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

SCHEDULE 13D

Under the Securities Exchange Act of 1934
(Amendment No. ________)*

GENOCEA BIOSCIENCES, INC.

(Name of Issuer)

Common Stock, Par Value $0.001

(Title of Class of Securities)

372427 10 4

(CUSIP Number)

Victoria A. Whyte

GlaxoSmithKline plc

980 Great West Road

Brentford, Middlesex TW8 9GS

England

Telephone: +44 (0)208 047 5000

(Name, Address and Telephone Number of Person
Authorized to Receive Notices and Communications)

February 5, 2014

(Date of Event which Requires Filing of this Statement)

If the filing person has previously filed a statement on Schedule 13G to report the acquisition that is the subject of this Schedule 13D, and is filing this schedule because of §§240.13d-1(e), 240.13d-1(f) or 240.13d-1(g), check the following box. 

Note: Schedules filed in paper format shall include a signed original and five copies of the schedule, including all exhibits. See §240.13d-7 for other parties to whom copies are to be sent.

^* The remainder of this cover page shall be filled out for a reporting person's initial filing on this form with respect to the subject class of securities, and for any subsequent amendment containing information which would alter disclosures provided in a prior cover page.

The information required on the remainder of this cover page shall not be deemed to be "filed" for the purpose of Section 18 of the Securities Exchange Act of 1934 (“Act”) or otherwise subject to the liabilities of that section of the Act but shall be subject to all other provisions of the Act.

Item 1.  Security and Issuer.

This statement on Schedule 13D (this “Statement”) relates to the shares of Common Stock, par value $0.001 per share (the “Common Stock”), of Genocea Biosciences, Inc., a Delaware corporation (the “Issuer”). The Issuer’s principal executive offices are located at Cambridge Discovery Park, 100 Acorn Park Drive, 5th Floor, Cambridge, Massachusetts 02140.

Item 2.  Identity and Background.

This Statement is being filed on behalf of GlaxoSmithKline plc, a public limited company incorporated under the laws of England and Wales. GlaxoSmithKline plc and its subsidiaries constitute a major global healthcare group engaged in the creation, discovery, development, manufacture and marketing of pharmaceutical and consumer health-related products with its principal offices located at 980 Great West Road, Brentford, Middlesex TW8 9GS, England. Set forth in Schedule 1 to this Statement are the name, business address and present principal occupation or employment and citizenship of each executive officer and director of GlaxoSmithKline plc. The Common Stock which is the subject of this Statement is held of record held by S.R. One, Limited (“S.R. One”), an indirect, wholly-owned subsidiary of GlaxoSmithKline plc.

During the last five years prior to the date hereof, neither GlaxoSmithKline plc nor, to the best knowledge of GlaxoSmithKline plc, any of the other persons with respect to whom information is given in response to this Item 2 has been convicted in a criminal proceeding or been a party to a civil proceeding ending in a judgment, decree or final order enjoining future violations of, or prohibiting or mandating activities subject to, federal or state securities laws, or finding any violation with respect to such laws.

Item 3.  Source or Amount of Funds or Other Consideration.

S.R. One acquired from the Issuer 143,773 shares of Common Stock on February 10, 2014 pursuant to the Issuer’s initial public offering (the “IPO”). The total consideration paid by S.R. One for these shares was $1,725,276, and such consideration was obtained from the working capital of S.R. One. S.R. One also acquired 1,527,894 shares of Common Stock on February 10, 2014 upon the conversion of (i) 9,230,769 shares of Series A Preferred Stock of the Issuer (the “Series A Preferred”) into 775,694 shares of Common Stock, (ii) 4,099,231 shares of Series B Preferred Stock of the Issuer (the “Series B Preferred”) into 344,473 shares of Common Stock, and (iii) 4,851,958 shares of Series C Preferred Stock of the Issuer (the “Series C Preferred” and, together with the Series A Preferred and the Series B Preferred, the “Preferred Stock”) into 407,727 shares of Common Stock, at the closing of the IPO. The conversion ratio was one share of Common Stock for every 11.9 shares of Preferred Stock.

