A Dose Finding and Expansion Study of RO7051790 Administered Orally in Participants With Relapsed, Extensive-Stage Disease Small Cell Lung Cancer (ED SCLC)

Inclusion Criteria:

* Life expectancy greater than or equal to (\>=) 12 weeks
* Participants must have histologically or cytologically confirmed diagnosis of SCLC
* Participants must have recurrent or refractory disease after receiving at least one prior platinum-containing chemotherapy regimen, or standard therapy is refused or not suitable. For participants in Canada: participants should also not be suitable for treatment with topotecan hydrochloride
* Acute toxicities from any prior treatment, surgery, or radiotherapy must be National Cancer Institute-Common Terminology Criteria for Adverse Events (NCI-CTCAE) version 4.03 Grade less than or equal to (\<=) 1
* Measureable disease per RECIST v1.1 prior to administration of study medication
* Eastern Cooperative Oncology Group (ECOG) performance status of 0 to 1
* Adequate bone marrow function
* Adequate renal function
* Participant must be able to swallow and retain orally administered study treatment
* Women of childbearing potential and men should agree to use an effective form of contraception and to continue its use for the duration of study treatment and for a period of time after the last dose of study treatment

Exclusion Criteria:

* Active malignancy other than SCLC within the previous 5 years
* Participants who have received radiotherapy less than 2 weeks prior to first dose of study medication
* Surgical procedure or clinically significant trauma within 2 weeks of first dose of study treatment
* Treatment with any investigational agent \<=3 weeks prior to first dose of study treatment
* Participants with gastrectomy or pre-existing gastrointestinal disorders that may interfere with the proper absorption of the drug(s), as per conclusion of the clinical Investigator
* Participants medicated with anti-depressants reported to have lysine-specific histone demethylase 1A (KDM1A)/lysine (K)-specific demethylase 1A (LSD1) inhibitory activity (such as tranylcypromine or phenelzine) within 28 days of treatment start
* History of allergic reactions attributed to components of the formulated product(s)
* History of seizure disorders
* Participants with untreated central nervous system metastases, or history of previously treated disease. Participants must have stable hematological parameters, satisfying eligibility, platelet count must be stable for \>=2 weeks prior to study drug administration
* Participants who have any severe and/or uncontrolled medical conditions or other conditions that could affect their participation in the study
* Participants with evidence of electrolyte imbalance
* Participants who are pregnant or breastfeeding
* Participants who refuse to potentially receive blood products and/or have a hypersensitivity to blood products
* Participants with known bone marrow disorders which may interfere with bone marrow recovery or participants with delayed recovery from prior chemoradiotherapy
* Participants with known coagulopathy, platelet disorder or history of non-drug-induced thrombocytopenia
* Hepatitis B virus (HBV), hepatitis C virus (HCV), or human immunodeficiency virus (HIV)-positive participants with active infection
* Use of strong Cytochrome P450 3A4 (CYP3A4) inducers while on study medication
* Participants with abnormal hepatic function
* Participants with history of clinically significant bleeding, specifically any history of intracranial hemorrhage/hemorrhagic cardiovascular accident (CVA), or participants with gastrointestinal bleeding within the 12 months prior to study entry
* Participants receiving therapeutic anti-coagulation or anti-platelet (anti-aggregant) therapies, except for therapeutic enoxaparin or low dose aspirin. Use of subcutaneous heparin prophylaxis, including low molecular weight heparin is also permitted