He started in a microbiology lab, detoured through patent law, and came back to run a drug company. Today David Earp is betting a clinical-stage biotech on the idea that cancer's so-called undruggable targets were only ever waiting for the right molecule.
Walk into Circle Pharma's offices at 681 Gateway Boulevard in South San Francisco and you'll find a 67-person company doing something most of the pharmaceutical industry decided was impossible. They are trying to drug cyclins - the proteins that act as the cell's internal clock, telling cancer when to divide. Block the clock and the tumor stalls. For decades the field treated these targets as off-limits.
David Earp runs the place. He has since October 2013, which in biotech years is close to forever. Most chief executives arrive after the science is proven and leave before the hard part. Earp did the opposite: he showed up when Circle was a platform and a promise, and stayed through the decade it took to put a molecule into a human being.
That molecule is CID-078, an oral macrocycle that directly inhibits cyclins A and B. In October 2024 the first patients with advanced solid tumors swallowed it. The same month, Boehringer Ingelheim signed a collaboration worth up to $607 million to chase a related target. A few weeks earlier, Circle had closed a $90 million Series D. For a quiet company, it was a loud autumn.
What makes Earp unusual is not the title. It is the route he took to it. He holds a PhD in biochemistry from Cambridge and a law degree, magna cum laude, from Lewis & Clark. He spent years as a patent attorney - the person who writes and defends the intellectual property that biotech is built on - before crossing the table to build the companies themselves.
Most people pick a lane. Earp collected three of them, then kept the most useful instincts from each. The scientist learns to read the data. The lawyer learns to read the deal. The CEO has to do both before lunch.
A B.Sc. in microbiology with first class honours from Leeds, then a PhD in biochemistry and molecular biology from the University of Cambridge. The lab credentials that let him interrogate his own pipeline.
A JD, magna cum laude, from Lewis & Clark. Partner at the IP firm Klarquist Sparkman in Portland. Then chief patent counsel and chief legal officer at Geron, building a broad portfolio and steering licensing deals.
At Geron he spun out nuclear-transfer technology into StART Licensing, chaired Viagen, and sold it to TransOva Genetics. Since 2013, the chief executive turning Circle Pharma's platform into clinical drugs.
Small drugs slip into cells easily but cannot grip large, flat targets. Big biologic drugs grip well but cannot get inside. Macrocycles - large ring-shaped molecules - try to have it both ways. Circle's MXMO platform engineers them to be cell-permeable and even orally available. Here is the logic in four moves.
Cyclins A and B drive the cell cycle. In cancer, that engine runs without brakes - but the targets are large and historically undruggable.
Structure-based rational design plus advanced synthetic chemistry shape macrocycles that fit the difficult binding surfaces.
The macrocycles are intrinsically cell-permeable, so they reach targets inside the cell - and can be delivered orally.
CID-078, a first-and-only-in-class oral cyclin A/B RxL inhibitor, is now in a Phase 1 trial for advanced solid tumors.
He holds a PhD from Cambridge and a JD earned magna cum laude. One person, two professions that rarely share a business card.
Before running a drug company, he wrote and litigated the patents that protect them - as a partner at an IP law firm.
At Geron he helped spin out and later sell a nuclear-transfer (cloning) business, navigating one of biotech's more controversial technologies.
His undergraduate degree is in microbiology from Leeds, earned with first class honours - the science came first, the law second.
Circle Pharma's name nods to the macrocycle - the ring-shaped molecule at the center of everything the company makes.
The 2024 Series D was led by The Column Group, with Nextech Invest and Euclidean Capital joining the syndicate.