On June 9, 2020 Karyopharm Therapeutics Inc. (Nasdaq:KPTI), an innovation-driven pharmaceutical company, reported dosing of the first patient in a Phase 1/2 clinical study evaluating oral selinexor in combination with standard of care therapy in patients with newly diagnosed or recurrent glioblastoma (GBM) (Press release, Karyopharm, JUN 9, 2020, View Source [SID1234560922]). This global study is expected to enroll approximately 400 patients at clinical sites in the U.S., Europe, and Israel.
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Selinexor is an oral selective inhibitor of nuclear export (SINE) compound which blocks the cellular protein XPO1, whose function includes playing a key role in regulating the activity of tumor suppressor proteins and other oncoproteins relevant in cancer cell biology. XPO1 may be an important, novel target in the treatment of patients with GBM as it is frequently overexpressed in both GBM and in high-grade gliomas, and the degree of XPO1 over-expression correlates with higher tumor grade and poor overall patient survival. Nonclinical studies indicate that selinexor has potent anti-GBM activity as monotherapy and is synergistic when combining with radiation, temozolomide and lomustine. Additionally, in previous clinical studies (KING study/NCT01986348), selinexor has demonstrated that it crosses the blood-brain barrier with adequate intra-tumoral penetration and single-agent efficacy with durable response and disease stabilization in heavily pretreated GBM patients further supporting the rationale for clinical development of selinexor to treat patients with brain cancers.
The randomized, multi-center, Phase 1/2 study (XPORT-GBM-029/NCT04421378) will be conducted in two phases: a Phase 1 dose finding study followed by a Phase 2 randomized efficacy exploration study, designed to independently evaluate three different combination regimens in three treatment arms in patients with newly diagnosed GBM (Arms A and B) or with recurrent GBM (Arm C). Arms A and B will investigate selinexor in combination with radiation therapy with or without the addition of temozolomide, while Arm C will evaluate the combination of selinexor and lomustine. The primary endpoints in the study are progression-free survival in patients with newly diagnosed GBM and overall survival (OS) in patients with recurrent GBM.
Yazmín Odia, M.D., Chief of Neuro-Oncology at Miami Cancer Institute, Baptist Health South Florida (BHSF), and investigator in the study, stated, "We are very excited about the launch of this innovative clinical trial on behalf of our patients who desperately need new treatment options for what is typically an incurable disease and given the few meaningful therapeutic advances in recent years."
"We are hopeful that this study evaluating the activity of selinexor in combination with currently used standard treatments will help us further identify promising novel approaches for the treatment of patients with both newly diagnosed and recurrent GBM," commented Minesh Mehta, M.D., Chief of Radiation Oncology at Miami Cancer Institute, BHSF, and investigator in the study.
"While selinexor has been most extensively studied in patients with hematologic malignancies, there is increasing evidence that selinexor may also play an important role in the treatment of a variety of solid tumors, including patients with GBM," said Sharon Shacham, PhD, MBA, President and Chief Scientific Officer of Karyopharm. "We were highly encouraged by the results from our previous Phase 2 KING study, which evaluated selinexor as a single agent in patients with recurrent GBM and demonstrated clear anti-cancer activity. We now look forward to assessing selinexor’s activity in combination with currently used standard of care treatments where we hope it will prove to be synergistic and even more effective."
Selinexor, marketed as XPOVIO, is currently approved by the U.S. Food and Drug Administration (FDA) as a treatment for patients with relapsed or refractory multiple myeloma. Selinexor is currently the only XPO1 inhibitor approved by the FDA and has been extensively tested in clinical trials across numerous cancer indications worldwide since 2012. Karyopharm has also submitted two additional supplemental New Drug Applications for XPOVIO which are currently under review by the FDA; one is for an expansion of XPOVIO’s label to include XPOVIO as a treatment for patients with multiple myeloma after at least one prior line of therapy and the other for the treatment of patients with relapsed or refractory diffuse large B-cell lymphoma (DLBCL).
About GBM
Glioblastoma Multiforme (GBM) is one of the most common and particularly aggressive forms of brain tumors of primarily glial cell origin. GBM is diagnosed in patients at a median age of 64 years but can occur at any age, including in childhood. GBM is an incurable disease and the prognosis for patients is typically poor due in part to its aggressive and extensive infiltration of surrounding central nervous system tissue and its frequent inaccessibility for surgical resection within the brain. In addition, the blood-brain barrier presents an obstacle for many chemotherapeutic agents, with only small, lipophilic molecules able to reach the tumor. Median survival in patients with newly diagnosed GBM is approximately 15 months and approximately five to seven months in patients with recurrent disease.
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. Karyopharm has also submitted a Marketing Authorization Application (MAA) to the European Medicines Agency (EMA) with a request for conditional approval of selinexor. A supplemental New Drug Application was accepted by the FDA seeking accelerated approval for selinexor as a new treatment for patients with relapsed or refractory diffuse large B-cell lymphoma (DLBCL), and selinexor has received Fast Track and Orphan designation and Priority Review from the FDA with a scheduled PDUFA date of June 23, 2020 for this patient population. Selinexor is also being evaluated in several other mid-and later-phase clinical trials across multiple cancer indications, including in multiple myeloma in a pivotal, randomized Phase 3 study in combination with Velcade (bortezomib) and low-dose dexamethasone (BOSTON), for which Karyopharm announced positive top-line results in March 2020. In May 2020, Karyopharm submitted a supplemental New Drug Application based on data from the Phase 3 BOSTON study. Additional, ongoing trials for selinexor include as a potential backbone therapy in combination with approved myeloma therapies (STOMP), in liposarcoma (SEAL) 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.
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IMPORTANT SAFETY INFORMATION
Thrombocytopenia
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.
Neutropenia
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 Toxicity
Gastrointestinal toxicities occurred in patients treated with XPOVIO.
Nausea/Vomiting
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
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/Weight Loss
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.
Hyponatremia
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.
Infections
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 Toxicity
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.
Embryo-Fetal Toxicity
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.
ADVERSE REACTIONS
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%.