Exhibit 10.4


 


2018 EMPLOYEE STOCK PURCHASE PLAN


 


The purpose of the Assembly Biosciences,
Inc. 2018 Employee Stock Purchase Plan (“the Plan”) is to provide eligible employees of Assembly Biosciences, Inc.
(the “Company”) and each Designated Subsidiary (as defined in Section 11) with opportunities to purchase shares
of the Company’s common stock, par value $0.01 per share (the “Common Stock”). An aggregate of 400,000 shares
of Common Stock have been approved and reserved for this purpose.


 


The Plan includes two components: a Code
Section 423 Component (the “423 Component”) and a non-Code Section 423 Component (the “Non-423 Component”).
It is intended for the 423 Component to constitute an “employee stock purchase plan” within the meaning of Section
423(b) of the U.S. Internal Revenue Code of 1986, as amended (the “Code”) and the 423 Component shall be interpreted
in accordance with that intent (although the Company makes no undertaking or representation to maintain such qualification). In
addition, this Plan authorizes the grant of options under the Non-423 Component that does not qualify as an “employee stock
purchase plan” under Section 423 of the Code. Except as otherwise provided herein, the Non-423 Component will operate
and be administered in the same manner as the 423 Component.


 


1.        Administration. The
Plan will be administered by the person or persons (the “Administrator”) appointed by the Company’s Board of
Directors (the “Board”) for such purpose. The Administrator has authority at any time to: (i) adopt, alter and
repeal such rules, guidelines and practices for the administration of the Plan and for its own acts and proceedings as it shall
deem advisable; (ii) interpret the terms and provisions of the Plan; (iii) make all determinations it deems advisable
for the administration of the Plan; (iv) decide all disputes arising in connection with the Plan; and (v) otherwise supervise
the administration of the Plan. All interpretations and decisions of the Administrator shall be binding on all persons, including
the Company and the Participants. No member of the Board or individual exercising administrative authority with respect to the
Plan shall be liable for any action or determination made in good faith with respect to the Plan or any option granted hereunder.


 


2.        Offerings. The Company
will make one or more offerings to eligible employees to purchase Common Stock under the Plan (“Offerings”). Unless
otherwise determined by the Administrator, the initial Offering will begin on June 15, 2018 and will end on the following November
14th (the “Initial Offering”). Thereafter, unless otherwise determined by the Administrator, an Offering
will begin on the first business day occurring on or after each November 15th and May 15th and will end on
the last business day occurring on or before the following May 14th and November 14th, respectively. The
Administrator may, in its discretion, designate a different period for any Offering, provided that no Offering shall exceed six
months in duration or overlap any other Offering.


 


3.        Eligibility. All individuals
classified as employees on the payroll records of the Company and each Designated Subsidiary are eligible to participate in any
one or more of the Offerings under the Plan, provided that as of the first day of the applicable Offering (the “Offering
Date”) they are employed by the Company or a Designated Subsidiary and have completed at least 30 days of employment. Notwithstanding
any other provision herein, individuals who are not contemporaneously classified as employees of the Company or a Designated Subsidiary
for purposes of the Company’s or applicable Designated Subsidiary’s payroll system are not considered to be eligible
employees of the Company or any Designated Subsidiary and shall not be eligible to participate in the Plan. In the event any such
individuals are reclassified as employees of the Company or a Designated Subsidiary for any purpose, including, without limitation,
common law or statutory employees, by any action of any third party, including, without limitation, any government agency, or as
a result of any private lawsuit, action or administrative proceeding, such individuals shall, notwithstanding such reclassification,
remain ineligible for participation. Notwithstanding the foregoing, the exclusive means for individuals who are not contemporaneously
classified as employees of the Company or a Designated Subsidiary on the Company’s or Designated Subsidiary’s payroll
system to become eligible to participate in this Plan is through an amendment to this Plan, duly executed by the Company, which
specifically renders such individuals eligible to participate herein.


 


4.        Participation.


 


(a) An eligible employee who is not a Participant
in any prior Offering may participate in a subsequent Offering by submitting an enrollment form to his or her appropriate payroll
location at least 15 business days before the Offering Date (or by such other deadline as shall be established by the Administrator
for the Offering).


 






     


     


    

 


(b) The enrollment form will (a) state
a whole percentage to be deducted from an eligible employee’s Compensation (as defined in Section 11) per pay period,
(b) authorize the purchase of Common Stock in each Offering in accordance with the terms of the Plan and (c) specify
the exact name or names in which shares of Common Stock purchased for such individual are to be issued pursuant to Section 10.
An employee who does not enroll in accordance with these procedures will be deemed to have waived the right to participate. Unless
a Participant files a new enrollment form or withdraws from the Plan, such Participant’s deductions and purchases will continue
at the same percentage of Compensation for future Offerings, provided he or she remains eligible.


