Checkpoint inhibitors — anti–PD-1, ipilimumab plus nivolumab, and nivolumab plus relatlimab
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Immunotherapy is the backbone of treatment for melanoma that has spread to lymph nodes or to distant organs. The drugs involved are called immune checkpoint inhibitors. They do not attack the cancer directly. Instead they release natural "brakes" on the immune system, so that a person's own T cells can recognize the melanoma and destroy it. For a broad picture of where these drugs sit among all the options, see melanoma treatment options.
Because the immune system now does the work, responses can be remarkably durable — some people stay free of melanoma for years after stopping treatment, an outcome doctors sometimes call a "functional cure." The same mechanism, though, can turn the immune system against healthy organs. That trade-off is covered in detail in managing the side effects of melanoma immunotherapy.
This article explains how checkpoint inhibitors work, the main first-line regimens and how they compare, how doctors choose among them, how long treatment lasts, why an early scan can be misleading, and what happens if a regimen stops working.
T cells carry molecules on their surface that act as "off switches," keeping the immune system from attacking healthy tissue. Melanoma exploits those switches to avoid being attacked. Checkpoint inhibitors are antibodies that block a specific switch, freeing T cells to go after the cancer. Three switches are targeted by drugs approved for melanoma:
Pembrolizumab and nivolumab block PD-1, a brake that melanoma cells press by displaying a matching protein (PD-L1). Anti–PD-1 drugs are the single most important class in melanoma and form the base of every first-line regimen.
Ipilimumab blocks CTLA-4, a brake that acts earlier, in the lymph nodes, as T cells are first being activated. Ipilimumab is used together with nivolumab rather than on its own in the first-line setting. It adds anti-tumor power but also the most side effects.
Relatlimab blocks LAG-3, a third brake that builds up on exhausted T cells inside tumors. It is given as a fixed-dose combination with nivolumab. Adding relatlimab improves on nivolumab alone while adding far less toxicity than ipilimumab does.
Three checkpoint inhibitor regimens are used first for advanced melanoma. All are given as an intravenous infusion in an outpatient clinic. They differ in how well they shrink and control melanoma and in how hard they are on the body.
There is no single best regimen for everyone. A medical oncologist weighs how aggressive the melanoma looks against how much toxicity a person can safely absorb. Common factors:
It is reasonable to ask for the expected response rate and the expected serious-side-effect rate for each regimen your team is considering, so the choice reflects your own priorities.
What sets immunotherapy apart from older melanoma drugs is that its benefit often lasts. When a person responds well, the immune system appears to "remember" the melanoma, and the response can continue long after treatment ends. In the longest follow-up studies, a meaningful share of people who responded remain free of active melanoma many years later with no ongoing therapy. Doctors sometimes call this a functional cure — not a promise that the cancer can never return, but a state of lasting control.
Responses are not always fast. Some people see tumors shrink within the first 6 to 12 weeks; others improve more slowly over several months. Because the effect can build over time, teams generally give a regimen a fair trial before judging it, unless the melanoma is clearly and rapidly worsening or the person is becoming unwell.
Not everyone benefits. A portion of melanomas never respond to checkpoint inhibitors, and some respond and then relapse. That is why close follow-up with scans continues throughout treatment.
For metastatic (stage IV) melanoma, checkpoint inhibitors are usually continued until the melanoma clearly progresses or until side effects become unacceptable. Many programs also stop treatment at around two years in people who are doing well, because the evidence suggests the immune memory persists without indefinite dosing. After surgery for stage III melanoma, adjuvant immunotherapy is typically given for one year.
Early in treatment, a scan can be hard to read. In a minority of people — well under one in ten — tumors briefly look larger, or a new spot appears, not because the cancer is growing but because immune cells have flooded into it. This is called pseudoprogression. When someone feels well and the picture is ambiguous, the team often keeps treating and repeats imaging in about 4 to 8 weeks, using response criteria designed for immunotherapy, before deciding whether the melanoma is truly progressing.
Genuine progression — clear growth confirmed on repeat imaging, new symptoms, or a rising LDH — is the signal to change the plan.
A first-line regimen failing is not the end of treatment. Options after progression include:
Checkpoint inhibitors have changed advanced melanoma from a disease measured in months into one where many people live for years and some appear to be cured. The choice is usually among single-agent anti–PD-1, nivolumab plus ipilimumab, and nivolumab plus relatlimab — a spectrum that trades more anti-tumor power for more toxicity. Where a person sits on that spectrum depends on how the melanoma is behaving and on what side-effect risk is acceptable to them.
Understanding how these drugs work, how responses are judged, and what comes next makes it easier to be an active partner in the decision. The companion article on managing side effects covers the other half of the picture.
Disclaimer: This article is for educational purposes only and not a substitute for professional medical advice. Always consult a qualified dermatologist or oncologist about your personal diagnosis and treatment plan.
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