Ventana SP263 Research Articles

Concordance among the three commercially available PD-L1 assays for esophageal squamous cell carcinoma.

4058 Background: Immune checkpoint inhibitors are now standard-of-care for patients with esophageal squamous cell carcinoma (ESCC). The predictive significance of PD-L1 expression in ESCC has been investigated by different antibodies, scoring algorithms and cutoff values in several phase III trials. However, it remains controversial whether PD-L1 is a predictive biomarker for response to PD-1/PD-L1 blockade. Evaluating the concordance of the commercially available PD-L1 assays is essential to understand the discrepancy in the ESCC clinical trials, and helpful to further investigate the predictive value of PD-L1 expression. Methods: 145 archival tumor samples were obtained from 131 patients with ESCC (stage I-IV) at National Taiwan University Hospital. Formalin-fixed, paraffin-embedded archival tumor samples were assessed by three commercially available PD-L1 assays: VENTANA SP263, Dako 22C3 and Dako 28-8 assays. Assays were performed in a College of American Pathologists accredited central laboratory and scored for PD-L1 staining by using multiple metrics including tumor cell score (TC), immune cell score (IC) and combined positive score (CPS) or tumor area percentage (TAP). Analytical concordance was calculated pairwise between assays using the Spearman (ρ) rank correlation coefficient. Classification concordance, including agreement between clinically relevant scoring algorithms, was investigated using positive percent agreement (PPA), negative percent agreement (NPA), and overall percent agreement (OPA) at multiple cutoff values to assess the overlap between populations by using different assays. Results: SP263, 22C3 and 28-8 assays showed good analytical correlation for TC staining (Spearman’s rank correlation coefficient 0.8–0.9). Correlation was lower for IC (Spearman’s rank correlation coefficient 0.59-0.61). There was moderate overlap between populations identified by SP263 and 28-8 or 22C3 based on CPS or TAP algorithm at multiple cutoff values. OPAs for these 3 assays ranged from 68%–88% at various matched algorithms. The SP263 and 22C3 PD-L1 assays appeared relatively more sensitive, assigning a higher proportion of patients as PD-L1 positive or high, compared to 28-8 assay. When using assay-specific clinically relevant algorithm, moderate classification agreement was seen for SP263 versus 22C3 or 28-8. Differences were observed between patient populations with tumor classified as PD-L1 high versus PD-L1 low/negative using CPS≥10, TAP≥10% and TC≥1%. The PPA between 22C3 CPS≥10 and SP263 TAP≥10 or 28-8 CPS≥10 or 28-8 TC≥1% were 75%, 57% and 68% respectively. Conclusions: This study is the first dataset to compare various PD-L1 assays in ESCC. Differences in classification of patients with PD-L1 high versus low/negative using clinically relevant algorithms suggest that caution should be taken when comparing data across the trials.

Metastatic breast cancer (MBC) with ultra-high tumor mutational burden (UHTMB): A comprehensive genomic profiling (CGP) study.

1036 Background: Pts with MBC whose tumors feature high TMB (≥ 10 mutations/Mb) are eligible for on label immune checkpoint inhibitor (ICI) treatment. This study evaluated the genomic landscape of MBC with “Ultra high” TMB, defined at > 20 mutations/Mb. Methods: 2049 MBC underwent hybrid capture-based CGP to evaluate all classes of genomic alterations (GA), TMB, microsatellite instability (MSI) and trinucleotide mutational signatures. HER2 IHC results were available in a subset of pts. PD-L1 expression on immunocytes was determined by IHC (Ventana SP142). Results: 45/2049 (2.2%) of MBC were UHTMB. 45 (100%) pts had metastatic disease. 38 (84%) had documented Stage IV disease and 7 documented axillary LN metastases at the time of sequencing. Local breast tumor was used for CGP in 19 (42.2%) MBC and metastatic site biopsy was used in 26 (57.8%). When compared with 2004 non-UHTMB pts with UHTMB were older (mean 64.6 yrs vs 58.2 yrs p < .0001), more often had lobular histology (40.0% vs 14.5% p < .0001) and ER+ disease (86.6% vs 70.0%). Of the 35 UHTMB cases with HER2 IHC data available, 11 (31.4%%) were HER2 IHC negative (0+), 21 (60.0%) were HER2-low status (9 1+ and 12 2+/ISH negative) and 3 (8.6%) were HER2 IHC positive (3+). 1/3 HER2 IHC2+ cases and 2/45 (4.4%) of all UHTMB cases were positive for HER2 copy number gain on CGP. UHTMB cases had more driver GA/tumor (mean 9.8 vs 5.7 p < .0001) and were less often TNBC (13.3% vs 27.0% p = .041) compared to non-UHTMB high cancers. Mutation signature analysis revealed APOBEC was predominant in UHTMB samples (82.5%); MMR signature was also observed in 10% of cases. MSI high status was significantly more frequent in UHTMB high cases (11.6% vs 0.4% p < .0001). GA more frequently identified in UHTMB cases included CDH1 (45.5% vs 14.3% p < .0001), PIK3CA (81.8% vs 37.9% p < .0001), CDKN2A (11.4% vs 3.2% p = .017), ARID1A (25.0% vs 5.0% p < .0001) and NF1 (20.5% vs 5.9% p = .0014). PD-L1 ( CD274) gene amplification (2.3% vs 1.3%) or protein expression by the Ventana SP142 assay (57.14% vs 51.10%) were not significantly different among groups. Conclusions: UHTMB MBC is a rare, yet clinically important subset of clinically advanced breast cancer driven by APOBEC mutagenesis, with high incidence of ER+ lobular histology and frequent alterations in CDH1 and PIK3CA. In addition to potential benefit from ICI based treatment, UHTMB MBC present with a high frequency of HER2-low status which may impact therapy decisions for this rare disease. [Table: see text]

PD-L1 in head and neck cancers: Audit for tertiary care centre in India.

e14565 Background: There is no data on the expression of Programmed Death Ligand 1 (PD-L1) in Head and Neck cancers (HNC) from the Indian population. Hence, this audit was done to estimate the incidence of PD-L1 expression in HNC’s and to detect factors affecting the same. Methods: Data was collected from 466 cases who were advised for PD-L1 gene expression testing from the HNC OPD of Tata Memorial Hospital, Mumbai. Ethics committee approval for this retrospective audit was obtained. Tumor Proportion Score (TPS) scoring for PD-L1 expression was performed using the VENTANA SP263 PD-L1 Assay. PD-L1 status was determined by the percentage of tumor cells with any membrane staining above the background. The demographic details and factors such as Eastern Cooperative Oncology Group (ECOG) performance status (PS), tobacco use, site of tumor, histopathology and time of biopsy. Descriptive statistics were used for analysis. Factors affecting PD-L1 gene expression were sorted using logistic regression analysis. Results: 466 patients were evaluated with a median age of 49 years (Range:16-85), PD-L1 expression was divided as scores and was observed that TPS-0% (Tumor proportion score) was seen in 73 patients (15.7%), TPS >0-20% was seen in 174 patients (37.3%), TPS >20-50% was seen in 88 patients (18.9%) and TPS >50% was seen in 131 patients (28.1%). Higher expression of PDL-1 was seen in oral cavity as site of tumor (p=0.000), squamous cell histology (p=0.000) and consumption of tobacco (p=0.001). Conclusions: This is one of the first studies evaluating real world data on the expression of PDL-1 in HNC’s in the Indian population and factors affecting it. PDL1 expression of 1% or more is seen in 84.3% of HN cancers in India. The histology of the tumor is the major impacting factor. The data provides novel insight into many factors affecting the expression of PDL-1 in HNC’s and in the future can be of help in developing treatment plans with various immunotherapies. [Table: see text]

Phase 3 trial of durvalumab combined with domvanalimab following concurrent chemoradiotherapy (cCRT) in patients with unresectable stage III NSCLC (PACIFIC-8).