 


(c) Notwithstanding the foregoing, participation
in the Plan will neither be permitted nor be denied contrary to the requirements of the Code.


 


5.        Employee
Contributions. Each eligible employee may authorize payroll deductions at a minimum of one percent up to a maximum of
15 percent of such employee’s Compensation for each pay period. The Company will maintain book accounts showing the
amount of payroll deductions made by each Participant for each Offering. No interest will accrue or be paid on payroll deductions.


 


6.       Deduction
Changes. Except as may be determined by the Administrator in advance of an Offering, a Participant may not increase or decrease
his or her payroll deduction during any Offering, but may increase or decrease his or her payroll deduction with respect to the
next Offering (subject to the limitations of Section 5) by filing a new enrollment form at least 15 business days before the
next Offering Date (or by such other deadline as shall be established by the Administrator for the Offering). The Administrator
may, in advance of any Offering, establish rules permitting a Participant to increase, decrease or terminate his or her payroll
deduction during an Offering.


 


7.        Withdrawal. A Participant
may withdraw from participation in the Plan by delivering a written notice of withdrawal to his or her appropriate payroll location.
The Participant’s withdrawal will be effective as of the next business day. Following a Participant’s withdrawal, the
Company will promptly refund such individual’s entire account balance under the Plan to him or her (after payment for any
Common Stock purchased before the effective date of withdrawal). Partial withdrawals are not permitted. Such an employee may not
begin participation again during the remainder of the Offering, but may enroll in a subsequent Offering in accordance with Section 4.


 


8.        Grant of Options. On
each Offering Date, the Company will grant to each eligible employee who is then a Participant in the Plan an option (“Option”)
to purchase on the last day of such Offering (the “Exercise Date”), at the Option Price hereinafter provided for, the
lowest of (a) a number of shares of Common Stock determined by dividing such Participant’s accumulated payroll deductions
on such Exercise Date by the Option Price (as defined herein), (b) 1,000 shares; or (c) such other lesser maximum number
of shares as shall have been established by the Administrator in advance of the Offering; provided, however, that such Option shall
be subject to the limitations set forth below. Each Participant’s Option shall be exercisable only to the extent of such
Participant’s accumulated payroll deductions on the Exercise Date. The purchase price for each share purchased under each
Option (the “Option Price”) will be 85 percent of the Fair Market Value of the Common Stock on the Offering Date
or the Exercise Date, whichever is less.


 


Notwithstanding the foregoing, no Participant
may be granted an option hereunder if such Participant, immediately after the option was granted, would be treated as owning stock
possessing five percent or more of the total combined voting power or value of all classes of stock of the Company or any
Parent or Subsidiary (as defined in Section 11). For purposes of the preceding sentence, the attribution rules of Section 424(d)
of the Code shall apply in determining the stock ownership of a Participant, and all stock which the Participant has a contractual
right to purchase shall be treated as stock owned by the Participant. In addition, no Participant may be granted an Option which
permits his or her rights to purchase stock under the Plan, and any other employee stock purchase plan of the Company and its Parents
and Subsidiaries, to accrue at a rate which exceeds $25,000 of the fair market value of such stock (determined on the option grant
date or dates) for each calendar year in which the Option is outstanding at any time. The purpose of the limitation in the preceding
sentence is to comply with Section 423(b)(8) of the Code and shall be applied taking Options into account in the order in
which they were granted.


 






     


     


    

 


9.        Exercise
of Option and Purchase of Shares. Each employee who continues to be a Participant in the Plan on the Exercise Date shall be
deemed to have exercised his or her Option on such date and shall acquire from the Company such number of whole shares of Common
Stock reserved for the purpose of the Plan as his or her accumulated payroll deductions on such date will purchase at the Option
Price, subject to any other limitations contained in the Plan. Any amount remaining in a Participant’s account at the end
of an Offering solely by reason of the inability to purchase a fractional share will be carried forward to the next Offering; any
other balance remaining in a Participant’s account at the end of an Offering will be refunded to the Participant promptly.


 


10.        Issuance of Certificates.
Certificates representing shares of Common Stock purchased under the Plan may be issued only in the name of the employee, in the
name of the employee and another person of legal age as joint tenants with rights of survivorship, or in the name of a broker authorized
by the employee to be his, her or their, nominee for such purpose.


 


11.        Definitions.


 


The term “Compensation” means
the amount of base pay, prior to salary reduction pursuant to Sections 125, 132(f) or 401(k) of the Code, but excluding overtime,
commissions, incentive or bonus awards, allowances and reimbursements for expenses such as relocation allowances or travel expenses,
income or gains on the exercise of Company stock options, and similar items.


