8-K

UNITED STATESSECURITIES AND EXCHANGE COMMISSIONWASHINGTON, D.C. 20549

FORM 8-K

CURRENT REPORT

Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934

PepGen Inc.

(Exact name of Registrant as Specified in Its Charter)

(Former Name or Former Address, if Changed Since Last Report)

Check the appropriate box below if the Form 8-K filing is intended to simultaneously satisfy the filing obligation of the registrant under any of the following provisions:

☐Written communications pursuant to Rule 425 under the Securities Act (17 CFR 230.425)

☐Soliciting material pursuant to Rule 14a-12 under the Exchange Act (17 CFR 240.14a-12)

☐Pre-commencement communications pursuant to Rule 14d-2(b) under the Exchange Act (17 CFR 240.14d-2(b))

☐Pre-commencement communications pursuant to Rule 13e-4(c) under the Exchange Act (17 CFR 240.13e-4(c))

Securities registered pursuant to Section 12(b) of the Act:

Indicate by check mark whether the registrant is an emerging growth company as defined in Rule 405 of the Securities Act of 1933 (§ 230.405 of this chapter) or Rule 12b-2 of the Securities Exchange Act of 1934 (§ 240.12b-2 of this chapter).

Emerging growth company ☒

If an emerging growth company, indicate by check mark if the registrant has elected not to use the extended transition period for complying with any new or revised financial accounting standards provided pursuant to Section 13(a) of the Exchange Act. ☐

Item 8.01 Other Events.

On December 8, 2025, PepGen Inc. (the “Company”) announced the appointment of Joseph Vittiglio, Esq., as the Company’s Chief Business and Legal Officer. A copy of the press release issued in connection with this announcement is being furnished as Exhibit 99.1 to this Current Report on Form 8-K.

Item 9.01 Financial Statements and Exhibits.

(d) Exhibits:

SIGNATURES

Pursuant to the requirements of the Securities Exchange Act of 1934, the registrant has duly caused this report to be signed on its behalf by the undersigned hereunto duly authorized.

EX-99.1

PepGen Appoints Joseph Vittiglio, Esq., as Chief Business and Legal Officer

BOSTON — December 8, 2025-- PepGen Inc. (Nasdaq: PEPG), a clinical-stage biotechnology company advancing the next generation of oligonucleotide therapies with the goal of transforming the treatment of severe neuromuscular and neurological diseases, today announced the appointment of Joseph Vittiglio, Esq., as Chief Business and Legal Officer. Mr. Vittiglio brings more than two decades of executive leadership experience across legal, compliance, corporate development, and corporate governance within public biotechnology companies.

“Joe is a deeply experienced legal and business leader with a proven track record guiding companies through complex transactions, regulatory milestones, financings, product launches, and strategic partnerships,” said James McArthur, PhD, President and Chief Executive Officer of PepGen. “We are excited to welcome him to PepGen’s executive leadership team as we continue to make significant progress advancing our PGN-EDODM1 program and prepare for the anticipated 2026 readouts from the 5 mg/kg and 10 mg/kg cohorts in our FREEDOM2-EDODM1 multiple ascending dose study in DM1 patients.”

Mr. Vittiglio joins PepGen after providing extensive consulting support to the Company in 2025. He most recently served as Chief Business and Legal Officer and Corporate Secretary at bluebird bio, where he led global legal, compliance, and business development; supported the approval and launch of three U.S. gene therapy products; advanced ex-U.S. partnering; and completed more than $400 million in financings. Prior to bluebird, he served as Chief Business and Legal Officer at Finch Therapeutics, guiding the company’s IPO, building its public-company governance and compliance functions, and overseeing a global IP portfolio of more than 50 patent families. Previously, he was Chief Business Officer and General Counsel at AMAG Pharmaceuticals, supporting major corporate transactions, multiple product launches, significant financings, and all legal, compliance, and business development for a commercial organization generating over $400 million annually. Earlier in his career, he held senior legal roles at Flexion Therapeutics, AVEO Pharmaceuticals, and Oscient Pharmaceuticals, after beginning his legal career at Mintz. Mr. Vittiglio holds a J.D. from Northeastern University School of Law and a B.A. in International Relations from Tufts University.

About PepGen

PepGen Inc. is a clinical-stage biotechnology company developing the next generation of oligonucleotide therapies with the goal of transforming the treatment of severe neuromuscular and neurological diseases. PepGen’s Enhanced Delivery Oligonucleotide (EDO) platform is founded on over a decade of research and development and leverages cell-penetrating peptides to improve the uptake and activity of conjugated oligonucleotide therapeutics. Using these EDO peptides, the Company is generating a pipeline of oligonucleotide therapeutic candidates designed to target the root cause of serious diseases.

For more information, please visit PepGen.com. Follow PepGen on LinkedIn and X.

Investor Contact Laurence Watts New Street Investor Relations laurence@newstreetir.com

Media Contact

Julia Deutsch

Lyra Strategic Advisory

Jdeutsch@lyraadvisory.com