Document:

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EXHIBIT 10.21

  SECOND AMENDMENT TO NORTHWEST BIOTHERAPEUTICS, INC. LOAN AGREEMENT, SECURITY
             AGREEMENT AND 10% CONVERTIBLE, SECURED PROMISSORY NOTE

      THIS SECOND AMENDMENT TO NORTHWEST BIOTHERAPEUTICS, INC. LOAN AGREEMENT,
SECURITY AGREEMENT AND 10% CONVERTIBLE, SECURED PROMISSORY NOTE (the "SECOND
AMENDMENT") is made and entered into as of November 14, 2005, by and among
NORTHWEST BIOTHERAPEUTICS, INC., a Delaware corporation (the "MAKER") and Toucan
Capital Fund II, L.P. (the "HOLDER"). This Second Amendment amends the Note (as
defined below).

                                    RECITALS

A. Section 17.6 of that certain Northwest Biotherapeutics, Inc. Loan Agreement,
Security Agreement and 10% Convertible, Secured Promissory Note, in the
principal amount of $2,000,000.00 dated as of July 30, 2004, by and between the
Maker and the Holder in the form attached to this Second Amendment as Exhibit A
and as amended by that First Amendment to Northwest Biotherapeutics, Inc. Loan
Agreement, Security Agreement and 10% Convertible, Secured Promissory Note in
the form attached to this Second Amendment as Exhibit B (as so amended, the
"NOTE"), states that any provision of such note may be amended or waived in
writing by the Holder and the Maker; and

B. The Maker and the Holder wish to amend the Note as provided below.

                                    AGREEMENT

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

1. Section 1 of the Note is hereby amended to provide that the Maturity Date is
January 17, 2006.

2. All other terms and conditions of the Note shall be unaffected hereby and
remain in full force and effect.

3. This Second Amendment shall be governed by and construed under the laws of
the state of Delaware without giving effect to principles of conflicts of laws
of the State of Delaware or any other state.

                            [SIGNATURE PAGE FOLLOWS]

                                        1
<PAGE>

      IN WITNESS WHEREOF, the parties hereto have executed this SECOND AMENDMENT
TO NORTHWEST BIOTHERAPEUTICS, INC. LOAN AGREEMENT, SECURITY AGREEMENT AND 10%
CONVERTIBLE, SECURED PROMISSORY NOTE as of the date first above written.

MAKER:

NORTHWEST BIOTHERAPEUTICS, INC.,
a Delaware corporation

By: /s/ Alton L. Boynton
    ---------------------
Name: Alton L. Boynton
Title: President

HOLDER:

Toucan Capital Fund II, L.P.

By: /s/ Linda Powers
    ---------------------------------
      Linda Powers, Managing Director

259029 v2/RE

                                        2<PAGE>

EXHIBIT 10.22

  SECOND AMENDMENT TO NORTHWEST BIOTHERAPEUTICS, INC. LOAN AGREEMENT, SECURITY
             AGREEMENT AND 10% CONVERTIBLE, SECURED PROMISSORY NOTE

      THIS SECOND AMENDMENT TO NORTHWEST BIOTHERAPEUTICS, INC. LOAN AGREEMENT,
SECURITY AGREEMENT AND 10% CONVERTIBLE, SECURED PROMISSORY NOTE (the "SECOND
AMENDMENT") is made and entered into as of November 14, 2005, by and among
NORTHWEST BIOTHERAPEUTICS, INC., a Delaware corporation (the "MAKER") and Toucan
Capital Fund II, L.P. (the "HOLDER"). This Second Amendment amends the Note (as
defined below).

                                    RECITALS

A. Section 17.6 of that certain Northwest Biotherapeutics, Inc. Loan Agreement,
Security Agreement and 10% Convertible, Secured Promissory Note, in the
principal amount of $500,000.00 dated as of October 22, 2004, by and between the
Maker and the Holder in the form attached to this Second Amendment as Exhibit A
and as amended by that First Amendment to Northwest Biotherapeutics, Inc. Loan
Agreement, Security Agreement and 10% Convertible, Secured Promissory Note in
the form attached to this Second Amendment as Exhibit B (as so amended, the
"NOTE"), states that any provision of such note may be amended or waived in
writing by the Holder and the Maker; and

B. The Maker and the Holder wish to amend the Note as provided below.

                                    AGREEMENT

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

1. Section 1 of the Note is hereby amended to provide that the Maturity Date is
January 17, 2006.

2. All other terms and conditions of the Note shall be unaffected hereby and
remain in full force and effect.

3. This Second Amendment shall be governed by and construed under the laws of
the state of Delaware without giving effect to principles of conflicts of laws
of the State of Delaware or any other state.

                            [SIGNATURE PAGE FOLLOWS]

                                        1
<PAGE>

      IN WITNESS WHEREOF, the parties hereto have executed this SECOND AMENDMENT
TO NORTHWEST BIOTHERAPEUTICS, INC. LOAN AGREEMENT, SECURITY AGREEMENT AND 10%
CONVERTIBLE, SECURED PROMISSORY NOTE as of the date first above written.

MAKER:

NORTHWEST BIOTHERAPEUTICS, INC.,
a Delaware corporation

By: /s/ Alton L. Boynton
    ---------------------
Name: Alton L. Boynton
Title: President

HOLDER:

Toucan Capital Fund II, L.P.

