SECURED PROMISSORY NOTE

Exhibit 10.1

S ECURED P ROMISSORY N OTE

FOR VALUE RECEIVED, the undersigned, BIOVEST INTERNATIONAL, INC. , a Delaware corporation (the “ Borrower ”), with a mailing address of 324 South Hyde Park Avenue, Suite 350, Tampa, Florida 33606, hereby promises to pay to the order of CORPS REAL, LLC, an Illinois limited liability company (the “ Lender ”), with a mailing address of 1602 W. Kimmel Street, Marion, Illinois 62929, the maximum principal amount of up to Three Million and No/100 Dollars ($3,000,000), together with interest on the unpaid Principal Amount (as defined below) outstanding from time to time at the rate or rates hereafter specified and any and all other sums which may be owing to the Lender by the Borrower hereunder.

On November 10, 2008, Accentia Biopharmaceuticals, Inc. and its subsidiaries, including the Borrower, filed their Voluntary Petitions for relief under Chapter 11 of the Bankruptcy Code with the United States Bankruptcy Court for the Middle District of Florida, Tampa Division (the “ Bankruptcy Court ”). This Secured Promissory Note (hereinafter, the “ Note ”) is being executed pursuant to the terms of that certain Interim Order Granting Debtor’s Emergency Motion for Authority to Obtain Postpetition Financing and Grant Senior Liens, Superpriority Administrative Expense Status and Adequate Protection Pursuant to 11 U.S.C. §§ 364(c) and (d) and F.R.B.P. 4001 dated December 22, 2008 [Doc. No. 119] (the “ Interim Order ”), entered by the Bankruptcy Court in In re: Accentia Biopharmaceuticals, Inc., et al., Case No. 8:08-bk-17795-KRM (the “ Chapter 11 Case ”). The Interim Order granted the Debtor’s Emergency Motion for Authority to Obtain Postpetition Financing and Grant Senior Liens, Superpriority Administrative Expense Status and Adequate Protection Pursuant to 11 U.S.C. §§ 364(c) and (d) and F.R.B.P. 4001 dated December 4, 2008 [Doc. No. 86] (the “ Financing Motion ”). Upon the execution of this Note, the principal amount available to be borrowed under this Note shall be up to $750,000 subject to being increased to $3,000,000 (as the context requires, the “ Principal Amount ”) upon the entry of, and in accordance with, a final order of the Bankruptcy Court granting the Financing Motion (the “ Final Order ”).

The following terms shall apply to this Note:

1. Security and Priority. As security for payment of the Obligations (as defined below) under this Note, the Borrower and the Lender have entered into that certain Security Agreement of even date herewith (the “ Security Agreement ”). The Security Agreement and the Note are sometimes hereinafter referred to as the “ Loan Documents .” The Borrower and the Lender have agreed that all Obligations under this Note will be secured by all of the Collateral (as that term is defined in the Security Agreement) of the Borrower pursuant to Sections 364(c)(2) and 364(d)(1) of the Bankruptcy Code, and the liens and security interests granted to the Lender will be senior to all prepetition and postpetition liens of all parties in the Collateral, all in accordance with the terms of the Interim Order and the Final Order as applicable.

2. Interest Rate. Interest shall accrue and be payable on the outstanding Principal Amount at a fixed rate of interest equal to sixteen percent (16.0%) per annum. Interest shall be calculated on the basis of a year of 360 days applied to the actual days on which there exists an unpaid balance under this Note. Interest shall be paid by the Borrower as follows: (i) interest in the amount of ten percent (10%) shall be paid monthly, and (ii) interest in the amount of six percent (6%) shall be accrued and be paid at maturity of this Note.

3. Advances under this Note. This Note will be a revolving credit note. Fixed advances under this Note (the “ Advances ”) will be as follows: (i) $500,000 to be advanced upon the entry of the Interim Order, (ii) $250,000 to be advanced on December 31, 2008 unless the Borrower, with the consent of Laurus Master Fund, Ltd. and its successors and assigns, including Valens U.S. SPV I, LLC, Valens Offshore SPV II, Corp. and PSource Structured Debt Limited (collectively, “ Valens ”), requests that a portion of the Advance scheduled for December 31, 2008 be delayed to a later date, and (iii) $250,000 to be advanced on January 31, 2009 unless the Borrower, with the consent of Valens, requests that a portion of the Advance scheduled for January 31, 2009 be delayed to a later date. In the event that the Borrower requests that any portion of the December 31, 2008 or the January 31, 2009 Advances be deferred to a later date, the deferred portion of such Advances will remain an irrevocable obligation of the Lender during the term of this Note and will subsequently be advanced by the Lender in good funds to the Borrower within two (2) business days of the Borrower’s written request. For all Advances in excess of the initial $1,000,000 advanced, the Lender and the Borrower shall, within thirty (30) days of the entry of the Interim Order, agree on a list of “milestone” events to be achieved by the Borrower through the use of these Advances, and the Borrower shall be required to make a written request(s) detailing the amount and use and the Lender shall, in its reasonable discretion, approve or reject the written request based upon whether the Borrower demonstrates reasonable progress in achieving the agreed milestones. If approved, the Advance shall be funded into the Borrower’s account within five (5) days of the written request. Notwithstanding the foregoing, if the BiovaxID vaccine is approved or if the Borrower has reasonable assurance that BiovaxID is likely to be approved (including, but not limited to, the United States Food and Drug Administration indicates that it will allow the Borrower to submit an application for approval based on accelerated or conditional approval) for commercial sale in the United States, EMEA countries, Japan, Australia, Switzerland or Russia, the Lender shall advance additional amounts up to an aggregate of $1,000,000 with loans based on monthly written request.

4. Term; Maturity Date. For purposes of this Note and the Security Agreement, the “ Maturity Date ” shall be the earlier of (i) December 31, 2010, (ii) dismissal of the Borrower’s Chapter 11 case currently pending in the Bankruptcy Court, (iii) conversion of the Borrower’s Chapter 11 case to a case under Chapter 7 of the Bankruptcy Code, or (iv) the effective date of the Borrower’s plan of reorganization. For the avoidance of doubt, this Note is a balloon promissory note that requires that all indebtedness be paid in full on the Maturity Date.

5. Closing Costs and Expenses. Upon the execution of this Note and funding of the first Advance by the Lender (the “ Closing ”), the Borrower shall pay to the Lender, in cash, an amount equal to four percent (4%) of the initial $1,000,000 of the Principal Amount (i.e., $40,000). At the time that the Borrower borrows in excess of $1,000,000, the Borrower shall pay to the Lender, in cash, an amount equal to four percent (4%) of the second $1,000,000 of the Principal Amount (i.e., $40,000). At the time that the Borrower borrows in excess of $2,000,000, the Borrower shall pay to the Lender, in cash, an amount equal to four percent (4%) of the third $1,000,000 of the Principal Amount (i.e., $40,000). The Borrower agrees to pay $25,000 to the Lender for its costs as provided in the Interim Order and the Final Order, as applicable, or as otherwise agreed to by Valens and the Committee.

6. Repayment Extension. If any payment of principal or interest shall be due on a Saturday, Sunday or any other day on which banking institutions in the Sta