One To Watch

Arcus Biosciences

Company Overview

A clinical-stage biotechnology company developing next-generation cancer immunotherapies, with a broad immuno-oncology pipeline spanning TIGIT, adenosine pathway, and PD-1/PD-L1 targets supported by a major Gilead Sciences collaboration. Arcus is built around the thesis that combination approaches — simultaneously targeting multiple immunosuppressive mechanisms — will outperform single-checkpoint blockade. The company has assembled one of the most clinically active immuno-oncology pipelines among mid-cap biotechs, with multiple assets advancing in non-small cell lung cancer, gastrointestinal cancers, and other solid tumors.

Headquarters and Global Presence

Arcus Biosciences is headquartered in Hayward, California, in the San Francisco Bay Area. The company operates primarily in the United States, with its discovery, translational, and clinical operations centered at its California campus.

Founding and History

Arcus was founded in 2015 by Terry Rosen and Juan Jaen, veterans of Corcept Therapeutics and other Bay Area biotechs, with the explicit goal of building a combination-focused immuno-oncology engine. The company completed its IPO on the New York Stock Exchange in 2018 under the ticker RCUS. A transformative option and collaboration agreement with Gilead Sciences, originally signed in 2020 and substantially expanded in subsequent years, has provided the company with significant non-dilutive capital and development infrastructure.

Therapy Areas and Focus

Arcus is focused exclusively on oncology, targeting solid tumors where the immune system is suppressed by multiple overlapping mechanisms. Its programs address non-small cell lung cancer, colorectal cancer, pancreatic cancer, and other difficult-to-treat solid tumor indications. The company's strategic rationale centers on the adenosine pathway and co-inhibitory receptors such as TIGIT, which suppress T-cell activity in the tumor microenvironment and have been underexploited relative to PD-1 blockade alone.

Technology Platforms and Modalities

Arcus's platform integrates small molecules and monoclonal antibodies designed to work in mechanistically complementary combinations. Its adenosine axis program targets CD73 and A2a/A2b receptors, which cancer cells exploit to generate immunosuppressive adenosine within the tumor microenvironment. The TIGIT franchise centers on domvanalimab, an Fc-silent anti-TIGIT antibody designed to block the checkpoint without triggering depletion of regulatory T cells — a key differentiator from first-generation TIGIT approaches. This multi-mechanism philosophy is embedded across all combination trials.

Key Pipeline and Programs

Domvanalimab is Arcus's lead anti-TIGIT antibody, being evaluated in combination with zimberelimab (anti-PD-1) in the STAR-121 Phase III trial in first-line non-small cell lung cancer. The Fc-silent design is intended to eliminate antibody-dependent cellular cytotoxicity against TIGIT-expressing effector T cells, a limitation associated with earlier TIGIT candidates from competitors. Quemliclustat (AB680) is a potent small-molecule CD73 inhibitor being developed in combination with chemotherapy and zimberelimab for pancreatic and colorectal cancers in Phase II studies. Etrumadenant is a dual A2a/A2b adenosine receptor antagonist in Phase II trials targeting colorectal and other gastrointestinal tumors, also combined with zimberelimab. AB308, an anti-PD-1 antibody with an engineered Fc region, represents a next-generation PD-1 program expanding the company's checkpoint portfolio. GLS-010, an anti-PD-1 antibody in-licensed from WuXi Biologics and Harbin Gloria Pharmaceuticals in a deal worth up to $816 million, has been added to the pipeline to broaden combination options.

Recent Developments

In June 2024, Arcus and WuXi Biologics, together with Harbin Gloria Pharmaceuticals, announced a deal worth up to $816 million for Arcus to in-license the anti-PD-1 antibody GLS-010, significantly expanding its PD-1 combination toolkit. That same month, Gilead Sciences deepened its immuno-oncology commitment through a further extension of its Arcus collaboration, though the announcement triggered a near-13% share price decline as investors weighed the dilutive and strategic implications. In a significant pipeline setback, Arcus pulled another TIGIT program trial in April 2026 as Gilead stepped back from certain TIGIT investments, reflecting broader industry headwinds facing the class.

Key Personnel

Terry Rosen serves as Chief Executive Officer and co-founder. He brings over two decades of drug discovery leadership, having previously served as President of Research at Corcept Therapeutics and in senior roles at Threshold Pharmaceuticals. Juan Jaen, co-founder and President, leads research and early development strategy, with a background in small-molecule immunology from his time at Arena Pharmaceuticals and Corcept. Jennifer Jarrett serves as Chief Financial Officer, overseeing the capital strategy underpinning the Gilead collaboration and equity programs.