By: /s/ Linda Powers
    ---------------------------------
      Linda Powers, Managing Director

259033 v2/RE

                                        2<PAGE>

EXHIBIT 10.23

   FIRST AMENDMENT TO NORTHWEST BIOTHERAPEUTICS, INC. LOAN AGREEMENT, SECURITY
             AGREEMENT AND 10% CONVERTIBLE, SECURED PROMISSORY NOTE

      THIS FIRST AMENDMENT TO NORTHWEST BIOTHERAPEUTICS, INC. LOAN AGREEMENT,
SECURITY AGREEMENT AND 10% CONVERTIBLE, SECURED PROMISSORY NOTE (the "FIRST
AMENDMENT") is made and entered into as of November 14, 2005, by and among
NORTHWEST BIOTHERAPEUTICS, INC., a Delaware corporation (the "MAKER") and Toucan
Capital Fund II, L.P. (the "HOLDER"). This First Amendment amends the Note (as
defined below).

                                    RECITALS

A. Section 17.6 of that certain Northwest Biotherapeutics, Inc. Loan Agreement,
Security Agreement and 10% Convertible, Secured Promissory Note, in the
principal amount of $500,000.00 dated as of November 10, 2004, by and between
the Maker and the Holder in the form attached to this First Amendment as Exhibit
A (the "NOTE"), states that any provision of such note may be amended or waived
in writing by the Holder and the Maker; and

B. The Maker and the Holder wish to amend the Note as provided below.

                                    AGREEMENT

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

1. Section 1 of the Note is hereby amended to provide that the Maturity Date is
January 17, 2006.

2. All other terms and conditions of the Note shall be unaffected hereby and
remain in full force and effect.

3. This First Amendment shall be governed by and construed under the laws of the
state of Delaware without giving effect to principles of conflicts of laws of
the State of Delaware or any other state.

                            [SIGNATURE PAGE FOLLOWS]

                                        1
<PAGE>

      IN WITNESS WHEREOF, the parties hereto have executed this FIRST AMENDMENT
TO NORTHWEST BIOTHERAPEUTICS, INC. LOAN AGREEMENT, SECURITY AGREEMENT AND 10%
CONVERTIBLE, SECURED PROMISSORY NOTE as of the date first above written.

MAKER:

NORTHWEST BIOTHERAPEUTICS, INC.,
a Delaware corporation

By: /s/ Alton L. Boynton
    --------------------
Name: Alton L. Boynton
Title: President

HOLDER:

Toucan Capital Fund II, L.P.

By: /s/ Linda Powers
    ---------------------------------
      Linda Powers, Managing Director

259038 v2/RE

                                        2<PAGE>

EXHIBIT 10.24

   FIRST AMENDMENT TO NORTHWEST BIOTHERAPEUTICS, INC. LOAN AGREEMENT, SECURITY
             AGREEMENT AND 10% CONVERTIBLE, SECURED PROMISSORY NOTE

      THIS FIRST AMENDMENT TO NORTHWEST BIOTHERAPEUTICS, INC. LOAN AGREEMENT,
SECURITY AGREEMENT AND 10% CONVERTIBLE, SECURED PROMISSORY NOTE (the "FIRST
AMENDMENT") is made and entered into as of November 14, 2005, by and among
NORTHWEST BIOTHERAPEUTICS, INC., a Delaware corporation (the "MAKER") and Toucan
Capital Fund II, L.P. (the "HOLDER"). This First Amendment amends the Note (as
defined below).

                                    RECITALS

A. Section 17.6 of that certain Northwest Biotherapeutics, Inc. Loan Agreement,
Security Agreement and 10% Convertible, Secured Promissory Note, in the
principal amount of $250,000.00 dated as of December 27, 2004, by and between
the Maker and the Holder in the form attached to this First Amendment as Exhibit
A (the "NOTE"), states that any provision of such note may be amended or waived
in writing by the Holder and the Maker; and

B. The Maker and the Holder wish to amend the Note as provided below.

                                    AGREEMENT

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

1. Section 1 of the Note is hereby amended to provide that the Maturity Date is
January 17, 2006.

2. All other terms and conditions of the Note shall be unaffected hereby and
remain in full force and effect.

3. This First Amendment shall be governed by and construed under the laws of the
state of Delaware without giving effect to principles of conflicts of laws of
the State of Delaware or any other state.

                            [SIGNATURE PAGE FOLLOWS]

                                        1
<PAGE>

      IN WITNESS WHEREOF, the parties hereto have executed this FIRST AMENDMENT
TO NORTHWEST BIOTHERAPEUTICS, INC. LOAN AGREEMENT, SECURITY AGREEMENT AND 10%
CONVERTIBLE, SECURED PROMISSORY NOTE as of the date first above written.

MAKER:

NORTHWEST BIOTHERAPEUTICS, INC.,
a Delaware corporation

By: /s/ Alton L. Boynton
    ----------------------
Name: Alton L. Boynton
Title: President

HOLDER:

Toucan Capital Fund II, L.P.

By: /s/ Linda Powers
    ----------------------------------
    Linda Powers, Managing Director

259039 v2/RE

                                        2

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