Exhibit 4.2


 


 





MOLECULIN BIOTECH, INC.


 


UNDERWRITER WARRANT TO PURCHASE COMMON
STOCK


 


 


Warrant No.: U-1


Number of Shares of Common Stock: 367,500


Date of Issuance:  March 29, 2019 (“Issuance Date”)


 


Moleculin Biotech, Inc., a company organized
under the laws of Delaware (the “Company”), hereby certifies that, for good and valuable consideration, the
receipt and sufficiency of which are hereby acknowledged, Oppenheimer & Co. Inc., the registered holder hereof or its
permitted assigns (the “Holder”), is entitled, subject to the terms set forth below, to purchase from the Company,
at the Exercise Price (as defined below) then in effect, at any time or times on or after March 29, 2019 (the “Initial
Exercisability Date”), but not after 11:59 p.m., New York time, on the Expiration Date, (as defined below), Three Hundred
Sixty-Seven Thousand Five Hundred (367,500) fully paid non-assessable shares of Common Stock (as defined below), subject to adjustment
as provided herein (the “Warrant Shares”).  Except as otherwise defined herein, capitalized terms in this
Underwriter Warrant to Purchase Common Stock (including any Underwriter Warrants to Purchase Common Stock issued in exchange, transfer
or replacement hereof, this “Warrant”), shall have the meanings set forth in Section 16.  This Warrant
is issued pursuant to (i) that certain Underwriting Agreement (the “Underwriting Agreement”), dated as
of March 27, 2019 (the “Effective Date”) by and between the Company and Oppenheimer & Co. Inc., as
representative of the several underwriters named therein, (ii) the Company’s Registration Statement on Form S-3 (File
number 333-219434) (the “Registration Statement”) and (iii) the Company’s prospectus supplement dated
March 27, 2019.


 


 


 


 






     

     


    

 


1. EXERCISE OF WARRANT.


 


(a) Mechanics of Exercise. 
Subject to the terms and conditions hereof (including, without limitation, the limitations set forth in Section 1(f)), this
Warrant may be exercised by the Holder at any time or times on or after the Initial Exercisability Date, in whole or in part (but
not as to fractional shares), by delivery (via electronic mail) of a written notice, in the form attached hereto as Exhibit A (the
“Exercise Notice”), of the Holder’s election to exercise this Warrant.  Within one (1) Trading
Day following the delivery of the Exercise Notice, the Holder shall make payment to the Company of an amount equal to the Exercise
Price in effect on the date of such exercise multiplied by the number of Warrant Shares as to which this Warrant is being exercised
(the “Aggregate Exercise Price”) in cash by wire transfer of immediately available funds (a “Cash Exercise”)
or, if the provisions of Section 1(d) are applicable, by notifying the Company that this Warrant is being exercised pursuant
to a Cashless Exercise (as defined in Section 1(d)).  The Holder shall not be required to deliver the original Warrant
in order to effect an exercise hereunder, nor shall any ink-original signature or medallion guarantee (or other type of guarantee
or notarization) with respect to any Exercise Notice be required, provided, that in the event of an exercise of this Warrant for
all Warrant Shares then issuable hereunder, this Warrant is surrendered to the Company by the fifth (5th) Trading Day following
the date on which the Company has received each of the Exercise Notice and, if this Warrant is being exercise pursuant to a Cash
Exercise, the Aggregate Exercise Price.  Execution and delivery of the Exercise Notice with respect to less than all of the
Warrant Shares shall have the same effect as cancellation of the original Warrant and issuance of a new Warrant evidencing the
right to purchase the remaining number of Warrant Shares.  On or before the first (1st) Trading Day following the date on
which the Holder has delivered the applicable Exercise Notice, the Company shall transmit by facsimile or electronic mail an acknowledgment
of confirmation of receipt of the Exercise Notice, in the form attached to the Exercise Notice, to the Holder and the Company’s
transfer agent (the “Transfer Agent”).  So long as the Holder delivers the Aggregate Exercise Price (or
notice of a Cashless Exercise) on or prior to the first (1st) Trading Day following the date on which the Exercise Notice has been
delivered to the Company, then on or prior to the earlier of (i) the second (2nd) Trading Day  and (ii) the number
of Trading Days comprising the Standard Settlement Period, in each case following the date on which the Exercise Notice has been
delivered to the Company, or, if the Holder does not deliver the Aggregate Exercise Price (or notice of a Cashless Exercise) on
or prior to the first (1st) Trading Day following the date on which the Exercise Notice has been delivered to the Company, then
on or prior to the first (1st) Trading Day following the date on which the Aggregate Exercise Price (or notice of a Cashless Exercise)
is delivered (such earlier date, the “Share Delivery Date”), the Company shall (X) provided that the Transfer
Agent is participating in The Depository Trust Company (“DTC”) Fast Automated Securities Transfer Program, credit
such aggregate number of Warrant Shares to which the Holder is entitled pursuant to such exercise to the Holder’s or its
designee’s balance account with DTC through its Deposit / Withdrawal At Custodian system, or (Y) if the Transfer Agent
is not participating in the DTC Fast Automated Securities Transfer Program, issue and dispatch by overnight courier to the address
as specified in the Exercise Notice, a certificate, registered in the name of the Holder or its designee, for the number of Warrant
Shares to which the Holder is entitled pursuant to such exercise.  The Company shall be responsible for all fees and expenses
of the Transfer Agent and all fees and expenses with respect to the issuance of Warrant Shares via DTC, if any, including without
limitation for same day processing.  Upon delivery of the Exercise Notice, the Holder shall be deemed for all corporate purposes
to have become the holder of record and beneficial owner of the Warrant Shares with respect to which this Warrant has been exercised,
irrespective of the date such Warrant Shares are credited to the Holder’s DTC account or the date of delivery of the certificates
evidencing such Warrant Shares, as the case may be, provided that the Holder delivers the Aggregate Exercise Price (or notice of
a Cashless Exercise) within one (1) Trading Day of delivery of the Exercise Notice.  If this Warrant is physically delivered
to the Company in connection with any exercise pursuant to this Section 1(a) and the number of Warrant Shares represented
by this Warrant submitted for exercise is greater than the number of Warrant Shares being acquired upon an exercise, then the Company
shall as soon as practicable and in no event later than three (3) Trading Days after any exercise and at its own expense,
issue and deliver to the Holder (or its designee) a new Warrant (in accordance with Section 7(d)) representing the right to
purchase the number of Warrant Shares issuable immediately prior to such exercise under this Warrant, less the number of Warrant
Shares with respect to which this Warrant is exercised.  No fractional Warrant Shares are to be issued upon the exercise of
this Warrant, but rather the number of Warrant Shares to be issued shall be rounded to the nearest whole number.  The Company
shall pay any and all transfer, stamp, issuance and similar taxes, costs and expenses (including, without limitation, fees and
expenses of the Transfer Agent) which may be payable with respect to the issuance and delivery of Warrant Shares upon exercise
of this Warrant, provided,  however, that the Company shall not be required to pay any tax which may be
payable based on the income of the Holder or in respect of any transfer involved in the registration of any certificates for Warrant
Shares or Warrants in a name other than that of the Holder or an affiliate thereof. The Holder shall be responsible for any tax
which may be payable based on the income of the Holder or in respect of any transfer involved in the registration of any certificate
for Warrant Shares or Warrants in a name other than that of the Holder or an affiliate thereof.  The Company’s
obligations to issue and deliver Warrant Shares in accordance with the terms and subject to the conditions hereof are absolute
and unconditional, irrespective of any action or inaction by the Holder to enforce the same, any waiver or consent with respect
to any provision hereof, the recovery of any judgment against any Person or any action to enforce the same, or any setoff, counterclaim,
recoupment, limitation or termination; provided,  however, that the Company shall not be required to deliver
Warrant Shares with respect to an exercise prior to the Holder’s delivery of the Aggregate Exercise Price (or notice of a
Cashless Exercise) with respect to such exercise.


 






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(b) Exercise Price.  For
purposes of this Warrant, “Exercise Price” means $1.10 per share, subject to adjustment as provided herein.


