What is the Phase 1 STARLYS trial?

Information for participants. Last reviewed: October 9, 2026.

The STARLYS trial is an early-stage, first-in-human (Phase 1) clinical trial evaluating an investigational experimental medicine called MST-0312 in adults with advanced solid tumors. During the trial, researchers will look to learn more about the safety, tolerability, and preliminary anti-tumor activity of MST-0312.

The science behind MST-0312

Cancer cells often evade detection by our natural defense mechanism, the immune system. However, the immune system can be very effective at fighting cancer when activated and directed in the right way.

The goal of treatment with MST-0312, an antibody (a type of protein-based therapeutic), is to activate the immune system at the tumor. MST-0312 is designed to promote the formation of specialized structures comprised of immune cells in tumors; these structures are called Tertiary Lymphoid Structures (TLS).

What are TLS?

TLS are specialized, organized groups of immune cells (including T cells, B cells, and dendritic cells) that can naturally form inside tumor tissue, as part of immune defenses. Researchers believe that immune cells in TLS in tumors may organize to recognize and target cancer cells. Specialized changes to blood vessels serve as entry points, helping immune cells travel directly into the tumor. For more information see our science page here.

Tertiary Lymphoid Structure in Pancreatic Adeno Carcinoma (PDAC) Vanhersecke Nature Cancer 2021

What the Scientific Literature Says:

Published medical research indicates that the natural presence of TLS in solid tumors is correlated with improved treatment response and extended overall survival in cancer patients. See References

Objectives of the STARLYS Study

The STARLYS study is an open-label, adaptive Phase 1 study. Its primary goals are to:

Evaluate Safety and Tolerability: Determine the MST-0312’s safety profile, monitor potential side effects, and identify a safe and appropriate dose for future studies
Study Pharmacokinetics and Pharmacodynamics (PK/PD): Measure how MST-0312 is absorbed, processed, and cleared by the body (PK), as well as its biological effects on the body and tumor tissue (PD), e.g. TLS formation within the tumor
Observe Early Clinical Activity: Assess potential preliminary anti-tumor activity when MST-0312 is administered alone (monotherapy) and in combination with an approved immunotherapy (pembrolizumab / Keytruda®)

Target Study Population

The STARLYS trial will initially enroll participants with cancers of the lung, gut, bladder, breast, and skin.

For further details

Please see our Clinical Trial Registration: NCT07610941

Important Regulatory & Medical Notice:

MST-0312 is an investigational agent currently under clinical evaluation and is not approved by the U.S. Food and Drug Administration (FDA), the European Medicines Agency (EMA), the UK Medicines and Healthcare products Regulatory Agency (MHRA), or any other regulatory body. Observations from clinical literature regarding TLS and survival relate to general medical scientific research and do not imply or establish that MST-0312 will provide therapeutic benefit or improve survival outcomes.

This page is provided solely for general informational purposes and does not constitute medical advice, a therapeutic endorsement, or an offer/invitation to participate in a clinical trial. People seeking information about treatment options or clinical trial participation should consult with their physician or qualified medical care team.