response to both immune- and angiogenesis-targeting drugs.Relative expression changes between archival and fresh biop-sies demonstrate changes in the TME with time and/or follow-ing targeted therapy. Lastly, cross-tumor comparisons supporta tumor-agnostic utility of this approach. Detailed comparisonsof this biomarker approach relative to other available bio-markers will be presented for standard of care drugs andthose in the Oncologie pipeline based on retrospectiveanalyses.Conclusions RNA based descriptors of biology may be a usefulapproach to enrich for response to targeted therapies whosemechanism of action is to modify the TME biology.

http://dx.doi.org/10.1136/jitc-2020-SITC2020.0257

258 SCIENTIFIC CORRELATIVES FROM LCCC 1525: A PHASEII STUDY OF A PRIMING DOSE OF CYCLOPHOSPHAMIDEPRIOR TO PEMBROLIZUMAB TO TREAT METASTATICTRIPLE NEGATIVE BREAST CANCER

1Mark Woodcock*, 2Carey Anders, 2Amanda Van Swearingen, 1Dominic Moore,1Maria Sambade, 1Luz Cuaboy, 1Amy Garrett, 1Karen McKinnon, 1Kristen Cowens,1Dante Bortone, 1Benjamin Calhoun, 1Lisa Carey, 1Claire Dees, 1Trevor Jolly, 1Hyman Muss,1Katherine Reeder-Hayes, 3Rebecca Kaltman, 4Rachel Jankowitz, 5Vinay Gudena,6Oludamilola Olajide, 1Charles Perou, 1Benjamin Vincent, 1Jonathan Serody. 1UNC ChapelHill, Lineberger Comprehensive Cancer Center, Chapel Hill, NC, USA; 2Duke University,Durham, NC, USA; 3George Washington University, Washington, DC, USA; 4University ofPittsburgh, Pittsburgh, PA, USA; 5Cone Health Cancer Center, Greensboro, NC, USA; 6RexHematology Oncology, Raleigh, NC, USA

Background In metastatic triple negative breast cancer(mTNBC), median progression-free survival (PFS) with chemo-therapy alone is approximately 2–4 months1 and improve-ments with single agent checkpoint inhibitors (CI) are limitedby modest response rates. Murine breast cancer models have

demonstrated a role for intratumoral regulatory T cells (Tregs)in modulating response to CIs.2 A phase II clinical trial wasconducted to test the hypothesis that a single, priming doseof cyclophosphamide prior to pembrolizumab would improve

Abstract 258 Figure 1 Gene set enrichment and immune genesignatures in preliminary RNA-Seq samples. Demonstrating pathways (A)and gene signatures (B) associated with B cell activation as significantin patients with clinical benefit on checkpoint inhibitor therapy

Abstract 258 Table 1 Gene set pathways, C2CP set fromMSigDB. To accompany gene sets in Figure 2b

Abstract 258 Figure 2 Tumor genomic and immune features. A-B:Differential gene expression (A) and gene set enrichment (B) results innon-nodal tumor samples, by treatment response. Genes in (A) passingFDR correction (Benjamini Hochberg) are labeled and in red. C:Frequently mutated genes implicated in breast cancer, samples sortedby response. Raw tumor mutational burden is noted at the top of eachsample column. Treatment response and tumor PAM50 subtype foreach sample is listed at bottom of each column. D-E: Sample PD-L1was not significantly associated with either clinical benefit (D) orresponse (E) to therapy (T-test; proportion of sample staining with 22C3antibody). F-G: Immune gene signatures significantly associated withclinical benefit (F) and response (G) in non-nodal tumor samples

