As filed with the Securities and Exchange Commission on April 1, 2021

Registration No. 333-239500

Registration No. 333-239894

UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

POST-EFFECTIVE AMENDMENT NO. 1 TO FORM S-1 REGISTRATION STATEMENT NO. 333-239500

POST-EFFECTIVE AMENDMENT NO. 1 TO FORM S-1 REGISTRATION STATEMENT NO. 333-239894

UNDER

THE SECURITIES ACT OF 1933

Pandion Therapeutics, Inc.

(Exact Name of Registrant as Specified in Its Charter)

Delaware

(State or Other Jurisdiction of Incorporation)

83-3015614

(I.R.S. Employer Identification Number)

134 Coolidge Avenue

Watertown, Massachusetts 02472

(617) 393-5925

(Address, Including Zip Code, and Telephone Number, Including Area Code, of Registrant’s Principal Executive Offices)

Rita A. Karachun

President

Pandion Therapeutics, Inc.

134 Coolidge Avenue

Watertown, Massachusetts 02472

(617) 393-5925

(Name, Address, Including Zip Code, and Telephone Number, Including Area Code, of Agent for Service)

Copies to:

Catherine J. Dargan, Esq.

Michael J. Riella, Esq.

Covington & Burling LLP

One CityCenter

850 Tenth Street, NW

Washington, DC 20001-4956

+1 (202) 662 6000

Approximate date of commencement of proposed sale to the public: Not applicable. Removal from registration of securities that were not sold pursuant to the above referenced registration statement.

If the only securities being registered on this Form are being offered pursuant to dividend or interest reinvestment plans, please check the following box.  ☐

If any of the securities being registered on this Form are to be offered on a delayed or continuous basis pursuant to Rule 415 under the Securities Act of 1933, other than securities offered only in connection with dividend or interest reinvestment plans, check the following box.  ☐

If this Form is filed to register additional securities for an offering pursuant to Rule 462(b) under the Securities Act, please check the following box and list the Securities Act registration statement number of the earlier effective registration statement for the same offering.  ☐

If this Form is a post-effective amendment filed pursuant to Rule 462(c) under the Securities Act, check the following box and list the Securities Act registration statement number of the earlier effective registration statement for the same offering.  ☐

If this Form is a registration statement pursuant to General Instruction I.D. or a post-effective amendment thereto that shall become effective upon filing with the Commission pursuant to Rule 462(e) under the Securities Act, check the following box.  ☐

If this Form is a post-effective amendment to a registration statement filed pursuant to General Instruction I.D. filed to register additional securities or additional classes of securities pursuant to Rule 413(b) under the Securities Act, check the following box.  ☐

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.

Large accelerated filer	☐	Accelerated filer	☐
Non-accelerated filer	☒	Smaller reporting company	☒
		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 7(a)(2)(B) of the Securities Act.  ☐

EXPLANATORY NOTE

DEREGISTRATION OF SECURITIES

This Post-Effective Amendment (this “Amendment”) relates to the following Registration Statements on Form S-1 (collectively, the “Registration Statements”) filed by Pandion Therapeutics, Inc., a Delaware corporation (“Pandion”) with the Securities and Exchange Commission (the “SEC”):

• Registration Statement on Form S-1 (No. 333-239500), filed with the SEC on June 26, 2020, as amended by Amendment No. 1 on July 13, 2020 and Amendment No. 2 on July 16, 2020; and

• Registration Statement on Form S-1 (No. 333-239894), filed with the SEC on July 16, 2020.

On February 24, 2021, Pandion entered into an agreement and plan of merger (the “Merger Agreement”) with Panama Merger Sub, Inc., a Delaware corporation (“Purchaser”) and wholly-owned subsidiary of Merck Sharp & Dohme Corp., a New Jersey corporation (“Parent”), and Parent. Pursuant to the Merger Agreement, on April 1, 2021, Purchaser merged with and into Pandion with Pandion surviving the merger as a wholly-owned subsidiary of Parent.

As a result of the consummation of the transactions contemplated by the Merger Agreement, Pandion has terminated all offerings of its securities pursuant to the Registration Statements and hereby removes and withdraws from registration any and all securities registered pursuant to the Registration Statements that remain unsold as of the date hereof.

SIGNATURES

Pursuant to the requirements of the Securities Act of 1933, as amended, the Registrant has duly caused this Post-Effective Amendment to the Registration Statements to be signed on its behalf by the undersigned, thereunto duly authorized, in the City of Watertown, Commonwealth of Massachusetts, on the 1st day of April, 2021. No other person is required to sign this Post-Effective Amendment to the Registration Statements in reliance on Rule 478 of the Securities Act of 1933, as amended.

PANDION THERAPEUTICS, INC.
By:	/s/ Kelly Grez
Name:	Kelly Grez
Title:	Assistant Secretary