UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

FORM 8-K

CURRENT REPORT

Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934

Date of Report (Date of earliest event reported): August 3, 2026

Supernus Pharmaceuticals, Inc.

(Exact name of registrant as specified in its charter)

Delaware	001-35518	20-2590184
(State or other jurisdiction of incorporation or organization)	(Commission File Number)	(I.R.S. Employer Identification No.)

9715 Key West Ave	Rockville	MD	20850
(Address of Principal Executive Offices)			(Zip Code)

Registrant’s telephone number, including area code: (301) 838-2500

Not Applicable

(Former name or former address, if changed since last report.)

Securities registered pursuant to Section 12(b) of the Exchange Act

Title of each class	Trading Symbol	Name of each exchange on which registered
Common Stock, $0.001 par value per share	SUPN	The Nasdaq Stock Market LLC

Check the appropriate box below if the Form 8-K filing is intended to simultaneously satisfy the filing obligation of the registrant under any of the following provisions (see General Instruction A.2. below):

x Written communications pursuant to Rule 425 under the Securities Act (17 CFR 230.425)

x Soliciting material pursuant to Rule 14a-12 under the Exchange Act (17 CFR 240.14a-12)

¨ Pre-commencement communications pursuant to Rule 14d-2(b) under the Exchange Act (17 CFR 240.14d-2(b))

¨ Pre-commencement communications pursuant to Rule 13e-4(c) under the Exchange Act (17 CFR 240.13e-4(c))

Indicate by check mark whether the registrant is an emerging growth company as defined in Rule 405 of the Securities Act of 1933 (§230.405 of this chapter) or Rule 12b-2 of the Securities Exchange Act of 1934 (§240.12b-2 of this chapter). ¨

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 13(a) of the Exchange Act. ¨

Item 8.01

Other Events.

As previously announced, on August 3, 2026, Supernus Pharmaceuticals, Inc. (the “Company”) and Indivior Pharmaceuticals Inc. (“Indivior”) are hosting a conference call and webcast at 8:30 a.m., Eastern Time, to present information regarding the proposed merger of the Company and Indivior. The Company intends to display the slides filed as Exhibit 99.1 hereto during the presentation.

Important Additional Information and Where to Find It

In connection with the proposed transaction, Indivior intends to file with the SEC a registration statement on Form S-4, which will include a document that serves as a prospectus of Indivior and a joint proxy statement of Indivior and Supernus (the “joint proxy statement/prospectus”). Each party also plans to file other relevant documents with the SEC regarding the proposed transaction. INVESTORS AND SECURITY HOLDERS ARE URGED TO READ THE JOINT PROXY STATEMENT/PROSPECTUS AND OTHER RELEVANT DOCUMENTS FILED WITH THE SEC WHEN THEY BECOME AVAILABLE, BECAUSE THEY WILL CONTAIN IMPORTANT INFORMATION ABOUT THE PROPOSED TRANSACTION. A definitive joint proxy statement/prospectus will be sent to Indivior’s stockholders and Supernus’ stockholders. Investors and securityholders may obtain a free copy of the joint proxy statement/prospectus (if and when it becomes available) and other relevant documents filed by Indivior and Supernus with the SEC at the SEC’s website at www.sec.gov. Copies of the documents filed by Indivior with the SEC will be available free of charge on Indivior’s website at www.indivior.com or by contacting Indivior’s Investor Relations at InvestorRelations@indivior.com. Copies of the documents filed by Supernus with the SEC will be available free of charge on Supernus’ website at www.supernus.com.

No Offer or Solicitation

This report and the information contained herein is for informational purposes only and does not constitute an offer to sell or the solicitation of an offer to buy or exchange any securities, or a solicitation of any vote or approval, nor shall there be any sale of securities in any jurisdiction in which such offer, solicitation or sale would be unlawful prior to registration or qualification under the securities laws of any such jurisdiction. This report does not constitute a prospectus or prospectus equivalent document. No offer of securities shall be made except by means of a prospectus meeting the requirements of Section 10 of the Securities Act of 1933, as amended.

