Document:

LOCK-UP
AGREEMENT

 

September
7, 2017

 

Ladies
and Gentlemen:

 

This
Agreement is being executed in connection with that certain Amended and Restated Retention Agreement by and between Marathon Patent
Group, Inc. (the “Company”) and Doug Croxall (the “Shareholder”)( and such agreement as may be amended
from time to time, the “Agreement” and the transactions contemplated thereby). The undersigned is an officer, director,
consultant or a beneficial owner of shares of capital stock, or securities convertible into or exercisable or exchangeable for
the capital stock of the Company to be issued to Shareholder pursuant to the Agreement (each, a “Company Security”)
For the absence of doubt, Company Security for purposes of this Agreement shall mean only those Company Shares issued or issuable
under the Agreement.

 

NOW,
THEREFORE, in consideration of the foregoing promises and the mutual covenants contained herein, the receipt and sufficiency of
which are hereby acknowledged, the parties hereto agree as follows:

 

1.
Agreement Amendment.

 

(A)
Section 2(b)(iv)(1) and (2) of the Agreement are hereby deleted and replaced in their entirety as follows with effect from the
date of the Agreement (other than as set forth herein the terms and conditions of the Agreement shall remain in full force and
effect):

 

(iv)
Equity Awards.

 

(1)
Upon the earlier of (A) December 31, 2017 and (B) the date of shareholder approval of the Company’s 2017 Equity Incentive
Plan (the “Incentive Plan”) the Company shall issue to Employee a total of 2,800,000 shares of restricted common stock
of the Company and issued to the Chief Financial Officer 200,000 shares of restricted common stock (the “Share Awards”)
pursuant to the Incentive Plan (the “Issuance Date”).

 

(2)
The Share Awards shall vest as follows:

 

16.67%
shall vest on the 30th day following the original date of issuance of the Share Awards and an additional 16.67% on each succeeding
monthly (30 day) period following the date of the initial vesting until fully vested.

 

Until
vested Employee may not sell, transfer, pledge or assign the Share Award. In the event of a material breach of this Agreement
by Employee all unvested Share Awards to Employee shall be immediately cancelled. The Parties acknowledge and agree that the Company
shall not file any registration statement with respect to the Share Awards (including without limitation, any registration statement
on Form S-8 for the Plan if it includes the Share Awards) without the written consent of investors as provided in the UPA.

 

    	 	 

    	 

    

 

(B)
Section 2(b)(iv)(3) is hereby amended by ending such subparagraph after the second sentence thereof, and renumbering the remaining
subparagraphs of Section 2(b) commencing with the subparagraph entitled “Waiver of Right to Severance Compensation”
which shall be renumbered as subsection 2(b)(v), and increasing by one numeral each subsequent subparagraph of such subsection
2(b) thereafter.

 

2. Lockup.
For good and valuable consideration, the receipt and sufficiency of which are hereby acknowledged, the undersigned agrees,
for the benefit of parties to the UPA (as defined in the Agreement) who shall be deemed third party beneficiaries of
such agreement that, during the period beginning on the date of closing of a Qualifying Transaction (as defined in the
Agreement) and ending on the six (6) months anniversary thereof (the “Lockup Period”), the undersigned will not
directly or indirectly, (i) offer, sell, offer to sell, contract to sell, hedge, pledge, sell any option or contract to
purchase, purchase any option or contract to sell, grant any option, right or warrant to purchase or sell (or announce any
offer, sale, offer of sale, contract of sale, hedge, pledge, sale of any option or contract to purchase, purchase of any
option or contract of sale, grant of any option, right or warrant to purchase or other sale or disposition), or otherwise
transfer or dispose of (or enter into any transaction or device that is designed to, or could be expected to, result in the
disposition by any person at any time in the future), any Share Awards, beneficially owned, within the meaning of Rule 13d-3
under the Securities Exchange Act of 1934, as amended (the “Exchange Act”), by the undersigned on the date
hereof or hereafter acquired or (ii) enter into any swap or other agreement or any transaction that transfers, in whole or in
part, directly or indirectly, the economic consequence of ownership of any Share Awards, whether or not any such swap or
transaction described in clause (i) or (ii) above is to be settled by delivery of any Parent Security.

 

3.
Permitted Transfer. Notwithstanding the foregoing, the undersigned (and any transferee of the undersigned) may transfer
any Share Awards: (i) as a bona fide gift or gifts, provided that prior to such transfer the donee or donees thereof agree in
writing to be bound by the restrictions set forth herein, (ii) to any trust, partnership, corporation or other entity formed for
the direct or indirect benefit of the undersigned or the immediate family of the undersigned, provided that prior to such transfer
a duly authorized officer, representative or trustee of such transferee agrees in writing to be bound by the restrictions set
forth herein, and provided further that any such transfer shall not involve a disposition for value, (iii) to non-profit organizations
qualified as charitable organizations under Section 501(c)(3) of the Internal Revenue Code of 1986, as amended, provided that
prior to such transfer a duly authorized officer, representative or trustee of such transferee agrees in writing to be bound by
the restrictions set forth herein; (iv) if such transfer occurs by operation of law, such as rules of descent and distribution,
statutes governing the effects of a merger or a qualified domestic order, provided that prior to such transfer the transferee
executes an agreement stating that the transferee is receiving and holding any Share Awards subject to the provisions of this
Agreement; or (v) up to 16.67% per month beginning on the 30th day following the closing of the Qualifying Transaction and an
additional 16.67% on each succeeding monthly (30 day) period following the date of the initial 30 day period. For purposes hereof,
“immediate family” shall mean any relationship by blood, marriage or adoption, not more remote than first cousin.

 

    	 	 

    	 

    

 

4.
Governing Law. This Agreement shall be governed by and construed in accordance with the laws of the State of New York irrespective
of any conflict of laws principles. The parties hereby agree that any action or proceeding with respect to this Agreement (and
any action or proceeding with respect to any amendments or replacements hereof or transactions relating hereto) may be brought
only in a federal or state court located in New York, State of New York and having jurisdiction with respect to such action or
proceeding. Each of the parties hereto irrevocably consents and submits to the jurisdiction of such courts.

 

5.
Miscellaneous. This Agreement will become a binding agreement among the undersigned as of the date hereof. This Agreement
(and the agreements reflected herein) may be terminated by the mutual agreement of the Company, Shareholder and the Designated
Purchaser (as defined in the UPA) and if not sooner terminated, will terminate upon the expiration date of the Lockup Period.
This Agreement may be duly executed by facsimile and in any number of counterparts, each of which shall be deemed an original,
and all of which together shall be deemed to constitute one and the same instrument. Signature pages from separate identical counterparts
may be combined with the same effect as if the parties signing such signature page had signed the same counterpart.

 

[SIGNATURE
PAGES FOLLOW]

 

    	 	 

    	 

    

 

	 	Very
    truly yours,
	 	 	 
	 	MARATHON
    PATENT GROUP, INC.
	 	 	 
