<DOCUMENT>
<TYPE>EX-4
<SEQUENCE>2
<FILENAME>s11-7783_ex41.txt
<DESCRIPTION>EXHIBIT 4.1
<TEXT>
                                                                     Exhibit 4.1

                                PROMISSORY NOTE

<TABLE>
<CAPTION>
======================= ================ ============== =============== ================= =================== ========= ===========
<S>                     <C>              <C>            <C>             <C>               <C>                 <C>       <C>
        Principal           Loan Date       Maturity        Loan No         Call / Coll          Account       Officer    Initials
       $500,000.00         09-27-2007      03-30-2010        200744             07               123186          029
======================= ================ ============== =============== ================= =================== ========= ===========

====================================================================================================================================
References in the boxes above are for Lender's use only and do not limit the
applicability of this document to any particular loan or item. Any item above
containing "***" has been omitted due to text length limitations.
====================================================================================================================================
</TABLE>

Borrower:   PIPEX PHARMACEUTICALS, INC. (TIN:     Lender:  Bank of Ann Arbor
            13-3808303)                                    Main Office
            3985 Research Park Dr.                         125 S. Fifth Avenue
            Ann Arbor, MI 48108                            Ann Arbor, MI 48104
                                                           (734) 662-1600

Principal Amount:               Initial Rate:                    Date of Note:
   $500,000.00                      9.750%                    September 27, 2007

PROMISE TO PAY. PIPEX PHARMACEUTICALS, INC. ("Borrower") promises to pay to Bank
of Ann Arbor  ("Lender"),  or order,  in lawful  money of the  United  States of
America,  the  principal  amount  of Five  Hundred  Thousand  &  00/100  Dollars
($500,000.00),  together  with  interest on the unpaid  principal  balance  from
September 27, 2007, until paid in full.

PAYMENT.  Subject to any payment  changes  resulting  from changes in the Index,
Borrower will pay this loan in 29 principal  payments of $16,667.00 each and one
final principal and interest  payment of $16,792.34.  Borrower's first principal
payment is due October 30, 2007, and all subsequent  principal  payments are due
on the same day of each month after that. In addition, Borrower will pay regular
monthly  payments of all accrued  unpaid  interest due as of each payment  date,
beginning  October 30, 2007, with all subsequent  interest payments to be due on
the same day of each month after that.  Borrower's  final  payment due March 30,
2010,  will be for all principal and all accrued  interest not yet paid.  Unless
otherwise  agreed or required by applicable law,  payments will be applied first
to any accrued unpaid interest; then to principal; then to any unpaid collection
costs;  and then to any late charges.  The annual interest rate for this Note is
computed  on a 365/360  basis;  that is,  by  applying  the ratio of the  annual
interest rate over a year of 360 days,  multiplied by the outstanding  principal
balance,  multiplied  by the  actual  number of days the  principal  balance  is
outstanding. Borrower will pay Lender at Lender's address shown above or at such
other place as Lender may designate in writing.

VARIABLE INTEREST RATE. The interest rate on this Note is subject to change from
time to time  based on  changes in an index  which is  Lender's  Prime Rate (the
"Index").  This is the rate Lender charges, or would charge, on 90-day unsecured
loans to the most creditworthy corporate customers.  This rate may or may not be
the lowest  rate  available  from  Lender at any given  time.  Lender  will tell
Borrower the current  Index rate upon  Borrower's  request.  The  interest  rate
change will not occur more often than each Day. Borrower understands that Lender
may make loans based on other rates as well.  The Index  currently is 7.750% per
annum.  The interest rate to be applied to the unpaid  principal  balance during
this Note will be at a rate of 2.000 percentage points over the Index,  adjusted
if  necessary  for any minimum and maximum  rate  limitations  described  below,
resulting in an initial rate of 9.750% per annum. NOTICE: Under no circumstances
will the  interest  rate on this Note be less than 4.750% per annum or more than
the maximum rate allowed by applicable law.

PREPAYMENT. Borrower may pay without penalty all or a portion of the amount owed
earlier than it is due. Early  payments will not,  unless agreed to by Lender in
writing,  relieve Borrower of Borrower's obligation to continue to make payments
under the payment  schedule.  Rather,  early  payments will reduce the principal
balance due and may result in Borrower's making fewer payments.  Borrower agrees
not to send  Lender  payments  marked  "paid in full",  "without  recourse",  or
similar language. If Borrower sends such a payment, Lender may accept it without
losing any of  Lender's  rights  under  this  Note,  and  Borrower  will  remain
obligated to pay any further amount owed to Lender.  All written  communications
concerning  disputed  amounts,  including any check or other payment  instrument
that indicates that the payment constitutes "payment in full" of the amount owed
or that is tendered with other conditions or limitations or as full satisfaction
of a disputed  amount must be mailed or delivered to: Bank of Ann Arbor,  125 S.
Fifth Avenue Ann Arbor, MI 48104.

