KPTI Karyopharm Therapeutics Inc

EXHIBIT 99.1

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Karyopharm Reports Third Quarter 2024 Financial Results and Highlights Recent Company Progress

– Achieves Third Quarter 2024 Total Revenue of $38.8 Million and U.S. XPOVIO^® (selinexor) Net Product Revenue of $29.5 Million; Continued Regulatory and Reimbursement Approvals Globally –

– Following FDA Alignment, Absolute Change in Total Symptom Score (Abs-TSS) Will Replace TSS50 as a Co-Primary Endpoint in Phase 3 SENTRY Trial in JAKi Naïve Myelofibrosis (MF); Expected Top-line Data Read-out Remains on Track for 2H 2025 –

– Narrows Full-Year 2024 Total Revenue Guidance Range to $145.0 Million to $155.0 Million; U.S. XPOVIO Net Product Revenue Guidance Range to $110.0 Million to $115.0 Million; R&D and SG&A Expense Guidance Range to $255.0 Million to $265.0 Million –

NEWTON, Mass. – November 5, 2024 – Karyopharm Therapeutics Inc. (Nasdaq: KPTI), a commercial-stage pharmaceutical company pioneering novel cancer therapies, today reported financial results for the quarter ended September 30, 2024, and highlighted select corporate milestones and progress on its key clinical development programs.

“This quarter, we delivered our third consecutive quarter of U.S. XPOVIO net product revenue growth in the highly competitive multiple myeloma marketplace. On our clinical pipeline, we are very excited with the change to our Phase 3 SENTRY myelofibrosis trial endpoints following engagement with the FDA, strengthening our confidence for a successful outcome for this trial. We continue to drive disciplined expense management and trial execution as we look forward to our next phase of growth with potential new indications in myelofibrosis and endometrial cancer,” said Richard Paulson, President and Chief Executive Officer of Karyopharm.

“A significant unmet need in myelofibrosis remains, as less than half of patients achieve SVR35 with each of the approved JAKi inhibitors. I am encouraged by the Phase 1 trial which evaluated the combination of selinexor and ruxolitinib, as it shows an approximate doubling of SVR35 to 80% compared to historical JAKi monotherapy and a meaningful 18.5 point improvement in Abs-TSS at week 24 compared to baseline,” said Dr. John Mascarenhas, Principal Investigator of the Phase 3 SENTRY trial, Professor of Medicine at the Icahn School of Medicine at Mount Sinai and Director of the Center of Excellence for Blood Cancers and Myeloid Disorders. “The change to Abs-TSS as a co-primary endpoint signifies a new era in the evaluation of combination therapy and reflects a growing willingness by the FDA to incorporate more sensitive methods of evaluating symptoms in trials with active comparators.”

Third Quarter 2024 and Recent Highlights

XPOVIO Commercial Performance

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Research and Development (R&D) Highlights

Myelofibrosis

Endometrial Cancer

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Multiple Myeloma

2024 Financial Outlook

Based on its current operating plans, Karyopharm has further narrowed its guidance for full year 2024 as follows:

Third Quarter 2024 Financial Results

Total revenue: Total revenue for the third quarter of 2024 was $38.8 million, compared to $36.0 million for the third quarter of 2023.

Net product revenue: Net product revenue for the third quarter of 2024 was $29.5 million, compared to $30.2 million for the third quarter of 2023.

License and other revenue: License and other revenue for the third quarter of 2024 was $9.3 million, compared to $5.8 million for the third quarter of 2023. The increase was primarily due to $6.0 million of milestone-related revenue recognized from Menarini, which was related to reimbursement approvals for NEXPOVIO in the third quarter of 2024, partially offset by a $3.3 million decrease in revenue related to the reimbursement of development-related expenses from Menarini due to timing of reimbursement.

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Cost of sales: Cost of sales for the third quarter of 2024 was $1.3 million, compared to $0.9 million for the third quarter of 2023. Cost of sales reflects the costs of XPOVIO units sold and the costs of products sold to our partners.

R&D expenses: R&D expenses for the third quarter of 2024 were $36.1 million, compared to $35.6 million for the third quarter of 2023. The increase was primarily due to an increase in clinical trial and related costs, mainly driven by increased activity in the ongoing Phase 3 SENTRY trial in myelofibrosis.

