Sundar Jagannath, MD,
“Despite the availability of proteasome inhibitors (PIs), immunomodulatory drugs (IMiDs), alkylating agents and monoclonal antibodies for the treatment of multiple myeloma, most patients will, regrettably, have disease that continues to progress. An increasing number of patients are developing highly refractory disease and have no remaining treatment options of known clinical benefit,” added
“We are pleased to have the STORM study results published in such a highly esteemed, peer-reviewed journal and this publication further supports the potential utility of oral XPOVIO in patients with highly refractory multiple myeloma,” said
A Marketing Authorization Application (MAA) seeking conditional approval for selinexor is currently under review by the
The full Prescribing Information for XPOVIO is available at www.XPOVIO.com.
The Phase 2b STORM Study Results
The published results are from Part 2 of the international, multi-center, single-arm Phase 2b STORM (Selinexor Treatment of Refractory Myeloma) study (NCT02336815), which enrolled 122 patients with heavily pretreated, triple class refractory multiple myeloma in the U.S. and Europe. These heavily pretreated patients had a median of seven previous therapeutic regimens, including a median of 10 unique anti-myeloma agents. Specifically, the myeloma patients who were eligible for the study had prior exposure to the two PIs, Velcade® (bortezomib) and Kyprolis® (carfilzomib), the two IMiDs, Revlimid® and Pomalyst, and the anti-CD38 monoclonal antibody Darzalex, as well as alkylating agents, and their disease was refractory to glucocorticoids, at least one PI, at least one IMiD, Darzalex, and their most recent therapy. Patients in the STORM study had rapidly progressing myeloma, with a 22% increase in disease burden in the 12 days from screening to initial therapy.
Given the rapid progression of penta-exposed, triple-class refractory myeloma, the window of opportunity to prevent further illness and death is small. Therefore, the regimen that was used in the STORM study began with a high dose of selinexor to achieve rapid disease control. Each patient started 80mg oral selinexor twice weekly in combination with low-dose dexamethasone (dex; 20mg twice weekly). Because most patients involved in the study were older and frail, with limited end-organ reserve and at increased risk for adverse events, dose modifications were anticipated and were specified along with supportive care in the protocol.
For the STORM study’s primary endpoint, oral selinexor achieved an overall response rate of 26% (95% confidence interval [CI], 19, 35), including two (2%) stringent complete responses (sCRs), six (5%) very good partial responses and 24 (20%) partial responses (PRs), and the trial therefore met its primary endpoint. Both patients who had relapsed after CAR-T therapy achieved PRs. Minimal response per IMWG criteria was observed in 16 (13%) patients and 48 patients (39%) had stable disease. Median time to partial response or better was 4.1 weeks. Clinical benefit rate (≥minimal response), was 39% (95% CI, 31, 49). All responses were adjudicated by an Independent Review Committee.
Median duration of response was 4.4 months (95% CI, 3.7, 10.8). Progression-free survival was 3.7 months (95% CI, 3.0, 5.3) and OS was 8.6 months (95% CI, 6.2, 11.3). In the 39% of patients who achieved a partial or minimal response or better, median OS was 15.6 months, compared to a median OS of 1.7 months in patients whose disease progressed or where response was not evaluable (p<0.0001).
