PROPOSAL NO. 1

If elected at the Annual Meeting, each of the above director nominees would serve until the 2023 Annual Meeting of Shareholders and until the director’s successor is elected and has qualified, or, if sooner, until the director’s death, resignation or removal.

As this is an uncontested election, each nominee for director must receive a majority of the votes cast in order to be elected, meaning the number of shares voted “for” each nominee must exceed the number of shares voted “against” such nominee.

In addition, under our Corporate Governance Guidelines, any nominee for director who receives a greater number of votes “against” his or her election than votes “for” such election is required to submit an offer of resignation for consideration by the Nominating and Corporate Governanace Committee, or the Governance Committee. In such case, the Governance Committee will then consider all of the relevant facts and circumstances and recommend to the full Board the action to be taken with respect to such offer of resignation.

If any nominee is unavailable for election due to an unexpected occurrence, such shares will be voted for the election of such substitute nominees as the Governance Committee may propose. Proxies may not be voted for a greater number of persons than the number of nominees named. Each person nominated for election has consented to being named as a nominee in this proxy statement and has agreed to serve if elected, and management has no reason to believe that any nominee will be unable to serve.

NOMINEES FOR THE BOARD OF DIRECTORS AND CONTINUING DIRECTORS

The names of the nominees and of the directors whose terms of office will continue after the Annual Meeting, their ages as of April 2, 2020, and certain other information about them are set forth below. Such information includes the specific and particular experience, qualifications, attributes or skills of each nominee and continuing director that led the Governance Committee and the Board to believe that such nominee or continuing director should continue to serve on the Board as of the date of this proxy statement.

CORPORATE GOVERNANCE

Our Board of Directors is committed to building long-term shareholder value and maintaining sound corporate governance practices. In furtherance of this commitment, we regularly monitor developments in the area of corporate governance and review our processes, policies and procedures in light of such developments.

DIRECTOR INDEPENDENCE; AUDIT COMMITTEE FINANCIAL EXPERT

Our Board of Directors has determined that all of our directors are independent directors within the meaning of Rule 5605(a)(2) of the Nasdaq listing standards, except for Clay B. Siegall, our President and Chief Executive Officer. In making this determination, our Board of Directors considered Dr. Baker’s role as a Co-Managing Member of Baker Brothers Investments, and the relationship Seattle Genetics has with Baker Brothers Investments and affiliated entities as significant shareholders in making the determination that Dr. Baker is independent.

Our Board of Directors has also determined that all of the members of the Compensation Committee currently serving are independent under the additional criteria for members of the Compensation Committee under the Nasdaq listing standards. In the case of Dr. Baker, our Board of Directors determined that, given his affiliation with our largest shareholder, his interests are aligned with other shareholders in seeking an appropriate executive compensation program for Seattle Genetics. In addition, the Board of Directors has determined that all of the members of the Audit Committee are independent within the meaning of Rules 5605(c)(2)(A)(i) and (ii) of the Nasdaq listing standards and that Mr. Gryska is an audit committee financial expert as defined in Item 407(d)(5)(ii) of Regulation S-K. There are no family relationships among any of the directors or executive officers of Seattle Genetics.

BOARD LEADERSHIP STRUCTURE

Our Board of Directors has chosen to combine the principal executive officer and Board chairman positions and, in addition, has appointed a separate lead independent director. Dr. Siegall has served as our principal executive officer and Board chairman since 2004. At the present time, the independent directors believe that Dr. Siegall’s in-depth knowledge of our operations and vision for our development make him the best-qualified director to serve as Board chairman. We believe that combining the positions of chief executive officer and Board chairman provides a single, clear chain of command to execute our strategic initiatives and business plans. In addition, we believe that a combined chief executive officer/Board chairman is better positioned to act as a bridge between management and the Board, facilitating the regular flow of information. We also believe that it is advantageous to have a Board chairman with an extensive history with and knowledge of Seattle Genetics (as is the case with our chief executive officer) as compared to an independent Board chairman with less direct involvement.

Under our Corporate Governance Guidelines, when the Board chairman also serves as our chief executive officer or as another executive officer of Seattle Genetics, the Board may designate an independent director who acts as a lead independent director. The position of lead independent director has been structured to serve as an effective balance to a combined chief executive officer/Board chairman. In addition, we believe that having a lead independent director, who is independent of management, creates an environment that is more conducive to objective evaluation and oversight of management’s performance, increasing management accountability and improving the ability of the Board of Directors to monitor whether management’s actions are in the best interests of Seattle Genetics and its shareholders. Since February 2005, Felix J. Baker has served as the lead independent director of the Board. His formal and informal duties include, among others:

In addition, as chair of our Compensation Committee, Dr. Baker provides additional oversight of management by leading the annual evaluation of the pay and performance of our chief executive officer and our other executive officers.

