September 28, 2018 Secured Convertible Promissory Note from the Company to Iliad Research and Trading, L.P

NEITHER THESE SECURITIES NOR THE SECURITIES INTO WHICH THESE SECURITIES ARE CONVERTIBLE HAVE BEEN REGISTERED WITH THE SECURITIES AND EXCHANGE COMMISSION IN RELIANCE UPON AN EXEMPTION FROM REGISTRATION UNDER THE SECURITIES ACT OF 1933, AS AMENDED (THE “SECURITIES ACT”), AND ACCORDINGLY, MAY NOT BE OFFERED OR SOLD EXCEPT PURSUANT TO AN EFFECTIVE REGISTRATION STATEMENT UNDER THE SECURITIES ACT OR PURSUANT TO AN AVAILABLE EXEMPTION FROM, OR IN A TRANSACTION NOT SUBJECT TO, THE REGISTRATION REQUIREMENTS OF THE SECURITIES ACT

SECURED CONVERTIBLE PROMISSORY NOTE

FOR VALUE RECEIVED, Hemispherx Biopharma, Inc., a Delaware corporation (“Borrower”), promises to pay to Iliad Research and Trading, L.P., a Utah limited partnership, or its successors or assigns (“Lender”), $3,170,000.00 and any interest, fees, charges, and late fees accrued hereunder on the date that is twelve (12) months after the Purchase Price Date (the “Maturity Date”) in accordance with the terms set forth herein and to pay interest on the Outstanding Balance at the rate of ten percent (10%) per annum from the Purchase Price Date until the same is paid in full. This Secured Convertible Promissory Note (this “Note”) is issued and made effective as of September 28, 2018 (the “Effective Date”). This Note is issued pursuant to that certain Securities Purchase Agreement dated September 28, 2018, as the same may be amended from time to time, by and between Borrower and Lender (the “Purchase Agreement”). Certain capitalized terms used herein are defined in Attachment 1 attached hereto and incorporated herein by this reference.

This Note carries an OID of $150,000.00. In addition, Borrower agrees to pay $20,000.00 to Lender to cover Lender’s legal fees, accounting costs, due diligence, monitoring and other transaction costs incurred in connection with the purchase and sale of this Note (the “Transaction Expense Amount”), all of which amount is included in the initial principal balance of this Note. The purchase price for this Note shall be $3,000,000.00 (the “Purchase Price”), computed as follows: $3,170,000.00 original principal balance, less the OID, less the Transaction Expense Amount. The Purchase Price shall be payable by Lender by wire transfer of immediately available funds.

1. Payment; Prepayment.

1.1. Payment. All payments owing hereunder shall be in lawful money of the United States of America or Conversion Shares (as defined below), as provided for herein, and delivered to Lender at the address or bank account furnished to Borrower for that purpose. All payments shall be applied first to (a) costs of collection, if any, then to (b) fees and charges, if any, then to (c) accrued and unpaid interest, and thereafter, to (d) principal.

1.2. Prepayment. Notwithstanding the foregoing, Borrower shall have the right to prepay all or any portion of the Outstanding Balance (less such portion of the Outstanding Balance for which Borrower has received a Lender Conversion Notice (as defined below) or a Redemption Notice (as defined below) from Lender where the applicable Conversion Shares have not yet been delivered. If Borrower exercises its right to prepay this Note, Borrower shall make payment to Lender of an amount in cash equal to 115% multiplied by the portion of the Outstanding Balance Borrower elects to repay.

2. Security. This Note is secured by that certain Security Agreement of even date herewith, as the same may be amended from time to time (the “Security Agreement”), executed by Borrower in favor of Lender encumbering certain of Borrower’s assets, as more specifically set forth in the Security Agreement, all the terms and conditions of which are hereby incorporated into and made a part of this Note.

3. Lender Optional Conversion.

3.1. Lender Conversions. Subject to Sections 12 and 13 below, Lender has the right at any time after the Purchase Price Date until the Outstanding Balance has been paid in full, at its election, to convert (“Lender Conversion”) all or any portion of the Outstanding Balance into shares (each instance of conversion is referred herein as a “Lender Conversion Shares”) of fully paid and non-assessable common stock, $0.001 par value per share (“Common Stock”), of Borrower as per the following conversion formula: the number of Lender Conversion Shares equals the amount being converted (the “Conversion Amount”) divided by the Lender Conversion Price (as defined below). Conversion notices in the form attached hereto as Exhibit A (each, a “Lender Conversion Notice”) may be effectively delivered to Borrower by any method set forth in Section 8.9 of the Purchase Agreement, and all Lender Conversions shall be cashless and not require further payment from Lender. Borrower shall deliver the Lender Conversion Shares from any Lender Conversion to Lender in accordance with Section 9 below.