LATE  CHARGE.  If a payment  is 10 days or more late,  Borrower  will be charged
3.000% of the  unpaid  portion  of the  regularly  scheduled  payment or $25.00,
whichever is greater.

INTEREST  AFTER  DEFAULT.  Upon  default,  including  failure  to pay upon final
maturity,  the  interest  rate on this Note shall be increased by adding a 3.000
percentage point margin  ("Default Rate Margin").  The Default Rate Margin shall
also apply to each  succeeding  interest rate change that would have applied had
there been no default.  However,  in no event will the interest  rate exceed the
maximum interest rate limitations under applicable law.

DEFAULT.  Each of the following shall  constitute an event of default ("Event of
Default") under this Note:

     Payment  Default.  Borrower  fails to make any payment  when due under this
     Note.

     Other Defaults. Borrower fails to comply with or to perform any other term,
     obligation,  covenant or condition  contained in this Note or in any of the
     related  documents  or to comply with or to perform  any term,  obligation,
     covenant or condition  contained in any other agreement  between Lender and
     Borrower.

     Default in Favor of Third Parties.  Borrower or any Grantor  defaults under
     any loan,  extension  of  credit,  security  agreement,  purchase  or sales
     agreement, or any other agreement, in favor of any other creditor or person
     that may materially affect any of Borrower's property or Borrower's ability
     to repay this Note or perform Borrower's obligations under this Note or any
     of the related documents.

     False  Statements.  Any  warranty,  representation  or  statement  made  or
     furnished to Lender by Borrower or on Borrower's  behalf under this Note or
     the related  documents  is false or  misleading  in any  material  respect,
     either now or at the time made or furnished or becomes  false or misleading
     at any time thereafter.

     Insolvency. The dissolution or termination of Borrower's existence as a
     going business, the insolvency of Borrower, the appointment of a receiver
     for any part of Borrower's property, any assignment for the benefit of
     creditors, any type of creditor workout, or the commencement of any
     proceeding under any bankruptcy or insolvency laws by or against Borrower.

     Creditor  or  Forfeiture   Proceedings.   Commencement  of  foreclosure  or
     forfeiture   proceedings,   whether  by  judicial  proceeding,   self-help,
     repossession  or any other  method,  by any  creditor of Borrower or by any
     governmental agency against any collateral securing the loan. This includes
     a garnishment of any of Borrower's  accounts,  including  deposit accounts,
     with Lender.  However,  this Event of Default shall not apply if there is a
     good faith dispute by Borrower as to the validity or  reasonableness of the
     claim which is the basis of the creditor or  forfeiture  proceeding  and if
     Borrower  gives  Lender  written  notice  of  the  creditor  or  forfeiture
     proceeding  and  deposits  with  Lender  monies  or a  surety  bond for the
     creditor or forfeiture  proceeding,  in an amount  determined by Lender, in
     its sole discretion, as being an adequate reserve or bond for the dispute.

     Events Affecting Guarantor. Any of the preceding events occurs with respect
     to any  Guarantor  of any of the  indebtedness  or any  Guarantor  dies  or
     becomes  incompetent,  or revokes or disputes the validity of, or liability
     under,  any guaranty of the  indebtedness  evidenced  by this Note.  In the
     event of a death, Lender, at its option, may, but shall not be required to,
     permit the  Guarantor's  estate to assume  unconditionally  the obligations
     arising  under the  guaranty in a manner  satisfactory  to Lender,  and, in
     doing so, cure any Event of Default.

     Change In Ownership.  Any change in ownership of twenty-five  percent (25%)
     or more of the common stock of Borrower.

     Adverse Change.  A material  adverse change occurs in Borrower's  financial
     condition,  or Lender  believes the prospect of payment or  performance  of
     this Note is impaired.

     Insecurity. Lender in good faith believes itself insecure.

     Cure Provisions. If any default, other than a default in payment is curable
     and if  Borrower  has not  been  given a  notice  of a  breach  of the same
     provision of this Note within the preceding  twelve (12) months,  it may be
     cured if Borrower,  after  receiving  written notice from Lender  demanding
     cure of such default: (1) cures the default within ten (10) days; or (2) if
     the cure  requires  more than ten (10) days,  immediately  initiates  steps
     which Lender deems in Lender's sole discretion to be sufficient to cure the
     default and thereafter continues and completes all reasonable and necessary
     steps sufficient to produce compliance as soon as reasonably practical.

