Exhibit 10.6


 


THIS PROMISSORY NOTE (“NOTE”) HAS
NOT BEEN REGISTERED UNDER THE SECURITIES ACT OF 1933, AS AMENDED (THE “SECURITIES ACT”). THIS NOTE HAS BEEN ACQUIRED FOR INVESTMENT
ONLY AND MAY NOT BE SOLD, TRANSFERRED OR ASSIGNED IN THE ABSENCE OF REGISTRATION OF THE RESALE THEREOF UNDER THE SECURITIES ACT OR AN
OPINION OF COUNSEL REASONABLY SATISFACTORY IN FORM, SCOPE AND SUBSTANCE TO THE COMPANY THAT SUCH REGISTRATION IS NOT REQUIRED.


 


PROMISSORY NOTE


 


	Principal Amount:  $300,000	 Dated as of January 29, 2021


 


FS Development Corp. III,
a Delaware corporation (the “Maker”), promises to pay to the order of FS Development Holdings III, LLC or its registered
assigns or successors in interest (the “Payee”), or order, the principal sum of Three Hundred Thousand Dollars ($300,000)
or such lesser amount as shall have been advanced to Payee to Maker and shall remain unpaid under this Note on the Maturity Date (as defined
below) in lawful money of the United States of America, on the terms and conditions described below. All payments on this Note shall be
made by check or wire transfer of immediately available funds or as otherwise determined by the Maker to such account as the Payee may
from time to time designate by written notice in accordance with the provisions of this Note.


 


1. Principal. The
entire unpaid principal balance of this Note shall be payable on the earlier of: (i) June 30, 2021 or (ii) the date on which Maker consummates
an initial public offering of its securities (such earlier date, the “Maturity Date”). The principal balance may be
prepaid at any time. Under no circumstances shall any individual, including but not limited to any officer, director, employee or stockholder
of the Maker, be obligated personally for any obligations or liabilities of the Maker hereunder.


 


2. Drawdown Requests.
Maker and Payee agree that Maker may request, from time to time, up to Three Hundred Thousand Dollars ($300,000) in drawdowns under this
Note to be used for costs and expenses related to Maker’s formation and the proposed initial public offering of its securities (the
“IPO”). Principal of this Note may be drawn down from time to time prior to the Maturity Date upon written request
from Maker to Payee (each, a “Drawdown Request”). Each Drawdown Request must state the amount to be drawn down, and
must not be an amount less than Ten Thousand Dollars ($10,000). Payee shall fund each Drawdown Request no later than three (3) business
days after receipt of a Drawdown Request; provided, however, that the maximum amount of drawdowns outstanding under this Note at any time
may not exceed Three Hundred Thousand Dollars ($300,000). No fees, payments or other amounts shall be due to Payee in connection with,
or as a result of, any Drawdown Request by Maker.


 


3. Interest. No interest
shall accrue on the unpaid principal balance of this Note.


 


4. Application of Payments.
All payments shall be applied first to payment in full of any costs incurred in the collection of any sum due under this Note, including
(without limitation) reasonable attorney’s fees, then to the payment in full of any late charges and finally to the reduction of
the unpaid principal balance of this Note.


 






     


    


    

 


5. Events of Default.
The following shall constitute an event of default (“Event of Default”):


 


(a) Failure to Make Required
Payments. Failure by Maker to pay the principal amount due pursuant to this Note within five (5) business days of the date specified
above.


 


(b) Voluntary Bankruptcy,
Etc. The commencement by Maker of a voluntary case under any applicable bankruptcy, insolvency, reorganization, rehabilitation or
other similar law, or the consent by it to the appointment of or taking possession by a receiver, liquidator, assignee, trustee, custodian,
sequestrator (or other similar official) of Maker or for any substantial part of its property, or the making by it of any assignment for
the benefit of creditors, or the failure of Maker generally to pay its debts as such debts become due, or the taking of corporate action
by Maker in furtherance of any of the foregoing.


 


(c) Involuntary Bankruptcy,
Etc. The entry of a decree or order for relief by a court having jurisdiction in the premises in respect of Maker in an involuntary
case under any applicable bankruptcy, insolvency or other similar law, or appointing a receiver, liquidator, assignee, custodian, trustee,
sequestrator (or similar official) of Maker or for any substantial part of its property, or ordering the winding-up or liquidation of
its affairs, and the continuance of any such decree or order unstayed and in effect for a period of 60 consecutive days.


