Washington, D.C. 20549 FORM 10-Q (Mark One) ☒QUARTERLY REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACTOF 1934 For the quarterly period ended March 31, 2026 OR ☐TRANSITION REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACTOF 1934 Collegium Pharmaceutical, Inc.(Exact name of registrant as specified in its charter) (781) 713-3699(Registrant’s telephone number, including area code)Securities registered pursuant to Section 12(b) of the Act: Indicate by check mark whether the registrant (1) has filed all reports required to be filed by Section 13 or 15(d) of the Securities Exchange Act of 1934during the preceding 12 months (or for such shorter period that the registrant was required to file such reports), and (2) has been subject to such filing requirements forthe past 90 days. YesNo Indicate by check mark whether the registrant has submitted electronically every Interactive Data File required to be submitted pursuant to Rule 405 ofRegulation S-T (§232.405 of this chapter) during the preceding 12 months (or for such shorter period that the registrant was required to submit such files). YesNo Indicate by check mark whether the registrant is a large accelerated filer, an accelerated filer, a non-accelerated filer, smaller reporting company, or anemerging growth company. See definitions of “large accelerated filer,” “accelerated filer,” “smaller reporting company,” and “emerging growth company” in Rule 12b-2of the Exchange Act. Large accelerated filer☒Accelerated filerNon-accelerated filerSmaller reporting companyEmerging growth company 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 orrevised financial accounting standards provided pursuant to Section 13(a) of the Exchange Act. Indicate by check mark whether the registrant is a shell company (as defined in Rule 12b-2 of the Exchange Act). YesNo TABLE OF CONTENTS PART I—FINANCIAL INFORMATION Condensed Consolidated Financial Statements (Unaudited)Management’s Discussion and Analysis of Financial Condition and Results of OperationsQuantitative and Qualitative Disclosures About Market RiskControls and Procedures PART II—OTHER INFORMATION Item 1.Legal ProceedingsItem 1A.Risk FactorsItem 2.Unregistered Sales of Equity Securities and Use of ProceedsItem 3.Defaults Upon Senior SecuritiesItem 4.Mine Safety DisclosuresItem 5.Other InformationItem 6.ExhibitsSignatures Forward-Looking Statements Statements made in this quarterly report on Form 10-Q (“Quarterly Report”) that are not statements of historical or current facts, such as thoseunder the heading “Management’s Discussion and Analysis of Financial Condition and Results of Operations,” are “forward-lookingstatements” within the meaning of the Private Securities Litigation Reform Act of 1995. Forward-looking statements discuss our currentexpectations and projections relating to our financial condition, results of operations, plans, objectives, future performance and business.These statements may be preceded by, followed by or include the words “aim,” “anticipate,” “believe,” “estimate,” “expect,” “forecast,”“intend,” “outlook,” “plan,” “potential,” “project,” “projection,” “seek,” “may,” “could,” “would,” “should,” “can,” “can have,” “likely,” thenegatives thereof and other words and terms of similar meaning. Forward-looking statements are inherently subject to risks, uncertainties and assumptions; they are not guarantees of performance. You shouldnot place undue reliance on these statements. We have based these forward-looking statements on our current expectations and projectionsabout future events. Although we believe that our assumptions made in connection with the forward-looking statements are reasonable, wecannot assure you that the assumptions and expectations will prove to be correct. You should understand that the following important factors could affect our future results and could cause those results or other outcomes todiffer materially from those expressed or implied in our forward-looking statements:•our ability to commercialize and grow sales of our products; •our ability to maintain regulatory approval of our products, and any related restrictions, limitations, and/or warnings in the label ofan approved product;•the size of the markets for our products, and our ability to service those markets;•the success of competing products that are or become available;•our ability to obtain and maintain reimbursement and third-party payor contracts with favorable terms for our products;•the costs of commercialization activities, including marketing, sales and distribution;•the rate and degree of market acceptance of our products;•the announcement and pendency of our acquisition of AZSTARYS®;•our ability to complete our announced acquisition of AZSTARYS®, successfully integrate AZSTARYS® into our organizationfollowing closing, and realize t