Exhibit 4.3


 


ALTERITY THERAPEUTICS LIMITED


(FORMERLY
PRANA


BIOTECHNOLOGY LIMITED) ABN


37 080 699 065


2018 AMERICAN DEPOSITARY SHARE (ADS)
OPTION PLAN, AS AMENDED


 


Alterity Therapeutics Limited (formerly Prana Biotechnology
Limited), a corporation formed under the laws of the Commonwealth of Australia (the “Company”), hereby amends the 2018
American Depository Share (ADS) Option Plan (the “Plan”), initially effective November 16, 2018 (the “Effective
Date”), following approval of the amended Plan by the majority of the shares entitled to vote at a duly constituted meeting
of the shareholders of the Company held on November 18, 2020. .


 


1.
Purpose.


 


The purpose of the Plan is to promote the
interests of the Company, its Subsidiaries and shareholders by enabling the Company and its Subsidiaries to attract and retain
outstanding employees, officers, consultants, independent contractors and directors (“Eligible Persons”) and align the
interests of Eligible Persons with those of the Company and its shareholders through the incentive inherent in the ownership of
ordinary shares of the Company (“Shares”). For purposes of the Plan, the term “Subsidiary” shall mean “subsidiary
corporation,” as such term is defined in Section 424(f) of the Internal Revenue Code of 1986, as amended (the “Code”).
For purposes of the Plan, the term “Award” shall mean a grant of an option to purchase American Depositary Shares (“ADSs”)
representing Shares.


 


2.
Shares Subject to Awards .


 


(a) Awards under the Plan (“Awards”)
may be granted in the following forms:


 


		(i)	incentive stock options (“Incentive Stock Options”)
as provided in Section 422 of the Code; provided, however, that no Award of Incentive Stock Options shall be made hereunder after
the date that is the tenth anniversary of the Effective Date; and



 


		(ii)	non-qualified stock options (“Non-qualified Options”)
(the term “Options” includes incentive stock options and non-qualified options).



 


(b) Subject to the adjustment provisions
of Section 11 hereof, the aggregate number of ADSs which may be issued under options under the Plan shall not exceed 3,333,333
(the equivalent of 200,000,000 Shares. ADSs delivered under the Plan may be authorized and unissued ADSs or issued ADSs reacquired
by the Company, or both. The ADSs that are forfeited under the terms of the Plan and ADSs that are the subject of Options that
expire unexercised or which are otherwise surrendered by the holder of such Option (the “Optionee”) without receiving
any payment or other benefit with respect thereto may again become available for new Awards under the Plan.


 


3.
Administration of the Plan.


 


The Plan shall be administered by a committee
(the “Committee”) comprised of members of the Board of Directors of the Company (the “Board”) selected
by the Board. The Board may remove from, add members to, or fill vacancies in the Committee. The Committee shall consist of a compensation
committee of the Board comprised solely of two or more “outside directors ” within the meaning of Section 162(m)(4)(C)(i)
of the Code, unless the Board determines that there is no need to comply with the requirements of Section 162(m) of the Code.


 


The Committee is authorized, subject to
the provisions of the Plan, to establish such rules and regulations as it may deem appropriate for the conduct of meetings and
proper administration of the Plan. All actions of the Committee shall be taken by majority vote of its members, except that the
members thereof may authorize any one or more of their number or any officer of the Company to execute and deliver documents on
behalf of the Committee. Subject to the provisions of the Plan, the Committee shall have authority, in its sole discretion, to
grant Awards under the Plan, to interpret the provisions of the Plan and to prescribe, amend, and rescind rules and regulations
relating to the Plan or any Award thereunder as it may deem necessary or advisable. All decisions made by the Committee pursuant
to the provisions of the Plan shall be final, conclusive and binding on all persons. No member of the Committee shall be liable
for anything done or omitted to be done by him or by any other member of the Committee in connection with the Plan, except for
his own willful misconduct or as expressly provided by statute.


 



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4.
Eligibility.