The adverse events that were observed in the study were a function of dose, schedule, and baseline clinical characteristics (e.g., cytopenias). The most common treatment-emergent adverse events (AEs) were thrombocytopenia (73%), fatigue (73%), nausea (72%) and anemia (67%). The most common Grade 3/4 treatment-emergent AEs were thrombocytopenia (59%), anemia (44%), hyponatremia (22%) and neutropenia (21%). Importantly, most non-hematologic AEs were limited in severity to Grades 1 or 2, with only 10% experiencing Grade 3 nausea and 3% experiencing grade 3 vomiting. In all, 18% of patients discontinued study treatment because of an AE considered by the investigator related to study drug, though such determinations for a new agent are imprecise. AEs leading to dose modification or holds occurred in 80% of patients, with the majority occurring in the first 2 cycles. The most common AEs leading to dose reduction or interruption were thrombocytopenia (43%), fatigue (16%), and neutropenia (11%). Supportive care, including granulocyte colony stimulating factors, thrombopoietin receptor agonists, optimization of fluid and caloric intake, appetite stimulants, psychostimulants and/or additional anti-nausea agents usually reduced the intensity and/or duration of AEs. Side effects were reversible without evidence of toxic effects in major organs (treatment-related cardiac, pulmonary, hepatic, or renal dysfunction of grade 3 or higher) or cumulative toxic effects, with irreversible acute kidney injury reported in 1 patient (1%).). Serious AEs occurred in 63% of patients, with pneumonia (11%), and sepsis (9%) being the most common. Twenty-eight patients died during the study: 16 from disease progression and 12 from an AE. Of these 12 patients, two were assessed by the investigator as related to treatment (pneumonia with concurrent disease progression [n=1], sepsis [n=1]).
The patient population described in this publication does not represent the population which formed the basis of XPOVIO’s accelerated
About Multiple Myeloma
According to the
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. In addition to receiving accelerated
IMPORTANT SAFETY INFORMATION
XPOVIO can cause thrombocytopenia, leading to potentially fatal hemorrhage. Thrombocytopenia was reported as an adverse reaction in 74% of patients, and severe (Grade 3-4) thrombocytopenia occurred in 61% of patients treated with XPOVIO. The median time to onset of the first event was 22 days. Bleeding occurred in 23% of patients with thrombocytopenia, clinically significant bleeding occurred in 5% of patients with thrombocytopenia and fatal hemorrhage occurred in <1% of patients.
Monitor platelet counts at baseline, during treatment, and as clinically indicated. Monitor more frequently during the first two months of treatment. Institute platelet transfusion and/or other treatments as clinically indicated. Monitor patients for signs and symptoms of bleeding and evaluate promptly. Interrupt and/or reduce dose, or permanently discontinue based on severity of adverse reaction.
XPOVIO can cause neutropenia, potentially increasing the risk of infection. Neutropenia was reported as an adverse reaction in 34% of patients, and severe (Grade 3-4) neutropenia occurred in 21% of patients treated with XPOVIO. The median time to onset of the first event was 25 days. Febrile neutropenia was reported in 3% of patients.
Obtain neutrophil counts at baseline, during treatment, and as clinically indicated. Monitor more frequently during the first two months of treatment. Monitor patients for signs and symptoms of concomitant infection and evaluate promptly. Consider supportive measures including antimicrobials for signs of infection and use of growth factors (e.g., G-CSF). Interrupt and/or reduce dose, or permanently discontinue based on severity of adverse reaction.
Gastrointestinal toxicities occurred in patients treated with XPOVIO.
Nausea was reported as an adverse reaction in 72% of patients, and Grade 3 nausea occurred in 9% of patients treated with XPOVIO. The median time to onset of the first nausea event was 3 days.
Vomiting was reported in 41% of patients, and Grade 3 vomiting occurred in 4% of patients treated with XPOVIO. The median time to onset of the first vomiting event was 5 days.
Provide prophylactic 5-HT3 antagonists and/or other anti-nausea agents, prior to and during treatment with XPOVIO. Manage nausea/vomiting by dose interruption, reduction, and/or discontinuation. Administer intravenous fluids and replace electrolytes to prevent dehydration in patients at risk. Use additional anti-nausea medications as clinically indicated.
Diarrhea was reported as an adverse reaction in 44% of patients, and Grade 3 diarrhea occurred in 6% of patients treated with XPOVIO. The median time to onset of diarrhea was 15 days.
Manage diarrhea by dose modifications and/or standard anti-diarrheal agents; administer intravenous fluids to prevent dehydration in patients at risk.
Anorexia was reported as an adverse reaction in 53% of patients, and Grade 3 anorexia occurred in 5% of patients treated with XPOVIO. The median time to onset of anorexia was 8 days.