Item 4.  Purpose of Transaction.

In February 2009, S.R. One appointed Simeon J. George, M.D., Vice President of S.R. One, to the board of directors of the Issuer pursuant to an investor rights agreement which terminated upon closing of the IPO. At the request of the Issuer, Dr. George currently remains on the Issuer’s board of directors. As of the IPO, S.R. One does not have the right to appoint or remove a director.

On October 21, 2013, the Issuer, S.R. One and certain other investors entered into the Fourth Amended and Restated Registration Rights Agreement (the “Registration Rights Agreement”), a copy of which is attached as Exhibit 1 hereto. The registration rights granted to S.R. One pursuant to the Registration Rights Agreement include the following:

S.R. One and certain other investors each entered into a lock up agreement (the “Lock Up Agreement”), a copy of which is attached as Exhibit 2 hereto, with Citigroup Global Markets Inc. and Cowen and Company, LLC (both in their capacity as representatives of the underwriters for the IPO) (the “Representatives”).

Pursuant to the Lockup Agreement, S.R. One has agreed that for a period of 180 days following the date of the underwriting agreement, it will not, without the prior written consent of the Representatives, offer, sell, contract to sell, pledge, or otherwise dispose of (or enter into a transaction which is designed to, or may reasonably be expected to result in the disposition of), directly or indirectly, including the filing of a registration statement with the Securities and Exchange Commission in respect of, or establish or increase a put equivalent position or liquidate or decrease a call equivalent position with respect to, any shares of capital stock of the Issuer or any securities convertible into, or exercisable or exchangeable for such capital stock, subject to specified exceptions, which include but are not limited to transactions relating to shares of Common Stock acquired by S.R. One in the IPO or in open market transactions subsequent to the closing of the IPO.

Other than as described above, S.R. One has no plans or proposals that would result in:

S.R. One expects to review from time to time its investment in the Issuer and may, depending on the Issuer’s business, assets, operations, financial condition, prospects and other factors, as well as (and subject to) the terms of the contracts described in Item 6 of this Schedule: (i) purchase additional shares of Common Stock, options or other securities of the Issuer in the open market, in privately negotiated transactions or otherwise; (ii) sell all or a portion of the shares of Common Stock, options or other securities now beneficially owned or hereafter acquired by it; (iii) propose one or more directors for the Issuer’s board of directors; (iv) engage in discussions, negotiations or enter into other transactions with a view to obtaining direct or indirect control of the Issuer; (v) acquire assets of the Issuer and its subsidiaries; and (vii) engage in such other proposals as S.R. One may deem appropriate under the circumstances, including plans or proposals which may relate to, or could result in, any of the matters referred to in clauses (a) through (j), above.

Also, consistent with its investment intent, S.R. One may engage in communications with, without limitation, one or more shareholders of the Issuer, one or more officers of the Issuer and/or one or more members of the board of directors of the Issuer regarding the Issuer, including but not limited to its operations, governance and control.

Item 5.  Interest in Securities of the Issuer.

Item 6.  Contracts, Arrangements, Understandings or Relationships with Respect to Securities of the Issuer.

Except as disclosed in Item 4 of this Statement, there are no contracts, arrangements, understandings or relationships (legal or otherwise) between GlaxoSmithKline plc or S.R. One and any other person with respect to any securities of the Company.

Item 7.  Material to Be Filed as Exhibits.

Descriptions of documents set forth on this Schedule are qualified in their entirety by reference to the exhibits listed in this Item 7.

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.

Date: February 14, 2014

GLAXOSMITHKLINE PLC

By: /s/ Simon Dingemans  

Name: Simon Dingemans
Title: Chief Financial Officer

SCHEDULE 1

Exhibit 2

Genocea Biosciences, Inc.
Public Offering of Common Stock

October 21, 2013

Citigroup Global Markets Inc.
Cowen and Company, LLC
As Representatives of the several Underwriters,
c/o Citigroup Global Markets Inc.
388 Greenwich Street
New York, New York 10013

Ladies and Gentlemen:

This letter is being delivered to you in connection with the proposed Underwriting Agreement (the “Underwriting Agreement”), between Genocea Biosciences, Inc., a Delaware corporation (the “Company”), and each of you as representatives of a group of Underwriters named therein, relating to an underwritten public offering of Common Stock, $0.001 par value (the “Common Stock”), of the Company (the “Offering”).

