Selinexor

Introduction Overview

Generic Name

selinexor

Brand Name

Xpovio

Dosage Form

oral tablet (20 mg, 40 mg, 50 mg, 60 mg)

Drug Class

Miscellaneous antineoplastics; selective inhibitors of nuclear export (SINE)

Pharmacokinetics

Absorption:
Selinexor is administered orally in tablet form with rapid absorption from the gastrointestinal tract. Following oral administration, peak plasma concentrations are typically achieved within 2 to 4 hours, indicating efficient absorption. Food may not significantly impair absorption but clinical studies often advise administration under fasting conditions or consistent with patient tolerance to optimize bioavailability. The exact absolute bioavailability has not been definitively published but clinical efficacy suggests substantial systemic exposure upon oral dosing.

Distribution:
Selinexor is moderately distributed into tissues, with a volume of distribution that suggests extensive tissue permeation. Plasma protein binding is high (approximately 95%), primarily to albumin and alpha-1 acid glycoprotein, which impacts free drug fraction and pharmacodynamics. Selinexor crosses into compartments relevant for its activity including bone marrow and lymphoid tissue, consistent with its efficacy in hematologic malignancies. CNS penetration is limited but neurological side effects indicate some CNS exposure.

Metabolism:
Selinexor undergoes hepatic metabolism primarily via cytochrome P450 enzymes, chiefly CYP3A4, with additional contributions by CYP1A2 and CYP2B6. Metabolic transformation results in multiple metabolites, some minor metabolites retain pharmacological activity. The drug’s metabolism can be affected by strong inhibitors or inducers of CYP3A4, impacting plasma levels and raising risks of adverse effects or reduced efficacy.

Elimination:
Elimination of selinexor involves both hepatic and biliary excretion pathways, with a half-life ranging between approximately 6 to 8 hours in adults, supporting its intermittent dosing schedule (1-2 times weekly). Renal clearance is minimal, thus renal impairment is not a major elimination consideration though caution is advised. The drug and its metabolites are eliminated predominantly via feces. Accumulation is minimal with dosing intervals used clinically, consistent with its pharmacokinetic profile and dosage recommendations.

Dosage Forms

Available Dosage Forms:
Xpovio is available as oral tablets formulated in the following strengths: 20 mg, 40 mg, 50 mg, and 60 mg. The tablets are film-coated and designed for whole swallowing without crushing, breaking, or chewing to maintain dosing integrity and optimize drug release.

Dosages for Adults and Adolescents:
- For multiple myeloma (in combination with bortezomib and dexamethasone): 100 mg taken once weekly orally.
- For multiple myeloma (in combination with dexamethasone alone): 80 mg orally administered twice weekly (on days 1 and 3).
- For relapsed or refractory diffuse large B-cell lymphoma (DLBCL): 60 mg orally administered twice weekly (on days 1 and 3).

Specific Patient Populations:
While the drug’s use in pediatric populations under 18 years has not been established and safety and efficacy data are lacking, adult dosing adjustments may be required based on tolerability, hepatic or renal function, and concomitant medications. No specific dosage forms are designed for pediatric use. Geriatric patients may require careful monitoring due to increased risk of toxicity. Dose modifications or treatment interruption may be necessary in response to adverse events, especially hematologic or neurologic toxicities.

Mechanism Of Action

Selinexor, marketed as Xpovio, is the first-in-class selective inhibitor of nuclear export (SINE) compounds. It specifically targets exportin 1 (XPO1), also known as chromosome region maintenance 1 (CRM1), a key nuclear export protein responsible for transporting tumor suppressor proteins, growth regulators, and other key molecules from the nucleus to the cytoplasm. By binding covalently and irreversibly to XPO1, selinexor inhibits its function resulting in the nuclear retention and accumulation of tumor suppressor proteins.

This nuclear sequestration reactivates tumor suppressor pathways leading to cell cycle arrest, induction of apoptosis, and suppression of oncogenic translation. Cancer cells, which frequently overexpress XPO1 to evade tumor suppression, are thereby selectively targeted. Normal cells are relatively spared because they maintain a balanced nuclear-cytoplasmic transport and have less reliance on XPO1-mediated export for survival.

Selinexor’s interference with nuclear export also disrupts the export of key oncogenic mRNAs and proteins, including those involved in DNA damage repair and survival pathways, increasing cellular stress and promoting apoptosis in malignant cells. Additionally, selinexor augments the cytotoxic effects of proteasome inhibitors and corticosteroids, explaining its clinical use in combination regimens for multiple myeloma.

Clinical studies have demonstrated that the unique mechanism of selinexor enables it to overcome resistance associated with conventional chemotherapy and targeted agents. This distinct mode of action underscores its efficacy in heavily pretreated hematologic malignancies such as relapsed/refractory multiple myeloma and diffuse large B-cell lymphoma, where nuclear export is dysregulated.

