# EDGAR Filing Document

**Accession Number:** 0001839947
**File Stem:** 0001193125-25-283064
**Filing Date:** 2025-11
**Character Count:** 21359
**Document Hash:** 58a7bf5fdaafbc8f735d6b2c538d445a
**Contains OCR:** False
**Source Format:** 

## Filing Content

## Filing Summary
**0001193125-25-283064.hdr.sgml**: 20251114

**ACCESSION NUMBER**: 0001193125-25-283064

**CONFORMED SUBMISSION TYPE**: SCHEDULE 13G/A

**PUBLIC DOCUMENT COUNT**: 2

**FILED AS OF DATE**: 20251114

**DATE AS OF CHANGE**: 20251114

**SUBJECT COMPANY**: 

**COMPANY DATA:**
- **COMPANY CONFORMED NAME:** Abivax S.A.
- **CENTRAL INDEX KEY:** 0001956827
- **STANDARD INDUSTRIAL CLASSIFICATION:** PHARMACEUTICAL PREPARATIONS [2834]
- **ORGANIZATION NAME:** 03 Life Sciences
- **EIN:** 000000000
- **STATE OF INCORPORATION:** I0
- **FISCAL YEAR END:** 1231

**FILING VALUES:**
- **FORM TYPE:** SCHEDULE 13G/A
- **SEC ACT:** 1934 Act
- **SEC FILE NUMBER:** 005-94198
- **FILM NUMBER:** 251486791

**BUSINESS ADDRESS:**
- **ADDRESS IS A NON US LOCATION:** YES
- **STREET 1:** 7 BD HAUSSMANN
- **CITY:** PARIS
- **PROVINCE COUNTRY:** I0
- **BUSINESS PHONE:** 01 53 83 09 63

**MAIL ADDRESS:**
- **ADDRESS IS A NON US LOCATION:** YES
- **STREET 1:** 7 BD HAUSSMANN
- **CITY:** PARIS
- **PROVINCE COUNTRY:** I0
**FILED BY**: 

**COMPANY DATA:**
- **COMPANY CONFORMED NAME:** TCG Crossover GP I, LLC
- **CENTRAL INDEX KEY:** 0001839947

**ORGANIZATION NAME:**
- **EIN:** 000000000
- **STATE OF INCORPORATION:** DE
- **FISCAL YEAR END:** 1231

**FILING VALUES:**
- **FORM TYPE:** SCHEDULE 13G/A

**BUSINESS ADDRESS:**
- **STREET 1:** 245 LYTTON AVE., SUITE 350
- **CITY:** PALO ALTO
- **STATE:** CA
- **BUSINESS PHONE:** 650-924-9424

**MAIL ADDRESS:**
- **STREET 1:** 245 LYTTON AVE., SUITE 350
- **CITY:** PALO ALTO
- **STATE:** CA

### Attached PDF Documents

**Attachment 1:** `ck0000000000-ex99_2.pdf`

_No text found in this document._

### UNITED STATES SECURITIES AND EXCHANGE COMMISSION
**Washington, D.C. 20549**

## SCHEDULE 13G

### Under the Securities Exchange Act of 1934

**(Amendment No. 1)**

**Issuer:** Abivax SA

**Title of Class of Securities:** Ordinary Shares, par value Euro 0.01 per share

**CUSIP Number:** 00370M103

**Date of Event Which Requires Filing of this Statement:** 09/30/2025

**Check the appropriate box to designate the rule pursuant to which this Schedule is filed:**

- [ ] Rule 13d-1(b)

- [x] Rule 13d-1(c)

- [ ] Rule 13d-1(d)

