附件 5.1

2023年12月22日

十四行詩 生物治療控股公司

100俯瞰中心，102套房

新澤西州普林斯頓郵編：08540

女士們、先生們：

本 意見是與表格S—3的註冊聲明（以下簡稱"註冊聲明"）相關的， 包括由Sonnet BioTherapeutics Holdings，Inc.提交的註冊聲明（以下簡稱"招股説明書"）的基本招股説明書，根據經修訂的1933年《證券法》（簡稱《證券法》），於2023年12月22日與美國證券交易委員會（簡稱《委員會》）簽署。

The Prospectus provides that it will be supplemented in the future by one or more prospectus supplements (each, a “Prospectus Supplement”). The Prospectus, as supplemented by the various Prospectus Supplements, will provide for the issuance and sale by the Company from time to time of up to $100,000,000 aggregate offering price of (i) shares of the Company’s common stock, par value $0.0001 per share (the “Common Stock”), (ii) shares of the Company’s preferred stock, par value $0.0001 per share (the “Preferred Stock”), in one or more series or classes, (iii) warrants to purchase shares of Common Stock (the “Warrants”), (iv) the Company’s senior debt securities and subordinated debt securities (collectively, the “Debt Securities”), which may be issued pursuant to a senior debt indenture (the “Senior Debt Indenture”) between the Company and the trustee to be named therein (the “Senior Debt Trustee”) and a subordinated debt indenture (the “Subordinated Debt Indenture,” and together with the Senior Debt Indenture, the “Indentures”) between the Company and the trustee to be named therein (the “Subordinated Debt Trustee” and, together with the Senior Debt Trustee, the “Trustees”), (v) subscription rights to purchase Common Stock, Preferred Stock or Debt Securities (the “Subscription Rights”) or (vi) units composed of any of the foregoing (the “Units”). The Common Stock, Preferred Stock, Warrants, Debt Securities, Subscription Rights and Units are collectively referred to herein as the “Securities.” The Warrants may be issued pursuant to a warrant agreement (the “Warrant Agreement”) between the Company and a bank or trust company as warrant agent. Any Preferred Stock may be exchangeable for and/or convertible into shares of Common Stock or another series of Preferred Stock. Any Debt Securities may be exchangeable and/or convertible into shares of Common Stock or Preferred Stock. The Units may be issued pursuant to a Unit Agreement (the “Unit Agreement”) between the Company and a bank or trust company as unit agent. The Securities are being registered for offering and sale from time to time pursuant to Rule 415 under the Securities Act.

In rendering our opinions set forth below, we have reviewed the Registration Statement and the exhibits thereto. We have also reviewed such corporate documents and records of the Company, such certificates of public officials and officers of the Company and such other matters as we have deemed necessary or appropriate for purposes of this opinion. In our examination, we have assumed: (i) the authenticity of original documents and the genuineness of all signatures; (ii) the conformity to the originals of all documents submitted to us as copies; (iii) the truth, accuracy and completeness of the information, representations and warranties contained in the instruments, documents, certificates and records we have reviewed; and (iv) the legal capacity for all purposes relevant hereto of all natural persons and, with respect to all parties to agreements or instruments relevant hereto other than the Company, that such parties had the requisite power and authority (corporate or otherwise) to execute, deliver and perform such agreements or instruments, that such agreements or instruments have been duly authorized by all requisite action (corporate or otherwise), executed and delivered by such parties and that such agreements or instruments are the valid, binding and enforceable obligations of such parties. As to any facts material to the opinions expressed herein that were not independently established or verified, we have relied upon oral or written statements and representations of officers and other representatives of the Company.

基於上述內容，並根據此處規定的假設、限制和條件，我們認為：

1. 對於普通股，當（a）普通股股份的發行和銷售條款已 公司董事會根據公司註冊證書和 章程正式授權時；（b）該等股份已在支付購買價款後發行並交付，金額超過其面值，根據適用的最終購買、承銷或類似協議，並按照註冊聲明、招股説明書和相關招股説明書補充文件的預期 ；及（c）在轉換、交換或行使任何優先股、認股權證或債務證券時發行該等普通股股份的範圍內，當該等 股份已按照適用優先股、與該等認股權證有關的認股權證協議 或與該等債務證券有關的契約的條款的預期正式發行和交付時，普通股股份將被 有效發行，全額支付，無需課税。

2. With respect to any particular series of shares of Preferred Stock, when (a) the issuance and the terms of the sale of the shares of Preferred Stock have been duly authorized by the Board of Directors of the Company in conformity with the Company’s certificate of incorporation and bylaws; (b) an appropriate certificate of designation relating to a series of the Preferred Stock to be sold under the Registration Statement has been duly authorized and adopted and filed with the Secretary of State of Delaware; (c) the terms of issuance and sale of shares of such series of Preferred Stock have been duly established in conformity with the Company’s certificate of incorporation and bylaws so as not to violate any applicable law or result in a default under or breach of any agreement or instrument binding upon the Company and comply with any requirement or restriction imposed by any court or governmental body having jurisdiction over the Company or any of its property; (d) such shares have been issued and delivered against payment of the purchase price therefor in an amount in excess of the par value thereof, in accordance with the applicable definitive purchase, underwriting or similar agreement, and as contemplated by the Registration Statement, the Prospectus and the related Prospectus Supplement; and (e) to the extent such shares of Preferred Stock are to be issued upon the conversion, exchange or exercise of any Preferred Stock, Warrants or Debt Securities, when such shares have been duly issued and delivered as contemplated by the terms of the applicable Preferred Stock, the Warrant Agreement relating to such Warrants or the Indenture relating to such Debt Securities, respectively, the shares of Preferred Stock will be validly issued, fully paid and nonassessable.

