As filed with the Securities and Exchange Commission on August 6, 2014

Registration No. 333-               

UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

FORM S-1

REGISTRATION STATEMENT

UNDER

THE SECURITIES ACT OF 1933

T2 Biosystems, Inc.

(Exact name of registrant as specified in its charter)

101 Hartwell Avenue

Lexington, Massachusetts 02421

(781) 457-1200

(Address, including zip code, and telephone number, including area code, of registrant’s principal executive offices)

John P. McDonough

President and Chief Executive Officer

T2 Biosystems, Inc.

101 Hartwell Avenue

Lexington, Massachusetts 02421

(781) 457-1200

(Name, address, including zip code, and telephone number, including area code, of agent for service)

Copies to:

Approximate date of commencement of proposed sale to the public:

As soon as practicable after this Registration Statement is declared effective.

If any of the securities being registered on this Form are to be offered on a delayed or continuous basis pursuant to Rule 415 under the Securities Act of 1933, check the following box. o

If this Form is filed to register additional securities for an offering pursuant to Rule 462(b) under the Securities Act, please check the following box and list the Securities Act registration statement number of the earlier effective registration statement for the same offering. x Registration No. 333-197193

If this Form is a post-effective amendment filed pursuant to Rule 462(c) under the Securities Act, check the following box and list the Securities Act registration statement number of the earlier effective registration statement for the same offering. o

If this Form is a post-effective amendment filed pursuant to Rule 462(d) under the Securities Act, check the following box and list the Securities Act registration statement number of the earlier effective registration statement for the same offering. o

Indicate by check mark whether the registrant is a large accelerated filer, an accelerated filer, a non-accelerated filer or a smaller reporting company.  See the definitions of “large accelerated filer,” “accelerated filer” and “smaller reporting company” in Rule 12b-2 of the Exchange Act.

CALCULATION OF REGISTRATION FEE

This Registration Statement shall become effective upon filing with the Securities and Exchange Commission in accordance with Rule 462(b) promulgated under the Securities Act.

EXPLANATORY NOTE AND INCORPORATION OF CERTAIN INFORMATION BY REFERENCE

This registration statement is being filed with the Securities and Exchange Commission (the “Commission”) pursuant to Rule 462(b) under the Securities Act of 1933, as amended.  This Registration Statement relates to the public offering of common stock, par value $0.001 per share, of the Registrant contemplated by the Registration Statement on Form S-1, as amended (File No. 333-197193), initially filed with the Commission by the Registrant on July 2, 2014 (as amended, the “Prior Registration Statement”), and is being filed for the sole purpose of registering additional securities of the same class as were included in the Prior Registration Statement.  The contents of the Prior Registration Statement and all exhibits thereto are hereby incorporated by reference.

The required opinion and consents are listed on an Exhibit Index attached hereto and filed herewith.

2

SIGNATURES

Pursuant to the requirements of the Securities Act, the registrant has duly caused this Registration Statement to be signed on its behalf by the undersigned, thereunto duly authorized, in the Town of Lexington, Commonwealth of Massachusetts, on this 6th day of August, 2014.

3

SIGNATURES

Pursuant to the requirements of the Securities Act of 1933, this Registration Statement on Form S-1 has been signed by the following persons in the capacities held on the dates indicated.

4

EXHIBIT INDEX

(1)                                 Previously filed as Exhibit 1.1 to the Registrant’s Registration Statement on Form S-1, as amended (File No. 333-197193), initially filed with the Securities and Exchange Commission on July 2, 2014 and incorporated by reference herein.

(2)                                 Included in Exhibit 5.1.

(3)                                 Previously filed on the signature page to the Registrant’s Registration Statement on Form S-1, as amended (File No. 333-197193), initially filed with the Securities and Exchange Commission on July 2, 2014 and incorporated by reference herein.

5

Exhibit 5.1

Re:                             Registration Statement No. 333-197193 and Registration Statement filed pursuant to Rule 462(b) promulgated under the Securities Act of 1933, as amended;

5,980,000 shares of Common Stock, $0.001 par value per share

Ladies and Gentlemen:

We have acted as special counsel to T2 Biosystems, Inc., a Delaware corporation (the “Company”), in connection with the registration of shares of the Company’s common stock, $0.001 par value per share (the “Common Stock”), pursuant to a registration statement on Form S-1/A under the Securities Act of 1933, as amended (the “Act”), filed with the Securities and Exchange Commission (the “Commission”) on July 28, 2014 (Registration No. 333-197193) (as amended, the “Initial Registration Statement”) and a registration statement relating to the Initial Registration Statement filed pursuant to Rule 462(b) promulgated under the Act (the “Post-Effective Amendment” and together with the Initial Registration Statement, the “Registration Statement”).  The Post-Effective Amendment relates to the registration of 1,380,000 additional shares of Common Stock (the “Additional Shares”).  This opinion is being furnished in connection with the requirements of Item 601(b)(5) of Regulation S-K under the Act, and no opinion is expressed herein as to any matter pertaining to the contents of the Registration Statement or related prospectus (the “Prospectus”), other than as expressly stated herein with respect to the issue of the Additional Shares.

As such counsel, we have examined such matters of fact and questions of law as we have considered appropriate for purposes of this letter.  With your consent, we have relied upon certificates and other assurances of officers of the Company and others as to factual matters without having independently verified such factual matters.  We are opining herein as to General Corporation Law of the State of Delaware (the “DGCL”) and we express no opinion with respect to any other laws.

Subject to the foregoing and the other matters set forth herein, it is our opinion that, as of the date hereof, the Additional Shares have been duly authorized by all necessary corporate action of the Company and are validly issued, fully paid and nonassessable.  In rendering the foregoing opinion, we have assumed that the Company will comply with all applicable notice requirements regarding uncertificated shares provided in the DGCL.

This opinion is for your benefit in connection with the Registration Statement and may be relied upon by you and by persons entitled to rely upon it pursuant to the applicable provisions of the Act.  We consent to your filing this opinion as an exhibit to the Registration Statement and to the reference to our firm in the Prospectus under the heading “Legal Matters.”  In giving such consent, we do not thereby admit that we are in the category of persons whose consent is required under Section 7 of the Act or the rules and regulations of the Commission thereunder.

2

Exhibit 23.1

CONSENT OF INDEPENDENT REGISTERED PUBLIC ACCOUNTING FIRM

We consent to the incorporation by reference in the Registration Statement on Form S-1 filed pursuant to Rule 462(b) of the Securities Act of 1933 of the reference to our firm under the caption “Experts” and our report dated April 24, 2014, (except for Note 17(a) and (b), as to which the date is July 15, 2014 and Note 17(c), as to which the date is July 25, 2014), relating to the financial statements of T2 Biosystems, Inc. included in Amendment No. 2 to the Registration Statement (Form S-1 No. 333-197193) and related Prospectus of T2 Biosystems, Inc. for the registration of its common stock.