A Study of ASP2998 Given by Itself and Given With Standard Therapies in People With Solid Tumors

Specific proteins found in tumors help the tumors spread and grow. People with solid tumors often have a protein called TROP2 in their tumor. ASP2998 is being developed to attach to TROP2 and then attack the tumor cells in people with solid tumors. ASP2998 will either be given by itself, or given together with one or more of standard cancer treatments pembrolizumab, carboplatin, and enfortumab vedotin.

This is an early development study to collect information about ASP2998 in people with solid tumors. In this study ASP2998 will be given to humans for the first time. Early development studies are mostly about safety, but also to find the most suitable dose. Other aims are to check if ASP2998 shows signs of reducing tumor growth, to learn how the body processes ASP2998, and to check if there are changes either in the TROP2 protein or in the immune system.

The main aim of the study is to check the safety of ASP2998 when given by itself and given with the standard cancer treatments, and how well it is tolerated.

People in this study will be adults with locally advanced, unresectable or metastatic solid tumors. Locally advanced means the cancer has spread to nearby tissue. Unresectable means the cancer cannot be removed by surgery. Metastatic means the cancer has spread to other parts of the body. People's cancer came back or became worse after previous treatment or they couldn't receive treatment. Some people who had previously refused treatment may be able to take part. This will depend on which study treatment they receive.

People will either have cancer in the bladder lining (urothelial cancer), non-small cell lung cancer (NSCLC), gastric cancer or cancer where the food pipe joins the stomach (gastroesophageal cancer, or GEJ), or certain types of breast cancer.

People cannot take part if the cancer cells have spread to the thin tissue covering the brain and spinal cord (leptomeningeal disease), have symptoms of cancer in the brain or nervous system, or need medicines to suppress their immune system.

In this study, ASP2998 will be given to humans for the first time. ASP2998 will either be given by itself, or given together with one or more of standard cancer treatments pembrolizumab, carboplatin and enfortumab vedotin. The standard cancer treatment given will depend on which cancer people have.

The study will have 2 parts.

In Part 1, different small groups of people will receive lower to higher doses of ASP2998 given by itself or together with one or more of the standard cancer treatments. Any medical problems will be recorded for each dose. This is done to find suitable doses of ASP2998 to use in Part 2.

In Part 2, other different small groups will receive suitable doses of ASP2998 worked out from Part 1. ASP2998 will either be given by itself or given together with one or more of the standard cancer treatments. This part will also check how each type of cancer responds to ASP2998 when given by itself or together with the standard cancer treatments.

In both parts of the study, safety checks will be done at each visit, and the doctors will continue to check for medical problems throughout the study. ASP2998 will be given slowly through a tube into a vein (infusion). People will continue to receive ASP2998 until their cancer gets worse, they can't tolerate ASP2998, they start other cancer treatment, they or the doctor decides the person should stop receiving ASP2998.