3.2. Lender Conversion Price. Subject to adjustment as set forth in this Note, the price at which Lender has the right to convert all or any portion of the Outstanding Balance into Common Stock is $0.30 per share of Common Stock (the “Lender Conversion Price”).

4. Defaults and Remedies.

4.1. Defaults. The following are events of default under this Note (each, an “Event of Default”): (a) Borrower fails to pay any principal, interest, fees, charges, or any other amount when due and payable hereunder; (b) subject to Section 12 and 13 below, Borrower fails to deliver any Lender Conversion Shares in accordance with the terms hereof and such default continues for two (2) Trading Days after written notice to Company by Lender of such default; (c) subject to Section 12 and 13 below, Borrower fails to deliver any Redemption Conversion Shares (as defined below) in accordance with the terms hereof and such default continues for two (2) Trading Days after written notice to Company by Lender of such default; (d) a receiver, trustee or other similar official shall be appointed over Borrower or a material part of its assets and such appointment shall remain uncontested for twenty (20) days or shall not be dismissed or discharged within sixty (60) days; (e) Borrower admits in writing its inability to pay, its debts as they become due, subject to applicable grace periods, if any; (f) Borrower makes a general assignment for the benefit of creditors; (g) Borrower files a petition for relief under any bankruptcy, insolvency or similar law (domestic or foreign); (h) an involuntary bankruptcy proceeding is commenced or filed against Borrower and is not dismissed within sixty (60) days; (i) Borrower or any pledgor, trustor, or guarantor of this Note defaults or otherwise fails to observe or perform any covenant, obligation, condition or agreement of Borrower or such pledgor, trustor, or guarantor contained herein or in any other Transaction Document (as defined in the Purchase Agreement), other than those specifically set forth in this Section 4.1 and Section 4 of the Purchase Agreement and such default or failure remains uncured for a period of ten (10) days after written notice to Company by Lender of such default or failure; (j) any representation, warranty or other statement made or furnished by or on behalf of Borrower or any pledgor, trustor, or guarantor of this Note to Lender herein, in any Transaction Document, or otherwise in connection with the issuance of this Note is false, incorrect, incomplete or misleading in any material respect when made or furnished; (k) the occurrence of a Fundamental Transaction without Lender’s prior written consent; (l) Borrower fails to maintain the Share Reserve (as defined in the Purchase Agreement) as required under the Purchase Agreement and such failure continues for five (5) days after written notice to Company by Lender of such failure; (m) Borrower effectuates a reverse split of its Common Stock without twenty (20) Trading Days prior written notice to Lender; (n) any money judgment, writ or similar process is entered or filed against Borrower or any subsidiary of Borrower or any of its property or other assets for more than $1,000,000.00, and shall remain unvacated, unbonded or unstayed for a period of twenty (20) calendar days unless otherwise consented to by Lender; (o) Borrower fails to be DWAC Eligible at any time after the six (6) month anniversary of the Closing and such failure continues for ten (10) days after written notice to Company by Lender of such failure; (p) [intentionally omitted]; (q) Borrower fails to observe or perform any covenant set forth in Section 4 of the Purchase Agreement (other than the covenant with respect to Unapproved Variable Security Issuances); or (r) Borrower makes any Unapproved Variable Security Issuance.

