Protagonist Therapeutics, Inc

UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

WASHINGTON, D.C. 20549

SCHEDULE 14A

Proxy Statement Pursuant to Section 14(a) of

the Securities Exchange Act of 1934

(Amendment No. )

Filed by the Registrant ☒

Filed by a Party other than the Registrant ☐

Check the appropriate box:

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Preliminary Proxy Statement

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Confidential, for Use of the Commission Only (as permitted by Rule 14a-6(e)(2))

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Definitive Proxy Statement

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Definitive Additional Materials

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Soliciting Material under §240.14a-12

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PROTAGONIST THERAPEUTICS, INC.

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(Name of Registrant as Specified In Its Charter)

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(Name of Person(s) Filing Proxy Statement, if other than The Registrant)

Payment of Filing Fee (Check all boxes that apply):

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No fee required.

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Fee paid previously with preliminary materials.

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Fee computed on table in exhibit required by Item 25(b) per Exchange Act Rules 14a-6(i)(1) and 0-11.

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7707 Gateway Blvd., Suite 140

Newark, California 94560

NOTICE OF ANNUAL MEETING OF STOCKHOLDERS

TO BE HELD ON JUNE 17, 2026

Dear Stockholder:

You are cordially invited to attend the 2026 Annual Meeting of Stockholders (the “Annual Meeting”) of Protagonist Therapeutics, Inc., a Delaware corporation (the “Company”). The meeting will be held exclusively online via live audio webcast atwww.virtualshareholdermeeting.com/PTGX2026 on Wednesday, June 17, 2026 at 10:00 a.m. Pacific Time for the following purposes:

To elect the two Class I director nominees named in the Proxy Statement to hold office until the 2029 Annual Meeting of Stockholders and until their successors are duly elected and qualified.

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To approve, on a non-binding, advisory basis, the compensation of the Company’s named executive officers.

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To ratify the selection of Ernst & Young LLP as the Company’s independent registered public accounting firm for its fiscal year ending December 31, 2026.

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To approve the adoption of the Company’s 2026 Equity Incentive Plan.

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To conduct any other business that may be properly brought before the meeting or any adjournment or postponement thereof.

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These items of business are more fully described in the Proxy Statement accompanying this Notice.

The Annual Meeting will be held virtually this year. Online check-in will begin at 9:45 a.m. Pacific Time and you should allow ample time for the check-in procedures. You will not be able to attend the Annual Meeting in person.

The record date for the Annual Meeting is April 22, 2026. Only stockholders of record at the close of business on that date may vote at the meeting or any adjournment or postponement thereof. To participate in the meeting, you must have your 16-digit control number shown on your proxy card, Notice of Internet Availability of Proxy Materials or on the instructions that accompanied your proxy materials.

Instructions for accessing the virtual Annual Meeting are provided in the Proxy Statement. In the event of a technical malfunction or other situation that the meeting chair determines may affect the ability of the Annual Meeting to satisfy the requirements for a meeting of stockholders to be held by means of remote communication under the Delaware General Corporation Law, or that otherwise makes it advisable to adjourn the Annual Meeting, the meeting chair or secretary will convene the meeting at 11:00 a.m. Pacific Time on the date specified above and at the Company’s address specified above solely for the purpose of adjourning the meeting to reconvene at a date, time and physical or virtual location announced by the meeting chair or secretary. Under either of the foregoing circumstances, we will post information regarding the announcement on the Investors page of the Company’s website atwww.protagonist-inc.com.

Your vote is very important. If you have any questions or require any assistance with voting your shares, please contact our proxy solicitor:

Innisfree M&A Incorporated

Stockholders Toll-Free: (877) 750-5837

Banks and Brokers: (212)750-5833

By Order of the Board of Directors,

Whether or not you expect to participate in the virtual Annual Meeting, please vote as promptly as possible in order to ensure your representation at the Annual Meeting. You may vote online or, if you requested printed copies of the proxy materials, by telephone or by using the proxy card or voting instruction form provided with the printed proxy materials.