Exhibit
10.21 


 


PROMISSORY
NOTE


 


THIS
NOTE IS NOT INTENDED TO BE A NEGOTIABLE INSTRUMENT UNDER THE UNIFORM COMMERCIAL CODE, AND THIS NOTE MAY NOT BE ASSIGNED, PLEDGED, TRANSFERRED
OR HYPOTHECATED BY THE LENDER, EXCEPT AS SET FORTH HEREIN.


 


this
NOTE was originally issued in a transaction exempt from registration under the United States Securities Act of 1933 (the “Securities
Act”), and this NOTE may not be offered, sold or otherwise transferred in the absence of such registration or an applicable
exemption therefrom.


 


	$424,055.65	 	DATED: December 1, 2020




 


FOR
VALUE RECEIVED, the undersigned, Shuttle Pharmaceuticals Holdings, Inc. (the “Borrower”), HEREBY PROMISES TO PAY to
the order of Joy Dritschilo (the “Lender”), pursuant to the terms of this promissory note (the “Note”),
on or before December 31, 2021 (the “Maturity Date”) the principal amount of FOUR HUNDRED TWENTY-FOUR THOUSAND FIFTY-FIVE
DOLLARS AND SIXTY-FIVE CENTS ($424,055.65). The Borrower further promises to pay interest on the unpaid principal amount of this Note
at a rate per annum equal to 7.5% from the date hereof until the Note is paid in full. Interest will be computed on the basis of a 360-day
year of twelve 30-day months for the actual number of days elapsed. (The Maturity Date may also be referred to as the “Payment
Date.”)


 


This
Note supersedes, amends and restates in their entirety, and combines the following promissory notes between the Borrower and the Lender:
(i) a $300,000 promissory note, dated January 25, 2018, as amended, together with accrued interest of $64,083.90, for a total of $364,083.90
(the “January 2018 Note”), and (ii) a $50,000 promissory note, dated April 4, 2018, as amended, together with accrued interest
of $9,971.75, for a total of $59,971.75 (the “April 2018 Note”) (together the January 2018 Note and the April 2018 Note are
referred to as the “Original Notes”). Following the issuance of this Note, the Original Notes are hereby rendered null and
void, ab initio.


 


Repayment
shall be made in the form of a single balloon payment of $[ ], including principal and interest, on December 31, 2021. The total interest
owed on this Note during the 12-month period will be $[ ].


 


In
the event that (i) the Borrower shall fail to pay any principal under this Note when due and payable hereunder, and such failure shall
continue for a period of five (5) days after receipt by Borrower of written notice by the Lender thereof; or (ii) the Borrower shall
fail to pay any interest or any other amount under this Note when due and payable hereunder, and such failure shall continue for a period
of five (5) days after receipt by Borrower of written notice by the Lender thereof; or (iii) a receiver, trustee or other similar official
shall be appointed over the Borrower or a material part of its assets and such appointment shall remain uncontested for twenty (20) days
or shall not be dismissed or discharged within sixty (60) days; or (iv) the Borrower shall become insolvent or generally fails to pay,
or admits in writing its inability to pay, its debts as they become due, subject to applicable grace periods, if any; or (v) the Borrower
shall make a general assignment for the benefit of creditors; or (vi) the Borrower shall file a petition for relief under any bankruptcy,
insolvency or similar law (domestic or foreign); or (vii) an involuntary proceeding shall be commenced or filed against the Borrower
under any bankruptcy, insolvency or similar law (domestic or foreign) and such petition shall not be dismissed within sixty (60) days
after commencement or filing (each event specified in clauses (i) through (vii) above, an “Event of Default”); then, in the
case of any of the events specified in clauses (iii), (iv), (vi), (vi) or (vii), the outstanding principal amount under this Note, together
with accrued and unpaid interest thereon, and all other amounts payable by Borrower under this Note shall become immediately due and
payable without any action on the part of the Lender, and in the case of any of the other events specified above, the Lender may by written
notice to the Borrower declare the outstanding principal amount under this Note, together with accrued and unpaid interest thereon, and
all other amounts payable by Borrower under this Note to be immediately due and payable, whereupon the same shall become immediately
due and payable, and, except for the notices specified in this sentence, Borrower waives demand, presentment, protest, notice of protest,
dishonor, notice of dishonor or any other notice of any kind. Any notice specified in this paragraph by Lender to Borrower of the occurrence
of a failure to pay or other default must be delivered as specified below and must clearly specify that it is a notice of default under
this paragraph.


