Phase 2 Study of Alisertib (MLN8237) in Combination With Paclitaxel Versus Placebo in Combination With Paclitaxel as Second Line Therapy for Small Cell Lung Cancer (SCLC)

Inclusion Criteria Each participant must meet all the following inclusion criteria to be enrolled in the study: 1. Male or female participants ≥ 18 years old. 2. Have a pathologically (histology or cytology) confirmed diagnosis of SCLC. 3. Have received and progressed after a platinum-based standard chemotherapy regimen for first line treatment of SCLC, either limited stage (LS) or extensive stage (ES). 4. Have measurable disease within ≤ 2 weeks before randomization. Clear radiographic evidence of disease progression after initial therapy should have been documented. 5. Eastern Cooperative Oncology Group (ECOG) performance status (PS) of 0 or 1 (PS 0-1). 6. Participants with treated brain metastases (surgery, whole or stereotactic brain radiation) are allowed provided the lesions have been stable for at least 2 weeks and the participant is off steroids or is on a stable dose of steroids. Participants should be without neurologic dysfunction that would confound the evaluation of neurological and/or other AEs. Exclusion Criteria Participants meeting any of the following exclusion criteria are not to be randomized to treatment: 1. Any prior therapy for second-line treatment of SCLC. 2. Participants who relapsed ≥ 180 days after their response to first-line treatment. 3. Prior treatment with an Aurora A specific-targeted or pan-Aurora-targeted agent, including alisertib, or any other investigational agent. 4. Prior treatment with paclitaxel or any other taxane agent. 5. Known hypersensitivity to Cremophor® EL, paclitaxel, or its components. 6. Any comorbid condition or unresolved toxicity that would preclude administration of alisertib or weekly paclitaxel. 7. Prior history of ≥ Grade 2 neurotoxicity that is not resolved to ≤ Grade 1. 8. Participants with symptomatic and/or progressive brain metastases or with carcinomatous meningitis. 9. Treatment with clinically significant enzyme inducers within 14 days prior to the first dose of alisertib and during study conduct. Major prohibited enzyme inducers include: phenytoin, carbamazepine, phenobarbital, rifampin, rifabutin, rifapentine, and St. John's wort. 10. Inability to swallow alisertib or other orally administered medications. 11. Requirement for administration of proton pump inhibitor (PPI), H2 antagonist, or pancreatic enzymes. 12. Diagnosed with or treated for another malignancy within 2 years before the first dose of study drug, or previously diagnosed with another malignancy and have any evidence of residual disease. 13. Other severe acute or chronic medical or psychiatric condition(s) per protocol. 14. History of myocardial infarction, unstable symptomatic ischemic heart disease, uncontrolled hypertension despite appropriate medical therapy, any ongoing cardiac arrhythmias of Grade \> 2, thromboembolic events (eg, deep vein thrombosis, pulmonary embolism, or symptomatic cerebrovascular events), or any other cardiac condition (eg, pericardial effusion or restrictive cardiomyopathy) within 6 months before receiving the first dose of study drug. 15. Known history of human immunodeficiency virus (HIV) infection, hepatitis B or hepatitis C. 16. Surgery within 3 weeks (or 2 weeks for a minor surgery) before study enrollment and not fully recovered to baseline or to a stable clinical status. 17. Participants who are pregnant, lactating, or do not agree to use effective methods of contraception during the study treatment period through 6 months after the last dose of study drug per protocol.