Karyopharm Announces Presentation of Updated Phase 2 Selinexor Data in Patients with Myelofibrosis at the American Society of Hematology 2021 Annual Meeting and Exposition

Rhea-AI Summary

Karyopharm Therapeutics (Nasdaq: KPTI) presented updated data from the Phase 2 ESSENTIAL study on selinexor for myelofibrosis patients at the ASH 2021 Annual Meeting. Results revealed that 40% of patients achieved a spleen volume reduction (SVR) of at least 35%, and 60% experienced an SVR of at least 25% after 24 weeks of treatment. The drug exhibited a favorable safety profile with manageable side effects. Additionally, the company has initiated a new Phase 2 study comparing selinexor to physician's choice in previously treated myelofibrosis patients.

Positive

• 40% of patients achieved SVR of at least 35%
• 60% of patients achieved SVR of at least 25%
• 91.7% two-year survival probability observed
• Initiation of a new Phase 2 study for further evaluation

Negative

• Common grade ≥3 adverse events included anemia and fatigue (33% incidence)
• Limited current market options for patients post-JAK inhibitor treatment

NEWTON, Mass., Dec. 11, 2021 /PRNewswire/ -- Karyopharm Therapeutics Inc. (Nasdaq:KPTI), a commercial-stage pharmaceutical company pioneering novel cancer therapies, today announced an oral presentation highlighting updated data from the Phase 2 ESSENTIAL study, an investigator-sponsored study evaluating single-agent selinexor, a first-in-class, oral Selective Inhibitor of Nuclear Export (SINE) compound, in patients with myelofibrosis (MF) previously treated with JAK inhibition.  These updated results were presented at the American Society of Hematology (ASH) 2021 Annual Meeting and Exposition taking place in Atlanta, GA on December 11-14, 2021.

"The results presented at ASH this year demonstrate that once weekly single-agent oral selinexor resulted in an impressive spleen volume reduction rates in myelofibrosis patients who received at least 24 weeks of treatment, with 40% and 60% of those patients achieving a response, defined as spleen volume reduction (SVR) of at least 35% and 25%, respectively. The durable responses and well-tolerated safety profile highlight selinexor's potential in patients with JAK-refractory myelofibrosis," said Srinivas Tantravahi, MBBS, MRCP, University of Utah Hospital and principal investigator of the Phase 2 ESSENTIAL study. "With JAK inhibitors being the only class of drugs approved for this disease and with less than half of patients responding, there remains a high unmet need for patients who either progress following treatment with a JAK inhibitor or are intolerant."

"Following the encouraging data from the Phase 2 ESSENTIAL trial, we recently dosed the first patient in Karyopharm's new Phase 2 study evaluating single-agent selinexor versus physician's choice in patients with previously treated myelofibrosis," said Sharon Shacham, PhD, MBA, Co-Founder and Chief Scientific Officer of Karyopharm. "As part of our strategic imperatives and pipeline priorities, we remain focused on diseases with the highest unmet needs and greatest potential to make an impact in patient outcomes."

Results from the Phase 2 ESSENTIAL Study Evaluating Single-Agent Selinexor in Patients with MF Refractory or Intolerant to JAK Inhibitors

The results were based on the open label, prospective, investigator-initiated single center ESSENTIAL study in adult patients with primary or secondary MF with resistance or intolerance to JAK inhibitor therapy (NCT03627403). Selinexor was administered orally at a dose of 80mg or 60mg once weekly to 12 patients. The primary endpoint of the study is to assess the efficacy of selinexor on SVR. Median duration of prior JAK inhibitor therapy was 22 months (range 0.5 to 96 months) and 92% (11 of 12) patients had MF refractory to ruxolitinib.

As of the data cutoff, the median duration of treatment was 11 months (range 2.8 to 28.8 months). Of the ten patients who were on treatment for at least 24 weeks, four (40%) patients achieved SVR of ≥35% and six (60%) patients achieved SVR of ≥25%. Of the five patients who were transfusion dependent at screening, two (40%) achieved transfusion independence. Of the three patients with hemoglobin <10g/dL at screening, improvement was observed in two (67%) patients. Reduction in marrow reticulin fibrosis from MF grade 3 to MF grade 1 was observed in a patient who had an assessment at week 72 demonstrating disease modification potential with longer treatment. While median overall survival was not yet reached, the two-year survival probability was assessed to be 91.7%. This compares favorably with a historical survival of 13-14 months in this population.

The most common grade ≥3 treatment emergent adverse events were anemia (33%) and fatigue (33%). These were manageable with treatment interruption and dose reduction, except in one patient who discontinued treatment.