 


Awards shall be made to such Eligible Persons
of the Company or any of its Subsidiaries as the Committee shall select from time to time; provided, however, that Incentive Stock
Options may only be granted to employees of the Company and its Subsidiaries (including, without limitation, officers and directors
who are also employees of the Company and its Subsidiaries) and shall not be granted to any owner of 10% or more of the total combined
voting power of all classes of stock of the Company and its Subsidiaries, as determined under Section 422(b)(6) of the Code. The
Committee’s designation of an Optionee in any year shall not require the Committee to designate such person to receive
Awards or grants in any other year.


 


5. Stock Option Agreements.
All Options granted pursuant to the Plan shall be evidenced in writing by option agreements (“Option Agreements”) in
such form and containing such terms and conditions as the Committee shall determine which are not inconsistent with the provisions
of the Plan, including the following:


 


(a) Type of Option; Number of ADSs.
Each Option shall be designated as either an Incentive Stock Option or a Non-qualified Option. Each Option Agreement shall state
the total number of ADSs to which it pertains. To the extent that the aggregate Fair Market Value, as defined below and determined
on the date that an Option is granted, of ADSs with respect to which Incentive Stock Option are exercisable for the first time
by an Optionee during any calendar year (under all plans of the Company and its Subsidiaries) exceeds U.S.$100,000, such Option
shall be treated as a Non-qualified Option.


 


(b) Option Price. The Option exercise
price per each ADS shall be determined by the Committee at the time any Option is granted and stated in the Option Agreement; provided,
that the exercise price per ADS of an Incentive Stock Option and an Option that needs to satisfy the requirements of Section 162(m)
of the Code shall not be less than 100% of the Fair Market Value of such ADS on the date of the Award. Notwithstanding the preceding
sentence, the price per ADS of an Incentive Stock Option awarded to an Optionee who, at the time such Option is granted, owns stock
representing more than 10% of the total combined voting power of all classes of stock of the Company or its Subsidiaries, shall
not be less than 110% of the Fair Market Value of such ADS on the date of the Award.


 


For all purposes under the Plan, Fair Market
Value shall mean the per ADS closing price of the ADSs for the day immediately preceding the date as of which Fair Market Value
is being determined (or if there was no reported closing price on such date, on the last preceding date on which the closing price
was reported) reported on the National Association of Securities Dealers Automated Quotations (NASDAQ) system, or other national
securities exchange on which the ADSs are then principally traded, and reported in the trading tables of The Wall Street Journal
..


 


(c) Option Term. The period for
which the Option is granted shall be determined by the Committee and set forth in the Option Agreement; provided, however, that
no Option shall be exercisable after the expiration of ten years from the date of its Award. Notwithstanding the preceding sentence,
in the case of an Incentive Stock Option granted to an Optionee who, at the time such Option is granted, owns stock representing
more than 10% of the combined voting power of all classes of stock of the Company or its Subsidiaries, the term of the Option shall
be five years from the date of the Award or such shorter term as may be provided in the Option Agreement. No Option may be exercised
after the expiration of its term.


 


(d) Vesting Period. Except as otherwise
provided in the Plan or by the Committee in an Option Agreement, Options shall become vested and exercisable in accordance with
the following vesting schedule:


 


	less than one year after date of Award.	0% of the total Award
	one year after date of Award.	25% of the total Award
	two years after date of Award.	50% of the total Award
	three years after date of Award.	75% of the total Award
	four years after date of Award.	100% of the total Award


 


Options shall automatically cease to vest
in accordance with the above schedule and, except as provided in Sections 7, 8, 9 and 10, shall become null and void upon the termination
of employment for any reason.