TPS8609 Background: The PACIFIC trial (NCT02125461) established up to 12 months of consolidation therapy with durvalumab as standard of care (SoC) for patients with unresectable stage III non-small-cell lung cancer (NSCLC) and no disease progression after platinum-based cCRT. To improve outcomes further in this population, novel immunotherapy combinations that build on the backbone of PD-L1 inhibition with durvalumab are being explored. Domvanalimab (AB154) is a Fc-silent humanized IgG1 monoclonal antibody that blocks interaction of the T cell immunoreceptor with Ig and ITIM domains (TIGIT; upregulated by immune cells) with CD112 and CD155 (expressed by tumor and antigen-presenting cells), reducing inhibition of T cells and natural killer cells and, thereby, promoting antitumor activity. The combination of TIGIT inhibition with PD-(L)1 inhibition has shown encouraging activity in phase 1 and 2 trials in metastatic NSCLC, with enriched benefit observed among patients with PD-L1 positive tumors (Rodriguez-Abreu, et al. 2020; Niu, et al. 2020). In ARC-7 (NCT04262856), a randomized, phase 2 trial, the combination of domvanalimab and PD-1 inhibition was associated with improvement in progression-free survival (PFS) versus PD-1 inhibition alone (HR, 0.55; 95% CI, 0.31–1.0) in treatment-naïve patients with metastatic NSCLC and high PD-L1 expression (tumor proportion score ≥50%) (Johnson, et al. 2022). PACIFIC-8 (NCT05211895) is assessing the efficacy and safety of durvalumab combined with domvanalimab as consolidation therapy in patients with PD-L1 positive, unresectable stage III NSCLC and no disease progression after platinum-based cCRT. Methods: PACIFIC-8 is a phase 3, double-blind, placebo-controlled, randomized, global trial. Eligible patients (aged ≥18 years) must have PD-L1 positive, unresectable stage III NSCLC (tumor cell [TC] expression ≥1% by central lab; VENTANA SP263 IHC assay), WHO performance status 0/1, documented EGFR/ALK wild-type tumor status, and not have progressed following definitive, platinum-based cCRT (≥2 cycles). Approximately 860 patients will be randomized (1:1) to receive SoC durvalumab (1500 mg IV) combined with either domvanalimab (20 mg/kg IV) or placebo, every 4 weeks for up to 12 months. The primary endpoint is PFS (RECIST v1.1) by blinded independent central review (BICR) in patients with PD-L1 TC ≥50%. Secondary endpoints include PFS (RECIST v1.1; BICR) in patients with PD-L1 TC ≥1%, overall survival, objective response rate and duration of response (RECIST v1.1; BICR), safety/tolerability, and patient-reported outcomes. Trial enrollment is ongoing. Previously presented at the European Society for Medical Oncology (ESMO) Congress 2022, FPN (Final Publication Number): 971TiP, Mustafa Özgüroğlu et al. – Reused with permission. Clinical trial information: NCT05211895 .

Neoadjuvant single-dose trilaciclib prior to combination chemotherapy in patients with early triple-negative breast cancer: Safety, efficacy, and immune correlate data from a phase 2 study.

603 Background: Trilaciclib, an intravenous CDK4/6 inhibitor, induces transient G1 cell cycle arrest. In preclinical studies, trilaciclib demonstrated immune-modulating effects by enhancing T-cell activation, favorably altering the tumor microenvironment (TME), and improving long-term immune surveillance. Preliminary data from this phase 2, single-arm, open-label study of neoadjuvant trilaciclib in triple-negative breast cancer (TNBC; NCT05112536) showed that single-dose trilaciclib increased CD8+ T-cell/Treg ratios within the TME. Here, we combine immune analysis with clinical outcomes to identify correlates of treatment response. Methods: Patients (pts) with early-stage TNBC received single-dose trilaciclib followed by trilaciclib + dose-dense anthracycline/cyclophosphamide and taxane (AC/T). Per investigator discretion, pts received pembrolizumab (pembro) 400 mg Q6W from cycle 1 and/or carboplatin (carbo) AUC 1.5 QW from cycle 5. Tumor biopsies and blood samples were collected prior to treatment, 7 days post single-dose trilaciclib, and during surgery, with an additional blood sample at cycle 2. PDL1 status was assessed per Ventana SP142 assay (positive immune cell score ≥ 1%). The primary objective is to evaluate the immune-based mechanism of action of single-dose trilaciclib. Results: As of January 3, 2023, 18/24 pts had completed treatment and/or had definitive surgery; 1 pt with neuroendocrine features discontinued due to disease progression. Median age was 57 years. At diagnosis, 79% of pts had stage II tumors (88% with ductal carcinoma; 38% with PDL1+ tumors). 18 pts received pembro + carbo, 3 pts pembro only, and 3 pts carbo only. Common treatment-related adverse events (TRAEs) were fatigue (79%), nausea, (67%), alopecia (67%), and neutropenia events (63%); 42% of pts had grade 3/4 neutropenia events. 4 serious TRAEs occurred in 2 (8%) pts: pembro-related colitis and hypertransaminasemia, trilaciclib/paclitaxel-related urosepsis, and AC-related febrile neutropenia. Response data were available for 15 pts; pathologic complete response (pCR) was observed in 7 (47%) pts, with pCR rates of 86% vs 13% for pts with PDL1+ vs PDL1– tumors, respectively. Immune analysis of the TME post trilaciclib monotherapy demonstrated several pCR-related features, such as increased stromal tumor-infiltrating lymphocytes and granzyme B+ cells. Correlative blood analysis revealed increased circulating baseline CD8+ T cells in pts achieving pCR. Conclusions: Safety and tolerability data are encouraging for trilaciclib in combination with AC/T ± pembrolizumab ± carboplatin in the neoadjuvant setting for early-stage TNBC. Preliminary efficacy data align with standard neoadjuvant chemotherapy regimens. Final pCR data from all pts and immune correlates from tumor and blood samples will be presented. Clinical trial information: NCT05112536 .

