Abstract 4891: A mass spectrometry-based serum test to predict outcome of treatment with nivolumab: Analysis of samples taken during therapy
Authors: Weber Jeffrey , Roder Heinrich , Asmellash Senait , Meyer Krista , Sayers Kevin , Steingrimsson Arni , Roder Joanna 
Published: July 2016

Abstract
Background. The durability of antitumor responses observed in patients treated with antibodies blocking PD-1 supports a central role for these drugs in current melanoma therapy. However, not all patients achieve a durable response, so identification of biomarkers able to aid therapeutic decision making is needed. We have recently reported on a mass-spectrometry-based test (BDX-008) able to stratify patients according to outcome following anti-PD1 therapy using pretreatment serum samples1. The test assigns a binary label of “Positive” or “Negative”, denoting the likelihood of good or poor outcome, respectively, following anti-PD 1 therapy. Here we present the results of an investigation of the use of this test on samples taken during administration of immunotherapy.
Materials and Methods. Pretreatment serum samples were available from 119 patients enrolled in a study of nivolumab with or without a peptide vaccine for the treatment of advanced melanoma (NCT01176461). Of these patients, 109 provided a serum sample taken at week 7 (WK7) and 91 also provided a sample collected at week 13 (WK13). The fully locked test was performed on all samples. The association of test classifications at all three timepoints with overall survival (OS) and time-to-progression (TTP) was assessed using Kaplan-Meier methods and log-rank p values.
Results. Test classifications were obtained for 107 WK7 samples and 90 WK13 samples. The proportion of patients classified as Positive was similar across the three timepoints (61% baseline, 69% WK7, 66% WK13). Of the 90 patients with three available classifications, 56 (62%) maintained their baseline classification across all timepoints. Classification significantly stratified OS at all three timepoints (baseline: HR = 0.38; WK7: HR = 0.24; WK 13: HR = 0.33; log-rank p for all times &lt; 0.001) and TTP at baseline and WK7 (HR = 0.50, log-rank p = 0.001 and HR = 0.33, log-rank p &lt;0.001, respectively). At WK13 TTP was numerically better for patients classified as Positive in the reduced set of patients (N = 64) without progression before sample collection (HR = 0.58, log-rank p = 0.11). Patients changing from a Negative classification at baseline to Positive at WK7 and WK13 (N = 14) had outcomes similar to those of patients maintaining an initial Positive classification (N = 41).
Conclusions. These results support previous data indicating the potential clinical utility for this test as an aid to physicians in their immunotherapy treatment decisions. Further validation of the test in pretreatment and monitoring settings is ongoing.
1. J Weber et al, Pre-treatment patient selection for nivolumab benefit based on serum mass spectra, SITC 2015.
Citation Format: Jeffrey Weber, Heinrich Roder, Senait Asmellash, Krista Meyer, Kevin Sayers, Arni Steingrimsson, Joanna Roder. A mass spectrometry-based serum test to predict outcome of treatment with nivolumab: Analysis of samples taken during therapy. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 4891.