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The MAHLER Trial

A Study to Explore Patient Response to Checkpoint Inhibitors in Advanced Melanoma

Why This Trial

Checkpoint inhibitor treatments release the brakes on the immune system so it can attack tumors more freely. While they have extended the lives of many patients, these blockbuster drugs do not always work for everyone.

PICI investigators aim to uncover why checkpoint inhibitors shrink tumors in some patients and not others – and whether two checkpoint therapies could help patients who did not initially respond to one checkpoint inhibitor alone.

To do that, they will hunt for “biomarkers for response” – tell-tale, measurable signs in the body that correlate to how well a patient may do on a given therapy.

About the Study

This phase 2 randomized trial was designed for patients with advanced melanoma whose tumors did not respond, or continued to grow, after treatment with checkpoint therapy targeting the protein PD-1.

Some patients received a single checkpoint inhibitor, ipilimumab, which targets the protein CTLA-4. Other patients were treated with a combination of ipilimumab and nivolumab, a checkpoint inhibitor that targets the PD-1 protein.

Different samples from each patient were collected throughout the study. As part of the analysis, the researchers will look for potential biomarkers that can predict which patients will respond to one or both treatments.

Who’s Eligible

Patients with inoperable, metastatic melanoma whose tumors did not respond or continued to grow after treatment with anti-PD-1 checkpoint inhibitors.

Treatments Tested

  • Ipilimumab
  • Ipilimumab and nivolumab

Where We’re At Now

The study completed enrollment in July 2018 and closed in August 2019.

PICI researchers are in the process of analyzing blood and tumor samples to study the impact of the immunotherapies. We expect to publish results in 2021.



Principal Investigators

  • Claire Friedman, MD | Memorial Sloan Kettering Cancer Center
  • Tara C. Mitchell, MD | University of Pennsylvania
  • Antoni Ribas, MD, PhD | University of California, Los Angeles
  • Hussein Tawbi, MD, PhD | The University of Texas MD Anderson Cancer Center
  • Katy Tsai, MD | University of California, San Francisco


For more information on this trial (NCT02731729), visit