Effect of prior treatments on selinexor, bortezomib, and dexamethasone in previously treated multiple myeloma.

Therapeutic regimens for previously treated multiple myeloma (MM) may not provide prolonged disease control and are often complicated by significant adverse events, including peripheral neuropathy. In patients with previously treated MM in the Phase 3 BOSTON study, once weekly selinexor, once weekly bortezomib, and 40 mg dexamethasone (XVd) demonstrated a significantly longer median progression-free survival (PFS), higher response rates, deeper responses, a trend to improved survival, and reduced incidence and severity of bortezomib-induced peripheral neuropathy when compared with standard twice weekly bortezomib and 80 mg dexamethasone (Vd). The pre-specified analyses described here evaluated the influence of the number of prior lines of therapy, prior treatment with lenalidomide, prior proteasome inhibitor (PI) therapy, prior immunomodulatory drug therapy, and prior autologous stem cell transplant (ASCT) on the efficacy and safety of XVd compared with Vd. In this 1:1 randomized study, enrolled patients were assigned to receive once weekly oral selinexor (100 mg) with once weekly subcutaneous bortezomib (1.3 mg/m2) and 40 mg per week dexamethasone (XVd) versus standard twice weekly bortezomib and 80 mg per week dexamethasone (Vd). XVd significantly improved PFS, overall response rate, time-to-next-treatment, and showed reduced all grade and grade ≥ 2 peripheral neuropathy compared with Vd regardless of prior treatments, but the benefits of XVd over Vd were more pronounced in patients treated earlier in their disease course who had either received only one prior therapy, had never been treated with a PI, or had prior ASCT. Treatment with XVd improved outcomes as compared to Vd regardless of prior therapies as well as manageable and generally reversible adverse events. XVd was associated with clinical benefit and reduced peripheral neuropathy compared to standard Vd in previously treated MM. These results suggest that the once weekly XVd regimen may be optimally administered to patients earlier in their course of disease, as their first bortezomib-containing regimen, and in those relapsing after ASCT.Trial registration: ClinicalTrials.gov (NCT03110562). Registered 12 April 2017. https://clinicaltrials.gov/ct2/show/NCT03110562 .

Once-per-week selinexor, bortezomib, and dexamethasone versus twice-per-week bortezomib and dexamethasone in patients with multiple myeloma (BOSTON): a randomised, open-label, phase 3 trial.

BACKGROUND: Selinexor combined with dexamethasone has shown activity in patients with heavily pre-treated multiple myeloma. In a phase 1b/2 study, the combination of oral selinexor with bortezomib (a proteasome inhibitor) and dexamethasone induced high response rates with low rates of peripheral neuropathy, the main dose-limiting toxicity of bortezomib. We aimed to evaluate the clinical benefit of weekly selinexor, bortezomib, and dexamethasone versus standard bortezomib and dexamethasone in patients with previously treated multiple myeloma. METHODS: This phase 3, randomised, open-label trial was done at 123 sites in 21 countries. Patients aged 18 years or older, who had multiple myeloma, and who had previously been treated with one to three lines of therapy, including proteasome inhibitors, were randomly allocated (1:1) to receive selinexor (100 mg once per week), bortezomib (1·3 mg/m2 once per week), and dexamethasone (20 mg twice per week), or bortezomib (1·3 mg/m2 twice per week for the first 24 weeks and once per week thereafter) and dexamethasone (20 mg four times per week for the first 24 weeks and twice per week thereafter). Randomisation was done using interactive response technology and stratified by previous proteasome inhibitor therapy, lines of treatment, and multiple myeloma stage. The primary endpoint was progression-free survival in the intention-to-treat population. Patients who received at least one dose of study treatment were included in the safety population. This trial is registered at ClinicalTrials.gov, NCT03110562. The trial is ongoing, with 55 patients remaining on randomised therapy as of Feb 20, 2020. FINDINGS: Of 457 patients screened for eligibility, 402 were randomly allocated-195 (49%) to the selinexor, bortezomib, and dexamethasone group and 207 (51%) to the bortezomib and dexamethasone group-and the first dose of study medication was given between June 6, 2017, and Feb 5, 2019. Median follow-up durations were 13·2 months [IQR 6·2-19·8] for the selinexor, bortezomib, and dexamethasone group and 16·5 months [9·4-19·8] for the bortezomib and dexamethasone group. Median progression-free survival was 13·93 months (95% CI 11·73-not evaluable) with selinexor, bortezomib, and dexamethasone and 9·46 months (8·11-10·78) with bortezomib and dexamethasone (hazard ratio 0·70 [95% CI 0·53-0·93], p=0·0075). The most frequent grade 3-4 adverse events were thrombocytopenia (77 [39%] of 195 patients in the selinexor, bortezomib, and dexamethasone group vs 35 [17%] of 204 in the bortezomib and dexamethasone group), fatigue (26 [13%] vs two [1%]), anaemia (31 [16%] vs 20 [10%]), and pneumonia (22 [11%] vs 22 [11%]). Peripheral neuropathy of grade 2 or above was less frequent with selinexor, bortezomib, and dexamethasone (41 [21%] patients) than with bortezomib and dexamethasone (70 [34%] patients; odds ratio 0·50 [95% CI 0·32-0·79], p=0·0013). 47 (24%) patients in the selinexor, bortezomib, and dexamethasone group and 62 (30%) in the bortezomib and dexamethasone group died. INTERPRETATION: A once-per-week regimen of selinexor, bortezomib, and dexamethasone is a novel, effective, and convenient treatment option for patients with multiple myeloma who have received one to three previous lines of therapy. FUNDING: Karyopharm Therapeutics.

Selinexor plus low-dose bortezomib and dexamethasone for patients with relapsed or refractory multiple myeloma.

Selinexor is an oral inhibitor of the nuclear export protein exportin 1. Preclinical studies demonstrated synergistic antimyeloma activity between selinexor and proteasome inhibitors (PI) through suppression of NF-κB signaling and nuclear retention of tumor suppressor proteins. We tested selinexor in combination with low-dose bortezomib and dexamethasone (SVd) for the treatment of relapsed or refractory multiple myeloma (MM). The primary objectives of this study were to determine the safety profile, overall response rate (ORR), and a recommended phase 2 dose (RP2D) of SVd. We enrolled 42 patients to receive selinexor (60, 80, or 100 mg orally) plus bortezomib (1.3 mg/m2 subcutaneously) and dexamethasone (20 mg orally) once or twice weekly in 21- or 35-day cycles. Patients had a median of 3 (range 1-11) prior lines of therapy, and 50% were refractory to a PI. Treatment-related grade 3 or 4 adverse events reported in ≥10% of patients were thrombocytopenia (45%), neutropenia (24%), fatigue (14%), and anemia (12%). Incidence (4 patients, 10%) and grade (≤2) of peripheral neuropathy were low. The ORR for the entire population was 63%: 84% ORR for PI nonrefractory and 43% for PI-refractory patients. The median progression-free survival for all patients was 9.0 months; 17.8 months for PI nonrefractory, and 6.1 months for PI refractory. SVd treatment produced high response rates in patients with relapsed or refractory MM, including borezomib-refractory MM, with no unexpected side effects. The RP2D is selinexor (100 mg once weekly), bortezomib (1.3 mg/m2 once weekly for 4 weeks), and dexamethasone (40 mg once weekly) per 35-day cycle. This trial was registered at www.clinicaltrials.gov as #NCT02343042.