NITE Nightstar Therapeutics Plc ADS

As filed with the Securities and Exchange Commission on June 10, 2019

Registration No. 333-230385

Registration No. 333-221005

UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

WASHINGTON, DC 20549

Post-Effective Amendment No. 1 to Form S-8

Registration Statement No. 333-230385

Post-Effective Amendment No. 1 to Form S-8

Registration Statement No. 333-221005

Under the

SECURITIES ACT OF 1933

2017 Equity Incentive Plan

(Full titles of the plans)

Nightstar Therapeutics PLC

c/o Biogen Inc.

Attn: Susan Alexander, Esq.

Executive Vice President, Chief Legal, Corporate Services and Secretary

225 Binney Street

Cambridge, MA 02142

(Name and address of agent for service)

(617) 679-2000

(Telephone number, including area code, of agent for service)

Please send copies of all communications to:

Zachary Blume

Paul Kinsella

Ropes & Gray LLP

Prudential Tower

800 Boylston Street

Boston, MA 02199-3600

617-951-7000

Indicate by check mark whether the registrant is a large accelerated filer, an accelerated filer, a non-accelerated filer, a smaller reporting company, or an emerging growth company. See the definitions of “large accelerated filer,” “accelerated filer, “smaller reporting company,” and “emerging growth company” in Rule 12b-2 of the Exchange Act.

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 7(a)(2)(B) of the Securities Act.  ☒

DEREGISTRATION OF SECURITIES

Nightstar Therapeutics plc, a public limited corporation incorporated in England and Wales (the “Registrant”), is filing these post-effective amendments to the following registration statements on Form S-8 (each, a “Registration Statement”, and collectively, the “Registration Statements”) to deregister any and all ordinary shares of the Registrant, nominal value £0.01 per share (“Ordinary Shares”), registered but unsold or otherwise unissued under each of the following Registration Statements as of the date hereof:

On June 7, 2019, pursuant to the Implementation Agreement, dated as of March 4, 2019, by and among the Registrant, Biogen Switzerland Holdings GmbH (“BSH”) and Tungsten Bidco Limited (“Bidco”), Bidco acquired the entire issued share capital of the Registrant for $25.50 in cash per Ordinary Share and the Registrant became a wholly-owned subsidiary of Bidco. Under the terms of the Implementation Agreement, the acquisition was implemented by means of a scheme of arrangement under Part 26 of the UK Companies Act 2006 (the “Scheme”).

In connection with the effectiveness of the Scheme, the offerings pursuant to the Registration Statements have been terminated. In accordance with undertakings made by the Registrant in the Registration Statements to remove from registration, by means of a post-effective amendment, any of the securities that remain unsold at the termination of the offerings, the Registrant hereby removes from registration all Ordinary Shares registered under the Registration Statements but not sold under the Registration Statements.