 


(e) Time and Manner of Payment.
Each Option Agreement shall provide that Options granted under the Plan shall be exercised by the Optionee (or by his executors,
administrators, guardian or legal representative) as to all or any portion of the ADSs covered thereby, by the giving of written
notice of exercise to the Company, specifying the number of ADSs to be purchased. Full payment of such purchase price shall be
made within ten business days following the receipt of such notice by the Company and shall be made (i) in cash, by certified check
or bank check, or (ii) in any other manner permitted in the discretion of the Committee. Such notice of exercise and full payment,
shall be delivered to the Company at its principal business office or such other office as the Committee may direct, and shall
be in such form, containing such further provisions consistent with the provisions of the Plan, as the Committee may prescribe.
In no event may any Option granted hereunder be exercised for a fraction of an ADS. The Company shall issue or cause to be issued
to the Optionee ADSs or American Depositary Receipts (“ADRs”) evidencing the ADSs as soon as practicable after an Option
is exercised, and, within a reasonable time thereafter, such issuance shall be evidenced on the books of the Company. No person
exercising an Option shall have any of the rights of a holder of ADSs prior to the date that such ADSs are issued following the
exercise of such Option. No adjustment shall be made for cash dividends or other rights for which the record date is prior to the
date of such issuance.


 



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(f) Other Provisions. An Option
Agreement may contain any other terms and conditions that the Committee, in its sole discretion, deems appropriate; provided, however,
that no such term or condition shall be inconsistent with the terms of the Plan or, in the case of an Incentive Stock Option, Section
422 of the Code. Each Option Agreement may condition the exercise of any Option upon the attainment of specified productivity goals
by a Company group or division or an individual Optionee.


 


6.
Non-Transferability of Options


 


No Option shall be assignable or transferable
by the Optionee, other than by will or the laws of descent and distribution, and may be exercised during the lifetime of the Optionee
only by the Optionee or his guardian or legal representative.


 


7.
Termination of Employment.


 


(a) Except as otherwise determined by the Committee or provided
in an Option Agreement, in the event of the termination of employment or service of an Optionee with the Company and its Subsidiaries
for any reason (other than termination for cause, death, disability or Change of Control of the Company as provided below), Options
granted to him that have not previously expired or been exercised shall, to the extent vested on the date of such termination,
be exercisable by the Optionee within 30 days after the date of such termination, unless such Option is earlier terminated pursuant
to its terms. All Options that are not exercisable as of the date of such termination or which are not exercised within 30 days
thereafter, shall be deemed cancelled and terminated as of such date.


 


(b) Except as otherwise determined by the Committee or provided
in an Option Agreement, in the event an Optionee retires from employment or service with the Company and its Subsidiaries, Options
granted to him shall become 100% vested as of the effective date of the Optionee’s retirement. Whether an Optionee has terminated
employment on account of retirement shall be determined by the Committee in its sole discretion.


 


(c) Except as otherwise determined by the
Committee or provided in an Option Agreement, in the event that an Optionee’s employment or service is terminated by the
Company or any of its Subsidiaries for “cause,” all Options, whether or not exercisable as of the date of such termination,
shall be canceled and terminated as of such date. For these purposes, termination for “cause” shall mean the following:
the Optionee’s violation of copyright, trademark and/or patent protection maintained by the Company or a Subsidiary; the
Optionee’s engaging or assisting in any business in competition with the Company or a Subsidiary as employee, owner, partner,
director, officer, stockholder, consultant or agent (ownership of minority interests in publicly-traded corporations, partnerships
or companies or of 5% or less of the equity of privately-held corporations, partnerships or companies shall not be considered competition
for purposes of this Plan); the Optionee’s dishonesty, or acting in any manner inconsistent with the utmost good faith and
loyalty in the performance of the Optionee’s duties; conviction of the Optionee by a court of law of competent jurisdiction
for fraud, misappropriation, embezzlement, or any felony; failure of the Optionee to perform his duties to the reasonable satisfaction
of the Company or its Subsidiaries.


 


8.
Death.


 


Except as otherwise determined by the Committee
or provided in an Option Agreement, in the event an Optionee dies while employed by or providing service to the Company or any
of its Subsidiaries, all unvested Options shall become 100% vested and any Option granted to him that has not previously expired
or been exercised shall be exercisable by the estate of such Optionee or by any person who acquired such Option by bequest or inheritance,
at any time within one year after the date of death of the Optionee, unless such Option is earlier terminated pursuant to its terms.
All Options not exercised within such one- year period shall be deemed canceled and terminated on the first anniversary of the
Optionee’s death.


