Background: PD-1/L1 blocking agents have transformed the treatment of multiple cancers, but some tumor types including MSS-CRC appear to be refractory. Monalizumab (anti-NKG2A) and Durvalumab (anti-PD-L1) may promote antitumor immunity via non-redundant mechanisms targeting innate and adaptive immunity. The safety and preliminary efficacy of this combination (NCT02671435) was previously reported (ASCO 2018). Here, we present the results of baseline and longitudinal pharmacodynamic biomarker assessments in peripheral blood and tumor in patients with MSS-CRC treated with Monalizumab plus Durvalumab. Methods: Peripheral biomarkers evaluated included NKG2A receptor occupancy (RO), and frequency and functional status of immune cells (N = 23). In tumors, changes in NK and CD8 cells in pre/post-tumor biopsies were evaluated by immunohistochemistry (IHC, N = 7). Gene expression profiling of tumors was determined by RNAseq in N = 15 pretreated and N = 4 paired biopsies. Results: In peripheral blood, full and sustained NKG2A RO was observed. Expansion of activated or proliferating NK cells was detected in 14/23 and 10/20 patients respectively, while increases in T cell proliferation (KI67+) were observed at levels expected for Durvalumab monotherapy (1.5-2-fold). In an in vitro assay system, similar changes on T/NK cell phenotyping were observed upon exposure to Monalizumab and Durvalumab. No consistent pharmacodynamics changes in tumoral NK and CD8 cells by gene expression or IHC were observed. However, modulation of pathways associated with metabolism, DNA repair and cell cycle were detected in tumors on treatment. Conclusions: In peripheral blood, pharmacodynamic effects consistent with the proposed mechanism of action of Monalizumab and Durvalumab were observed in patients with MSS-CRC. Clinical trial identification: NCT02671435; February 22, 2016. Legal entity responsible for the study: MedImmune. Funding: MedImmune. Disclosure: N. Standifer, M.L. Ascierto, C. Morehouse, H. Ghadially, J. Rodriguez Canales, M.C. Rebelatto, X. Song, D.C. Jones, X. Li, S. Marshall, S. Abdullah, M. Jure-Kunkel: Employee: MedImmune. All other authors have declared no conflicts of interest.

Programmed cell death-1 (PD-1) inhibits T-cell activation. Blocking the PD-1/programmed cell death ligand 1/2 (PD-L1/2) axis has an acceptable safety profile, induces antitumor responses, and provides clinical benefit across tumors. MEDI0680 is a humanized IgG4&kgr; mAb specific for human PD-1 that blocks interaction with PD-L1/2. This is an ongoing Phase 1, multicenter, open-label, first-in-human, dose-escalation and expansion study of single-agent MEDI0680 in immunotherapy-naïve pts with advanced solid tumors. Primary objectives are safety/tolerability and maximum tolerated dose (MTD). Secondary objectives include pharmacokinetics (PK), pharmacodynamics (PD) and antitumor activity (modified RECIST v1.1). As of 2 Nov 2015, 58 pts have enrolled across 9 cohorts (0.1–20 mg/kg given Q3W, Q2W, QWx2 then Q2W, or QWx4 then Q2W). MTD was not reached. Treatment-related AEs occurred in 46 pts; most common (>10%) were fatigue (21%), nausea (14%) and arthralgia (14%). Related Grade 3/4 AEs occurred in 10 pts; most common (>1 pt) were anemia, arthralgia and increased AST (3% each). 2 pts discontinued due to related AEs: pyrexia in 1 pt; and increased AST, myasthenia gravis and myositis in 1 pt. There were no Grade 5 related AEs. MEDI0680 had a linear PK profile with dose-proportional increases in peak serum concentration. Median PD-1 receptor occupancy on CD3+ T cells was ≥70% after 1 cycle of 10 or 20 mg/kg Q2W. Increased percentages of Ki67 + , ICOS+ and HLA-DR+ T cells; increased levels of plasma IFNγ; and enhanced intra-tumor gene expression for these factors were seen after treatment, demonstrating biological activity of MEDI0680. Of 51 evaluable pts, 9 (18%) had an objective response (8 had renal cancer or melanoma), including 1 (2%) complete response (renal cancer). 14 (28%) pts had stable disease as their best response. The recommended dose is 20 mg/kg Q2W, based on PK, PD, safety and efficacy. MEDI0680 has an acceptable safety profile, with preliminary signs of efficacy. A Phase 1 combination study with durvalumab to test the concept of complete PD-1/PD-L1 axis blockade is ongoing in advanced solid tumors.

Background: A high quality PD-L1 companion diagnostic may help predict which patients are more likely to respond to PD-1/PD-L1 antibody-based therapy. Here we describe a PD-L1 immunohistochemical (IHC) diagnostic test developed by Ventana Medical Systems for use with durvalumab. Methods: An anti-human PD-L1 rabbit monoclonal antibody (SP263) was optimized for use with Ventana OptiView DAB IHC Detection Kit on the automated BenchMark ULTRA platform. The PD-L1 IHC assay was validated for use in formalin-fixed, paraffin-embedded samples of NSCLC in a series of studies addressing sensitivity, specificity, robustness, and precision. Durvalumab is a human IgG1 mAb that blocks PD-L1 binding to PD-1 and CD80 with high affinity and selectivity. A subset of clinical trial samples from a Phase 1/2 study of durvalumab (NCT01693562) was analyzed to determine optimal cut-off for enriching response to durvalumab. Inter-reader precision was established by 3 pathologists who evaluated 81 NSCLC samples across the range of expression levels. Results: The Ventana PD-L1 IHC (SP263) assay met all pre-defined acceptance criteria. The scoring algorithm was defined using statistical analysis of clinical response data and PD-L1 staining parameters observed in a set of NCT01693562 clinical trial samples. Samples of both cancer types are considered test positive when the membrane of ≥ 25% of tumor cells stain for PD-L1 at any intensity. Inter-reader precision in determining PD-L1 status resulted in an overall percentage agreement of 97% for NSCLC. PD-L1+ patients identified by the scoring algorithm had a higher response rate than PD-L1- patients. Interlaboratory testing was performed at 3 external laboratories and demonstrated an overall agreement rate of 86.4%. Conclusions: These results highlight the robustness and reproducibility of the PD-L1 IHC (SP263) assay in a clinical setting. In NSCLC patients treated with durvalumab, PD-L1+ patients identified by the scoring algorithm had a higher response rate than PD-L1- patients. The clinical utility of the PD-L1 diagnostic assay will be further validated in a prospective manner using additional patients in this study and in other durvalumab studies. Citation Format: Marlon C. Rebelatto, Amita Mistry, Constantine Sabalos, Nicole Schechter, Jill Walker, Anita Midha, Keith E. Steele, Paul B. Robbins, Xia Li, Li Shi, John A. Blake-Haskins, Ramy A. Ibrahim, Laura Richman. An immunohistochemical PD-L1 companion diagnostic assay for treatment with durvalumab (MEDI4736) in NSCLC patients. [abstract]. In: Proceedings of the CRI-CIMT-EATI-AACR Inaugural International Cancer Immunotherapy Conference: Translating Science into Survival; September 16-19, 2015; New York, NY. Philadelphia (PA): AACR; Cancer Immunol Res 2016;4(1 Suppl):Abstract nr B005.