Document:

Preferred Unit Purchase Warrant and Global Amendment

 Exhibit 4.3 
 THIS WARRANT AND THE SECURITIES ISSUABLE UPON CONVERSION HEREOF HAVE NOT BEEN REGISTERED UNDER THE SECURITIES ACT OF 1933, AS AMENDED, OR APPLICABLE STATE SECURITIES LAWS. THIS WARRANT HAS BEEN ACQUIRED
FOR INVESTMENT AND NOT WITH A VIEW TO DISTRIBUTION OR RESALE. THIS WARRANT AND THE UNDERLYING SECURITIES MAY NOT BE SOLD, MORTGAGED, PLEDGED, HYPOTHECATED OR OTHERWISE TRANSFERRED WITHOUT AN EFFECTIVE REGISTRATION STATEMENT UNDER THE SECURITIES ACT
OF 1933, AS AMENDED, AND ANY APPLICABLE STATE SECURITIES LAWS, OR THE AVAILABILITY OF AN EXEMPTION FROM THE REGISTRATION PROVISIONS OF THE SECURITIES ACT OF 1933, AS AMENDED, AND APPLICABLE STATE SECURITIES LAWS. 

CEMPRA HOLDINGS, LLC 
 PREFERRED UNIT PURCHASE WARRANT 
 Void After August
    , 2018 
 This Preferred Unit Purchase Warrant (the “Warrant”) is issued as
of this the          day of August 2011, by CEMPRA HOLDINGS, LLC, a Delaware limited liability company (the “Company”), to
                    , or permitted assigns (the “Holder”). 

1. Issuance of Warrant; Term; Price. 
 1.1 Issuance. Concurrently herewith, the Holder is making a loan to the Company in the amount of $             (the
“Loan”) pursuant to the terms of that certain Unsecured Convertible Promissory Note and Warrant Purchase Agreement among the Company, the Holder and the Purchasers listed on Schedule A thereto, dated as of the date hereof (the
“Purchase Agreement”). The Loan is evidenced by an Unsecured Convertible Promissory Note dated as of the date hereof, in the original principal amount of
$            , payable to the order of the Holder, by the Company (together with any and all extensions, replacements and renewals thereof, the “Note”). In
consideration of the funding of the Loan, the receipt and sufficiency of which are hereby acknowledged, the Company hereby grants to Holder the right to purchase: (a) if there is no Qualified Private Financing (as defined in the Note) or
Qualified IPO (as defined in the Note) prior to August     , 2012 (the “Maturity Date”), or upon a Company Sale (as defined in the Note) or Subsidiary Sale (as defined in the Note) before the Maturity
Date, a number of units of Class C Units equal to twenty-five percent (25%) of the principal amount of the Note divided by $1.07857, subject to appropriate adjustment in the event of any unit distribution, unit split, combination,
reclassification or other similar recapitalization affecting such units (the “Class C Conversion Price”), or (b) alternatively, upon the first to occur of a Qualified Private Financing or a Qualified IPO before the Maturity
Date, a number of the securities issued in the Qualified Private Financing or Qualified IPO equal to twenty-five percent (25%) of the principal amount of the Note divided by either the price per unit of the securities issued in the Qualified
Private Financing or the offering price of the Company’s Common Units (or equivalent security) in the Qualified IPO, as the case may be, subject to appropriate adjustment in the event of any unit distribution, unit split, combination,
reclassification or other similar recapitalization affecting such units (the “Alternate Conversion  

  
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Price”). The unit of securities for which this Warrant may be exercisable from time to time shall be referred to herein as the “Warrant Units.” 

1.2 Term. The units of Warrant Units issuable upon exercise of this Warrant are hereinafter referred to as the
“Units.” This Warrant shall be exercisable at any time and from time to time in whole or in part from the date hereof until the date seven (7) years from the issue date of this Warrant referenced above. 

1.3 Exercise Price. The exercise price (the “Warrant Price”) for the Warrant shall equal either the Class C
Conversion Price or the Alternate Conversion Price, as the case may be, used to determine the number of securities issuable upon exercise of the Warrant under Section 1.1. 

2. Adjustment of Warrant Price, Number and Kind of Units. The Warrant Price and the number and kind of securities issuable upon
the exercise of this Warrant shall be subject to adjustment from time to time, and the Company agrees to provide ten (10) days written notice upon the happening of certain events, as follows: 

2.1 Dividends in Unit Adjustment. In case at any time or from time to time on or after the date hereof the holders of the Warrant
Units of the Company (or any other securities at the time receivable upon the exercise of this Warrant) shall have received, or, on or after the record date fixed for the determination of eligible unitholders, shall have become entitled to receive,
without payment therefor, other or additional securities or other property (other than cash) of the Company by way of dividend or distribution (except for distributions specifically provided for below in Section 2.3), then and in each case, the
holder of this Warrant shall, upon the exercise hereof, be entitled to receive, in addition to the number of units of Warrant Units receivable thereupon, and without payment of any additional consideration therefor, the amount of such other or
additional securities or other property (other than cash) of the Company which such holder would hold on the date of such exercise had it been the holder of record of such Units on the date hereof and had thereafter, during the period from the date
hereof to and including the date of such exercise, retained such Units and/or all other additional securities or other property receivable by it as aforesaid during such period, giving effect to all adjustments called for during such period by this
Section 2. 
 2.2 Reclassification or Reorganization Adjustment. In case of any changes in the class or kind of
securities issuable upon exercise of this Warrant or any reclassification or change of the outstanding securities of the Company or of any reorganization of the Company (or any other company the securities of which are at the time receivable upon
the exercise of this Warrant) or any spin-off by the Company of another entity owned or controlled by the Company at any time and from time to time on or after the date hereof, the holder of this Warrant, upon the exercise hereof at any time after
the consummation of such reclassification, change, reorganization, or spin-off shall be entitled to receive, in lieu of the units or other securities and property receivable upon the exercise hereof prior to such consummation, the units or other
securities or property to which such holder would have been entitled upon such consummation if such holder had exercised this Warrant immediately prior thereto and the Warrant Price therefore shall be appropriately adjusted, all subject to further
adjustment as provided in this Section 2. 

  
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 2.3 Unit Splits and Reverse Unit Splits. If at any time on or after the date hereof
the Company shall split, subdivide or otherwise change its outstanding units of any securities receivable upon exercise of this Warrant into a greater number of units, the Warrant Price in effect immediately prior to such subdivision shall thereby
be proportionately reduced and the number of Units receivable upon exercise of this Warrant shall thereby be proportionately increased; and, conversely, if at any time on or after the date hereof the outstanding number of units of any securities
receivable upon exercise of this Warrant shall be combined into a smaller number of units, the Warrant Price in effect immediately prior to such combination shall thereby be proportionately increased and the number of Units receivable upon exercise
of this Warrant shall thereby be proportionately decreased. 
 2.4 Conversion or Redemption of Warrant Units. If at the
time of any exercise of this Warrant there are no other units of Warrant Units that would otherwise be receivable upon exercise of this Warrant (all such units of such class having been converted or redeemed), this Warrant shall be exercisable for
Common Units in the same amounts, for the same prices and on the same terms, as though the Warrant had been exercised for units of the Warrant Units and immediately converted into Common Units, and all references herein to “Warrant Units”
shall be deemed to refer to the Common Units of the Company. 
 2.5 Company Sale. If at any time while this Warrant, or
any portion hereof, is outstanding and unexpired there shall occur a Company Sale, the Holder shall have the right thereafter to exercise this Warrant for the kind and amount of shares of stock or other securities, property or cash receivable upon
such Transaction by a holder of the number of Warrant Units into which this Warrant could have been exercised immediately prior to such Transaction, and provision shall be made therefor in the agreement, if any, relating to such Transaction. Such
certificate shall provide for adjustments which shall be as nearly equivalent as may be practicable to the adjustments provided for in this Section 2. The provisions of this Section 2.5 and any equivalent thereof in any such certificate
similarly shall apply to successive transactions. 
 2.6 Other Impairment. The Company shall not, by amendment of its
Second Amended and Restated Limited Liability Company Agreement, as amended from time to time (the “LLC Agreement”), or through any reorganization, transfer of assets, consolidation, merger, dissolution, issue or sale of securities
or any other voluntary action, avoid or seek to avoid the observance or performance of any of the terms of this Warrant, but shall at all times in good faith assist in the carrying out of all such terms and in the taking of all such action as may be
necessary or appropriate in order to protect the rights of the holder of this Warrant against impairment. 
 3. No Fractional
Units. No fractional units shall be issued in connection with any subscription hereunder. In lieu of any fractional units that would otherwise be issuable, the Company shall round the number of units issuable upon exercise of this Warrant to the
nearest whole number. 
 4. No Unitholder Rights. This Warrant as such shall not entitle its holder to any of the rights
of a unitholder of the Company. 