---

| 1. | Names of Reporting Persons<br>TCG Crossover GP I, LLC | Names of Reporting Persons<br>TCG Crossover GP I, LLC |
|:---|:---|:---|:---|
| 2. | Check the Appropriate Box if a Member of a Group (See Instructions)<br>(a) [ ] (b) [x] | Check the Appropriate Box if a Member of a Group (See Instructions)<br>(a) [ ] (b) [x] |
| 3. | SEC Use Only | SEC Use Only |
| 4. | Citizenship or Place of Organization<br>DE | Citizenship or Place of Organization<br>DE |
| Number of<br>Shares<br>Beneficially<br>Owned by<br>Each<br>Reporting<br>Person<br>With | 5. | Sole Voting Power<br>0 |
| Number of<br>Shares<br>Beneficially<br>Owned by<br>Each<br>Reporting<br>Person<br>With | 6. | Shared Voting Power<br>6456596 |
| Number of<br>Shares<br>Beneficially<br>Owned by<br>Each<br>Reporting<br>Person<br>With | 7. | Sole Dispositive Power<br>0 |
| Number of<br>Shares<br>Beneficially<br>Owned by<br>Each<br>Reporting<br>Person<br>With | 8. | Shared Dispositive Power<br>6456596 |
| 9. | Aggregate Amount Beneficially Owned by Each Reporting Person<br>6456596 | Aggregate Amount Beneficially Owned by Each Reporting Person<br>6456596 |
| 10. | Check if the Aggregate Amount in Row (9) Excludes Certain Shares (See Instructions) [ ] | Check if the Aggregate Amount in Row (9) Excludes Certain Shares (See Instructions) [ ] |
| 11. | Percent of Class Represented by Amount in Row (9)<br>8.3% | Percent of Class Represented by Amount in Row (9)<br>8.3% |
| 12. | Type of Reporting Person (See Instructions)<br>OO | Type of Reporting Person (See Instructions)<br>OO |

**Comment for Type of Reporting Person:** Consists of 6,456,596 ordinary shares (as defined in Item 2(d) below) in the form of American Depositary Shares ("ADSs") of the Issuer (as defined in Item 1(a) below) held of record by TCG Crossover I (as defined in Item 2(a) below). Each ADS represents one (1) ordinary share. TCG Crossover GP I (as defined in Item 2(a) below) is the general partner of TCG Crossover I and may be deemed to have voting, investment, and dispositive power with respect to these securities. Chen Yu is the sole managing member of TCG Crossover GP I and may be deemed to share voting, investment and dispositive power with respect to these securities.

Based on 77,830,067 ordinary shares outstanding as of September 30, 2025, as provided to the Reporting Persons by the Issuer.

---

| 1. | Names of Reporting Persons<br>TCG Crossover Fund I, L.P. | Names of Reporting Persons<br>TCG Crossover Fund I, L.P. |
|:---|:---|:---|:---|
| 2. | Check the Appropriate Box if a Member of a Group (See Instructions)<br>(a) [ ] (b) [x] | Check the Appropriate Box if a Member of a Group (See Instructions)<br>(a) [ ] (b) [x] |
| 3. | SEC Use Only | SEC Use Only |
| 4. | Citizenship or Place of Organization<br>DE | Citizenship or Place of Organization<br>DE |
| Number of<br>Shares<br>Beneficially<br>Owned by<br>Each<br>Reporting<br>Person<br>With | 5. | Sole Voting Power<br>0 |
| Number of<br>Shares<br>Beneficially<br>Owned by<br>Each<br>Reporting<br>Person<br>With | 6. | Shared Voting Power<br>6456596 |
| Number of<br>Shares<br>Beneficially<br>Owned by<br>Each<br>Reporting<br>Person<br>With | 7. | Sole Dispositive Power<br>0 |
| Number of<br>Shares<br>Beneficially<br>Owned by<br>Each<br>Reporting<br>Person<br>With | 8. | Shared Dispositive Power<br>6456596 |
| 9. | Aggregate Amount Beneficially Owned by Each Reporting Person<br>6456596 | Aggregate Amount Beneficially Owned by Each Reporting Person<br>6456596 |
| 10. | Check if the Aggregate Amount in Row (9) Excludes Certain Shares (See Instructions) [ ] | Check if the Aggregate Amount in Row (9) Excludes Certain Shares (See Instructions) [ ] |
| 11. | Percent of Class Represented by Amount in Row (9)<br>8.3% | Percent of Class Represented by Amount in Row (9)<br>8.3% |
| 12. | Type of Reporting Person (See Instructions)<br>PN | Type of Reporting Person (See Instructions)<br>PN |

