A Menlo Park biotech company says it has closed a $62 million funding round to push an experimental cancer drug closer to human trials, with the therapy designed to address resistance associated with payloads used in approved antibody-drug conjugates. Hexagon Bio announced the financing on Oct. 23, with plans to fund a Phase 1 trial of its lead drug candidate, HEX-360, expected to begin enrolling patients in the first half of 2027.
A Fresh Weapon Against HER2-Positive Tumors
The Series C round was led by The Column Group, a San Francisco-based life sciences venture capital firm that invests in early-stage drug discovery companies built around proprietary scientific platforms and provides capital and operational support to help those companies develop pipelines of multiple drug candidates, according to globenewswire.com. Existing backers Nextech Invest, Deviation Capital, 8VC and Canada Pension Plan Investment Board also participated, the release states. HEX-360 is an antibody-drug conjugate, a type of therapy that pairs an antibody engineered to bind to specific markers on cancer cells with a toxic drug payload meant to kill the tumor once it attaches. In this case, the antibody targets HER2, a protein expressed at elevated levels in certain cancers, including some breast and gastric tumors.
What sets HEX-360 apart, according to the company, is its payload: a translation inhibitor designed to disrupt a cancer cell's ability to produce proteins, rather than relying on the topoisomerase or tubulin inhibitors that many approved ADCs use. As citybiz reported, that distinction matters because cancer cells can develop resistance to the limited classes of payloads currently on the market — a problem Hexagon Bio's own science materials describe as a central obstacle the company is trying to solve.
Company Says Drug Beat an Enhertu-Like Comparator in Lab Models
Hexagon Bio reported that in cell-line and patient-derived tumor models, HEX-360 produced efficacy equal to or better than a comparator analogous to Enhertu, a widely used prescription antibody-drug conjugate, when matched for payload exposure. The company also says the drug produced deep, durable responses in models that had already become resistant to topoisomerase inhibitors, the class of payload used in many existing HER2-targeting ADCs, and showed favorable tolerability in rat and non-human primate studies. Hexagon Bio presented those preclinical findings at the American Association for Cancer Research's 2026 annual meeting. The company notes HEX-360 is currently in IND-enabling studies, the preclinical work required before a drug can be tested in people.
These figures are company-reported, and the dossier underlying this reporting does not include independent replication or peer-reviewed publication of the data. The broader scientific literature underscores why resistance is such a persistent problem in HER2-positive cancer: HER2 is overexpressed in 14 to 20 percent of breast cancer patients, and intratumor heterogeneity in HER2 expression has also been reported in patients with HER2-positive tumors, according to nature.com. That same research notes there are already eleven FDA-approved antibody-drug conjugates and more than 100 others in clinical trials, a crowded field that makes differentiation on resistance and tolerability a central competitive question for newer entrants like Hexagon Bio.
Part of a Wider Industry Push on Novel Payloads
Hexagon Bio is not alone in chasing multi-payload or novel-payload strategies to get around ADC resistance. Callio Therapeutics recently launched with $187 million in Series A funding and a license to technology for building ADCs that carry multiple tumor-killing payloads, including a HER2-focused candidate, as reported by biopharmadive.com. That outlet notes the added payload is meant to boost potency and help overcome resistance to ADCs like Enhertu, which deliver a topoisomerase 1 inhibitor to malignant cells. Hexagon Bio says it is similarly exploring combining multiple payloads within a single ADC, in addition to its lead translation-inhibitor approach.
Maureen Hillenmeyer, Hexagon Bio's co-founder and CEO, said the next generation of antibody-drug conjugates will focus on novel payloads capable of transforming treatment for many cancers. Hillenmeyer holds a bachelor's degree in biological sciences from the University of Notre Dame, earned in 2002, and a doctorate in biomedical informatics from Stanford University, earned in 2008, after conducting postdoctoral research in biochemistry at Stanford University School of Medicine.
From Microbial Genomes to the Clinic
Hexagon Bio's underlying technology relies on a proprietary natural-products discovery platform that analyzes microbial genomes to identify biologically active compounds that could serve as ADC payloads, according to the company. The approach is meant to surface molecules that attack cancer through mechanisms distinct from existing treatments, rather than relying on the same handful of payload classes used across the industry for years. This is not Hexagon Bio's first large raise: the company announced a $77.3 million Series B financing in February 2023 that also drew participation from The Column Group, Two Sigma Ventures, 8VC, Nextech and Canada Pension Plan Investment Board.
With the new Series C closed, Hexagon Bio says the funds will support not only the Phase 1 trial of HEX-360 but also the expansion of its broader pipeline of novel and dual-payload ADCs. Whether that first-in-human trial launches on the company's anticipated first-half-2027 timeline, and whether the lab results hold up once the drug reaches real patients, remain open questions the company has not yet answered.