  
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 5. Reservation of Units. The Company covenants that during the period this Warrant is
exercisable, the Company shall reserve from its authorized and unissued Warrant Units a sufficient number of units to provide for the issuance of Warrant Units upon the exercise of this Warrant. The Company agrees that its issuance of this Warrant
shall constitute full authority to its officers who are charged with the duty of executing securities to execute and issue the necessary certificates for units of Warrant Units upon the exercise of this Warrant. 

6. Exercise of Warrant. This Warrant may be exercised by Holder by the surrender of this Warrant at the principal office of the
Company, accompanied by payment in full of the purchase price of the units purchased thereby, as described above. This Warrant shall be deemed to have been exercised immediately prior to the close of business on the date of its surrender for
exercise as provided above, and the person or entity entitled to receive the units or other securities issuable upon such exercise shall be treated for all purposes as the holder of such units of record as of the close of business on such date. As
promptly as practicable, the Company shall issue and deliver to the person or entity entitled to receive the same a certificate or certificates for the number of full units of Warrant Units issuable upon such exercise, together with cash in lieu of
any fraction of a unit as provided above. The units of Warrant Units issuable upon exercise hereof shall, upon their issuance, be fully paid and nonassessable. If this Warrant shall be exercised in part only, the Company shall, at the time of
delivery of the certificate representing the Units or other securities in respect of which this Warrant has been exercised, deliver to the Holder a new Warrant evidencing the right to purchase the remaining Units or other securities purchasable
under this Warrant, which new warrant shall, in all other respects, be identical to this Warrant. 
 7. Net Issue
Election. 
 7.1 Right to Convert. In addition to and without limiting the rights of the Holder under the terms of
this Warrant, the Holder shall have the right to convert this Warrant or any portion hereof (the “Conversion Right”) into units of Warrant Units as provided in this Section 7. Upon exercise of the Conversion Right with respect
to a particular number of units subject to this Warrant (the “Converted Warrant Units”), the Company shall deliver to the Holder (without payment by the Holder of any cash or other consideration) that number of units of Warrant
Units equal to the quotient obtained by dividing (x) the value of this Warrant (or the specified portion hereof) on the Conversion Date (as defined in subsection 7.2 hereof), which value shall be determined by subtracting (A) the aggregate
Warrant Price of the Converted Warrant Units immediately prior to the exercise of the Conversion Right from (B) the aggregate fair market value of the Converted Warrant Units issuable upon exercise of this Warrant (or the specified portion
hereof) on the Conversion Date (as herein defined) by (y) the fair market value of one unit of Warrant Units on the Conversion Date (as herein defined). No fractional units shall be issuable upon exercise of the Conversion Right, and if the
number of units to be issued determined in accordance with the foregoing formula is other than a whole number, the Company shall round the number of units of Warrant Units issuable upon exercise of this Warrant to the nearest whole number.

 7.2 Method of Exercise. The Conversion Right may be exercised by the Holder by the surrender of this Warrant at the
principal office of the Company together with a written statement specifying that the Holder thereby intends to exercise the Conversion Right and indicating the number of units subject to this Warrant that are being surrendered (referred to

  
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in subsection 7.1 hereof as the Converted Warrant Units) in exercise of the Conversion Right. Such conversion shall be effective upon such surrender of this Warrant (the “Conversion
Date”). Certificates for the units of Warrant Units issuable upon exercise of the Conversion Right (or any other securities deliverable in lieu thereof under Section 2) shall be issued as of the Conversion Date and shall be delivered
to the Holder immediately following the Conversion Date, or, if requested at the time of surrender of this Warrant, held for pick-up by the Holder at the Company’s principal office. 

7.3 Determination of Fair Market Value. For purposes of this Section 7, fair market value (the “Market
Price”) of a unit of Warrant Units as of a particular date (the “Determination Date”) shall mean the average of the closing prices of such security’s sales on the principal securities exchanges on which such security
may at the time be listed, or, if there has been no sales on any such exchange on any day, the average of the highest bid and lowest asked prices on all such exchanges at the end of such day, or, if on any day such security is not so listed, the
average of the highest bid and lowest asked prices on such day in the domestic over-the-counter market as reported by the National Quotation Bureau, Incorporated, or any similar successor organization, in each such case averaged over a period of
five (5) days consisting of the day prior to the day as of which “Market Price” is being determined and the five (5) consecutive business days prior to such day. If at any time such security is not listed on any securities
exchange or quoted in the over-the-counter market, the “Market Price” shall be the fair value thereof as determined in good faith by the Company’s Board of Representatives. 

8. Certificate of Adjustment. Whenever the Warrant Price or number or type of securities issuable upon exercise of this Warrant is
adjusted, as herein provided, the Company shall promptly deliver to the record holder of this Warrant a certificate of an officer of the Company setting forth the nature of such adjustment and a brief statement of the facts requiring such
adjustment. 
 9. Notice of Proposed Transfers. This Warrant is transferable by the Holder hereof subject to compliance
with this Section 9. Prior to any proposed transfer of this Warrant or the units of Warrant Units received on the exercise of this Warrant (the “Securities”), unless there is in effect a registration statement under the
Securities Act of 1933, as amended (the “Securities Act”), covering the proposed transfer, the Holder thereof shall give written notice to the Company of such Holder’s intention to effect such transfer. Each such notice shall
describe the manner and circumstances of the proposed transfer in sufficient detail, and shall, if the Company so requests, be accompanied (except in transactions in compliance with Rule 144) by either (i) an unqualified written opinion of
legal counsel who shall be reasonably satisfactory to the Company addressed to the Company and reasonably satisfactory in form and substance to the Company’s counsel, to the effect that the proposed transfer of the Securities may be effected
without registration under the Securities Act and any applicable state securities laws, or (ii) a “no action” letter from the Securities Exchange Commission (the “Commission”) to the effect that the transfer of such
Securities without registration shall not result in a recommendation by the staff of the Commission that action be taken with respect thereto, whereupon the Holder of the Securities shall be entitled to transfer the Securities in accordance with the
terms of the notice delivered by the Holder to the Company; provided, however, no such registration statement or opinion of counsel shall be necessary for a transfer by a Holder to any affiliate of such Holder, or a transfer by a
Holder which is a partnership 

  
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to a partner of such partnership or a retired partner of such partnership who retires after the date hereof, or to the estate of any such partner or retired partner or the transfer by gift, will
or intestate succession of any partner to his spouse or lineal descendants or ancestors, if the transferee agrees in writing to be subject to the terms hereof to the same extent as if such transferee were the original Holder hereunder. Each
certificate evidencing the Securities transferred as above provided shall bear the appropriate restrictive legend set forth above, except that such certificate shall not bear such restrictive legend if in the opinion of counsel for the Company such
legend is not required in order to establish compliance with any provisions of the Securities Act. Further, prior to the transfer of this Warrant to any transferee as permitted under this Section 9, such transferee must agree in writing to
execute any documents necessary, including the Company’s form of joinder agreement, to become party to the Company’s LLC Agreement (or equivalent governing document), and subject to the terms thereof, upon any exercise or conversion of
this Warrant into units of the Company pursuant to the terms hereof. 
 10. Notice of Dividends and Distributions. For so
long as any part of this Warrant remains outstanding and unexercised, the Company shall, upon the declaration of a cash dividend upon its Common Units, Preferred Units or Warrant Units or other distribution to the Holders of its Common Units,
Preferred Units or Warrant Units and at least ten (10) days prior to the record date, notify the Holder hereof of such declaration, which notice will contain, at a minimum, the following information: (a) the date of the declaration of the
dividend or distribution; (b) the amount of such dividend or distribution; (c) the record date of such dividend or distribution; and (d) the payment date or distribution date of such dividend or distribution. 

