Excelsior Sciences

Excelsior Sciences is a New York-based company developing a form of small-molecule chemistry designed to be executed by machines and used by AI systems. Its platform is built on "smart bloccs" — automated synthesis-friendly, function-infused chemical building blocks that permit iterative carbon–carbon bond formation. Molecules are assembled by repeatedly snapping carbon–carbon bonds together, in a manner the company compares to sequential assembly of peptides or DNA. The bloccs are treated as tokens in a modular chemical "language," forming the basis of a chemistry language model in which AI can combine building blocks to predict compound properties and propose candidates.

The company couples this chemistry with closed-loop learning and closed-loop discovery workflows: AI-guided automated synthesis and testing intended either to reduce uncertainty in foundation models predicting molecular properties such as solubility, permeability, toxicity and metabolism, or to optimize toward molecules with multiple targeted functional properties. Synthesis, purification and biological testing are co-located in one facility; the company reports running approximately 20 biological assays with daily controls, and describes making molecules and testing them roughly 40 feet away. Its technology begins from about 2,000 FDA-approved small-molecule drugs, which are decomposed into smart bloccs used as building blocks for new molecules — an approach management contrasts with generative-AI methods that enumerate large numbers of novel compounds.

Excelsior is developing its own proprietary therapeutic pipeline while also collaborating with partners in pharmaceuticals, materials science and agtech. The company positions the same modular process for both discovery and scale-up, from first milligrams to kilogram-level production, and frames domestic automated production as a means of reshoring US drug discovery and manufacturing.

Founding story

Michael Foley and Jana Jensen first worked together at Deerfield Discovery & Development, Deerfield's in-house R&D engine. During the COVID-19 pandemic they observed research shutting down globally and supply chains being disrupted, reinforcing Foley's view that chemistry's practice remained dependent on skilled human presence in laboratories, and prompting a focus on onshoring. Deerfield's company-building relationship with Marty Burke, whose University of Illinois lab discovered and patented the insights behind smart blocc technology, produced the idea that sparked the company. Foley and Jensen cofounded Excelsior in 2024 with Burke and other chemists and incubated it in Deerfield's research space, Cure, on Park Avenue in Manhattan. Foley previously founded three biotech companies and headed chemical biology research at the Broad Institute of MIT and Harvard; Jensen previously worked at Bristol Myers Squibb, Merck & Co. and Pfizer.

Business model

Excelsior develops an internal proprietary therapeutic pipeline while partnering with companies across sectors where small molecules matter, including pharmaceuticals, materials science and agtech. Management states it expects to generate most of its revenue by creating advanced leads in collaboration with drug and biotech companies that would otherwise send that work offshore, and it invites organizations, institutions and researchers to register interest in partnering.

The company expects most revenue to come from generating advanced leads for pharmaceutical and biotech partners, alongside value from its own internal pipeline and partnerships across industry sectors.

Traction

The company reports operating roughly 20 biological assays with daily controls, an automated synthesis and assay laboratory at Cure, and a team spanning chemistry, automation engineering, informatics, biology and ADME functions, supplemented by Deerfield personnel. As of the December 2025 C&EN report, its research team included one chemist with a second being hired. Investors and participants include Deerfield Management, Khosla Ventures, Sofinnova Partners, New York's Empire State Development, Cornucopian Capital, Eli Lilly and Company, Illinois Ventures and MIT. Named scientific publications underpin the platform.

Latest developments

On December 3, 2025 Excelsior announced $95 million in total financing — a $70 million Series A co-led by Deerfield Management, Khosla Ventures and Sofinnova Partners plus a $25 million Empire State Development grant — and unveiled its partners, with proceeds directed to scaling the smart bloccs platform, its internal pipeline and cross-sector partnerships. Board additions accompanying the financing include Nessan Bermingham (Khosla Ventures), Jim Flynn (Deerfield) and Edward Kliphuis (Sofinnova Partners). The company is recruiting for drug discovery automation and research informatics software engineering roles in New York.