Details for the ASH 2021 presentation are as follows:

Title: A Phase 2 Study to Evaluate the Efficacy and Safety of Selinexor in Patients with Myelofibrosis Refractory or Intolerant to JAK Inhibitors
Presenter: Srinivas Tantravahi, University of Utah
Abstract #: 143
Session Type: Oral Presentation
Session: Myeloproliferative Syndromes: Clinical and Epidemiological: Non-JAK Inhibitor Therapies for Myelofibrosis

A PDF copy of the presentation is available here.

About XPOVIO® (selinexor)

XPOVIO is a first-in-class, oral Selective Inhibitor of Nuclear Export (SINE) compound. XPOVIO functions by selectively binding to and inhibiting the nuclear export protein exportin 1 (XPO1, also called CRM1). XPOVIO blocks the nuclear export of tumor suppressor, growth regulatory and anti-inflammatory proteins, leading to accumulation of these proteins in the nucleus and enhancing their anti-cancer activity in the cell. The forced nuclear retention of these proteins can counteract a multitude of the oncogenic pathways that, unchecked, allow cancer cells with severe DNA damage to continue to grow and divide in an unrestrained fashion. Karyopharm received accelerated U.S. Food and Drug Administration (FDA) approval of XPOVIO in July 2019 in combination with dexamethasone for the treatment of adult patients with relapsed refractory multiple myeloma (RRMM) who have received at least four prior therapies and whose disease is refractory to at least two proteasome inhibitors, at least two immunomodulatory agents, and an anti-CD38 monoclonal antibody. NEXPOVIO® (selinexor) has also been granted conditional marketing authorization for adult patients with heavily pretreated multiple myeloma by the European Commission. Karyopharm's supplemental New Drug Application (sNDA) requesting an expansion of its indication to include the treatment for patients with multiple myeloma after at least one prior therapy was approved by the FDA on December 18, 2020. In June 2020, Karyopharm received accelerated FDA approval of XPOVIO for its second indication in adult patients with relapsed or refractory diffuse large B-cell lymphoma (DLBCL), not otherwise specified, including DLBCL arising from follicular lymphoma, after at least 2 lines of systemic therapy. Selinexor is also being evaluated in several other mid-and later-phase clinical trials across multiple cancer indications, including as a potential backbone therapy in combination with approved myeloma therapies (STOMP) and in endometrial cancer (SIENDO), among others. Additional Phase 1, Phase 2 and Phase 3 studies are ongoing or currently planned, including multiple studies in combination with approved therapies in a variety of tumor types to further inform Karyopharm's clinical development priorities for selinexor. Additional clinical trial information for selinexor is available at www.clinicaltrials.gov.

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:

• In combination with bortezomib and dexamethasone for the treatment of adult patients with multiple myeloma who have received at least one prior therapy (XVd).
• In combination with dexamethasone for the treatment of adult patients with relapsed or refractory multiple myeloma who have received at least four prior therapies and whose disease is refractory to at least two proteasome inhibitors, at least two immunomodulatory agents, and an anti–CD38 monoclonal antibody (Xd).
• For the treatment of adult patients with relapsed or refractory diffuse large B–cell lymphoma (DLBCL), not otherwise specified, including DLBCL arising from follicular lymphoma, after at least 2 lines of systemic therapy. This indication is approved under accelerated approval based on response rate. Continued approval for this indication may be contingent upon verification and description of clinical benefit in confirmatory trial(s).

SELECT IMPORTANT SAFETY INFORMATION

Warnings and Precautions

• Thrombocytopenia: Monitor platelet counts throughout treatment. Manage with dose interruption and/or reduction and supportive care.
• Neutropenia: Monitor neutrophil counts throughout treatment. Manage with dose interruption and/or reduction and granulocyte colony–stimulating factors.
• Gastrointestinal Toxicity: Nausea, vomiting, diarrhea, anorexia, and weight loss may occur. Provide antiemetic prophylaxis. Manage with dose interruption and/or reduction, antiemetics, and supportive care.
• Hyponatremia: Monitor serum sodium levels throughout treatment. Correct for concurrent hyperglycemia and high serum paraprotein levels. Manage with dose interruption, reduction, or discontinuation, and supportive care.
• Serious Infection: Monitor for infection and treat promptly.
• Neurological Toxicity: Advise patients to refrain from driving and engaging in hazardous occupations or activities until neurological toxicity resolves. Optimize hydration status and concomitant medications to avoid dizziness or mental status changes.
• Embryo–Fetal Toxicity: Can cause fetal harm. Advise females of reproductive potential and males with a female partner of reproductive potential, of the potential risk to a fetus and use of effective contraception.
• Cataract: Cataracts may develop or progress. Treatment of cataracts usually requires surgical removal of the cataract.

