Clinical bottom line
Selective inhibitors of exportin-1 (XPO1), notably selinexor, represent a novel therapeutic class for patients with relapsed or refractory multiple myeloma (RRMM) who have exhausted standard options. These agents target nuclear export pathways to restore tumor suppressor function and induce apoptosis in myeloma cells. Clinical data support selinexor’s efficacy in heavily pretreated RRMM populations, often in combination regimens, though toxicity management remains a key consideration. While not yet frontline, XPO1 inhibitors offer a promising option for patients with limited alternatives, warranting integration into treatment algorithms alongside established therapies.
What the evidence shows
XPO1 is a nuclear export protein responsible for transporting tumor suppressor proteins and growth regulators from the nucleus to the cytoplasm, thereby impairing their function in cancer cells. Selinexor, a first-in-class selective inhibitor of nuclear export (SINE), binds covalently to XPO1, blocking this export and restoring nuclear retention of tumor suppressors, leading to apoptosis in multiple myeloma cells (Richard et al., 2020; Peterson et al., 2020).
Clinical trials have demonstrated selinexor’s activity in RRMM. The pivotal STORM study showed that selinexor combined with dexamethasone achieved an overall response rate (ORR) of approximately 26% in patients with penta-refractory disease, a population with otherwise dismal prognosis (Richard et al., 2020). Subsequent studies have explored selinexor in combination with proteasome inhibitors (e.g., bortezomib) and immunomodulatory drugs, showing enhanced efficacy and manageable safety profiles (Richard et al., 2022). Preclinical data also support synergy between XPO1 inhibition and topoisomerase II inhibitors, suggesting potential combination strategies to overcome drug resistance (Turner et al., 2016).
Mechanistically, selinexor’s inhibition of nuclear export reactivates multiple tumor suppressors and disrupts oncogenic signaling pathways, which may explain its broad activity across resistant myeloma clones (Richard et al., 2022). This mechanism differs from proteasome inhibition or immunomodulation, providing a complementary approach in RRMM management.
Caveats and uncertainty
Despite promising efficacy, selinexor is associated with notable adverse effects, including nausea, fatigue, thrombocytopenia, and hyponatremia, which can limit tolerability and adherence (Peterson et al., 2020). Optimal dosing and supportive care measures are critical to mitigate these toxicities. Furthermore, most clinical data derive from heavily pretreated, refractory populations, limiting generalizability to earlier lines of therapy.
Long-term outcomes and comparative effectiveness versus other emerging agents remain to be fully elucidated. The durability of responses and impact on quality of life require further study. Additionally, biomarkers predictive of response to XPO1 inhibition have not been established, complicating patient selection.
The integration of selinexor into combination regimens is evolving, with ongoing trials assessing synergy and sequencing with other novel agents. Resistance mechanisms to XPO1 inhibitors are also under investigation but remain incompletely understood.
How this may change practice
For hematologists managing RRMM, XPO1 inhibitors like selinexor provide a mechanistically distinct option for patients refractory to proteasome inhibitors, immunomodulatory drugs, and monoclonal antibodies. Incorporation of selinexor-based regimens may extend therapeutic options in heavily pretreated settings, potentially improving outcomes in a challenging population.
Clinicians should be vigilant about managing selinexor-associated toxicities through dose adjustments and supportive care. Patient education regarding side effect profiles is essential to optimize adherence. As evidence accrues, selinexor may move into earlier lines of therapy or be combined with other agents to enhance efficacy.
Ongoing and future clinical trials will clarify the optimal role of XPO1 inhibitors in multiple myeloma treatment algorithms, including potential biomarker-driven approaches. Meanwhile, selinexor represents a valuable addition to the expanding armamentarium against RRMM.