Oxurion : Supplement to the Prospectus of 30 August 2022

Oxurion NV

Gaston Geenslaan 1, 3001 Leuven, Belgium

SUPPLEMENT TO THE PROSPECTUS FOR THE ADMISSION TO LISTING AND TRADING ON EURONEXT

BRUSSELS DATED 30 AUGUST 2022

This document supplements the prospectus dated 30 August 2022 (the "EU Recovery Prospectus") relating to the admission to trading on the regulated market of Euronext Brussels of new shares of Oxurion NV ("Issuer" or "Oxurion" or the "Company") that may be issued by the Company upon conversion of up to 2,680 convertible bonds (the "Class B Convertible Bonds") to be issued as part of a funding program set out in the issuance and subscription agreement entered into by the Company with Negma on 26 August 2021 as amended by means of the addendum dated 2 September 2022 ( "Part B of the Funding Program") (the "New Shares"). This document constitutes a supplement (the "Supplement") to the EU Recovery Prospectus in accordance with article 23 of the Regulation (EU) 2017/1129, as amended from time to time (the "Prospectus Regulation"). This Supplement forms part of and must be read in conjunction with the EU Recovery Prospectus. Capitalised terms used herein have the meaning given to them in the EU Recovery Prospectus unless defined otherwise herein.

This Supplement covers up to 54,500,000 New Shares that have been and/or may be issued by the Company upon conversion of the Class B Convertible Bonds, which consist of the up to 30,500,000 New Shares covered by the EU Recovery Prospectus and an additional up to 24,000,000 New Shares added by means of this Supplement. On the date of this Supplement (and since the date of the EU Recovery Prospectus), 36,757,142 New Shares have been admitted to trading, covered (i) for up to 30,500,000 New Shares by this Supplement (in particular, by the up to 30,500,000 New Shares covered by the EU Recovery Prospectus) and (ii) for the balance, being 6,257,142 New Shares, by the 20% exemption rule,following the conversion of 660 Class B Convertible Bonds (of the, in aggregate, 1,600 Class B Convertible Bonds that have been issued under Part B of the Funding Program). In addition to the 36,757,142 issued New Shares that have already listed, this Supplement covers a further up to 24,000,000 New Shares that may be issued by the Company upon conversion of the Class B Convertible Bonds and that would, pursuant to such conversion, be admitted to trading prior to 30 August 2023. The Company intends to prepare a listing prospectus in accordance with article 14 of the Prospectus Regulation for additional New Shares to be issued upon conversion of the Class B Convertible Bonds.

An investment in the Shares involves significant risks and uncertainties and the investor could lose all or part of the invested capital. Prospective investors should read this entire Supplement in conjunction with the EU Recovery Prospectus, and, in particular, should see the "Summary" and "Part 4: Risk Factors" beginning on page 4 of the EU Recovery Prospectus and section 2 of this Supplement ("Update of information provided in risk factors") for a discussion of certain factors that should be considered in connection with an investment in the Shares. In "Part 4: Risk Factors" of the EU Recovery Prospectus (to be read in conjunction with section 2 of this Supplement ("Update of information provided in risk factors"), the most material risk factors have been presented first within each (sub)category. Potential investors should carefully consider the risks referred to and the other warnings contained in this Supplement and the EU Recovery Prospectus before making any investment decision.

The risks the Company faces include that it requires additional funding to continue the development of THR-149("THR-149" or the "Clinical Asset"). The Company is of the opinion that it currently does not have sufficient working capital to meet its capital requirements from fully committed sources over the 12-month period starting from the date of the EU Recovery Prospectus. The Company's ability to complete the milestones in the development of THR-149 would be put at risk if it is not able to access available funding due to the conditions attached to that funding, raise additional funding and/or reduce its expenditures when required to do so during this 12-month period starting from the date of the EU Recovery Prospectus, all of which is uncertain. Furthermore, if the Company is not able to access available funding due to the conditions attached to that funding, obtain additional funding and/or reduce its expenditures during this period, all of which is uncertain, its ability to continue as a going concern would be threatened.

The Company is also of the opinion that, even if it manages to attract sufficient funding allowing it to cover its working capital needs during the 12-month period starting from the date of the EU Recovery Prospectus, the Company would not have funds available at the end of this 12-month period, unless it is able to access its available funds given the conditions attached to that funding or to attract additional funding, and would therefore continue to face working capital difficulties and its ability to complete the milestones in the development of THR-149 would be put at risk unless in the interim it is able to access available funding in light of the conditions attached to that funding, raise additional funds, and/or reduce its working capital requirements when it is required to do so, all of which is uncertain. If the Company is not able to access available funding in light of the conditions attached to that funding, increase its funding, and/or reduce its expenditures when required to do so, all of which is uncertain, in the period starting 12 months after the date of the EU Recovery Prospectus, its ability to continue as a going concern would be threatened, which would have a material adverse impact on the Company and its shareholders leading to the potential total loss of their entire investment. The Company only has one clinical asset in development and it could fail, which would put the Company's ability to continue as a going concern at risk.