LENDER'S  RIGHTS.  Upon default,  Lender may declare the entire unpaid principal
balance under this Note and all accrued  unpaid  interest  immediately  due, and
then Borrower will pay that amount.

ATTORNEYS' FEES;  EXPENSES.  Lender may hire or pay someone else to help collect
this Note if Borrower does not pay.  Borrower will pay Lender that amount.  This
includes,  subject to any  limits  under  applicable  law,  Lender's  reasonable
attorneys'  fees and Lender's legal expenses  whether or not there is a lawsuit,
including  reasonable  attorneys'  fees and expenses for bankruptcy  proceedings
(including  efforts to modify or vacate any automatic stay or  injunction),  and
appeals.  If not prohibited by applicable law,  Borrower also will pay any court
costs, in addition to all other sums provided by law.

JURY WAIVER. Lender and Borrower hereby waive the right to any jury trial in any
action, proceeding, or counterclaim brought by either Lender or Borrower against
the other.

<PAGE>

                                 PROMISSORY NOTE
Loan No: 200744                    (Continued)                            Page 2
================================================================================


GOVERNING  LAW.  This Note will be governed by federal law  applicable to Lender
and,  to the  extent not  preempted  by  federal  law,  the laws of the State of
Michigan  without regard to its conflicts of law provisions.  This Note has been
accepted by Lender in the State of Michigan.

CHOICE OF VENUE. If there is a lawsuit, Borrower agrees upon Lender's request to
submit to the jurisdiction of the courts of Washtenaw County, State of Michigan.

RIGHT OF SETOFF.  To the extent  permitted by applicable  law, Lender reserves a
right of  setoff in all  Borrower's  accounts  with  Lender  (whether  checking,
savings,  or some other  account).  This  includes all accounts  Borrower  holds
jointly  with  someone  else and all  accounts  Borrower may open in the future.
However,  this does not include any IRA or Keogh accounts, or any trust accounts
for which setoff would be prohibited by law. Borrower  authorizes Lender, to the
extent  permitted by  applicable  law, to charge or setoff all sums owing on the
indebtedness  against any and all such  accounts,  and, at Lender's  option,  to
administratively  freeze all such  accounts to allow Lender to protect  Lender's
charge and setoff rights provided in this paragraph.

COLLATERAL.  Borrower acknowledges this Note is secured by a Commercial Security
Agreement,  three Commercial Pledge  Agreements,  four Commecial  Guaranties all
dated March 30, 2007 and a Business Loan Agreement dated an even date herewith.

SUCCESSOR INTERESTS.  The terms of this Note shall be binding upon Borrower, and
upon Borrower's heirs,  personal  representatives,  successors and assigns,  and
shall inure to the benefit of Lender and its successors and assigns.

NOTIFY US OF INACCURATE  INFORMATION WE REPORT TO CONSUMER  REPORTING  AGENCIES.
Please notify us if we report any inaccurate  information  about your account(s)
to a consumer  reporting  agency.  Your written  notice  describing the specific
inaccuracy(ies) should be sent to us at the following address: Bank of Ann Arbor
125 S. Fifth Avenue Ann Arbor, MI 48104.

GENERAL PROVISIONS.  If any part of this Note cannot be enforced, this fact will
not affect the rest of the Note.  Lender may delay or forgo enforcing any of its
rights or remedies under this Note without  losing them.  Borrower and any other
person who signs,  guarantees or endorses  this Note,  to the extent  allowed by
law, waive  presentment,  demand for payment,  and notice of dishonor.  Upon any
change in the terms of this  Note,  and  unless  otherwise  expressly  stated in
writing,   no  party  who  signs  this  Note,   whether  as  maker,   guarantor,
accommodation  maker or endorser,  shall be released  from  liability.  All such
parties agree that Lender may renew or extend  (repeatedly and for any length of
time) this loan or release any party or guarantor or collateral; or impair, fail
to realize upon or perfect  Lender's  security  interest in the collateral;  and
take any other  action  deemed  necessary  by Lender  without  the consent of or
notice to anyone.  All such  parties also agree that Lender may modify this loan
without  the  consent of or notice to anyone  other than the party with whom the
modification is made. The obligations under this Note are joint and several.

