EX-4.1



 Exhibit 4.1 
  






 
 NUMBER 
SHARES 
MK 
MyoKardia 
INCORPORATED UNDER THE LAWS OF THE STATE OF DELAWARE 
CUSIP 62857M 10 5 
SEE REVERSE FOR CERTAIN DEFINITIONS 
This certifies that 
SPECIMEN 
is the record holder of 
FULLY PAID AND NONASSESSABLE SHARES OF COMMON STOCK, $0.0001 PAR VALUE PER SHARE, OF

MYOKARDIA, INC. 
CERTIFICATE OF STOCK 
transferable on the books of the corporation in person or by duly authorized attorney upon surrender of this Certificate properly endorsed. This Certificate is not valid until
countersigned by the Transfer Agent and registered by the Registrar. 
WITNESS the facsimile seal of the Corporation and the facsimile signatures of its duly
authorized officers. 
Dated: 
MYOKARDIA, INC. 
CORPORATE 
President Chief Executive Officer 
SEAL 
Secretary 
JUNE 8, 2012 
DELAWARE 
COUNTERSIGNED AND REGISTERED: 
BROADRIDGE CORPORATE ISSUER SOLUTIONS, INC. 
1717 ARCH ST, 
TRANSFER AGENT 
SUITE 1300 
AND REGISTRAR 
PHILADELPHIA, PA 19103 
BY: 
AUTHORIZED SIGNATURE 







 The Corporation shall furnish without charge to each stockholder who so requests a statement of
the powers, designations, preferences and relative, participating, optional or other special rights of each class of stock of the Corporation or series thereof and the qualifications, limitations or restrictions of such preferences and/or rights.
Such requests shall be made to the Corporation’s Secretary at the principal office of the Corporation. 
 KEEP THIS CERTIFICATE IN A
SAFE PLACE. IF IT IS LOST, STOLEN, OR DESTROYED THE CORPORATION WILL REQUIRE A BOND INDEMNITY AS A CONDITION TO THE ISSUANCE OF A REPLACEMENT CERTIFICATE. 

The following abbreviations, when used in the inscription on the face of this certificate, shall be construed as though they were written out
in full according to applicable laws or regulations: 
  

																							
	TEN COM	 	–	 	as tenants in common	 		 	UNIF GIFT MIN ACT	 	–	 	  
	 	Custodian	  	  
	 	
	TEN ENT	 	–	 	as tenants by the entireties	 		 		 		 	(Cust)	 		  		 	(Minor) 	 	
	JT TEN	 	–	 	as joint tenants with right of survivorship and not as tenants in common	 		 		 		 	under Uniform Gifts to Minors Act 	 	
		 		 	 		 		 		 	  

		 		 	 		 		 		 	(State)	 	
	COM PROP	 	–	 	as community property	 		 	UNIF TRF MIN ACT	 	–	 	  
	 	Custodian (until age	 	  
	 	)
		 		 		 		 		 		 	(Cust)	 		 		  		 		 	
		 		 		 		 		 		 	  
	 	 under Uniform Transfers

		 		 		 		 		 		 	(Minor)	 		  		 		 	
		 		 		 		 		 		 	to Minors Act	 		 	  

		 		 		 		 		 		 		 		 	(State)

 Additional abbreviations may also be used though not in the above list. 

FOR VALUE RECEIVED,
                                        hereby
sell(s), assign(s) and transfer(s) unto 
  

					
	 PLEASE INSERT SOCIAL SECURITY OR OTHER IDENTIFYING NUMBER OF ASSIGNEE

 
	  		  	
	 	  		  	
	 	  		  	

  
  

 
 (PLEASE PRINT OR TYPEWRITE NAME AND
ADDRESS, INCLUDING ZIP CODE, OF ASSIGNEE) 
  
  

 
  

			
	  
	 	shares

 of the capital stock represented by within Certificate, and do hereby irrevocably constitute and appoint 

 

			
	  
	 	attorney-in-fact

 to transfer the said stock on the books of the within named Corporation with full power of the substitution in the premises.

  

			
	Dated	 	  



 

							
		    	X	  	  

			
		    	X	  	  

	Signature(s) Guaranteed:	    		  	NOTICE:	  	THE SIGNATURE TO THIS ASSIGNMENT MUST CORRESPOND WITH THE NAME AS WRITTEN UPON THE FACE OF THE CERTIFICATE IN EVERY PARTICULAR, WITHOUT ALTERATION OR ENLARGEMENT OR ANY CHANGE WHATSOEVER.

  

			
	By	 	  

	
	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. GUARANTEES BY A NOTARY PUBLIC ARE NOT ACCEPTABLE. SIGNATURE GUARANTEES MUST NOT BE DATED.