4.2. Remedies. At any time and from time to time after Lender becomes aware of the occurrence of any Event of Default, Lender may accelerate this Note by written notice to Borrower, with the Outstanding Balance becoming immediately due and payable in cash at the Mandatory Default Amount. Notwithstanding the foregoing, at any time following the occurrence of any Event of Default, Lender may, at its option, elect to increase the Outstanding Balance by applying the Default Effect (subject to the limitation set forth below) via written notice to Borrower without accelerating the Outstanding Balance, in which event the Outstanding Balance shall be increased as of the date of the occurrence of the applicable Event of Default pursuant to the Default Effect, but the Outstanding Balance shall not be immediately due and payable unless so declared by Lender (for the avoidance of doubt, if Lender elects to apply the Default Effect pursuant to this sentence, it shall reserve the right to declare the Outstanding Balance immediately due and payable at any time and no such election by Lender shall be deemed to be a waiver of its right to declare the Outstanding Balance immediately due and payable as set forth herein unless otherwise agreed to by Lender in writing). Notwithstanding the foregoing, upon the occurrence of any Event of Default described in clauses (d), (e), (f), (g) or (h) of Section 4.1, the Outstanding Balance as of the date of acceleration shall become immediately and automatically due and payable in cash at the Mandatory Default Amount, without any written notice required by Lender. At any time following the occurrence of any Event of Default, upon written notice given by Lender to Borrower, interest shall accrue on the Outstanding Balance beginning on the date the applicable Event of Default occurred at an interest rate equal to the lesser of 22% per annum or the maximum rate permitted under applicable law (“Default Interest”). For the avoidance of doubt, Lender may continue making Lender Conversions and Redemption Conversions (as defined below) at any time following an Event of Default until such time as the Outstanding Balance is paid in full. In connection with acceleration described herein, Lender need not provide, and Borrower hereby waives, any presentment, demand, protest or other notice of any kind, and Lender may immediately and without expiration of any grace period enforce any and all of its rights and remedies hereunder and all other remedies available to it under applicable law. Such acceleration may be rescinded and annulled by Lender at any time prior to payment hereunder and Lender shall have all rights as a holder of the Note until such time, if any, as Lender receives full payment pursuant to this Section 4.2. No such rescission or annulment shall affect any subsequent Event of Default or impair any right consequent thereon. Nothing herein shall limit Lender’s right to pursue any other remedies available to it at law or in equity including, without limitation, a decree of specific performance and/or injunctive relief with respect to Borrower’s failure to timely deliver Conversion Shares upon Conversion of the Note as required pursuant to the terms hereof.

5. Unconditional Obligation; No Offset. Borrower acknowledges that this Note is an unconditional, valid, binding and enforceable obligation of Borrower not subject to offset, deduction or counterclaim of any kind. Borrower hereby waives any rights of offset it now has or may have hereafter against Lender, its successors and assigns, and agrees to make the payments or Conversions called for herein in accordance with the terms of this Note.

6. Waiver. No waiver of any provision of this Note shall be effective unless it is in the form of a writing signed by the party granting the waiver. No waiver of any provision or consent to any prohibited action shall constitute a waiver of any other provision or consent to any other prohibited action, whether or not similar. No waiver or consent shall constitute a continuing waiver or consent or commit a party to provide a waiver or consent in the future except to the extent specifically set forth in writing.

7. Adjustment of Lender Conversion Price upon Subdivision or Combination of Common Stock. Without limiting any provision hereof, if Borrower 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 Lender Conversion Price in effect immediately prior to such subdivision will be proportionately reduced. Without limiting any provision hereof, if Borrower 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 Lender Conversion Price in effect immediately prior to such combination will be proportionately increased. Any adjustment pursuant to this Section 7 shall become effective immediately after the effective date of such subdivision or combination. If any event requiring an adjustment under this Section 7 occurs during the period that a Lender Conversion Price is calculated hereunder, then the calculation of such Lender Conversion Price shall be adjusted appropriately to reflect such event.

8. Borrower Redemptions.

8.1. Redemption Conversion Price. Subject to the adjustments set forth herein, the conversion price for each Redemption Conversion (the “Redemption Conversion Price”) shall be the lesser of (a) the Lender Conversion Price, and (b) the Market Price.

8.2. Redemption Conversions. Beginning on the date that is six (6) months from the Purchase Price Date, Lender shall have the right, exercisable at any time in its sole and absolute discretion, to redeem all or any portion of the Note (such amount, the “Redemption Amount”) by providing Borrower with a notice substantially in the form attached hereto as Exhibit B (each, a “Redemption Notice”, and each date on which Lender delivers a Redemption Notice, a “Redemption Date”). For the avoidance of doubt, Lender may submit to Borrower one (1) or more Redemption Notices in any given calendar month. Payments of each Redemption Amount may be made (a) in cash, or (b) by converting such Redemption Amount into shares of Common Stock (“Redemption Conversion Shares”, and together with the Lender Conversion Shares, the “Conversion Shares”) in accordance with this Section 8.2 (each, a “Redemption Conversion”) per the following formula: the number of Redemption Conversion Shares equals the portion of the applicable Redemption Amount being converted divided by the Redemption Conversion Price, or (c) by any combination of the foregoing, so long as the cash is delivered to Lender on the third (3^rd) Trading Day immediately following the applicable Redemption Date and the Redemption Conversion Shares are delivered to Lender on or before the applicable Delivery Date (as defined below). Notwithstanding that failure to repay this Note in full by the Maturity Date is an Event of Default, the Redemption Dates shall continue after the Maturity Date pursuant to this Section 8.2 until the Outstanding Balance is repaid in full.