11. Replacement of Warrants. Upon receipt by the Company of evidence reasonably satisfactory to the Company of the loss, theft,
destruction or mutilation of the Warrant, and in the case of any such loss, theft or destruction of the Warrant, on delivery of an indemnity agreement or security reasonably satisfactory in form and amount to the Company, and reimbursement to the
Company of all reasonable expenses incidental thereto, and upon surrender and cancellation of the Warrant if mutilated, the Company shall execute and deliver, in lieu thereof, a new Warrant of like tenor. 

12. Notices. All notices and other communications from the Company to the Holder shall be given in accordance with
Section 7.10 of the Purchase Agreement. 
 13. Miscellaneous. This Warrant shall be governed by the laws of the
State of Delaware. The headings in this Warrant are for purposes of convenience of reference only, and shall not be deemed to constitute a part hereof. The invalidity or unenforceability of any provision hereof shall in no way affect the validity or
enforceability of any other provisions. 
 14. Amendment. Any term of this Warrant may be amended or waived with the
written consent of the Company and the holders of Warrants representing a majority of the units of Warrant Units issuable upon exercise of the then outstanding unexercised warrants issued under the Purchase Agreement (the “Bridge
Warrants”); provided, however, that any such amendment or waiver that disproportionately affects any of the holders of the then outstanding unexercised warrants issued pursuant to the Purchase Agreement shall require the
written consent of all such holders. Any amendment or waiver effected in accordance with this Section 14 shall be binding upon each holder 

  
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of any Bridge Warrant, each future holder of all such Bridge Warrants and the Company, and the Company shall promptly give notice to all holders of outstanding Bridge Warrants of any amendment or
waiver effected in accordance with this Section 14. 
 15. Taxes. The Company shall pay all issue taxes and other
governmental charges (but not including any income taxes of Holder) that may be imposed in respect of the issuance or delivery of the units, or any portion thereof, upon exercise of this Warrant. 

16. Remedies. In the event of any default or threatened default by the Company in the performance of or observance with any of the
terms of this Warrant, it is agreed that remedies at law are not and shall not be adequate for the Holder and that such terms may be specifically enforced by a decree for the specific performance of any agreement contained herein or by an injunction
against a violation of any of the terms hereof or otherwise. 
 [Signature page follows.] 

  
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 IN WITNESS WHEREOF, the undersigned officer of the Company has executed this Preferred Unit
Purchase Warrant as of the date first above written. 
  

			
	COMPANY:
	
	CEMPRA HOLDINGS, LLC
		
	By:	 	  

	Name:	 	Prabhavathi Fernandes, Ph. D.
	Title:	 	Chief Executive Officer

 GLOBAL AMENDMENT TO 

PREFERRED UNIT PURCHASE WARRANTS 
 Issued August 5, 2011 
 THIS GLOBAL AMENDMENT TO
PREFERRED UNIT PURCHASE WARRANTS (the “Amendment”) is entered into this 11th day of October 2011, by and among Cempra Holdings LLC, a Delaware limited liability company (the “Company”), and the undersigned holders of Preferred Unit Purchase Warrants (the
“Bridge Warrants”) issued pursuant to that certain Unsecured Convertible Promissory Note and Warrant Purchase Agreement dated August 5, 2011 (the “Purchase Agreement”), by and among the Company and the
purchasers listed on Schedule A thereto (collectively, the “Warrant Holders”). 
 WHEREAS, each Bridge Warrant
provides in Section 14 thereof that it may be amended by the written consent of the Company and the holders of Bridge Warrants representing a majority of the units of Warrant Units (as defined therein) issuable upon exercise of the then
outstanding unexercised Bridge Warrants (the “Requisite Holders”) and that any such amendment effected in accordance with Section 14 will be binding on each holder of the Bridge Warrants; 

WHEREAS, the Company and the Warrant Holders desire to amend the Bridge Warrants to, among other things, modify the definition of the
term “Qualified IPO,” and provide for the issuance of a replacement warrant upon the occurrence of a “Qualified IPO”; and 
 WHEREAS, the undersigned Warrant Holders constitute the Requisite Holders required to amend the Bridge Warrants. 
 NOW, THEREFORE, in consideration of the mutual promises, covenants and conditions set forth in this Amendment, and other good and valuable consideration, the receipt of which is hereby acknowledged, and
pursuant to Section 14 of the Bridge Warrants, the parties to this Amendment mutually agree as follows: 
 1.
Capitalized Terms. All capitalized terms used herein that are not otherwise defined herein shall have the meanings assigned to them in the Bridge Warrants unless the context hereof requires otherwise. 

2. Amendments. The Bridge Warrants are hereby amended as follows. 

(A) Section 1.1 of the Bridge Warrants shall be amended by replacing the parenthetical phrase “(as defined in
the Note)” as it applies to the term “Qualified IPO” in clause (a) of the third sentence thereof with the parenthetical phrase “(as defined below)”. 

(B) Section 1 of the Bridge Warrants shall be amended by inserting the following Section 1.4 immediately
following Section 1.3. 
 “1.4 Definitions. For purposes of this Warrant, the term
“Qualified IPO” means the closing of the sale of the Company’s Common Units (or equivalent security) in 

 
a firm commitment underwritten public offering registered under the Securities Act of 1933, as amended.” 

(C) The following Section 17 shall be inserted immediately following Section 16: 

“17. Amended and Restated Warrant. Upon the occurrence of a Qualified IPO, the Company shall issue an Amended
and Restated Warrant as a replacement for this Warrant (the “Replacement Warrant”). The Replacement Warrant shall specify the number of shares of the Company’s Common Stock for which it is exercisable (calculated in accordance
with Section 1 hereof) and the exercise price for such shares of the Company’s Common Stock (calculated in accordance with Section 1 hereof). Upon the issuance of the Replacement Warrant, this Warrant shall automatically be cancelled
and the Holder shall cease to have any rights under this Warrant. To receive the Replacement Warrant, the Holder shall surrender this Warrant to the Company or its designee for cancellation; provided, however, that the cancellation of this Warrant
shall be effective at the time the Replacement Warrant is issued, whether or not the Holder has surrendered this Warrant for cancellation.” 
 (D) For all purposes, each and every reference to the word “Unit,” “Units,” “unit,” “units,” “Unitholder,” “Unitholders,” “unitholder”
and “unitholders” in the Bridge Warrants shall be deemed to be references to the words “Share,” “Shares,” “share,” “shares,” “Shareholder” “Shareholders,” “shareholder”
and “shareholders” respectively, provided, however, that the phrase “unit of securities” in the last sentence of Section 1.1 shall remain unchanged. 

3. Replacement Warrant. The “Replacement Warrant” referenced in the text of Section 2(C) of this Amendment shall be
in the form attached hereto as Exhibit A. 
 4. No Other Amendment. Except as specifically amended pursuant to
this Amendment, the Bridge Warrants shall remain in full force and effect in accordance with their terms. 
 5. Governing
Law. All questions concerning the construction, validity and interpretation of this Amendment will be governed by and construed in accordance with the internal law (and not the law of conflicts) of the State of Delaware. 

6. Counterparts. This Amendment may be executed in two or more counterparts, each of which shall be deemed an original, but all of
which together shall constitute one and the same instrument. 
 7. Binding Effect. This Amendment shall be binding upon
and shall inure to the benefit of the parties hereto, all the Warrant Holders and their heirs, successors and assigns. 
 [The
next page is the signature page.] 

  
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 IN WITNESS WHEREOF, the parties have executed this Global Amendment to Preferred Unit
Purchase Warrants as of the date first above written. 
  

							
	COMPANY:	 		 	CEMPRA HOLDINGS, LLC
				
		 		 	By:	 	/s/ Prabhavathi Fernandes
		 		 	Name:	 	Prabhavathi Fernandes, Ph.D.
		 		 	Title:	 	President
			
	WARRANT HOLDERS:	 		 	QUAKER BIOVENTURES II, L.P.
				
		 		 	By:	 	 Quaker Bioventures Capital II, L.P.,
 its General Partner

				
		 		 	By:	 	 Quaker Bioventures Capital II, LLC,
 its General Partner

				
		 		 	By:	 	/s/ Sherrill Neff
		 		 	Name:	 	P. Sherrill Neff
		 		 	Title:	 	Member
			
		 		 	DEVON PARK BIOVENTURES, L.P.
				