 


(c) Company’s Failure to Timely
Deliver Securities. If either (I) the Company shall fail for any reason or for no reason to issue to the Holder on or
prior to the applicable Share Delivery Date, if (x) the Transfer Agent is not participating in the DTC Fast Automated Securities
Transfer Program, a certificate for the number of shares of Common Stock to which the Holder is entitled and register such Common
Stock on the Company's share register or (y) the Transfer Agent is participating in the DTC Fast Automated Securities Transfer
Program, to credit the Holder's balance account with DTC, for such number of shares of Common Stock to which the Holder is entitled
upon the Holder's exercise of this Warrant or (II) a registration statement (which may be the Registration Statement) covering
the issuance or resale of the Warrant Shares that are the subject of the Exercise Notice (the "Exercise Notice Warrant
Shares") is not available for the issuance or resale, as applicable, of such Exercise Notice Warrant Shares and (x) the
Company fails to promptly, but in no event later than one (1) Business Day after such registration statement becomes unavailable,
to so notify the Holder and (y) upon a Cashless Exercise (as defined below) the Company is unable to deliver the Exercise Notice
Warrant Shares electronically without any restrictive legend by crediting such aggregate number of Exercise Notice Warrant Shares
to the Holder’s or its designee’s balance account with DTC through its Deposit / Withdrawal At Custodian system (the
event described in the immediately foregoing clause (II) is hereinafter referred as a "Notice Failure" and together
with the event described in clause (I) above, an "Exercise Failure"), then, in addition to all other remedies
available to the Holder, if on or prior to the applicable Share Delivery Date either (I) if the Transfer Agent is not participating
in the DTC Fast Automated Securities Transfer Program, the Company shall fail to issue and deliver a certificate to the Holder
and register such shares of Common Stock on the Company's share register or, if the Transfer Agent is participating in the DTC
Fast Automated Securities Transfer Program, credit the Holder's balance account with DTC for the number of shares of Common Stock
to which the Holder is entitled upon the Holder's exercise hereunder or pursuant to the Company's obligation pursuant to clause
(ii) below or (II) if a Notice Failure occurs, and if after such date the Holder is required by its broker to purchase (in an open
market transaction or otherwise) or the Holder’s brokerage firm otherwise purchases, shares of Common Stock to deliver in
satisfaction of a sale by the Holder of the Warrant Shares which the Holder anticipated receiving upon such exercise (a “Buy-In”),
then the Company shall (A) pay in cash to the Holder the amount, if any, by which (x) the Holder’s total purchase price (including
brokerage commissions, if any) for the shares of Common Stock so purchased exceeds (y) the amount obtained by multiplying (1) the
number of Warrant Shares that the Company was required to deliver to the Holder in connection with the exercise at issue times
(2) the price at which the sell order giving rise to such purchase obligation was executed, and (B) at the option of the Holder,
either reinstate the portion of the Warrant and equivalent number of Warrant Shares for which such exercise was not honored (in
which case such exercise shall be deemed rescinded) or deliver to the Holder the number of shares of Common Stock that would have
been issued had the Company timely complied with its exercise and delivery obligations hereunder. For example, if the Holder purchases
Common Stock having a total purchase price of $11,000 to cover a Buy-In with respect to an attempted exercise of shares of Common
Stock with an aggregate sale price giving rise to such purchase obligation of $10,000, under clause (A) of the immediately preceding
sentence the Company shall be required to pay the Holder $1,000. The Holder shall provide the Company written notice indicating
the amounts payable to the Holder in respect of the Buy-In and, upon request of the Company, evidence of the amount of such loss.
Nothing herein shall limit a Holder’s right to pursue any other remedies available to it hereunder, at law or in equity including,
without limitation, a decree of specific performance and/or injunctive relief with respect to the Company’s failure to timely
deliver shares of Common Stock upon exercise of the Warrant as required pursuant to the terms hereof. The Company’s current
transfer agent participates in the DTC Fast Automated Securities Transfer Program (“FAST”). In the event that the Company
changes transfer agents while this Warrant is outstanding, the Company shall use commercially reasonable efforts to select a transfer
agent that participates in FAST. While this Warrant is outstanding, the Company shall request its transfer agent to participate
in FAST with respect to this Warrant. In addition to the foregoing rights, (i) if the Company fails to deliver the applicable number
of Warrant Shares upon an exercise pursuant to Section 1 by the applicable Share Delivery Date, then the Holder shall have the
right to rescind such exercise in whole or in part and retain and/or have the Company return, as the case may be, any portion of
this Warrant that has not been exercised pursuant to such Exercise Notice; provided that the rescission of an exercise shall not
affect the Company’s obligation to make any payments that have accrued prior to the date of such notice pursuant to this
Section 1(c) or otherwise, and (ii) if a registration statement (which may be the Registration Statement) covering the issuance
or resale of the Warrant Shares that are subject to an Exercise Notice is not available for the issuance or resale, as applicable,
of such Exercise Notice Warrant Shares and the Holder has submitted an Exercise Notice prior to receiving notice of the non-availability
of such registration statement and the Company has not already delivered the Warrant Shares underlying such Exercise Notice electronically
without any restrictive legend by crediting such aggregate number of Warrant Shares to which the Holder is entitled pursuant to
such exercise to the Holder’s or its designee’s balance account with DTC through its Deposit / Withdrawal At Custodian
system, the Holder shall have the option, by delivery of notice to the Company, to (x) rescind such Exercise Notice in whole or
in part and retain or have returned, as the case may be, any portion of this Warrant that has not been exercised pursuant to such
Exercise Notice; provided that the rescission of an Exercise Notice shall not affect the Company’s obligation to make any
payments that have accrued prior to the date of such notice pursuant to this Section 1(c) or otherwise, and/or (y) switch some
or all of such Exercise Notice from a cash exercise to a Cashless Exercise. In addition to the foregoing, if the Company fails
for any reason to deliver to the Holder the Warrant Shares subject to an Exercise Notice by the second Trading Day following the
Share Delivery Date, the Company shall pay to the Holder, in cash, as liquidated damages and not as a penalty, for each $1,000
of Warrant Shares subject to such exercise (based on the Weighted Average Price of the Common Stock on the date of the applicable
Exercise Notice), $10 per Trading Day (increasing to $20 per Trading Day on the fifth Trading Day after such liquidated damages
begin to accrue) for each Trading Day after the second Trading Day following such Share Delivery Date until such Warrant Shares
are delivered or Holder rescinds such exercise. In addition to any other rights available to the Holder, if the Company fails to
cause the Transfer Agent to transmit to the Holder the Warrant Shares in accordance with the provisions of Section 1(a) above
pursuant to an exercise on or before the Share Delivery Date, and if after such date the Holder is required by its broker to purchase
(in an open market transaction or otherwise) or the Holder’s brokerage firm otherwise purchases, shares of Common Stock
to deliver in satisfaction of a sale by the Holder of the Warrant Shares which the Holder anticipated receiving upon such exercise
(a “Buy-In”), then the Company shall (A) pay in cash to the Holder the amount, if any, by which (x) the Holder’s
total purchase price (including brokerage commissions, if any) for the shares of Common Stock so purchased exceeds (y) the
amount obtained by multiplying (1) the number of Warrant Shares that the Company was required to deliver to the Holder in
connection with the exercise at issue times (2) the price at which the sell order giving rise to such purchase obligation
was executed, and (B) at the option of the Holder, either reinstate the portion of the Warrant and equivalent number of Warrant
Shares for which such exercise was not honored (in which case such exercise shall be deemed rescinded) or deliver to the Holder
the number of shares of Common Stock that would have been issued had the Company timely complied with its exercise and delivery
obligations hereunder.  For example, if the Holder purchases Common Stock having a total purchase price of $11,000 to cover
a Buy-In with respect to an attempted exercise of shares of Common Stock with an aggregate sale price giving rise to such purchase
obligation of $10,000, under clause (A) of the immediately preceding sentence the Company shall be required to pay the Holder
$1,000.


 






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(d) Cashless Exercise. 
Notwithstanding anything contained herein to the contrary, the Holder may, in its sole discretion, exercise this Warrant in whole
or in part and, in lieu of making the cash payment otherwise contemplated to be made to the Company upon such exercise in payment
of the Aggregate Exercise Price, elect instead to receive upon such exercise the “Net Number” of shares of Common Stock
determined according to the following formula (a “Cashless Exercise”):


 


Net Number = (A x B) - (A x C)


  B


 


For purposes of the foregoing formula:


 


A= the total number of shares
with respect to which this Warrant is then being exercised.