8.3. Allocation of Redemption Amounts. Following its receipt of a Redemption Notice, Borrower may either ratify Lender’s proposed allocation in the applicable Redemption Notice or elect to change the allocation by written notice to Lender by email or fax by the end of the next Trading Day immediately following the date of delivery of such Redemption Notice, with a copy of such written notice to the transfer agent of the Common Stock, so long as the sum of the cash payments and the amount of Redemption Conversions equal the applicable Redemption Amount. If Borrower fails to notify Lender of its election to change the allocation prior to the deadline set forth in the previous sentence, it shall be deemed to have ratified and accepted the allocation set forth in the applicable Redemption Notice prepared by Lender. Borrower acknowledges and agrees that the amounts and calculations set forth thereon are subject to correction or adjustment because of error, mistake, or any adjustment resulting from an Event of Default or other adjustment permitted under the Transaction Documents (an “Adjustment”). Furthermore, no error or mistake in the preparation of such notices, or failure to apply any Adjustment that could have been applied prior to the preparation of a Redemption Notice may be deemed a waiver of Lender’s right to enforce the terms of any Note, even if such error, mistake, or failure to include an Adjustment arises from Lender’s own calculation. Borrower shall deliver the Redemption Conversion Shares from any Redemption Conversion to Lender in accordance with Section 9 below on or before each applicable Delivery Date.

9. Method of Conversion Share Delivery. On or before the close of business on the third (3^rd) Trading Day following each Redemption Date or the third (3^rd) Trading Day following the date of delivery of a Lender Conversion Notice, as applicable (the “Delivery Date”), Borrower shall, provided it is DWAC Eligible at such time and such Conversion Shares are eligible for delivery via DWAC, deliver or cause its transfer agent to deliver the applicable Conversion Shares electronically via DWAC to the account designated by Lender in the applicable Lender Conversion Notice or Redemption Notice. If Borrower is not DWAC Eligible or such Conversion Shares are not eligible for delivery via DWAC, it shall deliver to Lender or its broker (as designated in the Lender Conversion Notice or Redemption Notice), via reputable overnight courier, a certificate representing the number of shares of Common Stock equal to the number of Conversion Shares to which Lender shall be entitled, registered in the name of Lender or its designee. For the avoidance of doubt, Borrower has not met its obligation to deliver Conversion Shares by the Delivery Date unless Lender or its broker, as applicable, has actually received the certificate representing the applicable Conversion Shares no later than the close of business on the relevant Delivery Date pursuant to the terms set forth above. Moreover, and notwithstanding anything to the contrary herein or in any other Transaction Document, in the event Borrower or its transfer agent refuses to deliver any Conversion Shares without a restrictive securities legend to Lender on grounds that such issuance is in violation of Rule 144 under the Securities Act of 1933, as amended (“Rule 144”), Borrower shall deliver or cause its transfer agent to deliver the applicable Conversion Shares to Lender with a restricted securities legend, but otherwise in accordance with the provisions of this Section 9. In conjunction therewith, Borrower will also deliver to Lender a written explanation from its counsel or its transfer agent’s counsel opining as to why the issuance of the applicable Conversion Shares violates Rule 144; provided, Lender acknowledges that any Conversion Shares issued prior to the six (6) month anniversary of the Closing Date will bear a restrictive securities legend, and Borrower shall have no obligation to deliver such opinion letter for any Conversion occurring prior to the six (6) month anniversary of the Closing Date.

