Exhibit 5.1

BeOne Medicines Ltd.
c/o BeOne Medicines I GmbH
Aeschengraben 27
21st Floor
4051 Basel
Switzerland Homburger AG
Prime Tower
Hardstrasse 201
CH-8005 Zürich
 
homburger.ch
+41 43 222 10 00

May 27, 2025

BeOne Medicines Ltd. (f/k/a BeiGene, Ltd.) / Form S-8 Post-Effective Amendment No. 1

We have acted as special Swiss counsel to BeOne Medicines Ltd., a company limited by shares pursuant to Article 620 et seq. of the Swiss Code of Obligations of March 30, 1911, as amended, incorporated under the laws of Switzerland (the Company), in connection with (a) its change of jurisdiction of incorporation from the Cayman Islands to Switzerland through a transaction known as a continuation (the Continuation) under Section 206 of the Companies Act of the Cayman Islands, as amended, and Article 161 of the Swiss Federal Act on Private International Law of December 18, 1987, as amended, and (b) the filing of the Post-Effective Amendment No. 1 (the Amendment) to the following Registration Statements on Form S−8 (collectively, the Registration Statement(s)): (i) Registration No. 333-209410; (ii) Registration No. 333-214064; (iii) Registration No. 333-216885; (iv) Registration No. 333-223319; (v) Registration No. 333-225543; (vi) Registration No. 333-228786; (vii) Registration No. 333-241697; (viii) Registration No. 333-266639; and (ix) Registration No. 333-279980, which relate to the Company’s registered ordinary shares (Namenaktien), par value USD 0.0001 per share (the Shares), to be issued from time to time pursuant to the Company’s 2011 Option Plan (the 2011 Plan), Fourth Amended and Restated 2016 Share Option and Incentive Plan (the 2016 Plan), Fifth Amended and Restated 2018 Employee Share Purchase Plan (the 2018 Plan, together with the 2011 Plan and 2016 Plan, the Plans) and certain non-plan share options (the Options). The Registration Statements were initially filed with the United States Securities and Exchange Commission (the SEC) under the Securities Act of 1933, as amended (the Act) by BeiGene, Ltd., formerly an exempted company with limited liability incorporated in the Cayman Islands, with registered offices at c/o Mourant Governance Services (Cayman) Limited, 94 Solaris Avenue, Camana Bay, PO Box 1348, Grand Cayman KY1-1108, Cayman Islands (BeiGene Cayman), prior to the effectiveness of the Continuation (the Effective Time). The Company is filing the Amendment to expressly adopt the Registration Statements, as amended, as its own for all purposes of the Act and the Securities Exchange Act of 1934 and to reflect the completion of the Continuation.

As such counsel, we have been requested to give our opinion as to certain legal matters under Swiss law.

Capitalized terms used but not defined herein have the meanings assigned to such terms in the Documents (as defined below).

I. Basis of Opinion

This opinion is confined to and given on the basis of the laws of Switzerland in force at the date hereof. Such laws and the interpretation thereof are subject to change. This opinion is also confined to the matters stated herein and the Documents (as defined below), and is not to be read as extending, by implication or otherwise, to any other document referred to in any of the Documents or any other matter.

For purposes of this opinion, we have not conducted any due diligence or similar investigation as to factual circumstances that are or may be referred to in the Documents, and we express no opinion as to the accuracy of representations and warranties of facts set out in the Documents or the factual background assumed therein.

In this opinion, Swiss legal concepts are expressed in English terms and not in their original language. These concepts may not be identical to the concepts described by the same English terms as they exist under the laws of other jurisdictions.

For purposes of this opinion, we have only reviewed the following documents (collectively, the Documents):

1. an electronic copy of the Amendment in the form to be filed on May 27, 2025 under the Act;

2. an electronic copy of each Registration Statement in the form when it was initially filed with the SEC under the Act;

3. an electronic copy of the minutes of the shareholder resolutions passed at the extraordinary general meeting of shareholders of BeiGene Cayman, held on April 28, 2025, resolving on, inter alia, the Continuation and the adoption of the Articles (as defined below), including the capital band and the conditional share capital pursuant to Articles 4a, 4b, and 4c (the Shareholders’ Resolutions);

4. an electronic copy of the articles of association (Statuten) of the Company in their version dated April 28, 2025, legalized by a notary public of the Canton of Zug on May 21, 2025 (the Articles);

5. an electronic copy of the organizational regulations (Organisationsreglement) of the Company effective as of May 27, 2025, as approved under the unanimous written resolutions of the board of directors of BeiGene Cayman (the Board) dated as of January 20, 2025 (the Organizational Regulations);

6. an electronic copy of the report issued by Ernst & Young AG dated May 22, 2025, confirming that the Company's share capital is fully covered (the Report);

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7. an electronic copy of a certified excerpt from the commercial register of the Canton of Basel-City, Switzerland, of the Company, dated as of May 27, 2025 (the Commercial Register Excerpt);

8. the 2011 Plan, filed as exhibit 99.1 to the Amendment;

9. the 2016 Plan, filed as exhibit 99.2.1 to the Amendment;

10. the 2018 Plan, filed as exhibit 99.3 to the Amendment; and

11. an electronic copy of the (a) minutes of a telephonic meeting of the Board duly convened on August 6, 2024, approving, inter alia, the Continuation, and (b) unanimous written resolutions of the Board passed on May 27, 2025 (the Board Resolutions) approving, among other things, the Plans.

