<PAGE>


                                                                 EXHIBIT 10.1.4

                             SUPPLEMENTAL AGREEMENT



         THIS AGREEMENT, made as of the 31st day of December, 2000, by and among
GENEREX PHARMACEUTICALS, INC. ("GPI"), an Ontario corporation, GENEREX
BIOTECHNOLOGY CORPORATION ("GBC"), a Delaware corporation, and PANKAJ MODI
("Modi"), an individual.

         WHEREAS, effective October 1, 1996, pursuant to a Consulting Agreement
dated as of that date between GPI and Modi (the "Consulting Agreement"), Modi
was engaged as a consultant by GPI and assigned and transferred to GPI all
Inventions (as defined in the Consulting Agreement) relating to the actual or
demonstrably anticipated business, work, undertaking or research and development
of GPI made or conceived by Modi during the term of the Consulting Agreement;
and

         WHEREAS, on January 7, 1998, the parties to this Supplemental
Agreement, together with GHI, Inc., a Turks and Cacos corporation, entered into
a Memorandum of Agreement (the "Memorandum of Agreement") that modified or
superseded portions of the Consulting Agreement, primarily relating to the
compensation due to Modi for his past and future services to GPI and GBC; and

         WHEREAS, the parties now wish to amend the term and compensation
arrangements provided for in the Consulting Agreement and the Memorandum of
Agreement (collectively, the "Prior Agreements"), and to provide additional
terms of Modi's engagement.

         NOW, THEREFORE, in consideration of the mutual promises herein
contained and for other good and valuable consideration, the parties agree as
follows:

         4. Extension of Terms of Consulting Agreement. Subject to the early
termination provisions set forth in Section 6 below, the Consulting Agreement,
as amended hereby, is extended to and including July 31, 2010 (the "Termination
Date"), and is hereinafter referred to as "this Agreement". During the extended
term of this Agreement, Modi shall continue to hold the position of Vice
President, Research and Development of GPI and of GBC.

         5. Base Compensation and Car Allowance. (a) For all services rendered
to GBC, GPI and other subsidiaries of GBC (collectively, "Generex"), Modi will
receive annual base compensation of $250,000* effective as of August 1, 2000.
The base compensation and all other compensation payable to Modi under this
Agreement may be allocated within Generex in the discretion of GBC. Whatever
allocation is made, however, GBC and GPI shall be jointly and severally
responsible for the payment to Modi of all amounts due under this Agreement.

                  (b) The difference between (i) the base compensation due to
Modi under paragraph 2(a) above for the period August 1, 2000, through December
31, 2000 (i.e., 5/12ths of $250,000, or $104,166.65, and (ii) the compensation
actually paid to Modi for services to Generex during that period, shall be paid
to Modi in a lump sum upon execution of this Agreement. Thereafter, commencing
January 1, 2001, Modi's Base Compensation shall be paid to him no less
frequently than semi-monthly, in arrears, or on such other basis as Modi and GBC
may agree upon.

                  (c) Commencing January 1, 2001, Modi shall be paid a monthly
car allowance of $1,500 for the lease, use and maintenance of, and insurance
upon, an automobile for his personal and business use. Modi shall maintain
insurance on such automobile for his own and Generex' benefits with carriers,
coverage and policy limits consistent with policies adopted by Generex for
insurance on company-owned automobiles and automobiles owned by Generex
executives but used from time to time on Generex business. The car allowance
shall be paid monthly in advance, unless Modi and GNBT otherwise agree.

--------------
* All dollar figures in this Agreement refer to US dollars.

<PAGE>

                  (d) Modi's Base Compensation and car allowance shall be
increased by 5% annually effective on January 1st in each calendar year
beginning in 2002 (e.g., to illustrate, in calendar year 2002, Modi's Base
Compensation shall be $262,500, and in calendar year 2003, Base Compensation
shall be $275,625).

         6. Bonus Compensation. In addition to base compensation, during the
term of this Agreement Modi shall receive bonus and incentive compensation for
services to Generex as follows:


                  (a) A bonus of $300,000 shall be paid in respect of Modi's
services in securing the development and license agreement dated September 5,
2000, between GBC and Eli Lilly and Company (the "Lilly Agreement"). This bonus
shall be paid as follows: $150,000 upon execution of this Agreement and $150,000
on February 15, 2001.

