RA Capital Healthcare Fund Form 3 Initial statement of insider ownership

SEC Form 3

FORM 3

UNITED STATES SECURITIES AND EXCHANGE COMMISSION
Washington, D.C. 20549

INITIAL STATEMENT OF BENEFICIAL OWNERSHIP OF SECURITIES

Filed pursuant to Section 16(a) of the Securities Exchange Act of 1934
or Section 30(h) of the Investment Company Act of 1940

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1. Name and Address of Reporting Person^*

RA CAPITAL MANAGEMENT, LLC

(Last) (First) (Middle)

20 PARK PLAZA, SUITE 1200

(Street)

BOSTON MA 02116

(City) (State) (Zip)

2. Date of Event Requiring Statement (Month/Day/Year)
12/06/2018

3. Issuer Name and Ticker or Trading Symbol
Synthorx, Inc. [ THOR ]

4. Relationship of Reporting Person(s) to Issuer
(Check all applicable)

Director	X	10% Owner
Officer (give title below)		Other (specify below)

5. If Amendment, Date of 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

Table I - Non-Derivative Securities Beneficially Owned
1. Title of Security (Instr. 4)	2. Amount of Securities Beneficially Owned (Instr. 4)	3. Ownership Form: Direct (D) or Indirect (I) (Instr. 5)	4. Nature of Indirect Beneficial Ownership (Instr. 5)

Table II - Derivative Securities Beneficially Owned (e.g., puts, calls, warrants, options, convertible securities)
1. Title of Derivative Security (Instr. 4)	2. Date Exercisable and Expiration Date (Month/Day/Year)		3. Title and Amount of Securities Underlying Derivative Security (Instr. 4)		4. Conversion or Exercise Price of Derivative Security	5. Ownership Form: Direct (D) or Indirect (I) (Instr. 5)	6. Nature of Indirect Beneficial Ownership (Instr. 5)
	Date Exercisable	Expiration Date	Title	Amount or Number of Shares
Series B Preferred Stock	(1)	(1)	Common Stock	1,525,235(2)	(1)	I	See Footnote(3)(4)(5)
Series C Preferred Stock	(6)	(6)	Common Stock	3,653,908(2)	(6)	I	See Footnote(4)(5)(7)

1. Name and Address of Reporting Person^*

RA CAPITAL MANAGEMENT, LLC

(Last) (First) (Middle)

20 PARK PLAZA, SUITE 1200

(Street)

BOSTON MA 02116

(City) (State) (Zip)

1. Name and Address of Reporting Person^*

RA Capital Healthcare Fund LP

(Last) (First) (Middle)

C/O RA CAPITAL MANAGEMENT, LLC

20 PARK PLAZA, SUITE 1200

(Street)

BOSTON MA 02116

(City) (State) (Zip)

Explanation of Responses:

1. The shares of Series B Preferred Stock have no expiration date and are convertible at any time at the election of the holder into shares of Common Stock without payment of further consideration. Each share of Series B Preferred Stock will automatically convert on a 1.60224-to-1 basis into shares of Common Stock upon the closing of the Issuer's initial public offering.

2. Share numbers give effect to the 1.60224-to-1 reverse stock split of the Issuer's Common Stock effected on November 26, 2018, which will be effective for the Preferred Stock upon its conversion to Common Stock upon the closing of the Issuer's initial public offering.

3. The shares are held as follows: 1,245,659 shares held by RA Capital Healthcare Fund, L.P. (the "Fund") and 279,576 shares held by a separately managed account (the "Account").

4. RA Capital Management, LLC (the "Adviser") is the general partner of the Fund and the investment adviser for the Account and therefore may be deemed to beneficially own the reported securities for purposes of Section 13(d) of the Securities Exchange Act of 1934. Additionally, Peter Kolchinsky is a director of the Issuer and the sole manager of the Adviser.

5. The Adviser disclaims beneficial ownership of the reported securities for purposes of Rule 16a-1(a)(1) under the Exchange Act in reliance on Rule 16a-1(a)(1)(v) and therefore disclaims any obligation to report ownership of the reported securities under Section 16(a) of the Exchange Act. The filing of this Form 3 shall not be construed as an admission that the Adviser is, for purposes of Rule 16a-1(a)(1) under the Exchange Act, the beneficial owner of any of the securities reported herein. The Adviser disclaims beneficial ownership of the securities reported herein for purposes of Rule 16a-1(a)(2) under the Exchange Act except to the extent of its pecuniary interest therein.

6. The shares of Series C Preferred Stock have no expiration date and are convertible at any time at the election of the holder into shares of Common Stock without payment of further consideration. Each share of Series C Preferred Stock will automatically convert on a 1.60224-to-1 basis into shares of Common Stock upon the closing of the Issuer's initial public offering.

7. The shares are held as follows: 2,941,397 shares held by the Fund and 712,511 shares held by the Account.

	/s/ Peter Kolchinsky, Manager of RA Capital Management, LLC	12/06/2018
	/s/ Peter Kolchinsky, Manager of RA Capital Management, LLC, the General Partner of RA Capital Healthcare Fund, L.P.	12/06/2018
	** Signature of Reporting Person	Date
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