IDRA Idera Pharmaceuticals Inc

SECURITIES AND EXCHANGE COMMISSION

WASHINGTON, DC 20549

SCHEDULE 13D

(Rule 13d-101)

INFORMATION TO BE INCLUDED IN STATEMENTS FILED PURSUANT

TO RULE 13d-1(a) AND AMENDMENTS THERETO FILED PURSUANT

TO RULE 13d-2(a)

(Amendment No. 15)*

Aceragen, Inc.

(Name of Issuer)

Common Stock, $0.001 par value per share

(Title of Class of Securities)

00445F109

(CUSIP number)

Youssef El Zein

c/o Stuarts Corporate Services Ltd.

Kensington House, 69 Dr. Roy’s Drive

Georgetown, Grand Cayman KY1-1104

Cayman Islands

(Name, Address and Telephone Number of Person Authorized to Receive Notices and Communications)

April 7, 2023

(Date of Event Which Requires Filing of this Statement)

If the filing person has previously filed a statement on Schedule 13G to report the acquisition that is the subject of this Schedule 13D, and is filing this schedule because of Rule 13d-1(e), 13d-1(f) or 13d-1(g), check the following box  ☐.

The information required on 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 (the “Act”) or otherwise subject to the liabilities of that section of the Act but shall be subject to all other provisions of the Act.

Pillar 6 directly holds (a) 135,540 shares of Common Stock and (b) 45,113 Common Warrants (the “Common Warrants”), which are exercisable for shares of Common Stock. Pursuant to the terms of the Common Warrants, a blocker provision limits the number of Common Warrants exercisable for shares of Common Stock to the extent such exercise would allow the percentage of Common Stock held directly to exceed 19.99% (the “Blocker Provision”).

Pillar Foundation directly holds (a) 427,468 shares of Common Stock and (b) 198,288 Common Warrants, which are exercisable for shares of Common Stock. These Common Warrants are subject to the Blocker Provision.

All of the Common Warrants held by Pillar 6 and Pillar Foundation are currently exercisable, subject to the Blocker Provision, to the extent applicable.

Mr. El Zein directly holds 1,547 shares of Common Stock and 1,579 options to buy shares of Common Stock. Mr. Umari directly holds 22,712 shares of Common Stock.

SCHEDULE 13D

Explanatory Note: This Amendment No. 15 to Schedule 13D (this “Amendment No. 15”) amends the Schedule 13D filed on November 14, 2011 (the “Original 13D”), as amended by Amendment No. 1 to Schedule 13D filed on November 16, 2012 (“Amendment No. 1”), Amendment No. 2 to Schedule 13D filed on June 5, 2013 (“Amendment No. 2”), Amendment No. 3 to Schedule 13D filed on October 9, 2013 (“Amendment No. 3”), Amendment No. 4 to Schedule 13D filed on October 17, 2016 (“Amendment No. 4”), Amendment No. 5 to Schedule 13D filed on July 25, 2019 (“Amendment No. 5”), Amendment No. 6 to Schedule 13D filed on May 7, 2020 (“Amendment No. 6”), Amendment No. 7 to Schedule 13D filed on August 17, 2020 (“Amendment No. 7”), Amendment No. 8 to Schedule 13D filed on December 30, 2020 (“Amendment No. 8”), Amendment No. 9 to Schedule 13D filed on April 1, 2021 (“Amendment No. 9”), Amendment No. 10 to Schedule 13D filed on June 7, 2021 (“Amendment No. 10”), Amendment No. 11 to Schedule 13D filed on June 24, 2022 (“Amendment No. 11”), Amendment No. 12 to Schedule 13D filed on July 1, 2022 (“Amendment No. 12”), Amendment No. 13 to Schedule 13D filed on October 5, 2022 (“Amendment No. 13”), and Amendment No. 14 to Schedule 13D filed on January 30, 2023 (together with the Original 13D, Amendment No. 1, Amendment No. 2, Amendment No. 3, Amendment No. 4, Amendment No. 5, Amendment No. 6, Amendment No. 7, Amendment No. 8, Amendment No. 9, Amendment No. 10, Amendment No. 11, Amendment No. 12, Amendment No. 13, and Amendment No. 15 the “Schedule 13D”) and relates to the Common Stock. The principal executive offices of the Issuer are located at 505 Eagleview Blvd., Suite 212, Exton, PA 19341.

Except as specifically amended by this Amendment No. 15, the disclosure in the Schedule 13D remains in full force and effect. Capitalized terms used in this Amendment No. 15 but not otherwise defined shall have the meanings given to such terms in the Schedule 13D.

(a) — (b)

The following sets forth, as of the date of this Amendment No. 15, the aggregate number of shares of Common Stock and percentage of shares of Common Stock beneficially owned by each of the Reporting Persons, as well as the number of shares of Common Stock as to which each Reporting Person has the sole power to vote or to direct the vote, shared power to vote or to direct the vote, sole power to dispose or to direct the disposition, or shared power to dispose or to direct the disposition of, as of the date hereof, based on 8,461,063 shares of Common Stock outstanding at January 17, 2023.

(c) No transactions in the Common Stock were effected by the Reporting Persons during the past 60-day period.

(d) No persons other than the Reporting Persons and their investment clients have the right to participate in the receipt of dividends from, or the proceeds from the sale of, the shares of Common Stock covered hereby.

(e) Not Applicable.

Item 4 to this Schedule 13D is hereby amended to add the following:

As previously disclosed, Pillar Foundation was a party to a Warrant to Purchase Common Stock of the Company issued in April 2020 (the “April 2020 Warrant Agreement”). Pursuant to its terms, the April 2020 Warrant Agreement automatically expired on April 7, 2023, and as such, Pillar Foundation’s right to exercise up to 178,795 Common Warrants expired.

SIGNATURE

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

EXECUTED as a sealed instrument this 10th day of April, 2023.