PURCHASE AGREEMENT

      This Amendment No. 1 to Stock Purchase Agreement dated as of October 25,
2004 (the "Amendment") amends the Stock Purchase Agreement (the "Agreement")
dated as of September 30, 2003 among ViaCell, Inc. ("ViaCell"), Kourion
Therapeutics AG (the "Company") and the Sellers party thereto (the "Sellers").
Capitalized terms used but not defined herein shall have the meanings given to
them in the Agreement.

      WHEREAS, ViaCell, the Company and the Sellers are parties to the Agreement
pursuant to which ViaCell purchased all of the outstanding shares of capital
stock of the Company on the terms set forth in the Agreement;

      WHEREAS, ViaCell, the Company and the Sellers have each acknowledged and
agreed, and further acknowledge and agree by their execution of this Amendment,
that the Agreement contains an error regarding the release of the Escrowed
Shares and the issuance of the Contingent Shares and did not at the time of
execution reflect the intention of the parties to the Agreement;

      NOW THEREFORE, the parties to this Amendment agree as follows:

      1.    Amendments to Agreement.

            a.    The definition of "Qualified Public Offering" in Section 1 of
                  the Agreement is hereby deleted in its entirety and replaced
                  with the following:

      "Qualified Public Offering" shall mean a firm commitment underwritten
initial public offering of the common stock of ViaCell at a price per share of
at least $9.70 (as appropriately adjusted to reflect any conversion of preferred
stock into common stock, any stock splits or combinations, or any declaration of
dividends or distributions or other similar recapitalization) in which the net
proceeds received by ViaCell equal or exceed $50 million.

      2.    Miscellaneous.

            a.    Except as modified hereby, ViaCell, the Company and the
                  Sellers acknowledge that the Agreement shall continue in full
                  force and effect in accordance with its terms.

            b.    This Amendment may be executed in any number of counterparts,
                  each of which will be deemed an original, but all of which
                  together will constitute but one and the same instrument. This
                  Amendment will become effective when duly executed by each
                  party hereto.
<PAGE>
      IN WITNESS WHEREOF, each of the undersigned has executed this Amendment as
an agreement under seal as of the date first above written.

  THE BUYER:                                 VIACELL, INC.

                                             By: /s/ Marc Beer
                                                ________________________________
                                                 Name:  Marc Beer
                                                 Title: CEO

  THE COMPANY:                               KOURION THERAPEUTICS AG

                                             By: /s/ Stephan Wnendt
                                                ________________________________
                                                 Name:  Stephan Wnendt
                                                 Title:

                   [SELLER SIGNATURES TO FOLLOW ON NEXT PAGE]
<PAGE>
  THE SELLERS:                             MPM BIOVENTURES II, L.P.

                                           By:    MPM Asset Management II, L.P.,
                                                  its General Partner
                                           By:    MPM Asset Management II LLC,
                                                  its General Partner

                                           By: /s/ Ansbert Gadicke
                                               _________________________________
                                                 Name:  Ansbert Gadicke
                                                 Title:    Manager

                                           MPM BIOVENTURES II-QP, L.P.

                                           By:    MPM Asset Management II, L.P.,
                                                  its General Partner
                                           By:    MPM Asset Management II LLC,
                                                  its General Partner

                                           By: /s/ Ansbert Gadicke
                                               _________________________________
                                                  Name:  Ansbert Gadicke
                                                  Title:    Manager

                                           MPM BIOVENTURES GMBH & CO.
                                             PARALLEL-BETEILIGUNGS KG

                                           By:    MPM Asset Management II, L.P.,
                                                  in its capacity as the
                                                  Special Limited Partner
                                           By:    MPM Asset Management II LLC,
                                                  its General Partner

                                           By: /s/ Ansbert Gadicke
                                               _________________________________
                                                  Name:  Ansbert Gadicke
                                                  Title:    Manager

                                           MPM ASSET MANAGEMENT INVESTORS
                                             2001 BVII LLC

                                           By: /s/ Ansbert Gadicke
                                               _________________________________
                                                 Name:  Ansbert Gadicke
                                                 Title:    Manager
<PAGE>
                                                        Amendment Signature Page

