TwoStep Therapeutics Raises $62.5M Series A as FDA Clears TS-104
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TwoStep Therapeutics has closed an oversubscribed $62.5 million Series A to carry its lead peptide-drug conjugate, TS-104, into the clinic as a treatment for solid tumors. The biotechnology company is based in Palo Alto, California, and announced the round on September 9, 2026.
Insight Partners and Medical Excellence Capital led the financing. Pfizer Ventures and M Ventures, the corporate venture arm of Merck KGaA, joined as co-lead investors. Earlier backers NFX and 2048 Ventures returned, and Stanford University, where the company’s core science originated before TwoStep launched in 2024, also took part. Total capital raised now stands at $71.2 million.
Alongside the funding, the US Food and Drug Administration cleared TwoStep’s investigational new drug application for TS-104. That clearance allows a first-in-human Phase 1 study, with patient enrollment expected to start later this year. The trial will be the first clinical test of the multi-specific targeting approach at the core of the company’s platform.
Most existing tumor-targeted therapies depend on a single cell-surface target, which may not be present uniformly across all patients or all tumor cells. TwoStep’s approach uses a polyspecific integrin-binding peptide, or PIP, designed to bind five tumor-associated integrins found across a range of solid tumors. TS-104 links that peptide to monomethyl auristatin E, a cytotoxic payload.
With the raise, TwoStep added four directors to its board: Matias Porras Paniagua, vice president at Insight Partners; John Prufeta, CEO of Medical Excellence Capital; Oliver Lyth, biotechnology investment associate at M Ventures; and Rana Al-Hallaq, head of operations at Pfizer Ventures. Co-founder and CEO Caitlyn Miller and NFX general partner Omri Amirav-Drory remain on the board.
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