Adverse Reactions

• The most common adverse reactions (≥20%) in patients with multiple myeloma who receive XVd are fatigue, nausea, decreased appetite, diarrhea, peripheral neuropathy, upper respiratory tract infection, decreased weight, cataract and vomiting. Grade 3–4 laboratory abnormalities (≥10%) are thrombocytopenia, lymphopenia, hypophosphatemia, anemia, hyponatremia and neutropenia. In the BOSTON trial, fatal adverse reactions occurred in 6% of patients within 30 days of last treatment. Serious adverse reactions occurred in 52% of patients. Treatment discontinuation rate due to adverse reactions was 19%.
• The most common adverse reactions (≥20%) in patients with multiple myeloma who receive Xd are thrombocytopenia, fatigue, nausea, anemia, decreased appetite, decreased weight, diarrhea, vomiting, hyponatremia, neutropenia, leukopenia, constipation, dyspnea and upper respiratory tract infection. In the STORM trial, fatal adverse reactions occurred in 9% of patients. Serious adverse reactions occurred in 58% of patients. Treatment discontinuation rate due to adverse reactions was 27%.
• The most common adverse reactions (incidence ≥20%) in patients with DLBCL, excluding laboratory abnormalities, are fatigue, nausea, diarrhea, appetite decrease, weight decrease, constipation, vomiting, and pyrexia. Grade 3–4 laboratory abnormalities (≥15%) are thrombocytopenia, lymphopenia, neutropenia, anemia, and hyponatremia. In the SADAL trial, fatal adverse reactions occurred in 3.7% of patients within 30 days, and 5% of patients within 60 days of last treatment; the most frequent fatal adverse reactions was infection (4.5% of patients). Serious adverse reactions occurred in 46% of patients; the most frequent serious adverse reaction was infection (21% of patients). Discontinuation due to adverse reactions occurred in 17% of patients.

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 pioneering novel cancer therapies and dedicated to the discovery, development, and commercialization of first-in-class drugs directed against nuclear export for the treatment of cancer and other diseases. Karyopharm's Selective Inhibitor of Nuclear Export (SINE) compounds function by binding with and inhibiting the nuclear export protein XPO1 (or CRM1). Karyopharm's lead compound, XPOVIO® (selinexor), is approved in the U.S. in multiple hematologic malignancy indications, including in combination with Velcade® (bortezomib) and dexamethasone for the treatment of adult patients with multiple myeloma after at least one prior therapy, in combination with dexamethasone for the treatment of adult patients with heavily pretreated multiple myeloma and as a monotherapy for the treatment of adult patients with relapsed or refractory diffuse large B-cell lymphoma. NEXPOVIO® (selinexor) has also been granted conditional marketing authorization in combination with dexamethasone for adult patients with heavily pretreated multiple myeloma by the European Commission. In addition to single-agent and combination activity against a variety of human cancers, SINE compounds have also shown biological activity in models of neurodegeneration, inflammation, autoimmune disease, certain viruses and wound-healing. Karyopharm has several investigational programs in clinical or preclinical development. For more information, please visit www.karyopharm.com.

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 the ability of selinexor or eltanexor to treat patients with multiple myeloma, diffuse large B-cell lymphoma, solid tumors and other diseases and expectations related to future clinical development and potential regulatory submissions of selinexor or eltanexor. 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; that regulators will grant confirmatory approval in the European Union based on the BOSTON study in adult patients with multiple myeloma; or that any of Karyopharm's drug candidates, including selinexor and eltanexor, 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 risk that the COVID-19 pandemic could disrupt Karyopharm's business more severely than it currently anticipates, including by negatively impacting sales of XPOVIO, interrupting or delaying research and development efforts, impacting the ability to procure sufficient supply for the development and commercialization of selinexor or other product candidates, delaying ongoing or planned clinical trials, impeding the execution of business plans, planned regulatory milestones and timelines, or inconveniencing patients; 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 studies, including subsequent analysis of existing data and new data received from ongoing and future studies; 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 studies; 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; development or regulatory approval of drug candidates by Karyopharm's competitors for products or product candidates in which Karyopharm is currently commercializing or developing; 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 September 30, 2021, which was filed with the Securities and Exchange Commission (SEC) on November 3, 2021, 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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SOURCE Karyopharm Therapeutics Inc.

FAQ

What were the results of the Phase 2 ESSENTIAL study on selinexor for myelofibrosis?

The study showed that 40% of patients achieved a spleen volume reduction of at least 35%, and 60% had a reduction of at least 25%.

What is the survival probability for patients treated with selinexor?

The two-year survival probability assessed was 91.7%, significantly higher than the historical average of 13-14 months.

What adverse effects were reported in the selinexor study?

The most common grade ≥3 adverse events were anemia and fatigue, each affecting 33% of patients.

What is the next step for Karyopharm following the Phase 2 study?

Karyopharm has commenced a new Phase 2 study evaluating selinexor against physician's choice for patients with prior treatment.

What is the significance of the ASH 2021 presentation for Karyopharm?

The presentation highlighted important efficacy data for selinexor, showcasing its potential to fill the treatment gap for JAK-refractory myelofibrosis patients.