Exhibit 4.3


 


[Form of Warrant Certificate]


 


[FACE]


 


Number


 


Warrants 


 


THIS WARRANT SHALL BE VOID IF NOT EXERCISED PRIOR
TO 


THE EXPIRATION OF THE EXERCISE PERIOD PROVIDED FOR



IN THE WARRANT AGREEMENT DESCRIBED BELOW 


 


KBL MERGER CORP. IV 


Incorporated Under the Laws of the State of Delaware


 


CUSIP 48242A 112


 


Warrant Certificate 


 


This Warrant
Certificate certifies that _______________, or registered assigns, is the registered holder of ____ warrant(s)
evidenced hereby (the “Warrants” and each, a
“Warrant”) to purchase shares of common stock, par value $0.0001 per share (the “Common
Stock”), of KBL MERGER CORP. IV, a Delaware corporation (the “Company”). Each whole
Warrant entitles the holder, upon exercise during the period set forth in the Warrant Agreement referred to below, to receive
from the Company that number of fully paid and nonassessable shares of Common Stock as set forth below, at the exercise price
(the “Exercise Price”) as determined pursuant to the Warrant Agreement, payable in lawful money (or
through “cashless exercise” as provided for in the Warrant Agreement) of the United States of America upon
surrender of this Warrant Certificate and payment of the Exercise Price at the office or agency of the Warrant Agent referred
to below, subject to the conditions set forth herein and in the Warrant Agreement. Defined terms used in this Warrant
Certificate but not defined herein shall have the meanings given to them in the Warrant Agreement.


 


Each Warrant is initially exercisable for
one-half of one fully paid and non-assessable share of Common Stock. The number of the shares of Common Stock issuable upon
exercise of the Warrants is subject to adjustment upon the occurrence of certain events set forth in the Warrant
Agreement.


 


The initial Exercise Price per share of Common
Stock for any Warrant is equal to $5.75 per half share ($11.50 per whole share), provided, however, that a Warrant may not be
exercised for a fractional share, so that only an even number of Warrants may be exercised at a given time. The Exercise Price
is subject to adjustment upon the occurrence of certain events set forth in the Warrant Agreement.


 


Subject to the conditions set forth in the Warrant
Agreement, the Warrants may be exercised only during the Exercise Period and to the extent not exercised by the end of such Exercise
Period, such Warrants shall become void.


 


Reference is hereby made to the further provisions
of this Warrant Certificate set forth on the reverse hereof and such further provisions shall for all purposes have the same effect
as though fully set forth at this place.


 


This Warrant Certificate shall not be valid unless
countersigned by the Warrant Agent, as such term is used in the Warrant Agreement.


 






     


     


    

 


This Warrant Certificate shall be governed by and
construed in accordance with the internal laws of the State of New York, without regard to conflicts of laws principles thereof.


 


	 	KBL
    MERGER CORP. IV
	 	 	 
	 	By:	
	 	Name:	Marlene
    Krauss, M.D. 
	 	Title:	Chief
    Executive Officer


 


	 	
        CONTINENTAL STOCK TRANSFER &

 TRUST COMPANY, as Warrant Agent

	 	 	 
	 	By:	                
	 	Name: 	
	 	Title: 	





 


 






     


     


    

 


[Form of Warrant Certificate]


 


[Reverse] 


 


The Warrants evidenced by this Warrant Certificate
are part of a duly authorized issue of Warrants entitling the holder on exercise to receive shares of Common Stock and are issued
or to be issued pursuant to a Warrant Agreement dated as of [_________], 2017 (the “Warrant Agreement”),
duly executed and delivered by the Company to Continental Stock Transfer & Trust Company, a New York corporation, as warrant
agent (the “Warrant Agent”), which Warrant Agreement is hereby incorporated by reference in and made
a part of this instrument and is hereby referred to for a description of the rights, limitation of rights, obligations, duties
and immunities thereunder of the Warrant Agent, the Company and the holders (the words “holders” or “holder”
meaning the Registered Holders or Registered Holder) of the Warrants. A copy of the Warrant Agreement may be obtained by the holder
hereof upon written request to the Company. Defined terms used in this Warrant Certificate but not defined herein shall have the
meanings given to them in the Warrant Agreement.


 


Warrants may be exercised at any time during the Exercise
Period set forth in the Warrant Agreement. The holder of Warrants evidenced by this Warrant Certificate may exercise them by surrendering
this Warrant Certificate, with the form of election to purchase set forth hereon properly completed and executed, together with
payment of the Exercise Price as specified in the Warrant Agreement (or through “cashless exercise” as provided for
in the Warrant Agreement) at the principal corporate trust office of the Warrant Agent. In the event that upon any exercise of
Warrants evidenced hereby the number of Warrants exercised shall be less than the total number of Warrants evidenced hereby, there
shall be issued to the holder hereof or his, her or its assignee, a new Warrant Certificate evidencing the number of Warrants not
exercised.


 


Notwithstanding anything else in this Warrant Certificate
or the Warrant Agreement, no Warrant may be exercised unless at the time of exercise (i) a registration statement covering the
shares of Common Stock to be issued upon exercise is effective under the Securities Act and (ii) a prospectus thereunder relating
to the shares of Common Stock is current, except through “cashless exercise” as provided for in the Warrant Agreement.


