Exhibit 4.2


 


DESCRIPTION OF COMMON STOCK 


 


The following description summarizes the most important terms
of our common stock. Because it is only a summary, it does not contain all the information that may be important to you. For a
complete description of the matters set forth in this “Description of Common Stock,” you should refer to our sixth
amended and restated certificate of incorporation, as amended (the “certificate of incorporation”), and second amended
and restated bylaws (the “bylaws”), which are included as exhibits to our Annual Report on Form 10-K, and to the applicable
provisions of Delaware law. Our authorized capital stock consists of 100,000,000 shares of common stock, $0.001 par value per share,
8,028 shares of Series 1 Preferred Stock, $0.001 par value per share and 9,991,972 shares of undesignated preferred stock, $0.001
par value per share. Our board of directors is authorized, without stockholder approval, except as required by the listing standards
of The Nasdaq Stock Market LLC, to issue additional shares of our capital stock. In addition, our board of directors may, without
further action by our stockholders, designate the rights, preferences, privileges, and restrictions of our preferred stock in one
or more series.


 


Voting Rights. Each holder of our 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. An election of directors by our stockholders
shall be determined by a plurality of votes cast by the stockholders entitled to vote on the election.


 


Dividends. Subject to preferences that may be
applicable to any then outstanding preferred stock, holders of our common stock are entitled to receive dividends, if any, as may
be declared from time to time by the 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 and the satisfaction of any liquidation
preference granted to the holders of any then outstanding shares of preferred stock.


 


Rights and Preferences. Holders of common stock
have no preemptive, conversion or subscription rights and there are no redemption or sinking fund provisions applicable to the
common stock. The rights, preferences and privileges of the holders of common stock are subject to, and may be adversely affected
by, the rights of the holders of shares of any series of preferred stock that we may designate in the future.


 


Delaware Anti-Takeover Law and Provisions of Our Amended
and Restated Certificate of Incorporation, as amended, and Bylaws, as amended


 


Our certificate of incorporation and our bylaws contain certain
provisions that could have the effect of delaying, deterring or preventing another party from acquiring control of us, and therefore
could adversely affect the market price of our common stock. These provisions and certain provisions of Delaware General Corporation
Law (the “DGCL”), which are summarized below, may also discourage coercive takeover practices and inadequate takeover
bids, and are designed, in part, to encourage persons seeking to acquire control of us to negotiate first with our board of directors.
We believe that the benefits of increased protection of our potential ability to negotiate more favorable terms with an unfriendly
or unsolicited acquirer outweigh the disadvantages of potentially discouraging a proposal to acquire us.


 


Delaware Anti-Takeover Law


 


We are subject to Section 203 of the DGCL (“Section 203”).
Section 203 generally prohibits a public Delaware corporation from engaging in a “business combination” with an “interested
stockholder” for a period of three years following the time that such stockholder became an interested stockholder, unless:


 


		●	prior to such time the board of directors of the corporation approved either the business combination or the transaction which
resulted in the stockholder becoming an interested stockholder;



 






     


     


    

 


		●	upon consummation of the transaction which resulted in the stockholder becoming an interested stockholder, the interested stockholder
owned at least 85% of the voting stock of the corporation outstanding at the time the transaction commenced, excluding for purposes
of determining the voting stock outstanding (but not the outstanding voting stock owned by the interested stockholder) those shares
owned (i) by persons who are directors and also officers and (ii) employee stock plans in which employee participants do not have
the right to determine confidentially whether shares held subject to the plan will be tendered in a tender or exchange offer; or



 


		●	at or subsequent to such time the business combination is approved by the board of directors and authorized at an annual or
special meeting of stockholders, and not by written consent, by the affirmative vote of at least 66 2/3% of the outstanding voting
stock which is not owned by the interested stockholder.



 


Section 203 defines a business combination to include:


 


		●	any merger or consolidation involving the corporation and the interested stockholder;



 


		●	any sale, transfer, pledge or other disposition involving the interested stockholder of 10% or more of the assets of the corporation;



 


		●	subject to exceptions, any transaction that results in the issuance or transfer by the corporation of any stock of the corporation
to the interested stockholder;



 


		●	subject to exceptions, any transaction involving the corporation that has the effect of increasing the proportionate share
of the stock of any class or series of the corporation beneficially owned by the interested stockholder; and



 


		●	the receipt by the interested stockholder of the benefit of any loans, advances, guarantees, pledges or other financial benefits
provided by or through the corporation.



 


In general, Section 203 defines an interested stockholder as
any entity or person beneficially owning 15% or more of the outstanding voting stock of the corporation and any entity or person
affiliated with or controlling or controlled by the entity or person.


 


Certificate of Incorporation and
Bylaws


 


Our certificate of incorporation and bylaws contain certain
provisions that are intended to enhance the likelihood of continuity and stability in the composition of the board of directors
and which may have the effect of delaying, deferring or preventing a future takeover or change in control unless such takeover
or change in control is approved by the board of directors. In addition, the authorization of undesignated preferred stock makes
it possible for our board of directors to issue preferred stock with voting or other rights or preferences that could impede the
success of any attempt to change our control. These provisions include:


 


Classified board of directors.