DIRECTOR COMMITMENTS

Our Board believes that all members of the Board must have sufficient time and attention to devote to Board duties and to otherwise fulfill the responsibilities required of directors. Over the past year, our Governance Committee reviewed institutional and proxy advisory firms’ policies on director time commitments and reviewed the policies of peers and other public companies. We also discussed this topic during investor engagements.

Based on this information, our Governance Committee and Board revised our Corporate Governance Guidelines as outlined below. All of our directors are in compliance with our policy.

Non-employee directors are required to notify the Governance Committee if they:

The Governance Committee will review the appropriateness of continued Board membership under the circumstances and the affected director will be expected to act in accordance with the Governance Committee’s recommendation.

In recommending to the full Board the re-election of Mr. Orwin, the members of the Governance Committee considered the Company’s policy as well as the policies at a few of the Company’s major shareholders regarding the number of outside boards on which an active CEO should participate. In addition to our Board, Mr. Orwin serves on the boards of directors of two other public companies: Retrophin and Atreca, where he also serves as CEO and President.

Our Governance Committee and Board believe that Mr. Orwin has demonstrated, and will continue to demonstrate, the ability to dedicate sufficient time to carry out his Board duties effectively and believes that it is in the Company’s best interest that he continue to serve as a director for the following reasons:

Based on all of the above considerations, our Governance Committee and Board believe that Mr. Orwin’s re-election is in the best interest of Seattle Genetics.

In addition to our Board, Dr. Simonian serves on the boards of directors of two other public companies: Evelo Biosciences, Inc., or Evelo, and Syros Pharmaceuticals, Inc., or Syros, where she also serves as CEO and President. However, our Board does not believe that Dr. Simonian’s outside boards or other commitments negatively impact her ability to devote sufficient time and attention to her duties as a director of Seattle Genetics based on her perfect attendance record both at our Board and Governance Committee meetings and at Evelo and Syros board meetings, and the high quality of her contributions to our Board and her leadership of our Governance Committee. In addition, the perspective and experience that Dr. Simonian continues to gain through both her role as a pharmaceutical company CEO and her leadership on two other pharmaceutical company boards enhances her ability to provide insightful and strategic contributions as a director of Seattle Genetics.

BOARD COMMITTEES

The Board has a standing Audit Committee, Compensation Committee and Governance Committee, each of which is made up solely of independent directors. Each of these committees operates under a written charter setting forth the functions and responsibilities of the committee, which is available on our website at www.seattlegenetics.com.

BOARD AND COMMITTEE MEETINGS AND ATTENDANCE

The Board met seven times and acted by written consent one time during 2019. On at least a quarterly basis, the Board meets in executive sessions of independent directors without management present. During 2019, the Audit Committee held six meetings, the Compensation Committee held seven meetings and acted by written consent three times and the Governance Committee met once and acted by written consent one time. Each of our directors attended at least 75% of the aggregate of Board and applicable committee meetings on which he or she served during 2019.

Although we do not have a formal policy regarding attendance by members of the Board of Directors at our Annual Meetings of Shareholders, directors are encouraged to attend. However, due to scheduling conflicts we held a meeting of the Board of Directors two weeks prior to our 2019 annual meeting of shareholders and as a result, with the exception of Dr. Siegall, none of our directors then serving attended the 2019 annual meeting of shareholders.

BOARD RISK OVERSIGHT

Our Board of Directors has overall responsibility for risk oversight with a focus on the most significant risks facing Seattle Genetics. Throughout the year, the Board and the committees to which it has delegated responsibility dedicate a portion of their meetings to reviewing and discussing specific risk topics in greater detail. Strategic and operational risks are presented and discussed in the context of the Chief Executive Officer’s report on operations to the Board at regularly scheduled Board meetings and at presentations to the Board and its committees by the respective

committee chairs, our Chief Financial Officer, our General Counsel and Executive Vice President, Legal Affairs, and other officers. In addition, management periodically reports to the Board on enterprise risk management. Our Board also retains responsibility for assessment of succession-related risks and succession planning.

The Board has delegated responsibility for the oversight of specific risks to Board committees as follows:

In addition, our General Counsel and Executive Vice President, Legal Affairs works with our committees and Board to develop risk identification, risk management and risk mitigation strategies and reports periodically to the Board and the committees on Seattle Genetics’ risk profile and various management and mitigation strategies.

COMPENSATION COMMITTEE PROCESS AND PROCEDURES

Information on the Compensation Committee’s processes and procedures for consideration of executive compensation are addressed in “Compensation Discussion and Analysis” below. For information regarding our processes and procedures for the consideration and determination of director compensation, please see “Director Compensation” below. In accordance with its charter, the Compensation Committee may delegate any of its authority or responsibility as appropriate, except to the extent inconsistent with any applicable laws and rules, including the Nasdaq listing standards. Our compensation committee does not, however, delegate any of its functions to others in determining or recommending executive or director compensation.