 




    	 



     


    

 


No
delay on the part of Lender in exercise of any right, power or remedy shall operate as a waiver thereof, nor shall any single or partial
exercise by Lender of any right, power or remedy preclude other or further exercise thereof, or the exercise of any other right, power
or remedy. No waiver of, or consent with respect to, any provision of this Note shall in any event be effective unless the same shall
be in writing and signed and delivered by Lender, and then any such waiver or consent shall be effective only in the specific instance
and for the specific purpose for which given.


 


Unless
otherwise agreed by the Lender and the Borrower, both principal and interest hereunder are payable to the Lender at the following address:


 


Joy
Dritschilo


8101
Fenway Road


Bethesda,
MD 20817


 


in
immediately available funds on the Payment Date, in the lawful currency of the United States of America. Whenever any payment to be made
hereunder shall be due on a Saturday, Sunday or public or bank holiday in New York City (any other day being a “Business Day”),
such payment shall be made on the next succeeding Business Day, and such extension of time shall be included in the computation of interest
payable.


 


The
Borrower has the right at any time on or before December 31, 2021, upon five Business Days’ written notice to the Lender, to prepay
in whole or in part the principal amount hereof, without premium or penalty, provided that the Borrower shall pay accrued interest on
the principal so prepaid to the date of such prepayment, and provided further that the Borrower shall reimburse the Lender for any reasonable
costs or other losses which the Lender may sustain as a result of such prepayment being made on a date that is not a Payment Date. Prior
to reimbursement, the Lender shall provide the Borrower with a certificate setting forth all of the costs or losses required to be reimbursed
and setting forth the method used to calculate such costs or losses. Any amounts so prepaid may not be reborrowed hereunder.


 


Neither
the Lender nor the Borrower shall have the right to assign its rights and obligations under this Note without the prior written consent
of the other party.


 


Notices,
confirmations and demands hereunder shall be in writing and will be sufficient if delivered by hand, by first class mail or nationally
recognized courier service postage prepaid, or by tested cable, or facsimile transmission, at the following addresses, or to such other
address as the recipient shall have designated to the sender by written notice hereunder.


 


If
to the Borrower:


 


	 	Shuttle
    Pharmaceuticals Holdings, Inc.
	 	One
    Research Court, Suite 450
	 	Rockville,
    MD 20850
	 	Attn:
    Anatoly Drischilo, M.D.


 


 


If
to the Lender:


 


	 	Joy
    Dritschilo
	 	8101
    Fenway Road
	 	Bethesda,
    MD 20817
	 	 


 


Notwithstanding
anything contained in this Note to the contrary, no interest shall accrue under this Note at a rate in excess of the highest applicable
rate permitted by law, and the payment of any interest (including any charge or fee held by the a court to be interest) in excess of
such rate shall constitute a payment of and be applied to principal.


 


WITHOUT
WAIVING ANY RIGHTS GIVEN TO THE LENDER HEREUNDER, IT IS UNDERSTOOD AND AGREED THAT THE PROVISIONS OF THE SECURITIES INVESTOR PROTECTION
ACT OF 1970 MAY NOT PROTECT LENDER WITH RESPECT TO THIS NOTE AND THAT, THEREFORE, THE COLLATERAL, IF ANY, SECURING THIS NOTE MAY CONSTITUTE
THE ONLY SOURCE OF SATISFACTION OF THE OBLIGATIONS OF THE BORROWER HEREUNDER.


 




    	 



     


    

 


This
Note shall be governed by and construed in accordance with the laws of the State of Maryland applicable to contracts made and to be performed
entirely within such State. Any judicial proceeding brought to enforce this Note may only be brought in a federal or Maryland State court
located in the County of Montgomery, State of Maryland. Each party to this Note waives any objection to jurisdiction of and venue in
such courts in any action instituted hereunder and shall not assert any defense based on lack of jurisdiction of or improper venue in
any such court or based upon forum non conveniens.


 


THE
BORROWER HEREBY WAIVES ANY RIGHT TO TRIAL BY JURY IN ANY ACTION, PROCEEDING OR COUNTERCLAIM ARISING UNDER OR RELATED TO THIS NOTE.


 


	 	SHUTTLE
    PHARMACEUTICALS HOLDINGS, INC.
	 	 	 
	 	By:	 
	 	 	Anatoly
    Dritschilo
	 	 	Chairman
    and Chief Executive Officer
	 	 	 
	 	Acknowledged
    and agreed:
	 	 	 
	 	JOY
    DRITSCHILO
	 	 
	 	Joy
    Dritschilo