Pharmacological Actions

Selective inhibition of exportin 1 (XPO1), leading to nuclear retention of tumor suppressor proteins.
Induction of apoptosis in malignant cells by reactivation of tumor suppressor pathways.
Disruption of nuclear export of oncogenic proteins and mRNA, impairing cancer cell survival.
Suppression of proliferation through cell cycle arrest in cancer cells.
Synergistic enhancement of proteasome inhibitor and corticosteroid activity in multiple myeloma.
Reduction of oncogenic translation contributing to selective cancer cell death.
Potential modulation of immune responses by altering nuclear export of inflammatory mediators.
Minimal cytotoxicity to normal cells due to selective targeting of dysregulated nuclear export in cancer cells.
Ability to overcome drug resistance mechanisms in relapsed and refractory hematologic malignancies.
Effects on DNA damage repair pathways increasing cancer cell vulnerability.
Induction of cellular stress responses leading to programmed cell death.
Targeting of a novel pathway distinct from traditional chemotherapy agents.

Therapeutic Or Clinical Uses

Treatment of multiple myeloma in adults who have received at least one prior therapy, in combination with bortezomib and dexamethasone.
Treatment of relapsed or refractory multiple myeloma in patients who have received at least four prior therapies including proteasome inhibitors, immunomodulatory agents, and anti-CD38 monoclonal antibodies, in combination with dexamethasone.
Therapeutic option for relapsed or refractory diffuse large B-cell lymphoma (DLBCL) after at least two lines of systemic therapy.
Management of hematologic malignancies with dysregulated nuclear export of tumor suppressor proteins.
Treatment choice for patients with multiple myeloma refractory to conventional treatments.
Use in combination regimens to enhance efficacy and overcome resistance mechanisms in multiple myeloma.
Palliative treatment to improve progression-free survival and reduce disease burden in heavily pretreated hematologic cancers.
Utilized within clinical trials investigating nuclear export inhibitors in oncology.
Option for patients ineligible for intense chemotherapy or stem cell transplant.
Part of salvage therapy protocols for relapsed hematologic cancers.
Potential use under accelerated approval pathways contingent on ongoing confirmatory trials.
Treatment requiring close monitoring for side effects and dose adjustments based on adverse event profiles.

Side Or Adverse Effects

Fatigue and tiredness frequently reported, impacting patient quality of life.
Anemia due to decreased red blood cell counts, necessitating monitoring and possible transfusions.
Constipation as a common gastrointestinal adverse effect.
Shortness of breath potentially related to anemia or other drug effects.
Hyperglycemia or elevated blood sugar levels during treatment.
Electrolyte disturbances including changes in body salts and minerals such as decreased sodium.
Altered kidney and liver function parameters detectable in blood tests.
Low platelet counts leading to increased bleeding risk, which may be severe and life-threatening.
Neutropenia and decreased white blood cell counts increasing infection susceptibility.
Severe nausea and vomiting, potentially causing dehydration and electrolyte imbalances.
Diarrhea with risk of fluid and electrolyte loss.
Loss of appetite (anorexia) and consequential weight loss.
Neurologic side effects such as dizziness, fainting, cognitive disturbances, hallucinations, and delirium.
Increased risk of serious and potentially fatal infections including pneumonia and sepsis.
Ophthalmologic adverse effects including new or worsening cataracts affecting vision.

Precautions

Regular blood monitoring is essential to detect hematologic toxicities such as thrombocytopenia and neutropenia.
Patients should be assessed for signs of infection promptly due to immunosuppression risk.
Preemptive antiemetic therapy should be administered to manage nausea and vomiting.
Hydration and electrolyte status should be maintained carefully to avoid dehydration.
Dose adjustments or interruptions may be necessary for severe adverse reactions.
Neurologic symptoms warrant caution in activities requiring alertness such as driving.
Patients should be monitored for signs of bleeding and bruising during therapy.
Fertility counseling is recommended as selinexor may impair reproductive capability.
Pregnancy testing and use of effective contraception are mandatory for females of reproductive potential.
Male patients with female partners of reproductive potential should use contraception during and shortly after treatment.
Breastfeeding is contraindicated during treatment due to unknown excretion in human milk.
Caution in patients with pre-existing liver or kidney dysfunction due to altered pharmacokinetics.
Avoid co-administration with drugs that increase central nervous system depression.
Close monitoring is required in elderly patients due to higher toxicity risk.
Prompt reporting of any new neurological symptoms or visual changes is advised.