Abstract CT005: AEGEAN: A phase 3 trial of neoadjuvant durvalumab + chemotherapy followed by adjuvant durvalumab in patients with resectable NSCLC

Abstract Background: Recent trials have demonstrated the clinical benefit of immunotherapy in either the neoadjuvant or adjuvant resectable (R) NSCLC setting. AEGEAN (NCT03800134) is a randomized, double-blind, placebo (PBO)-controlled trial assessing neoadjuvant durvalumab (D) + chemotherapy (CT) followed by surgery (Sx) and adjuvant D in patients (pts) with R-NSCLC. Methods: Adults with treatment (Tx)-naïve R-NSCLC (stage II-IIIB[N2]; AJCC 8th ed) and ECOG PS 0/1 were randomized (1:1) to receive D 1500 mg or PBO IV + platinum-based CT (every 3 weeks [Q3W] for 4 cycles) before Sx, then further D 1500 mg or PBO IV (Q4W, up to 12 cycles). Pts were stratified by disease stage (II vs III) and PD-L1 tumor cell expression (<1% vs ≥1%, Ventana SP263). Pts with documented EGFR/ALK aberrations were excluded from the modified intent-to-treat (mITT) population for efficacy analyses. The primary endpoints were pathological complete response (pCR), evaluated centrally, and event-free survival (EFS; using RECIST v1.1), evaluated by BICR. Safety was assessed in all pts who received ≥1 study Tx dose. Results: Between Jan 2, 2019, and Apr 19, 2022, 802 pts were randomized to the ITT population (n=740 in the mITT population) of whom 799 received Tx (D arm, n=400; PBO arm, n=399). Baseline characteristics were largely balanced (mITT). Overall, 84.7% in the D arm and 87.2% in PBO arm completed 4 cycles of platinum-doublet CT and 77.6% and 76.7%, respectively, completed Sx (mITT). As of Nov 10, 2022 (data cutoff), median EFS follow-up in censored pts was 11.7 months (mITT). The pCR rate was significantly higher and EFS significantly prolonged in the D vs PBO arms (mITT) (Table). In the safety analysis set, maximum grade 3/4 any-cause AEs occurred in 42.3% vs 43.4% in the D and PBO arms, respectively, during the overall Tx period. Conclusions: The AEGEAN trial met both of its primary endpoints of improved pCR and EFS. Perioperative D plus neoadjuvant CT was associated with a manageable safety profile. Clinical trial identification: NCT03800134 (release date: January 11, 2019) Endpoint D arm PBO arm Tx effect P value pCR n/N: 63/366 (17.2%) n/N: 16/374 (4.3%) Difference in pCR (95% CI), %: 13.0 (8.7-17.6)a 0.000036 (assessed at IA)b EFS n events/N: 98/366 (26.8%) n events/N: 138/374 (36.9%) HR (95% CI): 0.68 (0.53-0.88)d 0.003902e Median (95% CI), months: NR (31.9-NR)c Median (95% CI), months: 25.9 (18.9-NR)c aCIs by stratified Miettinen and Nurminen’s method. bStatistical significance was achieved at the IA (402 pts; data cutoff, Jan 14, 2022); no testing was performed at FA. The statistically significant p-value of 0.000036 was based on a Cochran-Mantel-Haenszel test. cKaplan-Meier method. dStratified Cox proportional hazards model. eStratified log-rank test. CI, confidence interval; FA, final analysis; HR, hazard ratio; IA, interim analysis; NR, not reached. Citation Format: John V. Heymach, David Harpole, Tetsuya Mitsudomi, Janis M. Taube, Gabriella Galffy, Maximilian Hochmair, Thomas Winder, Ruslan Zukov, Gabriel Garbaos, Shugeng Gao, Hiroaki Kuroda, Jian You, Kang-Yun Lee, Lorenzo Antonuzzo, Mike Aperghis, Gary J. Doherty, Helen Mann, Tamer M. Fouad, Martin Reck. AEGEAN: A phase 3 trial of neoadjuvant durvalumab + chemotherapy followed by adjuvant durvalumab in patients with resectable NSCLC [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 2 (Clinical Trials and Late-Breaking Research); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(8_Suppl):Abstract nr CT005.

Avelumab first-line maintenance plus best supportive care (BSC) vs. BSC alone for advanced urothelial carcinoma: JAVELIN Bladder 100 Asian subgroup analysis.

The phase 3 JAVELIN Bladder 100 trial showed significantly prolonged overall survival (OS) with avelumab first-line maintenance + best supportive care (BSC) vs. BSC alone in patients with advanced urothelial carcinoma (UC) that had not progressed with first-line platinum-containing chemotherapy. Here, efficacy and safety were assessed from the initial analysis of the JAVELIN Bladder 100 trial (data cutoff October 21, 2019) in patients enrolled in Asian countries. Patients with locally advanced or metastatic UC that had not progressed with 4 to 6 cycles of first-line platinum-containing chemotherapy (gemcitabine + cisplatin or carboplatin) were randomized 1:1 to receive avelumab first-line maintenance + BSC or BSC alone, stratified by best response to first-line chemotherapy and visceral vs. nonvisceral disease when initiating first-line chemotherapy. The primary endpoint was OS assessed from randomization in all patients and patients with PD-L1+ tumors (Ventana SP263 assay). Secondary endpoints included progression-free survival (PFS) and safety. A total of 147 patients in JAVELIN Bladder 100 were enrolled in Asian countries (Hong Kong, India, Japan, South Korea, and Taiwan). In this Asian subgroup, 73 and 74 patients received avelumab + BSC or BSC alone, respectively. Median OS was 25.3 months (95% CI, 18.6 to not estimable [NE]) in the avelumab + BSC arm vs. 18.7 months (95% CI, 12.8-NE) in the BSC alone arm (hazard ratio [HR], 0.74 [95% CI, 0.43-1.26]); median PFS was 5.6 months (95% CI, 2.0-7.5) vs. 1.9 months (95% CI, 1.9-1.9), respectively (HR, 0.58 [95% CI, 0.38-0.86]). In the avelumab + BSC vs. BSC alone arms, grade ≥3 treatment-emergent adverse events (any causality) occurred in 44.4% vs. 16.2%, respectively. The most common grade ≥3 treatment-emergent adverse events in the avelumab + BSC arm were anemia (9.7%), amylase increased (5.6%), and urinary tract infection (4.2%). Efficacy and safety results for avelumab first-line maintenance in the Asian subgroup of JAVELIN Bladder 100 were generally consistent with those in the overall trial population. These data support the use of avelumab first-line maintenance as standard of care for Asian patients with advanced UC that has not progressed with first-line platinum-containing chemotherapy. NCT02603432.

Subpopulations of B lymphocytes in patients with breast cancer depending on the PD-L1 status

Aim. To study the association between the functional potency and degree of maturity of B lymphocytes and PD-L1 expression in breast cancer patients.Materials and methods. The study included 37 patients with the morphologically verified diagnosis of invasive breast cancer of no special type (IBC NST). The PD-L1 status was determined immunohistochemically using the Ventana SP142 assay (Roche, USA). Using the multiplex flow cytometry-based assay and high-throughput sequencing of the tumor microenvironment, subpopulations of B lymphocytes and their CD27 and PD1 expression profiles were determined, taking into account the PD-L1 status.Results. In the tumor microenvironment, regardless of the PD-L1 status, expression signatures of five lymphocyte subpopulations were determined. However, in PD-L1-positive patients, the levels of B lymphocytes and immunoglobulin class-switched B lymphocytes were higher compared with PD-L1-negative patients. Evaluation of the number of different B lymphocyte subpopulations by flow cytometry showed that PD-1-positive B lymphocytes predominated in the tumor microenvironment in PD-L1-positive patients, regardless of the degree of lymphocyte maturity.Conclusion. The results of the study showed predominance of mature committed B lymphocytes and memory B lymphocytes capable of synthesizing immunoglobulins of different classes and Th2 cytokines involved in type 2 immune response in PD-L-positive tumor microenvironment. It suggests that immunotherapy with PD-L1 inhibitors is highly likely to activate cells with protumor potential and can ultimately contribute to breast cancer progression.

