**Exhibit
4.22.1**
 **PROMISSORY
NOTE & AGREEMENT**
  **Principal:**
    **$100,000**
    **Dated:**
    
    **April 4, 2005****Interest Rate:**
    **10%**
    **Maturity Date:**
    
    **May 15, 2005**
 
 **FOR
VALUE RECEIVED** , **Generex
Biotechnology Corporation** (the
“ Borrower ”) hereby
acknowledges itself indebted and promises to pay to **Omicron
Master Trust** (the
“ Holder ”), at
650 5 th Ave.,
24 th Floor,
New York, New York 10019 the principal sum of One Hundred Thousand Dollars
($100,000) in lawful money of the United States of America.
 
 The
Borrower shall pay interest on the said principal sum outstanding from time to
time at the rate of ten percent (10%) per annum (both before and after maturity
and before and after default or judgement with interest on overdue interest at
the same rate), such interest to accrue from the date hereof, to be calculated
monthly, and to be payable on May 15, 2005 (to the extent that the Holder has
not exercised the Conversion Entitlement in respect thereof (as that term is
hereinafter defined)).
 
 The whole
of the said principal sum outstanding shall become due and payable in full on
May 15, 2005 (to the extent that the Holder has not exercised the Conversion
Entitlement in respect thereof (as that term is hereinafter
defined)).
 
 At any
time after April 28, 2005 until this promissory note is no longer outstanding,
this promissory note and any accrued and unpaid interest in respect thereof
shall be convertible into shares of the Borrower’s common stock (“ Conversion
Shares ”) at the
option of the Holder, in whole or in part at any time and from time to time
(subject to the limitations on conversion hereinafter set forth), at the rate of
$0.82 per share (the “ Conversion
Entitlement ”). The
Holder shall exercise the Conversion Entitlement by delivering written notice
thereof to the Borrower specifying the amount of this promissory note to be
converted and the date on which such conversion is to be effected (the
“ Conversion
Date ”).
Conversions hereunder shall be applied firstly against accrued and unpaid
interest in respect of this promissory note as at the Conversion Date and
secondly against the outstanding principal amount of this promissory note as at
the Conversion Date.
 
 The
Holder’s exercise of the Conversion Entitlement shall be subject to the
participation rights of the holders of the 6% convertible debentures due
February 10, 2006 issued by the Borrower on November 10, 2004 (the “ Debentures ”).
 
 As
additional consideration for the transactions contemplated hereby, on April 28,
2005 the Borrower will issue to the Holder a warrant (the “ Warrant ”) to
purchase an aggregate of 243,902 shares of the Borrower’s common stock (the
“ Warrant
Shares ”) at a
per-share price of $0.82, such Warrant to expire on April 27, 2010.
 
 The
Holder hereby covenants and agrees that it will not exercise the Conversion
Entitlement or the Warrant, in whole or in part, to the extent that after giving
effect to any such conversion or exercise the Holder (together with its
affiliates) would beneficially own in excess of 9.99% of the number of shares of
the Borrower’s common stock outstanding immediately after giving effect to such
conversion or exercise (not including shares of the Borrower’s common stock
issuable upon (a) exercise of any remainder of the Conversion Entitlement or any
remainder of the Warrant, or (b) conversion or exercise of the non-converted or
unexercised portion of any other securities of the Borrower subject to a
limitation on conversion or exercise analogous to the limitation contained
herein beneficially owned by the Holder or any of its affiliates). To the extent
the foregoing limitation applies, the determination whether or not the
Conversion Entitlement or the Warrant is exercisable and to what extent shall be
in the sole discretion of the Holder.
 
 
 The
Borrower hereby covenants and agrees to qualify the Conversion Shares and the
Warrant Shares for public resale by including the same in the next registration
statement filed after the date hereof by the Borrower under the *Securities
Act of 1933* .
 
 The
Borrower hereby covenants and agrees that any and all net proceeds to the
Borrower of any debt or equity financings or any revenues received from third
parties as license, co-marketing, collaboration, distribution, joint venture,
strategic alliance or like fees shall be applied forthwith following the
Borrower’s receipt thereof, to the extent necessary, to the repayment of the
following debt obligations of the Borrower on a *pari
passu* basis:
(1) the then outstanding principal balance of the $500,000 principal amount
promissory note (together with any and all accrued and unpaid interest thereon)
dated March 28, 2005 executed and delivered by the Borrower to and in favour of
Cranshire Caiptal, L.P., and (2) the then outstanding principal balance of this
promissory note together with any and all accrued and unpaid interest
thereon.
 
 The
Holder hereby acknowledges and agrees that the obligations of the Borrower under
this promissory note are subordinate to the obligations of the Borrower under
the Debentures.
 
 The
Borrower hereby waives demand, presentment for payment, notice of non-payment,
protest and notice of protest of this promissory note.
 
 This
promissory note shall be governed by and construed in accordance with the laws
of the State of New York.
 
 **DATED** this
4 th day of
April, 2005.
  **GENEREX
      BIOTECHNOLOGY CORPORATION**Per:
    /s/ Anna
      E. GluskinName:Anna
      E. GluskinTitle:President,
      Chief Executive OfficerI have authority to bind the
corporation.
 ****OMICRON MASTER
  TRUST**By:
    /s/ Bruce BernsteinName:Bruce
      BernsteinTitle:Managing
      Partner**