This is a Phase II research study that is designed for patients who have small cell lung cancer (SCLC) that is no longer responding to treatment. Patients will receive picoplatin, a new platinum-based agent that is currently under investigation, in 21-day cycles.

Platinum drugs work by binding to DNA and preventing the rapid cell division of tumors. However, many tumors demonstrate a resistance to platinum drugs. Results from preclinical studies indicate that picoplatin (previously called AMD473 or ZD0473) may be able to overcome or partially overcome platinum resistance. More than 500 patients have received picoplatin in previous Phase I or Phase II clinical trials.

Main inclusion criteria:

1. Diagnosis of small cell lung cancer.
2. Patients must have had one prior chemotherapy regimen which must have included either cisplatin or carboplatin.

[Additional eligibility criteria apply.]

Exclusion Criteria:

• Prior radiotherapy that included > 30% of the bone marrow (i.e., the whole of the pelvis or half of the spine).
• Significant chronic or recent acute gastrointestinal disorder with diarrhea as a major symptom.
• Significant heart disease.
• Uncontrolled, untreated, unstable, or symptomatic brain tumors or central nervous system disease.
• Grade 2+ peripheral neuropathy (a condition caused by damage to the nerves in the peripheral nervous system).

[Additional exclusion criteria apply.]