Third Arc Bio

Third Arc Bio is a clinical-stage biotechnology company headquartered in Lower Gwynedd, Pennsylvania, developing multifunctional antibodies that build immune synapses to precisely activate or inhibit T cells. Its ARCStim platform targets solid tumors and its ARCTag platform pursues tissue-specific precision immune regulation for immunology and inflammation (I&I) indications; lead program ARC101 is a bispecific T-cell engager in a Phase 1 trial in patients with CLDN6-expressing solid tumors. The company launched in 2022 with seed financing from Omega Funds, raised an oversubscribed $165M Series A, and closed a $52M Series A extension in February 2026 with Andreessen Horowitz joining the syndicate. Third Arc Bio publishes no public API, developer portal, SDK or machine-readable specification — it is a therapeutics developer, not a software vendor.

Third Arc Bio is profiled on the APIs.io network. Tagged areas include Company, Biotechnology, Therapeutics, Antibodies, and Oncology.

Third Arc Bio’s developer surface includes engineering blog, support, and 6 more developer resources.

🌐 Visit website 📡 Source on GitHub

11.0/100 emerging ▬ flat Agent 0/100 human only Front door AI 1/6 silent Full breakdown ↓
scored 2026-09-25 · rubric v0.23.0

0 APIs

Company Biotechnology Therapeutics Antibodies Oncology Immunology Life Sciences Clinical Stage

Kin Score

Kin Score How this is scored →
scored 2026-09-25 · rubric v0.23.0

Composite quality — 11.0/100 · emerging

Contract Quality 0.0 / 21

Developer Ergonomics 1.2 / 17

Access Clarity 3.6 / 17

Operational Transparency 0.0 / 11

Contract Governance 0.0 / 10

Discoverability 4.7 / 9

Regulatory Posture 1.6 / 15

Agent readiness — 0/100 · human only

Machine-Readable Contract 0 / 18

Agentic Access Contract 0 / 10

Documented Reversibility 0 / 6

MCP Server 0 / 12

Machine-Readable Auth 0 / 10

Idempotency 0 / 9

Stable Error Semantics 0 / 8

Request/Response Examples 0 / 7

Rate-Limit Signaling 0 / 7

Typed Event Surface 0 / 6

Agent Skills 0 / 5

Well-Known Catalog 0 / 4

Consent & Bot Identity 0 / 3

A2A Agent Card 0 / 8

Dry-Run / Simulate Mode 0 / 4

Delegated User Identity 0 / 6

Protected Resource Metadata 0 / 5

Registration Without a Human 0 / 6

Agentic Commerce Well-Known Document 0 / 5

Regulatory Posture applies to this provider. Its tags matched the Health regime, so Regulatory Posture carries 15 points of the composite. If this regime is wrong for your business, say so on your provider repo — the applicability map is public and we will correct it.

Create-or-Update Ergonomics could not be measured. We hold no machine-readable contract for this provider to read, so there is nothing to measure a write surface against. Excluded rather than scored zero: never-measured and measured-empty are different facts. Publishing an OpenAPI is what makes this facet — and several others — scorable at all.

The six quality facets above are damped to 85 points between them, because the conditional facet above carries the other 15. That is why each facet's contribution is shown against a damped maximum: raising a quality facet moves the composite by 85% of its nominal weight, not 100%. The full arithmetic is at apis.io/rating/.

Improve this rating by publishing the missing artifacts — every area above can be raised, and the full rubric is at apis.io/rating/. Every facet and dimension name above is a link: it opens that measurement's own page — what it means, the exact checks that feed it, how the whole catalog distributes on it, and the providers at the top of it. This rating is computed from github.com/api-evangelist/third-arc-bio: open an issue to ask a question, or submit a pull request to add artifacts. Submit an artifact on GitHub — free → Manage your own listing — the Influence plan, $499/mo →

Security Posture 1

Authentication, domain security, vulnerability disclosure, and trust-center signals.

