Founders Fund Biotech portfolio in San Francisco

The fight against cancer needs new, big, bold ideas. At Siren, we’ve got one: Universal AAV Immuno-Gene Therapy.We are combining two transformative therapeutic technologies – AAV gene therapy and cytokine immunotherapy - into a single, reimagined modality that overcomes key challenges and redefines how we destroy tumor cells and elicit anti-tumor immunity.

• Grant
• 8 employees
• Founded 2020

Founded in 2008, Stemcentrx combines state-of-the-art research and GMP manufacturing capabilities. This has allowed us to advance from target discovery in our laboratory to treating patients in clinical trials at an accelerated pace. We are investigating many of the largest and most lethal cancers through our proprietary platforms that identify cancer stem cells, discover novel targets, engineer and manufacture antibodies and antibody drug conjugates.Our mission is to develop therapies that cure and significantly improve survival for cancer patients. We are pioneering new approaches to eliminate cancer stem cells, which initiate and perpetuate tumors. Stemcentrx has assembled a talented and motivated team committed to this mission. We are recruiting people with world-class expertise in their practice, versatility, high energy and an entrepreneurial spirit. Our state-of-the-art laboratories and manufacturing facilities are located in South San Francisco, California. We have a driven, ambitious, focused, hard-working, apolitical, fun, and collaborative culture that is more typical of Silicon Valley startups than large pharmaceutical companies. Our employees are compensated with salary, benefits and stock options.

• Series G
• 6 employees
• Founded 2008

Gamgee is building an AI-first genomics platform for personalised mRNA cancer vaccines, beginning with dogs. We connect tumour sequencing, computational target selection, patient-specific manufacturing, and clinical outcomes in a closed loop that learns from every patient

• Seed
• 4 employees
• Founded 2026