10. Conversion Delays. If Borrower fails to deliver Conversion Shares in accordance with the timeframe stated in Section 9, Lender may at any time prior to receiving the applicable Conversion Shares rescind in whole or in part such Conversion, with a corresponding increase to the Outstanding Balance (any returned amount will tack back to the Purchase Price Date for purposes of determining the holding period under Rule 144). In addition, for each Conversion, in the event that Conversion Shares are not delivered by the third (3^rd) Trading Day (inclusive of the day of the Conversion), a late fee equal to 2% of the applicable Conversion Share Value rounded to the nearest multiple of $100.00 but with a floor of $500.00 per day (but in any event the cumulative amount of such late fees for each Conversion shall not exceed 200% of the applicable Conversion Share Value) will be assessed for each day after the third (3^rd) Trading Day (inclusive of the day of the Conversion) until Conversion Share delivery is made; and such late fee will be added to the Outstanding Balance (such fees, the “Conversion Delay Late Fees”).

11. Approved Variable Security Issuance. The Outstanding Balance will automatically be increased by five percent (5%) for each Approved Variable Security Issuance made by Borrower (without the need for Lender to provide any notice to Borrower of such increase), which increase will be effective as of the date of each applicable Approved Variable Security Issuance.

12. Ownership Limitation. Notwithstanding anything to the contrary contained in this Note or the other Transaction Documents, the Company shall not effect any conversion of this Note, and Lender shall not have the right to convert any portion of this Note, and shall not deliver a Conversion Notice, to the extent that after giving effect to such conversion would cause Lender (together with its affiliates) to beneficially own a number of shares exceeding 4.99% of the number of shares of Common Stock outstanding on such date (including for such purpose the shares of Common Stock issuable upon such issuance) (the “Maximum Percentage”). For purposes of this section, beneficial ownership of Common Stock will be determined pursuant to Section 13(d) of the 1934 Act. Notwithstanding the forgoing, the term “4.99%” above shall be replaced with “9.99%” at such time as the Market Capitalization is less than $10,000,000.00. Notwithstanding any other provision contained herein, if the term “4.99%” is replaced with “9.99%” pursuant to the preceding sentence, such increase to “9.99%” shall remain at 9.99% until increased, decreased or waived by Lender as set forth below. By written notice to Borrower, Lender may increase, decrease or waive the Maximum Percentage as to itself but any such waiver will not be effective until the 61st day after delivery thereof. The foregoing 61-day notice requirement is enforceable, unconditional and non-waivable and shall apply to all affiliates and assigns of Lender.

13. Issuance Cap. Notwithstanding anything to the contrary contained in this Note or the other Transaction Documents, Borrower and Lender agree that the total cumulative number of shares of Common Stock issued to Lender hereunder together with all other Transaction Documents may not exceed the requirements of NYSE Listing Rule 312.03(c) (“NYSE 19.99% Cap”), except that such limitation will not apply following Approval (defined below). If the number of shares of Common Stock issued to Lender reaches the NYSE 19.99% Cap, so as not to violate the 20% limit established in NYSE Listing Rule 312.03(c), Borrower will use reasonable commercial efforts to obtain stockholder approval of the Note and the issuance of additional Conversion Shares, if necessary, in accordance with the requirements of NYSE Listing Rule 312.03(c) (the “Approval”), and until the Approval has been obtained, Lender shall not submit any Conversion Notice to the extent after giving effect to such conversion would exceed the NYSE 19.99% Cap. If the Borrower is unable to obtain such Approval, any remaining Outstanding Balance of this Note must be repaid in cash.

14. Opinion of Counsel. In the event that an opinion of counsel is needed for any matter related to this Note, Lender has the right to have any such opinion provided by its counsel.

15. Governing Law; Venue. This Note shall be construed and enforced in accordance with, and all questions concerning the construction, validity, interpretation and performance of this Note shall be governed by, the internal laws of the State of Utah, without giving effect to any choice of law or conflict of law provision or rule (whether of the State of Utah or any other jurisdiction) that would cause the application of the laws of any jurisdiction other than the State of Utah. The provisions set forth in the Purchase Agreement to determine the proper venue for any disputes are incorporated herein by this reference.

16. Arbitration of Disputes. By its issuance or acceptance of this Note, each party agrees to be bound by the Arbitration Provisions (as defined in the Purchase Agreement) set forth as an exhibit to the Purchase Agreement.

17. Cancellation. After repayment or conversion of the entire Outstanding Balance, this Note shall be deemed paid in full, shall automatically be deemed canceled, and shall not be reissued.

18. Amendments. The prior written consent of both parties hereto shall be required for any change or amendment to this Note.

