UNITED STATES
SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

SCHEDULE 13G

Under the Securities Exchange Act of 1934
(Amendment No. )*

APPGATE, INC.

(Name of Issuer)

Common Stock, par value $0.001 per share

(Title of Class of Securities)

03783X104

(CUSIP Number)

December 31, 2021

(Date of Event Which Requires Filing of this Statement)

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

x  Rule 13d-1(b)

¨  Rule 13d-1(c)

¨  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).

SCHEDULE 13G

This statement relates to the Shares (as defined herein) obtainable upon conversion of convertible debt held for Magnetar Constellation Master Fund, Ltd (“Constellation Master Fund”), Magnetar Constellation Fund II, Ltd (“Constellation Fund II”), Purpose Alternative Credit Fund – F LLC (“Purpose Fund”), Purpose Alternative Credit Fund – T LLC (“Purpose Fund - T”), Magnetar Lake Credit Fund LLC (“Lake Credit Fund”), Magnetar Xing He Master Fund Ltd (“Xing He Master Fund”), Magnetar SC Fund Ltd (“SC Fund”), Magnetar Structured Credit Fund, LP (“Structured Credit Fund”) and Magnetar Longhorn Fund, LP (“Longhorn Fund”), all Cayman Islands exempted companies except for Structured Credit Fund and Longhorn Fund, each of which is a Delaware limited partnership, and Purpose Fund, Purpose Fund – T and Lake Credit Fund, each of which is a Delaware limited liability company (collectively, the “Magnetar Funds”). Magnetar Financial serves as the investment adviser to each of Constellation Master Fund, Constellation Fund II, Xing He Master Fund, SC Fund, Structured Credit Fund and Longhorn Fund, and as manager to each of Purpose Fund, Purpose Fund – T, and Lake Credit Fund, and as such, Magnetar Financial exercises voting and investment power over the Units held for the Magnetar Funds’ accounts. Magnetar Capital Partners serves as the sole member and parent holding company of Magnetar Financial. Supernova Management is the general partner of Magnetar Capital Partners. The manager of Supernova Management is Mr. Litowitz.

The address of the principal business office of each of Magnetar Financial, Magnetar Capital Partners, Supernova Management, and Mr. Litowitz is 1603 Orrington Avenue, 13^th Floor, Evanston, Illinois 60201.

Common Stock, par value $0.001 per share (“Shares”)

03783X104

(e)  x An investment adviser in accordance with §240.13d–1(b)(1)(ii)(E)

(g)  x A parent holding company or control person in accordance with §240.13d–1(b)(1)(ii)(G)

As of December 31, 2021, each of Magnetar Financial, Magnetar Capital Partners, Supernova Management and Mr. Litowitz held 10,982,804 Shares. The amount consists of (A) 4,096,586 Shares obtainable upon conversion of convertible debt held for the account of Constellation Fund II; (B) 1,153,195 Shares obtainable upon conversion of convertible debt held for the account of Constellation Master Fund; (C) 483,243 Shares obtainable upon conversion of convertible debt held for the account of Longhorn Fund; (D) 1,394,816 Shares obtainable upon conversion of convertible debt held for the account of Xing He Master Fund; (E) 197,690 Shares obtainable upon conversion of convertible debt held for the account of Purpose Fund; (F) 911,573 Shares obtainable upon conversion of convertible debt held for the account of SC Fund; (G) 1,515,627 Shares held for the account of Structured Credit Fund; (H) 637,003 Shares obtainable upon conversion of convertible debt held for the account of Lake Credit Fund; and (I) 593,071 Shares obtainable upon conversion of convertible debt held of the account of Purpose Fund - T. The Shares held by the Magnetar Funds represent approximately 7.7% of the total number of Shares outstanding (calculated pursuant to Rule 13d-3(d)(1)(i)) of the outstanding shares of the Issuer).

(i) As of December 31, 2021, each of Reporting Persons were deemed to be the beneficial owner constituting approximately 7.7% of the total number of shares outstanding (based upon the information provided by the Issuer, there were 131,793,660 Shares outstanding as of December 31, 2021, plus 10,982,804 Shares issuable to the Reporting Persons upon conversion of convertible debt, for a total of approximately 142,776,465 Shares outstanding).

Magnetar Financial, Magnetar Capital Partners, Supernova Management, and Mr. Litowitz:

If this statement is being filed to report the fact that as of the date hereof the reporting person has ceased to be the beneficial owner of more than 5 percent of the class of securities, check the following [].

This Item 6 is not applicable.

This Item 7 is not applicable.

This Item 8 is not applicable.

This Item 9 is not applicable.

By signing below the Reporting Persons certifies that, to the best of their knowledge and belief, the securities referred to above were acquired and are 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.

SIGNATURE

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.

EXHIBIT INDEX

EXHIBIT A

JOINT FILING AGREEMENT

The undersigned hereby agree that the statement on Schedule 13G with respect to the Shares of Build Acquisition Corp dated as of December 31, 2021 is, and any amendments thereto (including amendments on Schedule 13D) signed by each of the undersigned shall be, filed on behalf of each of us pursuant to and in accordance with the previsions of Rule 13d-1(k) under the Securities Exchange Act of 1934, as amended.