UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549





FORM 10-Q/A

(Amendment No. 1)





(Mark One)

|☒ | QUARTERLY REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934
|- | ---------------------------------------------------------------------------------------

For the quarterly period ended March 31, 2017

OR



|☐ | TRANSITION REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934
|- | ----------------------------------------------------------------------------------------

For the transition period from
 to

Commission file number 0-32405





SEATTLE
GENETICS, INC.

(Exact name of registrant as specified in its charter)







|                                                               |  |                                     
|-------------------------------------------------------------- |  | ------------------------------------
|Delaware                                                       |  | 91-1874389                          
|(State or other jurisdiction of
incorporation or organization) |  | (I.R.S. Employer
Identification No.)

21823 30th Drive SE

Bothell, Washington 98021

(Address of principal executive offices, including zip code)

(Registrants telephone number, including area code): (425) 527-4000





Indicate by check mark whether the registrant (1) has filed all reports required to be filed by Section 13 or 15(d) of the Securities Exchange Act
of 1934 during the preceding 12 months (or for such shorter period that the registrant was required to file such reports), and (2) has been subject to such filing requirements for the past 90
days.    Yes  ☒    No  ☐

Indicate by check mark whether the registrant has
submitted electronically and posted on its corporate Web site, if any, every Interactive Data File required to be submitted and posted pursuant to Rule 405 of Regulation S-T during the preceding 12 months (or for such shorter period that the
registrant was required to submit and post such files).    Yes  ☒    No  ☐

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



|                        |  |                                                  |  |                           |  |  
|----------------------- |  | ------------------------------------------------ |  | ------------------------- |  | -
|Large accelerated filer |  | ☒                                                |  | Accelerated filer         |  | ☐
|                        |  |                                                  | 
|Non-accelerated filer   |  | ☐  (Do not check if a smaller reporting company) |  | Smaller reporting company |  | ☐
|                        |  |                                                  | 
|Emerging growth company |  | ☐                                                |  |                           |  |  

If an emerging growth company, indicate by check mark if the registrant has elected not to use the extended transition period
for complying with any new or revised financial accounting standards provided pursuant to Section 13(a) of the Exchange Act.    ☐

Indicate by check mark whether the registrant is a shell company (as defined in Rule 12b-2 of the Exchange
Act).    Yes  ☐    No  ☒

As of April 26, 2017, there were 142,716,597 shares of
the registrants common stock outstanding.









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EXPLANATORY NOTE

Seattle Genetics, Inc. (the Company) is filing this Amendment No. 1 to Quarterly Report on Form 10-Q/A (this
Amendment) to amend the Companys Quarterly Report on Form 10-Q for the quarterly period ended March 31, 2017, as filed with the Securities and Exchange Commission (the SEC) on May 1, 2017 (the
10-Q). This Amendment is being filed solely to re-file Exhibit 10.3 to the 10-Q (the Exhibit) and in connection therewith, to amend Part II, Item 6 of the 10-Q. Certain provisions of the Exhibit were redacted in
accordance with the Companys application for confidential treatment with the SEC. In response to SEC comments, the Exhibit, as re-filed, includes certain provisions that had previously been redacted. In addition, as required by Rule
12b-15 under the Securities Exchange Act of 1934, as amended, new certifications by our principal executive officer and principal financial officer are filed as exhibits to this Amendment.

No attempt has been made in this Amendment to modify or update the other disclosures presented in the 10-Q. This Amendment does not reflect
events occurring after the filing of the original 10-Q (i.e., those events occurring after May 1, 2017) or modify or update those disclosures that may be affected by subsequent events.



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|Item 6. | Exhibits
|------- | --------