                  (b) Modi shall receive a bonus of 5% of all milestone
payments, additional signing fees or initial fees received by Generex pursuant
to Sections 6.2 and 6.4 of the Lilly Agreement and any subsequent agreement
between Generex and Lilly providing for comparable payments (the "Lilly
Payments"), excluding the $1,000,000 signing fee received in October 2000.
Stated otherwise for purposes of clarity, Modi shall receive as a bonus $.05 for
each $1.00 of Lilly Payments that Generex receives after the date of this
Agreement. These bonus payments will be paid to Modi as and when the Lilly
Payments are received by Generex from Lilly.

                  (c) In addition to the bonus payable under paragraph (b) above
relating to Lilly Payments, Modi shall receive additional bonuses equal to (i)
25% of the first $1,000,000 of any signing fee, licensing fee or similar "up
front" payment not tied to a GBT performance milestone that is received during
the term of this Agreement (excluding Lilly Payments) pursuant to development,
marketing, licensing or similar agreements hereafter entered into by Generex to
the extent that such payments are received in consideration of rights granted to
third parties to develop, manufacture and/or market products based upon
Inventions ("Other Products"); (ii) 5% of all "up front fees of the nature
described in the preceding clause to the extent such fees exceed $1,000,000; and
(iii) 5% of all of milestone payments and similar payments tied to the
development of Other Products that are received by Generex. As used in this
Agreement, the term "Inventions" shall have the same meaning as in Section 9 of
the Consulting Agreement, except that "Generex", as defined herein, shall be
substituted for "Corporation" in such definition.

         9. Stock Options. (a) Modi shall be granted options to purchase 150,000
shares of GBC's common stock in each of the next ten fiscal years of GBC ending
during the term of this Agreement, i.e., beginning with the present fiscal year
ending July 31, 2001, and ending with the fiscal year ending July 31, 2010. The
options shall be granted as of the last Friday in July (the "date of grant") of
each such fiscal year, and shall have the following terms:

                           (i) The option price shall equal the average closing
sale price of publicly-traded shares of GBC common stock during normal trading
hours reported for the five trading days preceding the date of grant (the
"valuation period"). If GBC's common stock is not traded on an exchange or
quotation system that reports actual sales transactions on the date of grant,
the average closing bid price for the shares shall be used in lieu of the
closing sale price. If neither closing sales prices nor bid prices are reported
during the valuation period, the option price shall be the fair market value of
GBC's publicly traded shares of common stock on the date of grant as determined
by GBC's Board of Directors.

                           (ii) The terms of the options shall be five (5) years
from the date of grant, subject, however, to early termination pursuant to
Sections 7(c), (d) and (e) below.

                           (iii) The options shall vest immediately on the date
of grant.


                           (iv) The options shall not be transferable except by
gift or bequest to Modi's "family members" or pursuant to a "domestic relations
order", as those terms are described in the instruction to Form S-8 adopted
under the Securities Act of 1933.

                           (v) The number and kind of shares issuable upon the
exercise of options to be granted under this Agreement shall be adjusted to
reflect stock splits, recapitalizations, reorganizations and similar corporate
events affecting GBC. The exercise price of and number and kind of shares
subject to outstanding options shall be adjusted in the same manner as options
granted under GBC's 2000 Stock Option Plan pursuant to the express terms of that
Plan.

                           (vi) GBC shall use its best efforts to register under
the Securities Act of 1933 on Form S-8 or other available form for sale to Modi
and for resale by Modi all shares issuable upon the exercise of options granted
under this Agreement.
<PAGE>

                  (b) In accordance with the qualification requirements
applicable to issuers with securities included in The Nasdaq Stock Market, GBC's
obligations under this Section 4 are subject to approval by GBC's stockholders.
GBC agrees to submit these terms to shareholders for their approval at the Year
2000 Annual Meeting of GBC's shareholder. If for any reason the stock option
grants contemplated by this Agreement are not approved by shareholders, GBC
shall grant to Modi in lieu thereof stock appreciation rights (SARs) that will
provide to Modi the same potential economic benefits as the option plan,
excluding consideration of differences, if any, in income tax treatment under
applicable laws.

