San Carlos, California-based TwoStep Therapeutics has raised USD 62.5 million in an oversubscribed Series A financing round, coinciding with US FDA clearance of an investigational new drug application for TS-104, its lead multi-specific peptide-drug conjugate targeting solid tumors. The IND clearance positions the company to initiate a first-in-human Phase I trial, with patient enrollment expected before year-end.
The round was co-led by Insight Partners, Medical Excellence Capital, M Ventures — the corporate venture arm of Germany-based Merck KGaA — and Pfizer Ventures, with existing investors NFX and 2048 Ventures also participating. Stanford University joined as an additional investor, reflecting its institutional connection to the science underlying the company. TwoStep said proceeds will fund the Phase I trial of TS-104, advance a radioligand therapy program, and support expansion into next-generation peptide conjugates. The Series A brings total capital raised to USD 71.2 million.
TwoStep was founded in 2024 by Caitlyn Miller, who serves as chief executive officer, alongside three Stanford faculty members: Jennifer Cochran, Nobel laureate Carolyn Bertozzi, and Ronald Levy.
The company's platform centers on a polyspecific integrin-binding peptide (PIP), a small synthetic molecule designed to engage five tumor-associated integrins simultaneously. Because most solid tumors express integrins heterogeneously — and single-antigen targeting approaches can miss target-low or target-negative cell populations — TwoStep's multi-target design is intended to broaden tumor recognition across diverse patient populations. TS-104 pairs PIP with MMAE, a cytotoxic payload with established clinical precedent in antibody-drug conjugates. Beyond TS-104, the company is developing a radioligand therapy program using the same PIP scaffold with a different therapeutic payload.
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