Ownership Submission
FORM 4
Check this box if no longer subject to Section 16. Form 4 or Form 5 obligations may continue. See Instruction 1(b).
UNITED STATES SECURITIES AND EXCHANGE COMMISSION
Washington, D.C. 20549

STATEMENT OF CHANGES IN BENEFICIAL OWNERSHIP OF SECURITIES

Filed pursuant to Section 16(a) of the Securities Exchange Act of 1934, Section 17(a) of the Public Utility Holding Company Act of 1935 or Section 30(h) of the Investment Company Act of 1940
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(Print or Type Responses)
1. Name and Address of Reporting Person *
Merck & Co., Inc.
   2. Issuer Name and Ticker or Trading Symbol
OPGEN INC [OPGN] 		5. Relationship of Reporting Person(s) to Issuer
(Check all applicable)
_____ Director __X__ 10% Owner
_____ Officer (give title below) _____ Other (specify below)
(Last)
(First)
(Middle)
2000 GALLOPING HILL ROAD		 3. Date of Earliest Transaction (Month/Day/Year)
05/19/2016
(Street)

KENILWORTH, NJ 07033		 4. If Amendment, Date Original Filed(Month/Day/Year)
 6. Individual or Joint/Group Filing(Check Applicable Line)
___ Form filed by One Reporting Person
_X_ Form filed by More than One Reporting Person
(City)
(State)
(Zip)
Table I - Non-Derivative Securities Acquired, Disposed of, or Beneficially Owned
1.Title of Security
(Instr. 3)		 2. Transaction Date (Month/Day/Year) 2A. Deemed Execution Date, if any (Month/Day/Year) 3. Transaction Code
(Instr. 8)		 4. Securities Acquired (A) or Disposed of (D)
(Instr. 3, 4 and 5)		 5. Amount of Securities Beneficially Owned Following Reported Transaction(s)
(Instr. 3 and 4)		 6. Ownership Form: Direct (D) or Indirect (I)
(Instr. 4)		 7. Nature of Indirect Beneficial Ownership
(Instr. 4)
Code V Amount (A) or (D) Price
Common Stock 05/19/2016   A   1,200,000 A (1) 2,679,022 I See Footnote (2)

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Table II - Derivative Securities Acquired, Disposed of, or Beneficially Owned
(e.g., puts, calls, warrants, options, convertible securities)
1. Title of Derivative Security
(Instr. 3)		 2. Conversion or Exercise Price of Derivative Security 3. Transaction Date (Month/Day/Year) 3A. Deemed Execution Date, if any (Month/Day/Year) 4. Transaction Code
(Instr. 8)		 5. Number of Derivative Securities Acquired (A) or Disposed of (D)
(Instr. 3, 4, and 5)		 6. Date Exercisable and Expiration Date
(Month/Day/Year)		 7. Title and Amount of Underlying Securities
(Instr. 3 and 4)		 8. Price of Derivative Security
(Instr. 5)		 9. Number of Derivative Securities Beneficially Owned Following Reported Transaction(s)
(Instr. 4)		 10. Ownership Form of Derivative Security: Direct (D) or Indirect (I)
(Instr. 4)		 11. Nature of Indirect Beneficial Ownership
(Instr. 4)
Code V (A) (D) Date Exercisable Expiration Date Title Amount or Number of Shares
Warrants $ 1.3125 05/19/2016   P   900,000   08/17/2016 05/19/2021 Common Stock 900,000 (1) 900,000 I See Footnote (2)
Common Stock and Warrants (Obligation to buy Units) $ 1.1438 05/19/2016   P   2,734,427     (3)   (3) Common Stock 4,785,248 (3) 5,685,248 I See Footnote (2)

Reporting Owners

Reporting Owner Name / Address Relationships
 Director  10% Owner  Officer  Other
Merck & Co., Inc.
2000 GALLOPING HILL ROAD
KENILWORTH, NJ 07033		     X    
Merck Sharp & Dohme Corp.
ONE MERCK DRIVE
WHITEHOUSE STATION, NJ 08889		     X    
Merck Global Health Innovation Fund, LLC
ONE MERCK DRIVE
WHITEHOUSE STATION, NJ 08889		     X    

Signatures

 /s/Katie Fedosz as Attorney-In-Fact*   05/24/2016
**Signature of Reporting Person Date

Explanation of Responses:

* If the form is filed by more than one reporting person, see Instruction 4(b)(v).
** Intentional misstatements or omissions of facts constitute Federal Criminal Violations. See 18 U.S.C. 1001 and 15 U.S.C. 78ff(a).
(1) The reported securities are included within units ("Units") each Unit consisting of one share of the Company's common stock, par value $0.01 per share (the "Common Stock") and (ii) a warrant to acquire 0.75 of one share of Common Stock for a purchase price of $1.14375 per Unit.
(2) These shares are owned directly by Merck Global Health Innovation Fund, LLC ("MGHIF"), which is a wholly owned subsidiary of Merck Sharp & Dohme Corp. ("MSD"), which is a wholly owned subsidiary of Merck & Co., Inc. ("Merck"). MSD and Merck are indirect beneficial owners of the reported securities.
(3) Represents future obligation of MGHIF to purchase additional Units for a purchase price of $1.14375 per Unit within 60 days and subject to stockholder consent and notice to stockholders of same (including the filing of Schedule 14C and the twenty day waiting period), pursuant to the Amended and Restated Securities Purchase Agreement entered into on May 18, 2016.
 
Remarks:
* Ms. Katie Fedosz is signing as Attorney-in-Fact pursuant to power of attorney dated July 23, 2015 granted by each Reporting Person, a copy of which is filed as an exhibit and incorporated herein by reference.

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