Frontline Maintenance Selinexor Yields Significant PFS Benefit in Advanced or Recurrent Endometrial Cancer

The phase 3 SIENDO trial, examining the use of frontline maintenance selinexor after combination chemotherapy in patients with advanced or recurrent endometrial cancer, met its primary end point of a statistically significant improvement in progression-free survival.

Treatment with frontline maintenance selinexor (Xpovio) after a combination chemotherapy regimen resulted in a significant improvement in progression-free survival (PFS) for patients with advanced or recurrent endometrial cancer, according to a press release on findings from the phase 3 SIENDO trial (NCT03555422).

Patients treated with selinexor experienced a median PFS of 5.7 months compared with 3.8 months in the placebo arm, translating to a 50% improvement (HR, 0.70; P = .0486). Moreover, investigators reported a 30% reduction in risk of progression or death.

Developer Karyopharm Therapeutics has plans in place to work with the FDA to fully evaluate the study’s findings. Moreover, the company will submit a supplemental new drug application to the FDA and present the study findings at an upcoming medical meeting in the first half of 2022.

“We are thrilled to see a statistically significant improvement in median progression-free survival from the phase 3 SIENDO study because of what it represents for patients,” Sharon Shacham, PhD, MBA, chief scientific officer at Karyopharm, said in the press release. “If approved, XPOVIO would be the first and only maintenance therapy in advanced or recurrent endometrial cancer, following response to chemotherapy.”

A total of 263 patients with primary stage IV or recurrent disease were included in the global, multicenter, blinded, placebo-controlled, randomized study. The population was required to have a partial or complete response following at least 12 weeks of treatment with taxane/platinum chemotherapy. Following chemotherapy, patients received 80 mg of selinexor weekly or placebo. Treatment continued until disease progression.

Additional findings from the study indicated that the experimental therapy yielded a 12-month long-term improvement, as evidenced by a 37% increase in probability of remission among those treated with selinexor vs placebo.

Preliminary data indicated that a pre-specified group of patients who were p53 wild-type experienced a statistically significant reduction in risk of disease progression or death of 62%. Within this group, patients who received selinexor achieved a median PFS of 13.7 months vs 3.7 months in the placebo arm (HR, 0.38; P = .0006).

No new safety findings were observed, and 10.5% of patients discontinued treatment because of adverse effects.

“As an oral, chemotherapy-free treatment, selinexor has the potential to transform the way advanced or recurrent endometrial cancer is treated and I am intrigued to learn more about the patients with the wild-type p53,” principal investigator, Ignace Vergote, MD, PhD, a gynecologic oncologist, ENGOT and the Belgium and Luxembourg Gynaecological Oncology Group, University of Leuven, Leuven Cancer Institute, concluded. “This study brings us one step closer to offering patients a treatment option that can give them more time with their friends and families.”


Karyopharm announces phase 3 SIENDO study meets primary endpoint with statistically significant increase in progression-free survival in patients with advanced or recurrent endometrial cancer. News release. Karyopharm Therapeutics. February 8, 2022. Accessed February 8, 2022.