Abstracts

A156 J Immunother Cancer 2020;8(Suppl 3):A1–A559

on April 19, 2022 by guest. P

rotected by copyright.http://jitc.bm

j.com/

J Imm

unother Cancer: first published as 10.1136/jitc-2020-S

ITC

2020.0258 on 9 Novem

ber 2020. Dow

nloaded from

PFS in mTNBC. Here we present the correlative genomic andimmunologic analyses from this study.Methods This trial (https://clinicaltrials.gov/ct2/show/NCT02768701) recruited 40 patients with largely pretreatedmTNBC. Response was defined as >30% decrease in imaging-assessed disease burden. Clinical benefit was defined as treat-ment response or stable disease. Tumor specimens were col-lected prior to enrollment, and peripheral blood mononuclearcell (PBMC) samples taken prior to cyclophosphamide andbefore each cycle of pembrolizumab. RNA sequencing wasperformed on tumor samples for gene expression and immunerepertoire reconstruction. Targeted sequencing of the T-cellbeta chain, IG kappa, lambda and heavy chain (TRB, IGK,IGL, and IGH, respectively) on PBMCs captured the periph-eral immune repertoire. Whole exome sequencing was per-formed on tumor samples with PBMCs serving as a matchednormal.Results Of 40 patients enrolled, 31 patients had tumor RNA-seq and at least 15 had matched PBMC-derived immunechains capturing both pre and post treatment. When prelimi-nary RNA-seq samples (n=22) revealed upregulation in B-cellreceptor pathways and related gene signatures (figure 1), weupdated our planned analysis to exclude tumor specimens col-lected from lymph nodes. In our final analysis, response totherapy (4 of 25, 16%) was associated in tumor RNA-Seqwith gene pathways involving programmed cell death andMAPK activation, while non-responding tumors were enrichedin G-protein signaling and inhibition of insulin secretion (fig-ure 2a,b, table 1). Immune gene signatures related to NK cellsand B-cell activation, signaling and interaction with T follicu-lar helper cells,3–7 were associated with response (figure 2g).Pre-treatment immune repertoire measures demonstrated a sig-nificant association between increased peripheral IGH abun-dance and richness, and both future clinical benefit andresponse to therapy (figure 3a-d).Conclusions Response to CI therapy was associated withimmunogenomic features of programmed cell death and B-cellactivation. Pre-treatment circulating immunoglobulin diversity

measures (high IGH abundance and IGH richness) also corre-lated with future response to therapy. Taken together, thesedata suggest that B-cell activity contributes significantly toresponse to CI therapy in mTNBC.Acknowledgements UNC Office of Clinical and TranslationalResearch (OCTR), High Throughput Sequencing Facility(HTSF), and UNC Bioinformatics Core. We also thank thepatients in this study and their families, without whom thisstudy would not have been possible.Trial Registration Clinical Trials. gov: NCT02768701.Ethics Approval All patients provided written informed con-sent, and the study was approved by each institution’s institu-tional review board (No. NCT02768701).

REFERENCES1. Tutt A, Tovey H, Cheang MCU, et al. Carboplatin in BRCA1/2-mutated and triple-

negative breast cancer BRCAness subgroups: the TNT Trial. Nat Med 2018;24(5):628–637. doi:10.1038/s41591-018-0009-7

2. Taylor NA, Vick SC, Iglesia MD, et al. Treg depletion potentiates checkpoint inhib-ition in claudin-low breast cancer. J Clin Invest 2017;127(9):3472–3483.doi:10.1172/JCI90499

3. Hollern TFH B cell: Hollern DP, Xu N, Thennavan A, et al. B Cells and T FollicularHelper cells mediate response to checkpoint inhibitors in high mutation burdenmouse models of breast cancer. Cell 2019;179(5):1191–1206.e21. doi:10.1016/j.cell.2019.10.028

4. Iglesia B cell: Iglesia MD, Vincent BG, Parker JS, et al. Prognostic B-cell signaturesusing mRNA-seq in patients with subtype-specific breast and ovarian cancer. ClinCancer Res 2014;20(14):3818–3829. doi:10.1158/1078-0432.CCR-13-3368

5. Fan IGG: Fan C, Prat A, Parker JS, et al. Building prognostic models for breastcancer patients using clinical variables and hundreds of gene expression signa-tures. BMC Med Genomics 2011;4:3. Published 2011 Jan 9. doi:10.1186/1755-8794-4-3