Warnings

Severe thrombocytopenia can lead to fatal bleeding events; platelet counts should be monitored regularly.
Neutropenia can predispose to life-threatening infections; vigilance for infection signs is critical.
Nausea and vomiting can be severe, risk of dehydration necessitates early intervention.
Diarrhea may cause significant fluid and electrolyte imbalances requiring supportive care.
Neurologic toxicities including dizziness, confusion, hallucinations, and altered consciousness can be serious and require dose modification or discontinuation.
Risk of cataract formation or progression; ophthalmologic evaluations recommended in symptomatic patients.
Potential fetal harm and teratogenicity; contraindicated in pregnancy and requires effective contraception.
Do not crush, chew, divide, or break tablets to avoid unpredictable pharmacokinetics.
Avoid activities demanding full mental capacity in patients experiencing neurologic side effects.
Use cautiously in patients with active or recent infections due to immunosuppressive effects.
Strong CYP3A4 inhibitors and inducers may alter drug exposure leading to increased toxicity or reduced efficacy.
Careful patient selection and risk-benefit assessment needed due to serious adverse effect profile.
Withdrawal or dose reduction should be strongly considered in severe adverse events.
Not established safe or effective in pediatric patients; use limited to adults.
Infections such as pneumonia and sepsis can be fatal if not promptly treated.

Contraindication

Known hypersensitivity to selinexor or any component of the formulation.
Pregnancy due to teratogenic risk and potential fetal harm.
Breastfeeding during treatment and for one week after the last dose.
Patients with uncontrolled active infections or sepsis at treatment initiation.
Severe thrombocytopenia or bleeding disorders contraindicating administration without appropriate supportive care.
Concomitant use with agents that cause severe CNS depression without adequate monitoring.
Known severe hepatic impairment with inability to monitor drug clearance adequately.
Pediatric patients due to lack of safety and efficacy data.
Patients unable to swallow whole tablets as crushing or breaking the tablet is contraindicated.
Severe electrolyte imbalances or dehydration uncorrected prior to therapy.
Concurrent use with strong CYP3A4 inducers or inhibitors without dose adjustment.
History of severe neurologic adverse reactions to selective inhibitors of nuclear export agents.
Patients with hypersensitivity to excipients such as povidone K30 or sodium lauryl sulfate.
Known severe hypersensitivity or allergic reactions to miscellaneous antineoplastic agents.
Inability to comply with required monitoring or administration protocols.

Drug Interactions

Strong CYP3A4 inhibitors (e.g., ketoconazole, clarithromycin) may increase selinexor plasma concentrations, increasing toxicity risk.
CYP3A4 inducers (e.g., rifampin, phenytoin) can decrease selinexor efficacy by reducing plasma levels.
Concomitant use with other medications causing CNS depression (e.g., benzodiazepines, opioids) may exacerbate neurologic adverse events.
Drugs causing thrombocytopenia or neutropenia may potentiate hematologic toxicities when given with selinexor.
Potential interactions with anticoagulants requiring close monitoring due to bleeding risk.
Agents affecting electrolyte balance (e.g., diuretics) may worsen selinexor-associated electrolyte disturbances.
Co-administration with dexamethasone is standard in combination regimens and may alter metabolism of certain agents.
Drugs that prolong QT interval have not been widely studied with selinexor but caution is advised due to potential additive effects.
Medications metabolized by CYP3A4 may have altered pharmacokinetics when used concomitantly with selinexor.
Supplemental vitamins and herbal products (e.g., St. John's wort) inducing CYP3A4 could reduce selinexor effectiveness.
Antiemetics used prophylactically with selinexor may interact with cytochrome metabolism but are generally safe; dosage adjustments may be necessary.
Concomitant use with other antineoplastic agents requires monitoring for overlapping toxicities.
Potential additive effects with immunosuppressants should be considered.
Interactions with drugs altering hepatic or renal function may affect selinexor clearance.
Careful review of concomitant medications is essential to avoid unrecognized harmful interactions.

Preparations Of The Drug

Selinexor is supplied as oral tablets in 20 mg, 40 mg, 50 mg, and 60 mg strengths.
Tablets are film-coated with distinct color coding for identification.
Each tablet contains inactive ingredients including colloidal silicon dioxide, croscarmellose sodium, magnesium stearate, microcrystalline cellulose, Opadry 200 clear, Opadry II blue, povidone K30, and sodium lauryl sulfate.
Distributed in child-resistant blister packs for safety and protection from moisture.
Tablets are to be swallowed whole with water; crushing, breaking, or chewing is strictly prohibited.
Storage recommendations include maintaining temperature at or below 86°F (30°C) and keeping in original packaging to preserve stability.
Manufactured by Karyopharm Therapeutics Inc., with rigorous quality control standards.
Available only by prescription with specific labeling indicating indications for multiple myeloma and DLBCL.
Packaging includes detailed medication guide advising on administration, side effects, and safety precautions.
No generic formulations currently available; Xpovio is the trade name formulation.
Dosage forms are designed for adult use and not formulated for pediatric or parenteral administration.
Stable under recommended storage conditions with advised shelf life as per packaging.
Manufactured under Good Manufacturing Practice (GMP) guidelines ensuring consistent potency and purity.