424(b)(3)

Filed Pursuant to Rule 424(b)(3) and Rule 424(c)

Registration No. 333-150326

July 7, 2009

PROSPECTUS SUPPLEMENT NO. 13

14,000,000 SHARES OF COMMON STOCK

ANTIGENICS INC.

This prospectus supplement amends the prospectus dated March 16, 2009 (as supplemented on April 15, 2009, April 17, 2009, April 22, 2009, April 27, 2009, May 4, 2009, May 11, 2009, May 27, 2009, June 4, 2009, June 8, 2009, June 9, 2009, June 11, 2009, and June 15, 2009) to allow certain stockholders or their pledgees, donees, transferees, or other successors in interest (the “Selling Stockholders”), to sell, from time to time, up to 7,000,000 shares of our common stock, which they have acquired in a private placement in the United States, and up to 7,000,000 shares of our common stock issuable upon the exercise of warrants which are held by the Selling Stockholders named in the prospectus.

We would not receive any proceeds from any such sale of these shares. To the extent any of the warrants are exercised for cash, if at all, we will receive the exercise price for those warrants.

This prospectus supplement is being filed to include the information set forth in the Current Report on Form 8-K filed on June 15, 2009, which is set forth below. This prospectus supplement should be read in conjunction with the prospectus dated March 16, 2009, Prospectus Supplement No. 1 dated April 15, 2009, Prospectus Supplement No. 2 dated April 17, 2009, Prospectus Supplement No. 3 dated April 22, 2009, Prospectus Supplement No. 4 dated April 27, 2009, Prospectus Supplement No. 5 dated May 4, 2009, Prospectus Supplement No. 6 dated May 11, 2009, Prospectus Supplement No. 7 dated May 27, 2009, Prospectus Supplement No. 8 dated June 4, 2009, Prospectus Supplement No. 9 dated June 8, 2009, Prospectus Supplement No. 10 dated June 9, 2009, Prospectus Supplement No. 11 dated June 11, 2009, and Prospectus Supplement No. 12 dated June 15, 2009, which are to be delivered with this prospectus supplement.

Our common stock is quoted on The NASDAQ Capital Market (“NASDAQ”) under the ticker symbol “AGEN.” On July 6, 2009, the last reported closing price per share of our common stock was $1.80 per share.

Investing in our securities involves a high degree of risk. Before investing in any of our securities, you should read the discussion of material risks in investing in our common stock. See “Risk Factors” on page 1 of the prospectus.

Neither the Securities and Exchange Commission nor any state securities commission has approved or disapproved of these securities or passed upon the adequacy or accuracy of this prospectus. Any representation to the contrary is a criminal offense.

THE DATE OF THIS PROSPECTUS SUPPLEMENT NO. 13 IS JULY 7, 2009


UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

FORM 8-K

CURRENT REPORT

Pursuant to Section 13 or 15(d) of

The Securities Exchange Act of 1934

July 2, 2009

Date of Report (Date of earliest event reported)

ANTIGENICS INC.

(Exact name of registrant as specified in its charter)

 

DELAWARE   000-29089   06-1562417

(State or other jurisdiction

of incorporation)

 

(Commission

File Number)

 

(IRS Employer

Identification No.)

 

3 Forbes Rd.

Lexington, MA

  02421
(Address of principal executive offices)   (Zip Code)

781-674-4400

(Registrant’s telephone number, including area code)

Check the appropriate box below if the Form 8-K filing is intended to simultaneously satisfy the filing obligation of the registrant under any of the following provisions (see General Instruction A.2. below):

 

¨ Written communications pursuant to Rule 425 under the Securities Act (17 CFR 230.425)

 

¨ Soliciting material pursuant to Rule 14a-12 under the Exchange Act (17 CFR 240.14a-12)

 

¨ Pre-commencement communications pursuant to Rule 14d-2(b) under the Exchange Act (17 CFR 240.14d-2(b))

 

¨ Pre-commencement communications pursuant to Rule 13e-4(c) under the Exchange Act (17 CFR 240.13e-4(c))


Item 5.02 Departure of Directors or Certain Officers; Election of Directors; Appointment of Certain Officers; Compensatory Arrangements of Certain Officers

On July 2, 2009, Antigenics, Inc. (the “Company”) entered into amended employment agreements with Dr. Armen, Ms. Sharp, Ms. Valentine and Ms. Wentworth to accelerate the vesting of restricted stock awards in the event of a “change in control” as such term is defined in their respective employment agreements.


SIGNATURES

Pursuant to the requirements of the Securities Exchange Act of 1934, the Registrant has duly caused this report to be signed on its behalf by the undersigned hereunto duly authorized.

 

    ANTIGENICS INC.
Date: July 7, 2009     By:   /s/ Shalini Sharp
       

Shalini Sharp

Chief Financial Officer