Weight loss was reported as an adverse reaction in 47% of patients, and Grade 3 weight loss occurred in 1% of patients treated with XPOVIO. The median time to onset of weight loss was 15 days.
Monitor patient weight at baseline, during treatment, and as clinically indicated. Monitor more frequently during the first two months of treatment. Manage anorexia and weight loss with dose modifications, appetite stimulants, and nutritional support.
XPOVIO can cause hyponatremia; 39% of patients treated with XPOVIO experienced hyponatremia, 22% of patients experienced Grade 3 or 4 hyponatremia. The median time to onset of the first event was 8 days.
Monitor sodium level at baseline, during treatment, and as clinically indicated. Monitor more frequently during the first two months of treatment. Correct sodium levels for concurrent hyperglycemia (serum glucose >150 mg/dL) and high serum paraprotein levels. Treat hyponatremia per clinical guidelines (intravenous saline and/or salt tablets), including dietary review. Interrupt and/or reduce dose, or permanently discontinue based on severity of adverse reaction.
In patients receiving XPOVIO, 52% of patients experienced any grade of infection. Upper respiratory tract infection of any grade occurred in 21%, pneumonia in 13%, and sepsis in 6% of patients. Grade ≥3 infections were reported in 25% of patients, and deaths resulting from an infection occurred in 4% of patients. The most commonly reported Grade ≥3 infections were pneumonia in 9% of patients, followed by sepsis in 6%. The median time to onset was 54 days for pneumonia and 42 days for sepsis. Most infections were not associated with neutropenia and were caused by non-opportunistic organisms.
Neurological toxicities occurred in patients treated with XPOVIO.
Neurological adverse reactions including dizziness, syncope, depressed level of consciousness, and mental status changes (including delirium and confusional state) occurred in 30% of patients, and severe events (Grade 3-4) occurred in 9% of patients treated with XPOVIO. Median time to the first event was 15 days.
Optimize hydration status, hemoglobin level, and concomitant medications to avoid exacerbating dizziness or mental status changes.
Based on data from animal studies and its mechanism of action, XPOVIO can cause fetal harm when administered to a pregnant woman. Selinexor administration to pregnant animals during organogenesis resulted in structural abnormalities and alterations to growth at exposures below those occurring clinically at the recommended dose.
Advise pregnant women of the potential risk to a fetus. Advise females of reproductive potential and males with a female partner of reproductive potential to use effective contraception during treatment with XPOVIO and for 1 week after the last dose.
The most common adverse reactions (incidence ≥20%) are thrombocytopenia, fatigue, nausea, anemia, decreased appetite, decreased weight, diarrhea, vomiting, hyponatremia, neutropenia, leukopenia, constipation, dyspnea, and upper respiratory tract infection.
The treatment discontinuation rate due to adverse reactions was 27%; 53% of patients had a reduction in the XPOVIO dose, and 65.3% had the dose of XPOVIO interrupted. The most frequent adverse reactions requiring permanent discontinuation in 4% or greater of patients who received XPOVIO included fatigue, nausea, and thrombocytopenia. The rate of fatal adverse reactions was 8.9%.
Please see XPOVIO Full Prescribing Information available at www.XPOVIO.com.
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 our expectations relating to XPOVIO for the treatment of patients with RRMM, commercialization of XPOVIO or any of our drug candidates, submissions to, and the review and potential approval of selinexor by, regulatory authorities, including the anticipated timing of such submissions and actions and the potential availability of accelerated approval pathways, and the therapeutic potential of and potential clinical development plans for Karyopharm's drug candidates, especially 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 regulators will agree that selinexor qualifies for conditional approval in the E.U. as a result of the data from the STORM study or accelerated or conditional approval in the U.S. or EU, respectively, based on data from the SADAL study in patients with relapsed or refractory DLBCL, 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 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 timing and costs involved in commercializing XPOVIO or any of Karyopharm’s drug candidates that receive regulatory approval; the ability to 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
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Source: Karyopharm Therapeutics Inc.