Relative Bioavailability/Bioequivalence of Different Formulations of Selinexor, the Impact of Hepatic Impairment on Selinexor Pharmacokinetics, Tolerability and Antitumor Activity of Selinexor Combination Treatment

Up to 120 patients will be enrolled, of which, 20 with normal HF will be able to continue from Monotherapy to Combination therapy and up to 106 patients with normal HF will receive combination therapy in total. Patients with impaired hepatic function can only participate in the Monotherapy part of the study. Monotherapy Period: For the Monotherapy Period of Study KCP-330-027, patients with normal hepatic function (n=20), will be allocated to one of two test formulation treatment arms, and will receive a cross-over once weekly oral dosing, with either 1x100 mg or 5x20 mg selinexor, for 2 weeks, and then will have the option to move on to the combination treatment part of the study. Patients with either moderately or severely impaired hepatic functions will be treated with 2x20 mg selinexor weekly (with an option to increase the dose every 3 weeks by 20 mg increments, up to 80 mg). For the assessment of hepatic impairment, participants with any type of advanced or metastatic solid tumor who have moderate or severe hepatic impairment will be enrolled in Moderate Hepatic Impairment (MHI) (n=8) and Severe Hepatic Impairment (SHI) (n=6) arms, respectively and will be treated with 2 × 20 mg selinexor, weekly. For Weeks 1 and 2, following an overnight fast of at least 10 hours, patients will be fed a standard low-fat meal 30 minutes prior to administration of once weekly selinexor. Patients should finish the meal in 30 minutes or less; however, selinexor dose should be administered 30 minutes after start of the meal. Blood sampling for selinexor PK analyses will be collected ≤10 minutes (m) pre selinexor dose, and at 15m (±5m), 30m (±5m), 1 hour (h) (±5m), 1.5h (±5m), 2h (±10m), 3h (±10m), 4h (±10m), 5h (±10m), 6h (±10m), 8h (±20m), 10h (±20m; optional), 24h (±1h), 30h (±1h), and 48h (±2h) post selinexor dose. Practitioners must record the actual clock time for selinexor dose, and each sample drawn. If a patient experiences emesis during the first 6 hours of the PK sampling, the PK results for that week will be excluded from the PK analysis dataset, and all testing timepoints must be re-collected during the following week (in this case, the same dosing formulation should be repeated on the following week, and other dosing formulation will be given the week after that). Patients who will complete the Monotherapy Period will be reassessed for continuation to the Combination Therapy Period, as long as their Hepatic Function remains normal. If a patient experiences significant toxicity related to selinexor and can't start the combination therapy immediately following monotherapy, dose interruption and weekly retesting are allowed for up to 21 days after the end of Monotherapy treatment visit. Patients requiring \>21 days to recover from toxicities related to selinexor should be discussed with the Sponsor's Medical Monitor for documented approval to continue to the Combination Therapy Period. Reassessment may be extended then and following Medical Monitor approval up to 28 days. Combination Therapy Period: In the combination treatment period of the study, patients with normal hepatic functions will be allocated to one of 3 arms (with Arm C divided into 2 cohorts): Arm A (n= up to 40): Patients with NSCLC who have had up to 2 lines of prior systemic treatment with 1 line containing a CPI will receive 60 mg selinexor weekly, in combination with docetaxel 75 milligrams per meter square (mg/m\^2) once every 3 weeks; Arm B (n= up to 40): Patients with CRC (KRAS WT) who have had up to 3 lines of prior systemic treatment or patients with CRC (KRAS mutant \[KRAS Mut\]) who have had up to 2 lines of prior systemic treatment, with no lines containing a checkpoint inhibitor (CPI) will receive 80 mg selinexor weekly, in combination with pembrolizumab 200 mg once every 3 weeks; Arm C (n\<=26): Patients with CRC (regardless of KRAS status) who have had up to 2 lines of prior systemic treatment (regardless of CPI use) will receive either: (Cohort 1) selinexor 40 mg on days 1, 3, 15 and 18 in 28-day cycle + FOLFIRI; or (Cohort 2) selinexor 80 mg on days 1 and 15 in 28-day cycle + FOLFIRI. Combination Therapy Period Patients will receive combination treatment until progressive disease (PD) or intolerable toxicity. During both study periods, safety will be assessed through continuous reporting of adverse events (AEs), treatment-emergent adverse events (TEAEs), regularly scheduled clinical laboratory tests (hematologic and chemical), and physical examinations. Tumor assessment will be performed with either computed tomography (CT) or magnetic resonance imaging (MRI) (CT with contrast preferred; for each patient, the imaging method should remain the same throughout the study). Following treatment, patients will come in for a safety visit (approximately 30 days after the last dose of combination therapy) and will be followed for up to 2 years after that. Patients who discontinued due to PD will be followed for survival, and patients who discontinued for reasons other than PD will have tumor assessments until PD or until the start of new anti-neoplastic therapy, after which they will be followed for survival.