New Drug Combo Shows Promise in Advanced Skin Cancer, Despite Side Effects

A clinical trial found that adding an experimental HDAC inhibitor to immunotherapy significantly extended progression-free survival in patients with unresectable melanoma, especially those with normal LDH levels. The combination improved median PFS from 7.4 to 11.7 months and increased 24-month survival without disease progression. While side effects were more common, they were largely manageable, suggesting potential for broader use.

A phase III clinical trial, HBI-8000-303, conducted across 123 sites in 15 countries, demonstrated that adding the experimental HDAC inhibitor HBI-8000 to nivolumab significantly improved progression-free survival (PFS) in patients with unresectable melanoma. Median PFS rose from 7.36 months in the placebo group to 11.66 months in the combination arm, a 4.3-month gain representing a 27% reduction in the hazard of disease progression (P = 0.0141). At 24 months, 41.3% of patients on HBI-8000 plus nivolumab remained progression-free compared to 28.7% in the control group. The benefit was even more pronounced among patients with normal baseline lactate dehydrogenase (LDH) levels—median PFS reached 20.04 months, and 24-month PFS was 47.2% versus 32.6%. The trial included 404 treatment-naïve patients with stage III/IV melanoma, randomized to nivolumab plus HBI-8000 or placebo, with a median follow-up of 37 months. While the combination increased grade 3/4 treatment-related adverse events from 17.9% to 54.8%, these were largely manageable, with no significant increase in endocrine toxicities like hyperthyroidism or adrenal insufficiency. Hematologic toxicities such as thrombocytopenia and neutropenia were more common but not severe enough to halt treatment in most cases.

The trial builds on earlier phase Ib/II data showing a 65.8% objective response rate with the same combination, suggesting a strong biological rationale. HDAC inhibitors like HBI-8000 are believed to enhance antige