	 	By:	            
	 	Name:
    	 
	 	Title:	 

 

	Accepted
    and Agreed to:	 
	 	 
	DOUGLAS
    CROXALLExhibit 4.1

 

EXECUTION COPY 

 

REGISTRATION RIGHTS AGREEMENT

 

This Registration
Rights Agreement (the “Agreement”) is made and entered into as of this September 11, 2017 by and among
Synthetic Biologics, Inc., a Nevada corporation (the “Company”), and MSD Credit Opportunity Master Fund,
L.P., a Delaware limited partnership (together with each subsequent holder of Registrable Shares, collectively, the
“Holders” and, each individually, a “Holder”). Capitalized terms used herein have the
respective meanings ascribed thereto in that certain Share Purchase Agreement dated as of the date hereof by and among the
Company and the other parties signatory thereto (the “Purchase Agreement”) unless otherwise defined herein.

 

RECITALS

 

WHEREAS, the Company
has issued shares of Preferred Stock to the Holder signatory hereto; and

 

WHEREAS, in connection
with the consummation of the transactions contemplated by the Purchase Agreement, the parties desire to enter into this Agreement
in order to grant certain registration rights to the Holders as set forth below.

 

NOW, THEREFORE, in
consideration of the promises, covenants and conditions set forth herein, the parties hereto hereby agree as follows:

 

1.           Certain
Definitions. As used in this Agreement, the following terms shall have the following meanings:

 

“Commission”
means the U.S. Securities and Exchange Commission.

 

“Common Stock”
means the Company’s common stock, par value $0.001 per share, and any securities into which such shares may hereinafter be
reclassified.

 

“Conversion
Shares” shall mean collectively the shares of Common Stock of the Company or other Securities issuable upon conversion
of the Preferred Stock.

 

“Exchange
Act” means the Securities Exchange Act of 1934, as amended from time to time, and the rules and regulations promulgated
thereunder from time to time in effect.

 

“Initiating
Holder” means any Holder who properly initiates a registration request under this Agreement.

 

“Prospectus”
means (i) the prospectus included in any Registration Statement, as amended or supplemented by any prospectus supplement, with
respect to the terms of the offering of any portion of the Registrable Shares covered by such Registration Statement and by all
other amendments and supplements to the prospectus, including post-effective amendments and all material incorporated by reference
in such prospectus, and (ii) any “free writing prospectus” as defined in Rule 405 under the Securities Act.

 

    	 	 	 

     

    

  

“Qualifying
Holder” means any Holder that (a) is deemed to be an “affiliate” (as such term is defined in Rule 144(a))
of the Company or (b) beneficially owns (within the meaning of Section 13(d) of the Exchange Act and the rules and regulations
promulgated thereunder) at least ten percent (10%) of the Company’s Common Stock then outstanding (disregarding for this
purpose any and all limitations of any kind on conversion or exercise of any convertible securities owned by such Holder).

 

“Register,”
“registered” and “registration” refer to a registration made by preparing and filing a Registration
Statement or similar document in compliance with the Securities Act, and the declaration or ordering of effectiveness of such Registration
Statement or document.

 

“Registrable
Shares” means (i) any shares of Common Stock owned by the Holders, (ii) the Conversion Shares and (iii) any other securities
issued or issuable with respect to or in exchange for the Conversion Shares, whether by merger, charter amendment or otherwise;
provided, that, a security shall not be a Registrable Share (A) upon sale pursuant to a Registration Statement or Rule 144, or
(B) while such security is eligible for sale without restriction by the Holders pursuant to Rule 144, assuming, for purposes of
such determination with respect to each Holder, the full conversion or exercise by such Holder of all convertible securities held
by such Holder (disregarding for this purpose any and all limitations of any kind on conversion or exercise of any convertible
securities owned by such Holder).

 

“Registration
Statement” means any registration statement of the Company filed under the Securities Act that covers the resale of any
of the Registrable Shares pursuant to the provisions of this Agreement, amendments and supplements to such Registration Statement,
including post-effective amendments, all exhibits and all material incorporated by reference in such Registration Statement.

 

“Required
Holders” means the Holders holding at least a majority of the Conversion Shares, considered collectively, then outstanding
(disregarding for this purpose any and all limitations of any kind on conversion or exercise of any convertible securities owned
by such Holder).

 

“Rule 144”
means Rule 144 promulgated under the Securities Act or any successor rule thereto.

 

“Rule 430B”
means Rule 430B promulgated under the Securities Act or any successor rule thereto.

 

“Securities
Act” means the Securities Act of 1933, as amended from time to time, and the rules and regulations promulgated thereunder
from time to time in effect.

 

    	 	-2-	 

     

    

  

2.           Registration.

 

(a)          Filing
of the Registration Statement. At any time after the date hereof, any Qualifying Holder may request registration under the
Securities Act of the Registrable Shares. Upon receipt of such request, the Company shall (i) within five (5) Business Days after
the date such request is given, advise the Initiating Holder whether the Company is permitted to rely upon Rule 430B to omit certain
information from the Prospectus, (ii) within ten (10) days after the date such request is given, give notice thereof (the “Demand
Notice”) to all Holders other than the Initiating Holder and advise such Holders whether the Company is permitted to
rely upon Rule 430B to omit certain information from the Prospectus, (iii) cause to be prepared and filed with the Commission a
Registration Statement on Form S-3 (or, if the Company is not eligible to use Form S-3, on Form S-1) within sixty (60) days of
such request (the “Filing Deadline”) for purposes of registering for sale to the public the Registrable Shares,
and (iv) use its best efforts to cause such Registration Statement to be declared effective under the Securities Act by the Commission
as soon as practicable thereafter and in any event no later than one hundred twenty (120) days after the date of such request.
Any Holder may provide notice to the Company within ten (10) days of receipt of the Demand Notice that such Holder wishes to be
excluded from the selling stockholder table of such Registration Statement (the “Excluded Shares”). The Company
shall include all outstanding Registrable Shares on such Registration Statement, including the Excluded Shares, to the extent the
Company is permitted to rely upon Rule 430B to omit certain information from the Prospectus, including the names of those Holders
of Excluded Shares; provided, however, that the Company will not include the Excluded Shares on such Registration Statement if
the Company is not permitted to rely upon Rule 430B; provided, however, that the Company shall not be required to include any Holders
to be named in the Registration Statement unless they have provided the Company with their up to date share ownership information
within five (5) business days of the Company’s request. If the Company files the Registration Statement on Form S-1 and subsequently
becomes eligible to use Form S-3, the Company shall file a post-effective amendment to such Form S-1 on Form S-3 and use its best
efforts to cause the Registration Statement, as so amended, to become effective within sixty (60) days of the filing thereof. Subject
to any Commission comments, the foregoing Registration Statement shall include the plan of distribution attached hereto as Exhibit
A; provided, however, that no Holder shall be named as an “underwriter” in such Registration Statement without
such Holder’s prior written consent. If the Registration Statement covering the Registrable Shares is not filed with the
Commission on or prior to its Filing Deadline, the Company will make pro rata payments to each Holder that requested that its Registrable
Shares be included on such Registration Statement, as liquidated damages and not as a penalty, in an amount (A) at a rate per 30-day
period of 0.25% of the aggregate amount invested by such Holder pursuant to the Purchase Agreement that shall accrue daily, for
the first 30-day period (or pro rata portion thereof) following such Filing Deadline, (B) increasing by an additional 0.25% of
the aggregate amount invested by such Holder pursuant to the Purchase Agreement per 30-day period, that shall accrue daily, for
each subsequent 30-day period, and (C) up to a maximum of 2.0% of the aggregate amount invested by such Holder pursuant to the
Purchase Agreement per 30-day period Such payments shall be made to each such Holder in cash no later than three (3) Business Days
after the end of each 30-day period. Notwithstanding anything to the contrary set forth in this Section 2, in the event the Commission
does not permit the Company to register all of the Registrable Shares in the Registration Statement because of the Commission’s
application of Rule 415, (i) the number of Registrable Shares that may be registered on such Registration Statement shall be reduced
to the number permitted by the Commission and (ii) the Company shall send prompt notice of the amount of such reduction to each
Holder that requested that its Registrable Shares be included on such Registration Statement. The Company shall use its commercially
reasonable efforts to file additional Registration Statements (each, a “Subsequent Registration Statement”)
to register the Registrable Shares that were not registered in the initial Registration Statement as promptly as possible but in
no event later than on the Filing Deadline and in a manner permitted by the Commission.  For purposes of this Section
2(b), “Filing Deadline” means with respect to each Subsequent Registration Statement filed pursuant hereto,
the later of (i) sixty (60) days following the sale of substantially all of the Registrable Shares included in the initial Registration
Statement or any Subsequent Registration Statement and (ii) six (6) months following the effective date of the initial Registration
Statement or any Subsequent Registration Statement, as applicable, or such earlier date as permitted by the Commission.  For
purposes of this Section 2(b), “Effectiveness Date” means with respect to each Subsequent Registration Statement
filed pursuant hereto, the earlier of (A) the ninetieth (90th) day following the filing date of such Subsequent Registration Statement
(or in the event such Subsequent Registration Statement receives a “full review” by the Commission, the one hundred
twentieth (120th) day following such filing date) or (B) the date which is within three (3) Business Days after the date on which
the Commission informs the Company (i) that the Commission will not review such Subsequent Registration Statement or (ii) that
the Company may request the acceleration of the effectiveness of such Subsequent Registration Statement; provided, that,
if the Effectiveness Date falls on a Saturday, Sunday or any other day which shall be a legal holiday or a day on which the Commission
is authorized or required by law or other government actions to close, the Effectiveness Date shall be the following Business Day.