		 		 	By:	 	 Devon Park Associates, L.P.,

its General Partner

				
		 		 	By:	 	/s/ Devang V. Kantesaria
		 		 	Name:	 	Devang V. Kantesaria
		 		 	Title:	 	General Partner

 Signature Page to Global Amendment to Preferred Unit Purchase Warrants 

									
	WARRANT HOLDERS:	 		 	AISLING CAPITAL II, LP
					
		 		 		 	By:	 	 Aisling Capital Partners, LP,

its General Partner

					
		 		 		 	By:	 	/s/ Lloyd Appel
		 		 		 	Name:	 	Lloyd Appel
		 		 		 	Title:	 	CFO
				
		 		 		 	BLACKBOARD VENTURES INC.
					
		 		 		 	By:	 	/s/ Terry Woodward
		 		 		 	Name:	 	Terry Woodward
		 		 		 	Title:	 	Director
				
		 		 		 	INTERSOUTH PARTNERS VI, L.P.
					
		 		 		 	By:	 	 Intersouth Associates VI, LLC,

its General Partner

					
		 		 		 	By:	 	/s/ Richard Kent
		 		 		 	Name:	 	Richard Kent
		 		 		 	Title:	 	Member, acting pursuant to Power of Attorney
				
		 		 		 	INTERSOUTH PARTNERS VII, L.P.
					
		 		 		 	By:	 	 Intersouth Associates VII, LLC,

its General Partner

					
		 		 		 	By:	 	/s/ Richard Kent
		 		 		 	Name:	 	Richard Kent
		 		 		 	Title:	 	Member, acting pursuant to Power of Attorney

 Signature Page to Global Amendment to Preferred Unit Purchase Warrants 

									
	WARRANT HOLDERS:	 		 	/s/ I. Wistar Morris
		 		 	I. Wistar Morris, III
				
		 		 		 	/s/ Martha Morris
		 		 		 	Martha H. Morris
				
		 		 		 	COTSWOLD FOUNDATION
					
		 		 		 	By:	 	/s/ I. Wistar Morris and Martha Morris
		 		 		 	Name:	 	 
		 		 		 	Title:	 	 
				
		 		 		 	ELEVENTH GENERATION PARTNERSHIP, LP
					
		 		 		 	By:	 	/s/ Martha Morris
		 		 		 	Name:	 	 
		 		 		 	Title:	 	 

 Signature Page to Global Amendment to Preferred Unit Purchase Warrants 

 EXHIBIT A 

FORM OF REPLACEMENT WARRANT 

 THIS WARRANT AND THE SECURITIES ISSUABLE UPON CONVERSION HEREOF HAVE NOT BEEN REGISTERED UNDER THE
SECURITIES ACT OF 1933, AS AMENDED, OR APPLICABLE STATE SECURITIES LAWS. THIS WARRANT HAS BEEN ACQUIRED FOR INVESTMENT AND NOT WITH A VIEW TO DISTRIBUTION OR RESALE. THIS WARRANT AND THE UNDERLYING SECURITIES MAY NOT BE SOLD, MORTGAGED, PLEDGED,
HYPOTHECATED OR OTHERWISE TRANSFERRED WITHOUT AN EFFECTIVE REGISTRATION STATEMENT UNDER THE SECURITIES ACT OF 1933, AS AMENDED, AND ANY APPLICABLE STATE SECURITIES LAWS, OR THE AVAILABILITY OF AN EXEMPTION FROM THE REGISTRATION PROVISIONS OF THE
SECURITIES ACT OF 1933, AS AMENDED, AND APPLICABLE STATE SECURITIES LAWS. 
 CEMPRA, INC. 

AMENDED AND RESTATED WARRANT 
 Void After August 5, 2018 
 This Amended and Restated Purchase Warrant
(the “Warrant”) of CEMPRA, INC., a Delaware corporation (the “Company”) is made as of this the    day of    201  , and amends and restates the Preferred Unit
Purchase Warrant of the Company, dated as of August 5, 2011 (the “Original Warrant”), issued by the Company to (together with successors and assigns, the “Holder”) in connection with that certain Unsecured
Convertible Promissory Note and Warrant Purchase Agreement among the Company, the Holder and the Purchasers listed on Schedule A thereto dated August 5, 2011 (the “Purchase Agreement”). 

1. Issuance of Warrant; Term; Price. 
 1.1 Issuance. The Company hereby grants to Holder the right to purchase fully paid and non-assessable shares of Common Stock, $0.001 par value per share, of the Company for a purchase price per
share equal to $        . The shares of Common Stock for which this Warrant is exercisable from time to time shall be referred to herein as the “Warrant Stock.” 

1.2 Term. The shares of Warrant Stock issuable upon exercise of this Warrant are hereinafter referred to as the
“Shares.” This Warrant shall be exercisable at any time and from time to time in whole or in part from the date hereof until the date seven (7) years from the issue date of the Original Warrant. 

1.3 Exercise Price. The exercise price (the “Warrant Price”) for the Warrant shall equal
$        . 
 2. Adjustment of Warrant Price, Number and Kind of Shares. The
Warrant Price and the number and kind of shares issuable upon the exercise of this Warrant shall be subject to adjustment from time to time, and the Company agrees to provide ten (10) days written notice upon the happening of certain events, as
follows: 

 2.1 Dividends in Stock Adjustment. In case at any time or from time to time on or
after the date hereof the holders of the Warrant Stock of the Company (or any other securities at the time receivable upon the exercise of this Warrant) shall have received, or, on or after the record date fixed for the determination of eligible
stockholders, shall have become entitled to receive, without payment therefor, other or additional securities or other property (other than cash) of the Company by way of dividend or distribution (except for distributions specifically provided for
below in Section 2.3), then and in each case, the holder of this Warrant shall, upon the exercise hereof, be entitled to receive, in addition to the number of Warrant Stock receivable thereupon, and without payment of any additional
consideration therefor, the amount of such other or additional securities or other property (other than cash) of the Company which such holder would hold on the date of such exercise had it been the holder of record of such Shares on the date hereof
and had thereafter, during the period from the date hereof to and including the date of such exercise, retained such Shares and/or all other additional securities or other property receivable by it as aforesaid during such period, giving effect to
all adjustments called for during such period by this Section 2. 
 2.2 Reclassification or Reorganization
Adjustment. In case of any changes in the class or kind of securities issuable upon exercise of this Warrant or any reclassification or change of the outstanding securities of the Company or of any reorganization of the Company (or any other
company the securities of which are at the time receivable upon the exercise of this Warrant) or any spin-off by the Company of another entity owned or controlled by the Company at any time and from time to time on or after the date hereof, the
holder of this Warrant, upon the exercise hereof at any time after the consummation of such reclassification, change, reorganization, or spin-off shall be entitled to receive, in lieu of the shares or other securities and property receivable upon
the exercise hereof prior to such consummation, the shares or other securities or property to which such holder would have been entitled upon such consummation if such holder had exercised this Warrant immediately prior thereto and the Warrant Price
therefore shall be appropriately adjusted, all subject to further adjustment as provided in this Section 2. 
 2.3 Stock
Splits and Reverse Stock Splits. If at any time on or after the date hereof the Company shall split, subdivide or otherwise change its outstanding shares of any securities receivable upon exercise of this Warrant into a greater number of shares,
the Warrant Price in effect immediately prior to such subdivision shall thereby be proportionately reduced and the number of Shares receivable upon exercise of this Warrant shall thereby be proportionately increased; and, conversely, if at any time
on or after the date hereof the outstanding number of shares of any securities receivable upon exercise of this Warrant shall be combined into a smaller number of shares, the Warrant Price in effect immediately prior to such combination shall
thereby be proportionately increased and the number of Shares receivable upon exercise of this Warrant shall thereby be proportionately decreased. 
 2.4 Other Impairment. The Company shall not, by amendment of its Certificate of Incorporation or Bylaws or through any reorganization, transfer of assets, consolidation, merger, dissolution, issue
or sale of securities or any other voluntary action, avoid or seek to avoid the observance or performance of any of the terms of this Warrant, but shall at all times in good faith 

  
 2 

 
assist in the carrying out of all such terms and in the taking of all such action as may be necessary or appropriate in order to protect the rights of the holder of this Warrant against
impairment. 
 3. No Fractional Shares. No fractional shares shall be issued in connection with any subscription
hereunder. In lieu of any fractional shares that would otherwise be issuable, the Company shall round the number of shares issuable upon exercise of this Warrant to the nearest whole number. 