**Comment for Type of Reporting Person:** Consists of 6,456,596 ordinary shares in the form of ADSs of the Issuer held of record by TCG Crossover I. Each ADS represents one (1) ordinary share. TCG Crossover GP I is the general partner of TCG Crossover I and may be deemed to have voting, investment, and dispositive power with respect to these securities. Chen Yu is the sole managing member of TCG Crossover GP I and may be deemed to share voting, investment and dispositive power with respect to these securities.

Based on 77,830,067 ordinary shares outstanding as of September 30, 2025, as provided to the Reporting Persons by the Issuer.

---

| 1. | Names of Reporting Persons<br>TCG Crossover GP II, LLC | Names of Reporting Persons<br>TCG Crossover GP II, LLC |
|:---|:---|:---|:---|
| 2. | Check the Appropriate Box if a Member of a Group (See Instructions)<br>(a) [ ] (b) [x] | Check the Appropriate Box if a Member of a Group (See Instructions)<br>(a) [ ] (b) [x] |
| 3. | SEC Use Only | SEC Use Only |
| 4. | Citizenship or Place of Organization<br>DE | Citizenship or Place of Organization<br>DE |
| Number of<br>Shares<br>Beneficially<br>Owned by<br>Each<br>Reporting<br>Person<br>With | 5. | Sole Voting Power<br>0 |
| Number of<br>Shares<br>Beneficially<br>Owned by<br>Each<br>Reporting<br>Person<br>With | 6. | Shared Voting Power<br>655000 |
| Number of<br>Shares<br>Beneficially<br>Owned by<br>Each<br>Reporting<br>Person<br>With | 7. | Sole Dispositive Power<br>0 |
| Number of<br>Shares<br>Beneficially<br>Owned by<br>Each<br>Reporting<br>Person<br>With | 8. | Shared Dispositive Power<br>655000 |
| 9. | Aggregate Amount Beneficially Owned by Each Reporting Person<br>655000 | Aggregate Amount Beneficially Owned by Each Reporting Person<br>655000 |
| 10. | Check if the Aggregate Amount in Row (9) Excludes Certain Shares (See Instructions) [ ] | Check if the Aggregate Amount in Row (9) Excludes Certain Shares (See Instructions) [ ] |
| 11. | Percent of Class Represented by Amount in Row (9)<br>0.8% | Percent of Class Represented by Amount in Row (9)<br>0.8% |
| 12. | Type of Reporting Person (See Instructions)<br>OO | Type of Reporting Person (See Instructions)<br>OO |

**Comment for Type of Reporting Person:** Consists of 655,000 ordinary shares in the form of ADSs of the Issuer held of record by TCG Crossover II (as defined in Item 2(a) below). Each ADS represents one (1) ordinary share. TCG Crossover GP II (as defined in Item 2(a) below) is the general partner of TCG Crossover II and may be deemed to have voting, investment, and dispositive power with respect to these securities. Chen Yu is the sole managing member of TCG Crossover GP II and may be deemed to share voting, investment and dispositive power with respect to these securities.

Based on 77,830,067 ordinary shares outstanding as of September 30, 2025, as provided to the Reporting Persons by the Issuer.

