[S-8 POS] IGM Biosciences, Inc. SEC Filing

Rhea-AI Filing Summary

IGM Biosciences completed a merger and terminated its Form S-8 offerings. Under a Merger Agreement dated July 1, 2025, the company merged into a subsidiary of Concentra Biosciences and became a wholly owned subsidiary of Parent on August 14, 2025. Each outstanding public share (with limited exceptions) converted into $1.247 in cash plus one non-transferable contractual contingent value right (CVR) per share. As a result, the registrant terminated all offerings under the referenced Form S-8 registration statements and filed post-effective amendments to withdraw and remove any unissued and unsold securities from registration.

Positive

• Share consideration defined: Each outstanding share converted into $1.247 cash plus one CVR, giving clear, disclosed consideration to shareholders.
• Regulatory close-out: The registrant filed post-effective amendments to properly withdraw and remove unsold securities from its Form S-8 registration statements, completing the administrative close-out.

Negative

• Public equity terminated: The Merger resulted in the company becoming a wholly owned subsidiary and ended public trading of shares, removing market liquidity for former shareholders.
• Employee equity issuance capacity ended: All offerings under the referenced Form S-8 registrations were terminated, preventing future issuance under those employee plans pursuant to those registrations.

Insights

Financial Analyst

TL;DR: Merger materially changes shareholder liquidity and equity availability; cash-out at $1.247 plus CVRs replaces publicly tradable shares.

The filing confirms a definitive change of control where public shareholders were cashed out at $1.247 per share and received CVRs, eliminating publicly traded equity and terminating Form S-8 registrations for option and employee plans. This is a material corporate action that removes future equity issuance capacity under these registration statements and converts remaining equity to contingent recoveries. The transaction crystallizes value for holders but ends the company’s standalone public equity trajectory.

Corporate Governance Expert

TL;DR: The post-effective amendment properly withdraws unsold registered securities after a merger that converted shares into cash and CVRs.

The registrant fulfilled its contractual undertakings by filing post-effective amendments to remove unsold securities from multiple Form S-8 registration statements. The description is procedural and compliant: it documents termination of offerings, conversion mechanics for outstanding shares, and the company’s change into a wholly owned subsidiary. For governance, the filing evidences completion of closing mechanics and removal of registration obligations tied to the pre-merger public company.

As filed with the Securities and Exchange Commission on August 14, 2025

Registration No. 333-233826

Registration No. 333-237411

Registration No. 333-248111

Registration No. 333-254877

Registration No. 333-263927

Registration No. 333-270991

Registration No. 333-277744

Registration No. 333-285602

UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

POST-EFFECTIVE AMENDMENT NO. 1 TO FORM S-8 REGISTRATION STATEMENT NO. 333-233826

POST-EFFECTIVE AMENDMENT NO. 1 TO FORM S-8 REGISTRATION STATEMENT NO. 333-237411

POST-EFFECTIVE AMENDMENT NO. 1 TO FORM S-8 REGISTRATION STATEMENT NO. 333-248111

POST-EFFECTIVE AMENDMENT NO. 1 TO FORM S-8 REGISTRATION STATEMENT NO. 333-254877

POST-EFFECTIVE AMENDMENT NO. 1 TO FORM S-8 REGISTRATION STATEMENT NO. 333-263927

POST-EFFECTIVE AMENDMENT NO. 1 TO FORM S-8 REGISTRATION STATEMENT NO. 333-270991

POST-EFFECTIVE AMENDMENT NO. 1 TO FORM S-8 REGISTRATION STATEMENT NO. 333-277744

POST-EFFECTIVE AMENDMENT NO. 1 TO FORM S-8 REGISTRATION STATEMENT NO. 333-285602

FORM S-8

REGISTRATION STATEMENT

UNDER

THE SECURITIES ACT OF 1933

IGM BIOSCIENCES, INC.

(Exact name of registrant as specified in its charter)

Delaware		77-0349194
(State or other jurisdiction of incorporation or organization)		(IRS employer identification number)

4747 Executive Drive, Suite 210

San Diego, California 92121

(Address of Principal Executive Offices, including Zip Code)

Amended and Restated 2018 Omnibus Incentive Plan

Amended and Restated 2019 Employee Stock Purchase Plan

Amended and Restated 2010 Stock Plan

(Full title of the Plans)

Michael Hearne

Chief Financial Officer

IGM Biosciences, Inc.

4747 Executive Drive, Suite 210

San Diego, California 92121

(858) 281-5372

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

Copies to:

Ryan A. Murr

Gibson, Dunn & Crutcher LLP

One Embarcadero Center Suite 2600

San Francisco, California 94111

(415) 393-8200

Tony Jeffries

Robert T. Ishii

Jennifer Knapp

Ethan Lutske

Wilson Sonsini Goodrich & Rosati, P.C.

650 Page Mill Road

Palo Alto, California 94304

(650) 493-9300

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 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 UNSOLD SECURITIES

These Post-Effective Amendments (the “Post-Effective Amendments”) filed by IGM Biosciences, Inc., a Delaware corporation (the “Registrant”), to deregister all shares of the Registrant’s common stock, $0.01 par value per share (the “Shares”), remaining unissued under the following Registration Statements on Form S-8 (each, a “Registration Statement”, and collectively, the “Registration Statements”) filed by the Registrant with the U.S. Securities and Exchange Commission (the “Commission”).