4. No Stockholder Rights. This Warrant as such shall not entitle its holder to any of the rights of a stockholder of the Company.

 5. Reservation of Stock. The Company covenants that during the period this Warrant is exercisable, the Company shall
reserve from its authorized and unissued Warrant Stock a sufficient number of shares to provide for the issuance of Warrant Stock upon the exercise of this Warrant. The Company agrees that its issuance of this Warrant shall constitute full authority
to its officers who are charged with the duty of executing securities to execute and issue the necessary certificates for shares of Warrant Stock upon the exercise of this Warrant. 

6. Exercise of Warrant. This Warrant may be exercised by Holder by the surrender of this Warrant at the principal office of the
Company, accompanied by payment in full of the purchase price of the shares purchased thereby, as described above. This Warrant shall be deemed to have been exercised immediately prior to the close of business on the date of its surrender for
exercise as provided above, and the person or entity entitled to receive the shares or other securities issuable upon such exercise shall be treated for all purposes as the holder of such shares of record as of the close of business on such date. As
promptly as practicable, the Company shall issue and deliver to the person or entity entitled to receive the same a certificate or certificates for the number of full shares of Warrant Stock issuable upon such exercise. The shares of Warrant Stock
issuable upon exercise hereof shall, upon their issuance, be fully paid and nonassessable. If this Warrant shall be exercised in part only, the Company shall, at the time of delivery of the certificate representing the Shares or other securities in
respect of which this Warrant has been exercised, deliver to the Holder a new Warrant evidencing the right to purchase the remaining Shares or other securities purchasable under this Warrant, which new warrant shall, in all other respects, be
identical to this Warrant. 
 7. Net Issue Election. 

7.1 Right to Convert. In addition to and without limiting the rights of the Holder under the terms of this Warrant, the Holder
shall have the right to convert this Warrant or any portion hereof (the “Conversion Right”) into shares of Warrant Stock as provided in this Section 7. Upon exercise of the Conversion Right with respect to a particular number
of shares subject to this Warrant (the “Converted Warrant Stock”), the Company shall deliver to the Holder (without payment by the Holder of any cash or other consideration) that number of shares of Warrant Stock equal to the
quotient obtained by dividing (x) the value of this Warrant (or the specified portion hereof) on the Conversion Date (as defined in subsection 7.2 hereof), which value shall be determined by subtracting (A) the aggregate Warrant Price of
the Converted Warrant Stock immediately prior to the exercise of the Conversion Right from (B) the aggregate fair market value of the Converted Warrant Stock issuable upon exercise of this Warrant (or the specified portion hereof) on the
Conversion Date (as herein defined) by (y) the fair market value 

  
 3 

 
of one share of Warrant Stock on the Conversion Date (as herein defined). No fractional shares shall be issuable upon exercise of the Conversion Right, and if the number of shares to be issued
determined in accordance with the foregoing formula is other than a whole number, the Company shall round the number of shares of Warrant Stock issuable upon exercise of this Warrant to the nearest whole number. 

7.2 Method of Exercise. The Conversion Right may be exercised by the Holder by the surrender of this Warrant at the principal
office of the Company together with a written statement specifying that the Holder thereby intends to exercise the Conversion Right and indicating the number of shares subject to this Warrant that are being surrendered (referred to in subsection 7.1
hereof as the Converted Warrant Stock) in exercise of the Conversion Right. Such conversion shall be effective upon such surrender of this Warrant (the “Conversion Date”). Certificates for the shares of Warrant Stock issuable upon
exercise of the Conversion Right (or any other securities deliverable in lieu thereof under Section 2) shall be issued as of the Conversion Date and shall be delivered to the Holder immediately following the Conversion Date, or, if requested at
the time of surrender of this Warrant, held for pick-up by the Holder at the Company’s principal office. 
 7.3
Determination of Fair Market Value. For purposes of this Section 7, fair market value (the “Market Price”) of a share of Warrant Stock as of a particular date (the “Determination Date”) shall mean the
average of the closing prices of such security’s sales on the principal securities exchanges on which such security may at the time be listed, or, if there has been no sales on any such exchange on any day, the average of the highest bid and
lowest asked prices on all such exchanges at the end of such day, or, if on any day such security is not so listed, the average of the highest bid and lowest asked prices on such day in the domestic over-the-counter market as reported by the
National Quotation Bureau, Incorporated, or any similar successor organization, in each such case averaged over a period of five (5) days consisting of the day prior to the day as of which “Market Price” is being determined and the
five (5) consecutive business days prior to such day. If at any time such security is not listed on any securities exchange or quoted in the over-the-counter market, the “Market Price” shall be the fair value thereof as determined in
good faith by the Company’s Board of Directors. 
 8. Certificate of Adjustment. Whenever the Warrant Price or
number or type of securities issuable upon exercise of this Warrant is adjusted, as herein provided, the Company shall promptly deliver to the record holder of this Warrant a certificate of an officer of the Company setting forth the nature of such
adjustment and a brief statement of the facts requiring such adjustment. 
 9. Notice of Proposed Transfers. This Warrant
is transferable by the Holder hereof subject to compliance with this Section 9. Prior to any proposed transfer of this Warrant or the shares of Warrant Stock received on the exercise of this Warrant (the “Securities”), unless
there is in effect a registration statement under the Securities Act of 1933, as amended (the “Securities Act”), covering the proposed transfer, the Holder thereof shall give written notice to the Company of such Holder’s
intention to effect such transfer. Each such notice shall describe the manner and circumstances of the proposed transfer in sufficient detail, and shall, if the Company so requests, be accompanied (except in transactions in compliance with Rule 144)
by either (i) an unqualified 

  
 4 

 
written opinion of legal counsel who shall be reasonably satisfactory to the Company addressed to the Company and reasonably satisfactory in form and substance to the Company’s counsel, to
the effect that the proposed transfer of the Securities may be effected without registration under the Securities Act and any applicable state securities laws, or (ii) a “no action” letter from the Securities Exchange Commission (the
“Commission”) to the effect that the transfer of such Securities without registration shall not result in a recommendation by the staff of the Commission that action be taken with respect thereto, whereupon the Holder of the
Securities shall be entitled to transfer the Securities in accordance with the terms of the notice delivered by the Holder to the Company; provided, however, no such registration statement or opinion of counsel shall be necessary for a
transfer by a Holder to any affiliate of such Holder, or a transfer by a Holder which is a partnership to a partner of such partnership or a retired partner of such partnership who retires after the date hereof, or to the estate of any such partner
or retired partner or the transfer by gift, will or intestate succession of any partner to his spouse or lineal descendants or ancestors, if the transferee agrees in writing to be subject to the terms hereof to the same extent as if such transferee
were the original Holder hereunder. Each certificate evidencing the Securities transferred as above provided shall bear the appropriate restrictive legend set forth above, except that such certificate shall not bear such restrictive legend if in the
opinion of counsel for the Company such legend is not required in order to establish compliance with any provisions of the Securities Act. 
 10. Notice of Dividends and Distributions. For so long as any part of this Warrant remains outstanding and unexercised, the Company shall, upon the declaration of a cash dividend upon its Common
Stock or other distribution to the Holders of its Common Stock and at least ten (10) days prior to the record date, notify the Holder hereof of such declaration, which notice will contain, at a minimum, the following information: (a) the
date of the declaration of the dividend or distribution; (b) the amount of such dividend or distribution; (c) the record date of such dividend or distribution; and (d) the payment date or distribution date of such dividend or
distribution. 
 11. Replacement of Warrants. Upon receipt by the Company of evidence reasonably satisfactory to the
Company of the loss, theft, destruction or mutilation of the Warrant, and in the case of any such loss, theft or destruction of the Warrant, on delivery of an indemnity agreement or security reasonably satisfactory in form and amount to the Company,
and reimbursement to the Company of all reasonable expenses incidental thereto, and upon surrender and cancellation of the Warrant if mutilated, the Company shall execute and deliver, in lieu thereof, a new Warrant of like tenor. 