6. Bindea: Bindea G, Mlecnik B, Tosolini M, et al. Spatiotemporal dynamics of intra-tumoral immune cells reveal the immune landscape in human cancer. Immunity2013;39(4):782–795. doi:10.1016/j.immuni.2013.10.003

7. Prat Claudin: Prat A, Parker JS, Karginova O, et al. Phenotypic and molecularcharacterization of the claudin-low intrinsic subtype of breast cancer. Breast Can-cer Res 2010;12(5):R68. doi:10.1186/bcr2635

http://dx.doi.org/10.1136/jitc-2020-SITC2020.0258

259 PHASE IB/II OPEN-LABEL, RANDOMIZED EVALUATIONOF ATEZOLIZUMAB (ATEZO) + SELICRELUMAB (SELI) +GEMCITABINE+NAB-PACLITAXEL (GEM+NABP) ORBEVACIZUMAB (BEV) VS CONTROL IN MORPHEUS-PDAC, -TNBC AND -CRC

1Gulam Manji*, 2Nathan Bahary, 3Vincent Chung, 4Florence Dalenc, 5Michel Ducreux,4Carlos Gomez-Roca, 6Seock-Ah Im, 7Jeremy Kortmansky, 7Jill Lacy, 8Neil Segal,9Olivier Tredan, 10Olivera Cirovic, 11Kelly DuPree, 12Christelle Lenain, 13Danny Lu,11Lidia Robert, 14Jeffrey Xu, 11Xiaosong Zhang, 15Sung-Bae Kim. 1Columbia UniversityMedical Center, New York, NY, USA; 2University of Pittsburgh Medical Center, Pittsburgh,PA, USA; 3City of Hope National Medical Center, Duarte, CA, USA; 4Institut ClaudiusRegaud, IUCT-Oncopole, Toulouse, France; 5Institut Gustave Roussy, Villejuif, France; 6SeoulNational University Hospital, Seoul, Korea, Republic of; 7Yale University School of Medicine,New Haven, CT, USA; 8Memorial Sloan Kettering Cancer Center, New York, NY, USA;9Centre Léon Bérard, Lyon, France; 10Roche Innovation Center Basel, Basel, Switzerland;11Genentech, Inc., South San Francisco, CA, USA; 12F. Hoffmann-La Roche AG, Basel,Switzerland; 13Hoffmann-La Roche Limited, Mississauga, Canada; 14Roche (China) HoldingLtd, Shanghai, China; 15Asan Medical Center, Seoul, Korea, Republic of

Background The MORPHEUS platform comprises multiplerandomized Phase Ib/II trials to identify early safety and effi-cacy signals for treatment combinations across cancers. Seliinteracts with CD40 on antigen presenting cells, resulting inactivation and priming of CD8 T-cells. Atezo (anti-PD-L1)+seli (CD40 agonist) was evaluated with gem+nabP for pan-creatic ductal adenocarcinoma (PDAC), or with bev for triple-negative breast cancer (TNBC) and colorectal cancer (CRC).

Abstract 258 Figure 3 Tumor and peripheral immune repertoirediversity. A-D: In tumor RNA-Seq, higher IGH chain abundance andrichness was associated with both clinical benefit (A, C) and response(B, D) (n=31). E-F: Inter-group comparisons showed fewer TRB chainsimilarities between patients who derived clinical benefit (E) or response(F) versus those who did not, in pre-treatment PBMC samples. G-I:Univariate Cox proportional hazards models for PFS showing immunediversity measures derived from pre-treatment tumor RNA-Seq (G),PBMC-derived amplicon sequencing pre-pembrolizumab (H), and PBCM-derived amplicon sequencing post-pembrolizumab (I)

Abstracts

J Immunother Cancer 2020;8(Suppl 3):A1–A559 A157

on April 19, 2022 by guest. P

rotected by copyright.http://jitc.bm

j.com/

J Imm

unother Cancer: first published as 10.1136/jitc-2020-S

ITC

2020.0258 on 9 Novem

ber 2020. Dow

nloaded from