 


9. Disability.


 


Except as otherwise determined by the Committee
or provided in an Option Agreement, in the event of the termination of employment of an Optionee due to total disability, the Optionee
or his guardian or legal representative, shall have the right to exercise any Option which has not been previously exercised or
expired and which the Optionee was eligible to exercise as of the first date of total disability, at any time within one year after
such termination, unless such Option is earlier terminated pursuant to its terms. All Options that are not exercisable as of the
date of the Optionee’s termination or which are not exercised within one year thereafter shall be deemed canceled and terminated
as of such applicable date. The term “total disability” shall, for purposes of this Plan, be defined in the same manner
as such term is defined in Section 22(e)(3) of the Code and shall be determined by the Committee in its sole discretion.


 


10.
Change of Control.


 


(a) In the event of a proposed sale or conveyance of all or
substantially all of the assets of the Company, or the merger or consolidation of the Company and/or its Subsidiaries with or into
another corporation, each outstanding Option shall be assumed or an equivalent option shall be substituted by the successor corporation
or a parent or subsidiary of the successor corporation. In the event that such successor corporation refuses to assume such Option
or to substitute an equivalent option, such Option may, at the discretion of the Committee, become 100% vested upon the consummation
of the merger or sale of assets.


 



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(b) Except as otherwise determined by the Committee or provided
in an Option Agreement, in the event of the involuntary termination of employment or service of an Optionee from the Company and
its Subsidiaries on account of and within six months of a Change of Control of the Company, as determined by the Committee, Options
granted to such Optionee that have not previously expired or been exercised shall become 100% vested as of the date of such termination
of employment and shall be exercisable by the Optionee within 30 days after such date, unless such Option is earlier terminated
pursuant to its terms. A Change of Control shall be deemed to have occurred when:


 


(i) any person (as such term is used in
Section 13 of the Exchange Act and the rules and regulations thereunder), and any person acting in concert with such person, directly
or indirectly, acquires or otherwise becomes entitled to vote more than 50% of the voting power entitled to be cast at elections
for directors of the Company; or


 


(ii) there occurs any merger or consolidation
of the Company, or any sale, lease or exchange of all or any substantial part of the consolidated assets of the Company and its
Subsidiaries to any other person, and (A) in the case of a merger or consolidation, the holders of outstanding stock of the Company
entitled to vote in elections of directors of the Company immediately before such merger or consolidation (excluding for this purpose
any person that directly or indirectly owns or is entitled to vote 20% or more of the voting power of the Company) hold less than
50% of the voting power of the survivor of such merger or consolidation or its parent, or (B) in the case of any such sale, lease
or exchange, the Company does not own at least 50% of the voting power of the other person; or


 


(iii) one or more new directors of the
Company are elected and at such time five or more directors (or, if less, a majority of the directors) then holding office were
not nominated as candidates by a majority of the directors in office immediately before such election.


 


11.
Adjustments.


 


Except in the case of a Change of Control
of the Company as provided in Section 10, in the event that the Committee shall determine that any dividend or other distribution
(whether in the form of cash, ADSs, other securities, or other property), recapitalization, stock split, reverse stock split, reorganization,
merger, consolidation, split-up, spin-off, combination, repurchase, or exchange of ADSs or other securities, the issuance of warrants
or other rights to purchase ADSs or other securities, or other similar corporate transaction or event affects the ADSs with respect
to which Options have been or may be issued under the Plan, such that an adjustment is determined by the Committee to be appropriate
in order to prevent dilution or enlargement of the benefits or potential benefits intended to be made available under the Plan,
then the Committee shall, in such manner as the Committee may deem equitable, adjust any or all of (i) the number and type of shares
that thereafter may be made the subject of Options, (ii) the number and type of shares subject to outstanding Options, and (iii)
the exercise price with respect to any Option, or, if deemed appropriate, make provision for a cash payment to the holder of any
outstanding Option; provided, however, that the number of ADSs subject to any Option denominated in ADSs shall always be a whole
number.