12. Notices. All notices and other communications from the Company to the Holder shall be given in accordance with
Section 7.10 of the Purchase Agreement. 
 13. Miscellaneous. This Warrant shall be governed by the laws of the
State of Delaware. The headings in this Warrant are for purposes of convenience of reference only, and shall not be deemed to constitute a part hereof. The invalidity or unenforceability of any provision hereof shall in no way affect the validity or
enforceability of any other provisions. 
 14. Amendment. Any term of this Warrant may be amended or waived with the
written consent of the Company and the Holder of Warrants representing a majority of the shares of Warrant Stock issuable upon exercise of the then outstanding unexercised warrants issued under the

  
 5 

 
Purchase Agreement (the “Bridge Warrants”); provided, however, that any such amendment or waiver that disproportionately affects any of the holders of the then
outstanding unexercised warrants issued pursuant to the Purchase Agreement shall require the written consent of all such holders. Any amendment or waiver effected in accordance with this Section 14 shall be binding upon each holder of any
Bridge Warrant, each future holder of all such Bridge Warrants and the Company, and the Company shall promptly give notice to all holders of outstanding Bridge Warrants of any amendment or waiver effected in accordance with this Section 14.

 15. Taxes. The Company shall pay all issue taxes and other governmental charges (but not including any income taxes of
Holder) that may be imposed in respect of the issuance or delivery of the shares, or any portion thereof, upon exercise of this Warrant. 
 16. Remedies. In the event of any default or threatened default by the Company in the performance of or observance with any of the terms of this Warrant, it is agreed that remedies at law are not
and shall not be adequate for the Holder and that such terms may be specifically enforced by a decree for the specific performance of any agreement contained herein or by an injunction against a violation of any of the terms hereof or otherwise.

 [Signature page follows.] 

  
 6 

 IN WITNESS WHEREOF, the undersigned officer of the Company has executed this Amended and
Restated Warrant as of the date first above written. 
  

			
	COMPANY:
	
	 CEMPRA, INC.

		
	By:	 	  

		
	Name:	 	 Prabhavathi Fernandes, Ph. D.

		
	Title:	 	 Chief Executive OfficerUnsecured Convertible Promissory Note and Global Amendment

 Exhibit 4.4 
 THIS NOTE AND THE SECURITIES ISSUABLE UPON CONVERSION HEREOF HAVE NOT BEEN REGISTERED UNDER THE SECURITIES ACT OF 1933, AS AMENDED, OR APPLICABLE STATE SECURITIES LAWS. THIS NOTE HAS BEEN ACQUIRED FOR
INVESTMENT AND NOT WITH A VIEW TO DISTRIBUTION OR RESALE. THIS NOTE AND THE UNDERLYING SECURITIES MAY NOT BE SOLD, MORTGAGED, PLEDGED, HYPOTHECATED OR OTHERWISE TRANSFERRED WITHOUT AN EFFECTIVE REGISTRATION STATEMENT UNDER THE SECURITIES ACT OF
1933, AS AMENDED, AND ANY APPLICABLE STATE SECURITIES LAWS, OR THE AVAILABILITY OF AN EXEMPTION FROM THE REGISTRATION PROVISIONS OF THE SECURITIES ACT OF 1933, AS AMENDED, AND APPLICABLE STATE SECURITIES LAWS. 

CEMPRA HOLDINGS, LLC 
 UNSECURED CONVERTIBLE PROMISSORY NOTE 
  

					
	$            	  		  	August 5, 2011

 1. Principal. Cempra Holdings, LLC, a Delaware limited liability company (the
“Company”), for value received, hereby promises to pay             , or its assigns (the “Holder”) in lawful money of the United States of
America at the address for notices to Holder set forth in the Purchase Agreement (as defined below), the principal amount of $            , together with interest as set forth below.
This Unsecured Convertible Promissory Note (the “Note”) is being issued pursuant to that certain Unsecured Convertible Promissory Note and Warrant Purchase Agreement among the Company, the Holder and the Purchasers listed on
Schedule A thereto, dated as of the date hereof (the “Purchase Agreement”), and is subject to its terms. 
 2.
Interest and Maturity. The Company promises to pay interest on the unpaid principal amount from the date hereof until such principal amount is paid in full. Interest shall be computed on the basis of a 360-day year of twelve 30-day months and
shall not be compounded. Interest shall accrue at the rate of ten percent (10%) per annum, or such lesser rate as shall be the maximum rate allowable under applicable law. Notwithstanding the foregoing, unless converted or prepaid as set forth
below, if an Event of Default (as defined below) shall occur and be continuing, all outstanding principal on this Note shall bear interest at twelve percent (12%) per annum (the “Default Rate”). Principal and accrued interest
on the Note shall be due and payable on August 4, 2012 (the “Maturity Date”). This Note and the other Unsecured Convertible Promissory Notes issued pursuant to the Purchase Agreement are collectively referred to herein as the
“Bridge Notes.” In the event of any conflict between this Note and the Purchase Agreement, the terms of the Purchase Agreement shall control. 

  
 1 

 3. Prepayment. 

3.1 This Note may not be prepaid prior to the Maturity Date without the consent of holders of at least a majority of the aggregate
outstanding principal of the Bridge Notes then outstanding (the “Majority Holders”), which consent may be withheld for any or no reason. Any such consent of the Majority Holders shall be binding on the Holder and all other holders
of Bridge Notes (as well as any subsequent transferees or assignees). 
 3.2 Any prepayment of this Note shall be credited first
against accrued interest, then principal. Upon payment in full of the amount of all principal and interest payable hereunder, this Note shall be surrendered to the Company for cancellation. 

4. Conversion. 
 4.1 Conversion upon Maturity. Notwithstanding any other provision hereof, in lieu of accepting repayment of principal and accrued interest under this Note on or after the Maturity Date, the Holder
may, at its option, elect to convert the outstanding principal and all accrued but unpaid interest thereon into a number of units of Class C Units equal to (i) the aggregate outstanding principal and unpaid accrued interest due under this Note
as of the date of such election, divided by (ii) $1.07857, subject to appropriate adjustment in the event of any unit distribution, unit split, combination, reclassification or other similar recapitalization affecting such units (the
“Class C Conversion Price”). 
 4.2 Conversion upon a Qualified Private Financing. In the event of a
Qualified Private Financing (as defined below) on or prior to the Maturity Date, all unpaid principal on this Note and all unpaid accrued interest shall be automatically converted into the type, kind and character of securities (the
“Securities”) issued in such Qualified Private Financing in an amount equal to (i) the aggregate outstanding principal and unpaid accrued interest due under this Note, divided by (ii) the purchase price for such
Securities. Upon such conversion, the Holder shall receive the same rights, preferences and privileges as are received by other investors, and such Securities shall be issued pursuant to and governed by the same agreements relating to the issuance
of the Securities in the Qualified Private Financing, which agreements Holder shall evidence its consent to by execution of appropriate documentation. 
 4.3 Conversion upon a Qualified IPO. Effective as of the closing of a Qualified IPO (as defined below) on or prior to the Maturity Date, all principal and accrued interest under this Note shall
automatically convert into a number of Company Common Units (or equivalent security) equal to (i) the aggregate outstanding principal and unpaid accrued interest under this Note, divided by (ii) the offering price of the Company’s
Common Units (or equivalent security) in the Qualified IPO. 
 4.4 Company Sale or Subsidiary Sale. In the event a
Company Sale (as defined below) or Subsidiary Sale (as defined below) is completed prior to the Maturity Date, the Holder may, at its option, prior to the closing of such transaction, elect to (a) convert all principal and accrued interest
under this Note into a number of units of Class C Units equal to (i) the 

  
 2 

 
aggregate outstanding principal and accrued unpaid interest under this Note, divided by (ii) the Class C Conversion Price or (b) be paid an amount equal to the aggregate outstanding
principal of the Note plus all accrued unpaid interest, plus an additional repayment premium amount equal to the aggregate outstanding principal of the Note. In the event a Company Sale is completed prior to the earlier to occur of August 4,
2012 or a Qualified Private Financing or a Qualified IPO, the Maturity Date of the Note shall be accelerated to the closing date of the Company Sale and, notwithstanding anything to the contrary contained in this Note, the provisions of this
Section 4.4 shall apply. 
 4.5 Effect of Conversion. No fractional units shall be issued in connection with any
conversion hereunder. In lieu of any fractional units that would otherwise be issuable, the Company shall round the number of units issuable upon conversion of this Note to the nearest whole number. Upon conversion of this Note pursuant to this
Section 4, the applicable amount of outstanding principal and accrued but unpaid interest of this Note shall be converted without any further action by the Holder, and upon such conversion all principal and interest payable hereunder shall be
deemed paid in full; provided, however, that the Company shall not be obligated to issue certificates evidencing the units of the securities issuable upon such conversion unless such Note is either delivered to the Company or its
transfer agent, or the holder notifies the Company or its transfer agent that such Note has been lost, stolen or destroyed and executes and delivers an agreement satisfactory to the Company to indemnify it from any loss incurred by it in connection
with such Note. The Company shall, as soon as practicable after such delivery, issue and deliver at such office to such Holder of such Note, a certificate or certificates for the securities to which the Holder shall be entitled. The person or
persons entitled to receive securities issuable upon such conversion shall be treated for all purposes as the record holder or holders of such securities on the date of such conversion. 