Strategic Partnerships

The cornerstone of Arcus's strategy is its option, collaboration, and license agreement with Gilead Sciences, originally struck in 2020 for $175 million upfront and expanded multiple times, granting Gilead options to co-develop and co-commercialize Arcus pipeline assets. The June 2024 GLS-010 in-license from WuXi Biologics and Harbin Gloria Pharmaceuticals, valued at up to $816 million, adds a clinically validated PD-1 antibody to complement domvanalimab combination regimens. These two partnerships collectively define the company's development and commercial trajectory.

FAQ Section

The Gilead agreement, first signed in 2020 for $175 million upfront, grants Gilead options to co-develop and co-commercialize individual Arcus programs, providing substantial non-dilutive funding and commercial infrastructure. This structure allows Arcus to advance a broad pipeline without bearing full development costs, while retaining meaningful economics on programs Gilead does not option. However, Gilead's April 2026 decision to step back from certain TIGIT investments — prompting the cancellation of an additional TIGIT trial — illustrates the strategic risk of a partnership where the larger party controls key go/no-go decisions.

Adenosine accumulates in the tumor microenvironment through enzymatic conversion of extracellular ATP by CD39 and CD73, and signals through A2a and A2b receptors on T cells and NK cells to suppress anti-tumor immunity. Because this axis is mechanistically distinct from PD-1 or CTLA-4 signaling, combining adenosine blockade with checkpoint inhibition can theoretically address immunosuppression that monotherapy leaves intact. Arcus has built two complementary programs — quemliclustat targeting CD73 and etrumadenant targeting A2a/A2b — to intercept this pathway at different nodes.

Most anti-TIGIT antibodies carry a functional Fc region that can engage Fc receptors on immune effector cells, potentially depleting TIGIT-expressing CD8+ T cells that the therapy is intended to activate. Domvanalimab's Fc-silent engineering eliminates this effector function, aiming to preserve tumor-infiltrating T cells while still blocking the TIGIT checkpoint. This design distinguishes it from earlier TIGIT candidates, including tiragolumab, that have faced efficacy setbacks — though the broader class has struggled to demonstrate clear clinical benefit in pivotal trials.

STAR-121 is a Phase III trial evaluating domvanalimab in combination with zimberelimab (Arcus's anti-PD-1) in first-line non-small cell lung cancer. The trial represents the most advanced and highest-stakes program in the Arcus portfolio, as first-line NSCLC is one of the largest oncology markets. The April 2026 withdrawal of a separate TIGIT trial amid Gilead's strategic recalibration has increased scrutiny on STAR-121 as the pivotal readout that will validate or challenge the TIGIT combination hypothesis for Arcus.

Non-small cell lung cancer is the primary target for the domvanalimab and zimberelimab combination, reflecting the large addressable market and established role of PD-1 blockade in that setting. Gastrointestinal cancers — particularly colorectal and pancreatic — are the focus of the adenosine pathway programs, etrumadenant and quemliclustat, where conventional checkpoint inhibitors have largely failed. The GLS-010 in-license from WuXi Biologics and Harbin Gloria adds flexibility to extend combinations into additional solid tumor indications.

Arcus is a late-clinical-stage company, with domvanalimab in a registrational Phase III trial and multiple assets in Phase II. The company is past the proof-of-concept stage for its key mechanisms but has not yet achieved a regulatory approval. The STAR-121 readout for domvanalimab plus zimberelimab in first-line NSCLC is the most significant near-term data catalyst, alongside Phase II data updates for quemliclustat in gastrointestinal cancers.

The key watchpoints for Arcus include both near-term catalysts and structural risks:

STAR-121 Phase III data readout for domvanalimab plus zimberelimab in first-line NSCLC — the most binary event for the stock and the TIGIT thesis.
Gilead's ongoing option decisions on pipeline programs, which directly affect co-development funding and commercial prospects.
The TIGIT class-level headwinds following multiple competitor failures and Arcus's own April 2026 trial withdrawal — raising questions about whether Fc-silent design is sufficient to rescue efficacy.
Phase II data for quemliclustat and etrumadenant in gastrointestinal cancers, where adenosine pathway inhibition could differentiate from standard checkpoint blockade.
Integration and development timelines for GLS-010 following the $816 million WuXi/Harbin Gloria in-licensing deal.

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