---

| 1. | Names of Reporting Persons<br>TCG Crossover Fund II, L.P. | Names of Reporting Persons<br>TCG Crossover Fund II, L.P. |
|:---|:---|:---|:---|
| 2. | Check the Appropriate Box if a Member of a Group (See Instructions)<br>(a) [ ] (b) [x] | Check the Appropriate Box if a Member of a Group (See Instructions)<br>(a) [ ] (b) [x] |
| 3. | SEC Use Only | SEC Use Only |
| 4. | Citizenship or Place of Organization<br>DE | Citizenship or Place of Organization<br>DE |
| Number of<br>Shares<br>Beneficially<br>Owned by<br>Each<br>Reporting<br>Person<br>With | 5. | Sole Voting Power<br>0 |
| Number of<br>Shares<br>Beneficially<br>Owned by<br>Each<br>Reporting<br>Person<br>With | 6. | Shared Voting Power<br>655000 |
| Number of<br>Shares<br>Beneficially<br>Owned by<br>Each<br>Reporting<br>Person<br>With | 7. | Sole Dispositive Power<br>0 |
| Number of<br>Shares<br>Beneficially<br>Owned by<br>Each<br>Reporting<br>Person<br>With | 8. | Shared Dispositive Power<br>655000 |
| 9. | Aggregate Amount Beneficially Owned by Each Reporting Person<br>655000 | Aggregate Amount Beneficially Owned by Each Reporting Person<br>655000 |
| 10. | Check if the Aggregate Amount in Row (9) Excludes Certain Shares (See Instructions) [ ] | Check if the Aggregate Amount in Row (9) Excludes Certain Shares (See Instructions) [ ] |
| 11. | Percent of Class Represented by Amount in Row (9)<br>0.8% | Percent of Class Represented by Amount in Row (9)<br>0.8% |
| 12. | Type of Reporting Person (See Instructions)<br>PN | Type of Reporting Person (See Instructions)<br>PN |

**Comment for Type of Reporting Person:** Consists of 655,000 ordinary shares in the form of ADSs of the Issuer held of record by TCG Crossover II. Each ADS represents one (1) ordinary share. TCG Crossover GP II is the general partner of TCG Crossover II and may be deemed to have voting, investment, and dispositive power with respect to these securities. Chen Yu is the sole managing member of TCG Crossover GP II and may be deemed to share voting, investment and dispositive power with respect to these securities.

Based on 77,830,067 ordinary shares outstanding as of September 30, 2025, as provided to the Reporting Persons by the Issuer.

---

| 1. | Names of Reporting Persons<br>Chen Yu | Names of Reporting Persons<br>Chen Yu |
|:---|:---|:---|:---|
| 2. | Check the Appropriate Box if a Member of a Group (See Instructions)<br>(a) [ ] (b) [x] | Check the Appropriate Box if a Member of a Group (See Instructions)<br>(a) [ ] (b) [x] |
| 3. | SEC Use Only | SEC Use Only |
| 4. | Citizenship or Place of Organization<br>X1 | Citizenship or Place of Organization<br>X1 |
| Number of<br>Shares<br>Beneficially<br>Owned by<br>Each<br>Reporting<br>Person<br>With | 5. | Sole Voting Power<br>0 |
| Number of<br>Shares<br>Beneficially<br>Owned by<br>Each<br>Reporting<br>Person<br>With | 6. | Shared Voting Power<br>7111596 |
| Number of<br>Shares<br>Beneficially<br>Owned by<br>Each<br>Reporting<br>Person<br>With | 7. | Sole Dispositive Power<br>0 |
| Number of<br>Shares<br>Beneficially<br>Owned by<br>Each<br>Reporting<br>Person<br>With | 8. | Shared Dispositive Power<br>7111596 |
| 9. | Aggregate Amount Beneficially Owned by Each Reporting Person<br>7111596 | Aggregate Amount Beneficially Owned by Each Reporting Person<br>7111596 |
| 10. | Check if the Aggregate Amount in Row (9) Excludes Certain Shares (See Instructions) [ ] | Check if the Aggregate Amount in Row (9) Excludes Certain Shares (See Instructions) [ ] |
| 11. | Percent of Class Represented by Amount in Row (9)<br>9.1% | Percent of Class Represented by Amount in Row (9)<br>9.1% |
| 12. | Type of Reporting Person (See Instructions)<br>IN | Type of Reporting Person (See Instructions)<br>IN |

**Comment for Type of Reporting Person:** Consists of (i) 6,456,596 ordinary shares in the form of ADSs of the Issuer held of record by TCG Crossover I and (ii) 655,000 ordinary shares in the form of ADSs of the Issuer held of record by TCG Crossover II. TCG Crossover GP I is the general partner of TCG Crossover I and may be deemed to have voting, investment, and dispositive power with respect to the securities held of record by TCG Crossover I. TCG Crossover GP II is the general partner of TCG Crossover II and may be deemed to have voting, investment, and dispositive power with respect to the securities held of record by TCG Crossover II. Chen Yu is the sole managing member of each of TCG Crossover GP I and TCG Crossover GP II and may be deemed to share voting, investment and dispositive power with respect to the securities held of record by TCG Crossover II and TCG Crossover II.