 

    	 	-3-	 

     

    

  

(b)          Effectiveness.

 

(i)          Following
the declaration of effectiveness by the Commission of the Registration Statement filed pursuant to Section 2(a), the Company shall
(i) use commercially reasonable efforts to cause such Registration Statement to remain effective and provide all requisite financial
statements until such time as there cease to be Registrable Shares, (ii) use commercially reasonable efforts to prepare and
file with the Commission such amendments and supplements to such Registration Statement and the Prospectus used in connection
therewith as may be necessary to keep such Registration Statement effective until such time as there cease to be Registrable Shares,
(iii) furnish to each Holder offering Registrable Shares under such Registration Statement such number of copies of a summary
Prospectus or other Prospectus, including a preliminary Prospectus complying with the requirements of the Securities Act, as such
Holder may reasonably request, (iv) comply with the provisions of the Securities Act with respect to the disposition of all Registrable
Shares covered by the Registration Statement during such period in accordance with the intended methods of distribution by the
selling holders thereof set forth in the Registration Statement, and (v) prior to any public offering of Registrable Shares, cooperate
with the selling holders and the underwriter(s), if any, in connection with the registration and qualification of the Registrable
Shares under the state securities or “blue sky” laws of such jurisdictions within the United States of America as
the selling holders or underwriter(s), if any, may reasonably request and to use commercially reasonable efforts to do any and
all other acts or things necessary or advisable to permit the disposition in such jurisdictions of the Registrable Shares covered
by the Registration Statement in a manner that is in compliance with the applicable laws of such jurisdiction or, in the event
that the registration does not involve an underwritten public offering, as each such selling holder shall reasonably request.
The Company will promptly, and in any event within one (1) Business Day of having received notice of the following, notify each
Holder of (1) any stop order issued or, to the knowledge of the Company, threatened by the Commission and take all commercially
reasonable actions to obtain the withdrawal or lifting of such order if it has been issued or prevent the entry of such stop order
if it has not yet been issued; (2) when the Registration Statement or any post-effective amendment thereto has been filed with
the Commission and when the Registration Statement or any post-effective amendment thereto has become effective; (3) any request
by the Commission for amendments or supplements to the Registration Statement or the Prospectus included therein or for additional
information; and (4) any notification with respect to the suspension of the qualification of the Registrable Shares included therein
for sale in any jurisdiction or the initiation or threatening of any proceeding for such purpose.

 

    	 	-4-	 

     

    

  

(ii)         If
after a Registration Statement has been declared effective by the Commission sales cannot be made pursuant to such Registration
Statement for any reason (including without limitation by reason of a stop order, or the Company’s failure to update the
Registration Statement), but excluding the inability of any Holder to sell the Registrable Shares covered thereby due to market
conditions, then the Company will make pro rata payments to each Holder that requested that its Registrable Shares be included
on such Registration Statement, as liquidated damages and not as a penalty, in an amount (A) at a rate per 30-day period of 0.25%
of the aggregate amount invested by such Holder pursuant to the Purchase Agreement that shall accrue daily, for the first 30-day
period (or pro rata portion thereof) following the date by which such Registration Statement should have been effective, (B) increasing
by an additional 0.25% of the aggregate amount invested by such Holder pursuant to the Purchase Agreement per 30-day period, that
shall accrue daily, for each subsequent 30-day period, and (C) up to a maximum of 2.0% of the aggregate amount invested by such
Holder pursuant to the Purchase Agreement per 30-day period. Such payments shall be made to each such Holder in cash no later than
three (3) Business Days after the end of each 30-day period.

 

(iii)        Any
Holder of Excluded Shares may request to be added as a selling stockholder to such effective Registration Statement to the extent
permitted under Rule 430B. To the extent not permitted under Rule 430B, a Qualifying Holder may request registration of such Holder’s
Registrable Shares pursuant to Section 2(a) above.

 

(c)          Right
to Piggyback Registration.