PRIOR TO SIGNING THIS NOTE,  BORROWER READ AND  UNDERSTOOD ALL THE PROVISIONS OF
THIS NOTE,  INCLUDING THE VARIABLE INTEREST RATE PROVISIONS.  BORROWER AGREES TO
THE TERMS OF THE NOTE.

BORROWER ACKNOWLEDGES RECEIPT OF A COMPLETED COPY OF THIS PROMISSORY NOTE.

BORROWER:

PIPEX PHARMACEUTICALS, INC.

By: /s/ STEVE KANZER
    ----------------------------
     STEVE KANZER, CEO of PIPEX
     PHARMACEUTICALS, INC.

<PAGE>

                     DISBURSEMENT REQUEST AND AUTHORIZATION

<TABLE>
<CAPTION>
======================= ================ ============== =============== ================= =================== ========= ===========
<S>                     <C>              <C>            <C>             <C>               <C>                 <C>       <C>
        Principal           Loan Date       Maturity        Loan No         Call / Coll          Account       Officer    Initials
       $500,000.00         09-27-2007      03-30-2010        200744             07               123186          029
======================= ================ ============== =============== ================= =================== ========= ===========

====================================================================================================================================
References in the boxes above are for Lender's use only and do not limit the
applicability of this document to any particular loan or item. Any item above
containing "***" has been omitted due to text length limitations.
====================================================================================================================================
</TABLE>

Borrower:   PIPEX PHARMACEUTICALS, INC. (TIN:     Lender:  Bank of Ann Arbor
            13-3808303)                                    Main Office
            3985 Research Park Dr.                         125 S. Fifth Avenue
            Ann Arbor, MI 48108                            Ann Arbor, MI 48104
                                                           (734) 662-1600

================================================================================

LOAN TYPE.  This is a Variable Rate  Nondisclosable  Loan to a  Corporation  for
$500,000.00  due on March 30, 2010.  The reference rate (Bank of Ann Arbor Prime
Rate,  with an interest rate floor of 4.750%  currently  7.750%) is added to the
margin of 2.000%, resulting in an initial rate of 9.750.

PRIMARY PURPOSE OF LOAN. The primary purpose of this loan is for:

           [   ] Personal, Family, or Household Purposes or Personal Investment.

           [ X ] Business (Including Real Estate Investment).

SPECIFIC  PURPOSE.  The specific  purpose of this loan is: to finance  equipment
purchases & leasehold improvements.

DISBURSEMENT  INSTRUCTIONS.  Borrower  understands that no loan proceeds will be
disbursed  until  all of  Lender's  conditions  for  making  the loan  have been
satisfied. Please disburse the loan proceeds of $500,000.00 as follows:

                 Amount paid to Borrower directly:                   $500,000.00
                 $500,000.00 Deposited to Checking Account # 600000228
                                                                     -----------

                 Note Principal:                                     $500,000.00

CHARGES  PAID IN CASH.  Borrower  has paid or will pay in cash,  as agreed,  the
following  charges and, if applicable,  authorize Lender to pay such fees to the
appropriate third parties:

                 Prepaid Finance Charges Paid in Cash:                     $0.00

                 Other Charges Paid in Cash:                           $7,500.00
                   $7,500.00 Loan Fee -Bank of Ann Arbor
                                                                     -----------

                 Total Charges Paid in Cash:                           $7,500.00

AUTOMATIC  PAYMENTS.  Borrower hereby authorizes Lender  automatically to deduct
from Borrower's Demand Deposit -Checking account, numbered 600000228, the amount
of any loan payment.  If the funds in the account are  insufficient to cover any
payment, Lender shall not be obligated to advance funds to cover the payment. At
any time and for any  reason,  Borrower  or  Lender  may  voluntarily  terminate
Automatic Payments.

FINANCIAL  CONDITION.  BY SIGNING THIS  AUTHORIZATION,  BORROWER  REPRESENTS AND
WARRANTS TO LENDER THAT THE  INFORMATION  PROVIDED ABOVE IS TRUE AND CORRECT AND
THAT THERE HAS BEEN NO MATERIAL ADVERSE CHANGE IN BORROWER'S FINANCIAL CONDITION
AS DISCLOSED  IN  BORROWER'S  MOST RECENT  FINANCIAL  STATEMENT TO LENDER.  THIS
AUTHORIZATION IS DATED SEPTEMBER 27, 2007.

BORROWER:

PIPEX PHARMACEUTICALS, INC.

By: /s/ STEVE KANZER
    ----------------------------
     STEVE KANZER, CEO of PIPEX
     PHARMACEUTICALS, INC.
</TEXT>
</DOCUMENT>
