Karyopharm Announces Strategic Financing Transactions to Support Growth; Extends Cash Runway Into Second Quarter of 2026, Beyond Expected Top-Line Readout of Phase 3 SENTRY[...]

Karyopharm Announces Strategic Financing Transactions to Support Growth; Extends

Cash Runway Into Second Quarter of 2026, Beyond Expected Top-Line Readout of

Phase 3 SENTRY Trial in Myelofibrosis

- Transactions Provide Karyopharm with $100 Million of Financial Flexibility and Additional Capital -

- Preliminary Total Revenue and U.S. XPOVIO^® (selinexor) Net Product Revenue for the Third Quarter of

2025 Expected to be in the Range of $42 to $44 Million and Approximately $32 Million, Respectively -

- Top-Line Data from the Phase 3 SENTRY Trial in Myelofibrosis on Track for March 2026 -

NEWTON, Mass. - October 8, 2025 - Karyopharm Therapeutics Inc. (Nasdaq: KPTI), a commercial-stage pharmaceutical company pioneering novel cancer therapies, today announced that it has entered into comprehensive financing and capital structure transactions expected to provide the Company with $100 million of financial flexibility and additional capital, extending the Company's cash runway into the second quarter of 2026 based on the Company's current operating plans.

"Following the recent completion of enrollment of our Phase 3 SENTRY trial in myelofibrosis, we are excited to announce this strategic financing which is expected to provide us with the resources needed to deliver top-line data from this pivotal trial," said Richard Paulson, President and Chief Executive Officer of Karyopharm. "I would like to thank our lenders, noteholders and equity investors for their ongoing support to strengthen our balance sheet, equitize near-term debt maturities and support our potentially transformational Phase 3 myelofibrosis program. We believe that selinexor plus ruxolitinib has the potential to be the first combination therapy approved for the treatment of myelofibrosis. By combining selinexor with the current standard of care, we have the potential to redefine the way people living with myelofibrosis are treated."

Each of the financing and capital structure transactions is expected to close on or around October 10, 2025 (Closing Date), subject to the satisfaction of customary closing conditions. The Company's existing senior lenders have agreed to multi-faceted financing transactions with the following key components:

In addition, the Company has entered into a securities purchase agreement for a private placement in which the Company agreed to sell 1,487,917 shares of common stock and accompanying warrants to purchase 1,317,771 shares of common stock with an exercise price of $6.64 per share. The warrants issued in the private placement will be exercisable on or before the 30^th day following the public announcement of top-line results from the Company's XPORT-EC-042 trial in endometrial cancer, which is anticipated in mid-2026. The private placement is expected to result in gross proceeds of approximately $8.75 million before deducting any offering expenses.

1

The Company intends to use the proceeds of the financing transactions to pay transaction expenses and for general corporate purposes, including to support the Company's ongoing and planned clinical trial activities.

At closing of the financing transactions, the Company will issue an aggregate of 7,223,982 newly issued shares of common stock, newly issued pre-funded warrants to purchase an aggregate of 2,913,136 shares of common stock, and newly issued warrants to purchase an aggregate of 5,918,358 shares of common stock with an exercise price of $6.64 per share, a 15% premium to the Nasdaq minimum price. In addition, the Company will reduce the exercise price of outstanding warrants to purchase 3,068,417 shares from $16.50 per share to $6.64 per share. The financing transactions are intended to comply with Nasdaq rules, including being priced at the "minimum price" (as defined in the Nasdaq rules). Following consummation of the transactions, the Company expects to have an aggregate of 15,926,939 shares of common stock outstanding (assuming no exercise of any pre-funded warrants or warrants or conversions of any outstanding convertible notes).

Additional details on the financing transactions will be available in a Form 8-K that the Company will file with the United States Securities and Exchange Commission.

Preliminary Third Quarter 2025 Financial Results

Based on preliminary financial information, the Company expects total revenue, which includes license and royalty revenue from partners, to be in the range of $42 to $44 million and U.S. XPOVIO net product revenue to be approximately $32 million for the three months ended September 30, 2025.

Prior to the receipt of approximately $36 million of gross proceeds from the financing transactions, the Company expects to report that it had cash, cash equivalents, restricted cash and investments as of September 30, 2025 of approximately $46 million.

The financial information presented in this press release reflects the Company's estimates with respect to total revenue, U.S. XPOVIO net product revenue and its cash balance and is based on currently available information, which is preliminary. The Company's final results may vary from these preliminary estimates as a result of the completion of customary quarterly review procedures, including those conducted by the Company's external auditors.

Endometrial Cancer Program

Enrollment continues in the Phase 3 XPORT-EC-042 (NCT05611931) trial evaluating selinexor as a maintenance-only therapy following systemic therapy versus placebo in patients with TP53 wild-type advanced or recurrent endometrial cancer. The Company continues to expect to report top-line data from this event-driven trial in mid-2026.

Ongoing Efforts to Further Enhance Liquidity and Maximize Value

The Company expects to continue exploring potential financing and strategic alternatives to enhance liquidity and maximize value with the assistance of its advisors, including its financial advisor Centerview Partners LLC.

2

Centerview Partners LLC and J. Wood Capital Advisors LLC acted as financial advisors to Karyopharm and Sidley Austin LLP acted as legal counsel to Karyopharm in connection with these transactions.

The offer and sale of the shares of common stock, pre-funded warrants, warrants, the New 2028 Notes, the New 2029 Notes or any other securities (including the shares of common stock issuable upon conversion of the New 2028 Notes, the New 2029 Notes and the shares of common stock issuable upon exercise of the warrants and pre-funded warrants issued in the financing transactions) are not being registered under the Securities Act, or any state securities laws. The shares of common stock, pre-funded warrants, warrants, the New 2028 Notes, the New 2029 Notes or any other securities (including the shares of common stock issuable upon conversion of the New 2028 Notes, the New 2029 Notes and the shares of common stock issuable upon exercise of the warrants and pre-funded warrants issued in the financing transactions) may not be offered or sold in the United States except pursuant to an exemption from the registration requirements of the Securities Act and any applicable state securities laws.