Anlotinib hydrochloride is a multi-targeted receptor tyrosine kinase inhibitor that targets angiogenesis-related kinases such as VEGFR1/2/3, FGFR1/2/3, and other tumor-associated kinases involved in cell proliferation such as PDGFRα/β, c-Kit, and Ret have significant inhibitory activities.

Inclusion Criteria:

1. Small cell lung cancer patients.
2. The clinical stage at baseline is extensive.
3. A measurable lesion.
4. Disease progression.
5. ≥ 18 years old; Eastern Cooperative Oncology Group (ECOG) performance status of 0 to 1; Life expectancy ≥ 3 months.
6. Adequate laboratory indicators.
7. No pregnant or breastfeeding women, and a negative pregnancy test.
8. Understood and signed an informed consent form.

Exclusion Criteria:

1. Has used topotecan and anlotinib hydrochloride capsules.
2. Has used other anti-angiogenic drugs and immunologically targeted drugs.
3. Has other malignant tumors within 5 years.
4. Symptomatic brain metastasis.
5. Has a variety of factors affecting oral medications.
6. Uncontrolled pleural effusion, pericardial effusion or ascites requiring repeated drainage.
7. Spinal cord compression.
8. Has received radiotherapy, chemotherapy, surgery less than 4 weeks before randomization.
9. Adverse events caused by previous treatment did not recover to grade 1.
10. Has received major surgical treatment within 4 weeks before randomization.
11. Arteriovenous thrombosis occurred within 6 months.
12. Has drug abuse history that unable to abstain from or mental disorders.
13. Has severe or uncontrolled disease.
14. Participated in other clinical trials within 4 weeks.
15. Tumor invades the large blood vessels.
16. Daily hemoptysis ≥2.5 mL within 1 month before the first dose.
17. According to the investigators' judgement.