Absolute lymphocyte count as a prognostic biomarker for overall survival in patients with advanced melanoma treated with ipilimumab.

Biomarkers are needed to estimate which patients benefit most from combination ipilimumab and nivolumab immunotherapy. Rigorous biomarker analyses from prior ipilimumab randomized studies without nivolumab are likely to inform which biomarker analyses should be prioritized when examining patients treated with the combination. For the first time, the current analyses investigate absolute lymphocyte count (ALC) in randomized, controlled trials of ipilimumab without nivolumab to assess whether ALC is prognostic or predictive of ipilimumab treatment benefit. Data included patients (n = 1136) treated in the two randomized, controlled phase III studies MDX010-20 and CA184-024. ALC was measured at pretreatment baseline and every 3 weeks for up to 12 weeks, before each dose of ipilimumab. Cox proportional hazards models were used to estimate and test associations between ALC measures and overall survival (OS). In both randomized studies, baseline ALC and ALC halfway through induction (at week 6) were associated with OS not only in ipilimumab-treated patients but also in patients treated with non-ipilimumab control treatments. ALC increased in patients receiving ipilimumab, but this degree of change was not predictive of ipilimumab treatment benefit. Using data from randomized, controlled studies, we were able to conclude for the first time that baseline ALC, ALC halfway through induction (week 6) and the degree of ALC change from baseline to week 6 are prognostic biomarkers in melanoma patients, and do not appear to be predictive of ipilimumab treatment benefit. This more comprehensive understanding of ALC as a biomarker from ipilimumab trials will inform subsequent biomarker investigations in ongoing ipilimumab combination studies such as ipilimumab in combination with nivolumab.