II. Assumptions

In rendering the opinion below, we have assumed the following:

1. all documents produced to us as originals are authentic and complete, and all documents produced to us as copies (including, without limitation, fax and electronic copies) conform to the original;

2. all documents produced to us as originals and the originals of all documents produced to us as copies were duly executed and certified, as applicable, by the individuals purported to have executed or certified, as the case may be, such documents, and any electronic signatures on any such document have been affixed thereto by the individual to whom such electronic signature belongs and such individual has saved and submitted such document as so electronically signed in such a manner so as to prevent removal or other alteration of such signature;

3. all factual information contained in the Registration Statements is true and accurate;

4. the Amendment will be duly filed by the Company;

5. (a) the Commercial Register Excerpt and the Report are correct, complete, and up-to-date as of the date hereof, and (b) the Articles and the Organizational Regulations are in full force and effect and have not been amended subsequent to the date set forth above;

6. all resolutions of the Board and BeiGene Cayman's shareholders necessary to effect the Continuation and adopt and approve the Articles and the Plans, including the Shareholders' Resolutions and the Board Resolutions, (a) were duly passed in the manner set forth in the BeiGene Cayman’s then-effective memorandum of association and articles of association and pursuant to the laws of the Cayman Islands, (b) are in full force and effect, (c) are valid and enforceable under the laws of the Cayman Islands, and (d) have not been amended, revoked, or superseded; and

7. with respect to any issuance of new Shares by the Company after the date hereof, (a) the nominal amount for any such new Shares has been fully paid-in (liberiert), (b) any such new Shares have been duly authorized by the board of directors of the Company and, if required, the general meeting of shareholders of the Company, (c) any such new Shares, to the extent required under applicable Swiss law, have been registered in the competent commercial register in Switzerland, and (d) all other requirements under Swiss law, the Articles, and the Organizational Regulations in connection with the creation and issuance of any such new Shares, including, but not limited to, the payment in cash or by way of set-off of the issue price for such Shares, have been complied with.

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III. Opinion

Based on the foregoing and subject to the qualifications set out below, we are of the opinion that (a) all Shares registered in the commercial register of Basel, Canton of Basel-City, as of the date hereof and delivered by the Company pursuant to the terms of the Plans or upon exercise of the Options in accordance with their terms have been duly and validly issued, and (b) any new Shares to be issued by the Company and delivered pursuant to the terms of the Plans or upon exercise of the Options in accordance with their terms, if and when issued by the Company, will be validly issued, fully paid as to their nominal value, and non-assessable.

IV. Qualifications

1. The lawyers of our firm are members of the Zurich bar and do not hold themselves out to be experts in any laws other than the laws of Switzerland. Accordingly, we are opining herein as to Swiss law only, based on our independent professional judgment. We express no opinion regarding the applicability or effect of the laws of any other jurisdiction concerning the matters covered herein.

2. Under Swiss law, shares issued out of Conditional Share Capital cannot be paid-in by way of contribution in kind. Share issuances based on the existing Conditional Share Capital are limited to 462,292,769 new Shares.

3. Shares issuances based on the Company's existing capital band pursuant to article 4a of the Articles are limited to 770,487,949 new Shares.

4. The exercise of voting rights and rights related thereto with respect to any Shares is only permissible after registration in the Company's share register as a shareholder with voting rights in accordance with the provisions of, and subject to the limitations provided in, the Articles.

5. Any issuance of the Shares based on the Conditional Share Capital must be confirmed by the auditor of the Company, and amended Articles reflecting the issuance of Shares from Conditional Share Capital, together with said confirmation by the Company's auditor, must be filed with the competent commercial register no later than three months after the end of the Company's fiscal year.

6. We express no opinion as to any commercial, accounting, tax, auditing or other non-legal matters.

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We have issued this opinion as of the date hereof and we assume no obligation to advise you of any changes in fact or in law that are made or brought to our attention hereafter.

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We hereby consent to the filing of this opinion as an exhibit to the Amendment. In giving such consent, we neither hereby concede that we are within the category of persons whose consent is required under Section 7 of the Act, or the rules or regulations of the SEC thereunder, nor thereby admit that we are experts with respect to any part of the Registration Statements, as amended by the Amendment, within the meaning of the term “expert” as used in the Act or the rules and regulations promulgated thereunder.

This opinion is governed by and shall be construed in accordance with the laws of Switzerland.

Sincerely yours,

/s/ Homburger AG

HOMBURGER AG

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