In order to induce you and the other Underwriters to enter into the Underwriting Agreement, the undersigned will not, without the prior written consent of each of Citigroup Global Markets Inc. (“Citigroup”) and Cowen and Company, LLC (“Cowen”, and together with Citigroup, the “Representatives”), offer, sell, contract to sell, pledge or otherwise dispose of, (or enter into any transaction which is designed to, or might reasonably be expected to, result in the disposition (whether by actual disposition or effective economic disposition due to cash settlement or otherwise) by the undersigned or any affiliate of the undersigned or any person in privity with the undersigned or any affiliate of the undersigned), directly or indirectly, including the filing (or participation in the filing) of a registration statement with the Securities and Exchange Commission in respect of, or establish or increase a put equivalent position or liquidate or decrease a call equivalent position within the meaning of Section 16 of the Securities Exchange Act of 1934, as amended, (the “Exchange Act”) and the rules and regulations of the Securities and Exchange Commission promulgated thereunder with respect to, any shares of capital stock of the Company or any securities convertible into, or exercisable or exchangeable for such capital stock, or publicly announce an intention to effect any such transaction, for a period from the date hereof until 180 days after the date of the Underwriting Agreement, other than (i) shares of Common Stock disposed of as bona fide gifts where each recipient of a gift of shares agrees in writing to be bound by the same restrictions in place for the undersigned pursuant to this letter for the duration that such restrictions remain in effect at the time of transfer; (ii) exercise of options to purchase shares or Common Stock or the receipt of shares of Common Stock upon the vesting of restricted stock awards disclosed in the Prospectus or any related transfer of shares of Common Stock to the Company (x) deemed to occur upon the cashless exercise of such options or (y) for the purpose of paying the exercise price of such options or for paying taxes due as a result of the exercise of such options or as a result of the vesting of such shares of Common Stock, it being understood that all shares of Common Stock received upon such exercise or transfer will remain subject to the restrictions of this agreement during the 180-day period referred to above; (iii) transfers of common stock to any affiliate (as such term is defined in Rule

405 of the Securities Act of 1933, as amended), limited partners, general partners, limited liability company members of stockholders of the undersigned, or if the undersigned is a corporation to any wholly-owned subsidiary of such corporation, provided that in each case (x) the recipient agrees to be bound in writing by the same restrictions set forth herein, (y) no filing under Section 13 or Section16(a) of the Exchange Act reporting a reduction in beneficial ownership of shares of Common Stock shall be required during the 180-day period referred to above, and (z) no filing under Section 13 or Section 16(a) of the Exchange Act shall be voluntarily made by the undersigned or the transferee during the 180-day period referred to above; and (iv) the establishment of a trading plan pursuant to Rule 10b-5-1 under the Exchange Act for the transfer of shares of Common Stock, provided that such plan does not provide for the transfer of shares of Common Stock during the restricted period specified in this letter and no filing or other public announcement shall be required during the 180-day period referred to above. The foregoing restrictions shall not apply to transactions relating to shares of Common Stock acquired by the undersigned in the Offering or in open market transactions subsequent to the closing of the Offering, provided that (i) no filing under Section 13 or Section 16(a) of the Exchange Act reporting a reduction in beneficial ownership of shares of Common Stock shall be required and (ii) no filing under Section 13 or Section 16(a) of the Exchange Act shall be voluntarily made by the undersigned, in the case of both clauses (i) and (ii), during the 180-day period referred to above. If the undersigned is an officer or director of the Company, the undersigned further agrees that the foregoing restrictions shall be equally applicable to any issuer-directed shares of Common Stock the undersigned may purchase in the Offering.