Third Arc Bio Domain Security

TLSv1.3 · HSTS · DMARC

SECURITY

Resources

Agent Surfaces 1

MCP servers, agent skills, and machine-readable catalogs

LLMsTxt

LLMsTxt

Access & Security 1

Authentication, authorization, and security posture

DomainSecurity

DomainSecurity

Operate 1

Status, limits, changes, and where to get help

Support

Support

Commercial 2

Pricing, plans, and the legal terms of use

PrivacyPolicy

PrivacyPolicy

TermsOfService

TermsOfService

Company 3

The organization behind the API

Website

Website

Blog

Blog

LinkedIn

Source (apis.yml)

aid: third-arc-bio
name: Third Arc Bio
description: Third Arc Bio is a clinical-stage biotechnology company headquartered in Lower Gwynedd, Pennsylvania, developing
  multifunctional antibodies that build immune synapses to precisely activate or inhibit T cells. Its ARCStim platform targets
  solid tumors and its ARCTag platform pursues tissue-specific precision immune regulation for immunology and inflammation
  (I&I) indications; lead program ARC101 is a bispecific T-cell engager in a Phase 1 trial in patients with CLDN6-expressing
  solid tumors. The company launched in 2022 with seed financing from Omega Funds, raised an oversubscribed $165M Series A,
  and closed a $52M Series A extension in February 2026 with Andreessen Horowitz joining the syndicate. Third Arc Bio publishes
  no public API, developer portal, SDK or machine-readable specification — it is a therapeutics developer, not a software
  vendor.
accessModel:
  pricing: unknown
  onboarding: unknown
  trial: false
  try_now: false
  public: false
  label: Unknown
  confidence: low
  source:
  - security
  generated: '2026-09-02'
  method: derived
image: https://thirdarcbio.com/thirdarc-og-image.png
url: https://raw.githubusercontent.com/api-evangelist/third-arc-bio/refs/heads/main/apis.yml
x-type: company
x-source: harvest:secondary-market
x-tier: profiled
x-tier-reason: enrichment-pass-no-api-surface
specificationVersion: '0.20'
created: '2026-08-30'
modified: '2026-08-30'
tags:
- Company
- Biotechnology
- Therapeutics
- Antibodies
- Oncology
- Immunology
- Life Sciences
- Clinical Stage
apis: []
maintainers:
- FN: Kin Lane
  email: kin@apievangelist.com
- FN: APIs.json
  email: info@apis.io
common:
- type: DomainSecurity
  url: security/third-arc-bio-domain-security.yml
- type: Website
  url: https://thirdarcbio.com/
- type: PrivacyPolicy
  url: https://thirdarcbio.com/privacy-policy/
- type: TermsOfService
  url: https://thirdarcbio.com/terms-of-service/
- type: Blog
  url: https://thirdarcbio.com/news/
- type: Support
  url: mailto:info@thirdarcbio.com
- type: LinkedIn
  url: https://www.linkedin.com/company/third-arc-bio/
- type: LLMsTxt
  url: llms/third-arc-bio-llms.txt
x-enrichment:
  date: '2026-08-30'
  status: minimal
  artifacts_added: 3
  pass: local-v1
x-coverage:
  state: none
  reason: not-a-software-company
  detail: Third Arc Bio is a clinical-stage antibody therapeutics developer; thirdarcbio.com is a Gatsby static marketing
    site with only science, pipeline, team, news and policy pages, and every contract-discovery path (/openapi.json, /swagger.json,
    /api-docs, /docs, /developers, /api, /graphql, /llms.txt) plus every /.well-known/ document returns the site's 404 body,
    while api., developer., docs. and mcp. subdomains do not resolve in DNS.
  evidence:
  - url: https://thirdarcbio.com/
    status: 200
  - url: https://thirdarcbio.com/openapi.json
    status: 404
  - url: https://thirdarcbio.com/developers
    status: 404
  - url: https://thirdarcbio.com/.well-known/agent-card.json
    status: 404
  - url: https://thirdarcbio.com/.well-known/api-catalog
    status: 404
  checked: '2026-08-30'

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