Function first. Chemistry second.
In January 2025 a small San Diego company stepped out of stealth with a name borrowed from cavalry and a thesis borrowed from contrarians. Light Horse Therapeutics launched with $62 million in Series A money and, on the same day, a Novartis collaboration that could be worth up to a billion dollars. At the front of it was Markus Renschler, a board-certified medical oncologist who has spent his career doing the unglamorous, decade-long work of turning molecules into medicine.
Most drug discovery starts with chemistry and hopes. You screen libraries against a protein, you wait, you pray something sticks. Light Horse runs the film backwards. Its "function-first" platform uses precision genetic editing to interrogate proteins inside living cells, mapping the functional sites that actually drive disease before anyone goes looking for a molecule to hit them. Find what the protein does. Then build the key. The targets it goes after are the ones the industry had quietly filed under "historically challenging" - a polite term for undruggable.
That is the kind of bet you make only if you have the patience to see it through, and Renschler's resume is a study in patience. He has touched cancer drugs at every stage there is: basic laboratory research, clinical trials, regulatory approval, and the commercial launch at the end. Few biotech CEOs can honestly claim the whole arc. He can.
Before Light Horse, he was president and CEO of Cyteir Therapeutics, which he carried from a private, discovery-stage idea all the way to a publicly traded clinical-stage company - the journey every founder talks about and few actually complete. Before that came the years that built the instinct: senior roles in clinical R&D, business development and medical affairs at Celgene, Pharmion and Pharmacyclics, where he helped develop and launch some of the most consequential cancer drugs of the era.
The list reads like a syllabus of modern oncology: lenalidomide and pomalidomide for blood cancers, nab-paclitaxel for solid tumors, azacitidine for the diseases in between. He directed successful global registrations across breast cancer, non-small cell lung cancer and pancreatic cancer. These are not slide-deck accomplishments. They are drugs that reached patients, in country after country, because someone managed the unsexy machinery of approval.
A vaccine for one person
Long before the term sheets, Renschler was a post-doctoral fellow in Ronald Levy's lab at Stanford - the lab that helped invent the antibody-based treatment of lymphoma. His work there was almost poetic in its specificity: patient-specific vaccines and antibody therapies for Non-Hodgkin lymphoma. Medicine tailored not to a population, but to a single immune system.
He kept a foot in the clinic far longer than most who cross into industry. As an adjunct clinical associate professor of medicine at Stanford, he taught and treated lymphoma patients through 2015, years into a career that could have pulled him entirely into boardrooms. The credentials underneath all of it are clean and unfashionably classical: a BA from Princeton, an MD from Stanford, and board certification in medical oncology.
So when Light Horse pairs three academic superstars - Ben Cravatt of Scripps, Nathanael Gray of Stanford, Brian Liau of Harvard - with one operator who has actually shipped drugs, the division of labor is obvious. The professors supply the science. Renschler supplies the part where science becomes a company.