Nicole K. Paulk, PhD, CEO, founder, and president, Siren Biotechnology
A startup committed to developing the world’s first universal adeno-associated viral (AAV) vector-based gene therapy for solid tumor cancers, with an initial focus on brain cancers, is borrowing a successful high-tech financing technique in hopes of surmounting biotech’s age-old hurdle of raising early-stage capital.
Siren Biotechnology is reaching out to the broad oncology community—from investors to patients—to garner the funding it needs for research and development. The company has launched a community investment round seeking to raise between $50,000 and $5 million.
The minimum is set by funding platforms (Wefunder, in Siren’s case) while the maximum is set by the U.S. Securities and Exchange Commission (SEC). Startups can access their proceeds during the raise as needed, as long as the total capital raised remains within the $5 million limit. Individual investors can invest as little as $100, but must be 18 years of age or older.
Siren said proceeds will go toward investigational new drug (IND)-enabling animal studies and clinical-grade production of therapy. Upon FDA approval of an IND application, Siren plans to start on Series B financing as well as start enrolling and dosing patients in a multi-site Phase I/II clinical trial.
“In consumer-facing tech, you ping all of your users and ask them, do you want to become investors in the company since you love our product? We don’t have app users, but we certainly have patients,” Nicole K. Paulk, PhD, Siren’s CEO, founder, and president, told GEN Edge. “I became enamored with the idea of what if you brought a bunch of patients and their families, their advocates, folks who had perhaps just lost someone to cancer and wanted to do something in tribute? What if you brought all of those people onto your cap[italization] table and gave them agency and gave them a voice?”
Getting the word out
How is Siren getting the word out to potential funders?
“We’re reaching out to patient groups, advocacy groups, and colleagues in the space that we’re aware of. We are learning as we go,” Paulk said. “We’re trying to get in front of patients and patient groups, trying to put the word out at some upcoming big events.”
Those events include the upcoming annual meeting of the American Society of Gene & Cell Therapy (ASGCT), set for May 13-17 in New Orleans.
While patients looking to fund R&D have traditionally donated to philanthropic organizations, and you hailed them as fantastic organizations, those organizations face the challenge of needing months to years to raise sufficient funds to award grants to researchers, who in turn need years to continue their studies let alone spin out companies based on that research.
“In the brain cancer space, many of these patients don’t have that time to wait,” Paulk noted. “If you gave a startup that same $10,000, that might be the amount of money that, together with other patients, actually makes it so that a company could get to trial in a timeframe that might benefit you.”
Siren is one year out from launching a first-in-human clinical trial for its first off-the-shelf AAV immuno-gene therapy for cancer. Last fall, the company disclosed its lead asset SRN-101, a recombinant AAV vector designed to safely and durably express an engineered cytokine in order to treat high-grade gliomas.
Gliomas are among the more than 125 primary brain cancers that Siren could treat initially through its gene therapy platform, which combines AAV gene therapy with cytokine immunotherapy.
To facilitate those future trials, Siren launched a strategic partnership last year with Catalent, designed to provide process development and cGMP manufacturing of Siren’s AAV vector-based gene therapy candidates. Catalent also agreed to further support process optimization at its process and clinical development center in Baltimore.
The FDA has granted SRN-101 its Orphan Drug designation, supporting development for high-grade gliomas, as well as its Rare Pediatric Disease designation, supporting development for pediatric-type diffuse high-grade gliomas.
Funding challenge, community answer
Siren is looking to a public fundraising effort at a time when biotech startups continue to see challenges in raising capital for early stages.
More than $5 billion in venture funding was raised by biotechs during the first quarter of 2025, according to PitchBook data cited by LifeSciVC, the biotech venture capital blog of Bruce Booth, DPhil, a partner with Atlas Venture. But most of that funding came in later, post Series A rounds—an important reason why the first quarter saw the lowest quarterly level of new biotech startup formation in the United States in a decade, some 50 startups vs. 170+ in Q1 2021, as investors poured money into new companies, buoyed by the scramble to develop COVID-19 vaccines and drugs.
Siren isn’t the only biotech that is pursuing community fundraising efforts. Curertopia, a blockchain-based decentralized autonomous organization (DAO) focused on eradicating rare disease, recently raised a $2 million community round using the Solana blockchain platform and Bio Protocol. DAOs let members own and manage an organization collectively, using tokens to vote and decide how it operates, while Bio Protocol lets anyone fund, develop, and govern tokenized scientific intellectual property from universities, companies, and researchers worldwide.
“Crypto is the emerging option for biotech builders—if you can stomach the vol[ume],” Curetopia founder and CEO Ethan Perlstein, who is also CEO of the biotech public benefit corporation Perlara, posted on X. “But hey, it’s not like TradBio fundraising is any less gut wrenching. So might as well try something new!”
UCSF spinout
Siren spun out of Paulk’s lab at the University of California, San Francisco (UCSF), in 2021, where she is now an affiliate assistant professor in neurologic oncology, and a member of the UCSF Helen Diller Family Comprehensive Cancer Center. Siren said its name was inspired by the powerful signal its universal AAV immuno-gene therapy sends to the immune system, which in turn stimulates an immediate and comprehensive anti-tumor response.
Siren then came out of stealth in 2023 and has raised $28 million to date from venture capital investors, including Founders Fund, Lux Capital, and many more. Siren currently has “runway” stretching into the second quarter of 2026. As of March, Siren told investors it had $16.9 million cash in hand.
Also in 2023, Siren reported preclinical data showing its universal AAV immuno-gene therapies exhibit potent anti-tumor effects in preclinical models of brain cancer. The company won a $4 million translational research grant toward developing those therapies from the California Institute for Regenerative Medicine (CIRM).
Siren has also won grants from organizations that include Beckman Coulter, Genscript, Merck & Co., and MilliporeSigma, the U.S. and Canada Life Science business of Merck KGaA, Darmstadt, Germany. Last year, MilliporeSigma selected Siren as the North American winner of its 13th Advance Biotech Grant Program. That enabled Siren to receive products, technologies, and contract testing services from MilliporeSigma for use in developing gene therapy treatments for cancer.
San Francisco-based Siren maintains a headcount of seven people, a number that may rise to eight or nine by the time of its planned clinical trial next year.
That doesn’t include Siren’s Clinical and Scientific Advisory Board, which last month named three new members: Samuel C. Blackman, MD, PhD, co-founder and former head of R&D at Day One Biopharmaceuticals; Mustafa Khasraw, MD, a professor and medical oncologist at Duke University School of Medicine and member of the Duke Cancer Institute; and Leonidas Platanias, MD, PhD, director of the Robert H. Lurie Comprehensive Cancer Center at Northwestern University.
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