19. Assignments. Borrower may not assign this Note without the prior written consent of Lender. Subject to compliance with any applicable securities laws and the immediately following sentence, this Note and any shares of Common Stock issued upon conversion of this Note may be offered, sold, assigned or transferred by Lender without the consent of Borrower. If at the time of any transfer of this Note or any shares of Common Stock issued upon conversion of this Note, the transfer of such Securities shall not be either (i) registered pursuant to an effective registration statement under the 1933 Act and under applicable state securities or blue sky laws or (ii) eligible for resale without volume or manner-of-sale restrictions or current public information requirements pursuant to Rule 144, the Company may require, as a condition of allowing such transfer, that Lender or transferee, as the case may be, comply with the transfer restrictions set forth on the restrictive legend on the face of such Security.

20. Notices. Whenever notice is required to be given under this Note, unless otherwise provided herein, such notice shall be given in accordance with the subsection of the Purchase Agreement titled “Notices.”

21. Liquidated Damages. Lender and Borrower agree that in the event Borrower fails to comply with any of the terms or provisions of this Note, Lender’s damages would be uncertain and difficult (if not impossible) to accurately estimate because of the parties’ inability to predict future interest rates, future share prices, future trading volumes and other relevant factors. Accordingly, Lender and Borrower agree that any fees, balance adjustments, Default Interest or other charges assessed under this Note are not penalties but instead are intended by the parties to be, and shall be deemed, liquidated damages (under Lender’s and Borrower’s expectations that any such liquidated damages will tack back to the Purchase Price Date for purposes of determining the holding period under Rule 144).

22. Severability. If any part of this Note is construed to be in violation of any law, such part shall be modified to achieve the objective of Borrower and Lender to the fullest extent permitted by law and the balance of this Note shall remain in full force and effect.

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IN WITNESS WHEREOF, Borrower has caused this Note to be duly executed as of the Effective Date.

ACKNOWLEDGED, ACCEPTED AND AGREED:

LENDER:

Iliad Research and Trading, L.P.

[Signature Page to Secured Convertible Promissory Note]

ATTACHMENT 1

DEFINITIONS

For purposes of this Note, the following terms shall have the following meanings:

A1. “Approved Variable Security Issuance” means a Variable Security Issuance (as defined in the Purchase Agreement) for which Borrower received Lender’s written consent prior to the applicable issuance.

A2. “Bloomberg” means Bloomberg L.P. (or if that service is not then reporting the relevant information regarding the Common Stock, a comparable reporting service of national reputation selected by Lender and reasonably satisfactory to Borrower).

A3. “Closing Bid Price” and “Closing Trade Price” means the last closing bid price and last closing trade price, respectively, for the Common Stock on its principal market, as reported by Bloomberg, or, if its principal market begins to operate on an extended hours basis and does not designate the closing bid price or the closing trade price (as the case may be) then the last bid price or last trade price, respectively, of the Common Stock prior to 4:00:00 p.m., New York time, as reported by Bloomberg, or, if its principal market is not the principal securities exchange or trading market for the Common Stock, the last closing bid price or last trade price, respectively, of the Common Stock on the principal securities exchange or trading market where the Common Stock is listed or traded as reported by Bloomberg, or if the foregoing do not apply, the last closing bid price or last trade price, respectively, of the Common Stock in the over-the-counter market on the electronic bulletin board for the Common Stock as reported by Bloomberg, or, if no closing bid price or last trade price, respectively, is reported for the Common Stock by Bloomberg, the average of the bid prices, or the ask prices, respectively, of any market makers for the Common Stock as reported by OTC Markets Group, Inc., and any successor thereto. If the Closing Bid Price or the Closing Trade Price cannot be calculated for the Common Stock on a particular date on any of the foregoing bases, the Closing Bid Price or the Closing Trade Price (as the case may be) of the Common Stock on such date shall be the fair market value as mutually determined by Lender and Borrower. All such determinations shall be appropriately adjusted for any stock dividend, stock split, stock combination or other similar transaction during such period.

A4. “Conversion” means a Lender Conversion under Section 3 or a Redemption Conversion under Section 8.

A5. “Conversion Factor” means 80%.

A6. “Conversion Share Value” means the product of the number of Conversion Shares deliverable pursuant to any Conversion Notice multiplied by the Closing Trade Price of the Common Stock on the Delivery Date for such Conversion.

