UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

WASHINGTON, D.C. 20549

____________

SCHEDULE 13G

Under the Securities Exchange Act of 1934

Achillion Pharmaceuticals, Inc.

(Name of Issuer)

Common Stock, $0.001 par value per share

(Title of Class of Securities)

00448Q201

(CUSIP Number)

October 31, 2013

(Date of Event Which Requires Filing of this Statement)

Check the appropriate box to designate the rule pursuant to which the Schedule is filed:

¨ Rule 13d-1(b)

x Rule 13d-1(c)

¨ Rule 13d-1(d)

Blackwell Partners, LLC (“Blackwell”), Duke University, and DUMAC, Inc. (“DUMAC”), (collectively, the “Reporting Persons”) are filing this Statement of Beneficial Ownership on Schedule 13G to report the shares of Common Stock, par value $0.001 per share (the “Common Stock”) of Achillion Pharmaceuticals, Inc., a Delaware corporation (“Achillion”) over which they could acquire beneficial ownership if they were to terminate their investment management agreement with RA Capital Management, LLC.

DUMAC is a North Carolina non-profit corporation. DUMAC manages the investment of endowment and other assets of Duke University and Blackwell. DUMAC does not hold legal title to its clients’ assets. The members of the board of directors of DUMAC are appointed by the executive committee of the board of trustees of Duke University.

Blackwell is a Georgia limited liability company that is managed by an entity that qualifies as a support corporation of Duke University under Section 509(a)(3) of the Internal Revenue Code.

Achillion Pharmaceuticals, Inc.

300 George Street

New Haven, CT 06511

Blackwell Partners, LLC

Duke University

DUMAC, Inc.

Blackwell Partners, LLC

c/o DUMAC, Inc.

280 S Mangum St., Suite 210

Durham, NC 27701

Duke University

c/o DUMAC, Inc.

280 S Mangum St., Suite 210

Durham, NC 27701

DUMAC, Inc.

280 S Mangum St., Suite 210

Durham, NC 27701

Blackwell Partners, LLC

Georgia

Duke University

North Carolina

DUMAC, Inc.

North Carolina

Common Stock, $.001 par value per share

00448Q201

As of the date of this filing, Blackwell beneficially owns 5,240,892 shares of Common Stock of Achillion, which constitutes approximately 5.4% of Achillion’s outstanding Common Stock as reported in its Annual Report on Form 10-K for the year ended December 31, 2013 filed on March 7, 2014. Of the above 5,240,892 shares of Achillion’s Common Stock, Blackwell has sole voting and dispositive power over 5,240,892 shares of Common Stock of Achillion and shared dispositive power over 0 shares of Common Stock of Achillion.

Duke University beneficially owns, and has shared voting and dispositive power over, 5,240,892 shares of Common Stock of Achillion, which constitutes approximately 5.4% of Achillion’s outstanding Common Stock. DUMAC beneficially owns, and has shared voting and dispositive power over, 5,240,892 shares of Common Stock of Achillion, which constitutes approximately 5.4% of Achillion’s outstanding Common Stock.

This Schedule 13G has been filed for informational purposes to reflect that DUMAC makes investment decisions for each of Duke University and Blackwell. Beneficial ownership of Achillion’s shares beneficially owned by Blackwell, Duke University, and DUMAC is also reflected in Schedule 13D, as amended, filed by RA Capital Management, LLC. The Reporting Persons disclaim beneficial ownership over the shares of Common Stock reported above.

If this statement is being filed to report the fact that as of the date hereof the reporting person has ceased to be the beneficial owner of more than 5 percent of the class of securities, check the following [ ].

Not applicable.

By signing below I certify that, to the best of my knowledge and belief, the securities referred to above were acquired and are not held for the purpose of or with the effect of changing or influencing the control of the issuer of the securities and were not acquired and are not held in connection with or as a participant in any transaction having that purpose or effect.

Joint Filing Agreement, dated March 26, 2014, by and among Blackwell, DUMAC, and Duke University.

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SIGNATURE

After reasonable inquiry and to the best of my knowledge and belief, I certify that the information set forth in this statement is true, complete and correct.

EXHIBIT 99.1

JOINT FILING AGREEMENT

                In accordance with Rule 13d-1(k) under the Securities Exchange Act of 1934, as amended, the undersigned agree to the joint filing on behalf of each of them of a Statement on Schedule 13G (including any and all amendments thereto) with respect to the Shares of Common Stock, of Achillion Pharmaceuticals, Inc., and further agree that this Joint Filing Agreement shall be included as an Exhibit to such joint filings.

                The undersigned further agree that each party hereto is responsible for the timely filing of such Statement on Schedule 13G and any amendments thereto, and for the accuracy and completeness of the information concerning such party contained therein; provided, however, that no party is responsible for the accuracy or completeness of the information concerning any other party, unless such party knows or has reason to believe that such information is inaccurate.

                This Joint Filing Agreement may be signed in counterparts with the same effect as if the signature on each counterpart were upon the same instrument.

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IN WITNESS WHEREOF, the undersigned have executed this Agreement as of March 26, 2014.