Inclusion criteria:

1. Histologically or cytologically documented extensive disease. Brain metastases; must be asymptomatic or treated and stable off steroids and anti-convulsants for at least 1 month prior to study treatment.
2. Suitable to receive a platinum-based chemotherapy regimen as 1st line treatment.
3. Life expectancy ≥12 weeks at Day 1.
4. ECOG 0 or 1 at enrolment.
5. No prior exposure to immune-mediated therapy excluding therapeutic anticancer vaccines.

Exclusion criteria:

1. Any history of radiotherapy to the chest prior to systemic therapy or planned consolidation chest radiation therapy (except paliative care outside of the chest).
2. Paraneoplastic syndrome of autoimmune nature, requiring systemic treatment or clinical symptomatology suggesting worsening of PNS
3. Active infection including tuberculosis, HIV, hepatitis B anc C
4. Active or prior documented autoimmune or inflammatory disorders
5. Uncontrolled intercurrent illness, including but not limited to interstitial lung disease.