# Callio Therapeutics

> Callio Therapeutics is a clinical-stage biotechnology company developing dual-payload antibody-drug conjugates, or ADCs, that carry two complementary medicines to the same tumor cell. Its lead candidate, CLIO-8221, targets HER2 and couples the topoisomerase 1 inhibitor exatecan with the ATR inhibitor berzosertib in an effort to counter a known route of treatment resistance. Launched in 2025 with $187 million and technology licensed from Hummingbird Bioscience, the Seattle- and Singapore-based company began a Phase 1/2 study in 2026.

- **Founded:** 2025
- **Headquarters:** Seattle, United States and Singapore, Singapore
- **Founders:** Piers Ingram (Co-founder and founding CEO), Jerome Boyd-Kirkup (Co-founder and Chief Scientific Officer)
- **Team size:** Approximately 19 employees; LinkedIn lists 11-50 employees.
- **Products:** CLIO-8221, Dual-payload ADC platform, Additional dual-payload ADC programs
- **Notable:** Launched in March 2025 with a US$187 million Series A, one of the year's larger biotechnology debut financings., Secured an exclusive worldwide oncology license to Hummingbird Bioscience's multi-payload ADC platform and related pipeline., Advanced CLIO-8221 from company launch to first-patient dosing in roughly one year.

## Products & services

- **CLIO-8221** — A clinical-stage HER2-targeted dual-payload ADC that uses an Fc-engineered trastuzumab, a proprietary protease-cleavable hydrophilic linker, exatecan and the ATR inhibitor berzosertib. It is being studied in advanced HER2-expressing solid tumors, including disease previously treated with trastuzumab deruxtecan.
- **Dual-payload ADC platform** — A modular oncology platform exclusively licensed from Hummingbird Bioscience. It is designed to support stable, developable conjugates across payload combinations and drug-to-antibody ratios while pairing mechanisms intended to address resistance.
- **Additional dual-payload ADC programs** — A preclinical pipeline of additional ADC candidates using rationally selected payload combinations; targets and candidate details have not all been publicly disclosed.

## Achievements

- Launched in March 2025 with a US$187 million Series A, one of the year's larger biotechnology debut financings.
- Secured an exclusive worldwide oncology license to Hummingbird Bioscience's multi-payload ADC platform and related pipeline.
- Advanced CLIO-8221 from company launch to first-patient dosing in roughly one year.
- Received U.S. FDA IND clearance for CLIO-8221 in March 2026.
- Opened a Phase 1/2 study in Australia and the United States with estimated enrollment of 306 participants.
- Presented the CLIO-8221 trial design at the 2026 ASCO Annual Meeting.

## Latest updates

- **2026-07** — Callio's official website listed Zachary Hornby as Chief Executive Officer, succeeding founding CEO Piers Ingram; the site did not state the transition date.
- **2026-06** — The company said CLIO-8221 was moving through Phase 1 dose escalation and that emerging clinical data were expected later in 2026.
- **2026-05** — Callio and investigators presented the design of the CLIO-8221 Phase 1/2 study at ASCO 2026.
- **2026-03** — The first patient was dosed in Australia and the FDA cleared the U.S. IND for CLIO-8221.
- **2025-03** — Callio launched with US$187 million in Series A financing and an exclusive worldwide oncology license from Hummingbird Bioscience.

## Links

- Website: https://calliotx.com
- LinkedIn: https://www.linkedin.com/company/calliotx

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Profile page: https://yespress.io/callio-therapeutics
Published by YesPress — https://yespress.io
Last updated: 2026-08-17