The Company's shares have a relatively limited trading volume. Any sale of a significant number of the Shares on the public markets, or the perception that such sales could or will occur, may adversely affect the market price of the Shares. In particular, the sale of shares issued upon conversion of the convertible bonds under the Funding Program may continue to exert significant pressure on the market price as the Company continues to draw significant amounts under the Funding Program by issuing convertible bonds.

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Neither the Company nor any of its representatives is making any representation to any investor regarding the legality of an investment in the Shares by such investor under the laws applicable to such investor. Each investor should consult with his or her own advisors as to the legal, tax, business, financial and related aspects of an investment in the Shares in their country of residence arising from the acquisition, holding or disposal of the Shares.

This Supplement may not be used for the purpose of, or in connection with, any offer or solicitation by anyone in any jurisdiction in which such offer or solicitation is not authorized or to any person to whom it is unlawful to make such offer or solicitation. This Supplement does not constitute an offer to sell, or an invitation of an offer to purchase, any Shares in any jurisdiction in which such offer or invitation would be unlawful. The Company requires persons into whose possession this Supplement comes to inform themselves of and observe all such restrictions. Any failure to comply with these restrictions may constitute a violation of the securities laws of any such jurisdiction. The Company accepts no legal responsibility for any violation by any person, whether or not a prospective purchaser of Shares, of any such restrictions.

The Company has not authorized any offer of the Shares to the public in any Member State of the European Economic Area or elsewhere. The Shares have not been and will not be registered under the U.S. Securities Act or the applicable securities laws of any state or other jurisdiction of the United States and may not be offered, sold, pledged or transferred within the United States, except pursuant to an applicable exemption from, or in a transaction not subject to, the registration requirements of the U.S. Securities Act. Prospective purchasers are hereby notified that sellers of the Shares may be relying on an applicable exemption from the provisions of Section 5 of the U.S. Securities Act.

Supplement dated 8 November 2022

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1. NUMBER OF SECURITIES COVERED BY THE EU RECOVERY PROSPECTUS

This Supplement relates to an increase of the number of New Shares covered under the EU Recovery Prospectus from 30,500,000 to 54,500,000 New Shares. Therefore, this Supplement covers up to 54,500,000 New Shares that have been and/or may be issued by the Company upon conversion of the Class B Convertible Bonds, which consist of up to 30,500,000 New Shares covered by the EU Recovery Prospectus and an additional up to 24,000,000 New Shares added by means of this Supplement

At the time of its publication, the EU Recovery Prospectus related to the admission to trading on the regulated market of Euronext Brussels of up to 30,500,000 New Shares to be issued by the Company upon conversion of up to 2,680 Class B Convertible Bonds to be issued under Part B of the Funding Program. As the Conversion Price depends on the volume weighted average price of the Shares on Euronext Brussels prior to the conversion notice by Negma, the Conversion Price and therefore the dilution caused upon conversion of the Convertible Bonds, could not be determined on the date of the EU Recovery Prospectus and cannot be determined at the date of this Supplement. The Conversion Price for the Class B Convertible Bonds is equal to 80% of the lowest closing volume weighted average price of the Shares on Euronext Brussels over a period of 15 consecutive trading days expiring on the trading day immediately preceding the date of issuance of a conversion notice by Negma. Since the date of the EU Recovery Prospectus, the stock price of the Shares on Euronext Brussels has fallen significantly, from a closing price of EUR 0.22 on 30 August 2022 to a closing price of EUR 0.02 on 31 October 2022.

