What Third Arc Bio does

Third Arc Bio is a clinical-stage biotechnology company developing multifunctional, multispecific antibodies designed to generate immune synapses that precisely activate or inhibit T cells. The company operates two proprietary technology platforms: ARCStim, which leverages combined CD3 engagement and conditionally active CD28 co-stimulation (available as both a two-molecule bispecific and a single-molecule trispecific) for solid tumor therapeutics, and ARCTag, a tethered agonist approach for immunology and inflammation that localizes checkpoint agonists at disease sites to achieve tissue-specific immune suppression while sparing systemic immunity. It also has a license to Adagene's SAFEbody precision-masking technology for tumor-microenvironment-conditional antibody activation, used in two additional masked CD3 T cell engagers. The disclosed pipeline comprises seven candidates, including the lead asset ARC101 (CLDN6 x CD3 bispecific T cell engager) currently in Phase 1 dose escalation for CLDN6-positive solid tumors such as ovarian, endometrial, and lung cancers, plus earlier-stage programs across additional solid tumor targets and autoimmune indications including rheumatoid arthritis.

The company was founded in 2022 with seed financing from Omega Funds and is headquartered in Spring House, Pennsylvania, with a legal/contact address in Boston. Through July 2024 and February 2026, Third Arc Bio raised a total of approximately $217 million in Series A financing (a $165M round co-led by Vida Ventures, Cormorant Asset Management, and Hillhouse Investment, plus a $52M extension led by Andreessen Horowitz), bringing in a syndicate that includes Goldman Sachs Alternatives, T. Rowe Price, AbbVie Ventures, Galapagos, BVF Partners, Marshall Wace, abrdn, and Alderline Group.

Third Arc Bio is pre-revenue. Its revenue model is anchored on long-term pharmaceutical partnerships, exemplified by the November 2025 licensing deal with Adagene (carrying a $5 million upfront and up to $840 million in potential milestones plus royalties), with future revenue contingent on regulatory approval and commercialization of pipeline assets either independently or through additional pharma partnerships. The go-to-market motion is enterprise-focused: clinical development is conducted through clinical trial sites, while commercial distribution is intended to flow through licensing and co-development arrangements with large pharmaceutical companies. The leadership team is dominated by senior R&D, clinical, regulatory, and business development executives, many with prior senior roles at Johnson & Johnson, GlaxoSmithKline, Merck, Bristol Myers Squibb, and Amgen, collectively credited with over 35 drug approvals.

Name

Third Arc Bio

Legal name

Third Arc Bio, Inc.

Website

https://thirdarcbio.com

Company type

Private

Founded year

2022

Operating status

Operating

Headcount range

11–50 employees

Short description

Third Arc Bio is a clinical-stage biotech developing multifunctional bispecific T cell engagers for oncology and immunology/inflammation, with lead asset ARC101 in Phase 1 trials for CLDN6-positive solid tumors.

Ownership category

akta.pro rank

Product category

Biopharmaceutical Therapeutics

NAICS

Biological Product (except Diagnostic) Manufacturing (325414), Research and Development in Biotechnology (except Nanobiotechnology) (541714)

SIC

Biological Products, (No Disgnostic Substances) (2836)

akta.pro primary industry

Bispecific & Multispecific Antibodies (HLAAAAAF)

akta.pro secondary industries

Antibody Discovery & Engineering Platforms (display tech, bispecifics, Fc engineering) (HLAAAIAB), Immunology & Inflammation Pharmaceuticals (HLAIAAAD)

Keywords

• Multifunctional antibodies
• Bispecific T cell engagers
• Oncology therapeutics
• Immunology inflammation
• Clinical stage biotech

Headquarters

HQ city

Boston

HQ country

United States

HQ region

North America

Offices2 records

Markets served

GTM type

B2B

Offering type

Services

Cost components

Technology or R&D, Personnel, Operations, Marketing or Sales, Infrastructure

Revenue model

1. Pipeline Development & Commercialization: As a clinical-stage biotech company, Third Arc Bio is pre-revenue. The company is developing a pipeline of multifunctional antibody candidates for oncology and immunology indications. Revenue will be generated through eventual product sales if clinical programs receive regulatory approval, as well as through potential milestone payments and royalties from partnership agreements.

Go-to-market motion1 record

Distribution channels2 records

Marketing channels4 records

Core offering

Third Arc Bio is a clinical-stage biopharmaceutical company developing a pipeline of multifunctional bispecific and trispecific antibody therapeutics for oncology and immunology & inflammation (I&I) indications. The company engineers antibodies that generate immune synapses to precisely activate or inhibit T cells, leveraging its proprietary ARCStim platform (CD3/CD28 co-stimulation) for solid tumors and ARCTag platform (tethered agonists) for autoimmune disease. Lead asset ARC101, a CLDN6 x CD3 bispecific T cell engager, is in Phase 1 clinical trials, with additional candidates in IND-enabling and lead identification stages.