 

(i)          If
at any time following the date of this Agreement that any Registrable Shares remain outstanding the Company proposes for any reason
to register any shares of Common Stock under the Securities Act (other than pursuant to a registration statement on Form S-4 or
Form S-8 (or a similar or successor form)) with respect to an offering of Common Stock by the Company for its own account or for
the account of any of its stockholders, it shall at each such time promptly give written notice to the Holders, in accordance with
the provisions of Section 5(b) below, of its intention to do so (but in no event less than thirty (30) days before the anticipated
filing date) and, to the extent permitted under the provisions of Rule 415 under the Securities Act, include in such registration
all Registrable Shares with respect to which the Company has received written requests for inclusion therein within fifteen (15)
days after receipt of the Company’s notice (a “Piggyback Registration”). Such notice shall offer the Holders
the opportunity to register such number of shares of Registrable Shares as each such Holder may
request and shall indicate the intended method of distribution of such Registrable Shares. By written notice delivered to the Company,
any Holder (an “Opting-Out Holder”) may elect to waive its right to participate in Piggyback Registrations (“Registration
Opt-Out”), until such time as such written notice is rescinded in writing.  During such time as a Registration Opt-Out
is in effect:  (x) the Opting-Out Holder shall not receive notices of any proposed Piggyback Registration and (y) shall not
be entitled to participate in any such Piggyback Registration pursuant to this Section 2(c). Notwithstanding anything to
the contrary set forth in this Section 2(c)(i), in the event the Commission does not permit the Company to register all of the
Registrable Shares in the Registration Statement because of the Commission’s application of Rule 415, the number of Registrable
Shares that may be registered on such Registration Statement shall be allocated in the following priority: first, the Common
Stock being registered by the Company for its own account and second, pro rata among the Holders and the other stockholders
of the Company.

 

    	 	-5-	 

     

    

  

(ii)         Notwithstanding
the foregoing, (A) if such registration involves an underwritten public offering, the Holders must sell their Registrable Shares
to, if applicable, the underwriter(s) at the same price and subject to the same underwriting discounts and commissions that apply
to the other securities sold in such offering (it being acknowledged that the Company shall be responsible for other expenses as
set forth in Section 3(b)) and subject to the Holders entering into customary underwriting documentation for selling stockholders
in an underwritten public offering, and (B) if, at any time after giving written notice of its intention to register any Registrable
Shares pursuant to Section 2(c)(i) and prior to the effective date of the registration statement filed in connection with such
registration, the Company shall determine for any reason not to cause such registration statement to become effective under the
Securities Act, the Company shall deliver written notice to the Holders and, thereupon, shall be relieved of its obligation to
register any Registrable Shares in connection with such registration; provided, however, that nothing contained in this Section
2(c)(ii) shall limit the Company’s liabilities and/or obligations under this Agreement, including, without limitation, the
obligation to pay liquidated damages under this Section 2.

 

(d)          Underwriting
Requirements.

 

(i)          If,
at any time after the filing of a registration statement pursuant to Section 2(a), any Holder intends to distribute at least $15
million of Registrable Shares (including Registrable Shares held by other Holders) by means of an underwriting, then such Holder
(the “Requesting Holder”) shall so advise the Company. The underwriter(s) will be selected by the Requesting
Holder, subject only to the reasonable approval of the Company. In such event, the right of any Holder to include such Holder’s
Registrable Shares in such registration shall be conditioned upon such Holder’s participation in such underwriting and the
inclusion of such Holder’s Registrable Shares in the underwriting to the extent provided herein. All Holders proposing to
distribute their securities through such underwriting shall (together with the Company as provided in Section 2(d)(iii)) enter
into an underwriting agreement in customary form with the underwriter(s) selected for such underwriting; provided, however, that
in no event shall the Holders be required to sign a lock-up agreement restricting such Holders for a period longer than (i) imposed
upon the Company or its officers and directors or (ii) six (6) months following the effective date of the Registration Statement.
Any discretionary waiver or termination of the lock-up restrictions described above by the Company or the underwriter(s) shall
apply pro rata to all Holders subject to such lock-up restrictions, based on the number of Registrable Shares included in such
underwriting. Notwithstanding any other provision of this Section 2(d)(i), if the managing underwriter(s) advise(s) the Requesting
Holder in writing that marketing factors require a limitation on the number of shares to be underwritten, then the Requesting Holder
shall so advise all Holders that otherwise would be underwritten pursuant hereto, and the number of Registrable Shares that may
be included in the underwriting shall be allocated among such Holders, including the Requesting Holder, in proportion (as nearly
as practicable) to the number of Registrable Shares owned by each Holder or in such other proportion as shall mutually be agreed
to by all such selling Holders; provided, however, that the number of Registrable Shares held by the Holders to be included in
such underwriting shall not be reduced unless all other securities are first entirely excluded from the underwriting.

 

    	 	-6-	 

     

    

  

(ii)         In
connection with any offering involving an underwriting of shares of the Company’s capital stock pursuant to Section 2(c),
the Company shall not be required to include any of the Holders’ Registrable Shares in such underwriting unless the Holders
accept the terms of the underwriting as agreed upon between the Company and its underwriters, and then only in such quantity as
the underwriters in their sole discretion determine will not jeopardize the success of the offering by the Company; provided, however,
that in no event shall the Holders be required to sign a lock-up agreement restricting such Holders for a period longer than (i)
imposed upon the Company or its officers and directors or (ii) six (6) months following the effective date of the Registration
Statement. Any discretionary waiver or termination of the lock-up restrictions described above by the Company or the underwriters
shall apply pro rata to all Holders subject to such lock-up restrictions, based on the number of Registrable Shares included in
such underwriting. If the total number of securities, including Registrable Shares, requested by stockholders to be included in
such offering exceeds the number of securities to be sold (other than by the Company) that the underwriters in their reasonable
discretion determine is compatible with the success of the offering, then the Company shall be required to include in the offering
only that number of such securities, including Registrable Shares, which the underwriters and the Company in their sole discretion
determine will not jeopardize the success of the offering. If the underwriters determine that less than all of the Registrable
Shares requested to be registered can be included in such offering, then the Registrable Shares that are included in such offering
shall be allocated among the selling Holders in proportion (as nearly as practicable) to the number of Registrable Shares owned
by each selling Holder or in such other proportions as shall mutually be agreed to by all such selling Holders. Notwithstanding
the foregoing, in no event shall the number of Registrable Shares included in the offering be reduced unless all other securities
(other than securities to be sold by the Company) are first entirely excluded from the offering. For purposes of the provision
in this Section 2(d)(ii) concerning apportionment, for any selling Holder that is a partnership, limited liability company, or
corporation, the partners, members, retired partners, retired members, stockholders, and Affiliates of such Holder, or the estates
and immediate family members of any such partners, retired partners, members, and retired members and any trusts for the benefit
of any of the foregoing Persons, shall be deemed to be a single “selling Holder,” and any pro rata reduction with respect
to such “selling Holder” shall be based upon the aggregate number of Registrable Shares owned by all Persons included
in such “selling Holder,” as defined in this sentence.

 

(iii)        In
connection with any offering involving an underwriting of shares of the Company’s capital stock pursuant to Section 2(c),
the Company shall enter into and perform its obligations under an underwriting agreement, in customary form, with the underwriter(s)
of such offering and the Company shall comply with all customary requests by such underwriter(s), including, but not limited to,
the delivery of a legal opinion, negative assurance letter and comfort letter, providing due diligence materials as reasonably
requested by the underwriter(s) and participating in a road show if requested by the underwriter(s).