4.6 Reservation of Units. The Company covenants that during the period this Note is outstanding, the Company will:
(a) reserve from its authorized and unissued capital units a sufficient number of Class C Units to provide for the conversion in full of this Note; and (b) reserve from its authorized and unissued Common Units a sufficient number of units
to provide for the issuance of Common Units upon conversion of any such Class C Units issued or issuable upon conversion of this Note. 
 4.7 Notice. The Company shall provide the Holder with at least ten (10) days prior notice of (i) a Qualified Private Financing, (ii) a Qualified IPO, (iii) a Company Sale, or
(iv) a Subsidiary Sale. Such notice shall be in writing and given in accordance with Section 7.10 of the Purchase Agreement. 
 4.8 Definitions. For purposes of this Note, the following terms shall have the meanings set forth below: 
 (a) “Qualified Private Financing” means the sale of at least $20,000,000 in preferred equity securities to one or more institutional, venture capital, corporate partner, or private
investor in the Company in a private placement (which shall include for such purpose the principal and accrued unpaid interest on the Bridge Notes). 

  
 3 

 (b) “Qualified IPO” shall have the meaning set forth in the Company’s
Second Amended and Restated Limited Liability Company Agreement dated May 13, 2009, as amended from time to time (the “LLC Agreement”). 
 (c) “Company Sale” shall have the meaning set forth in the LLC Agreement. 
 (d) “Subsidiary Sale” shall have the meaning set forth in the LLC Agreement. 
 5. Attorney’s Fees. If the indebtedness represented by this Note or any part thereof is collected in bankruptcy, receivership or other judicial proceedings or if this Note is placed in the
hands of attorneys for collection after default, the Company agrees to pay, in addition to the principal and interest payable hereunder, reasonable attorneys’ fees and costs actually incurred by Holder in collecting amounts that become due
under this Note. 
 6. Notices. All notices and other communications from the Company to the Holder shall be given in
accordance with Section 7.10 of the Purchase Agreement. 
 7. Defaults and Remedies. 

7.1 Events of Default. An “Event of Default” shall occur hereunder if: 

(i) the Company shall default in the payment of the principal or accrued but unpaid interest on this Note, when and as the
same shall become due and payable and such amount remains unpaid for 10 calendar days after the date of receipt of written notice of such default; or 
 (ii) the Company shall default in the payment of any principal or interest on any of the Bridge Notes issued pursuant to the Purchase Agreement, when and as the same shall become due and payable and such
amount remains unpaid for 10 calendar days after the date of receipt of written notice of such default; or 

(iii) the Company shall default in the due observance or performance of any covenant, representation, warranty, condition
or agreement on the part of the Company to be observed or performed pursuant to the terms hereof or pursuant to the Purchase Agreement, and such default is not remedied or waived after the Company receives written notice of such default within the
time periods permitted therein, or if no cure period is provided therein, within thirty (30) days after the Company receives written notice of such default; or 

(iv) any representation, warranty, certification or statement made by or on behalf of the Company in the Purchase
Agreement shall have been incorrect when made and such inaccuracy taken individually or in the aggregate shall constitute a material adverse effect upon the business, financial condition or operations of the Company or its properties;
or 

  
 4 

 (v) if the Company shall commence any voluntary proceeding in bankruptcy or
for dissolution, liquidation, winding-up, composition or other relief under state or federal bankruptcy laws; or 

(vi) if proceedings in bankruptcy or for dissolution, liquidation, winding-up, composition or other relief under state or
federal bankruptcy laws are commenced against the Company, or a receiver or trustee is appointed for the Company or a substantial part of its property, and such proceeding or appointment is not dismissed or discharged within sixty (60) calendar
days after its commencement. 
 7.2 Acceleration. If an Event of Default occurs under Section 7.1 (v) or (vi),
then the outstanding principal of and accrued but unpaid interest on this Note shall automatically become immediately due and payable, without presentment, demand, protest or notice of any kind, all of which are expressly waived. If any other Event
of Default occurs and is continuing, the Majority Holders, by written notice to the Company, may declare the outstanding principal of and accrued but unpaid interest on the Bridge Notes to be due and payable immediately. Upon any such declaration of
acceleration, such principal and interest shall become immediately due and payable and the Holder shall be entitled to exercise all of its rights and remedies hereunder and under the Purchase Agreement whether at law or in equity. The failure of the
Majority Holders to declare this Note due and payable shall not be a waiver of such Majority Holders’ right to do so in the future, and the Majority Holders shall retain the right to declare this Note due and payable at any time an Event of
Default (other than pursuant to Section 7.1(v) or (vi)) is continuing. 
 8. Other Impairment. The Company shall
not, by amendment of the LLC Agreement, or through any reorganization, transfer of assets, consolidation, merger, dissolution, issue or sale of securities or any other voluntary action, avoid or seek to avoid the observance or performance of any of
the terms of this Note, but shall at all times in good faith assist in the carrying out of all such terms and in the taking of all such action as may be necessary or appropriate in order to protect the rights of the holder of this Note against
impairment. 
 9. Waiver of Notice of Presentment. The Company hereby waives presentment, demand for performance, notice
of non-performance, protest, notice of protest and notice of dishonor. No delay on the part of Holder in exercising any right hereunder shall operate as a waiver of such right or any other right. 

10. No Waiver. The failure of the Holder to enforce or exercise any right or remedy provided in this Note or at law or in equity
upon any default or breach shall not be construed as waiving the rights to enforce or exercise such or any other right or remedy at any later date. No exercise of the rights and powers granted in or held pursuant to this Note by the Holder, and no
delays or omissions in the exercise of such rights and powers shall be held to exhaust the same or be construed as a waiver thereof, and every such right and power may be exercised at any time and from time to time. 

11. Notice of Proposed Transfers. This Note is transferable by the Holder hereof subject to compliance with this Section 11.
Prior to any proposed transfer of this Note, unless there 

  
 5 

 
is in effect a registration statement under the Securities Act of 1933, as amended (the “Securities Act”), covering the proposed transfer, the Holder thereof shall give written
notice to the Company of such Holder’s intention to effect such transfer. Each such notice shall describe the manner and circumstances of the proposed transfer in sufficient detail, and shall, if the Company so requests, be accompanied (except
in transactions in compliance with Rule 144) by either (i) an unqualified written opinion of legal counsel who shall be reasonably satisfactory to the Company addressed to the Company and reasonably satisfactory in form and substance to the
Company’s counsel, to the effect that the proposed transfer of the Note may be effected without registration under the Securities Act and any applicable state securities laws, or (ii) a “no action” letter from the Securities
Exchange Commission (the “Commission”) to the effect that the transfer of such Note without registration shall not result in a recommendation by the staff of the Commission that action be taken with respect thereto, whereupon the
Holder of the Note shall be entitled to transfer the Note in accordance with the terms of the notice delivered by the Holder to the Company; provided, however, no such registration statement or opinion of counsel shall be necessary for
a transfer by a Holder to any affiliate of such Holder, or a transfer by a Holder which is a partnership to a partner of such partnership or a retired partner of such partnership who retires after the date hereof, or to the estate of any such
partner or retired partner or the transfer by gift, will or intestate succession of any partner to his spouse or lineal descendants or ancestors, if the transferee agrees in writing to be subject to the terms hereof to the same extent as if such
transferee were the original Holder hereunder. Each certificate evidencing the Notes transferred as above provided shall bear the appropriate restrictive legend set forth above, except that such certificate shall not bear such restrictive legend if
in the opinion of counsel for the Company such legend is not required in order to establish compliance with any provisions of the Securities Act. Further, prior to the transfer of this Note to any transferee as permitted under this Section 11,
such transferee must agree in writing to execute any documents necessary, including the Company’s form of joinder agreement, to become party to the Company’s LLC Agreement (or equivalent governing document), and subject to the terms
thereof, upon any conversion of this Note into units of the Company pursuant to the terms hereof. 
 12. Miscellaneous.
This Note shall be governed by the laws of the State of Delaware. The headings in this Note are for purposes of convenience of reference only, and shall not be deemed to constitute a part hereof. The invalidity or unenforceability of any provision
hereof shall in no way affect the validity or enforceability of any other provisions. 
 13. Taxes. The Company shall pay
all issue taxes and other governmental charges (but not including any income taxes of a Holder) that may be imposed in respect of the issuance or delivery of the units, or any portion thereof, upon conversion of this Note. 