The 2,680 Class B Convertible Bonds issued or to be issued under Part B of the Funding Program represent a total principal amount of EUR 6,700,000. Since the date of the EU Recovery Prospectus, 1,600 Class B Convertible Bonds have been issued, ie 1,080 Class B Convertible Bonds were issued on 5 September 2022 and 520 Class B Convertible Bonds were issued on 21 October 2022. Of these 1,600 Class B Convertible Bonds, 790 Class B Convertible Bonds have been converted: (i) 133 Class B Convertible Bonds have been converted on 12 October 2022 at a Conversion Price of EUR 0.07, (ii) 106 Class B Convertible Bonds have been converted on 19 October 2022 at a Conversion Price of EUR 0.07, (iii) 58 Class B Convertible Bonds have been converted on 19 October 2022 at a Conversion Price of EUR 0.07, (iv) 120 Class B Convertible Bonds have been converted on 24 October 2022 at a Conversion Price of EUR 0.06, (v) 123 Class B Convertible Bonds have been converted on 26 October 2022 at a Conversion Price of EUR 0.05, (vi) 120 Class B Convertible Bonds have been converted on 2 November 2022 at a Conversion Price of EUR 0.02 and 130 Class B Convertible Bonds have been converted on 7 November 2022 at a Conversion Price of EUR 0.02. On the date of this Supplement (and since the date of the EU Recovery Prospectus), 36,757,142 New Shares have been admitted to trading, covered (i) for up to 30,500,000 New Shares by this Supplement (in particular, by the up to 30,500,000 New Shares covered by the EU Recovery Prospectus) and (ii) for the balance, being 6,257,142 New Shares, by the 20% exemption rule, following the conversion of 660 Class B Convertible Bonds (of the, in aggregate, 790 Class B Convertible Bonds already converted). In addition to the 36,757,142 issued New Shares that have already listed, this Supplement covers a further up to 24,000,000New Shares that may be issued by the Company upon conversion of the Class B Convertible Bonds (for the avoidance of doubt, including the New Shares issued pursuant to the remaining 130 of the 790 Class B Convertible Bonds already converted). At the date of this Supplement, 810 Class B Convertible Bonds have been issued but not yet converted and up to 1,080 remaining Class B Convertible Bonds can be issued under Part B of the Funding Program for a total principal amount of EUR 2,700,000. If those 1,890 Class B Convertible Bonds would be converted at a hypothetical Conversion Price of EUR 0.02, the total number of additional New Shares to be admitted to trading would be 236,250,000. Please see below under Section 5 for an illustration of the potential dilution.

Under article 14(a) of the Prospectus Regulation, the Company may only draw up an EU Recovery prospectus provided that the number of shares intended to be admitted to trading represents, together with the number of shares already admitted to trading via an EU Recovery prospectus over a period of 12 months, no more than 150 % of the number of shares already admitted to trading on a regulated market on the date of approval of the EU Recovery prospectus. Therefore, the number of New Shares covered under the EU Recovery Prospectus, as supplemented by this Supplement, is limited to 54,500,000 New Shares that may be issued by the Company upon conversion of the Class B Convertible Bonds. Of these 54,500,000 New Shares covered by this Supplement, 36,757,142 New Shares have been admitted to trading (see above). Considering the 30,500,000 issued New Shares that are already covered by this Supplement, this Supplement covers a further up to 24,000,000 New Shares that may be issued by the Company upon conversion of the Class B Convertible Bonds and that would, pursuant to such conversion, be admitted to trading prior to 30 August 2023. The Company intends to prepare a listing prospectus in accordance with article 14 of the Prospectus Regulation for additional New Shares to be issued upon conversion of Class B Convertible Bonds.

The market price of the Shares of the Company has historically been volatile, ranging during the last 12 months prior to the date of approval of this Supplement from a high of EUR 2.37 on 3 November 2021 and a low of EUR 0.02 on 31 October 2022. The Company's existing shares have a relatively limited trading volume. Any sale of a significant number of the Shares on the public markets, or the perception that such sales could or will occur, may adversely affect the market price of the Shares. In particular, the sale of shares issued upon conversion of the convertible bonds under the Funding Program may continue to exert significant pressure on the market price as the Company continues to draw significant amounts under the Funding Program by issuing convertible bonds. In additional thereto, the market price of the Shares may continue to fluctuate significantly in response to a number of factors, some of which are beyond the Company's control, including fluctuations caused by results of the Company's clinical trial, changes in estimates by securities analysts and the potential or actual sales of the Shares, which is exacerbated

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because the Company has limited news flow and analyst coverage with approximately five analysts covering the stock. In addition, stock markets have recently experienced significant price and volume fluctuations, especially with respect to biotech stocks, including in the Company's view as a result of the ongoing COVID-19 pandemic on the macroeconomic outlook. These fluctuations and the Russian invasion in Ukraine have not always been related to the performance of the specific companies whose shares are traded.

2. UPDATE OF INFORMATION PROVIDED IN RISK FACTORS

The information provided in the following risk factors under the EU Recovery Prospectus is updated as follows to reflect the current situation. The underlined and strike through below indicate the relevant changes to the text of the risk factors under the EU Recovery Prospectus.

