A Three-Drug Strategy Nearly Doubled Survival in Advanced Melanoma—but Researchers Urge Caution
A real-world study of patients with unresectable advanced melanoma in China has found that adding the cancer drug anlotinib to a combination of an anti-PD-1 immunotherapy and IFN-α1b was associated with substantially longer survival. Patients who received the three-drug regimen had a median overall survival of 35.8 months, compared with 16.2 months among those treated with the two-drug combination, according to research published in Cancer Immunology, Immunotherapy. The findings offer a striking signal for people with stage III or IV melanoma whose tumors cannot be removed surgically, particularly those with mucosal disease or very low PD-L1 expression. But because the analysis was retrospective rather than a randomized clinical trial, the result cannot yet establish that anlotinib itself caused the survival advantage.
The study addressed a persistent problem in advanced melanoma: immune checkpoint inhibitors can produce durable responses, but their benefits are unevenly distributed. Anti-PD-1 antibodies work by releasing a molecular brake on T cells. Tumors often exploit the PD-1 pathway by engaging PD-L1 on immune cells, dampening the attack that would otherwise help eliminate malignant cells. Blocking PD-1 can restore T-cell activity, yet some melanomas remain immunologically “cold,” with few active immune cells entering the tumor or with biological features that make immune recognition difficult. Acral melanoma, which arises on the palms, soles and nail beds, and mucosal melanoma, which develops in tissues such as the nasal cavity or gastrointestinal and genital tracts, are especially important in Asian populations and have often shown less favorable responses to immunotherapy alone.
The investigators, led by researchers at Xijing Hospital of the Fourth Military Medical University and collaborating institutions, analyzed medical records from 211 people treated between June 2020 and June 2024. All had stage III or IV unresectable melanoma and received first-line treatment with an anti-PD-1 monoclonal antibody plus IFN-α1b, either with or without anlotinib. The majority—179 patients—received the doublet regimen, while 32 received the triplet. IFN-α1b is a form of interferon, a signaling protein that can influence tumor-cell behavior and stimulate components of the immune system. In principle, combining interferon signaling with checkpoint blockade could make the tumor environment more receptive to immune attack, while anlotinib may add a separate pressure on the tumor’s blood-vessel supply and growth pathways.
Anlotinib is an orally administered multitarget tyrosine kinase inhibitor that interferes with signaling proteins involved in angiogenesis, the process by which tumors recruit new blood vessels. A growing tumor requires oxygen and nutrients, and cancer-associated blood vessels can also contribute to an immune-suppressive microenvironment. Abnormal tumor vasculature may prevent immune cells from reaching malignant tissue efficiently, while pro-angiogenic signals can support populations of cells that restrain immune responses. Blocking selected vascular growth signals could therefore have effects beyond starving the tumor: it may help normalize the disorganized blood-vessel network and potentially improve immune-cell access. The study did not prove that this mechanism explained the clinical results, but it provides a biological rationale for testing anlotinib alongside immunotherapy and interferon rather than viewing the drugs as unrelated additions.
To reduce the influence of differences between the treatment groups, the researchers used propensity score overlap weighting. This statistical method estimates the likelihood that each patient would receive one regimen based on measured characteristics, then gives greater analytical weight to patients whose profiles overlap between the two groups. The approach can make comparisons more balanced for factors recorded in the medical files, such as disease features and baseline health status. After weighting, the triplet regimen was associated with a 58 percent lower estimated risk of death than the doublet regimen, reflected by a hazard ratio of 0.42 and a 95 percent confidence interval of 0.24 to 0.72. The hazard ratio summarizes differences in the rate at which events occur over time; it is not a direct statement that 58 percent of individual patients will live longer.
The researchers also reported a progression-free survival advantage. Median progression-free survival—the time before cancer growth, spread or death—was 9.4 months with the triplet and 5.2 months with the doublet. The corresponding hazard ratio was 0.52, with a 95 percent confidence interval of 0.34 to 0.80. These results suggest that the three-drug strategy was associated both with a longer period before the disease worsened and with longer overall survival. Yet the objective response rates tell a more nuanced story. After weighting, tumors shrank by the study’s predefined response criteria in 45.1 percent of patients receiving the triplet and 38.1 percent receiving the doublet. That numerical difference was not statistically significant, with a P value of 0.165. The survival signal may therefore reflect not only how often tumors initially shrink, but also how long disease control lasts or how treatment affects patients whose tumors do not meet the formal definition of response.
Exploratory analyses pointed to potentially greater benefit in patients whose tumors had PD-L1 expression below 1 percent and in those with mucosal melanoma. PD-L1 is a protein used by some cancers to weaken T-cell activity, and low expression is often associated with less predictable benefit from PD-1 blockade. A regimen that alters blood-vessel signaling or stimulates broader immune pathways could, in theory, help overcome some of the limitations of checkpoint therapy in these tumors. However, the subgroup findings were adjusted for false discovery rate and remain hypothesis-generating. Subgroups were small, particularly within the 32-person triplet cohort, making estimates less stable and increasing the possibility that apparent differences arose through chance. The authors specifically emphasized that these observations require confirmation rather than immediate adoption as proof of a biomarker-defined treatment strategy.
The trade-off was increased toxicity. Grade 3 or 4 adverse events, representing severe or medically significant treatment-related effects, occurred in 21.9 percent of patients receiving the triplet compared with 8.9 percent of those receiving the doublet. Although the study reported no treatment-related deaths, the difference indicates that adding anlotinib may create a clinically meaningful burden requiring monitoring and dose management. The source report did not provide a detailed breakdown of every severe adverse event in its abstract, so the overall rates should not be interpreted as a complete safety profile for individual patients. In clinical practice, the risks of an additional targeted drug would need to be weighed against expected disease severity, organ function, previous conditions and the availability of established melanoma treatments.
The study’s most important limitation is its design. Treatment was chosen in routine care rather than assigned randomly, and only measured baseline factors could be balanced through statistical weighting. Differences that were not recorded—or that influenced physicians’ decisions—could still have shaped the results. The uneven sample sizes also make the triplet group vulnerable to imprecise estimates, while the single-center-heavy Chinese clinical context may limit how readily the findings apply to patients elsewhere. The results nonetheless highlight a potentially important direction for melanoma research: combining immune checkpoint blockade with agents that modify interferon signaling and the tumor vasculature. Properly powered prospective randomized trials will be needed to determine whether the apparent survival improvement persists when the three-drug regimen is tested under controlled conditions, and whether its benefits justify the additional toxicity.