                                           MPM FOUNDERS LLC

                                           By: /s/ Ansbert Gadicke
                                               _________________________________
                                                 Name:  Ansbert Gadicke
                                                 Title:    Member
<PAGE>
                                                        Amendment Signature Page

                                           KOURION RM (REGENERATIVE MEDIZIN)
                                           GMBH

                                           By:  /s/ Peter Wernet
                                              __________________________________
                                                Name:  Peter Wernet
                                                Title:  Founder

                                           PHILIP COELHO

                                           By:  /s/ Philip Coelho
                                              __________________________________
                                                Name:  Philip Coelho

                                           DR. JOHANNES FISCHER

                                           By:  /s/ Stephan Wnendt
                                              __________________________________
                                                Name:  Dr. Stephan Wnendt
                                                Title:  Seller's Representative

                                           IRK-VERMOGENSVERWALTUNGS GMBH

                                           By:  /s/ Stephan Wnendt
                                              __________________________________
                                                Name:  Dr. Stephan Wnendt
                                                Title:  Seller's Representative

                                           TTHU TECHNOLOGIETRANSFER HEINRICH-
                                           HEINE-UNIVERSITAT GMBH

                                           By:  /s/ Stephan Wnendt
                                              __________________________________
                                                Name:  Dr. Stephan Wnendt
                                                Title:  Seller's Representative
<PAGE>
                                                        Amendment Signature Page

                                           GESELLSCHAFT VON FREUNDEN UND
                                           FORDERERN AN DER HEINRICH-HEINE-
                                           UNIVERSITAT DUSSELDORF E.V.

                                           By:  /s/  Dr. Stephan Wnendt
                                              _________________________________
                                                Name:  Dr. Stephan Wnendt
                                                Title:  Seller's Representative

                                           DR. ANDREAS KNIPPER

                                           By:  /s/  Dr. Stephan Wnendt
                                              _________________________________
                                                Name:  Dr. Stephan Wnendt
                                                Title:  Seller's Representative

                                           DR. HANS-DIETER ROYER

                                           By:  /s/  Dr. Stephan Wnendt
                                              _________________________________
                                                Name:  Dr. Stephan Wnendt
                                                Title:  Seller's Representative<PAGE>
                                                                 Exhibit 10.26.1

                           FIRST AMENDMENT TO SUBLEASE

      This First Amendment to Sublease, dated as of February 14, 2003 (this
"First Amendment"), is by and between ARIAD Corporation, a Delaware corporation
("Sublandlord"), with a place of business at 26 Landsdowne Street, Cambridge,
Massachusetts 02139, and ViaCell, Inc., a Delaware corporation ("Subtenant")
with an address of 131 Clarendon Street, 3rd Floor, Boston, MA 02116.

                              PRELIMINARY STATEMENT

      By Lease dated January 8, 1992 ("Original Lease"), ARIAD Pharmaceuticals,
Inc. leased from Forest City Cambridge, Inc. ("Prime Landlord") approximately
100,361 rentable square feet of space in the building known as The Jackson
Building, having a street address of 26 Landsdowne Street, Cambridge,
Massachusetts ("Building"). The Prime Lease Premises (defined below) are more
particularly described in the Prime Lease (defined herein).

      ARIAD Pharmaceuticals, Inc. assigned its interest in the Original Lease to
Sublandlord, which assignment was executed on October 19, 1992, and recorded
with the Middlesex County Southern District Registry of Deeds in Book 22527,
Page 581, and filed with the Middlesex County Southern Registry District of the
Land Court as Document No. 888025 noted on Certificate of Title No. 157415.

      The Original Lease as amended by the First and the Second Amendments to
Lease, each dated May 12, 1994, the Third Amendment to Lease, dated June 1,
1994, a letter agreement dated December 16, 1996 (the Fourth Amendment to
Lease), a letter agreement dated July 31, 1998 (the Fifth Amendment to Lease),
the Sixth Amendment to Lease, dated December 31, 1999, and the Seventh Amendment
to Lease, dated June 1, 2001, as amended by Letter dated October 2, 2001, as the
same may from time to time be further amended and supplemented, are hereinafter
referred to collectively as the "Prime Lease." All of the space in the Building
that is now or hereafter leased by Sublandlord pursuant to the Prime Lease is
hereinafter referred to as the "Prime Lease Premises."