 


The Warrant Agreement provides that upon the occurrence
of certain events the number of shares of Common Stock issuable upon exercise of the Warrants set forth on the face hereof may,
subject to certain conditions, be adjusted. If, upon exercise of a Warrant, the holder thereof would be entitled to receive a fractional
interest in a share of Common Stock, the Company shall, upon exercise, round down to the nearest whole number of shares of Common
Stock to be issued to the holder of the Warrant.


 


Warrant Certificates, when surrendered at the principal
corporate trust office of the Warrant Agent by the Registered Holder thereof in person or by legal representative or attorney duly
authorized in writing, may be exchanged, in the manner and subject to the limitations provided in the Warrant Agreement, but without
payment of any service charge, for another Warrant Certificate or Warrant Certificates of like tenor evidencing in the aggregate
a like number of Warrants.


 


Upon due presentation for registration of transfer
of this Warrant Certificate at the office of the Warrant Agent, a new Warrant Certificate or Warrant Certificates of like tenor
and evidencing in the aggregate a like number of Warrants shall be issued to the transferee(s) in exchange for this Warrant Certificate,
subject to the limitations provided in the Warrant Agreement, without charge except for any tax or other governmental charge imposed
in connection therewith.


 


The Company and the Warrant Agent may deem and treat
the Registered Holder(s) hereof as the absolute owner(s) of this Warrant Certificate (notwithstanding any notation of ownership
or other writing hereon made by anyone) for the purpose of any exercise hereof, of any distribution to the holder(s) hereof, and
for all other purposes, and neither the Company nor the Warrant Agent shall be affected by any notice to the contrary. Neither
the Warrants nor this Warrant Certificate entitles any holder hereof to any rights of a stockholder of the Company.


 


Election to Purchase


 


(To Be Executed Upon Exercise of Warrant)


 






     


     


    

 


The undersigned hereby irrevocably elects to exercise
the right, represented by this Warrant Certificate, to receive shares of Common Stock and herewith tenders payment for such shares
to the order of KBL MERGER CORP. IV (the “Company”) in the amount of $[____] in accordance with the terms
hereof. The undersigned requests that a certificate for such shares be registered in the name of [__________________], whose address
is and that such shares be delivered to whose address is [__________________]. If said number of shares is less than all of the
shares of Common Stock purchasable hereunder, the undersigned requests that a new Warrant Certificate representing the remaining
balance of such shares be registered in the name of [_________], whose address is [______________], and that such Warrant Certificate
be delivered to [___________], whose address is [___________].


 


In the event that the Warrant has been called for redemption
by the Company pursuant to Section 6 of the Warrant Agreement and the Company has required cashless exercise pursuant to
Section 6.3 of the Warrant Agreement, the number of shares that this Warrant is exercisable for shall be determined in accordance
with subsection 3.3.1(b) and Section 6.3 of the Warrant Agreement.


 


In the event that the Warrant is a Private Placement
Warrant that is to be exercised on a “cashless” basis pursuant to subsection 3.3.1(c) of the Warrant Agreement,
the number of shares that this Warrant is exercisable for shall be determined in accordance with subsection 3.3.1(c) of
the Warrant Agreement.


 


In the event that the Warrant is to be exercised on
a “cashless” basis pursuant to Section 3.3.1 of the Warrant Agreement, the number of shares that this Warrant
is exercisable for shall be determined in accordance with Section 3.3.1 of the Warrant Agreement.


 


In the event that the Warrant may be exercised, to
the extent allowed by the Warrant Agreement, through cashless exercise (i) the number of shares that this Warrant is exercisable
for would be determined in accordance with the relevant section of the Warrant Agreement which allows for such cashless exercise
and (ii) the holder hereof shall complete the following: The undersigned hereby irrevocably elects to exercise the right, represented
by this Warrant Certificate, through the cashless exercise provisions of the Warrant Agreement, to receive shares of Common Stock.
If said number of shares is less than all of the shares of Common Stock purchasable hereunder (after giving effect to the cashless
exercise), the undersigned requests that a new Warrant Certificate representing the remaining balance of such shares be registered
in the name of [______], whose address is [_________], and that such Warrant Certificate be delivered to [__________________],
whose address is [__________________].


 


[Signature Page Follows]








 






     


     


    

 


	 	 
	 	 
	Date:       , 20  	(Signature)
	 	 
	 	 
	 	(Address)
	 	 
	 	
	 	(Tax
    Identification Number)


 


	 	 
	Signature Guaranteed:	 
	 	 
		 


 


THE SIGNATURE(S) SHOULD BE GUARANTEED BY AN ELIGIBLE GUARANTOR INSTITUTION
(BANKS, STOCKBROKERS, SAVINGS AND LOAN ASSOCIATIONS AND CREDIT UNIONS WITH MEMBERSHIP IN AN APPROVED SIGNATURE GUARANTEE MEDALLION
PROGRAM, PURSUANT TO S.E.C. RULE 17Ad-15).