 


B= as applicable: (i) the Closing
Sale Price of the Common Stock on the Trading Day immediately preceding the date of the applicable Exercise Notice if such Exercise
Notice is (1) both executed and delivered pursuant to Section 1(a) hereof on a day that is not a Trading Day or (2) both executed
and delivered pursuant to Section 1(a) hereof on a Trading Day prior to the opening of “regular trading hours” (as
defined in Rule 600(b)(64) of Regulation NMS promulgated under the federal securities laws) on such Trading Day, (ii) at the option
of the Holder, either (y) the Weighted Average Price on the Trading Day immediately preceding the date of the applicable Notice
of Exercise or (z) the Bid Price of the Common Stock as of the time of the Holder’s execution of the applicable Exercise
Notice if such Exercise Notice is executed during “regular trading hours” on a Trading Day and is delivered within
two (2) hours thereafter (including until two (2) hours after the close of “regular trading hours” on a Trading Day)
pursuant to Section 1(a) hereof or (iii) the Closing Sale Price of the Common Stock on the date of the applicable Exercise Notice
if the date of such Exercise Notice is a Trading Day and such Exercise Notice is both executed and delivered pursuant to Section
1(a) hereof after the close of “regular trading hours” on such Trading Day.


 


C= the Exercise Price then
in effect for the applicable Warrant Shares at the time of such exercise.


 


If Warrant Shares are issued in such a cashless
exercise, the Company acknowledges and agrees that in accordance with Section 3(a)(9) of the Securities Act of 1933, as amended,
the Warrant Shares shall take on the registered characteristics of the Warrant, and the holding period of the Warrant may be tacked
on to the holding period of the Warrant Shares.  The Company agrees not to take any position contrary to this Section 1(d).
Without limiting the rights of a Holder to receive Warrant Shares on a “cashless exercise,” and to receive the cash
payments contemplated pursuant to Sections 1(c) and 4(b), in no event will the Company be required to net cash settle a Warrant
exercise.


 


(e) Disputes.  In the case
of a dispute as to the determination of the Exercise Price or the arithmetic calculation of the Warrant Shares, the Company shall
promptly issue to the Holder the number of Warrant Shares that are not disputed and resolve such dispute in accordance with Section 11.


 






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(f) Beneficial Ownership. 
Notwithstanding anything to the contrary contained herein, the Company shall not effect the exercise of any portion of this Warrant,
and the Holder shall not have the right to exercise any portion of this Warrant, pursuant to the terms and conditions of this Warrant
and any such exercise shall be null and void and treated as if never made, to the extent that after giving effect to such exercise,
the Holder together with the other Attribution Parties collectively would beneficially own in excess of 4.99% (the “Maximum
Percentage”) of the number of shares of Common Stock outstanding immediately after giving effect to such exercise. 
For purposes of the foregoing sentence, the aggregate number of shares of Common Stock beneficially owned by the Holder and the
other Attribution Parties shall include the number of shares of Common Stock held by the Holder and all other Attribution Parties
plus the number of shares of Common Stock issuable upon exercise of this Warrant with respect to which the determination of such
sentence is being made, but shall exclude the number of shares of Common Stock which would be issuable upon (A) exercise of
the remaining, unexercised portion of this Warrant beneficially owned by the Holder or any of the other Attribution Parties and
(B) exercise or conversion of the unexercised or unconverted portion of any other securities of the Company (including, without
limitation, any convertible notes or convertible preferred stock or warrants) beneficially owned by the Holder or any other Attribution
Party subject to a limitation on conversion or exercise analogous to the limitation contained in this Section 1(f). 
For purposes of this Section 1(f), beneficial ownership shall be calculated in accordance with Section 13(d) of
the Securities Exchange Act of 1934, as amended (the “1934 Act”), it being acknowledged that the Company is
not representing to the Holder that such calculation is in compliance with Section 13(d) of the 1934 Act, and the Holder
is solely responsible for any schedules required to be filed in accordance therewith.  For purposes of this Warrant, in determining
the number of outstanding shares of Common Stock the Holder may acquire upon the exercise of this Warrant without exceeding the
Maximum Percentage, the Holder may rely on the number of outstanding shares of Common Stock as reflected in (x) the Company’s
most recent Annual Report on Form 10-K, Quarterly Report on Form 10-Q and Current Reports on Form 8-K or other public
filing with the Securities and Exchange Commission (the “SEC”), as the case may be, (y) a more recent public
announcement by the Company or (3) any other written notice by the Company or the Transfer Agent setting forth the number
of shares of Common Stock outstanding (the “Reported Outstanding Share Number”).  For any reason at any
time, upon the written or oral request of the Holder, where such request indicates that it is being made pursuant to this Warrant,
the Company shall within one (1) Trading Day confirm orally and in writing or by electronic mail to the Holder the number
of shares of Common Stock then outstanding.  In any case, the number of outstanding shares of Common Stock shall be determined
after giving effect to the conversion or exercise of securities of the Company, including this Warrant, by the Holder and any other
Attribution Party since the date as of which the Reported Outstanding Share Number was reported.  In the event that the issuance
of Common Stock to the Holder upon exercise of this Warrant results in the Holder and the other Attribution Parties being deemed
to beneficially own, in the aggregate, more than the Maximum Percentage of the number of outstanding shares of Common Stock (as
determined under Section 13(d) of the 1934 Act), upon written notice by the Holder to the Company, the number of shares
so issued by which the Holder’s and the other Attribution Parties’ aggregate beneficial ownership exceeds the Maximum
Percentage (the “Excess Shares”) shall be deemed null and void and shall be cancelled ab initio, and the Holder
shall not have the power to vote or to transfer the Excess Shares.  As soon as reasonably practicable after the issuance of
the Excess Shares has been deemed null and void, the Company shall return to the Holder the exercise price paid by the Holder for
the Excess Shares.  Upon delivery of a written notice to the Company, the Holder may from time to time increase or decrease
the Maximum Percentage to any other percentage not in excess of 4.99% as specified in such notice; provided that (i) any such
increase in the Maximum Percentage will not be effective until the sixty-first (61st) day after such notice is delivered to the
Company and (ii) any such increase or decrease will apply only to the Holder and the other Attribution Parties.  For
purposes of clarity, the shares of Common Stock issuable pursuant to the terms of this Warrant in excess of the Maximum Percentage
shall not be deemed to be beneficially owned by the Holder for any purpose including for purposes of Section 13(d) or
Rule 16a-1(a)(1) of the 1934 Act, it being acknowledged that the Company is not representing to the Holder that such
calculation is in compliance with Section 13(d) of the 1934 Act, and the Holder is solely responsible for any schedules
required to be filed in accordance therewith.  No prior inability to exercise this Warrant pursuant to this paragraph shall
have any effect on the applicability of the provisions of this paragraph with respect to any subsequent determination of exercisability. 
The provisions of this paragraph shall be construed and implemented in a manner otherwise than in strict conformity with the terms
of this Section 1(f) to the extent necessary to correct this paragraph or any portion of this paragraph which may be
defective or inconsistent with the intended beneficial ownership limitation contained in this Section 1(f) or to make
changes or supplements necessary or desirable to properly give effect to such limitation.  The limitation contained in this
paragraph may not be waived and shall apply to a successor holder of this Warrant.


 






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(g) Required Reserve Amount. 
So long as this Warrant remains outstanding, the Company shall at all times keep reserved for issuance under this Warrant a number
of shares of Common Stock at least equal to 100% of the maximum number of shares of Common Stock as shall be necessary to satisfy
the Company’s obligation to issue shares of Common Stock under the Warrant (without regard to any limitations on exercise)
(the “Required Reserve Amount”); provided that at no time shall the number of shares of Common
Stock reserved pursuant to this Section 1(g) be reduced other than in connection with any exercise of the Warrant, in
whole or in part, or such other event covered by Section 2(c) below.