If the undersigned is an officer or director of the Company, (i) the Representatives agree that, at least three business days before the effective date of any release or waiver of the foregoing restrictions in connection with a transfer of shares of Common Stock, the Representatives will notify the Company of the impending release or waiver, and (ii) the Company has agreed in the Underwriting Agreement to announce the impending release or waiver by press release through a major news service at least two business days before the effective date of the release or waiver. Any release or waiver granted by the Representatives hereunder to any such officer or director shall only be effective two business days after the publication date of such press release. The provisions of this paragraph will not apply if (a) the release or waiver is effected solely to permit a transfer not for consideration and (b) the transferee has agreed in writing to be bound by the same terms described in this letter to the extent and for the duration that such terms remain in effect at the time of the transfer.

In the event that the Representatives release, in full or in part, any officer, director or equity holder of the Company (a “Stockholder”) from the restrictions of any lock-up agreement signed by such Stockholder with the Underwriters (a “Triggering Release”), then the undersigned shall be released in the same manner from the restrictions of this Agreement (i.e., in an amount equal to the same percentage of the shares of Common Stock being released in the Triggering Release relative to the undersigned’s ownership of Common Stock at the time of the request of the Triggering Release); provided that (i) in order to request a Triggering Release, the Stockholder requesting the Triggering Release must make a request in writing to the Company setting forth the number of shares of Common Stock to be released; (ii) the Company must notify the other Stockholders of the requested Triggering Release within three business days; (iii) any other Stockholder that intends to request a release of a pro rata portion of the shares of Common Stock held by them (the “Pro Rata Stockholders”) must (x) make such a request in writing to the Company and (y) certify in writing to the Underwriters and the Company the total number of shares of Common Stock held by such Pro Rata Stockholder; (iv) the Company must (x) make a request in writing to the Representatives setting forth for the Stockholder requesting the Triggering Release and for each Pro Rata Stockholder the number of shares of Common Stock for which each such Stockholder is requesting a release and (y) provide to the Representatives the total number of shares of common stock of the Company outstanding as of the date of the request of such Triggering Release and certify in writing to the Underwriters that such number is true and accurate. If the Company fails to notify the undersigned within three business days of the request of the Triggering Release, the

failure to give such notice shall not give rise to any claim or liability against the Representatives or the Underwriters.

Notwithstanding the foregoing, (i) no release by the Representatives of any shares of Common Stock due to financial hardship will constitute a Triggering Release if the aggregate of such releases granted to any individual Stockholder requesting a release does not exceed $50,000 worth of shares of Common Stock during the Lock-Up Period (such value to be calculated using the closing or last reported sale price of the Common Stock on the day of each such release) (for the avoidance of doubt, each individual affiliate of the undersigned that is a party to a separate lock-up agreement with the Underwriters shall be treated as a separate Stockholder); (ii) if the release, in full or in part, of any shares of Common Stock from the restrictions of its lock-up agreement is in connection with a follow-on offering of common stock (the “Follow-On Offering”), then the shares of Common Stock held by the undersigned shall be released only if the undersigned enters into a new lock-up agreement with the underwriters with respect to the shares of Common Stock that are not being released, upon terms and conditions reasonably satisfactory to the Underwriters but with restrictions that will be no more restrictive than those set forth herein and only to the extent that the undersigned agrees to participate as a selling stockholder in the Follow-On Offering and to sell any of the shares of Common Stock released from the restrictions of this agreement in such Follow-On Offering; and (iii) the Representatives shall not release, in full or in part, any Stockholder from the restrictions of any lock-up agreement signed by such Stockholder with the Underwriters unless such Stockholder shall have first made a request pursuant to the clause (i) of the preceding paragraph.

This agreement shall automatically terminate upon the earliest to occur, if any, of (i) the date that the Company advises the Representatives, in writing, prior to the execution of the Underwriting Agreement, that it has determined not to proceed with the Offering, (ii) the date of termination of the Underwriting Agreement if prior to the closing of the Offering, or (iii) September 30, 2014 if the Offering has not been completed by such date.

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Yours very truly,

S.R. ONE, LIMITED

By: /s/ Brian Gallagher

Name: Brian Gallagher

Title: Vice President & Partner

Address: 161 Washington Street              

Suite 500                                                

Conshohocken, PA 19428