On June 2, 2021 Karyopharm Therapeutics Inc. (Nasdaq: KPTI), a commercial-stage pharmaceutical company pioneering novel cancer therapies, reported that on May 26, 2021 the UK’s Medicines & Healthcare Products Regulatory Agency (MHRA) granted conditional marketing authorization for NEXPOVIO (selinexor), the Company’s first-in-class, oral Selective Inhibitor of Nuclear Export (SINE) medicine, in combination with dexamethasone for the treatment of multiple myeloma in adult patients who have received at least four prior therapies and whose disease is refractory to at least two proteasome inhibitors, two immunomodulatory agents, and an anti-CD38 monoclonal antibody, and who have demonstrated disease progression on the last therapy (Press release, Karyopharm, JUN 2, 2021, View Source [SID1234583380]).
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Conditional marketing authorization is supported by data from the positive Phase 2b STORM study, which evaluated selinexor in adult patients with heavily pretreated, triple class refractory multiple myeloma and was published in the New England Journal of Medicine (Chari, et al.) in August 2019. Under the provisions of conditional approval by the MHRA, continued authorization for this indication is contingent upon verification and description of clinical benefit in a confirmatory trial and is subject to additional monitoring. This marketing authorization follows a similar authorization granted by the European Commission and valid in all 27 European Union (EU) member countries which was announced on March 29, 2021.
About the Phase 2b STORM Pivotal Trial
The Phase 2b STORM trial (Selinexor Treatment of Refractory Myeloma) was an international, multi-center, single-arm, open-label study which enrolled 123 adult patients (Part 2 of the trial) with heavily pretreated, triple class refractory multiple myeloma. Adult patients in the trial had a median of seven previous therapeutic regimens, including a median of 10 unique anti-myeloma agents.
For the study’s primary endpoint, oral selinexor achieved an overall response rate of 26% (95% confidence interval [CI], 19, 35) and the trial therefore met its primary endpoint (n=123). Minimal response per IMWG criteria was observed in 16 (13%) patients and 48 patients (39%) had stable disease. All responses were adjudicated by an Independent Review Committee. Among the modified intent to treat population enrolled in STORM Part 2, eighty–three (83) patients had relapse and/or refractory multiple myeloma that was refractory to two proteasome inhibitors (bortezomib, carfilzomib), two immunomodulators (lenalidomide, pomalidomide) and an anti-CD38 monoclonal antibody (daratumumab), the efficacy analysis was based on these 83 patients. A secondary efficacy endpoint included overall survival (OS), defined as the duration from start of study treatment to death due to any cause. The median OS was 8.6 months in the total population (n=123) studied and 15.6 months in adult patients who had a minimal response or better.
Karyopharm’s request for conditional authorization in the UK was based upon the same patient population that served as the basis for accelerated FDA approval of XPOVIO (selinexor) in the U.S. The overall response rate in this patient population (n=83) was 25.3 % (95% confidence interval [CI], 16.4, 36).
The most common adverse reactions in the STORM trial (≥20%) were 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 adult patients. Serious adverse reactions occurred in 58% of adult patients. Treatment discontinuation rate due to adverse reactions was 27%.
About Multiple Myeloma in Europe
Multiple myeloma (MM) is an incurable cancer with significant morbidity and the second most common hematologic malignancy. In 2020, there were approximately 51,000 new cases and 32,000 deaths from MM in Europe1. While the treatment of MM has improved over the last 20 years, and overall survival has increased considerably, the disease remains incurable, and nearly all adult patients will eventually relapse and develop disease that is refractory to all authorized anti-MM therapies. Therefore, there continues to be a high unmet medical need for new therapies, particularly those with novel mechanisms of action.
About NEXPOVIO (selinexor)
NEXPOVIO, which is marketed as XPOVIO in the U.S., is a first-in-class, oral Selective Inhibitor of Nuclear Export (SINE) compound. NEXPOVIO functions by selectively binding to and inhibiting the nuclear export protein exportin 1 (XPO1, also called CRM1). NEXPOVIO 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. NEXPOVIO has been granted conditional marketing authorization by the European Commission in combination with dexamethasone for the treatment of multiple myeloma in adult patients who have received at least four prior therapies and whose disease is refractory to at least two proteasome inhibitors, two immunomodulatory agents, and an anti-CD38 monoclonal antibody, and who have demonstrated disease progression on the last therapy.
