EX-4.3






 Exhibit 4.3 

DESCRIPTION OF REGISTRANT’S SECURITIES REGISTERED PURSUANT TO SECTION 12 OF 

THE SECURITIES EXCHANGE ACT OF 1934 

As of March 24, 2021, Sana Biotechnology, Inc. had one class of common stock registered under Section 12 of the Securities Exchange
Act of 1934, as amended (the “Exchange Act”). The shares are listed on the Nasdaq Global Select Market under the trading symbol “SANA.”

The following summary describes our common stock and the material provisions of our restated certificate of incorporation, our restated
bylaws, the amended and restated investors’ rights agreement (the “investors’ rights agreement”) to which we and certain of our stockholders are parties and of the Delaware General Corporation Law (the “DGCL”). Because
the following is only a summary, it does not contain all of the information that may be important to you. For a complete description, you should refer to our certificate of incorporation, bylaws and investors’ rights agreement, filed as
exhibits 3.1, 3.2 and 10.1, respectively, to our Annual Report on Form 10-K filed with the Securities Exchange Commission, of which this Exhibit 4.3 is a part. We encourage you to read those
documents and the DGCL carefully. 
 General 

Our authorized capital stock will consist of 750,000,000 shares of common stock, par value $0.0001 per share, and 50,000,000 shares of
preferred stock, par value $0.0001 per share. 
 Common Stock 

Voting Rights 
 Each holder of
common stock is entitled to one vote for each share on all matters submitted to a vote of the stockholders, including the election of directors. Our stockholders do not have cumulative voting rights in the election of directors. Accordingly, holders
of a majority of the voting shares are able to elect all of the directors. In addition, the affirmative vote of holders of 66 2/3% of the voting power of all of the then outstanding voting stock will be required to take certain actions, including
amending certain provisions of our amended and restated certificate of incorporation, including the provisions relating to amending our amended and restated bylaws, the classified board and director liability. 

Dividends 
 Subject to preferences
that may be applicable to any then outstanding preferred stock, holders of our common stock are entitled to receive dividends as may be declared from time to time by our board of directors out of legally available funds. 

Liquidation 
 In the event of our
liquidation, dissolution or winding up, holders of our common stock will be entitled to share ratably in the net assets legally available for distribution to stockholders after the payment of all of our debts and other liabilities, subject to the
satisfaction of any liquidation preference granted to the holders of any then outstanding shares of preferred stock. 
 Rights, Preferences, and
Privileges 
 Holders of our common stock have no preemptive, conversion or subscription rights, and there are no redemption or
sinking fund provisions applicable to our common stock. The rights, preferences and privileges of the holders of our common stock are subject to, and may be adversely affected by, the rights of the holders of shares of any series of our preferred
stock that we may designate and issue in the future. 













 Fully Paid and Nonassessable 

All of our outstanding shares of common stock are fully paid and nonassessable. 

Preferred Stock 
 Our board of directors
will have the authority, without further action by our stockholders, to issue up to 50,000,000 shares of preferred stock in one or more series and to fix the rights, preferences, privileges and restrictions thereof. These rights, preferences and
privileges could include dividend rights, conversion rights, voting rights, terms of redemption, liquidation preferences, sinking fund terms and the number of shares constituting, or the designation of, such series, any or all of which may be
greater than the rights of our common stock. The issuance of our preferred stock could adversely affect the voting power of holders of common stock and the likelihood that such holders will receive dividend payments and payments upon our
liquidation. In addition, the issuance of preferred stock could have the effect of delaying, deferring or preventing a change in control of our company or other corporate action. 

Registration Rights 
 Certain holders of
shares of our common stock are entitled to certain rights with respect to registration of their shares under the Securities Act. These shares are referred to as registrable securities. The holders of these registrable securities possess registration
rights pursuant to the terms of our amended and restated investors’ rights agreement and are described in additional detail below. The registration of shares of our common stock pursuant to the exercise of the registration rights described
below would enable the holders to trade these shares without restriction under the Securities Act when the applicable registration statement is declared effective. We will pay the registration expenses, other than underwriting discounts, selling
commissions and stock transfer taxes, of the shares registered pursuant to the demand, piggyback and Form S-3 registrations described below. 