 


(h) Insufficient Authorized Shares. 
If at any time while this Warrant remains outstanding the Company does not have a sufficient number of authorized and unreserved
shares of Common Stock to satisfy its obligation to reserve for issuance the Required Reserve Amount (an “Authorized Share
Failure”), then the Company shall promptly take all action reasonably necessary to increase the Company’s authorized
shares of Common Stock to an amount sufficient to allow the Company to reserve the Required Reserve Amount for this Warrant then
outstanding.  Without limiting the generality of the foregoing sentence, as soon as practicable after the date of the occurrence
of an Authorized Share Failure, but in no event later than ninety (90) days after the occurrence of such Authorized Share Failure,
the Company shall hold a meeting of its stockholders for the approval of an increase in the number of authorized shares of Common
Stock.  In connection with such meeting, the Company shall provide each stockholder with a proxy statement and shall use its
reasonable best efforts to solicit its stockholders’ approval of such increase in authorized shares of Common Stock and to
cause its board of directors to recommend to the stockholders that they approve such proposal.  Notwithstanding the foregoing,
if any such time of an Authorized Share Failure, the Company is able to obtain the written consent of a majority of the shares
of its issued and outstanding shares of Common Stock to approve the increase in the number of authorized shares of Common Stock,
the Company may satisfy this obligation by obtaining such consent and submitting for filing with the SEC an Information Statement
on Schedule 14C.


 


2. ADJUSTMENT OF EXERCISE PRICE AND
NUMBER OF WARRANT SHARES.  The Exercise Price and the number of Warrant Shares shall be adjusted from time to time as
follows:


 


(a) Intentionally omitted.


 


(b) Voluntary Adjustment By Company.
 The Company may at any time during the term of this Warrant reduce the then current Exercise Price to any amount and for
any period of time deemed appropriate by the Board of Directors of the Company.


 


(c) Adjustment Upon Subdivision
or Combination of Common Stock.  If the Company at any time on or after the Effective Date subdivides (by any stock split,
stock dividend, recapitalization or otherwise) one or more classes of its outstanding shares of Common Stock into a greater number
of shares, the Exercise Price in effect immediately prior to such subdivision will be proportionately reduced and the number of
Warrant Shares will be proportionately increased.  If the Company at any time on or after the Effective Date combines (by
combination, reverse stock split or otherwise) one or more classes of its outstanding shares of Common Stock into a smaller number
of shares, the Exercise Price in effect immediately prior to such combination will be proportionately increased and the number
of Warrant Shares will be proportionately decreased.  Any adjustment under this Section 2(c) shall become effective
at the close of business on the date the subdivision or combination becomes effective.


 






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3. RIGHTS UPON DISTRIBUTION OF ASSETS. 
In addition to any adjustments pursuant to Section 2 above, if, on or after the Effective Date and on or prior to the Expiration
Date, the Company shall declare or make any dividend or other distribution of its assets (or rights to acquire its assets) to holders
of shares of Common Stock, by way of return of capital or otherwise (including, without limitation, any distribution of cash, stock
or other securities, property, options, evidence of indebtedness or any other assets by way of a dividend, spin off, reclassification,
corporate rearrangement, scheme of arrangement or other similar transaction) (a “Distribution”), at any time
after the issuance of this Warrant, then, in each such case, the Holder shall be entitled to participate in such Distribution to
the same extent that the Holder would have participated therein if the Holder had held the number of shares of Common Stock acquirable
upon complete exercise of this Warrant (without regard to any limitations or restrictions on exercise of this Warrant, including
without limitation, the Maximum Percentage) immediately before the date on which a record is taken for such Distribution, or, if
no such record is taken, the date as of which the record holders of shares of Common Stock are to be determined for the participation
in such Distribution (provided,  however, that to the extent that the Holder’s right to participate in
any such Distribution would result in the Holder and the other Attribution Parties exceeding the Maximum Percentage, then the Holder
shall not be entitled to participate in such Distribution to such extent (and shall not be entitled to beneficial ownership of
such shares of Common Stock as a result of such Distribution (and beneficial ownership) to such extent) and the portion of such
Distribution shall be held in abeyance for the benefit of the Holder until such time or times as its right thereto would not result
in the Holder and the other Attribution Parties exceeding the Maximum Percentage, at which time or times the Holder shall be granted
such Distribution (and any Distributions declared or made on such initial Distribution or on any subsequent Distribution held similarly
in abeyance) to the same extent as if there had been no such limitation).


 


4. FUNDAMENTAL TRANSACTIONS. 
The Company shall not enter into or be party to a Fundamental Transaction unless the Successor Entity assumes in writing all of
the obligations of the Company under this Warrant in accordance with the provisions of this Section 4(b), including agreements
to deliver to the Holder in exchange for this Warrant a security of the Successor Entity evidenced by a written instrument substantially
similar in form and substance to this Warrant, including, without limitation, which is exercisable for a corresponding number of
shares of capital stock equivalent to the shares of Common Stock acquirable and receivable upon exercise of this Warrant (without
regard to any limitations on the exercise of this Warrant) prior to such Fundamental Transaction, and with an exercise price which
applies the exercise price hereunder to such shares of capital stock (but taking into account the relative value of the shares
of Common Stock pursuant to such Fundamental Transaction and the value of such shares of capital stock, such adjustments to the
number of shares of capital stock and such exercise price being for the purpose of protecting the economic value of this Warrant
immediately prior to the consummation of such Fundamental Transaction). Upon the consummation of each Fundamental Transaction,
the Successor Entity shall succeed to, and be substituted for the Company (so that from and after the date of the applicable Fundamental
Transaction, the provisions of this Warrant and the other Transaction Documents referring to the “Company” shall refer
instead to the Successor Entity), and may exercise every right and power of the Company and shall assume all of the obligations
of the Company under this Warrant with the same effect as if such Successor Entity had been named as the Company herein. Upon consummation
of each Fundamental Transaction, the Successor Entity shall deliver to the Holder confirmation that there shall be issued upon
exercise of this Warrant at any time after the consummation of the applicable Fundamental Transaction, in lieu of the shares of
Common Stock (or other securities, cash, assets or other property (except such items still issuable under Sections 3 and 4(a) above,
which shall continue to be receivable thereafter)) issuable upon the exercise of this Warrant prior to the applicable Fundamental
Transaction, such shares of common stock (or its equivalent) of the Successor Entity (including its Parent Entity) which the Holder
would have been entitled to receive upon the happening of the applicable Fundamental Transaction had this Warrant been exercised
immediately prior to the applicable Fundamental Transaction (without regard to any limitations on the exercise of this Warrant),
as adjusted in accordance with the provisions of this Warrant. Notwithstanding the foregoing, and without limiting Section 1(f)
hereof, the Holder may elect, at its sole option, by delivery of written notice to the Company to waive this Section 4(b) to permit
the Fundamental Transaction without the assumption of this Warrant. In addition to and not in substitution for any other rights
hereunder, prior to the consummation of each Fundamental Transaction pursuant to which holders of shares of Common Stock are entitled
to receive securities or other assets with respect to or in exchange for shares of Common Stock (a “Corporate Event”),
the Company shall make appropriate provision to insure that the Holder will thereafter have the right to receive upon an exercise
of this Warrant at any time after the consummation of the applicable Fundamental Transaction but prior to the Expiration Date,
in lieu of the shares of the Common Stock (or other securities, cash, assets or other property (except such items still issuable
under Sections 3 and 4(a) above, which shall continue to be receivable thereafter)) issuable upon the exercise of the Warrant prior
to such Fundamental Transaction, such shares of stock, securities, cash, assets or any other property whatsoever (including warrants
or other purchase or subscription rights) (collectively, the “Corporate Event Consideration”) which the Holder would
have been entitled to receive upon the happening of the applicable Fundamental Transaction had this Warrant been exercised immediately
prior to the applicable Fundamental Transaction (without regard to any limitations on the exercise of this Warrant). The provision
made pursuant to the preceding sentence shall be in a form and substance reasonably satisfactory to the Holder. The provisions
of this Section 4(b) shall apply similarly and equally to successive Fundamental Transactions and Corporate Events. Notwithstanding
the foregoing, in the event of a Change of Control, at the request of the Holder delivered before the 30th day after such Change
of Control, the Company (or the Successor Entity) shall purchase this Warrant from the Holder by paying to the Holder, within five
(5) Business Days after such request (or, if later, on the effective date of the Change of Control), an amount equal to the Black
Scholes Value of the remaining unexercised portion of this Warrant on the effective date of such Change of Control, payable in
cash; provided, however, that, if the Change of Control is not within the Company's control, including not approved by the Company's
Board of Directors, Holder shall only be entitled to receive from the Company or any Successor Entity, as of the date of consummation
of such Change of Control, the same type or form of consideration (and in the same proportion), at the Black Scholes Value of the
unexercised portion of this Warrant, that is being offered and paid to the holders of Common Stock of the Company in connection
with the Change of Control, whether that consideration be in the form of cash, stock or any combination thereof, or whether the
holders of Common Stock are given the choice to receive from among alternative forms of consideration in connection with the Change
of Control.