Therapeutic indication for NEXPOVIO in the UK, EU as well as the EEA Countries of Iceland, Liechtenstein and Norway
NEXPOVIO is indicated in combination with dexamethasone for the treatment of multiple myeloma in adult patients who have received at least four prior therapies and whose disease is refractory to at least two proteasome inhibitors, two immunomodulatory agents and an anti-CD38 monoclonal antibody, and who have demonstrated disease progression on the last therapy.
SELECT IMPORTANT SAFETY INFORMATION
NEXPOVIO is subject to additional monitoring. This will allow quick identification of new safety information. You can help by reporting any side effects you may get. See www.mhra.gov.uk/yellowcard for how to report side effects.
Contraindications: Hypersensitivity to selinexor.
Special warnings and precautions for use:
Recommended concomitant treatments
Adult patients should be advised to maintain adequate fluid and caloric intake throughout treatment. Intravenous hydration should be considered for adult patients at risk of dehydration.
Prophylactic concomitant treatment with a 5-HT3 antagonist and/or other anti-nausea agents should be provided prior to and during treatment with NEXPOVIO.
Haematology
Adult patients should have their complete blood counts (CBC) assessed at baseline, during treatment, and as clinically indicated. Monitor more frequently during the first two months of treatment.
Thrombocytopenia: Thrombocytopenic events (thrombocytopenia and platelet count decreased) were frequently reported in adult patients receiving selinexor, which can be severe (Grade 3/4). Adult patients should be monitored for signs and symptoms of bleeding and evaluated promptly.
Neutropenia: Severe neutropenia (Grade 3/4) has been reported with selinexor.
Adult patients with neutropenia should be monitored for signs of infection and evaluated promptly.
Gastrointestinal toxicity: Nausea, vomiting, diarrhoea, which sometimes can be severe and may require the use of anti-emetic and anti-diarrhoeal medicinal products.
Weight loss and anorexia: Adult patients should have their body weight, nutritional status and volume checked at baseline, during treatment, and as clinically indicated. Monitoring should be more frequent during the first two months of treatment.
Confusional state and dizziness: Patients should be instructed to avoid situations where dizziness or confusional state may be a problem and to not take other medicinal products that may cause dizziness or confusional state without adequate medical advice. Patients should be advised not to drive or operate heavy machinery until symptoms resolve.
Hyponatraemia: Adult patients should have their sodium levels checked at baseline, during treatment, and as clinically indicated. Monitoring should be more frequent during the first two months of treatment.
Tumour lysis syndrome (TLS): TLS has been reported in adult patients receiving therapy with selinexor. Adult patients at a high risk for TLS should be monitored closely. Treat promptly in accordance with institutional guidelines.
Fertility, pregnancy and lactation
Women of childbearing potential/contraception in males and females: Women of childbearing potential and male adult patients of reproductive potential should be advised to use effective contraceptive measures or abstain from sexual activity to prevent pregnancy during treatment with selinexor and for at least 1 week following the last dose of selinexor.
Breast-feeding: It is unknown whether selinexor or its metabolites are excreted in human milk. A risk to breast-fed children cannot be excluded. Breast-feeding should be discontinued during treatment with selinexor and for 1 week after the last dose.
Elderly population
Patients 75 years and older had a higher incidence of discontinuation due to an adverse reaction, higher incidence of serious adverse reactions, and higher incidence of fatal adverse reactions.
Undesirable effects
Summary of the safety profile
The most frequent adverse reactions (≥30%) of selinexor in combination with dexamethasone were nausea, thrombocytopenia, fatigue, anaemia, decreased appetite, decreased weight, diarrhoea, vomiting, hyponatraemia, neutropenia and leukopenia.
The most commonly reported serious adverse reactions (≥3%) were pneumonia, sepsis, thrombocytopenia, acute kidney injury, and anaemia.
Description of selected adverse reactions
Infections: Infection was the most common non-haematological toxicity. Upper respiratory tract infection and pneumonia were the most commonly reported infections with 25% of reported infections being serious and fatal infections occurring in 3% of treated adult patients.
Reporting of suspected adverse reactions
Reporting of suspected adverse reactions after authorization of the medicinal product is important. It allows continued monitoring of the benefit/risk balance of the medicinal product. Healthcare professionals are asked to report any suspected adverse reactions via the national reporting system listed in Appendix V.