Based on 77,830,067 ordinary shares outstanding as of September 30, 2025, as provided to the Reporting Persons by the Issuer.

---

**Item 1(a). Name of Issuer:**
Abivax SA

**Item 1(b). Address of Issuer's Principal Executive Offices:**
7-11 boulevard Haussman, Paris, France, 75009

**Item 2(a). Name of Person Filing:**
This Amendment No. 1 (Amendment No. 1) amends and supplements the Schedule 13G initially filed with the Commission on April 19, 2024 (the Original Schedule 13G) and is being filed by TCG Crossover Fund I, L.P. (TCG Crossover I), TCG Crossover GP I, LLC (TCG Crossover GP I), TCG Crossover Fund II, L.P. (TCG Crossover II) and TCG Crossover GP II, LLC (TCG Crossover GP II and together with TCG Crossover I, TCG Crossover GP I and TCG Crossover II, the Reporting Entities) and Chen Yu (the Reporting Individual). The Reporting Entities and the Reporting Individual are collectively referred to as the Reporting Persons. The Reporting Persons expressly disclaim status as a group for purposes of this Schedule 13G. The agreement among the Reporting Persons to file jointly in accordance with the provisions of Rule 13d-1(k)(1) under the Act is attached to this Statement as Exhibit 2. Other than those securities reported herein as being held directly by such Reporting Person, each Reporting Person disclaims beneficial ownership of all securities reported in this Amendment No. 1 except to the extent of such Reporting Person's pecuniary interest therein.

**Item 2(b). Address of Principal Business Office:**
The address of the principal business office of each Reporting Person is 245 Lytton Ave., Suite 350, Palo Alto, CA 94301.

**Item 2(c). Citizenship:**
TCG Crossover GP I and TCG Crossover GP II are each a limited liability company organized under the laws of the State of Delaware. TCG Crossover I and TCG Crossover II are each a limited partnership organized under the laws of the State of Delaware. The Reporting Individual is a citizen of the United States of America.

**Item 2(d). Title of Class of Securities:**
Ordinary Shares, par value Euro 0.01 per share

**Item 2(e). CUSIP Number:**
00370M103

**Item 3. If this statement is filed pursuant to §§ 240.13d-1(b) or 240.13d-2(b) or (c), check whether the person filing is a:**

(a) [ ] Broker or dealer registered under section 15 of the Act (15 U.S.C. 78o).

(b) [ ] Bank as defined in section 3(a)(6) of the Act (15 U.S.C. 78c).

(c) [ ] Insurance company as defined in section 3(a)(19) of the Act (15 U.S.C. 78c).

(d) [ ] Investment company registered under section 8 of the Investment Company Act of 1940 (15 U.S.C. 80a-8).

(e) [ ] An investment adviser in accordance with § 240.13d-1(b)(1)(ii)(E);

(f) [ ] An employee benefit plan or endowment fund in accordance with § 240.13d-1(b)(1)(ii)(F);

(g) [ ] A parent holding company or control person in accordance with § 240.13d-1(b)(1)(ii)(G);

(h) [ ] A savings associations as defined in Section 3(b) of the Federal Deposit Insurance Act (12 U.S.C. 1813);

(i) [ ] A church plan that is excluded from the definition of an investment company under section 3(c)(14) of the Investment Company Act of 1940 (15 U.S.C. 80a-3);

(j) [ ] A non-U.S. institution in accordance with § 240.13d-1(b)(1)(ii)(J), if filing as a non-U.S. institution in accordance with § 240.13d-1(b)(1)(ii)(J), please specify the type of institution:

(k) [ ] Group, in accordance with Rule 240.13d-1(b)(1)(ii)(K).

