Aduro Biotech: The Fourth Company for a Berkeley Serial Entrepreneur
Company founded: 2007
Founder: Stephen Isaacs (UC Berkeley Bachelor of Arts, 1973, biochemistry, PhD, organic chemistry)
Stephen Isaacs graduated from UC Berkeley in 1973, with a biochemistry degree. He describes himself back then as a “long-haired, dope-smoking, Sproul Hall window-breaking Vietnam War protestor—sometimes in search of bail money.” After a two-year gig as one of the original street vendors on Telegraph Avenue, where he and his girlfriend (now wife of fifty-four years) had a terrarium business, Isaacs returned to the campus to work as a lab assistant in the chemistry department. There he serendipitously met chemistry professor John Hearst, who set Isaacs on his path of a life sciences serial entrepreneur and “semi-respectable public company CEO who has done some good things to make the world a better place.”1
In Hearst’s lab Isaacs worked on small molecules called psoralens. These compounds can prevent DNA and RNA from replicating, effectively “killing” the organism—be it a virus, a bacterium, a fungus, or a eucaryotic cell. Hearst tasked Isaacs with improving the reactivity of the psoralens by synthesizing new derivatives that “worked better”—that is, had higher reactivity with DNA and RNA. Isaacs came up with a superior psoralen. In 1976, Isaacs and his lab collaborators, including the PI, published their work in Biochemistry and received many requests for improved psoralens, which they distributed freely. Isaacs also developed methods to radiolabel the psoralens so they could be tracked. UC Berkeley obtained multiple patents on the compounds. The research was done in collaboration with well-known organic chemist and professor Henry Rapoport.
With ongoing requests for compounds and his business experience with terrariums, Isaacs realized that he “could sell these compounds, and we could start a little business.” In 1979, that led to Isaacs’s second business, HRI Associates, which stood for “Hearst, Rapoport, and Isaacs.” Isaacs found some space in a nearby abandoned building (with some very questionable tenants) that Shell Development Company had vacated. He licensed the psoralen patents from the university and managed to secure a radioactive materials license. His girlfriend helped him build a glove box to make custom-synthesized compounds with radioactive tags in specific positions that people would pay a lot of money for. HRI expanded to work with the National Cancer Institute and early biotech companies commercializing PCR (including biotech companies with UC Berkeley roots, such as Cetus and Chiron). However, like the terrariums, HRI’s business had limited potential.
In 1989, Isaacs started collaborating with UC San Francisco on the pressing issue of blood contaminated with HIV. They realized that UC Berkeley’s patented psoralen technology could kill viruses and bacteria in blood, making it safe for transfusion. That inspired the 1991 launch of the Cerus Corporation, Isaacs’s third company.
At the time Baxter was the major manufacturer of blood collection and transfusion equipment. The company was under siege from people getting infected with HIV and “non-A-non-B” hepatitis—now Hepatitis C. Baxter came to Cerus and established a collaboration that ultimately provided more than $100 million in revenues to Cerus. The company went public in 1997 as a Wall Street “darling” and reached a $2 billion valuation by 2000. However, Cerus’s business was complicated. It encountered many ups and downs. Nonetheless, as of 2025, Cerus’s Intercept Blood Systems is approved in some seventy-five countries and has saved countless lives by preventing transfusion-transmitted diseases.
Isaacs was Cerus’s founding CEO for fourteen years, until 2004. While at Cerus, Isaacs became intrigued with other emerging life science technologies, one of which was developed in the lab of UC Berkeley professor Daniel Portnoy. The technology used proteins typically found on the surface of cancer cells to activate an immune response using T-cells that kill cancer. That led to the 2007 launch of Aduro BioTech, Isaacs’s fourth company. Aduro licensed the technology from UC Berkeley and set out to use a bacterium called Listeria monocytogenes to deliver the proteins that would stimulate the anticancer response. Early success in late-stage pancreatic and other types of cancer generated lots of interest. Aduro launched numerous clinical trials and received several multimillion-dollar upfront payments from deals with companies such as Johnson & Johnson for lung and prostate cancer. Unfortunately, Aduro’s approach ultimately failed in late-stage trials.
At about the same time, Aduro was also conducting R&D in STING biology based on technology developed in the lab of UC Berkeley professor Russell Vance. Aduro licensed the patents from UC Berkeley. In 2015, the company’s improvements on the technology led to a $250 million upfront payment from Novartis and an initial public offering a month later with a $3 billion valuation. But, once again, despite all the initial glory and hope, in the end the technology didn’t work in late-stage clinical trials—which is an all-too-common outcome in biotech. In 2019, Aduro merged with Chinook Therapeutics, a company with complementary expertise. In 2023, Novartis bought the merged company for $3.5 billion.
Isaacs was Aduro’s founding CEO for thirteen years, until 2020. While leading Aduro, he started several initiatives, including the Alliance for Global Health and Science and the Immunotherapeutics and Vaccine Research Initiative, which Aduro supported with about $10 million in research grants. While at Aduro, Isaacs helped launch X-Biotix to address the problem of antimicrobial resistance. He was the company’s chairman. In 2021, X-Biotix set out to use the immune system to fight bacteria in a way that can bypass microbial resistance. As of 2025, Isaacs is the chairman and CEO of X-Biotix, which has collaboratively sponsored research agreements with several universities, including eleven faculty at UC Berkeley in chemistry, immunology, and bacteriology.
Looking back on the societal impact of his long career, Isaac acknowledges it was all enabled by his scientific education at UC Berkeley, getting a break from Professor Hearst, and leveraging UC Berkeley’s world-class research enterprise.
1 Quotations throughout this section are taken from an email and presentation that Stephen Isaacs sent to Mike Cohen, February 18, 2025. The presentation is titled, “Forty Years of Science and Biotech: A Personal Journey.”
Published in Startup Campus: How UC Berkeley Became an Unexpected Leader in Entrepreneurship and Startups, August 2025