3. 關於認股權證，當（a）認股權證的發行和銷售條款已得到公司董事會 正式授權時；（b）認股權證及其發行及出售的條款已正式確立，不會 違反任何適用法律或導致違反任何對本公司具約束力的協議或文書，及 遵守對公司或其任何 財產擁有管轄權的任何法院或政府機構所施加的任何要求或限制；（c）認股權證及與認股權證有關的適用認股權證協議（如有）已妥為籤立 及副署，認股權證已根據適用的最終購買而發行及出售，承銷 或類似協議，如登記聲明、招股説明書和相關招股説明書補充文件所述；及 （d）本公司已收到登記聲明書、 招股章程及相關招股章程補充文件所預期的認股權證的適用代價，認股權證將構成本公司有效及具約束力的責任。

4. 關於債務證券，當（a）債務證券的發行和銷售條款已獲得公司董事會正式授權 時；（b）債務證券及其發行和銷售的條款已正式確立 ，從而不會違反任何適用法律或導致違約或違反對 具有約束力的任何協議或文書並遵守對 公司或其任何財產具有管轄權的任何法院或政府機構施加的任何要求或限制；（c）債務證券及與債務證券有關的適用契約已 妥為籤立及副署，如契約，則經受託人妥為認證，及債務證券已 按登記聲明書、招股章程及相關招股章程補充文件的預期發行及出售；及 （d）本公司已收到登記聲明所述債務證券的適用代價， 招股説明書及相關招股説明書補充文件，債務證券將構成 公司有效且具約束力的義務。

5. 就認購權而言，當：（a）認購權的發行及出售條款 已獲本公司董事會正式授權時；（b）認購權及其發行 和銷售的條款已正式確立，不會違反任何適用法律或導致違約或違反任何協議 或對公司具有約束力的文書，並遵守對公司或其任何財產具有管轄權的任何法院或政府機構實施的任何要求或限制；及（c）有關認購權的協議已 正式授權、有效簽署及交付，則認購權將是公司有效且具有約束力的 義務，可根據其條款對公司強制執行。

6. 關於基金單位，當（a）基金單位的發行和銷售條款已得到公司 董事會正式授權時；（b）基金單位及其發行和銷售的條款已正式確立，不會違反 任何適用法律或導致違約或違反對公司有約束力的任何協議或文書，並遵守 對本公司或其任何財產具有司法管轄權的任何法院或政府機構施加的任何要求或限制； （c）單位協議及單位已正式籤立及副署，且單位已根據註冊聲明、招股章程及相關招股章程補充文件所述 適用單位協議發行及出售； 及（d）本公司已收到註冊聲明書、 招股章程及相關招股章程補充文件所述的基金單位的適用代價，則該等基金單位將構成本公司的有效及具約束力的責任。

In rendering the opinions set forth above, we have assumed that (i) the Registration Statement (and any applicable post-effective amendment thereto) will have become effective under the Securities Act, a Prospectus Supplement will have been prepared and filed with the Commission describing the Securities offered thereby and such Securities will have been issued and sold in accordance with the terms of such Prospectus Supplement and in compliance with all applicable laws; and (ii) a definitive purchase, underwriting or similar agreement with respect to such Securities (if applicable) will have been duly authorized, executed and delivered by the Company and the other parties thereto; (iii) the Securities will be duly authorized by all necessary corporate action by the Company and any agreement pursuant to which such Securities may be issued will be duly authorized, executed and delivered by the Company and the other parties thereto; (iv) the Company will remain duly organized, validly existing and in good standing under applicable state law; and (v) the Company has reserved a sufficient number of shares of its duly authorized, but unissued, Common Stock and Preferred Stock as is necessary to provide for the issuance of the shares of Common Stock and Preferred Stock pursuant to the Registration Statement.

The opinions set forth above are subject to the following exceptions, limitations and qualifications: (i) the effect of bankruptcy, insolvency, reorganization, fraudulent conveyance, moratorium or other similar laws now or hereafter in effect relating to or affecting the rights and remedies of creditors; (ii) the effect of general principles of equity, including without limitation, concepts of materiality, reasonableness, good faith and fair dealing and the possible unavailability of specific performance or injunctive relief, regardless of whether enforcement is considered in a proceeding in equity or at law, and the discretion of the court before which any proceeding therefor may be brought; and (iii) the unenforceability under certain circumstances under law or court decisions of provisions providing for the indemnification of, or contribution to, a party with respect to liability where such indemnification or contribution is contrary to public policy. We express no opinion concerning the enforceability of any waiver of rights or defenses with respect to stay, extension or usury laws. Our opinion expressed herein is also subject to the qualification that no term or provision shall be included in any certificate of designation relating to any series of the Preferred Stock, Warrant Agreement, Indenture, Unit Agreement or any other agreement or instrument pursuant to which any of the Securities are to be issued that would affect the validity of such opinion.

我們的意見僅限於美國聯邦法律、特拉華州公司法總則(包括已報道的解釋特拉華州公司法總法的司法裁決)和紐約州。我們對任何其他司法管轄區的法律效力不發表任何意見。我們的意見是自本協議發佈之日起發表的，我們沒有義務將法律或事實的變化(或其對本協議所表達的意見的影響)通知您，我們隨後可能會注意到這些變化。

我們 特此同意將本意見作為註冊説明書的附件5.1，並在其中和招股説明書中，以及在任何招股説明書副刊中“法律事項”的標題下提及我公司。在給予我們的同意時， 我們不承認我們屬於證券法第7節或其下的規則和條例所要求的同意的類別。

非常 真正的您，