Abstract 5829: Differential expression of PD-L1 and PD-L2 is associated with M2 tumor-associated macrophages and tumor differentiation in non-small cell lung cancer

Abstract Objectives: To improve the treatment strategy of immune-checkpoint inhibitors for non-small cell lung cancer (NSCLC), a comprehensive analysis of programmed death-ligand (PD-L)1 and PD-L2 expression is clinically important. The expression of PD-L1 and PD-L2 on tumor cells (TCs) and tumor-infiltrating immune cells (ICs) was investigated with respect to M2 tumor-associated macrophages (TAMs), which are key components of the tumor microenvironment. Methods: We performed immunohistochemical studies to evaluate the M2 TAM distribution by CD163 staining, PD-L1 expression on TCs and ICs by the Ventana SP263 assay, and PD-L2 expression on TCs and ICs, using the Ventana BenchMark GX system, in 175 patients with resected NSCLC. Results: M2 TAM density revealed high levels of variation among the 175 tumor tissues (mean ± standard deviation (SD), 382.5 ± 381.9 cells per mm2). The percentage of PD-L1-positive TCs and PD-L1-positive ICs varied greatly among the 175 tumor tissues (mean ± SD; 15.6 ± 27.0% and 9.4 ± 10.9%, respectively). In addition, the percentage of PD-L2-positive TCs and PD-L2-positive ICs also ranged widely among the 175 tumor tissues (mean ± SD, 14.6 ± 22.9% and 12.5 ± 18.4%, respectively). M2 TAM density was significantly associated with the expression of PD-L1 on TCs and ICs (P < 0.0001 and P < 0.0001, respectively). M2 TAM density was also significantly associated with the expression of PD-L2 on TCs and ICs (P = 0.0452 and P = 0.0125, respectively). The percentage of PD-L1-positive TCs was significantly correlated with the percentage of PD-L1-positive ICs (r = 0.396; P < 0.0001). In addition, the percentage of PD-L2-positive TCs also was significantly correlated with the percentage of PD-L2-positive ICs (r = 0.488; P < 0.0001). However, there was no correlation between the percentage of PD-L1-positive TCs and the percentage of PD-L2-positive TCs (r = 0.019; P = 0.8049). Meanwhile, tumor differentiation was significantly associated with PD-L1 expression on TCs and ICs (P = 0.0002 and P < 0.0001, respectively). By contrast, tumor differentiation was inversely associated with PD-L2 expression on TCs and ICs (P = 0.0260 and P = 0.0326, respectively). Conclusions: PD-L1 and PD-L2 expression on TCs and ICs was associated with M2 TAMs in NSCLC, although there was no correlation between PD-L1 and PD-L2 expression on TCs. The combined evaluation of PD-L1 and PD-L2 expression could be clinically important in the treatment strategy of immune-checkpoint inhibitors in patients with NSCLC. In particular, the evaluation of PD-L2 expression may be necessary for patients with PD-L1-negative NSCLC. Citation Format: Ryota Sumitomo, Huang Cheng-long, Hiroshi Date. Differential expression of PD-L1 and PD-L2 is associated with M2 tumor-associated macrophages and tumor differentiation in non-small cell lung cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 5829.

Abstract P2-23-03: Genomic Evaluation of Malignant Phyllodes Tumors Reveals Multiple Targetable Opportunities

Abstract Background: Malignant phyllodes tumors (MPT) are rare fibroepithelial breast tumors that disproportionately affect young women. Despite high local and distant recurrence rates, treatment is almost exclusively surgical. With no known effective chemotherapy or targeted systemic therapy options, metastatic progression portends dismal prognosis. Current national guidelines do not recommend biomarker testing in the non-metastatic setting. Management of metastatic disease follows principles of soft tissue sarcoma recommending Next-Generation Sequencing on an individual basis for patients who may qualify for clinical trials or are refractory to standard therapies. In the largest genomic profiling effort of MPT to date, we sought to describe the genomic landscape of MPTs through comprehensive genomic profiling (CGP) and immunotherapeutic biomarker analysis. Methods: Cases of sequenced MPT were identified from a CLIA-certified, CAP-accredited laboratory database (Foundation Medicine, Cambridge, MA). Cases were categorized as localized/locally recurrent or metastatic. All cases underwent CGP by DNA extraction from FFPE samples using a hybrid capture, adaptor ligation-based next generation sequencing assay, and all classes of genomic alterations, microsatellite instability (MSI), and tumor mutational burden (TMB) were evaluated. PD-L1 expression by IHC was measured by the DAKO 22C3 assay (scored CPS) or the Ventana SP142 assay (scored as IC). Patient characteristics and results of CGP of MPT were summarized by either N (%) or median (range). Factors from MPT were compared to all cases of breast carcinoma in the lab database. Fisher’s Exact Tests were used to test for differences between groups and analysis of variance was used to test for differences for continuous variables. Results: Of 135 MPT cases identified; 94 (69.6%) were localized/locally recurrent (breast, chest wall, soft tissue, skin, or lymph node) and 41 (30.4%) were metastatic (73% lung, followed by bone, liver, other intraabdominal). All patients were female with a median age of 54 years (range 14-86). The median TMB across samples was 2.5 mut/Mb and only 3 were TMB-high tumors (>10mut/Mb). Over 1/3 (36.8%) of samples were PD-L1+ via Ventana SP142 assay (≥1) and 21.4% were PD-L1+ via Dako 22C3 assay (CPS ≥10). All evaluable cases (N=132) were microsatellite stable. The ten most commonly altered genes included TERT-promoter (69.7%), CDKN2A (45.9%), TP53 (37.8%), NF1 (35.6%), CDKN2B (33.3%), MED12 (28.9%), MTAP (27.7%), KMT2D (22.2%), PIK3CA (20.0%), PTEN (18.5%), and RB1 (18.5%); notably distinct in frequency from the breast carcinoma cohort (Table 1). Alterations in genes affecting cell cycle regulation (i.e. CDKN2A/B and TP53) were mutually exclusive from one another (p< 0.001). Several tumors harbored genomic alterations with FDA-approved indications in other tumor types were found including: NF1, PIK3CA, EGFR Exon 19/20 insertions, and BRAF V600E mutations. There were no statistically significant differences between alterations in localized/locally recurrent versus metastatic specimens. Conclusions: In the largest genomic evaluation of localized/locally recurrent or metastatic MPTs to date, multiple clinically actionable mutations for further exploration were found. TERT-promoter was altered in the majority of cases. PDL-1 was expressed in over 1/3 of cases suggesting that clinical investigation of immunotherapeutic strategies is warranted. Routine sequencing of metastatic MPT may provide additional information to guide treatment decisions and clinical trial enrollment. Table 1. Frequency of Genomic Alterations identified in 135 cases of Malignant Phyllodes Tumors. Citation Format: Laura H. Rosenberger, Richard F. Riedel, Natalie A. Danziger, Ethan Sokol, Jeffrey S. Ross, Sarah L. Sammons. Genomic Evaluation of Malignant Phyllodes Tumors Reveals Multiple Targetable Opportunities [abstract]. In: Proceedings of the 2022 San Antonio Breast Cancer Symposium; 2022 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2023;83(5 Suppl):Abstract nr P2-23-03.