 

    	 	-7-	 

     

    

  

3.           Qualifications;
Obligations; Restrictions. The obligations of the Company under Section 2 are subject to the following qualifications:

 

(a)          the
Company shall not include in any registration, qualification or compliance requested pursuant to Section 2(a) any other securities
(including, without limitation, those to be issued and sold by the Company) without the prior written consent of the Required Holders;

 

(b)          the
Company shall pay all expenses incurred in complying with Section 2, including, all registration and filing fees, printing expenses,
fees and disbursements of counsel for the Company and reasonable and documented fees and disbursements of one counsel for all of
the Holders selected by the Holders of a majority of the Registrable Shares to be included in such registration, expenses of any
special audits incident to or required by any such registration and expenses of complying with the securities or “blue sky”
laws of any jurisdictions pursuant to Section 2(b)(i);

 

(c)          the
Company shall not grant any right relating to the registration of its securities if the exercise thereof conflicts with or restricts
the exercise and enjoyment of any of the rights granted under this Agreement, without the written consent of the Required Holders,
which consent may be given or withheld in the sole discretion of such Holders. The Company will not permit at any time after the
date hereof any of its Subsidiaries to grant any right relating to the registration of its securities until the termination of
this Agreement;

 

(d)          the
Company shall use its best efforts to cause all Registrable Shares covered by a Registration Statement to be listed on each securities
exchange, interdealer quotation system or other market on which similar securities issued by the Company are then listed; and

 

(e)          the
Company shall, with a view to making available to the Holders the benefits of Rule 144 (or its successor rule) and any other rule
or regulation of the Commission that may at any time permit the Holders to sell shares of Common Stock to the public without registration,
the Company covenants and agrees to: (i) make and keep public information available, as those terms are understood and defined
in Rule 144, until the earlier of (A) six months after such date as all of the Registrable Shares may be sold without restriction
by the holders thereof pursuant to Rule 144 or any other rule of similar effect or (B) such date as all of the Registrable Shares
shall have been resold; (ii) file with the Commission in a timely manner all reports and other documents required of the Company
under the Exchange Act; and (iii) furnish to each Holder upon request, as long as such Holder owns any Registrable Shares, (A)
a written statement by the Company that it has complied with the reporting requirements of the Exchange Act, (B) a copy of the
Company’s most recent Annual Report on Form 10-K or Quarterly Report on Form 10-Q, and (C) such other information as may
be reasonably requested in order to avail such Holder of any rule or regulation of the Commission that permits the selling of any
such Registrable Shares without registration (any filing with the SEC on the Edgar filing system shall satisfy the delivery requirements
under clause B).

 

    	 	-8-	 

     

    

  

4.           Obligations
of Holders of Registrable Shares.

 

(a)          Subject
to the provisions of this Section 4, following the effectiveness of a Registration Statement, the Company may direct the Holders,
in accordance with Section 4(b), to suspend sales of Registrable Shares pursuant to such Registration Statement and the use of
any Prospectus or preliminary Prospectus contained therein for the shortest amount of time as the Company reasonably determines
is necessary and advisable (but in no event for more than an aggregate of 60 days in any consecutive 12-month period commencing
on the date hereof or more than an aggregate of 30 days in any consecutive 180-day period (a “Suspension Period”)),
if any of the following events shall occur: (1) the majority of the Company’s board of directors determines in good faith,
upon the advice of counsel, that an event has occurred or is continuing as a result of which the Registration Statement or Prospectus
contained therein contains an untrue statement of a material fact or omits any fact necessary to make the statements therein not
misleading causing such Registration Statement or the Prospectus contained therein not to be usable for resale of the Registrable
Shares during the period required by this Agreement; (2) the majority of the Company’s board of directors determines in good
faith, upon the advice of counsel, that the sale of Registrable Shares pursuant to such Registration Statement would require disclosure
of material non-public information not otherwise required to be disclosed under applicable laws and the Company has a bona fide
business purpose for preserving the confidentiality of such information or disclosure of such information would have a material
adverse effect on the Company, in each case under circumstances that would make it impractical or inadvisable to cause the Registration
Statement to become effective or to promptly amend or supplement the Registration Statement on a post-effective basis, as applicable;
or (3) the majority of the Company’s board of directors determines in good faith, upon the advice of counsel, that it is
required by law, rule or regulation or Commission-published release or interpretation to supplement the Registration Statement
or file a post-effective amendment to the Registration Statement in order to incorporate information into the Registration Statement,
including for the purpose of (a) including in the Registration Statement any Prospectus required under Section 10(a)(3) of the
Securities Act, (b) reflecting in the Prospectus any facts or events arising after the effective date of the Registration Statement
(or of the most recent post-effective amendment) that, individually or in the aggregate, represents a fundamental change in the
information set forth therein, or (c) including in the Prospectus any material information with respect to the plan of distribution
not disclosed in the Registration Statement or any material change to such information (each of the events in clause (1), (2) and
(3), a “Suspension Event”). Upon the occurrence of any such Suspension Event, the Company shall use commercially
reasonable efforts to cause the Registration Statement to become effective or to promptly amend or supplement the Registration
Statement on a post-effective basis or to take such action as is necessary to permit the Holders to resume sales of such securities
as soon as possible and to promptly make available to each selling Holder any such supplement or amendment.

 

    	 	-9-	 

     

    

  

(b)          Upon
the occurrence of a Suspension Event, the Company shall provide to each Holder a notice (a “Suspension Notice”),
which notice shall not include any material non-public information, that a Suspension Event has occurred or is occurring, and each
Holder agrees that upon receipt of a Suspension Notice, such Holder will forthwith discontinue disposition of Registrable Shares
pursuant to the Registration Statement until (A) such Holder’s receipt of the copies of the supplemented or amended Prospectus
that addresses the reasons for providing the Suspension Notice, or (B) it is advised in writing by the Company that the use of
the Prospectus may be resumed, and has received copies of any additional or supplemental filings that are incorporated by reference
in the Prospectus. Each Holder receiving a Suspension Notice hereby agrees that it will, at such Holder’s election, either
(1) destroy any Prospectuses, other than permanent file copies, then in such Holder’s possession that have been replaced
by the Company with more recently dated Prospectuses, or (2) deliver to the Company (at the Company’s expense) all copies,
other than permanent file copies then in such Holder’s possession, of the Prospectus covering such Registrable Shares that
was current at the time of receipt of such notice. Notwithstanding anything herein to the contrary, (A) a Holder shall be entitled
to inquire of the Company further details regarding the nature of a Suspension Event for which it has been served a Suspension
Notice, and the Company shall use its commercially reasonable efforts to provide any information requested about the Suspension
Event to such Holder and (B) the Company shall not serve a Suspension Notice to the Holders, unless, concurrently therewith, it
has suspended sales under all other effective registration statements relating to the resale of the Company’s securities.

 

(c)          Each
Holder, by its acceptance of the Registrable Shares, agrees to cooperate with the Company as reasonably requested by the Company
in connection with the preparation and filing of a Registration Statement hereunder, unless such Holder has notified the Company
in writing of its election to exclude all of its Registrable Shares from such Registration Statement.