4.1.1 The Company is of the opinion that it currently does not have sufficient working capital to meet its capital requirements from fully committed sources over the 12-month period starting from the date of this EU Recovery Prospectus. The Company's ability to complete the milestones in the development of THR-149 will be put at risk if it is not able to access available funding due to the conditions attached to that funding, raise additional funding and/or reduce its expenditures when required to do so during the 12-month period starting from the date of this EU Recovery Prospectus, all of which is uncertain. Furthermore, if the Company is not able to access available funding due to the conditions attached to that funding, increase its funding and/or reduce its expenditures when required to do so, all of which is uncertain, during the 12-month period starting from the date of this EU Recovery Prospectus, its ability to continue as a going concern will be threatened, which would have a material adverse impact on the Company and its shareholders leading to the potential total loss of their entire investment

The Company is of the opinion that it currently does not have sufficient working capital from fully committed sources to meet its capital requirements over the 12-month period following the approval of this EU Recovery Prospectus, as reflected in the qualified working capital statement set out in Section 12 of this EU Recovery Prospectus.

The Company included a statement in its 2020 Annual Report and its 2021 Annual Report that there is a material uncertainty with respect to the Company's ability to continue as a going concern. Furthermore, the Board of Directors has established that the net assets of the Company fell below one quarter of the share capital and convened a special general shareholders' meeting that took place on 9 November 2021in accordance with article 7:228 of the BCCA, at which the shareholders decided (i) to continue the Company's operations and (ii) to approve the recovery measures proposed by the Board of Directors to improve the Company's equity.

Concerning the possible sources of funding, the Company has entered into an issuance and subscription agreement with Negma on 26 August 2021 pursuant to which Negma has committed to subscribe to up to EUR 30 million in the Company's equity through mandatory convertible bonds to be issued in tranches and subject to certain conditions (herein referred to as the "Funding Program"). The undertaking of Negma to subscribe to a new tranche is, among other things, subject to the fulfilment of (or waiver thereof) the condition that the average daily value traded over a period of fifteen trading days has not been lower than EUR 50,000 (the Liquidity Condition). There is no such Liquidity Condition under the Part B of the Funding Program. The Company's average daily volume traded (between 10 October 2022 and 31 October 2022) is 2,376,040 shares or EUR 166,322.80 (at a conversion price of EUR 0.07). During such period, the average daily volume traded has been lower than EUR 50,000 on 10, 11, 12, 13 and 20 October 2022.Under Part A ofthe Funding Program, the Company currently has called EUR 5,000,000 out of the total commitment of up to EUR 30,000,000, in exchange for the issuance of 2,000 convertible bonds to Negma. In addition, the Company has paid to Negma EUR 525,000 in commitment fee convertible bonds (i.e., 210 commitment fee convertible bonds) in consideration for the commitment of Negma under the Funding Program. At the date of this EU Recovery Prospectus, ofall 2,210 convertible bonds that have been issued under Part A ofthe Funding Program, 2,010 convertible bondshave been converted into shares of the Company upon conversion requests of Negma.

On 2 September 2022, the Company has entered into an addendum to the initial issuance and subscription agreement with Negma, pursuant to which the Company and Negma have agreed to amend the terms and conditions of part of the Funding Program for a total commitment amount of up to EUR 6 million in the Company's equity through mandatory convertible bonds to be issued in tranches and subject to certain conditions (herein referred to as "Part B of the Funding Program"). As set out above, the remaining part of the Funding Program, for which the initial terms and conditions as set forth in the issuance and subscription agreement with Negma shall apply and remain unchanged, is referred to as "Part A of the Funding Program".

The terms of the Funding Program are more fully described in the board reports prepared in accordance with article 7:198 juncto articles 7:180, 7:191 and 7:193 of the BCCA dated 15 July 2021 (link)and 2 September 2022 and published on the Company's website (link) (respectively, the "Negma Base Board Report" and the "Negma Class B Board Report").

Under the Funding Program, based on the amounts drawn thus far, the Company potentially has access to up to EUR 2521.7million provided the Company can and does draw the maximum tranche on a monthly basis. The Company's ability to draw a tranche is subject to certain conditions such that it may not be able to draw a tranche when it desires to do so. Since the Liquidity Condition under Part A of the Funding Program is expressed as an amount in EUR and taking into account the Company's (reduced) stock price, it is currently uncertain whether the Company would be able to meet this condition and draw under Part A of the Funding Program in the future absent trading from Negma (see also further below).