Abstract PD11-11: PD11-11 Results from ALICE – Atezolizumab Combined with Immunogenic Chemotherapy in Patients with Metastatic Triple Negative Breast Cancer, a Randomized Phase IIb Trial

Abstract Background: Immune checkpoint inhibitors (CPI) have shown efficacy against metastatic triple negative breast cancer (mTNBC), but only for PD-L1 positive tumors. It is not known if so-called immunogenic chemotherapies may yield clinical relevant synergies with CPI. We addressed these issues, by conducting a trial evaluating atezolizumab (anti-PD-L1) in combination with doxorubicin, which has been reported to provoke immunogenic cell death, and low-dose metronomic cyclophosphamide, which has been reported to counter immunosuppressive cells. The pegylated liposomal form of doxorubicin (PLD) was selected to avoid steroids and allow for long term therapy in responders. To our knowledge, this is the first randomized trial reporting on the concomitant addition of CPI to antracyclines in mTNBC. Methods: The trial enrolled patients with mTNBC and maximum one previous line of chemotherapy in the metastatic setting. Patients were randomized 2:3 into arm A (n=28), receiving chemotherapy alone, or arm B (n=40), receiving chemotherapy in combination with atezolizumab (840 mg every 2nd week). The chemotherapy consisted of PLD (20mg/m2 every 2nd week) + oral cyclophosphamide (cyclo; 50mg/day, 2/4 weeks) in both arms. The per protocol (PP) population was defined as patients receiving > 3 doses of atezolizumab and >2 doses of PLD. The primary efficacy endpoint was progression-free survival (PFS) in the PP population. The protocol power analysis focused on durable response, as measured by 15 months PFS. Safety, a co-primary endpoint, was evaluated in all patients that started therapy (Full Analysis Set; FAS). Secondary endpoints included PFS in FAS, objective response rate (ORR), clinical benefit rate (CBR), durable response rate (>6 months; DRR), overall survival (OS) and biomarkers. PD-L1 status was determined retrospectively by the Ventana SP142 assay, as tumor-infiltrating immune cells with cut-off ≥ 1%. Efficacy data are given in the PP population unless stated otherwise. Hazard ratios (HR) are given with 95% confidence intervals (CI). Results: A total of 68 patients started therapy (FAS), of which 59 were in the PP population and 57% had not received previous chemotherapy in the metastatic setting. PFS was significantly improved in arm B compared to arm A in both the PP population (HR 0.57; CI 0.33-0.99; p=0.0477) and in the FAS (HR 0.56; CI 0.33-0.95; p=0.0326). Median PFS was 4.3 months in arm B versus 3.5 months in arm A. The progression-free proportion after 15 months was 14.7% (CI 6.4-30.1%) in arm B versus 0% in arm A. The ORR was 30.6%/21.7%, CBR was 52.8%/43.5% and DRR was 13.9%/4.3% in arm B/A. The PFS advantage was observed for both PD-L1+ (n=27; HR 0.58) and PD-L1- subjects (n=31; HR 0.66). All five patients without progression after 15 months belonged to arm B, and three out of these patients were PD-L1 negative. Serious adverse events occurred for 48% in arm B and 29% in arm A (FAS). The most common immune related adverse events of any grade in arm B/A were hypothyroidism (10.0%/7.1 %), pneumonitis (10.0%/3.6%), hyperthyroidism (5.0%/7.1%) and rash (7.5%/3.6%). Further biomarker analyses and assessments of immunological changes during therapy are ongoing. Conclusions: The addition of atezolizumab to PLD and low-dose metronomic cyclophosphamide significantly improved PFS. A benefit was indicated also in patients with PD-L1 negative disease. The combination regimen was well tolerated with no new safety signals. Results from the ongoing analyses of consecutive tumor and blood samples will be important to assess the hypothesized immunological effects of the chemotherapy and to investigate biomarkers associated with the response to the combined treatment. Citation Format: Jon Amund Kyte, Andreas H. Røssevold, Nikolai K. Andresen, Christina Annette Bjerre, Bjørnar Gilje, Erik Hugger Jakobsen, Sunil Xavier Raj, Ragnhild Sørum Falk, Elin Borgen, Thea Jahr, Øystein Garred, Jon Lømo, Randi Margit Mathiesen, Bjørn Naume. PD11-11 Results from ALICE – Atezolizumab Combined with Immunogenic Chemotherapy in Patients with Metastatic Triple Negative Breast Cancer, a Randomized Phase IIb Trial [abstract]. In: Proceedings of the 2022 San Antonio Breast Cancer Symposium; 2022 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2023;83(5 Suppl):Abstract nr PD11-11.

Abstract P2-23-09: Ultra-high Tumor Mutation Burden in Metastatic/Clinically Advanced Breast Cancer (MBC)

Abstract Background: High (HTMB) tumor mutation burden (TMB) defined as ≥10 mutations/megabase (Mb) identifies breast cancer patients who could benefit from pembrolizumab. The higher the TMB the greater the likelihood of benefit. The goal of this analysis was to determine the frequency and genomic landscape of MBC with ultra-high TMB (UHTMB) defined as a TMB > 20 mutations/Mb. Design 2,049 MBC patients (pts) underwent hybrid capture based comprehensive genomic profiling for genomic alterations (GA) in at least 324 genes including determination of TMB to guide therapy decisions using the FoundationOne®CDx assay. ER, PR and HER2 expression were abstracted from submitted pathology reports. Results: 165 of 2049 MBC (8.1%) had HTMB > 10 mutations/Mb, among these 45 (2.2% of all cases) had UHTMB. When compared with the 2,004 non-UHTMB MBC pts with TMB < 20 mutations/Mb, the 45 UHTMB pts were older (mean 64.6 yrs vs 58.2 yrs; p<.0001), more often had lobular histology (40.00% vs 14.5%; p<.0001) and ER+ disease (86.6% vs 70.0%), had higher average driver GA/tumor (9.84 vs 5.7; p<.0001), and less often had TNBC (13.3% vs 27.0%; p=.041) compared to non-UHTMB high cancers. There were no significant differences in ancestry. Mutation signature analysis revealed that APOBEC was predominant in UHTMB samples (82.5%) with a minor portion with an MMR signature (10%), however, MSI-H status was significantly higher in UHTMB high cases (11.6% vs 0.40%; p<.0001). GA more frequently identified in UHTMB cases included CDH1 (45.50% vs 14.32%; p<.0001), PIK3CA (81.80% vs 37.86%; p<.0001), CDKN2A (11.40% vs 3.19%; p=.017), ARID1A (25.00% vs 5.01%; p<.0001) and NF1 (20.50% vs 5.94%; p=.0014). PD-L1 (CD274) gene amplification (2.3% vs 1.3%) or protein expression by the Ventana SP142 assay (57.14% vs 51.10%) were not significantly different. Conclusions: UHTMB MBC is a rare but clinically important subset in breast cancer that could have high response rates to single agent pembrolizumab. This phenotype is driven by APOBEC mutagenesis, more often seen in ER+ lobular cancers, and have higher frequencies of MSI-high status and mutations in CDH1 and PIK3CA. Citation Format: Kristina Fanucci, maryam lustberg, Neal Fischbach, Maureen Pelletier, Abirami Sivapiragasam, Prashanth Ashok Kumar, Mansi Kallem, Natalie A. Danziger, Ethan Sokol, Smruthy Sivakumar, Dean Pavlick, Jeffrey S. Ross, Lajos Pusztai. Ultra-high Tumor Mutation Burden in Metastatic/Clinically Advanced Breast Cancer (MBC) [abstract]. In: Proceedings of the 2022 San Antonio Breast Cancer Symposium; 2022 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2023;83(5 Suppl):Abstract nr P2-23-09.