 

5.           Due
Diligence Review; Information.

 

(a)          The
Company shall make available, during normal business hours upon at least five (5) Business Days’ prior notice, for inspection
and review by the Holders, advisors to and representatives of the Holders (who may or may not be affiliated with the Holders and
who are reasonably acceptable to the Company), and any underwriter(s), all financial and other records, all filings with the Commission,
and all other corporate documents and properties of the Company as may be reasonably necessary for the purpose of such review,
and cause the Company’s officers, directors and employees, within a reasonable time period, to supply all such information
reasonably requested by the Holders or any such representative, advisor or underwriter in connection with the Registration Statement
(including, without limitation, in response to all questions and other inquiries reasonably made or submitted by any of them),
prior to and from time to time after the filing and effectiveness of each Registration Statement for the sole purpose of enabling
the Holders and such representatives, advisors and underwriters and their respective accountants and attorneys to conduct initial
and ongoing due diligence with respect to the Company and the accuracy of the Registration Statement; provided, however that all
information obtained in connection with any such inspection shall be subject to a confidentiality agreement in a form mutually
agreed upon by the Corporation and any Holder conducting such inspection.

 

    	 	-10-	 

     

    

  

(b)          Notwithstanding
anything contained herein to the contrary, the Company shall not disclose material nonpublic information to the Holders, or to
advisors to or representatives of the Holders, unless prior to disclosure of such information the Company identifies such information
as being material nonpublic information and provides the Holders, such advisors and representatives with the opportunity to accept
or refuse to accept such material nonpublic information for review and any Holder wishing to obtain such information enters into
an appropriate confidentiality agreement with the Company with respect thereto.

 

6.           Indemnification.

 

(a)          To
the extent permitted by law, the Company shall indemnify each Holder, and each person controlling such Holder within the meaning
of Section 15 of the Securities Act, with respect to which any registration that has been effected pursuant to this Agreement,
against all claims, losses, damages and liabilities (or action in respect thereof), including any of the foregoing incurred in
settlement of any litigation, commenced or threatened (subject to Section 6(c) below), arising out of or based on any untrue statement
(or alleged untrue statement) of a material fact contained in the Registration Statement, Prospectus, any amendment or supplement
thereof or based on any omission (or alleged omission) to state therein a material fact required to be stated therein or necessary
to make the statements therein not misleading, in light of the circumstances in which they were made, or any violation by the Company
of any rule or regulation promulgated by the Securities Act applicable to the Company and relating to any action or inaction required
of the Company in connection with any such registration and will reimburse each Holder and each person controlling such Holder
for reasonable legal and other expenses reasonably incurred in connection with investigating or defending any such claim, loss,
damage, liability or action as incurred; provided, however, that the Company will not be liable in any such case to the extent
that any untrue statement or omission or allegation thereof is made in reliance upon and in conformity with written information
furnished to the Company by or on behalf of such Holder expressly for use in preparation of such Registration Statement, Prospectus,
or any amendment or supplement thereof; provided further, however, that the Company will not be liable in any such case where the
claim, loss, damage or liability arises out of or is related to the failure of the Holder to comply with the covenants and agreements
contained in this Agreement respecting sales of Registrable Shares, and except that the foregoing indemnity agreement is subject
to the condition that, insofar as it relates to any such untrue statement or alleged untrue statement or omission or alleged omission
made in the preliminary Prospectus but eliminated or remedied in the amended Prospectus on file with the Commission at the time
the Registration Statement becomes effective or in the amended Prospectus filed with the SEC pursuant to Rule 424(b) or in the
Prospectus subject to completion under Rule 434 of the Securities Act, which together meet the requirements of Section 10(a) of
the Securities Act (the “Final Prospectus”), such indemnity shall not inure to the benefit of any such Holder
or any such controlling person, if a copy of the Final Prospectus furnished by the Company to the Holder for delivery was not furnished
to the person or entity asserting the loss, liability, claim or damage at or prior to the time such furnishing is required by the
Securities Act and the Final Prospectus would have cured the defect giving rise to such loss, liability, claim or damage.

 

    	 	-11-	 

     

    

  

(b)          Each
party entitled to indemnification under this Section 6 (the “Indemnified Party”) shall give notice to the party
required to provide indemnification (the “Indemnifying Party”) promptly after such Indemnified Party has actual
knowledge of any claim as to which indemnity may be sought, and shall permit the Indemnifying Party (at its expense) to assume
the defense of any such claim or any litigation resulting therefrom, provided, however, that counsel for the Indemnifying Party,
who shall conduct the defense of such claim or litigation, shall be approved by the Indemnified Party (whose approval shall not
unreasonably be withheld), and the Indemnified Party may participate in such defense provided that all legal and other expenses
incurred by the Indemnified Party in connection therewith shall be at such Indemnified Party’s expense, and, provided further,
that the failure of any Indemnified Party to give notice as provided herein shall not relieve the Indemnifying Party of its obligations
under this Agreement, unless such failure is materially prejudicial to the Indemnifying Party in defending such claim or litigation.
An Indemnifying Party shall not be liable for any settlement of an action or claim effected without its written consent (which
consent will not be unreasonably withheld). No Indemnifying Party, in its defense of any such claim or litigation, shall, except
with the consent of each Indemnified Party, consent to entry of any judgment or enter into any settlement which does not include
as an unconditional term thereof the giving by the claimant or plaintiff to such Indemnified Party of a release from all liability
in respect to such claim or litigation. Notwithstanding the foregoing, the Company shall not, in connection with any one such action
or proceeding or separate but substantially similar or related actions or proceedings in the same jurisdiction arising out of the
same general allegations or circumstances, be liable for the reasonable fees and expenses of more than one separate firm of attorneys
(in addition to any local counsel) at any time for indemnified Holders as a group, which firm shall be designated by such Holders.

 

(c)          If
the indemnification provided for in this Section 6 is held by a court of competent jurisdiction to be unavailable to an Indemnified
Party with respect to any loss, liability, claim, damage or expense referred to therein, then the Indemnifying Party, in lieu of
indemnifying such Indemnified Party thereunder, shall contribute to the amount paid or payable by such Indemnified Party as a result
of such loss, liability, claim, damage or expense in such proportion as is appropriate to reflect the relative fault of the Indemnifying
Party on the one hand and of the Indemnified Party on the other in connection with the statements or omissions which resulted in
such loss, liability, claim, damage or expense as well as any other relevant equitable considerations. The relative fault of the
Indemnifying Party and of the Indemnified Party shall be determined by reference to, among other things, whether the untrue or
alleged untrue statement of a material fact or the omission or alleged omission to state a material fact relates to information
supplied by the Indemnifying Party or by the Indemnified Party and the parties’ relative intent, knowledge, access to information
and opportunity to correct or prevent such statement or omission.

 

7.           Miscellaneous.

 

(a)          Amendments
and Waivers. This Agreement may be amended only by a writing signed by the Company and the Required Holders. 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 shall
have obtained the written consent to such amendment, action or omission to act, of the Required Holders. Notwithstanding the foregoing,
this Agreement may not be amended or terminated and the observance of any term hereof may not be waived with respect to any Holder
without the written consent of such Holder, unless such amendment, termination, or waiver applies to all Holders in the same fashion.