 


12.
Tax Withholding.


The Company shall notify an Optionee of
any income tax withholding requirements arising as a result of the grant of any Award or exercise of an Option. The Company shall
have the right to withhold from the Optionee such withholding taxes as may be required by law, or to otherwise require the Optionee
to pay such withholding taxes. If the Optionee shall fail to make such tax payments as are required, the Company or its Subsidiaries
shall, to the extent permitted by law, have the right to retain and withhold a number of ADSs, otherwise due to such Optionee,
having a market value not less than the amount of such taxes required to be withheld by the Company to reimburse the Company for
any such taxes and cancel (in whole or in part) any such ADSs so withheld.


 


13.
Right of Discharge Reserved.


 


Nothing in the Plan nor the grant of an
Award hereunder shall confer upon any employee, officer, director, consultant, independent contractor or other individual the right
to continue in the employment of or service with the Company or any of its Subsidiaries or affect any right that the Company or
any Subsidiary may have to terminate the employment or service of (or to demote or to exclude from future Options under the Plan)
any such employee, officer, director, consultant, independent contractor or other individual at any time for any reason. Except
as specifically provided by the Committee, the Company shall not be liable for the loss of existing or potential profit from an
Award granted in the event of termination of an employment or service or other relationship even if the termination is in violation
of an obligation of the Company or any Subsidiary of the Company to the employee, officer, director, consultant or independent
contractor.


 


14.
Severability.


 


If any provision of the Plan shall be held
unlawful or otherwise invalid or unenforceable in whole or in part, such unlawfulness, invalidity or unenforceability shall not
affect any other provision of the Plan or part thereof, each of which remain in full force and effect. If the making of any payment
or the provision of any other benefit required under the Plan shall be held unlawful or otherwise invalid or unenforceable, such
unlawfulness, invalidity or unenforceability shall not prevent any other payment or benefit from being made or provided under the
Plan, to the extent that it would not be unlawful, invalid or unenforceable, and the maximum payment or benefit that would not
be unlawful, invalid or unenforceable shall be made or provided under the Plan.


 



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15.
Amendment and Termination of the Plan.


 


The Board may, from time to time, alter, amend, suspend or terminate
the Plan with respect to Options that have not been granted, subject to any requirement for stockholder approval imposed by applicable
law or any rule of any stock exchange or quotation system on which ADSs are listed or quoted; provided, however, that the Board
may not amend the Plan in any manner that would result in non-compliance with any applicable law. Neither the Board nor the Committee
may, without the consent of the Optionee, alter or in any way impair the rights of such Optionee under any Award previously granted.
Neither the termination of the Plan nor the Change of Control of the Company shall affect any Option previously granted.


 


If the approval of the Plan by the stockholders
is not obtained within 12 months of the Effective Date, the Plan shall be null and void and each Award of an Option hereunder shall
be null and void.


 


16.
Conditions Upon Issuance of ADSs.


 


ADSs shall not be issued pursuant to the exercise of an Option
unless the exercise of such Option and the issuance and delivery of such ADSs or the ADRs evidencing such ADSs shall comply with
applicable laws and the securities trading policy and other applicable governance policies (as applying at the time) and shall
be further subject to the approval of counsel for the Company with respect to such compliance. As a condition to exercise of an
Option, the Committee may require the person exercising the Option to represent and warrant at the time of exercise that the exercise
complies with the applicable laws, the securities trading policy and other applicable governance policies of the Company and that
the ADSs are being purchased only for investment and without any present intention to sell or distributed such ADSs.


 


17.
Gender and Number.


 


Any masculine terminology used in this
Plan document shall also include the feminine, and the definition of any term herein in the singular shall also include the plural
except when otherwise indicated by the context.


 


18.
Governing Law.


 


The Plan and all determinations made and
actions taken thereunder, to the extent not otherwise governed by the Code or the laws of the United States, shall be governed
by the laws of the State of New York and construed accordingly.


 


 


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