Generally, in an underwritten offering, the managing underwriter, if any, has the right, subject to specified conditions and limitations, to
limit the number of shares the holders may include. The demand, piggyback and Form S-3 registration rights described below will terminate upon the earliest of (i) with respect to
each stockholder, such date, on which all registrable shares held by such stockholder may immediately be sold during any 90-day period pursuant to Rule 144 of the Securities Act, or Rule 144; and
(ii) the occurrence of a deemed liquidation event, as defined in our amended and restated certificate of incorporation, as currently in effect. 

Demand Registration Rights 

Holders of approximately 134.1 million shares of our common stock are entitled to certain demand registration rights. Beginning 180 days
following the effectiveness of the registration statement filed in connection with our initial public offering, certain major investors holding, collectively, holding at least 40% of registrable securities may, on not more than two occasions,
request that we register all or a portion of their shares, subject to certain specified exceptions. If any of these holders exercises its demand registration rights, then holders of approximately 134.1 million shares of our common stock are
entitled to register their shares, subject to specified conditions and limitations in the corresponding offering. 
 Piggyback Registration Rights

 In the event that we propose to register any of our securities under the Securities Act in an underwritten registered offering,
either for our own account or for the account of other security holders, the holders of registrable securities will be entitled to certain “piggyback” registration rights allowing them to include their shares in such registration, subject
to specified conditions and limitations. 
 S-3 Registration Rights 

Holders of approximately 134.1 million shares of our common stock are entitled
to certain Form S-3 registration rights. Certain major investors holding at least 25% of registrable securities may, on not more than two registrations on Form S-3 within any 12-month period, request that we register all or a portion of their shares on Form S-3 if we are
qualified to file a registration statement on Form S-3, subject to specified exceptions. Such request for
registration on Form S-3 must cover securities with an aggregate offering price which equals or exceeds $15.0 million, net of selling expenses. The right to have such shares registered on Form S-3 is further subject to other specified conditions and limitations. 













 Election and Removal of Directors; Vacancies 

Our board of directors will consist of between five and fifteen directors. The exact number of directors will be fixed from time to
time by resolution of the board. Directors will be elected by a plurality of the votes of the shares of our capital stock present in person or represented by proxy at the meeting and entitled to vote on the election of directors. 

No director may be removed except for cause, and directors may be removed for cause only by an affirmative vote of shares representing not
less than a majority of the shares then entitled to vote at an election of directors. 
 Any vacancy occurring on the board of directors and
any newly created directorship may be filled only by a majority of the remaining directors in office. 
 Staggered Board 

Our board of directors is divided into three classes serving staggered three-year terms. Class I, Class II, and
Class III directors will serve until our annual meetings of stockholders in 2022, 2023, and 2024, respectively. At each annual meeting of stockholders, directors will be elected to succeed the class of directors whose terms have expired.
This classification of our board of directors could have the effect of increasing the length of time necessary to change the composition of a majority of the board of directors. In general, at least two annual meetings of stockholders will typically
be necessary for stockholders to effect a change in a majority of the members of the board of directors. 
 Limitation on Action by Written Consent

 Our amended and restated certificate of incorporation and our amended and restated bylaws provide that holders of our common stock
will not be able to act by written consent without a meeting. 
 Stockholder Meetings 

Our amended and restated certificate of incorporation and our amended and restated bylaws provide that special meetings of our stockholders may
be called only by a the chairman of the board, our chief executive officer (or president, in the absence of a chief executive officer) or a majority of the directors. Our amended and restated certificate of incorporation and our amended and restated
bylaws specifically deny any power of any other person to call a special meeting. 
 Amendment of Certificate of Incorporation 