      Pursuant to that certain Sublease dated November 1, 2001 (the "Sublease"),
Sublandlord leased to Subtenant a portion of the Prime Lease Premises which
comprises approximately 3,226 rentable square feet of laboratory space on the
fifth floor of the Building and is known as and numbered Suite 580 (the "Sublet
Premises"). The expiration date of the Sublease is April 30, 2003 (the "Sublease
Expiration Date").

      Sublandlord and Subtenant desire to extend the Sublease Expiration Date to
April 30, 2004.

      Capitalized terms used in this First Amendment to Sublease and not
otherwise defined in the Sublease shall have the meanings established in the
Prime Lease.
<PAGE>
      NOW, THEREFORE, in consideration of the mutual covenants and agreements
set forth below, and for other good and valuable consideration, the receipt and
sufficiency of which are hereby acknowledged, the parties hereto covenant and
agree as follows:

      1. Extended Sublease Expiration Date/Increased Additional Rent.
Sublandlord and Subtenant hereby extend the Sublease Expiration Date from April
30, 2003 to April 30, 2004 (the "Extended Sublease Expiration Date"). The period
from May 1, 2003 through and including the Extended Sublease Expiration Date
shall be referred to as the "Extended Sublease Term," which Extended Sublease
Term shall be on all of the same terms and conditions as the Sublease; provided,
however, that during the Extended Sublease Term, Subtenant's monthly additional
rent amount payable by Subtenant to Sublandlord pursuant to Section 4(b) of the
Sublease shall be increased from $8,825.28 to $9,225.28. In addition, Subtenant
agrees to reimburse Sublandlord, within ten (10) days following presentation to
Subtenant of an invoice therefor, for the cost of maintaining a service
agreement for the chilling equipment previously installed for Subtenant's
benefit, which cost to Subtenant shall not exceed the sum of $2,000.00 in any
twelve-month period.

      2. Brokers. Each of Sublandlord and Subtenant warrants and represents that
such party has not dealt with any broker in connection with the consummation of
this First Amendment; and in the event any claim is made against either party by
any other broker or agent alleging dealings with the representing party, the
party against whom the claim is made shall defend, save harmless and indemnify
the other on account of any loss, cost, damage and expense (including, without
limitation, reasonable attorneys' fees and disbursement) which may be suffered
or incurred by the indemnified party by reason of such claim.

      3. Costs. At the time of execution of this First Amendment, Subtenant
agrees to pay to Sublandlord a sum equal to Sublandlord's legal fees incurred in
connection with the preparation of this First Amendment, which cost shall not
exceed $3,000.

      4. EFFECT OF AMENDMENT. Except as set forth herein, the Sublease shall
remain unchanged and in full force and effect. All references to the "Sublease"
shall be deemed to be references to the Sublease as amended by this First
Amendment.

      5. CONSENT OF PRIME LANDLORD. This First Amendment to Sublease is
expressly conditioned upon Sublandlord and Subtenant first obtaining the prior
written consent of Prime Landlord pursuant to the terms of the Prime Lease.

                            Signatures on next page.

                                      -2-
<PAGE>
      EXECUTED in one or more counterparts by persons or officers hereunto duly
authorized as of the date and year first above written.

                                            SUBLANDLORD:
                                            ARIAD Corporation

Attest: /s/ Kervie Kneeland                 By: /s/ Edmond M. Fitzgerald
       ---------------------------------       ---------------------------------
       Name:  Kervie Kneeland               Name:  Edmond M. Fitzgerald
       Title: Assistant to Edward           Title: Chief Financial Officer
              Fitzgerald

                                            SUBTENANT:
                                            ViaCell, Inc.

Attest:                                     By: /s/ Jeffrey A. Sacher
       ---------------------------------       ---------------------------------
       Name:                                Name:  Jeffrey A. Sacher
       Title:                               Title: CFO

Source: [{"source": "alea-institute/alea-institute/kl3m-data-edgar-agreements/train-00073-of-00352.parquet"}, [{"source": "alea-institute/alea-institute/kl3m-data-edgar-agreements/train-00073-of-00352.parquet"}]]