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Under Part B of the Funding Program, the Company potentially has access to an amount up to EUR 6 million (minus the aggregate amount of EUR 3,300,000 drawn so far (see also further below))by the end of financial year 2022 provided the Company can and does draw the maximum tranches and the other conditions are met. Part A of the Funding Program is suspended from 2 September 2022 (i.e., the date of the aforementioned addendum) until 31 December 2022, unless expressly agreed otherwise between the Company and Negma in writing. Upon expiry of such period, Part A of the Funding Program will be automatically reactivated and the initial terms and conditions as set forth in the issuance and subscription agreement with Negma shall fully apply again for the remaining part of the total commitment of up to EUR 30 million (including, for the avoidance of doubt, all Class B Convertible Bonds that have not been issued and subscribed to in full within the relevant commitment period). However, since the Liquidity Condition under Part A of the Funding Program is expressed as an amount in EUR and taking into account the Company's (reduced) stock price (ie 0.02 on 31 October 2022), it is uncertain whether the Company would be able to meet this Liquidity Condition absent trading from Negma. Therefore, unless the Company's stock price increases, it is uncertain whether the Company would be able to draw under Part A of the Funding Program in the future, except to the extent that such trading continues. As indicated above, the Liquidition Condition does not apply under Part B of the Funding Program.

At the date of this Supplement, 1,600 Class B Convertible bonds have been issued under Part B of the Funding Program and 660 Class B Convertible Bonds have been converted into 36,757,142 New Shares of the Company upon conversion request of Negma. Hence, at the date of this Supplement, a total of 3,810 convertible bonds have been issued under Part A of the Funding Program and Part B of the Funding Program together, and, of these bonds, 2,870 convertible bonds have been converted into 47,307,776 shares of the Company upon conversion requests of Negma.

Besides its possibility to draw future tranches from the Funding Program, the Company expects to meet its working capital requirements through a combination of debt and equity, including accessing the debt markets and/or raising additional equity capital and/or entering into licensing arrangements, all of which is uncertain, in particular taking into account the Company's current market capitalization.

Furthermore, the Company may consider outlicensing THR-149, which could reduce its costs because the licensor could pay all or part of the relevant trial, and potentially increase its revenues through upfront and milestone payments (and eventually royalties). For example, the Company may decide to out-licenseTHR-149 in specific geographic markets. However, if due to cash constraints, the Company enters into a license at an inopportune moment or on disadvantageous terms, this could have a significant negative impact on the Company's valuation and on its shareholders.

The Company's ability to complete the milestones in the development of THR-149 will be put at risk if it is not able to access available funding due to the conditions attached to that funding, raise additional funding and/or reduce its expenditures when required to do so, all of which is uncertain, during the 12-month period starting from the date of this EU Recovery Prospectus. Furthermore, if the Company is not able to access available funding due to the conditions attached to that funding, increase its funding and/or reduce its expenditures when required to do so, all of which is uncertain, during the 12-month period starting from the date of this EU Recovery Prospectus, its ability to continue as a going concern will be threatened, which would have a material adverse impact on the Company and its shareholders leading to the potential total loss of their entire investment (please refer to Section 5.1 'Financial Statements Incorporated by Reference' and Section 12 'Working Capital Statement', for further information).

4.1.2 The Company is also of the opinion that, even if it manages to attract sufficient funding allowing it to cover its working capital needs during the 12-month period starting from the date of this EU Recovery Prospectus, the Company will not have funds available at the end of this 12-month period, unless it is able to access its available funds given the conditions attached to that funding or to attract additional funding, and will therefore continue to face working capital difficulties and its ability to complete the milestones in the development of its Clinical Asset will be put at risk unless in the interim it is able to access available funding in light of the conditions attached to that funding, raise additional funds, and/or reduce its working capital requirements when it is required to do so, all of which is uncertain. If the Company is not able to access available funding in light of the conditions attached to that funding, increase its funding, and/or reduce its expenditures when required to do so, all of which is uncertain, in the period starting 12 months after the date of this EU Recovery Prospectus, its ability to continue as a going concern will be threatened, which would have a material adverse impact on the Company and its shareholders leading to the potential total loss of their entire investment

In addition to the period of 12 months following the approval of this EU Recovery Prospectus as described in Section 4.1.1 of Section 4 'Risk Factors', the Company is also of the opinion that, even if it manages to attract sufficient funding allowing it to cover its working capital needs during the 12-month period starting from the date of this EU Recovery Prospectus, the Company will not have funds available at the end of this 12-month period unless it is able to access its available funds given the conditions attached to that funding or to attract additional funding. The Company will therefore continue to face working capital difficulties unless in the interim it is able to access available funding in light of the conditions attached to that funding, raise additional funds, and/or reduce its working capital requirements when it is required to do so, all of which is uncertain, in particular taking into account the Company's current market capitalization(please refer to Section 12 'Working Capital Statement', for further information).

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