Sutter Hill leads $55m Series A for physics and AI drug designer Fathom Therapeutics

Fathom Therapeutics, a small-molecule drug design company, has closed an oversubscribed $55 million Series A led by Sutter Hill Ventures, with Kos Biotechnology Partners announcing its participation on 6 November 2026¹.

The round and the platform

Kos invested through Kos BioVentures, its first life sciences fund. The firm is based in New York and Athens, manages $125 million in assets and positions itself as a bridge between US and European biopharma¹. The release says other investors joined Sutter Hill in the round but does not name them or give the size of individual cheques¹.

Fathom's product is a proprietary platform called Microcosmos. It pairs physics-based molecular simulation and quantum chemistry with AI to predict, at atomic resolution, how proteins move and how drug molecules bind to them¹. The company intends to use the platform on its own small-molecule pipeline and in strategic partnerships, both of which Kos says it will support as Fathom scales¹.

The founding team is the main asset on offer. Chief executive Huafeng Xu co-founded the company with chief technology officer Yujie Wu and chief computational scientist Jesús Izaguirre. Kos describes the group as including the scientists behind the Anton supercomputer and computational methods for predicting protein-drug interactions that are now widely used¹.

What it means for the market

The round adds to the capital flowing into computational chemistry companies that pitch physics-based simulation alongside machine learning rather than relying on learned models alone. Kos frames the bet in terms of targets that have been out of reach: Alex Tzoukas, Kos co-founder and managing partner, said "differentiated technologies that improve drug discovery productivity and address previously inaccessible targets can create significant value for patients and investors alike"¹. His fellow co-founder Simos Simeonidis pointed to targets "historically been considered undruggable" as the area of greatest potential¹.

For pharma companies shopping for discovery partners, Fathom is one more platform company with a pipeline of its own and an appetite for alliances, a model that tends to set the terms of later licensing talks. For investors, the presence of a Greek-American fund in a round led by a Silicon Valley firm is a small sign of European specialist money following US AI drug discovery deals. Kos has also described its strategy as backing tech-enabled pharma services and globally competitive biopharma businesses¹.

Caveats

The announcement comes from an investor rather than from Fathom, and it gives no valuation, no named programmes, no disease areas and no partners. Kos says the platform has "already demonstrated compelling early results", but the release offers no data to judge them by¹. Until Fathom names its first programmes or a pharma partner, the round is a bet on the team and the method rather than on assets.