Exhibit 10.2


 


 


  


September 17, 2021


 


Petra Acquisition, Inc.


5 West 21st Street


New York, NY 10010


Attn: Andreas Typaldos


 


		Re:	Amendment to Engagement Letter Agreement



 


Dear Mr. Typaldos:


 


This letter amends that certain
engagement letter agreement dated November 3, 2020 (the “Agreement), by and between Petra Acquisition, Inc., a Delaware corporation
(collectively, with its subsidiaries and affiliates, the “Company”) and LifeSci Capital LLC (“LifeSci”),
attached hereto as “Exhibit A,” pursuant to which LifeSci agreed to provide certain investment banking and financial advisory
services to the Company with respect to the Company’s efforts to engage in an initial business combination transaction. Capitalized
terms used herein and not otherwise defined have the meetings ascribed to them in the Agreement.


 


For good and valuable consideration,
the receipt and sufficiency of which are hereby acknowledged, the Company and LifeSci agree as follows:


 


		1.	Paragraph 3 (providing for Placement Agent Services) shall be deleted in its entirety.



 


		2.	Paragraphs 6(a) and 6(b) of the Agreement are hereby amended by deleting them in their entirety and replacing
them with the following:



 


(a) In the event there is a transaction
(or series of related transactions) (a “Transaction”) pursuant to which Petra effectuates a merger, consolidation, reorganization,
equity sale, asset sale or other business combination or similar acquisition transaction with or involving one or more potential target
companies (each a “Target”) or a Target’s affiliate which qualifies as Petra’s initial business combination as
described in Petra’s final prospectus, dated as of October 7, 2020 and filed with the U.S. Securities and Exchange Commission (File
No. 333-240175) on October 13, 2020 that is consummated during the term of the LifeSci Engagement Letter (as extended under paragraph
5(a)), Petra shall pay LifeSci as compensation for investment banking and financial advisory services an advisory fee (the “M&A
Advisory Fee”) of three and one-half percent (3.5%) of the Total Consideration (as defined below). The M&A Advisory Fee shall
be payable as follows:


 


(i) Petra shall pay to LifeSci a cash
fee equal to one percent (1.0%) of the Total Consideration in accordance with clause (b) below; and


 


(ii) Petra shall issue to LifeSci (or
another entity designated by LifeSci) equity interests in the post-Transaction surviving entity with value upon issuance to LifeSci equal
to two and one half percent (2.5%) of the Total Consideration in accordance with clause (b) below.


 



     


     


    

 


In addition, and notwithstanding the earlier
termination of the LifeSci Engagement Letter, in the event that during the period of eighteen (18) months after termination of the LifeSci
Engagement Letter (the “Tail Period”), Petra consummates a Transaction or enters into a definitive agreement with respect
to a Transaction which is subsequently consummated (even if consummated after the end of the Tail Period), LifeSci shall be entitled to
the M&A Advisory Fee with respect to such Transaction,(which shall be reduced by any “break-up,” “termination”
or similar fee or payment from the Target as a result of the termination of an agreement to engage in a Transaction actually received
by LifeSci in connection with such Transaction).


 


(b) For the purposes of the LifeSci
Engagement Letter, “Total Consideration” means the total market value of, without duplication, all cash, securities, debt
or other property paid or transferred at the closing of a Transaction by or to the Target or the Target’s shareholders or to be
paid or transferred in the future to the Target’s shareholders with respect to such Transaction (other than payments of interest
or dividends), including to the extent applicable, any net value paid in respect of (i) the assets of the Target, (ii) amounts paid under
contractual arrangements (including lease arrangements and management fees) or for agreements not to compete or similar agreements, and
(iii) the capital stock of the Target (and the spread value of any “in the money” securities convertible into options, warrants
or other rights to acquire such capital stock), after giving effect to the assumption, retirement or defeasance, directly or indirectly
(by operation of law or otherwise), of any long-term liabilities of the Target or repayment of indebtedness, including indebtedness secured
by the assets of the Target, capital leases or preferred stock obligations; provided, that for the avoidance of doubt, any funds in a
trust account established by Petra (as may be applicable in the case of a Transaction) or financing proceeds raised in connection with
the closing of the Transaction (including by way of an offering of newly issued private equity or equity-linked securities of Petra for
cash, that will be a Private Investment in Public Equity transaction closed immediately prior to or contemporaneously with the Transaction,
the compensation to LifeSci for which is provided for above), in either case, that are not paid to the Target’s shareholders as
consideration in the Transaction will not be included as part of the Total Consideration. In connection with a sale, transfer or other
disposition of 50% or more of the outstanding capital stock of the Target, the Total Consideration will be calculated as if 100% of the
outstanding capital stock on a fully diluted basis had been acquired at the same per share amount paid in such Transaction.


 


		3.	Paragraphs 6 (d) and (e) shall be deleted in their entirety.



 


		4.	All other references to “Placement Agent Services” to be performed
by LifeSci Capital LLC such as in, but not limited to, Paragraphs 4 (a) and 6(f) shall be deleted.



 


		5.	All other references to a “Capital Markets Advisory Fee” payable
to LifeSci Capital such as in, but not limited to, Paragraph 6 (f) shall be deleted.



 






     


     


    

 


		6.	The parties acknowledge that Petra has entered into that certain Agreement
and Plan of Merger with Revelation Biosciences, Inc. dated August 29, 2021 (the “Revelation Merger Agreement”), which provides
for a cap on total transaction expenses. Notwithstanding anything to the contrary in this amendment, in the event the transactions contemplated
by the Revelation Merger Agreement are completed, the maximum fee payable to LifeSci Capital shall be $2,650,000 in cash and $2,650,000
in shares of Parent (as defined in the Revelation Merger Agreement) common stock.



 


		7.	Except as specifically amended hereby, the Agreement shall remain in full
force and effect and all other terms of the Agreement remain unchanged. To the extent any provision of the Agreement is inconsistent with
this letter agreement, this letter agreement shall control. 



 


		8.	This letter agreement may be executed in counterparts and by facsimile,
each of which, when taken together, shall constitute one and the same agreement. Execution and delivery of such counterparts by electronic
means shall not impair the validity of such execution and delivery.



 


	 	Yours truly,
	 	 
	 	LIFESCI CAPITAL LLC
	 	  
	 	By: 	 
	 	Name:	 
	 	Title:	 



  


Accepted and agreed to as
of the date first written above:


 


	PETRA ACQUISITION, INC.	 
	 	 
	By:	 /s/ Andreas Typaldos	 
	Name: Andreas Typaldos	 
	Title: Chief Executive Officer