 

(b)          Notices.
All notices and other communications provided for or permitted hereunder shall be made as set forth in Section 5.3 of the Purchase
Agreement.

 

    	 	-12-	 

     

    

  

(c)          Assignments
and Transfers by Holders. The provisions of this Agreement shall be binding upon and inure to the benefit of the Holders and
their respective successors and assigns. A Holder may transfer or assign, in whole or from time to time in part, to one or more
persons its rights hereunder in connection with the transfer of any shares of Preferred Stock or Registrable Shares by such Holder
to such person, provided that such Holder complies with all laws applicable thereto and provides written notice of assignment to
the Company promptly after such assignment is effected. Following any such transfer or assignment, such transferee or assignee
shall be considered a “Holder” under this Agreement.

 

(d)          Assignments
and Transfers by the Company. This Agreement may not be assigned by the Company (whether by operation of law or otherwise)
without the prior written consent of the Required Holders, provided, however, that in the event that the Company is a party to
a merger, consolidation, share exchange or similar business combination transaction in which the Common Stock is converted into
the equity securities of another Person, from and after the effective time of such transaction, such Person shall, by virtue of
such transaction, be deemed to have assumed the obligations of the Company hereunder, the term “Company” shall be deemed
to refer to such Person and the term “Registrable Shares” shall be deemed to include the securities received by the
Holders in connection with such transaction unless such securities are otherwise freely tradable by the Holders after giving effect
to such transaction.

 

(e)          Benefits
of the Agreement. The terms and conditions of this Agreement shall inure to the benefit of and be binding upon the respective
permitted successors and assigns of the parties. Nothing in this Agreement, express or implied, is intended to confer upon any
party other than the parties hereto or their respective successors and assigns any rights, remedies, obligations, or liabilities
under or by reason of this Agreement, except as expressly provided in this Agreement.

 

(f)           Counterparts;
Electronic Transmission. This Agreement may be executed in two or more counterparts, each of which shall be deemed an original,
but all of which together shall constitute one and the same instrument. This Agreement may also be executed via facsimile or other
electronic transmission, which shall be deemed an original.

 

(g)          Titles
and Subtitles. The titles and subtitles used in this Agreement are used for convenience only and are not to be considered in
construing or interpreting this Agreement.

 

(h)          Severability.
Any provision of this Agreement that is prohibited or unenforceable in any jurisdiction shall, as to such jurisdiction, be ineffective
to the extent of such prohibition or unenforceability without invalidating the remaining provisions hereof but shall be interpreted
as if it were written so as to be enforceable to the maximum extent permitted by applicable law, and any such prohibition or unenforceability
in any jurisdiction shall not invalidate or render unenforceable such provision in any other jurisdiction. To the extent permitted
by applicable law, the parties hereby waive any provision of law which renders any provisions hereof prohibited or unenforceable
in any respect.

 

    	 	-13-	 

     

    

  

(i)           Further
Assurances. The parties shall execute and deliver all such further instruments and documents and take all such other actions
as may reasonably be required to carry out the transactions contemplated hereby and to evidence the fulfillment of the agreements
herein contained.

 

(j)           Entire
Agreement. This Agreement is intended by the parties as a final expression of their agreement and intended to be a complete
and exclusive statement of the agreement and understanding of the parties hereto in respect of the subject matter contained herein.
This Agreement supersedes all prior agreements and understandings between the parties with respect to such subject matter. If any
provision of this Agreement is found to conflict with the Purchase Agreement, the provisions of this Agreement shall prevail.

 

(k)          Governing
Law. THIS AGREEMENT SHALL BE CONSTRUED AND ENFORCED IN ACCORDANCE WITH, AND THE RIGHTS OF THE PARTIES SHALL BE GOVERNED BY,
THE INTERNAL LAW OF THE STATE OF NEW YORK, EXCLUDING CHOICE-OF-LAW PRINCIPLES OF THE LAW OF SUCH STATE THAT WOULD PERMIT THE APPLICATION
OF THE LAWS OF A JURISDICTION OTHER THAN SUCH STATE.

 

(l)           Personal
Jurisdiction.

 

(i)          The
Company irrevocably submits to the non-exclusive jurisdiction of any New York State or federal court sitting in the Borough of
Manhattan. The City of New York, over any suit, action or proceeding arising out of or relating to this Agreement or any of the
agreements, documents or instruments delivered in connection herewith or therewith. To the fullest extent permitted by applicable
law, the Company irrevocably waives and agrees not to assert, by way of motion, as a defense or otherwise, any claim that it is
not subject to the jurisdiction of any such court, any objection that it may now or hereafter have to the laying of the venue of
any such suit, action or proceeding brought in any such court and any claim that any such suit, action or proceeding brought in
any such court has been brought in an inconvenient forum.

 

(ii)         Nothing
in this Section 7(l) shall affect the right of the Holders to serve process in any manner permitted by law, or limit any right
that the Holders may have to bring proceedings against the Company in the courts of any appropriate jurisdiction or to enforce
in any lawful manner a judgment obtained in one jurisdiction in any other jurisdiction.

 

(m)         WAIVER
OF JURY TRIAL. THE COMPANY AND EACH OF THE PURCHASERS EACH IRREVOCABLY WAIVES ALL RIGHT TO TRIAL BY JURY IN ANY ACTION, PROCEEDING
OR COUNTERCLAIM (WHETHER BASED ON CONTRACT, TORT OR OTHERWISE) ARISING OUT OF OR RELATING TO THIS AGREEMENT OR ANY OTHER AGREEMENT,
DOCUMENT OR INSTRUMENT DELIVERED IN CONNECTION HEREWITH OR THEREWITH OR THE ACTIONS OF THE PURCHASERS IN THE NEGOTIATION, ADMINISTRATION,
PERFORMANCE OR ENFORCEMENT HEREOF OR THEREOF.

 

(n)          No
Inconsistent Agreements. Neither the Company nor any of its subsidiaries has entered, as of the date hereof, nor shall the
Company or any of its subsidiaries, on or after the date of this Agreement, enter into any agreement with respect to its securities,
that would have the effect of impairing the rights granted to the Holders in this Agreement or otherwise conflicts with the provisions
hereof. Neither the Company nor any of its subsidiaries has previously entered into any agreement granting any registration rights
with respect to any of its securities to any Person that have not been satisfied in full.

 

    	 	-14-	 

     

    

  

(o)          Independent
Nature of Holders’ Obligations and Rights. The obligations of each Holder hereunder are several and not joint with the
obligations of any other Holder hereunder, and no Holder shall be responsible in any way for the performance of the obligations
of any other Holder hereunder. Nothing contained herein or in any other agreement or document delivered at any closing, and no
action taken by any Holder pursuant hereto or thereto, shall be deemed to constitute the Holders as a partnership, an association,
a joint venture or any other kind of group or entity, or create a presumption that the Holders are in any way acting in concert
or as a group or entity with respect to such obligations or the transactions contemplated by this Agreement or any other matters,
and the Company acknowledges that the Holders are not acting in concert or as a group, and the Company shall not assert any such
claim, with respect to such obligations or transactions. Each Holder shall be entitled to protect and enforce its rights, including
without limitation the rights arising out of this Agreement, and it shall not be necessary for any other Holder to be joined as
an additional party in any proceeding for such purpose. The use of a single agreement with respect to the obligations of the Company
contained was solely in the control of the Company, not the action or decision of any Holder, and was done solely for the convenience
of the Company and not because it was required or requested to do so by any Holder. It is expressly understood and agreed that
each provision contained in this Agreement is between the Company and a Holder, solely, and not between the Company and the Holders
collectively and not between and among Holders.

