Callio Therapeutics
Callio Therapeutics makes antibodies that carry two different cancer-killing drugs at once to HER2-positive tumours, to stop cancers escaping treatment. Its first medicine entered human trials in 2026.
Overview
Callio Therapeutics is a clinical-stage biotech headquartered in Seattle and Singapore, launched in March 2025 by Frazier Life Sciences with technology and programmes exclusively licensed from Hummingbird Bioscience. Its platform pairs a modular linker with two rationally selected synergistic payloads on one antibody, aiming to block the dominant resistance mechanisms that limit single-payload ADCs. The lead candidate CLIO-8221 is a HER2-targeted dual-payload ADC co-delivering exatecan (a topoisomerase 1 inhibitor) and an ATR inhibitor; a phase 1/2 study in advanced HER2-expressing solid tumours was presented as a trials-in-progress poster at ASCO 2026 after preclinical data at AACR 2026. A second undisclosed ADC programme is also funded. The USD 187 million Series A was led by Frazier Life Sciences with significant participation from Jeito Capital. Zachary Hornby was appointed CEO in September 2026.
Funding
All startups| Round | Year | Amount | Source |
|---|---|---|---|
| Series A | 2025 | $187M | prnewswire.com |
Amounts only where the cited source states them. Rounds without a public source are not listed.
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