Metastatic melanoma: anti-ipilimumab antibodies tied to worse OS

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  • In patients with metastatic melanoma treated with ipilimumab, low serum levels of ipilimumab and development of antidrug antibodies (ADAs) are associated with reduced survival.

Why this matters

  • Little is currently known about the clinical effects of ADA development.

Key results

  • Low serum levels of ipilimumab before the second infusion (n=24) were associated with reduced OS (HR, 1.3 per 1 μg/mL; P=.01) and PFS (HR, 1.2 per 1 μg/mL; P=.02).
  • Low serum levels of ipilimumab before the fourth infusion (n=20) were not significantly associated with OS or PFS (data not shown).
  • 26% of patients were ADA-positive at the second or fourth infusion.
  • ADA positivity was associated with reduced OS (HR, 3.0; P=.03).
  • 50% of ADA-positive patients vs 13% of ADA-negative patients discontinued therapy before the fourth infusion due to disease progression.
  • ADA positivity and lower serum levels of ipilimumab were not significantly associated (data not shown).

Study design

  • 31 patients with ipilimumab-treated metastatic melanoma were analyzed for drug serum levels, and ADAs to ipilimumab at baseline and the second and fourth infusions.
  • 77% received 4 infusions.
  • Primary endpoints were OS and PFS.
  • Funding: None disclosed.


  • Small patient sample size.
  • Retrospective design.