附件 5.1

2023年12月22日

十四行诗 生物治疗控股公司

100俯瞰中心，102套房

新泽西州普林斯顿邮编：08540

女士们、先生们：

本 意见是与表格S—3的注册声明（以下简称"注册声明"）相关的， 包括由Sonnet BioTherapeutics Holdings，Inc.提交的注册声明（以下简称"招股说明书"）的基本招股说明书，根据经修订的1933年《证券法》（简称《证券法》），于2023年12月22日与美国证券交易委员会（简称《委员会》）签署。

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.

基于上述内容，并根据此处规定的假设、限制和条件，我们认为：

1. 对于普通股，当（a）普通股股份的发行和销售条款已 公司董事会根据公司注册证书和 章程正式授权时；（b）该等股份已在支付购买价款后发行并交付，金额超过其面值，根据适用的最终购买、承销或类似协议，并按照注册声明、招股说明书和相关招股说明书补充文件的预期 ；及（c）在转换、交换或行使任何优先股、认股权证或债务证券时发行该等普通股股份的范围内，当该等 股份已按照适用优先股、与该等认股权证有关的认股权证协议 或与该等债务证券有关的契约的条款的预期正式发行和交付时，普通股股份将被 有效发行，全额支付，无需课税。

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. 关于认股权证，当（a）认股权证的发行和销售条款已得到公司董事会 正式授权时；（b）认股权证及其发行及出售的条款已正式确立，不会 违反任何适用法律或导致违反任何对本公司具约束力的协议或文书，及 遵守对公司或其任何 财产拥有管辖权的任何法院或政府机构所施加的任何要求或限制；（c）认股权证及与认股权证有关的适用认股权证协议（如有）已妥为签立 及副署，认股权证已根据适用的最终购买而发行及出售，承销 或类似协议，如登记声明、招股说明书和相关招股说明书补充文件所述；及 （d）本公司已收到登记声明书、 招股章程及相关招股章程补充文件所预期的认股权证的适用代价，认股权证将构成本公司有效及具约束力的责任。

4. 关于债务证券，当（a）债务证券的发行和销售条款已获得公司董事会正式授权 时；（b）债务证券及其发行和销售的条款已正式确立 ，从而不会违反任何适用法律或导致违约或违反对 具有约束力的任何协议或文书并遵守对 公司或其任何财产具有管辖权的任何法院或政府机构施加的任何要求或限制；（c）债务证券及与债务证券有关的适用契约已 妥为签立及副署，如契约，则经受托人妥为认证，及债务证券已 按登记声明书、招股章程及相关招股章程补充文件的预期发行及出售；及 （d）本公司已收到登记声明所述债务证券的适用代价， 招股说明书及相关招股说明书补充文件，债务证券将构成 公司有效且具约束力的义务。

5. 就认购权而言，当：（a）认购权的发行及出售条款 已获本公司董事会正式授权时；（b）认购权及其发行 和销售的条款已正式确立，不会违反任何适用法律或导致违约或违反任何协议 或对公司具有约束力的文书，并遵守对公司或其任何财产具有管辖权的任何法院或政府机构实施的任何要求或限制；及（c）有关认购权的协议已 正式授权、有效签署及交付，则认购权将是公司有效且具有约束力的 义务，可根据其条款对公司强制执行。

6. 关于基金单位，当（a）基金单位的发行和销售条款已得到公司 董事会正式授权时；（b）基金单位及其发行和销售的条款已正式确立，不会违反 任何适用法律或导致违约或违反对公司有约束力的任何协议或文书，并遵守 对本公司或其任何财产具有司法管辖权的任何法院或政府机构施加的任何要求或限制； （c）单位协议及单位已正式签立及副署，且单位已根据注册声明、招股章程及相关招股章程补充文件所述 适用单位协议发行及出售； 及（d）本公司已收到注册声明书、 招股章程及相关招股章程补充文件所述的基金单位的适用代价，则该等基金单位将构成本公司的有效及具约束力的责任。

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.

我们的意见仅限于美国联邦法律、特拉华州公司法总则(包括已报道的解释特拉华州公司法总法的司法裁决)和纽约州。我们对任何其他司法管辖区的法律效力不发表任何意见。我们的意见是自本协议发布之日起发表的，我们没有义务将法律或事实的变化(或其对本协议所表达的意见的影响)通知您，我们随后可能会注意到这些变化。

我们 特此同意将本意见作为注册说明书的附件5.1，并在其中和招股说明书中，以及在任何招股说明书副刊中“法律事项”的标题下提及我公司。在给予我们的同意时， 我们不承认我们属于证券法第7节或其下的规则和条例所要求的同意的类别。

非常 真正的您，