 


Our certificate of incorporation provides that the board of
directors is divided into three classes of directors, with the classes as nearly equal in number as possible. Any additional directorships
resulting from an increase in the number of directors will be apportioned by the board of directors among the three classes. The
classification of directors will have the effect of making it more difficult for stockholders to change the composition of the
board of directors.


 


Our certificate of incorporation provides that, subject to any
rights of holders of preferred stock to elect additional directors under specified circumstances, the number of directors will
be fixed exclusively pursuant to a resolution adopted by the board of directors. Any additional directorships resulting from an
increase in the number of directors will be distributed among the three classes so that, as nearly as possible, each class shall
consist of one third of the board of directors.


 






    2 


     


    

 


Action by Written Consent; Special Meetings
of Stockholders.


 


Our certificate of incorporation provides that stockholder action
can be taken only at an annual or special meeting of stockholders and cannot be taken by written consent in lieu of a meeting.
Our certificate of incorporation and bylaws also provide that, except as otherwise required by law, special meetings of the stockholders
can be called only by or at the direction of the board of directors pursuant to a resolution adopted by a majority of the total
number of directors. Except as described above, stockholders will not be permitted to call a special meeting or to require the
board of directors to call a special meeting.


 


Removal of Directors.


 


Our certificate of incorporation provides that our directors
may be removed only for cause by the affirmative vote of at least 75% of the voting power of our outstanding shares of capital
stock, voting together as a single class and entitled to vote in the election of directors. This requirement of a supermajority
vote to remove directors could enable a minority of our stockholders to prevent a change in the composition of the board of directors.


 


Advance Notice Procedures.


 


Our bylaws include an advance notice procedure for stockholder
proposals to be brought before an annual meeting of our stockholders, including proposed nominations of persons for election to
the board of directors. Stockholders at an annual meeting will only be able to consider proposals or nominations specified in the
notice of meeting or brought before the meeting by or at the direction of the board of directors or by a stockholder who was a
stockholder of record on the record date for the meeting, who is entitled to vote at the meeting and who has given our Secretary
timely written notice, in proper form, of the stockholder’s intention to bring that business before the meeting. Although the bylaws
do not give the board of directors the power to approve or disapprove stockholder nominations of candidates or proposals regarding
other business to be conducted at a special or annual meeting, the bylaws may have the effect of precluding the conduct of certain
business at a meeting if the proper procedures are not followed or may discourage or deter a potential acquirer from conducting
a solicitation of proxies to elect its own slate of directors or otherwise attempting to obtain control of us.


 


Super Majority Approval Requirements.


 


The Delaware General Corporation Law generally provides that
the affirmative vote of a majority of the shares entitled to vote on any matter is required to amend a corporation’s certificate
of incorporation or bylaws, unless either a corporation’s certificate of incorporation or bylaws requires a greater percentage.
Our certificate of incorporation and bylaws provide that the affirmative vote of holders of at least 75% of the outstanding shares
of capital stock, voting together as a single class and entitled to vote in the election of directors will be required to amend,
alter, change or repeal the bylaws and the certificate of incorporation. This requirement of a supermajority vote to approve amendments
to our bylaws could enable a minority of our stockholders to exercise veto power over any such amendments.


 


Authorized but Unissued Shares.


 


Our authorized but unissued shares of common stock will be available
for future issuance without stockholder approval. These additional shares may be utilized for a variety of corporate purposes,
including future public offerings to raise additional capital, corporate acquisitions and employee benefit plans. The existence
of authorized but unissued shares of common stock could render more difficult or discourage an attempt to obtain control of a majority
of our common stock by means of a proxy contest, tender offer, merger or otherwise.


 






    3 


     


    

 


Exclusive Forum.


 


Our certificate of incorporation provides that, subject to limited
exceptions, the state or federal courts located in the State of Delaware will be the sole and exclusive forum for (i) any derivative
action or proceeding brought on our behalf, (ii) any action asserting a claim of breach of a fiduciary duty owed by any of our
directors, officers or other employees to us or our stockholders, (iii) any action asserting a claim against us arising pursuant
to any provision of the Delaware General Corporation Law, our certificate of incorporation or our bylaws, or (iv) any other action
asserting a claim against our that is governed by the internal affairs doctrine; provided, that these provisions will not apply
to actions or proceedings brought to enforce a duty or liability created by the Securities Act of 1933, as amended, the Securities
Exchange Act of 1934, as amended, or any other claim for which the federal courts have exclusive jurisdiction. Any person or entity
purchasing or otherwise acquiring any interest in shares of our capital stock shall be deemed to have notice of and to have consented
to the provisions of our certificate of incorporation described above. Although we believes these provisions benefit us by providing
increased consistency in the application of Delaware law for the specified types of actions and proceedings, the provisions may
have the effect of discouraging lawsuits against our directors and officers. The enforceability of similar choice of forum provisions
in other companies’ certificates of incorporation has been challenged in legal proceedings, and it is possible that, in connection
with one or more actions or proceedings described above, a court could find the choice of forum provisions contained in our certificate
of incorporation to be inapplicable or unenforceable.


 


Transfer Agent and Registrar



 


The transfer agent and registrar for our common stock is Computershare
Trust Company, N.A.


 


Listing


 


Our common stock is listed on The Nasdaq Capital Market under
the symbol “TARA.”


 


 


4