 






    	 	- 7 -	 



     


    

 


5. NONCIRCUMVENTION.  The
Company hereby covenants and agrees that the Company will not, by amendment of its Certificate of Incorporation or Bylaws, or through
any reorganization, transfer of assets, consolidation, merger, scheme of arrangement, dissolution, issuance or sale of securities,
or any other voluntary action, avoid or seek to avoid the observance or performance of any of the terms of this Warrant, and will
at all times in good faith carry out all of the provisions of this Warrant and take all action as may be required to protect the
rights of the Holder.  Without limiting the generality of the foregoing, the Company (i) shall not increase the par value
of any shares of Common Stock receivable upon the exercise of this Warrant above the Exercise Price then in effect, (ii) shall
take all such actions as may be necessary or appropriate in order that the Company may validly and legally issue fully paid and
nonassessable shares of Common Stock upon the exercise of this Warrant, and (iii) shall, so long as any portion of the Warrant
remains outstanding, take all action necessary to reserve and keep available out of its authorized and unissued shares of Common
Stock, solely for the purpose of effecting the exercise of the Warrant, the number of shares of Common Stock as shall from time
to time be necessary to effect the exercise of the portion of the Warrant then outstanding (without regard to any limitations on
exercise).


 


6. WARRANT HOLDER NOT DEEMED A STOCKHOLDER. 
Except as otherwise specifically provided herein, the Holder, solely in such Person’s capacity as a holder of this Warrant,
shall not be entitled to vote or receive dividends or be deemed the holder of capital stock of the Company for any purpose, nor
shall anything contained in this Warrant be construed to confer upon the Holder, solely in such Person’s capacity as the
Holder of this Warrant, any of  the rights of a stockholder of the Company or any right to vote, give or withhold consent
to any corporate action (whether any reorganization, issue of stock, reclassification of stock, consolidation, merger, conveyance
or otherwise), receive notice of meetings, receive dividends or subscription rights, or otherwise, prior to the issuance to the
Holder of the Warrant Shares which such Person is then entitled to receive upon the due exercise of this Warrant.  In addition,
nothing contained in this Warrant shall be construed as imposing any liabilities on the Holder to purchase any securities (upon
exercise of this Warrant or otherwise) or as a stockholder of the Company, whether such liabilities are asserted by the Company
or by creditors of the Company.  Notwithstanding this Section 6, the Company shall provide the Holder with copies of
the same notices and other information given to the stockholders of the Company generally, contemporaneously with the giving thereof
to the stockholders.


 






    	 	- 8 -	 



     


    

 


7. REISSUANCE OF WARRANT.


 


(a) Transfer of Warrant. 
If this Warrant is to be transferred, the Holder shall surrender this Warrant to the Company, whereupon the Company will forthwith
issue and deliver upon the order of the Holder a new Warrant (in accordance with Section 7(d)), registered as the Holder may request,
representing the right to purchase the number of Warrant Shares being transferred by the Holder and, if less than the total number
of Warrant Shares then underlying this Warrant is being transferred, a new Warrant (in accordance with Section 7(d)) to the Holder
representing the right to purchase the number of Warrant Shares not being transferred.


 


(b) Lost, Stolen or Mutilated Warrant. 
Upon receipt by the Company of evidence reasonably satisfactory to the Company of the loss, theft, destruction or mutilation of
this Warrant, and, in the case of loss, theft or destruction, of any indemnification undertaking by the Holder to the Company in
customary form (but without the obligation to post a bond) and, in the case of mutilation, upon surrender and cancellation of this
Warrant, the Company shall execute and deliver to the Holder a new Warrant (in accordance with Section 7(d)) representing
the right to purchase the Warrant Shares then underlying this Warrant.


 


(c) Exchangeable for Multiple Warrants. 
This Warrant is exchangeable, upon the surrender hereof by the Holder at the principal office of the Company, for a new Warrant
or Warrants (in accordance with Section 7(d)) representing in the aggregate the right to purchase the number of Warrant Shares
then underlying this Warrant, and each such new Warrant will represent the right to purchase such portion of such Warrant Shares
as is designated by the Holder at the time of such surrender, provided, however, that the Company shall not be required to issue
Warrants for fractional shares of Common Stock hereunder.


 


(d) Issuance of New Warrants. 
Whenever the Company is required to issue a new Warrant pursuant to the terms of this Warrant, such new Warrant (i) shall
be of like tenor with this Warrant, (ii) shall represent, as indicated on the face of such new Warrant, the right to
purchase the Warrant Shares then underlying this Warrant (or in the case of a new Warrant being issued pursuant to Section 7(a) or
Section 7(c), the Warrant Shares designated by the Holder which, when added to the number of shares of Common Stock underlying
the other new Warrants issued in connection with such issuance, does not exceed the number of Warrant Shares then underlying this
Warrant), (iii) shall have an issuance date, as indicated on the face of such new Warrant which is the same as the Issuance
Date, and (iv) shall have the same rights and conditions as this Warrant.


 






    	 	- 9 -	 



     


    

 


8. NOTICES.  Whenever notice
is required to be given under this Warrant, including, without limitation, an Exercise Notice, unless otherwise provided herein,
such notice shall be given in writing, (i) if delivered (a) from within the domestic United States, by first-class registered
or certified airmail, or nationally recognized overnight express courier, postage prepaid, electronic mail or by facsimile or (b) from
outside the United States, by International Federal Express, electronic mail or facsimile, and (ii) will be deemed given (A) if
delivered by first-class registered or certified mail domestic, three (3) Trading Days after so mailed, (B) if delivered
by nationally recognized overnight carrier, one (1) Trading Day after so mailed, (C) if delivered by International Federal
Express, two  (2) Trading Days after so mailed and (D) on the date of transmission, if delivered by electronic mail
to each of the email addresses specified in this Section 8 prior to 5:00 p.m. (New York time) on a Trading Day, and (E) the
next Trading Day after the date of transmission, if delivered by electronic mail to each of the email addresses specified in this
Section 8 on a day that is not a Trading Day or later than 5:00 p.m. (New York time) on any Trading Day, and will be
delivered and addressed as follows:


 


(i) if to the Company, to:


Moleculin Biotech, Inc.

5300 Memorial Drive, Suite 950

Houston, TX 77007

Telephone: (713) 300-5160


Attention: Jonathan P. Foster, Chief Financial
Officer


Email: jfoster@moleculin.com


 


(ii) if to the Holder, at such address or
other contact information delivered by the Holder to Company or as is on the books and records of the Company.


 


The Company shall provide the Holder with prompt written notice
of all actions taken pursuant to this Warrant, including in reasonable detail a description of such action and the reason therefor. 
Without limiting the generality of the foregoing, the Company will give written notice to the Holder (i) reasonably promptly
upon any adjustment of the Exercise Price, setting forth in reasonable detail, and certifying, the calculation of such adjustment
and (ii) at least ten (10) days prior to the date on which the Company closes its books or takes a record (A) with
respect to any dividend or distribution upon the shares of Common Stock, (B) with respect to any grants, issuances or sales
of any Options, Convertible Securities or rights to purchase stock, warrants, securities or other property pro rata to holders
of any class of shares of Common Stock or (C) for determining rights to vote with respect to any Fundamental Transaction,
dissolution or liquidation; provided in each case that such information shall be made known to the public prior
to or in conjunction with such notice being provided to the Holder.  It is expressly understood and agreed that the time of
exercise specified by the Holder in each Exercise Notice shall be definitive and may not be disputed or challenged by the Company.


 


9. AMENDMENT AND WAIVER. 
Except as otherwise provided herein, the provisions of this Warrant may be amended or waived and the Company may take any action
herein prohibited, or omit to perform any act herein required to be performed by it, only if the Company has obtained the written
consent of the Holder.