 


The term “Designated Subsidiary”
means any present or future Subsidiary (as defined below) that has been designated by the Board to participate in the Plan. The
Board may so designate any Subsidiary, or revoke any such designation, at any time and from time to time, either before or after
the Plan is approved by the stockholders and may further designate such Subsidiaries as participating in the 423 Component or the
Non-423 Component. The current list of Designated Subsidiaries is attached hereto as Appendix A.


 


The term “Fair Market Value of the
Common Stock” on any given date means the fair market value of the Common Stock determined in good faith by the Administrator;
provided, however, that if the Common Stock


 


is admitted to quotation on the National Association of Securities
Dealers Automated Quotation System (“NASDAQ”), NASDAQ Global Select Market or The NASDAQ Capital Market of The NASDAQ
Stock Market LLC or another national securities exchange, the determination shall be made by reference to the closing price on
such date. If there is no closing price for such date, the determination shall be made by reference to the last date preceding
such date for which there is a closing price.


 


The term “Parent” means a
“parent corporation” with respect to the Company, as defined in Section 424(e) of the Code.


 


The term “Participant” means
an individual who is eligible as determined in Section 3 and who has complied with the provisions of Section 4.


 


The term “Subsidiary” means
a “subsidiary corporation” with respect to the Company, as defined in Section 424(f) of the Code.


 


The
term “Corporate Transaction” means any of the following transactions, provided, however, that the Administrator shall
determine under parts (iv) and (v) whether multiple transactions are related, and its determination shall be final, binding and
conclusive: 


 


(i)       a
merger or consolidation in which the Company is not the surviving entity, except for a transaction the principal purpose of which
is to change the state in which the Company is incorporated;


 


(ii)       the
sale, transfer or other disposition of all or substantially all of the assets of the Company;


 


(iii)       the
complete liquidation or dissolution of the Company;


 






     


     


    

 


(iv)       any
reverse merger or series of related transactions culminating in a reverse merger (including, but not limited to, a tender offer
followed by a reverse merger) in which the Company is the surviving entity but (A) the shares of Common Stock outstanding immediately
prior to such merger are converted or exchanged by virtue of the merger into other property, whether in the form of securities,
cash or otherwise, or (B) in which securities possessing more than fifty percent (50%) of the total combined voting power of the
Company’s outstanding securities are transferred to a person or persons different from those who held such securities immediately
prior to such merger or the initial transaction culminating in such merger; or


 


(v)       acquisition
in a single or series of related transactions by any person or related group of persons (other than the Company or by a Company-sponsored
employee benefit plan) of beneficial ownership (within the meaning of Rule 13d-3 of the Exchange Act) of securities possessing
more than fifty percent (50%) of the total combined voting power of the Company’s outstanding securities.


 


12.        Rights on Termination
of Employment. If a Participant’s employment terminates for any reason before the Exercise Date for any Offering, no
payroll deduction will be taken from any pay due and owing to the Participant and the balance in the Participant’s account
will be paid to such Participant or, in the case of such Participant’s death, to his or her designated beneficiary as if
such Participant had withdrawn from the Plan under Section 7. An employee will be deemed to have terminated employment, for
this purpose, if the corporation that employs him or her, having been a Designated Subsidiary, ceases to be a Subsidiary, or if
the employee is transferred to any corporation other than the Company or a Designated Subsidiary. An employee will not be deemed
to have terminated employment for this purpose, if the employee is on an approved leave of absence for military service or sickness
or for any other purpose approved by the Company, if the employee’s right to reemployment is guaranteed either by a statute
or by contract or under the policy pursuant to which the leave of absence was granted or if the Administrator otherwise provides
in writing.


 


13.         Special Rules.
Notwithstanding anything herein to the contrary, the Administrator may adopt special rules applicable to the employees of a particular
Designated Subsidiary, whenever the Administrator determines that such rules are necessary or appropriate for the implementation
of the Plan in a jurisdiction where such Designated Subsidiary has employees; provided that if such rules are inconsistent with
the requirements of Section 423(b) of the Code, these employees will participate in the Non-423 Component. Any special rules established
pursuant to this Section 13 shall, to the extent possible, result in the employees subject to such rules having substantially
the same rights as other Participants in the Plan.


 


14.        Optionees
Not Stockholders. Neither the granting of an Option to a Participant nor the deductions from his or her pay shall constitute
such Participant a holder of the shares of Common Stock covered by an Option under the Plan until such shares have been purchased
by and issued to him or her.


 


15.        Rights Not Transferable.
Rights under the Plan are not transferable by a Participant other than by will or the laws of descent and distribution, and are
exercisable during the Participant’s lifetime only by the Participant.