Abstract P5-14-10: Targetable alterations and genomic signatures within breast cancer brain metastases: Data from comprehensive genomic profiling of 761 breast cancer brain metastases

Abstract Background: Breast cancer brain metastasis (BCBM) represents an area of unmet clinical need. We previously demonstrated the genomic differences between primary BC and BCBM. In this study we examined the genomic differences between BCBM by BC subtypes and the potential actionable targets that might be taken forward for each subtype in clinical trials. Material and Methods: A total of 761 BCBMs were analyzed by comprehensive genomic profiling (CGP) for alterations in up to 395 genes (Foundation Medicine, USA). The samples were classified by immunohistochemistry (IHC) of the BCBM to ER+ (ER+/HER2-, ER+/HER2+), ER-/HER2+ and ER-/HER2-. Homologous recombination deficiency (HRD-gLOH; cutoff 16%), tumour mutational burden (TMB; cutoff 10 mutations/Mb), microsatellite instability (MSI) and PD-L1 prevalence and expression by IHC using the VENTANA SP142 assay (Immune Cell Score [IC] cutoff 1%) were also investigated. Results: For all BC subtypes the most enriched gene alterations in BCBM (>20% prevalence) were: TP53, MYC and PIK3CA. ESR1 and ERBB2 were more prevalent in ER+ and HER2+ tumours respectively, with ESR1 alterations significantly enriched in ER+/HER2- BCBMs (p< 0.0001). Frequently altered genes by BCBM subtype were: ER+/HER2-: CDH1 (8%) and BRCA2 (7%); ER+/HER2+: PIK3C2B (11%), MDM4 (11%), TBX3 (9%) and AKT2 (8%); ER-/HER2+: LYN (9%). Significantly enriched genes (p< 0.01) by BCBM subtype were: HER2+: CDK12 (15%); ER-/HER2-: BRCA1 (14%), CCND3 (9%), VEGFA, JAK2 (8% each) and the immune checkpoint inhibition (ICPI) biomarkers PDCD1LG2 (PDL2), CD274 (PDL1) (7% each). HRD-gLOH was high in ER+/HER2-: (43%) and ER-/HER2-: (70%). TMB and MSI were present in 10%-21% and 1-3% of BCBM respectively, whereas PDL1 protein expression by subtypes was: ER+/HER2- 23%, ER+/HER2+ 27%, ER-/HER2+ 57% , ER-/HER2- 48%. Table 1 summarizes the proportion of BCBMs with actionable alterations and selected clinical trials in BCBM. Conclusion: Clinically-relevant genomic alterations were identified across all BCBM subtypes. High HRD-gLOH, TMB and MSI were observed across all the BCBMs subtypes whereas PDL1/PDL2 alterations were a distinctive feature of ER-/HER2- BCBM. These data highlight the need to assess the genomic landscape of BCBM to enable rational treatment decisions with targeted agents, as well as to enable enrichment of relevant populations within clinical trials. Table 1. Selected studies with targeted therapy and/or immunotherapy in breast cancer brain metastases. The percentage (%) of actionable alterations by ER and HER2 status is summarized. ND: Not Detectable. Citation Format: Athina Giannoudis, Ethan Sokol, Shakti Ramkissoon, Talvinder Bhogal, Jeff Ross, Kimberly McGregor, Evangelia Razis, Rupert Bartsch, Richard S. Huang, Carlo Palmieri. Targetable alterations and genomic signatures within breast cancer brain metastases: Data from comprehensive genomic profiling of 761 breast cancer brain metastases [abstract]. In: Proceedings of the 2022 San Antonio Breast Cancer Symposium; 2022 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2023;83(5 Suppl):Abstract nr P5-14-10.

Rationale 305: Phase 3 study of tislelizumab plus chemotherapy vs placebo plus chemotherapy as first-line treatment (1L) of advanced gastric or gastroesophageal junction adenocarcinoma (GC/GEJC).

286 Background: In a phase 2 study, tislelizumab (TIS), an anti-PD-1 monoclonal antibody, plus chemotherapy demonstrated durable antitumor activity as 1L in Chinese GC/GEJC patients (Xu et al, 2020). RATIONALE 305 (NCT03777657) was a global, double-blind, phase 3 study comparing 1L TIS plus investigator-chosen chemotherapy (TIS+ICC) vs placebo plus ICC (P+ICC) in GC/GEJC patients. Results from the interim analysis (IA) in the PD-L1+ population are presented; ITT population outcomes will be presented after final analysis. Methods: Adults with previously untreated, unresectable locally advanced or metastatic GC/GEJC, regardless of PD-L1 expression, were randomized (1:1) to receive TIS (200 mg IV Q3W) plus ICC (oxaliplatin [130 mg/m² IV Q3W] and oral capecitabine [1,000 mg/m² BID, Days 1-14 Q3W] or cisplatin [80 mg/m² IV Q3W] and 5-fluorouracil [800 mg/m²/day IV, Days 1-5 Q3W]) or P+ICC. Randomization was stratified by region, PD-L1 expression, peritoneal metastasis, and ICC. Patients with known HER2-positive status were excluded. RATIONALE 305 had dual primary endpoints of OS in the PD-L1+ and ITT analysis set; PD-L1+ was defined as PD-L1 TAP score ≥5% (VENTANA SP263 assay) assessed by blinded independent central laboratory. Secondary endpoints include PFS, ORR and DoR per RECIST 1.1, HRQoL, and safety profile. The prespecified IA was conducted after ~70% of total OS events had occurred. Results: Of 546 PD-L1+ patients enrolled from 13 counties/regions (73.8 % Asia; 26.2% Europe/ North America), 274 were randomized to receive TIS+ICC and 272 to receive P+ICC. As of 8 Oct 2021, median follow-up was 11.8 (TIS+ICC) and 11.7 mo (P+ICC). TIS+ICC showed statistically significant and clinically meaningful OS improvement vs P+ICC (HR 0.74 [95% CI: 0.59-0.94], mOS 17.2 vs 12.6 mo; 1-sided P= .0056). Compared with P+ICC, TIS+ICC also had longer PFS (mPFS 7.2 vs 5.9 mo; HR 0.67 [95% CI: 0.55-0.83]), higher ORR (50.4% vs 43.0%), and more durable response (mDoR 9.0 vs 7.1 mo). Patients treated with TIS+ICC reported better HRQoL than patients treated with P+ICC, as indicated by EORTC-QLQ-C30 global health status and physical functioning scores as well as the QLQST022 index score. No new safety signals were observed with TIS+ICC or P+ICC. While TEAEs leading to discontinuation of any treatment were higher with TIS+ICC than P+ICC (22.4% vs 12.1%), incidence rates of grade ≥3 TEAEs (64.7% vs 62.9%), serious TEAEs (42.3% vs 36.8%), and TEAEs leading to death (8.8% vs 7.7%) were comparable between both arms. Conclusions: In RATIONALE 305, TIS+ICC provided significant and clinically meaningful improvement in OS vs P+ICC with well acceptable safety as 1L in PD-L1+ patients with advanced GC/GEJC. These data suggest this combination is a new 1L option for this patient population. Clinical trial information: NCT03777657 .