 






    	 	- 10 -	 



     


    

 


10. GOVERNING LAW; JURISDICTION; JURY
TRIAL.  This Warrant shall be governed by and construed and enforced in accordance with, and all questions concerning
the construction, validity, interpretation and performance of this Warrant shall be governed by, the internal laws of the State
of New York, without giving effect to any choice of law or conflict of law provision or rule (whether of the State of New
York or any other jurisdictions) that would cause the application of the laws of any jurisdictions other than the State of New
York. The Company hereby irrevocably submits to the exclusive jurisdiction of the state and federal courts sitting in The City
of New York, Borough of Manhattan, for the adjudication of any dispute hereunder or in connection herewith or with any transaction
contemplated hereby or discussed herein, and hereby irrevocably waives, and agrees not to assert in any suit, action or proceeding,
any claim that it is not personally subject to the jurisdiction of any such court, that such suit, action or proceeding is brought
in an inconvenient forum or that the venue of such suit, action or proceeding is improper.  The Company hereby irrevocably
waives personal service of process and consents to process being served in any such suit, action or proceeding by mailing a copy
thereof to the Company at the address set forth in Section 8(i) above or such other address as the Company subsequently
delivers to the Holder and agrees that such service shall constitute good and sufficient service of process and notice thereof.
Nothing contained herein shall be deemed to limit in any way any right to serve process in any manner permitted by law.  Nothing
contained herein shall be deemed or operate to preclude the Holder from bringing suit or taking other legal action against the
Company in any other jurisdiction to collect on the Company’s obligations to the Holder, to realize on any collateral or
any other security for such obligations, or to enforce a judgment or other court ruling in favor of the Holder.  If either
party shall commence an action, suit or proceeding to enforce any provisions of this Warrant, the prevailing party in such action,
suit or proceeding shall be reimbursed by the other party for their reasonable attorneys’ fees and other costs and expenses
incurred with the investigation, preparation and prosecution of such action or proceeding.   THE COMPANY HEREBY IRREVOCABLY
WAIVES ANY RIGHT IT MAY HAVE, AND AGREES NOT TO REQUEST, A JURY TRIAL FOR THE ADJUDICATION OF ANY DISPUTE HEREUNDER OR IN
CONNECTION WITH OR ARISING OUT OF THIS WARRANT OR ANY TRANSACTION CONTEMPLATED HEREBY.


 


11. DISPUTE RESOLUTION. 
In the case of a dispute as to the determination of the Exercise Price or the arithmetic calculation of the Warrant Shares, the
Company shall submit the disputed determinations or arithmetic calculations via facsimile or electronic mail within two (2) Trading
Days of receipt of the Exercise Notice or other event giving rise to such dispute, as the case may be, to the Holder.  If
the Holder and the Company are unable to agree upon such determination or calculation of the Exercise Price or the Warrant Shares
within five (5) Trading Days of such disputed determination or arithmetic calculation being submitted to the Holder, then
the Company shall, within two (2) Trading Days submit via facsimile or electronic mail (a) the disputed determination
of the Exercise Price to an independent, reputable investment bank selected by the Company and approved by the Holder  or
(b) the disputed arithmetic calculation of the Warrant Shares to the Company’s independent, outside accountant. 
The Company shall cause the investment bank or the accountant, as the case may be, to perform the determinations or calculations
and notify the Company and the Holder of the results no later than ten (10) Trading Days from the time it receives the disputed
determinations or calculations.  Such investment bank’s or accountant’s determination or calculation, as the case
may be, shall be binding upon all parties absent demonstrable error. The expenses of the investment bank and accountant will be
borne by the Company unless the investment bank or accountant determines that the determination of the Exercise Price or the arithmetic
calculation of the Warrant Shares by the Company was correct, in which case the expenses of the investment bank and accountant
will be borne by the Holder.


 






    	 	- 11 -	 



     


    

 


12. REMEDIES, OTHER OBLIGATIONS, BREACHES
AND INJUNCTIVE RELIEF.  The remedies provided in this Warrant shall be cumulative and in addition to all other remedies
available under this Warrant, at law or in equity (including a decree of specific performance and/or other injunctive relief),
and nothing herein shall limit the right of the Holder to pursue actual damages for any failure by the Company to comply with the
terms of this Warrant.  The Company acknowledges that a breach by it of its obligations hereunder will cause irreparable harm
to the Holder and that the remedy at law for any such breach may be inadequate.  The Company therefore agrees that, in the
event of any such breach or threatened breach, the holder of this Warrant shall be entitled, in addition to all other available
remedies, to seek an injunction restraining any breach, without the necessity of showing economic loss and without any bond or
other security being required. Notwithstanding the foregoing or anything else herein to the contrary, but without limiting the
Holder’s rights to cashless exercise under Section 1(d) or the right to cash payments pursuant to Section 1(c) if the Company
is for any reason unable to issue and deliver Warrant Shares upon exercise of this Warrant as required pursuant to the terms hereof,
the Company shall have no obligation to pay to the Holder any cash or other consideration or otherwise “net cash settle”
this Warrant.


 


13. TRANSFER.  Subject to
applicable laws and restrictions set forth in this paragraph, this Warrant may be offered for sale, sold, transferred or assigned
without the consent of the Company.  The Holder agrees that, pursuant to the Lock-Up Period (as defined below) contained in
Rule 5110(g)(1) of the Financial Industry Regulatory Authority, Inc. (“FINRA”), it will not (a) sell,
transfer, assign, pledge, hypothecate or otherwise transfer this Warrant (including any Warrant Shares issued or issuable hereunder)
other than to a bona fide officer or partner of the Holder or any selected dealer in connection with the offering contemplated
by the Underwriting Agreement, in each case in accordance with FINRA Conduct Rule 5110(g)(1), or (b) cause this Warrant
or any Warrant Shares issued or issuable hereunder to be the subject of any hedging, short sale, derivative, put or call transaction
that would result in the effective economic disposition of this Warrant or any Warrant Shares issued or issuable hereunder, except
as provided for in FINRA Rule 5110(g)(2).  As used herein, the term “Lock-Up Period” means the period beginning
on the Effective Date and ending on the one hundred eightieth day anniversary of the Effective Date.


 


14. SEVERABILITY; CONSTRUCTION; HEADINGS. 
If any provision of this Warrant is prohibited by law or otherwise determined to be invalid or unenforceable by a court of competent
jurisdiction, the provision that would otherwise be prohibited, invalid or unenforceable shall be deemed amended to apply to the
broadest extent that it would be valid and enforceable, and the invalidity or unenforceability of such provision shall not affect
the validity of the remaining provisions of this Warrant so long as this Warrant as so modified continues to express, without material
change, the original intentions of the parties as to the subject matter hereof and the prohibited nature, invalidity or unenforceability
of the provision(s) in question does not substantially impair the respective expectations or reciprocal obligations of the
parties or the practical realization of the benefits that would otherwise be conferred upon the parties.  The parties will
endeavor in good faith negotiations to replace the prohibited, invalid or unenforceable provision(s) with a valid provision(s),
the effect of which comes as close as possible to that of the prohibited, invalid or unenforceable provision(s).  This Warrant
shall be deemed to be jointly drafted by the Company and the Holder and shall not be construed against any Person as the drafter
hereof.  The headings of this Warrant are for convenience of reference and shall not form part of, or affect the interpretation
of, this Warrant.


 


15. DISCLOSURE.  Upon receipt
or delivery by the Company of any notice in accordance with the terms of this Warrant, unless the Company has in good faith determined
that the matters relating to such notice do not constitute material, nonpublic information relating to the Company or its subsidiaries,
the Company shall contemporaneously with any such receipt or delivery publicly disclose such material, nonpublic information on
a Current Report on Form 8-K or otherwise.  In the event that the Company believes that a notice contains material, nonpublic
information relating to the Company or its subsidiaries, the Company so shall indicate to such Holder contemporaneously with delivery
of such notice, and in the absence of any such indication, the Holder shall be allowed to presume that all matters relating to
such notice do not constitute material, nonpublic information relating to the Company or its subsidiaries.


 






    	 	- 12 -	 



     


    

 


16. CERTAIN DEFINITIONS. 
For purposes of this Warrant, the following terms shall have the following meanings:


 


(a) “Affiliate”
means, with respect to any Person, any other Person that directly or indirectly controls, is controlled by, or is under common
control with, such Person, it being understood for purposes of this definition that “control” of a Person means the
power directly or indirectly either to vote 10% or more of the stock having ordinary voting power for the election of directors
of such Person or direct or cause the direction of the management and policies of such Person whether by contract or otherwise.