14. Amendment. Any provision of this Note may be amended or waived with the written consent of the Company and the Majority
Holders; provided, however, that any such amendment or waiver that disproportionately affects any of the holders of the Bridge Notes shall require the written consent of all such holders. Any amendment or waiver effected in accordance
with this Section 14 shall be binding on each holder of any Bridge Notes, each future holder of all such Bridge Notes and the Company, and the Company shall promptly give notice to all holders of outstanding Bridge Notes of any amendment or
waiver effected in accordance with this Section 14. 

  
 6 

 15. No Unitholder Rights. This Note as such shall not entitle its holder to any of
the rights of a unitholder of the Company. 
 [Signature page follows.] 

  
 7 

 IN WITNESS WHEREOF, the undersigned officer of the Company has executed this Unsecured
Convertible Promissory Note as of the year and date first above written. 
  

			
	 COMPANY:

 

	 CEMPRA HOLDINGS, LLC

 

	By:	 	  

	Name:	 	Prabhavathi Fernandes, Ph. D.
	Title:	 	Chief Executive Officer

 GLOBAL AMENDMENT TO 

UNSECURED CONVERTIBLE PROMISSORY NOTES 
 Issued August 5, 2011 
 THIS GLOBAL AMENDMENT TO
UNSECURED CONVERTIBLE PROMISSORY NOTES (the “Amendment”) is entered into this 11th day of October 2011, by and among Cempra Holdings LLC, a Delaware limited liability company (the “Company”), and the undersigned holders of Unsecured Convertible Promissory Notes (the
“Bridge Notes”) issued pursuant to that certain Unsecured Convertible Promissory Note and Warrant Purchase Agreement dated August 5, 2011 (the “Purchase Agreement”), by and among the Company and the purchasers
listed on Schedule A thereto (collectively, the “Note Holders”). 
 WHEREAS, the Bridge Notes provide in
Section 14 thereof that they may be amended by the written consent of the Company and the Majority Holders (as defined therein) and that any such amendment effected in accordance with Section 14 will be binding on the holders of each of
the Bridge Notes; 
 WHEREAS, the Company and the Note Holders desire to, among other things, amend the Bridge Notes to modify
the definition of the term “Qualified IPO” therein; and 
 WHEREAS, the undersigned Note Holders constitute the
Majority Holders required to amend the Bridge Notes. 
 NOW, THEREFORE, in consideration of the mutual promises, covenants and
conditions set forth in this Amendment, and other good and valuable consideration, the receipt of which is hereby acknowledged, and pursuant to Section 14 of the Bridge Notes, the parties to this Amendment mutually agree as follows: 

1. Capitalized Terms. All capitalized terms used herein that are not otherwise defined herein shall have the meanings assigned to
them in the Bridge Notes unless the context hereof requires otherwise. 
 2. Amendment. The Bridge Notes are hereby
amended as follows. 
 (A) Section 4.8(b) of the Bridge Notes shall be deleted in its entirety and replaced
with the following: 
 “(b) “Qualified IPO” means the sale of the Company’s Common
Units (or equivalent security) in a firm commitment underwritten public offering registered under the Securities Act of 1933, as amended.” 
 (B) For all purposes, effective as of the date hereof, each and every reference to the words “Unit,” “Units,” “unit,” “units,” “Unitholder,”
“Unitholders,” “unitholder” and “unitholders” in the Bridge Notes shall be deemed to be references to the words “Share,” “Shares,” “share,” “shares,” “Shareholder”
“Shareholders,” “shareholder” and “shareholders” respectively. 

 3. No Other Amendment. Except as specifically amended pursuant to this Amendment, the
Bridge Notes shall remain in full force and effect in accordance with their terms. 
 4. Governing Law. All questions
concerning the construction, validity and interpretation of this Amendment will be governed by and construed in accordance with the internal law (and not the law of conflicts) of the State of Delaware. 

5. Counterparts. This Amendment may be executed in two or more counterparts, each of which shall be deemed an original, but all of
which together shall constitute one and the same instrument. 
 6. Binding Effect. This Amendment shall be binding upon
and shall inure to the benefit of the parties hereto, all the Note Holders and their heirs, successors and assigns. 
 [The
next page is the signature page.] 

  
 2 

 IN WITNESS WHEREOF, the parties have executed this Global Amendment to Unsecured Convertible
Promissory Notes as of the date first above written. 
  

									
	COMPANY:	 		 	CEMPRA HOLDINGS, LLC
					
		 		 		 	By:	 	/s/ Prabhavathi Fernandes
		 		 		 	Name:	 	Prabhavathi Fernandes, Ph.D.
		 		 		 	Title:	 	President
			
	NOTE HOLDERS:	 		 	QUAKER BIOVENTURES II, L.P.
				
		 		 	By:	 	 Quaker Bioventures Capital II, L.P.,
 its General Partner

				
		 		 	By:	 	 Quaker Bioventures Capital II, LLC,
 its General Partner

				
		 		 	By:	 	/s/ Sherrill Neff
		 		 	Name:	 	P. Sherrill Neff
		 		 	Title:	 	 Member

			
		 		 	DEVON PARK BIOVENTURES, L.P.
				
		 		 	By:	 	 Devon Park Associates, L.P.,

its General Partner

				
		 		 	By:	 	/s/ Devang V. Kantesaria
		 		 	Name:	 	Devang V. Kantesaria
		 		 	Title:	 	General Partner

 Signature Page to Global Amendment to Unsecured Convertible Promissory Notes 

									
	NOTE HOLDERS:	 		 	AISLING CAPITAL II, LP
					
		 		 		 	By:	 	 Aisling Capital Partners, LP,

its General Partner

					
		 		 		 	By:	 	/s/ Lloyd Appel
		 		 		 	Name:	 	Lloyd Appel
		 		 		 	Title:	 	CFO
				
		 		 		 	BLACKBOARD VENTURES INC.
					
		 		 		 	By:	 	/s/ Terry Woodward
		 		 		 	Name:	 	Terry Woodward
		 		 		 	Title:	 	Director
				
		 		 		 	INTERSOUTH PARTNERS VI, L.P.
					
		 		 		 	By:	 	 Intersouth Associates VI, LLC,
 its General Partner

					
		 		 		 	By:	 	/s/ Richard Kent
		 		 		 	Name:	 	Richard Kent
		 		 		 	Title:	 	Member, acting pursuant to Power of Attorney
				
		 		 		 	INTERSOUTH PARTNERS VII, L.P.
					
		 		 		 	By:	 	 Intersouth Associates VII, LLC,
 its General Partner

					
		 		 		 	By:	 	/s/ Richard Kent
		 		 		 	Name:	 	Richard Kent
		 		 		 	Title:	 	Member, acting pursuant to Power of Attorney

 Signature Page to Global Amendment to Unsecured Convertible Promissory Notes 

									
	NOTE HOLDERS:	 		 	/s/ I. Wistar Morris
		 		 	I. Wistar Morris, III
				
		 		 		 	/s/ Martha Morris
		 		 		 	Martha H. Morris
				
		 		 		 	COTSWOLD FOUNDATION
					
		 		 		 	By:	 	/s/ I. Wistar Morris and Martha Morris
		 		 		 	Name:	 	 
		 		 		 	Title:	 	 
				
		 		 		 	ELEVENTH GENERATION PARTNERSHIP, LP
					
		 		 		 	By:	 	/s/ Martha Morris
		 		 		 	Name:	 	 
		 		 		 	Title:	 	 

 Signature Page to Global Amendment to Unsecured Convertible Promissory Note

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