         10. Additional Authority. During the term of this Agreement, Modi shall
have final authority with respect to the hiring and continued employment of all
Generex personnel (including consultants) engaged in research and development
activities relating to products based upon Inventions, within budgetary and
personnel constraints approved by Boards of Directors of GBC (or GPI in the case
of employees or consultants employed or engaged by GPI). Notwithstanding the
foregoing, if Modi fails to fill any research and development position that (a)
is created by GBC's Board of Directors (or GPI's Board of Directors in the case
of employees or consultants employed or engaged by GPI), or (b) becomes
available due to termination of the employment or engagement of another employee
or consultant, within the 90 day period following the creation or opening of
such position, such position may be filled by a candidate approved by the
President of GBC (or GPI, in the case of employees or consultants employed or
engaged by GPI).

         11. Early Termination. Section 7 of the Consulting Agreement, as
amended and restated by Section 3 of the Memorandum of Agreement, is superseded
in its entirety by the following provisions of this Agreement:

                  (a) This Agreement shall terminate upon Modi's death or the
declaration by a court of competent jurisdiction that Modi is a mentally
incompetent person or incapable of handling his affairs due to mental
incompetence.

                  (b) This Agreement may be terminated by GBC if Modi is unable,
as a result of a bona fide illness, physical or mental, to attend to his duties
hereunder for a period of six (6) consecutive months, which period shall be
deemed to commence with such inability and shall continue until Modi is once
again able to attend to his duties hereunder on a regular basis.

                  (c) This Agreement may be terminated at any time by mutual
agreement, in writing, of GBC and Modi.

                  (d) This Agreement may be terminated by Modi or by GBC,
without cause, at any time after January 1, 2003, upon twelve (12) months prior
written notice.

                  (e) This Agreement may be terminated by GBC for just cause at
any time by giving thirty (30) days written notice thereof to Modi. As used
herein, the term "just cause" shall mean and be limited to (i) a material breach
of trust by Modi which causes or threatens serious injury to Generex, or (ii)
any action by Modi taken with the intent to materially and adversely affect a
material interest of Generex, or with knowledge that such action would result in
such a material adverse affect to Generex, whether or not such affect is
prevented from occurring by Generex or any other person or by events unrelated
to Modi's actions.

         12. Effect of Early Termination. If this Agreement is terminated prior
to the Termination Date pursuant to Section 6 hereof, then, lieu of base
compensation, bonus and incentive compensation and stock options to which Modi
is entitled under this Agreement, the following provisions shall apply

                  (a) If this Agreement is terminated under Section 6(a) or (b)
above: (i) Generex shall pay to Modi (or his legal representative) in a lump sum
within sixty (60) days from such early termination an amount equal to the lesser
of $500,000 or the aggregate amount that would have been paid to Modi under
Section 2 above from the date of such termination to the Termination Date had
such early termination not occurred;


<PAGE>

                           (ii) Generex shall pay to Modi all bonus payments
that would have been paid to Modi under Sections 3(b) and 3(c) of this Agreement
as and when such payment would have been made had such early termination not
occurred, provided that no bonus payments shall be due with respect to milestone
payments, signing fees or similar payments received by Generex under license or
other agreements entered into by Generex after the date of such early
termination unless and to the extent that such post-early termination contracts
replace or supersede contractual obligations in force as of the date of such
early termination; and

                           (iii) All options granted to Modi prior to the date
of such early termination shall remain in full force, unaffected by such early
termination.

                  (b) If this Agreement is terminated under Section 6(c), the
provisions of Section 7(a) above shall apply unless the parties otherwise
provide in the written agreement pursuant to which such early termination is
effected.

                  (c) If this Agreement is terminated by GBC under Section 6(d)
above, then the provisions of Section 7(a) shall apply except (x) that the
minimum payment referred to in Section 7(a)(i) shall be the greater of
$1,000,000 or the amount that would have been paid to Modi under Section 2 above
from the date of such early termination to the Termination Date had such early
termination not occurred, and (y) Modi shall be entitled to bonus payments in
respect of any milestone payments, signing fees or similar payments received by
Generex pursuant to license or other agreements relating to Inventions,
irrespective of whether or not such licenses or agreements were entered into
prior to the date of such early termination.

                  (d) If this Agreement is terminated by Modi under Section 6(d)
above, then (i)Generex shall pay to Modi all bonus payments that would have been
paid to Modi under Sections 3(b) and 3(c) of this Agreement as and when such
payment would have been made had such early termination not occurred, provided
that no bonus payments shall be due with respect to milestone payments, signing
fees or similar payments received by Generex under license or other agreements
entered into by Generex after the date of such early termination unless and to
the extent that such post-early termination contracts replace or supersede
contractual obligations in force as of the date of such early termination; and
(ii) all options granted to Modi under this Agreement prior to the date of such
early termination shall terminate on the first anniversary of the date of such
early termination.