 


(b) “Attribution Parties”
means, collectively, the following Persons and entities: (i) any investment vehicle, including, any funds, feeder funds or
managed accounts, currently, or from time to time after the Effective Date, directly or indirectly managed or advised by the Holder’s
investment manager or any of its Affiliates or principals, (ii) any direct or indirect Affiliates of the Holder or any of
the foregoing, (iii) any Person acting or who could be deemed to be acting as a Group together with the Holder or any of the
foregoing and (iv) any other Persons whose beneficial ownership of the Company’s Common Stock would or could be aggregated
with the Holder’s and the other Attribution Parties for purposes of Section 13(d) of the 1934 Act.  For clarity,
the purpose of the foregoing is to subject collectively the Holder and all other Attribution Parties to the Maximum Percentage.


 


(c) Bid Price”  means,
for any security as of the particular time of determination, the bid price for such security on the Principal Market as reported
by Bloomberg as of such time of determination, or, if the Principal Market is not the principal securities exchange or trading
market for such security, the bid price of such security on the principal securities exchange or trading market where such security
is listed or traded as reported by Bloomberg as of such time of determination, or if the foregoing does not apply, the bid price
of such security in the over-the-counter market on the electronic bulletin board for such security as reported by Bloomberg as
of such time of determination, or, if no bid price is reported for such security by Bloomberg as of such time of determination,
the average of the bid prices of any market makers for such security as reported in the "pink sheets" by OTC Markets
Group Inc. (formerly Pink Sheets LLC) as of such time of determination.  If the Bid Price cannot be calculated for a
security as of the particular time of determination on any of the foregoing bases, the Bid Price of such security as of such time
of determination shall be the fair market value as mutually determined by the Company and the Holder.  If the Company
and the Holder are unable to agree upon the fair market value of such security, then such dispute shall be resolved in accordance
with the procedures in Section 11. All such determinations shall be appropriately adjusted for any stock dividend, stock split,
stock combination or other similar transaction during such period. 


 


(d)   “Black Scholes
Value” means the value of this Warrant based on the Black-Scholes Option Pricing Model obtained from the "OV"
function on Bloomberg determined as of the day immediately following the first public announcement of the applicable Change of
Control, or, if the Change of Control is not publicly announced, the date the Change of Control is consummated, for pricing purposes
and reflecting (i) a risk-free interest rate corresponding to the U.S. Treasury rate for a period equal to the remaining term of
this Warrant as of such date of request, (ii) an expected volatility equal to 100% (iii) the underlying price per share used in
such calculation shall be the greater of (a) the highest Weighted Average Price during the five (5) Trading Days prior to the closing
of the Change of Control and (b) the sum of the price per share being offered in cash, if any, plus the value of any non-cash consideration,
if any, being offered in such Change of Control, (iv) a zero cost of borrow and (v) a 360 day annualization factor.


 


(e) “Bloomberg”
means Bloomberg Financial Markets.


 






    	 	- 13 -	 



     


    

 


(f) “Business Day”
means any day other than Saturday, Sunday or other day on which commercial banks in The City of New York are authorized or required
by law to remain closed.


 


(g) “Change of Control”
means any Fundamental Transaction other than (i) any reorganization, recapitalization or reclassification of the Common Stock in
which holders of the Company’s voting power immediately prior to such reorganization, recapitalization or reclassification
continue after such reorganization, recapitalization or reclassification to hold publicly traded securities and, directly or indirectly,
are, in all material respect, the holders of the voting power of the surviving entity (or entities with the authority or voting
power to elect the members of the board of directors (or their equivalent if other than a corporation) of such entity or entities)
after such reorganization, recapitalization or reclassification, (ii) pursuant to a migratory merger effected solely for the purpose
of changing the jurisdiction of incorporation of the Company or (iii) a merger in connection with a bona fide acquisition by the
Company of any Person in which (x) the gross consideration paid, directly or indirectly, by the Company in such acquisition is
not greater than 20% of the Company’s market capitalization as calculated on the date of the consummation of such merger
and (y) such merger does not contemplate a change to the identity of a majority of the board of directors of the Company. Notwithstanding
anything herein to the contrary, any transaction or series of transaction that, directly or indirectly, results in the Company
or the Successor Entity not having Common Stock or common stock, as applicable, registered under the 1934 Act and listed on an
Eligible Market shall be deemed a Change of Control.


 


(h)    “Closing
Sale Price” means, for any security as of any date, the last closing trade price for such security on the Principal Market,
as reported by Bloomberg, or, if the Principal Market begins to operate on an extended hours basis and does not designate the closing
trade price then the last trade price of such security prior to 4:00:00 p.m., New York time, as reported by Bloomberg, or, if the
Principal Market is not the principal securities exchange or trading market for such security, the last trade price of such
security on the principal securities exchange or trading market where such security is listed or traded as reported by Bloomberg,
or if the foregoing do not apply, the last trade price of such security in the over-the-counter market on the electronic bulletin
board for such security as reported by Bloomberg, or, if no last trade price is reported for such security by Bloomberg, the average
of the ask prices of any market makers for such security as reported in the OTC Link or "pink sheets" by OTC Markets
Group Inc. (formerly Pink OTC Markets Inc.).  If the Closing Sale Price cannot be calculated for a security on a particular
date on any of the foregoing bases, the Closing Sale Price of such security on such date shall be the fair market value as mutually
determined by the Company and the Holder.  If the Company and the Holder are unable to agree upon the fair market value
of such security, then such dispute shall be resolved pursuant to Section 11.  All such determinations to be appropriately
adjusted for any stock dividend, stock split, stock combination, reclassification or other similar transaction during the applicable
calculation period.


  


(i) “Common Stock”
means (i) the Company’s Common Stock, par value $0.001 per share, and (ii) any capital stock into which such Common
Stock shall have been changed or any capital stock resulting from a reclassification of such Common Stock.


 


(j) “Convertible Securities”
means any stock or securities (other than Options) directly or indirectly convertible into or exercisable or exchangeable for shares
of Common Stock.


 


(k) “Eligible Market”
means The NASDAQ Capital Market, the NYSE American LLC, The NASDAQ Global Select Market, The NASDAQ Global Market or The New York
Stock Exchange, Inc.


 






    	 	- 14 -	 



     


    

 


(l) “Expiration Date”
means the date sixty (60) months after the Initial Exercisability Date or, if such date falls on a day other than a Trading
Day, the next day that is a Trading Day, which date may not be more than five years from the effective date of the offering pursuant
to FINRA Rule 5110(f)(2)(G)(i).


 


