In this study, people go through a screening period and testing to learn more about their cancer. Based on special features of the cancer, called biomarkers, they are placed into one of three groups. In each group, people are also placed by chance into one of two treatment options.

In all groups, one option is to receive a medicine called durvalumab. The other option is to receive durvalumab together with another medicine. The extra medicine depends on the group and may be saruparib, ceralasertib, or monalizumab.

The goal of the study is to see which treatment works best for different types of cancer based on their specific features.

This study is for people with extensive small cell lung cancer (ES-SCLC)

People can join this study if they are 18 years old or older and have a certain type of lung cancer called extensive stage small cell lung cancer. They must not have another cancer that could affect the study, and they must not have had an earlier stage of this lung cancer in the past.

Some people can join if they have not started treatment yet and plan to begin standard chemotherapy with a medicine called durvalumab. Others can join if they have already started this treatment and completed a few cycles. People cannot join if they have had certain types of immunotherapy before or if they are taking other cancer treatments at the same time.

The screening part of this study is used to learn more about each persons tumor. Doctors will test the tumor to see which type it is, called subtypes A, N, P, or I, and to check for a protein called SLFN11. These results are needed to decide if a person can join the treatment part of the study.

This screening also helps researchers learn if these tests can help doctors choose the best treatment for each patient based on the specific features of their cancer.