A7. “Default Effect” means multiplying the Outstanding Balance as of the date the applicable Event of Default occurred by (a) fifteen percent (15%) for each occurrence of any Major Default, (b) ten percent (10%) for each occurrence of an Unapproved Variable Security Issuance Default, or (c) five percent (5%) for each occurrence of any Minor Default, and then adding the resulting product to the Outstanding Balance as of the date the applicable Event of Default occurred, with the sum of the foregoing then becoming the Outstanding Balance under this Note as of the date the applicable Event of Default occurred; provided that the aggregate amount of the Default Effect for all Major Defaults and Minor Defaults shall not exceed twenty-five percent (25%); and provided further that the Default Effect shall not apply to any Event of Default pursuant to Section 4.1(b) hereof. There shall be no limit on the number of times the Default Effect may be applied with respect to Unapproved Variable Security Issuance Defaults.

A8. “DTC” means the Depository Trust Company or any successor thereto.

A9. “DTC/FAST Program” means the DTC’s Fast Automated Securities Transfer program.

A10. “DWAC” means the DTC’s Deposit/Withdrawal at Custodian system.

A11. “DWAC Eligible” means that (a) Borrower’s Common Stock is eligible at DTC for full services pursuant to DTC’s operational arrangements, including without limitation transfer through DTC’s DWAC system; (b) Borrower has been approved (without revocation) by DTC’s underwriting department; (c) Borrower’s transfer agent is approved as an agent in the DTC/FAST Program; (d) the Conversion Shares are otherwise eligible for delivery via DWAC other than due to the actions or status of Lender; and (e) Borrower’s transfer agent does not have a policy prohibiting or limiting delivery of the Conversion Shares via DWAC.

A12. “Fundamental Transaction” means that (a) (i) Borrower shall, directly or indirectly, in one or more related transactions, consolidate or merge with or into (whether or not Borrower or any of its subsidiaries is the surviving corporation) any other person or entity, or (ii) Borrower shall, directly or indirectly, in one or more related transactions, sell, lease, license, assign, transfer, convey or otherwise dispose of all or substantially all of its respective properties or assets to any other person or entity, or (iii) Borrower shall, directly or indirectly, in one or more related transactions, allow any other person or entity to make a purchase, tender or exchange offer that is accepted by the holders of more than 50% of the outstanding shares of voting stock of Borrower (not including any shares of voting stock of Borrower held by the person or persons making or party to, or associated or affiliated with the persons or entities making or party to, such purchase, tender or exchange offer), or (iv) Borrower shall, directly or indirectly, in one or more related transactions, consummate a stock or share purchase agreement or other business combination (including, without limitation, a reorganization, recapitalization, spin-off or scheme of arrangement) with any other person or entity whereby such other person or entity acquires more than 50% of the outstanding shares of voting stock of Borrower (not including any shares of voting stock of Borrower held by the other persons or entities making or party to, or associated or affiliated with the other persons or entities making or party to, such stock or share purchase agreement or other business combination), or (v) Borrower shall, directly or indirectly, in one or more related transactions, reorganize, recapitalize or reclassify the Common Stock, other than an increase in the number of authorized shares of Borrower’s Common Stock, or (b) any “person” or “group” (as these terms are used for purposes of Sections 13(d) and 14(d) of the 1934 Act and the rules and regulations promulgated thereunder) is or shall become the “beneficial owner” (as defined in Rule 13d-3 under the 1934 Act), directly or indirectly, of 50% of the aggregate ordinary voting power represented by issued and outstanding voting stock of Borrower.

A13. “Major Default” means any Event of Default occurring under Sections 4.1(a), 4.1(c), 4.1(l), or 4.1(q) of this Note.

A14. “Mandatory Default Amount” means the Outstanding Balance following the application of the Default Effect.

A15. “Market Capitalization” means a number equal to (a) the average VWAP of the Common Stock for the immediately preceding fifteen (15) Trading Days, multiplied by (b) the aggregate number of outstanding shares of Common Stock as reported on Borrower’s most recently filed Form 10-Q or Form 10-K.

A16. “Market Price” means the Conversion Factor multiplied by the lowest daily VWAP during the ten (10) Trading Days immediately preceding the applicable measurement date.

A17. “Minor Default” means any Event of Default that is not a Major Default or an Unapproved Variable Security Issuance Default.

A18. “OID” means an original issue discount.