The provisions of our amended and restated certificate of incorporation described under “—Election and Removal of Directors;
Vacancies,” “—Stockholder Meetings,” “—Limitation on Action by Written Consent,” “—Limitation of Liability of Directors and Officers,” “—Common Stock—Voting Rights,” and
“—Forum Selection” and provisions relating to amendments to our amended and restated certificate of incorporation may be amended only by the affirmative vote of holders of at least 66 2/3% of the voting power of our outstanding
shares of voting stock. The affirmative vote of holders of at least a majority of the voting power of our outstanding shares of stock will generally be required to amend other provisions of our amended and restated certificate of incorporation. 

Amendment of Bylaws 
 Certain provisions
of our amended and restated bylaws may generally be altered, amended, or repealed, and new bylaws may be adopted, with the affirmative vote of a majority of directors present at any regular or special meeting of the board of directors called for
that purpose, provided that any alteration, amendment, or repeal of, or adoption of any bylaw inconsistent with specified provisions of the bylaws, including those related to special and annual meetings of stockholders, action of stockholders by
written consent, nomination of directors, transfers of capital stock and dividends requires the affirmative vote of at least 66 2/3% of all directors in office at a meeting called for that purpose. 













 All other provisions of our amended and restated bylaws may generally be altered, amended,
or repealed, and new bylaws may be adopted, with the affirmative vote of holders of 66 2/3% of the voting power of our outstanding shares of voting stock. 

Other Limitations on Stockholder Actions 

Our amended and restated bylaws impose some procedural requirements on stockholders who wish to: 

 

	 	•	 	 make nominations in the election of directors; 



 

	 	•	 	 propose that a director be removed; 



 

	 	•	 	 propose any repeal or change in our amended and restated bylaws; or 



 

	 	•	 	 propose any other business to be brought before an annual or special meeting of stockholders.



 Under these procedural requirements, in order to bring a proposal before a meeting of stockholders, a stockholder must
deliver timely notice of a proposal pertaining to a proper subject for presentation at the meeting to our corporate secretary along with the following: 
  

	 	•	 	 a description of the business or nomination to be brought before the meeting and the reasons for conducting such
business at the meeting; 


  

	 	•	 	 the stockholder’s name and address; 



 

	 	•	 	 any material interest of the stockholder in the proposal; 



 

	 	•	 	 the number of shares beneficially owned by the stockholder and evidence of such ownership; and



  

	 	•	 	 the names and addresses of all persons with whom the stockholder is acting in concert and a description of all
arrangements and understandings with those persons, and the number of shares such persons beneficially own. 


 To be
timely, a stockholder must generally deliver notice: 
  

	 	•	 	 in connection with an annual meeting of stockholders, not less than 120 nor more than 150 days prior to the date
on which the annual meeting of stockholders was held in the immediately preceding year, but in the event that the date of the annual meeting is more than 30 days before or more than 70 days after the anniversary date of the preceding annual
meeting of stockholders, a stockholder notice will be timely if received by us not later than the close of business on the later of (i) not less than 70 nor more than 120 days prior to the date of the annual meeting and (ii) the 10th day
following the day on which we first publicly announce the date of the annual meeting; or 


  

	 	•	 	 in connection with the election of a director at a special meeting of stockholders, during the period not less
than 120 nor more than 150 days prior to the date of the special meeting, or the 10th day following the day on which a notice of the date of the special meeting was mailed to the stockholders or the public disclosure of that date was made.



 In order to submit a nomination for our board of directors, a stockholder must also submit all information with respect
to the nominee that would be required to be included in a proxy statement, as well as other information. If a stockholder fails to follow the required procedures, the stockholder’s proposal or nominee will be ineligible and will not be voted on
by our stockholders. 













