Marengo Therapeutics’ invikafusp alfa (STAR0602) received expanded FDA Fast Track designation across TMB-H solid tumors, including patients whose disease progressed after prior therapy such as checkpoint inhibition. The agency’s action positions the drug as a biomarker-selected, tissue-agnostic immuno-oncology option. The company previously reported Phase 1/2 START-001 data presented at ESMO 2025, showing an objective response rate of 20.5% and disease control rate of 79.5% in TMB-H tumors. Subgroup results were also reported in gastrointestinal cancers and metastatic colorectal cancer within the TMB-H category. Marengo framed the update as support for its strategy to use invikafusp alfa as a backbone for combination regimens, leveraging the Fast Track timeline to accelerate development. In START-001, Phase 1 enrollment targets TMB-H, MSI-H/dMMR and virally associated tumors, while Phase 2 is restricted to TMB-H and MSI-H/dMMR disease. The expansion matters for developers targeting advanced solid tumors by biomarker rather than tissue origin, because Fast Track status can affect trial design cadence and the level of early regulatory interaction.