(m) “Fundamental Transaction”
means (A) that the Company shall, directly or indirectly, including through subsidiaries, Affiliates or otherwise, in one
or more related transactions, (i) consolidate or merge with or into (whether or not the Company is the surviving corporation)
another Subject Entity, or (ii) sell, assign, transfer, convey or otherwise dispose of all or substantially all of the properties
or assets of the Company or any of its “significant subsidiaries” (as defined in Rule 1-02 of Regulation S-X)
to one or more Subject Entities, or (iii) make, or allow one or more Subject Entities to make, or allow the Company to be
subject to or have its shares of Common Stock be subject to or party to one or more Subject Entities making, a purchase, tender
or exchange offer that is accepted by the holders of at least either (x) 50% of the outstanding shares of Common Stock, (y) 50%
of the outstanding shares of Common Stock calculated as if any shares of Common Stock held by all Subject Entities making or party
to, or Affiliated with any Subject Entities making or party to, such purchase, tender or exchange offer were not outstanding; or
(z) such number of shares of Common Stock such that all Subject Entities making or party to, or Affiliated with any Subject
Entity making or party to, such purchase, tender or exchange offer, become collectively the beneficial owners (as defined
in Rule 13d-3 under the 1934 Act) of at least 50% of the outstanding shares of Common Stock, or (iv) consummate a stock
purchase agreement or other business combination (including, without limitation, a reorganization, recapitalization, spin-off or
scheme of arrangement) with one or more Subject Entities whereby all such Subject Entities, individually or in the aggregate, acquire,
either (x) at least 50% of the outstanding shares of Common Stock, (y) at least 50% of the outstanding shares of Common
Stock calculated as if any shares of Common Stock held by all the Subject Entities making or party to, or Affiliated with any Subject
Entity making or party to, such stock purchase agreement or other business combination were not outstanding; or (z) such number
of shares of Common Stock such that the Subject Entities become collectively the beneficial owners (as defined in Rule 13d-3
under the 1934 Act) of at least 50% of the outstanding shares of Common Stock, or (v) reorganize, recapitalize or reclassify
its shares of Common Stock (other than a reorganization, recapitalization or reclassification subject to Section 2(c)), (B) that
the Company shall, directly or indirectly, including through subsidiaries, Affiliates or otherwise, in one or more related transactions,
allow any Subject Entity individually or the Subject Entities in the aggregate to be or become the “beneficial owner”
(as defined in Rule 13d-3 under the 1934 Act), directly or indirectly, whether through acquisition, purchase, assignment,
conveyance, tender, tender offer, exchange, reduction in outstanding shares of Common Stock, merger, consolidation, business combination,
reorganization, recapitalization, spin-off, scheme of arrangement, reorganization, recapitalization or reclassification or otherwise
in any manner whatsoever, of either (x) at least 50% of the aggregate ordinary voting power represented by issued and outstanding
shares of Common Stock, (y) at least 50% of the aggregate ordinary voting power represented by issued and outstanding shares
of Common Stock not held by all such Subject Entities as of the Effective Date calculated as if any shares of Common Stock held
by all such Subject Entities were not outstanding, or (z) a percentage of the aggregate ordinary voting power represented
by issued and outstanding shares of Common Stock or other equity securities of the Company sufficient to allow such Subject Entities
to effect a statutory short form merger or other transaction requiring other stockholders of the Company to surrender their Common
Stock without approval of the stockholders of the Company or (C) directly or indirectly, including through subsidiaries, Affiliates
or otherwise, in one or more related transactions, the issuance of or the entering into any other instrument or transaction structured
in a manner to circumvent, or that circumvents, the intent of this definition in which case this definition shall be construed
and implemented in a manner otherwise than in strict conformity with the terms of this definition to the extent necessary to correct
this definition or any portion of this definition which may be defective or inconsistent with the intended treatment of such instrument
or transaction.


 






    	 	- 15 -	 



     


    

 


(n) “Group” means
a “group” as that term is used in Section 13(d) of the 1934 Act and as defined in Rule 13d-5 thereunder.


 


(o) “Options” means
any rights, warrants or options to subscribe for or purchase shares of Common Stock or Convertible Securities.


 


(p) “Parent Entity”
of a Person means an entity that, directly or indirectly, controls the applicable Person, including such entity whose common stock
or equivalent equity security is quoted or listed on an Eligible Market (or, if so elected by the Holder, any other market, exchange
or quotation system), or, if there is more than one such Person or such entity, the Person or such entity designated by the Holder
or in the absence of  such designation, such Person or entity with the largest public market capitalization as of the
date of consummation of the Fundamental Transaction.


 


(q) “Person” means
an individual, a limited liability company, a partnership, a joint venture, a corporation, a trust, an unincorporated organization,
any other entity and a government or any department or agency thereof.


 


(r) “Principal Market”
means The NASDAQ Capital Market.


 


(s) “Standard Settlement Period”
means the standard settlement period, expressed in a number of Trading Days, for the Company’s primary trading market or
quotation system with respect to the Common Stock that is in effect on the date of receipt of an applicable Exercise Notice.


 


(t) “Subject Entity”
means any Person, Persons or Group or any Affiliate or associate of any such Person, Persons or Group.


 


(u) “Successor Entity”
means one or more Person or Persons (or, if so elected by the Holder, the Company or Parent Entity) formed by, resulting from or
surviving any Fundamental Transaction or one or more Person or Persons (or, if so elected by the Holder, the Company or the Parent
Entity) with which such Fundamental Transaction shall have been entered into.


 


(v) “Trading Day”
means any day on which the Common Stock is traded on the Principal Market.


 






    	 	- 16 -	 



     


    

 


(w) "Weighted Average Price"
means, for any security as of any date, the dollar volume-weighted average price for such security on the Principal Market during
the period beginning at 9:30:01 a.m., New York time (or such other time as the Principal Market publicly announces is the official
open of trading), and ending at 4:00:00 p.m., New York time (or such other time as the Principal Market publicly announces is the
official close of trading), as reported by Bloomberg through its "Volume at Price" function or, if the foregoing does
not apply, the dollar volume-weighted average price of such security in the over-the-counter market on the electronic bulletin
board for such security during the period beginning at 9:30:01 a.m., New York time (or such other time as such market publicly
announces is the official open of trading), and ending at 4:00:00 p.m., New York time (or such other time as such market publicly
announces is the official close of trading), as reported by Bloomberg, or, if no dollar volume-weighted average price is reported
for such security by Bloomberg for such hours, the average of the highest Closing Bid Price and the lowest closing ask price of
any of the market makers for such security as reported in the OTC Link or "pink sheets" by OTC Markets Group Inc. (formerly
Pink OTC Markets Inc.). If the Weighted Average Price cannot be calculated for a security on a particular date on any of the foregoing
bases, the Weighted Average Price of such security on such date shall be the fair market value as mutually determined by the Company
and the Holder. If the Company and the Holder are unable to agree upon the fair market value of such security, then such dispute
shall be resolved pursuant to Section 11 with the term "Weighted Average Price" being substituted for the term "Exercise
Price." All such determinations shall be appropriately adjusted for any stock dividend, stock split, stock combination, reclassification
or other similar transaction during the applicable calculation period.


 


[Signature Page Follows]


 


 




    	 	- 17 -	 



     


    

 





IN WITNESS WHEREOF, the Company
has caused this Underwriter Warrant to Purchase Common Stock to be duly executed as of the Issuance Date set out above.


 


 


	 	MOLCULIN BIOTECH, INC.
	 	 
	 	 
	 	By:___________________________
	 	Name:
	 	Title:


 


 


 


 


 


 




    	 	- 18 -	 



     


    

 





EXHIBIT A


 


EXERCISE NOTICE


 


TO BE EXECUTED BY THE REGISTERED HOLDER
TO EXERCISE THIS


UNDERWRITER WARRANT TO PURCHASE COMMON
STOCK


 


MOLECULIN BIOTECH, INC.


 


The undersigned holder hereby exercises
the right to purchase                   shares
of Common Stock (“Warrant Shares”) of Moleculin Biotech, Inc., a company organized under the laws of Delaware
(the “Company”), evidenced by the attached Underwriter Warrant to Purchase Common Stock (the “Warrant”). 
Capitalized terms used herein and not otherwise defined shall have the respective meanings set forth in the Warrant.


 


1.  Form of Exercise Price. 
The Holder intends that payment of the Exercise Price shall be made as:


 


a “Cash Exercise” with
respect to                   Warrant Shares;
and/or


 


a  “Cashless Exercise” with
respect to                 Warrant Shares.


 


2.  Payment of Exercise Price. 
In the event that the holder has elected a Cash Exercise with respect to some or all of the Warrant Shares to be issued pursuant
hereto, the holder shall pay the Aggregate Exercise Price in the sum of $                   
to the Company in accordance with the terms of the Warrant.


 


3.  Delivery of Warrant Shares. 
The Company shall deliver to the holder            Warrant Shares in accordance
with the terms of the Warrant.


 


4. Representations and Warranties. By its
delivery of this Exercise Notice, the undersigned represents and warrants to the Company that in giving effect to the exercise
evidenced hereby the Holder will not beneficially own in excess of the number of shares of Common Stock (determined in accordance
with Section 13(d) of the Securities Exchange Act of 1934, as amended) permitted to be owned under Section 1(f) of
this Warrant to which this notice relates.


 


Date:                
  ,


 


	 	 
	Name of Registered Holder
	 
	 
	By:	 	 
	 	Name:	 
	 	Title:	 


 


 



    	 	- 19 -	 



     


    




 


ACKNOWLEDGMENT


 


The Company hereby acknowledges this Exercise
Notice and hereby directs VStock Transfer, LLC to issue the above indicated number of shares of Common Stock on or prior to the
applicable Share Delivery Date.


 


	 	MOLECULIN BIOTECH, INC.
	 	 
	 	 
	 	 
	 	By:________________________________
	 	Name:
	 	Title:


 


 


 


 


 








    	 	- 20 -