**Item 4. Ownership:**

**(a) Amount beneficially owned:**

See Row 9 of the cover page for each Reporting Person and the corresponding footnotes. Each of the Reporting Persons disclaims beneficial ownership as to such securities, except to the extent of his or its pecuniary interest therein.

**(b) Percent of class:**

See Row 11 of the cover page for each Reporting Person and the corresponding footnotes. Each of the Reporting Persons disclaims beneficial ownership as to such securities, except to the extent of his or its pecuniary interest therein.

**(c) Number of shares as to which the person has:**

**(i) Sole power to vote or to direct the vote:**

See Row 5 of the cover page for each Reporting Person and the corresponding footnotes. Each of the Reporting Persons disclaims beneficial ownership as to such securities, except to the extent of his or its pecuniary interest therein.

**(ii) Shared power to vote or to direct the vote:**

See Row 6 of the cover page for each Reporting Person and the corresponding footnotes. Each of the Reporting Persons disclaims beneficial ownership as to such securities, except to the extent of his or its pecuniary interest therein.

**(iii) Sole power to dispose or to direct the disposition of:**

See Row 7 of the cover page for each Reporting Person and the corresponding footnotes. Each of the Reporting Persons disclaims beneficial ownership as to such securities, except to the extent of his or its pecuniary interest therein.

**(iv) Shared power to dispose or to direct the disposition of:**

See Row 8 of the cover page for each Reporting Person and the corresponding footnotes. Each of the Reporting Persons disclaims beneficial ownership as to such securities, except to the extent of his or its pecuniary interest therein.

**Item 5. Ownership of Five Percent or Less of a Class.**

[x] If this statement is being filed to report the fact that as of the date hereof the reporting person has ceased to be the beneficial owner of more than five percent of the class of securities, check the following.

**Item 6. Ownership of More than 5 Percent on Behalf of Another Person.**

Under certain circumstances set forth in the limited partnership agreements of TCG Crossover I and TCG Crossover II and the limited liability company agreements of TCG Crossover GP I and TCG Crossover GP II, the general and limited partners or members, as the case may be, of each of such entities may be deemed to have the right to receive dividends from, or the proceeds from, the sale of securities of the Issuer owned by each such entity of which they are a partner or member, as the case may be.

**Item 7. Identification and Classification of the Subsidiary**

Not Applicable

**Item 8. Identification and Classification of Members of the Group**

Not Applicable

**Item 9. Notice of Dissolution of Group**

Not Applicable

**Item 10. Certification:**

By signing below I certify that, to the best of my knowledge and belief, the securities referred to above were not acquired and are not held for the purpose of or with the effect of changing or influencing the control of the issuer of the securities and were not acquired and are not held in connection with or as a participant in any transaction having that purpose or effect, other than activities solely in connection with a nomination under ?? 240.14a-11.

### SIGNATURE

After reasonable inquiry and to the best of my knowledge and belief, I certify that the information set forth in this statement is true, complete and correct.

**TCG Crossover GP I, LLC**

**Date:** 11/14/2025

**By:** /s/ Craig Skaling

**Name & Title:** Craig Skaling, Authorized Signatory

**TCG Crossover Fund I, L.P.**

**Date:** 11/14/2025

**By:** /s/ Craig Skaling

**Name & Title:** Craig Skaling, Authorized Signatory

**TCG Crossover GP II, LLC**

**Date:** 11/14/2025

**By:** /s/ Craig Skaling

**Name & Title:** Craig Skaling, Authorized Signatory

**TCG Crossover Fund II, L.P.**

**Date:** 11/14/2025

**By:** /s/ Craig Skaling

**Name & Title:** Craig Skaling, Authorized Signatory

**Chen Yu**

**Date:** 11/14/2025

**By:** /s/ Craig Skaling

**Name & Title:** Craig Skaling, as Attorney-in-Fact for Chen Yu