HUYABIO's HBI-8000 combo nearly doubles PFS versus nivolumab alone in melanoma
The Phase 3 HBI-8000-303 trial hit its primary endpoint at 11.7 versus 7.4 months median PFS, giving the HDAC inhibitor a shot at frontline melanoma where it faces no direct HDAC-class rival.
Executive Summary
- HUYABIO's Phase 3 melanoma trial met its primary endpoint, with the HBI-8000 combination roughly doubling median progression-free survival over nivolumab alone.
- The trial stands as the only Phase 3 test of an HDAC inhibitor added to checkpoint blockade in this setting, giving the result outsized weight for that specific combination strategy even as the broader HDAC field has cooled.
- The disclosure is topline only: the sponsor has not yet reported safety data or the full statistical package behind the result, which will determine how the finding holds up under scrutiny.
- A positive frontline melanoma readout for an already-approved oral HDAC inhibitor changes the calculus for pairing epigenetic therapy with immunotherapy, an approach that has lagged BRAF/MEK and newer checkpoint combinations in this disease.
The readout
HUYABIO International announced on July 14, 2026 that HBI-8000-303, a global Phase 3 trial testing HBI-8000 (tucidinostat) plus nivolumab against nivolumab plus placebo in advanced melanoma, met its primary endpoint. Patients on the combination reached a median progression-free survival of 11.7 months, versus 7.4 months on nivolumab plus placebo, which the company described as a statistically significant 58% improvement. The trial enrolled 404 patients across 15 countries and is HUYABIO's largest oncology study to date. "These results represent an exciting milestone for patients and the future of melanoma treatment," said Mireille Gillings, HUYABIO's CEO and Executive Chair. HUYABIOHUYABIO International Delivers Significant Landmark Phase 3 Results in Advanced MelanomaJul 14, 2026
The trial and the drug
NCT04674683 is a randomized, registrational Phase 3 study that began enrolling in August 2021 and moved to Active, not recruiting status in June 2024, when its enrollment target was set at 450. HBI-8000, an oral HDAC1/2/3/10 inhibitor, is already approved for lymphoma in China and Japan and has been prescribed to more than 90,000 patients, giving the combination an established single-agent safety base even though the melanoma trial's own safety data have not yet been reported. The trial's primary completion date moved from December 2024 to July 2026, a shift of roughly 19 months logged in the registry in September 2025, ahead of this topline disclosure. NCT04674683+1Study Comparing Investigational Drug HBI-8000 + Nivolumab vs. Placebo + Nivolumab in Patients With Advanced MelanomaNCT04674683HUYABIO International Delivers Significant Landmark Phase 3 Results in Advanced MelanomaJul 14, 2026
Where it sits competitively
No other HDAC1-targeting asset has reached Phase 3 in melanoma or uveal melanoma; the closest comparator in the broader competitive field, quisinostat, is in Phase 2 testing for uveal melanoma at the University of Miami. Melanoma's Phase 3 activity is otherwise dominated by BRAF/MEK inhibitors such as dabrafenib and encorafenib and by PD-1/PD-L1 checkpoint agents, none of which share HBI-8000's HDAC mechanism. HDAC-class activity across indications has thinned broadly: field activity for HDAC1 shows 22 recent trials against 503 older ones, and the nearest in-class Phase 3 programs, tucidinostat and belinostat, are both running in lymphoma rather than melanoma. That leaves HBI-8000-303 without a direct in-class precedent to benchmark against inside this indication.
What the win establishes
A positive Phase 3 primary endpoint for an HDAC inhibitor paired with a PD-1 antibody in frontline advanced melanoma is a new data point for a combination strategy that has not previously reached this stage in this disease. The trial's registrational design and 404-patient randomized comparison against an active nivolumab control give the finding decision-grade weight for that specific question, even though the sponsor has said further statistical analysis is still underway and full data, including safety, will be presented at a future medical meeting. HUYABIOHUYABIO International Delivers Significant Landmark Phase 3 Results in Advanced MelanomaJul 14, 2026
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