Participants in the Solicitation

Indivior and Supernus and their respective directors, executive officers and other members of management and employees may be deemed to be participants in the solicitation of proxies in respect of the proposed transaction. Information about directors and executive officers of Indivior is available in the Indivior proxy statement for its 2026 Annual Meeting, which was filed with the SEC on March 27, 2026. Information about directors and executive officers of Supernus is available in the Supernus proxy statement for its 2026 Annual Meeting, which was filed with the SEC on April 30, 2026. Other information regarding the participants in the proxy solicitation and a description of their direct and indirect interests, by security holdings or otherwise, will be contained in the joint proxy statement/prospectus and other relevant materials filed with the SEC regarding the proposed transaction when they become available. Investors should read the joint proxy statement/prospectus carefully when it becomes available before making any voting or investment decisions. Investors may obtain free copies of these documents from Indivior and Supernus as indicated above.

Forward-Looking Statements

This report contains forward-looking statements within the meaning of the U.S. Private Securities Litigation Reform Act of 1995 and other federal securities laws. From time to time, oral or written forward-looking statements may also be included in other information released to the public. These forward-looking statements are intended to provide Supernus’s and Indivior’s respective management’s current expectations or plans for our future operating and financial performance, based on assumptions currently believed to be valid. Words such as “anticipate,” “believe,” “estimate,” “expect,” “intend,” “plan,” “project,” “may,” “will,” “would,” “could,” “should,” and similar expressions are intended to identify forward-looking statements, although not all forward-looking statements contain these words. All forward-looking statements involve risks, uncertainties and other factors that may cause actual results to differ materially from those expressed or implied in the forward-looking statements. These statements, including statements regarding the proposed merger of equals of Supernus and Indivior, the expected timing of the closing, and the anticipated benefits and prospects of the combined company, are based on management’s current expectations and are subject to risks and uncertainties that could cause actual results to differ materially, including, among others: the risk that the proposed merger may not be completed in a timely manner or at all; the failure to obtain the required approvals of Supernus' or Indivior’s stockholders; the failure or delay in obtaining required regulatory approvals, or the imposition of conditions in connection therewith; the failure to satisfy the other conditions to closing; the possibility that a competing or superior acquisition proposal is made; the fact that the exchange ratio is fixed and will not be adjusted for changes in the market price of Supernus or Indivior shares; the effect of the announcement, pendency or completion of the transaction on the market price of Supernus and Indivior shares; the effect of the additional indebtedness incurred to fund the Special Dividend on the combined company; the effects of business disruption resulting from the announcement or pendency of the transaction; the diversion of management’s attention and resources from ongoing business operations; the effect of the transaction on the parties’ ability to retain and hire key personnel and to maintain relationships with customers, suppliers and other business partners; restrictions during the pendency of the transaction that may limit the parties’ ability to pursue business opportunities or strategic transactions; the risk that the anticipated benefits, synergies and cost savings may not be realized within the expected timeframe or at all; the difficulties and costs of integrating the two businesses; significant transaction costs and/or unknown or inestimable liabilities; the risk that the merger does not qualify for its intended treatment as a tax-free reorganization; the occurrence of any event that could give rise to termination of the merger agreement, including in circumstances requiring payment of a termination fee; the risk of stockholder litigation in connection with the transaction; the impact of macroeconomic and market conditions, including economic downturns, international conflict, trade disputes and tariffs; and the other risks identified in Supernus' and Indivior’s filings with the SEC and in the joint proxy statement/prospectus when it becomes available. There can be no assurance that the proposed merger will in fact be consummated in the manner described or at all. These forward-looking statements speak only as of the date of this report and neither Supernus nor Indivior undertakes any obligation to update any forward-looking statement, except as required by applicable law.

Item 9.01

Financial Statements and Exhibits.

(d)

Exhibits

Exhibit 99.1 - Investor Presentation, dated August 3, 2026.

Exhibit 104 - The cover page from this Current Report on Form 8-K, formatted in Inline XBRL.

SIGNATURES

Pursuant to the requirements of the Securities Exchange Act of 1934, the registrant has duly caused this report to be signed on its behalf by the undersigned hereunto duly authorized.

	SUPERNUS PHARMACEUTICALS, INC.

DATED: August 3, 2026	By:	/s/ Timothy C. Dec
		Timothy C. Dec
		Senior Vice President and Chief Financial Officer