 Limitation of Liability of Directors and Officers 

Our amended and restated certificate of incorporation provides that no director will be personally liable to us or our stockholders for
monetary damages for breach of fiduciary duty as a director, except as required by applicable law, as in effect from time to time. Section 102(b)(7) of the Delaware General Corporation Law permits a corporation to provide in its certificate of
incorporation that a director of the corporation shall not be personally liable to the corporation or its stockholders for monetary damages for breach of fiduciary duty as a director, except for liability for: 

 

	 	•	 	 any breach of the director’s duty of loyalty to our company or our stockholders; 



 

	 	•	 	 any act or omission not in good faith or which involved intentional misconduct or a knowing violation of law;



  

	 	•	 	 unlawful payments of dividends or unlawful stock repurchases or redemptions as provided in Section 174 of
the Delaware General Corporation Law; and 


  

	 	•	 	 any transaction from which the director derived an improper personal benefit. 



As a result, neither we nor our stockholders have the right, through stockholders’ derivative suits on our behalf, to recover monetary
damages against a director for breach of fiduciary duty as a director, including breaches resulting from grossly negligent behavior, except in the situations described above. 

Our amended and restated certificate of incorporation also provides that, to the fullest extent permitted by law, we will indemnify any
officer or director of our company against all damages, claims, and liabilities arising out of the fact that the person is or was our director or officer, or served any other enterprise at our request as a director or officer. Amending this
provision will not reduce our indemnification obligations relating to actions taken before an amendment. 
 Forum Selection 

Our current certificate of incorporation provides, and our amended and restated certificate of incorporation provide that the Court of Chancery
of the State of Delaware will be the sole and exclusive forum for the following types of actions or proceedings under Delaware statutory or common law: (i) any derivative action or proceeding brought on behalf of us; (ii) any action
asserting a claim of breach of fiduciary duty owed by any director, officer, or other employee of our company to us or our stockholders; (iii) any action asserting a claim arising pursuant to any provision of the Delaware General Corporation
Law or our amended and restated certificate of incorporation and bylaws; or (iv) any action asserting a claim governed by the internal affairs doctrine. This provision would not apply to claims brought to enforce a duty or liability created by
the Securities Exchange Act of 1934, as amended, or any other claim for which the federal courts have exclusive jurisdiction. 

Furthermore, our amended and restated certificate of incorporation also provide that unless we consent in writing to the selection of an
alternative forum, the federal district courts of the United States shall be the exclusive forum for the resolution of any complaint asserting a cause of action arising under the Securities Act of 1933, as amended. Any person or entity purchasing or
otherwise acquiring any interest in our shares of capital stock shall be deemed to have notice of and consented to the foregoing forum selection provisions. 

Our exclusive forum provision will not relieve us of our duties to comply with the federal securities laws and the rules and regulations
thereunder, and our stockholders will not be deemed to have waived our compliance with these laws, rules and regulations. 
 The
enforceability of similar federal court choice of forum provisions in other companies’ certificates of incorporation has been challenged in legal proceedings, and it is possible that a court could find this type of provision to be inapplicable
or unenforceable. If a court were to find either of the choice of forum provisions contained in our amended and restated certificate of incorporation or amended and restated bylaws to be inapplicable or unenforceable in an action, we may incur
additional costs associated with resolving such action in other jurisdictions. 













 The choice of forum provisions may limit a stockholder’s ability to bring a claim in a
judicial forum that it finds favorable for disputes with the company or its directors, officers or other employees, which may discourage such lawsuits against the company and its directors, officers and other employees and result in increased costs
for investors to bring a claim. 
 Delaware Business Combination Statute 

We have elected to be subject to Section 203 of the Delaware General Corporation Law. Section 203 prevents an “interested
stockholder,” which is defined generally as a person owning 15% or more of a corporation’s voting stock, or any affiliate or associate of that person, from engaging in a broad range of “business combinations” with the corporation
for three years after becoming an interested stockholder unless: 
  

	 	•	 	 the board of directors of the corporation had previously approved either the business combination or the
transaction that resulted in the stockholder becoming an interested stockholder; 


  

	 	•	 	 upon completion of the transaction that resulted in the stockholder becoming an interested stockholder, that
person owned at least 85% of the voting stock of the corporation outstanding at the time the transaction commenced, other than statutorily excluded shares; or 



 

	 	•	 	 following the transaction in which that person became an interested stockholder, the business combination is
approved by the board of directors of the corporation and holders of at least two-thirds of the outstanding voting stock not owned by the interested stockholder. 