• Registration Statement on Form S-8 (No. 333-233826) pertaining to the registration of (i) 4,372,807 Shares issuable under the Amended and Restated 2018 Omnibus Incentive Plan (the “2018 Plan”), (ii) 280,000 Shares issuable under the Amended and Restated 2019 Employee Stock Purchase Plan (the “ESPP”) and (iii) 595,832 Shares issuable under the Amended and Restated 2010 Stock Plan.

• Registration Statement on Form S-8 (No. 333-237411) pertaining to the registration of (i) 964,487 Shares issuable under the 2018 Plan and (ii) 241,121 Shares issuable under the ESPP.

• Registration Statement on Form S-8 (No. 333-248111) pertaining to the registration of (i) 257,248 Shares issuable under the 2018 Plan and (ii) 64,312 Shares issuable under the ESPP.

• Registration Statement on Form S-8 (No. 333-254877) pertaining to the registration of (i) 1,278,965 Shares issuable under the 2018 Plan and (ii) 319,741 Shares issuable under the ESPP.

• Registration Statement on Form S-8 (No. 333-263927) pertaining to the registration of (i) 1,299,920 Shares issuable under the 2018 Plan and (ii) 324,980 Shares issuable under the ESPP.

• Registration Statement on Form S-8 (No. 333-270991) pertaining to the registration of (i) 1,723,292 Shares issuable under the 2018 Plan and (ii) 430,823 Shares issuable under the ESPP.

• Registration Statement on Form S-8 (No. 333-277744) pertaining to the registration of (i) 4,507,245 Shares issuable under the 2018 Plan and (ii) 560,000 Shares issuable under the ESPP.

• Registration Statement on Form S-8 (No. 333-285602) pertaining to the registration of (i) 2,385,497 Shares issuable under the 2018 Plan and (ii) 560,000 Shares issuable under the ESPP.

The Registrant is filing these Post-Effective Amendments to withdraw and remove any unissued and unsold securities issuable by Registration pursuant to the above-referenced Registration Statements.

On July 1, 2025, the Registrant entered into an Agreement and Plan of Merger (the “Merger Agreement”) with Concentra Biosciences, LLC, a Delaware limited liability company (“Parent”), and Concentra Merger Sub V, Inc., a Delaware corporation and wholly owned subsidiary of Parent (“Merger Sub”). Pursuant to the Merger Agreement, on August 14, 2025, Merger Sub was merged with and into the Registrant with the Registrant surviving as a wholly owned subsidiary of Parent (the “Merger”). In the Merger, each share of Common Stock (the “Shares”) (other than (i) Shares owned or held in the Company’s treasury immediately prior to the Effective Time, (ii) Shares owned directly or indirectly by Parent or Merger Sub immediately prior to the Effective Time and (iii) Shares held by any stockholder of the Registrant who properly exercised appraisal rights under Delaware law) was converted into the right to receive (i) $1.247 per Share in cash and (ii) one non-transferable contractual contingent value right for each Share.

As a result of the Merger, the Registrant has terminated all offerings of its securities pursuant to the Registration Statements. In accordance with an undertaking made by the Registrant in each of the Registration Statements to remove from registration, by means of a post-effective amendment, any of the securities that had been registered for issuance that remain unsold at the termination of the offerings, the Registrant hereby removes from registration all such securities registered under the Registration Statements that remain unsold as of the date hereof and terminates the effectiveness of the Registration Statements.

SIGNATURE

Pursuant to the requirements of the Securities Act of 1933, the Registrant certifies that it has reasonable grounds to believe that it meets all of the requirements for filing on Form S-8 and has duly caused these Post-Effective Amendments to be signed on its behalf by the undersigned, thereunto duly authorized, in the City of San Diego, State of California, on August 14, 2025. No other person is required to sign these Post-Effective Amendment to the Registration Statements in reliance on Rule 478 of the Securities Act of 1933, as amended.

IGM BIOSCIENCES, INC.

By: /s/ Michael Hearne

Name: Michael Hearne

Title: Chief Financial Officer

FAQ

What did IGM Biosciences (IGMS) shareholders receive in the merger?

Each outstanding share (with limited exceptions) was converted into $1.247 in cash and one non-transferable contractual contingent value right (CVR) per share.

Why did IGM file post-effective amendments to its Form S-8 registration statements?

The company filed post-effective amendments to withdraw and remove any unissued and unsold securities registered under the Form S-8 statements because the Merger terminated the offerings and the company became a wholly owned subsidiary.

Did the merger change IGM’s corporate status?

Yes. As of the Merger, IGM survived as a wholly owned subsidiary of Concentra Biosciences, and it is no longer an independent public company.

Are employee equity awards still issuable under the terminated S-8 registrations?

No. The filing states that all offerings of securities pursuant to the referenced Form S-8 registration statements were terminated and unsold securities were removed from registration.

Were any shares excluded from the cash-and-CVR conversion?

Yes. Excluded shares include shares in the company’s treasury immediately prior to the Effective Time, shares owned by Parent or Merger Sub immediately prior to the Effective Time, and shares held by stockholders who properly exercised appraisal rights under Delaware law.

What is a CVR in this context?

The filing describes a CVR as a non-transferable contractual contingent value right issued for each converted share; specific terms of the CVR are not detailed in this filing.