Product overview

Third Arc Bio is a clinical-stage biopharmaceutical company developing a differentiated pipeline of bispecific T cell engagers for oncology and autoimmune diseases. The company's lead product is ARC101, a CLDN6 x CD3 bispecific T cell engager in Phase 1 dose escalation for CLDN6-positive solid tumors. The ARCStim platform powers solid tumor co-stimulation candidates (ARC151, ARC152), while the ARCTag platform supports immunology and inflammation programs (ARC201, ARC202). The broader pipeline includes ARC102, ARC103 and additional programs targeting ovarian, pancreatic, endometrial, gastrointestinal, and autoimmune indications.

Differentiator

Problem solved

Functional benefit

Products and services

• ARC101 Bispecific T cell engager targeting CLDN6 x CD3 for the treatment of CLDN6-positive advanced solid tumors including ovarian, endometrial, and lung cancers. Currently in Phase 1 dose escalation. The asset exhibits high specificity with no off-target binding to other Claudin family proteins.
• ARC102 Bispecific T cell engager targeting Target 2 x CD3 for ovarian, pancreatic, and endometrial cancers. Currently in IND-enabling stage.

Quantifiable outcome

• ARC101 exhibits high specificity with no off-target binding and avoids other Claudin family proteins
• +1 more outcomes

Segments2 records

Ideal customer profiles1 record

Technology focussed Yes

API detail

Has API

No

API docs

API detail

Core technology

AI maturity

App detail

Feature3 records

Partnerships

One partnership is on record.

• AdagenecoreTechnology or Integration · 13 November 2025Licensing agreement where Third Arc Bio utilizes Adagene's SAFEbody technology to develop two masked CD3 T cell engagers targeting tumor antigens. Third Arc received worldwide rights to two candidate molecules. Adagene received $5 million upfront payment with potential milestones up to $840 million plus royalties. Adagene retains option for development in Greater China, Singapore, and South Korea.

Scale indicators4 records

Recent moves5 records

Expansion highlights6 records

Direct peers

• Janux Therapeutics: Clinical-stage biotech developing tumor-activated T cell engagers (TRACTr platform) for solid tumors. Most directly comparable to Third Arc Bio's ARCStim-based solid tumor programs given shared focus on engineering T cell engagers with improved therapeutic index in oncology.
• Harpoon Therapeutics: Developed TriTAC and ProTriTAC T cell engagers for solid tumors and hematologic malignancies; acquired by Merck in 2024. Direct competitor in the bispecific/multispecific T cell engager space targeting similar oncology indications.
• Maverick Therapeutics: Develops COBRA (Conditional Bispecific Redirected Activation) T cell engagers designed for tumor-selective activity in solid tumors. Comparable to Third Arc Bio's conditionally active CD28 co-stimulation and masked T cell engager approach.
• Dragonfly Therapeutics: Develops multispecific antibodies (including TriNKets and CytoSynAbs) that engage multiple receptors across immune cell types for oncology and autoimmune indications. Directly comparable multifunctional/multispecific antibody platform play.
• Compass Therapeutics: Clinical-stage biotech developing bispecific antibodies for oncology and autoimmune diseases using a proprietary antibody discovery platform. Comparable pipeline scope spanning oncology and I&I with bispecific antibody candidates.
• Adagene: Clinical-stage biotech developing precision-masked antibodies using SAFEbody and POWERbody platforms; also Third Arc Bio's licensing partner. Closely comparable in the masked/probody antibody space and uses CD3-based T cell engagers.
• Cullinan Oncology: Clinical-stage oncology biotech developing a diversified pipeline including bispecific antibodies and immune engagers. Comparable in developing multiple oncology candidates with engineered immune engagement mechanisms.
• CytomX Therapeutics: Develops masked (Probody) antibody therapeutics that are activated in the tumor microenvironment. Closely analogous to Third Arc Bio's use of Adagene's SAFEbody masking technology, with a similar precision-oncology platform thesis.

Broad incumbents

• Zymeworks: Established clinical-stage biotech with the Azymetric bispecific antibody platform and additional multispecific technologies. A broader incumbent in the bispecific antibody space with multiple platform technologies and partnered programs.
• Macrogenics: Clinical-stage biotech with the DART and TRIDENT bispecific/multispecific antibody platforms, developing candidates across oncology and autoimmune diseases. A broader incumbent in the engineered antibody space with comparable target indications.

Market position

Strengths5 records

Weaknesses4 records

Competitive moat3 records

Key risks5 records

Key highlights6 records

Customer concentration

Revenue estimate

Valuation estimate

Number of profiles

Profiles15 records

Funding overview

Funding rounds3 records

Investors17 records

Funding detail is available on the Subscription and Enterprise plan.Contact sales →

M&A

Investments

M&A and investment is available on the Subscription and Enterprise plan.Contact sales →

Frequently asked questions about Third Arc Bio