 


16.        Designation of Beneficiary.


 


(a)       A
Participant may file a written designation of a beneficiary who is to receive any shares of Common Stock and/or cash, if any, from
the Participant’s account under the Plan in the event of such Participant’s death subsequent to the end of an Offering
but prior to delivery to the Participant of such shares of Common Stock or cash. In addition, a Participant may file a written
designation of a beneficiary who is to receive any cash from the Participant’s account under the Plan in the event of such
Participant’s death during an Offering. Any such designation shall be on a form provided by or otherwise acceptable to the
Company.


 


(b)       The
Participant may change such designation of beneficiary at any time by written notice to the Company. In the event of the death
of a Participant and in the absence of a beneficiary validly designated under the Plan who is living at the time of such Participant’s
death, the Company shall deliver such shares of Common Stock and/or cash to the executor or administrator of the estate of the
Participant, or if no such executor or administrator has been appointed (to the knowledge of the Company), the Company, in its
sole discretion, may deliver such shares of Common Stock and/or cash to the spouse or to any one or more dependents or relatives
of the Participant, or if no spouse, dependent or relative is known to the Company, then to such other person as the Company may
designate.


 






     


     


    

 


17.        Application of Funds.
All funds received or held by the Company under the Plan may be combined with other corporate funds and may be used for any corporate
purpose.


 


18.         Adjustment in Case
of Changes Affecting Common Stock; Corporate Transaction.


 


(a)       In
the event of a subdivision of outstanding shares of Common Stock, the payment of a dividend in Common Stock or any other change
affecting the Common Stock, the number of shares approved for the Plan and the share limitation set forth in Section 8 shall
be equitably or proportionately adjusted to give proper effect to such event.


 


(b)        In
the event of a Corporate Transaction, then the Participants’ accumulated payroll deductions under an ongoing Offering shall
be used to purchase shares of Common Stock subject to the limitations in this Plan on a date determined by the Company within ten
(10) business days prior to the closing of the Corporate Transaction, which date shall constitute the Exercise Date under this
Plan, and the Plan shall terminate immediately after such Exercise Date and the issuance of the shares purchased on such Exercise
Date.


 


	 	 	 	 	 


19.       Amendment
of the Plan. The Board may at any time and from time to time amend the Plan in any respect, except that without the approval
within 12 months of such Board action by the stockholders, no amendment shall be made increasing the number of shares approved
for the Plan or making any other change that would require stockholder approval in order for the Plan, as amended, to qualify as
an “employee stock purchase plan” under Section 423(b) of the Code.


 


20.        Insufficient Shares.
If the total number of shares of Common Stock that would otherwise be purchased on any Exercise Date plus the number of shares
purchased under previous Offerings under the Plan exceeds the maximum number of shares issuable under the Plan, the shares then
available shall be apportioned among Participants in proportion to the amount of payroll deductions accumulated on behalf of each
Participant that would otherwise be used to purchase Common Stock on such Exercise Date.


 


21.         Termination of
the Plan. Except as otherwise contemplated under Section 18(b) with respect to a Corporate Transaction, the Plan may be terminated
at any time by the Board. Upon termination of the Plan, all amounts in the accounts of Participants shall be promptly refunded.


 


22.        Governmental
Regulations. The Company’s obligation to sell and deliver Common Stock under the Plan is subject to obtaining all governmental
approvals required in connection with the authorization, issuance, or sale of such stock.


 


23.         Governing
Law. This Plan and all Options and actions taken thereunder shall be governed by, and construed in accordance with, the laws
of the State of Delaware, applied without regard to conflict of law principles.


 


24.        Issuance
of Shares. Shares may be issued upon exercise of an Option from authorized but unissued Common Stock, from shares held in the
treasury of the Company, or from any other proper source.


 


25.        Tax Withholding.
Participation in the Plan is subject to any minimum required tax withholding on income of the Participant in connection with the
Plan. Each Participant agrees, by entering the Plan, that the Company and its Subsidiaries shall have the right to deduct any such
taxes from any payment of any kind otherwise due to the Participant, including shares issuable under the Plan.


 


26.        Notification
Upon Sale of Shares. Each Participant agrees, by entering the Plan, to give the Company prompt notice of any disposition of
shares purchased under the Plan where such disposition occurs within two years after the date of grant of the Option pursuant to
which such shares were purchased or within one year after the date such shares were purchased.





 


27.       Effective Date and
Approval of Shareholders. The Plan shall take effect on the later of the date it is adopted by the Board and the date it is
approved by the holders of a majority of the votes cast at a meeting of stockholders at which a quorum is present or by written
consent of the stockholders.


  




     


     


    

 


 


APPENDIX A 


 


Designated Subsidiaries


 


 


 


None