|               |  |                                                                                                                                                 |  |                            |  |              |  |         |  |            
|-------------- |  | ----------------------------------------------------------------------------------------------------------------------------------------------- |  | -------------------------- |  | ------------ |  | ------- |  | -----------
|               |  |                                                                                                                                                 |  | Incorporation By Reference
|Exhibit
Number |  | Exhibit Description                                                                                                                             |  | Form                       |  | SEC File No. |  | Exhibit |  | Filing Date
|               |  |                                                                                                                                                 |  |                            | 
|3.1            |  | Fourth Amended and Restated Certificate of Incorporation of Seattle Genetics, Inc.                                                              |  | 10-Q                       |  | 000-32405    |  | 3.1     |  | 11/07/2008 
|               |  |                                                                                                                                                 |  |                            | 
|3.2            |  | Certificate of Amendment of Fourth Amended and Restated Certificate of Incorporation of Seattle Genetics, Inc.                                  |  | 8-K                        |  | 000-32405    |  | 3.3     |  | 05/26/2011 
|               |  |                                                                                                                                                 |  |                            | 
|3.3            |  | Amended and Restated Bylaws of Seattle Genetics, Inc.                                                                                           |  | 8-K                        |  | 000-32405    |  | 3.1     |  | 11/25/2015 
|               |  |                                                                                                                                                 |  |                            | 
|4.1            |  | Specimen Stock Certificate.                                                                                                                     |  | S-1/A                      |  | 333-50266    |  | 4.1     |  | 02/08/2001 
|               |  |                                                                                                                                                 |  |                            | 
|4.2            |  | Investor Rights Agreement dated July 8, 2003 among Seattle Genetics, Inc. and certain of its stockholders.                                      |  | 10-Q                       |  | 000-32405    |  | 4.3     |  | 11/07/2008 
|               |  |                                                                                                                                                 |  |                            | 
|4.3            |  | Registration Rights Agreement, dated September 
10, 2015, between Seattle Genetics, Inc. and the persons listed on Schedule A attached thereto. |  | 8-K                        |  | 000-32405    |  | 10.1    |  | 09/11/2015 
|               |  |                                                                                                                                                 |  |                            | 
|10.1*          |  | Seattle Genetics, Inc. Senior Executive Annual Bonus Plan.                                                                                      |  | 8-K                        |  | 000-32405    |  | 10.1    |  | 02/01/2017 
|               |  |                                                                                                                                                 |  |                            | 
|10.2*          |  | Compensation Information for Executive Officers and Directors.                                                                                  |  | 10-K                       |  | 000-32405    |  | 10.56   |  | 02/21/2017 
|               |  |                                                                                                                                                 |  |                            | 
|10.3+         |  | Development and License Agreement dated February 10, 2017 between Seattle Genetics, Inc. and Immunomedics, Inc.                                 |  |                           |  |             |  |        |  |           
|               |  |                                                                                                                                                 |  |                            | 
|10.4           |  | Stock Purchase Agreement, dated February 10, 2017 between Seattle Genetics, Inc. and Immunomedics, Inc.                                         |  | 10-Q                       |  | 000-32405    |  | 10.4    |  | 05/01/2017 
|               |  |                                                                                                                                                 |  |                            | 
|10.5           |  | Registration Rights Agreement, dated February 10, 2017 between Seattle Genetics, Inc. and Immunomedics, Inc.                                    |  | 10-Q                       |  | 000-32405    |  | 10.5    |  | 05/01/2017 
|               |  |                                                                                                                                                 |  |                            | 
|10.6           |  | Immunomedics, Inc. Common Stock Purchase Warrant, dated February 16, 2017.                                                                      |  | 10-Q                       |  | 000-32405    |  | 10.6    |  | 05/01/2017 
|               |  |                                                                                                                                                 |  |                            | 
|10.7           |  | Warrant Agreement, dated February 
16, 2017, between Immunomedics, Inc. and Broadridge Corporate Issuer Solutions, Inc., as Warrant Agent.      |  | 10-Q                       |  | 000-32405    |  | 10.7    |  | 05/01/2017 
|               |  |                                                                                                                                                 |  |                            | 
|31.1+          |  | Certification of Chief Executive Officer pursuant to Rule 13a-14(a).                                                                            |  |                           |  |             |  |        |  |           
|               |  |                                                                                                                                                 |  |                            | 
|31.2+          |  | Certification of Chief Financial Officer pursuant to Rule 13a-14(a).                                                                            |  |                           |  |             |  |        |  |           
|               |  |                                                                                                                                                 |  |                            | 
|32.1           |  | Certification of Chief Executive Officer pursuant to 18 U.S.C. Section 1350.                                                                    |  | 10-Q                       |  | 000-32405    |  | 32.1    |  | 05/01/2017 
|               |  |                                                                                                                                                 |  |                            | 
|32.2           |  | Certification of Chief Financial Officer pursuant to 18 U.S.C. Section 1350.                                                                    |  | 10-Q                       |  | 000-32405    |  | 32.2    |  | 05/01/2017 
|               |  |                                                                                                                                                 |  |                            | 
|101.INS        |  | XBRL Instance Document.                                                                                                                         |  | 10-Q                       |  | 000-32405    |  | 101.INS |  | 05/01/2017 
|               |  |                                                                                                                                                 |  |                            | 
|101.SCH        |  | XBRL Taxonomy Extension Schema Document.                                                                                                        |  | 10-Q                       |  | 000-32405    |  | 101.SCH |  | 05/01/2017 
|               |  |                                                                                                                                                 |  |                            | 
|101.CAL        |  | XBRL Taxonomy Extension Calculation Linkbase Document.                                                                                          |  | 10-Q                       |  | 000-32405    |  | 101.CAL |  | 05/01/2017 
|               |  |                                                                                                                                                 |  |                            | 
|101.DEF        |  | XBRL Taxonomy Extension Definition Linkbase Document.                                                                                           |  | 10-Q                       |  | 000-32405    |  | 101.DEF |  | 05/01/2017 
|               |  |                                                                                                                                                 |  |                            | 
|101.LAB        |  | XBRL Taxonomy Extension Labels Linkbase Document.                                                                                               |  | 10-Q                       |  | 000-32405    |  | 101.LAB |  | 05/01/2017 
|               |  |                                                                                                                                                 |  |                            | 
|101.PRE        |  | XBRL Taxonomy Extension Presentation Linkbase Document.                                                                                         |  | 10-Q                       |  | 000-32405    |  | 101.PRE |  | 05/01/2017 



|+ | Filed herewith.
|- | ---------------

| | Pursuant to a request for confidential treatment, portions of this Exhibit have been redacted from the publicly filed document and have been furnished separately to the Securities and Exchange Commission as required by Rule 24b-2 under the Securities Exchange Act of 1934.
|- | --------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------

|* | Indicates a management contract or compensatory plan or arrangement.
|- | --------------------------------------------------------------------



3



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SIGNATURE

Pursuant to the requirements of Section 13 or 15(d) of the Securities Exchange Act of 1934, the Registrant has duly caused this report to
be signed on its behalf by the undersigned, thereunto duly authorized.



|                       |  |                                                                                                         
|---------------------- |  | --------------------------------------------------------------------------------------------------------
|SEATTLE GENETICS, INC.
|                       | 
|By:                    |  | /s/    TODD E. SIMPSON                                                                                  
|                       |  | Todd E. Simpson
Duly Authorized and Chief Financial Officer
(Principal Financial and Accounting Officer)

Date: September 15, 2017



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