 

[Remainder of Page Intentionally Left
Blank]

 

    	 	-15-	 

     

    

 

IN WITNESS WHEREOF,
the parties have executed this Agreement or caused their duly authorized officers to execute this Agreement as of the date first
above written.

 

	The Company:	SYNTHETIC BIOLOGICS, INC.
	 	 	 
	 	By:	/s/ Jeffrey L. Riley
	 	Name:  Jeffrey L. Riley
	 	Title: Chief Executive Officer

 

[Company signature page to Registration
Rights Agreement]

 

    	 	 	 

     

    

 

	The Holder:	MSD CREDIT OPPORTUNITY MASTER FUND, L.P.

 

	 	By:	/s/ Marcello Liguori
	 	Name:	Marcello Liguori
	 	Title:	Managing Director

 

[Holder signature page to Registration
Rights Agreement]

  

    	 	 	 

     

    

  

Exhibit A

 

Plan of Distribution

 

The selling stockholders,
which as used herein includes donees, pledgees, transferees or other successors-in-interest selling shares of common stock or interests
in shares of common stock received after the date of this prospectus from a selling stockholder as a gift, pledge, partnership
distribution or other transfer, may, from time to time, sell, transfer or otherwise dispose of any or all of their shares of common
stock or interests in shares of common stock on any stock exchange, market or trading facility on which the shares are traded or
in private transactions. These dispositions may be at fixed prices, at prevailing market prices at the time of sale, at prices
related to the prevailing market price, at varying prices determined at the time of sale, or at negotiated prices.

 

The selling stockholders
may use any one or more of the following methods when disposing of shares or interests therein:

 

		-	ordinary brokerage transactions and transactions in which
the broker-dealer solicits purchasers;

 

		-	block trades in which the broker-dealer will attempt to
sell the shares as agent, but may position and resell a portion of the block as principal to facilitate the transaction;

 

		-	purchases by a broker-dealer as principal and resale by
the broker-dealer for its account;

 

		-	an exchange distribution in accordance with the rules of
the applicable exchange;

 

		-	privately negotiated transactions;

 

		-	short sales effected after the date the registration statement
of which this Prospectus is a part is declared effective by the Commission;

 

		-	through the writing or settlement of options or other hedging
transactions, whether through an options exchange or otherwise;

 

		-	broker-dealers may agree with the selling stockholders
to sell a specified number of such shares at a stipulated price per share;

 

		-	a combination of any such methods of sale; and

 

		-	any other method permitted by applicable law.

 

    	 	 	 

     

    

 

The selling stockholders
may, from time to time, pledge or grant a security interest in some or all of the shares of common stock owned by them and, if
they default in the performance of their secured obligations, the pledgees or secured parties may offer and sell the shares of
common stock, from time to time, under this prospectus, or under an amendment to this prospectus under Rule 424(b)(3) or other
applicable provision of the Securities Act amending the list of selling stockholders to include the pledgee, transferee or other
successors in interest as selling stockholders under this prospectus. The selling stockholders also may transfer the shares of
common stock in other circumstances, in which case the transferees, pledgees or other successors in interest will be the selling
beneficial owners for purposes of this prospectus.

 

In connection with
the sale of our common stock or interests therein, the selling stockholders may enter into hedging transactions with broker-dealers
or other financial institutions, which may in turn engage in short sales of the common stock in the course of hedging the positions
they assume. The selling stockholders may also sell shares of our common stock short and deliver these securities to close out
their short positions, or loan or pledge the common stock to broker-dealers that in turn may sell these securities. The selling
stockholders may also enter into option or other transactions with broker-dealers or other financial institutions or the creation
of one or more derivative securities which require the delivery to such broker-dealer or other financial institution of shares
offered by this prospectus, which shares such broker-dealer or other financial institution may resell pursuant to this prospectus
(as supplemented or amended to reflect such transaction).

 

The aggregate proceeds
to the selling stockholders from the sale of the common stock offered by them will be the purchase price of the common stock less
discounts or commissions, if any. Each of the selling stockholders reserves the right to accept and, together with their agents
from time to time, to reject, in whole or in part, any proposed purchase of common stock to be made directly or through agents.
We will not receive any of the proceeds from this offering.

 

The selling stockholders
also may resell all or a portion of the shares in open market transactions in reliance upon Rule 144 under the Securities Act of
1933, provided that they meet the criteria and conform to the requirements of that rule.

 

The selling stockholders
and any underwriters, broker-dealers or agents that participate in the sale of the common stock or interests therein may be “underwriters”
within the meaning of Section 2(11) of the Securities Act. Any discounts, commissions, concessions or profit they earn on any resale
of the shares may be underwriting discounts and commissions under the Securities Act. Selling stockholders who are “underwriters”
within the meaning of Section 2(11) of the Securities Act will be subject to the prospectus delivery requirements of the Securities
Act.

 

To the extent required,
the shares of our common stock to be sold, the names of the selling stockholders, the respective purchase prices and public offering
prices, the names of any agents, dealer or underwriter, any applicable commissions or discounts with respect to a particular offer
will be set forth in an accompanying prospectus supplement or, if appropriate, a post-effective amendment to the registration statement
that includes this prospectus.

 

In order to comply
with the securities laws of some states, if applicable, the common stock may be sold in these jurisdictions only through registered
or licensed brokers or dealers. In addition, in some states the common stock may not be sold unless it has been registered or qualified
for sale or an exemption from registration or qualification requirements is available and is complied with.

 

    	 	 	 

     

    

  

We have advised the
selling stockholders that the anti-manipulation rules of Regulation M under the Exchange Act may apply to sales of shares in the
market and to the activities of the selling stockholders and their affiliates. In addition, to the extent applicable we will make
copies of this prospectus (as it may be supplemented or amended from time to time) available to the selling stockholders for the
purpose of satisfying the prospectus delivery requirements of the Securities Act. The selling stockholders may indemnify any broker-dealer
that participates in transactions involving the sale of the shares against certain liabilities, including liabilities arising under
the Securities Act.

 

We have agreed to indemnify
the selling stockholders against liabilities, including liabilities under the Securities Act and state securities laws, relating
to the registration of the shares offered by this prospectus.

 

We have agreed with
the selling stockholders to keep the registration statement of which this prospectus constitutes a part effective until the earlier
of (1) such time as all of the shares covered by this prospectus have been disposed of pursuant to and in accordance with the registration
statement or (2) the date on which all of the shares may be sold without restriction pursuant to Rule 144 of the Securities Act.

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