Accipiter Biosciences

Seattle de novo protein-design spinout from the Baker lab ecosystem; Pfizer and Kite deals, immunology and oncology programs, ~$23M seed.

1. Core Product / Service

Accipiter designs de novo multifunctional biologics: proteins built from scratch rather than adapted from antibodies or natural proteins [1]. Its signature format combines several mechanisms in one stable molecule. One example is an agonist that activates more than one pathway on the same cell, whereas conventional antibodies and multispecifics mostly block pathways [1]. The company calls this "post-evolutionary biologics". It uses AI design tools that originated at the University of Washington's Institute for Protein Design (IPD), led by david-baker [2].

Its own programs are preclinical, in immunology and oncology, and have not been named [1]. The seed round was meant to bring up to two programs to pre-IND. After the 2026 extension, management said it plans to push three or four programs toward the clinic [3].

Wet lab. The company describes its platform as computational design paired with "high-throughput experimentation". It claims under two months from in-silico design to lab data, a company figure [1]. The team had grown to 22 people by mid-2026 [3]. Lab address, area and CRO partners are undisclosed, and no current lab job posts were found.

2. Target Users & Pain Points

• Pharma partners: Pfizer (multi-target biologics) and Kite/Gilead (binders for cell therapies) license designs and pay upfront fees, milestones and royalties [1].
• Patients (own pipeline): autoimmune and oncology indications where combining several signals in one molecule could beat single-target drugs.
• Pain addressed: multispecific and agonist biologics are hard to engineer from natural scaffolds; de novo design aims to make stability and geometry programmable.

3. Competitive Landscape

4. Unique Observations

• Pharma deals before the public launch. Accipiter came out of stealth already holding a Pfizer license with more than $330M in potential milestones, plus a Kite option deal [1]. For a seed-stage company this means partner money funds much of the platform. This is the hybrid model that IPD spinouts tend to adopt.
• Founding date is clean. SEC Form D lists 2023 as the year of incorporation, with a $650K pre-seed sale in April 2023 [5].
• Lineage from the first de novo drug. The founders say they were on the team that took the first fully de novo-designed protein therapeutic into clinical trials, a Neoleukin program [1]. That gives them direct experience of the gap between design and clinic.

5. Financials / Funding

• Total: ~$23.2M announced; Form D filings total ~$24.7M [5].
• Partner economics: Pfizer upfront (undisclosed) plus >$330M milestones and royalties; Kite upfront, option, milestones and royalties [1].

6. People & Relationships

• Co-founder & CEO: Matthew Bick. Co-founder & CTO: Javier Castellanos. Co-founder & CSO: Hector Rincon. COO/CSO (strategy): William Canestaro [1].
• Backgrounds: Seagen, Merck, Neoleukin, UW Institute for Protein Design [1].
• Partners: Pfizer; Kite (Gilead).
• Ecosystem: david-baker / IPD; peers xaira-therapeutics, latent-labs.

Sources

• [1] Accipiter press release via BioSpace (2025-11-06; accessed 2026-10-14)
• [2] GeekWire, "Seattle startup Accipiter Bio emerges with $12.7M and big pharma deals" (2025-11; via search excerpt, accessed 2026-10-14)
• [3] GeekWire, "Accipiter Bio quietly tops up seed round with $10.5M" (2026-07; via search excerpt); Dealroom news (2026-07-31; accessed 2026-10-14)
• [4] Capital-Riesgo / Columbus Venture Partners announcement (2025-11; accessed 2026-10-14)
• [5] SEC Form D filings, CIK 1973963 (2023-05 to 2026-07; accessed 2026-10-14)