BOARD REFRESHMENT

Under our Corporate Governance Guidelines, our Governance Committee is responsible for assessing the appropriate balance of experience, skills and characteristics required of the Board. In this regard, our Governance Committee identifies and evaluates individuals qualified to serve as Board members, including evaluating incumbent directors for re-election, and recommends to the Board nominees for election as directors. On an annual basis, our Governance Committee assesses the qualities, experiences, skills and attributes that qualify each director to be a member of the Board in light of our business structure and long-term strategy and assesses the committee’s effectiveness in diversifying the Board. Our Governance Committee also oversees an annual Board self-evaluation process. Director responses are collated into a summary by an outside third party, and the results are discussed with the full Board.

CRITERIA FOR BOARD MEMBERSHIP AND NOMINATION PROCESS

The Governance Committee assesses many characteristics and diversity considerations when reviewing director candidates and these characteristics are set forth in our Corporate Governance Guidelines. Among the characteristics to be considered are:

In determining whether to recommend a director for re-election, the Governance Committee also considers the director’s past attendance at meetings and participation in and contributions to the activities of the Board and its committees, as well as the nature and time involved in a director’s service on other boards. In 2019, we amended our Corporate Governance Guidelines to provide that the Governance Committee seeks nominees with:

We believe that the backgrounds and qualifications of our directors, considered as a group, should provide a significant composite mix of experience, knowledge and abilities that will allow the Board to fulfill its responsibilities and should represent an appropriate balance between institutional knowledge and fresh perspectives.

The Governance Committee identifies nominees by first evaluating the current members of the Board willing to continue in service. Current members of the Board with skills and experience that are relevant to our business and who are willing to continue in service are considered for re-nomination. If there is a vacancy on the Board as a result of a resignation or otherwise, or if the Board decides not to nominate a member for re-election or decides to add a member to the Board, the Governance Committee identifies the desired skills and experience of a new nominee in light of the criteria above and the Board’s needs. Current members of the Board are asked to submit suggestions as to individuals meeting the criteria described above.

SHAREHOLDER DIRECTOR NOMINATIONS AND RECOMMENDATIONS

In accordance with our bylaws and applicable law, nominations for directors may be made by any shareholder of record entitled to vote for the election of directors at shareholder meetings held for such purpose. The requirements a shareholder must follow for nominating persons for election as directors are set forth in our bylaws and under the heading “Frequently Asked Questions and Other Information—When are proposals and nominations due for the 2021 Annual Meeting?” below in this proxy statement.

The Governance Committee will also consider director candidates recommended by shareholders. In order to recommend director candidates to the Governance Committee, shareholders should follow the procedures in our bylaws for director nominations. If a shareholder complies with these procedures for recommending persons for

election as directors, the Governance Committee will conduct the appropriate and necessary inquiries into the backgrounds, qualifications and skills of the recommended candidates and, in the exercise of the Governance Committee’s independent judgment in accordance with the policies and procedures adopted in the Governance Committee’s charter, will determine whether to recommend the candidate(s) recommended by the shareholders to the Board for inclusion in the list of candidates for election as directors at the next shareholder meeting held to elect directors. The Governance Committee does not intend to alter the manner in which it evaluates director candidates based on whether or not the candidate was recommended by a shareholder.

COMMUNICATIONS WITH THE BOARD OF DIRECTORS

Our Board of Directors currently does not have a formal process for shareholders to send communications to the Board of Directors. Nevertheless, efforts are made to ensure that the views of shareholders are heard by the Board or individual directors, as applicable, and that appropriate responses are provided to shareholders on a timely basis. The Board does not recommend that formal communication procedures be adopted at this time because it believes that informal communications are sufficient to communicate questions, comments and observations that could be useful to the Board. Shareholders wishing to formally communicate with the Board of Directors may send communications directly to Seattle Genetics, Inc., Attention: Investor Relations, 21823 – 30th Drive SE, Bothell, Washington 98021, and the communication will be forwarded, as appropriate. If the communication regards a shareholder proposal to be considered at an annual meeting of shareholders, the methods and timing for submitting a shareholder proposal are covered under the heading “Frequently Asked Questions and Other Information—When are proposals and nominations due for the 2021 Annual Meeting?”