A19. “Other Agreements” means, collectively, (a) all existing and future agreements and instruments between, among or by Borrower (or an affiliate), on the one hand, and Lender (or an affiliate), on the other hand, and (b) any financing agreement or a material agreement that affects Borrower’s ongoing business operations.

A20. “Outstanding Balance” means as of any date of determination, the Purchase Price, as reduced or increased, as the case may be, pursuant to the terms hereof for payment, Conversion, offset, or otherwise, plus the OID, the Transaction Expense Amount, accrued but unpaid interest, collection and enforcements costs (including attorneys’ fees) incurred by Lender, transfer, stamp, issuance and similar taxes and fees related to Conversions, and any other fees or charges (including without limitation Conversion Delay Late Fees) incurred under this Note.

A21. “Purchase Price Date” means the date the Purchase Price is delivered by Lender to Borrower.

A22. “Trading Day” means any day on which the New York Stock Exchange (or such other principal market for the Common Stock) is open for trading.

A23. “Unapproved Variable Security Issuance” means a Variable Security Issuance for which Borrower did not receive Lender’s written consent prior to the applicable issuance.

A24. “Unapproved Variable Security Issuance Default” means an Event of Default occurring under Section 4.1(r) of this Note.

A25. “VWAP” means the volume weighted average price of the Common stock on the principal market for a particular Trading Day or set of Trading Days, as the case may be, as reported by Bloomberg.

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EXHIBIT A

Iliad Research and Trading, L.P.

303 East Wacker Drive, Suite 1040

Chicago, Illinois 60601

LENDER CONVERSION NOTICE

The above-captioned Lender hereby gives notice to Hemispherx Biopharma, Inc., a Delaware corporation (the “Borrower”), pursuant to that certain Secured Convertible Promissory Note made by Borrower in favor of Lender on September 28, 2018 (the “Note”), that Lender elects to convert the portion of the Note balance set forth below into fully paid and non-assessable shares of Common Stock of Borrower as of the date of conversion specified below. Said conversion shall be based on the Lender Conversion Price set forth below. In the event of a conflict between this Lender Conversion Notice and the Note, the Note shall govern, or, in the alternative, at the election of Lender in its sole discretion, Lender may provide a new form of Lender Conversion Notice to conform to the Note. Capitalized terms used in this notice without definition shall have the meanings given to them in the Note.

* Subject to adjustments for corrections, defaults, interest and other adjustments permitted by the Transaction Documents (as defined in the Purchase Agreement), the terms of which shall control in the event of any dispute between the terms of this Lender Conversion Notice and such Transaction Documents.

Please transfer the Lender Conversion Shares electronically (via DWAC) to the following account:

To the extent the Lender Conversion Shares are not able to be delivered to Lender electronically via the DWAC system, deliver all such certificated shares to Lender via reputable overnight courier after receipt of this Lender Conversion Notice (by facsimile transmission or otherwise) to:

[Signature Page Follows]

Sincerely,

Lender:

Iliad Research and Trading, L.P.

EXHIBIT B

Iliad Research and Trading, L.P.

303 East Wacker Drive, Suite 1040

Chicago, Illinois 60601

REDEMPTION NOTICE

The above-captioned Lender hereby gives notice to Hemispherx Biopharma, Inc., a Delaware corporation (the “Borrower”), pursuant to that certain Secured Convertible Promissory Note made by Borrower in favor of Lender on September 28, 2018 (the “Note”), that Lender elects to redeem a portion of the Note in Redemption Conversion Shares or in cash as set forth below. In the event of a conflict between this Redemption Notice and the Note, the Note shall govern, or, in the alternative, at the election of Lender in its sole discretion, Lender may provide a new form of Redemption Notice to conform to the Note. Capitalized terms used in this notice without definition shall have the meanings given to them in the Note.

REDEMPTION INFORMATION

* Subject to adjustments for corrections, defaults, interest and other adjustments permitted by the Transaction Documents (as defined in the Purchase Agreement), the terms of which shall control in the event of any dispute between the terms of this Redemption Notice and such Transaction Documents.

Please transfer the Redemption Conversion Shares, if applicable, electronically (via DWAC) to the following account:

To the extent the Redemption Conversion Shares are not able to be delivered to Lender electronically via the DWAC system, deliver all such certificated shares to Lender via reputable overnight courier after receipt of this Redemption Notice (by facsimile transmission or otherwise) to:

Sincerely,

Lender:

Iliad Research and Trading, L.P.