                  (e) If this Agreement is terminated by Generex under Section
6(e), then Modi shall be entitled to base compensation and bonus payments
accrued to the date of such early termination, and no more, and all options
granted pursuant to Section 4 above shall terminate at the close of business on
the fifth business day following the date of such early termination.

         13. Counsel for the Transaction. Each of the parties hereto has
requested Joseph Chicco ("Chicco") of the firm Eckert Seamans Cherin & Mellott,
LLC, Philadelphia, PA, to represent him/it in connection with the preparation
and execution of this Supplemental Agreement. Each such party understands that
Chicco and his firm are regularly employed as attorneys for GBC and GPI in
numerous matters wholly unrelated to this transaction, but that the business of
GPI and GPC is materially dependent on Modi's research and inventions. With
respect to the transactions contemplated by this Agreement, however, no
communications to Chicco by a party shall be considered confidential so as to
preclude disclosure to other parties, and the parties acknowledge that Chicco
has advised them that he may communicate information obtained from one party to
one or more other parties, and will communicate all such information received to
another party upon its request. The parties understand that, in this capacity,
Chicco cannot be and will not be an advocate for the interest of any party
against the interest of one or more of the other parties. Rather , Chicco's role
shall be to advise each party on the effect and meaning of various terms that
may be proposed by one or more of the parties, and to attempt to mediate and
facilitate a resolution of any disputed proposals.

         (b) Each of the parties waives all real and potential conflicts of
interests that arise out of Chicco's multiple representation of the parties in
this transaction, and agrees that Chicco's fees and expenses in connection with
the negotiation, preparation and execution of this Agreement shall be paid by
GBC.


<PAGE>

         14. Governing Law. This Agreement shall be governed by the laws of the
Province of Ontario and of Canada applicable therein, and the parties hereby
irrevocably consent to the jurisdiction of the courts of the Province of
Ontario, except that (a) the parties' rights and obligations with respect to
Section 6 of the Consulting Agreement relating to Modi's Special Voting Rights
Preferred Stock and the provisions of this Agreement relating to the grant of
stock options shall be governed by the laws of the State of Delaware, and (b)
where applicable, US securities laws shall control the construction and
enforcement of this Agreement.

         15. Prior Agreements. (a) The Consulting Agreement, the Memorandum of
Agreement and the Supplemental Agreement shall be construed as a single
Agreement. In the event of any inconsistency between the Consulting Agreement
and the Memorandum of Agreement, the Memorandum of Agreement shall control. In
the event of any inconsistency between either of the Prior Agreements and the
Supplemental Agreement, the Supplemental Agreement shall control. To the extent
that they relate to Modi's compensation, the terms of the Prior Agreements are
intended to be and are superseded by the terms of the Supplemental Agreement.

         (b) Modi acknowledges that he has received all compensation to which he
is entitled under the Prior Agreements, including shares of GBC common stock
held by GHI referred to in the Memorandum of Agreement.

         (c) Except to the extent that they are superseded by a later term of
this Agreement, the Prior Agreements remain in full force and effect.

         (d) The parties expressly acknowledge that Modi's obligations under
Section 9 of the Consulting Agreement shall survive any termination of this
Agreement.

         IN WITNESS WHEREOF, the parties have executive and delivered this
Memorandum of Agreement as of the date first written above.

Witness:

                                       GENEREX PHARMACEUTICALS INC.


                                       Per:     /s/ Anna E. Gluskin
                                           ------------------------------------
                                                Anna E. Gluskin, President


                                       Per:     /s/ E. Mark Perri
                                           ------------------------------------
                                                E. Mark Perri, Chairman

                                       GENEREX BIOTECHNOLOGY
                                                CORPORATION


                                       Per:     /s/ Anna E. Gluskin
                                           ------------------------------------
                                                Anna E. Gluskin, President


                                       Per:     /s/ E. Mark Perri
                                           ------------------------------------
                                                E. Mark Perri, Chairman


                                                /s/ Pankaj Modi
                                       ----------------------------------------
                                                Pankaj Modi