Tom Willis

Tom Willis wasn't trained to be a biologist. He studied physics at Yale, then took his PhD in physics at Stanford. But he ended up at the Stanford Genome Technology Center right as the Human Genome Project was cranking into full gear - and that accident of geography changed what the words "cancer diagnosis" might eventually mean.

At Stanford's Genome Technology Center, Willis didn't just work on sequencing. He co-invented Molecular Inversion Probe technology - a method for high-throughput genotyping that would eventually anchor his first company. Most researchers in that era were racing to read the genome. Willis was already thinking about how to read it efficiently, at scale, for diagnostic purposes.

In 2001 he co-founded ParAllele BioScience to commercialize MIP technology. By 2005 Affymetrix had acquired it. It was a clean exit for a first-time founder who had gone from a physics PhD to a biotech acquisition without detours. Most people would have taken the next venture fund meeting. Willis went back to the lab problem.

The next company - Sequenta, founded 2008 - tackled a different question: how do you measure the immune system's response to cancer, precisely enough to tell whether residual disease remains after treatment? The answer was a sequencing-based platform for immune repertoire assessment. The lead product became ClonoSEQ, a diagnostic test for minimal residual disease in leukemia and lymphoma. By the time Sequenta merged with Adaptive Biotechnologies in 2015, ClonoSEQ had become the NCCN-endorsed standard of care - the test oncologists reach for when they need to know whether leukemia is truly gone or merely hiding.

After Sequenta, Willis didn't start another company. He went to Illumina Ventures as a partner - specifically to understand the genomics landscape from the capital side, evaluating investments in medical tools and diagnostics. He sat on boards at Cernostics, Rebus Biosystems, and SonoThera. For roughly ten years, he saw every pitch deck, every promising platform, every technology that claimed to be the next inflection point in genomics.

That decade of observation is why the Arima story is unusual. Willis didn't leave Illumina Ventures to start something new. He left to run a company he had already been watching from the inside - one he concluded, after reviewing the field systematically, did something no other platform could replicate. That is a different kind of career decision than most founder-CEO transitions.

Willis describes Arima's core insight in terms that physicists recognize immediately: conventional DNA sequencing extracts the molecule from the cell nucleus and sequences it after the structure has been destroyed. All the spatial information - which segments of DNA were physically adjacent to which other segments inside the nucleus - is lost. Arima's Hi-C technology preserves proximity ligation data before sequencing. The result is a map of not just what the DNA says, but how it was folded and organized. Willis puts it plainly: "DNA in cells is packed into a really dense spaghetti ball. We retained index information about which pieces were next to others."

Arima Genomics was already a serious scientific enterprise before Willis arrived. The founder, Sid Selvaraj - now COO - built the underlying Hi-C platform on a body of work that by 2025 comprised more than 1,500 peer-reviewed academic publications. The technology had proven itself at the bench. The transition Willis was brought in to manage is the harder one: from validated research platform to clinical diagnostic tool used across hospitals and cancer centers.

The case study that Willis returns to repeatedly happened in 2022, before he joined. A teenage glioblastoma patient had been through exhaustive DNA and RNA profiling - standard workup, multiple rounds. Nothing actionable found. Arima's 3D genomic assay identified an actionable cancer driver that all prior testing had missed. The patient received matched therapy. Willis uses that case not as marketing but as orientation: it defines the problem he came to solve at scale.

Willis estimates roughly 30,000 cancer patients annually could benefit from Arima's approach - patients whose tumors harbor large-scale structural DNA changes, chromosomal translocations, or gene fusions that current sequencing cannot reliably detect. His commercial strategy involves both research use and clinical adoption, with an eye toward replacing traditional FISH-based tests for fusions and rearrangements in specific cancer subtypes. The Aventa Lymphoma test is the first clinical-stage product moving along that trajectory.

The $22 million Series C that coincided with Willis's appointment in June 2025 was led by Illumina Ventures - the firm where he had spent the previous decade. The partnership with Fox Chase Cancer Center, announced subsequently, advances the clinical validation needed for broader diagnostic adoption. Willis is building, again, from the scientific edge toward clinical standard of care - the arc he ran at Sequenta, now with more clinical infrastructure already in place.

Arima Genomics has raised $29M in total funding. The latest $22M Series C, closed in June 2025 alongside Willis's appointment as CEO, was led by Illumina Ventures. The prior rounds established the scientific platform; the Series C is explicitly aimed at commercial growth and clinical adoption.