Series B AI companies in San Francisco

Companies building AI products, foundation models, and applied ML platforms. Filtered to Series B-stage companies headquartered in San Francisco.

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Ranked by current headcount across Series B AI companies in San Francisco. Refreshed monthly.

1
Vial· San Francisco, California, United States
Vial is a next-generation pharma company. Focused on advancing a pipeline of potentially best-in-class biologics and RNA therapeutics across areas of unmet need.
- Series B
- 158 employees
- Founded 2020
2
Stämm· San Francisco, California, United States
Stämm is a biotechnology company dedicated to making biomanufacturing easy, scalable, sustainable, and repeatable. We are developing accessible, plug-and-play manufacturing solutions, allowing an automatized, continuous, and more efficient production of biologics and cell therapies.
- Series B
- 141 employees
- Founded 2016
3
Ohalo· South San Francisco, California, United States
To support a growing population efficiently, we need to shrink the land, water and energy footprint of our crops. Breeding is directed evolution, but it is slow and inefficient. Ohalo's technology shrinks the breeding cycles of plants. Our speed, accuracy and scalability create entirely new varieties of the world's most loved and consumed crops.
- Series B
- 126 employees
- Founded 2019
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4
Arena· San Francisco, California, United States
Created by researchers from UC Berkeley, Arena (formerly LMArena) is a community-powered platform to measure and advance the frontier of AI for real-world use. Tens of millions of builders, researchers, and creative professionals come to Arena to use frontier models and give feedback on their responses, shaping a public leaderboard grounded in real-world use.
- Series B
- 96 employees
- Founded 2025
5
SonoThera· South San Francisco, California, United States
SonoThera is developing ultrasound-mediated nonviral genetic therapies.
- Series B
- 52 employees
- Founded 2022

6
T-knife Therapeutics· San Francisco, California, United States
T-knife is a clinical-stage biotechnology company developing next-generation engineered T cell therapies and in vivo cell therapies for solid tumors. The company combines proprietary engager technology, synthetic biology, and a deep understanding of solid tumors to create armored supercharged T cell therapies designed to achieve broad, deep, and durable responses for patients in high unmet-need indications.T-knife’s lead oncology program, TK-6302, is a potentially best-in-class engineered TCR-T cell therapy targeting PRAME, a clinically validated cancer antigen expressed across multiple high-value solid tumor indications, including ovarian cancer, melanoma, non-small cell lung cancer (NSCLC), endometrial cancer, and triple-negative breast cancer (TNBC). TK-6302 has been specifically designed to overcome barriers in the solid tumor microenvironment leading to improved persistence of highly functional T-cells.T-knife is also advancing two proprietary in vivo cell therapy programs for solid tumors aimed at reprogramming immune cells directly within the patient. These first- and best-in-class in vivo T cell therapy candidates are leveraging the company's broad solid tumors technology toolbox and incorporate innovative designs to improve in vivo cell therapy efficacy in solid tumors.Founded by leading experts in T cell biology, immunology, and cancer immunotherapy, T-knife was built on pioneering research from the Max Delbrück Center for Molecular Medicine and Charité – Universitätsmedizin Berlin. The company is led by an experienced biotech leadership team and backed by leading global life science investors, including Andera Partners, EQT Life Sciences, RA Capital Management, and Versant Ventures.
- Series B
- 41 employees
- Founded 2019
7
Marea Therapeutics· San Francisco, California, United States
Marea Therapeutics is a clinical-stage biotechnology company harnessing the latest advances in human genetics to develop first-in-class, next-generation medicines for cardio-endocrine diseases. The company’s lead program, MAR001, is in Phase 2 clinical development for adults with metabolic dysfunction and high risk for cardiovascular disease. The company is also advancing MAR002 for the treatment of acromegaly.
- Series B
- 41 employees
- Founded 2022
8
Unknown· South San Francisco, California, United States
Abdera Therapeutics Inc. is a precision oncology company developing next-generation targeted radiation therapies - one of the most cutting-edge and highly promising areas of drug development. The company is built on a proprietary modular technology platform optimized for the delivery of radioisotopes to selectively destroy tumor cells while sparing healthy cells. Abdera is using this platform to enable the rapid development of a broad range of safe and efficacious therapies serving cancer patients with limited treatment options.Abdera Therapeutics is growing rapidly and seeking key new team members who thrive at the cutting-edge of innovation. Come join us and be a part of the ground-breaking team set to unlock the power of targeted radiotherapy!
- Series B
- 34 employees
- Founded 2021
9
AltruBio Inc.· San Francisco, California, United States
AltruBio is developing first-in-class immune-modulators targeting diseases of #immunology and #inflammation. Its world-class global team brings a breadth of expertise in immunology and drug development that will help advance their biologic treatments to patients. Learn more at https://www.altrubio.com/altrubio/en
- Series B
- 30 employees
- Founded 2020
10
Moonwalk Biosciences· South San Francisco, California, United States
Moonwalk Biosciences is pioneering novel therapeutics in adipose biology and tissue, driven by deep genetic and epigenetic evidence and insights. It utilizes its discovery platform to identify novel targets involved in obesity and cardiometabolic disease, and is advancing an early stage pipeline of therapeutic candidates.
- Series B
- 21 employees
- Founded 2022

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Find engineers at Series B AI companies in San Francisco

Searching for “engineers at top Series B AI companies in San Francisco” surfaces this slice of the market. The list above ranks AI companies headquartered in San Francisco whose latest disclosed round is Series B, by current headcount, drawn from public LinkedIn and Crunchbase records. With 16 matching companies in Refolk’s index, this is a tight read on where the AI talent in San Francisco is heating up.

Three filters at once narrows the field hard. The companies that survive all three - Series B, AI, in San Francisco - are usually the most targeted recruiting pool a hiring manager can ask for. Senior engineers, founding designers, and product leads here are about to become AI’s next operators and angel investors.

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Refolk pulled AI companies headquartered in San Francisco whose latest disclosed funding round is Series B from public LinkedIn and Crunchbase records, ranked them by current employee count, and kept those with at least 3 employees. The list refreshes monthly.

Last refreshed: Sun, 18 Oct 2026 21:50:52 GMT

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