MAJORITY VOTING IN UNCONTESTED ELECTIONS

In January 2020, the Board amended and restated our bylaws to implement a majority voting standard in uncontested director elections, instead of plurality voting. Under the Amended and Restated Bylaws, in uncontested elections, a director must be elected by a majority of the votes cast with respect to the election of such director (meaning the number of shares voted “for” such nominee’s election must exceed the number of votes cast “against” his or her election) at any meeting for the election of directors at which a quorum is present. However, in the event of a contested election of directors, directors shall be elected by the highest number of votes, or a plurality of votes, cast.

In addition, under our Corporate Governance Guidelines, any nominee for director who receives a greater number of votes “against” his or her election than votes “for” such election is required to submit an offer of resignation for consideration by the Governance Committee. In such case, the Governance Committee will then consider all of the relevant facts and circumstances and recommend to the full Board the action to be taken with respect to such offer of resignation.

BOARD CLASSIFICATION

The Board believes that there is no single approach to corporate governance that is appropriate for all companies and that the key consideration in determining whether to implement a particular governance practice is whether that practice promotes the interests of shareholders, taking into account the specific circumstances of Seattle Genetics. While the Board acknowledges that declassification proposals have received popular support, the Board has reviewed the rationale for its current classified structure and continues to believe that a classified board is the appropriate board structure for Seattle Genetics at this time and is in the best interest of our shareholders for the reasons set forth below:

In sum, Seattle Genetics has benefited from the independence and continuity of experienced leadership provided by our Board of Directors under the classified structure, and we believe these factors have been critical drivers of the significant growth in shareholder value that Seattle Genetics has generated over time.

SUCCESSION PLANNING

Succession planning is an important part of planning for the long-term success of our business. Under our Corporate Governance Guidelines, our Board is responsible for CEO succession planning, and they discuss CEO and executive officer performance and succession in executive session. In addition, our CEO and senior executives discuss future candidates for leadership positions at all levels within our organization.

CORPORATE GOVERNANCE GUIDELINES

As a part of the Board’s commitment to building long-term shareholder value and maintaining sound corporate governance, the Board has adopted a set of Corporate Governance Guidelines, which guides the operation of the Board and its committees. Our Corporate Governance Guidelines cover, among other topics, Board composition, structure and functioning, including our director resignation policy, Board membership criteria, director independence, Board self-evaluations, committees of the Board, Board access to management and independent advisers, stock ownership guidelines for members of the Board and our executive officers, and succession and leadership development. A copy of the Corporate Governance Guidelines can be viewed on our website at www.seattlegenetics.com.

STOCK OWNERSHIP GUIDELINES

Our Corporate Governance Guidelines include stock ownership guidelines for our directors and executive officers. For more information about these guidelines, please see “Director Compensation—Director Stock Ownership Guidelines” and “Compensation of Executive Officers—Compensation Discussion and Analysis—Stock Ownership Guidelines” below.

CODE OF CONDUCT AND BUSINESS ETHICS

The Board of Directors has adopted a Code of Conduct and Business Ethics, or the Code of Ethics, for all directors, officers and employees of Seattle Genetics, Inc. A copy of the Code of Ethics can be viewed on our website at www.seattlegenetics.com. We intend to satisfy the disclosure requirement under Item 5.05 of Form 8-K regarding an amendment to, or waiver from, a provision of the Code of Ethics by posting such information on our website at the website address specified above.

WHISTLEBLOWER POLICY

Seattle Genetics has adopted a Whistleblower Policy applicable to its employees that provides for protection from retaliation or discrimination by Seattle Genetics due to reporting issues relating to concerns involving questionable accounting or auditing matters and compliance with applicable laws and regulations.

PROHIBITIONS ON HEDGING, PLEDGING AND SHORT-TERM SPECULATIVE TRANSACTIONS

Under the terms of our insider trading policy, no employees (including executive officers) of Seattle Genetics or its subsidiaries, members of our Board or consultants who know or have access to material information regarding Seattle Genetics that has not been fully disclosed to the public may engage in any hedging or monetization transactions relating to Seattle Genetics or its securities, including through the use of financial instruments such as prepaid variable forwards, equity swaps, collars and exchange funds, nor may any of these persons engage in short-term speculative transactions involving Seattle Genetics securities (or derivatives of Seattle Genetics securities), including short sales and the buying and selling of put or call options. In addition, none of these persons may hold Seattle Genetics securities in a margin account or otherwise pledge Seattle Genetics securities as collateral for a loan.

CORPORATE RESPONSIBILITY

At Seattle Genetics, we are committed to developing transformative medicines for patients with cancer in a socially responsible and sustainable manner. We are dedicated to providing patients access to our medicines and education about their disease. We also believe that fostering a culture of inclusion with diverse perspectives and operating with integrity are key to our success. We continue to support the community both locally and through nonprofits that are dedicated to patients and advancing research. Finally, as grow, we are striving to limit our environmental impact and operate in an increasingly sustainable manner.