A $62.5 million Series A lands in the 95th percentile of every U.S. health-care Series A round on record. TwoStep Therapeutics closed that round on September 9. The same morning, the FDA cleared its lead drug for human testing.
Pfizer Ventures and Merck KGaA's M Ventures co-led the round, a signal that large pharma wants delivery chemistry, not another antibody.
The FDA clearance moves TS-104 into a first-in-human Phase 1 this year. For solid tumors, that is where the difficult questions begin.
Precision oncology has a delivery problem. Capital is moving toward whoever solves it.
The delivery wall that stopped precision oncology
Targeted cancer drugs work best when a tumor wears one clear marker on its surface. Blood cancers often oblige. Solid tumors rarely do.
An antibody-drug conjugate (ADC) is the standard answer: an antibody that recognizes one antigen and carries a toxic payload. When the antigen sits on every cancer cell, the logic holds. When it appears on a third of them, the drug misses the rest.
The company came at the delivery problem from the chemistry side. Its platform rests on a polyspecific integrin-binding peptide, or PIP, a synthetic molecule engineered to bind several tumor-associated integrins simultaneously. The company launched in June 2024 from Stanford's Innovative Medicines Accelerator, with a $6.5 million seed round led by NFX.
Solid tumors account for roughly 90% of all cancers, and most lack the clean surface target an antibody needs. That gap is the market TwoStep is selling into.
Oversubscribed Series A, September 2026
Led by Insight Partners and Medical Excellence Capital, with Pfizer Ventures and Merck KGaA's M Ventures as co-lead investors. · Company release, 2026
The number reads large against a subdued financing market, which is the point. It raised a round sized for a platform, not a single program.
One peptide, five targets
TS-104 is the company's lead multi-specific peptide-drug conjugate. It uses PIP to bind five tumor-associated integrins that appear across a range of solid tumors, then delivers a payload to whatever it latches onto. The company calls the targeting agent modality-agnostic, meaning the same delivery vehicle can carry different payload types.
| Parameter | Antibody-drug conjugate | TwoStep's peptide conjugate |
|---|---|---|
| Targeting | One antigen, high uniform expression | Five tumor-associated integrins |
| Payload | Typically a cytotoxic drug | Modality-agnostic; cytotoxic, radioligand, immuno |
| Solid-tumor reach | Limited to high-marker subsets | Broad targeting across solid tumors |
| Stage | Approved products on market | Phase 1, first-in-human |
The design trades specificity for reach. A single antibody hits one antigen; the peptide accepts several. That widens the number of tumors it can address. It also raises the question Phase 1 exists to answer: whether hitting five targets at once stays tolerable in a human body.
The founders' edge, and the caveat it carries
Its scientific founding team is unusually credentialed. Jennifer Cochran, a Stanford bioengineering professor, developed the PIP molecule in her lab. Ronald Levy is a pioneer of monoclonal antibody therapy. Carolyn Bertozzi shared the 2022 Nobel Prize in Chemistry for bioorthogonal chemistry and is one of the most cited researchers in antibody-drug conjugate science. Caitlyn Miller, the chief executive, co-founded the company with them.
Pedigree lowers the cost of the first check. It does not shorten a clinical trial, and readers of this beat have learned to separate the two. As we wrote in September, the first RAS-targeted pancreatic cancer drug changed the math for a hard tumor type, but it did so after years of failures from better-funded teams.
This financing, together with FDA clearance of the IND, marks an important inflection point for TwoStep and positions us to advance TS-104, our lead peptide-drug conjugate, through Phase 1 clinical development in oncology.— Caitlyn Miller, PhD, Co-Founder and CEO, TwoStep Therapeutics
What the FDA clearance actually clears
An investigational new drug (IND) clearance lets a company dose humans for the first time. The clearance opens a trial. It does not show the drug works. The company expects patient enrollment to begin later this year.
The round and the clearance arrived together, which shapes how the company gets read. Dealroom places the $62.5 million in the 95th percentile of U.S. health-care Series A rounds on its books, across 5,904 deals. That puts the financing in the top 5% of a tightly tracked cohort.
Who wrote the check, and why it matters
Delivery is that problem. Antibody-drug conjugates have become one of the most contested formats in oncology, with a crowded top of the market and a thin middle where the biology is hardest. The unmet need sits in solid tumors whose markers appear inconsistently, the exact cases a single-antigen antibody handles poorly.
TwoStep's answer is to stop requiring a perfect target. Buy reach with a peptide that accepts several, and let the payload do the rest. Whether that trade produces a tolerable drug is a clinical question, and the $62.5 million buys the company the time to ask it.
Will peptide conjugates reach patients faster than ADCs did?
Probability: 55% — the platform is preclinical, solid-tumor delivery is unproven in humans, and early-phase oncology timelines rarely compress.
✅ Arguments for
A modality-agnostic platform can advance a radioligand program in parallel, widening the pipeline without a second targeting discovery effort.
Confirmation criteria: enrollment opens this year and a first patient is dosed without an early safety stop.
❌ Arguments against
The company has no human data. A $62.5 million round funds a first trial, not a registrational one.
Disconfirmation criteria: dose-limiting toxicity in the first cohort, or enrollment that slips past the stated window.
Development scenarios
🟢 Optimistic scenario (25%)
Implications: A validated delivery platform lifts the value of every payload attached to it.
🟡 Base-case scenario (55%)
Implications: The platform story survives; the timeline stretches by a year or more.
🔴 Pessimistic scenario (20%)
Implications: A multi-target peptide that cannot spare normal tissue is a delivery problem, not a solution.
Phase 1 enrollment opening on the stated timeline
First reported dose-limiting toxicity rate
Whether the radioligand program advances on its own milestones
Follow-on capital from the same corporate venture backers
TwoStep is one test of a larger idea: that in oncology, delivery now matters as much as the payload. The next twelve months will show whether that idea survives contact with a human trial.
