Cosibelimab Shows Sustained Results in Advanced CSCC at 2.5 Years

A pivotal open-label study of cosibelimab, an anti-PD-L1 antibody, has now delivered efficacy and safety results in advanced cutaneous squamous cell carcinoma with a median follow-up of at least 2.5 years — the longest look yet at the drug in this population. Nikhil I. Khushalani, MD, of Moffitt Cancer Center in Tampa, Florida, presented the updated findings at the 2026 ESMO Congress.

The update matters because durability is the question that defines immunotherapy in skin cancer. The study enrolled patients with locally advanced or metastatic cutaneous squaneous cell carcinoma — a population in which tumors have grown beyond what surgery or radiation can reasonably control.

What is cosibelimab, and who was studied?

Cosibelimab is an anti-PD-L1 antibody. That class works by blocking the PD-L1 protein on tumor cells, releasing the brake on T-cell activity. It is a design point worth flagging: PD-L1 agents and PD-1 agents target the same immune checkpoint pathway from opposite ends.

The trial behind this update is a pivotal open-label study. Open-label means everyone enrolled — patients and investigators alike — knew the treatment being given. That design is standard in oncology when the disease course and the expected effect are hard to mistake for placebo outcomes.

The cohort: patients with locally advanced or metastatic CSCC. Median follow-up has now reached at least 2.5 years, giving clinicians a substantially longer view of both response durability and safety than earlier data cuts allowed.

Why does a 2.5-year follow-up matter?

Early response rates can flatter a drug. The harder test is whether responses hold over years, and whether late toxicities emerge as exposure lengthens. In skin-cancer drug development, extended follow-up separates drugs that merely shrink tumors from drugs that keep them controlled.

For patients with advanced CSCC, that distinction is not academic. These are often older patients with limited treatment alternatives once surgery and radiation are exhausted. A drug's value in that setting rests on sustained control, not on a single scan.

The update from Khushalani covers both sides of that ledger: efficacy and safety. In other words, how well the drug worked and how well patients tolerated it over the longer horizon.

Where was the data presented?

The findings debuted at the 2026 ESMO Congress, one of the largest annual gatherings in oncology. Congress presentations of pivotal-trial updates typically carry weight because they reach a global audience of treating oncologists quickly, often ahead of or alongside full journal publication.

Khushalani's review of the data adds an expert interpretive layer. As a clinician at Moffitt Cancer Center, a major US cancer center, his read of the update helps translate trial numbers into practice-relevant context for colleagues managing advanced CSCC.

What should dermatology readers watch next?

The full response-rate figures, duration-of-response data, and safety tables sit in the detailed congress materials, and Derm Field readers managing CSCC patients will want to track the study as results mature further.

The key development is that the pivotal cosibelimab experience in locally advanced and metastatic CSCC now rests on a median follow-up of at least 2.5 years, and clinicians should watch for the peer-reviewed publication that follows this ESMO presentation.