Identification of Immune Phenotypes Associated with Improved Progression Free and Overall Survival for Patients with Multiple Myeloma Treated with Autologous Hematopoietic Cell Transplantation
Authors: Ho Christine M. , Hahn Theresa , Wallace Paul K. , Zhang Yali , Fora Ahmad , Chen George L. , Holstein Sarah A. , Mellors Patrick , McCarthy Benjamin , Balderman Sophia R. , McCarthy Philip L. 
Published: October 2019

Abstract
The treatment of transplant-eligible multiple myeloma (MM) patients usually consists of induction therapy followed by autologous hematopoietic cell transplant (AHCT). Many patients relapse or have disease progression post-AHCT, however selected patients will maintain long term disease control. In addition to standard prognostic features, we investigated whether immune phenotypes predict progression and/or long term disease control after AHCT.
In a cohort of 101 MM patients who received high dose melphalan with AHCT between 8/2007 and 9/2014, we performed a comprehensive peripheral blood immunophenotyping panel including 35 T-, B-, NK- and Dendritic Cell (DC) subsets at a median of 25 days pre-ASCT and at day +100 post-ASCT. The immunophenotyping panel included total numbers of T cells (CD3+, CD4+, CD8+), B cells (CD19+, CD20+), NK cells (CD56+CD16+) and myeloid (CD11c+) and plasmacytoid (CD123+) dendritic cells. T cell subsets included the relative proportions of double positive (CD3+CD4+CD8+), double negative (CD3+CD4-CD8-), CD4+ and CD8+ Naïve (CD3+ CD45RA+ CD45RO- CD27+), CD4+ and CD8+ central memory (CD3+ CD45RA- CD45RO+ CD27+), CD4+ and CD8+ effector memory (CD3+ CD45RA- CD45RO+ CD27-), recent thymic emigrants (CD3+ CD4+ CD45RA+ CD31+), and T-regulatory cells (CD3+ CD4+ CD25(br), CD3+CD4+CD25+CD127(d), CD3+CD4+CD25+CD127-HLADr+). B cell subsets included proportions of naïve (CD19+ CD27-), and memory (CD19+ CD27+, pre-switch CD19+ IgD+ CD27+, post-switch CD19+ IgD- CD27) cells. We also performed limited immune profiling on the apheresis product which included T-cell subsets (CD3+, CD4+, CD8+, double positive (CD3+CD4+CD8+), double negative (CD3+CD4-CD8-) cells) and NK cells (CD16+CD56+). All patients survived to day +100. We examined MM response to AHCT, recovery of absolute lymphocyte count (ALC) by day +15 post-AHCT, PFS and OS.
Characteristics in 101 patients pre-AHCT were: median (range) age 60 (28-75) yrs; 55% female; 29% KPS ≥90; response to most recent therapy was 16% in CR/sCR, 39% in VGPR, 37% in PR, 9% <PR. MM responses at day + 100 included: 44% achieved or maintained CR/sCR, 23% VGPR, 7% PR, and 5% progressed. The peripheral blood immune profile was not representative of the apheresis product immune profile. Also, immune profiling in the apheresis product did not significantly correlate with day +100 peripheral blood immune profiles or PFS/OS. Achievement of CR/sCR at day +100 post-AHCT was not associated with any peripheral blood immunophenotypes tested at either pre-AHCT or day +100 post-AHCT. ALC recovery by day +15 post-AHCT was not associated with significantly longer median PFS or OS than those who did not recover ALC by day +15, in contrast to prior reports.
Improved 2-year PFS and OS correlated with select pre-AHCT peripheral blood B cell populations. Elevated pre-AHCT total CD19+ B cell count was significantly associated with improved 2 year PFS (53% for the lowest (<25%) quartile, 59% for middle quartiles (25-75%), and 83% for the upper (>75%) quartile (P=0.01)) and OS (Figure 1). In addition, increased CD20+ B cell count and increased naïve and memory B cells counts were associated with improved PFS/OS.
Higher day +100 post-AHCT gamma/delta T cell absolute count correlated with improved 2 year PFS: 45% for the lowest (<25%) quartile and 65% for highest (≥25%) quartiles (P=0.02), and OS (see Figure 2). Elevated day +100 AHCT absolute CD4+ central memory cell counts were associated with OS (Figure 3), but not with PFS.
We demonstrate that select subsets of B cell and T cell populations at day +100 post-AHCT correlate with PFS and OS. We are investigating whether these phenotypic changes directly correlate with PFS/OS or are associated with an intermediate event or treatment. Additional studies are planned to examine whether these changes are associated with individual, innate patient immune characteristics or if an individual patient's immune system may be modified to express these favorable immune phenotypes.

Disclosures
Hahn: Novartis: Equity Ownership; NIH: Research Funding. Holstein:Millennium: Membership on an entity's Board of Directors or advisory committees; Amgen: Membership on an entity's Board of Directors or advisory committees; Celgene: Membership on an entity's Board of Directors or advisory committees. McCarthy:Sanofi: Honoraria, Membership on an entity's Board of Directors or advisory committees; The Binding Site: Honoraria, Membership on an entity's Board of Directors or advisory committees; Gamida Cell: Honoraria, Membership on an entity's Board of Directors or advisory committees; Bristol Myers Squibb: Honoraria, Membership on an entity's Board of Directors or advisory committees; Karyopharm: Honoraria, Membership on an entity's Board of Directors or advisory committees; Celgene: Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; Janssen: Honoraria, Membership on an entity's Board of Directors or advisory committees; Onyx: Honoraria, Membership on an entity's Board of Directors or advisory committees.