Spatial Profile of Tumor Microenvironment in PD-L1-Negative and PD-L1-Positive Triple-Negative Breast Cancer.

The problem of finding more precise stratification criteria for identifying the cohort of patients who would obtain the maximum benefit from immunotherapy is acute in modern times. In our study were enrolled 18 triple-negative breast cancer patients. The Ventana SP142 test was used for PD-L1 detection. Spatial transcriptomic analysis by 10x Genomics was used to compare PD-L1-positive and PD-L1-negative tumors. The seven-color multiplex immunofluorescence (by Akoya) was used for the detection of the type of cells that carried the PD1 receptor and the PD-L1 ligand. Using pathway analysis, we showed that PD-L1-positive tumors demonstrate signatures of a cell response to cytokines, among others, and PD-L1-negative tumors demonstrate signatures of antigen presentation. PD-L1-positive and PD-L1-negative tumors have different tumor microenvironment (TME) compositions according to CIBERSORT analysis. Multiplex immunohistochemistry (IHC) confirmed the prevalence of PD1-negative M2 macrophages and PD1-negative T lymphocytes in PD-L1-positive tumors. PD-L1-positive tumors are not characterized by direct contact between cells carrying the PD1 receptor and the PD-L1 ligand. So, the absence of specific immune reactions against the tumor, predominance of pro-tumor microenvironment, and rare contact between PDL1 and PD1-positive cells may be the potential reasons for the lack of an immune checkpoint inhibitor (ICI) effect in triple-negative breast cancer patients.

Impact of adjuvant chemotherapy and radiotherapy on tumour-infiltrating lymphocytes and PD-L1 expression in metastatic breast cancer

BackgroundChemotherapy and radiotherapy were postulated to induce an inflamed tumour microenvironment. We aimed to evaluate the effects of adjuvant chemotherapy/radiotherapy on tumour-infiltrating lymphocytes (TILs) and programmed death-ligand 1 (PD-L1) expression in metastatic breast cancer.MethodsWe identified paired primary and metastatic tumours in 85 patients with breast cancer. Stromal TILs were assessed according to international guidelines. PD-L1 expression was evaluated using the VENTANA SP142 assay.ResultsTILs were significantly lower in metastatic tumours than in primary tumours (12.2 vs. 8.3%, p = 0.049). PD-L1 positivity was similar between primary and metastatic tumours (21.2 vs. 14.1%, p = 0.23). TILs were significantly lower in patients who received adjuvant chemotherapy than in those who did not (−9.07 vs. 1.19%, p = 0.01). However, radiotherapy had no significant effect on TILs (p = 0.44). Decreased TILs predicted worse post-recurrence survival (hazard ratio, 2.94; 95% confidence interval [CI]: 1.41–6.13, p = 0.003), while increased TILs was associated with a better prognosis (HR, 0.12; 95% CI: 0.02–0.08, p = 0.04).ConclusionsTILs decreased in metastatic tumours, particularly in patients who relapsed after adjuvant chemotherapy. Changes in TILs from primary to metastatic sites could be a prognostic factor after recurrence.

Biomarker Analysis of Zanubrutinib and Tislelizumab Combination Therapy in Patients with Relapsed/Refractory B-Cell Malignancies

Background/Introduction: Diffuse large B-cell lymphoma (DLBCL) is the most common non-Hodgkin lymphoma world-wide. Although frontline therapies have yielded positive outcomes in most patients with DLBCL, about one-third of patients are refractory to or relapse after standard therapy (Sehn et al. J Clin Oncol 2005;23(22):5027-33). The antitumor efficacy of zanubrutinib and tislelizumab combination therapy has been demonstrated in patients with B-cell malignancies (Tam et al. Blood 2019;134:1594). Herein, we performed a comprehensive analysis to examine biomarkers associated with response or resistance to zanubrutinib and tislelizumab combination therapy in patients with B-cell malignancies. Methods: Biomarker analysis was performed in 24 patients with published response data determined by the investigator using Lugano 2014 criteria (Cheson et al. J Clin Oncol 2014;32(27):3059-68). Programmed death-ligand 1 (PD-L1) gene amplification was assessed in the baseline tumor of 11 patients with non-germinal center B-cell (GCB) subtype of DLBCL by fluorescence in situ hybridization (Empire Genomics). PD-L1 protein expression was examined in the baseline tumor (8 DLBCL) by immunohistochemistry (IHC) (Ventana PD-L1 [SP263] assay; Roche). DLBCL subtype and gene expression were examined in the baseline tumor (14 DLBCL) by HTG EdgeSeq DLBCL cell of origin assay (HTG Molecular Diagnostics). Gene mutation was examined in the baseline tumor (17 DLBCL) by DNA-seq (CGI NGS 220-Gene Panel assay; Cancer Genetic Inc.). PD-L1 and CD8 protein expression were examined in paired biopsy samples (1 DLBCL, 3 transformed follicular lymphoma [tFL], 1 follicular lymphoma [FL], 1 mantle cell lymphoma) before and 8 days after zanubrutinib treatment by IHC (Ventana SP263, CONFIRM CD8 SP57). Gene expression profiles were examined in paired biopsy samples (3 tFL, 1 FL, 1 chronic lymphocytic leukemia) by RNA-seq (RNA Access assay; Illumina). Results:PD-L1 gene alteration was observed in 2 of 11 patients with non-GCB DLBCL, including 1 with gene amplification and 1 with chromosome 9 polysomy. A higher overall response rate (ORR; 2/2 [100%] vs 3/9 [33.3%]) and complete response (CR) rate (2/2 [100%] vs 2/9 [22.2%]) was observed in patients with PD-L1 gene alteration than in patients without. Two of 8 [25%] evaluable patients with DLBCL harbored PD-L1+ tumor cells (defined using a PD-L1 protein expression cut-off ≥1%). A higher ORR (1/2 [50%] vs 2/6 [33%]) and CR rate (1/2 [50%] vs 1/6 [16.7%]) was observed in patients with PD-L1+ tumor cells than in those without. High mRNA levels of CD3D (P < 0.05), HLA-DRA (P < 0.07), and LAG3 (P < 0.05) were enriched in responders, suggesting an inflamed tumor microenvironment (TME). In contrast, non-responders harbored high mRNA levels of the NF-kB pathway-related gene REL (P < 0.05). High mRNA levels of REL were associated with an inferior clinical outcome to zanubrutinib and tislelizumab combination therapy (P < 0.05). Mutations in the tumor suppressor gene TP53 (5/10 [50%] vs 0/7 [0%]) were enriched in non-responders. Non-responders harbored higher frequency of mutations in genesinvolved in immune evasion (3/10 [30%] vs 1/7 [14.3%]), epigenetic modifications (2/10 [20%] vs 1/7 [14.3%]), and cell survival (2/10 [20%] vs 0/7 [0%]) than responders, suggesting that non-responders may have complex resistance mechanisms. Results from paired tumor biopsies from 5 patients before and after zanubrutinib treatment revealed that zanubrutinib treatment downregulated B-cell and MYC target-related gene sets and upregulated the NK cell-related gene set NK-2. Zanubrutinib treatment seemed to have no effect on the frequency of PD-L1+ cells and CD8+ T cells (using a CD8 expression cutoff of ≥1%) in the TME, although the sample size was too small to draw a definitive conclusion. Conclusion: Patients with PD-L1 gene amplification, PD-L1+ tumor cells, and high mRNA levels of CD3D, HLA-DRA, and LAG3 in baseline tumor tissue may be more responsive to zanubrutinib and tislelizumab combination therapy. A high mRNA level of REL or mutations in TP53 may contribute to resistance of zanubrutinib and tislelizumab combination therapy. Due to the limited number of samples, results must be interpreted with caution.

