Stratification of Responders and Non-Responders in the Reach-1 Trial Based on Serum Proteomic Analysis

Acute graft versus host disease (aGVHD) is a serious and potentially life-threatening condition that can develop in patients receiving hematopoietic stem cell transplantation (HSCT). Acute GVHD is characterized by increased levels of inflammatory mediators and signaling through the Janus Kinases (JAKs), leading to tissue and organ damage. Ruxolitinib, an oral JAK1/JAK2 inhibitor, is the first FDA-approved treatment for steroid refractory aGVHD. The current study evaluated proteomic signatures from participants in the REACH-1 clinical trial to identify those individuals which have an increased probability for success when treated with ruxolitinib in combination with corticosteroids.

Plasma was collected for 42 participants enrolled in the REACH-1 clinical trial (NCT02953678) prior to and at designated times following treatment. Broad proteomic analysis of more than 1000 proteins was conducted using the OLINK proximity extension assay. Participants were separated into responders (complete responders, very good partial responders, partial responders) (n=36) or non-responders (mixed responders, progressive disease) (n=6) based on their clinical response at Day 28 of treatment. Baseline differences in day 28 responders versus non-responders were compared using t-tests. Pharmacodynamics changes within responders and non-responders were assessed using paired t-tests. Significance of statistical tests was conferred at p<0.05.

Broad proteomic analysis of plasma identified a total of 145 differentially expressed proteins (p<0.05) between the responders and non-responders at baseline. Thirty-five proteins were elevated and 110 proteins were lower in responders compared to non-responders. At baseline, IL-8, IL-6, and IL-24 were among the most significantly down-regulated while SCF was one of the most significantly up-regulated in responders compared to non-responders. Pharmacodynamic analyses revealed 493 significantly modulated proteins in responders and 92 in non-responders. IL2-RA was among the most significantly down-regulated from baseline to day 28 in both responders and non-responders.

This study suggests that proteomic characterization has the potential to stratify responders and non-responders to ruxolitinib and corticosteroid treatment in steroid refractory aGVHD. Additionally, this study demonstrated robust pharmacodynamic and correlative changes in responders following treatment with ruxolitinib and corticosteroids suggesting that defining a responder population could enrich for patients predisposed to positive therapeutic response; however, this should be prospectively validated in additional studies.