SG&A expenses: SG&A expenses for the third quarter of 2024 were $27.6 million, compared to $30.8 million for the third quarter of 2023. The decrease was primarily due to our ongoing cost reduction initiatives and lower headcount.

Interest income: Interest income for the third quarter of 2024 was $1.8 million, compared to $2.8 million for the third quarter of 2023 due to a lower cash and investments balance quarter-over-quarter.

Interest expense: Interest expense for the third quarter of 2024 was $11.4 million, compared to $6.1 million for the third quarter of 2023. The increase in interest expense was due to the Company’s new term loan and new secured convertible senior notes.

Other income: Other income for the third quarter of 2024 was $3.8 million due to a non-cash gain recognized in connection with the remeasurement of embedded derivatives and liability classified common stock warrants. The Company had immaterial other income in the third quarter of 2023.

Net loss: Karyopharm reported a net loss of $32.1 million, or $0.26 loss per basic and diluted share, for the third quarter of 2024, compared to a net loss of $34.5 million, or $0.30 loss per basic and diluted share, for the third quarter of 2023.

Cash position: Cash, cash equivalents, restricted cash and investments as of September 30, 2024 totaled $133.9 million, compared to $192.4 million as of December 31, 2023.

Conference Call Information

Karyopharm will host a conference call today, November 5, 2024, at 8:00 a.m. Eastern Time, to discuss the third quarter 2024 financial results and provide business highlights. To access the conference call, please dial (800) 836-8184 (local) or (646) 357-8785 (international) at least 10 minutes prior to the start time and ask to be joined into the Karyopharm Therapeutics call. A live audio webcast of the call, along with accompanying slides, will be available under “Events & Presentations” in the Investor section of the Company’s website. An archived webcast will be available on the Company’s website approximately two hours after the event.

About XPOVIO^® (selinexor)

XPOVIO is a first-in-class, oral exportin 1 (XPO1) inhibitor and the first of Karyopharm’s Selective Inhibitor of Nuclear Export (SINE) compounds for the treatment of cancer. XPOVIO functions by selectively binding to and inhibiting the nuclear export protein XPO1. XPOVIO is approved in the U.S. and marketed by Karyopharm in multiple oncology indications, including: (i) in combination with VELCADE^® (bortezomib) and dexamethasone (XVd) in patients with multiple myeloma after at least one prior therapy; (ii) in combination with dexamethasone in patients with heavily pre-treated multiple myeloma; and (iii) under accelerated approval in patients with diffuse large B-cell lymphoma (DLBCL), including DLBCL arising from follicular lymphoma, after at least two lines of

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systemic therapy. XPOVIO (also known as NEXPOVIO^® in certain countries) has received regulatory approvals in a growing number of ex-U.S. territories and countries, including Europe, the United Kingdom, China, South Korea and Israel, and is marketed in those areas by Karyopharm’s global partners. Selinexor is also being investigated in several other mid- and late-stage clinical trials across multiple high unmet need cancer indications, including in endometrial cancer and myelofibrosis.

For more information about Karyopharm’s products or clinical trials, please contact the Medical Information department at: Tel: +1 (888) 209-9326; Email: medicalinformation@karyopharm.com

XPOVIO^® (selinexor) is a prescription medicine approved:

SELECT IMPORTANT SAFETY INFORMATION

Warnings and Precautions

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Adverse Reactions

Use In Specific Populations

Lactation: Advise not to breastfeed.

For additional product information, including full prescribing information, please visit www.XPOVIO.com.

To report SUSPECTED ADVERSE REACTIONS, contact Karyopharm Therapeutics Inc. at 1-888-209-9326 or FDA at 1-800-FDA-1088 or www.fda.gov/medwatch.

About Karyopharm Therapeutics

Karyopharm Therapeutics Inc. (Nasdaq: KPTI) is a commercial-stage pharmaceutical company whose dedication to pioneering novel cancer therapies is fueled by a belief in the extraordinary strength and courage of patients with cancer. Since its founding, Karyopharm has been an industry leader in oral compounds that address nuclear export dysregulation, a fundamental mechanism of oncogenesis. Karyopharm’s lead compound and first-in-class, oral exportin 1 (XPO1) inhibitor, XPOVIO^® (selinexor), is approved in the U.S. and marketed by the Company in three oncology indications. It has also received regulatory approvals in various indications in a growing number of ex-U.S. territories and countries, including Europe and the United Kingdom (as NEXPOVIO^®) and China. Karyopharm has a focused pipeline targeting indications in multiple high unmet need cancers, including in multiple myeloma, endometrial cancer, myelofibrosis, and diffuse large B-cell lymphoma (DLBCL). For more information about our people, science and pipeline, please visit www.karyopharm.com, and follow us on LinkedIn and on X at @Karyopharm.