The Ring Study: an international comparison of PD-L1 diagnostic assays and their interpretation in non-small cell lung cancer, head and neck squamous cell cancer and urothelial cancer

PD-L1 immunohistochemistry has been approved as a diagnostic assay for immunotherapy. However, an international comparison across multiple cancers is lacking. This study aimed to assess the performance of PD-L1 diagnostic assays in non-small cell lung cancer (NSCLC), head and neck squamous cell cancer (HNSCC) and urothelial cancer (UC). The excisional specimens of NSCLC, HNSCC and UC were assayed by Ventana SP263 and scored at three sites in each country, including Australia, Brazil, Korea, Mexico, Russia and Taiwan. All slides were rotated to two other sites for interobserver scoring. The same cohort of NSCLC was assessed with Dako 22C3 pharmDx PD-L1 for comparison. The PD-L1 immunopositivity was scored according to the approved PD-L1 scoring algorithms which were the percentage of PD-L1-expressing tumour cell (TC) and tumour proportion score (TPS) by Ventana SP263 and Dako 22C3 staining, respectively. In NSCLC, the comparison demonstrated the comparability of the SP263 and 22C3 assays (cut-off of 1%, κ=0.71; 25%, κ=0.75; 50%, κ=0.81). The interobserver comparisons showed moderate to almost perfect agreement for SP263 in TC staining at 25% cut-off (NSCLC, κ=0.72 to 0.86; HNSCC, κ=0.60 to 0.82; UC, κ=0.68 to 0.91) and at 50% cut-off for NSCLC (κ=0.64 to 0.90). Regarding the immune cell (IC) scoring in UC, there was a lower correlation (concordance correlation coefficient=0.10 to 0.68) and poor to substantial agreements at the 1%, 5%, 10% and 25% cut-offs (κ= -0.04 to 0.76). The interchangeability of SP263 and 22C3 in NSCLC might be acceptable, especially at the 50% cut-off. In HNSCC, the performance of SP263 is comparable across five countries. In UC, there was low concordance of IC staining, which may affect treatment decisions. Overall, the study showed the reliability and reproducibility of SP263 in NSCLC, HNSCC and UC.

Comparison of PD-L1 tumor cell expression with 22C3, 28-8, and SP142 IHC assays across multiple tumor types

BackgroundMultiple PD-L1 immunohistochemistry (IHC) assays, including DAKO 22C3, DAKO 28-8, and Ventana SP142 PD-L1 IHC assays, have been approved by the Food and Drug Administration as a companion diagnostic (CDx)...

971TiP Phase III trial of durvalumab combined with domvanalimab following concurrent chemoradiotherapy (cCRT) in patients with unresectable stage III NSCLC (PACIFIC-8)

The PACIFIC trial established up to 12 months consolidation therapy with durvalumab as standard of care (SoC) for patients (pts) with unresectable Stage III non-small-cell lung cancer (NSCLC) and no progression after platinum-based cCRT. To improve outcomes further in this population, novel immunotherapy combinations that build on the backbone of PD-L1 inhibition with durvalumab are being explored. Domvanalimab (AB154) is an Fc-silent humanised IgG1 MoAb that blocks interaction of the T cell immunoreceptor with Ig and ITIM domains (TIGIT; upregulated by immune cells) with CD112 and CD155 (expressed by tumour and antigen-presenting cells), reducing inhibition of T cells and natural killer cells and, thereby, promoting antitumour activity. The combination of TIGIT inhibition with PD-(L)1 inhibition has shown encouraging activity in phase 1 and 2 trials in metastatic NSCLC, with enriched benefit observed among pts with PD-L1 positive tumours (Rodriguez-Abreu, et al. 2020; Niu, et al. 2020). PACIFIC-8 (NCT05211895) is assessing the efficacy and safety of durvalumab combined with domvanalimab as consolidation therapy in pts with unresectable Stage III NSCLC and PD-L1 tumour cell (TC) expression. PACIFIC-8 is a phase 3, double-blind, placebo (pbo)-controlled randomised global trial. Eligible pts (≥18 years) must have PD-L1 positive, unresectable Stage III NSCLC (TC expression ≥1% by central lab; VENTANA SP263 IHC assay), WHO performance status 0/1, documented EGFR/ALK wild-type tumour status and not have progressed following definitive platinum-based cCRT (≥2 cycles). Pts (N∼860) will be randomised (1:1) to receive SoC durvalumab (1500 mg IV) combined with either domvanalimab (20 mg/kg IV) or pbo, every 4 weeks for up to 12 months. The primary endpoint is progression-free survival (PFS; RECIST v1.1; BICR) in pts with PD-L1 TC ≥50%. Secondary endpoints include PFS (RECIST v1.1; BICR) in pts with PD-L1 TC ≥1%, overall survival, objective response rate and duration of response (RECIST v1.1; BICR), safety/tolerability, and pt-reported outcomes. Enrolment is ongoing. NCT05211895, release date: January 27, 2022. Medical writing support for the development of this abstract, under the direction of the authors, was provided by Aaron Korpal, PhD, and Andrew Gannon, MS, MA, of Ashfield MedComms (Manchester, UK), an Ashfield Health company. AstraZeneca.