This is a two part study to investigate the safety and anti-tumour effects of standard chemotherapy, plus an investigational drug (CDP791), in patients with advanced non small cell lung cancer.

In part one, patients receive carboplatin and paclitaxel chemotherapy together with one of 2 doses of CDP791. The main aim of this part is to investigate safety and tolerability of carboplatin/paclitaxel plus CDP791.

If part one confirms that the combination of drugs is safe and well tolerated, 156 patients will enter part 2. They will be randomized to receive either carboplatin/paclitaxel (C/P) alone, or C/P plus one of 2 doses of CDP791. The main aim of this part of the study is to compare the anti-tumor effects of CDP791 plus C/T with those of C/T alone. Participants will receive up to six cycles of chemotherapy with or without CDP791. Those whose disease stabilizes, or responds, will be eligible to continue to receive CDP791. Participants in the C/T alone arm whose disease progresses will be eligible to receive CDP791 monotherapy.

Participants will be followed up longterm, so that survival can be measured.

Inclusion Criteria:

• Male and female subjects with Stage IIIb (with malignant pleural effusion), Stage IV, or recurrent non-squamous, non-small-cell lung carcinoma.
• The subject must be aged 18 years or above.
• The subject must have ECOG performance status of 0 or 1 and a life expectancy of at least three months.
• Subjects will have measurable disease.
• The subject must be able to understand the information provided to them and to give written informed consent.
• Female subjects must be either postmenopausal, surgically sterilized, or using a method of contraception judged reliable by the Investigator.
• Male subjects must be using a method of contraception judged reliable by the Investigator.

Exclusion Criteria:

• Subjects with squamous cell lung carcinoma.
• Subjects with lung lesions located centrally in the chest that involve major blood vessels.
• Concurrent active malignancy other than nonmelanoma skin cancer or carcinoma in situ of the cervix. Subjects with previous malignancies are eligible provided that they have been disease free for five years or more.
• Presence of additional major chronic disease such as hepatic or renal dysfunction, cardiac dysfunction, peripheral vascular disease, evidence of a myocardial infarction within six months of Screening visit, tuberculosis or epilepsy.
• Subjects known to be infected with hepatitis B or C virus or HIV 1 or 2.
• Any evidence of serious active infection (ie requiring an iv antibiotic or antiviral agent).