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Forward-Looking Statements

This press release contains forward-looking statements within the meaning of The Private Securities Litigation Reform Act of 1995. Such forward-looking statements include those regarding Karyopharm’s guidance on its 2024 total revenue, 2024 U.S. net product revenue and 2024 R&D and SG&A expenses; Karyopharm’s expected cash runway; expectations with respect to commercialization efforts; the ability of selinexor to treat patients with multiple myeloma, endometrial cancer, myelofibrosis, diffuse large B-cell lymphoma, and other diseases; and expectations with respect to the clinical development plans and potential regulatory submissions of selinexor. Such statements are subject to numerous important factors, risks and uncertainties, many of which are beyond Karyopharm’s control, that may cause actual events or results to differ materially from Karyopharm’s current expectations. For example, there can be no guarantee that Karyopharm will successfully commercialize XPOVIO or that any of Karyopharm’s drug candidates, including selinexor, will successfully complete necessary clinical development phases or that development of any of Karyopharm’s drug candidates will continue. Further, there can be no guarantee that any positive developments in the development or commercialization of Karyopharm’s drug candidate portfolio will result in stock price appreciation. Management’s expectations and, therefore, any forward-looking statements in this press release could also be affected by risks and uncertainties relating to a number of other factors, including the following: the adoption of XPOVIO in the commercial marketplace, the timing and costs involved in commercializing XPOVIO or any of Karyopharm’s drug candidates that receive regulatory approval; the ability to obtain and retain regulatory approval of XPOVIO or any of Karyopharm’s drug candidates that receive regulatory approval; Karyopharm’s results of clinical trials and preclinical trials, including subsequent analysis of existing data and new data received from ongoing and future trials; the content and timing of decisions made by the U.S. Food and Drug Administration and other regulatory authorities, investigational review boards at clinical trial sites and publication review bodies, including with respect to the need for additional clinical trials; the ability of Karyopharm or its third party collaborators or successors in interest to fully perform their respective obligations under the applicable agreement and the potential future financial implications of such agreement; Karyopharm’s ability to enroll patients in its clinical trials; unplanned cash requirements and expenditures; substantial doubt exists regarding Karyopharm’s ability to continue as a going concern; development or regulatory approval of drug candidates by Karyopharm’s competitors for products or product candidates in which Karyopharm is currently commercializing or developing; the direct or indirect impact of the COVID-19 pandemic or any future pandemic on Karyopharm’s business, results of operations and financial condition; and Karyopharm’s ability to obtain, maintain and enforce patent and other intellectual property protection for any of its products or product candidates. These and other risks are described under the caption “Risk Factors” in Karyopharm’s Quarterly Report on Form 10-Q for the quarter ended June 30, 2024, which was filed with the Securities and Exchange Commission (SEC) on August 6, 2024, and in other filings that Karyopharm may make with the SEC in the future. Any forward-looking statements contained in this press release speak only as of the date hereof, and, except as required by law, Karyopharm expressly disclaims any obligation to update any forward-looking statements, whether as a result of new information, future events or otherwise.

XPOVIO^® and NEXPOVIO^® are registered trademarks of Karyopharm Therapeutics Inc. Any other trademarks referred to in this release are the property of their respective owners.

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Contacts

Investors:

Elhan Webb, CFA

Senior Vice President, Investor Relations

617.658.0600 | elhan.webb@karyopharm.com

Media:

David Rosen

Argot Partners

646.461.6387 | david.rosen@argotpartners.com

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KARYOPHARM THERAPEUTICS INC.

CONDENSED CONSOLIDATED STATEMENTS OF OPERATIONS

(unaudited); (in thousands, except per share amounts)

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KARYOPHARM THERAPEUTICS INC.

CONDENSED CONSOLIDATED BALANCE SHEETS

(unaudited); (in thousands)

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