Collegium Pharmaceutical, Inc.

Item 1.01 Entry into a Material Definitive Agreement. Equity Purchase Agreement On March 19, 2026, Collegium Pharmaceutical, Inc. (the “Company”), entered into an Equity Purchase Agreement (the “Purchase Agreement”) with Corium Therapeutics Holdings, LLC, a Delaware limited liability company (“Commave Seller”), and Corium, LLC, a Delaware limited liability company (“Corium Seller” and, together with Commave Seller, the “Seller Parties” and each, a “Seller Party”). Pursuant to the Purchase Agreement, the Company will acquire (i) all of the issued and outstanding limited liability interests of GPC Commave Holding, LLC, a Delaware limited liability company and wholly-owned subsidiary of Commave Seller (“GPC”) from Commave Seller, and (ii) all of the issued and outstanding limited liability interests of a newly formed Delaware limited liability company and wholly-owned subsidiary of Corium Seller (“NewCo”) from Corium Seller ((i) and (ii) collectively, the “Equity Purchase”). Pursuant to the terms of the Purchase Agreement, the Company will acquire AZSTARYS®, a central nervous system stimulant prescription medicine used for the treatment of Attention Deficit Hyperactivity Disorder (“ADHD”) for $650 million in cash, subject to customary purchase price adjustments at the closing of the Equity Purchase (the “Closing”). The Purchase Agreement also provides for potential regulatory and commercial milestone payments of up to $135 million in the aggregate in cash to be made to Corium Seller upon the achievement of such milestones. The Purchase Agreement contains customary representations, warranties, indemnities and covenants of the Company, GPC, NewCo and the Seller Parties. The consummation of the Equity Purchase is subject to customary closing conditions, including that all applicable waiting periods under the Hart-Scott-Rodino Act having expired or been terminated. Following the Closing, the Company will own all of the issued and outstanding limited liability interests of GPC and NewCo. The Closing is expected to occur in the second quarter of 2026. The Purchase Agreement contains certain termination rights, including the right of either the Company or the Seller Parties to terminate the Purchase Agreement: (i) if the transactions contemplated thereby have not been consummated by March 19, 2027 (provided, that such date may be extended to September 19, 2027 by either party if the only condition that has not been satisfied or waived is approval under the Hart-Scott-Rodino Act); (ii) in the event that any final and non-appealable order is issued prohibiting the consummation of the transactions; or (iii) if the other party materially breaches any of its representations, warranties or covenants under the Purchase Agreement such that any of the conditions to Closing would not be satisfied. The Purchase Agreement also provides that, in connection with the termination of the Purchase Agreement under specified circumstances, the Company will be required to pay the Seller Parties a termination fee equal to $24 million. The foregoing description of the Purchase Agreement does not purport to be complete and is qualified in its entirety by the full text of the Purchase Agreement, a copy of which is attached hereto as Exhibit 2.1, and incorporated by reference herein. The Purchase Agreement has been included to provide investors with information regarding its terms. It is not intended to provide any other factual information about the Company, GPC, NewCo, the Seller Parties, or their respective subsidiaries or affiliates, or to modify or supplement any factual disclosures about the Company that it includes in its public reports filed with the U.S. Securities and Exchange Commission (“SEC”). The representations, warranties, and covenants contained in the Purchase Agreement were made only for purposes of the Purchase Agreement and as of specific dates, were solely for the benefit of the parties to the Purchase Agreement, may be subject to limitations agreed upon by the contracting parties, including being qualified by confidential disclosures made for the purposes of allocating contractual risk between the parties to the Purchase Agreement instead of establishing these matters as facts, and may be subject to standards of materiality applicable to the contracting parties that differ from those applicable to investors. Investors are not third-party beneficiaries under the Purchase Agreement and should not rely on the representations, warranties, and covenants or any descriptions thereof as characterizations of the actual state of facts or condition of the parties thereto or any of their respective subsidiaries or affiliates at the time they were made or at any other time. Moreover, information concerning the subject matter of representations and warranties may change after the date of the Purchase Agreement, which subsequent information may or may not be fully reflected in the Company’s public disclosures. The Purchase Agreement should not be read alone, but should instead be read in conjunction with the other reports and filings that the Company makes from time to time with the SEC.

Item 7.01 Regulation FD Disclosure. On March 19, 2026, the Company issued a press release announcing that the Company will acquire AZSTARYS® (the “Press Release”). A copy of the Press Release is furnished as Exhibit 99.1 to this Current Report on Form 8-K. Also, on March 19, 2026, the Company held a conference call to discuss, among other things, the announcement of the acquisition of AZSTARYS®. A copy of the presentation is furnished as Exhibit 99.2 to this Current Report on Form 8-K. The information included in this item, Exhibit 99.1 and Exhibit 99.2 are not deemed to be “filed” for purposes of Section 18 of the Securities Exchange Act of 1934, as amended (the “Exchange Act”), nor shall this item, Exhibit 99.1 or Exhibit 99.2 be incorporated by reference into the Company’s filings under the Securities Act of 1933, as amended (the “Securities Act”) or the Exchange Act, except as expressly set forth by specific reference in such future filing.