The STARLYS trial is an adaptive, modular, Phase 1, open-label, multi-part, clinical trial evaluating MST-0312 in selected solid tumors. MST-0312 is a targeted bispecific antibody that is designed to locally stimulate the lymphotoxin beta receptor (LTBR) in order to boost the body's immune response to cancer. The LTBR pathway is important in forming tertiary lymphoid structures and high endothelial venules in tumors, which have been associated with improved patient outcomes. The purpose of this study is to determine the safety and tolerability, pharmacodynamics, pharmacokinetics and anti-tumor activity of MST-0312 in subjects with solid malignancies (initially non-small cell lung cancer (NSCLC), melanoma, bladder cancer, colorectal cancer (CRC) and triple negative breast cancer (TNBC)) when administered either as monotherapy or in combination with anti-cancer treatments (initially pembrolizumab). The STARLYS trial is the first time MST-0312 has been administered to humans.

Inclusion Criteria:

• Male and female subjects of any ethnic origin, aged 18 years and over.
• Must have given written informed consent and must be able to understand the full nature and purpose of the trial, including possible risks and adverse effects.
• Subject must have a solid malignancy (non-small cell lung cancer (NSCLC), melanoma, bladder cancer, colorectal cancer (CRC) and triple negative breast cancer (TNBC)).
• An ECOG performance status of 0 or 1 with no deterioration over the previous two weeks.
• Willing to permit access to stored historical tumour tissue and prior tumour radiological assessments, cancer treatment history, including response to treatment, and tumour biomarker data, where available.
• Willing and able to comply with all scheduled visits, treatment plans, laboratory tests, and other trial procedures.

Exclusion Criteria:

• Any unresolved toxicity (except alopecia) from prior therapy of ≥2 CTCAE Grade.
• Active or documented history of autoimmune disease requiring interventional therapy.
• Active infection requiring systemic antibiotic, antifungal, or antiviral medication within 14 days prior to first dose of IMP.
• Male or female subjects of childbearing potential unwilling to comply with contraception requirements.