 


6. Remedies.


 


(a) Upon the occurrence of
an Event of Default specified in Section 4(a) hereof, Payee may, by written notice to Maker, declare this Note to be due immediately and
payable, whereupon the unpaid principal amount of this Note, and all other amounts payable hereunder, shall become immediately due and
payable without presentment, demand, protest or other notice of any kind, all of which are hereby expressly waived, anything contained
herein or in the documents evidencing the same to the contrary notwithstanding.


 


(b) Upon the occurrence of
an Event of Default specified in Sections 5(b) or 5(c), the unpaid principal balance of this Note, and all other sums payable with regard
to this Note, shall automatically and immediately become due and payable, in all cases without any action on the part of Payee.


 


7. Waivers. Maker
and all endorsers and guarantors of, and sureties for, this Note waive presentment for payment, demand, notice of dishonor, protest, and
notice of protest with regard to the Note, all errors, defects and imperfections in any proceedings instituted by Payee under the terms
of this Note, and all benefits that might accrue to Maker by virtue of any present or future laws exempting any property, real or personal,
or any part of the proceeds arising from any sale of any such property, from attachment, levy or sale under execution, or providing for
any stay of execution, exemption from civil process, or extension of time for payment; and Maker agrees that any real estate that may
be levied upon pursuant to a judgment obtained by virtue hereof or any writ of execution issued hereon, may be sold upon any such writ
in whole or in part in any order desired by Payee.


 






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8. Unconditional Liability.
Maker hereby waives all notices in connection with the delivery, acceptance, performance, default, or enforcement of the payment of this
Note, and agrees that its liability shall be unconditional, without regard to the liability of any other party, and shall not be affected
in any manner by any indulgence, extension of time, renewal, waiver or modification granted or consented to by Payee, and consents to
any and all extensions of time, renewals, waivers, or modifications that may be granted by Payee with respect to the payment or other
provisions of this Note, and agrees that additional makers, endorsers, guarantors, or sureties may become parties hereto without notice
to Maker or affecting Maker’s liability hereunder.


 


9. Notices. All notices,
statements or other documents which are required or contemplated by this Note shall be: (i) in writing and delivered personally or sent
by first class registered or certified mail, overnight courier service or facsimile or electronic transmission to the address designated
in writing, (ii) by facsimile to the number most recently provided to such party or such other address or fax number as may be designated
in writing by such party and (iii) by electronic mail, to the electronic mail address most recently provided to such party or such other
electronic mail address as may be designated in writing by such party. Any notice or other communication so transmitted shall be deemed
to have been given on the day of delivery, if delivered personally, on the business day following receipt of written confirmation, if
sent by facsimile or electronic transmission, one (1) business day after delivery to an overnight courier service or five (5) days after
mailing if sent by mail.


 


10. Construction.
THIS NOTE SHALL BE CONSTRUED AND ENFORCED IN ACCORDANCE WITH THE LAWS OF NEW YORK, WITHOUT REGARD TO CONFLICT OF LAW PROVISIONS THEREOF.


 


11. Severability.
Any provision contained in this Note which is prohibited or unenforceable in any jurisdiction shall, as to such jurisdiction, be ineffective
to the extent of such prohibition or unenforceability without invalidating the remaining provisions hereof, and any such prohibition or
unenforceability in any jurisdiction shall not invalidate or render unenforceable such provision in any other jurisdiction.


 


12. Trust Waiver.
Notwithstanding anything herein to the contrary, the Payee hereby waives any and all right, title, interest or claim of any kind (“Claim”)
in or to any distribution of or from the trust account to be established in which the proceeds of the IPO conducted by the Maker (including
the deferred underwriters discounts and commissions) and the proceeds of the sale of the warrants issued in a private placement to occur
prior to the consummation of the IPO are to be deposited, as described in greater detail in the registration statement and prospectus
to be filed with the Securities and Exchange Commission in connection with the IPO, and hereby agrees not to seek recourse, reimbursement,
payment or satisfaction for any Claim against the trust account for any reason whatsoever.


 


13. Amendment; Waiver.
Any amendment hereto or waiver of any provision hereof may be made with, and only with, the written consent of the Maker and the Payee.


 


14. Assignment. No
assignment or transfer of this Note or any rights or obligations hereunder may be made by any party hereto (by operation of law or otherwise)
without the prior written consent of the other party hereto and any attempted assignment without the required consent shall be void.


 


[Signature page follows]


 




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IN WITNESS WHEREOF,
Maker, intending to be legally bound hereby, has caused this Note to be duly executed by the undersigned as of the day and year first
above written.


 


	 	FS DEVELOPMENT Corp. III
	 	 	 
	 	By:	/s/ Dennis Ryan
	 	 	Name: Dennis Ryan
	 	 	Title: Chief Financial Officer