Under Section 203, the restrictions described above also do not apply to specific business combinations proposed by an interested
stockholder following the announcement or notification of designated extraordinary transactions involving the corporation and a person who had not been an interested stockholder during the previous three years or who became an interested stockholder
with the approval of a majority of the corporation’s directors, if such extraordinary transaction is approved or not opposed by a majority of the directors who were directors prior to any person becoming an interested stockholder during the
previous three years or were recommended for election or elected to succeed such directors by a majority of such directors. 

Section 203 may make it more difficult for a person who would be an interested stockholder to effect various business combinations with a
corporation for a three-year period. Section 203 also may have the effect of preventing changes in our management and could make it more difficult to accomplish transactions that our stockholders may otherwise deem to be in their best
interests. 
 Washington Business Corporation Act 

The laws of Washington, where our principal executive offices are located, impose restrictions on certain transactions between certain foreign
corporations and significant stockholders. In particular, the Washington Business Corporation Act (WBCA), prohibits a “target corporation,” with certain exceptions, from engaging in certain “significant business transactions”
with a person or group of persons which beneficially owns 10% or more of the voting securities of the target corporation, an “acquiring person,” for a period of five years after such acquisition, unless the transaction or acquisition of
shares is approved by a majority of the members of the target corporation’s board of directors prior to the time of acquisition. Such prohibited transactions may include, among other things: 

 

	 	•	 	 any merger or consolidation with, disposition of assets to, or issuance or redemption of stock to or from, the
acquiring person; 


  

	 	•	 	 any termination of 5% or more of the employees of the target corporation as a result of the acquiring
person’s acquisition of 10% or more of the shares; and 


  

	 	•	 	 allowing the acquiring person to receive any disproportionate benefit as a stockholder. 



After the five-year period, a significant business transaction may take place as long as it complies with certain fair price
provisions of the statute or is approved at an annual or special meeting of stockholders. 













 We will be considered a “target corporation” so long as our principal executive
office is located in Washington, and: (i) a majority of our employees are residents of the state of Washington or we employ more than one thousand residents of the state of Washington; (ii) a majority of our tangible assets, measured by
market value, are located in the state of Washington or we have more than $50.0 million worth of tangible assets located in the state of Washington; and (iii) any one of the following: (a) more than 10% of our stockholders of record
are resident in the state of Washington; (b) more than 10% of our shares are owned of record by state residents; or (c) 1,000 or more of our stockholders of record are resident in the state. 

If we meet the definition of a target corporation, the WBCA may have the effect of delaying, deferring or preventing a change of control. 

Anti-Takeover Effects of Some Provisions 

Certain provisions of our amended and restated certificate of incorporation and amended and restated bylaws could make the following more
difficult: 
  

	 	•	 	 acquisition of control of us by means of a proxy contest, tender offer, or otherwise; or 



 

	 	•	 	 removal of our incumbent officers and directors. 



These provisions, as well as our ability to issue preferred stock, are designed to discourage coercive takeover practices and inadequate
takeover bids. These provisions are also designed to encourage persons seeking to acquire control of us to first negotiate with our board of directors. We believe that the benefits of increased protection give us the potential ability to negotiate
with the proponent of an unfriendly or unsolicited proposal to acquire or restructure us, and that the benefits of this increased protection outweigh the disadvantages of discouraging those proposals, because negotiation of those proposals could
result in an improvement of their terms. 
 Transfer Agent and Registrar 

The transfer agent and registrar for the common stock will be American Stock Transfer & Trust Company, LLC. The transfer agent’s
address is 6201 15th Avenue, Brooklyn, NY 11219.