UNITED STATES

SECURITIES AND EXCHANGE COMMISSION
Washington, DC 20549

SCHEDULE 13G

Under the Securities Exchange Act of 1934

Check the appropriate box to designate the rule pursuant to which this Schedule is filed:

o Rule 13d-1(b)

x Rule 13d-1(c)

o Rule 13d-1(d)

*The remainder of this cover page shall be filled out for a reporting person’s initial filing on this form with respect to the subject class of securities, and for any subsequent amendment containing information which would alter the disclosures provided in a prior cover page.

The information required in the remainder of this cover page shall not be deemed to be “filed” for the purpose of Section 18 of the Securities Exchange Act of 1934 (“Act”) or otherwise subject to the liabilities of that section of the Act but shall be subject to all other provisions of the Act (however, see the Notes).

* This percentage is calculated based upon 28,525,774 outstanding shares of common stock, par value $0.001 per share (the “Shares”) of Pandion Therapeutics, Inc. (the “Issuer”), as set forth in the Issuer’s Rule 424(b)(4) Prospectus filed with the Securities and Exchange Commission on July 16, 2020.

* This percentage is calculated based upon 28,525,774 outstanding shares of common stock, par value $0.001 per share (the “Shares”) of Pandion Therapeutics, Inc. (the “Issuer”), as set forth in the Issuer’s Rule 424(b)(4) Prospectus filed with the Securities and Exchange Commission on July 16, 2020.

* This percentage is calculated based upon 28,525,774 outstanding shares of common stock, par value $0.001 per share (the “Shares”) of Pandion Therapeutics, Inc. (the “Issuer”), as set forth in the Issuer’s Rule 424(b)(4) Prospectus filed with the Securities and Exchange Commission on July 16, 2020.

* This percentage is calculated based upon 28,525,774 outstanding shares of common stock, par value $0.001 per share (the “Shares”) of Pandion Therapeutics, Inc. (the “Issuer”), as set forth in the Issuer’s Rule 424(b)(4) Prospectus filed with the Securities and Exchange Commission on July 16, 2020.

Pandion Therapeutics, Inc.

134 Coolidge Avenue

Watertown, Massachusetts 02472

This Schedule 13G is being filed by OrbiMed Advisors LLC (“Advisors”), a limited liability company organized under the laws of Delaware, OrbiMed Capital GP VII LLC (“GP VII”), a limited liability company organized under the laws of Delaware, OrbiMed Genesis GP LLC (“OrbiMed Genesis”), a limited liability company organized under the laws of Delaware, and OrbiMed Capital LLC (“Capital”), a limited liability company organized under the laws of Delaware (collectively, the “Reporting Persons”).

See Exhibit A for the Reporting Persons’ agreement for a joint filing of a single statement on their behalf.

601 Lexington Avenue, 54th Floor

New York, NY 10022

Please refer to Item 4 on each cover sheet for each filing person.

Common Stock

698340106

Item 4. Ownership:

GP VII is the general partner of OrbiMed Private Investments VII, LP (“OPI VII”), which holds 747,414 Shares and OrbiMed Genesis is the general partner of OrbiMed Genesis Master Fund, L.P. (“Genesis Master Fund”), which holds 293,411 Shares. Advisors is an investment advisor in accordance with Rule 13d-1(b)(1)(ii)(E) under the Securities Exchange Act of 1934, as amended, and is the managing member of GP VII and OrbiMed Genesis. As a result, Advisors and GP VII share the power to direct the vote and the disposition of the Shares held of record by OPI VII and Advisors and OrbiMed Genesis share the power to direct the vote and the disposition of the Shares held of record by Genesis Master Fund. Advisors exercises this investment and voting power through a management committee comprised of Carl L. Gordon, Sven H. Borho, and Jonathan T. Silverstein. On the basis of these relationships, GP VII and Advisors may be deemed to share beneficial ownership of the Shares held by OPI VII and OrbiMed Genesis and Advisors may be deemed to share beneficial ownership of the Shares held by Genesis Master Fund. Capital, a registered investment adviser under the Investment Advisers Act, acts as the investment advisor to The Biotech Growth Trust PLC (“BIOG”), which holds 440,115 Shares. Capital has discretionary investment management authority with respect to the assets of BIOG, which includes the power to vote and otherwise dispose of securities purchased by BIOG. Capital exercises this investment and voting power through a management committee comprised of Carl L. Gordon, Sven H. Borho, and Jonathan T. Silverstein. On the basis of this relationship, Capital may be deemed to have beneficial ownership of the Shares held by BIOG. Advisors, GP VII, and OrbiMed Genesis disclaim beneficial ownership of the Shares held indirectly by Capital, and Capital disclaims beneficial ownership of the Shares held indirectly by Advisors, GP VII, and OrbiMed Genesis.

(a) Amount beneficially owned: See the response(s) to Item 9 on the attached cover page(s).

(b) Percent of class: See the response(s) to Item 11 on the attached cover page(s).

(c) Number of shares as to which such person has:

(i) Sole power to vote or to direct the vote: See the response(s) to Item 5 on the attached cover page(s).

(ii) Shared power to vote or to direct the vote: See the response(s) to Item 6 on the attached cover page(s).

(iii) Sole power to dispose or to direct the disposition of: See the response(s) to Item 7 on the attached cover page(s).

(iv) Shared power to dispose or to direct the disposition of: See the response(s) to Item 8 on the attached cover page(s).

Item 5. Ownership of Five Percent or Less of a Class.

Not Applicable.

Item 6. Ownership of More Than Five Percent on Behalf of Another Person.

See Item 4.

Item 7. Identification and Classification of the Subsidiary which Acquired the Security Being Reported on by the Parent Holding Company or Control Person.

Not Applicable.

Item 8. Identification and Classification of Members of the Group.

Not Applicable.

Item 9. Notice of Dissolution of Group.

Not Applicable.

Item 10. Certification.

By signing below, I certify that, to the best of my knowledge and belief, the securities referred to above were acquired and held in the ordinary course of business and were not acquired and are not held for the purpose of or with the effect of changing or influencing the control of the issuer of the securities and were not acquired and are not held in connection with or as a participant in any transaction having that purpose or effect.

SIGNATURES

After reasonable inquiry and to the best of my knowledge and belief, I certify that the information set forth in this statement is true, complete and correct.

Dated: July 27, 2020

EXHIBIT A

JOINT FILING AGREEMENT

The undersigned hereby agree that the Statement on this Schedule 13G dated July 27, 2020 (the “Schedule 13G”), with respect to the Common Stock of Pandion Therapeutics, Inc. is filed on behalf of each of us pursuant to and in accordance with the provisions of Rule 13d-1(k) under the Securities Exchange Act of 1934, as amended, and that this Agreement shall be included as an Exhibit to the Schedule 13G. Each of the undersigned agrees to be responsible for the timely filing of the Schedule 13G, and for the completeness and accuracy of the information concerning itself contained therein. This Agreement may be executed in any number of counterparts, all of which taken together shall constitute one and the same instrument.

IN WITNESS WHEREOF, the undersigned have executed this Agreement as of July 27, 2020.